linux-kernel - Re: [RFC PATCH v3 3/3] blk-mq: Lockout tagset iterator when exiting elevator

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Message-ID: <b4e39d48-3524-ac34-c20e-0dadcf15e3d6@huawei.com>
Date:   Wed, 10 Mar 2021 08:52:15 +0000
From:   John Garry <john.garry@...wei.com>
To:     Bart Van Assche <bvanassche@....org>, <hare@...e.de>,
        <ming.lei@...hat.com>, <axboe@...nel.dk>, <hch@....de>
CC:     <linux-block@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <pragalla@...eaurora.org>, <kashyap.desai@...adcom.com>,
        <yuyufen@...wei.com>
Subject: Re: [RFC PATCH v3 3/3] blk-mq: Lockout tagset iterator when exiting
 elevator

On 09/03/2021 19:21, Bart Van Assche wrote:
> On 3/9/21 9:47 AM, John Garry wrote:
>> This does fall over if some tags are allocated without associated
>> request queue, which I do not know exists.
> 

Hi Bart,

> The only tag allocation mechanism I know of is blk_mq_get_tag(). The
> only blk_mq_get_tag() callers I know of are __blk_mq_alloc_request() and
> blk_mq_alloc_request_hctx(). So I think all allocated tags are
> associated with a request queue.
> 

ok, good.

> Regarding this patch series, I have shared the feedback I wanted to
> share so I would appreciate it if someone else could also take a look.
> 

So I can incorporate any changes and suggestions so far and send a 
non-RFC version - that may get more attention if none extra comes.

As mentioned on the cover letter, if patch 2+3/3 are accepted, then 
patch 1/3 could be simplified. But I plan to leave as is.

BTW, any issue with putting your suggested-by on patch 2/3?

Thanks,
John