From: Ming Lei <ming.lei@redhat.com> To: Christoph Hellwig <hch@lst.de> Cc: Jens Axboe <axboe@kernel.dk>, Jeffle Xu <jefflexu@linux.alibaba.com>, Damien Le Moal <Damien.LeMoal@wdc.com>, Keith Busch <kbusch@kernel.org>, Sagi Grimberg <sagi@grimberg.me>, "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 14/16] block: switch polling to be bio based Date: Wed, 13 Oct 2021 17:59:57 +0800 [thread overview] Message-ID: <YWauHUIqvS29pLnW@T590> (raw) In-Reply-To: <20211012111226.760968-15-hch@lst.de> On Tue, Oct 12, 2021 at 01:12:24PM +0200, Christoph Hellwig wrote: > Replace the blk_poll interface that requires the caller to keep a queue > and cookie from the submissions with polling based on the bio. > > Polling for the bio itself leads to a few advantages: > > - the cookie construction can made entirely private in blk-mq.c > - the caller does not need to remember the request_queue and cookie > separately and thus sidesteps their lifetime issues > - keeping the device and the cookie inside the bio allows to trivially > support polling BIOs remapping by stacking drivers > - a lot of code to propagate the cookie back up the submission path can > be removed entirely. > > Signed-off-by: Christoph Hellwig <hch@lst.de> > Tested-by: Mark Wunderlich <mark.wunderlich@intel.com> > --- ... > +/** > + * bio_poll - poll for BIO completions > + * @bio: bio to poll for > + * @flags: BLK_POLL_* flags that control the behavior > + * > + * Poll for completions on queue associated with the bio. Returns number of > + * completed entries found. > + * > + * 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); > + int ret; > + > + 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); > + > + if (blk_queue_enter(q, BLK_MQ_REQ_NOWAIT)) > + return 0; Now bdev, gendisk and request_queue are freed after RCU grace period, so this way is safe since 340e84573878 ("block: delay freeing the gendisk"). Thanks, Ming
WARNING: multiple messages have this Message-ID (diff)
From: Ming Lei <ming.lei@redhat.com> To: Christoph Hellwig <hch@lst.de> Cc: Jens Axboe <axboe@kernel.dk>, Jeffle Xu <jefflexu@linux.alibaba.com>, Damien Le Moal <Damien.LeMoal@wdc.com>, Keith Busch <kbusch@kernel.org>, Sagi Grimberg <sagi@grimberg.me>, "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 14/16] block: switch polling to be bio based Date: Wed, 13 Oct 2021 17:59:57 +0800 [thread overview] Message-ID: <YWauHUIqvS29pLnW@T590> (raw) In-Reply-To: <20211012111226.760968-15-hch@lst.de> On Tue, Oct 12, 2021 at 01:12:24PM +0200, Christoph Hellwig wrote: > Replace the blk_poll interface that requires the caller to keep a queue > and cookie from the submissions with polling based on the bio. > > Polling for the bio itself leads to a few advantages: > > - the cookie construction can made entirely private in blk-mq.c > - the caller does not need to remember the request_queue and cookie > separately and thus sidesteps their lifetime issues > - keeping the device and the cookie inside the bio allows to trivially > support polling BIOs remapping by stacking drivers > - a lot of code to propagate the cookie back up the submission path can > be removed entirely. > > Signed-off-by: Christoph Hellwig <hch@lst.de> > Tested-by: Mark Wunderlich <mark.wunderlich@intel.com> > --- ... > +/** > + * bio_poll - poll for BIO completions > + * @bio: bio to poll for > + * @flags: BLK_POLL_* flags that control the behavior > + * > + * Poll for completions on queue associated with the bio. Returns number of > + * completed entries found. > + * > + * 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); > + int ret; > + > + 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); > + > + if (blk_queue_enter(q, BLK_MQ_REQ_NOWAIT)) > + return 0; Now bdev, gendisk and request_queue are freed after RCU grace period, so this way is safe since 340e84573878 ("block: delay freeing the gendisk"). Thanks, Ming _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme
