linux-kernel - Re: [PATCH v2] nvme-tcp: Check if request has started before processing it

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Message-ID: <20210401062031.GA25424@lst.de>
Date:   Thu, 1 Apr 2021 08:20:31 +0200
From:   Christoph Hellwig <hch@....de>
To:     Sagi Grimberg <sagi@...mberg.me>
Cc:     "Ewan D. Milne" <emilne@...hat.com>,
        Hannes Reinecke <hare@...e.de>,
        Keith Busch <kbusch@...nel.org>,
        Daniel Wagner <dwagner@...e.de>,
        linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Jens Axboe <axboe@...com>, Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v2] nvme-tcp: Check if request has started before
 processing it

On Wed, Mar 31, 2021 at 03:24:49PM -0700, Sagi Grimberg wrote:
>
>>> What we can do, though, is checking the 'state' field in the tcp
>>> request, and only allow completions for commands which are in a state
>>> allowing for completions.
>>>
>>> Let's see if I can whip up a patch.
>>
>> That would be great.  BTW in the crash dump I am looking at now, it
>> looks like pdu->command_id was zero in nvme_tcp_recv_data(), and
>> blk_mq_tag_to_rq() returned a request struct that had not been used.
>> So I think we do need to check that the tag was actually allocated.
>
> request tag can't be zero? I forget...

Of course it can.  But the reserved tags are before the normal tags,
so 0 would be a reserved tag for nvme.