fs/ext4/page-io.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * linux/fs/ext4/page-io.c
  *
  * This contains the new page_io functions for ext4
  *
  * Written by Theodore Ts'o, 2010.
  */

 #include <linux/fs.h>
 #include <linux/time.h>
 #include <linux/highuid.h>
 #include <linux/pagemap.h>
 #include <linux/quotaops.h>
 #include <linux/string.h>
 #include <linux/buffer_head.h>
 #include <linux/writeback.h>
 #include <linux/pagevec.h>
 #include <linux/mpage.h>
 #include <linux/namei.h>
 #include <linux/uio.h>
 #include <linux/bio.h>
 #include <linux/workqueue.h>
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/mm.h>
 #include <linux/sched/mm.h>

 #include "ext4_jbd2.h"
 #include "xattr.h"
 #include "acl.h"

 static struct kmem_cache *io_end_cachep;
 static struct kmem_cache *io_end_vec_cachep;

 int __init ext4_init_pageio(void)
 {
 	io_end_cachep = KMEM_CACHE(ext4_io_end, SLAB_RECLAIM_ACCOUNT);
 	if (io_end_cachep == NULL)
 		return -ENOMEM;

 	io_end_vec_cachep = KMEM_CACHE(ext4_io_end_vec, 0);
 	if (io_end_vec_cachep == NULL) {
 		kmem_cache_destroy(io_end_cachep);
 		return -ENOMEM;
 	}
 	return 0;
 }

 void ext4_exit_pageio(void)
 {
 	kmem_cache_destroy(io_end_cachep);
 	kmem_cache_destroy(io_end_vec_cachep);
 }

 struct ext4_io_end_vec *ext4_alloc_io_end_vec(ext4_io_end_t *io_end)
 {
 	struct ext4_io_end_vec *io_end_vec;

 	io_end_vec = kmem_cache_zalloc(io_end_vec_cachep, GFP_NOFS);
 	if (!io_end_vec)
 		return ERR_PTR(-ENOMEM);
 	INIT_LIST_HEAD(&io_end_vec->list);
 	list_add_tail(&io_end_vec->list, &io_end->list_vec);
 	return io_end_vec;
 }

 static void ext4_free_io_end_vec(ext4_io_end_t *io_end)
 {
 	struct ext4_io_end_vec *io_end_vec, *tmp;

 	if (list_empty(&io_end->list_vec))
 		return;
 	list_for_each_entry_safe(io_end_vec, tmp, &io_end->list_vec, list) {
 		list_del(&io_end_vec->list);
 		kmem_cache_free(io_end_vec_cachep, io_end_vec);
 	}
 }

 struct ext4_io_end_vec *ext4_last_io_end_vec(ext4_io_end_t *io_end)
 {
 	BUG_ON(list_empty(&io_end->list_vec));
 	return list_last_entry(&io_end->list_vec, struct ext4_io_end_vec, list);
 }

 /*
  * Print an buffer I/O error compatible with the fs/buffer.c.  This
  * provides compatibility with dmesg scrapers that look for a specific
  * buffer I/O error message.  We really need a unified error reporting
  * structure to userspace ala Digital Unix's uerf system, but it's
  * probably not going to happen in my lifetime, due to LKML politics...
  */
 static void buffer_io_error(struct buffer_head *bh)
 {
 	printk_ratelimited(KERN_ERR "Buffer I/O error on device %pg, logical block %llu\n",
 		       bh->b_bdev,
 			(unsigned long long)bh->b_blocknr);
 }

 static void ext4_finish_bio(struct bio *bio)
 {
 	struct folio_iter fi;

 	bio_for_each_folio_all(fi, bio) {
 		struct folio *folio = fi.folio;
 		struct folio *io_folio = NULL;
 		struct buffer_head *bh, *head;
 		size_t bio_start = fi.offset;
 		size_t bio_end = bio_start + fi.length;
 		unsigned under_io = 0;
 		unsigned long flags;

 		if (fscrypt_is_bounce_folio(folio)) {
 			io_folio = folio;
 			folio = fscrypt_pagecache_folio(folio);
 		}

 		if (bio->bi_status) {
 			int err = blk_status_to_errno(bio->bi_status);
 			folio_set_error(folio);
 			mapping_set_error(folio->mapping, err);
 		}
 		bh = head = folio_buffers(folio);
 		/*
 		 * We check all buffers in the folio under b_uptodate_lock
 		 * to avoid races with other end io clearing async_write flags
 		 */
 		spin_lock_irqsave(&head->b_uptodate_lock, flags);
 		do {
 			if (bh_offset(bh) < bio_start ||
 			    bh_offset(bh) + bh->b_size > bio_end) {
 				if (buffer_async_write(bh))
 					under_io++;
 				continue;
 			}
 			clear_buffer_async_write(bh);
 			if (bio->bi_status) {
 				set_buffer_write_io_error(bh);
 				buffer_io_error(bh);
 			}
 		} while ((bh = bh->b_this_page) != head);
 		spin_unlock_irqrestore(&head->b_uptodate_lock, flags);
 		if (!under_io) {
 			fscrypt_free_bounce_page(&io_folio->page);
 			folio_end_writeback(folio);
 		}
 	}
 }

 static void ext4_release_io_end(ext4_io_end_t *io_end)
 {
 	struct bio *bio, *next_bio;

