From: Christoph Hellwig <hch@lst.de>
To: Ming Lei <ming.lei@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>, 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 13/16] block: switch polling to be bio based
Date: Fri, 18 Jun 2021 16:01:47 +0200 [thread overview]
Message-ID: <20210618140147.GA16258@lst.de> (raw)
In-Reply-To: <YMliP6sFVuPhMbOB@T590>
On Wed, Jun 16, 2021 at 10:30:23AM +0800, Ming Lei wrote:
> Not sure disk is valid, we only hold the disk when opening a bdev, but
> the bdev can be closed during polling.
How? On a block device the caller needs to hold the block device open
to read/write from it. On a file systems the file systems needs to
be mounted, which also holds a bdev reference.
> Also disk always holds one
> reference on request queue, so if disk is valid, no need to grab queue's
> refcnt in bio_poll().
But we need to avoid going into the lowlevel blk-mq polling code to not
reference the potentially freed hctxs or tags as correctly pointed by
yourself on the previous iteration.
WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: Ming Lei <ming.lei@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>, 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 13/16] block: switch polling to be bio based
Date: Fri, 18 Jun 2021 16:01:47 +0200 [thread overview]
Message-ID: <20210618140147.GA16258@lst.de> (raw)
In-Reply-To: <YMliP6sFVuPhMbOB@T590>
On Wed, Jun 16, 2021 at 10:30:23AM +0800, Ming Lei wrote:
> Not sure disk is valid, we only hold the disk when opening a bdev, but
> the bdev can be closed during polling.
How? On a block device the caller needs to hold the block device open
to read/write from it. On a file systems the file systems needs to
be mounted, which also holds a bdev reference.
> Also disk always holds one
> reference on request queue, so if disk is valid, no need to grab queue's
> refcnt in bio_poll().
But we need to avoid going into the lowlevel blk-mq polling code to not
reference the potentially freed hctxs or tags as correctly pointed by
yourself on the previous iteration.
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next prev parent reply other threads:[~2021-06-18 14:01 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-15 13:10 switch block layer polling to a bio based model v4 Christoph Hellwig
2021-06-15 13:10 ` Christoph Hellwig
2021-06-15 13:10 ` [PATCH 01/16] direct-io: remove blk_poll support Christoph Hellwig
2021-06-15 13:10 ` Christoph Hellwig
2021-06-15 13:10 ` [PATCH 02/16] block: don't try to poll multi-bio I/Os in __blkdev_direct_IO Christoph Hellwig
2021-06-15 13:10 ` Christoph Hellwig
2021-06-15 13:10 ` [PATCH 03/16] iomap: don't try to poll multi-bio I/Os in __iomap_dio_rw Christoph Hellwig
2021-06-15 13:10 ` Christoph Hellwig
2021-06-15 13:10 ` [PATCH 04/16] blk-mq: factor out a blk_qc_to_hctx helper Christoph Hellwig
2021-06-15 13:10 ` Christoph Hellwig
2021-06-15 13:10 ` [PATCH 05/16] blk-mq: factor out a "classic" poll helper Christoph Hellwig
2021-06-15 13:10 ` Christoph Hellwig
2021-06-15 13:10 ` [PATCH 06/16] blk-mq: remove blk_qc_t_to_tag and blk_qc_t_is_internal Christoph Hellwig
2021-06-15 13:10 ` Christoph Hellwig
2021-06-15 13:10 ` [PATCH 07/16] blk-mq: remove blk_qc_t_valid Christoph Hellwig
2021-06-15 13:10 ` Christoph Hellwig
2021-06-15 13:10 ` [PATCH 08/16] block: replace the spin argument to blk_iopoll with a flags argument Christoph Hellwig
2021-06-15 13:10 ` Christoph Hellwig
2021-06-15 13:10 ` [PATCH 09/16] io_uring: don't sleep when polling for I/O Christoph Hellwig
2021-06-15 13:10 ` Christoph Hellwig
2021-06-15 13:10 ` [PATCH 10/16] block: rename REQ_HIPRI to REQ_POLLED Christoph Hellwig
2021-06-15 13:10 ` Christoph Hellwig
2021-06-15 13:10 ` [PATCH 11/16] block: use SLAB_TYPESAFE_BY_RCU for the bio slab Christoph Hellwig
2021-06-15 13:10 ` Christoph Hellwig
2021-06-15 13:10 ` [PATCH 12/16] block: define 'struct bvec_iter' as packed Christoph Hellwig
2021-06-15 13:10 ` Christoph Hellwig
2021-06-15 13:10 ` [PATCH 13/16] block: switch polling to be bio based Christoph Hellwig
2021-06-15 13:10 ` Christoph Hellwig
2021-06-16 2:30 ` Ming Lei
2021-06-16 2:30 ` Ming Lei
2021-06-18 14:01 ` Christoph Hellwig [this message]
2021-06-18 14:01 ` Christoph Hellwig
2021-06-18 14:27 ` Ming Lei
2021-06-18 14:27 ` Ming Lei
2021-06-21 7:20 ` Christoph Hellwig
2021-06-21 7:20 ` Christoph Hellwig
2021-06-21 8:35 ` Ming Lei
2021-06-21 8:35 ` Ming Lei
2021-06-15 13:10 ` [PATCH 14/16] block: don't allow writing to the poll queue attribute Christoph Hellwig
2021-06-15 13:10 ` Christoph Hellwig
2021-06-15 13:10 ` [PATCH 15/16] nvme-multipath: set QUEUE_FLAG_NOWAIT Christoph Hellwig
2021-06-15 13:10 ` Christoph Hellwig
2021-06-15 13:10 ` [PATCH 16/16] nvme-multipath: enable polled I/O Christoph Hellwig
2021-06-15 13:10 ` Christoph Hellwig
2021-06-15 14:37 ` switch block layer polling to a bio based model v4 Keith Busch
2021-06-15 14:37 ` Keith Busch
2021-06-15 16:06 ` Christoph Hellwig
2021-06-15 16:06 ` Christoph Hellwig
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