[PATCH v1 00/16] NFS/RDMA server patches maybe for v5.7

[PATCH v1 00/16] NFS/RDMA server patches maybe for v5.7

[Chuck Lever]

Hey Bruce-

Here's the part of the RFC patch series I recently sent out that is
likely to be ready for the v5.7 merge window. These need a little
more soak-time. Please review them and let me know if there's
something terribly objectionable.

Again, the direction of the larger series is eventual support for
the server's RPC/RDMA transport to deal correctly with multiple
Write chunks in an RPC. Today the server transport supports only
one Write chunk per RPC. That's somewhat less than compliant with
RFC 8166, though good enough for any operation the Linux NFS/RDMA
client uses, and most every operation Solaris can send.

The patches below are clean-ups and optimizations that prepare the
way for multi-Write chunk support.

---

Chuck Lever (16):
      nfsd: Fix NFSv4 READ on RDMA when using readv
      NFSD: Clean up nfsd4_encode_readv
      svcrdma: Fix double svc_rdma_send_ctxt_put() in an error path
      SUNRPC: Add xdr_pad_size() helper
      svcrdma: Create a generic tracing class for displaying xdr_buf layout
      svcrdma: Remove svcrdma_cm_event() trace point
      svcrdma: Use struct xdr_stream to decode ingress transport headers
      svcrdma: De-duplicate code that locates Write and Reply chunks
      svcrdma: Update synopsis of svc_rdma_send_reply_chunk()
      svcrdma: Update synopsis of svc_rdma_map_reply_msg()
      svcrdma: Update synopsis of svc_rdma_send_reply_msg()
      svcrdma: Rename svcrdma_encode trace points in send routines
      SUNRPC: Add encoders for list item discriminators
      svcrdma: Refactor chunk list encoders
      svcrdma: Fix double sync of transport header buffer
      svcrdma: Avoid DMA mapping small RPC Replies


 fs/nfsd/nfs4xdr.c                          |   29 +-
 include/linux/sunrpc/rpc_rdma.h            |    3 
 include/linux/sunrpc/svc.h                 |    3 
 include/linux/sunrpc/svc_rdma.h            |   23 +
 include/linux/sunrpc/svc_xprt.h            |    2 
 include/linux/sunrpc/xdr.h                 |   54 +++
 include/trace/events/rpcrdma.h             |   67 ++--
 include/trace/events/sunrpc.h              |   43 ++
 net/sunrpc/auth_gss/auth_gss.c             |    4 
 net/sunrpc/auth_gss/svcauth_gss.c          |    4 
 net/sunrpc/svc.c                           |   16 +
 net/sunrpc/svc_xprt.c                      |    6 
 net/sunrpc/svcsock.c                       |    8 
 net/sunrpc/xprt.c                          |    4 
 net/sunrpc/xprtrdma/rpc_rdma.c             |   39 --
 net/sunrpc/xprtrdma/svc_rdma_backchannel.c |   16 +
 net/sunrpc/xprtrdma/svc_rdma_recvfrom.c    |  248 +++++++++-----
 net/sunrpc/xprtrdma/svc_rdma_rw.c          |   55 ++-
 net/sunrpc/xprtrdma/svc_rdma_sendto.c      |  504 ++++++++++++++++------------
 net/sunrpc/xprtrdma/svc_rdma_transport.c   |    8 
 20 files changed, 693 insertions(+), 443 deletions(-)

--
Chuck Lever

[PATCH v1 01/16] nfsd: Fix NFSv4 READ on RDMA when using readv

[Chuck Lever]

svcrdma expects that the payload falls precisely into the xdr_buf
page vector. This does not seem to be the case for
nfsd4_encode_readv().

This code is called only when fops->splice_read is missing or when
RQ_SPLICE_OK is clear, so it's not a noticeable problem in many
common cases.

Add new transport method: ->xpo_read_payload so that when a READ
payload does not fit exactly in rq_res's page vector, the XDR
encoder can inform the RPC transport exactly where that payload is,
without the payload's XDR pad.

That way, when a Write chunk is present, the transport knows what
byte range in the Reply message is supposed to be matched with the
chunk.

Note that the Linux NFS server implementation of NFS/RDMA can
currently handle only one Write chunk per RPC-over-RDMA message.
This simplifies the implementation of this fix.

Fixes: b04209806384 ("nfsd4: allow exotic read compounds")
Buglink: https://bugzilla.kernel.org/show_bug.cgi?id=198053
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 fs/nfsd/nfs4xdr.c                        |   20 ++++++++-------
 include/linux/sunrpc/svc.h               |    3 ++
 include/linux/sunrpc/svc_rdma.h          |    8 +++++-
 include/linux/sunrpc/svc_xprt.h          |    2 ++
 net/sunrpc/svc.c                         |   16 ++++++++++++
 net/sunrpc/svcsock.c                     |    8 ++++++
 net/sunrpc/xprtrdma/svc_rdma_recvfrom.c  |    1 +
 net/sunrpc/xprtrdma/svc_rdma_rw.c        |   30 ++++++++++++++---------
 net/sunrpc/xprtrdma/svc_rdma_sendto.c    |   40 +++++++++++++++++++++++++++++-
 net/sunrpc/xprtrdma/svc_rdma_transport.c |    1 +
 10 files changed, 106 insertions(+), 23 deletions(-)

diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 9761512674a0..60be969d8be1 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -3594,17 +3594,17 @@ static __be32 nfsd4_encode_readv(struct nfsd4_compoundres *resp,
 	u32 zzz = 0;
 	int pad;
 
+	/*
+	 * svcrdma requires every READ payload to start somewhere
+	 * in xdr->pages.
+	 */
+	if (xdr->iov == xdr->buf->head) {
+		xdr->iov = NULL;
+		xdr->end = xdr->p;
+	}
+
 	len = maxcount;
 	v = 0;
-
-	thislen = min_t(long, len, ((void *)xdr->end - (void *)xdr->p));
-	p = xdr_reserve_space(xdr, (thislen+3)&~3);
-	WARN_ON_ONCE(!p);
-	resp->rqstp->rq_vec[v].iov_base = p;
-	resp->rqstp->rq_vec[v].iov_len = thislen;
-	v++;
-	len -= thislen;
-
 	while (len) {
 		thislen = min_t(long, len, PAGE_SIZE);
 		p = xdr_reserve_space(xdr, (thislen+3)&~3);
@@ -3623,6 +3623,8 @@ static __be32 nfsd4_encode_readv(struct nfsd4_compoundres *resp,
 	read->rd_length = maxcount;
 	if (nfserr)
 		return nfserr;
+	if (svc_encode_read_payload(resp->rqstp, starting_len + 8, maxcount))
+		return nfserr_io;
 	xdr_truncate_encode(xdr, starting_len + 8 + ((maxcount+3)&~3));
 
