Re: [patch v4 2/2] xfs: Fix in xfs_rtalloc_query_range()

["Nirjhar Roy (IBM)" <nirjhar.roy.lists@gmail.com>]

On 2/25/26 17:49, Carlos Maiolino wrote:
> On Wed, Feb 25, 2026 at 04:58:26PM +0530, Nirjhar Roy (IBM) wrote:
>> On 2/25/26 16:10, Carlos Maiolino wrote:
>>> On Wed, Feb 04, 2026 at 08:36:27PM +0530, Nirjhar Roy (IBM) wrote:
>>>> xfs_rtalloc_query_range() should not return 0 by doing a NOP when
>>>> start == end i.e, when the rtgroup size is 1. This causes incorrect
>>>> calculation of free rtextents i.e, the count is reduced by 1 since
>>>> the last rtgroup's rtextent count is not taken and hence xfs_scrub
>>>> throws false summary counter report (from xchk_fscounters()).
>>> This causes a regression in xfstests's generic/475 running on a RT
>>> device.
>>>
>>> I'm dropping this patch until I have time to investigate what's wrong.
>>
>> I just took a quick glance at generic/475 - It does something related to
>> recovery. I am not sure how this fix is affecting this test. Maybe this fix
>> is triggering some other bug which needs to be fixed. Can you please share
>> the error logs and the local.config you used?
> I will get the info and let you know, I don't have access to my test
> system right now to get the details.


Okay sure, thank you.

>
> What config did you use? I'll give it a try later tonight and see if I
> spot any differences.


I haven't run it yet. But I usually use the following configuration

[xfs_4k]
export TEST_DEV=/dev/loop0
export TEST_DIR=/mnt1/test
export SCRATCH_DEV=/dev/loop1
export SCRATCH_MNT=/mnt1/scratch
export SCRATCH_RTDEV=/dev/loop2
export USE_EXTERNAL=yes

Most of the options are the default ones and/or used by the test script 
itself.

--NR

>
>
>> --NR
>>
>>>> A simple way to reproduce the above bug:
>>>>
>>>> $ mkfs.xfs -f -m metadir=1 \
>>>> 	-r rtdev=/dev/loop2,extsize=4096,rgcount=4,size=1G \
>>>> 	-d size=1G /dev/loop1
>>>> meta-data=/dev/loop1             isize=512    agcount=4, agsize=65536 blks
>>>>            =                       sectsz=512   attr=2, projid32bit=1
>>>>            =                       crc=1        finobt=1, sparse=1, rmapbt=1
>>>>            =                       reflink=0    bigtime=1 inobtcount=1 nrext64=1
>>>>            =                       exchange=1   metadir=1
>>>> data     =                       bsize=4096   blocks=262144, imaxpct=25
>>>>            =                       sunit=0      swidth=0 blks
>>>> naming   =version 2              bsize=4096   ascii-ci=0, ftype=1, parent=0
>>>> log      =internal log           bsize=4096   blocks=16384, version=2
>>>>            =                       sectsz=512   sunit=0 blks, lazy-count=1
>>>> realtime =/dev/loop2             extsz=4096   blocks=262144, rtextents=262144
>>>>            =                       rgcount=4    rgsize=65536 extents
>>>>            =                       zoned=0      start=0 reserved=0
>>>> Discarding blocks...Done.
>>>> Discarding blocks...Done.
>>>> $ mount -o rtdev=/dev/loop2 /dev/loop1 /mnt1/scratch
>>>> $ xfs_growfs -R $(( 65536 * 4 + 1 ))  /mnt1/scratch
>>>> meta-data=/dev/loop1             isize=512    agcount=4, agsize=65536 blks
>>>>            =                       sectsz=512   attr=2, projid32bit=1
>>>>            =                       crc=1        finobt=1, sparse=1, rmapbt=1
>>>>            =                       reflink=0    bigtime=1 inobtcount=1 nrext64=1
>>>>            =                       exchange=1   metadir=1
>>>> data     =                       bsize=4096   blocks=262144, imaxpct=25
>>>>            =                       sunit=0      swidth=0 blks
>>>> naming   =version 2              bsize=4096   ascii-ci=0, ftype=1, parent=0
>>>> log      =internal log           bsize=4096   blocks=16384, version=2
>>>>            =                       sectsz=512   sunit=0 blks, lazy-count=1
>>>> realtime =/dev/loop2             extsz=4096   blocks=262144, rtextents=262144
>>>>            =                       rgcount=4    rgsize=65536 extents
>>>>            =                       zoned=0      start=0 reserved=0
>>>> calling xfsctl with in.newblocks = 262145
>>>> realtime blocks changed from 262144 to 262145
>>>> $ xfs_scrub -n   -v /mnt1/scratch
>>>> Phase 1: Find filesystem geometry.
>>>> /mnt1/scratch: using 2 threads to scrub.
>>>> Phase 2: Check internal metadata.
>>>> Corruption: rtgroup 4 realtime summary: Repairs are required.
>>>> Phase 3: Scan all inodes.
>>>> Phase 5: Check directory tree.
>>>> Info: /mnt1/scratch: Filesystem has errors, skipping connectivity checks.
>>>> Phase 7: Check summary counters.
>>>> Corruption: filesystem summary counters: Repairs are required.
>>>> 125.0MiB data used;  8.0KiB realtime data used;  15 inodes used.
>>>> 64.3MiB data found; 4.0KiB realtime data found; 18 inodes found.
>>>> 18 inodes counted; 18 inodes checked.
>>>> Phase 8: Trim filesystem storage.
>>>> /mnt1/scratch: corruptions found: 2
>>>> /mnt1/scratch: Re-run xfs_scrub without -n.
>>>>
>>>> Cc: <stable@vger.kernel.org> # v6.13
>>>> Fixes: e3088ae2dcae3c ("xfs: move RT bitmap and summary information to the rtgroup")
>>>> Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
>>>> Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
>>>> Signed-off-by: Nirjhar Roy (IBM) <nirjhar.roy.lists@gmail.com>
>>>> ---
>>>>    fs/xfs/libxfs/xfs_rtbitmap.c | 2 +-
>>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/fs/xfs/libxfs/xfs_rtbitmap.c b/fs/xfs/libxfs/xfs_rtbitmap.c
>>>> index 618061d898d4..8f552129ffcc 100644
>>>> --- a/fs/xfs/libxfs/xfs_rtbitmap.c
>>>> +++ b/fs/xfs/libxfs/xfs_rtbitmap.c
>>>> @@ -1170,7 +1170,7 @@ xfs_rtalloc_query_range(
>>>>    	if (start > end)
>>>>    		return -EINVAL;
>>>> -	if (start == end || start >= rtg->rtg_extents)
>>>> +	if (start >= rtg->rtg_extents)
>>>>    		return 0;
>>>>    	end = min(end, rtg->rtg_extents - 1);
>>>> -- 
>>>> 2.43.5
>>>>
>>>>
>> -- 
>> Nirjhar Roy
>> Linux Kernel Developer
>> IBM, Bangalore
>>
-- 
Nirjhar Roy
Linux Kernel Developer
IBM, Bangalore