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

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Message-ID: <de3dec73-c8fc-d14f-5bbb-7023ccc6b57e@acm.org>
Date:   Tue, 9 Mar 2021 11:21:41 -0800
From:   Bart Van Assche <bvanassche@....org>
To:     John Garry <john.garry@...wei.com>, 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 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.

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.

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.

Thanks,

Bart.