diff --git a/fs/bcachefs/Makefile b/fs/bcachefs/Makefile
index 0a4d2fe..9c00dab 100644
--- a/fs/bcachefs/Makefile
+++ b/fs/bcachefs/Makefile
@@ -46,7 +46,9 @@
 	fs-io-pagecache.o	\
 	fsck.o			\
 	inode.o			\
-	io.o			\
+	io_read.o		\
+	io_misc.o		\
+	io_write.o		\
 	journal.o		\
 	journal_io.o		\
 	journal_reclaim.o	\
diff --git a/fs/bcachefs/alloc_foreground.c b/fs/bcachefs/alloc_foreground.c
index e02749d..8e1888a 100644
--- a/fs/bcachefs/alloc_foreground.c
+++ b/fs/bcachefs/alloc_foreground.c
@@ -25,7 +25,7 @@
 #include "disk_groups.h"
 #include "ec.h"
 #include "error.h"
-#include "io.h"
+#include "io_write.h"
 #include "journal.h"
 #include "movinggc.h"
 #include "nocow_locking.h"
diff --git a/fs/bcachefs/btree_io.c b/fs/bcachefs/btree_io.c
index 0edbb73..00f53cb 100644
--- a/fs/bcachefs/btree_io.c
+++ b/fs/bcachefs/btree_io.c
@@ -14,7 +14,7 @@
 #include "debug.h"
 #include "error.h"
 #include "extents.h"
-#include "io.h"
+#include "io_write.h"
 #include "journal_reclaim.h"
 #include "journal_seq_blacklist.h"
 #include "recovery.h"
diff --git a/fs/bcachefs/btree_io.h b/fs/bcachefs/btree_io.h
index cd99bbb..7e03dd7 100644
--- a/fs/bcachefs/btree_io.h
+++ b/fs/bcachefs/btree_io.h
@@ -7,7 +7,7 @@
 #include "btree_locking.h"
 #include "checksum.h"
 #include "extents.h"
-#include "io_types.h"
+#include "io_write_types.h"
 
 struct bch_fs;
 struct btree_write;
diff --git a/fs/bcachefs/compress.c b/fs/bcachefs/compress.c
index 6b17f7c..f165180 100644
--- a/fs/bcachefs/compress.c
+++ b/fs/bcachefs/compress.c
@@ -3,7 +3,6 @@
 #include "checksum.h"
 #include "compress.h"
 #include "extents.h"
-#include "io.h"
 #include "super-io.h"
 
 #include <linux/lz4.h>
diff --git a/fs/bcachefs/data_update.c b/fs/bcachefs/data_update.c
index 81518f2..29576c4 100644
--- a/fs/bcachefs/data_update.c
+++ b/fs/bcachefs/data_update.c
@@ -9,7 +9,7 @@
 #include "ec.h"
 #include "error.h"
 #include "extents.h"
-#include "io.h"
+#include "io_write.h"
 #include "keylist.h"
 #include "move.h"
 #include "nocow_locking.h"
diff --git a/fs/bcachefs/data_update.h b/fs/bcachefs/data_update.h
index 49e9055..7ca1f98 100644
--- a/fs/bcachefs/data_update.h
+++ b/fs/bcachefs/data_update.h
@@ -4,7 +4,7 @@
 #define _BCACHEFS_DATA_UPDATE_H
 
 #include "bkey_buf.h"
-#include "io_types.h"
+#include "io_write_types.h"
 
 struct moving_context;
 
diff --git a/fs/bcachefs/debug.c b/fs/bcachefs/debug.c
index ae47e185..5f3e65f 100644
--- a/fs/bcachefs/debug.c
+++ b/fs/bcachefs/debug.c
@@ -19,7 +19,6 @@
 #include "extents.h"
 #include "fsck.h"
 #include "inode.h"
-#include "io.h"
 #include "super.h"
 
 #include <linux/console.h>
diff --git a/fs/bcachefs/ec.c b/fs/bcachefs/ec.c
index 67a5453..40e72b9 100644
--- a/fs/bcachefs/ec.c
+++ b/fs/bcachefs/ec.c
@@ -11,10 +11,11 @@
 #include "btree_update.h"
 #include "btree_write_buffer.h"
 #include "buckets.h"
+#include "checksum.h"
 #include "disk_groups.h"
 #include "ec.h"
 #include "error.h"
-#include "io.h"
+#include "io_read.h"
 #include "keylist.h"
 #include "recovery.h"
 #include "replicas.h"
diff --git a/fs/bcachefs/errcode.c b/fs/bcachefs/errcode.c
index dc906fc..8d58f2c 100644
--- a/fs/bcachefs/errcode.c
+++ b/fs/bcachefs/errcode.c
@@ -61,3 +61,10 @@ int __bch2_err_class(int err)
 
 	return -err;
 }
+
+const char *bch2_blk_status_to_str(blk_status_t status)
+{
+	if (status == BLK_STS_REMOVED)
+		return "device removed";
+	return blk_status_to_str(status);
+}
diff --git a/fs/bcachefs/errcode.h b/fs/bcachefs/errcode.h
index f7fa874..379d9d7 100644
--- a/fs/bcachefs/errcode.h
+++ b/fs/bcachefs/errcode.h
@@ -249,4 +249,8 @@ static inline long bch2_err_class(long err)
 	return err < 0 ? __bch2_err_class(err) : err;
 }
 
+#define BLK_STS_REMOVED		((__force blk_status_t)128)
+
+const char *bch2_blk_status_to_str(blk_status_t);
+
 #endif /* _BCACHFES_ERRCODE_H */
diff --git a/fs/bcachefs/error.c b/fs/bcachefs/error.c
index 39009cf..2a5af88 100644
--- a/fs/bcachefs/error.c
+++ b/fs/bcachefs/error.c
@@ -1,7 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0
 #include "bcachefs.h"
 #include "error.h"
-#include "io.h"
 #include "super.h"
 
 #define FSCK_ERR_RATELIMIT_NR	10
diff --git a/fs/bcachefs/fs-io-buffered.c b/fs/bcachefs/fs-io-buffered.c
index dc22182..2034d63 100644
--- a/fs/bcachefs/fs-io-buffered.c
+++ b/fs/bcachefs/fs-io-buffered.c
@@ -8,7 +8,8 @@
 #include "fs-io-buffered.h"
 #include "fs-io-direct.h"
 #include "fs-io-pagecache.h"
-#include "io.h"
+#include "io_read.h"
+#include "io_write.h"
 
 #include <linux/backing-dev.h>
 #include <linux/pagemap.h>
diff --git a/fs/bcachefs/fs-io-direct.c b/fs/bcachefs/fs-io-direct.c
index 2b29abd..219bc11 100644
--- a/fs/bcachefs/fs-io-direct.c
+++ b/fs/bcachefs/fs-io-direct.c
@@ -7,7 +7,8 @@
 #include "fs-io.h"
 #include "fs-io-direct.h"
 #include "fs-io-pagecache.h"
-#include "io.h"
+#include "io_read.h"
+#include "io_write.h"
 
 #include <linux/kthread.h>
 #include <linux/pagemap.h>
diff --git a/fs/bcachefs/fs-io.c b/fs/bcachefs/fs-io.c
index ceab12f..0b0b3b0 100644
--- a/fs/bcachefs/fs-io.c
+++ b/fs/bcachefs/fs-io.c
@@ -3,6 +3,7 @@
 
 #include "bcachefs.h"
 #include "alloc_foreground.h"
+#include "bkey_buf.h"
 #include "btree_update.h"
 #include "buckets.h"
 #include "clock.h"
@@ -16,7 +17,7 @@
 #include "fsck.h"
 #include "inode.h"
 #include "journal.h"
-#include "io.h"
+#include "io_misc.h"
 #include "keylist.h"
 #include "quota.h"
 #include "reflink.h"
diff --git a/fs/bcachefs/fs-io.h b/fs/bcachefs/fs-io.h
index bb5b709..bc6e843 100644
--- a/fs/bcachefs/fs-io.h
+++ b/fs/bcachefs/fs-io.h
@@ -6,7 +6,7 @@
 
 #include "buckets.h"
 #include "fs.h"
-#include "io_types.h"
+#include "io_write_types.h"
 #include "quota.h"
 
