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Date: Wed, 29 Nov 2017 12:54:10 +0800
From: Ming Lei <ming.lei@redhat.com>
To: "chenxiang (M)" <chenxiang66@hisilicon.com>
Cc: Jens Axboe <axboe@fb.com>, linux-block@vger.kernel.org,
        Christoph Hellwig <hch@infradead.org>,
        Omar Sandoval <osandov@fb.com>,
        Bart Van Assche <bart.vanassche@sandisk.com>,
        Hannes Reinecke <hare@suse.com>,
        Wen Xiong <wenxiong@us.ibm.com>,
        Mauricio Faria de Oliveira <mauricfo@linux.vnet.ibm.com>,
        Linuxarm <linuxarm@huawei.com>
Subject: Re: [PATCH V2 0/2] block: fix queue freeze and cleanup
Message-ID: <20171129045408.GB11430@ming.t460p>
References: <20171123044800.25251-1-ming.lei@redhat.com>
 <20171127124147.GA16095@ming.t460p>
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Hi Chenxiang,

On Wed, Nov 29, 2017 at 10:57:06AM +0800, chenxiang (M) wrote:
> 在 2017/11/27 20:41, Ming Lei 写道:
> > On Thu, Nov 23, 2017 at 12:47:58PM +0800, Ming Lei wrote:
> > > Hi Jens,
> > > 
> > > The 1st patch runs queue in blk_freeze_queue_start() for fixing one
> > > regression by 055f6e18e08f("block: Make q_usage_counter also track legacy
> > > requests").
> > > 
> > > The 2nd patch drians blkcg part of request_queue for both blk-mq and
> > > legacy, which can be a fix on blk-mq's queue cleanup.
> > > 
> > > V2:
> > > 	- follow Bart's suggestion to use run queue instead of drain queue
> > > 	- drians blkcg part of request_queue for blk-mq
> > > 
> > Hi Jens,
> > 
> > Without this patchset, IO hang can be triggered in Mauricio's disk
> > pull test, and this IO hang won't happen any more after this patchset
> > is applied.
> > 
> > So could you make it in V4.15 if you are fine with the two patches?
> 
> Hi Lei Ming,
> 
> I applied this v2 patchset to kernel 4.15-rc1, running fio on a SATA disk,
> then disable the disk with sysfs interface

I guess it is a SAS disk?

> (echo 0 > /sys/class/sas_phy/phy-1:0:1/enable), and find system is hung. But
> with v1 patch, it doesn't
> has this issue. Please have a check.

Thanks for your test!

Then looks even though V2 can fix Mauricio's issue, it still can't fix
yours, which is a regression caused by 055f6e18e08f("block: Make q_usage_counter
also track legacy requests").

Given V1 can fix both your issue and Mauricio's, I will post V3 which falls
back to original V1.


Thanks,
Ming