 	BUG_ON(!list_empty(&io_end->list));
 	BUG_ON(io_end->flag & EXT4_IO_END_UNWRITTEN);
 	WARN_ON(io_end->handle);

 	for (bio = io_end->bio; bio; bio = next_bio) {
 		next_bio = bio->bi_private;
 		ext4_finish_bio(bio);
 		bio_put(bio);
 	}
 	ext4_free_io_end_vec(io_end);
 	kmem_cache_free(io_end_cachep, io_end);
 }

 /*
  * Check a range of space and convert unwritten extents to written. Note that
  * we are protected from truncate touching same part of extent tree by the
  * fact that truncate code waits for all DIO to finish (thus exclusion from
  * direct IO is achieved) and also waits for PageWriteback bits. Thus we
  * cannot get to ext4_ext_truncate() before all IOs overlapping that range are
  * completed (happens from ext4_free_ioend()).
  */
 static int ext4_end_io_end(ext4_io_end_t *io_end)
 {
 	struct inode *inode = io_end->inode;
 	handle_t *handle = io_end->handle;
 	int ret = 0;

 	ext4_debug("ext4_end_io_nolock: io_end 0x%p from inode %lu,list->next 0x%p,"
 		   "list->prev 0x%p\n",
 		   io_end, inode->i_ino, io_end->list.next, io_end->list.prev);

 	io_end->handle = NULL;	/* Following call will use up the handle */
 	ret = ext4_convert_unwritten_io_end_vec(handle, io_end);
 	if (ret < 0 && !ext4_forced_shutdown(inode->i_sb)) {
 		ext4_msg(inode->i_sb, KERN_EMERG,
 			 "failed to convert unwritten extents to written "
 			 "extents -- potential data loss!  "
 			 "(inode %lu, error %d)", inode->i_ino, ret);
 	}
 	ext4_clear_io_unwritten_flag(io_end);
 	ext4_release_io_end(io_end);
 	return ret;
 }

 static void dump_completed_IO(struct inode *inode, struct list_head *head)
 {
 #ifdef	EXT4FS_DEBUG
 	struct list_head *cur, *before, *after;
 	ext4_io_end_t *io_end, *io_end0, *io_end1;

 	if (list_empty(head))
 		return;

 	ext4_debug("Dump inode %lu completed io list\n", inode->i_ino);
 	list_for_each_entry(io_end, head, list) {
 		cur = &io_end->list;
 		before = cur->prev;
 		io_end0 = container_of(before, ext4_io_end_t, list);
 		after = cur->next;
 		io_end1 = container_of(after, ext4_io_end_t, list);

 		ext4_debug("io 0x%p from inode %lu,prev 0x%p,next 0x%p\n",
 			    io_end, inode->i_ino, io_end0, io_end1);
 	}
 #endif
 }

 /* Add the io_end to per-inode completed end_io list. */
 static void ext4_add_complete_io(ext4_io_end_t *io_end)
 {
 	struct ext4_inode_info *ei = EXT4_I(io_end->inode);
 	struct ext4_sb_info *sbi = EXT4_SB(io_end->inode->i_sb);
 	struct workqueue_struct *wq;
 	unsigned long flags;

 	/* Only reserved conversions from writeback should enter here */
 	WARN_ON(!(io_end->flag & EXT4_IO_END_UNWRITTEN));
 	WARN_ON(!io_end->handle && sbi->s_journal);
 	spin_lock_irqsave(&ei->i_completed_io_lock, flags);
 	wq = sbi->rsv_conversion_wq;
 	if (list_empty(&ei->i_rsv_conversion_list))
 		queue_work(wq, &ei->i_rsv_conversion_work);
 	list_add_tail(&io_end->list, &ei->i_rsv_conversion_list);
 	spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
 }

 static int ext4_do_flush_completed_IO(struct inode *inode,
 				      struct list_head *head)
 {
 	ext4_io_end_t *io_end;
 	struct list_head unwritten;
 	unsigned long flags;
 	struct ext4_inode_info *ei = EXT4_I(inode);
 	int err, ret = 0;

 	spin_lock_irqsave(&ei->i_completed_io_lock, flags);
 	dump_completed_IO(inode, head);
 	list_replace_init(head, &unwritten);
 	spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);

 	while (!list_empty(&unwritten)) {
 		io_end = list_entry(unwritten.next, ext4_io_end_t, list);
 		BUG_ON(!(io_end->flag & EXT4_IO_END_UNWRITTEN));
 		list_del_init(&io_end->list);

 		err = ext4_end_io_end(io_end);
 		if (unlikely(!ret && err))
 			ret = err;
 	}
 	return ret;
 }

