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btrfs: qgroup: fix a wrong length calculation in qgroup_free_reserved_data()

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In that function, we round down the start position and round up the
ending position.

But during the calculation of @len, we use "round_up(start + len,
sectorsize)", which is the rounded up end position, not the rounded up
length.

Which results a much larger length, and later we are still using
"start + len", which is completely incorrect.

Fix it by declaring a local @aligned_start and @aligned_len and use them
instead.

Fixes: bc42bda223 ("btrfs: qgroup: Fix qgroup reserved space underflow by only freeing reserved ranges")
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Qu Wenruo 2026-07-28 12:09:26 +09:30 committed by David Sterba
parent e0e6df7294
commit 9102b17951
1 changed files with 11 additions and 7 deletions
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18
fs/btrfs/qgroup.c
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@ -4339,12 +4339,13 @@ static int qgroup_free_reserved_data(struct btrfs_inode *inode,
struct ulist_node *unode;
struct ulist_iterator uiter;
struct extent_changeset changeset;
const u32 sectorsize = root->fs_info->sectorsize;
const u64 aligned_start = round_down(start, sectorsize);
const u64 aligned_len = round_up(start + len, sectorsize) - aligned_start;
u64 freed = 0;
int ret;
extent_changeset_init_bytes_only(&changeset);
len = round_up(start + len, root->fs_info->sectorsize);
start = round_down(start, root->fs_info->sectorsize);
ULIST_ITER_INIT(&uiter);
while ((unode = ulist_next(&reserved->range_changed, &uiter))) {
@ -4356,12 +4357,15 @@ static int qgroup_free_reserved_data(struct btrfs_inode *inode,
extent_changeset_release(&changeset);
/* Only free range in range [start, start + len) */
if (range_start >= start + len ||
range_start + range_len <= start)
/*
* Only free the range within
* [aligned_start, aligned_start + aligned_len).
*/
if (range_start >= aligned_start + aligned_len ||
range_start + range_len <= aligned_start)
continue;
free_start = max(range_start, start);
free_len = min(start + len, range_start + range_len) -
free_start = max(range_start, aligned_start);
free_len = min(aligned_start + aligned_len, range_start + range_len) -
free_start;
/*
* TODO: To also modify reserved->ranges_reserved to reflect