fs/btrfs/extent-tree.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2007 Oracle.  All rights reserved.
 */

#include <linux/sched.h>
#include <linux/sched/signal.h>
#include <linux/pagemap.h>
#include <linux/writeback.h>
#include <linux/blkdev.h>
#include <linux/sort.h>
#include <linux/rcupdate.h>
#include <linux/kthread.h>
#include <linux/slab.h>
#include <linux/ratelimit.h>
#include <linux/percpu_counter.h>
#include <linux/lockdep.h>
#include <linux/crc32c.h>
#include "misc.h"
#include "tree-log.h"
#include "disk-io.h"
#include "print-tree.h"
#include "volumes.h"
#include "raid56.h"
#include "locking.h"
#include "free-space-cache.h"
#include "free-space-tree.h"
#include "sysfs.h"
#include "qgroup.h"
#include "ref-verify.h"
#include "space-info.h"
#include "block-rsv.h"
#include "delalloc-space.h"
#include "block-group.h"
#include "discard.h"
#include "rcu-string.h"
#include "zoned.h"
#include "dev-replace.h"

#undef SCRAMBLE_DELAYED_REFS


static int __btrfs_free_extent(struct btrfs_trans_handle *trans,
			       struct btrfs_delayed_ref_node *node, u64 parent,
			       u64 root_objectid, u64 owner_objectid,
			       u64 owner_offset, int refs_to_drop,
			       struct btrfs_delayed_extent_op *extra_op);
static void __run_delayed_extent_op(struct btrfs_delayed_extent_op *extent_op,
				    struct extent_buffer *leaf,
				    struct btrfs_extent_item *ei);
static int alloc_reserved_file_extent(struct btrfs_trans_handle *trans,
				      u64 parent, u64 root_objectid,
				      u64 flags, u64 owner, u64 offset,
				      struct btrfs_key *ins, int ref_mod);
static int alloc_reserved_tree_block(struct btrfs_trans_handle *trans,
				     struct btrfs_delayed_ref_node *node,
				     struct btrfs_delayed_extent_op *extent_op);
static int find_next_key(struct btrfs_path *path, int level,
			 struct btrfs_key *key);

static int block_group_bits(struct btrfs_block_group *cache, u64 bits)
{
	return (cache->flags & bits) == bits;
}

int btrfs_add_excluded_extent(struct btrfs_fs_info *fs_info,
			      u64 start, u64 num_bytes)
{
	u64 end = start + num_bytes - 1;
	set_extent_bits(&fs_info->excluded_extents, start, end,
			EXTENT_UPTODATE);
	return 0;
}

void btrfs_free_excluded_extents(struct btrfs_block_group *cache)
{
	struct btrfs_fs_info *fs_info = cache->fs_info;
	u64 start, end;

	start = cache->start;
	end = start + cache->length - 1;

	clear_extent_bits(&fs_info->excluded_extents, start, end,
			  EXTENT_UPTODATE);
}

/* simple helper to search for an existing data extent at a given offset */
int btrfs_lookup_data_extent(struct btrfs_fs_info *fs_info, u64 start, u64 len)
{
	int ret;
	struct btrfs_key key;
	struct btrfs_path *path;

	path = btrfs_alloc_path();
	if (!path)
		return -ENOMEM;

	key.objectid = start;
	key.offset = len;
	key.type = BTRFS_EXTENT_ITEM_KEY;
	ret = btrfs_search_slot(NULL, fs_info->extent_root, &key, path, 0, 0);
	btrfs_free_path(path);
	return ret;
}

/*
 * helper function to lookup reference count and flags of a tree block.
 *
 * the head node for delayed ref is used to store the sum of all the
 * reference count modifications queued up in the rbtree. the head
 * node may also store the extent flags to set. This way you can check
 * to see what the reference count and extent flags would be if all of
 * the delayed refs are not processed.
 */
int btrfs_lookup_extent_info(struct btrfs_trans_handle *trans,
			     struct btrfs_fs_info *fs_info, u64 bytenr,
			     u64 offset, int metadata, u64 *refs, u64 *flags)
{
	struct btrfs_delayed_ref_head *head;
	struct btrfs_delayed_ref_root *delayed_refs;
	struct btrfs_path *path;
	struct btrfs_extent_item *ei;
	struct extent_buffer *leaf;
	struct btrfs_key key;
	u32 item_size;
	u64 num_refs;
	u64 extent_flags;
	int ret;

	/*
	 * If we don't have skinny metadata, don't bother doing anything
	 * different
	 */
	if (metadata && !btrfs_fs_incompat(fs_info, SKINNY_METADATA)) {
		offset = fs_info->nodesize;
		metadata = 0;
	}

	path = btrfs_alloc_path();
	if (!path)
		return -ENOMEM;

	if (!trans) {
		path->skip_locking = 1;
		path->search_commit_root = 1;
	}

search_again:
	key.objectid = bytenr;
	key.offset = offset;
	if (metadata)
		key.type = BTRFS_METADATA_ITEM_KEY;
	else
		key.type = BTRFS_EXTENT_ITEM_KEY;

	ret = btrfs_search_slot(NULL, fs_info->extent_root, &key, path, 0, 0);
	if (ret < 0)
		goto out_free;

	if (ret > 0 && metadata && key.type == BTRFS_METADATA_ITEM_KEY) {
		if (path->slots[0]) {
			path->slots[0]--;
			btrfs_item_key_to_cpu(path->nodes[0], &key,
					      path->slots[0]);
			if (key.objectid == bytenr &&
			    key.type == BTRFS_EXTENT_ITEM_KEY &&
			    key.offset == fs_info->nodesize)
				ret = 0;
		}
	}

	if (ret == 0) {
		leaf = path->nodes[0];
		item_size = btrfs_item_size_nr(leaf, path->slots[0]);
		if (item_size >= sizeof(*ei)) {
			ei = btrfs_item_ptr(leaf, path->slots[0],
					    struct btrfs_extent_item);
			num_refs = btrfs_extent_refs(leaf, ei);
			extent_flags = btrfs_extent_flags(leaf, ei);
		} else {
			ret = -EINVAL;
			btrfs_print_v0_err(fs_info);
			if (trans)
				btrfs_abort_transaction(trans, ret);
			else
				btrfs_handle_fs_error(fs_info, ret, NULL);

			goto out_free;
		}

		BUG_ON(num_refs == 0);
	} else {
		num_refs = 0;
		extent_flags = 0;
		ret = 0;
	}

	if (!trans)
		goto out;

	delayed_refs = &trans->transaction->delayed_refs;
	spin_lock(&delayed_refs->lock);
	head = btrfs_find_delayed_ref_head(delayed_refs, bytenr);
	if (head) {
		if (!mutex_trylock(&head->mutex)) {
			refcount_inc(&head->refs);
			spin_unlock(&delayed_refs->lock);

			btrfs_release_path(path);

			/*
			 * Mutex was contended, block until it's released and try
			 * again
			 */
			mutex_lock(&head->mutex);
			mutex_unlock(&head->mutex);
			btrfs_put_delayed_ref_head(head);
			goto search_again;
		}
		spin_lock(&head->lock);
		if (head->extent_op && head->extent_op->update_flags)
			extent_flags |= head->extent_op->flags_to_set;
		else
			BUG_ON(num_refs == 0);

		num_refs += head->ref_mod;
		spin_unlock(&head->lock);
		mutex_unlock(&head->mutex);
	}
	spin_unlock(&delayed_refs->lock);
out:
	WARN_ON(num_refs == 0);
	if (refs)
		*refs = num_refs;
	if (flags)
		*flags = extent_flags;
out_free:
	btrfs_free_path(path);
	return ret;
}

/*
 * Back reference rules.  Back refs have three main goals:
 *
 * 1) differentiate between all holders of references to an extent so that
 *    when a reference is dropped we can make sure it was a valid reference
 *    before freeing the extent.
 *
 * 2) Provide enough information to quickly find the holders of an extent
 *    if we notice a given block is corrupted or bad.
 *
 * 3) Make it easy to migrate blocks for FS shrinking or storage pool
 *    maintenance.  This is actually the same as #2, but with a slightly
 *    different use case.
 *
 * There are two kinds of back refs. The implicit back refs is optimized
 * for pointers in non-shared tree blocks. For a given pointer in a block,
 * back refs of this kind provide information about the block's owner tree
 * and the pointer's key. These information allow us to find the block by
 * b-tree searching. The full back refs is for pointers in tree blocks not
 * referenced by their owner trees. The location of tree block is recorded
 * in the back refs. Actually the full back refs is generic, and can be
 * used in all cases the implicit back refs is used. The major shortcoming
 * of the full back refs is its overhead. Every time a tree block gets
 * COWed, we have to update back refs entry for all pointers in it.
 *
 * For a newly allocated tree block, we use implicit back refs for
 * pointers in it. This means most tree related operations only involve
 * implicit back refs. For a tree block created in old transaction, the
 * only way to drop a reference to it is COW it. So we can detect the
 * event that tree block loses its owner tree's reference and do the
 * back refs conversion.
 *
 * When a tree block is COWed through a tree, there are four cases:
 *
 * The reference count of the block is one and the tree is the block's
 * owner tree. Nothing to do in this case.
 *
 * The reference count of the block is one and the tree is not the
 * block's owner tree. In this case, full back refs is used for pointers
 * in the block. Remove these full back refs, add implicit back refs for
 * every pointers in the new block.
 *
 * The reference count of the block is greater than one and the tree is
 * the block's owner tree. In this case, implicit back refs is used for
 * pointers in the block. Add full back refs for every pointers in the
 * block, increase lower level extents' reference counts. The original
 * implicit back refs are entailed to the new block.
 *
 * The reference count of the block is greater than one and the tree is
 * not the block's owner tree. Add implicit back refs for every pointer in
 * the new block, increase lower level extents' reference count.
 *
 * Back Reference Key composing:
 *
 * The key objectid corresponds to the first byte in the extent,
 * The key type is used to differentiate between types of back refs.
 * There are different meanings of the key offset for different types
 * of back refs.
 *
 * File extents can be referenced by:
 *
 * - multiple snapshots, subvolumes, or different generations in one subvol
 * - different files inside a single subvolume
 * - different offsets inside a file (bookend extents in file.c)
 *
 * The extent ref structure for the implicit back refs has fields for:
 *
 * - Objectid of the subvolume root
 * - objectid of the file holding the reference
 * - original offset in the file
 * - how many bookend extents
 *
 * The key offset for the implicit back refs is hash of the first
 * three fields.
 *
 * The extent ref structure for the full back refs has field for:
 *
 * - number of pointers in the tree leaf
 *
 * The key offset for the implicit back refs is the first byte of
 * the tree leaf
 *
 * When a file extent is allocated, The implicit back refs is used.
 * the fields are filled in:
 *
 *     (root_key.objectid, inode objectid, offset in file, 1)
 *
 * When a file extent is removed file truncation, we find the
 * corresponding implicit back refs and check the following fields:
 *
 *     (btrfs_header_owner(leaf), inode objectid, offset in file)
 *
 * Btree extents can be referenced by:
 *
 * - Different subvolumes
 *
 * Both the implicit back refs and the full back refs for tree blocks
 * only consist of key. The key offset for the implicit back refs is
 * objectid of block's owner tree. The key offset for the full back refs
 * is the first byte of parent block.
 *
 * When implicit back refs is used, information about the lowest key and
 * level of the tree block are required. These information are stored in
 * tree block info structure.
 */