 /*
  * work on completed IO, to convert unwritten extents to extents
  */
 void ext4_end_io_rsv_work(struct work_struct *work)
 {
 	struct ext4_inode_info *ei = container_of(work, struct ext4_inode_info,
 						  i_rsv_conversion_work);
 	ext4_do_flush_completed_IO(&ei->vfs_inode, &ei->i_rsv_conversion_list);
 }

 ext4_io_end_t *ext4_init_io_end(struct inode *inode, gfp_t flags)
 {
 	ext4_io_end_t *io_end = kmem_cache_zalloc(io_end_cachep, flags);

 	if (io_end) {
 		io_end->inode = inode;
 		INIT_LIST_HEAD(&io_end->list);
 		INIT_LIST_HEAD(&io_end->list_vec);
 		refcount_set(&io_end->count, 1);
 	}
 	return io_end;
 }

 void ext4_put_io_end_defer(ext4_io_end_t *io_end)
 {
 	if (refcount_dec_and_test(&io_end->count)) {
 		if (!(io_end->flag & EXT4_IO_END_UNWRITTEN) ||
 				list_empty(&io_end->list_vec)) {
 			ext4_release_io_end(io_end);
 			return;
 		}
 		ext4_add_complete_io(io_end);
 	}
 }

 int ext4_put_io_end(ext4_io_end_t *io_end)
 {
 	int err = 0;

 	if (refcount_dec_and_test(&io_end->count)) {
 		if (io_end->flag & EXT4_IO_END_UNWRITTEN) {
 			err = ext4_convert_unwritten_io_end_vec(io_end->handle,
 								io_end);
 			io_end->handle = NULL;
 			ext4_clear_io_unwritten_flag(io_end);
 		}
 		ext4_release_io_end(io_end);
 	}
 	return err;
 }

 ext4_io_end_t *ext4_get_io_end(ext4_io_end_t *io_end)
 {
 	refcount_inc(&io_end->count);
 	return io_end;
 }

 /* BIO completion function for page writeback */
 static void ext4_end_bio(struct bio *bio)
 {
 	ext4_io_end_t *io_end = bio->bi_private;
 	sector_t bi_sector = bio->bi_iter.bi_sector;

 	if (WARN_ONCE(!io_end, "io_end is NULL: %pg: sector %Lu len %u err %d\n",
 		      bio->bi_bdev,
 		      (long long) bio->bi_iter.bi_sector,
 		      (unsigned) bio_sectors(bio),
 		      bio->bi_status)) {
 		ext4_finish_bio(bio);
 		bio_put(bio);
 		return;
 	}
 	bio->bi_end_io = NULL;

 	if (bio->bi_status) {
 		struct inode *inode = io_end->inode;

 		ext4_warning(inode->i_sb, "I/O error %d writing to inode %lu "
 			     "starting block %llu)",
 			     bio->bi_status, inode->i_ino,
 			     (unsigned long long)
 			     bi_sector >> (inode->i_blkbits - 9));
 		mapping_set_error(inode->i_mapping,
 				blk_status_to_errno(bio->bi_status));
 	}

 	if (io_end->flag & EXT4_IO_END_UNWRITTEN) {
 		/*
 		 * Link bio into list hanging from io_end. We have to do it
 		 * atomically as bio completions can be racing against each
 		 * other.
 		 */
 		bio->bi_private = xchg(&io_end->bio, bio);
 		ext4_put_io_end_defer(io_end);
 	} else {
 		/*
 		 * Drop io_end reference early. Inode can get freed once
 		 * we finish the bio.
 		 */
 		ext4_put_io_end_defer(io_end);
 		ext4_finish_bio(bio);
 		bio_put(bio);
 	}
 }

 void ext4_io_submit(struct ext4_io_submit *io)
 {
 	struct bio *bio = io->io_bio;

 	if (bio) {
 		if (io->io_wbc->sync_mode == WB_SYNC_ALL)
 			io->io_bio->bi_opf |= REQ_SYNC;
 		submit_bio(io->io_bio);
 	}
 	io->io_bio = NULL;
 }

 void ext4_io_submit_init(struct ext4_io_submit *io,
 			 struct writeback_control *wbc)
 {
 	io->io_wbc = wbc;
 	io->io_bio = NULL;
 	io->io_end = NULL;
 }

 static void io_submit_init_bio(struct ext4_io_submit *io,
 			       struct buffer_head *bh)
 {
 	struct bio *bio;

 	/*
 	 * bio_alloc will _always_ be able to allocate a bio if
 	 * __GFP_DIRECT_RECLAIM is set, see comments for bio_alloc_bioset().
 	 */
 	bio = bio_alloc(bh->b_bdev, BIO_MAX_VECS, REQ_OP_WRITE, GFP_NOIO);
 	fscrypt_set_bio_crypt_ctx_bh(bio, bh, GFP_NOIO);
 	bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
 	bio->bi_end_io = ext4_end_bio;
 	bio->bi_private = ext4_get_io_end(io->io_end);
 	io->io_bio = bio;
 	io->io_next_block = bh->b_blocknr;
 	wbc_init_bio(io->io_wbc, bio);
 }

 static void io_submit_add_bh(struct ext4_io_submit *io,
 			     struct inode *inode,
 			     struct folio *folio,
 			     struct folio *io_folio,
 			     struct buffer_head *bh)
 {
 	if (io->io_bio && (bh->b_blocknr != io->io_next_block ||
 			   !fscrypt_mergeable_bio_bh(io->io_bio, bh))) {
 submit_and_retry:
 		ext4_io_submit(io);
 	}
 	if (io->io_bio == NULL)
 		io_submit_init_bio(io, bh);
 	if (!bio_add_folio(io->io_bio, io_folio, bh->b_size, bh_offset(bh)))
 		goto submit_and_retry;
 	wbc_account_cgroup_owner(io->io_wbc, &folio->page, bh->b_size);
 	io->io_next_block++;
 }

 int ext4_bio_write_folio(struct ext4_io_submit *io, struct folio *folio,
 		size_t len)
 {
 	struct folio *io_folio = folio;
 	struct inode *inode = folio->mapping->host;
 	unsigned block_start;
 	struct buffer_head *bh, *head;
 	int ret = 0;
 	int nr_to_submit = 0;
 	struct writeback_control *wbc = io->io_wbc;
 	bool keep_towrite = false;