 #include <linux/uio.h>
diff --git a/fs/bcachefs/fs.c b/fs/bcachefs/fs.c
index 08f8109..0648874 100644
--- a/fs/bcachefs/fs.c
+++ b/fs/bcachefs/fs.c
@@ -19,7 +19,7 @@
 #include "fs-io-pagecache.h"
 #include "fsck.h"
 #include "inode.h"
-#include "io.h"
+#include "io_read.h"
 #include "journal.h"
 #include "keylist.h"
 #include "quota.h"
diff --git a/fs/bcachefs/io.c b/fs/bcachefs/io.c
deleted file mode 100644
index 3c614c8..0000000
--- a/fs/bcachefs/io.c
+++ /dev/null
@@ -1,3051 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-/*
- * Some low level IO code, and hacks for various block layer limitations
- *
- * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
- * Copyright 2012 Google, Inc.
- */
-
-#include "bcachefs.h"
-#include "alloc_background.h"
-#include "alloc_foreground.h"
-#include "bkey_buf.h"
-#include "bset.h"
-#include "btree_update.h"
-#include "buckets.h"
-#include "checksum.h"
-#include "compress.h"
-#include "clock.h"
-#include "data_update.h"
-#include "debug.h"
-#include "disk_groups.h"
-#include "ec.h"
-#include "error.h"
-#include "extent_update.h"
-#include "inode.h"
-#include "io.h"
-#include "journal.h"
-#include "keylist.h"
-#include "move.h"
-#include "nocow_locking.h"
-#include "rebalance.h"
-#include "subvolume.h"
-#include "super.h"
-#include "super-io.h"
-#include "trace.h"
-
-#include <linux/blkdev.h>
-#include <linux/prefetch.h>
-#include <linux/random.h>
-#include <linux/sched/mm.h>
-
-const char *bch2_blk_status_to_str(blk_status_t status)
-{
-	if (status == BLK_STS_REMOVED)
-		return "device removed";
-	return blk_status_to_str(status);
-}
-
-#ifndef CONFIG_BCACHEFS_NO_LATENCY_ACCT
-
-static bool bch2_target_congested(struct bch_fs *c, u16 target)
-{
-	const struct bch_devs_mask *devs;
-	unsigned d, nr = 0, total = 0;
-	u64 now = local_clock(), last;
-	s64 congested;
-	struct bch_dev *ca;
-
-	if (!target)
-		return false;
-
-	rcu_read_lock();
-	devs = bch2_target_to_mask(c, target) ?:
-		&c->rw_devs[BCH_DATA_user];
-
-	for_each_set_bit(d, devs->d, BCH_SB_MEMBERS_MAX) {
-		ca = rcu_dereference(c->devs[d]);
-		if (!ca)
-			continue;
-
-		congested = atomic_read(&ca->congested);
-		last = READ_ONCE(ca->congested_last);
-		if (time_after64(now, last))
-			congested -= (now - last) >> 12;
-
-		total += max(congested, 0LL);
-		nr++;
-	}
-	rcu_read_unlock();
-
-	return bch2_rand_range(nr * CONGESTED_MAX) < total;
-}
-
-static inline void bch2_congested_acct(struct bch_dev *ca, u64 io_latency,
-				       u64 now, int rw)
-{
-	u64 latency_capable =
-		ca->io_latency[rw].quantiles.entries[QUANTILE_IDX(1)].m;
-	/* ideally we'd be taking into account the device's variance here: */
-	u64 latency_threshold = latency_capable << (rw == READ ? 2 : 3);
-	s64 latency_over = io_latency - latency_threshold;
-
-	if (latency_threshold && latency_over > 0) {
-		/*
-		 * bump up congested by approximately latency_over * 4 /
-		 * latency_threshold - we don't need much accuracy here so don't
-		 * bother with the divide:
-		 */
-		if (atomic_read(&ca->congested) < CONGESTED_MAX)
-			atomic_add(latency_over >>
-				   max_t(int, ilog2(latency_threshold) - 2, 0),
-				   &ca->congested);
-
-		ca->congested_last = now;
-	} else if (atomic_read(&ca->congested) > 0) {
-		atomic_dec(&ca->congested);
-	}
-}
-
-void bch2_latency_acct(struct bch_dev *ca, u64 submit_time, int rw)
-{
-	atomic64_t *latency = &ca->cur_latency[rw];
-	u64 now = local_clock();
-	u64 io_latency = time_after64(now, submit_time)
-		? now - submit_time
-		: 0;
-	u64 old, new, v = atomic64_read(latency);
-
-	do {
-		old = v;
-
-		/*
-		 * If the io latency was reasonably close to the current
-		 * latency, skip doing the update and atomic operation - most of
-		 * the time:
-		 */
-		if (abs((int) (old - io_latency)) < (old >> 1) &&
-		    now & ~(~0U << 5))
-			break;
-
-		new = ewma_add(old, io_latency, 5);
-	} while ((v = atomic64_cmpxchg(latency, old, new)) != old);
-
-	bch2_congested_acct(ca, io_latency, now, rw);
-
-	__bch2_time_stats_update(&ca->io_latency[rw], submit_time, now);
-}
-
-#else
-
-static bool bch2_target_congested(struct bch_fs *c, u16 target)
-{
-	return false;
-}
-
-#endif
-
-/* Allocate, free from mempool: */
-
-void bch2_bio_free_pages_pool(struct bch_fs *c, struct bio *bio)
-{
-	struct bvec_iter_all iter;
-	struct bio_vec *bv;
-
-	bio_for_each_segment_all(bv, bio, iter)
-		if (bv->bv_page != ZERO_PAGE(0))
-			mempool_free(bv->bv_page, &c->bio_bounce_pages);
-	bio->bi_vcnt = 0;
-}
-
-static struct page *__bio_alloc_page_pool(struct bch_fs *c, bool *using_mempool)
-{
-	struct page *page;
-
-	if (likely(!*using_mempool)) {
-		page = alloc_page(GFP_NOFS);
-		if (unlikely(!page)) {
-			mutex_lock(&c->bio_bounce_pages_lock);
-			*using_mempool = true;
-			goto pool_alloc;
-
-		}
-	} else {
-pool_alloc:
-		page = mempool_alloc(&c->bio_bounce_pages, GFP_NOFS);
-	}
-
-	return page;
-}
-
-void bch2_bio_alloc_pages_pool(struct bch_fs *c, struct bio *bio,
-			       size_t size)
-{
-	bool using_mempool = false;
-
-	while (size) {
-		struct page *page = __bio_alloc_page_pool(c, &using_mempool);
-		unsigned len = min_t(size_t, PAGE_SIZE, size);
-
-		BUG_ON(!bio_add_page(bio, page, len, 0));
-		size -= len;
-	}
-
-	if (using_mempool)
-		mutex_unlock(&c->bio_bounce_pages_lock);
-}
-
-/* Extent update path: */
-
-int bch2_sum_sector_overwrites(struct btree_trans *trans,
-			       struct btree_iter *extent_iter,
-			       struct bkey_i *new,
-			       bool *usage_increasing,
-			       s64 *i_sectors_delta,
-			       s64 *disk_sectors_delta)
-{
-	struct bch_fs *c = trans->c;
-	struct btree_iter iter;
-	struct bkey_s_c old;
-	unsigned new_replicas = bch2_bkey_replicas(c, bkey_i_to_s_c(new));
-	bool new_compressed = bch2_bkey_sectors_compressed(bkey_i_to_s_c(new));
-	int ret = 0;
-
-	*usage_increasing	= false;
-	*i_sectors_delta	= 0;
-	*disk_sectors_delta	= 0;
-
-	bch2_trans_copy_iter(&iter, extent_iter);
-
-	for_each_btree_key_upto_continue_norestart(iter,
-				new->k.p, BTREE_ITER_SLOTS, old, ret) {
-		s64 sectors = min(new->k.p.offset, old.k->p.offset) -
-			max(bkey_start_offset(&new->k),
-			    bkey_start_offset(old.k));
-
-		*i_sectors_delta += sectors *
-			(bkey_extent_is_allocation(&new->k) -
-			 bkey_extent_is_allocation(old.k));
-
-		*disk_sectors_delta += sectors * bch2_bkey_nr_ptrs_allocated(bkey_i_to_s_c(new));
-		*disk_sectors_delta -= new->k.p.snapshot == old.k->p.snapshot
-			? sectors * bch2_bkey_nr_ptrs_fully_allocated(old)
-			: 0;
-
-		if (!*usage_increasing &&
-		    (new->k.p.snapshot != old.k->p.snapshot ||
-		     new_replicas > bch2_bkey_replicas(c, old) ||
-		     (!new_compressed && bch2_bkey_sectors_compressed(old))))
-			*usage_increasing = true;
-
-		if (bkey_ge(old.k->p, new->k.p))
-			break;
-	}
-
-	bch2_trans_iter_exit(trans, &iter);
-	return ret;
-}
-
-static inline int bch2_extent_update_i_size_sectors(struct btree_trans *trans,
-						    struct btree_iter *extent_iter,
-						    u64 new_i_size,
-						    s64 i_sectors_delta)
-{
-	struct btree_iter iter;
-	struct bkey_i *k;
-	struct bkey_i_inode_v3 *inode;
-	unsigned inode_update_flags = BTREE_UPDATE_NOJOURNAL;
-	int ret;
-
-	k = bch2_bkey_get_mut_noupdate(trans, &iter, BTREE_ID_inodes,
-			      SPOS(0,
-				   extent_iter->pos.inode,
-				   extent_iter->snapshot),
-			      BTREE_ITER_CACHED);
-	ret = PTR_ERR_OR_ZERO(k);
-	if (unlikely(ret))
-		return ret;
-
-	if (unlikely(k->k.type != KEY_TYPE_inode_v3)) {
-		k = bch2_inode_to_v3(trans, k);
-		ret = PTR_ERR_OR_ZERO(k);
-		if (unlikely(ret))
-			goto err;
-	}
-
-	inode = bkey_i_to_inode_v3(k);
-
-	if (!(le64_to_cpu(inode->v.bi_flags) & BCH_INODE_I_SIZE_DIRTY) &&
-	    new_i_size > le64_to_cpu(inode->v.bi_size)) {
-		inode->v.bi_size = cpu_to_le64(new_i_size);
-		inode_update_flags = 0;
-	}
-
-	if (i_sectors_delta) {
-		le64_add_cpu(&inode->v.bi_sectors, i_sectors_delta);
-		inode_update_flags = 0;
-	}
-
-	if (inode->k.p.snapshot != iter.snapshot) {
-		inode->k.p.snapshot = iter.snapshot;
-		inode_update_flags = 0;
-	}
-
-	ret = bch2_trans_update(trans, &iter, &inode->k_i,
-				BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE|
-				inode_update_flags);
-err:
-	bch2_trans_iter_exit(trans, &iter);
-	return ret;
-}
-
-int bch2_extent_update(struct btree_trans *trans,
-		       subvol_inum inum,
-		       struct btree_iter *iter,
-		       struct bkey_i *k,
-		       struct disk_reservation *disk_res,
-		       u64 new_i_size,
-		       s64 *i_sectors_delta_total,
-		       bool check_enospc)
-{
-	struct bpos next_pos;
-	bool usage_increasing;
-	s64 i_sectors_delta = 0, disk_sectors_delta = 0;
-	int ret;
-
-	/*
-	 * This traverses us the iterator without changing iter->path->pos to
-	 * search_key() (which is pos + 1 for extents): we want there to be a
-	 * path already traversed at iter->pos because
-	 * bch2_trans_extent_update() will use it to attempt extent merging
-	 */
-	ret = __bch2_btree_iter_traverse(iter);
-	if (ret)
-		return ret;
-
-	ret = bch2_extent_trim_atomic(trans, iter, k);
-	if (ret)
-		return ret;
-
-	next_pos = k->k.p;
-
-	ret = bch2_sum_sector_overwrites(trans, iter, k,
-			&usage_increasing,
-			&i_sectors_delta,
-			&disk_sectors_delta);
-	if (ret)
-		return ret;
-
-	if (disk_res &&
-	    disk_sectors_delta > (s64) disk_res->sectors) {
-		ret = bch2_disk_reservation_add(trans->c, disk_res,
-					disk_sectors_delta - disk_res->sectors,
-					!check_enospc || !usage_increasing
-					? BCH_DISK_RESERVATION_NOFAIL : 0);
-		if (ret)
-			return ret;
-	}
-
-	/*
-	 * Note:
-	 * We always have to do an inode update - even when i_size/i_sectors
-	 * aren't changing - for fsync to work properly; fsync relies on
-	 * inode->bi_journal_seq which is updated by the trigger code:
-	 */
-	ret =   bch2_extent_update_i_size_sectors(trans, iter,
-						  min(k->k.p.offset << 9, new_i_size),
-						  i_sectors_delta) ?:
-		bch2_trans_update(trans, iter, k, 0) ?:
-		bch2_trans_commit(trans, disk_res, NULL,
-				BTREE_INSERT_NOCHECK_RW|
-				BTREE_INSERT_NOFAIL);
-	if (unlikely(ret))
-		return ret;
-
-	if (i_sectors_delta_total)
-		*i_sectors_delta_total += i_sectors_delta;
-	bch2_btree_iter_set_pos(iter, next_pos);
-	return 0;
-}
-
-/* Overwrites whatever was present with zeroes: */
-int bch2_extent_fallocate(struct btree_trans *trans,
-			  subvol_inum inum,
-			  struct btree_iter *iter,
-			  unsigned sectors,
-			  struct bch_io_opts opts,
-			  s64 *i_sectors_delta,
-			  struct write_point_specifier write_point)
-{
-	struct bch_fs *c = trans->c;
-	struct disk_reservation disk_res = { 0 };
-	struct closure cl;
-	struct open_buckets open_buckets = { 0 };
-	struct bkey_s_c k;
-	struct bkey_buf old, new;
-	unsigned sectors_allocated = 0;
-	bool have_reservation = false;
-	bool unwritten = opts.nocow &&
-	    c->sb.version >= bcachefs_metadata_version_unwritten_extents;
-	int ret;
-
-	bch2_bkey_buf_init(&old);
-	bch2_bkey_buf_init(&new);
-	closure_init_stack(&cl);
-
-	k = bch2_btree_iter_peek_slot(iter);
-	ret = bkey_err(k);
-	if (ret)
-		return ret;
-
-	sectors = min_t(u64, sectors, k.k->p.offset - iter->pos.offset);
-
-	if (!have_reservation) {
-		unsigned new_replicas =
-			max(0, (int) opts.data_replicas -
-			    (int) bch2_bkey_nr_ptrs_fully_allocated(k));
-		/*
-		 * Get a disk reservation before (in the nocow case) calling
-		 * into the allocator:
-		 */
-		ret = bch2_disk_reservation_get(c, &disk_res, sectors, new_replicas, 0);
-		if (unlikely(ret))
-			goto err;
-
-		bch2_bkey_buf_reassemble(&old, c, k);
-	}
-
-	if (have_reservation) {
-		if (!bch2_extents_match(k, bkey_i_to_s_c(old.k)))
-			goto err;
-
-		bch2_key_resize(&new.k->k, sectors);
-	} else if (!unwritten) {
-		struct bkey_i_reservation *reservation;
-
-		bch2_bkey_buf_realloc(&new, c, sizeof(*reservation) / sizeof(u64));
-		reservation = bkey_reservation_init(new.k);
-		reservation->k.p = iter->pos;
-		bch2_key_resize(&reservation->k, sectors);
-		reservation->v.nr_replicas = opts.data_replicas;
-	} else {
-		struct bkey_i_extent *e;
-		struct bch_devs_list devs_have;
-		struct write_point *wp;
-		struct bch_extent_ptr *ptr;
-
-		devs_have.nr = 0;
-
-		bch2_bkey_buf_realloc(&new, c, BKEY_EXTENT_U64s_MAX);
-
-		e = bkey_extent_init(new.k);
-		e->k.p = iter->pos;
-
-		ret = bch2_alloc_sectors_start_trans(trans,
-				opts.foreground_target,
-				false,
-				write_point,
-				&devs_have,
-				opts.data_replicas,
-				opts.data_replicas,
-				BCH_WATERMARK_normal, 0, &cl, &wp);
-		if (bch2_err_matches(ret, BCH_ERR_operation_blocked))
-			ret = -BCH_ERR_transaction_restart_nested;
-		if (ret)
-			goto err;
-
-		sectors = min(sectors, wp->sectors_free);
-		sectors_allocated = sectors;
-
-		bch2_key_resize(&e->k, sectors);
-
-		bch2_open_bucket_get(c, wp, &open_buckets);
-		bch2_alloc_sectors_append_ptrs(c, wp, &e->k_i, sectors, false);
-		bch2_alloc_sectors_done(c, wp);
-
-		extent_for_each_ptr(extent_i_to_s(e), ptr)
-			ptr->unwritten = true;
-	}
-
-	have_reservation = true;
-
-	ret = bch2_extent_update(trans, inum, iter, new.k, &disk_res,
-				 0, i_sectors_delta, true);
-err:
-	if (!ret && sectors_allocated)
-		bch2_increment_clock(c, sectors_allocated, WRITE);
-
-	bch2_open_buckets_put(c, &open_buckets);
-	bch2_disk_reservation_put(c, &disk_res);
-	bch2_bkey_buf_exit(&new, c);
-	bch2_bkey_buf_exit(&old, c);
-
-	if (closure_nr_remaining(&cl) != 1) {
-		bch2_trans_unlock(trans);
-		closure_sync(&cl);
-	}
-
-	return ret;
-}
-
-/*
- * Returns -BCH_ERR_transacton_restart if we had to drop locks:
- */
-int bch2_fpunch_at(struct btree_trans *trans, struct btree_iter *iter,
-		   subvol_inum inum, u64 end,
-		   s64 *i_sectors_delta)
-{
-	struct bch_fs *c	= trans->c;
-	unsigned max_sectors	= KEY_SIZE_MAX & (~0 << c->block_bits);
-	struct bpos end_pos = POS(inum.inum, end);
-	struct bkey_s_c k;
-	int ret = 0, ret2 = 0;
-	u32 snapshot;
-
-	while (!ret ||
-	       bch2_err_matches(ret, BCH_ERR_transaction_restart)) {
-		struct disk_reservation disk_res =
-			bch2_disk_reservation_init(c, 0);
-		struct bkey_i delete;
-
-		if (ret)
-			ret2 = ret;
-
-		bch2_trans_begin(trans);
-
-		ret = bch2_subvolume_get_snapshot(trans, inum.subvol, &snapshot);
-		if (ret)
-			continue;
-
-		bch2_btree_iter_set_snapshot(iter, snapshot);
-
-		/*
-		 * peek_upto() doesn't have ideal semantics for extents:
-		 */
-		k = bch2_btree_iter_peek_upto(iter, end_pos);
-		if (!k.k)
-			break;
-
-		ret = bkey_err(k);
-		if (ret)
-			continue;
-
-		bkey_init(&delete.k);
-		delete.k.p = iter->pos;
-
-		/* create the biggest key we can */
-		bch2_key_resize(&delete.k, max_sectors);
-		bch2_cut_back(end_pos, &delete);
-
-		ret = bch2_extent_update(trans, inum, iter, &delete,
-				&disk_res, 0, i_sectors_delta, false);
-		bch2_disk_reservation_put(c, &disk_res);
-	}
-
-	return ret ?: ret2;
-}
-
-int bch2_fpunch(struct bch_fs *c, subvol_inum inum, u64 start, u64 end,
-		s64 *i_sectors_delta)
-{
-	struct btree_trans trans;
-	struct btree_iter iter;
-	int ret;
-
-	bch2_trans_init(&trans, c, BTREE_ITER_MAX, 1024);
-	bch2_trans_iter_init(&trans, &iter, BTREE_ID_extents,
-			     POS(inum.inum, start),
-			     BTREE_ITER_INTENT);
-
-	ret = bch2_fpunch_at(&trans, &iter, inum, end, i_sectors_delta);
-
-	bch2_trans_iter_exit(&trans, &iter);
-	bch2_trans_exit(&trans);
-
-	if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
-		ret = 0;
-
-	return ret;
-}
-
-static int bch2_write_index_default(struct bch_write_op *op)
-{
-	struct bch_fs *c = op->c;
-	struct bkey_buf sk;
-	struct keylist *keys = &op->insert_keys;
-	struct bkey_i *k = bch2_keylist_front(keys);
-	struct btree_trans trans;
-	struct btree_iter iter;
-	subvol_inum inum = {
-		.subvol = op->subvol,
-		.inum	= k->k.p.inode,
-	};
-	int ret;
-
-	BUG_ON(!inum.subvol);
-
-	bch2_bkey_buf_init(&sk);
-	bch2_trans_init(&trans, c, BTREE_ITER_MAX, 1024);
-
-	do {
-		bch2_trans_begin(&trans);
-
-		k = bch2_keylist_front(keys);
-		bch2_bkey_buf_copy(&sk, c, k);
-
-		ret = bch2_subvolume_get_snapshot(&trans, inum.subvol,
-						  &sk.k->k.p.snapshot);
-		if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
-			continue;
-		if (ret)
-			break;
-
-		bch2_trans_iter_init(&trans, &iter, BTREE_ID_extents,
-				     bkey_start_pos(&sk.k->k),
-				     BTREE_ITER_SLOTS|BTREE_ITER_INTENT);
-
-		ret = bch2_extent_update(&trans, inum, &iter, sk.k,
-					 &op->res,
-					 op->new_i_size, &op->i_sectors_delta,
-					 op->flags & BCH_WRITE_CHECK_ENOSPC);
-		bch2_trans_iter_exit(&trans, &iter);
-
-		if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
-			continue;
-		if (ret)
-			break;
-
-		if (bkey_ge(iter.pos, k->k.p))
-			bch2_keylist_pop_front(&op->insert_keys);
-		else
-			bch2_cut_front(iter.pos, k);
-	} while (!bch2_keylist_empty(keys));
-
-	bch2_trans_exit(&trans);
-	bch2_bkey_buf_exit(&sk, c);
-
-	return ret;
-}
-
-/* Writes */
-
-void bch2_submit_wbio_replicas(struct bch_write_bio *wbio, struct bch_fs *c,
-			       enum bch_data_type type,
-			       const struct bkey_i *k,
-			       bool nocow)
-{
-	struct bkey_ptrs_c ptrs = bch2_bkey_ptrs_c(bkey_i_to_s_c(k));
-	const struct bch_extent_ptr *ptr;
-	struct bch_write_bio *n;
-	struct bch_dev *ca;
-
-	BUG_ON(c->opts.nochanges);
-
-	bkey_for_each_ptr(ptrs, ptr) {
-		BUG_ON(ptr->dev >= BCH_SB_MEMBERS_MAX ||
-		       !c->devs[ptr->dev]);
-
-		ca = bch_dev_bkey_exists(c, ptr->dev);
-
-		if (to_entry(ptr + 1) < ptrs.end) {
-			n = to_wbio(bio_alloc_clone(NULL, &wbio->bio,
-						GFP_NOFS, &ca->replica_set));
-
-			n->bio.bi_end_io	= wbio->bio.bi_end_io;
-			n->bio.bi_private	= wbio->bio.bi_private;
-			n->parent		= wbio;
-			n->split		= true;
-			n->bounce		= false;
-			n->put_bio		= true;
-			n->bio.bi_opf		= wbio->bio.bi_opf;
-			bio_inc_remaining(&wbio->bio);
-		} else {
-			n = wbio;
-			n->split		= false;
-		}
-
-		n->c			= c;
-		n->dev			= ptr->dev;
-		n->have_ioref		= nocow || bch2_dev_get_ioref(ca,
-					type == BCH_DATA_btree ? READ : WRITE);
-		n->nocow		= nocow;
-		n->submit_time		= local_clock();
-		n->inode_offset		= bkey_start_offset(&k->k);
-		n->bio.bi_iter.bi_sector = ptr->offset;
-
-		if (likely(n->have_ioref)) {
-			this_cpu_add(ca->io_done->sectors[WRITE][type],
-				     bio_sectors(&n->bio));
-
-			bio_set_dev(&n->bio, ca->disk_sb.bdev);
-
-			if (type != BCH_DATA_btree && unlikely(c->opts.no_data_io)) {
-				bio_endio(&n->bio);
-				continue;
-			}
-
-			submit_bio(&n->bio);
-		} else {
-			n->bio.bi_status	= BLK_STS_REMOVED;
-			bio_endio(&n->bio);
-		}
-	}
-}
-
-static void __bch2_write(struct bch_write_op *);
-
-static void bch2_write_done(struct closure *cl)
-{
-	struct bch_write_op *op = container_of(cl, struct bch_write_op, cl);
-	struct bch_fs *c = op->c;
-
-	EBUG_ON(op->open_buckets.nr);
-
-	bch2_time_stats_update(&c->times[BCH_TIME_data_write], op->start_time);
-	bch2_disk_reservation_put(c, &op->res);
-
-	if (!(op->flags & BCH_WRITE_MOVE))
-		bch2_write_ref_put(c, BCH_WRITE_REF_write);
-	bch2_keylist_free(&op->insert_keys, op->inline_keys);
-
-	EBUG_ON(cl->parent);
-	closure_debug_destroy(cl);
-	if (op->end_io)
-		op->end_io(op);
-}
-
-static noinline int bch2_write_drop_io_error_ptrs(struct bch_write_op *op)
-{
-	struct keylist *keys = &op->insert_keys;
-	struct bch_extent_ptr *ptr;
-	struct bkey_i *src, *dst = keys->keys, *n;
-
-	for (src = keys->keys; src != keys->top; src = n) {
-		n = bkey_next(src);
-
-		if (bkey_extent_is_direct_data(&src->k)) {
-			bch2_bkey_drop_ptrs(bkey_i_to_s(src), ptr,
-					    test_bit(ptr->dev, op->failed.d));
-
-			if (!bch2_bkey_nr_ptrs(bkey_i_to_s_c(src)))
-				return -EIO;
-		}
-
-		if (dst != src)
-			memmove_u64s_down(dst, src, src->k.u64s);
-		dst = bkey_next(dst);
-	}
-
-	keys->top = dst;
-	return 0;
-}
-
-/**
- * bch_write_index - after a write, update index to point to new data
- */
-static void __bch2_write_index(struct bch_write_op *op)
-{
-	struct bch_fs *c = op->c;
-	struct keylist *keys = &op->insert_keys;
-	struct bkey_i *k;
-	unsigned dev;
-	int ret = 0;
-
-	if (unlikely(op->flags & BCH_WRITE_IO_ERROR)) {
-		ret = bch2_write_drop_io_error_ptrs(op);
-		if (ret)
-			goto err;
-	}
-
-	/*
-	 * probably not the ideal place to hook this in, but I don't
-	 * particularly want to plumb io_opts all the way through the btree
-	 * update stack right now
-	 */
-	for_each_keylist_key(keys, k)
-		bch2_rebalance_add_key(c, bkey_i_to_s_c(k), &op->opts);
-
-	if (!bch2_keylist_empty(keys)) {
-		u64 sectors_start = keylist_sectors(keys);
-
-		ret = !(op->flags & BCH_WRITE_MOVE)
-			? bch2_write_index_default(op)
-			: bch2_data_update_index_update(op);
-
-		BUG_ON(bch2_err_matches(ret, BCH_ERR_transaction_restart));
-		BUG_ON(keylist_sectors(keys) && !ret);
-
-		op->written += sectors_start - keylist_sectors(keys);
-
-		if (ret && !bch2_err_matches(ret, EROFS)) {
-			struct bkey_i *k = bch2_keylist_front(&op->insert_keys);
-
-			bch_err_inum_offset_ratelimited(c,
-				k->k.p.inode, k->k.p.offset << 9,
-				"write error while doing btree update: %s",
-				bch2_err_str(ret));
-		}
-
-		if (ret)
-			goto err;
-	}
-out:
-	/* If some a bucket wasn't written, we can't erasure code it: */
-	for_each_set_bit(dev, op->failed.d, BCH_SB_MEMBERS_MAX)
-		bch2_open_bucket_write_error(c, &op->open_buckets, dev);
-
-	bch2_open_buckets_put(c, &op->open_buckets);
-	return;
-err:
-	keys->top = keys->keys;
-	op->error = ret;
-	op->flags |= BCH_WRITE_DONE;
-	goto out;
-}
-
-static inline void __wp_update_state(struct write_point *wp, enum write_point_state state)
-{
-	if (state != wp->state) {
-		u64 now = ktime_get_ns();
-
-		if (wp->last_state_change &&
-		    time_after64(now, wp->last_state_change))
-			wp->time[wp->state] += now - wp->last_state_change;
-		wp->state = state;
-		wp->last_state_change = now;
-	}
-}
-
-static inline void wp_update_state(struct write_point *wp, bool running)
-{
-	enum write_point_state state;
-
-	state = running			 ? WRITE_POINT_running :
-		!list_empty(&wp->writes) ? WRITE_POINT_waiting_io
-					 : WRITE_POINT_stopped;
-
-	__wp_update_state(wp, state);
-}
-
-static void bch2_write_index(struct closure *cl)
-{
-	struct bch_write_op *op = container_of(cl, struct bch_write_op, cl);
-	struct write_point *wp = op->wp;
-	struct workqueue_struct *wq = index_update_wq(op);
-	unsigned long flags;
-
-	if ((op->flags & BCH_WRITE_DONE) &&
-	    (op->flags & BCH_WRITE_MOVE))
-		bch2_bio_free_pages_pool(op->c, &op->wbio.bio);
-
-	spin_lock_irqsave(&wp->writes_lock, flags);
-	if (wp->state == WRITE_POINT_waiting_io)
-		__wp_update_state(wp, WRITE_POINT_waiting_work);
-	list_add_tail(&op->wp_list, &wp->writes);
-	spin_unlock_irqrestore (&wp->writes_lock, flags);
-
-	queue_work(wq, &wp->index_update_work);
-}
-
-static inline void bch2_write_queue(struct bch_write_op *op, struct write_point *wp)
-{
-	op->wp = wp;
-
-	if (wp->state == WRITE_POINT_stopped) {
-		spin_lock_irq(&wp->writes_lock);
-		__wp_update_state(wp, WRITE_POINT_waiting_io);
-		spin_unlock_irq(&wp->writes_lock);
-	}
-}
-
-void bch2_write_point_do_index_updates(struct work_struct *work)
-{
-	struct write_point *wp =
-		container_of(work, struct write_point, index_update_work);
-	struct bch_write_op *op;
-
-	while (1) {
-		spin_lock_irq(&wp->writes_lock);
-		op = list_first_entry_or_null(&wp->writes, struct bch_write_op, wp_list);
-		if (op)
-			list_del(&op->wp_list);
-		wp_update_state(wp, op != NULL);
-		spin_unlock_irq(&wp->writes_lock);
-
-		if (!op)
-			break;
-
-		op->flags |= BCH_WRITE_IN_WORKER;
-
-		__bch2_write_index(op);
-
-		if (!(op->flags & BCH_WRITE_DONE))
-			__bch2_write(op);
-		else
-			bch2_write_done(&op->cl);
-	}
-}
-
-static void bch2_write_endio(struct bio *bio)
-{
-	struct closure *cl		= bio->bi_private;
-	struct bch_write_op *op		= container_of(cl, struct bch_write_op, cl);
-	struct bch_write_bio *wbio	= to_wbio(bio);
-	struct bch_write_bio *parent	= wbio->split ? wbio->parent : NULL;
-	struct bch_fs *c		= wbio->c;
-	struct bch_dev *ca		= bch_dev_bkey_exists(c, wbio->dev);
-
-	if (bch2_dev_inum_io_err_on(bio->bi_status, ca,
-				    op->pos.inode,
-				    wbio->inode_offset << 9,
-				    "data write error: %s",
-				    bch2_blk_status_to_str(bio->bi_status))) {
-		set_bit(wbio->dev, op->failed.d);
-		op->flags |= BCH_WRITE_IO_ERROR;
-	}
-
-	if (wbio->nocow)
-		set_bit(wbio->dev, op->devs_need_flush->d);
-
-	if (wbio->have_ioref) {
-		bch2_latency_acct(ca, wbio->submit_time, WRITE);
-		percpu_ref_put(&ca->io_ref);
-	}
-
-	if (wbio->bounce)
-		bch2_bio_free_pages_pool(c, bio);
-
-	if (wbio->put_bio)
-		bio_put(bio);
-
-	if (parent)
-		bio_endio(&parent->bio);
-	else
-		closure_put(cl);
-}
-
-static void init_append_extent(struct bch_write_op *op,
-			       struct write_point *wp,
-			       struct bversion version,
-			       struct bch_extent_crc_unpacked crc)
-{
-	struct bkey_i_extent *e;
-
-	op->pos.offset += crc.uncompressed_size;
-
-	e = bkey_extent_init(op->insert_keys.top);
-	e->k.p		= op->pos;
-	e->k.size	= crc.uncompressed_size;
-	e->k.version	= version;
-
-	if (crc.csum_type ||
-	    crc.compression_type ||
-	    crc.nonce)
-		bch2_extent_crc_append(&e->k_i, crc);
-
-	bch2_alloc_sectors_append_ptrs_inlined(op->c, wp, &e->k_i, crc.compressed_size,
-				       op->flags & BCH_WRITE_CACHED);
-
-	bch2_keylist_push(&op->insert_keys);
-}
-
-static struct bio *bch2_write_bio_alloc(struct bch_fs *c,
-					struct write_point *wp,
-					struct bio *src,
-					bool *page_alloc_failed,
-					void *buf)
-{
-	struct bch_write_bio *wbio;
-	struct bio *bio;
-	unsigned output_available =
-		min(wp->sectors_free << 9, src->bi_iter.bi_size);
-	unsigned pages = DIV_ROUND_UP(output_available +
-				      (buf
-				       ? ((unsigned long) buf & (PAGE_SIZE - 1))
-				       : 0), PAGE_SIZE);
-
-	pages = min(pages, BIO_MAX_VECS);
-
-	bio = bio_alloc_bioset(NULL, pages, 0,
-			       GFP_NOFS, &c->bio_write);
-	wbio			= wbio_init(bio);
-	wbio->put_bio		= true;
-	/* copy WRITE_SYNC flag */
-	wbio->bio.bi_opf	= src->bi_opf;
-
-	if (buf) {
-		bch2_bio_map(bio, buf, output_available);
-		return bio;
-	}
-
-	wbio->bounce		= true;
-
-	/*
-	 * We can't use mempool for more than c->sb.encoded_extent_max
-	 * worth of pages, but we'd like to allocate more if we can:
-	 */
-	bch2_bio_alloc_pages_pool(c, bio,
-				  min_t(unsigned, output_available,
-					c->opts.encoded_extent_max));
-
-	if (bio->bi_iter.bi_size < output_available)
-		*page_alloc_failed =
-			bch2_bio_alloc_pages(bio,
-					     output_available -
-					     bio->bi_iter.bi_size,
-					     GFP_NOFS) != 0;
-
-	return bio;
-}
-
-static int bch2_write_rechecksum(struct bch_fs *c,
-				 struct bch_write_op *op,
-				 unsigned new_csum_type)
-{
-	struct bio *bio = &op->wbio.bio;
-	struct bch_extent_crc_unpacked new_crc;
-	int ret;
-
-	/* bch2_rechecksum_bio() can't encrypt or decrypt data: */
-
-	if (bch2_csum_type_is_encryption(op->crc.csum_type) !=
-	    bch2_csum_type_is_encryption(new_csum_type))
-		new_csum_type = op->crc.csum_type;
-
-	ret = bch2_rechecksum_bio(c, bio, op->version, op->crc,
-				  NULL, &new_crc,
-				  op->crc.offset, op->crc.live_size,
-				  new_csum_type);
-	if (ret)
-		return ret;
-
-	bio_advance(bio, op->crc.offset << 9);
-	bio->bi_iter.bi_size = op->crc.live_size << 9;
-	op->crc = new_crc;
-	return 0;
-}
-
-static int bch2_write_decrypt(struct bch_write_op *op)
-{
-	struct bch_fs *c = op->c;
-	struct nonce nonce = extent_nonce(op->version, op->crc);
-	struct bch_csum csum;
-	int ret;
-
-	if (!bch2_csum_type_is_encryption(op->crc.csum_type))
-		return 0;
-
-	/*
-	 * If we need to decrypt data in the write path, we'll no longer be able
-	 * to verify the existing checksum (poly1305 mac, in this case) after
-	 * it's decrypted - this is the last point we'll be able to reverify the
-	 * checksum:
-	 */
-	csum = bch2_checksum_bio(c, op->crc.csum_type, nonce, &op->wbio.bio);
-	if (bch2_crc_cmp(op->crc.csum, csum))
-		return -EIO;
-
-	ret = bch2_encrypt_bio(c, op->crc.csum_type, nonce, &op->wbio.bio);
-	op->crc.csum_type = 0;
-	op->crc.csum = (struct bch_csum) { 0, 0 };
-	return ret;
-}
-
-static enum prep_encoded_ret {
-	PREP_ENCODED_OK,
-	PREP_ENCODED_ERR,
-	PREP_ENCODED_CHECKSUM_ERR,
-	PREP_ENCODED_DO_WRITE,
-} bch2_write_prep_encoded_data(struct bch_write_op *op, struct write_point *wp)
-{
-	struct bch_fs *c = op->c;
-	struct bio *bio = &op->wbio.bio;
-
-	if (!(op->flags & BCH_WRITE_DATA_ENCODED))
-		return PREP_ENCODED_OK;
-
-	BUG_ON(bio_sectors(bio) != op->crc.compressed_size);
-
-	/* Can we just write the entire extent as is? */
-	if (op->crc.uncompressed_size == op->crc.live_size &&
-	    op->crc.compressed_size <= wp->sectors_free &&
-	    (op->crc.compression_type == bch2_compression_opt_to_type(op->compression_opt) ||
-	     op->incompressible)) {
-		if (!crc_is_compressed(op->crc) &&
-		    op->csum_type != op->crc.csum_type &&
-		    bch2_write_rechecksum(c, op, op->csum_type) &&
-		    !c->opts.no_data_io)
-			return PREP_ENCODED_CHECKSUM_ERR;
-
-		return PREP_ENCODED_DO_WRITE;
-	}
-
-	/*
-	 * If the data is compressed and we couldn't write the entire extent as
-	 * is, we have to decompress it:
-	 */
-	if (crc_is_compressed(op->crc)) {
-		struct bch_csum csum;
-
-		if (bch2_write_decrypt(op))
-			return PREP_ENCODED_CHECKSUM_ERR;
-
-		/* Last point we can still verify checksum: */
-		csum = bch2_checksum_bio(c, op->crc.csum_type,
-					 extent_nonce(op->version, op->crc),
-					 bio);
-		if (bch2_crc_cmp(op->crc.csum, csum) && !c->opts.no_data_io)
-			return PREP_ENCODED_CHECKSUM_ERR;
-
-		if (bch2_bio_uncompress_inplace(c, bio, &op->crc))
-			return PREP_ENCODED_ERR;
-	}
-
-	/*
-	 * No longer have compressed data after this point - data might be
-	 * encrypted:
-	 */
-
-	/*
-	 * If the data is checksummed and we're only writing a subset,
-	 * rechecksum and adjust bio to point to currently live data:
-	 */
-	if ((op->crc.live_size != op->crc.uncompressed_size ||
-	     op->crc.csum_type != op->csum_type) &&
-	    bch2_write_rechecksum(c, op, op->csum_type) &&
-	    !c->opts.no_data_io)
-		return PREP_ENCODED_CHECKSUM_ERR;
-
-	/*
-	 * If we want to compress the data, it has to be decrypted:
-	 */
-	if ((op->compression_opt ||
-	     bch2_csum_type_is_encryption(op->crc.csum_type) !=
-	     bch2_csum_type_is_encryption(op->csum_type)) &&
-	    bch2_write_decrypt(op))
-		return PREP_ENCODED_CHECKSUM_ERR;
-
-	return PREP_ENCODED_OK;
-}
-
-static int bch2_write_extent(struct bch_write_op *op, struct write_point *wp,
-			     struct bio **_dst)
-{
-	struct bch_fs *c = op->c;
-	struct bio *src = &op->wbio.bio, *dst = src;
-	struct bvec_iter saved_iter;
-	void *ec_buf;
-	unsigned total_output = 0, total_input = 0;
-	bool bounce = false;
-	bool page_alloc_failed = false;
-	int ret, more = 0;
-
-	BUG_ON(!bio_sectors(src));
-
-	ec_buf = bch2_writepoint_ec_buf(c, wp);
-
-	switch (bch2_write_prep_encoded_data(op, wp)) {
-	case PREP_ENCODED_OK:
-		break;
-	case PREP_ENCODED_ERR:
-		ret = -EIO;
-		goto err;
-	case PREP_ENCODED_CHECKSUM_ERR:
-		goto csum_err;
-	case PREP_ENCODED_DO_WRITE:
-		/* XXX look for bug here */
-		if (ec_buf) {
-			dst = bch2_write_bio_alloc(c, wp, src,
-						   &page_alloc_failed,
-						   ec_buf);
-			bio_copy_data(dst, src);
-			bounce = true;
-		}
-		init_append_extent(op, wp, op->version, op->crc);
-		goto do_write;
-	}
-
-	if (ec_buf ||
-	    op->compression_opt ||
-	    (op->csum_type &&
-	     !(op->flags & BCH_WRITE_PAGES_STABLE)) ||
-	    (bch2_csum_type_is_encryption(op->csum_type) &&
-	     !(op->flags & BCH_WRITE_PAGES_OWNED))) {
-		dst = bch2_write_bio_alloc(c, wp, src,
-					   &page_alloc_failed,
-					   ec_buf);
-		bounce = true;
-	}
-
-	saved_iter = dst->bi_iter;
-
-	do {
-		struct bch_extent_crc_unpacked crc = { 0 };
-		struct bversion version = op->version;
-		size_t dst_len, src_len;
-
-		if (page_alloc_failed &&
-		    dst->bi_iter.bi_size  < (wp->sectors_free << 9) &&
-		    dst->bi_iter.bi_size < c->opts.encoded_extent_max)
-			break;
-
-		BUG_ON(op->compression_opt &&
-		       (op->flags & BCH_WRITE_DATA_ENCODED) &&
-		       bch2_csum_type_is_encryption(op->crc.csum_type));
-		BUG_ON(op->compression_opt && !bounce);
-
-		crc.compression_type = op->incompressible
-			? BCH_COMPRESSION_TYPE_incompressible
-			: op->compression_opt
-			? bch2_bio_compress(c, dst, &dst_len, src, &src_len,
-					    op->compression_opt)
-			: 0;
-		if (!crc_is_compressed(crc)) {
-			dst_len = min(dst->bi_iter.bi_size, src->bi_iter.bi_size);
-			dst_len = min_t(unsigned, dst_len, wp->sectors_free << 9);
-
-			if (op->csum_type)
-				dst_len = min_t(unsigned, dst_len,
-						c->opts.encoded_extent_max);
-
-			if (bounce) {
-				swap(dst->bi_iter.bi_size, dst_len);
-				bio_copy_data(dst, src);
-				swap(dst->bi_iter.bi_size, dst_len);
-			}
-
-			src_len = dst_len;
-		}
-
-		BUG_ON(!src_len || !dst_len);
-
-		if (bch2_csum_type_is_encryption(op->csum_type)) {
-			if (bversion_zero(version)) {
-				version.lo = atomic64_inc_return(&c->key_version);
-			} else {
-				crc.nonce = op->nonce;
-				op->nonce += src_len >> 9;
-			}
-		}
-
-		if ((op->flags & BCH_WRITE_DATA_ENCODED) &&
-		    !crc_is_compressed(crc) &&
-		    bch2_csum_type_is_encryption(op->crc.csum_type) ==
-		    bch2_csum_type_is_encryption(op->csum_type)) {
-			u8 compression_type = crc.compression_type;
-			u16 nonce = crc.nonce;
-			/*
-			 * Note: when we're using rechecksum(), we need to be
-			 * checksumming @src because it has all the data our
-			 * existing checksum covers - if we bounced (because we
-			 * were trying to compress), @dst will only have the
-			 * part of the data the new checksum will cover.
-			 *
-			 * But normally we want to be checksumming post bounce,
-			 * because part of the reason for bouncing is so the
-			 * data can't be modified (by userspace) while it's in
-			 * flight.
-			 */
-			if (bch2_rechecksum_bio(c, src, version, op->crc,
-					&crc, &op->crc,
-					src_len >> 9,
-					bio_sectors(src) - (src_len >> 9),
-					op->csum_type))
-				goto csum_err;
-			/*
-			 * rchecksum_bio sets compression_type on crc from op->crc,
-			 * this isn't always correct as sometimes we're changing
-			 * an extent from uncompressed to incompressible.
-			 */
-			crc.compression_type = compression_type;
-			crc.nonce = nonce;
-		} else {
-			if ((op->flags & BCH_WRITE_DATA_ENCODED) &&
-			    bch2_rechecksum_bio(c, src, version, op->crc,
-					NULL, &op->crc,
-					src_len >> 9,
-					bio_sectors(src) - (src_len >> 9),
-					op->crc.csum_type))
-				goto csum_err;
-
-			crc.compressed_size	= dst_len >> 9;
-			crc.uncompressed_size	= src_len >> 9;
-			crc.live_size		= src_len >> 9;
-
-			swap(dst->bi_iter.bi_size, dst_len);
-			ret = bch2_encrypt_bio(c, op->csum_type,
-					       extent_nonce(version, crc), dst);
-			if (ret)
-				goto err;
-
-			crc.csum = bch2_checksum_bio(c, op->csum_type,
-					 extent_nonce(version, crc), dst);
-			crc.csum_type = op->csum_type;
-			swap(dst->bi_iter.bi_size, dst_len);
-		}
-
-		init_append_extent(op, wp, version, crc);
-
-		if (dst != src)
-			bio_advance(dst, dst_len);
-		bio_advance(src, src_len);
-		total_output	+= dst_len;
-		total_input	+= src_len;
-	} while (dst->bi_iter.bi_size &&
-		 src->bi_iter.bi_size &&
-		 wp->sectors_free &&
-		 !bch2_keylist_realloc(&op->insert_keys,
-				      op->inline_keys,
-				      ARRAY_SIZE(op->inline_keys),
-				      BKEY_EXTENT_U64s_MAX));
-
-	more = src->bi_iter.bi_size != 0;
-
-	dst->bi_iter = saved_iter;
-
-	if (dst == src && more) {
-		BUG_ON(total_output != total_input);
-
-		dst = bio_split(src, total_input >> 9,
-				GFP_NOFS, &c->bio_write);
-		wbio_init(dst)->put_bio	= true;
-		/* copy WRITE_SYNC flag */
-		dst->bi_opf		= src->bi_opf;
-	}
-
-	dst->bi_iter.bi_size = total_output;
-do_write:
-	*_dst = dst;
-	return more;
-csum_err:
-	bch_err(c, "error verifying existing checksum while rewriting existing data (memory corruption?)");
-	ret = -EIO;
-err:
-	if (to_wbio(dst)->bounce)
-		bch2_bio_free_pages_pool(c, dst);
-	if (to_wbio(dst)->put_bio)
-		bio_put(dst);
-
-	return ret;
-}
-
-static bool bch2_extent_is_writeable(struct bch_write_op *op,
-				     struct bkey_s_c k)
-{
-	struct bch_fs *c = op->c;
-	struct bkey_s_c_extent e;
-	struct extent_ptr_decoded p;
-	const union bch_extent_entry *entry;
-	unsigned replicas = 0;
-
-	if (k.k->type != KEY_TYPE_extent)
-		return false;
-
-	e = bkey_s_c_to_extent(k);
-	extent_for_each_ptr_decode(e, p, entry) {
-		if (p.crc.csum_type ||
-		    crc_is_compressed(p.crc) ||
-		    p.has_ec)
-			return false;
-
-		replicas += bch2_extent_ptr_durability(c, &p);
-	}
-
-	return replicas >= op->opts.data_replicas;
-}
-
-static inline void bch2_nocow_write_unlock(struct bch_write_op *op)
-{
-	struct bch_fs *c = op->c;
-	const struct bch_extent_ptr *ptr;
-	struct bkey_i *k;
-
-	for_each_keylist_key(&op->insert_keys, k) {
-		struct bkey_ptrs_c ptrs = bch2_bkey_ptrs_c(bkey_i_to_s_c(k));
-
-		bkey_for_each_ptr(ptrs, ptr)
-			bch2_bucket_nocow_unlock(&c->nocow_locks,
-					       PTR_BUCKET_POS(c, ptr),
-					       BUCKET_NOCOW_LOCK_UPDATE);
-	}
-}
-
-static int bch2_nocow_write_convert_one_unwritten(struct btree_trans *trans,
-						  struct btree_iter *iter,
-						  struct bkey_i *orig,
