linux-kernel - Re: [PATCH 1/3] nvme: do not check for ns on rw path

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Message-ID: <20171106144303.GA11677@localhost.localdomain>
Date:   Mon, 6 Nov 2017 07:43:04 -0700
From:   Keith Busch <keith.busch@...el.com>
To:     Christoph Hellwig <hch@....de>
Cc:     Javier González <jg@...htnvm.io>,
        sagi@...mberg.me, linux-nvme@...ts.infradead.org,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        Javier González <javier@...xlabs.com>
Subject: Re: [PATCH 1/3] nvme: do not check for ns on rw path

On Mon, Nov 06, 2017 at 10:13:24AM +0100, Christoph Hellwig wrote:
> On Sat, Nov 04, 2017 at 09:38:45AM -0600, Keith Busch wrote:
> > That's not quite right. For non-PI metadata formats, we use the
> > 'nop_profile', which gets the metadata buffer allocated so we can safely
> > use a metadata formatted namespace. There's no in-kernel user of the
> > allocated payload, but we still need the metadata buffer in order to
> > use the namespace at all.
> 
> You're right.  But that means we will indeed always have a matching
> integrity payload here and the check should not be needed.
> 
> Are you fine with turning it into something like:
> 
> 	if (WARN_ON_ONCE(ns->ms && !blk_integrity_rq(req)))
> 		return BLK_STS_IOERR;
> 
> ?

Yes, that looks fine. You're right that we are not supposed to be able
to get into this path for read/write since the driver sets the capacity
to 0 if a metadata format doesn't have integrity support, so hitting
this warning would indicate something has gone wrong.