 	BUG_ON(!folio_test_locked(folio));
 	BUG_ON(folio_test_writeback(folio));

 	folio_clear_error(folio);

 	/*
 	 * Comments copied from block_write_full_page:
 	 *
 	 * The folio straddles i_size.  It must be zeroed out on each and every
 	 * writepage invocation because it may be mmapped.  "A file is mapped
 	 * in multiples of the page size.  For a file that is not a multiple of
 	 * the page size, the remaining memory is zeroed when mapped, and
 	 * writes to that region are not written out to the file."
 	 */
 	if (len < folio_size(folio))
 		folio_zero_segment(folio, len, folio_size(folio));
 	/*
 	 * In the first loop we prepare and mark buffers to submit. We have to
 	 * mark all buffers in the folio before submitting so that
 	 * folio_end_writeback() cannot be called from ext4_end_bio() when IO
 	 * on the first buffer finishes and we are still working on submitting
 	 * the second buffer.
 	 */
 	bh = head = folio_buffers(folio);
 	do {
 		block_start = bh_offset(bh);
 		if (block_start >= len) {
 			clear_buffer_dirty(bh);
 			set_buffer_uptodate(bh);
 			continue;
 		}
 		if (!buffer_dirty(bh) || buffer_delay(bh) ||
 		    !buffer_mapped(bh) || buffer_unwritten(bh)) {
 			/* A hole? We can safely clear the dirty bit */
 			if (!buffer_mapped(bh))
 				clear_buffer_dirty(bh);
 			/*
 			 * Keeping dirty some buffer we cannot write? Make sure
 			 * to redirty the folio and keep TOWRITE tag so that
 			 * racing WB_SYNC_ALL writeback does not skip the folio.
 			 * This happens e.g. when doing writeout for
 			 * transaction commit or when journalled data is not
 			 * yet committed.
 			 */
 			if (buffer_dirty(bh) ||
 			    (buffer_jbd(bh) && buffer_jbddirty(bh))) {
 				if (!folio_test_dirty(folio))
 					folio_redirty_for_writepage(wbc, folio);
 				keep_towrite = true;
 			}
 			continue;
 		}
 		if (buffer_new(bh))
 			clear_buffer_new(bh);
 		set_buffer_async_write(bh);
 		clear_buffer_dirty(bh);
 		nr_to_submit++;
 	} while ((bh = bh->b_this_page) != head);

 	/* Nothing to submit? Just unlock the folio... */
 	if (!nr_to_submit)
 		return 0;

 	bh = head = folio_buffers(folio);

 	/*
 	 * If any blocks are being written to an encrypted file, encrypt them
 	 * into a bounce page.  For simplicity, just encrypt until the last
 	 * block which might be needed.  This may cause some unneeded blocks
 	 * (e.g. holes) to be unnecessarily encrypted, but this is rare and
 	 * can't happen in the common case of blocksize == PAGE_SIZE.
 	 */
 	if (fscrypt_inode_uses_fs_layer_crypto(inode)) {
 		gfp_t gfp_flags = GFP_NOFS;
 		unsigned int enc_bytes = round_up(len, i_blocksize(inode));
 		struct page *bounce_page;

 		/*
 		 * Since bounce page allocation uses a mempool, we can only use
 		 * a waiting mask (i.e. request guaranteed allocation) on the
 		 * first page of the bio.  Otherwise it can deadlock.
 		 */
 		if (io->io_bio)
 			gfp_flags = GFP_NOWAIT | __GFP_NOWARN;
 	retry_encrypt:
 		bounce_page = fscrypt_encrypt_pagecache_blocks(&folio->page,
 					enc_bytes, 0, gfp_flags);
 		if (IS_ERR(bounce_page)) {
 			ret = PTR_ERR(bounce_page);
 			if (ret == -ENOMEM &&
 			    (io->io_bio || wbc->sync_mode == WB_SYNC_ALL)) {
 				gfp_t new_gfp_flags = GFP_NOFS;
 				if (io->io_bio)
 					ext4_io_submit(io);
 				else
 					new_gfp_flags |= __GFP_NOFAIL;
 				memalloc_retry_wait(gfp_flags);
 				gfp_flags = new_gfp_flags;
 				goto retry_encrypt;
 			}

 			printk_ratelimited(KERN_ERR "%s: ret = %d\n", __func__, ret);
 			folio_redirty_for_writepage(wbc, folio);
 			do {
 				if (buffer_async_write(bh)) {
 					clear_buffer_async_write(bh);
 					set_buffer_dirty(bh);
 				}
 				bh = bh->b_this_page;
 			} while (bh != head);

 			return ret;
 		}
 		io_folio = page_folio(bounce_page);
 	}

 	__folio_start_writeback(folio, keep_towrite);

 	/* Now submit buffers to write */
 	do {
 		if (!buffer_async_write(bh))
 			continue;
 		io_submit_add_bh(io, inode, folio, io_folio, bh);
 	} while ((bh = bh->b_this_page) != head);

 	return 0;
 }
	// SPDX-License-Identifier: GPL-2.0
	/*
	* linux/fs/ext4/page-io.c
	*
	* This contains the new page_io functions for ext4
	*
	* Written by Theodore Ts'o, 2010.
	*/