 	tmp = htonl(eof);
diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 1afe38eb33f7..82665ff360fd 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -517,6 +517,9 @@ void		   svc_wake_up(struct svc_serv *);
 void		   svc_reserve(struct svc_rqst *rqstp, int space);
 struct svc_pool *  svc_pool_for_cpu(struct svc_serv *serv, int cpu);
 char *		   svc_print_addr(struct svc_rqst *, char *, size_t);
+int		   svc_encode_read_payload(struct svc_rqst *rqstp,
+					   unsigned int offset,
+					   unsigned int length);
 unsigned int	   svc_fill_write_vector(struct svc_rqst *rqstp,
 					 struct page **pages,
 					 struct kvec *first, size_t total);
diff --git a/include/linux/sunrpc/svc_rdma.h b/include/linux/sunrpc/svc_rdma.h
index 40f65888dd38..04e4a34d1c6a 100644
--- a/include/linux/sunrpc/svc_rdma.h
+++ b/include/linux/sunrpc/svc_rdma.h
@@ -137,6 +137,8 @@ struct svc_rdma_recv_ctxt {
 	unsigned int		rc_page_count;
 	unsigned int		rc_hdr_count;
 	u32			rc_inv_rkey;
+	unsigned int		rc_read_payload_offset;
+	unsigned int		rc_read_payload_length;
 	struct page		*rc_pages[RPCSVC_MAXPAGES];
 };
 
@@ -170,7 +172,9 @@ extern int svc_rdma_recv_read_chunk(struct svcxprt_rdma *rdma,
 				    struct svc_rqst *rqstp,
 				    struct svc_rdma_recv_ctxt *head, __be32 *p);
 extern int svc_rdma_send_write_chunk(struct svcxprt_rdma *rdma,
-				     __be32 *wr_ch, struct xdr_buf *xdr);
+				     __be32 *wr_ch, struct xdr_buf *xdr,
+				     unsigned int offset,
+				     unsigned long length);
 extern int svc_rdma_send_reply_chunk(struct svcxprt_rdma *rdma,
 				     __be32 *rp_ch, bool writelist,
 				     struct xdr_buf *xdr);
@@ -189,6 +193,8 @@ extern int svc_rdma_map_reply_msg(struct svcxprt_rdma *rdma,
 				  struct svc_rdma_send_ctxt *ctxt,
 				  struct xdr_buf *xdr, __be32 *wr_lst);
 extern int svc_rdma_sendto(struct svc_rqst *);
+extern int svc_rdma_read_payload(struct svc_rqst *rqstp, unsigned int offset,
+				 unsigned int length);
 
 /* svc_rdma_transport.c */
 extern int svc_rdma_create_listen(struct svc_serv *, int, struct sockaddr *);
diff --git a/include/linux/sunrpc/svc_xprt.h b/include/linux/sunrpc/svc_xprt.h
index ea6f46be9cb7..9e1e046de176 100644
--- a/include/linux/sunrpc/svc_xprt.h
+++ b/include/linux/sunrpc/svc_xprt.h
@@ -21,6 +21,8 @@ struct svc_xprt_ops {
 	int		(*xpo_has_wspace)(struct svc_xprt *);
 	int		(*xpo_recvfrom)(struct svc_rqst *);
 	int		(*xpo_sendto)(struct svc_rqst *);
+	int		(*xpo_read_payload)(struct svc_rqst *, unsigned int,
+					    unsigned int);
 	void		(*xpo_release_rqst)(struct svc_rqst *);
 	void		(*xpo_detach)(struct svc_xprt *);
 	void		(*xpo_free)(struct svc_xprt *);
diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index 187dd4e73d64..18676d36f490 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -1636,6 +1636,22 @@ u32 svc_max_payload(const struct svc_rqst *rqstp)
 }
 EXPORT_SYMBOL_GPL(svc_max_payload);
 
+/**
+ * svc_encode_read_payload - mark a range of bytes as a READ payload
+ * @rqstp: svc_rqst to operate on
+ * @offset: payload's byte offset in rqstp->rq_res
+ * @length: size of payload, in bytes
+ *
+ * Returns zero on success, or a negative errno if a permanent
+ * error occurred.
+ */
+int svc_encode_read_payload(struct svc_rqst *rqstp, unsigned int offset,
+			    unsigned int length)
+{
+	return rqstp->rq_xprt->xpt_ops->xpo_read_payload(rqstp, offset, length);
+}
+EXPORT_SYMBOL_GPL(svc_encode_read_payload);
+
 /**
  * svc_fill_write_vector - Construct data argument for VFS write call
  * @rqstp: svc_rqst to operate on
diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index 2934dd711715..758ab10690de 100644
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -279,6 +279,12 @@ static int svc_sendto(struct svc_rqst *rqstp, struct xdr_buf *xdr)
 	return len;
 }
 
+static int svc_sock_read_payload(struct svc_rqst *rqstp, unsigned int offset,
+				 unsigned int length)
+{
+	return 0;
+}
+
 /*
  * Report socket names for nfsdfs
  */
@@ -653,6 +659,7 @@ static const struct svc_xprt_ops svc_udp_ops = {
 	.xpo_create = svc_udp_create,
 	.xpo_recvfrom = svc_udp_recvfrom,
 	.xpo_sendto = svc_udp_sendto,
+	.xpo_read_payload = svc_sock_read_payload,
 	.xpo_release_rqst = svc_release_udp_skb,
 	.xpo_detach = svc_sock_detach,
 	.xpo_free = svc_sock_free,
@@ -1171,6 +1178,7 @@ static const struct svc_xprt_ops svc_tcp_ops = {
 	.xpo_create = svc_tcp_create,
 	.xpo_recvfrom = svc_tcp_recvfrom,
 	.xpo_sendto = svc_tcp_sendto,
+	.xpo_read_payload = svc_sock_read_payload,
 	.xpo_release_rqst = svc_release_skb,
 	.xpo_detach = svc_tcp_sock_detach,
 	.xpo_free = svc_sock_free,
diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
index 96bccd398469..71127d898562 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
@@ -193,6 +193,7 @@ svc_rdma_recv_ctxt_get(struct svcxprt_rdma *rdma)
 
 out:
 	ctxt->rc_page_count = 0;
+	ctxt->rc_read_payload_length = 0;
 	return ctxt;
 
 out_empty:
diff --git a/net/sunrpc/xprtrdma/svc_rdma_rw.c b/net/sunrpc/xprtrdma/svc_rdma_rw.c
index 48fe3b16b0d9..b0ac535c8728 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_rw.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_rw.c
@@ -482,18 +482,19 @@ static int svc_rdma_send_xdr_kvec(struct svc_rdma_write_info *info,
 				     vec->iov_len);
 }
 
