linux-kernel - Re: [PATCH 6/6] blk-mq: remove REQ_ATOM

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Message-ID: <1513117238.2999.54.camel@wdc.com>
Date:   Tue, 12 Dec 2017 22:20:39 +0000
From:   Bart Van Assche <Bart.VanAssche@....com>
To:     "tj@...nel.org" <tj@...nel.org>,
        "axboe@...nel.dk" <axboe@...nel.dk>
CC:     "kernel-team@...com" <kernel-team@...com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "osandov@...com" <osandov@...com>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "oleg@...hat.com" <oleg@...hat.com>, "hch@....de" <hch@....de>
Subject: Re: [PATCH 6/6] blk-mq: remove REQ_ATOM_STARTED

On Tue, 2017-12-12 at 11:01 -0800, Tejun Heo wrote:
> @@ -409,7 +407,7 @@ static void hctx_show_busy_rq(struct request *rq, void *data, bool reserved)
>         const struct show_busy_params *params = data;
>  
>         if (blk_mq_map_queue(rq->q, rq->mq_ctx->cpu) == params->hctx &&
> -           test_bit(REQ_ATOM_STARTED, &rq->atomic_flags))
> +           blk_mq_rq_state(rq) != MQ_RQ_IDLE)
>                 __blk_mq_debugfs_rq_show(params->m,
>                                          list_entry_rq(&rq->queuelist));

The above code should show all requests owned by the block driver. Patch
"blk-mq-debugfs: Also show requests that have not yet been started" (not yet
in Jens' tree) changes the REQ_ATOM_STARTED test into list_empty(&rq->queuelist).
Can that change be supported with the existing MQ_RQ_* states or will a new
state have to be introduced to support this? See also
https://marc.info/?l=linux-block&m=151252188411991.

Thanks,

Bart.