-						  struct bkey_s_c k,
-						  u64 new_i_size)
-{
-	struct bkey_i *new;
-	struct bkey_ptrs ptrs;
-	struct bch_extent_ptr *ptr;
-	int ret;
-
-	if (!bch2_extents_match(bkey_i_to_s_c(orig), k)) {
-		/* trace this */
-		return 0;
-	}
-
-	new = bch2_bkey_make_mut_noupdate(trans, k);
-	ret = PTR_ERR_OR_ZERO(new);
-	if (ret)
-		return ret;
-
-	bch2_cut_front(bkey_start_pos(&orig->k), new);
-	bch2_cut_back(orig->k.p, new);
-
-	ptrs = bch2_bkey_ptrs(bkey_i_to_s(new));
-	bkey_for_each_ptr(ptrs, ptr)
-		ptr->unwritten = 0;
-
-	/*
-	 * Note that we're not calling bch2_subvol_get_snapshot() in this path -
-	 * that was done when we kicked off the write, and here it's important
-	 * that we update the extent that we wrote to - even if a snapshot has
-	 * since been created. The write is still outstanding, so we're ok
-	 * w.r.t. snapshot atomicity:
-	 */
-	return  bch2_extent_update_i_size_sectors(trans, iter,
-					min(new->k.p.offset << 9, new_i_size), 0) ?:
-		bch2_trans_update(trans, iter, new,
-				  BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE);
-}
-
-static void bch2_nocow_write_convert_unwritten(struct bch_write_op *op)
-{
-	struct bch_fs *c = op->c;
-	struct btree_trans trans;
-	struct btree_iter iter;
-	struct bkey_i *orig;
-	struct bkey_s_c k;
-	int ret;
-
-	bch2_trans_init(&trans, c, 0, 0);
-
-	for_each_keylist_key(&op->insert_keys, orig) {
-		ret = for_each_btree_key_upto_commit(&trans, iter, BTREE_ID_extents,
-				     bkey_start_pos(&orig->k), orig->k.p,
-				     BTREE_ITER_INTENT, k,
-				     NULL, NULL, BTREE_INSERT_NOFAIL, ({
-			bch2_nocow_write_convert_one_unwritten(&trans, &iter, orig, k, op->new_i_size);
-		}));
-
-		if (ret && !bch2_err_matches(ret, EROFS)) {
-			struct bkey_i *k = bch2_keylist_front(&op->insert_keys);
-
-			bch_err_inum_offset_ratelimited(c,
-				k->k.p.inode, k->k.p.offset << 9,
-				"write error while doing btree update: %s",
-				bch2_err_str(ret));
-		}
-
-		if (ret) {
-			op->error = ret;
-			break;
-		}
-	}
-
-	bch2_trans_exit(&trans);
-}
-
-static void __bch2_nocow_write_done(struct bch_write_op *op)
-{
-	bch2_nocow_write_unlock(op);
-
-	if (unlikely(op->flags & BCH_WRITE_IO_ERROR)) {
-		op->error = -EIO;
-	} else if (unlikely(op->flags & BCH_WRITE_CONVERT_UNWRITTEN))
-		bch2_nocow_write_convert_unwritten(op);
-}
-
-static void bch2_nocow_write_done(struct closure *cl)
-{
-	struct bch_write_op *op = container_of(cl, struct bch_write_op, cl);
-
-	__bch2_nocow_write_done(op);
-	bch2_write_done(cl);
-}
-
-static void bch2_nocow_write(struct bch_write_op *op)
-{
-	struct bch_fs *c = op->c;
-	struct btree_trans trans;
-	struct btree_iter iter;
-	struct bkey_s_c k;
-	struct bkey_ptrs_c ptrs;
-	const struct bch_extent_ptr *ptr;
-	struct {
-		struct bpos	b;
-		unsigned	gen;
-		struct nocow_lock_bucket *l;
-	} buckets[BCH_REPLICAS_MAX];
-	unsigned nr_buckets = 0;
-	u32 snapshot;
-	int ret, i;
-
-	if (op->flags & BCH_WRITE_MOVE)
-		return;
-
-	bch2_trans_init(&trans, c, 0, 0);
-retry:
-	bch2_trans_begin(&trans);
-
-	ret = bch2_subvolume_get_snapshot(&trans, op->subvol, &snapshot);
-	if (unlikely(ret))
-		goto err;
-
-	bch2_trans_iter_init(&trans, &iter, BTREE_ID_extents,
-			     SPOS(op->pos.inode, op->pos.offset, snapshot),
-			     BTREE_ITER_SLOTS);
-	while (1) {
-		struct bio *bio = &op->wbio.bio;
-
-		nr_buckets = 0;
-
-		k = bch2_btree_iter_peek_slot(&iter);
-		ret = bkey_err(k);
-		if (ret)
-			break;
-
-		/* fall back to normal cow write path? */
-		if (unlikely(k.k->p.snapshot != snapshot ||
-			     !bch2_extent_is_writeable(op, k)))
-			break;
-
-		if (bch2_keylist_realloc(&op->insert_keys,
-					op->inline_keys,
-					ARRAY_SIZE(op->inline_keys),
-					k.k->u64s))
-			break;
-
-		/* Get iorefs before dropping btree locks: */
-		ptrs = bch2_bkey_ptrs_c(k);
-		bkey_for_each_ptr(ptrs, ptr) {
-			buckets[nr_buckets].b = PTR_BUCKET_POS(c, ptr);
-			buckets[nr_buckets].gen = ptr->gen;
-			buckets[nr_buckets].l =
-				bucket_nocow_lock(&c->nocow_locks,
-						  bucket_to_u64(buckets[nr_buckets].b));
-
-			prefetch(buckets[nr_buckets].l);
-
-			if (unlikely(!bch2_dev_get_ioref(bch_dev_bkey_exists(c, ptr->dev), WRITE)))
-				goto err_get_ioref;
-
-			nr_buckets++;
-
-			if (ptr->unwritten)
-				op->flags |= BCH_WRITE_CONVERT_UNWRITTEN;
-		}
-
-		/* Unlock before taking nocow locks, doing IO: */
-		bkey_reassemble(op->insert_keys.top, k);
-		bch2_trans_unlock(&trans);
-
-		bch2_cut_front(op->pos, op->insert_keys.top);
-		if (op->flags & BCH_WRITE_CONVERT_UNWRITTEN)
-			bch2_cut_back(POS(op->pos.inode, op->pos.offset + bio_sectors(bio)), op->insert_keys.top);
-
-		for (i = 0; i < nr_buckets; i++) {
-			struct bch_dev *ca = bch_dev_bkey_exists(c, buckets[i].b.inode);
-			struct nocow_lock_bucket *l = buckets[i].l;
-			bool stale;
-
-			__bch2_bucket_nocow_lock(&c->nocow_locks, l,
-						 bucket_to_u64(buckets[i].b),
-						 BUCKET_NOCOW_LOCK_UPDATE);
-
-			rcu_read_lock();
-			stale = gen_after(*bucket_gen(ca, buckets[i].b.offset), buckets[i].gen);
-			rcu_read_unlock();
-
-			if (unlikely(stale))
-				goto err_bucket_stale;
-		}
-
-		bio = &op->wbio.bio;
-		if (k.k->p.offset < op->pos.offset + bio_sectors(bio)) {
-			bio = bio_split(bio, k.k->p.offset - op->pos.offset,
-					GFP_KERNEL, &c->bio_write);
-			wbio_init(bio)->put_bio = true;
-			bio->bi_opf = op->wbio.bio.bi_opf;
-		} else {
-			op->flags |= BCH_WRITE_DONE;
-		}
-
-		op->pos.offset += bio_sectors(bio);
-		op->written += bio_sectors(bio);
-
-		bio->bi_end_io	= bch2_write_endio;
-		bio->bi_private	= &op->cl;
-		bio->bi_opf |= REQ_OP_WRITE;
-		closure_get(&op->cl);
-		bch2_submit_wbio_replicas(to_wbio(bio), c, BCH_DATA_user,
-					  op->insert_keys.top, true);
-
-		bch2_keylist_push(&op->insert_keys);
-		if (op->flags & BCH_WRITE_DONE)
-			break;
-		bch2_btree_iter_advance(&iter);
-	}
-out:
-	bch2_trans_iter_exit(&trans, &iter);
-err:
-	if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
-		goto retry;
-
-	if (ret) {
-		bch_err_inum_offset_ratelimited(c,
-				op->pos.inode,
-				op->pos.offset << 9,
-				"%s: btree lookup error %s",
-				__func__, bch2_err_str(ret));
-		op->error = ret;
-		op->flags |= BCH_WRITE_DONE;
-	}
-
-	bch2_trans_exit(&trans);
-
-	/* fallback to cow write path? */
-	if (!(op->flags & BCH_WRITE_DONE)) {
-		closure_sync(&op->cl);
-		__bch2_nocow_write_done(op);
-		op->insert_keys.top = op->insert_keys.keys;
-	} else if (op->flags & BCH_WRITE_SYNC) {
-		closure_sync(&op->cl);
-		bch2_nocow_write_done(&op->cl);
-	} else {
-		/*
-		 * XXX
-		 * needs to run out of process context because ei_quota_lock is
-		 * a mutex
-		 */
-		continue_at(&op->cl, bch2_nocow_write_done, index_update_wq(op));
-	}
-	return;
-err_get_ioref:
-	for (i = 0; i < nr_buckets; i++)
-		percpu_ref_put(&bch_dev_bkey_exists(c, buckets[i].b.inode)->io_ref);
-
-	/* Fall back to COW path: */
-	goto out;
-err_bucket_stale:
-	while (--i >= 0)
-		bch2_bucket_nocow_unlock(&c->nocow_locks,
-					 buckets[i].b,
-					 BUCKET_NOCOW_LOCK_UPDATE);
-	for (i = 0; i < nr_buckets; i++)
-		percpu_ref_put(&bch_dev_bkey_exists(c, buckets[i].b.inode)->io_ref);
-
-	/* We can retry this: */
-	ret = -BCH_ERR_transaction_restart;
-	goto out;
-}
-
-static void __bch2_write(struct bch_write_op *op)
-{
-	struct bch_fs *c = op->c;
-	struct write_point *wp = NULL;
-	struct bio *bio = NULL;
-	unsigned nofs_flags;
-	int ret;
-
-	nofs_flags = memalloc_nofs_save();
-
-	if (unlikely(op->opts.nocow && c->opts.nocow_enabled)) {
-		bch2_nocow_write(op);
-		if (op->flags & BCH_WRITE_DONE)
-			goto out_nofs_restore;
-	}
-again:
-	memset(&op->failed, 0, sizeof(op->failed));
-
-	do {
-		struct bkey_i *key_to_write;
-		unsigned key_to_write_offset = op->insert_keys.top_p -
-			op->insert_keys.keys_p;
-
-		/* +1 for possible cache device: */
-		if (op->open_buckets.nr + op->nr_replicas + 1 >
-		    ARRAY_SIZE(op->open_buckets.v))
-			break;
-
-		if (bch2_keylist_realloc(&op->insert_keys,
-					op->inline_keys,
-					ARRAY_SIZE(op->inline_keys),
-					BKEY_EXTENT_U64s_MAX))
-			break;
-
-		/*
-		 * The copygc thread is now global, which means it's no longer
-		 * freeing up space on specific disks, which means that
-		 * allocations for specific disks may hang arbitrarily long:
-		 */
-		ret = bch2_trans_do(c, NULL, NULL, 0,
-			bch2_alloc_sectors_start_trans(&trans,
-				op->target,
-				op->opts.erasure_code && !(op->flags & BCH_WRITE_CACHED),
-				op->write_point,
-				&op->devs_have,
-				op->nr_replicas,
-				op->nr_replicas_required,
-				op->watermark,
-				op->flags,
-				(op->flags & (BCH_WRITE_ALLOC_NOWAIT|
-					      BCH_WRITE_ONLY_SPECIFIED_DEVS))
-				? NULL : &op->cl, &wp));
-		if (unlikely(ret)) {
-			if (bch2_err_matches(ret, BCH_ERR_operation_blocked))
-				break;
-
-			goto err;
-		}
-
-		EBUG_ON(!wp);
-
-		bch2_open_bucket_get(c, wp, &op->open_buckets);
-		ret = bch2_write_extent(op, wp, &bio);
-
-		bch2_alloc_sectors_done_inlined(c, wp);
-err:
-		if (ret <= 0) {
-			op->flags |= BCH_WRITE_DONE;
-
-			if (ret < 0) {
-				op->error = ret;
-				break;
-			}
-		}
-
-		bio->bi_end_io	= bch2_write_endio;
-		bio->bi_private	= &op->cl;
-		bio->bi_opf |= REQ_OP_WRITE;
-
-		closure_get(bio->bi_private);
-
-		key_to_write = (void *) (op->insert_keys.keys_p +
-					 key_to_write_offset);
-
-		bch2_submit_wbio_replicas(to_wbio(bio), c, BCH_DATA_user,
-					  key_to_write, false);
-	} while (ret);
-
-	/*
-	 * Sync or no?
-	 *
-	 * If we're running asynchronously, wne may still want to block
-	 * synchronously here if we weren't able to submit all of the IO at
-	 * once, as that signals backpressure to the caller.
-	 */
-	if ((op->flags & BCH_WRITE_SYNC) ||
-	    (!(op->flags & BCH_WRITE_DONE) &&
-	     !(op->flags & BCH_WRITE_IN_WORKER))) {
-		closure_sync(&op->cl);
-		__bch2_write_index(op);
-
-		if (!(op->flags & BCH_WRITE_DONE))
-			goto again;
-		bch2_write_done(&op->cl);
-	} else {
-		bch2_write_queue(op, wp);
-		continue_at(&op->cl, bch2_write_index, NULL);
-	}
-out_nofs_restore:
-	memalloc_nofs_restore(nofs_flags);
-}
-
-static void bch2_write_data_inline(struct bch_write_op *op, unsigned data_len)
-{
-	struct bio *bio = &op->wbio.bio;
-	struct bvec_iter iter;
-	struct bkey_i_inline_data *id;
-	unsigned sectors;
-	int ret;
-
-	op->flags |= BCH_WRITE_WROTE_DATA_INLINE;
-	op->flags |= BCH_WRITE_DONE;
-
-	bch2_check_set_feature(op->c, BCH_FEATURE_inline_data);
-
-	ret = bch2_keylist_realloc(&op->insert_keys, op->inline_keys,
-				   ARRAY_SIZE(op->inline_keys),
-				   BKEY_U64s + DIV_ROUND_UP(data_len, 8));
-	if (ret) {
-		op->error = ret;
-		goto err;
-	}
-
-	sectors = bio_sectors(bio);
-	op->pos.offset += sectors;
-
-	id = bkey_inline_data_init(op->insert_keys.top);
-	id->k.p		= op->pos;
-	id->k.version	= op->version;
-	id->k.size	= sectors;
-
-	iter = bio->bi_iter;
-	iter.bi_size = data_len;
-	memcpy_from_bio(id->v.data, bio, iter);
-
-	while (data_len & 7)
-		id->v.data[data_len++] = '\0';
-	set_bkey_val_bytes(&id->k, data_len);
-	bch2_keylist_push(&op->insert_keys);
-
-	__bch2_write_index(op);
-err:
-	bch2_write_done(&op->cl);
-}
-
-/**
- * bch_write - handle a write to a cache device or flash only volume
- *
- * This is the starting point for any data to end up in a cache device; it could
- * be from a normal write, or a writeback write, or a write to a flash only
- * volume - it's also used by the moving garbage collector to compact data in
- * mostly empty buckets.
- *
- * It first writes the data to the cache, creating a list of keys to be inserted
- * (if the data won't fit in a single open bucket, there will be multiple keys);
- * after the data is written it calls bch_journal, and after the keys have been
- * added to the next journal write they're inserted into the btree.
- *
- * If op->discard is true, instead of inserting the data it invalidates the
- * region of the cache represented by op->bio and op->inode.
- */
-void bch2_write(struct closure *cl)
-{
-	struct bch_write_op *op = container_of(cl, struct bch_write_op, cl);
-	struct bio *bio = &op->wbio.bio;
-	struct bch_fs *c = op->c;
-	unsigned data_len;
-
-	EBUG_ON(op->cl.parent);
-	BUG_ON(!op->nr_replicas);
-	BUG_ON(!op->write_point.v);
-	BUG_ON(bkey_eq(op->pos, POS_MAX));
-
-	op->start_time = local_clock();
-	bch2_keylist_init(&op->insert_keys, op->inline_keys);
-	wbio_init(bio)->put_bio = false;
-
-	if (bio->bi_iter.bi_size & (c->opts.block_size - 1)) {
-		bch_err_inum_offset_ratelimited(c,
-			op->pos.inode,
-			op->pos.offset << 9,
-			"misaligned write");
-		op->error = -EIO;
-		goto err;
-	}
-
-	if (c->opts.nochanges) {
-		op->error = -BCH_ERR_erofs_no_writes;
-		goto err;
-	}
-
-	if (!(op->flags & BCH_WRITE_MOVE) &&
-	    !bch2_write_ref_tryget(c, BCH_WRITE_REF_write)) {
-		op->error = -BCH_ERR_erofs_no_writes;
-		goto err;
-	}
-
-	this_cpu_add(c->counters[BCH_COUNTER_io_write], bio_sectors(bio));
-	bch2_increment_clock(c, bio_sectors(bio), WRITE);
-
-	data_len = min_t(u64, bio->bi_iter.bi_size,
-			 op->new_i_size - (op->pos.offset << 9));
-
-	if (c->opts.inline_data &&
-	    data_len <= min(block_bytes(c) / 2, 1024U)) {
-		bch2_write_data_inline(op, data_len);
-		return;
-	}
-
-	__bch2_write(op);
-	return;
-err:
-	bch2_disk_reservation_put(c, &op->res);
-
-	closure_debug_destroy(&op->cl);
-	if (op->end_io)
-		op->end_io(op);
-}
-
-static const char * const bch2_write_flags[] = {
-#define x(f)	#f,
-	BCH_WRITE_FLAGS()
-#undef x
-	NULL
-};
-
-void bch2_write_op_to_text(struct printbuf *out, struct bch_write_op *op)
-{
-	prt_str(out, "pos: ");
-	bch2_bpos_to_text(out, op->pos);
-	prt_newline(out);
-	printbuf_indent_add(out, 2);
-
-	prt_str(out, "started: ");
-	bch2_pr_time_units(out, local_clock() - op->start_time);
-	prt_newline(out);
-
-	prt_str(out, "flags: ");
-	prt_bitflags(out, bch2_write_flags, op->flags);
-	prt_newline(out);
-
-	prt_printf(out, "ref: %u", closure_nr_remaining(&op->cl));
-	prt_newline(out);
-
-	printbuf_indent_sub(out, 2);
-}
-
-/* Cache promotion on read */
-
-struct promote_op {
-	struct rcu_head		rcu;
-	u64			start_time;
-
-	struct rhash_head	hash;
-	struct bpos		pos;
-
-	struct data_update	write;
-	struct bio_vec		bi_inline_vecs[0]; /* must be last */
-};
-
-static const struct rhashtable_params bch_promote_params = {
-	.head_offset	= offsetof(struct promote_op, hash),
-	.key_offset	= offsetof(struct promote_op, pos),
-	.key_len	= sizeof(struct bpos),
-};
-
-static inline bool should_promote(struct bch_fs *c, struct bkey_s_c k,
-				  struct bpos pos,
-				  struct bch_io_opts opts,
-				  unsigned flags)
-{
-	if (!(flags & BCH_READ_MAY_PROMOTE))
-		return false;
-
-	if (!opts.promote_target)
-		return false;
-
-	if (bch2_bkey_has_target(c, k, opts.promote_target))
-		return false;
-
-	if (bkey_extent_is_unwritten(k))
-		return false;
-
-	if (bch2_target_congested(c, opts.promote_target)) {
-		/* XXX trace this */
-		return false;
-	}
-
-	if (rhashtable_lookup_fast(&c->promote_table, &pos,
-				   bch_promote_params))
-		return false;
-
-	return true;
-}
-
-static void promote_free(struct bch_fs *c, struct promote_op *op)
-{
-	int ret;
-
-	bch2_data_update_exit(&op->write);
-
-	ret = rhashtable_remove_fast(&c->promote_table, &op->hash,
-				     bch_promote_params);
-	BUG_ON(ret);
-	bch2_write_ref_put(c, BCH_WRITE_REF_promote);
-	kfree_rcu(op, rcu);
-}
-
-static void promote_done(struct bch_write_op *wop)
-{
-	struct promote_op *op =
-		container_of(wop, struct promote_op, write.op);
-	struct bch_fs *c = op->write.op.c;
-
-	bch2_time_stats_update(&c->times[BCH_TIME_data_promote],
-			       op->start_time);
-	promote_free(c, op);
-}
-
-static void promote_start(struct promote_op *op, struct bch_read_bio *rbio)
-{
-	struct bio *bio = &op->write.op.wbio.bio;
-
-	trace_and_count(op->write.op.c, read_promote, &rbio->bio);
-
-	/* we now own pages: */
-	BUG_ON(!rbio->bounce);
-	BUG_ON(rbio->bio.bi_vcnt > bio->bi_max_vecs);
-
-	memcpy(bio->bi_io_vec, rbio->bio.bi_io_vec,
-	       sizeof(struct bio_vec) * rbio->bio.bi_vcnt);
-	swap(bio->bi_vcnt, rbio->bio.bi_vcnt);
-
-	bch2_data_update_read_done(&op->write, rbio->pick.crc);
-}
-
-static struct promote_op *__promote_alloc(struct btree_trans *trans,
-					  enum btree_id btree_id,
-					  struct bkey_s_c k,
-					  struct bpos pos,
-					  struct extent_ptr_decoded *pick,
-					  struct bch_io_opts opts,
-					  unsigned sectors,
-					  struct bch_read_bio **rbio)
-{
-	struct bch_fs *c = trans->c;
-	struct promote_op *op = NULL;
-	struct bio *bio;
-	unsigned pages = DIV_ROUND_UP(sectors, PAGE_SECTORS);
-	int ret;
-
-	if (!bch2_write_ref_tryget(c, BCH_WRITE_REF_promote))
-		return NULL;
-
-	op = kzalloc(sizeof(*op) + sizeof(struct bio_vec) * pages, GFP_NOFS);
-	if (!op)
-		goto err;
-
-	op->start_time = local_clock();
-	op->pos = pos;
-
-	/*
-	 * We don't use the mempool here because extents that aren't
-	 * checksummed or compressed can be too big for the mempool:
-	 */
-	*rbio = kzalloc(sizeof(struct bch_read_bio) +
-			sizeof(struct bio_vec) * pages,
-			GFP_NOFS);
-	if (!*rbio)
-		goto err;
-
-	rbio_init(&(*rbio)->bio, opts);
-	bio_init(&(*rbio)->bio, NULL, (*rbio)->bio.bi_inline_vecs, pages, 0);
-
-	if (bch2_bio_alloc_pages(&(*rbio)->bio, sectors << 9,
-				 GFP_NOFS))
-		goto err;
-
-	(*rbio)->bounce		= true;
-	(*rbio)->split		= true;
-	(*rbio)->kmalloc	= true;
-
-	if (rhashtable_lookup_insert_fast(&c->promote_table, &op->hash,
-					  bch_promote_params))
-		goto err;
-
-	bio = &op->write.op.wbio.bio;
-	bio_init(bio, NULL, bio->bi_inline_vecs, pages, 0);
-
-	ret = bch2_data_update_init(trans, NULL, &op->write,
-			writepoint_hashed((unsigned long) current),
-			opts,
-			(struct data_update_opts) {
-				.target		= opts.promote_target,
-				.extra_replicas	= 1,
-				.write_flags	= BCH_WRITE_ALLOC_NOWAIT|BCH_WRITE_CACHED,
-			},
-			btree_id, k);
-	/*
-	 * possible errors: -BCH_ERR_nocow_lock_blocked,
-	 * -BCH_ERR_ENOSPC_disk_reservation:
-	 */
-	if (ret) {
-		ret = rhashtable_remove_fast(&c->promote_table, &op->hash,
-					bch_promote_params);
-		BUG_ON(ret);
-		goto err;
-	}
-
-	op->write.op.end_io = promote_done;
-
-	return op;
-err:
-	if (*rbio)
-		bio_free_pages(&(*rbio)->bio);
-	kfree(*rbio);
-	*rbio = NULL;
-	kfree(op);
-	bch2_write_ref_put(c, BCH_WRITE_REF_promote);
-	return NULL;
-}
-
-noinline
-static struct promote_op *promote_alloc(struct btree_trans *trans,
-					struct bvec_iter iter,
-					struct bkey_s_c k,
-					struct extent_ptr_decoded *pick,
-					struct bch_io_opts opts,
-					unsigned flags,
-					struct bch_read_bio **rbio,
-					bool *bounce,
-					bool *read_full)
-{
-	struct bch_fs *c = trans->c;
-	bool promote_full = *read_full || READ_ONCE(c->promote_whole_extents);
-	/* data might have to be decompressed in the write path: */
-	unsigned sectors = promote_full
-		? max(pick->crc.compressed_size, pick->crc.live_size)
-		: bvec_iter_sectors(iter);
-	struct bpos pos = promote_full
-		? bkey_start_pos(k.k)
-		: POS(k.k->p.inode, iter.bi_sector);
-	struct promote_op *promote;
-
-	if (!should_promote(c, k, pos, opts, flags))
-		return NULL;
-
-	promote = __promote_alloc(trans,
-				  k.k->type == KEY_TYPE_reflink_v
-				  ? BTREE_ID_reflink
-				  : BTREE_ID_extents,
-				  k, pos, pick, opts, sectors, rbio);
-	if (!promote)
-		return NULL;
-
-	*bounce		= true;
-	*read_full	= promote_full;
-	return promote;
-}
-
-/* Read */
-
-#define READ_RETRY_AVOID	1
-#define READ_RETRY		2
-#define READ_ERR		3
-
-enum rbio_context {
-	RBIO_CONTEXT_NULL,
-	RBIO_CONTEXT_HIGHPRI,
-	RBIO_CONTEXT_UNBOUND,
-};
-
-static inline struct bch_read_bio *
-bch2_rbio_parent(struct bch_read_bio *rbio)
-{
-	return rbio->split ? rbio->parent : rbio;
-}
-
-__always_inline
-static void bch2_rbio_punt(struct bch_read_bio *rbio, work_func_t fn,
-			   enum rbio_context context,
-			   struct workqueue_struct *wq)
-{
-	if (context <= rbio->context) {
-		fn(&rbio->work);
-	} else {
-		rbio->work.func		= fn;
-		rbio->context		= context;
-		queue_work(wq, &rbio->work);
-	}
-}
-
-static inline struct bch_read_bio *bch2_rbio_free(struct bch_read_bio *rbio)
-{
-	BUG_ON(rbio->bounce && !rbio->split);
-
-	if (rbio->promote)
-		promote_free(rbio->c, rbio->promote);
-	rbio->promote = NULL;
-
-	if (rbio->bounce)
-		bch2_bio_free_pages_pool(rbio->c, &rbio->bio);
-
-	if (rbio->split) {
-		struct bch_read_bio *parent = rbio->parent;
-
-		if (rbio->kmalloc)
-			kfree(rbio);
-		else
-			bio_put(&rbio->bio);
-
-		rbio = parent;
-	}
-
-	return rbio;
-}
-
-/*
- * Only called on a top level bch_read_bio to complete an entire read request,
- * not a split:
- */
-static void bch2_rbio_done(struct bch_read_bio *rbio)
-{
-	if (rbio->start_time)
-		bch2_time_stats_update(&rbio->c->times[BCH_TIME_data_read],
-				       rbio->start_time);
-	bio_endio(&rbio->bio);
-}
-
-static void bch2_read_retry_nodecode(struct bch_fs *c, struct bch_read_bio *rbio,
-				     struct bvec_iter bvec_iter,
-				     struct bch_io_failures *failed,
-				     unsigned flags)
-{
-	struct btree_trans trans;
-	struct btree_iter iter;
-	struct bkey_buf sk;
-	struct bkey_s_c k;
-	int ret;
-
-	flags &= ~BCH_READ_LAST_FRAGMENT;
-	flags |= BCH_READ_MUST_CLONE;
-
-	bch2_bkey_buf_init(&sk);
-	bch2_trans_init(&trans, c, 0, 0);
-
-	bch2_trans_iter_init(&trans, &iter, rbio->data_btree,
-			     rbio->read_pos, BTREE_ITER_SLOTS);
-retry:
-	rbio->bio.bi_status = 0;
-
-	k = bch2_btree_iter_peek_slot(&iter);
-	if (bkey_err(k))
-		goto err;
-
-	bch2_bkey_buf_reassemble(&sk, c, k);
-	k = bkey_i_to_s_c(sk.k);
-	bch2_trans_unlock(&trans);
-
-	if (!bch2_bkey_matches_ptr(c, k,
-				   rbio->pick.ptr,
-				   rbio->data_pos.offset -
-				   rbio->pick.crc.offset)) {
-		/* extent we wanted to read no longer exists: */
-		rbio->hole = true;
-		goto out;
-	}
-
-	ret = __bch2_read_extent(&trans, rbio, bvec_iter,
-				 rbio->read_pos,
-				 rbio->data_btree,
-				 k, 0, failed, flags);
-	if (ret == READ_RETRY)
-		goto retry;
-	if (ret)
-		goto err;
-out:
-	bch2_rbio_done(rbio);
-	bch2_trans_iter_exit(&trans, &iter);
-	bch2_trans_exit(&trans);
-	bch2_bkey_buf_exit(&sk, c);
-	return;
-err:
-	rbio->bio.bi_status = BLK_STS_IOERR;
-	goto out;
-}
-
-static void bch2_rbio_retry(struct work_struct *work)
-{
-	struct bch_read_bio *rbio =
-		container_of(work, struct bch_read_bio, work);
-	struct bch_fs *c	= rbio->c;
-	struct bvec_iter iter	= rbio->bvec_iter;
-	unsigned flags		= rbio->flags;
-	subvol_inum inum = {
-		.subvol = rbio->subvol,
-		.inum	= rbio->read_pos.inode,
-	};
-	struct bch_io_failures failed = { .nr = 0 };
-
-	trace_and_count(c, read_retry, &rbio->bio);
-
-	if (rbio->retry == READ_RETRY_AVOID)
-		bch2_mark_io_failure(&failed, &rbio->pick);
-
-	rbio->bio.bi_status = 0;
-
-	rbio = bch2_rbio_free(rbio);
-
-	flags |= BCH_READ_IN_RETRY;
-	flags &= ~BCH_READ_MAY_PROMOTE;
-
-	if (flags & BCH_READ_NODECODE) {
-		bch2_read_retry_nodecode(c, rbio, iter, &failed, flags);
-	} else {
-		flags &= ~BCH_READ_LAST_FRAGMENT;
-		flags |= BCH_READ_MUST_CLONE;
-
-		__bch2_read(c, rbio, iter, inum, &failed, flags);
-	}
-}
-
-static void bch2_rbio_error(struct bch_read_bio *rbio, int retry,
-			    blk_status_t error)
-{
-	rbio->retry = retry;
-
-	if (rbio->flags & BCH_READ_IN_RETRY)
-		return;
-
-	if (retry == READ_ERR) {
-		rbio = bch2_rbio_free(rbio);
-
-		rbio->bio.bi_status = error;
-		bch2_rbio_done(rbio);
-	} else {
-		bch2_rbio_punt(rbio, bch2_rbio_retry,
-			       RBIO_CONTEXT_UNBOUND, system_unbound_wq);
-	}
-}
-
-static int __bch2_rbio_narrow_crcs(struct btree_trans *trans,
-				   struct bch_read_bio *rbio)
-{
-	struct bch_fs *c = rbio->c;
-	u64 data_offset = rbio->data_pos.offset - rbio->pick.crc.offset;
-	struct bch_extent_crc_unpacked new_crc;
-	struct btree_iter iter;
-	struct bkey_i *new;
-	struct bkey_s_c k;
-	int ret = 0;
-
-	if (crc_is_compressed(rbio->pick.crc))
-		return 0;
-
-	k = bch2_bkey_get_iter(trans, &iter, rbio->data_btree, rbio->data_pos,
-			       BTREE_ITER_SLOTS|BTREE_ITER_INTENT);
-	if ((ret = bkey_err(k)))
-		goto out;
-
-	if (bversion_cmp(k.k->version, rbio->version) ||
-	    !bch2_bkey_matches_ptr(c, k, rbio->pick.ptr, data_offset))
-		goto out;
-
-	/* Extent was merged? */
-	if (bkey_start_offset(k.k) < data_offset ||
-	    k.k->p.offset > data_offset + rbio->pick.crc.uncompressed_size)
-		goto out;
-
-	if (bch2_rechecksum_bio(c, &rbio->bio, rbio->version,
-			rbio->pick.crc, NULL, &new_crc,
-			bkey_start_offset(k.k) - data_offset, k.k->size,
-			rbio->pick.crc.csum_type)) {
-		bch_err(c, "error verifying existing checksum while narrowing checksum (memory corruption?)");
-		ret = 0;
-		goto out;
-	}
-
-	/*
-	 * going to be temporarily appending another checksum entry:
-	 */
-	new = bch2_trans_kmalloc(trans, bkey_bytes(k.k) +
-				 sizeof(struct bch_extent_crc128));
-	if ((ret = PTR_ERR_OR_ZERO(new)))
-		goto out;
-
-	bkey_reassemble(new, k);
-
-	if (!bch2_bkey_narrow_crcs(new, new_crc))
-		goto out;
-
-	ret = bch2_trans_update(trans, &iter, new,
-				BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE);
-out:
-	bch2_trans_iter_exit(trans, &iter);
-	return ret;
-}
-
-static noinline void bch2_rbio_narrow_crcs(struct bch_read_bio *rbio)
-{
-	bch2_trans_do(rbio->c, NULL, NULL, BTREE_INSERT_NOFAIL,
-		      __bch2_rbio_narrow_crcs(&trans, rbio));
-}
-
-/* Inner part that may run in process context */
-static void __bch2_read_endio(struct work_struct *work)
-{
-	struct bch_read_bio *rbio =
-		container_of(work, struct bch_read_bio, work);
-	struct bch_fs *c	= rbio->c;
-	struct bch_dev *ca	= bch_dev_bkey_exists(c, rbio->pick.ptr.dev);
-	struct bio *src		= &rbio->bio;
-	struct bio *dst		= &bch2_rbio_parent(rbio)->bio;
-	struct bvec_iter dst_iter = rbio->bvec_iter;
-	struct bch_extent_crc_unpacked crc = rbio->pick.crc;
-	struct nonce nonce = extent_nonce(rbio->version, crc);
-	unsigned nofs_flags;
-	struct bch_csum csum;
-	int ret;
-
-	nofs_flags = memalloc_nofs_save();
-
-	/* Reset iterator for checksumming and copying bounced data: */
-	if (rbio->bounce) {
-		src->bi_iter.bi_size		= crc.compressed_size << 9;
-		src->bi_iter.bi_idx		= 0;
-		src->bi_iter.bi_bvec_done	= 0;
-	} else {
-		src->bi_iter			= rbio->bvec_iter;
-	}
-
-	csum = bch2_checksum_bio(c, crc.csum_type, nonce, src);
-	if (bch2_crc_cmp(csum, rbio->pick.crc.csum) && !c->opts.no_data_io)
-		goto csum_err;
-
-	/*
-	 * XXX
-	 * We need to rework the narrow_crcs path to deliver the read completion
-	 * first, and then punt to a different workqueue, otherwise we're
-	 * holding up reads while doing btree updates which is bad for memory
-	 * reclaim.
-	 */
-	if (unlikely(rbio->narrow_crcs))
-		bch2_rbio_narrow_crcs(rbio);
-
-	if (rbio->flags & BCH_READ_NODECODE)
-		goto nodecode;
-
-	/* Adjust crc to point to subset of data we want: */
-	crc.offset     += rbio->offset_into_extent;
-	crc.live_size	= bvec_iter_sectors(rbio->bvec_iter);
-
-	if (crc_is_compressed(crc)) {
-		ret = bch2_encrypt_bio(c, crc.csum_type, nonce, src);
-		if (ret)
-			goto decrypt_err;
-
-		if (bch2_bio_uncompress(c, src, dst, dst_iter, crc) &&
-		    !c->opts.no_data_io)
-			goto decompression_err;
-	} else {
-		/* don't need to decrypt the entire bio: */
-		nonce = nonce_add(nonce, crc.offset << 9);
-		bio_advance(src, crc.offset << 9);
-
-		BUG_ON(src->bi_iter.bi_size < dst_iter.bi_size);
-		src->bi_iter.bi_size = dst_iter.bi_size;
-
-		ret = bch2_encrypt_bio(c, crc.csum_type, nonce, src);
-		if (ret)
-			goto decrypt_err;
-
-		if (rbio->bounce) {
-			struct bvec_iter src_iter = src->bi_iter;
-
-			bio_copy_data_iter(dst, &dst_iter, src, &src_iter);
-		}
-	}
-
-	if (rbio->promote) {
-		/*
-		 * Re encrypt data we decrypted, so it's consistent with
-		 * rbio->crc:
-		 */
-		ret = bch2_encrypt_bio(c, crc.csum_type, nonce, src);
-		if (ret)
-			goto decrypt_err;
-
-		promote_start(rbio->promote, rbio);
-		rbio->promote = NULL;
-	}
-nodecode:
-	if (likely(!(rbio->flags & BCH_READ_IN_RETRY))) {
-		rbio = bch2_rbio_free(rbio);
-		bch2_rbio_done(rbio);
-	}
-out:
-	memalloc_nofs_restore(nofs_flags);
-	return;
-csum_err:
-	/*
-	 * Checksum error: if the bio wasn't bounced, we may have been
-	 * reading into buffers owned by userspace (that userspace can
-	 * scribble over) - retry the read, bouncing it this time:
-	 */
-	if (!rbio->bounce && (rbio->flags & BCH_READ_USER_MAPPED)) {
-		rbio->flags |= BCH_READ_MUST_BOUNCE;
-		bch2_rbio_error(rbio, READ_RETRY, BLK_STS_IOERR);
-		goto out;
-	}
-
-	bch_err_inum_offset_ratelimited(ca,
-		rbio->read_pos.inode,
-		rbio->read_pos.offset << 9,
-		"data checksum error: expected %0llx:%0llx got %0llx:%0llx (type %s)",
-		rbio->pick.crc.csum.hi, rbio->pick.crc.csum.lo,
-		csum.hi, csum.lo, bch2_csum_types[crc.csum_type]);
-	bch2_io_error(ca);
-	bch2_rbio_error(rbio, READ_RETRY_AVOID, BLK_STS_IOERR);
-	goto out;
-decompression_err:
-	bch_err_inum_offset_ratelimited(c, rbio->read_pos.inode,
-					rbio->read_pos.offset << 9,
-					"decompression error");
-	bch2_rbio_error(rbio, READ_ERR, BLK_STS_IOERR);
-	goto out;
-decrypt_err:
-	bch_err_inum_offset_ratelimited(c, rbio->read_pos.inode,
-					rbio->read_pos.offset << 9,
-					"decrypt error");
-	bch2_rbio_error(rbio, READ_ERR, BLK_STS_IOERR);
-	goto out;
-}
-
-static void bch2_read_endio(struct bio *bio)
-{
-	struct bch_read_bio *rbio =
-		container_of(bio, struct bch_read_bio, bio);
-	struct bch_fs *c	= rbio->c;
-	struct bch_dev *ca	= bch_dev_bkey_exists(c, rbio->pick.ptr.dev);
-	struct workqueue_struct *wq = NULL;
-	enum rbio_context context = RBIO_CONTEXT_NULL;
-
-	if (rbio->have_ioref) {
-		bch2_latency_acct(ca, rbio->submit_time, READ);
-		percpu_ref_put(&ca->io_ref);
-	}
-
-	if (!rbio->split)
-		rbio->bio.bi_end_io = rbio->end_io;
-
-	if (bch2_dev_inum_io_err_on(bio->bi_status, ca,
-				    rbio->read_pos.inode,
-				    rbio->read_pos.offset,
-				    "data read error: %s",
-			       bch2_blk_status_to_str(bio->bi_status))) {
-		bch2_rbio_error(rbio, READ_RETRY_AVOID, bio->bi_status);
-		return;
-	}
-
-	if (((rbio->flags & BCH_READ_RETRY_IF_STALE) && race_fault()) ||
-	    ptr_stale(ca, &rbio->pick.ptr)) {
-		trace_and_count(c, read_reuse_race, &rbio->bio);
-
-		if (rbio->flags & BCH_READ_RETRY_IF_STALE)
-			bch2_rbio_error(rbio, READ_RETRY, BLK_STS_AGAIN);
-		else
-			bch2_rbio_error(rbio, READ_ERR, BLK_STS_AGAIN);
-		return;
-	}
-
-	if (rbio->narrow_crcs ||
-	    rbio->promote ||
-	    crc_is_compressed(rbio->pick.crc) ||
-	    bch2_csum_type_is_encryption(rbio->pick.crc.csum_type))
-		context = RBIO_CONTEXT_UNBOUND,	wq = system_unbound_wq;
-	else if (rbio->pick.crc.csum_type)
-		context = RBIO_CONTEXT_HIGHPRI,	wq = system_highpri_wq;
-
-	bch2_rbio_punt(rbio, __bch2_read_endio, context, wq);
-}
-
-int __bch2_read_indirect_extent(struct btree_trans *trans,
-				unsigned *offset_into_extent,
-				struct bkey_buf *orig_k)
-{
-	struct btree_iter iter;
-	struct bkey_s_c k;
-	u64 reflink_offset;
-	int ret;
-
-	reflink_offset = le64_to_cpu(bkey_i_to_reflink_p(orig_k->k)->v.idx) +
-		*offset_into_extent;
-
-	k = bch2_bkey_get_iter(trans, &iter, BTREE_ID_reflink,
-			       POS(0, reflink_offset), 0);
-	ret = bkey_err(k);
-	if (ret)
-		goto err;
-
-	if (k.k->type != KEY_TYPE_reflink_v &&
-	    k.k->type != KEY_TYPE_indirect_inline_data) {
-		bch_err_inum_offset_ratelimited(trans->c,
-			orig_k->k->k.p.inode,
-			orig_k->k->k.p.offset << 9,
-			"%llu len %u points to nonexistent indirect extent %llu",
-			orig_k->k->k.p.offset,
-			orig_k->k->k.size,
-			reflink_offset);
-		bch2_inconsistent_error(trans->c);
-		ret = -EIO;
-		goto err;
-	}
-
-	*offset_into_extent = iter.pos.offset - bkey_start_offset(k.k);
-	bch2_bkey_buf_reassemble(orig_k, trans->c, k);
-err:
-	bch2_trans_iter_exit(trans, &iter);
-	return ret;
-}
-
-static noinline void read_from_stale_dirty_pointer(struct btree_trans *trans,
-						   struct bkey_s_c k,
-						   struct bch_extent_ptr ptr)
-{
-	struct bch_fs *c = trans->c;
-	struct bch_dev *ca = bch_dev_bkey_exists(c, ptr.dev);
-	struct btree_iter iter;
-	struct printbuf buf = PRINTBUF;
-	int ret;
-
-	bch2_trans_iter_init(trans, &iter, BTREE_ID_alloc,
-			     PTR_BUCKET_POS(c, &ptr),
-			     BTREE_ITER_CACHED);
-
-	prt_printf(&buf, "Attempting to read from stale dirty pointer:");
-	printbuf_indent_add(&buf, 2);
-	prt_newline(&buf);
-
-	bch2_bkey_val_to_text(&buf, c, k);
-	prt_newline(&buf);
-
-	prt_printf(&buf, "memory gen: %u", *bucket_gen(ca, iter.pos.offset));
-
-	ret = lockrestart_do(trans, bkey_err(k = bch2_btree_iter_peek_slot(&iter)));
-	if (!ret) {
-		prt_newline(&buf);
-		bch2_bkey_val_to_text(&buf, c, k);
-	}
-
-	bch2_fs_inconsistent(c, "%s", buf.buf);
-
-	bch2_trans_iter_exit(trans, &iter);
-	printbuf_exit(&buf);
-}
-
-int __bch2_read_extent(struct btree_trans *trans, struct bch_read_bio *orig,
-		       struct bvec_iter iter, struct bpos read_pos,
-		       enum btree_id data_btree, struct bkey_s_c k,
-		       unsigned offset_into_extent,
-		       struct bch_io_failures *failed, unsigned flags)
-{
-	struct bch_fs *c = trans->c;
-	struct extent_ptr_decoded pick;
-	struct bch_read_bio *rbio = NULL;
-	struct bch_dev *ca = NULL;
-	struct promote_op *promote = NULL;
-	bool bounce = false, read_full = false, narrow_crcs = false;
-	struct bpos data_pos = bkey_start_pos(k.k);
-	int pick_ret;
-
-	if (bkey_extent_is_inline_data(k.k)) {
-		unsigned bytes = min_t(unsigned, iter.bi_size,
-				       bkey_inline_data_bytes(k.k));
-
-		swap(iter.bi_size, bytes);
-		memcpy_to_bio(&orig->bio, iter, bkey_inline_data_p(k));
-		swap(iter.bi_size, bytes);
-		bio_advance_iter(&orig->bio, &iter, bytes);
-		zero_fill_bio_iter(&orig->bio, iter);
-		goto out_read_done;
-	}
-retry_pick:
-	pick_ret = bch2_bkey_pick_read_device(c, k, failed, &pick);
-
-	/* hole or reservation - just zero fill: */
-	if (!pick_ret)
-		goto hole;
-
-	if (pick_ret < 0) {
-		bch_err_inum_offset_ratelimited(c,
-				read_pos.inode, read_pos.offset << 9,
-				"no device to read from");
-		goto err;
-	}
-
-	ca = bch_dev_bkey_exists(c, pick.ptr.dev);
-
-	/*
-	 * Stale dirty pointers are treated as IO errors, but @failed isn't
-	 * allocated unless we're in the retry path - so if we're not in the
-	 * retry path, don't check here, it'll be caught in bch2_read_endio()
-	 * and we'll end up in the retry path:
-	 */
-	if ((flags & BCH_READ_IN_RETRY) &&
-	    !pick.ptr.cached &&
-	    unlikely(ptr_stale(ca, &pick.ptr))) {
-		read_from_stale_dirty_pointer(trans, k, pick.ptr);
-		bch2_mark_io_failure(failed, &pick);
-		goto retry_pick;
-	}
-
-	/*
-	 * Unlock the iterator while the btree node's lock is still in
-	 * cache, before doing the IO:
-	 */
-	bch2_trans_unlock(trans);
-
-	if (flags & BCH_READ_NODECODE) {
-		/*
-		 * can happen if we retry, and the extent we were going to read
-		 * has been merged in the meantime:
-		 */
-		if (pick.crc.compressed_size > orig->bio.bi_vcnt * PAGE_SECTORS)
-			goto hole;
-
-		iter.bi_size	= pick.crc.compressed_size << 9;
-		goto get_bio;
-	}
-
-	if (!(flags & BCH_READ_LAST_FRAGMENT) ||
-	    bio_flagged(&orig->bio, BIO_CHAIN))
-		flags |= BCH_READ_MUST_CLONE;
-
-	narrow_crcs = !(flags & BCH_READ_IN_RETRY) &&
-		bch2_can_narrow_extent_crcs(k, pick.crc);
-
-	if (narrow_crcs && (flags & BCH_READ_USER_MAPPED))
-		flags |= BCH_READ_MUST_BOUNCE;
-
-	EBUG_ON(offset_into_extent + bvec_iter_sectors(iter) > k.k->size);
-
-	if (crc_is_compressed(pick.crc) ||
-	    (pick.crc.csum_type != BCH_CSUM_none &&
-	     (bvec_iter_sectors(iter) != pick.crc.uncompressed_size ||
-	      (bch2_csum_type_is_encryption(pick.crc.csum_type) &&
-	       (flags & BCH_READ_USER_MAPPED)) ||
-	      (flags & BCH_READ_MUST_BOUNCE)))) {
-		read_full = true;
-		bounce = true;
-	}
-
-	if (orig->opts.promote_target)
-		promote = promote_alloc(trans, iter, k, &pick, orig->opts, flags,
-					&rbio, &bounce, &read_full);
-
-	if (!read_full) {
-		EBUG_ON(crc_is_compressed(pick.crc));
-		EBUG_ON(pick.crc.csum_type &&
-			(bvec_iter_sectors(iter) != pick.crc.uncompressed_size ||
-			 bvec_iter_sectors(iter) != pick.crc.live_size ||
-			 pick.crc.offset ||
-			 offset_into_extent));
-
-		data_pos.offset += offset_into_extent;
-		pick.ptr.offset += pick.crc.offset +
-			offset_into_extent;
-		offset_into_extent		= 0;
-		pick.crc.compressed_size	= bvec_iter_sectors(iter);
-		pick.crc.uncompressed_size	= bvec_iter_sectors(iter);
-		pick.crc.offset			= 0;
-		pick.crc.live_size		= bvec_iter_sectors(iter);
-		offset_into_extent		= 0;
-	}
-get_bio:
-	if (rbio) {
-		/*
-		 * promote already allocated bounce rbio:
-		 * promote needs to allocate a bio big enough for uncompressing
-		 * data in the write path, but we're not going to use it all
-		 * here:
-		 */
-		EBUG_ON(rbio->bio.bi_iter.bi_size <
-		       pick.crc.compressed_size << 9);
-		rbio->bio.bi_iter.bi_size =
-			pick.crc.compressed_size << 9;
-	} else if (bounce) {
-		unsigned sectors = pick.crc.compressed_size;
-
-		rbio = rbio_init(bio_alloc_bioset(NULL,
-						  DIV_ROUND_UP(sectors, PAGE_SECTORS),
-						  0,
-						  GFP_NOFS,
-						  &c->bio_read_split),
-				 orig->opts);
-
-		bch2_bio_alloc_pages_pool(c, &rbio->bio, sectors << 9);
-		rbio->bounce	= true;
-		rbio->split	= true;
-	} else if (flags & BCH_READ_MUST_CLONE) {
-		/*
-		 * Have to clone if there were any splits, due to error
-		 * reporting issues (if a split errored, and retrying didn't
