From 21037b8c2258ec40de3b31be9ced43ceb3b784f7 Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Tue, 5 Oct 2021 10:17:59 -0400 Subject: [PATCH] xprtrdma: Provide a buffer to pad Write chunks of unaligned length This is a buffer to be left persistently registered while a connection is up. Connection tear-down will automatically DMA-unmap, invalidate, and dereg the MR. A persistently registered buffer is lower in cost to provide, and it can never be coalesced into the RDMA segment that carries the data payload. An RPC that provisions a Write chunk with a non-aligned length now uses this MR rather than the tail buffer of the RPC's rq_rcv_buf. Reviewed-By: Tom Talpey Signed-off-by: Chuck Lever Signed-off-by: Trond Myklebust --- include/trace/events/rpcrdma.h | 13 ++++++++++--- net/sunrpc/xprtrdma/frwr_ops.c | 35 +++++++++++++++++++++++++++++++++++ net/sunrpc/xprtrdma/rpc_rdma.c | 23 ++++++++++++++--------- net/sunrpc/xprtrdma/verbs.c | 1 + net/sunrpc/xprtrdma/xprt_rdma.h | 5 +++++ 5 files changed, 65 insertions(+), 12 deletions(-) diff --git a/include/trace/events/rpcrdma.h b/include/trace/events/rpcrdma.h index de41954..afb2e39 100644 --- a/include/trace/events/rpcrdma.h +++ b/include/trace/events/rpcrdma.h @@ -375,10 +375,16 @@ DECLARE_EVENT_CLASS(xprtrdma_mr_class, TP_fast_assign( const struct rpcrdma_req *req = mr->mr_req; - const struct rpc_task *task = req->rl_slot.rq_task; - __entry->task_id = task->tk_pid; - __entry->client_id = task->tk_client->cl_clid; + if (req) { + const struct rpc_task *task = req->rl_slot.rq_task; + + __entry->task_id = task->tk_pid; + __entry->client_id = task->tk_client->cl_clid; + } else { + __entry->task_id = 0; + __entry->client_id = -1; + } __entry->mr_id = mr->mr_ibmr->res.id; __entry->nents = mr->mr_nents; __entry->handle = mr->mr_handle; @@ -639,6 +645,7 @@ TRACE_EVENT(xprtrdma_nomrs_err, DEFINE_RDCH_EVENT(read); DEFINE_WRCH_EVENT(write); DEFINE_WRCH_EVENT(reply); +DEFINE_WRCH_EVENT(wp); TRACE_DEFINE_ENUM(rpcrdma_noch); TRACE_DEFINE_ENUM(rpcrdma_noch_pullup); diff --git a/net/sunrpc/xprtrdma/frwr_ops.c b/net/sunrpc/xprtrdma/frwr_ops.c index f700b34..3eccf36 100644 --- a/net/sunrpc/xprtrdma/frwr_ops.c +++ b/net/sunrpc/xprtrdma/frwr_ops.c @@ -666,3 +666,38 @@ void frwr_unmap_async(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req) */ rpcrdma_force_disconnect(ep); } + +/** + * frwr_wp_create - Create an MR for padding Write chunks + * @r_xprt: transport resources to use + * + * Return 0 on success, negative errno on failure. + */ +int frwr_wp_create(struct rpcrdma_xprt *r_xprt) +{ + struct rpcrdma_ep *ep = r_xprt->rx_ep; + struct rpcrdma_mr_seg seg; + struct rpcrdma_mr *mr; + + mr = rpcrdma_mr_get(r_xprt); + if (!mr) + return -EAGAIN; + mr->mr_req = NULL; + ep->re_write_pad_mr = mr; + + seg.mr_len = XDR_UNIT; + seg.mr_page = virt_to_page(ep->re_write_pad); + seg.mr_offset = offset_in_page(ep->re_write_pad); + if (IS_ERR(frwr_map(r_xprt, &seg, 1, true, xdr_zero, mr))) + return -EIO; + trace_xprtrdma_mr_fastreg(mr); + + mr->mr_cqe.done = frwr_wc_fastreg; + mr->mr_regwr.wr.next = NULL; + mr->mr_regwr.wr.wr_cqe = &mr->mr_cqe; + mr->mr_regwr.wr.num_sge = 