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Subject: Re: [PATCH] nvme-tcp: Check if request has started before processing
 it
To:     Keith Busch <kbusch@kernel.org>
Cc:     Daniel Wagner <dwagner@suse.de>, linux-nvme@lists.infradead.org,
        linux-kernel@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
        Jens Axboe <axboe@fb.com>, Hannes Reinecke <hare@suse.de>
References: <20210212181738.79274-1-dwagner@suse.de>
 <c3a682d3-58f7-f5cc-caaa-75c36ca464e2@grimberg.me>
 <20210212210929.GA3851@redsun51.ssa.fujisawa.hgst.com>
From:   Sagi Grimberg <sagi@grimberg.me>
Message-ID: <ddf87227-1ad3-b8be-23ba-460433f70a85@grimberg.me>
Date:   Fri, 12 Feb 2021 13:49:32 -0800
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>>> blk_mq_tag_to_rq() will always return a request if the command_id is
>>> in the valid range. Check if the request has been started. If we
>>> blindly process the request we might double complete a request which
>>> can be fatal.
>>
>> How did you get to this one? did the controller send a completion for
>> a completed/bogus request?
> 
> If that is the case, then that must mean it's possible the driver could
> have started the command id just before the bogus completion check. Data
> iorruption, right?

Yes, which is why I don't think this check is very useful..