2023-09-14 10:12:51

by Anastasia Belova

Subject: [PATCH 5.10] btrfs: fix region size in count_bitmap_extents

count_bitmap_extents was deleted in version 5.11, but
there is possible mistake in versions 5.6-5.10.

Region size should be calculated by subtracting
the end from the beginning.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: dfb79ddb130e ("btrfs: track discardable extents for async discard")
Signed-off-by: Anastasia Belova <[email protected]>
---
fs/btrfs/free-space-cache.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 4989c60b1df9..a34e266a0969 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -1930,7 +1930,7 @@ static int count_bitmap_extents(struct btrfs_free_space_ctl *ctl,

bitmap_for_each_set_region(bitmap_info->bitmap, rs, re, 0,
BITS_PER_BITMAP) {
- bytes -= (rs - re) * ctl->unit;
+ bytes -= (re - rs) * ctl->unit;
count++;

if (!bytes)
--
2.30.2

2023-10-03 12:48:47

by Anastasia Belova

Subject: Re: [PATCH 5.10] btrfs: fix region size in count_bitmap_extents

03/10/23 15:39, Anastasia Belova пишет:
>
> 14/09/23 12:45, Anastasia Belova пишет:
>> count_bitmap_extents was deleted in version 5.11, but
>> there is possible mistake in versions 5.6-5.10.
>>
>> Region size should be calculated by subtracting
>> the end from the beginning.
> Do I understand correctly that bytes should decrease and
> (rs - re) is always negative and should be replaced by (re - rs)?
>> Found by Linux Verification Center (linuxtesting.org) with SVACE.
>>
>> Fixes: dfb79ddb130e ("btrfs: track discardable extents for async discard")
>> Signed-off-by: Anastasia Belova<[email protected]>
>> ---
>> fs/btrfs/free-space-cache.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
>> index 4989c60b1df9..a34e266a0969 100644
>> --- a/fs/btrfs/free-space-cache.c
>> +++ b/fs/btrfs/free-space-cache.c
>> @@ -1930,7 +1930,7 @@ static int count_bitmap_extents(struct btrfs_free_space_ctl *ctl,
>>
>> bitmap_for_each_set_region(bitmap_info->bitmap, rs, re, 0,
>> BITS_PER_BITMAP) {
>> - bytes -= (rs - re) * ctl->unit;
>> + bytes -= (re - rs) * ctl->unit;
>> count++;
>>
>> if (!bytes)
> Anastasia
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