0; + mr->mr_regwr.wr.opcode = IB_WR_REG_MR; + mr->mr_regwr.wr.send_flags = 0; + + return ib_post_send(ep->re_id->qp, &mr->mr_regwr.wr, NULL); +} diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c index c335c136..8035a98 100644 --- a/net/sunrpc/xprtrdma/rpc_rdma.c +++ b/net/sunrpc/xprtrdma/rpc_rdma.c @@ -255,15 +255,7 @@ rpcrdma_convert_iovs(struct rpcrdma_xprt *r_xprt, struct xdr_buf *xdrbuf, page_base = 0; } - if (type == rpcrdma_readch) - goto out; - - /* When encoding a Write chunk, some servers need to see an - * extra segment for non-XDR-aligned Write chunks. The upper - * layer provides space in the tail iovec that may be used - * for this purpose. - */ - if (type == rpcrdma_writech && r_xprt->rx_ep->re_implicit_roundup) + if (type == rpcrdma_readch || type == rpcrdma_writech) goto out; if (xdrbuf->tail[0].iov_len) @@ -405,6 +397,7 @@ static int rpcrdma_encode_write_list(struct rpcrdma_xprt *r_xprt, enum rpcrdma_chunktype wtype) { struct xdr_stream *xdr = &req->rl_stream; + struct rpcrdma_ep *ep = r_xprt->rx_ep; struct rpcrdma_mr_seg *seg; struct rpcrdma_mr *mr; int nsegs, nchunks; @@ -443,6 +436,18 @@ static int rpcrdma_encode_write_list(struct rpcrdma_xprt *r_xprt, nsegs -= mr->mr_nents; } while (nsegs); + if (xdr_pad_size(rqst->rq_rcv_buf.page_len)) { + if (encode_rdma_segment(xdr, ep->re_write_pad_mr) < 0) + return -EMSGSIZE; + + trace_xprtrdma_chunk_wp(rqst->rq_task, ep->re_write_pad_mr, + nsegs); + r_xprt->rx_stats.write_chunk_count++; + r_xprt->rx_stats.total_rdma_request += mr->mr_length; + nchunks++; + nsegs -= mr->mr_nents; + } + /* Update count of segments in this Write chunk */ *segcount = cpu_to_be32(nchunks); diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c index aaec3c9..c3784b7 100644 --- a/net/sunrpc/xprtrdma/verbs.c +++ b/net/sunrpc/xprtrdma/verbs.c @@ -551,6 +551,7 @@ int rpcrdma_xprt_connect(struct rpcrdma_xprt *r_xprt) goto out; } rpcrdma_mrs_create(r_xprt); + frwr_wp_create(r_xprt); out: trace_xprtrdma_connect(r_xprt, rc); diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h index d91f54e..b6d8b3e 100644 --- a/net/sunrpc/xprtrdma/xprt_rdma.h +++ b/net/sunrpc/xprtrdma/xprt_rdma.h @@ -68,12 +68,14 @@ /* * RDMA Endpoint -- connection endpoint details */ +struct rpcrdma_mr; struct rpcrdma_ep { struct kref re_kref; struct rdma_cm_id *re_id; struct ib_pd *re_pd; unsigned int re_max_rdma_segs; unsigned int re_max_fr_depth; + struct rpcrdma_mr *re_write_pad_mr; bool re_implicit_roundup; enum ib_mr_type re_mrtype; struct completion re_done; @@ -97,6 +99,8 @@ struct rpcrdma_ep { unsigned int re_inline_recv; /* negotiated */ atomic_t re_completion_ids; + + char re_write_pad[XDR_UNIT]; }; /* Pre-allocate extra Work Requests for handling reverse-direction @@ -535,6 +539,7 @@ int frwr_send(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req); void frwr_reminv(struct rpcrdma_rep *rep, struct list_head *mrs); void frwr_unmap_sync(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req); void frwr_unmap_async(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req); +int frwr_wp_create(struct rpcrdma_xprt *r_xprt); /* * RPC/RDMA protocol calls - xprtrdma/rpc_rdma.c -- 2.7.4