From: Keith Busch <kbusch@kernel.org>
To: Sagi Grimberg <sagi@grimberg.me>
Cc: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
Jeffle Xu <jefflexu@linux.alibaba.com>,
Ming Lei <ming.lei@redhat.com>,
Damien Le Moal <Damien.LeMoal@wdc.com>,
"Wunderlich, Mark" <mark.wunderlich@intel.com>,
"Vasudevan, Anil" <anil.vasudevan@intel.com>,
linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-nvme@lists.infradead.org
Subject: Re: [PATCH 12/15] block: switch polling to be bio based
Date: Wed, 12 May 2021 15:12:37 -0700 [thread overview]
Message-ID: <20210512221237.GA2270434@dhcp-10-100-145-180.wdc.com> (raw)
In-Reply-To: <45d66945-165c-ae48-69f4-75dc553b0386@grimberg.me>
On Wed, May 12, 2021 at 03:03:40PM -0700, Sagi Grimberg wrote:
> On 5/12/21 6:15 AM, Christoph Hellwig wrote:
> > + *
> > + * Note: the caller must either be the context that submitted @bio, or
> > + * be in a RCU critical section to prevent freeing of @bio.
> > + */
> > +int bio_poll(struct bio *bio, unsigned int flags)
> > +{
> > + struct request_queue *q = bio->bi_bdev->bd_disk->queue;
> > + blk_qc_t cookie = READ_ONCE(bio->bi_cookie);
> > +
> > + if (cookie == BLK_QC_T_NONE ||
> > + !test_bit(QUEUE_FLAG_POLL, &q->queue_flags))
> > + return 0;
> > +
> > + if (current->plug)
> > + blk_flush_plug_list(current->plug, false);
> > +
> > + /* not yet implemented, so this should not happen */
> > + if (WARN_ON_ONCE(!queue_is_mq(q)))
>
> What happens if the I/O wasn't (yet) queued to the bottom device
> (i.e. no available path in nvme-mpath)?
>
> In this case the disk would be the mpath device node (which is
> not mq...)
The bi_cookie should remain BLK_QC_T_NONE in that case, so we wouldn't
get to the warning. But if that does happen, it doesn't appear that
anyone is going to wake up thread that needs to poll for this bio's
completion when a path becomes available for dispatch. I think it would
make sense for nvme-mpath to just clear the REQ_POLLED flag if it
doesn't immediately have viable path.
next prev parent reply other threads:[~2021-05-12 22:58 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-12 13:15 switch block layer polling to a bio based model v3 Christoph Hellwig
2021-05-12 13:15 ` [PATCH 01/15] direct-io: remove blk_poll support Christoph Hellwig
2021-05-12 13:15 ` [PATCH 02/15] block: don't try to poll multi-bio I/Os in __blkdev_direct_IO Christoph Hellwig
2021-05-12 20:54 ` Sagi Grimberg
2021-05-16 18:01 ` Kanchan Joshi
2021-05-12 13:15 ` [PATCH 03/15] iomap: don't try to poll multi-bio I/Os in __iomap_dio_rw Christoph Hellwig
2021-05-12 21:32 ` Darrick J. Wong
2021-05-12 13:15 ` [PATCH 04/15] blk-mq: factor out a blk_qc_to_hctx helper Christoph Hellwig
2021-05-12 20:58 ` Sagi Grimberg
2021-05-12 13:15 ` [PATCH 05/15] blk-mq: factor out a "classic" poll helper Christoph Hellwig
2021-05-12 20:59 ` Sagi Grimberg
2021-05-12 13:15 ` [PATCH 06/15] blk-mq: remove blk_qc_t_to_tag and blk_qc_t_is_internal Christoph Hellwig
2021-05-12 21:42 ` Sagi Grimberg
2021-05-12 13:15 ` [PATCH 07/15] blk-mq: remove blk_qc_t_valid Christoph Hellwig
2021-05-12 21:43 ` Sagi Grimberg
2021-05-12 13:15 ` [PATCH 08/15] io_uring: don't sleep when polling for I/O Christoph Hellwig
2021-05-12 21:55 ` Sagi Grimberg
2021-05-19 13:02 ` Christoph Hellwig
2021-05-12 13:15 ` [PATCH 09/15] block: rename REQ_HIPRI to REQ_POLLED Christoph Hellwig
2021-05-12 21:56 ` Sagi Grimberg
2021-05-12 22:43 ` Chaitanya Kulkarni
2021-05-12 13:15 ` [PATCH 10/15] block: use SLAB_TYPESAFE_BY_RCU for the bio slab Christoph Hellwig
2021-05-12 13:15 ` [PATCH 11/15] block: define 'struct bvec_iter' as packed Christoph Hellwig
2021-05-12 21:58 ` Sagi Grimberg
2021-05-12 13:15 ` [PATCH 12/15] block: switch polling to be bio based Christoph Hellwig
2021-05-12 22:03 ` Sagi Grimberg
2021-05-12 22:12 ` Keith Busch [this message]
2021-05-14 2:50 ` Keith Busch
2021-05-14 16:26 ` Keith Busch
2021-05-14 16:28 ` Christoph Hellwig
2021-05-13 1:26 ` Ming Lei
2021-05-13 1:23 ` Ming Lei
2021-05-12 13:15 ` [PATCH 13/15] block: don't allow writing to the poll queue attribute Christoph Hellwig
2021-05-12 22:04 ` Sagi Grimberg
2021-05-12 13:15 ` [PATCH 14/15] nvme-multipath: set QUEUE_FLAG_NOWAIT Christoph Hellwig
2021-05-12 13:15 ` [PATCH 15/15] nvme-multipath: enable polled I/O Christoph Hellwig
2021-05-12 22:10 ` Sagi Grimberg
2021-05-12 22:16 ` Keith Busch
2021-05-13 23:33 ` switch block layer polling to a bio based model v3 Wunderlich, Mark
-- strict thread matches above, loose matches on Subject: below --
2021-04-27 16:16 switch block layer polling to a bio based model v2 Christoph Hellwig
2021-04-27 16:16 ` [PATCH 12/15] block: switch polling to be bio based Christoph Hellwig
2021-04-28 2:28 ` Ming Lei
2021-04-29 7:20 ` Christoph Hellwig
2021-04-29 7:36 ` Ming Lei
2021-04-29 9:50 ` Christoph Hellwig
2021-04-29 14:42 ` Ming Lei
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