Commit 816f589b authored by Christoph Hellwig's avatar Christoph Hellwig Committed by David Sterba
Browse files

btrfs: atomically insert the new extent in btrfs_split_ordered_extent 



Currently there is a small race window in btrfs_split_ordered_extent,
where the reduced old extent can be looked up on the per-inode rbtree
or the per-root list while the newly split out one isn't visible yet.

Fix this by open coding btrfs_alloc_ordered_extent in
btrfs_split_ordered_extent, and holding the tree lock and
root->ordered_extent_lock over the entire tree and extent manipulation.

Note that this introduces new lock ordering because previously
ordered_extent_lock was never held over the tree lock.

Reviewed-by: default avatarJohannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 53d9981c

fs/btrfs/ordered-data.c

+27 −16
Original line number Diff line number Diff line
@@ -1135,15 +1135,17 @@ bool btrfs_try_lock_ordered_range(struct btrfs_inode *inode, u64 start, u64 end, 
struct btrfs_ordered_extent *btrfs_split_ordered_extent(

			struct btrfs_ordered_extent *ordered, u64 len)

{

	struct inode *inode = ordered->inode;

	struct btrfs_ordered_inode_tree *tree = &BTRFS_I(inode)->ordered_tree;

	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);

	struct btrfs_inode *inode = BTRFS_I(ordered->inode);

	struct btrfs_ordered_inode_tree *tree = &inode->ordered_tree;

	struct btrfs_root *root = inode->root;

	struct btrfs_fs_info *fs_info = root->fs_info;

	u64 file_offset = ordered->file_offset;

	u64 disk_bytenr = ordered->disk_bytenr;

	unsigned long flags = ordered->flags & BTRFS_ORDERED_TYPE_FLAGS;

	struct btrfs_ordered_extent *new;

	struct rb_node *node;



	trace_btrfs_ordered_extent_split(BTRFS_I(inode), ordered);

	trace_btrfs_ordered_extent_split(inode, ordered);



	ASSERT(!(flags & (1U << BTRFS_ORDERED_COMPRESSED)));
@@ -1163,7 +1165,16 @@ struct btrfs_ordered_extent *btrfs_split_ordered_extent( 
	if (WARN_ON_ONCE(!list_empty(&ordered->list)))

		return ERR_PTR(-EINVAL);



	spin_lock_irq(&tree->lock);

	new = alloc_ordered_extent(inode, file_offset, len, len, disk_bytenr,

				   len, 0, flags, ordered->compress_type);

	if (IS_ERR(new))

		return new;



	/* One ref for the tree. */

	refcount_inc(&new->refs);



	spin_lock_irq(&root->ordered_extent_lock);

	spin_lock(&tree->lock);

	/* Remove from tree once */

	node = &ordered->rb_node;

	rb_erase(node, &tree->tree);
@@ -1184,17 +1195,17 @@ struct btrfs_ordered_extent *btrfs_split_ordered_extent( 
			"zoned: inconsistency in ordered tree at offset %llu",

			ordered->file_offset);



	spin_unlock_irq(&tree->lock);



	/*

	 * The splitting extent is already counted and will be added again in

	 * btrfs_alloc_ordered_extent(). Subtract len to avoid double counting.

	 */

	percpu_counter_add_batch(&fs_info->ordered_bytes, -len, fs_info->delalloc_batch);

	node = tree_insert(&tree->tree, new->file_offset, &new->rb_node);

	if (node)

		btrfs_panic(fs_info, -EEXIST,

			"zoned: inconsistency in ordered tree at offset %llu",

			new->file_offset);

	spin_unlock(&tree->lock);



	return btrfs_alloc_ordered_extent(BTRFS_I(inode), file_offset, len, len,

					  disk_bytenr, len, 0, flags,

					  ordered->compress_type);

	list_add_tail(&new->root_extent_list, &root->ordered_extents);

	root->nr_ordered_extents++;

	spin_unlock_irq(&root->ordered_extent_lock);

	return new;

}



int __init ordered_data_init(void)