/*
 * is_data == BTRFS_REF_TYPE_BLOCK, tree block type is required,
 * is_data == BTRFS_REF_TYPE_DATA, data type is requiried,
 * is_data == BTRFS_REF_TYPE_ANY, either type is OK.
 */
int btrfs_get_extent_inline_ref_type(const struct extent_buffer *eb,
				     struct btrfs_extent_inline_ref *iref,
				     enum btrfs_inline_ref_type is_data)
{
	int type = btrfs_extent_inline_ref_type(eb, iref);
	u64 offset = btrfs_extent_inline_ref_offset(eb, iref);

	if (type == BTRFS_TREE_BLOCK_REF_KEY ||
	    type == BTRFS_SHARED_BLOCK_REF_KEY ||
	    type == BTRFS_SHARED_DATA_REF_KEY ||
	    type == BTRFS_EXTENT_DATA_REF_KEY) {
		if (is_data == BTRFS_REF_TYPE_BLOCK) {
			if (type == BTRFS_TREE_BLOCK_REF_KEY)
				return type;
			if (type == BTRFS_SHARED_BLOCK_REF_KEY) {
				ASSERT(eb->fs_info);
				/*
				 * Every shared one has parent tree block,
				 * which must be aligned to sector size.
				 */
				if (offset &&
				    IS_ALIGNED(offset, eb->fs_info->sectorsize))
					return type;
			}
		} else if (is_data == BTRFS_REF_TYPE_DATA) {
			if (type == BTRFS_EXTENT_DATA_REF_KEY)
				return type;
			if (type == BTRFS_SHARED_DATA_REF_KEY) {
				ASSERT(eb->fs_info);
				/*
				 * Every shared one has parent tree block,
				 * which must be aligned to sector size.
				 */
				if (offset &&
				    IS_ALIGNED(offset, eb->fs_info->sectorsize))
					return type;
			}
		} else {
			ASSERT(is_data == BTRFS_REF_TYPE_ANY);
			return type;
		}
	}

	btrfs_print_leaf((struct extent_buffer *)eb);
	btrfs_err(eb->fs_info,
		  "eb %llu iref 0x%lx invalid extent inline ref type %d",
		  eb->start, (unsigned long)iref, type);
	WARN_ON(1);

	return BTRFS_REF_TYPE_INVALID;
}

u64 hash_extent_data_ref(u64 root_objectid, u64 owner, u64 offset)
{
	u32 high_crc = ~(u32)0;
	u32 low_crc = ~(u32)0;
	__le64 lenum;

	lenum = cpu_to_le64(root_objectid);
	high_crc = btrfs_crc32c(high_crc, &lenum, sizeof(lenum));
	lenum = cpu_to_le64(owner);
	low_crc = btrfs_crc32c(low_crc, &lenum, sizeof(lenum));
	lenum = cpu_to_le64(offset);
	low_crc = btrfs_crc32c(low_crc, &lenum, sizeof(lenum));

	return ((u64)high_crc << 31) ^ (u64)low_crc;
}

static u64 hash_extent_data_ref_item(struct extent_buffer *leaf,
				     struct btrfs_extent_data_ref *ref)
{
	return hash_extent_data_ref(btrfs_extent_data_ref_root(leaf, ref),
				    btrfs_extent_data_ref_objectid(leaf, ref),
				    btrfs_extent_data_ref_offset(leaf, ref));
}

static int match_extent_data_ref(struct extent_buffer *leaf,
				 struct btrfs_extent_data_ref *ref,
				 u64 root_objectid, u64 owner, u64 offset)
{
	if (btrfs_extent_data_ref_root(leaf, ref) != root_objectid ||
	    btrfs_extent_data_ref_objectid(leaf, ref) != owner ||
	    btrfs_extent_data_ref_offset(leaf, ref) != offset)
		return 0;
	return 1;
}

static noinline int lookup_extent_data_ref(struct btrfs_trans_handle *trans,
					   struct btrfs_path *path,
					   u64 bytenr, u64 parent,
					   u64 root_objectid,
					   u64 owner, u64 offset)
{
	struct btrfs_root *root = trans->fs_info->extent_root;
	struct btrfs_key key;
	struct btrfs_extent_data_ref *ref;
	struct extent_buffer *leaf;
	u32 nritems;
	int ret;
	int recow;
	int err = -ENOENT;

	key.objectid = bytenr;
	if (parent) {
		key.type = BTRFS_SHARED_DATA_REF_KEY;
		key.offset = parent;
	} else {
		key.type = BTRFS_EXTENT_DATA_REF_KEY;
		key.offset = hash_extent_data_ref(root_objectid,
						  owner, offset);
	}
again:
	recow = 0;
	ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
	if (ret < 0) {
		err = ret;
		goto fail;
	}

	if (parent) {
		if (!ret)
			return 0;
		goto fail;
	}

	leaf = path->nodes[0];
	nritems = btrfs_header_nritems(leaf);
	while (1) {
		if (path->slots[0] >= nritems) {
			ret = btrfs_next_leaf(root, path);
			if (ret < 0)
				err = ret;
			if (ret)
				goto fail;

			leaf = path->nodes[0];
			nritems = btrfs_header_nritems(leaf);
			recow = 1;
		}

		btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
		if (key.objectid != bytenr ||
		    key.type != BTRFS_EXTENT_DATA_REF_KEY)
			goto fail;

		ref = btrfs_item_ptr(leaf, path->slots[0],
				     struct btrfs_extent_data_ref);

		if (match_extent_data_ref(leaf, ref, root_objectid,
					  owner, offset)) {
			if (recow) {
				btrfs_release_path(path);
				goto again;
			}
			err = 0;
			break;
		}
		path->slots[0]++;
	}
fail:
	return err;
}

static noinline int insert_extent_data_ref(struct btrfs_trans_handle *trans,
					   struct btrfs_path *path,
					   u64 bytenr, u64 parent,
					   u64 root_objectid, u64 owner,
					   u64 offset, int refs_to_add)
{
	struct btrfs_root *root = trans->fs_info->extent_root;
	struct btrfs_key key;
	struct extent_buffer *leaf;
	u32 size;
	u32 num_refs;
	int ret;

	key.objectid = bytenr;
	if (parent) {
		key.type = BTRFS_SHARED_DATA_REF_KEY;
		key.offset = parent;
		size = sizeof(struct btrfs_shared_data_ref);
	} else {
		key.type = BTRFS_EXTENT_DATA_REF_KEY;
		key.offset = hash_extent_data_ref(root_objectid,
						  owner, offset);
		size = sizeof(struct btrfs_extent_data_ref);
	}

	ret = btrfs_insert_empty_item(trans, root, path, &key, size);
	if (ret && ret != -EEXIST)
		goto fail;

	leaf = path->nodes[0];
	if (parent) {
		struct btrfs_shared_data_ref *ref;
		ref = btrfs_item_ptr(leaf, path->slots[0],
				     struct btrfs_shared_data_ref);
		if (ret == 0) {
			btrfs_set_shared_data_ref_count(leaf, ref, refs_to_add);
		} else {
			num_refs = btrfs_shared_data_ref_count(leaf, ref);
			num_refs += refs_to_add;
			btrfs_set_shared_data_ref_count(leaf, ref, num_refs);
		}
	} else {
		struct btrfs_extent_data_ref *ref;
		while (ret == -EEXIST) {
			ref = btrfs_item_ptr(leaf, path->slots[0],
					     struct btrfs_extent_data_ref);
			if (match_extent_data_ref(leaf, ref, root_objectid,
						  owner, offset))
				break;
			btrfs_release_path(path);
			key.offset++;
			ret = btrfs_insert_empty_item(trans, root, path, &key,
						      size);
			if (ret && ret != -EEXIST)
				goto fail;

			leaf = path->nodes[0];
		}
		ref = btrfs_item_ptr(leaf, path->slots[0],
				     struct btrfs_extent_data_ref);
		if (ret == 0) {
			btrfs_set_extent_data_ref_root(leaf, ref,
						       root_objectid);
			btrfs_set_extent_data_ref_objectid(leaf, ref, owner);
			btrfs_set_extent_data_ref_offset(leaf, ref, offset);
			btrfs_set_extent_data_ref_count(leaf, ref, refs_to_add);
		} else {
			num_refs = btrfs_extent_data_ref_count(leaf, ref);
			num_refs += refs_to_add;
			btrfs_set_extent_data_ref_count(leaf, ref, num_refs);
		}
	}
	btrfs_mark_buffer_dirty(leaf);
	ret = 0;
fail:
	btrfs_release_path(path);
	return ret;
}

static noinline int remove_extent_data_ref(struct btrfs_trans_handle *trans,
					   struct btrfs_path *path,
					   int refs_to_drop, int *last_ref)
{
	struct btrfs_key key;
	struct btrfs_extent_data_ref *ref1 = NULL;
	struct btrfs_shared_data_ref *ref2 = NULL;
	struct extent_buffer *leaf;
	u32 num_refs = 0;
	int ret = 0;

	leaf = path->nodes[0];
	btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);

	if (key.type == BTRFS_EXTENT_DATA_REF_KEY) {
		ref1 = btrfs_item_ptr(leaf, path->slots[0],
				      struct btrfs_extent_data_ref);
		num_refs = btrfs_extent_data_ref_count(leaf, ref1);
	} else if (key.type == BTRFS_SHARED_DATA_REF_KEY) {
		ref2 = btrfs_item_ptr(leaf, path->slots[0],
				      struct btrfs_shared_data_ref);
		num_refs = btrfs_shared_data_ref_count(leaf, ref2);
	} else if (unlikely(key.type == BTRFS_EXTENT_REF_V0_KEY)) {
		btrfs_print_v0_err(trans->fs_info);
		btrfs_abort_transaction(trans, -EINVAL);
		return -EINVAL;
	} else {
		BUG();
	}

	BUG_ON(num_refs < refs_to_drop);
	num_refs -= refs_to_drop;

	if (num_refs == 0) {
		ret = btrfs_del_item(trans, trans->fs_info->extent_root, path);
		*last_ref = 1;
	} else {
		if (key.type == BTRFS_EXTENT_DATA_REF_KEY)
			btrfs_set_extent_data_ref_count(leaf, ref1, num_refs);
		else if (key.type == BTRFS_SHARED_DATA_REF_KEY)
			btrfs_set_shared_data_ref_count(leaf, ref2, num_refs);
		btrfs_mark_buffer_dirty(leaf);
	}
	return ret;
}

static noinline u32 extent_data_ref_count(struct btrfs_path *path,
					  struct btrfs_extent_inline_ref *iref)
{
	struct btrfs_key key;
	struct extent_buffer *leaf;
	struct btrfs_extent_data_ref *ref1;
	struct btrfs_shared_data_ref *ref2;
	u32 num_refs = 0;
	int type;

	leaf = path->nodes[0];
	btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);

	BUG_ON(key.type == BTRFS_EXTENT_REF_V0_KEY);
	if (iref) {
		/*
		 * If type is invalid, we should have bailed out earlier than
		 * this call.
		 */
		type = btrfs_get_extent_inline_ref_type(leaf, iref, BTRFS_REF_TYPE_DATA);
		ASSERT(type != BTRFS_REF_TYPE_INVALID);
		if (type == BTRFS_EXTENT_DATA_REF_KEY) {
			ref1 = (struct btrfs_extent_data_ref *)(&iref->offset);
			num_refs = btrfs_extent_data_ref_count(leaf, ref1);
		} else {
			ref2 = (struct btrfs_shared_data_ref *)(iref + 1);
			num_refs = btrfs_shared_data_ref_count(leaf, ref2);
		}
	} else if (key.type == BTRFS_EXTENT_DATA_REF_KEY) {
		ref1 = btrfs_item_ptr(leaf, path->slots[0],
				      struct btrfs_extent_data_ref);
		num_refs = btrfs_extent_data_ref_count(leaf, ref1);
	} else if (key.type == BTRFS_SHARED_DATA_REF_KEY) {
		ref2 = btrfs_item_ptr(leaf, path->slots[0],
				      struct btrfs_shared_data_ref);
		num_refs = btrfs_shared_data_ref_count(leaf, ref2);
	} else {
		WARN_ON(1);
	}
	return num_refs;
}

static noinline int lookup_tree_block_ref(struct btrfs_trans_handle *trans,
					  struct btrfs_path *path,
					  u64 bytenr, u64 parent,
					  u64 root_objectid)
{
	struct btrfs_root *root = trans->fs_info->extent_root;
	struct btrfs_key key;
	int ret;

	key.objectid = bytenr;
	if (parent) {
		key.type = BTRFS_SHARED_BLOCK_REF_KEY;
		key.offset = parent;
	} else {
		key.type = BTRFS_TREE_BLOCK_REF_KEY;
		key.offset = root_objectid;
	}

	ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
	if (ret > 0)
		ret = -ENOENT;
	return ret;
}

static noinline int insert_tree_block_ref(struct btrfs_trans_handle *trans,
					  struct btrfs_path *path,
					  u64 bytenr, u64 parent,
					  u64 root_objectid)
{
	struct btrfs_key key;
	int ret;

	key.objectid = bytenr;
	if (parent) {
		key.type = BTRFS_SHARED_BLOCK_REF_KEY;
		key.offset = parent;
	} else {
		key.type = BTRFS_TREE_BLOCK_REF_KEY;
		key.offset = root_objectid;
	}

	ret = btrfs_insert_empty_item(trans, trans->fs_info->extent_root,
				      path, &key, 0);
	btrfs_release_path(path);
	return ret;
}

static inline int extent_ref_type(u64 parent, u64 owner)
{
	int type;
	if (owner < BTRFS_FIRST_FREE_OBJECTID) {
		if (parent > 0)
			type = BTRFS_SHARED_BLOCK_REF_KEY;
		else
			type = BTRFS_TREE_BLOCK_REF_KEY;
	} else {
		if (parent > 0)
			type = BTRFS_SHARED_DATA_REF_KEY;
		else
			type = BTRFS_EXTENT_DATA_REF_KEY;
	}
	return type;
}

static int find_next_key(struct btrfs_path *path, int level,
			 struct btrfs_key *key)

{
	for (; level < BTRFS_MAX_LEVEL; level++) {
		if (!path->nodes[level])
			break;
		if (path->slots[level] + 1 >=
		    btrfs_header_nritems(path->nodes[level]))
			continue;
		if (level == 0)
			btrfs_item_key_to_cpu(path->nodes[level], key,
					      path->slots[level] + 1);
		else
			btrfs_node_key_to_cpu(path->nodes[level], key,
					      path->slots[level] + 1);
		return 0;
	}
	return 1;
}