-/* Send an xdr_buf's page list by itself. A Write chunk is
- * just the page list. a Reply chunk is the head, page list,
- * and tail. This function is shared between the two types
- * of chunk.
+/* Send an xdr_buf's page list by itself. A Write chunk is just
+ * the page list. A Reply chunk is @xdr's head, page list, and
+ * tail. This function is shared between the two types of chunk.
  */
 static int svc_rdma_send_xdr_pagelist(struct svc_rdma_write_info *info,
-				      struct xdr_buf *xdr)
+				      struct xdr_buf *xdr,
+				      unsigned int offset,
+				      unsigned long length)
 {
 	info->wi_xdr = xdr;
-	info->wi_next_off = 0;
+	info->wi_next_off = offset - xdr->head[0].iov_len;
 	return svc_rdma_build_writes(info, svc_rdma_pagelist_to_sg,
-				     xdr->page_len);
+				     length);
 }
 
 /**
@@ -501,6 +502,8 @@ static int svc_rdma_send_xdr_pagelist(struct svc_rdma_write_info *info,
  * @rdma: controlling RDMA transport
  * @wr_ch: Write chunk provided by client
  * @xdr: xdr_buf containing the data payload
+ * @offset: payload's byte offset in @xdr
+ * @length: size of payload, in bytes
  *
  * Returns a non-negative number of bytes the chunk consumed, or
  *	%-E2BIG if the payload was larger than the Write chunk,
@@ -510,19 +513,20 @@ static int svc_rdma_send_xdr_pagelist(struct svc_rdma_write_info *info,
  *	%-EIO if rdma_rw initialization failed (DMA mapping, etc).
  */
 int svc_rdma_send_write_chunk(struct svcxprt_rdma *rdma, __be32 *wr_ch,
-			      struct xdr_buf *xdr)
+			      struct xdr_buf *xdr,
+			      unsigned int offset, unsigned long length)
 {
 	struct svc_rdma_write_info *info;
 	int ret;
 
-	if (!xdr->page_len)
+	if (!length)
 		return 0;
 
 	info = svc_rdma_write_info_alloc(rdma, wr_ch);
 	if (!info)
 		return -ENOMEM;
 
-	ret = svc_rdma_send_xdr_pagelist(info, xdr);
+	ret = svc_rdma_send_xdr_pagelist(info, xdr, offset, length);
 	if (ret < 0)
 		goto out_err;
 
@@ -531,7 +535,7 @@ int svc_rdma_send_write_chunk(struct svcxprt_rdma *rdma, __be32 *wr_ch,
 		goto out_err;
 
 	trace_svcrdma_encode_write(xdr->page_len);
-	return xdr->page_len;
+	return length;
 
 out_err:
 	svc_rdma_write_info_free(info);
@@ -571,7 +575,9 @@ int svc_rdma_send_reply_chunk(struct svcxprt_rdma *rdma, __be32 *rp_ch,
 	 * client did not provide Write chunks.
 	 */
 	if (!writelist && xdr->page_len) {
-		ret = svc_rdma_send_xdr_pagelist(info, xdr);
+		ret = svc_rdma_send_xdr_pagelist(info, xdr,
+						 xdr->head[0].iov_len,
+						 xdr->page_len);
 		if (ret < 0)
 			goto out_err;
 		consumed += xdr->page_len;
diff --git a/net/sunrpc/xprtrdma/svc_rdma_sendto.c b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
index f3f108090aa4..a11983c2056f 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_sendto.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
@@ -858,7 +858,18 @@ int svc_rdma_sendto(struct svc_rqst *rqstp)
 
 	if (wr_lst) {
 		/* XXX: Presume the client sent only one Write chunk */
-		ret = svc_rdma_send_write_chunk(rdma, wr_lst, xdr);
+		unsigned long offset;
+		unsigned int length;
+
+		if (rctxt->rc_read_payload_length) {
+			offset = rctxt->rc_read_payload_offset;
+			length = rctxt->rc_read_payload_length;
+		} else {
+			offset = xdr->head[0].iov_len;
+			length = xdr->page_len;
+		}
+		ret = svc_rdma_send_write_chunk(rdma, wr_lst, xdr, offset,
+						length);
 		if (ret < 0)
 			goto err2;
 		svc_rdma_xdr_encode_write_list(rdma_resp, wr_lst, ret);
@@ -900,3 +911,30 @@ int svc_rdma_sendto(struct svc_rqst *rqstp)
 	ret = -ENOTCONN;
 	goto out;
 }
+
+/**
+ * svc_rdma_read_payload - special processing for a READ payload
+ * @rqstp: svc_rqst to operate on
+ * @offset: payload's byte offset in @xdr
+ * @length: size of payload, in bytes
+ *
+ * Returns zero on success.
+ *
+ * For the moment, just record the xdr_buf location of the READ
+ * payload. svc_rdma_sendto will use that location later when
+ * we actually send the payload.
+ */
+int svc_rdma_read_payload(struct svc_rqst *rqstp, unsigned int offset,
+			  unsigned int length)
+{
+	struct svc_rdma_recv_ctxt *rctxt = rqstp->rq_xprt_ctxt;
+
+	/* XXX: Just one READ payload slot for now, since our
+	 * transport implementation currently supports only one
+	 * Write chunk.
+	 */
+	rctxt->rc_read_payload_offset = offset;
+	rctxt->rc_read_payload_length = length;
+
+	return 0;
+}
diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c
index 145a3615c319..f6aad2798063 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_transport.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c
@@ -82,6 +82,7 @@ static const struct svc_xprt_ops svc_rdma_ops = {
 	.xpo_create = svc_rdma_create,
 	.xpo_recvfrom = svc_rdma_recvfrom,
 	.xpo_sendto = svc_rdma_sendto,
+	.xpo_read_payload = svc_rdma_read_payload,
 	.xpo_release_rqst = svc_rdma_release_rqst,
 	.xpo_detach = svc_rdma_detach,
 	.xpo_free = svc_rdma_free,

[PATCH v1 02/16] NFSD: Clean up nfsd4_encode_readv

[Chuck Lever]

Address some minor nits I noticed while working on this function.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 fs/nfsd/nfs4xdr.c |    9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 60be969d8be1..262f9fc76e4e 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -3591,7 +3591,6 @@ static __be32 nfsd4_encode_readv(struct nfsd4_compoundres *resp,
 	__be32 nfserr;
 	__be32 tmp;
 	__be32 *p;
-	u32 zzz = 0;
 	int pad;
 
 	/*
@@ -3607,7 +3606,7 @@ static __be32 nfsd4_encode_readv(struct nfsd4_compoundres *resp,
 	v = 0;
 	while (len) {
 		thislen = min_t(long, len, PAGE_SIZE);
-		p = xdr_reserve_space(xdr, (thislen+3)&~3);
+		p = xdr_reserve_space(xdr, thislen);
 		WARN_ON_ONCE(!p);
 		resp->rqstp->rq_vec[v].iov_base = p;
 		resp->rqstp->rq_vec[v].iov_len = thislen;
@@ -3616,7 +3615,6 @@ static __be32 nfsd4_encode_readv(struct nfsd4_compoundres *resp,
 	}
 	read->rd_vlen = v;
 
