From: Bart Van Assche <Bart.VanAssche@wdc.com>
To: "jbacik@fb.com" <jbacik@fb.com>, "tj@kernel.org" <tj@kernel.org>,
"jack@suse.cz" <jack@suse.cz>, "clm@fb.com" <clm@fb.com>,
"axboe@kernel.dk" <axboe@kernel.dk>
Cc: "kernel-team@fb.com" <kernel-team@fb.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"peterz@infradead.org" <peterz@infradead.org>,
"linux-btrfs@vger.kernel.org" <linux-btrfs@vger.kernel.org>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
"jianchao.w.wang@oracle.com" <jianchao.w.wang@oracle.com>
Subject: Re: [PATCH 6/8] blk-mq: remove REQ_ATOM_COMPLETE usages from blk-mq
Date: Mon, 8 Jan 2018 23:36:20 +0000 [thread overview]
Message-ID: <1515454580.2909.39.camel@wdc.com> (raw)
In-Reply-To: <20180108191542.379478-7-tj@kernel.org>
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WARNING: multiple messages have this Message-ID (diff)
From: Bart Van Assche <Bart.VanAssche@wdc.com>
To: "jbacik@fb.com" <jbacik@fb.com>, "tj@kernel.org" <tj@kernel.org>,
"jack@suse.cz" <jack@suse.cz>, "clm@fb.com" <clm@fb.com>,
"axboe@kernel.dk" <axboe@kernel.dk>
Cc: "kernel-team@fb.com" <kernel-team@fb.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"peterz@infradead.org" <peterz@infradead.org>,
"linux-btrfs@vger.kernel.org" <linux-btrfs@vger.kernel.org>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
"jianchao.w.wang@oracle.com" <jianchao.w.wang@oracle.com>
Subject: Re: [PATCH 6/8] blk-mq: remove REQ_ATOM_COMPLETE usages from blk-mq
Date: Mon, 8 Jan 2018 23:36:20 +0000 [thread overview]
Message-ID: <1515454580.2909.39.camel@wdc.com> (raw)
In-Reply-To: <20180108191542.379478-7-tj@kernel.org>
On Mon, 2018-01-08 at 11:15 -0800, Tejun Heo wrote:
> After the recent updates to use generation number and state based
> synchronization, blk-mq no longer depends on REQ_ATOM_COMPLETE except
> to avoid firing the same timeout multiple times.
>
> Remove all REQ_ATOM_COMPLETE usages and use a new rq_flags flag
> RQF_MQ_TIMEOUT_EXPIRED to avoid firing the same timeout multiple
> times. This removes atomic bitops from hot paths too.
>
> v2: Removed blk_clear_rq_complete() from blk_mq_rq_timed_out().
>
> v3: Added RQF_MQ_TIMEOUT_EXPIRED flag.
I think it's unfortunate that this patch spreads the request state over two
struct request members, namely the lower two bits of gstate and the
RQF_MQ_TIMEOUT_EXPIRED flag in req->rq_flags. Please consider to drop the
RQF_MQ_TIMEOUT_EXPIRED flag and to represent the "timeout has been processed"
state as a MQ_RQ_* state in gstate. That will avoid that every state update
has to be reviewed whether or not perhaps an update of the
RQF_MQ_TIMEOUT_EXPIRED flag is missing.
Thanks,
Bart.
next prev parent reply other threads:[~2018-01-08 23:36 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-08 19:15 [PATCHSET v4] blk-mq: reimplement timeout handling Tejun Heo
2018-01-08 19:15 ` [PATCH 1/8] blk-mq: move hctx lock/unlock into a helper Tejun Heo
2018-01-08 19:24 ` Bart Van Assche
2018-01-08 19:24 ` Bart Van Assche
2018-01-08 19:15 ` [PATCH 2/8] blk-mq: protect completion path with RCU Tejun Heo
2018-01-08 19:57 ` Holger Hoffstätte
2018-01-08 20:15 ` Jens Axboe
2018-01-08 22:55 ` Jens Axboe
2018-01-08 23:27 ` Holger Hoffstätte
2018-01-08 23:33 ` Holger Hoffstätte
2018-01-09 7:08 ` Hannes Reinecke
2018-01-09 15:22 ` Jens Axboe
2018-01-09 16:12 ` Bart Van Assche
2018-01-09 16:12 ` Bart Van Assche
2018-01-09 16:17 ` Jens Axboe
2018-01-09 16:19 ` tj
2018-01-09 16:22 ` Jens Axboe
2018-01-08 19:15 ` [PATCH 3/8] blk-mq: replace timeout synchronization with a RCU and generation based scheme Tejun Heo
2018-01-08 21:06 ` Bart Van Assche
2018-01-08 21:06 ` Bart Van Assche
2018-01-09 15:46 ` tj
2018-01-08 23:29 ` Bart Van Assche
2018-01-08 23:29 ` Bart Van Assche
2018-01-09 15:46 ` tj
2018-01-08 19:15 ` [PATCH 4/8] blk-mq: use blk_mq_rq_state() instead of testing REQ_ATOM_COMPLETE Tejun Heo
2018-01-08 22:03 ` Bart Van Assche
2018-01-08 22:03 ` Bart Van Assche
2018-01-08 19:15 ` [PATCH 5/8] blk-mq: make blk_abort_request() trigger timeout path Tejun Heo
2018-01-08 22:10 ` Bart Van Assche
2018-01-08 22:10 ` Bart Van Assche
2018-01-09 16:02 ` tj
2018-01-08 19:15 ` [PATCH 6/8] blk-mq: remove REQ_ATOM_COMPLETE usages from blk-mq Tejun Heo
2018-01-08 23:36 ` Bart Van Assche [this message]
2018-01-08 23:36 ` Bart Van Assche
2018-01-08 19:15 ` [PATCH 7/8] blk-mq: remove REQ_ATOM_STARTED Tejun Heo
2018-01-08 23:47 ` Bart Van Assche
2018-01-08 23:47 ` Bart Van Assche
2018-01-08 19:15 ` [PATCH 8/8] blk-mq: rename blk_mq_hw_ctx->queue_rq_srcu to ->srcu Tejun Heo
2018-01-08 23:48 ` Bart Van Assche
2018-01-08 23:48 ` Bart Van Assche
2018-01-09 16:29 [PATCHSET v5] blk-mq: reimplement timeout handling Tejun Heo
2018-01-09 16:29 ` [PATCH 6/8] blk-mq: remove REQ_ATOM_COMPLETE usages from blk-mq Tejun Heo
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