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Date: Fri, 16 Jan 2026 13:33:10 +0200
From: Leon Romanovsky <leon@kernel.org>
To: Christoph Hellwig <hch@lst.de>
Cc: Chuck Lever <cel@kernel.org>, Jason Gunthorpe <jgg@nvidia.com>,
	linux-rdma@vger.kernel.org, linux-nfs@vger.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>,
	Chuck Lever <chuck.lever@oracle.com>
Subject: Re: [PATCH v1 1/4] RDMA/core: add bio_vec based RDMA read/write API
Message-ID: <20260116113310.GF14359@unreal>
References: <20260114143948.3946615-1-cel@kernel.org>
 <20260114143948.3946615-2-cel@kernel.org>
 <20260115155334.GB14083@lst.de>
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In-Reply-To: <20260115155334.GB14083@lst.de>

On Thu, Jan 15, 2026 at 04:53:34PM +0100, Christoph Hellwig wrote:
> > +static int rdma_rw_init_single_wr_bvec(struct rdma_rw_ctx *ctx,
> > +		struct ib_qp *qp, const struct bio_vec *bvec, u32 offset,
> > +		u64 remote_addr, u32 rkey, enum dma_data_direction dir)
> > +{
> > +	struct ib_device *dev = qp->pd->device;
> > +	struct ib_rdma_wr *rdma_wr = &ctx->single.wr;
> > +	struct bio_vec adjusted = *bvec;
> > +	u64 dma_addr;
> > +
> > +	ctx->nr_ops = 1;
> > +
> > +	if (offset) {
> > +		adjusted.bv_offset += offset;
> > +		adjusted.bv_len -= offset;
> > +	}
> 
> Hmm, if we need to split/adjust bvecs, it might be better to
> pass a bvec_iter and let the iter handle the iteration?
> 
> > +static int rdma_rw_init_map_wrs_bvec(struct rdma_rw_ctx *ctx, struct ib_qp *qp,
> > +		const struct bio_vec *bvec, u32 nr_bvec, u32 offset,
> > +		u64 remote_addr, u32 rkey, enum dma_data_direction dir)
> 
> Much of this seems to duplicate rdma_rw_init_map_wrs.  I wonder if
> having a low-level helper that gets either a scatterlist or bvec array
> (or bvec_iter) and just has different inner loops for them would
> make more sense?  If not we'll just need to migrate everyone off
> the scatterlist version ASAP :)

I had short offline discussion with Jason about this series and both of
us would be more than happy to get rid of "scatterlist version".

Thanks