[PATCH V5 0/4] blk-mq: implement queue quiesce via percpu_ref for BLK_MQ_F_BLOCKING

[Jens Axboe]

On 9/11/20 12:34 PM, Sagi Grimberg wrote:
> 
>>> Hi Jens,
>>>
>>> The 1st patch add .mq_quiesce_mutex for serializing quiesce/unquiesce,
>>> and prepares for replacing srcu with percpu_ref.
>>>
>>> The 2nd patch replaces srcu with percpu_ref.
>>>
>>> The 3rd patch adds tagset quiesce interface.
>>>
>>> The 4th patch applies tagset quiesce interface for NVMe subsystem.
>>
>> Tested some reset storms and target restarts during traffic with
>> nvme-tcp.
>>
>> Seems that no apparent breakage.
>>
>> So:
>>
>> Tested-by: Sagi Grimberg <sagi at grimberg.me>
> 
> Probably unrelated to this patches, but I do see new
> kmemleak complaints in the form of:
> --
> unreferenced object 0xffff9440dbf3c240 (size 64):
>    comm "systemd", pid 1, jiffies 4306444056 (age 25034.440s)
>    hex dump (first 32 bytes):
>      00 00 00 00 00 00 00 00 b0 fe 13 99 ff ff ff ff  ................
>      00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>    backtrace:
>      [<00000000f1d0b20e>] percpu_ref_init+0x5f/0xf0
>      [<000000009598103f>] cgroup_mkdir+0xe9/0x440
>      [<0000000001b93c19>] kernfs_iop_mkdir+0x57/0x80
>      [<000000001ed0f985>] vfs_mkdir+0x10e/0x1d0
>      [<00000000cac65f7e>] do_mkdirat+0xec/0x120
>      [<00000000956db630>] do_syscall_64+0x33/0x80
>      [<000000001c2b0e1a>] entry_SYSCALL_64_after_hwframe+0x44/0xa9

Looks more related to the percpu_ref changes that allocate it
dynamically, causing issues on cases that forget to exit the ref.

-- 
Jens Axboe