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
next prev parent reply other threads:[~2021-10-13 10:00 UTC|newest]
Thread overview: 35+ 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 ` [PATCH 01/16] direct-io: remove blk_poll support Christoph Hellwig
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 ` [PATCH 03/16] iomap: don't try to poll multi-bio I/Os in __iomap_dio_rw 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 ` [PATCH 05/16] blk-mq: factor out a blk_qc_to_hctx helper 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 ` [PATCH 07/16] blk-mq: remove blk_qc_t_to_tag and blk_qc_t_is_internal Christoph Hellwig
2021-10-12 11:12 ` [PATCH 08/16] blk-mq: remove blk_qc_t_valid Christoph Hellwig
2021-10-12 11:12 ` [PATCH 09/16] block: replace the spin argument to blk_iopoll with a flags argument Christoph Hellwig
2021-10-13 10:44 ` Sagi Grimberg
2021-10-12 11:12 ` [PATCH 10/16] io_uring: don't sleep when polling for I/O Christoph Hellwig
2021-10-13 10:45 ` Sagi Grimberg
2021-10-12 11:12 ` [PATCH 11/16] block: rename REQ_HIPRI to REQ_POLLED Christoph Hellwig
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 ` [PATCH 13/16] block: define 'struct bvec_iter' as packed Christoph Hellwig
2021-10-12 11:12 ` [PATCH 14/16] block: switch polling to be bio based Christoph Hellwig
2021-10-13 9:59 ` Ming Lei [this message]
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 ` [PATCH 16/16] nvme-multipath: enable polled I/O Christoph Hellwig
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 14:57 ` Sagi Grimberg
2021-10-12 14:58 ` Jens Axboe
2021-10-12 15:09 ` Sagi Grimberg
2021-10-12 15:06 ` Christoph Hellwig
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