/*
 * look for inline back ref. if back ref is found, *ref_ret is set
 * to the address of inline back ref, and 0 is returned.
 *
 * if back ref isn't found, *ref_ret is set to the address where it
 * should be inserted, and -ENOENT is returned.
 *
 * if insert is true and there are too many inline back refs, the path
 * points to the extent item, and -EAGAIN is returned.
 *
 * NOTE: inline back refs are ordered in the same way that back ref
 *	 items in the tree are ordered.
 */
static noinline_for_stack
int lookup_inline_extent_backref(struct btrfs_trans_handle *trans,
				 struct btrfs_path *path,
				 struct btrfs_extent_inline_ref **ref_ret,
				 u64 bytenr, u64 num_bytes,
				 u64 parent, u64 root_objectid,
				 u64 owner, u64 offset, int insert)
{
	struct btrfs_fs_info *fs_info = trans->fs_info;
	struct btrfs_root *root = fs_info->extent_root;
	struct btrfs_key key;
	struct extent_buffer *leaf;
	struct btrfs_extent_item *ei;
	struct btrfs_extent_inline_ref *iref;
	u64 flags;
	u64 item_size;
	unsigned long ptr;
	unsigned long end;
	int extra_size;
	int type;
	int want;
	int ret;
	int err = 0;
	bool skinny_metadata = btrfs_fs_incompat(fs_info, SKINNY_METADATA);
	int needed;

	key.objectid = bytenr;
	key.type = BTRFS_EXTENT_ITEM_KEY;
	key.offset = num_bytes;

	want = extent_ref_type(parent, owner);
	if (insert) {
		extra_size = btrfs_extent_inline_ref_size(want);
		path->search_for_extension = 1;
		path->keep_locks = 1;
	} else
		extra_size = -1;

	/*
	 * Owner is our level, so we can just add one to get the level for the
	 * block we are interested in.
	 */
	if (skinny_metadata && owner < BTRFS_FIRST_FREE_OBJECTID) {
		key.type = BTRFS_METADATA_ITEM_KEY;
		key.offset = owner;
	}

again:
	ret = btrfs_search_slot(trans, root, &key, path, extra_size, 1);
	if (ret < 0) {
		err = ret;
		goto out;
	}

	/*
	 * We may be a newly converted file system which still has the old fat
	 * extent entries for metadata, so try and see if we have one of those.
	 */
	if (ret > 0 && skinny_metadata) {
		skinny_metadata = false;
		if (path->slots[0]) {
			path->slots[0]--;
			btrfs_item_key_to_cpu(path->nodes[0], &key,
					      path->slots[0]);
			if (key.objectid == bytenr &&
			    key.type == BTRFS_EXTENT_ITEM_KEY &&
			    key.offset == num_bytes)
				ret = 0;
		}
		if (ret) {
			key.objectid = bytenr;
			key.type = BTRFS_EXTENT_ITEM_KEY;
			key.offset = num_bytes;
			btrfs_release_path(path);
			goto again;
		}
	}

	if (ret && !insert) {
		err = -ENOENT;
		goto out;
	} else if (WARN_ON(ret)) {
		err = -EIO;
		goto out;
	}

	leaf = path->nodes[0];
	item_size = btrfs_item_size_nr(leaf, path->slots[0]);
	if (unlikely(item_size < sizeof(*ei))) {
		err = -EINVAL;
		btrfs_print_v0_err(fs_info);
		btrfs_abort_transaction(trans, err);
		goto out;
	}

	ei = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_extent_item);
	flags = btrfs_extent_flags(leaf, ei);

	ptr = (unsigned long)(ei + 1);
	end = (unsigned long)ei + item_size;

	if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK && !skinny_metadata) {
		ptr += sizeof(struct btrfs_tree_block_info);
		BUG_ON(ptr > end);
	}

	if (owner >= BTRFS_FIRST_FREE_OBJECTID)
		needed = BTRFS_REF_TYPE_DATA;
	else
		needed = BTRFS_REF_TYPE_BLOCK;

	err = -ENOENT;
	while (1) {
		if (ptr >= end) {
			WARN_ON(ptr > end);
			break;
		}
		iref = (struct btrfs_extent_inline_ref *)ptr;
		type = btrfs_get_extent_inline_ref_type(leaf, iref, needed);
		if (type == BTRFS_REF_TYPE_INVALID) {
			err = -EUCLEAN;
			goto out;
		}

		if (want < type)
			break;
		if (want > type) {
			ptr += btrfs_extent_inline_ref_size(type);
			continue;
		}

		if (type == BTRFS_EXTENT_DATA_REF_KEY) {
			struct btrfs_extent_data_ref *dref;
			dref = (struct btrfs_extent_data_ref *)(&iref->offset);
			if (match_extent_data_ref(leaf, dref, root_objectid,
						  owner, offset)) {
				err = 0;
				break;
			}
			if (hash_extent_data_ref_item(leaf, dref) <
			    hash_extent_data_ref(root_objectid, owner, offset))
				break;
		} else {
			u64 ref_offset;
			ref_offset = btrfs_extent_inline_ref_offset(leaf, iref);
			if (parent > 0) {
				if (parent == ref_offset) {
					err = 0;
					break;
				}
				if (ref_offset < parent)
					break;
			} else {
				if (root_objectid == ref_offset) {
					err = 0;
					break;
				}
				if (ref_offset < root_objectid)
					break;
			}
		}
		ptr += btrfs_extent_inline_ref_size(type);
	}
	if (err == -ENOENT && insert) {
		if (item_size + extra_size >=
		    BTRFS_MAX_EXTENT_ITEM_SIZE(root)) {
			err = -EAGAIN;
			goto out;
		}
		/*
		 * To add new inline back ref, we have to make sure
		 * there is no corresponding back ref item.
		 * For simplicity, we just do not add new inline back
		 * ref if there is any kind of item for this block
		 */
		if (find_next_key(path, 0, &key) == 0 &&
		    key.objectid == bytenr &&
		    key.type < BTRFS_BLOCK_GROUP_ITEM_KEY) {
			err = -EAGAIN;
			goto out;
		}
	}
	*ref_ret = (struct btrfs_extent_inline_ref *)ptr;
out:
	if (insert) {
		path->keep_locks = 0;
		path->search_for_extension = 0;
		btrfs_unlock_up_safe(path, 1);
	}
	return err;
}

/*
 * helper to add new inline back ref
 */
static noinline_for_stack
void setup_inline_extent_backref(struct btrfs_fs_info *fs_info,
				 struct btrfs_path *path,
				 struct btrfs_extent_inline_ref *iref,
				 u64 parent, u64 root_objectid,
				 u64 owner, u64 offset, int refs_to_add,
				 struct btrfs_delayed_extent_op *extent_op)
{
	struct extent_buffer *leaf;
	struct btrfs_extent_item *ei;
	unsigned long ptr;
	unsigned long end;
	unsigned long item_offset;
	u64 refs;
	int size;
	int type;

	leaf = path->nodes[0];
	ei = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_extent_item);
	item_offset = (unsigned long)iref - (unsigned long)ei;

	type = extent_ref_type(parent, owner);
	size = btrfs_extent_inline_ref_size(type);

	btrfs_extend_item(path, size);

	ei = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_extent_item);
	refs = btrfs_extent_refs(leaf, ei);
	refs += refs_to_add;
	btrfs_set_extent_refs(leaf, ei, refs);
	if (extent_op)
		__run_delayed_extent_op(extent_op, leaf, ei);

	ptr = (unsigned long)ei + item_offset;
	end = (unsigned long)ei + btrfs_item_size_nr(leaf, path->slots[0]);
	if (ptr < end - size)
		memmove_extent_buffer(leaf, ptr + size, ptr,
				      end - size - ptr);

	iref = (struct btrfs_extent_inline_ref *)ptr;
	btrfs_set_extent_inline_ref_type(leaf, iref, type);
	if (type == BTRFS_EXTENT_DATA_REF_KEY) {
		struct btrfs_extent_data_ref *dref;
		dref = (struct btrfs_extent_data_ref *)(&iref->offset);
		btrfs_set_extent_data_ref_root(leaf, dref, root_objectid);
		btrfs_set_extent_data_ref_objectid(leaf, dref, owner);
		btrfs_set_extent_data_ref_offset(leaf, dref, offset);
		btrfs_set_extent_data_ref_count(leaf, dref, refs_to_add);
	} else if (type == BTRFS_SHARED_DATA_REF_KEY) {
		struct btrfs_shared_data_ref *sref;
		sref = (struct btrfs_shared_data_ref *)(iref + 1);
		btrfs_set_shared_data_ref_count(leaf, sref, refs_to_add);
		btrfs_set_extent_inline_ref_offset(leaf, iref, parent);
	} else if (type == BTRFS_SHARED_BLOCK_REF_KEY) {
		btrfs_set_extent_inline_ref_offset(leaf, iref, parent);
	} else {
		btrfs_set_extent_inline_ref_offset(leaf, iref, root_objectid);
	}
	btrfs_mark_buffer_dirty(leaf);
}

static int lookup_extent_backref(struct btrfs_trans_handle *trans,
				 struct btrfs_path *path,
				 struct btrfs_extent_inline_ref **ref_ret,
				 u64 bytenr, u64 num_bytes, u64 parent,
				 u64 root_objectid, u64 owner, u64 offset)
{
	int ret;

	ret = lookup_inline_extent_backref(trans, path, ref_ret, bytenr,
					   num_bytes, parent, root_objectid,
					   owner, offset, 0);
	if (ret != -ENOENT)
		return ret;

	btrfs_release_path(path);
	*ref_ret = NULL;

	if (owner < BTRFS_FIRST_FREE_OBJECTID) {
		ret = lookup_tree_block_ref(trans, path, bytenr, parent,
					    root_objectid);
	} else {
		ret = lookup_extent_data_ref(trans, path, bytenr, parent,
					     root_objectid, owner, offset);
	}
	return ret;
}

/*
 * helper to update/remove inline back ref
 */
static noinline_for_stack
void update_inline_extent_backref(struct btrfs_path *path,
				  struct btrfs_extent_inline_ref *iref,
				  int refs_to_mod,
				  struct btrfs_delayed_extent_op *extent_op,
				  int *last_ref)
{
	struct extent_buffer *leaf = path->nodes[0];
	struct btrfs_extent_item *ei;
	struct btrfs_extent_data_ref *dref = NULL;
	struct btrfs_shared_data_ref *sref = NULL;
	unsigned long ptr;
	unsigned long end;
	u32 item_size;
	int size;
	int type;
	u64 refs;

	ei = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_extent_item);
	refs = btrfs_extent_refs(leaf, ei);
	WARN_ON(refs_to_mod < 0 && refs + refs_to_mod <= 0);
	refs += refs_to_mod;
	btrfs_set_extent_refs(leaf, ei, refs);
	if (extent_op)
		__run_delayed_extent_op(extent_op, leaf, ei);

	/*
	 * If type is invalid, we should have bailed out after
	 * lookup_inline_extent_backref().
	 */
	type = btrfs_get_extent_inline_ref_type(leaf, iref, BTRFS_REF_TYPE_ANY);
	ASSERT(type != BTRFS_REF_TYPE_INVALID);

	if (type == BTRFS_EXTENT_DATA_REF_KEY) {
		dref = (struct btrfs_extent_data_ref *)(&iref->offset);
		refs = btrfs_extent_data_ref_count(leaf, dref);
	} else if (type == BTRFS_SHARED_DATA_REF_KEY) {
		sref = (struct btrfs_shared_data_ref *)(iref + 1);
		refs = btrfs_shared_data_ref_count(leaf, sref);
	} else {
		refs = 1;
		BUG_ON(refs_to_mod != -1);
	}