-		 * work, when it reports the error to its parent (us) we don't
-		 * know if the error was from our bio, and we should retry, or
-		 * from the whole bio, in which case we don't want to retry and
-		 * lose the error)
-		 */
-		rbio = rbio_init(bio_alloc_clone(NULL, &orig->bio, GFP_NOFS,
-						 &c->bio_read_split),
-				 orig->opts);
-		rbio->bio.bi_iter = iter;
-		rbio->split	= true;
-	} else {
-		rbio = orig;
-		rbio->bio.bi_iter = iter;
-		EBUG_ON(bio_flagged(&rbio->bio, BIO_CHAIN));
-	}
-
-	EBUG_ON(bio_sectors(&rbio->bio) != pick.crc.compressed_size);
-
-	rbio->c			= c;
-	rbio->submit_time	= local_clock();
-	if (rbio->split)
-		rbio->parent	= orig;
-	else
-		rbio->end_io	= orig->bio.bi_end_io;
-	rbio->bvec_iter		= iter;
-	rbio->offset_into_extent= offset_into_extent;
-	rbio->flags		= flags;
-	rbio->have_ioref	= pick_ret > 0 && bch2_dev_get_ioref(ca, READ);
-	rbio->narrow_crcs	= narrow_crcs;
-	rbio->hole		= 0;
-	rbio->retry		= 0;
-	rbio->context		= 0;
-	/* XXX: only initialize this if needed */
-	rbio->devs_have		= bch2_bkey_devs(k);
-	rbio->pick		= pick;
-	rbio->subvol		= orig->subvol;
-	rbio->read_pos		= read_pos;
-	rbio->data_btree	= data_btree;
-	rbio->data_pos		= data_pos;
-	rbio->version		= k.k->version;
-	rbio->promote		= promote;
-	INIT_WORK(&rbio->work, NULL);
-
-	rbio->bio.bi_opf	= orig->bio.bi_opf;
-	rbio->bio.bi_iter.bi_sector = pick.ptr.offset;
-	rbio->bio.bi_end_io	= bch2_read_endio;
-
-	if (rbio->bounce)
-		trace_and_count(c, read_bounce, &rbio->bio);
-
-	this_cpu_add(c->counters[BCH_COUNTER_io_read], bio_sectors(&rbio->bio));
-	bch2_increment_clock(c, bio_sectors(&rbio->bio), READ);
-
-	/*
-	 * If it's being moved internally, we don't want to flag it as a cache
-	 * hit:
-	 */
-	if (pick.ptr.cached && !(flags & BCH_READ_NODECODE))
-		bch2_bucket_io_time_reset(trans, pick.ptr.dev,
-			PTR_BUCKET_NR(ca, &pick.ptr), READ);
-
-	if (!(flags & (BCH_READ_IN_RETRY|BCH_READ_LAST_FRAGMENT))) {
-		bio_inc_remaining(&orig->bio);
-		trace_and_count(c, read_split, &orig->bio);
-	}
-
-	if (!rbio->pick.idx) {
-		if (!rbio->have_ioref) {
-			bch_err_inum_offset_ratelimited(c,
-					read_pos.inode,
-					read_pos.offset << 9,
-					"no device to read from");
-			bch2_rbio_error(rbio, READ_RETRY_AVOID, BLK_STS_IOERR);
-			goto out;
-		}
-
-		this_cpu_add(ca->io_done->sectors[READ][BCH_DATA_user],
-			     bio_sectors(&rbio->bio));
-		bio_set_dev(&rbio->bio, ca->disk_sb.bdev);
-
-		if (unlikely(c->opts.no_data_io)) {
-			if (likely(!(flags & BCH_READ_IN_RETRY)))
-				bio_endio(&rbio->bio);
-		} else {
-			if (likely(!(flags & BCH_READ_IN_RETRY)))
-				submit_bio(&rbio->bio);
-			else
-				submit_bio_wait(&rbio->bio);
-		}
-
-		/*
-		 * We just submitted IO which may block, we expect relock fail
-		 * events and shouldn't count them:
-		 */
-		trans->notrace_relock_fail = true;
-	} else {
-		/* Attempting reconstruct read: */
-		if (bch2_ec_read_extent(c, rbio)) {
-			bch2_rbio_error(rbio, READ_RETRY_AVOID, BLK_STS_IOERR);
-			goto out;
-		}
-
-		if (likely(!(flags & BCH_READ_IN_RETRY)))
-			bio_endio(&rbio->bio);
-	}
-out:
-	if (likely(!(flags & BCH_READ_IN_RETRY))) {
-		return 0;
-	} else {
-		int ret;
-
-		rbio->context = RBIO_CONTEXT_UNBOUND;
-		bch2_read_endio(&rbio->bio);
-
-		ret = rbio->retry;
-		rbio = bch2_rbio_free(rbio);
-
-		if (ret == READ_RETRY_AVOID) {
-			bch2_mark_io_failure(failed, &pick);
-			ret = READ_RETRY;
-		}
-
-		if (!ret)
-			goto out_read_done;
-
-		return ret;
-	}
-
-err:
-	if (flags & BCH_READ_IN_RETRY)
-		return READ_ERR;
-
-	orig->bio.bi_status = BLK_STS_IOERR;
-	goto out_read_done;
-
-hole:
-	/*
-	 * won't normally happen in the BCH_READ_NODECODE
-	 * (bch2_move_extent()) path, but if we retry and the extent we wanted
-	 * to read no longer exists we have to signal that:
-	 */
-	if (flags & BCH_READ_NODECODE)
-		orig->hole = true;
-
-	zero_fill_bio_iter(&orig->bio, iter);
-out_read_done:
-	if (flags & BCH_READ_LAST_FRAGMENT)
-		bch2_rbio_done(orig);
-	return 0;
-}
-
-void __bch2_read(struct bch_fs *c, struct bch_read_bio *rbio,
-		 struct bvec_iter bvec_iter, subvol_inum inum,
-		 struct bch_io_failures *failed, unsigned flags)
-{
-	struct btree_trans trans;
-	struct btree_iter iter;
-	struct bkey_buf sk;
-	struct bkey_s_c k;
-	u32 snapshot;
-	int ret;
-
-	BUG_ON(flags & BCH_READ_NODECODE);
-
-	bch2_bkey_buf_init(&sk);
-	bch2_trans_init(&trans, c, 0, 0);
-retry:
-	bch2_trans_begin(&trans);
-	iter = (struct btree_iter) { NULL };
-
-	ret = bch2_subvolume_get_snapshot(&trans, inum.subvol, &snapshot);
-	if (ret)
-		goto err;
-
-	bch2_trans_iter_init(&trans, &iter, BTREE_ID_extents,
-			     SPOS(inum.inum, bvec_iter.bi_sector, snapshot),
-			     BTREE_ITER_SLOTS);
-	while (1) {
-		unsigned bytes, sectors, offset_into_extent;
-		enum btree_id data_btree = BTREE_ID_extents;
-
-		/*
-		 * read_extent -> io_time_reset may cause a transaction restart
-		 * without returning an error, we need to check for that here:
-		 */
-		ret = bch2_trans_relock(&trans);
-		if (ret)
-			break;
-
-		bch2_btree_iter_set_pos(&iter,
-				POS(inum.inum, bvec_iter.bi_sector));
-
-		k = bch2_btree_iter_peek_slot(&iter);
-		ret = bkey_err(k);
-		if (ret)
-			break;
-
-		offset_into_extent = iter.pos.offset -
-			bkey_start_offset(k.k);
-		sectors = k.k->size - offset_into_extent;
-
-		bch2_bkey_buf_reassemble(&sk, c, k);
-
-		ret = bch2_read_indirect_extent(&trans, &data_btree,
-					&offset_into_extent, &sk);
-		if (ret)
-			break;
-
-		k = bkey_i_to_s_c(sk.k);
-
-		/*
-		 * With indirect extents, the amount of data to read is the min
-		 * of the original extent and the indirect extent:
-		 */
-		sectors = min(sectors, k.k->size - offset_into_extent);
-
-		bytes = min(sectors, bvec_iter_sectors(bvec_iter)) << 9;
-		swap(bvec_iter.bi_size, bytes);
-
-		if (bvec_iter.bi_size == bytes)
-			flags |= BCH_READ_LAST_FRAGMENT;
-
-		ret = __bch2_read_extent(&trans, rbio, bvec_iter, iter.pos,
-					 data_btree, k,
-					 offset_into_extent, failed, flags);
-		if (ret)
-			break;
-
-		if (flags & BCH_READ_LAST_FRAGMENT)
-			break;
-
-		swap(bvec_iter.bi_size, bytes);
-		bio_advance_iter(&rbio->bio, &bvec_iter, bytes);
-
-		ret = btree_trans_too_many_iters(&trans);
-		if (ret)
-			break;
-	}
-err:
-	bch2_trans_iter_exit(&trans, &iter);
-
-	if (bch2_err_matches(ret, BCH_ERR_transaction_restart) ||
-	    ret == READ_RETRY ||
-	    ret == READ_RETRY_AVOID)
-		goto retry;
-
-	bch2_trans_exit(&trans);
-	bch2_bkey_buf_exit(&sk, c);
-
-	if (ret) {
-		bch_err_inum_offset_ratelimited(c, inum.inum,
-						bvec_iter.bi_sector << 9,
-						"read error %i from btree lookup", ret);
-		rbio->bio.bi_status = BLK_STS_IOERR;
-		bch2_rbio_done(rbio);
-	}
-}
-
-void bch2_fs_io_exit(struct bch_fs *c)
-{
-	if (c->promote_table.tbl)
-		rhashtable_destroy(&c->promote_table);
-	mempool_exit(&c->bio_bounce_pages);
-	bioset_exit(&c->bio_write);
-	bioset_exit(&c->bio_read_split);
-	bioset_exit(&c->bio_read);
-}
-
-int bch2_fs_io_init(struct bch_fs *c)
-{
-	if (bioset_init(&c->bio_read, 1, offsetof(struct bch_read_bio, bio),
-			BIOSET_NEED_BVECS))
-		return -BCH_ERR_ENOMEM_bio_read_init;
-
-	if (bioset_init(&c->bio_read_split, 1, offsetof(struct bch_read_bio, bio),
-			BIOSET_NEED_BVECS))
-		return -BCH_ERR_ENOMEM_bio_read_split_init;
-
-	if (bioset_init(&c->bio_write, 1, offsetof(struct bch_write_bio, bio),
-			BIOSET_NEED_BVECS))
-		return -BCH_ERR_ENOMEM_bio_write_init;
-
-	if (mempool_init_page_pool(&c->bio_bounce_pages,
-				   max_t(unsigned,
-					 c->opts.btree_node_size,
-					 c->opts.encoded_extent_max) /
-				   PAGE_SIZE, 0))
-		return -BCH_ERR_ENOMEM_bio_bounce_pages_init;
-
-	if (rhashtable_init(&c->promote_table, &bch_promote_params))
-		return -BCH_ERR_ENOMEM_promote_table_init;
-
-	return 0;
-}
diff --git a/fs/bcachefs/io.h b/fs/bcachefs/io.h
deleted file mode 100644
index 831e3f1..0000000
--- a/fs/bcachefs/io.h
+++ /dev/null
@@ -1,202 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-#ifndef _BCACHEFS_IO_H
-#define _BCACHEFS_IO_H
-
-#include "checksum.h"
-#include "bkey_buf.h"
-#include "io_types.h"
-
-#define to_wbio(_bio)			\
-	container_of((_bio), struct bch_write_bio, bio)
-
-#define to_rbio(_bio)			\
-	container_of((_bio), struct bch_read_bio, bio)
-
-void bch2_bio_free_pages_pool(struct bch_fs *, struct bio *);
-void bch2_bio_alloc_pages_pool(struct bch_fs *, struct bio *, size_t);
-
-#ifndef CONFIG_BCACHEFS_NO_LATENCY_ACCT
-void bch2_latency_acct(struct bch_dev *, u64, int);
-#else
-static inline void bch2_latency_acct(struct bch_dev *ca, u64 submit_time, int rw) {}
-#endif
-
-void bch2_submit_wbio_replicas(struct bch_write_bio *, struct bch_fs *,
-			       enum bch_data_type, const struct bkey_i *, bool);
-
-#define BLK_STS_REMOVED		((__force blk_status_t)128)
-
-const char *bch2_blk_status_to_str(blk_status_t);
-
-#define BCH_WRITE_FLAGS()		\
-	x(ALLOC_NOWAIT)			\
-	x(CACHED)			\
-	x(DATA_ENCODED)			\
-	x(PAGES_STABLE)			\
-	x(PAGES_OWNED)			\
-	x(ONLY_SPECIFIED_DEVS)		\
-	x(WROTE_DATA_INLINE)		\
-	x(FROM_INTERNAL)		\
-	x(CHECK_ENOSPC)			\
-	x(SYNC)				\
-	x(MOVE)				\
-	x(IN_WORKER)			\
-	x(DONE)				\
-	x(IO_ERROR)			\
-	x(CONVERT_UNWRITTEN)
-
-enum __bch_write_flags {
-#define x(f)	__BCH_WRITE_##f,
-	BCH_WRITE_FLAGS()
-#undef x
-};
-
-enum bch_write_flags {
-#define x(f)	BCH_WRITE_##f = BIT(__BCH_WRITE_##f),
-	BCH_WRITE_FLAGS()
-#undef x
-};
-
-static inline struct workqueue_struct *index_update_wq(struct bch_write_op *op)
-{
-	return op->watermark == BCH_WATERMARK_copygc
-		? op->c->copygc_wq
-		: op->c->btree_update_wq;
-}
-
-int bch2_sum_sector_overwrites(struct btree_trans *, struct btree_iter *,
-			       struct bkey_i *, bool *, s64 *, s64 *);
-int bch2_extent_update(struct btree_trans *, subvol_inum,
-		       struct btree_iter *, struct bkey_i *,
-		       struct disk_reservation *, u64, s64 *, bool);
-int bch2_extent_fallocate(struct btree_trans *, subvol_inum, struct btree_iter *,
-			  unsigned, struct bch_io_opts, s64 *,
-			  struct write_point_specifier);
-
-int bch2_fpunch_at(struct btree_trans *, struct btree_iter *,
-		   subvol_inum, u64, s64 *);
-int bch2_fpunch(struct bch_fs *c, subvol_inum, u64, u64, s64 *);
-
-static inline void bch2_write_op_init(struct bch_write_op *op, struct bch_fs *c,
-				      struct bch_io_opts opts)
-{
-	op->c			= c;
-	op->end_io		= NULL;
-	op->flags		= 0;
-	op->written		= 0;
-	op->error		= 0;
-	op->csum_type		= bch2_data_checksum_type(c, opts);
-	op->compression_opt	= opts.compression;
-	op->nr_replicas		= 0;
-	op->nr_replicas_required = c->opts.data_replicas_required;
-	op->watermark		= BCH_WATERMARK_normal;
-	op->incompressible	= 0;
-	op->open_buckets.nr	= 0;
-	op->devs_have.nr	= 0;
-	op->target		= 0;
-	op->opts		= opts;
-	op->subvol		= 0;
-	op->pos			= POS_MAX;
-	op->version		= ZERO_VERSION;
-	op->write_point		= (struct write_point_specifier) { 0 };
-	op->res			= (struct disk_reservation) { 0 };
-	op->new_i_size		= U64_MAX;
-	op->i_sectors_delta	= 0;
-	op->devs_need_flush	= NULL;
-}
-
-void bch2_write(struct closure *);
-
-void bch2_write_point_do_index_updates(struct work_struct *);
-
-static inline struct bch_write_bio *wbio_init(struct bio *bio)
-{
-	struct bch_write_bio *wbio = to_wbio(bio);
-
-	memset(&wbio->wbio, 0, sizeof(wbio->wbio));
-	return wbio;
-}
-
-void bch2_write_op_to_text(struct printbuf *, struct bch_write_op *);
-
-struct bch_devs_mask;
-struct cache_promote_op;
-struct extent_ptr_decoded;
-
-int __bch2_read_indirect_extent(struct btree_trans *, unsigned *,
-				struct bkey_buf *);
-
-static inline int bch2_read_indirect_extent(struct btree_trans *trans,
-					    enum btree_id *data_btree,
-					    unsigned *offset_into_extent,
-					    struct bkey_buf *k)
-{
-	if (k->k->k.type != KEY_TYPE_reflink_p)
-		return 0;
-
-	*data_btree = BTREE_ID_reflink;
-	return __bch2_read_indirect_extent(trans, offset_into_extent, k);
-}
-
-enum bch_read_flags {
-	BCH_READ_RETRY_IF_STALE		= 1 << 0,
-	BCH_READ_MAY_PROMOTE		= 1 << 1,
-	BCH_READ_USER_MAPPED		= 1 << 2,
-	BCH_READ_NODECODE		= 1 << 3,
-	BCH_READ_LAST_FRAGMENT		= 1 << 4,
-
-	/* internal: */
-	BCH_READ_MUST_BOUNCE		= 1 << 5,
-	BCH_READ_MUST_CLONE		= 1 << 6,
-	BCH_READ_IN_RETRY		= 1 << 7,
-};
-
-int __bch2_read_extent(struct btree_trans *, struct bch_read_bio *,
-		       struct bvec_iter, struct bpos, enum btree_id,
-		       struct bkey_s_c, unsigned,
-		       struct bch_io_failures *, unsigned);
-
-static inline void bch2_read_extent(struct btree_trans *trans,
-			struct bch_read_bio *rbio, struct bpos read_pos,
-			enum btree_id data_btree, struct bkey_s_c k,
-			unsigned offset_into_extent, unsigned flags)
-{
-	__bch2_read_extent(trans, rbio, rbio->bio.bi_iter, read_pos,
-			   data_btree, k, offset_into_extent, NULL, flags);
-}
-
-void __bch2_read(struct bch_fs *, struct bch_read_bio *, struct bvec_iter,
-		 subvol_inum, struct bch_io_failures *, unsigned flags);
-
-static inline void bch2_read(struct bch_fs *c, struct bch_read_bio *rbio,
-			     subvol_inum inum)
-{
-	struct bch_io_failures failed = { .nr = 0 };
-
-	BUG_ON(rbio->_state);
-
-	rbio->c = c;
-	rbio->start_time = local_clock();
-	rbio->subvol = inum.subvol;
-
-	__bch2_read(c, rbio, rbio->bio.bi_iter, inum, &failed,
-		    BCH_READ_RETRY_IF_STALE|
-		    BCH_READ_MAY_PROMOTE|
-		    BCH_READ_USER_MAPPED);
-}
-
-static inline struct bch_read_bio *rbio_init(struct bio *bio,
-					     struct bch_io_opts opts)
-{
-	struct bch_read_bio *rbio = to_rbio(bio);
-
-	rbio->_state	= 0;
-	rbio->promote	= NULL;
-	rbio->opts	= opts;
-	return rbio;
-}
-
-void bch2_fs_io_exit(struct bch_fs *);
-int bch2_fs_io_init(struct bch_fs *);
-
-#endif /* _BCACHEFS_IO_H */
diff --git a/fs/bcachefs/io_misc.c b/fs/bcachefs/io_misc.c
new file mode 100644
index 0000000..c04e5da
--- /dev/null
+++ b/fs/bcachefs/io_misc.c
@@ -0,0 +1,215 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * io_misc.c - fallocate, fpunch, truncate:
+ */
+
+#include "bcachefs.h"
+#include "alloc_foreground.h"
+#include "bkey_buf.h"
+#include "btree_update.h"
+#include "buckets.h"
+#include "clock.h"
+#include "extents.h"
+#include "io_misc.h"
+#include "io_write.h"
+#include "subvolume.h"
+
+/* Overwrites whatever was present with zeroes: */
+int bch2_extent_fallocate(struct btree_trans *trans,
+			  subvol_inum inum,
+			  struct btree_iter *iter,
+			  unsigned sectors,
+			  struct bch_io_opts opts,
+			  s64 *i_sectors_delta,
+			  struct write_point_specifier write_point)
+{
+	struct bch_fs *c = trans->c;
+	struct disk_reservation disk_res = { 0 };
+	struct closure cl;
+	struct open_buckets open_buckets = { 0 };
+	struct bkey_s_c k;
+	struct bkey_buf old, new;
+	unsigned sectors_allocated = 0;
+	bool have_reservation = false;
+	bool unwritten = opts.nocow &&
+	    c->sb.version >= bcachefs_metadata_version_unwritten_extents;
+	int ret;
+
+	bch2_bkey_buf_init(&old);
+	bch2_bkey_buf_init(&new);
+	closure_init_stack(&cl);
+
+	k = bch2_btree_iter_peek_slot(iter);
+	ret = bkey_err(k);
+	if (ret)
+		return ret;
+
+	sectors = min_t(u64, sectors, k.k->p.offset - iter->pos.offset);
+
+	if (!have_reservation) {
+		unsigned new_replicas =
+			max(0, (int) opts.data_replicas -
+			    (int) bch2_bkey_nr_ptrs_fully_allocated(k));
+		/*
+		 * Get a disk reservation before (in the nocow case) calling
+		 * into the allocator:
+		 */
+		ret = bch2_disk_reservation_get(c, &disk_res, sectors, new_replicas, 0);
+		if (unlikely(ret))
+			goto err;
+
+		bch2_bkey_buf_reassemble(&old, c, k);
+	}
+
+	if (have_reservation) {
+		if (!bch2_extents_match(k, bkey_i_to_s_c(old.k)))
+			goto err;
+
+		bch2_key_resize(&new.k->k, sectors);
+	} else if (!unwritten) {
+		struct bkey_i_reservation *reservation;
+
+		bch2_bkey_buf_realloc(&new, c, sizeof(*reservation) / sizeof(u64));
+		reservation = bkey_reservation_init(new.k);
+		reservation->k.p = iter->pos;
+		bch2_key_resize(&reservation->k, sectors);
+		reservation->v.nr_replicas = opts.data_replicas;
+	} else {
+		struct bkey_i_extent *e;
+		struct bch_devs_list devs_have;
+		struct write_point *wp;
+		struct bch_extent_ptr *ptr;
+
+		devs_have.nr = 0;
+
+		bch2_bkey_buf_realloc(&new, c, BKEY_EXTENT_U64s_MAX);
+
+		e = bkey_extent_init(new.k);
+		e->k.p = iter->pos;
+
+		ret = bch2_alloc_sectors_start_trans(trans,
+				opts.foreground_target,
+				false,
+				write_point,
+				&devs_have,
+				opts.data_replicas,
+				opts.data_replicas,
+				BCH_WATERMARK_normal, 0, &cl, &wp);
+		if (bch2_err_matches(ret, BCH_ERR_operation_blocked))
+			ret = -BCH_ERR_transaction_restart_nested;
+		if (ret)
+			goto err;
+
+		sectors = min(sectors, wp->sectors_free);
+		sectors_allocated = sectors;
+
+		bch2_key_resize(&e->k, sectors);
+
+		bch2_open_bucket_get(c, wp, &open_buckets);
+		bch2_alloc_sectors_append_ptrs(c, wp, &e->k_i, sectors, false);
+		bch2_alloc_sectors_done(c, wp);
+
+		extent_for_each_ptr(extent_i_to_s(e), ptr)
+			ptr->unwritten = true;
+	}
+
+	have_reservation = true;
+
+	ret = bch2_extent_update(trans, inum, iter, new.k, &disk_res,
+				 0, i_sectors_delta, true);
+err:
+	if (!ret && sectors_allocated)
+		bch2_increment_clock(c, sectors_allocated, WRITE);
+
+	bch2_open_buckets_put(c, &open_buckets);
+	bch2_disk_reservation_put(c, &disk_res);
+	bch2_bkey_buf_exit(&new, c);
+	bch2_bkey_buf_exit(&old, c);
+
+	if (closure_nr_remaining(&cl) != 1) {
+		bch2_trans_unlock(trans);
+		closure_sync(&cl);
+	}
+
+	return ret;
+}
+
+/*
+ * Returns -BCH_ERR_transacton_restart if we had to drop locks:
+ */
+int bch2_fpunch_at(struct btree_trans *trans, struct btree_iter *iter,
+		   subvol_inum inum, u64 end,
+		   s64 *i_sectors_delta)
+{
+	struct bch_fs *c	= trans->c;
+	unsigned max_sectors	= KEY_SIZE_MAX & (~0 << c->block_bits);
+	struct bpos end_pos = POS(inum.inum, end);
+	struct bkey_s_c k;
+	int ret = 0, ret2 = 0;
+	u32 snapshot;
+
+	while (!ret ||
+	       bch2_err_matches(ret, BCH_ERR_transaction_restart)) {
+		struct disk_reservation disk_res =
+			bch2_disk_reservation_init(c, 0);
+		struct bkey_i delete;
+
+		if (ret)
+			ret2 = ret;
+
+		bch2_trans_begin(trans);
+
+		ret = bch2_subvolume_get_snapshot(trans, inum.subvol, &snapshot);
+		if (ret)
+			continue;
+
+		bch2_btree_iter_set_snapshot(iter, snapshot);
+
+		/*
+		 * peek_upto() doesn't have ideal semantics for extents:
+		 */
+		k = bch2_btree_iter_peek_upto(iter, end_pos);
+		if (!k.k)
+			break;
+
+		ret = bkey_err(k);
+		if (ret)
+			continue;
+
+		bkey_init(&delete.k);
+		delete.k.p = iter->pos;
+
+		/* create the biggest key we can */
+		bch2_key_resize(&delete.k, max_sectors);
+		bch2_cut_back(end_pos, &delete);
+
+		ret = bch2_extent_update(trans, inum, iter, &delete,
+				&disk_res, 0, i_sectors_delta, false);
+		bch2_disk_reservation_put(c, &disk_res);
+	}
+
+	return ret ?: ret2;
+}
+
+int bch2_fpunch(struct bch_fs *c, subvol_inum inum, u64 start, u64 end,
+		s64 *i_sectors_delta)
+{
+	struct btree_trans trans;
+	struct btree_iter iter;
+	int ret;
+
+	bch2_trans_init(&trans, c, BTREE_ITER_MAX, 1024);
+	bch2_trans_iter_init(&trans, &iter, BTREE_ID_extents,
+			     POS(inum.inum, start),
+			     BTREE_ITER_INTENT);
+
+	ret = bch2_fpunch_at(&trans, &iter, inum, end, i_sectors_delta);
+
+	bch2_trans_iter_exit(&trans, &iter);
+	bch2_trans_exit(&trans);
+
+	if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
+		ret = 0;
+
+	return ret;
+}
diff --git a/fs/bcachefs/io_misc.h b/fs/bcachefs/io_misc.h
new file mode 100644
index 0000000..46e9ce3
--- /dev/null
+++ b/fs/bcachefs/io_misc.h
@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _BCACHEFS_IO_MISC_H
+#define _BCACHEFS_IO_MISC_H
+
+int bch2_extent_fallocate(struct btree_trans *, subvol_inum, struct btree_iter *,
+			  unsigned, struct bch_io_opts, s64 *,
+			  struct write_point_specifier);
+int bch2_fpunch_at(struct btree_trans *, struct btree_iter *,
+		   subvol_inum, u64, s64 *);
+int bch2_fpunch(struct bch_fs *c, subvol_inum, u64, u64, s64 *);
+
+#endif /* _BCACHEFS_IO_MISC_H */
diff --git a/fs/bcachefs/io_read.c b/fs/bcachefs/io_read.c
new file mode 100644
index 0000000..cd62bf7
--- /dev/null
+++ b/fs/bcachefs/io_read.c
@@ -0,0 +1,1207 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Some low level IO code, and hacks for various block layer limitations
+ *
+ * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
+ * Copyright 2012 Google, Inc.
+ */
+
+#include "bcachefs.h"
+#include "alloc_background.h"
+#include "alloc_foreground.h"
+#include "btree_update.h"
+#include "buckets.h"
+#include "checksum.h"
+#include "clock.h"
+#include "compress.h"
+#include "data_update.h"
+#include "disk_groups.h"
+#include "ec.h"
+#include "error.h"
+#include "io_read.h"
+#include "io_misc.h"
+#include "io_write.h"
+#include "subvolume.h"
+#include "trace.h"
+
+#ifndef CONFIG_BCACHEFS_NO_LATENCY_ACCT
+
+static bool bch2_target_congested(struct bch_fs *c, u16 target)
+{
+	const struct bch_devs_mask *devs;
+	unsigned d, nr = 0, total = 0;
+	u64 now = local_clock(), last;
+	s64 congested;
+	struct bch_dev *ca;
+
+	if (!target)
+		return false;
+
+	rcu_read_lock();
+	devs = bch2_target_to_mask(c, target) ?:
+		&c->rw_devs[BCH_DATA_user];
+
+	for_each_set_bit(d, devs->d, BCH_SB_MEMBERS_MAX) {
+		ca = rcu_dereference(c->devs[d]);
+		if (!ca)
+			continue;
+
+		congested = atomic_read(&ca->congested);
+		last = READ_ONCE(ca->congested_last);
+		if (time_after64(now, last))
+			congested -= (now - last) >> 12;
+
+		total += max(congested, 0LL);
+		nr++;
+	}
+	rcu_read_unlock();
+
+	return bch2_rand_range(nr * CONGESTED_MAX) < total;
+}
+
+#else
+
+static bool bch2_target_congested(struct bch_fs *c, u16 target)
+{
+	return false;
+}
+
+#endif
+
+/* Cache promotion on read */
+
+struct promote_op {
+	struct rcu_head		rcu;
+	u64			start_time;
+
+	struct rhash_head	hash;
+	struct bpos		pos;
+
+	struct data_update	write;
+	struct bio_vec		bi_inline_vecs[0]; /* must be last */
+};
+
+static const struct rhashtable_params bch_promote_params = {
+	.head_offset	= offsetof(struct promote_op, hash),
+	.key_offset	= offsetof(struct promote_op, pos),
+	.key_len	= sizeof(struct bpos),
+};
+
+static inline bool should_promote(struct bch_fs *c, struct bkey_s_c k,
+				  struct bpos pos,
+				  struct bch_io_opts opts,
+				  unsigned flags)
+{
+	if (!(flags & BCH_READ_MAY_PROMOTE))
+		return false;
+
+	if (!opts.promote_target)
+		return false;
+
+	if (bch2_bkey_has_target(c, k, opts.promote_target))
+		return false;
+
+	if (bkey_extent_is_unwritten(k))
+		return false;
+
+	if (bch2_target_congested(c, opts.promote_target)) {
+		/* XXX trace this */
+		return false;
+	}
+
+	if (rhashtable_lookup_fast(&c->promote_table, &pos,
+				   bch_promote_params))
+		return false;
+
+	return true;
+}
+
+static void promote_free(struct bch_fs *c, struct promote_op *op)
+{
+	int ret;
+
+	bch2_data_update_exit(&op->write);
+
+	ret = rhashtable_remove_fast(&c->promote_table, &op->hash,
+				     bch_promote_params);
+	BUG_ON(ret);
+	bch2_write_ref_put(c, BCH_WRITE_REF_promote);
+	kfree_rcu(op, rcu);
+}
+
+static void promote_done(struct bch_write_op *wop)
+{
+	struct promote_op *op =
+		container_of(wop, struct promote_op, write.op);
+	struct bch_fs *c = op->write.op.c;
+
+	bch2_time_stats_update(&c->times[BCH_TIME_data_promote],
+			       op->start_time);
+	promote_free(c, op);
+}
+
+static void promote_start(struct promote_op *op, struct bch_read_bio *rbio)
+{
+	struct bio *bio = &op->write.op.wbio.bio;
+
+	trace_and_count(op->write.op.c, read_promote, &rbio->bio);
+
+	/* we now own pages: */
+	BUG_ON(!rbio->bounce);
+	BUG_ON(rbio->bio.bi_vcnt > bio->bi_max_vecs);
+
+	memcpy(bio->bi_io_vec, rbio->bio.bi_io_vec,
+	       sizeof(struct bio_vec) * rbio->bio.bi_vcnt);
+	swap(bio->bi_vcnt, rbio->bio.bi_vcnt);
+
+	bch2_data_update_read_done(&op->write, rbio->pick.crc);
+}
+
+static struct promote_op *__promote_alloc(struct btree_trans *trans,
+					  enum btree_id btree_id,
+					  struct bkey_s_c k,
+					  struct bpos pos,
+					  struct extent_ptr_decoded *pick,
+					  struct bch_io_opts opts,
+					  unsigned sectors,
+					  struct bch_read_bio **rbio)
+{
+	struct bch_fs *c = trans->c;
+	struct promote_op *op = NULL;
+	struct bio *bio;
+	unsigned pages = DIV_ROUND_UP(sectors, PAGE_SECTORS);
+	int ret;
+
+	if (!bch2_write_ref_tryget(c, BCH_WRITE_REF_promote))
+		return NULL;
+
+	op = kzalloc(sizeof(*op) + sizeof(struct bio_vec) * pages, GFP_NOFS);
+	if (!op)
+		goto err;
+
+	op->start_time = local_clock();
+	op->pos = pos;
+
+	/*
+	 * We don't use the mempool here because extents that aren't
+	 * checksummed or compressed can be too big for the mempool:
+	 */
+	*rbio = kzalloc(sizeof(struct bch_read_bio) +
+			sizeof(struct bio_vec) * pages,
+			GFP_NOFS);
+	if (!*rbio)
+		goto err;
+
+	rbio_init(&(*rbio)->bio, opts);
+	bio_init(&(*rbio)->bio, NULL, (*rbio)->bio.bi_inline_vecs, pages, 0);
+
+	if (bch2_bio_alloc_pages(&(*rbio)->bio, sectors << 9,
+				 GFP_NOFS))
+		goto err;
+
+	(*rbio)->bounce		= true;
+	(*rbio)->split		= true;
+	(*rbio)->kmalloc	= true;
+
+	if (rhashtable_lookup_insert_fast(&c->promote_table, &op->hash,
+					  bch_promote_params))
+		goto err;
+
+	bio = &op->write.op.wbio.bio;
+	bio_init(bio, NULL, bio->bi_inline_vecs, pages, 0);
+
+	ret = bch2_data_update_init(trans, NULL, &op->write,
+			writepoint_hashed((unsigned long) current),
+			opts,
+			(struct data_update_opts) {
+				.target		= opts.promote_target,
+				.extra_replicas	= 1,
+				.write_flags	= BCH_WRITE_ALLOC_NOWAIT|BCH_WRITE_CACHED,
+			},
+			btree_id, k);
+	/*
+	 * possible errors: -BCH_ERR_nocow_lock_blocked,
+	 * -BCH_ERR_ENOSPC_disk_reservation:
+	 */
+	if (ret) {
+		ret = rhashtable_remove_fast(&c->promote_table, &op->hash,
+					bch_promote_params);
+		BUG_ON(ret);
+		goto err;
+	}
+
+	op->write.op.end_io = promote_done;
+
+	return op;
+err:
+	if (*rbio)
+		bio_free_pages(&(*rbio)->bio);
+	kfree(*rbio);
+	*rbio = NULL;
+	kfree(op);
+	bch2_write_ref_put(c, BCH_WRITE_REF_promote);
+	return NULL;
+}
+
+noinline
+static struct promote_op *promote_alloc(struct btree_trans *trans,
+					struct bvec_iter iter,
+					struct bkey_s_c k,
+					struct extent_ptr_decoded *pick,
+					struct bch_io_opts opts,
+					unsigned flags,
+					struct bch_read_bio **rbio,
+					bool *bounce,
+					bool *read_full)
+{
+	struct bch_fs *c = trans->c;
+	bool promote_full = *read_full || READ_ONCE(c->promote_whole_extents);
+	/* data might have to be decompressed in the write path: */
+	unsigned sectors = promote_full
+		? max(pick->crc.compressed_size, pick->crc.live_size)
+		: bvec_iter_sectors(iter);
+	struct bpos pos = promote_full
+		? bkey_start_pos(k.k)
+		: POS(k.k->p.inode, iter.bi_sector);
+	struct promote_op *promote;
+
+	if (!should_promote(c, k, pos, opts, flags))
+		return NULL;
+
+	promote = __promote_alloc(trans,
+				  k.k->type == KEY_TYPE_reflink_v
+				  ? BTREE_ID_reflink
+				  : BTREE_ID_extents,
+				  k, pos, pick, opts, sectors, rbio);
+	if (!promote)
+		return NULL;
+
+	*bounce		= true;
+	*read_full	= promote_full;
+	return promote;
+}
+
+/* Read */
+
+#define READ_RETRY_AVOID	1
+#define READ_RETRY		2
+#define READ_ERR		3
+
+enum rbio_context {
+	RBIO_CONTEXT_NULL,
+	RBIO_CONTEXT_HIGHPRI,
+	RBIO_CONTEXT_UNBOUND,
+};
+
+static inline struct bch_read_bio *
+bch2_rbio_parent(struct bch_read_bio *rbio)
+{
+	return rbio->split ? rbio->parent : rbio;
+}
+
+__always_inline
+static void bch2_rbio_punt(struct bch_read_bio *rbio, work_func_t fn,
+			   enum rbio_context context,
+			   struct workqueue_struct *wq)
+{
+	if (context <= rbio->context) {
+		fn(&rbio->work);
+	} else {
+		rbio->work.func		= fn;
+		rbio->context		= context;
+		queue_work(wq, &rbio->work);
+	}
+}
+
+static inline struct bch_read_bio *bch2_rbio_free(struct bch_read_bio *rbio)
+{
+	BUG_ON(rbio->bounce && !rbio->split);
+
+	if (rbio->promote)
+		promote_free(rbio->c, rbio->promote);
+	rbio->promote = NULL;
+
+	if (rbio->bounce)
+		bch2_bio_free_pages_pool(rbio->c, &rbio->bio);
+
+	if (rbio->split) {
+		struct bch_read_bio *parent = rbio->parent;
+
+		if (rbio->kmalloc)
+			kfree(rbio);
+		else
+			bio_put(&rbio->bio);
+
+		rbio = parent;
+	}
+
+	return rbio;
+}
+
+/*
+ * Only called on a top level bch_read_bio to complete an entire read request,
+ * not a split:
+ */
+static void bch2_rbio_done(struct bch_read_bio *rbio)
+{
+	if (rbio->start_time)
+		bch2_time_stats_update(&rbio->c->times[BCH_TIME_data_read],
+				       rbio->start_time);
+	bio_endio(&rbio->bio);
+}
+
+static void bch2_read_retry_nodecode(struct bch_fs *c, struct bch_read_bio *rbio,
+				     struct bvec_iter bvec_iter,
+				     struct bch_io_failures *failed,
+				     unsigned flags)
+{
+	struct btree_trans trans;
+	struct btree_iter iter;
+	struct bkey_buf sk;
+	struct bkey_s_c k;
+	int ret;
+
+	flags &= ~BCH_READ_LAST_FRAGMENT;
+	flags |= BCH_READ_MUST_CLONE;
+
+	bch2_bkey_buf_init(&sk);
+	bch2_trans_init(&trans, c, 0, 0);
+
+	bch2_trans_iter_init(&trans, &iter, rbio->data_btree,
+			     rbio->read_pos, BTREE_ITER_SLOTS);
+retry:
+	rbio->bio.bi_status = 0;
+
+	k = bch2_btree_iter_peek_slot(&iter);
+	if (bkey_err(k))
+		goto err;
+
+	bch2_bkey_buf_reassemble(&sk, c, k);
+	k = bkey_i_to_s_c(sk.k);
+	bch2_trans_unlock(&trans);
+
+	if (!bch2_bkey_matches_ptr(c, k,
+				   rbio->pick.ptr,
+				   rbio->data_pos.offset -
+				   rbio->pick.crc.offset)) {
+		/* extent we wanted to read no longer exists: */
+		rbio->hole = true;
+		goto out;
+	}
+
+	ret = __bch2_read_extent(&trans, rbio, bvec_iter,
+				 rbio->read_pos,
+				 rbio->data_btree,
+				 k, 0, failed, flags);
+	if (ret == READ_RETRY)
+		goto retry;
+	if (ret)
+		goto err;
+out:
+	bch2_rbio_done(rbio);
+	bch2_trans_iter_exit(&trans, &iter);
+	bch2_trans_exit(&trans);
+	bch2_bkey_buf_exit(&sk, c);
+	return;
+err:
+	rbio->bio.bi_status = BLK_STS_IOERR;
+	goto out;
+}
+
+static void bch2_rbio_retry(struct work_struct *work)
+{
+	struct bch_read_bio *rbio =
+		container_of(work, struct bch_read_bio, work);
+	struct bch_fs *c	= rbio->c;
+	struct bvec_iter iter	= rbio->bvec_iter;
+	unsigned flags		= rbio->flags;
+	subvol_inum inum = {
+		.subvol = rbio->subvol,
+		.inum	= rbio->read_pos.inode,
+	};
+	struct bch_io_failures failed = { .nr = 0 };
+
+	trace_and_count(c, read_retry, &rbio->bio);
+
+	if (rbio->retry == READ_RETRY_AVOID)
+		bch2_mark_io_failure(&failed, &rbio->pick);
+
+	rbio->bio.bi_status = 0;
+
+	rbio = bch2_rbio_free(rbio);
+
+	flags |= BCH_READ_IN_RETRY;
+	flags &= ~BCH_READ_MAY_PROMOTE;
+
+	if (flags & BCH_READ_NODECODE) {
+		bch2_read_retry_nodecode(c, rbio, iter, &failed, flags);
+	} else {
+		flags &= ~BCH_READ_LAST_FRAGMENT;
+		flags |= BCH_READ_MUST_CLONE;
+
+		__bch2_read(c, rbio, iter, inum, &failed, flags);
+	}
+}
+
+static void bch2_rbio_error(struct bch_read_bio *rbio, int retry,
+			    blk_status_t error)
+{
+	rbio->retry = retry;
+
+	if (rbio->flags & BCH_READ_IN_RETRY)
+		return;
+
+	if (retry == READ_ERR) {
+		rbio = bch2_rbio_free(rbio);
+
+		rbio->bio.bi_status = error;
+		bch2_rbio_done(rbio);
+	} else {
+		bch2_rbio_punt(rbio, bch2_rbio_retry,
+			       RBIO_CONTEXT_UNBOUND, system_unbound_wq);
+	}
+}
+
+static int __bch2_rbio_narrow_crcs(struct btree_trans *trans,
+				   struct bch_read_bio *rbio)
+{
+	struct bch_fs *c = rbio->c;
+	u64 data_offset = rbio->data_pos.offset - rbio->pick.crc.offset;
+	struct bch_extent_crc_unpacked new_crc;
+	struct btree_iter iter;
+	struct bkey_i *new;
+	struct bkey_s_c k;
+	int ret = 0;
+
+	if (crc_is_compressed(rbio->pick.crc))
+		return 0;
+
+	k = bch2_bkey_get_iter(trans, &iter, rbio->data_btree, rbio->data_pos,
+			       BTREE_ITER_SLOTS|BTREE_ITER_INTENT);
+	if ((ret = bkey_err(k)))
+		goto out;
+
+	if (bversion_cmp(k.k->version, rbio->version) ||
+	    !bch2_bkey_matches_ptr(c, k, rbio->pick.ptr, data_offset))
+		goto out;
+
+	/* Extent was merged? */
+	if (bkey_start_offset(k.k) < data_offset ||
+	    k.k->p.offset > data_offset + rbio->pick.crc.uncompressed_size)
+		goto out;
+
+	if (bch2_rechecksum_bio(c, &rbio->bio, rbio->version,
+			rbio->pick.crc, NULL, &new_crc,
+			bkey_start_offset(k.k) - data_offset, k.k->size,
+			rbio->pick.crc.csum_type)) {
+		bch_err(c, "error verifying existing checksum while narrowing checksum (memory corruption?)");
+		ret = 0;
+		goto out;
+	}
+
+	/*
+	 * going to be temporarily appending another checksum entry:
+	 */
+	new = bch2_trans_kmalloc(trans, bkey_bytes(k.k) +
+				 sizeof(struct bch_extent_crc128));
+	if ((ret = PTR_ERR_OR_ZERO(new)))
+		goto out;
+
+	bkey_reassemble(new, k);
+
+	if (!bch2_bkey_narrow_crcs(new, new_crc))
+		goto out;
+
+	ret = bch2_trans_update(trans, &iter, new,
+				BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE);
+out:
+	bch2_trans_iter_exit(trans, &iter);
+	return ret;
+}
+
+static noinline void bch2_rbio_narrow_crcs(struct bch_read_bio *rbio)
+{
+	bch2_trans_do(rbio->c, NULL, NULL, BTREE_INSERT_NOFAIL,
+		      __bch2_rbio_narrow_crcs(&trans, rbio));
+}
+
+/* Inner part that may run in process context */
+static void __bch2_read_endio(struct work_struct *work)
+{
+	struct bch_read_bio *rbio =
+		container_of(work, struct bch_read_bio, work);
+	struct bch_fs *c	= rbio->c;
+	struct bch_dev *ca	= bch_dev_bkey_exists(c, rbio->pick.ptr.dev);
+	struct bio *src		= &rbio->bio;
+	struct bio *dst		= &bch2_rbio_parent(rbio)->bio;
+	struct bvec_iter dst_iter = rbio->bvec_iter;
+	struct bch_extent_crc_unpacked crc = rbio->pick.crc;
+	struct nonce nonce = extent_nonce(rbio->version, crc);
+	unsigned nofs_flags;
+	struct bch_csum csum;
+	int ret;
+
+	nofs_flags = memalloc_nofs_save();
+
+	/* Reset iterator for checksumming and copying bounced data: */
+	if (rbio->bounce) {
+		src->bi_iter.bi_size		= crc.compressed_size << 9;
+		src->bi_iter.bi_idx		= 0;
+		src->bi_iter.bi_bvec_done	= 0;
+	} else {
+		src->bi_iter			= rbio->bvec_iter;
+	}
+
+	csum = bch2_checksum_bio(c, crc.csum_type, nonce, src);
+	if (bch2_crc_cmp(csum, rbio->pick.crc.csum) && !c->opts.no_data_io)
+		goto csum_err;
+
+	/*
+	 * XXX
+	 * We need to rework the narrow_crcs path to deliver the read completion
+	 * first, and then punt to a different workqueue, otherwise we're
+	 * holding up reads while doing btree updates which is bad for memory
+	 * reclaim.
+	 */
+	if (unlikely(rbio->narrow_crcs))
+		bch2_rbio_narrow_crcs(rbio);
+
+	if (rbio->flags & BCH_READ_NODECODE)
+		goto nodecode;
+
+	/* Adjust crc to point to subset of data we want: */
+	crc.offset     += rbio->offset_into_extent;
+	crc.live_size	= bvec_iter_sectors(rbio->bvec_iter);
+
+	if (crc_is_compressed(crc)) {
+		ret = bch2_encrypt_bio(c, crc.csum_type, nonce, src);
+		if (ret)
+			goto decrypt_err;
+
+		if (bch2_bio_uncompress(c, src, dst, dst_iter, crc) &&
+		    !c->opts.no_data_io)
+			goto decompression_err;
+	} else {
+		/* don't need to decrypt the entire bio: */
+		nonce = nonce_add(nonce, crc.offset << 9);
+		bio_advance(src, crc.offset << 9);
+
+		BUG_ON(src->bi_iter.bi_size < dst_iter.bi_size);
+		src->bi_iter.bi_size = dst_iter.bi_size;
+
+		ret = bch2_encrypt_bio(c, crc.csum_type, nonce, src);
+		if (ret)
+			goto decrypt_err;
+
+		if (rbio->bounce) {
+			struct bvec_iter src_iter = src->bi_iter;
+
+			bio_copy_data_iter(dst, &dst_iter, src, &src_iter);
+		}
+	}
+
+	if (rbio->promote) {
+		/*
+		 * Re encrypt data we decrypted, so it's consistent with
+		 * rbio->crc:
+		 */
+		ret = bch2_encrypt_bio(c, crc.csum_type, nonce, src);
+		if (ret)
+			goto decrypt_err;
+
+		promote_start(rbio->promote, rbio);
+		rbio->promote = NULL;
+	}
+nodecode:
+	if (likely(!(rbio->flags & BCH_READ_IN_RETRY))) {
+		rbio = bch2_rbio_free(rbio);
+		bch2_rbio_done(rbio);
+	}
+out:
+	memalloc_nofs_restore(nofs_flags);
+	return;
+csum_err:
+	/*
+	 * Checksum error: if the bio wasn't bounced, we may have been
+	 * reading into buffers owned by userspace (that userspace can
+	 * scribble over) - retry the read, bouncing it this time:
+	 */
+	if (!rbio->bounce && (rbio->flags & BCH_READ_USER_MAPPED)) {
+		rbio->flags |= BCH_READ_MUST_BOUNCE;
+		bch2_rbio_error(rbio, READ_RETRY, BLK_STS_IOERR);
+		goto out;
+	}
+
+	bch_err_inum_offset_ratelimited(ca,
+		rbio->read_pos.inode,
+		rbio->read_pos.offset << 9,
+		"data checksum error: expected %0llx:%0llx got %0llx:%0llx (type %s)",
+		rbio->pick.crc.csum.hi, rbio->pick.crc.csum.lo,
+		csum.hi, csum.lo, bch2_csum_types[crc.csum_type]);
+	bch2_io_error(ca);
+	bch2_rbio_error(rbio, READ_RETRY_AVOID, BLK_STS_IOERR);
+	goto out;
+decompression_err:
+	bch_err_inum_offset_ratelimited(c, rbio->read_pos.inode,
+					rbio->read_pos.offset << 9,
+					"decompression error");
+	bch2_rbio_error(rbio, READ_ERR, BLK_STS_IOERR);
+	goto out;
+decrypt_err:
+	bch_err_inum_offset_ratelimited(c, rbio->read_pos.inode,
+					rbio->read_pos.offset << 9,
+					"decrypt error");
+	bch2_rbio_error(rbio, READ_ERR, BLK_STS_IOERR);
+	goto out;
+}
+
+static void bch2_read_endio(struct bio *bio)
+{
+	struct bch_read_bio *rbio =
+		container_of(bio, struct bch_read_bio, bio);
+	struct bch_fs *c	= rbio->c;
+	struct bch_dev *ca	= bch_dev_bkey_exists(c, rbio->pick.ptr.dev);
+	struct workqueue_struct *wq = NULL;
+	enum rbio_context context = RBIO_CONTEXT_NULL;
+
+	if (rbio->have_ioref) {