next prev parent reply other threads:[~2021-10-13 10:00 UTC|newest] Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-10-12 11:12 switch block layer polling to a bio based model v4 Christoph Hellwig 2021-10-12 11:12 ` Christoph Hellwig 2021-10-12 11:12 ` [PATCH 01/16] direct-io: remove blk_poll support Christoph Hellwig 2021-10-12 11:12 ` Christoph Hellwig 2021-10-13 10:42 ` Sagi Grimberg 2021-10-13 10:42 ` Sagi Grimberg 2021-10-28 1:26 ` Chaitanya Kulkarni 2021-10-12 11:12 ` [PATCH 02/16] block: don't try to poll multi-bio I/Os in __blkdev_direct_IO Christoph Hellwig 2021-10-12 11:12 ` Christoph Hellwig 2021-10-12 11:12 ` [PATCH 03/16] iomap: don't try to poll multi-bio I/Os in __iomap_dio_rw Christoph Hellwig 2021-10-12 11:12 ` Christoph Hellwig 2021-10-12 11:12 ` [PATCH 04/16] io_uring: fix a layering violation in io_iopoll_req_issued Christoph Hellwig 2021-10-12 11:12 ` Christoph Hellwig 2021-10-12 11:12 ` [PATCH 05/16] blk-mq: factor out a blk_qc_to_hctx helper Christoph Hellwig 2021-10-12 11:12 ` Christoph Hellwig 2021-10-12 11:12 ` [PATCH 06/16] blk-mq: factor out a "classic" poll helper Christoph Hellwig 2021-10-12 11:12 ` Christoph Hellwig 2021-10-12 11:12 ` [PATCH 07/16] blk-mq: remove blk_qc_t_to_tag and blk_qc_t_is_internal Christoph Hellwig 2021-10-12 11:12 ` Christoph Hellwig 2021-10-12 11:12 ` [PATCH 08/16] blk-mq: remove blk_qc_t_valid Christoph Hellwig 2021-10-12 11:12 ` Christoph Hellwig 2021-10-12 11:12 ` [PATCH 09/16] block: replace the spin argument to blk_iopoll with a flags argument Christoph Hellwig 2021-10-12 11:12 ` Christoph Hellwig 2021-10-13 10:44 ` Sagi Grimberg 2021-10-13 10:44 ` Sagi Grimberg 2021-10-12 11:12 ` [PATCH 10/16] io_uring: don't sleep when polling for I/O Christoph Hellwig 2021-10-12 11:12 ` Christoph Hellwig 2021-10-13 10:45 ` Sagi Grimberg 2021-10-13 10:45 ` Sagi Grimberg 2021-10-12 11:12 ` [PATCH 11/16] block: rename REQ_HIPRI to REQ_POLLED Christoph Hellwig 2021-10-12 11:12 ` Christoph Hellwig 2021-10-13 10:45 ` Sagi Grimberg 2021-10-13 10:45 ` Sagi Grimberg 2021-10-12 11:12 ` [PATCH 12/16] block: use SLAB_TYPESAFE_BY_RCU for the bio slab Christoph Hellwig 2021-10-12 11:12 ` Christoph Hellwig 2021-10-12 11:12 ` [PATCH 13/16] block: define 'struct bvec_iter' as packed Christoph Hellwig 2021-10-12 11:12 ` Christoph Hellwig 2021-10-12 11:12 ` [PATCH 14/16] block: switch polling to be bio based Christoph Hellwig 2021-10-12 11:12 ` Christoph Hellwig 2021-10-13 9:59 ` Ming Lei [this message] 2021-10-13 9:59 ` Ming Lei 2021-10-13 10:45 ` Sagi Grimberg 2021-10-13 10:45 ` Sagi Grimberg 2021-10-15 8:30 ` Pankaj Raghav 2021-10-15 13:24 ` Christoph Hellwig 2021-11-03 7:11 ` chenxiang (M) 2021-11-03 7:22 ` Christoph Hellwig 2021-11-03 8:05 ` chenxiang (M) 2021-10-12 11:12 ` [PATCH 15/16] block: don't allow writing to the poll queue attribute Christoph Hellwig 2021-10-12 11:12 ` Christoph Hellwig 2021-10-12 11:12 ` [PATCH 16/16] nvme-multipath: enable polled I/O Christoph Hellwig 2021-10-12 11:12 ` Christoph Hellwig 2021-10-13 10:46 ` Sagi Grimberg 2021-10-13 10:46 ` Sagi Grimberg 2021-10-12 14:47 ` switch block layer polling to a bio based model v4 Jens Axboe 2021-10-12 14:47 ` Jens Axboe 2021-10-12 14:57 ` Sagi Grimberg 2021-10-12 14:57 ` Sagi Grimberg 2021-10-12 14:58 ` Jens Axboe 2021-10-12 14:58 ` Jens Axboe 2021-10-12 15:09 ` Sagi Grimberg 2021-10-12 15:09 ` Sagi Grimberg 2021-10-12 15:06 ` Christoph Hellwig 2021-10-12 15:06 ` Christoph Hellwig
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