Re: memleak in libfs report

[Vlad Buslov <vladbu@nvidia.com>]

On Sun 22 Oct 2023 at 23:28, Chuck Lever III <chuck.lever@oracle.com> wrote:
> [ ... adding shmem maintainers ... ]
>
>> On Oct 11, 2023, at 12:06 PM, Chuck Lever III <chuck.lever@oracle.com> wrote:
>> 
>>> On Oct 11, 2023, at 11:52 AM, Vlad Buslov <vladbu@nvidia.com> wrote:
>>> 
>>> On Wed 11 Oct 2023 at 15:34, Chuck Lever III <chuck.lever@oracle.com> wrote:
>>>>> On Oct 11, 2023, at 11:15 AM, Vlad Buslov <vladbu@nvidia.com> wrote:
>>>>> 
>>>>> Hello Chuck,
>>>>> 
>>>>> We have been getting memleaks in offset_ctx->xa in our networking tests:
>>>>> 
>>>>> unreferenced object 0xffff8881004cd080 (size 576):
>>>>> comm "systemd", pid 1, jiffies 4294893373 (age 1992.864s)
>>>>> hex dump (first 32 bytes):
>>>>>  00 00 06 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>>>>>  38 5c 7c 02 81 88 ff ff 98 d0 4c 00 81 88 ff ff  8\|.......L.....
>>>>> backtrace:
>>>>>  [<000000000f554608>] xas_alloc+0x306/0x430
>>>>>  [<0000000075537d52>] xas_create+0x4b4/0xc80
>>>>>  [<00000000a927aab2>] xas_store+0x73/0x1680
>>>>>  [<0000000020a61203>] __xa_alloc+0x1d8/0x2d0
>>>>>  [<00000000ae300af2>] __xa_alloc_cyclic+0xf1/0x310
>>>>>  [<000000001032332c>] simple_offset_add+0xd8/0x170
>>>>>  [<0000000073229fad>] shmem_mknod+0xbf/0x180
>>>>>  [<00000000242520ce>] vfs_mknod+0x3b0/0x5c0
>>>>>  [<000000001ef218dd>] unix_bind+0x2c2/0xdb0
>>>>>  [<0000000009b9a8dd>] __sys_bind+0x127/0x1e0
>>>>>  [<000000003c949fbb>] __x64_sys_bind+0x6e/0xb0
>>>>>  [<00000000b8a767c7>] do_syscall_64+0x3d/0x90
>>>>>  [<000000006132ae0d>] entry_SYSCALL_64_after_hwframe+0x46/0xb0
>>>>> 
>>>>> It looks like those may be caused by recent commit 6faddda69f62 ("libfs:
>>>>> Add directory operations for stable offsets")
>>>> 
>>>> That sounds plausible.
>>>> 
>>>> 
>>>>> but we don't have a proper
>>>>> reproduction, just sometimes arbitrary getting the memleak complains
>>>>> during/after the regression run.
>>>> 
>>>> If the leak is a trickle rather than a flood, than can you take
>>>> some time to see if you can narrow down a reproducer? If it's a
>>>> flood, I can look at this immediately.
>>> 
>>> No, it is not a flood, we are not getting setups ran out of memory
>>> during testing or anything. However, I don't have any good idea how to
>>> narrow down the repro since as you can see from memleak trace it is a
>>> result of some syscall performed by systemd and none of our tests do
>>> anything more advanced with it than 'systemctl restart ovs-vswitchd'.
>>> Basically it is a setup with Fedora and an upstream kernel that executes
>>> bunch of network offload tests with Open vSwitch, iproute2 tc, Linux
>>> bridge, etc.
>> 
>> OK, I'll see what I can do for a reproducer. Thank you for the
>> report.
>
> I've had kmemleak enabled on several systems for a week, and there
> have been no tmpfs-related leaks detected. That suggests we don't
> have a problem with normal workloads.
>
> My next step is to go look at the ovs-vswitchd.service unit to
> see if there are any leads there. We might ask Lennart or the
> VSwitch folks if they have any suggestions too.
>
> Meantime, can I ask that you open a bug on bugzilla.kernel.org
> where we can collect troubleshooting information? Looks like
> "Memory Management / Other" is appropriate for shmem, and Hugh
> or Andrew can re-assign ownership to me.

Thanks for investigating this. Bug created:
https://bugzilla.kernel.org/show_bug.cgi?id=218039