+		bch2_latency_acct(ca, rbio->submit_time, READ);
+		percpu_ref_put(&ca->io_ref);
+	}
+
+	if (!rbio->split)
+		rbio->bio.bi_end_io = rbio->end_io;
+
+	if (bch2_dev_inum_io_err_on(bio->bi_status, ca,
+				    rbio->read_pos.inode,
+				    rbio->read_pos.offset,
+				    "data read error: %s",
+			       bch2_blk_status_to_str(bio->bi_status))) {
+		bch2_rbio_error(rbio, READ_RETRY_AVOID, bio->bi_status);
+		return;
+	}
+
+	if (((rbio->flags & BCH_READ_RETRY_IF_STALE) && race_fault()) ||
+	    ptr_stale(ca, &rbio->pick.ptr)) {
+		trace_and_count(c, read_reuse_race, &rbio->bio);
+
+		if (rbio->flags & BCH_READ_RETRY_IF_STALE)
+			bch2_rbio_error(rbio, READ_RETRY, BLK_STS_AGAIN);
+		else
+			bch2_rbio_error(rbio, READ_ERR, BLK_STS_AGAIN);
+		return;
+	}
+
+	if (rbio->narrow_crcs ||
+	    rbio->promote ||
+	    crc_is_compressed(rbio->pick.crc) ||
+	    bch2_csum_type_is_encryption(rbio->pick.crc.csum_type))
+		context = RBIO_CONTEXT_UNBOUND,	wq = system_unbound_wq;
+	else if (rbio->pick.crc.csum_type)
+		context = RBIO_CONTEXT_HIGHPRI,	wq = system_highpri_wq;
+
+	bch2_rbio_punt(rbio, __bch2_read_endio, context, wq);
+}
+
+int __bch2_read_indirect_extent(struct btree_trans *trans,
+				unsigned *offset_into_extent,
+				struct bkey_buf *orig_k)
+{
+	struct btree_iter iter;
+	struct bkey_s_c k;
+	u64 reflink_offset;
+	int ret;
+
+	reflink_offset = le64_to_cpu(bkey_i_to_reflink_p(orig_k->k)->v.idx) +
+		*offset_into_extent;
+
+	k = bch2_bkey_get_iter(trans, &iter, BTREE_ID_reflink,
+			       POS(0, reflink_offset), 0);
+	ret = bkey_err(k);
+	if (ret)
+		goto err;
+
+	if (k.k->type != KEY_TYPE_reflink_v &&
+	    k.k->type != KEY_TYPE_indirect_inline_data) {
+		bch_err_inum_offset_ratelimited(trans->c,
+			orig_k->k->k.p.inode,
+			orig_k->k->k.p.offset << 9,
+			"%llu len %u points to nonexistent indirect extent %llu",
+			orig_k->k->k.p.offset,
+			orig_k->k->k.size,
+			reflink_offset);
+		bch2_inconsistent_error(trans->c);
+		ret = -EIO;
+		goto err;
+	}
+
+	*offset_into_extent = iter.pos.offset - bkey_start_offset(k.k);
+	bch2_bkey_buf_reassemble(orig_k, trans->c, k);
+err:
+	bch2_trans_iter_exit(trans, &iter);
+	return ret;
+}
+
+static noinline void read_from_stale_dirty_pointer(struct btree_trans *trans,
+						   struct bkey_s_c k,
+						   struct bch_extent_ptr ptr)
+{
+	struct bch_fs *c = trans->c;
+	struct bch_dev *ca = bch_dev_bkey_exists(c, ptr.dev);
+	struct btree_iter iter;
+	struct printbuf buf = PRINTBUF;
+	int ret;
+
+	bch2_trans_iter_init(trans, &iter, BTREE_ID_alloc,
+			     PTR_BUCKET_POS(c, &ptr),
+			     BTREE_ITER_CACHED);
+
+	prt_printf(&buf, "Attempting to read from stale dirty pointer:");
+	printbuf_indent_add(&buf, 2);
+	prt_newline(&buf);
+
+	bch2_bkey_val_to_text(&buf, c, k);
+	prt_newline(&buf);
+
+	prt_printf(&buf, "memory gen: %u", *bucket_gen(ca, iter.pos.offset));
+
+	ret = lockrestart_do(trans, bkey_err(k = bch2_btree_iter_peek_slot(&iter)));
+	if (!ret) {
+		prt_newline(&buf);
+		bch2_bkey_val_to_text(&buf, c, k);
+	}
+
+	bch2_fs_inconsistent(c, "%s", buf.buf);
+
+	bch2_trans_iter_exit(trans, &iter);
+	printbuf_exit(&buf);
+}
+
+int __bch2_read_extent(struct btree_trans *trans, struct bch_read_bio *orig,
+		       struct bvec_iter iter, struct bpos read_pos,
+		       enum btree_id data_btree, struct bkey_s_c k,
+		       unsigned offset_into_extent,
+		       struct bch_io_failures *failed, unsigned flags)
+{
+	struct bch_fs *c = trans->c;
+	struct extent_ptr_decoded pick;
+	struct bch_read_bio *rbio = NULL;
+	struct bch_dev *ca = NULL;
+	struct promote_op *promote = NULL;
+	bool bounce = false, read_full = false, narrow_crcs = false;
+	struct bpos data_pos = bkey_start_pos(k.k);
+	int pick_ret;
+
+	if (bkey_extent_is_inline_data(k.k)) {
+		unsigned bytes = min_t(unsigned, iter.bi_size,
+				       bkey_inline_data_bytes(k.k));
+
+		swap(iter.bi_size, bytes);
+		memcpy_to_bio(&orig->bio, iter, bkey_inline_data_p(k));
+		swap(iter.bi_size, bytes);
+		bio_advance_iter(&orig->bio, &iter, bytes);
+		zero_fill_bio_iter(&orig->bio, iter);
+		goto out_read_done;
+	}
+retry_pick:
+	pick_ret = bch2_bkey_pick_read_device(c, k, failed, &pick);
+
+	/* hole or reservation - just zero fill: */
+	if (!pick_ret)
+		goto hole;
+
+	if (pick_ret < 0) {
+		bch_err_inum_offset_ratelimited(c,
+				read_pos.inode, read_pos.offset << 9,
+				"no device to read from");
+		goto err;
+	}
+
+	ca = bch_dev_bkey_exists(c, pick.ptr.dev);
+
+	/*
+	 * Stale dirty pointers are treated as IO errors, but @failed isn't
+	 * allocated unless we're in the retry path - so if we're not in the
+	 * retry path, don't check here, it'll be caught in bch2_read_endio()
+	 * and we'll end up in the retry path:
+	 */
+	if ((flags & BCH_READ_IN_RETRY) &&
+	    !pick.ptr.cached &&
+	    unlikely(ptr_stale(ca, &pick.ptr))) {
+		read_from_stale_dirty_pointer(trans, k, pick.ptr);
+		bch2_mark_io_failure(failed, &pick);
+		goto retry_pick;
+	}
+
+	/*
+	 * Unlock the iterator while the btree node's lock is still in
+	 * cache, before doing the IO:
+	 */
+	bch2_trans_unlock(trans);
+
+	if (flags & BCH_READ_NODECODE) {
+		/*
+		 * can happen if we retry, and the extent we were going to read
+		 * has been merged in the meantime:
+		 */
+		if (pick.crc.compressed_size > orig->bio.bi_vcnt * PAGE_SECTORS)
+			goto hole;
+
+		iter.bi_size	= pick.crc.compressed_size << 9;
+		goto get_bio;
+	}
+
+	if (!(flags & BCH_READ_LAST_FRAGMENT) ||
+	    bio_flagged(&orig->bio, BIO_CHAIN))
+		flags |= BCH_READ_MUST_CLONE;
+
+	narrow_crcs = !(flags & BCH_READ_IN_RETRY) &&
+		bch2_can_narrow_extent_crcs(k, pick.crc);
+
+	if (narrow_crcs && (flags & BCH_READ_USER_MAPPED))
+		flags |= BCH_READ_MUST_BOUNCE;
+
+	EBUG_ON(offset_into_extent + bvec_iter_sectors(iter) > k.k->size);
+
+	if (crc_is_compressed(pick.crc) ||
+	    (pick.crc.csum_type != BCH_CSUM_none &&
+	     (bvec_iter_sectors(iter) != pick.crc.uncompressed_size ||
+	      (bch2_csum_type_is_encryption(pick.crc.csum_type) &&
+	       (flags & BCH_READ_USER_MAPPED)) ||
+	      (flags & BCH_READ_MUST_BOUNCE)))) {
+		read_full = true;
+		bounce = true;
+	}
+
+	if (orig->opts.promote_target)
+		promote = promote_alloc(trans, iter, k, &pick, orig->opts, flags,
+					&rbio, &bounce, &read_full);
+
+	if (!read_full) {
+		EBUG_ON(crc_is_compressed(pick.crc));
+		EBUG_ON(pick.crc.csum_type &&
+			(bvec_iter_sectors(iter) != pick.crc.uncompressed_size ||
+			 bvec_iter_sectors(iter) != pick.crc.live_size ||
+			 pick.crc.offset ||
+			 offset_into_extent));
+
+		data_pos.offset += offset_into_extent;
+		pick.ptr.offset += pick.crc.offset +
+			offset_into_extent;
+		offset_into_extent		= 0;
+		pick.crc.compressed_size	= bvec_iter_sectors(iter);
+		pick.crc.uncompressed_size	= bvec_iter_sectors(iter);
+		pick.crc.offset			= 0;
+		pick.crc.live_size		= bvec_iter_sectors(iter);
+		offset_into_extent		= 0;
+	}
+get_bio:
+	if (rbio) {
+		/*
+		 * promote already allocated bounce rbio:
+		 * promote needs to allocate a bio big enough for uncompressing
+		 * data in the write path, but we're not going to use it all
+		 * here:
+		 */
+		EBUG_ON(rbio->bio.bi_iter.bi_size <
+		       pick.crc.compressed_size << 9);
+		rbio->bio.bi_iter.bi_size =
+			pick.crc.compressed_size << 9;
+	} else if (bounce) {
+		unsigned sectors = pick.crc.compressed_size;
+
+		rbio = rbio_init(bio_alloc_bioset(NULL,
+						  DIV_ROUND_UP(sectors, PAGE_SECTORS),
+						  0,
+						  GFP_NOFS,
+						  &c->bio_read_split),
+				 orig->opts);
+
+		bch2_bio_alloc_pages_pool(c, &rbio->bio, sectors << 9);
+		rbio->bounce	= true;
+		rbio->split	= true;
+	} else if (flags & BCH_READ_MUST_CLONE) {
+		/*
+		 * Have to clone if there were any splits, due to error
+		 * reporting issues (if a split errored, and retrying didn't
+		 * work, when it reports the error to its parent (us) we don't
+		 * know if the error was from our bio, and we should retry, or
+		 * from the whole bio, in which case we don't want to retry and
+		 * lose the error)
+		 */
+		rbio = rbio_init(bio_alloc_clone(NULL, &orig->bio, GFP_NOFS,
+						 &c->bio_read_split),
+				 orig->opts);
+		rbio->bio.bi_iter = iter;
+		rbio->split	= true;
+	} else {
+		rbio = orig;
+		rbio->bio.bi_iter = iter;
+		EBUG_ON(bio_flagged(&rbio->bio, BIO_CHAIN));
+	}
+
+	EBUG_ON(bio_sectors(&rbio->bio) != pick.crc.compressed_size);
+
+	rbio->c			= c;
+	rbio->submit_time	= local_clock();
+	if (rbio->split)
+		rbio->parent	= orig;
+	else
+		rbio->end_io	= orig->bio.bi_end_io;
+	rbio->bvec_iter		= iter;
+	rbio->offset_into_extent= offset_into_extent;
+	rbio->flags		= flags;
+	rbio->have_ioref	= pick_ret > 0 && bch2_dev_get_ioref(ca, READ);
+	rbio->narrow_crcs	= narrow_crcs;
+	rbio->hole		= 0;
+	rbio->retry		= 0;
+	rbio->context		= 0;
+	/* XXX: only initialize this if needed */
+	rbio->devs_have		= bch2_bkey_devs(k);
+	rbio->pick		= pick;
+	rbio->subvol		= orig->subvol;
+	rbio->read_pos		= read_pos;
+	rbio->data_btree	= data_btree;
+	rbio->data_pos		= data_pos;
+	rbio->version		= k.k->version;
+	rbio->promote		= promote;
+	INIT_WORK(&rbio->work, NULL);
+
+	rbio->bio.bi_opf	= orig->bio.bi_opf;
+	rbio->bio.bi_iter.bi_sector = pick.ptr.offset;
+	rbio->bio.bi_end_io	= bch2_read_endio;
+
+	if (rbio->bounce)
+		trace_and_count(c, read_bounce, &rbio->bio);
+
+	this_cpu_add(c->counters[BCH_COUNTER_io_read], bio_sectors(&rbio->bio));
+	bch2_increment_clock(c, bio_sectors(&rbio->bio), READ);
+
+	/*
+	 * If it's being moved internally, we don't want to flag it as a cache
+	 * hit:
+	 */
+	if (pick.ptr.cached && !(flags & BCH_READ_NODECODE))
+		bch2_bucket_io_time_reset(trans, pick.ptr.dev,
+			PTR_BUCKET_NR(ca, &pick.ptr), READ);
+
+	if (!(flags & (BCH_READ_IN_RETRY|BCH_READ_LAST_FRAGMENT))) {
+		bio_inc_remaining(&orig->bio);
+		trace_and_count(c, read_split, &orig->bio);
+	}
+
+	if (!rbio->pick.idx) {
+		if (!rbio->have_ioref) {
+			bch_err_inum_offset_ratelimited(c,
+					read_pos.inode,
+					read_pos.offset << 9,
+					"no device to read from");
+			bch2_rbio_error(rbio, READ_RETRY_AVOID, BLK_STS_IOERR);
+			goto out;
+		}
+
+		this_cpu_add(ca->io_done->sectors[READ][BCH_DATA_user],
+			     bio_sectors(&rbio->bio));
+		bio_set_dev(&rbio->bio, ca->disk_sb.bdev);
+
+		if (unlikely(c->opts.no_data_io)) {
+			if (likely(!(flags & BCH_READ_IN_RETRY)))
+				bio_endio(&rbio->bio);
+		} else {
+			if (likely(!(flags & BCH_READ_IN_RETRY)))
+				submit_bio(&rbio->bio);
+			else
+				submit_bio_wait(&rbio->bio);
+		}
+
+		/*
+		 * We just submitted IO which may block, we expect relock fail
+		 * events and shouldn't count them:
+		 */
+		trans->notrace_relock_fail = true;
+	} else {
+		/* Attempting reconstruct read: */
+		if (bch2_ec_read_extent(c, rbio)) {
+			bch2_rbio_error(rbio, READ_RETRY_AVOID, BLK_STS_IOERR);
+			goto out;
+		}
+
+		if (likely(!(flags & BCH_READ_IN_RETRY)))
+			bio_endio(&rbio->bio);
+	}
+out:
+	if (likely(!(flags & BCH_READ_IN_RETRY))) {
+		return 0;
+	} else {
+		int ret;
+
+		rbio->context = RBIO_CONTEXT_UNBOUND;
+		bch2_read_endio(&rbio->bio);
+
+		ret = rbio->retry;
+		rbio = bch2_rbio_free(rbio);
+
+		if (ret == READ_RETRY_AVOID) {
+			bch2_mark_io_failure(failed, &pick);
+			ret = READ_RETRY;
+		}
+
+		if (!ret)
+			goto out_read_done;
+
+		return ret;
+	}
+
+err:
+	if (flags & BCH_READ_IN_RETRY)
+		return READ_ERR;
+
+	orig->bio.bi_status = BLK_STS_IOERR;
+	goto out_read_done;
+
+hole:
+	/*
+	 * won't normally happen in the BCH_READ_NODECODE
+	 * (bch2_move_extent()) path, but if we retry and the extent we wanted
+	 * to read no longer exists we have to signal that:
+	 */
+	if (flags & BCH_READ_NODECODE)
+		orig->hole = true;
+
+	zero_fill_bio_iter(&orig->bio, iter);
+out_read_done:
+	if (flags & BCH_READ_LAST_FRAGMENT)
+		bch2_rbio_done(orig);
+	return 0;
+}
+
+void __bch2_read(struct bch_fs *c, struct bch_read_bio *rbio,
+		 struct bvec_iter bvec_iter, subvol_inum inum,
+		 struct bch_io_failures *failed, unsigned flags)
+{
+	struct btree_trans trans;
+	struct btree_iter iter;
+	struct bkey_buf sk;
+	struct bkey_s_c k;
+	u32 snapshot;
+	int ret;
+
+	BUG_ON(flags & BCH_READ_NODECODE);
+
+	bch2_bkey_buf_init(&sk);
+	bch2_trans_init(&trans, c, 0, 0);
+retry:
+	bch2_trans_begin(&trans);
+	iter = (struct btree_iter) { NULL };
+
+	ret = bch2_subvolume_get_snapshot(&trans, inum.subvol, &snapshot);
+	if (ret)
+		goto err;
+
+	bch2_trans_iter_init(&trans, &iter, BTREE_ID_extents,
+			     SPOS(inum.inum, bvec_iter.bi_sector, snapshot),
+			     BTREE_ITER_SLOTS);
+	while (1) {
+		unsigned bytes, sectors, offset_into_extent;
+		enum btree_id data_btree = BTREE_ID_extents;
+
+		/*
+		 * read_extent -> io_time_reset may cause a transaction restart
+		 * without returning an error, we need to check for that here:
+		 */
+		ret = bch2_trans_relock(&trans);
+		if (ret)
+			break;
+
+		bch2_btree_iter_set_pos(&iter,
+				POS(inum.inum, bvec_iter.bi_sector));
+
+		k = bch2_btree_iter_peek_slot(&iter);
+		ret = bkey_err(k);
+		if (ret)
+			break;
+
+		offset_into_extent = iter.pos.offset -
+			bkey_start_offset(k.k);
+		sectors = k.k->size - offset_into_extent;
+
+		bch2_bkey_buf_reassemble(&sk, c, k);
+
+		ret = bch2_read_indirect_extent(&trans, &data_btree,
+					&offset_into_extent, &sk);
+		if (ret)
+			break;
+
+		k = bkey_i_to_s_c(sk.k);
+
+		/*
+		 * With indirect extents, the amount of data to read is the min
+		 * of the original extent and the indirect extent:
+		 */
+		sectors = min(sectors, k.k->size - offset_into_extent);
+
+		bytes = min(sectors, bvec_iter_sectors(bvec_iter)) << 9;
+		swap(bvec_iter.bi_size, bytes);
+
+		if (bvec_iter.bi_size == bytes)
+			flags |= BCH_READ_LAST_FRAGMENT;
+
+		ret = __bch2_read_extent(&trans, rbio, bvec_iter, iter.pos,
+					 data_btree, k,
+					 offset_into_extent, failed, flags);
+		if (ret)
+			break;
+
+		if (flags & BCH_READ_LAST_FRAGMENT)
+			break;
+
+		swap(bvec_iter.bi_size, bytes);
+		bio_advance_iter(&rbio->bio, &bvec_iter, bytes);
+
+		ret = btree_trans_too_many_iters(&trans);
+		if (ret)
+			break;
+	}
+err:
+	bch2_trans_iter_exit(&trans, &iter);
+
+	if (bch2_err_matches(ret, BCH_ERR_transaction_restart) ||
+	    ret == READ_RETRY ||
+	    ret == READ_RETRY_AVOID)
+		goto retry;
+
+	bch2_trans_exit(&trans);
+	bch2_bkey_buf_exit(&sk, c);
+
+	if (ret) {
+		bch_err_inum_offset_ratelimited(c, inum.inum,
+						bvec_iter.bi_sector << 9,
+						"read error %i from btree lookup", ret);
+		rbio->bio.bi_status = BLK_STS_IOERR;
+		bch2_rbio_done(rbio);
+	}
+}
+
+void bch2_fs_io_read_exit(struct bch_fs *c)
+{
+	if (c->promote_table.tbl)
+		rhashtable_destroy(&c->promote_table);
+	bioset_exit(&c->bio_read_split);
+	bioset_exit(&c->bio_read);
+}
+
+int bch2_fs_io_read_init(struct bch_fs *c)
+{
+	if (bioset_init(&c->bio_read, 1, offsetof(struct bch_read_bio, bio),
+			BIOSET_NEED_BVECS))
+		return -BCH_ERR_ENOMEM_bio_read_init;
+
+	if (bioset_init(&c->bio_read_split, 1, offsetof(struct bch_read_bio, bio),
+			BIOSET_NEED_BVECS))
+		return -BCH_ERR_ENOMEM_bio_read_split_init;
+
+	if (rhashtable_init(&c->promote_table, &bch_promote_params))
+		return -BCH_ERR_ENOMEM_promote_table_init;
+
+	return 0;
+}
diff --git a/fs/bcachefs/io_read.h b/fs/bcachefs/io_read.h
new file mode 100644
index 0000000..d9c18bb
--- /dev/null
+++ b/fs/bcachefs/io_read.h
@@ -0,0 +1,158 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _BCACHEFS_IO_READ_H
+#define _BCACHEFS_IO_READ_H
+
+#include "bkey_buf.h"
+
+struct bch_read_bio {
+	struct bch_fs		*c;
+	u64			start_time;
+	u64			submit_time;
+
+	/*
+	 * Reads will often have to be split, and if the extent being read from
+	 * was checksummed or compressed we'll also have to allocate bounce
+	 * buffers and copy the data back into the original bio.
+	 *
+	 * If we didn't have to split, we have to save and restore the original
+	 * bi_end_io - @split below indicates which:
+	 */
+	union {
+	struct bch_read_bio	*parent;
+	bio_end_io_t		*end_io;
+	};
+
+	/*
+	 * Saved copy of bio->bi_iter, from submission time - allows us to
+	 * resubmit on IO error, and also to copy data back to the original bio
+	 * when we're bouncing:
+	 */
+	struct bvec_iter	bvec_iter;
+
+	unsigned		offset_into_extent;
+
+	u16			flags;
+	union {
+	struct {
+	u16			bounce:1,
+				split:1,
+				kmalloc:1,
+				have_ioref:1,
+				narrow_crcs:1,
+				hole:1,
+				retry:2,
+				context:2;
+	};
+	u16			_state;
+	};
+
+	struct bch_devs_list	devs_have;
+
+	struct extent_ptr_decoded pick;
+
+	/*
+	 * pos we read from - different from data_pos for indirect extents:
+	 */
+	u32			subvol;
+	struct bpos		read_pos;
+
+	/*
+	 * start pos of data we read (may not be pos of data we want) - for
+	 * promote, narrow extents paths:
+	 */
+	enum btree_id		data_btree;
+	struct bpos		data_pos;
+	struct bversion		version;
+
+	struct promote_op	*promote;
+
+	struct bch_io_opts	opts;
+
+	struct work_struct	work;
+
+	struct bio		bio;
+};
+
+#define to_rbio(_bio)		container_of((_bio), struct bch_read_bio, bio)
+
+struct bch_devs_mask;
+struct cache_promote_op;
+struct extent_ptr_decoded;
+
+int __bch2_read_indirect_extent(struct btree_trans *, unsigned *,
+				struct bkey_buf *);
+
+static inline int bch2_read_indirect_extent(struct btree_trans *trans,
+					    enum btree_id *data_btree,
+					    unsigned *offset_into_extent,
+					    struct bkey_buf *k)
+{
+	if (k->k->k.type != KEY_TYPE_reflink_p)
+		return 0;
+
+	*data_btree = BTREE_ID_reflink;
+	return __bch2_read_indirect_extent(trans, offset_into_extent, k);
+}
+
+enum bch_read_flags {
+	BCH_READ_RETRY_IF_STALE		= 1 << 0,
+	BCH_READ_MAY_PROMOTE		= 1 << 1,
+	BCH_READ_USER_MAPPED		= 1 << 2,
+	BCH_READ_NODECODE		= 1 << 3,
+	BCH_READ_LAST_FRAGMENT		= 1 << 4,
+
+	/* internal: */
+	BCH_READ_MUST_BOUNCE		= 1 << 5,
+	BCH_READ_MUST_CLONE		= 1 << 6,
+	BCH_READ_IN_RETRY		= 1 << 7,
+};
+
+int __bch2_read_extent(struct btree_trans *, struct bch_read_bio *,
+		       struct bvec_iter, struct bpos, enum btree_id,
+		       struct bkey_s_c, unsigned,
+		       struct bch_io_failures *, unsigned);
+
+static inline void bch2_read_extent(struct btree_trans *trans,
+			struct bch_read_bio *rbio, struct bpos read_pos,
+			enum btree_id data_btree, struct bkey_s_c k,
+			unsigned offset_into_extent, unsigned flags)
+{
+	__bch2_read_extent(trans, rbio, rbio->bio.bi_iter, read_pos,
+			   data_btree, k, offset_into_extent, NULL, flags);
+}
+
+void __bch2_read(struct bch_fs *, struct bch_read_bio *, struct bvec_iter,
+		 subvol_inum, struct bch_io_failures *, unsigned flags);
+
+static inline void bch2_read(struct bch_fs *c, struct bch_read_bio *rbio,
+			     subvol_inum inum)
+{
+	struct bch_io_failures failed = { .nr = 0 };
+
+	BUG_ON(rbio->_state);
+
+	rbio->c = c;
+	rbio->start_time = local_clock();
+	rbio->subvol = inum.subvol;
+
+	__bch2_read(c, rbio, rbio->bio.bi_iter, inum, &failed,
+		    BCH_READ_RETRY_IF_STALE|
+		    BCH_READ_MAY_PROMOTE|
+		    BCH_READ_USER_MAPPED);
+}
+
+static inline struct bch_read_bio *rbio_init(struct bio *bio,
+					     struct bch_io_opts opts)
+{
+	struct bch_read_bio *rbio = to_rbio(bio);
+
+	rbio->_state	= 0;
+	rbio->promote	= NULL;
+	rbio->opts	= opts;
+	return rbio;
+}
+
+void bch2_fs_io_read_exit(struct bch_fs *);
+int bch2_fs_io_read_init(struct bch_fs *);
+
+#endif /* _BCACHEFS_IO_READ_H */
diff --git a/fs/bcachefs/io_types.h b/fs/bcachefs/io_types.h
deleted file mode 100644
index 737f16d..0000000
--- a/fs/bcachefs/io_types.h
+++ /dev/null
@@ -1,165 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-#ifndef _BCACHEFS_IO_TYPES_H
-#define _BCACHEFS_IO_TYPES_H
-
-#include "alloc_types.h"
-#include "btree_types.h"
-#include "buckets_types.h"
-#include "extents_types.h"
-#include "keylist_types.h"
-#include "opts.h"
-#include "super_types.h"
-
-#include <linux/llist.h>
-#include <linux/workqueue.h>
-
-struct bch_read_bio {
-	struct bch_fs		*c;
-	u64			start_time;
-	u64			submit_time;
-
-	/*
-	 * Reads will often have to be split, and if the extent being read from
-	 * was checksummed or compressed we'll also have to allocate bounce
-	 * buffers and copy the data back into the original bio.
-	 *
-	 * If we didn't have to split, we have to save and restore the original
-	 * bi_end_io - @split below indicates which:
-	 */
-	union {
-	struct bch_read_bio	*parent;
-	bio_end_io_t		*end_io;
-	};
-
-	/*
-	 * Saved copy of bio->bi_iter, from submission time - allows us to
-	 * resubmit on IO error, and also to copy data back to the original bio
-	 * when we're bouncing:
-	 */
-	struct bvec_iter	bvec_iter;
-
-	unsigned		offset_into_extent;
-
-	u16			flags;
-	union {
-	struct {
-	u16			bounce:1,
-				split:1,
-				kmalloc:1,
-				have_ioref:1,
-				narrow_crcs:1,
-				hole:1,
-				retry:2,
-				context:2;
-	};
-	u16			_state;
-	};
-
-	struct bch_devs_list	devs_have;
-
-	struct extent_ptr_decoded pick;
-
-	/*
-	 * pos we read from - different from data_pos for indirect extents:
-	 */
-	u32			subvol;
-	struct bpos		read_pos;
-
-	/*
-	 * start pos of data we read (may not be pos of data we want) - for
-	 * promote, narrow extents paths:
-	 */
-	enum btree_id		data_btree;
-	struct bpos		data_pos;
-	struct bversion		version;
-
-	struct promote_op	*promote;
-
-	struct bch_io_opts	opts;
-
-	struct work_struct	work;
-
-	struct bio		bio;
-};
-
-struct bch_write_bio {
-	struct_group(wbio,
-	struct bch_fs		*c;
-	struct bch_write_bio	*parent;
-
-	u64			submit_time;
-	u64			inode_offset;
-
-	struct bch_devs_list	failed;
-	u8			dev;
-
-	unsigned		split:1,
-				bounce:1,
-				put_bio:1,
-				have_ioref:1,
-				nocow:1,
-				used_mempool:1,
-				first_btree_write:1;
-	);
-
-	struct bio		bio;
-};
-
-struct bch_write_op {
-	struct closure		cl;
-	struct bch_fs		*c;
-	void			(*end_io)(struct bch_write_op *);
-	u64			start_time;
-
-	unsigned		written; /* sectors */
-	u16			flags;
-	s16			error; /* dio write path expects it to hold -ERESTARTSYS... */
-
-	unsigned		compression_opt:8;
-	unsigned		csum_type:4;
-	unsigned		nr_replicas:4;
-	unsigned		nr_replicas_required:4;
-	unsigned		watermark:3;
-	unsigned		incompressible:1;
-	unsigned		stripe_waited:1;
-
-	struct bch_devs_list	devs_have;
-	u16			target;
-	u16			nonce;
-	struct bch_io_opts	opts;
-
-	u32			subvol;
-	struct bpos		pos;
-	struct bversion		version;
-
-	/* For BCH_WRITE_DATA_ENCODED: */
-	struct bch_extent_crc_unpacked crc;
-
-	struct write_point_specifier write_point;
-
-	struct write_point	*wp;
-	struct list_head	wp_list;
-
-	struct disk_reservation	res;
-
-	struct open_buckets	open_buckets;
-
-	u64			new_i_size;
-	s64			i_sectors_delta;
-
-	struct bch_devs_mask	failed;
-
-	struct keylist		insert_keys;
-	u64			inline_keys[BKEY_EXTENT_U64s_MAX * 2];
-
-	/*
-	 * Bitmask of devices that have had nocow writes issued to them since
-	 * last flush:
-	 */
-	struct bch_devs_mask	*devs_need_flush;
-
-	/* Must be last: */
-	struct bch_write_bio	wbio;
-};
-
-#endif /* _BCACHEFS_IO_TYPES_H */
diff --git a/fs/bcachefs/io_write.c b/fs/bcachefs/io_write.c
new file mode 100644
index 0000000..7f29fd2f
--- /dev/null
+++ b/fs/bcachefs/io_write.c
@@ -0,0 +1,1670 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
+ * Copyright 2012 Google, Inc.
+ */
+
+#include "bcachefs.h"
+#include "alloc_foreground.h"
+#include "bkey_buf.h"
+#include "bset.h"
+#include "btree_update.h"
+#include "buckets.h"
+#include "checksum.h"
+#include "clock.h"
+#include "compress.h"
+#include "debug.h"
+#include "ec.h"
+#include "error.h"
+#include "extent_update.h"
+#include "inode.h"
+#include "io_write.h"
+#include "journal.h"
+#include "keylist.h"
+#include "move.h"
+#include "nocow_locking.h"
+#include "rebalance.h"
+#include "subvolume.h"
+#include "super.h"
+#include "super-io.h"
+#include "trace.h"
+
+#include <linux/blkdev.h>
+#include <linux/prefetch.h>
+#include <linux/random.h>
+#include <linux/sched/mm.h>
+
+#ifndef CONFIG_BCACHEFS_NO_LATENCY_ACCT
+
+static inline void bch2_congested_acct(struct bch_dev *ca, u64 io_latency,
+				       u64 now, int rw)
+{
+	u64 latency_capable =
+		ca->io_latency[rw].quantiles.entries[QUANTILE_IDX(1)].m;
+	/* ideally we'd be taking into account the device's variance here: */
+	u64 latency_threshold = latency_capable << (rw == READ ? 2 : 3);
+	s64 latency_over = io_latency - latency_threshold;
+
+	if (latency_threshold && latency_over > 0) {
+		/*
+		 * bump up congested by approximately latency_over * 4 /
+		 * latency_threshold - we don't need much accuracy here so don't
+		 * bother with the divide:
+		 */
+		if (atomic_read(&ca->congested) < CONGESTED_MAX)
+			atomic_add(latency_over >>
+				   max_t(int, ilog2(latency_threshold) - 2, 0),
+				   &ca->congested);
+
+		ca->congested_last = now;
+	} else if (atomic_read(&ca->congested) > 0) {
+		atomic_dec(&ca->congested);
+	}
+}
+
+void bch2_latency_acct(struct bch_dev *ca, u64 submit_time, int rw)
+{
+	atomic64_t *latency = &ca->cur_latency[rw];
+	u64 now = local_clock();
+	u64 io_latency = time_after64(now, submit_time)
+		? now - submit_time
+		: 0;
+	u64 old, new, v = atomic64_read(latency);
+
+	do {
+		old = v;
+
+		/*
+		 * If the io latency was reasonably close to the current
+		 * latency, skip doing the update and atomic operation - most of
+		 * the time:
+		 */
+		if (abs((int) (old - io_latency)) < (old >> 1) &&
+		    now & ~(~0U << 5))
+			break;
+
+		new = ewma_add(old, io_latency, 5);
+	} while ((v = atomic64_cmpxchg(latency, old, new)) != old);
+
+	bch2_congested_acct(ca, io_latency, now, rw);
+
+	__bch2_time_stats_update(&ca->io_latency[rw], submit_time, now);
+}
+
+#endif
+
+/* Allocate, free from mempool: */
+
+void bch2_bio_free_pages_pool(struct bch_fs *c, struct bio *bio)
+{
+	struct bvec_iter_all iter;
+	struct bio_vec *bv;
+
+	bio_for_each_segment_all(bv, bio, iter)
+		if (bv->bv_page != ZERO_PAGE(0))
+			mempool_free(bv->bv_page, &c->bio_bounce_pages);
+	bio->bi_vcnt = 0;
+}
+
+static struct page *__bio_alloc_page_pool(struct bch_fs *c, bool *using_mempool)
+{
+	struct page *page;
+
+	if (likely(!*using_mempool)) {
+		page = alloc_page(GFP_NOFS);
+		if (unlikely(!page)) {
+			mutex_lock(&c->bio_bounce_pages_lock);
+			*using_mempool = true;
+			goto pool_alloc;
+
+		}
+	} else {
+pool_alloc:
+		page = mempool_alloc(&c->bio_bounce_pages, GFP_NOFS);
+	}
+
+	return page;
+}
+
+void bch2_bio_alloc_pages_pool(struct bch_fs *c, struct bio *bio,
+			       size_t size)
+{
+	bool using_mempool = false;
+
+	while (size) {
+		struct page *page = __bio_alloc_page_pool(c, &using_mempool);
+		unsigned len = min_t(size_t, PAGE_SIZE, size);
+
+		BUG_ON(!bio_add_page(bio, page, len, 0));
+		size -= len;
+	}
+
+	if (using_mempool)
+		mutex_unlock(&c->bio_bounce_pages_lock);
+}
+
+/* Extent update path: */
+
+int bch2_sum_sector_overwrites(struct btree_trans *trans,
+			       struct btree_iter *extent_iter,
+			       struct bkey_i *new,
+			       bool *usage_increasing,
+			       s64 *i_sectors_delta,
+			       s64 *disk_sectors_delta)
+{
+	struct bch_fs *c = trans->c;
+	struct btree_iter iter;
+	struct bkey_s_c old;
+	unsigned new_replicas = bch2_bkey_replicas(c, bkey_i_to_s_c(new));
+	bool new_compressed = bch2_bkey_sectors_compressed(bkey_i_to_s_c(new));
+	int ret = 0;
+
+	*usage_increasing	= false;
+	*i_sectors_delta	= 0;
+	*disk_sectors_delta	= 0;
+
+	bch2_trans_copy_iter(&iter, extent_iter);
+
+	for_each_btree_key_upto_continue_norestart(iter,
+				new->k.p, BTREE_ITER_SLOTS, old, ret) {
+		s64 sectors = min(new->k.p.offset, old.k->p.offset) -
+			max(bkey_start_offset(&new->k),
+			    bkey_start_offset(old.k));
+
+		*i_sectors_delta += sectors *
+			(bkey_extent_is_allocation(&new->k) -
+			 bkey_extent_is_allocation(old.k));
+
+		*disk_sectors_delta += sectors * bch2_bkey_nr_ptrs_allocated(bkey_i_to_s_c(new));
+		*disk_sectors_delta -= new->k.p.snapshot == old.k->p.snapshot
+			? sectors * bch2_bkey_nr_ptrs_fully_allocated(old)
+			: 0;
+
+		if (!*usage_increasing &&
+		    (new->k.p.snapshot != old.k->p.snapshot ||
+		     new_replicas > bch2_bkey_replicas(c, old) ||
+		     (!new_compressed && bch2_bkey_sectors_compressed(old))))
+			*usage_increasing = true;
+
+		if (bkey_ge(old.k->p, new->k.p))
+			break;
+	}
+
+	bch2_trans_iter_exit(trans, &iter);
+	return ret;
+}
+
+static inline int bch2_extent_update_i_size_sectors(struct btree_trans *trans,
+						    struct btree_iter *extent_iter,
+						    u64 new_i_size,
+						    s64 i_sectors_delta)
+{
+	struct btree_iter iter;
+	struct bkey_i *k;
+	struct bkey_i_inode_v3 *inode;
+	unsigned inode_update_flags = BTREE_UPDATE_NOJOURNAL;
+	int ret;
+
+	k = bch2_bkey_get_mut_noupdate(trans, &iter, BTREE_ID_inodes,
+			      SPOS(0,
+				   extent_iter->pos.inode,
+				   extent_iter->snapshot),
+			      BTREE_ITER_CACHED);
+	ret = PTR_ERR_OR_ZERO(k);
+	if (unlikely(ret))
+		return ret;
+
+	if (unlikely(k->k.type != KEY_TYPE_inode_v3)) {
+		k = bch2_inode_to_v3(trans, k);
+		ret = PTR_ERR_OR_ZERO(k);
+		if (unlikely(ret))
+			goto err;
+	}
+
+	inode = bkey_i_to_inode_v3(k);
+
+	if (!(le64_to_cpu(inode->v.bi_flags) & BCH_INODE_I_SIZE_DIRTY) &&
+	    new_i_size > le64_to_cpu(inode->v.bi_size)) {
+		inode->v.bi_size = cpu_to_le64(new_i_size);
+		inode_update_flags = 0;
+	}
+
+	if (i_sectors_delta) {
+		le64_add_cpu(&inode->v.bi_sectors, i_sectors_delta);
+		inode_update_flags = 0;
+	}
+
+	if (inode->k.p.snapshot != iter.snapshot) {
+		inode->k.p.snapshot = iter.snapshot;
+		inode_update_flags = 0;
+	}
+
+	ret = bch2_trans_update(trans, &iter, &inode->k_i,
+				BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE|
+				inode_update_flags);
+err:
+	bch2_trans_iter_exit(trans, &iter);
+	return ret;
+}
+
+int bch2_extent_update(struct btree_trans *trans,
+		       subvol_inum inum,
+		       struct btree_iter *iter,
+		       struct bkey_i *k,
+		       struct disk_reservation *disk_res,
+		       u64 new_i_size,
+		       s64 *i_sectors_delta_total,
+		       bool check_enospc)
+{
+	struct bpos next_pos;
+	bool usage_increasing;
+	s64 i_sectors_delta = 0, disk_sectors_delta = 0;
+	int ret;
+
+	/*
+	 * This traverses us the iterator without changing iter->path->pos to
+	 * search_key() (which is pos + 1 for extents): we want there to be a
+	 * path already traversed at iter->pos because
+	 * bch2_trans_extent_update() will use it to attempt extent merging
+	 */
+	ret = __bch2_btree_iter_traverse(iter);
+	if (ret)
+		return ret;
+
+	ret = bch2_extent_trim_atomic(trans, iter, k);
+	if (ret)
+		return ret;
+
+	next_pos = k->k.p;
+
+	ret = bch2_sum_sector_overwrites(trans, iter, k,
+			&usage_increasing,
+			&i_sectors_delta,
+			&disk_sectors_delta);
+	if (ret)
+		return ret;
+
+	if (disk_res &&
+	    disk_sectors_delta > (s64) disk_res->sectors) {
+		ret = bch2_disk_reservation_add(trans->c, disk_res,
+					disk_sectors_delta - disk_res->sectors,
+					!check_enospc || !usage_increasing
+					? BCH_DISK_RESERVATION_NOFAIL : 0);
+		if (ret)
+			return ret;
+	}
+
+	/*
+	 * Note:
+	 * We always have to do an inode update - even when i_size/i_sectors
+	 * aren't changing - for fsync to work properly; fsync relies on
+	 * inode->bi_journal_seq which is updated by the trigger code:
+	 */
+	ret =   bch2_extent_update_i_size_sectors(trans, iter,
+						  min(k->k.p.offset << 9, new_i_size),
+						  i_sectors_delta) ?:
+		bch2_trans_update(trans, iter, k, 0) ?:
+		bch2_trans_commit(trans, disk_res, NULL,
+				BTREE_INSERT_NOCHECK_RW|
+				BTREE_INSERT_NOFAIL);
+	if (unlikely(ret))
+		return ret;
+
+	if (i_sectors_delta_total)
+		*i_sectors_delta_total += i_sectors_delta;
+	bch2_btree_iter_set_pos(iter, next_pos);
+	return 0;
+}
+
+static int bch2_write_index_default(struct bch_write_op *op)
+{
+	struct bch_fs *c = op->c;
+	struct bkey_buf sk;
+	struct keylist *keys = &op->insert_keys;
+	struct bkey_i *k = bch2_keylist_front(keys);
+	struct btree_trans trans;
+	struct btree_iter iter;
+	subvol_inum inum = {
+		.subvol = op->subvol,
+		.inum	= k->k.p.inode,
+	};
+	int ret;
+
+	BUG_ON(!inum.subvol);
+
+	bch2_bkey_buf_init(&sk);
+	bch2_trans_init(&trans, c, BTREE_ITER_MAX, 1024);
+
+	do {
+		bch2_trans_begin(&trans);
+
+		k = bch2_keylist_front(keys);
+		bch2_bkey_buf_copy(&sk, c, k);
+
+		ret = bch2_subvolume_get_snapshot(&trans, inum.subvol,
+						  &sk.k->k.p.snapshot);
+		if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
+			continue;
+		if (ret)
+			break;
+
+		bch2_trans_iter_init(&trans, &iter, BTREE_ID_extents,
+				     bkey_start_pos(&sk.k->k),
+				     BTREE_ITER_SLOTS|BTREE_ITER_INTENT);
+
+		ret = bch2_extent_update(&trans, inum, &iter, sk.k,
+					 &op->res,
+					 op->new_i_size, &op->i_sectors_delta,
+					 op->flags & BCH_WRITE_CHECK_ENOSPC);
+		bch2_trans_iter_exit(&trans, &iter);
+
+		if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
+			continue;
+		if (ret)
+			break;
+
+		if (bkey_ge(iter.pos, k->k.p))
+			bch2_keylist_pop_front(&op->insert_keys);
+		else
+			bch2_cut_front(iter.pos, k);
+	} while (!bch2_keylist_empty(keys));
+
+	bch2_trans_exit(&trans);
+	bch2_bkey_buf_exit(&sk, c);
+
+	return ret;
+}
+
+/* Writes */
+
+void bch2_submit_wbio_replicas(struct bch_write_bio *wbio, struct bch_fs *c,
+			       enum bch_data_type type,
+			       const struct bkey_i *k,
+			       bool nocow)
+{
+	struct bkey_ptrs_c ptrs = bch2_bkey_ptrs_c(bkey_i_to_s_c(k));
+	const struct bch_extent_ptr *ptr;
+	struct bch_write_bio *n;
+	struct bch_dev *ca;
+
+	BUG_ON(c->opts.nochanges);
+
+	bkey_for_each_ptr(ptrs, ptr) {
+		BUG_ON(ptr->dev >= BCH_SB_MEMBERS_MAX ||
+		       !c->devs[ptr->dev]);
+
+		ca = bch_dev_bkey_exists(c, ptr->dev);
+
+		if (to_entry(ptr + 1) < ptrs.end) {
+			n = to_wbio(bio_alloc_clone(NULL, &wbio->bio,
+						GFP_NOFS, &ca->replica_set));
+
+			n->bio.bi_end_io	= wbio->bio.bi_end_io;
+			n->bio.bi_private	= wbio->bio.bi_private;
+			n->parent		= wbio;
+			n->split		= true;
+			n->bounce		= false;
+			n->put_bio		= true;
+			n->bio.bi_opf		= wbio->bio.bi_opf;
+			bio_inc_remaining(&wbio->bio);
+		} else {
+			n = wbio;
+			n->split		= false;
+		}
+
+		n->c			= c;
+		n->dev			= ptr->dev;
+		n->have_ioref		= nocow || bch2_dev_get_ioref(ca,
+					type == BCH_DATA_btree ? READ : WRITE);
+		n->nocow		= nocow;
+		n->submit_time		= local_clock();
+		n->inode_offset		= bkey_start_offset(&k->k);
+		n->bio.bi_iter.bi_sector = ptr->offset;
+
+		if (likely(n->have_ioref)) {
+			this_cpu_add(ca->io_done->sectors[WRITE][type],
+				     bio_sectors(&n->bio));
+
+			bio_set_dev(&n->bio, ca->disk_sb.bdev);
+
+			if (type != BCH_DATA_btree && unlikely(c->opts.no_data_io)) {
+				bio_endio(&n->bio);
+				continue;
+			}
+
+			submit_bio(&n->bio);
+		} else {
+			n->bio.bi_status	= BLK_STS_REMOVED;
+			bio_endio(&n->bio);
+		}
+	}
+}
+
+static void __bch2_write(struct bch_write_op *);
+
+static void bch2_write_done(struct closure *cl)
+{
+	struct bch_write_op *op = container_of(cl, struct bch_write_op, cl);
+	struct bch_fs *c = op->c;
+
+	EBUG_ON(op->open_buckets.nr);
+
+	bch2_time_stats_update(&c->times[BCH_TIME_data_write], op->start_time);
+	bch2_disk_reservation_put(c, &op->res);
+
+	if (!(op->flags & BCH_WRITE_MOVE))
+		bch2_write_ref_put(c, BCH_WRITE_REF_write);
+	bch2_keylist_free(&op->insert_keys, op->inline_keys);
+
+	EBUG_ON(cl->parent);
+	closure_debug_destroy(cl);
+	if (op->end_io)
+		op->end_io(op);
+}
+
+static noinline int bch2_write_drop_io_error_ptrs(struct bch_write_op *op)
+{
+	struct keylist *keys = &op->insert_keys;
+	struct bch_extent_ptr *ptr;
+	struct bkey_i *src, *dst = keys->keys, *n;
+
+	for (src = keys->keys; src != keys->top; src = n) {
+		n = bkey_next(src);
+
+		if (bkey_extent_is_direct_data(&src->k)) {
+			bch2_bkey_drop_ptrs(bkey_i_to_s(src), ptr,
+					    test_bit(ptr->dev, op->failed.d));
+
+			if (!bch2_bkey_nr_ptrs(bkey_i_to_s_c(src)))
+				return -EIO;
+		}
+
+		if (dst != src)
+			memmove_u64s_down(dst, src, src->k.u64s);
+		dst = bkey_next(dst);
+	}
+
+	keys->top = dst;
+	return 0;
+}
+
+/**
+ * bch_write_index - after a write, update index to point to new data
+ */
+static void __bch2_write_index(struct bch_write_op *op)
+{
+	struct bch_fs *c = op->c;
+	struct keylist *keys = &op->insert_keys;
+	struct bkey_i *k;
+	unsigned dev;
+	int ret = 0;
+
+	if (unlikely(op->flags & BCH_WRITE_IO_ERROR)) {
+		ret = bch2_write_drop_io_error_ptrs(op);
+		if (ret)
+			goto err;
+	}
+
+	/*
+	 * probably not the ideal place to hook this in, but I don't
+	 * particularly want to plumb io_opts all the way through the btree
+	 * update stack right now
+	 */
+	for_each_keylist_key(keys, k)
+		bch2_rebalance_add_key(c, bkey_i_to_s_c(k), &op->opts);
+
+	if (!bch2_keylist_empty(keys)) {
+		u64 sectors_start = keylist_sectors(keys);
+
+		ret = !(op->flags & BCH_WRITE_MOVE)
+			? bch2_write_index_default(op)
+			: bch2_data_update_index_update(op);
+
+		BUG_ON(bch2_err_matches(ret, BCH_ERR_transaction_restart));
+		BUG_ON(keylist_sectors(keys) && !ret);
+
+		op->written += sectors_start - keylist_sectors(keys);
+
+		if (ret && !bch2_err_matches(ret, EROFS)) {
+			struct bkey_i *k = bch2_keylist_front(&op->insert_keys);
+
+			bch_err_inum_offset_ratelimited(c,
+				k->k.p.inode, k->k.p.offset << 9,
+				"write error while doing btree update: %s",
+				bch2_err_str(ret));
+		}
+
+		if (ret)
+			goto err;
+	}
+out:
+	/* If some a bucket wasn't written, we can't erasure code it: */
