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

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Message-ID: <20190315092020.GA2405@lst.de>
Date:   Fri, 15 Mar 2019 10:20:20 +0100
From:   Christoph Hellwig <hch@....de>
To:     Jianchao Wang <jianchao.w.wang@...cle.com>
Cc:     axboe@...nel.dk, hch@....de, 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 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).