-	len = maxcount;
 	nfserr = nfsd_readv(resp->rqstp, read->rd_fhp, file, read->rd_offset,
 			    resp->rqstp->rq_vec, read->rd_vlen, &maxcount,
 			    &eof);
@@ -3625,16 +3623,17 @@ static __be32 nfsd4_encode_readv(struct nfsd4_compoundres *resp,
 		return nfserr;
 	if (svc_encode_read_payload(resp->rqstp, starting_len + 8, maxcount))
 		return nfserr_io;
-	xdr_truncate_encode(xdr, starting_len + 8 + ((maxcount+3)&~3));
+	xdr_truncate_encode(xdr, starting_len + 8 + xdr_align_size(maxcount));
 
 	tmp = htonl(eof);
 	write_bytes_to_xdr_buf(xdr->buf, starting_len    , &tmp, 4);
 	tmp = htonl(maxcount);
 	write_bytes_to_xdr_buf(xdr->buf, starting_len + 4, &tmp, 4);
 
+	tmp = xdr_zero;
 	pad = (maxcount&3) ? 4 - (maxcount&3) : 0;
 	write_bytes_to_xdr_buf(xdr->buf, starting_len + 8 + maxcount,
-								&zzz, pad);
+								&tmp, pad);
 	return 0;
 
 }

[PATCH v1 03/16] svcrdma: Fix double svc_rdma_send_ctxt_put() in an error path

[Chuck Lever]

This error path is almost never executed. Found by code inspection.

Fixes: 99722fe4d5a6 ("svcrdma: Persistently allocate and DMA-map Send buffers")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 net/sunrpc/xprtrdma/svc_rdma_sendto.c |    9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/net/sunrpc/xprtrdma/svc_rdma_sendto.c b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
index a11983c2056f..354c5619176a 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_sendto.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
@@ -786,7 +786,6 @@ static int svc_rdma_send_error_msg(struct svcxprt_rdma *rdma,
 				   struct svc_rqst *rqstp)
 {
 	__be32 *p;
-	int ret;
 
 	p = ctxt->sc_xprt_buf;
 	trace_svcrdma_err_chunk(*p);
@@ -798,13 +797,7 @@ static int svc_rdma_send_error_msg(struct svcxprt_rdma *rdma,
 	svc_rdma_save_io_pages(rqstp, ctxt);
 
 	ctxt->sc_send_wr.opcode = IB_WR_SEND;
-	ret = svc_rdma_send(rdma, &ctxt->sc_send_wr);
-	if (ret) {
-		svc_rdma_send_ctxt_put(rdma, ctxt);
-		return ret;
-	}
-
-	return 0;
+	return svc_rdma_send(rdma, &ctxt->sc_send_wr);
 }
 
 /**

[PATCH v1 04/16] SUNRPC: Add xdr_pad_size() helper

[Chuck Lever]

Introduce a helper function to compute the XDR pad size of a
variable-length XDR object.

Clean up: Replace open-coded calculation of XDR pad sizes.
I'm sure I haven't found every instance of this calculation.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 include/linux/sunrpc/xdr.h            |   16 ++++++++++++++++
 net/sunrpc/auth_gss/auth_gss.c        |    4 ++--
 net/sunrpc/auth_gss/svcauth_gss.c     |    4 ++--
 net/sunrpc/xprtrdma/rpc_rdma.c        |    3 ++-
 net/sunrpc/xprtrdma/svc_rdma_sendto.c |    9 ++-------
 5 files changed, 24 insertions(+), 12 deletions(-)

diff --git a/include/linux/sunrpc/xdr.h b/include/linux/sunrpc/xdr.h
index b41f34977995..80972512edfd 100644
--- a/include/linux/sunrpc/xdr.h
+++ b/include/linux/sunrpc/xdr.h
@@ -300,6 +300,22 @@ xdr_align_size(size_t n)
 	return (n + mask) & ~mask;
 }
 
+/**
+ * xdr_pad_size - Calculate size of an object's pad
+ * @n: Size of an object being XDR encoded (in bytes)
+ *
+ * This implementation avoids the need for conditional
+ * branches or modulo division.
+ *
+ * Return value:
+ *   Size (in bytes) of the needed XDR pad
+ */
+static inline size_t
+xdr_pad_size(size_t n)
+{
+	return xdr_align_size(n) - n;
+}
+
 /**
  * xdr_stream_encode_u32 - Encode a 32-bit integer
  * @xdr: pointer to xdr_stream
diff --git a/net/sunrpc/auth_gss/auth_gss.c b/net/sunrpc/auth_gss/auth_gss.c
index 24ca861815b1..60a8f46973dc 100644
--- a/net/sunrpc/auth_gss/auth_gss.c
+++ b/net/sunrpc/auth_gss/auth_gss.c
@@ -1877,7 +1877,7 @@ static int gss_wrap_req_priv(struct rpc_cred *cred, struct gss_cl_ctx *ctx,
 	else
 		iov = snd_buf->head;
 	p = iov->iov_base + iov->iov_len;
-	pad = 3 - ((snd_buf->len - offset - 1) & 3);
+	pad = xdr_pad_size(snd_buf->len - offset);
 	memset(p, 0, pad);
 	iov->iov_len += pad;
 	snd_buf->len += pad;
@@ -1949,7 +1949,7 @@ gss_unwrap_resp_integ(struct rpc_task *task, struct rpc_cred *cred,
 	if (unlikely(!p))
 		goto unwrap_failed;
 	integ_len = be32_to_cpup(p++);
-	if (integ_len & 3)
+	if (xdr_pad_size(integ_len))
 		goto unwrap_failed;
 	data_offset = (u8 *)(p) - (u8 *)rcv_buf->head[0].iov_base;
 	mic_offset = integ_len + data_offset;
diff --git a/net/sunrpc/auth_gss/svcauth_gss.c b/net/sunrpc/auth_gss/svcauth_gss.c
index 65b67b257302..dd03096922c9 100644
--- a/net/sunrpc/auth_gss/svcauth_gss.c
+++ b/net/sunrpc/auth_gss/svcauth_gss.c
@@ -961,7 +961,7 @@ unwrap_priv_data(struct svc_rqst *rqstp, struct xdr_buf *buf, u32 seq, struct gs
 	/* XXX: This is very inefficient.  It would be better to either do
 	 * this while we encrypt, or maybe in the receive code, if we can peak
 	 * ahead and work out the service and mechanism there. */
-	offset = buf->head[0].iov_len % 4;
+	offset = xdr_pad_size(buf->head[0].iov_len);
 	if (offset) {
 		buf->buflen = RPCSVC_MAXPAYLOAD;
 		xdr_shift_buf(buf, offset);
@@ -1680,7 +1680,7 @@ svcauth_gss_wrap_resp_integ(struct svc_rqst *rqstp)
 		goto out;
 	integ_offset = (u8 *)(p + 1) - (u8 *)resbuf->head[0].iov_base;
 	integ_len = resbuf->len - integ_offset;
-	BUG_ON(integ_len % 4);
+	BUG_ON(xdr_pad_size(integ_len));
 	*p++ = htonl(integ_len);
 	*p++ = htonl(gc->gc_seq);
 	if (xdr_buf_subsegment(resbuf, &integ_buf, integ_offset, integ_len)) {
diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
index 28020ec104d4..b51e92d43dfd 100644
--- a/net/sunrpc/xprtrdma/rpc_rdma.c
+++ b/net/sunrpc/xprtrdma/rpc_rdma.c
@@ -1305,7 +1305,8 @@ rpcrdma_decode_msg(struct rpcrdma_xprt *r_xprt, struct rpcrdma_rep *rep,
 	base = (char *)xdr_inline_decode(xdr, 0);
 	rpclen = xdr_stream_remaining(xdr);
 	r_xprt->rx_stats.fixup_copy_count +=
-		rpcrdma_inline_fixup(rqst, base, rpclen, writelist & 3);
+		rpcrdma_inline_fixup(rqst, base, rpclen,
+				     xdr_pad_size(writelist));
 
