From: Christoph Hellwig <hch@lst.de>
To: Ming Lei <ming.lei@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, John Garry <john.garry@huawei.com>,
Bart Van Assche <bvanassche@acm.org>,
Hannes Reinecke <hare@suse.com>, Christoph Hellwig <hch@lst.de>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH V11 11/12] blk-mq: re-submit IO in case that hctx is inactive
Date: Wed, 13 May 2020 14:21:47 +0200 [thread overview]
Message-ID: <20200513122147.GF6297@lst.de> (raw)
In-Reply-To: <20200513034803.1844579-12-ming.lei@redhat.com>
Use of the BLK_MQ_REQ_FORCE is pretty bogus here..
> + if (rq->rq_flags & RQF_PREEMPT)
> + flags |= BLK_MQ_REQ_PREEMPT;
> + if (reserved)
> + flags |= BLK_MQ_REQ_RESERVED;
> + /*
> + * Queue freezing might be in-progress, and wait freeze can't be
> + * done now because we have request not completed yet, so mark this
> + * allocation as BLK_MQ_REQ_FORCE for avoiding this allocation &
> + * freeze hung forever.
> + */
> + flags |= BLK_MQ_REQ_FORCE;
> +
> + /* avoid allocation failure by clearing NOWAIT */
> + nrq = blk_get_request(rq->q, rq->cmd_flags & ~REQ_NOWAIT, flags);
> + if (!nrq)
> + return;
blk_get_request returns an ERR_PTR.
But I'd rather avoid the magic new BLK_MQ_REQ_FORCE hack when we can
just open code it and document what is going on:
static struct blk_mq_tags *blk_mq_rq_tags(struct request *rq)
{
struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
if (rq->q->elevator)
return hctx->sched_tags;
return hctx->tags;
}
static void blk_mq_resubmit_rq(struct request *rq)
{
struct blk_mq_alloc_data alloc_data = {
.cmd_flags = rq->cmd_flags & ~REQ_NOWAIT;
};
struct request *nrq;
if (rq->rq_flags & RQF_PREEMPT)
alloc_data.flags |= BLK_MQ_REQ_PREEMPT;
if (blk_mq_tag_is_reserved(blk_mq_rq_tags(rq), rq->internal_tag))
alloc_data.flags |= BLK_MQ_REQ_RESERVED;
/*
* We must still be able to finish a resubmission due to a hotplug
* even even if a queue freeze is in progress.
*/
percpu_ref_get(&q->q_usage_counter);
nrq = blk_mq_get_request(rq->q, NULL, &alloc_data);
blk_queue_exit(q);
if (!nrq)
return; // XXX: warn?
if (nrq->q->mq_ops->initialize_rq_fn)
rq->mq_ops->initialize_rq_fn(nrq);
blk_rq_copy_request(nrq, rq);
...
next prev parent reply other threads:[~2020-05-13 12:21 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-13 3:47 [PATCH V11 00/12] blk-mq: improvement CPU hotplug Ming Lei
2020-05-13 3:47 ` [PATCH V11 01/12] block: clone nr_integrity_segments and write_hint in blk_rq_prep_clone Ming Lei
2020-05-13 3:47 ` [PATCH V11 02/12] block: add helper for copying request Ming Lei
2020-05-13 3:47 ` [PATCH V11 03/12] blk-mq: mark blk_mq_get_driver_tag as static Ming Lei
2020-05-13 3:47 ` [PATCH V11 04/12] blk-mq: assign rq->tag in blk_mq_get_driver_tag Ming Lei
2020-05-13 3:47 ` [PATCH V11 05/12] blk-mq: add blk_mq_all_tag_iter Ming Lei
2020-05-13 11:56 ` Christoph Hellwig
2020-05-13 3:47 ` [PATCH V11 06/12] blk-mq: prepare for draining IO when hctx's all CPUs are offline Ming Lei
2020-05-13 6:35 ` Hannes Reinecke
2020-05-13 11:58 ` Christoph Hellwig
2020-05-14 0:33 ` Ming Lei
2020-05-13 3:47 ` [PATCH V11 07/12] blk-mq: stop to handle IO and drain IO before hctx becomes inactive Ming Lei
2020-05-13 11:59 ` Christoph Hellwig
2020-05-14 0:36 ` Ming Lei
2020-05-14 1:12 ` Bart Van Assche
2020-05-14 3:10 ` Ming Lei
2020-05-13 3:47 ` [PATCH V11 08/12] block: add blk_end_flush_machinery Ming Lei
2020-05-13 12:00 ` Christoph Hellwig
2020-05-13 3:48 ` [PATCH V11 09/12] blk-mq: add blk_mq_hctx_handle_dead_cpu for handling cpu dead Ming Lei
2020-05-13 12:06 ` Christoph Hellwig
2020-05-13 3:48 ` [PATCH V11 10/12] block: add request allocation flag of BLK_MQ_REQ_FORCE Ming Lei
2020-05-13 10:34 ` [PATCH V12 " Ming Lei
2020-05-13 3:48 ` [PATCH V11 11/12] blk-mq: re-submit IO in case that hctx is inactive Ming Lei
2020-05-13 9:21 ` John Garry
2020-05-13 12:21 ` Christoph Hellwig [this message]
2020-05-13 15:03 ` Bart Van Assche
2020-05-14 0:45 ` Ming Lei
2020-05-14 0:40 ` Ming Lei
2020-05-13 3:48 ` [PATCH V11 12/12] block: deactivate hctx when the hctx is actually inactive Ming Lei
2020-05-13 7:34 ` [PATCH V11 00/12] blk-mq: improvement CPU hotplug John Garry
2020-05-13 10:37 ` Ming Lei
2020-05-13 11:33 ` John Garry
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