linux-kernel - Re: [PATCH] nvme-tcp: Do not reset transport on data digest errors

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Message-ID: <20210811103146.ytqj5mqpioiba56x@carbon.lan>
Date:   Wed, 11 Aug 2021 12:31:46 +0200
From:   Daniel Wagner <dwagner@...e.de>
To:     Sagi Grimberg <sagi@...mberg.me>
Cc:     linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Hannes Reinecke <hare@...e.de>, yi.he@....com
Subject: Re: [PATCH] nvme-tcp: Do not reset transport on data digest errors

On Tue, Aug 10, 2021 at 06:02:36PM -0700, Sagi Grimberg wrote:
> 
> > Hi Sagi,
> > 
> > On Fri, Aug 06, 2021 at 12:42:00PM -0700, Sagi Grimberg wrote:
> > > > @@ -89,6 +89,7 @@ struct nvme_tcp_queue {
> > > >    	size_t			data_remaining;
> > > >    	size_t			ddgst_remaining;
> > > >    	unsigned int		nr_cqe;
> > > > +	u16			status;
> > > 
> > > Why is this a queue member and not a request member?
> > 
> > I was not sure if the TCP transport specific error handling should
> > impact all other transport (size of struct request). Also I tried to
> > avoid accessing cachelines which are not already in use. Except this I
> > don't see there should be no problem to put this to struct request.
> 
> It is the correct place, lets see that it doesn't increase the struct.

It should not according pahole:

        /* XXX 7 bytes hole, try to pack */

        void *                     pdu;                  /*   144     8 */
        int                        pdu_remaining;        /*   152     4 */
        int                        pdu_offset;           /*   156     4 */
        size_t                     data_remaining;       /*   160     8 */
        size_t                     ddgst_remaining;      /*   168     8 */
        unsigned int               nr_cqe;               /*   176     4 */
        u16                        status;               /*   180     2 */

        /* XXX 2 bytes hole, try to pack */

Daniel