From: Ming Lei <tom.leiming@gmail.com>
To: Bart Van Assche <Bart.VanAssche@sandisk.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"hch@infradead.org" <hch@infradead.org>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
"axboe@fb.com" <axboe@fb.com>,
"yizhan@redhat.com" <yizhan@redhat.com>,
"tj@kernel.org" <tj@kernel.org>
Subject: Re: [PATCH 2/2] blk-mq: start to freeze queue just after setting dying
Date: Fri, 10 Mar 2017 10:16:09 +0800 [thread overview]
Message-ID: <CACVXFVP0e6jdVTtQYWP+Wksycn9wNZ=ehRuVT7bLeDpF_wKEnQ@mail.gmail.com> (raw)
In-Reply-To: <1489078694.2597.5.camel@sandisk.com>
On Fri, Mar 10, 2017 at 12:58 AM, Bart Van Assche
<Bart.VanAssche@sandisk.com> wrote:
> On Thu, 2017-03-09 at 21:02 +0800, Ming Lei wrote:
>> Before commit 780db2071a(blk-mq: decouble blk-mq freezing
>> from generic bypassing), the dying flag is checked before
>> entering queue, and Tejun converts the checking into .mq_freeze_depth,
>> and assumes the counter is increased just after dying flag
>> is set. Unfortunately we doesn't do that in blk_set_queue_dying().
>>
>> This patch calls blk_mq_freeze_queue_start() for blk-mq in
>> blk_set_queue_dying(), so that we can block new I/O coming
>> once the queue is set as dying.
>>
>> Given blk_set_queue_dying() is always called in remove path
>> of block device, and queue will be cleaned up later, we don't
>> need to worry about undo of the counter.
>>
>> Cc: Tejun Heo <tj@kernel.org>
>> Signed-off-by: Ming Lei <tom.leiming@gmail.com>
>> ---
>> block/blk-core.c | 7 +++++--
>> 1 file changed, 5 insertions(+), 2 deletions(-)
>>
>> diff --git a/block/blk-core.c b/block/blk-core.c
>> index 0eeb99ef654f..559487e58296 100644
>> --- a/block/blk-core.c
>> +++ b/block/blk-core.c
>> @@ -500,9 +500,12 @@ void blk_set_queue_dying(struct request_queue *q)
>> queue_flag_set(QUEUE_FLAG_DYING, q);
>> spin_unlock_irq(q->queue_lock);
>>
>> - if (q->mq_ops)
>> + if (q->mq_ops) {
>> blk_mq_wake_waiters(q);
>> - else {
>> +
>> + /* block new I/O coming */
>> + blk_mq_freeze_queue_start(q);
>> + } else {
>> struct request_list *rl;
>>
>> spin_lock_irq(q->queue_lock);
>
> The comment above blk_mq_freeze_queue_start() should explain more clearly
> why that call is needed. Additionally, I think this patch makes the
The comment of "block new I/O coming" has been added, and let me know what
others are needed, :-)
> blk_freeze_queue() call in blk_cleanup_queue() superfluous. How about the
> (entirely untested) patch below?
I don't think we need to wait in blk_set_queue_dying(), and the purpose
of this patch is to block new I/O coming once dying iset as pointed in the
comment, and the change in blk_cleanup_queue() isn't necessary too, since
that is exactly where we should drain the queue.
Thanks,
Ming Lei
prev parent reply other threads:[~2017-03-10 2:16 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-09 13:02 [PATCH 0/2] blk-mq: dying queue fix & improvement Ming Lei
2017-03-09 13:02 ` Ming Lei
2017-03-09 13:02 ` [PATCH 1/2] blk-mq: don't complete un-started request in timeout handler Ming Lei
2017-03-15 0:07 ` Bart Van Assche
2017-03-15 12:18 ` Ming Lei
2017-03-15 12:40 ` Ming Lei
2017-03-15 15:36 ` Bart Van Assche
2017-03-15 16:22 ` Ming Lei
2017-03-15 16:46 ` Ming Lei
2017-03-15 21:35 ` Bart Van Assche
2017-03-16 0:07 ` Ming Lei
2017-03-16 21:35 ` Bart Van Assche
2017-03-17 0:07 ` Ming Lei
2017-03-15 21:34 ` Bart Van Assche
2017-03-15 23:41 ` Ming Lei
2017-03-15 14:11 ` Yi Zhang
2017-03-16 21:37 ` Bart Van Assche
2017-03-09 13:02 ` [PATCH 2/2] blk-mq: start to freeze queue just after setting dying Ming Lei
2017-03-09 16:58 ` Bart Van Assche
2017-03-10 2:16 ` Ming Lei [this message]
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