linux-kernel - Re: [PATCH 0/8]: blk-mq: use static

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Message-ID: <20190315133017.lnr5cvtapo5nxilu@MacBook-Pro-91.local>
Date:   Fri, 15 Mar 2019 09:30:18 -0400
From:   Josef Bacik <josef@...icpanda.com>
To:     Christoph Hellwig <hch@....de>
Cc:     Jianchao Wang <jianchao.w.wang@...cle.com>, axboe@...nel.dk,
        jthumshirn@...e.de, hare@...e.de, josef@...icpanda.com,
        bvanassche@....org, sagi@...mberg.me, keith.busch@...el.com,
        jsmart2021@...il.com, linux-block@...r.kernel.org,
        linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/8]: blk-mq: use static_rqs to iterate busy tags

On Fri, Mar 15, 2019 at 10:20:20AM +0100, Christoph Hellwig wrote:
> On Fri, Mar 15, 2019 at 04:57:36PM +0800, Jianchao Wang wrote:
> > Hi Jens
> > 
> > As we know, there is a risk of accesing stale requests when iterate
> > in-flight requests with tags->rqs[] and this has been talked in following
> > thread,
> > [1] https://marc.info/?l=linux-scsi&m=154511693912752&w=2
> > [2] https://marc.info/?l=linux-block&m=154526189023236&w=2
> 
> I'd rather take one step back and figure out why we are iterating
> the busy requests.  There really shouldn't be any reason why a driver
> is even doings that (vs some error handling helpers in the core
> block code that can properly synchronize).

I use it in NBD to error out any pending requests for forced disconnects.  I'd
be happy to use some other blessed interface, I'm not married to this one.
Thanks,

Josef