	#include <linux/fs.h>
	#include <linux/time.h>
	#include <linux/highuid.h>
	#include <linux/pagemap.h>
	#include <linux/quotaops.h>
	#include <linux/string.h>
	#include <linux/buffer_head.h>
	#include <linux/writeback.h>
	#include <linux/pagevec.h>
	#include <linux/mpage.h>
	#include <linux/namei.h>
	#include <linux/uio.h>
	#include <linux/bio.h>
	#include <linux/workqueue.h>
	#include <linux/kernel.h>
	#include <linux/slab.h>
	#include <linux/mm.h>
	#include <linux/sched/mm.h>

	#include "ext4_jbd2.h"
	#include "xattr.h"
	#include "acl.h"

	static struct kmem_cache *io_end_cachep;
	static struct kmem_cache *io_end_vec_cachep;

	int __init ext4_init_pageio(void)
	{
	io_end_cachep = KMEM_CACHE(ext4_io_end, SLAB_RECLAIM_ACCOUNT);
	if (io_end_cachep == NULL)
	return -ENOMEM;

	io_end_vec_cachep = KMEM_CACHE(ext4_io_end_vec, 0);
	if (io_end_vec_cachep == NULL) {
	kmem_cache_destroy(io_end_cachep);
	return -ENOMEM;
	}
	return 0;
	}

	void ext4_exit_pageio(void)
	{
	kmem_cache_destroy(io_end_cachep);
	kmem_cache_destroy(io_end_vec_cachep);
	}

	struct ext4_io_end_vec ext4_alloc_io_end_vec(ext4_io_end_t io_end)
	{
	struct ext4_io_end_vec *io_end_vec;

	io_end_vec = kmem_cache_zalloc(io_end_vec_cachep, GFP_NOFS);
	if (!io_end_vec)
	return ERR_PTR(-ENOMEM);
	INIT_LIST_HEAD(&io_end_vec->list);
	list_add_tail(&io_end_vec->list, &io_end->list_vec);
	return io_end_vec;
	}

	static void ext4_free_io_end_vec(ext4_io_end_t *io_end)
	{
	struct ext4_io_end_vec io_end_vec, tmp;

	if (list_empty(&io_end->list_vec))
	return;
	list_for_each_entry_safe(io_end_vec, tmp, &io_end->list_vec, list) {
	list_del(&io_end_vec->list);
	kmem_cache_free(io_end_vec_cachep, io_end_vec);
	}
	}

	struct ext4_io_end_vec ext4_last_io_end_vec(ext4_io_end_t io_end)
	{
	BUG_ON(list_empty(&io_end->list_vec));
	return list_last_entry(&io_end->list_vec, struct ext4_io_end_vec, list);
	}

	/*
	* Print an buffer I/O error compatible with the fs/buffer.c. This
	* provides compatibility with dmesg scrapers that look for a specific
	* buffer I/O error message. We really need a unified error reporting
	* structure to userspace ala Digital Unix's uerf system, but it's
	* probably not going to happen in my lifetime, due to LKML politics...
	*/
	static void buffer_io_error(struct buffer_head *bh)
	{
	printk_ratelimited(KERN_ERR "Buffer I/O error on device %pg, logical block %llu\n",
	bh->b_bdev,
	(unsigned long long)bh->b_blocknr);
	}

	static void ext4_finish_bio(struct bio *bio)
	{
	struct folio_iter fi;

	bio_for_each_folio_all(fi, bio) {
	struct folio *folio = fi.folio;
	struct folio *io_folio = NULL;
	struct buffer_head bh, head;
	size_t bio_start = fi.offset;
	size_t bio_end = bio_start + fi.length;
	unsigned under_io = 0;
	unsigned long flags;

	if (fscrypt_is_bounce_folio(folio)) {
	io_folio = folio;
	folio = fscrypt_pagecache_folio(folio);
	}

	if (bio->bi_status) {
	int err = blk_status_to_errno(bio->bi_status);
	folio_set_error(folio);
	mapping_set_error(folio->mapping, err);
	}
	bh = head = folio_buffers(folio);
	/*
	* We check all buffers in the folio under b_uptodate_lock
	* to avoid races with other end io clearing async_write flags
	*/
	spin_lock_irqsave(&head->b_uptodate_lock, flags);
	do {
	if (bh_offset(bh) < bio_start \|\|
	bh_offset(bh) + bh->b_size > bio_end) {
	if (buffer_async_write(bh))
	under_io++;
	continue;
	}
	clear_buffer_async_write(bh);
	if (bio->bi_status) {
	set_buffer_write_io_error(bh);
	buffer_io_error(bh);
	}
	} while ((bh = bh->b_this_page) != head);
	spin_unlock_irqrestore(&head->b_uptodate_lock, flags);
	if (!under_io) {
	fscrypt_free_bounce_page(&io_folio->page);
	folio_end_writeback(folio);
	}
	}
	}

	static void ext4_release_io_end(ext4_io_end_t *io_end)
	{
	struct bio bio, next_bio;

