Re: [BUG] btrfs potential failure on 32 core LTP test (fallocate05)

[Josef Bacik]

On 6/29/21 1:26 PM, Krzysztof Kozlowski wrote:
> On 29/06/2021 19:24, Josef Bacik wrote:
> > On 6/29/21 1:00 PM, Krzysztof Kozlowski wrote:
> > > Dear BTRFS folks,
> > >
> > > I am hitting a potential regression of btrfs, visible only with
> > > fallocate05 test from LTP (Linux Test Project) only on 32+ core Azure
> > > instances (x86_64).
> > >
> > > Tested:
> > > v5.8 (Ubuntu with our stable patches): PASS
> > > v5.11 (Ubuntu with our stable patches): FAIL
> > > v5.13 mainline: FAIL
> > >
> > > PASS means test passes on all instances
> > > FAIL means test passes on other instance types (e.g. 4 or 16 core) but
> > > fails on 32 and 64 core instances (did not test higher),
> > > e.g.: Standard_F32s_v2, Standard_F64s_v2, Standard_D32s_v3,
> > > Standard_E32s_v3
> > >
> > > Reproduction steps:
> > > git clone https://github.com/linux-test-project/ltp.git
> > > cd ltp
> > > ./build.sh && make install -j8
> > > cd ../ltp-install
> > > sudo ./runltp -f syscalls -s fallocate05
> > >
> > > Failure output:
> > > tst_test.c:1379: TINFO: Testing on btrfs
> > > tst_test.c:888: TINFO: Formatting /dev/loop4 with btrfs opts='' extra opts=''
> > > tst_test.c:1311: TINFO: Timeout per run is 0h 05m 00s
> > > tst_fill_fs.c:32: TINFO: Creating file mntpoint/file0 size 21710183
> > > tst_fill_fs.c:32: TINFO: Creating file mntpoint/file1 size 8070086
> > > tst_fill_fs.c:32: TINFO: Creating file mntpoint/file2 size 3971177
> > > tst_fill_fs.c:32: TINFO: Creating file mntpoint/file3 size 36915315
> > > tst_fill_fs.c:32: TINFO: Creating file mntpoint/file4 size 70310993
> > > tst_fill_fs.c:32: TINFO: Creating file mntpoint/file5 size 4807935
> > > tst_fill_fs.c:32: TINFO: Creating file mntpoint/file6 size 90739786
> > > tst_fill_fs.c:32: TINFO: Creating file mntpoint/file7 size 76896492
> > > tst_fill_fs.c:32: TINFO: Creating file mntpoint/file8 size 72228649
> > > tst_fill_fs.c:32: TINFO: Creating file mntpoint/file9 size 36207821
> > > tst_fill_fs.c:32: TINFO: Creating file mntpoint/file10 size 81483962
> > > tst_fill_fs.c:59: TINFO: write(): ENOSPC (28)
> > > fallocate05.c:81: TPASS: write() wrote 65536 bytes
> > > fallocate05.c:102: TINFO: fallocate()d 0 extra blocks on full FS
> > > fallocate05.c:114: TPASS: fallocate() on full FS
> > > fallocate05.c:130: TPASS: fallocate(FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE)
> > > fallocate05.c:134: TFAIL: write(): ENOSPC (28)
> > >
> > > Test code:
> > > https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/syscalls/fallocate/fallocate05.c#L134
> > >
> > > See also: https://bugs.launchpad.net/ubuntu-kernel-tests/+bug/1933112
> > >
> > > Other FS tests succeed on that machines/kernels. Other file systems
> > > also pass - only btrfs fails. The issue was not bisected. Full test
> > > log attached.
> >
> > Also it looks like you're using a loop device, the instructions you gave me
> > aren't complete enough for me to reproduce.  What is the actual setup you are
> > using?  How big is your loop device?  Is it a backing device?  I had to do -b
> > <device> to get the test to even start to run, but I've got a 2tib ssd, am I
> > supposed to be using something else?  Thanks,
>
> The test takes care about loop device, nothing is needed from your side.
> Just run the test and wait till you see:
> "tst_test.c:1379: TINFO: Testing on btrfs"
>
> That's where the interesting part starts :)

*cough*
# CONFIG_BLK_DEV_LOOP is not set
*cough*

I think I found the problem, my bad,

Josef