From: Tejun Heo <tj@kernel.org>
To: "jianchao.wang" <jianchao.w.wang@oracle.com>
Cc: jbacik@fb.com, jack@suse.cz, axboe@kernel.dk, clm@fb.com,
kernel-team@fb.com, linux-kernel@vger.kernel.org,
linux-btrfs@vger.kernel.org, peterz@infradead.org,
Bart.VanAssche@wdc.com
Subject: Re: [PATCH 5/7] blk-mq: remove REQ_ATOM_COMPLETE usages from blk-mq
Date: Thu, 21 Dec 2017 05:50:51 -0800 [thread overview]
Message-ID: <20171221135051.GE1084507@devbig577.frc2.facebook.com> (raw)
In-Reply-To: <64dfa760-d433-1537-9bc6-b12cda3c9dc6@oracle.com>
Hello,
On Thu, Dec 21, 2017 at 11:56:49AM +0800, jianchao.wang wrote:
> It's worrying that even though the blk_mark_rq_complete() here is intended to synchronize with
> timeout path, but it indeed give the blk_mq_complete_request() the capability to exclude with
> itself. Maybe this capability should be reserved.
Can you explain further how that'd help? The problem there is that if
you have two competing completions, where one isn't a timeout, there's
nothing synchronizing the reuse of the request. IOW, the losing one
can easily complete the next recycle instance. The atomic bitops
might feel like more protection but it's just feels.
Thanks.
--
tejun
next prev parent reply other threads:[~2017-12-21 13:50 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-16 12:07 [PATCHSET v3] blk-mq: reimplement timeout handling Tejun Heo
2017-12-16 12:07 ` [PATCH 1/7] blk-mq: protect completion path with RCU Tejun Heo
2017-12-29 10:04 ` Christoph Hellwig
2018-01-08 17:12 ` Tejun Heo
2017-12-16 12:07 ` [PATCH 2/7] blk-mq: replace timeout synchronization with a RCU and generation based scheme Tejun Heo
2017-12-16 12:07 ` [PATCH 3/7] blk-mq: use blk_mq_rq_state() instead of testing REQ_ATOM_COMPLETE Tejun Heo
2017-12-16 12:07 ` [PATCH 4/7] blk-mq: make blk_abort_request() trigger timeout path Tejun Heo
2017-12-29 10:07 ` Christoph Hellwig
2017-12-16 12:07 ` [PATCH 5/7] blk-mq: remove REQ_ATOM_COMPLETE usages from blk-mq Tejun Heo
2017-12-21 3:56 ` jianchao.wang
2017-12-21 13:50 ` Tejun Heo [this message]
2017-12-22 4:02 ` jianchao.wang
2018-01-08 17:27 ` Tejun Heo
2018-01-09 3:08 ` jianchao.wang
2018-01-09 3:37 ` Tejun Heo
2018-01-09 5:59 ` jianchao.wang
2017-12-16 12:07 ` [PATCH 6/7] blk-mq: remove REQ_ATOM_STARTED Tejun Heo
2017-12-16 12:07 ` [PATCH 7/7] blk-mq: rename blk_mq_hw_ctx->queue_rq_srcu to ->srcu Tejun Heo
2017-12-29 10:02 ` [PATCHSET v3] blk-mq: reimplement timeout handling Christoph Hellwig
2018-01-08 17:03 ` Tejun Heo
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