	BUG_ON(!list_empty(&io_end->list));
	BUG_ON(io_end->flag & EXT4_IO_END_UNWRITTEN);
	WARN_ON(io_end->handle);

	for (bio = io_end->bio; bio; bio = next_bio) {
	next_bio = bio->bi_private;
	ext4_finish_bio(bio);
	bio_put(bio);
	}
	ext4_free_io_end_vec(io_end);
	kmem_cache_free(io_end_cachep, io_end);
	}

	/*
	* Check a range of space and convert unwritten extents to written. Note that
	* we are protected from truncate touching same part of extent tree by the
	* fact that truncate code waits for all DIO to finish (thus exclusion from
	* direct IO is achieved) and also waits for PageWriteback bits. Thus we
	* cannot get to ext4_ext_truncate() before all IOs overlapping that range are
	* completed (happens from ext4_free_ioend()).
	*/
	static int ext4_end_io_end(ext4_io_end_t *io_end)
	{
	struct inode *inode = io_end->inode;
	handle_t *handle = io_end->handle;
	int ret = 0;

	ext4_debug("ext4_end_io_nolock: io_end 0x%p from inode %lu,list->next 0x%p,"
	"list->prev 0x%p\n",
	io_end, inode->i_ino, io_end->list.next, io_end->list.prev);

	io_end->handle = NULL; /* Following call will use up the handle */
	ret = ext4_convert_unwritten_io_end_vec(handle, io_end);
	if (ret < 0 && !ext4_forced_shutdown(inode->i_sb)) {
	ext4_msg(inode->i_sb, KERN_EMERG,
	"failed to convert unwritten extents to written "
	"extents -- potential data loss! "
	"(inode %lu, error %d)", inode->i_ino, ret);
	}
	ext4_clear_io_unwritten_flag(io_end);
	ext4_release_io_end(io_end);
	return ret;
	}

	static void dump_completed_IO(struct inode inode, struct list_head head)
	{
	#ifdef EXT4FS_DEBUG
	struct list_head cur, before, *after;
	ext4_io_end_t io_end, io_end0, *io_end1;

	if (list_empty(head))
	return;

	ext4_debug("Dump inode %lu completed io list\n", inode->i_ino);
	list_for_each_entry(io_end, head, list) {
	cur = &io_end->list;
	before = cur->prev;
	io_end0 = container_of(before, ext4_io_end_t, list);
	after = cur->next;
	io_end1 = container_of(after, ext4_io_end_t, list);

	ext4_debug("io 0x%p from inode %lu,prev 0x%p,next 0x%p\n",
	io_end, inode->i_ino, io_end0, io_end1);
	}
	#endif
	}

	/* Add the io_end to per-inode completed end_io list. */
	static void ext4_add_complete_io(ext4_io_end_t *io_end)
	{
	struct ext4_inode_info *ei = EXT4_I(io_end->inode);
	struct ext4_sb_info *sbi = EXT4_SB(io_end->inode->i_sb);
	struct workqueue_struct *wq;
	unsigned long flags;

	/* Only reserved conversions from writeback should enter here */
	WARN_ON(!(io_end->flag & EXT4_IO_END_UNWRITTEN));
	WARN_ON(!io_end->handle && sbi->s_journal);
	spin_lock_irqsave(&ei->i_completed_io_lock, flags);
	wq = sbi->rsv_conversion_wq;
	if (list_empty(&ei->i_rsv_conversion_list))
	queue_work(wq, &ei->i_rsv_conversion_work);
	list_add_tail(&io_end->list, &ei->i_rsv_conversion_list);
	spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
	}

	static int ext4_do_flush_completed_IO(struct inode *inode,
	struct list_head *head)
	{
	ext4_io_end_t *io_end;
	struct list_head unwritten;
	unsigned long flags;
	struct ext4_inode_info *ei = EXT4_I(inode);
	int err, ret = 0;

	spin_lock_irqsave(&ei->i_completed_io_lock, flags);
	dump_completed_IO(inode, head);
	list_replace_init(head, &unwritten);
	spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);

	while (!list_empty(&unwritten)) {
	io_end = list_entry(unwritten.next, ext4_io_end_t, list);
	BUG_ON(!(io_end->flag & EXT4_IO_END_UNWRITTEN));
	list_del_init(&io_end->list);

	err = ext4_end_io_end(io_end);
	if (unlikely(!ret && err))
	ret = err;
	}
	return ret;
	}

