Commit 1cab1375 authored by Filipe Manana's avatar Filipe Manana Committed by David Sterba
Browse files

btrfs: reuse cloned extent buffer during fiemap to avoid re-allocations 



During fiemap we may have to visit multiple leaves of the subvolume's
inode tree, and each time we are freeing and allocating an extent buffer
to use as a clone of each visited leaf. Optimize this by reusing cloned
extent buffers, to avoid the freeing and re-allocation both of the extent
buffer structure itself and more importantly of the pages attached to the
extent buffer.

Reviewed-by: default avatarJosef Bacik <josef@toxicpanda.com>
Signed-off-by: default avatarFilipe Manana <fdmanana@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 978b63f7

fs/btrfs/extent_io.c

+24 −8
Original line number Diff line number Diff line
@@ -2752,7 +2752,7 @@ static int emit_last_fiemap_cache(struct fiemap_extent_info *fieinfo, 


static int fiemap_next_leaf_item(struct btrfs_inode *inode, struct btrfs_path *path)

{

	struct extent_buffer *clone;

	struct extent_buffer *clone = path->nodes[0];

	struct btrfs_key key;

	int slot;

	int ret;
@@ -2761,29 +2761,45 @@ static int fiemap_next_leaf_item(struct btrfs_inode *inode, struct btrfs_path *p 
	if (path->slots[0] < btrfs_header_nritems(path->nodes[0]))

		return 0;



	/*

	 * Add a temporary extra ref to an already cloned extent buffer to

	 * prevent btrfs_next_leaf() freeing it, we want to reuse it to avoid

	 * the cost of allocating a new one.

	 */

	ASSERT(test_bit(EXTENT_BUFFER_UNMAPPED, &clone->bflags));

	atomic_inc(&clone->refs);



	ret = btrfs_next_leaf(inode->root, path);

	if (ret != 0)

		return ret;

		goto out;



	/*

	 * Don't bother with cloning if there are no more file extent items for

	 * our inode.

	 */

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

	if (key.objectid != btrfs_ino(inode) || key.type != BTRFS_EXTENT_DATA_KEY)

		return 1;

	if (key.objectid != btrfs_ino(inode) || key.type != BTRFS_EXTENT_DATA_KEY) {

		ret = 1;

		goto out;

	}



	/* See the comment at fiemap_search_slot() about why we clone. */

	clone = btrfs_clone_extent_buffer(path->nodes[0]);

	if (!clone)

		return -ENOMEM;

	copy_extent_buffer_full(clone, path->nodes[0]);

	/*

	 * Important to preserve the start field, for the optimizations when

	 * checking if extents are shared (see extent_fiemap()).

	 */

	clone->start = path->nodes[0]->start;



	slot = path->slots[0];

	btrfs_release_path(path);

	path->nodes[0] = clone;

	path->slots[0] = slot;

out:

	if (ret)

		free_extent_buffer(clone);



	return 0;

	return ret;

}



/*