 	r_xprt->rx_stats.total_rdma_reply += writelist;
 	return rpclen + xdr_align_size(writelist);
diff --git a/net/sunrpc/xprtrdma/svc_rdma_sendto.c b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
index 354c5619176a..4add875277f8 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_sendto.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
@@ -322,11 +322,6 @@ int svc_rdma_send(struct svcxprt_rdma *rdma, struct ib_send_wr *wr)
 	return ret;
 }
 
-static u32 xdr_padsize(u32 len)
-{
-	return (len & 3) ? (4 - (len & 3)) : 0;
-}
-
 /* Returns length of transport header, in bytes.
  */
 static unsigned int svc_rdma_reply_hdr_len(__be32 *rdma_resp)
@@ -595,7 +590,7 @@ static int svc_rdma_pull_up_reply_msg(struct svcxprt_rdma *rdma,
 	if (wr_lst) {
 		u32 xdrpad;
 
-		xdrpad = xdr_padsize(xdr->page_len);
+		xdrpad = xdr_pad_size(xdr->page_len);
 		if (taillen && xdrpad) {
 			tailbase += xdrpad;
 			taillen -= xdrpad;
@@ -670,7 +665,7 @@ int svc_rdma_map_reply_msg(struct svcxprt_rdma *rdma,
 	if (wr_lst) {
 		base = xdr->tail[0].iov_base;
 		len = xdr->tail[0].iov_len;
-		xdr_pad = xdr_padsize(xdr->page_len);
+		xdr_pad = xdr_pad_size(xdr->page_len);
 
 		if (len && xdr_pad) {
 			base += xdr_pad;

[PATCH v1 05/16] svcrdma: Create a generic tracing class for displaying xdr_buf layout

[Chuck Lever]

This class can be used to create trace points in either the RPC
client or RPC server paths. It simply displays the length of each
part of an xdr_buf, which is useful to determine that the transport
and XDR codecs are operating correctly.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 include/trace/events/sunrpc.h |   43 +++++++++++++++++++++++++++++++++++++++++
 net/sunrpc/svc_xprt.c         |    6 +++++-
 net/sunrpc/xprt.c             |    4 ++--
 3 files changed, 50 insertions(+), 3 deletions(-)

diff --git a/include/trace/events/sunrpc.h b/include/trace/events/sunrpc.h
index ee993575d2fa..1577223add43 100644
--- a/include/trace/events/sunrpc.h
+++ b/include/trace/events/sunrpc.h
@@ -14,6 +14,49 @@
 #include <linux/net.h>
 #include <linux/tracepoint.h>
 
+DECLARE_EVENT_CLASS(xdr_buf_class,
+	TP_PROTO(
+		const struct xdr_buf *xdr
+	),
+
+	TP_ARGS(xdr),
+
+	TP_STRUCT__entry(
+		__field(const void *, head_base)
+		__field(size_t, head_len)
+		__field(const void *, tail_base)
+		__field(size_t, tail_len)
+		__field(unsigned int, page_len)
+		__field(unsigned int, msg_len)
+	),
+
+	TP_fast_assign(
+		__entry->head_base = xdr->head[0].iov_base;
+		__entry->head_len = xdr->head[0].iov_len;
+		__entry->tail_base = xdr->tail[0].iov_base;
+		__entry->tail_len = xdr->tail[0].iov_len;
+		__entry->page_len = xdr->page_len;
+		__entry->msg_len = xdr->len;
+	),
+
+	TP_printk("head=[%p,%zu] page=%u tail=[%p,%zu] len=%u",
+		__entry->head_base, __entry->head_len, __entry->page_len,
+		__entry->tail_base, __entry->tail_len, __entry->msg_len
+	)
+);
+
+#define DEFINE_XDRBUF_EVENT(name)					\
+		DEFINE_EVENT(xdr_buf_class, name,			\
+				TP_PROTO(				\
+					const struct xdr_buf *xdr	\
+				),					\
+				TP_ARGS(xdr))
+
+DEFINE_XDRBUF_EVENT(xprt_sendto);
+DEFINE_XDRBUF_EVENT(xprt_recvfrom);
+DEFINE_XDRBUF_EVENT(svc_recvfrom);
+DEFINE_XDRBUF_EVENT(svc_sendto);
+
 TRACE_DEFINE_ENUM(RPC_AUTH_OK);
 TRACE_DEFINE_ENUM(RPC_AUTH_BADCRED);
 TRACE_DEFINE_ENUM(RPC_AUTH_REJECTEDCRED);
diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
index de3c077733a7..081564449e98 100644
--- a/net/sunrpc/svc_xprt.c
+++ b/net/sunrpc/svc_xprt.c
@@ -802,6 +802,8 @@ static int svc_handle_xprt(struct svc_rqst *rqstp, struct svc_xprt *xprt)
 			len = svc_deferred_recv(rqstp);
 		else
 			len = xprt->xpt_ops->xpo_recvfrom(rqstp);
+		if (len > 0)
+			trace_svc_recvfrom(&rqstp->rq_arg);
 		rqstp->rq_stime = ktime_get();
 		rqstp->rq_reserved = serv->sv_max_mesg;
 		atomic_add(rqstp->rq_reserved, &xprt->xpt_reserved);
@@ -912,8 +914,10 @@ int svc_send(struct svc_rqst *rqstp)
 	if (test_bit(XPT_DEAD, &xprt->xpt_flags)
 			|| test_bit(XPT_CLOSE, &xprt->xpt_flags))
 		len = -ENOTCONN;
-	else
+	else {
+		trace_svc_sendto(xb);
 		len = xprt->xpt_ops->xpo_sendto(rqstp);
+	}
 	mutex_unlock(&xprt->xpt_mutex);
 	trace_svc_send(rqstp, len);
 	svc_xprt_release(rqstp);
diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index 1aafe8d3f3f4..30989d9b61a0 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -1117,9 +1117,8 @@ void xprt_complete_rqst(struct rpc_task *task, int copied)
 	struct rpc_rqst *req = task->tk_rqstp;
 	struct rpc_xprt *xprt = req->rq_xprt;
 