	/*
	* work on completed IO, to convert unwritten extents to extents
	*/
	void ext4_end_io_rsv_work(struct work_struct *work)
	{
	struct ext4_inode_info *ei = container_of(work, struct ext4_inode_info,
	i_rsv_conversion_work);
	ext4_do_flush_completed_IO(&ei->vfs_inode, &ei->i_rsv_conversion_list);
	}

	ext4_io_end_t ext4_init_io_end(struct inode inode, gfp_t flags)
	{
	ext4_io_end_t *io_end = kmem_cache_zalloc(io_end_cachep, flags);

	if (io_end) {
	io_end->inode = inode;
	INIT_LIST_HEAD(&io_end->list);
	INIT_LIST_HEAD(&io_end->list_vec);
	refcount_set(&io_end->count, 1);
	}
	return io_end;
	}

	void ext4_put_io_end_defer(ext4_io_end_t *io_end)
	{
	if (refcount_dec_and_test(&io_end->count)) {
	if (!(io_end->flag & EXT4_IO_END_UNWRITTEN) \|\|
	list_empty(&io_end->list_vec)) {
	ext4_release_io_end(io_end);
	return;
	}
	ext4_add_complete_io(io_end);
	}
	}

	int ext4_put_io_end(ext4_io_end_t *io_end)
	{
	int err = 0;

	if (refcount_dec_and_test(&io_end->count)) {
	if (io_end->flag & EXT4_IO_END_UNWRITTEN) {
	err = ext4_convert_unwritten_io_end_vec(io_end->handle,
	io_end);
	io_end->handle = NULL;
	ext4_clear_io_unwritten_flag(io_end);
	}
	ext4_release_io_end(io_end);
	}
	return err;
	}

	ext4_io_end_t ext4_get_io_end(ext4_io_end_t io_end)
	{
	refcount_inc(&io_end->count);
	return io_end;
	}

	/* BIO completion function for page writeback */
	static void ext4_end_bio(struct bio *bio)
	{
	ext4_io_end_t *io_end = bio->bi_private;
	sector_t bi_sector = bio->bi_iter.bi_sector;

	if (WARN_ONCE(!io_end, "io_end is NULL: %pg: sector %Lu len %u err %d\n",
	bio->bi_bdev,
	(long long) bio->bi_iter.bi_sector,
	(unsigned) bio_sectors(bio),
	bio->bi_status)) {
	ext4_finish_bio(bio);
	bio_put(bio);
	return;
	}
	bio->bi_end_io = NULL;

	if (bio->bi_status) {
	struct inode *inode = io_end->inode;

	ext4_warning(inode->i_sb, "I/O error %d writing to inode %lu "
	"starting block %llu)",
	bio->bi_status, inode->i_ino,
	(unsigned long long)
	bi_sector >> (inode->i_blkbits - 9));
	mapping_set_error(inode->i_mapping,
	blk_status_to_errno(bio->bi_status));
	}

	if (io_end->flag & EXT4_IO_END_UNWRITTEN) {
	/*
	* Link bio into list hanging from io_end. We have to do it
	* atomically as bio completions can be racing against each
	* other.
	*/
	bio->bi_private = xchg(&io_end->bio, bio);
	ext4_put_io_end_defer(io_end);
	} else {
	/*
	* Drop io_end reference early. Inode can get freed once
	* we finish the bio.
	*/
	ext4_put_io_end_defer(io_end);
	ext4_finish_bio(bio);
	bio_put(bio);
	}
	}

	void ext4_io_submit(struct ext4_io_submit *io)
	{
	struct bio *bio = io->io_bio;

	if (bio) {
	if (io->io_wbc->sync_mode == WB_SYNC_ALL)
	io->io_bio->bi_opf \|= REQ_SYNC;
	submit_bio(io->io_bio);
	}
	io->io_bio = NULL;
	}

	void ext4_io_submit_init(struct ext4_io_submit *io,
	struct writeback_control *wbc)
	{
	io->io_wbc = wbc;
	io->io_bio = NULL;
	io->io_end = NULL;
	}

	static void io_submit_init_bio(struct ext4_io_submit *io,
	struct buffer_head *bh)
	{
	struct bio *bio;

	/*
	* bio_alloc will _always_ be able to allocate a bio if
	* __GFP_DIRECT_RECLAIM is set, see comments for bio_alloc_bioset().
	*/
	bio = bio_alloc(bh->b_bdev, BIO_MAX_VECS, REQ_OP_WRITE, GFP_NOIO);
	fscrypt_set_bio_crypt_ctx_bh(bio, bh, GFP_NOIO);
	bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
	bio->bi_end_io = ext4_end_bio;
	bio->bi_private = ext4_get_io_end(io->io_end);
	io->io_bio = bio;
	io->io_next_block = bh->b_blocknr;
	wbc_init_bio(io->io_wbc, bio);
	}

	static void io_submit_add_bh(struct ext4_io_submit *io,
	struct inode *inode,
	struct folio *folio,
	struct folio *io_folio,
	struct buffer_head *bh)
	{
	if (io->io_bio && (bh->b_blocknr != io->io_next_block \|\|
	!fscrypt_mergeable_bio_bh(io->io_bio, bh))) {
	submit_and_retry:
	ext4_io_submit(io);
	}
	if (io->io_bio == NULL)
	io_submit_init_bio(io, bh);
	if (!bio_add_folio(io->io_bio, io_folio, bh->b_size, bh_offset(bh)))
	goto submit_and_retry;
	wbc_account_cgroup_owner(io->io_wbc, &folio->page, bh->b_size);
	io->io_next_block++;
	}

	int ext4_bio_write_folio(struct ext4_io_submit io, struct folio folio,
	size_t len)
	{
	struct folio *io_folio = folio;
	struct inode *inode = folio->mapping->host;
	unsigned block_start;
	struct buffer_head bh, head;
	int ret = 0;
	int nr_to_submit = 0;
	struct writeback_control *wbc = io->io_wbc;
	bool keep_towrite = false;