	BUG_ON(refs_to_mod < 0 && refs < -refs_to_mod);
	refs += refs_to_mod;

	if (refs > 0) {
		if (type == BTRFS_EXTENT_DATA_REF_KEY)
			btrfs_set_extent_data_ref_count(leaf, dref, refs);
		else
			btrfs_set_shared_data_ref_count(leaf, sref, refs);
	} else {
		*last_ref = 1;
		size =  btrfs_extent_inline_ref_size(type);
		item_size = btrfs_item_size_nr(leaf, path->slots[0]);
		ptr = (unsigned long)iref;
		end = (unsigned long)ei + item_size;
		if (ptr + size < end)
			memmove_extent_buffer(leaf, ptr, ptr + size,
					      end - ptr - size);
		item_size -= size;
		btrfs_truncate_item(path, item_size, 1);
	}
	btrfs_mark_buffer_dirty(leaf);
}

static noinline_for_stack
int insert_inline_extent_backref(struct btrfs_trans_handle *trans,
				 struct btrfs_path *path,
				 u64 bytenr, u64 num_bytes, u64 parent,
				 u64 root_objectid, u64 owner,
				 u64 offset, int refs_to_add,
				 struct btrfs_delayed_extent_op *extent_op)
{
	struct btrfs_extent_inline_ref *iref;
	int ret;

	ret = lookup_inline_extent_backref(trans, path, &iref, bytenr,
					   num_bytes, parent, root_objectid,
					   owner, offset, 1);
	if (ret == 0) {
		/*
		 * We're adding refs to a tree block we already own, this
		 * should not happen at all.
		 */
		if (owner < BTRFS_FIRST_FREE_OBJECTID) {
			btrfs_crit(trans->fs_info,
"adding refs to an existing tree ref, bytenr %llu num_bytes %llu root_objectid %llu",
				   bytenr, num_bytes, root_objectid);
			if (IS_ENABLED(CONFIG_BTRFS_DEBUG)) {
				WARN_ON(1);
				btrfs_crit(trans->fs_info,
			"path->slots[0]=%d path->nodes[0]:", path->slots[0]);
				btrfs_print_leaf(path->nodes[0]);
			}
			return -EUCLEAN;
		}
		update_inline_extent_backref(path, iref, refs_to_add,
					     extent_op, NULL);
	} else if (ret == -ENOENT) {
		setup_inline_extent_backref(trans->fs_info, path, iref, parent,
					    root_objectid, owner, offset,
					    refs_to_add, extent_op);
		ret = 0;
	}
	return ret;
}

static int remove_extent_backref(struct btrfs_trans_handle *trans,
				 struct btrfs_path *path,
				 struct btrfs_extent_inline_ref *iref,
				 int refs_to_drop, int is_data, int *last_ref)
{
	int ret = 0;

	BUG_ON(!is_data && refs_to_drop != 1);
	if (iref) {
		update_inline_extent_backref(path, iref, -refs_to_drop, NULL,
					     last_ref);
	} else if (is_data) {
		ret = remove_extent_data_ref(trans, path, refs_to_drop,
					     last_ref);
	} else {
		*last_ref = 1;
		ret = btrfs_del_item(trans, trans->fs_info->extent_root, path);
	}
	return ret;
}

static int btrfs_issue_discard(struct block_device *bdev, u64 start, u64 len,
			       u64 *discarded_bytes)
{
	int j, ret = 0;
	u64 bytes_left, end;
	u64 aligned_start = ALIGN(start, 1 << 9);

	if (WARN_ON(start != aligned_start)) {
		len -= aligned_start - start;
		len = round_down(len, 1 << 9);
		start = aligned_start;
	}

	*discarded_bytes = 0;

	if (!len)
		return 0;

	end = start + len;
	bytes_left = len;

	/* Skip any superblocks on this device. */
	for (j = 0; j < BTRFS_SUPER_MIRROR_MAX; j++) {
		u64 sb_start = btrfs_sb_offset(j);
		u64 sb_end = sb_start + BTRFS_SUPER_INFO_SIZE;
		u64 size = sb_start - start;

		if (!in_range(sb_start, start, bytes_left) &&
		    !in_range(sb_end, start, bytes_left) &&
		    !in_range(start, sb_start, BTRFS_SUPER_INFO_SIZE))
			continue;

		/*
		 * Superblock spans beginning of range.  Adjust start and
		 * try again.
		 */
		if (sb_start <= start) {
			start += sb_end - start;
			if (start > end) {
				bytes_left = 0;
				break;
			}
			bytes_left = end - start;
			continue;
		}

		if (size) {
			ret = blkdev_issue_discard(bdev, start >> 9, size >> 9,
						   GFP_NOFS, 0);
			if (!ret)
				*discarded_bytes += size;
			else if (ret != -EOPNOTSUPP)
				return ret;
		}

		start = sb_end;
		if (start > end) {
			bytes_left = 0;
			break;
		}
		bytes_left = end - start;
	}

	if (bytes_left) {
		ret = blkdev_issue_discard(bdev, start >> 9, bytes_left >> 9,
					   GFP_NOFS, 0);
		if (!ret)
			*discarded_bytes += bytes_left;
	}
	return ret;
}

static int do_discard_extent(struct btrfs_io_stripe *stripe, u64 *bytes)
{
	struct btrfs_device *dev = stripe->dev;
	struct btrfs_fs_info *fs_info = dev->fs_info;
	struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
	u64 phys = stripe->physical;
	u64 len = stripe->length;
	u64 discarded = 0;
	int ret = 0;

	/* Zone reset on a zoned filesystem */
	if (btrfs_can_zone_reset(dev, phys, len)) {
		u64 src_disc;

		ret = btrfs_reset_device_zone(dev, phys, len, &discarded);
		if (ret)
			goto out;

		if (!btrfs_dev_replace_is_ongoing(dev_replace) ||
		    dev != dev_replace->srcdev)
			goto out;

		src_disc = discarded;

		/* Send to replace target as well */
		ret = btrfs_reset_device_zone(dev_replace->tgtdev, phys, len,
					      &discarded);
		discarded += src_disc;
	} else if (blk_queue_discard(bdev_get_queue(stripe->dev->bdev))) {
		ret = btrfs_issue_discard(dev->bdev, phys, len, &discarded);
	} else {
		ret = 0;
		*bytes = 0;
	}

out:
	*bytes = discarded;
	return ret;
}

int btrfs_discard_extent(struct btrfs_fs_info *fs_info, u64 bytenr,
			 u64 num_bytes, u64 *actual_bytes)
{
	int ret = 0;
	u64 discarded_bytes = 0;
	u64 end = bytenr + num_bytes;
	u64 cur = bytenr;
	struct btrfs_io_context *bioc = NULL;

	/*
	 * Avoid races with device replace and make sure our bioc has devices
	 * associated to its stripes that don't go away while we are discarding.
	 */
	btrfs_bio_counter_inc_blocked(fs_info);
	while (cur < end) {
		struct btrfs_io_stripe *stripe;
		int i;

		num_bytes = end - cur;
		/* Tell the block device(s) that the sectors can be discarded */
		ret = btrfs_map_block(fs_info, BTRFS_MAP_DISCARD, cur,
				      &num_bytes, &bioc, 0);
		/*
		 * Error can be -ENOMEM, -ENOENT (no such chunk mapping) or
		 * -EOPNOTSUPP. For any such error, @num_bytes is not updated,
		 * thus we can't continue anyway.
		 */
		if (ret < 0)
			goto out;

		stripe = bioc->stripes;
		for (i = 0; i < bioc->num_stripes; i++, stripe++) {
			u64 bytes;
			struct btrfs_device *device = stripe->dev;

			if (!device->bdev) {
				ASSERT(btrfs_test_opt(fs_info, DEGRADED));
				continue;
			}

			if (!test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state))
				continue;

			ret = do_discard_extent(stripe, &bytes);
			if (!ret) {
				discarded_bytes += bytes;
			} else if (ret != -EOPNOTSUPP) {
				/*
				 * Logic errors or -ENOMEM, or -EIO, but
				 * unlikely to happen.
				 *
				 * And since there are two loops, explicitly
				 * go to out to avoid confusion.
				 */
				btrfs_put_bioc(bioc);
				goto out;
			}

			/*
			 * Just in case we get back EOPNOTSUPP for some reason,
			 * just ignore the return value so we don't screw up
			 * people calling discard_extent.
			 */
			ret = 0;
		}
		btrfs_put_bioc(bioc);
		cur += num_bytes;
	}
out:
	btrfs_bio_counter_dec(fs_info);

	if (actual_bytes)
		*actual_bytes = discarded_bytes;


	if (ret == -EOPNOTSUPP)
		ret = 0;
	return ret;
}

/* Can return -ENOMEM */
int btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
			 struct btrfs_ref *generic_ref)
{
	struct btrfs_fs_info *fs_info = trans->fs_info;
	int ret;

	ASSERT(generic_ref->type != BTRFS_REF_NOT_SET &&
	       generic_ref->action);
	BUG_ON(generic_ref->type == BTRFS_REF_METADATA &&
	       generic_ref->tree_ref.owning_root == BTRFS_TREE_LOG_OBJECTID);

	if (generic_ref->type == BTRFS_REF_METADATA)
		ret = btrfs_add_delayed_tree_ref(trans, generic_ref, NULL);
	else
		ret = btrfs_add_delayed_data_ref(trans, generic_ref, 0);

	btrfs_ref_tree_mod(fs_info, generic_ref);

	return ret;
}

/*
 * __btrfs_inc_extent_ref - insert backreference for a given extent
 *
 * The counterpart is in __btrfs_free_extent(), with examples and more details
 * how it works.
 *
 * @trans:	    Handle of transaction
 *
 * @node:	    The delayed ref node used to get the bytenr/length for
 *		    extent whose references are incremented.
 *
 * @parent:	    If this is a shared extent (BTRFS_SHARED_DATA_REF_KEY/
 *		    BTRFS_SHARED_BLOCK_REF_KEY) then it holds the logical
 *		    bytenr of the parent block. Since new extents are always
 *		    created with indirect references, this will only be the case
 *		    when relocating a shared extent. In that case, root_objectid
 *		    will be BTRFS_TREE_RELOC_OBJECTID. Otherwise, parent must
 *		    be 0
 *
 * @root_objectid:  The id of the root where this modification has originated,
 *		    this can be either one of the well-known metadata trees or
 *		    the subvolume id which references this extent.
 *
 * @owner:	    For data extents it is the inode number of the owning file.
 *		    For metadata extents this parameter holds the level in the
 *		    tree of the extent.
 *
 * @offset:	    For metadata extents the offset is ignored and is currently
 *		    always passed as 0. For data extents it is the fileoffset
 *		    this extent belongs to.
 *
 * @refs_to_add     Number of references to add
 *
 * @extent_op       Pointer to a structure, holding information necessary when
 *                  updating a tree block's flags
 *
 */
static int __btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
				  struct btrfs_delayed_ref_node *node,
				  u64 parent, u64 root_objectid,
				  u64 owner, u64 offset, int refs_to_add,
				  struct btrfs_delayed_extent_op *extent_op)
{
	struct btrfs_path *path;
	struct extent_buffer *leaf;
	struct btrfs_extent_item *item;
	struct btrfs_key key;
	u64 bytenr = node->bytenr;
	u64 num_bytes = node->num_bytes;
	u64 refs;
	int ret;

	path = btrfs_alloc_path();
	if (!path)
		return -ENOMEM;

	/* this will setup the path even if it fails to insert the back ref */
	ret = insert_inline_extent_backref(trans, path, bytenr, num_bytes,
					   parent, root_objectid, owner,
					   offset, refs_to_add, extent_op);
	if ((ret < 0 && ret != -EAGAIN) || !ret)
		goto out;

	/*
	 * Ok we had -EAGAIN which means we didn't have space to insert and
	 * inline extent ref, so just update the reference count and add a
	 * normal backref.
	 */
	leaf = path->nodes[0];
	btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
	item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_extent_item);
	refs = btrfs_extent_refs(leaf, item);
	btrfs_set_extent_refs(leaf, item, refs + refs_to_add);
	if (extent_op)
		__run_delayed_extent_op(extent_op, leaf, item);

	btrfs_mark_buffer_dirty(leaf);
	btrfs_release_path(path);