-	dprintk("RPC: %5u xid %08x complete (%d bytes received)\n",
-			task->tk_pid, ntohl(req->rq_xid), copied);
 	trace_xprt_complete_rqst(xprt, req->rq_xid, copied);
+	trace_xprt_recvfrom(&req->rq_rcv_buf);
 
 	xprt->stat.recvs++;
 
@@ -1462,6 +1461,7 @@ xprt_request_transmit(struct rpc_rqst *req, struct rpc_task *snd_task)
 	 */
 	req->rq_ntrans++;
 
+	trace_xprt_sendto(&req->rq_snd_buf);
 	connect_cookie = xprt->connect_cookie;
 	status = xprt->ops->send_request(req);
 	if (status != 0) {

[PATCH v1 06/16] svcrdma: Remove svcrdma_cm_event() trace point

[Chuck Lever]

Clean up. This trace point is no longer needed because the RDMA/core
CMA code has an equivalent trace point that was added by commit
ed999f820a6c ("RDMA/cma: Add trace points in RDMA Connection
Manager").

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 include/trace/events/rpcrdma.h           |   28 ----------------------------
 net/sunrpc/xprtrdma/svc_rdma_transport.c |    7 -------
 2 files changed, 35 deletions(-)

diff --git a/include/trace/events/rpcrdma.h b/include/trace/events/rpcrdma.h
index c0e4c93324f5..545fe936a0cc 100644
--- a/include/trace/events/rpcrdma.h
+++ b/include/trace/events/rpcrdma.h
@@ -1813,34 +1813,6 @@ TRACE_EVENT(svcrdma_post_rw,
 DEFINE_SENDCOMP_EVENT(read);
 DEFINE_SENDCOMP_EVENT(write);
 
-TRACE_EVENT(svcrdma_cm_event,
-	TP_PROTO(
-		const struct rdma_cm_event *event,
-		const struct sockaddr *sap
-	),
-
-	TP_ARGS(event, sap),
-
-	TP_STRUCT__entry(
-		__field(unsigned int, event)
-		__field(int, status)
-		__array(__u8, addr, INET6_ADDRSTRLEN + 10)
-	),
-
-	TP_fast_assign(
-		__entry->event = event->event;
-		__entry->status = event->status;
-		snprintf(__entry->addr, sizeof(__entry->addr) - 1,
-			 "%pISpc", sap);
-	),
-
-	TP_printk("addr=%s event=%s (%u/%d)",
-		__entry->addr,
-		rdma_show_cm_event(__entry->event),
-		__entry->event, __entry->status
-	)
-);
-
 TRACE_EVENT(svcrdma_qp_error,
 	TP_PROTO(
 		const struct ib_event *event,
diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c
index f6aad2798063..8bb99980ae85 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_transport.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c
@@ -241,10 +241,6 @@ static void handle_connect_req(struct rdma_cm_id *new_cma_id,
 static int rdma_listen_handler(struct rdma_cm_id *cma_id,
 			       struct rdma_cm_event *event)
 {
-	struct sockaddr *sap = (struct sockaddr *)&cma_id->route.addr.src_addr;
-
-	trace_svcrdma_cm_event(event, sap);
-
 	switch (event->event) {
 	case RDMA_CM_EVENT_CONNECT_REQUEST:
 		dprintk("svcrdma: Connect request on cma_id=%p, xprt = %p, "
@@ -266,12 +262,9 @@ static int rdma_listen_handler(struct rdma_cm_id *cma_id,
 static int rdma_cma_handler(struct rdma_cm_id *cma_id,
 			    struct rdma_cm_event *event)
 {
-	struct sockaddr *sap = (struct sockaddr *)&cma_id->route.addr.dst_addr;
 	struct svcxprt_rdma *rdma = cma_id->context;
 	struct svc_xprt *xprt = &rdma->sc_xprt;
 
-	trace_svcrdma_cm_event(event, sap);
-
 	switch (event->event) {
 	case RDMA_CM_EVENT_ESTABLISHED:
 		/* Accept complete */

[PATCH v1 07/16] svcrdma: Use struct xdr_stream to decode ingress transport headers

[Chuck Lever]

The logic that checks incoming network headers has to be scrupulous.

De-duplicate: replace open-coded buffer overflow checks with the use
of xdr_stream helpers that are used most everywhere else XDR
decoding is done.

One minor change to the sanity checks: instead of checking the
length of individual segments, cap the length of the whole chunk
to be sure it can fit in the set of pages available in rq_pages.
This should be a better test of whether the server can handle the
chunks in each request.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 include/linux/sunrpc/rpc_rdma.h         |    3 
 include/linux/sunrpc/svc_rdma.h         |    1 
 include/trace/events/rpcrdma.h          |    7 +
 net/sunrpc/xprtrdma/svc_rdma_recvfrom.c |  207 +++++++++++++++++++------------
 4 files changed, 131 insertions(+), 87 deletions(-)

diff --git a/include/linux/sunrpc/rpc_rdma.h b/include/linux/sunrpc/rpc_rdma.h
index 92d182fd8e3b..320c672d84de 100644
--- a/include/linux/sunrpc/rpc_rdma.h
+++ b/include/linux/sunrpc/rpc_rdma.h
@@ -58,7 +58,8 @@ enum {
 enum {
 	rpcrdma_fixed_maxsz	= 4,
 	rpcrdma_segment_maxsz	= 4,
-	rpcrdma_readchunk_maxsz	= 2 + rpcrdma_segment_maxsz,
+	rpcrdma_readseg_maxsz	= 1 + rpcrdma_segment_maxsz,
+	rpcrdma_readchunk_maxsz	= 1 + rpcrdma_readseg_maxsz,
 };
 
 /*
diff --git a/include/linux/sunrpc/svc_rdma.h b/include/linux/sunrpc/svc_rdma.h
index 04e4a34d1c6a..c790dbb0dd90 100644
--- a/include/linux/sunrpc/svc_rdma.h
+++ b/include/linux/sunrpc/svc_rdma.h
@@ -132,6 +132,7 @@ struct svc_rdma_recv_ctxt {
 	struct ib_sge		rc_recv_sge;
 	void			*rc_recv_buf;
 	struct xdr_buf		rc_arg;
+	struct xdr_stream	rc_stream;
 	bool			rc_temp;
 	u32			rc_byte_len;
 	unsigned int		rc_page_count;
diff --git a/include/trace/events/rpcrdma.h b/include/trace/events/rpcrdma.h
index 545fe936a0cc..814b73bd2cc7 100644
--- a/include/trace/events/rpcrdma.h
+++ b/include/trace/events/rpcrdma.h
@@ -1469,7 +1469,7 @@ DECLARE_EVENT_CLASS(svcrdma_segment_event,
 );
 
