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Date: Mon, 26 Jan 2026 07:14:33 +0100
From: Christoph Hellwig <hch@lst.de>
To: Chuck Lever <cel@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>, Jason Gunthorpe <jgg@nvidia.com>,
	Leon Romanovsky <leon@kernel.org>, NeilBrown <neilb@ownmail.net>,
	Jeff Layton <jlayton@kernel.org>,
	Olga Kornievskaia <okorniev@redhat.com>,
	Dai Ngo <dai.ngo@oracle.com>, Tom Talpey <tom@talpey.com>,
	linux-rdma@vger.kernel.org, linux-nfs@vger.kernel.org,
	Chuck Lever <chuck.lever@oracle.com>
Subject: Re: [PATCH v3 2/5] RDMA/core: use IOVA-based DMA mapping for bvec
 RDMA operations
Message-ID: <20260126061433.GA1638@lst.de>
References: <20260122220401.1143331-1-cel@kernel.org> <20260122220401.1143331-3-cel@kernel.org> <20260123062844.GB25786@lst.de> <d70b5896-2de8-4417-a149-0fd1c55f4d2d@app.fastmail.com>
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User-Agent: Mutt/1.5.17 (2007-11-01)

On Fri, Jan 23, 2026 at 10:04:07AM -0500, Chuck Lever wrote:
> On Fri, Jan 23, 2026, at 1:28 AM, Christoph Hellwig wrote:
> >> +	/* Link all bvecs into the IOVA space */
> >> +	link_iter = *iter;
> >> +	while (link_iter.bi_size) {
> >> +		struct bio_vec bv = mp_bvec_iter_bvec(bvec, link_iter);
> >> +
> >> +		ret = dma_iova_link(dma_dev, &ctx->iova.state, bvec_phys(&bv),
> >> +				    mapped_len, bv.bv_len, dir, 0);
> >> +		if (ret)
> >> +			goto out_destroy;
> >> +
> >> +		mapped_len += bv.bv_len;
> >> +		bvec_iter_advance(bvec, &link_iter, bv.bv_len);
> >> +	}
> >
> > Why is this using a local link_iter?  We're not using iter later.
> 
> I think we don't want to leak a partially-updated iter if the
> API call returns an error.

That's how all the block layer bvec_iter-based API work.  The
functions consume the iter.  If a caller needs to save it for
some reason, it stashes away a copy.