	/* now insert the actual backref */
	if (owner < BTRFS_FIRST_FREE_OBJECTID) {
		BUG_ON(refs_to_add != 1);
		ret = insert_tree_block_ref(trans, path, bytenr, parent,
					    root_objectid);
	} else {
		ret = insert_extent_data_ref(trans, path, bytenr, parent,
					     root_objectid, owner, offset,
					     refs_to_add);
	}
	if (ret)
		btrfs_abort_transaction(trans, ret);
out:
	btrfs_free_path(path);
	return ret;
}

static int run_delayed_data_ref(struct btrfs_trans_handle *trans,
				struct btrfs_delayed_ref_node *node,
				struct btrfs_delayed_extent_op *extent_op,
				int insert_reserved)
{
	int ret = 0;
	struct btrfs_delayed_data_ref *ref;
	struct btrfs_key ins;
	u64 parent = 0;
	u64 ref_root = 0;
	u64 flags = 0;

	ins.objectid = node->bytenr;
	ins.offset = node->num_bytes;
	ins.type = BTRFS_EXTENT_ITEM_KEY;

	ref = btrfs_delayed_node_to_data_ref(node);
	trace_run_delayed_data_ref(trans->fs_info, node, ref, node->action);

	if (node->type == BTRFS_SHARED_DATA_REF_KEY)
		parent = ref->parent;
	ref_root = ref->root;

	if (node->action == BTRFS_ADD_DELAYED_REF && insert_reserved) {
		if (extent_op)
			flags |= extent_op->flags_to_set;
		ret = alloc_reserved_file_extent(trans, parent, ref_root,
						 flags, ref->objectid,
						 ref->offset, &ins,
						 node->ref_mod);
	} else if (node->action == BTRFS_ADD_DELAYED_REF) {
		ret = __btrfs_inc_extent_ref(trans, node, parent, ref_root,
					     ref->objectid, ref->offset,
					     node->ref_mod, extent_op);
	} else if (node->action == BTRFS_DROP_DELAYED_REF) {
		ret = __btrfs_free_extent(trans, node, parent,
					  ref_root, ref->objectid,
					  ref->offset, node->ref_mod,
					  extent_op);
	} else {
		BUG();
	}
	return ret;
}

static void __run_delayed_extent_op(struct btrfs_delayed_extent_op *extent_op,
				    struct extent_buffer *leaf,
				    struct btrfs_extent_item *ei)
{
	u64 flags = btrfs_extent_flags(leaf, ei);
	if (extent_op->update_flags) {
		flags |= extent_op->flags_to_set;
		btrfs_set_extent_flags(leaf, ei, flags);
	}

	if (extent_op->update_key) {
		struct btrfs_tree_block_info *bi;
		BUG_ON(!(flags & BTRFS_EXTENT_FLAG_TREE_BLOCK));
		bi = (struct btrfs_tree_block_info *)(ei + 1);
		btrfs_set_tree_block_key(leaf, bi, &extent_op->key);
	}
}

static int run_delayed_extent_op(struct btrfs_trans_handle *trans,
				 struct btrfs_delayed_ref_head *head,
				 struct btrfs_delayed_extent_op *extent_op)
{
	struct btrfs_fs_info *fs_info = trans->fs_info;
	struct btrfs_key key;
	struct btrfs_path *path;
	struct btrfs_extent_item *ei;
	struct extent_buffer *leaf;
	u32 item_size;
	int ret;
	int err = 0;
	int metadata = !extent_op->is_data;

	if (TRANS_ABORTED(trans))
		return 0;

	if (metadata && !btrfs_fs_incompat(fs_info, SKINNY_METADATA))
		metadata = 0;

	path = btrfs_alloc_path();
	if (!path)
		return -ENOMEM;

	key.objectid = head->bytenr;

	if (metadata) {
		key.type = BTRFS_METADATA_ITEM_KEY;
		key.offset = extent_op->level;
	} else {
		key.type = BTRFS_EXTENT_ITEM_KEY;
		key.offset = head->num_bytes;
	}

again:
	ret = btrfs_search_slot(trans, fs_info->extent_root, &key, path, 0, 1);
	if (ret < 0) {
		err = ret;
		goto out;
	}
	if (ret > 0) {
		if (metadata) {
			if (path->slots[0] > 0) {
				path->slots[0]--;
				btrfs_item_key_to_cpu(path->nodes[0], &key,
						      path->slots[0]);
				if (key.objectid == head->bytenr &&
				    key.type == BTRFS_EXTENT_ITEM_KEY &&
				    key.offset == head->num_bytes)
					ret = 0;
			}
			if (ret > 0) {
				btrfs_release_path(path);
				metadata = 0;

				key.objectid = head->bytenr;
				key.offset = head->num_bytes;
				key.type = BTRFS_EXTENT_ITEM_KEY;
				goto again;
			}
		} else {
			err = -EIO;
			goto out;
		}
	}

	leaf = path->nodes[0];
	item_size = btrfs_item_size_nr(leaf, path->slots[0]);

	if (unlikely(item_size < sizeof(*ei))) {
		err = -EINVAL;
		btrfs_print_v0_err(fs_info);
		btrfs_abort_transaction(trans, err);
		goto out;
	}

	ei = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_extent_item);
	__run_delayed_extent_op(extent_op, leaf, ei);

	btrfs_mark_buffer_dirty(leaf);
out:
	btrfs_free_path(path);
	return err;
}

static int run_delayed_tree_ref(struct btrfs_trans_handle *trans,
				struct btrfs_delayed_ref_node *node,
				struct btrfs_delayed_extent_op *extent_op,
				int insert_reserved)
{
	int ret = 0;
	struct btrfs_delayed_tree_ref *ref;
	u64 parent = 0;
	u64 ref_root = 0;

	ref = btrfs_delayed_node_to_tree_ref(node);
	trace_run_delayed_tree_ref(trans->fs_info, node, ref, node->action);

	if (node->type == BTRFS_SHARED_BLOCK_REF_KEY)
		parent = ref->parent;
	ref_root = ref->root;

	if (node->ref_mod != 1) {
		btrfs_err(trans->fs_info,
	"btree block(%llu) has %d references rather than 1: action %d ref_root %llu parent %llu",
			  node->bytenr, node->ref_mod, node->action, ref_root,
			  parent);
		return -EIO;
	}
	if (node->action == BTRFS_ADD_DELAYED_REF && insert_reserved) {
		BUG_ON(!extent_op || !extent_op->update_flags);
		ret = alloc_reserved_tree_block(trans, node, extent_op);
	} else if (node->action == BTRFS_ADD_DELAYED_REF) {
		ret = __btrfs_inc_extent_ref(trans, node, parent, ref_root,
					     ref->level, 0, 1, extent_op);
	} else if (node->action == BTRFS_DROP_DELAYED_REF) {
		ret = __btrfs_free_extent(trans, node, parent, ref_root,
					  ref->level, 0, 1, extent_op);
	} else {
		BUG();
	}
	return ret;
}

/* helper function to actually process a single delayed ref entry */
static int run_one_delayed_ref(struct btrfs_trans_handle *trans,
			       struct btrfs_delayed_ref_node *node,
			       struct btrfs_delayed_extent_op *extent_op,
			       int insert_reserved)
{
	int ret = 0;

	if (TRANS_ABORTED(trans)) {
		if (insert_reserved)
			btrfs_pin_extent(trans, node->bytenr, node->num_bytes, 1);
		return 0;
	}

	if (node->type == BTRFS_TREE_BLOCK_REF_KEY ||
	    node->type == BTRFS_SHARED_BLOCK_REF_KEY)
		ret = run_delayed_tree_ref(trans, node, extent_op,
					   insert_reserved);
	else if (node->type == BTRFS_EXTENT_DATA_REF_KEY ||
		 node->type == BTRFS_SHARED_DATA_REF_KEY)
		ret = run_delayed_data_ref(trans, node, extent_op,
					   insert_reserved);
	else
		BUG();
	if (ret && insert_reserved)
		btrfs_pin_extent(trans, node->bytenr, node->num_bytes, 1);
	return ret;
}

static inline struct btrfs_delayed_ref_node *
select_delayed_ref(struct btrfs_delayed_ref_head *head)
{
	struct btrfs_delayed_ref_node *ref;

	if (RB_EMPTY_ROOT(&head->ref_tree.rb_root))
		return NULL;

	/*
	 * Select a delayed ref of type BTRFS_ADD_DELAYED_REF first.
	 * This is to prevent a ref count from going down to zero, which deletes
	 * the extent item from the extent tree, when there still are references
	 * to add, which would fail because they would not find the extent item.
	 */
	if (!list_empty(&head->ref_add_list))
		return list_first_entry(&head->ref_add_list,
				struct btrfs_delayed_ref_node, add_list);

	ref = rb_entry(rb_first_cached(&head->ref_tree),
		       struct btrfs_delayed_ref_node, ref_node);
	ASSERT(list_empty(&ref->add_list));
	return ref;
}

static void unselect_delayed_ref_head(struct btrfs_delayed_ref_root *delayed_refs,
				      struct btrfs_delayed_ref_head *head)
{
	spin_lock(&delayed_refs->lock);
	head->processing = 0;
	delayed_refs->num_heads_ready++;
	spin_unlock(&delayed_refs->lock);
	btrfs_delayed_ref_unlock(head);
}

static struct btrfs_delayed_extent_op *cleanup_extent_op(
				struct btrfs_delayed_ref_head *head)
{
	struct btrfs_delayed_extent_op *extent_op = head->extent_op;

	if (!extent_op)
		return NULL;

	if (head->must_insert_reserved) {
		head->extent_op = NULL;
		btrfs_free_delayed_extent_op(extent_op);
		return NULL;
	}
	return extent_op;
}

static int run_and_cleanup_extent_op(struct btrfs_trans_handle *trans,
				     struct btrfs_delayed_ref_head *head)
{
	struct btrfs_delayed_extent_op *extent_op;
	int ret;

	extent_op = cleanup_extent_op(head);
	if (!extent_op)
		return 0;
	head->extent_op = NULL;
	spin_unlock(&head->lock);
	ret = run_delayed_extent_op(trans, head, extent_op);
	btrfs_free_delayed_extent_op(extent_op);
	return ret ? ret : 1;
}

void btrfs_cleanup_ref_head_accounting(struct btrfs_fs_info *fs_info,
				  struct btrfs_delayed_ref_root *delayed_refs,
				  struct btrfs_delayed_ref_head *head)
{
	int nr_items = 1;	/* Dropping this ref head update. */

	/*
	 * We had csum deletions accounted for in our delayed refs rsv, we need
	 * to drop the csum leaves for this update from our delayed_refs_rsv.
	 */
	if (head->total_ref_mod < 0 && head->is_data) {
		spin_lock(&delayed_refs->lock);
		delayed_refs->pending_csums -= head->num_bytes;
		spin_unlock(&delayed_refs->lock);
		nr_items += btrfs_csum_bytes_to_leaves(fs_info, head->num_bytes);
	}

	btrfs_delayed_refs_rsv_release(fs_info, nr_items);
}

static int cleanup_ref_head(struct btrfs_trans_handle *trans,
			    struct btrfs_delayed_ref_head *head)
{

	struct btrfs_fs_info *fs_info = trans->fs_info;
	struct btrfs_delayed_ref_root *delayed_refs;
	int ret;

	delayed_refs = &trans->transaction->delayed_refs;

	ret = run_and_cleanup_extent_op(trans, head);
	if (ret < 0) {
		unselect_delayed_ref_head(delayed_refs, head);
		btrfs_debug(fs_info, "run_delayed_extent_op returned %d", ret);
		return ret;
	} else if (ret) {
		return ret;
	}

	/*
	 * Need to drop our head ref lock and re-acquire the delayed ref lock
	 * and then re-check to make sure nobody got added.
	 */
	spin_unlock(&head->lock);
	spin_lock(&delayed_refs->lock);
	spin_lock(&head->lock);
	if (!RB_EMPTY_ROOT(&head->ref_tree.rb_root) || head->extent_op) {
		spin_unlock(&head->lock);
		spin_unlock(&delayed_refs->lock);
		return 1;
	}
	btrfs_delete_ref_head(delayed_refs, head);
	spin_unlock(&head->lock);
	spin_unlock(&delayed_refs->lock);

	if (head->must_insert_reserved) {
		btrfs_pin_extent(trans, head->bytenr, head->num_bytes, 1);
		if (head->is_data) {
			ret = btrfs_del_csums(trans, fs_info->csum_root,
					      head->bytenr, head->num_bytes);
		}
	}

	btrfs_cleanup_ref_head_accounting(fs_info, delayed_refs, head);

	trace_run_delayed_ref_head(fs_info, head, 0);
	btrfs_delayed_ref_unlock(head);
	btrfs_put_delayed_ref_head(head);
	return ret;
}

static struct btrfs_delayed_ref_head *btrfs_obtain_ref_head(
					struct btrfs_trans_handle *trans)
{
	struct btrfs_delayed_ref_root *delayed_refs =
		&trans->transaction->delayed_refs;
	struct btrfs_delayed_ref_head *head = NULL;
	int ret;

	spin_lock(&delayed_refs->lock);
	head = btrfs_select_ref_head(delayed_refs);
	if (!head) {
		spin_unlock(&delayed_refs->lock);
		return head;
	}

	/*
	 * Grab the lock that says we are going to process all the refs for
	 * this head
	 */
	ret = btrfs_delayed_ref_lock(delayed_refs, head);
	spin_unlock(&delayed_refs->lock);

	/*
	 * We may have dropped the spin lock to get the head mutex lock, and
	 * that might have given someone else time to free the head.  If that's
	 * true, it has been removed from our list and we can move on.
	 */
	if (ret == -EAGAIN)
		head = ERR_PTR(-EAGAIN);

	return head;
}

static int btrfs_run_delayed_refs_for_head(struct btrfs_trans_handle *trans,
				    struct btrfs_delayed_ref_head *locked_ref,
				    unsigned long *run_refs)
{
	struct btrfs_fs_info *fs_info = trans->fs_info;
	struct btrfs_delayed_ref_root *delayed_refs;
	struct btrfs_delayed_extent_op *extent_op;
	struct btrfs_delayed_ref_node *ref;
	int must_insert_reserved = 0;
	int ret;

	delayed_refs = &trans->transaction->delayed_refs;

	lockdep_assert_held(&locked_ref->mutex);
	lockdep_assert_held(&locked_ref->lock);

	while ((ref = select_delayed_ref(locked_ref))) {
		if (ref->seq &&
		    btrfs_check_delayed_seq(fs_info, ref->seq)) {
			spin_unlock(&locked_ref->lock);
			unselect_delayed_ref_head(delayed_refs, locked_ref);
			return -EAGAIN;
		}