+	for_each_set_bit(dev, op->failed.d, BCH_SB_MEMBERS_MAX)
+		bch2_open_bucket_write_error(c, &op->open_buckets, dev);
+
+	bch2_open_buckets_put(c, &op->open_buckets);
+	return;
+err:
+	keys->top = keys->keys;
+	op->error = ret;
+	op->flags |= BCH_WRITE_DONE;
+	goto out;
+}
+
+static inline void __wp_update_state(struct write_point *wp, enum write_point_state state)
+{
+	if (state != wp->state) {
+		u64 now = ktime_get_ns();
+
+		if (wp->last_state_change &&
+		    time_after64(now, wp->last_state_change))
+			wp->time[wp->state] += now - wp->last_state_change;
+		wp->state = state;
+		wp->last_state_change = now;
+	}
+}
+
+static inline void wp_update_state(struct write_point *wp, bool running)
+{
+	enum write_point_state state;
+
+	state = running			 ? WRITE_POINT_running :
+		!list_empty(&wp->writes) ? WRITE_POINT_waiting_io
+					 : WRITE_POINT_stopped;
+
+	__wp_update_state(wp, state);
+}
+
+static void bch2_write_index(struct closure *cl)
+{
+	struct bch_write_op *op = container_of(cl, struct bch_write_op, cl);
+	struct write_point *wp = op->wp;
+	struct workqueue_struct *wq = index_update_wq(op);
+	unsigned long flags;
+
+	if ((op->flags & BCH_WRITE_DONE) &&
+	    (op->flags & BCH_WRITE_MOVE))
+		bch2_bio_free_pages_pool(op->c, &op->wbio.bio);
+
+	spin_lock_irqsave(&wp->writes_lock, flags);
+	if (wp->state == WRITE_POINT_waiting_io)
+		__wp_update_state(wp, WRITE_POINT_waiting_work);
+	list_add_tail(&op->wp_list, &wp->writes);
+	spin_unlock_irqrestore (&wp->writes_lock, flags);
+
+	queue_work(wq, &wp->index_update_work);
+}
+
+static inline void bch2_write_queue(struct bch_write_op *op, struct write_point *wp)
+{
+	op->wp = wp;
+
+	if (wp->state == WRITE_POINT_stopped) {
+		spin_lock_irq(&wp->writes_lock);
+		__wp_update_state(wp, WRITE_POINT_waiting_io);
+		spin_unlock_irq(&wp->writes_lock);
+	}
+}
+
+void bch2_write_point_do_index_updates(struct work_struct *work)
+{
+	struct write_point *wp =
+		container_of(work, struct write_point, index_update_work);
+	struct bch_write_op *op;
+
+	while (1) {
+		spin_lock_irq(&wp->writes_lock);
+		op = list_first_entry_or_null(&wp->writes, struct bch_write_op, wp_list);
+		if (op)
+			list_del(&op->wp_list);
+		wp_update_state(wp, op != NULL);
+		spin_unlock_irq(&wp->writes_lock);
+
+		if (!op)
+			break;
+
+		op->flags |= BCH_WRITE_IN_WORKER;
+
+		__bch2_write_index(op);
+
+		if (!(op->flags & BCH_WRITE_DONE))
+			__bch2_write(op);
+		else
+			bch2_write_done(&op->cl);
+	}
+}
+
+static void bch2_write_endio(struct bio *bio)
+{
+	struct closure *cl		= bio->bi_private;
+	struct bch_write_op *op		= container_of(cl, struct bch_write_op, cl);
+	struct bch_write_bio *wbio	= to_wbio(bio);
+	struct bch_write_bio *parent	= wbio->split ? wbio->parent : NULL;
+	struct bch_fs *c		= wbio->c;
+	struct bch_dev *ca		= bch_dev_bkey_exists(c, wbio->dev);
+
+	if (bch2_dev_inum_io_err_on(bio->bi_status, ca,
+				    op->pos.inode,
+				    wbio->inode_offset << 9,
+				    "data write error: %s",
+				    bch2_blk_status_to_str(bio->bi_status))) {
+		set_bit(wbio->dev, op->failed.d);
+		op->flags |= BCH_WRITE_IO_ERROR;
+	}
+
+	if (wbio->nocow)
+		set_bit(wbio->dev, op->devs_need_flush->d);
+
+	if (wbio->have_ioref) {
+		bch2_latency_acct(ca, wbio->submit_time, WRITE);
+		percpu_ref_put(&ca->io_ref);
+	}
+
+	if (wbio->bounce)
+		bch2_bio_free_pages_pool(c, bio);
+
+	if (wbio->put_bio)
+		bio_put(bio);
+
+	if (parent)
+		bio_endio(&parent->bio);
+	else
+		closure_put(cl);
+}
+
+static void init_append_extent(struct bch_write_op *op,
+			       struct write_point *wp,
+			       struct bversion version,
+			       struct bch_extent_crc_unpacked crc)
+{
+	struct bkey_i_extent *e;
+
+	op->pos.offset += crc.uncompressed_size;
+
+	e = bkey_extent_init(op->insert_keys.top);
+	e->k.p		= op->pos;
+	e->k.size	= crc.uncompressed_size;
+	e->k.version	= version;
+
+	if (crc.csum_type ||
+	    crc.compression_type ||
+	    crc.nonce)
+		bch2_extent_crc_append(&e->k_i, crc);
+
+	bch2_alloc_sectors_append_ptrs_inlined(op->c, wp, &e->k_i, crc.compressed_size,
+				       op->flags & BCH_WRITE_CACHED);
+
+	bch2_keylist_push(&op->insert_keys);
+}
+
+static struct bio *bch2_write_bio_alloc(struct bch_fs *c,
+					struct write_point *wp,
+					struct bio *src,
+					bool *page_alloc_failed,
+					void *buf)
+{
+	struct bch_write_bio *wbio;
+	struct bio *bio;
+	unsigned output_available =
+		min(wp->sectors_free << 9, src->bi_iter.bi_size);
+	unsigned pages = DIV_ROUND_UP(output_available +
+				      (buf
+				       ? ((unsigned long) buf & (PAGE_SIZE - 1))
+				       : 0), PAGE_SIZE);
+
+	pages = min(pages, BIO_MAX_VECS);
+
+	bio = bio_alloc_bioset(NULL, pages, 0,
+			       GFP_NOFS, &c->bio_write);
+	wbio			= wbio_init(bio);
+	wbio->put_bio		= true;
+	/* copy WRITE_SYNC flag */
+	wbio->bio.bi_opf	= src->bi_opf;
+
+	if (buf) {
+		bch2_bio_map(bio, buf, output_available);
+		return bio;
+	}
+
+	wbio->bounce		= true;
+
+	/*
+	 * We can't use mempool for more than c->sb.encoded_extent_max
+	 * worth of pages, but we'd like to allocate more if we can:
+	 */
+	bch2_bio_alloc_pages_pool(c, bio,
+				  min_t(unsigned, output_available,
+					c->opts.encoded_extent_max));
+
+	if (bio->bi_iter.bi_size < output_available)
+		*page_alloc_failed =
+			bch2_bio_alloc_pages(bio,
+					     output_available -
+					     bio->bi_iter.bi_size,
+					     GFP_NOFS) != 0;
+
+	return bio;
+}
+
+static int bch2_write_rechecksum(struct bch_fs *c,
+				 struct bch_write_op *op,
+				 unsigned new_csum_type)
+{
+	struct bio *bio = &op->wbio.bio;
+	struct bch_extent_crc_unpacked new_crc;
+	int ret;
+
+	/* bch2_rechecksum_bio() can't encrypt or decrypt data: */
+
+	if (bch2_csum_type_is_encryption(op->crc.csum_type) !=
+	    bch2_csum_type_is_encryption(new_csum_type))
+		new_csum_type = op->crc.csum_type;
+
+	ret = bch2_rechecksum_bio(c, bio, op->version, op->crc,
+				  NULL, &new_crc,
+				  op->crc.offset, op->crc.live_size,
+				  new_csum_type);
+	if (ret)
+		return ret;
+
+	bio_advance(bio, op->crc.offset << 9);
+	bio->bi_iter.bi_size = op->crc.live_size << 9;
+	op->crc = new_crc;
+	return 0;
+}
+
+static int bch2_write_decrypt(struct bch_write_op *op)
+{
+	struct bch_fs *c = op->c;
+	struct nonce nonce = extent_nonce(op->version, op->crc);
+	struct bch_csum csum;
+	int ret;
+
+	if (!bch2_csum_type_is_encryption(op->crc.csum_type))
+		return 0;
+
+	/*
+	 * If we need to decrypt data in the write path, we'll no longer be able
+	 * to verify the existing checksum (poly1305 mac, in this case) after
+	 * it's decrypted - this is the last point we'll be able to reverify the
+	 * checksum:
+	 */
+	csum = bch2_checksum_bio(c, op->crc.csum_type, nonce, &op->wbio.bio);
+	if (bch2_crc_cmp(op->crc.csum, csum))
+		return -EIO;
+
+	ret = bch2_encrypt_bio(c, op->crc.csum_type, nonce, &op->wbio.bio);
+	op->crc.csum_type = 0;
+	op->crc.csum = (struct bch_csum) { 0, 0 };
+	return ret;
+}
+
+static enum prep_encoded_ret {
+	PREP_ENCODED_OK,
+	PREP_ENCODED_ERR,
+	PREP_ENCODED_CHECKSUM_ERR,
+	PREP_ENCODED_DO_WRITE,
+} bch2_write_prep_encoded_data(struct bch_write_op *op, struct write_point *wp)
+{
+	struct bch_fs *c = op->c;
+	struct bio *bio = &op->wbio.bio;
+
+	if (!(op->flags & BCH_WRITE_DATA_ENCODED))
+		return PREP_ENCODED_OK;
+
+	BUG_ON(bio_sectors(bio) != op->crc.compressed_size);
+
+	/* Can we just write the entire extent as is? */
+	if (op->crc.uncompressed_size == op->crc.live_size &&
+	    op->crc.compressed_size <= wp->sectors_free &&
+	    (op->crc.compression_type == bch2_compression_opt_to_type(op->compression_opt) ||
+	     op->incompressible)) {
+		if (!crc_is_compressed(op->crc) &&
+		    op->csum_type != op->crc.csum_type &&
+		    bch2_write_rechecksum(c, op, op->csum_type) &&
+		    !c->opts.no_data_io)
+			return PREP_ENCODED_CHECKSUM_ERR;
+
+		return PREP_ENCODED_DO_WRITE;
+	}
+
+	/*
+	 * If the data is compressed and we couldn't write the entire extent as
+	 * is, we have to decompress it:
+	 */
+	if (crc_is_compressed(op->crc)) {
+		struct bch_csum csum;
+
+		if (bch2_write_decrypt(op))
+			return PREP_ENCODED_CHECKSUM_ERR;
+
+		/* Last point we can still verify checksum: */
+		csum = bch2_checksum_bio(c, op->crc.csum_type,
+					 extent_nonce(op->version, op->crc),
+					 bio);
+		if (bch2_crc_cmp(op->crc.csum, csum) && !c->opts.no_data_io)
+			return PREP_ENCODED_CHECKSUM_ERR;
+
+		if (bch2_bio_uncompress_inplace(c, bio, &op->crc))
+			return PREP_ENCODED_ERR;
+	}
+
+	/*
+	 * No longer have compressed data after this point - data might be
+	 * encrypted:
+	 */
+
+	/*
+	 * If the data is checksummed and we're only writing a subset,
+	 * rechecksum and adjust bio to point to currently live data:
+	 */
+	if ((op->crc.live_size != op->crc.uncompressed_size ||
+	     op->crc.csum_type != op->csum_type) &&
+	    bch2_write_rechecksum(c, op, op->csum_type) &&
+	    !c->opts.no_data_io)
+		return PREP_ENCODED_CHECKSUM_ERR;
+
+	/*
+	 * If we want to compress the data, it has to be decrypted:
+	 */
+	if ((op->compression_opt ||
+	     bch2_csum_type_is_encryption(op->crc.csum_type) !=
+	     bch2_csum_type_is_encryption(op->csum_type)) &&
+	    bch2_write_decrypt(op))
+		return PREP_ENCODED_CHECKSUM_ERR;
+
+	return PREP_ENCODED_OK;
+}
+
+static int bch2_write_extent(struct bch_write_op *op, struct write_point *wp,
+			     struct bio **_dst)
+{
+	struct bch_fs *c = op->c;
+	struct bio *src = &op->wbio.bio, *dst = src;
+	struct bvec_iter saved_iter;
+	void *ec_buf;
+	unsigned total_output = 0, total_input = 0;
+	bool bounce = false;
+	bool page_alloc_failed = false;
+	int ret, more = 0;
+
+	BUG_ON(!bio_sectors(src));
+
+	ec_buf = bch2_writepoint_ec_buf(c, wp);
+
+	switch (bch2_write_prep_encoded_data(op, wp)) {
+	case PREP_ENCODED_OK:
+		break;
+	case PREP_ENCODED_ERR:
+		ret = -EIO;
+		goto err;
+	case PREP_ENCODED_CHECKSUM_ERR:
+		goto csum_err;
+	case PREP_ENCODED_DO_WRITE:
+		/* XXX look for bug here */
+		if (ec_buf) {
+			dst = bch2_write_bio_alloc(c, wp, src,
+						   &page_alloc_failed,
+						   ec_buf);
+			bio_copy_data(dst, src);
+			bounce = true;
+		}
+		init_append_extent(op, wp, op->version, op->crc);
+		goto do_write;
+	}
+
+	if (ec_buf ||
+	    op->compression_opt ||
+	    (op->csum_type &&
+	     !(op->flags & BCH_WRITE_PAGES_STABLE)) ||
+	    (bch2_csum_type_is_encryption(op->csum_type) &&
+	     !(op->flags & BCH_WRITE_PAGES_OWNED))) {
+		dst = bch2_write_bio_alloc(c, wp, src,
+					   &page_alloc_failed,
+					   ec_buf);
+		bounce = true;
+	}
+
+	saved_iter = dst->bi_iter;
+
+	do {
+		struct bch_extent_crc_unpacked crc = { 0 };
+		struct bversion version = op->version;
+		size_t dst_len, src_len;
+
+		if (page_alloc_failed &&
+		    dst->bi_iter.bi_size  < (wp->sectors_free << 9) &&
+		    dst->bi_iter.bi_size < c->opts.encoded_extent_max)
+			break;
+
+		BUG_ON(op->compression_opt &&
+		       (op->flags & BCH_WRITE_DATA_ENCODED) &&
+		       bch2_csum_type_is_encryption(op->crc.csum_type));
+		BUG_ON(op->compression_opt && !bounce);
+
+		crc.compression_type = op->incompressible
+			? BCH_COMPRESSION_TYPE_incompressible
+			: op->compression_opt
+			? bch2_bio_compress(c, dst, &dst_len, src, &src_len,
+					    op->compression_opt)
+			: 0;
+		if (!crc_is_compressed(crc)) {
+			dst_len = min(dst->bi_iter.bi_size, src->bi_iter.bi_size);
+			dst_len = min_t(unsigned, dst_len, wp->sectors_free << 9);
+
+			if (op->csum_type)
+				dst_len = min_t(unsigned, dst_len,
+						c->opts.encoded_extent_max);
+
+			if (bounce) {
+				swap(dst->bi_iter.bi_size, dst_len);
+				bio_copy_data(dst, src);
+				swap(dst->bi_iter.bi_size, dst_len);
+			}
+
+			src_len = dst_len;
+		}
+
+		BUG_ON(!src_len || !dst_len);
+
+		if (bch2_csum_type_is_encryption(op->csum_type)) {
+			if (bversion_zero(version)) {
+				version.lo = atomic64_inc_return(&c->key_version);
+			} else {
+				crc.nonce = op->nonce;
+				op->nonce += src_len >> 9;
+			}
+		}
+
+		if ((op->flags & BCH_WRITE_DATA_ENCODED) &&
+		    !crc_is_compressed(crc) &&
+		    bch2_csum_type_is_encryption(op->crc.csum_type) ==
+		    bch2_csum_type_is_encryption(op->csum_type)) {
+			u8 compression_type = crc.compression_type;
+			u16 nonce = crc.nonce;
+			/*
+			 * Note: when we're using rechecksum(), we need to be
+			 * checksumming @src because it has all the data our
+			 * existing checksum covers - if we bounced (because we
+			 * were trying to compress), @dst will only have the
+			 * part of the data the new checksum will cover.
+			 *
+			 * But normally we want to be checksumming post bounce,
+			 * because part of the reason for bouncing is so the
+			 * data can't be modified (by userspace) while it's in
+			 * flight.
+			 */
+			if (bch2_rechecksum_bio(c, src, version, op->crc,
+					&crc, &op->crc,
+					src_len >> 9,
+					bio_sectors(src) - (src_len >> 9),
+					op->csum_type))
+				goto csum_err;
+			/*
+			 * rchecksum_bio sets compression_type on crc from op->crc,
+			 * this isn't always correct as sometimes we're changing
+			 * an extent from uncompressed to incompressible.
+			 */
+			crc.compression_type = compression_type;
+			crc.nonce = nonce;
+		} else {
+			if ((op->flags & BCH_WRITE_DATA_ENCODED) &&
+			    bch2_rechecksum_bio(c, src, version, op->crc,
+					NULL, &op->crc,
+					src_len >> 9,
+					bio_sectors(src) - (src_len >> 9),
+					op->crc.csum_type))
+				goto csum_err;
+
+			crc.compressed_size	= dst_len >> 9;
+			crc.uncompressed_size	= src_len >> 9;
+			crc.live_size		= src_len >> 9;
+
+			swap(dst->bi_iter.bi_size, dst_len);
+			ret = bch2_encrypt_bio(c, op->csum_type,
+					       extent_nonce(version, crc), dst);
+			if (ret)
+				goto err;
+
+			crc.csum = bch2_checksum_bio(c, op->csum_type,
+					 extent_nonce(version, crc), dst);
+			crc.csum_type = op->csum_type;
+			swap(dst->bi_iter.bi_size, dst_len);
+		}
+
+		init_append_extent(op, wp, version, crc);
+
+		if (dst != src)
+			bio_advance(dst, dst_len);
+		bio_advance(src, src_len);
+		total_output	+= dst_len;
+		total_input	+= src_len;
+	} while (dst->bi_iter.bi_size &&
+		 src->bi_iter.bi_size &&
+		 wp->sectors_free &&
+		 !bch2_keylist_realloc(&op->insert_keys,
+				      op->inline_keys,
+				      ARRAY_SIZE(op->inline_keys),
+				      BKEY_EXTENT_U64s_MAX));
+
+	more = src->bi_iter.bi_size != 0;
+
+	dst->bi_iter = saved_iter;
+
+	if (dst == src && more) {
+		BUG_ON(total_output != total_input);
+
+		dst = bio_split(src, total_input >> 9,
+				GFP_NOFS, &c->bio_write);
+		wbio_init(dst)->put_bio	= true;
+		/* copy WRITE_SYNC flag */
+		dst->bi_opf		= src->bi_opf;
+	}
+
+	dst->bi_iter.bi_size = total_output;
+do_write:
+	*_dst = dst;
+	return more;
+csum_err:
+	bch_err(c, "error verifying existing checksum while rewriting existing data (memory corruption?)");
+	ret = -EIO;
+err:
+	if (to_wbio(dst)->bounce)
+		bch2_bio_free_pages_pool(c, dst);
+	if (to_wbio(dst)->put_bio)
+		bio_put(dst);
+
+	return ret;
+}
+
+static bool bch2_extent_is_writeable(struct bch_write_op *op,
+				     struct bkey_s_c k)
+{
+	struct bch_fs *c = op->c;
+	struct bkey_s_c_extent e;
+	struct extent_ptr_decoded p;
+	const union bch_extent_entry *entry;
+	unsigned replicas = 0;
+
+	if (k.k->type != KEY_TYPE_extent)
+		return false;
+
+	e = bkey_s_c_to_extent(k);
+	extent_for_each_ptr_decode(e, p, entry) {
+		if (p.crc.csum_type ||
+		    crc_is_compressed(p.crc) ||
+		    p.has_ec)
+			return false;
+
+		replicas += bch2_extent_ptr_durability(c, &p);
+	}
+
+	return replicas >= op->opts.data_replicas;
+}
+
+static inline void bch2_nocow_write_unlock(struct bch_write_op *op)
+{
+	struct bch_fs *c = op->c;
+	const struct bch_extent_ptr *ptr;
+	struct bkey_i *k;
+
+	for_each_keylist_key(&op->insert_keys, k) {
+		struct bkey_ptrs_c ptrs = bch2_bkey_ptrs_c(bkey_i_to_s_c(k));
+
+		bkey_for_each_ptr(ptrs, ptr)
+			bch2_bucket_nocow_unlock(&c->nocow_locks,
+					       PTR_BUCKET_POS(c, ptr),
+					       BUCKET_NOCOW_LOCK_UPDATE);
+	}
+}
+
+static int bch2_nocow_write_convert_one_unwritten(struct btree_trans *trans,
+						  struct btree_iter *iter,
+						  struct bkey_i *orig,
+						  struct bkey_s_c k,
+						  u64 new_i_size)
+{
+	struct bkey_i *new;
+	struct bkey_ptrs ptrs;
+	struct bch_extent_ptr *ptr;
+	int ret;
+
+	if (!bch2_extents_match(bkey_i_to_s_c(orig), k)) {
+		/* trace this */
+		return 0;
+	}
+
+	new = bch2_bkey_make_mut_noupdate(trans, k);
+	ret = PTR_ERR_OR_ZERO(new);
+	if (ret)
+		return ret;
+
+	bch2_cut_front(bkey_start_pos(&orig->k), new);
+	bch2_cut_back(orig->k.p, new);
+
+	ptrs = bch2_bkey_ptrs(bkey_i_to_s(new));
+	bkey_for_each_ptr(ptrs, ptr)
+		ptr->unwritten = 0;
+
+	/*
+	 * Note that we're not calling bch2_subvol_get_snapshot() in this path -
+	 * that was done when we kicked off the write, and here it's important
+	 * that we update the extent that we wrote to - even if a snapshot has
+	 * since been created. The write is still outstanding, so we're ok
+	 * w.r.t. snapshot atomicity:
+	 */
+	return  bch2_extent_update_i_size_sectors(trans, iter,
+					min(new->k.p.offset << 9, new_i_size), 0) ?:
+		bch2_trans_update(trans, iter, new,
+				  BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE);
+}
+
+static void bch2_nocow_write_convert_unwritten(struct bch_write_op *op)
+{
+	struct bch_fs *c = op->c;
+	struct btree_trans trans;
+	struct btree_iter iter;
+	struct bkey_i *orig;
+	struct bkey_s_c k;
+	int ret;
+
+	bch2_trans_init(&trans, c, 0, 0);
+
+	for_each_keylist_key(&op->insert_keys, orig) {
+		ret = for_each_btree_key_upto_commit(&trans, iter, BTREE_ID_extents,
+				     bkey_start_pos(&orig->k), orig->k.p,
+				     BTREE_ITER_INTENT, k,
+				     NULL, NULL, BTREE_INSERT_NOFAIL, ({
+			bch2_nocow_write_convert_one_unwritten(&trans, &iter, orig, k, op->new_i_size);
+		}));
+
+		if (ret && !bch2_err_matches(ret, EROFS)) {
+			struct bkey_i *k = bch2_keylist_front(&op->insert_keys);
+
+			bch_err_inum_offset_ratelimited(c,
+				k->k.p.inode, k->k.p.offset << 9,
+				"write error while doing btree update: %s",
+				bch2_err_str(ret));
+		}
+
+		if (ret) {
+			op->error = ret;
+			break;
+		}
+	}
+
+	bch2_trans_exit(&trans);
+}
+
+static void __bch2_nocow_write_done(struct bch_write_op *op)
+{
+	bch2_nocow_write_unlock(op);
+
+	if (unlikely(op->flags & BCH_WRITE_IO_ERROR)) {
+		op->error = -EIO;
+	} else if (unlikely(op->flags & BCH_WRITE_CONVERT_UNWRITTEN))
+		bch2_nocow_write_convert_unwritten(op);
+}
+
+static void bch2_nocow_write_done(struct closure *cl)
+{
+	struct bch_write_op *op = container_of(cl, struct bch_write_op, cl);
+
+	__bch2_nocow_write_done(op);
+	bch2_write_done(cl);
+}
+
+static void bch2_nocow_write(struct bch_write_op *op)
+{
+	struct bch_fs *c = op->c;
+	struct btree_trans trans;
+	struct btree_iter iter;
+	struct bkey_s_c k;
+	struct bkey_ptrs_c ptrs;
+	const struct bch_extent_ptr *ptr;
+	struct {
+		struct bpos	b;
+		unsigned	gen;
+		struct nocow_lock_bucket *l;
+	} buckets[BCH_REPLICAS_MAX];
+	unsigned nr_buckets = 0;
+	u32 snapshot;
+	int ret, i;
+
+	if (op->flags & BCH_WRITE_MOVE)
+		return;
+
+	bch2_trans_init(&trans, c, 0, 0);
+retry:
+	bch2_trans_begin(&trans);
+
+	ret = bch2_subvolume_get_snapshot(&trans, op->subvol, &snapshot);
+	if (unlikely(ret))
+		goto err;
+
+	bch2_trans_iter_init(&trans, &iter, BTREE_ID_extents,
+			     SPOS(op->pos.inode, op->pos.offset, snapshot),
+			     BTREE_ITER_SLOTS);
+	while (1) {
+		struct bio *bio = &op->wbio.bio;
+
+		nr_buckets = 0;
+
+		k = bch2_btree_iter_peek_slot(&iter);
+		ret = bkey_err(k);
+		if (ret)
+			break;
+
+		/* fall back to normal cow write path? */
+		if (unlikely(k.k->p.snapshot != snapshot ||
+			     !bch2_extent_is_writeable(op, k)))
+			break;
+
+		if (bch2_keylist_realloc(&op->insert_keys,
+					op->inline_keys,
+					ARRAY_SIZE(op->inline_keys),
+					k.k->u64s))
+			break;
+
+		/* Get iorefs before dropping btree locks: */
+		ptrs = bch2_bkey_ptrs_c(k);
+		bkey_for_each_ptr(ptrs, ptr) {
+			buckets[nr_buckets].b = PTR_BUCKET_POS(c, ptr);
+			buckets[nr_buckets].gen = ptr->gen;
+			buckets[nr_buckets].l =
+				bucket_nocow_lock(&c->nocow_locks,
+						  bucket_to_u64(buckets[nr_buckets].b));
+
+			prefetch(buckets[nr_buckets].l);
+
+			if (unlikely(!bch2_dev_get_ioref(bch_dev_bkey_exists(c, ptr->dev), WRITE)))
+				goto err_get_ioref;
+
+			nr_buckets++;
+
+			if (ptr->unwritten)
+				op->flags |= BCH_WRITE_CONVERT_UNWRITTEN;
+		}
+
+		/* Unlock before taking nocow locks, doing IO: */
+		bkey_reassemble(op->insert_keys.top, k);
+		bch2_trans_unlock(&trans);
+
+		bch2_cut_front(op->pos, op->insert_keys.top);
+		if (op->flags & BCH_WRITE_CONVERT_UNWRITTEN)
+			bch2_cut_back(POS(op->pos.inode, op->pos.offset + bio_sectors(bio)), op->insert_keys.top);
+
+		for (i = 0; i < nr_buckets; i++) {
+			struct bch_dev *ca = bch_dev_bkey_exists(c, buckets[i].b.inode);
+			struct nocow_lock_bucket *l = buckets[i].l;
+			bool stale;
+
+			__bch2_bucket_nocow_lock(&c->nocow_locks, l,
+						 bucket_to_u64(buckets[i].b),
+						 BUCKET_NOCOW_LOCK_UPDATE);
+
+			rcu_read_lock();
+			stale = gen_after(*bucket_gen(ca, buckets[i].b.offset), buckets[i].gen);
+			rcu_read_unlock();
+
+			if (unlikely(stale))
+				goto err_bucket_stale;
+		}
+
+		bio = &op->wbio.bio;
+		if (k.k->p.offset < op->pos.offset + bio_sectors(bio)) {
+			bio = bio_split(bio, k.k->p.offset - op->pos.offset,
+					GFP_KERNEL, &c->bio_write);
+			wbio_init(bio)->put_bio = true;
+			bio->bi_opf = op->wbio.bio.bi_opf;
+		} else {
+			op->flags |= BCH_WRITE_DONE;
+		}
+
+		op->pos.offset += bio_sectors(bio);
+		op->written += bio_sectors(bio);
+
+		bio->bi_end_io	= bch2_write_endio;
+		bio->bi_private	= &op->cl;
+		bio->bi_opf |= REQ_OP_WRITE;
+		closure_get(&op->cl);
+		bch2_submit_wbio_replicas(to_wbio(bio), c, BCH_DATA_user,
+					  op->insert_keys.top, true);
+
+		bch2_keylist_push(&op->insert_keys);
+		if (op->flags & BCH_WRITE_DONE)
+			break;
+		bch2_btree_iter_advance(&iter);
+	}
+out:
+	bch2_trans_iter_exit(&trans, &iter);
+err:
+	if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
+		goto retry;
+
+	if (ret) {
+		bch_err_inum_offset_ratelimited(c,
+				op->pos.inode,
+				op->pos.offset << 9,
+				"%s: btree lookup error %s",
+				__func__, bch2_err_str(ret));
+		op->error = ret;
+		op->flags |= BCH_WRITE_DONE;
+	}
+
+	bch2_trans_exit(&trans);
+
+	/* fallback to cow write path? */
+	if (!(op->flags & BCH_WRITE_DONE)) {
+		closure_sync(&op->cl);
+		__bch2_nocow_write_done(op);
+		op->insert_keys.top = op->insert_keys.keys;
+	} else if (op->flags & BCH_WRITE_SYNC) {
+		closure_sync(&op->cl);
+		bch2_nocow_write_done(&op->cl);
+	} else {
+		/*
+		 * XXX
+		 * needs to run out of process context because ei_quota_lock is
+		 * a mutex
+		 */
+		continue_at(&op->cl, bch2_nocow_write_done, index_update_wq(op));
+	}
+	return;
+err_get_ioref:
+	for (i = 0; i < nr_buckets; i++)
+		percpu_ref_put(&bch_dev_bkey_exists(c, buckets[i].b.inode)->io_ref);
+
+	/* Fall back to COW path: */
+	goto out;
+err_bucket_stale:
+	while (--i >= 0)
+		bch2_bucket_nocow_unlock(&c->nocow_locks,
+					 buckets[i].b,
+					 BUCKET_NOCOW_LOCK_UPDATE);
+	for (i = 0; i < nr_buckets; i++)
+		percpu_ref_put(&bch_dev_bkey_exists(c, buckets[i].b.inode)->io_ref);
+
+	/* We can retry this: */
+	ret = -BCH_ERR_transaction_restart;
+	goto out;
+}
+
+static void __bch2_write(struct bch_write_op *op)
+{
+	struct bch_fs *c = op->c;
+	struct write_point *wp = NULL;
+	struct bio *bio = NULL;
+	unsigned nofs_flags;
+	int ret;
+
+	nofs_flags = memalloc_nofs_save();
+
+	if (unlikely(op->opts.nocow && c->opts.nocow_enabled)) {
+		bch2_nocow_write(op);
+		if (op->flags & BCH_WRITE_DONE)
+			goto out_nofs_restore;
+	}
+again:
+	memset(&op->failed, 0, sizeof(op->failed));
+
+	do {
+		struct bkey_i *key_to_write;
+		unsigned key_to_write_offset = op->insert_keys.top_p -
+			op->insert_keys.keys_p;
+
+		/* +1 for possible cache device: */
+		if (op->open_buckets.nr + op->nr_replicas + 1 >
+		    ARRAY_SIZE(op->open_buckets.v))
+			break;
+
+		if (bch2_keylist_realloc(&op->insert_keys,
+					op->inline_keys,
+					ARRAY_SIZE(op->inline_keys),
+					BKEY_EXTENT_U64s_MAX))
+			break;
+
+		/*
+		 * The copygc thread is now global, which means it's no longer
+		 * freeing up space on specific disks, which means that
+		 * allocations for specific disks may hang arbitrarily long:
+		 */
+		ret = bch2_trans_do(c, NULL, NULL, 0,
+			bch2_alloc_sectors_start_trans(&trans,
+				op->target,
+				op->opts.erasure_code && !(op->flags & BCH_WRITE_CACHED),
+				op->write_point,
+				&op->devs_have,
+				op->nr_replicas,
+				op->nr_replicas_required,
+				op->watermark,
+				op->flags,
+				(op->flags & (BCH_WRITE_ALLOC_NOWAIT|
+					      BCH_WRITE_ONLY_SPECIFIED_DEVS))
+				? NULL : &op->cl, &wp));
+		if (unlikely(ret)) {
+			if (bch2_err_matches(ret, BCH_ERR_operation_blocked))
+				break;
+
+			goto err;
+		}
+
+		EBUG_ON(!wp);
+
+		bch2_open_bucket_get(c, wp, &op->open_buckets);
+		ret = bch2_write_extent(op, wp, &bio);
+
+		bch2_alloc_sectors_done_inlined(c, wp);
+err:
+		if (ret <= 0) {
+			op->flags |= BCH_WRITE_DONE;
+
+			if (ret < 0) {
+				op->error = ret;
+				break;
+			}
+		}
+
+		bio->bi_end_io	= bch2_write_endio;
+		bio->bi_private	= &op->cl;
+		bio->bi_opf |= REQ_OP_WRITE;
+
+		closure_get(bio->bi_private);
+
+		key_to_write = (void *) (op->insert_keys.keys_p +
+					 key_to_write_offset);
+
+		bch2_submit_wbio_replicas(to_wbio(bio), c, BCH_DATA_user,
+					  key_to_write, false);
+	} while (ret);
+
+	/*
+	 * Sync or no?
+	 *
+	 * If we're running asynchronously, wne may still want to block
+	 * synchronously here if we weren't able to submit all of the IO at
+	 * once, as that signals backpressure to the caller.
+	 */
+	if ((op->flags & BCH_WRITE_SYNC) ||
+	    (!(op->flags & BCH_WRITE_DONE) &&
+	     !(op->flags & BCH_WRITE_IN_WORKER))) {
+		closure_sync(&op->cl);
+		__bch2_write_index(op);
+
+		if (!(op->flags & BCH_WRITE_DONE))
+			goto again;
+		bch2_write_done(&op->cl);
+	} else {
+		bch2_write_queue(op, wp);
+		continue_at(&op->cl, bch2_write_index, NULL);
+	}
+out_nofs_restore:
+	memalloc_nofs_restore(nofs_flags);
+}
+
+static void bch2_write_data_inline(struct bch_write_op *op, unsigned data_len)
+{
+	struct bio *bio = &op->wbio.bio;
+	struct bvec_iter iter;
+	struct bkey_i_inline_data *id;
+	unsigned sectors;
+	int ret;
+
+	op->flags |= BCH_WRITE_WROTE_DATA_INLINE;
+	op->flags |= BCH_WRITE_DONE;
+
+	bch2_check_set_feature(op->c, BCH_FEATURE_inline_data);
+
+	ret = bch2_keylist_realloc(&op->insert_keys, op->inline_keys,
+				   ARRAY_SIZE(op->inline_keys),
+				   BKEY_U64s + DIV_ROUND_UP(data_len, 8));
+	if (ret) {
+		op->error = ret;
+		goto err;
+	}
+
+	sectors = bio_sectors(bio);
+	op->pos.offset += sectors;
+
+	id = bkey_inline_data_init(op->insert_keys.top);
+	id->k.p		= op->pos;
+	id->k.version	= op->version;
+	id->k.size	= sectors;
+
+	iter = bio->bi_iter;
+	iter.bi_size = data_len;
+	memcpy_from_bio(id->v.data, bio, iter);
+
+	while (data_len & 7)
+		id->v.data[data_len++] = '\0';
+	set_bkey_val_bytes(&id->k, data_len);
+	bch2_keylist_push(&op->insert_keys);
+
+	__bch2_write_index(op);
+err:
+	bch2_write_done(&op->cl);
+}
+
+/**
+ * bch_write - handle a write to a cache device or flash only volume
+ *
+ * This is the starting point for any data to end up in a cache device; it could
+ * be from a normal write, or a writeback write, or a write to a flash only
+ * volume - it's also used by the moving garbage collector to compact data in
+ * mostly empty buckets.
+ *
+ * It first writes the data to the cache, creating a list of keys to be inserted
+ * (if the data won't fit in a single open bucket, there will be multiple keys);
+ * after the data is written it calls bch_journal, and after the keys have been
+ * added to the next journal write they're inserted into the btree.
+ *
+ * If op->discard is true, instead of inserting the data it invalidates the
+ * region of the cache represented by op->bio and op->inode.
+ */
+void bch2_write(struct closure *cl)
+{
+	struct bch_write_op *op = container_of(cl, struct bch_write_op, cl);
+	struct bio *bio = &op->wbio.bio;
+	struct bch_fs *c = op->c;
+	unsigned data_len;
+
+	EBUG_ON(op->cl.parent);
+	BUG_ON(!op->nr_replicas);
+	BUG_ON(!op->write_point.v);
+	BUG_ON(bkey_eq(op->pos, POS_MAX));
+
+	op->start_time = local_clock();
+	bch2_keylist_init(&op->insert_keys, op->inline_keys);
+	wbio_init(bio)->put_bio = false;
+
+	if (bio->bi_iter.bi_size & (c->opts.block_size - 1)) {
+		bch_err_inum_offset_ratelimited(c,
+			op->pos.inode,
+			op->pos.offset << 9,
+			"misaligned write");
+		op->error = -EIO;
+		goto err;
+	}
+
+	if (c->opts.nochanges) {
+		op->error = -BCH_ERR_erofs_no_writes;
+		goto err;
+	}
+
+	if (!(op->flags & BCH_WRITE_MOVE) &&
+	    !bch2_write_ref_tryget(c, BCH_WRITE_REF_write)) {
+		op->error = -BCH_ERR_erofs_no_writes;
+		goto err;
+	}
+
+	this_cpu_add(c->counters[BCH_COUNTER_io_write], bio_sectors(bio));
+	bch2_increment_clock(c, bio_sectors(bio), WRITE);
+
+	data_len = min_t(u64, bio->bi_iter.bi_size,
+			 op->new_i_size - (op->pos.offset << 9));
+
+	if (c->opts.inline_data &&
+	    data_len <= min(block_bytes(c) / 2, 1024U)) {
+		bch2_write_data_inline(op, data_len);
+		return;
+	}
+
+	__bch2_write(op);
+	return;
+err:
+	bch2_disk_reservation_put(c, &op->res);
+
+	closure_debug_destroy(&op->cl);
+	if (op->end_io)
+		op->end_io(op);
+}
+
+static const char * const bch2_write_flags[] = {
+#define x(f)	#f,
+	BCH_WRITE_FLAGS()
+#undef x
+	NULL
+};
+
+void bch2_write_op_to_text(struct printbuf *out, struct bch_write_op *op)
+{
+	prt_str(out, "pos: ");
+	bch2_bpos_to_text(out, op->pos);
+	prt_newline(out);
+	printbuf_indent_add(out, 2);
+
+	prt_str(out, "started: ");
+	bch2_pr_time_units(out, local_clock() - op->start_time);
+	prt_newline(out);
+
+	prt_str(out, "flags: ");
+	prt_bitflags(out, bch2_write_flags, op->flags);
+	prt_newline(out);
+
+	prt_printf(out, "ref: %u", closure_nr_remaining(&op->cl));
+	prt_newline(out);
+
+	printbuf_indent_sub(out, 2);
+}
+
+void bch2_fs_io_write_exit(struct bch_fs *c)
+{
+	mempool_exit(&c->bio_bounce_pages);
+	bioset_exit(&c->bio_write);
+}
+
+int bch2_fs_io_write_init(struct bch_fs *c)
+{
+	if (bioset_init(&c->bio_write, 1, offsetof(struct bch_write_bio, bio),
+			BIOSET_NEED_BVECS))
+		return -BCH_ERR_ENOMEM_bio_write_init;
+
+	if (mempool_init_page_pool(&c->bio_bounce_pages,
+				   max_t(unsigned,
+					 c->opts.btree_node_size,
+					 c->opts.encoded_extent_max) /
+				   PAGE_SIZE, 0))
+		return -BCH_ERR_ENOMEM_bio_bounce_pages_init;
+
+	return 0;
+}
diff --git a/fs/bcachefs/io_write.h b/fs/bcachefs/io_write.h
new file mode 100644
index 0000000..9323167
--- /dev/null
+++ b/fs/bcachefs/io_write.h
@@ -0,0 +1,110 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _BCACHEFS_IO_WRITE_H
+#define _BCACHEFS_IO_WRITE_H
+
+#include "checksum.h"
+#include "io_write_types.h"
+
+#define to_wbio(_bio)			\
+	container_of((_bio), struct bch_write_bio, bio)
+
+void bch2_bio_free_pages_pool(struct bch_fs *, struct bio *);
+void bch2_bio_alloc_pages_pool(struct bch_fs *, struct bio *, size_t);
+
+#ifndef CONFIG_BCACHEFS_NO_LATENCY_ACCT
+void bch2_latency_acct(struct bch_dev *, u64, int);
+#else
+static inline void bch2_latency_acct(struct bch_dev *ca, u64 submit_time, int rw) {}
+#endif
+
+void bch2_submit_wbio_replicas(struct bch_write_bio *, struct bch_fs *,
+			       enum bch_data_type, const struct bkey_i *, bool);
+
+#define BCH_WRITE_FLAGS()		\
+	x(ALLOC_NOWAIT)			\
+	x(CACHED)			\
+	x(DATA_ENCODED)			\
+	x(PAGES_STABLE)			\
+	x(PAGES_OWNED)			\
+	x(ONLY_SPECIFIED_DEVS)		\
+	x(WROTE_DATA_INLINE)		\
+	x(FROM_INTERNAL)		\
+	x(CHECK_ENOSPC)			\
+	x(SYNC)				\
+	x(MOVE)				\
+	x(IN_WORKER)			\
+	x(DONE)				\
+	x(IO_ERROR)			\
+	x(CONVERT_UNWRITTEN)
+
+enum __bch_write_flags {
+#define x(f)	__BCH_WRITE_##f,
+	BCH_WRITE_FLAGS()
+#undef x
+};
+
+enum bch_write_flags {
+#define x(f)	BCH_WRITE_##f = BIT(__BCH_WRITE_##f),
+	BCH_WRITE_FLAGS()
+#undef x
+};
+
+static inline struct workqueue_struct *index_update_wq(struct bch_write_op *op)
+{
+	return op->watermark == BCH_WATERMARK_copygc
+		? op->c->copygc_wq
+		: op->c->btree_update_wq;
+}
+
+int bch2_sum_sector_overwrites(struct btree_trans *, struct btree_iter *,
+			       struct bkey_i *, bool *, s64 *, s64 *);
+int bch2_extent_update(struct btree_trans *, subvol_inum,
+		       struct btree_iter *, struct bkey_i *,
+		       struct disk_reservation *, u64, s64 *, bool);
+
+static inline void bch2_write_op_init(struct bch_write_op *op, struct bch_fs *c,
+				      struct bch_io_opts opts)
+{
+	op->c			= c;
+	op->end_io		= NULL;
+	op->flags		= 0;
+	op->written		= 0;
+	op->error		= 0;
+	op->csum_type		= bch2_data_checksum_type(c, opts);
+	op->compression_opt	= opts.compression;
+	op->nr_replicas		= 0;
+	op->nr_replicas_required = c->opts.data_replicas_required;
+	op->watermark		= BCH_WATERMARK_normal;
+	op->incompressible	= 0;
+	op->open_buckets.nr	= 0;
+	op->devs_have.nr	= 0;
+	op->target		= 0;
+	op->opts		= opts;
+	op->subvol		= 0;
+	op->pos			= POS_MAX;
+	op->version		= ZERO_VERSION;
+	op->write_point		= (struct write_point_specifier) { 0 };
+	op->res			= (struct disk_reservation) { 0 };
+	op->new_i_size		= U64_MAX;
+	op->i_sectors_delta	= 0;
+	op->devs_need_flush	= NULL;
+}
+
+void bch2_write(struct closure *);
+
+void bch2_write_point_do_index_updates(struct work_struct *);
+
+static inline struct bch_write_bio *wbio_init(struct bio *bio)
+{
+	struct bch_write_bio *wbio = to_wbio(bio);
+
+	memset(&wbio->wbio, 0, sizeof(wbio->wbio));
+	return wbio;
+}
+
+void bch2_write_op_to_text(struct printbuf *, struct bch_write_op *);
+
+void bch2_fs_io_write_exit(struct bch_fs *);
+int bch2_fs_io_write_init(struct bch_fs *);
+
+#endif /* _BCACHEFS_IO_WRITE_H */
diff --git a/fs/bcachefs/io_write_types.h b/fs/bcachefs/io_write_types.h
new file mode 100644
index 0000000..c7f97c2
--- /dev/null
+++ b/fs/bcachefs/io_write_types.h
@@ -0,0 +1,96 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _BCACHEFS_IO_WRITE_TYPES_H
+#define _BCACHEFS_IO_WRITE_TYPES_H
+
+#include "alloc_types.h"
+#include "btree_types.h"
+#include "buckets_types.h"
+#include "extents_types.h"
+#include "keylist_types.h"
+#include "opts.h"
+#include "super_types.h"
+
+#include <linux/llist.h>
+#include <linux/workqueue.h>
+
+struct bch_write_bio {
+	struct_group(wbio,
+	struct bch_fs		*c;
+	struct bch_write_bio	*parent;
+
+	u64			submit_time;
+	u64			inode_offset;
+
+	struct bch_devs_list	failed;
+	u8			dev;
+
+	unsigned		split:1,
+				bounce:1,
+				put_bio:1,
+				have_ioref:1,
+				nocow:1,
+				used_mempool:1,
+				first_btree_write:1;
+	);
+
+	struct bio		bio;
+};
+
+struct bch_write_op {
+	struct closure		cl;
+	struct bch_fs		*c;
+	void			(*end_io)(struct bch_write_op *);
+	u64			start_time;
+
+	unsigned		written; /* sectors */
+	u16			flags;
+	s16			error; /* dio write path expects it to hold -ERESTARTSYS... */
+
+	unsigned		compression_opt:8;
+	unsigned		csum_type:4;
+	unsigned		nr_replicas:4;
+	unsigned		nr_replicas_required:4;
+	unsigned		watermark:3;
+	unsigned		incompressible:1;
+	unsigned		stripe_waited:1;
+
+	struct bch_devs_list	devs_have;
+	u16			target;
+	u16			nonce;
+	struct bch_io_opts	opts;
+
+	u32			subvol;
+	struct bpos		pos;
+	struct bversion		version;
+
+	/* For BCH_WRITE_DATA_ENCODED: */
+	struct bch_extent_crc_unpacked crc;
+
+	struct write_point_specifier write_point;
+
+	struct write_point	*wp;
+	struct list_head	wp_list;
+
+	struct disk_reservation	res;
+
+	struct open_buckets	open_buckets;
+
+	u64			new_i_size;
+	s64			i_sectors_delta;
+
+	struct bch_devs_mask	failed;
+
+	struct keylist		insert_keys;
+	u64			inline_keys[BKEY_EXTENT_U64s_MAX * 2];
+
+	/*
+	 * Bitmask of devices that have had nocow writes issued to them since
+	 * last flush:
+	 */
+	struct bch_devs_mask	*devs_need_flush;
+
+	/* Must be last: */
+	struct bch_write_bio	wbio;
+};
+
+#endif /* _BCACHEFS_IO_WRITE_TYPES_H */
diff --git a/fs/bcachefs/journal_io.c b/fs/bcachefs/journal_io.c
index 34740dc..0e60600 100644
--- a/fs/bcachefs/journal_io.c
+++ b/fs/bcachefs/journal_io.c
@@ -8,7 +8,6 @@
 #include "checksum.h"
 #include "disk_groups.h"
 #include "error.h"
-#include "io.h"
 #include "journal.h"
 #include "journal_io.h"
 #include "journal_reclaim.h"
diff --git a/fs/bcachefs/migrate.c b/fs/bcachefs/migrate.c
index 3d7c5b9..4746dfa 100644
--- a/fs/bcachefs/migrate.c
+++ b/fs/bcachefs/migrate.c
@@ -10,7 +10,7 @@
 #include "buckets.h"
 #include "errcode.h"
 #include "extents.h"
-#include "io.h"
+#include "io_write.h"
 #include "journal.h"
 #include "keylist.h"
 #include "migrate.h"
diff --git a/fs/bcachefs/move.c b/fs/bcachefs/move.c
index fb76a1d..ac4df53 100644
--- a/fs/bcachefs/move.c
+++ b/fs/bcachefs/move.c
@@ -14,7 +14,8 @@
 #include "errcode.h"
 #include "error.h"
 #include "inode.h"
-#include "io.h"
+#include "io_read.h"
+#include "io_write.h"
 #include "journal_reclaim.h"
 #include "keylist.h"
 #include "move.h"
diff --git a/fs/bcachefs/move.h b/fs/bcachefs/move.h
index c3136ab..cbdd58d 100644
--- a/fs/bcachefs/move.h
+++ b/fs/bcachefs/move.h
@@ -2,6 +2,7 @@
 #ifndef _BCACHEFS_MOVE_H
 #define _BCACHEFS_MOVE_H
 
