!6397 btrfs: fix data race at btrfs_use_block_rsv() when accessing block reserve

		       u64 start, u64 end);

void btrfs_mark_bg_unused(struct btrfs_block_group_cache *bg);

/*

 * Get the size of a block reserve in a context where getting a stale value is

 * acceptable, instead of accessing it directly and trigger data race warning

 * from KCSAN.

 */

static inline u64 btrfs_block_rsv_size(struct btrfs_block_rsv *rsv)

{

	u64 ret;

	spin_lock(&rsv->lock);

	ret = rsv->size;

	spin_unlock(&rsv->lock);

	return ret;

}

/* ctree.c */

int btrfs_bin_search(struct extent_buffer *eb, const struct btrfs_key *key,

		     int level, int *slot);

	block_rsv = get_block_rsv(trans, root);

	if (unlikely(block_rsv->size == 0))

	if (unlikely(btrfs_block_rsv_size(block_rsv) == 0))

		goto try_reserve;

again:

	ret = block_rsv_use_bytes(block_rsv, blocksize);