		(*run_refs)++;
		ref->in_tree = 0;
		rb_erase_cached(&ref->ref_node, &locked_ref->ref_tree);
		RB_CLEAR_NODE(&ref->ref_node);
		if (!list_empty(&ref->add_list))
			list_del(&ref->add_list);
		/*
		 * When we play the delayed ref, also correct the ref_mod on
		 * head
		 */
		switch (ref->action) {
		case BTRFS_ADD_DELAYED_REF:
		case BTRFS_ADD_DELAYED_EXTENT:
			locked_ref->ref_mod -= ref->ref_mod;
			break;
		case BTRFS_DROP_DELAYED_REF:
			locked_ref->ref_mod += ref->ref_mod;
			break;
		default:
			WARN_ON(1);
		}
		atomic_dec(&delayed_refs->num_entries);

		/*
		 * Record the must_insert_reserved flag before we drop the
		 * spin lock.
		 */
		must_insert_reserved = locked_ref->must_insert_reserved;
		locked_ref->must_insert_reserved = 0;

		extent_op = locked_ref->extent_op;
		locked_ref->extent_op = NULL;
		spin_unlock(&locked_ref->lock);

		ret = run_one_delayed_ref(trans, ref, extent_op,
					  must_insert_reserved);

		btrfs_free_delayed_extent_op(extent_op);
		if (ret) {
			unselect_delayed_ref_head(delayed_refs, locked_ref);
			btrfs_put_delayed_ref(ref);
			btrfs_debug(fs_info, "run_one_delayed_ref returned %d",
				    ret);
			return ret;
		}

		btrfs_put_delayed_ref(ref);
		cond_resched();

		spin_lock(&locked_ref->lock);
		btrfs_merge_delayed_refs(trans, delayed_refs, locked_ref);
	}

	return 0;
}

/*
 * Returns 0 on success or if called with an already aborted transaction.
 * Returns -ENOMEM or -EIO on failure and will abort the transaction.
 */
static noinline int __btrfs_run_delayed_refs(struct btrfs_trans_handle *trans,
					     unsigned long nr)
{
	struct btrfs_fs_info *fs_info = trans->fs_info;
	struct btrfs_delayed_ref_root *delayed_refs;
	struct btrfs_delayed_ref_head *locked_ref = NULL;
	ktime_t start = ktime_get();
	int ret;
	unsigned long count = 0;
	unsigned long actual_count = 0;

	delayed_refs = &trans->transaction->delayed_refs;
	do {
		if (!locked_ref) {
			locked_ref = btrfs_obtain_ref_head(trans);
			if (IS_ERR_OR_NULL(locked_ref)) {
				if (PTR_ERR(locked_ref) == -EAGAIN) {
					continue;
				} else {
					break;
				}
			}
			count++;
		}
		/*
		 * We need to try and merge add/drops of the same ref since we
		 * can run into issues with relocate dropping the implicit ref
		 * and then it being added back again before the drop can
		 * finish.  If we merged anything we need to re-loop so we can
		 * get a good ref.
		 * Or we can get node references of the same type that weren't
		 * merged when created due to bumps in the tree mod seq, and
		 * we need to merge them to prevent adding an inline extent
		 * backref before dropping it (triggering a BUG_ON at
		 * insert_inline_extent_backref()).
		 */
		spin_lock(&locked_ref->lock);
		btrfs_merge_delayed_refs(trans, delayed_refs, locked_ref);

		ret = btrfs_run_delayed_refs_for_head(trans, locked_ref,
						      &actual_count);
		if (ret < 0 && ret != -EAGAIN) {
			/*
			 * Error, btrfs_run_delayed_refs_for_head already
			 * unlocked everything so just bail out
			 */
			return ret;
		} else if (!ret) {
			/*
			 * Success, perform the usual cleanup of a processed
			 * head
			 */
			ret = cleanup_ref_head(trans, locked_ref);
			if (ret > 0 ) {
				/* We dropped our lock, we need to loop. */
				ret = 0;
				continue;
			} else if (ret) {
				return ret;
			}
		}

		/*
		 * Either success case or btrfs_run_delayed_refs_for_head
		 * returned -EAGAIN, meaning we need to select another head
		 */

		locked_ref = NULL;
		cond_resched();
	} while ((nr != -1 && count < nr) || locked_ref);

	/*
	 * We don't want to include ref heads since we can have empty ref heads
	 * and those will drastically skew our runtime down since we just do
	 * accounting, no actual extent tree updates.
	 */
	if (actual_count > 0) {
		u64 runtime = ktime_to_ns(ktime_sub(ktime_get(), start));
		u64 avg;

		/*
		 * We weigh the current average higher than our current runtime
		 * to avoid large swings in the average.
		 */
		spin_lock(&delayed_refs->lock);
		avg = fs_info->avg_delayed_ref_runtime * 3 + runtime;
		fs_info->avg_delayed_ref_runtime = avg >> 2;	/* div by 4 */
		spin_unlock(&delayed_refs->lock);
	}
	return 0;
}

#ifdef SCRAMBLE_DELAYED_REFS
/*
 * Normally delayed refs get processed in ascending bytenr order. This
 * correlates in most cases to the order added. To expose dependencies on this
 * order, we start to process the tree in the middle instead of the beginning
 */
static u64 find_middle(struct rb_root *root)
{
	struct rb_node *n = root->rb_node;
	struct btrfs_delayed_ref_node *entry;
	int alt = 1;
	u64 middle;
	u64 first = 0, last = 0;

	n = rb_first(root);
	if (n) {
		entry = rb_entry(n, struct btrfs_delayed_ref_node, rb_node);
		first = entry->bytenr;
	}
	n = rb_last(root);
	if (n) {
		entry = rb_entry(n, struct btrfs_delayed_ref_node, rb_node);
		last = entry->bytenr;
	}
	n = root->rb_node;

	while (n) {
		entry = rb_entry(n, struct btrfs_delayed_ref_node, rb_node);
		WARN_ON(!entry->in_tree);

		middle = entry->bytenr;

		if (alt)
			n = n->rb_left;
		else
			n = n->rb_right;

		alt = 1 - alt;
	}
	return middle;
}
#endif

/*
 * this starts processing the delayed reference count updates and
 * extent insertions we have queued up so far.  count can be
 * 0, which means to process everything in the tree at the start
 * of the run (but not newly added entries), or it can be some target
 * number you'd like to process.
 *
 * Returns 0 on success or if called with an aborted transaction
 * Returns <0 on error and aborts the transaction
 */
int btrfs_run_delayed_refs(struct btrfs_trans_handle *trans,
			   unsigned long count)
{
	struct btrfs_fs_info *fs_info = trans->fs_info;
	struct rb_node *node;
	struct btrfs_delayed_ref_root *delayed_refs;
	struct btrfs_delayed_ref_head *head;
	int ret;
	int run_all = count == (unsigned long)-1;

	/* We'll clean this up in btrfs_cleanup_transaction */
	if (TRANS_ABORTED(trans))
		return 0;

	if (test_bit(BTRFS_FS_CREATING_FREE_SPACE_TREE, &fs_info->flags))
		return 0;

	delayed_refs = &trans->transaction->delayed_refs;
	if (count == 0)
		count = delayed_refs->num_heads_ready;

again:
#ifdef SCRAMBLE_DELAYED_REFS
	delayed_refs->run_delayed_start = find_middle(&delayed_refs->root);
#endif
	ret = __btrfs_run_delayed_refs(trans, count);
	if (ret < 0) {
		btrfs_abort_transaction(trans, ret);
		return ret;
	}

	if (run_all) {
		btrfs_create_pending_block_groups(trans);

		spin_lock(&delayed_refs->lock);
		node = rb_first_cached(&delayed_refs->href_root);
		if (!node) {
			spin_unlock(&delayed_refs->lock);
			goto out;
		}
		head = rb_entry(node, struct btrfs_delayed_ref_head,
				href_node);
		refcount_inc(&head->refs);
		spin_unlock(&delayed_refs->lock);

		/* Mutex was contended, block until it's released and retry. */
		mutex_lock(&head->mutex);
		mutex_unlock(&head->mutex);

		btrfs_put_delayed_ref_head(head);
		cond_resched();
		goto again;
	}
out:
	return 0;
}

int btrfs_set_disk_extent_flags(struct btrfs_trans_handle *trans,
				struct extent_buffer *eb, u64 flags,
				int level, int is_data)
{
	struct btrfs_delayed_extent_op *extent_op;
	int ret;

	extent_op = btrfs_alloc_delayed_extent_op();
	if (!extent_op)
		return -ENOMEM;

	extent_op->flags_to_set = flags;
	extent_op->update_flags = true;
	extent_op->update_key = false;
	extent_op->is_data = is_data ? true : false;
	extent_op->level = level;

	ret = btrfs_add_delayed_extent_op(trans, eb->start, eb->len, extent_op);
	if (ret)
		btrfs_free_delayed_extent_op(extent_op);
	return ret;
}

static noinline int check_delayed_ref(struct btrfs_root *root,
				      struct btrfs_path *path,
				      u64 objectid, u64 offset, u64 bytenr)
{
	struct btrfs_delayed_ref_head *head;
	struct btrfs_delayed_ref_node *ref;
	struct btrfs_delayed_data_ref *data_ref;
	struct btrfs_delayed_ref_root *delayed_refs;
	struct btrfs_transaction *cur_trans;
	struct rb_node *node;
	int ret = 0;

	spin_lock(&root->fs_info->trans_lock);
	cur_trans = root->fs_info->running_transaction;
	if (cur_trans)
		refcount_inc(&cur_trans->use_count);
	spin_unlock(&root->fs_info->trans_lock);
	if (!cur_trans)
		return 0;

	delayed_refs = &cur_trans->delayed_refs;
	spin_lock(&delayed_refs->lock);
	head = btrfs_find_delayed_ref_head(delayed_refs, bytenr);
	if (!head) {
		spin_unlock(&delayed_refs->lock);
		btrfs_put_transaction(cur_trans);
		return 0;
	}

	if (!mutex_trylock(&head->mutex)) {
		refcount_inc(&head->refs);
		spin_unlock(&delayed_refs->lock);

		btrfs_release_path(path);

		/*
		 * Mutex was contended, block until it's released and let
		 * caller try again
		 */
		mutex_lock(&head->mutex);
		mutex_unlock(&head->mutex);
		btrfs_put_delayed_ref_head(head);
		btrfs_put_transaction(cur_trans);
		return -EAGAIN;
	}
	spin_unlock(&delayed_refs->lock);

	spin_lock(&head->lock);
	/*
	 * XXX: We should replace this with a proper search function in the
	 * future.
	 */
	for (node = rb_first_cached(&head->ref_tree); node;
	     node = rb_next(node)) {
		ref = rb_entry(node, struct btrfs_delayed_ref_node, ref_node);
		/* If it's a shared ref we know a cross reference exists */
		if (ref->type != BTRFS_EXTENT_DATA_REF_KEY) {
			ret = 1;
			break;
		}

		data_ref = btrfs_delayed_node_to_data_ref(ref);

		/*
		 * If our ref doesn't match the one we're currently looking at
		 * then we have a cross reference.
		 */
		if (data_ref->root != root->root_key.objectid ||
		    data_ref->objectid != objectid ||
		    data_ref->offset != offset) {
			ret = 1;
			break;
		}
	}
	spin_unlock(&head->lock);
	mutex_unlock(&head->mutex);
	btrfs_put_transaction(cur_trans);
	return ret;
}

static noinline int check_committed_ref(struct btrfs_root *root,
					struct btrfs_path *path,
					u64 objectid, u64 offset, u64 bytenr,
					bool strict)
{
	struct btrfs_fs_info *fs_info = root->fs_info;
	struct btrfs_root *extent_root = fs_info->extent_root;
	struct extent_buffer *leaf;
	struct btrfs_extent_data_ref *ref;
	struct btrfs_extent_inline_ref *iref;
	struct btrfs_extent_item *ei;
	struct btrfs_key key;
	u32 item_size;
	int type;
	int ret;

	key.objectid = bytenr;
	key.offset = (u64)-1;
	key.type = BTRFS_EXTENT_ITEM_KEY;

	ret = btrfs_search_slot(NULL, extent_root, &key, path, 0, 0);
	if (ret < 0)
		goto out;
	BUG_ON(ret == 0); /* Corruption */

	ret = -ENOENT;
	if (path->slots[0] == 0)
		goto out;

	path->slots[0]--;
	leaf = path->nodes[0];
	btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);

	if (key.objectid != bytenr || key.type != BTRFS_EXTENT_ITEM_KEY)
		goto out;

	ret = 1;
	item_size = btrfs_item_size_nr(leaf, path->slots[0]);
	ei = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_extent_item);

	/* If extent item has more than 1 inline ref then it's shared */
	if (item_size != sizeof(*ei) +
	    btrfs_extent_inline_ref_size(BTRFS_EXTENT_DATA_REF_KEY))
		goto out;