+#include "bcachefs_ioctl.h"
 #include "btree_iter.h"
 #include "buckets.h"
 #include "data_update.h"
diff --git a/fs/bcachefs/movinggc.c b/fs/bcachefs/movinggc.c
index ac658e9..2371fd6 100644
--- a/fs/bcachefs/movinggc.c
+++ b/fs/bcachefs/movinggc.c
@@ -13,25 +13,17 @@
 #include "btree_write_buffer.h"
 #include "buckets.h"
 #include "clock.h"
-#include "disk_groups.h"
 #include "errcode.h"
 #include "error.h"
-#include "extents.h"
-#include "eytzinger.h"
-#include "io.h"
-#include "keylist.h"
 #include "lru.h"
 #include "move.h"
 #include "movinggc.h"
-#include "super-io.h"
 #include "trace.h"
 
-#include <linux/bsearch.h>
 #include <linux/freezer.h>
 #include <linux/kthread.h>
 #include <linux/math64.h>
 #include <linux/sched/task.h>
-#include <linux/sort.h>
 #include <linux/wait.h>
 
 struct buckets_in_flight {
diff --git a/fs/bcachefs/rebalance.c b/fs/bcachefs/rebalance.c
index 016cf08..568f1e8 100644
--- a/fs/bcachefs/rebalance.c
+++ b/fs/bcachefs/rebalance.c
@@ -8,8 +8,6 @@
 #include "compress.h"
 #include "disk_groups.h"
 #include "errcode.h"
-#include "extents.h"
-#include "io.h"
 #include "move.h"
 #include "rebalance.h"
 #include "super-io.h"
diff --git a/fs/bcachefs/reflink.c b/fs/bcachefs/reflink.c
index 39f711d..f155428 100644
--- a/fs/bcachefs/reflink.c
+++ b/fs/bcachefs/reflink.c
@@ -5,9 +5,11 @@
 #include "buckets.h"
 #include "extents.h"
 #include "inode.h"
-#include "io.h"
+#include "io_misc.h"
+#include "io_write.h"
 #include "reflink.h"
 #include "subvolume.h"
+#include "super-io.h"
 
