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Date:   Wed, 27 Jul 2022 07:52:27 -0600
From:   Keith Busch <kbusch@kernel.org>
To:     Al Viro <viro@zeniv.linux.org.uk>
Cc:     Keith Busch <kbusch@fb.com>, linux-nvme@lists.infradead.org,
        linux-block@vger.kernel.org, io-uring@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, axboe@kernel.dk, hch@lst.de
Subject: Re: [PATCH 2/5] iov_iter: introduce type for preregistered dma tags
Message-ID: <YuFDG1x/4//TYDNL@kbusch-mbp.dhcp.thefacebook.com>
References: <20220726173814.2264573-1-kbusch@fb.com>
 <20220726173814.2264573-3-kbusch@fb.com>
 <YuB0ado/bhkow+LY@ZenIV>
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On Wed, Jul 27, 2022 at 12:10:33AM +0100, Al Viro wrote:
> On Tue, Jul 26, 2022 at 10:38:11AM -0700, Keith Busch wrote:
> 
> > +void iov_iter_dma_tag(struct iov_iter *i, unsigned int direction,
> > +			void *dma_tag, unsigned int dma_offset,
> > +			unsigned long nr_segs, size_t count)
> > +{
> > +	WARN_ON(direction & ~(READ | WRITE));
> > +	*i = (struct iov_iter){
> > +		.iter_type = ITER_DMA_TAG,
> > +		.data_source = direction,
> > +		.nr_segs = nr_segs,
> 
> Could you can that cargo-culting?  Just what the hell is nr_segs
> here?

Thanks for the catch. Setting nr_segs here is useless carry-over from an
earlier version when I thought it would be used to build the request. Turns out
it's not used at all.