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The FRWR registration path converts data through three representations: xdr_buf -> rpcrdma_mr_seg[] -> scatterlist[] -> ib_map_mr_sg(). The rpcrdma_mr_seg intermediate is a relic of when multiple registration strategies existed (FMR, physical, FRWR). Only FRWR remains, so this indirection and the 6240-byte rl_segments[260] array embedded in each rpcrdma_req serve no purpose. Introduce struct rpcrdma_xdr_cursor to track position within an xdr_buf during iterative MR registration. Rewrite frwr_map to populate scatterlist entries directly from the xdr_buf regions (head kvec, page list, tail kvec). The boundary logic for non-SG_GAPS devices is simpler because the xdr_buf structure guarantees that page-region entries after the first start at offset 0, and that head/tail kvecs are separate regions that naturally break at MR boundaries. Fix a pre-existing bug in rpcrdma_encode_write_list where the write-pad statistics accumulator added mr->mr_length from the last data MR rather than the write-pad MR. The refactored code uses ep->re_write_pad_mr->mr_length. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>