Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [BUG] btrfs potential failure on 32 core LTP test (fallocate05)
To:     Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>,
        Chris Mason <clm@fb.com>, David Sterba <dsterba@suse.com>,
        linux-btrfs@vger.kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "kernel-team@lists.ubuntu.com" <kernel-team@lists.ubuntu.com>,
        "ltp@lists.linux.it" <ltp@lists.linux.it>,
        Qu Wenruo <wqu@suse.com>, Filipe Manana <fdmanana@suse.com>
References: <a3b42abc-6996-ab06-ea9f-238e7c6f08d7@canonical.com>
 <124d7ead-6600-f369-7af1-a1bc27df135c@toxicpanda.com>
 <667133e5-44cb-8d95-c40a-12ac82f186f0@canonical.com>
From:   Josef Bacik <josef@toxicpanda.com>
Message-ID: <0b6a502a-8db8-ef27-f48e-5001f351ef24@toxicpanda.com>
Date:   Tue, 29 Jun 2021 13:28:49 -0400
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0)
 Gecko/20100101 Thunderbird/78.11.0
MIME-Version: 1.0
In-Reply-To: <667133e5-44cb-8d95-c40a-12ac82f186f0@canonical.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Precedence: bulk

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