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From: Ming Lei <ming.lei@redhat.com>
To: Jens Axboe <axboe@kernel.dk>, Mike Snitzer <snitzer@redhat.com>
Cc: linux-block@vger.kernel.org,
	Jeffle Xu <jefflexu@linux.alibaba.com>,
	dm-devel@redhat.com, Christoph Hellwig <hch@lst.de>
Subject: Re: [dm-devel] [RFC PATCH V2 3/3] dm: support bio polling
Date: Fri, 18 Jun 2021 07:08:59 +0800	[thread overview]
Message-ID: <YMvWC2vNCsnTkfrc@T590> (raw)
In-Reply-To: <20210617103549.930311-4-ming.lei@redhat.com>

On Thu, Jun 17, 2021 at 06:35:49PM +0800, Ming Lei wrote:
> Support bio(REQ_POLLED) polling in the following approach:
> 
> 1) only support io polling on normal READ/WRITE, and other abnormal IOs
> still fallback on IRQ mode, so the target io is exactly inside the dm
> io.
> 
> 2) hold one refcnt on io->io_count after submitting this dm bio with
> REQ_POLLED
> 
> 3) support dm native bio splitting, any dm io instance associated with
> current bio will be added into one list which head is bio->bi_end_io
> which will be recovered before ending this bio
> 
> 4) implement .poll_bio() callback, call bio_poll() on the single target
> bio inside the dm io which is retrieved via bio->bi_bio_drv_data; call
> dec_pending() after the target io is done in .poll_bio()
> 
> 4) enable QUEUE_FLAG_POLL if all underlying queues enable QUEUE_FLAG_POLL,
> which is based on Jeffle's previous patch.
> 
> Signed-off-by: Ming Lei <ming.lei@redhat.com>

...

> @@ -938,8 +945,12 @@ static void dec_pending(struct dm_io *io, blk_status_t error)
>  		end_io_acct(io);
>  		free_io(md, io);
>  
> -		if (io_error == BLK_STS_DM_REQUEUE)
> +		if (io_error == BLK_STS_DM_REQUEUE) {
> +			/* not poll any more in case of requeue */
> +			if (bio->bi_opf & REQ_POLLED)
> +				bio->bi_opf &= ~REQ_POLLED;

It becomes not necessary to clear REQ_POLLED before requeuing since
every dm_io is added into the hlist_head which is reused from
bio->bi_end_io, so all dm-io(include the one to be requeued) will be
polled.

Thanks,
Ming

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  reply	other threads:[~2021-06-17 23:09 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-17 10:35 [dm-devel] [RFC PATCH V2 0/3] block/dm: support bio polling Ming Lei
2021-06-17 10:35 ` [dm-devel] [RFC PATCH V2 1/3] block: add helper of blk_queue_poll Ming Lei
2021-06-21  7:20   ` Christoph Hellwig
2021-06-21  8:38     ` Ming Lei
2021-06-17 10:35 ` [dm-devel] [RFC PATCH V2 2/3] block: add ->poll_bio to block_device_operations Ming Lei
2021-06-21  7:25   ` Christoph Hellwig
2021-06-21  8:41     ` Ming Lei
2021-06-17 10:35 ` [dm-devel] [RFC PATCH V2 3/3] dm: support bio polling Ming Lei
2021-06-17 23:08   ` Ming Lei [this message]
2021-06-18  8:19   ` JeffleXu
2021-06-18 13:29     ` Ming Lei
2021-06-18 14:39     ` Ming Lei
2021-06-18 20:56       ` Mike Snitzer
2021-06-19  0:27         ` Ming Lei
2021-06-21  1:32         ` JeffleXu
2021-06-21 11:33       ` JeffleXu
2021-06-21 14:04         ` Ming Lei
2021-06-22  2:26           ` JeffleXu
2021-06-22  2:45             ` Ming Lei
2021-06-22  7:45               ` JeffleXu
2021-06-30  8:30         ` Ming Lei
2021-06-21  7:36   ` Christoph Hellwig
2021-06-21  9:09     ` Ming Lei

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