Re: [PATCH v1 3/4] RDMA/core: add MR support for bvec-based RDMA operations

[Christoph Hellwig <hch@lst.de>]

On Wed, Jan 14, 2026 at 09:39:47AM -0500, Chuck Lever wrote:
> From: Chuck Lever <chuck.lever@oracle.com>
> 
> The bvec-based RDMA API currently returns -EOPNOTSUPP when Memory
> Region registration is required. This prevents iWARP devices from
> using the bvec path, since iWARP requires MR registration for RDMA
> READ operations. The force_mr debug parameter is also unusable with
> bvec input.
> 
> Add rdma_rw_init_mr_wrs_bvec() to handle MR registration for bvec
> arrays. The approach creates a synthetic scatterlist populated with
> DMA addresses from the bvecs, then reuses the existing ib_map_mr_sg()
> infrastructure. This avoids driver changes while keeping the
> implementation small.
> 
> The synthetic scatterlist is stored in the rdma_rw_ctx for cleanup.
> On destroy, the MRs are returned to the pool and the bvec DMA
> mappings are released using the stored addresses.

I wish we'd just have a bvec based MR API, and could use that.
But I don't want to hold this work back, because of that.