Re: memleak in libfs report

[Vlad Buslov <vladbu@nvidia.com>]

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.