	/*
	 * If extent created before last snapshot => it's shared unless the
	 * snapshot has been deleted. Use the heuristic if strict is false.
	 */
	if (!strict &&
	    (btrfs_extent_generation(leaf, ei) <=
	     btrfs_root_last_snapshot(&root->root_item)))
		goto out;

	iref = (struct btrfs_extent_inline_ref *)(ei + 1);

	/* If this extent has SHARED_DATA_REF then it's shared */
	type = btrfs_get_extent_inline_ref_type(leaf, iref, BTRFS_REF_TYPE_DATA);
	if (type != BTRFS_EXTENT_DATA_REF_KEY)
		goto out;

	ref = (struct btrfs_extent_data_ref *)(&iref->offset);
	if (btrfs_extent_refs(leaf, ei) !=
	    btrfs_extent_data_ref_count(leaf, ref) ||
	    btrfs_extent_data_ref_root(leaf, ref) !=
	    root->root_key.objectid ||
	    btrfs_extent_data_ref_objectid(leaf, ref) != objectid ||
	    btrfs_extent_data_ref_offset(leaf, ref) != offset)
		goto out;

	ret = 0;
out:
	return ret;
}

int btrfs_cross_ref_exist(struct btrfs_root *root, u64 objectid, u64 offset,
			  u64 bytenr, bool strict)
{
	struct btrfs_path *path;
	int ret;

	path = btrfs_alloc_path();
	if (!path)
		return -ENOMEM;

	do {
		ret = check_committed_ref(root, path, objectid,
					  offset, bytenr, strict);
		if (ret && ret != -ENOENT)
			goto out;

		ret = check_delayed_ref(root, path, objectid, offset, bytenr);
	} while (ret == -EAGAIN);

out:
	btrfs_free_path(path);
	if (btrfs_is_data_reloc_root(root))
		WARN_ON(ret > 0);
	return ret;
}

static int __btrfs_mod_ref(struct btrfs_trans_handle *trans,
			   struct btrfs_root *root,
			   struct extent_buffer *buf,
			   int full_backref, int inc)
{
	struct btrfs_fs_info *fs_info = root->fs_info;
	u64 bytenr;
	u64 num_bytes;
	u64 parent;
	u64 ref_root;
	u32 nritems;
	struct btrfs_key key;
	struct btrfs_file_extent_item *fi;
	struct btrfs_ref generic_ref = { 0 };
	bool for_reloc = btrfs_header_flag(buf, BTRFS_HEADER_FLAG_RELOC);
	int i;
	int action;
	int level;
	int ret = 0;

	if (btrfs_is_testing(fs_info))
		return 0;

	ref_root = btrfs_header_owner(buf);
	nritems = btrfs_header_nritems(buf);
	level = btrfs_header_level(buf);

	if (!test_bit(BTRFS_ROOT_SHAREABLE, &root->state) && level == 0)
		return 0;

	if (full_backref)
		parent = buf->start;
	else
		parent = 0;
	if (inc)
		action = BTRFS_ADD_DELAYED_REF;
	else
		action = BTRFS_DROP_DELAYED_REF;

	for (i = 0; i < nritems; i++) {
		if (level == 0) {
			btrfs_item_key_to_cpu(buf, &key, i);
			if (key.type != BTRFS_EXTENT_DATA_KEY)
				continue;
			fi = btrfs_item_ptr(buf, i,
					    struct btrfs_file_extent_item);
			if (btrfs_file_extent_type(buf, fi) ==
			    BTRFS_FILE_EXTENT_INLINE)
				continue;
			bytenr = btrfs_file_extent_disk_bytenr(buf, fi);
			if (bytenr == 0)
				continue;

			num_bytes = btrfs_file_extent_disk_num_bytes(buf, fi);
			key.offset -= btrfs_file_extent_offset(buf, fi);
			btrfs_init_generic_ref(&generic_ref, action, bytenr,
					       num_bytes, parent);
			btrfs_init_data_ref(&generic_ref, ref_root, key.objectid,
					    key.offset, root->root_key.objectid,
					    for_reloc);
			if (inc)
				ret = btrfs_inc_extent_ref(trans, &generic_ref);
			else
				ret = btrfs_free_extent(trans, &generic_ref);
			if (ret)
				goto fail;
		} else {
			bytenr = btrfs_node_blockptr(buf, i);
			num_bytes = fs_info->nodesize;
			btrfs_init_generic_ref(&generic_ref, action, bytenr,
					       num_bytes, parent);
			btrfs_init_tree_ref(&generic_ref, level - 1, ref_root,
					    root->root_key.objectid, for_reloc);
			if (inc)
				ret = btrfs_inc_extent_ref(trans, &generic_ref);
			else
				ret = btrfs_free_extent(trans, &generic_ref);
			if (ret)
				goto fail;
		}
	}
	return 0;
fail:
	return ret;
}

int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
		  struct extent_buffer *buf, int full_backref)
{
	return __btrfs_mod_ref(trans, root, buf, full_backref, 1);
}

int btrfs_dec_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
		  struct extent_buffer *buf, int full_backref)
{
	return __btrfs_mod_ref(trans, root, buf, full_backref, 0);
}

static u64 get_alloc_profile_by_root(struct btrfs_root *root, int data)
{
	struct btrfs_fs_info *fs_info = root->fs_info;
	u64 flags;
	u64 ret;

	if (data)
		flags = BTRFS_BLOCK_GROUP_DATA;
	else if (root == fs_info->chunk_root)
		flags = BTRFS_BLOCK_GROUP_SYSTEM;
	else
		flags = BTRFS_BLOCK_GROUP_METADATA;

	ret = btrfs_get_alloc_profile(fs_info, flags);
	return ret;
}

static u64 first_logical_byte(struct btrfs_fs_info *fs_info, u64 search_start)
{
	struct btrfs_block_group *cache;
	u64 bytenr;

	spin_lock(&fs_info->block_group_cache_lock);
	bytenr = fs_info->first_logical_byte;
	spin_unlock(&fs_info->block_group_cache_lock);

	if (bytenr < (u64)-1)
		return bytenr;

	cache = btrfs_lookup_first_block_group(fs_info, search_start);
	if (!cache)
		return 0;

	bytenr = cache->start;
	btrfs_put_block_group(cache);

	return bytenr;
}

static int pin_down_extent(struct btrfs_trans_handle *trans,
			   struct btrfs_block_group *cache,
			   u64 bytenr, u64 num_bytes, int reserved)
{
	struct btrfs_fs_info *fs_info = cache->fs_info;

	spin_lock(&cache->space_info->lock);
	spin_lock(&cache->lock);
	cache->pinned += num_bytes;
	btrfs_space_info_update_bytes_pinned(fs_info, cache->space_info,
					     num_bytes);
	if (reserved) {
		cache->reserved -= num_bytes;
		cache->space_info->bytes_reserved -= num_bytes;
	}
	spin_unlock(&cache->lock);
	spin_unlock(&cache->space_info->lock);

	set_extent_dirty(&trans->transaction->pinned_extents, bytenr,
			 bytenr + num_bytes - 1, GFP_NOFS | __GFP_NOFAIL);
	return 0;
}

int btrfs_pin_extent(struct btrfs_trans_handle *trans,
		     u64 bytenr, u64 num_bytes, int reserved)
{
	struct btrfs_block_group *cache;

	cache = btrfs_lookup_block_group(trans->fs_info, bytenr);
	BUG_ON(!cache); /* Logic error */

	pin_down_extent(trans, cache, bytenr, num_bytes, reserved);

	btrfs_put_block_group(cache);
	return 0;
}

/*
 * this function must be called within transaction
 */
int btrfs_pin_extent_for_log_replay(struct btrfs_trans_handle *trans,
				    u64 bytenr, u64 num_bytes)
{
	struct btrfs_block_group *cache;
	int ret;

	cache = btrfs_lookup_block_group(trans->fs_info, bytenr);
	if (!cache)
		return -EINVAL;

	/*
	 * pull in the free space cache (if any) so that our pin
	 * removes the free space from the cache.  We have load_only set
	 * to one because the slow code to read in the free extents does check
	 * the pinned extents.
	 */
	btrfs_cache_block_group(cache, 1);
	/*
	 * Make sure we wait until the cache is completely built in case it is
	 * missing or is invalid and therefore needs to be rebuilt.
	 */
	ret = btrfs_wait_block_group_cache_done(cache);
	if (ret)
		goto out;

	pin_down_extent(trans, cache, bytenr, num_bytes, 0);

	/* remove us from the free space cache (if we're there at all) */
	ret = btrfs_remove_free_space(cache, bytenr, num_bytes);
out:
	btrfs_put_block_group(cache);
	return ret;
}

static int __exclude_logged_extent(struct btrfs_fs_info *fs_info,
				   u64 start, u64 num_bytes)
{
	int ret;
	struct btrfs_block_group *block_group;

	block_group = btrfs_lookup_block_group(fs_info, start);
	if (!block_group)
		return -EINVAL;

	btrfs_cache_block_group(block_group, 1);
	/*
	 * Make sure we wait until the cache is completely built in case it is
	 * missing or is invalid and therefore needs to be rebuilt.
	 */
	ret = btrfs_wait_block_group_cache_done(block_group);
	if (ret)
		goto out;

	ret = btrfs_remove_free_space(block_group, start, num_bytes);
out:
	btrfs_put_block_group(block_group);
	return ret;
}

int btrfs_exclude_logged_extents(struct extent_buffer *eb)
{
	struct btrfs_fs_info *fs_info = eb->fs_info;
	struct btrfs_file_extent_item *item;
	struct btrfs_key key;
	int found_type;
	int i;
	int ret = 0;

	if (!btrfs_fs_incompat(fs_info, MIXED_GROUPS))
		return 0;

	for (i = 0; i < btrfs_header_nritems(eb); i++) {
		btrfs_item_key_to_cpu(eb, &key, i);
		if (key.type != BTRFS_EXTENT_DATA_KEY)
			continue;
		item = btrfs_item_ptr(eb, i, struct btrfs_file_extent_item);
		found_type = btrfs_file_extent_type(eb, item);
		if (found_type == BTRFS_FILE_EXTENT_INLINE)
			continue;
		if (btrfs_file_extent_disk_bytenr(eb, item) == 0)
			continue;
		key.objectid = btrfs_file_extent_disk_bytenr(eb, item);
		key.offset = btrfs_file_extent_disk_num_bytes(eb, item);
		ret = __exclude_logged_extent(fs_info, key.objectid, key.offset);
		if (ret)
			break;
	}

	return ret;
}

static void
btrfs_inc_block_group_reservations(struct btrfs_block_group *bg)
{
	atomic_inc(&bg->reservations);
}

/*
 * Returns the free cluster for the given space info and sets empty_cluster to
 * what it should be based on the mount options.
 */
static struct btrfs_free_cluster *
fetch_cluster_info(struct btrfs_fs_info *fs_info,
		   struct btrfs_space_info *space_info, u64 *empty_cluster)
{
	struct btrfs_free_cluster *ret = NULL;

	*empty_cluster = 0;
	if (btrfs_mixed_space_info(space_info))
		return ret;

	if (space_info->flags & BTRFS_BLOCK_GROUP_METADATA) {
		ret = &fs_info->meta_alloc_cluster;
		if (btrfs_test_opt(fs_info, SSD))
			*empty_cluster = SZ_2M;
		else
			*empty_cluster = SZ_64K;
	} else if ((space_info->flags & BTRFS_BLOCK_GROUP_DATA) &&
		   btrfs_test_opt(fs_info, SSD_SPREAD)) {
		*empty_cluster = SZ_2M;
		ret = &fs_info->data_alloc_cluster;
	}

	return ret;
}

static int unpin_extent_range(struct btrfs_fs_info *fs_info,
			      u64 start, u64 end,
			      const bool return_free_space)
{
	struct btrfs_block_group *cache = NULL;
	struct btrfs_space_info *space_info;
	struct btrfs_block_rsv *global_rsv = &fs_info->global_block_rsv;
	struct btrfs_free_cluster *cluster = NULL;
	u64 len;
	u64 total_unpinned = 0;
	u64 empty_cluster = 0;
	bool readonly;

	while (start <= end) {
		readonly = false;
		if (!cache ||
		    start >= cache->start + cache->length) {
			if (cache)
				btrfs_put_block_group(cache);
			total_unpinned = 0;
			cache = btrfs_lookup_block_group(fs_info, start);
			BUG_ON(!cache); /* Logic error */

			cluster = fetch_cluster_info(fs_info,
						     cache->space_info,
						     &empty_cluster);
			empty_cluster <<= 1;
		}

		len = cache->start + cache->length - start;
		len = min(len, end + 1 - start);

		down_read(&fs_info->commit_root_sem);
		if (start < cache->last_byte_to_unpin && return_free_space) {
			u64 add_len = min(len, cache->last_byte_to_unpin - start);

			btrfs_add_free_space(cache, start, add_len);
		}
		up_read(&fs_info->commit_root_sem);

		start += len;
		total_unpinned += len;
		space_info = cache->space_info;