 #include <linux/sched/signal.h>
 
diff --git a/fs/bcachefs/super-io.c b/fs/bcachefs/super-io.c
index f01883e..5a11153 100644
--- a/fs/bcachefs/super-io.c
+++ b/fs/bcachefs/super-io.c
@@ -6,7 +6,6 @@
 #include "disk_groups.h"
 #include "ec.h"
 #include "error.h"
-#include "io.h"
 #include "journal.h"
 #include "journal_sb.h"
 #include "journal_seq_blacklist.h"
diff --git a/fs/bcachefs/super.c b/fs/bcachefs/super.c
index 7cfc049..5517602 100644
--- a/fs/bcachefs/super.c
+++ b/fs/bcachefs/super.c
@@ -35,7 +35,8 @@
 #include "fs-io-direct.h"
 #include "fsck.h"
 #include "inode.h"
-#include "io.h"
+#include "io_read.h"
+#include "io_write.h"
 #include "journal.h"
 #include "journal_reclaim.h"
 #include "journal_seq_blacklist.h"
@@ -483,7 +484,8 @@ static void __bch2_fs_free(struct bch_fs *c)
 	bch2_fs_fsio_exit(c);
 	bch2_fs_ec_exit(c);
 	bch2_fs_encryption_exit(c);
-	bch2_fs_io_exit(c);
+	bch2_fs_io_write_exit(c);
+	bch2_fs_io_read_exit(c);
 	bch2_fs_buckets_waiting_for_journal_exit(c);
 	bch2_fs_btree_interior_update_exit(c);
 	bch2_fs_btree_iter_exit(c);
@@ -848,7 +850,8 @@ static struct bch_fs *bch2_fs_alloc(struct bch_sb *sb, struct bch_opts opts)
 	    bch2_fs_buckets_waiting_for_journal_init(c) ?:
 	    bch2_fs_btree_write_buffer_init(c) ?:
 	    bch2_fs_subvolumes_init(c) ?:
-	    bch2_fs_io_init(c) ?:
+	    bch2_fs_io_read_init(c) ?:
+	    bch2_fs_io_write_init(c) ?:
 	    bch2_fs_nocow_locking_init(c) ?:
 	    bch2_fs_encryption_init(c) ?:
 	    bch2_fs_compress_init(c) ?: