Re: [PATCH 1/4] generic/371: Fix the test to be compatible block sizes upto 64k

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

On 11/1/25 17:06, Zorro Lang wrote:
> On Tue, Oct 21, 2025 at 02:27:46PM +0530, Nirjhar Roy (IBM) wrote:
>> On 9/26/25 22:07, Zorro Lang wrote:
>>> On Tue, Sep 16, 2025 at 03:30:09PM +0000, Nirjhar Roy (IBM) wrote:
>>>> When this test was ran with btrfs with 64k sector/block size, it
>>>> failed with
>>>>
>>>>        QA output created by 371
>>>>        Silence is golden
>>>>       +fallocate: No space left on device
>>>>       +pwrite: No space left on device
>>>>       +fallocate: No space left on device
>>>>       +pwrite: No space left on device
>>>>       +pwrite: No space left on device
>>>>       ...
>>>>
>>>> This is what is going on:
>>>>
>>>> Let us see the following set of operations:
>>>>
>>>> --- With 4k sector size ---
>>>> $ mkfs.btrfs -f -b 256m -s 4k -n 4k /dev/loop0
>>>> $ mount /dev/loop0 /mnt1/scratch/
>>>> $ df -h /dev/loop0
>>>> Filesystem      Size  Used Avail Use% Mounted on
>>>> /dev/loop0      256M  1.5M  175M   1% /mnt1/scratch
>>>>
>>>> $ xfs_io -f -c "pwrite 0 80M" /mnt1/scratch/t1
>>>> wrote 83886080/83886080 bytes at offset 0
>>>> 80 MiB, 20480 ops; 0.4378 sec (182.693 MiB/sec and 46769.3095 ops/sec)
>>>>
>>>> $ df -h /dev/loop0
>>>> Filesystem      Size  Used Avail Use% Mounted on
>>>> /dev/loop0      256M  1.5M  175M   1% /mnt1/scratch
>>>>
>>>> $ sync
>>>> $ df -h /dev/loop0
>>>> Filesystem      Size  Used Avail Use% Mounted on
>>>> /dev/loop0      256M   82M   95M  47% /mnt1/scratch
>>>>
>>>> $ xfs_io -f -c "pwrite 0 80M" /mnt1/scratch/t2
>>>> wrote 83886080/83886080 bytes at offset 0
>>>> 80 MiB, 20480 ops; 0:00:01.25 (63.881 MiB/sec and 16353.4648 ops/sec)
>>>>
>>>> $ df -h /dev/loop0
>>>> Filesystem      Size  Used Avail Use% Mounted on
>>>> /dev/loop0      256M  137M   40M  78% /mnt1/scratch
>>>>
>>>> $ sync
>>>> $ df -h /dev/loop0
>>>> Filesystem      Size  Used Avail Use% Mounted on
>>>> /dev/loop0      256M  162M   15M  92% /mnt1/scratch
>>>>
>>>> Now let us repeat with 64k sector size
>>>> --- With 64k sector size ---
>>>> $ mkfs.btrfs -f -b 256m -s 64k -n 64k /dev/loop0
>>>> $ mount /dev/loop0 /mnt1/scratch/
>>>> $ df -h /dev/loop0
>>>> Filesystem      Size  Used Avail Use% Mounted on
>>>> /dev/loop0      256M   24M  175M  12% /mnt1/scratch
>>>>
>>>> $ xfs_io -f -c "pwrite 0 80M" /mnt1/scratch/t1
>>>> wrote 83886080/83886080 bytes at offset 0
>>>> 80 MiB, 20480 ops; 0.8460 sec (94.553 MiB/sec and 24205.4914 ops/sec)
>>>> $
>>>> $ df -h /dev/loop0
>>>> Filesystem      Size  Used Avail Use% Mounted on
>>>> /dev/loop0      256M   24M  175M  12% /mnt1/scratch
>>>>
>>>> $ sync
>>>> $ df -h /dev/loop0
>>>> Filesystem      Size  Used Avail Use% Mounted on
>>>> /dev/loop0      256M  104M   95M  53% /mnt1/scratch
>>>>
>>>> $ xfs_io -f -c "pwrite 0 80M" /mnt1/scratch/t2
>>>> pwrite: No space left on device
>>>>
>>>> Now, we can see that with 64k node size, 256M is not sufficient
>>>> to hold 2 files worth 80M. For 64k, we can also see that the initial
>>>> space usage on a fresh filesystem is 24M and for 4k its 1.5M. So
>>>> because of higher node size, more metadata space is getting used.
>>>> This test requires the size of the filesystem to be at least capable
>>>> to hold 2 80M files.
>>>> Fix this by increasing the fs size from 256M to 330M.
>>> Thanks for this detailed explanation. As this's a ENOSPC test, so we
>>> must make sure this case still can uncover the original bug, before
>>> increasing the fs size. Can you make sure that? Or maybe we can replace
>>> that "80M" with a variable (according to "Avail" size).
>> Hi Filipe, Zorro, Wang,
>>
>> The original commit message of generic/371 says that this test catches some
>> excess space usage issues. Is(Are) there any patch(es) that fix this issue -
>> so that I can remove the commits and check if the test expectedly fails with
>> slightly large fssize i.e, 330M?
>>
>> I did find some related commits [1] and I ran the test with 330M and
>> 256M(the default size) after removing the commits[1] but the test passes
>> with both the filesystem sizes. So I am guessing, this is not the patch that
>> can test generic/371.
>>
>> [1] https://lore.kernel.org/linux-btrfs/cover.1610747242.git.josef@toxicpanda.com/
> Hi,
>
> I'm not familiar with btrfs patches, but from the commit history, I suspect
> it *might* be related with below commit:
>
> commit 18513091af9483ba84328d42092bd4d42a3c958f
> Author: Wang Xiaoguang <wangxg.fnst@cn.fujitsu.com>
> Date:   Mon Jul 25 15:51:40 2016 +0800
>
>      btrfs: update btrfs_space_info's bytes_may_use timely
>
> Or "c0d2f6104e8ab2eb75e58e72494ad4b69c5227f8" :)
Thank you for the pointers. I tried running the test by checking out the 
commits before the above 2 mentioned commits, but the test seems to pass 
with the existing fs size.

--NR
>
> Thanks,
> Zorro
>
>> --NR
>>
>>> Thanks,
>>> Zorro
>>>
>>>> Reported-by: Disha Goel <disgoel@linux.ibm.com>
>>>> Signed-off-by: Nirjhar Roy (IBM) <nirjhar.roy.lists@gmail.com>
>>>> ---
>>>>    tests/generic/371 | 2 +-
>>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/tests/generic/371 b/tests/generic/371
>>>> index b312c450..95af308e 100755
>>>> --- a/tests/generic/371
>>>> +++ b/tests/generic/371
>>>> @@ -19,7 +19,7 @@ _require_scratch
>>>>    _require_xfs_io_command "falloc"
>>>>    test "$FSTYP" = "xfs" && _require_xfs_io_command "extsize"
>>>> -_scratch_mkfs_sized $((256 * 1024 * 1024)) >> $seqres.full 2>&1
>>>> +_scratch_mkfs_sized $((330 * 1024 * 1024)) >> $seqres.full 2>&1
>>>>    _scratch_mount
>>>>    # Disable speculative post-EOF preallocation on XFS, which can grow fast enough
>>>> -- 
>>>> 2.34.1
>>>>
>> -- 
>> Nirjhar Roy
>> Linux Kernel Developer
>> IBM, Bangalore
>>
-- 
Nirjhar Roy
Linux Kernel Developer
IBM, Bangalore