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btrfs: allocate path on stack in load_block_group_size_class()

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Instead of allocating and freeing a path in every iteration of
load_block_group_size_class(), through its helper function
sample_block_group_extent_item(), allocate the path in the former and
pass it to the later. The path is allocated on stack since it's short
and we are in a workqueue context so there's not much stack usage.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Filipe Manana 2026-01-20 11:55:14 +00:00 committed by David Sterba
parent 17078525e5
commit e46a9f84bf
1 changed files with 19 additions and 13 deletions
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32
fs/btrfs/block-group.c
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@ -579,24 +579,24 @@ int btrfs_add_new_free_space(struct btrfs_block_group *block_group, u64 start,
* @index: the integral step through the block group to grab from
* @max_index: the granularity of the sampling
* @key: return value parameter for the item we find
* @path: path to use for searching in the extent tree
*
* Pre-conditions on indices:
* 0 <= index <= max_index
* 0 < max_index
*
* Returns: 0 on success, 1 if the search didn't yield a useful item, negative
* error code on error.
* Returns: 0 on success, 1 if the search didn't yield a useful item.
*/
static int sample_block_group_extent_item(struct btrfs_caching_control *caching_ctl,
struct btrfs_block_group *block_group,
int index, int max_index,
struct btrfs_key *found_key)
struct btrfs_key *found_key,
struct btrfs_path *path)
{
struct btrfs_fs_info *fs_info = block_group->fs_info;
struct btrfs_root *extent_root;
u64 search_offset;
const u64 search_end = btrfs_block_group_end(block_group);
BTRFS_PATH_AUTO_FREE(path);
struct btrfs_key search_key;
int ret = 0;
@ -606,17 +606,9 @@ static int sample_block_group_extent_item(struct btrfs_caching_control *caching_
lockdep_assert_held(&caching_ctl->mutex);
lockdep_assert_held_read(&fs_info->commit_root_sem);
path = btrfs_alloc_path();
if (!path)
return -ENOMEM;
extent_root = btrfs_extent_root(fs_info, max_t(u64, block_group->start,
BTRFS_SUPER_INFO_OFFSET));
path->skip_locking = true;
path->search_commit_root = true;
path->reada = READA_FORWARD;
search_offset = index * div_u64(block_group->length, max_index);
search_key.objectid = block_group->start + search_offset;
search_key.type = BTRFS_EXTENT_ITEM_KEY;
@ -679,23 +671,37 @@ static int sample_block_group_extent_item(struct btrfs_caching_control *caching_
static void load_block_group_size_class(struct btrfs_caching_control *caching_ctl,
struct btrfs_block_group *block_group)
{
BTRFS_PATH_AUTO_RELEASE(path);
struct btrfs_fs_info *fs_info = block_group->fs_info;
struct btrfs_key key;
int i;
u64 min_size = block_group->length;
enum btrfs_block_group_size_class size_class = BTRFS_BG_SZ_NONE;
/*
* Since we run in workqueue context, we allocate the path on stack to
* avoid memory allocation failure, as the stack in a work queue task
* is not deep.
*/
ASSERT(current_work() == &caching_ctl->work.normal_work);
if (!btrfs_block_group_should_use_size_class(block_group))
return;
path.skip_locking = true;
path.search_commit_root = true;
path.reada = READA_FORWARD;
lockdep_assert_held(&caching_ctl->mutex);
lockdep_assert_held_read(&fs_info->commit_root_sem);
for (i = 0; i < 5; ++i) {
int ret;
ret = sample_block_group_extent_item(caching_ctl, block_group, i, 5, &key);
ret = sample_block_group_extent_item(caching_ctl, block_group,
i, 5, &key, &path);
if (ret < 0)
return;
btrfs_release_path(&path);
if (ret > 0)
continue;
min_size = min_t(u64, min_size, key.offset);