linux-kernel - Re: [PATCH V4 5/8] ublk_drv: consider recovery feature in aborting mechanism

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Message-ID: <8b595d99-9d77-dcbe-4d1a-14bbb12b912b@linux.alibaba.com>
Date:   Thu, 22 Sep 2022 10:06:30 +0800
From:   Ziyang Zhang <ZiyangZhang@...ux.alibaba.com>
To:     Ming Lei <ming.lei@...hat.com>
Cc:     axboe@...nel.dk, xiaoguang.wang@...ux.alibaba.com,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        joseph.qi@...ux.alibaba.com
Subject: Re: [PATCH V4 5/8] ublk_drv: consider recovery feature in aborting
 mechanism

On 2022/9/22 08:18, Ming Lei wrote:
> On Wed, Sep 21, 2022 at 05:58:46PM +0800, ZiyangZhang wrote:
>> With USER_RECOVERY feature enabled, the monitor_work schedules
>> quiesce_work after finding a dying ubq_daemon. The monitor_work
>> should also abort all rqs issued to userspace before the ubq_daemon is
>> dying. The quiesce_work's job is to:
>> (1) quiesce request queue.
>> (2) check if there is any INFLIGHT rq. If so, we retry until all these
>>     rqs are requeued and become IDLE. These rqs should be requeued by
>> 	ublk_queue_rq(), task work, io_uring fallback wq or monitor_work.
>> (3) complete all ioucmds by calling io_uring_cmd_done(). We are safe to
>>     do so because no ioucmd can be referenced now.
>> (5) set ub's state to UBLK_S_DEV_QUIESCED, which means we are ready for
>>     recovery. This state is exposed to userspace by GET_DEV_INFO.
>>
>> The driver can always handle STOP_DEV and cleanup everything no matter
>> ub's state is LIVE or QUIESCED. After ub's state is UBLK_S_DEV_QUIESCED,
>> user can recover with new process.
>>
>> Note: we do not change the default behavior with reocvery feature
>> disabled. monitor_work still schedules stop_work and abort inflight
>> rqs. And finally ublk_device is released.
>>
>> Signed-off-by: ZiyangZhang <ZiyangZhang@...ux.alibaba.com>
> 
> This version is close to be ready, just some debug logging needs
> be removed, see inline comment. Also I'd suggest you to learn to
> use bpftrace a bit, then basically you needn't to rely on kernel
> logging.
> 
> If these logging is removed, you will see how simple the patch becomes
> compared with previous version.

Current version is simpler, thanks for reviewing, Ming.
Debug logging will be removed in V5 and I will send it out soon.

Regards,
Zhang