[PATCH 5.10] btrfs: fix region size in count_bitmap_extents

[PATCH 5.10] btrfs: fix region size in count_bitmap_extents

[Anastasia Belova]

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 <abelova@astralinux.ru>
---
 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

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

[kernel test robot]

Hi,

Thanks for your patch.

FYI: kernel test robot notices the stable kernel rule is not satisfied.

The check is based on https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html/#option-3

Rule: The upstream commit ID must be specified with a separate line above the commit text.
Subject: [PATCH 5.10] btrfs: fix region size in count_bitmap_extents
Link: https://lore.kernel.org/stable/20230914094555.25657-1-abelova%40astralinux.ru

Please ignore this mail if the patch is not relevant for upstream.

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

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

[Анастасия Любимова]

14/09/23 12:47, kernel test:
> Hi,
>
> Thanks for your patch.
>
> FYI: kernel test robot notices the stable kernel rule is not satisfied.
>
> The check is based on https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html/#option-3
>
> Rule: The upstream commit ID must be specified with a separate line above the commit text.
> Subject: [PATCH 5.10] btrfs: fix region size in count_bitmap_extents
> Link: https://lore.kernel.org/stable/20230914094555.25657-1-abelova%40astralinux.ru
>
> Please ignore this mail if the patch is not relevant for upstream.
Right, this patch can not be applied to upstream because this part of 
code was deleted in version 5.11.
However there is still a possible typo.

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

[Анастасия Любимова]

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<abelova@astralinux.ru>
>> ---
>>   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
Sorry for sending html accidentally