		/*
		 * If this space cluster has been marked as fragmented and we've
		 * unpinned enough in this block group to potentially allow a
		 * cluster to be created inside of it go ahead and clear the
		 * fragmented check.
		 */
		if (cluster && cluster->fragmented &&
		    total_unpinned > empty_cluster) {
			spin_lock(&cluster->lock);
			cluster->fragmented = 0;
			spin_unlock(&cluster->lock);
		}

		spin_lock(&space_info->lock);
		spin_lock(&cache->lock);
		cache->pinned -= len;
		btrfs_space_info_update_bytes_pinned(fs_info, space_info, -len);
		space_info->max_extent_size = 0;
		if (cache->ro) {
			space_info->bytes_readonly += len;
			readonly = true;
		} else if (btrfs_is_zoned(fs_info)) {
			/* Need reset before reusing in a zoned block group */
			space_info->bytes_zone_unusable += len;
			readonly = true;
		}
		spin_unlock(&cache->lock);
		if (!readonly && return_free_space &&
		    global_rsv->space_info == space_info) {
			u64 to_add = len;

			spin_lock(&global_rsv->lock);
			if (!global_rsv->full) {
				to_add = min(len, global_rsv->size -
					     global_rsv->reserved);
				global_rsv->reserved += to_add;
				btrfs_space_info_update_bytes_may_use(fs_info,
						space_info, to_add);
				if (global_rsv->reserved >= global_rsv->size)
					global_rsv->full = 1;
				len -= to_add;
			}
			spin_unlock(&global_rsv->lock);
		}
		/* Add to any tickets we may have */
		if (!readonly && return_free_space && len)
			btrfs_try_granting_tickets(fs_info, space_info);
		spin_unlock(&space_info->lock);
	}

	if (cache)
		btrfs_put_block_group(cache);
	return 0;
}

int btrfs_finish_extent_commit(struct btrfs_trans_handle *trans)
{
	struct btrfs_fs_info *fs_info = trans->fs_info;
	struct btrfs_block_group *block_group, *tmp;
	struct list_head *deleted_bgs;
	struct extent_io_tree *unpin;
	u64 start;
	u64 end;
	int ret;

	unpin = &trans->transaction->pinned_extents;

	while (!TRANS_ABORTED(trans)) {
		struct extent_state *cached_state = NULL;

		mutex_lock(&fs_info->unused_bg_unpin_mutex);
		ret = find_first_extent_bit(unpin, 0, &start, &end,
					    EXTENT_DIRTY, &cached_state);
		if (ret) {
			mutex_unlock(&fs_info->unused_bg_unpin_mutex);
			break;
		}

		if (btrfs_test_opt(fs_info, DISCARD_SYNC))
			ret = btrfs_discard_extent(fs_info, start,
						   end + 1 - start, NULL);

		clear_extent_dirty(unpin, start, end, &cached_state);
		unpin_extent_range(fs_info, start, end, true);
		mutex_unlock(&fs_info->unused_bg_unpin_mutex);
		free_extent_state(cached_state);
		cond_resched();
	}

	if (btrfs_test_opt(fs_info, DISCARD_ASYNC)) {
		btrfs_discard_calc_delay(&fs_info->discard_ctl);
		btrfs_discard_schedule_work(&fs_info->discard_ctl, true);
	}

	/*
	 * Transaction is finished.  We don't need the lock anymore.  We
	 * do need to clean up the block groups in case of a transaction
	 * abort.
	 */
	deleted_bgs = &trans->transaction->deleted_bgs;
	list_for_each_entry_safe(block_group, tmp, deleted_bgs, bg_list) {
		u64 trimmed = 0;

		ret = -EROFS;
		if (!TRANS_ABORTED(trans))
			ret = btrfs_discard_extent(fs_info,
						   block_group->start,
						   block_group->length,
						   &trimmed);

		list_del_init(&block_group->bg_list);
		btrfs_unfreeze_block_group(block_group);
		btrfs_put_block_group(block_group);

		if (ret) {
			const char *errstr = btrfs_decode_error(ret);
			btrfs_warn(fs_info,
			   "discard failed while removing blockgroup: errno=%d %s",
				   ret, errstr);
		}
	}

	return 0;
}

/*
 * Drop one or more refs of @node.
 *
 * 1. Locate the extent refs.
 *    It's either inline in EXTENT/METADATA_ITEM or in keyed SHARED_* item.
 *    Locate it, then reduce the refs number or remove the ref line completely.
 *
 * 2. Update the refs count in EXTENT/METADATA_ITEM
 *
 * Inline backref case:
 *
 * in extent tree we have:
 *
 * 	item 0 key (13631488 EXTENT_ITEM 1048576) itemoff 16201 itemsize 82
 *		refs 2 gen 6 flags DATA
 *		extent data backref root FS_TREE objectid 258 offset 0 count 1
 *		extent data backref root FS_TREE objectid 257 offset 0 count 1
 *
 * This function gets called with:
 *
 *    node->bytenr = 13631488
 *    node->num_bytes = 1048576
 *    root_objectid = FS_TREE
 *    owner_objectid = 257
 *    owner_offset = 0
 *    refs_to_drop = 1
 *
 * Then we should get some like:
 *
 * 	item 0 key (13631488 EXTENT_ITEM 1048576) itemoff 16201 itemsize 82
 *		refs 1 gen 6 flags DATA
 *		extent data backref root FS_TREE objectid 258 offset 0 count 1
 *
 * Keyed backref case:
 *
 * in extent tree we have:
 *
 *	item 0 key (13631488 EXTENT_ITEM 1048576) itemoff 3971 itemsize 24
 *		refs 754 gen 6 flags DATA
 *	[...]
 *	item 2 key (13631488 EXTENT_DATA_REF <HASH>) itemoff 3915 itemsize 28
 *		extent data backref root FS_TREE objectid 866 offset 0 count 1
 *
 * This function get called with:
 *
 *    node->bytenr = 13631488
 *    node->num_bytes = 1048576
 *    root_objectid = FS_TREE
 *    owner_objectid = 866
 *    owner_offset = 0
 *    refs_to_drop = 1
 *
 * Then we should get some like:
 *
 *	item 0 key (13631488 EXTENT_ITEM 1048576) itemoff 3971 itemsize 24
 *		refs 753 gen 6 flags DATA
 *
 * And that (13631488 EXTENT_DATA_REF <HASH>) gets removed.
 */
static int __btrfs_free_extent(struct btrfs_trans_handle *trans,
			       struct btrfs_delayed_ref_node *node, u64 parent,
			       u64 root_objectid, u64 owner_objectid,
			       u64 owner_offset, int refs_to_drop,
			       struct btrfs_delayed_extent_op *extent_op)
{
	struct btrfs_fs_info *info = trans->fs_info;
	struct btrfs_key key;
	struct btrfs_path *path;
	struct btrfs_root *extent_root = info->extent_root;
	struct extent_buffer *leaf;
	struct btrfs_extent_item *ei;
	struct btrfs_extent_inline_ref *iref;
	int ret;
	int is_data;
	int extent_slot = 0;
	int found_extent = 0;
	int num_to_del = 1;
	u32 item_size;
	u64 refs;
	u64 bytenr = node->bytenr;
	u64 num_bytes = node->num_bytes;
	int last_ref = 0;
	bool skinny_metadata = btrfs_fs_incompat(info, SKINNY_METADATA);

	path = btrfs_alloc_path();
	if (!path)
		return -ENOMEM;

	is_data = owner_objectid >= BTRFS_FIRST_FREE_OBJECTID;

	if (!is_data && refs_to_drop != 1) {
		btrfs_crit(info,
"invalid refs_to_drop, dropping more than 1 refs for tree block %llu refs_to_drop %u",
			   node->bytenr, refs_to_drop);
		ret = -EINVAL;
		btrfs_abort_transaction(trans, ret);
		goto out;
	}

	if (is_data)
		skinny_metadata = false;

	ret = lookup_extent_backref(trans, path, &iref, bytenr, num_bytes,
				    parent, root_objectid, owner_objectid,
				    owner_offset);
	if (ret == 0) {
		/*
		 * Either the inline backref or the SHARED_DATA_REF/
		 * SHARED_BLOCK_REF is found
		 *
		 * Here is a quick path to locate EXTENT/METADATA_ITEM.
		 * It's possible the EXTENT/METADATA_ITEM is near current slot.
		 */
		extent_slot = path->slots[0];
		while (extent_slot >= 0) {
			btrfs_item_key_to_cpu(path->nodes[0], &key,
					      extent_slot);
			if (key.objectid != bytenr)
				break;
			if (key.type == BTRFS_EXTENT_ITEM_KEY &&
			    key.offset == num_bytes) {
				found_extent = 1;
				break;
			}
			if (key.type == BTRFS_METADATA_ITEM_KEY &&
			    key.offset == owner_objectid) {
				found_extent = 1;
				break;
			}

			/* Quick path didn't find the EXTEMT/METADATA_ITEM */
			if (path->slots[0] - extent_slot > 5)
				break;
			extent_slot--;
		}

		if (!found_extent) {
			if (iref) {
				btrfs_crit(info,
"invalid iref, no EXTENT/METADATA_ITEM found but has inline extent ref");
				btrfs_abort_transaction(trans, -EUCLEAN);
				goto err_dump;
			}
			/* Must be SHARED_* item, remove the backref first */
			ret = remove_extent_backref(trans, path, NULL,
						    refs_to_drop,
						    is_data, &last_ref);
			if (ret) {
				btrfs_abort_transaction(trans, ret);
				goto out;
			}
			btrfs_release_path(path);

			/* Slow path to locate EXTENT/METADATA_ITEM */
			key.objectid = bytenr;
			key.type = BTRFS_EXTENT_ITEM_KEY;
			key.offset = num_bytes;

			if (!is_data && skinny_metadata) {
				key.type = BTRFS_METADATA_ITEM_KEY;
				key.offset = owner_objectid;
			}

			ret = btrfs_search_slot(trans, extent_root,
						&key, path, -1, 1);
			if (ret > 0 && skinny_metadata && path->slots[0]) {
				/*
				 * Couldn't find our skinny metadata item,
				 * see if we have ye olde extent item.
				 */
				path->slots[0]--;
				btrfs_item_key_to_cpu(path->nodes[0], &key,
						      path->slots[0]);
				if (key.objectid == bytenr &&
				    key.type == BTRFS_EXTENT_ITEM_KEY &&
				    key.offset == num_bytes)
					ret = 0;
			}

			if (ret > 0 && skinny_metadata) {
				skinny_metadata = false;
				key.objectid = bytenr;
				key.type = BTRFS_EXTENT_ITEM_KEY;
				key.offset = num_bytes;
				btrfs_release_path(path);
				ret = btrfs_search_slot(trans, extent_root,
							&key, path, -1, 1);
			}

			if (ret) {
				btrfs_err(info,
					  "umm, got %d back from search, was looking for %llu",
					  ret, bytenr);
				if (ret > 0)
					btrfs_print_leaf(path->nodes[0]);
			}
			if (ret < 0) {
				btrfs_abort_transaction(trans, ret);
				goto out;
			}
			extent_slot = path->slots[0];
		}
	} else if (WARN_ON(ret == -ENOENT)) {
		btrfs_print_leaf(path->nodes[0]);
		btrfs_err(info,
			"unable to find ref byte nr %llu parent %llu root %llu  owner %llu offset %llu",
			bytenr, parent, root_objectid, owner_objectid,
			owner_offset);
		btrfs_abort_transaction(trans, ret);
		goto out;
	} else {
		btrfs_abort_transaction(trans, ret);
		goto out;
	}

	leaf = path->nodes[0];
	item_size = btrfs_item_size_nr(leaf, extent_slot);
	if (unlikely(item_size < sizeof(*ei))) {
		ret = -EINVAL;
		btrfs_print_v0_err(info);
		btrfs_abort_transaction(trans, ret);
		goto out;
	}
	ei = btrfs_item_ptr(leaf, extent_slot,
			    struct btrfs_extent_item);
	if (owner_objectid < BTRFS_FIRST_FREE_OBJECTID &&
	    key.type == BTRFS_EXTENT_ITEM_KEY) {
		struct btrfs_tree_block_info *bi;
		if (item_size < sizeof(*ei) + sizeof(*bi)) {
			btrfs_crit(info,
"invalid extent item size for key (%llu, %u, %llu) owner %llu, has %u expect >= %zu",
				   key.objectid, key.type, key.offset,
				   owner_objectid, item_size,
				   sizeof(*ei) + sizeof(*bi));
			btrfs_abort_transaction(trans, -EUCLEAN);
			goto err_dump;
		}
		bi = (struct btrfs_tree_block_info *)(ei + 1);
		WARN_ON(owner_objectid != btrfs_tree_block_level(leaf, bi));
	}

	refs = btrfs_extent_refs(leaf, ei);
	if (refs < refs_to_drop) {
		btrfs_crit(info,
		"trying to drop %d refs but we only have %llu for bytenr %llu",