 #define DEFINE_SEGMENT_EVENT(name)					\
-		DEFINE_EVENT(svcrdma_segment_event, svcrdma_encode_##name,\
+		DEFINE_EVENT(svcrdma_segment_event, svcrdma_##name,\
 				TP_PROTO(				\
 					u32 handle,			\
 					u32 length,			\
@@ -1477,8 +1477,9 @@ DECLARE_EVENT_CLASS(svcrdma_segment_event,
 				),					\
 				TP_ARGS(handle, length, offset))
 
-DEFINE_SEGMENT_EVENT(rseg);
-DEFINE_SEGMENT_EVENT(wseg);
+DEFINE_SEGMENT_EVENT(decode_wseg);
+DEFINE_SEGMENT_EVENT(encode_rseg);
+DEFINE_SEGMENT_EVENT(encode_wseg);
 
 DECLARE_EVENT_CLASS(svcrdma_chunk_event,
 	TP_PROTO(
diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
index 71127d898562..7db151b7dfd3 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
@@ -358,15 +358,14 @@ static void svc_rdma_build_arg_xdr(struct svc_rqst *rqstp,
 	arg->len = ctxt->rc_byte_len;
 }
 
-/* This accommodates the largest possible Write chunk,
- * in one segment.
+/* This accommodates the largest possible Write chunk.
  */
-#define MAX_BYTES_WRITE_SEG	((u32)(RPCSVC_MAXPAGES << PAGE_SHIFT))
+#define MAX_BYTES_WRITE_CHUNK	((u32)(RPCSVC_MAXPAGES << PAGE_SHIFT))
 
 /* This accommodates the largest possible Position-Zero
- * Read chunk or Reply chunk, in one segment.
+ * Read chunk or Reply chunk.
  */
-#define MAX_BYTES_SPECIAL_SEG	((u32)((RPCSVC_MAXPAGES + 2) << PAGE_SHIFT))
+#define MAX_BYTES_SPECIAL_CHUNK	((u32)((RPCSVC_MAXPAGES + 2) << PAGE_SHIFT))
 
 /* Sanity check the Read list.
  *
@@ -374,7 +373,7 @@ static void svc_rdma_build_arg_xdr(struct svc_rqst *rqstp,
  * - This implementation supports only one Read chunk.
  *
  * Sanity checks:
- * - Read list does not overflow buffer.
+ * - Read list does not overflow Receive buffer.
  * - Segment size limited by largest NFS data payload.
  *
  * The segment count is limited to how many segments can
@@ -382,30 +381,44 @@ static void svc_rdma_build_arg_xdr(struct svc_rqst *rqstp,
  * buffer. That's about 40 Read segments for a 1KB inline
  * threshold.
  *
- * Returns pointer to the following Write list.
+ * Return values:
+ *       %true: Read list is valid. @rctxt's xdr_stream is updated
+ *		to point to the first byte past the Read list.
+ *      %false: Read list is corrupt. @rctxt's xdr_stream is left
+ *      	in an unknown state.
  */
-static __be32 *xdr_check_read_list(__be32 *p, const __be32 *end)
+static bool xdr_check_read_list(struct svc_rdma_recv_ctxt *rctxt)
 {
-	u32 position;
+	u32 position, len;
 	bool first;
+	__be32 *p;
+
+	p = xdr_inline_decode(&rctxt->rc_stream, sizeof(*p));
+	if (!p)
+		return false;
 
+	len = 0;
 	first = true;
-	while (*p++ != xdr_zero) {
+	while (*p != xdr_zero) {
+		p = xdr_inline_decode(&rctxt->rc_stream,
+				      rpcrdma_readseg_maxsz * sizeof(*p));
+		if (!p)
+			return false;
+
 		if (first) {
-			position = be32_to_cpup(p++);
+			position = be32_to_cpup(p);
 			first = false;
-		} else if (be32_to_cpup(p++) != position) {
-			return NULL;
+		} else if (be32_to_cpup(p) != position) {
+			return false;
 		}
-		p++;	/* handle */
-		if (be32_to_cpup(p++) > MAX_BYTES_SPECIAL_SEG)
-			return NULL;
-		p += 2;	/* offset */
+		p += 2;
+		len += be32_to_cpup(p);
 
-		if (p > end)
-			return NULL;
+		p = xdr_inline_decode(&rctxt->rc_stream, sizeof(*p));
+		if (!p)
+			return false;
 	}
-	return p;
+	return len <= MAX_BYTES_SPECIAL_CHUNK;
 }
 
 /* The segment count is limited to how many segments can
@@ -413,67 +426,94 @@ static __be32 *xdr_check_read_list(__be32 *p, const __be32 *end)
  * buffer. That's about 60 Write segments for a 1KB inline
  * threshold.
  */
-static __be32 *xdr_check_write_chunk(__be32 *p, const __be32 *end,
-				     u32 maxlen)
+static bool xdr_check_write_chunk(struct svc_rdma_recv_ctxt *rctxt,
+				  u32 maxlen)
 {
-	u32 i, segcount;
+	u32 i, segcount, total;
+	__be32 *p;
+
+	p = xdr_inline_decode(&rctxt->rc_stream, sizeof(*p));
+	if (!p)
+		return false;
+	segcount = be32_to_cpup(p);
 
-	segcount = be32_to_cpup(p++);
+	total = 0;
 	for (i = 0; i < segcount; i++) {
-		p++;	/* handle */
-		if (be32_to_cpup(p++) > maxlen)
-			return NULL;
-		p += 2;	/* offset */
+		u32 handle, length;
+		u64 offset;
 
-		if (p > end)
-			return NULL;
-	}
+		p = xdr_inline_decode(&rctxt->rc_stream,
+				      rpcrdma_segment_maxsz * sizeof(*p));
+		if (!p)
+			return false;
+
+		handle = be32_to_cpup(p++);
+		length = be32_to_cpup(p++);
+		xdr_decode_hyper(p, &offset);
+		trace_svcrdma_decode_wseg(handle, length, offset);
 
-	return p;
+		total += length;
+	}
+	return total <= maxlen;
 }
 
 /* Sanity check the Write list.
  *
  * Implementation limits:
- * - This implementation supports only one Write chunk.
+ * - This implementation currently supports only one Write chunk.
  *
  * Sanity checks:
- * - Write list does not overflow buffer.
- * - Segment size limited by largest NFS data payload.
- *
- * Returns pointer to the following Reply chunk.
+ * - Write list does not overflow Receive buffer.
+ * - Chunk size limited by largest NFS data payload.
+ *
+ * Return values:
+ *       %true: Write list is valid. @rctxt's xdr_stream is updated
+ *		to point to the first byte past the Write list.
+ *      %false: Write list is corrupt. @rctxt's xdr_stream is left
+ *      	in an unknown state.
  */
-static __be32 *xdr_check_write_list(__be32 *p, const __be32 *end)
+static bool xdr_check_write_list(struct svc_rdma_recv_ctxt *rctxt)
 {
-	u32 chcount;
+	u32 chcount = 0;
+	__be32 *p;
 
