Re: [PATCH v1 0/4] Add a bio_vec based API to core/rw.c

[Leon Romanovsky <leon@kernel.org>]

On Wed, Jan 14, 2026 at 09:39:44AM -0500, Chuck Lever wrote:
> From: Chuck Lever <chuck.lever@oracle.com>
> 
> This series introduces a bio_vec based API for RDMA read and write
> operations in the RDMA core, eliminating unnecessary scatterlist
> conversions for callers that already work with bvecs.
> 
> Current users of rdma_rw_ctx_init() must convert their native data
> structures into scatterlists. For subsystems like svcrdma that
> maintain data in bvec format, this conversion adds overhead both in
> CPU cycles and memory footprint. The new API accepts bvec arrays
> directly.
> 
> For hardware RDMA devices, the implementation uses the IOVA-based
> DMA mapping API to reduce IOTLB synchronization overhead from O(n)
> per-page syncs to a single O(1) sync after all mappings complete.
> Software RDMA devices (rxe, siw) continue using virtual addressing.
> 
> The series includes MR registration support for bvec arrays,
> enabling iWARP devices and the force_mr debug parameter. The MR
> path reuses existing ib_map_mr_sg() infrastructure by constructing
> a synthetic scatterlist from the bvec DMA addresses.
> 
> The final patch adds the first consumer for the new API: svcrdma.
> It replaces its scatterlist conversion code, significantly reducing
> the svc_rdma_rw_ctxt structure size. The previous implementation
> embedded a scatterlist array of RPCSVC_MAXPAGES entries (4KB or
> more per context); the new implementation uses a pointer to a
> dynamically allocated bvec array.
> 
> Based on v6.19-rc5.
> 
> Chuck Lever (4):
>   RDMA/core: add bio_vec based RDMA read/write API
>   RDMA/core: use IOVA-based DMA mapping for bvec RDMA operations
>   RDMA/core: add MR support for bvec-based RDMA operations
>   svcrdma: use bvec-based RDMA read/write API

Amazing, thanks a lot.

I haven’t done a deep‑dive review yet, but from what I’ve seen so far  
it looks solid and well put together.

Thanks.

> 
>  drivers/infiniband/core/rw.c      | 492 ++++++++++++++++++++++++++++++
>  include/rdma/ib_verbs.h           |  35 +++
>  include/rdma/rw.h                 |  26 ++
>  net/sunrpc/xprtrdma/svc_rdma_rw.c | 115 ++++---
>  4 files changed, 608 insertions(+), 60 deletions(-)
> 
> -- 
> 2.52.0
>