	BUG_ON(!folio_test_locked(folio));
	BUG_ON(folio_test_writeback(folio));

	folio_clear_error(folio);

	/*
	* Comments copied from block_write_full_page:
	*
	* The folio straddles i_size. It must be zeroed out on each and every
	* writepage invocation because it may be mmapped. "A file is mapped
	* in multiples of the page size. For a file that is not a multiple of
	* the page size, the remaining memory is zeroed when mapped, and
	* writes to that region are not written out to the file."
	*/
	if (len < folio_size(folio))
	folio_zero_segment(folio, len, folio_size(folio));
	/*
	* In the first loop we prepare and mark buffers to submit. We have to
	* mark all buffers in the folio before submitting so that
	* folio_end_writeback() cannot be called from ext4_end_bio() when IO
	* on the first buffer finishes and we are still working on submitting
	* the second buffer.
	*/
	bh = head = folio_buffers(folio);
	do {
	block_start = bh_offset(bh);
	if (block_start >= len) {
	clear_buffer_dirty(bh);
	set_buffer_uptodate(bh);
	continue;
	}
	if (!buffer_dirty(bh) \|\| buffer_delay(bh) \|\|
	!buffer_mapped(bh) \|\| buffer_unwritten(bh)) {
	/* A hole? We can safely clear the dirty bit */
	if (!buffer_mapped(bh))
	clear_buffer_dirty(bh);
	/*
	* Keeping dirty some buffer we cannot write? Make sure
	* to redirty the folio and keep TOWRITE tag so that
	* racing WB_SYNC_ALL writeback does not skip the folio.
	* This happens e.g. when doing writeout for
	* transaction commit or when journalled data is not
	* yet committed.
	*/
	if (buffer_dirty(bh) \|\|
	(buffer_jbd(bh) && buffer_jbddirty(bh))) {
	if (!folio_test_dirty(folio))
	folio_redirty_for_writepage(wbc, folio);
	keep_towrite = true;
	}
	continue;
	}
	if (buffer_new(bh))
	clear_buffer_new(bh);
	set_buffer_async_write(bh);
	clear_buffer_dirty(bh);
	nr_to_submit++;
	} while ((bh = bh->b_this_page) != head);

	/* Nothing to submit? Just unlock the folio... */
	if (!nr_to_submit)
	return 0;

	bh = head = folio_buffers(folio);

	/*
	* If any blocks are being written to an encrypted file, encrypt them
	* into a bounce page. For simplicity, just encrypt until the last
	* block which might be needed. This may cause some unneeded blocks
	* (e.g. holes) to be unnecessarily encrypted, but this is rare and
	* can't happen in the common case of blocksize == PAGE_SIZE.
	*/
	if (fscrypt_inode_uses_fs_layer_crypto(inode)) {
	gfp_t gfp_flags = GFP_NOFS;
	unsigned int enc_bytes = round_up(len, i_blocksize(inode));
	struct page *bounce_page;

	/*
	* Since bounce page allocation uses a mempool, we can only use
	* a waiting mask (i.e. request guaranteed allocation) on the
	* first page of the bio. Otherwise it can deadlock.
	*/
	if (io->io_bio)
	gfp_flags = GFP_NOWAIT \| __GFP_NOWARN;
	retry_encrypt:
	bounce_page = fscrypt_encrypt_pagecache_blocks(&folio->page,
	enc_bytes, 0, gfp_flags);
	if (IS_ERR(bounce_page)) {
	ret = PTR_ERR(bounce_page);
	if (ret == -ENOMEM &&
	(io->io_bio \|\| wbc->sync_mode == WB_SYNC_ALL)) {
	gfp_t new_gfp_flags = GFP_NOFS;
	if (io->io_bio)
	ext4_io_submit(io);
	else
	new_gfp_flags \|= __GFP_NOFAIL;
	memalloc_retry_wait(gfp_flags);
	gfp_flags = new_gfp_flags;
	goto retry_encrypt;
	}

	printk_ratelimited(KERN_ERR "%s: ret = %d\n", __func__, ret);
	folio_redirty_for_writepage(wbc, folio);
	do {
	if (buffer_async_write(bh)) {
	clear_buffer_async_write(bh);
	set_buffer_dirty(bh);
	}
	bh = bh->b_this_page;
	} while (bh != head);

	return ret;
	}
	io_folio = page_folio(bounce_page);
	}

	__folio_start_writeback(folio, keep_towrite);

	/* Now submit buffers to write */
	do {
	if (!buffer_async_write(bh))
	continue;
	io_submit_add_bh(io, inode, folio, io_folio, bh);
	} while ((bh = bh->b_this_page) != head);

	return 0;
	}