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

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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: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Filipe Manana 2024-02-28 14:36:33 +00:00 committed by David Sterba
parent 978b63f746
commit 1cab1375ba
1 changed files with 24 additions and 8 deletions
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32
fs/btrfs/extent_io.c
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@ -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;
}
/*