linux-kernel - Re: [PATCH V3 0/7] blk-mq: don't allocate driver tag beforehand for flush rq

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Message-ID: <38f3a132-0c0d-4ae1-ac05-86a492720a5f@kernel.dk>
Date:   Sat, 4 Nov 2017 12:49:06 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Ming Lei <ming.lei@...hat.com>, linux-block@...r.kernel.org,
        Christoph Hellwig <hch@...radead.org>
Cc:     Omar Sandoval <osandov@...com>,
        Bart Van Assche <bart.vanassche@...disk.com>,
        Hannes Reinecke <hare@...e.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3 0/7] blk-mq: don't allocate driver tag beforehand for
 flush rq

On 11/04/2017 08:18 AM, Jens Axboe wrote:
> On 11/03/2017 10:17 PM, Ming Lei wrote:
>> On Thu, Nov 02, 2017 at 11:24:31PM +0800, Ming Lei wrote:
>>> Hi Jens,
>>>
>>> This patchset avoids to allocate driver tag beforehand for flush rq
>>> in case of I/O scheduler, then flush rq isn't treated specially
>>> wrt. get/put driver tag, code gets cleanup much, such as,
>>> reorder_tags_to_front() is removed, and we needn't to worry
>>> about request order in dispatch list for avoiding I/O deadlock.
>>>
>>> 'dbench -t 30 -s 64' has been run on different devices(shared tag,
>>> multi-queue, singele queue, ...), and no issues are observed,
>>> even very low queue depth test are run, debench still works well.
>>>
>>> Please consider it for V4.15, thanks!
>>
>> Hi Jens,
>>
>> As we discussed before, this patch is a good cleanup on handling flush
>> request, could you share your opinion on V3?
> 
> It looks fine to me. But I'd really like to have the potential hang
> in the current 4.15 branch ironed out, before we pile more stuff on
> top. Meanwhile, I'll see if this passes my testing.

Passes testing. I applied it, but a heads-up that I rewrote most of
your changelogs and also changed formatting. Please at least follow
the 72 char line rule for commit messages, otherwise git log ends
up looking like a mess really quick.

-- 
Jens Axboe