-	chcount = 0;
-	while (*p++ != xdr_zero) {
-		p = xdr_check_write_chunk(p, end, MAX_BYTES_WRITE_SEG);
+	p = xdr_inline_decode(&rctxt->rc_stream, sizeof(*p));
+	if (!p)
+		return false;
+	while (*p != xdr_zero) {
+		if (!xdr_check_write_chunk(rctxt, MAX_BYTES_WRITE_CHUNK))
+			return false;
+		++chcount;
+		p = xdr_inline_decode(&rctxt->rc_stream, sizeof(*p));
 		if (!p)
-			return NULL;
-		if (chcount++ > 1)
-			return NULL;
+			return false;
 	}
-	return p;
+	return chcount < 2;
 }
 
 /* Sanity check the Reply chunk.
  *
  * Sanity checks:
- * - Reply chunk does not overflow buffer.
- * - Segment size limited by largest NFS data payload.
- *
- * Returns pointer to the following RPC header.
+ * - Reply chunk does not overflow Receive buffer.
+ * - Chunk size limited by largest NFS data payload.
+ *
+ * Return values:
+ *       %true: Reply chunk is valid. @rctxt's xdr_stream is updated
+ *		to point to the first byte past the Reply chunk.
+ *      %false: Reply chunk is corrupt. @rctxt's xdr_stream is left
+ *      	in an unknown state.
  */
-static __be32 *xdr_check_reply_chunk(__be32 *p, const __be32 *end)
+static bool xdr_check_reply_chunk(struct svc_rdma_recv_ctxt *rctxt)
 {
-	if (*p++ != xdr_zero) {
-		p = xdr_check_write_chunk(p, end, MAX_BYTES_SPECIAL_SEG);
-		if (!p)
-			return NULL;
-	}
-	return p;
+	__be32 *p;
+
+	p = xdr_inline_decode(&rctxt->rc_stream, sizeof(*p));
+	if (!p)
+		return false;
+	if (*p != xdr_zero)
+		if (!xdr_check_write_chunk(rctxt, MAX_BYTES_SPECIAL_CHUNK))
+			return false;
+	return true;
 }
 
 /* RPC-over-RDMA Version One private extension: Remote Invalidation.
@@ -538,60 +578,61 @@ static void svc_rdma_get_inv_rkey(struct svcxprt_rdma *rdma,
 	ctxt->rc_inv_rkey = be32_to_cpu(inv_rkey);
 }
 
-/* On entry, xdr->head[0].iov_base points to first byte in the
- * RPC-over-RDMA header.
+/**
+ * svc_rdma_xdr_decode_req - Decode the transport header
+ * @rq_arg: xdr_buf containing ingress RPC/RDMA message
+ * @rctxt: state of decoding
+ *
+ * On entry, xdr->head[0].iov_base points to first byte of the
+ * RPC-over-RDMA transport header.
  *
  * On successful exit, head[0] points to first byte past the
  * RPC-over-RDMA header. For RDMA_MSG, this is the RPC message.
+ *
  * The length of the RPC-over-RDMA header is returned.
  *
  * Assumptions:
  * - The transport header is entirely contained in the head iovec.
  */
-static int svc_rdma_xdr_decode_req(struct xdr_buf *rq_arg)
+static int svc_rdma_xdr_decode_req(struct xdr_buf *rq_arg,
+				   struct svc_rdma_recv_ctxt *rctxt)
 {
-	__be32 *p, *end, *rdma_argp;
+	__be32 *p, *rdma_argp;
 	unsigned int hdr_len;
 
-	/* Verify that there's enough bytes for header + something */
-	if (rq_arg->len <= RPCRDMA_HDRLEN_ERR)
-		goto out_short;
-
 	rdma_argp = rq_arg->head[0].iov_base;
-	if (*(rdma_argp + 1) != rpcrdma_version)
-		goto out_version;
+	xdr_init_decode(&rctxt->rc_stream, rq_arg, rdma_argp, NULL);
 
-	switch (*(rdma_argp + 3)) {
+	p = xdr_inline_decode(&rctxt->rc_stream,
+			      rpcrdma_fixed_maxsz * sizeof(*p));
+	if (unlikely(!p))
+		goto out_short;
+	p++;
+	if (*p != rpcrdma_version)
+		goto out_version;
+	p += 2;
+	switch (*p) {
 	case rdma_msg:
 		break;
 	case rdma_nomsg:
 		break;
-
 	case rdma_done:
 		goto out_drop;
-
 	case rdma_error:
 		goto out_drop;
-
 	default:
 		goto out_proc;
 	}
 
-	end = (__be32 *)((unsigned long)rdma_argp + rq_arg->len);
-	p = xdr_check_read_list(rdma_argp + 4, end);
-	if (!p)
+	if (!xdr_check_read_list(rctxt))
 		goto out_inval;
-	p = xdr_check_write_list(p, end);
-	if (!p)
-		goto out_inval;
-	p = xdr_check_reply_chunk(p, end);
-	if (!p)
+	if (!xdr_check_write_list(rctxt))
 		goto out_inval;
-	if (p > end)
+	if (!xdr_check_reply_chunk(rctxt))
 		goto out_inval;
 
-	rq_arg->head[0].iov_base = p;
-	hdr_len = (unsigned long)p - (unsigned long)rdma_argp;
+	rq_arg->head[0].iov_base = rctxt->rc_stream.p;
+	hdr_len = xdr_stream_pos(&rctxt->rc_stream);
 	rq_arg->head[0].iov_len -= hdr_len;
 	rq_arg->len -= hdr_len;
 	trace_svcrdma_decode_rqst(rdma_argp, hdr_len);
@@ -786,7 +827,7 @@ int svc_rdma_recvfrom(struct svc_rqst *rqstp)
 	rqstp->rq_next_page = rqstp->rq_respages;
 
 	p = (__be32 *)rqstp->rq_arg.head[0].iov_base;
-	ret = svc_rdma_xdr_decode_req(&rqstp->rq_arg);
+	ret = svc_rdma_xdr_decode_req(&rqstp->rq_arg, ctxt);
 	if (ret < 0)
 		goto out_err;
 	if (ret == 0)

[PATCH v1 08/16] svcrdma: De-duplicate code that locates Write and Reply chunks

[Chuck Lever]

Cache the locations of the Requester-provided Write list and Reply
chunk so that the Send path doesn't need to parse the Call header
again.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 include/linux/sunrpc/svc_rdma.h         |    2 ++
 net/sunrpc/xprtrdma/svc_rdma_recvfrom.c |    8 ++++++-
 net/sunrpc/xprtrdma/svc_rdma_sendto.c   |   38 +++----------------------------
 3 files changed, 13 insertions(+), 35 deletions(-)

diff --git a/include/linux/sunrpc/svc_rdma.h b/include/linux/sunrpc/svc_rdma.h
index c790dbb0dd90..e714e4d90ac5 100644
--- a/include/linux/sunrpc/svc_rdma.h
+++ b/include/linux/sunrpc/svc_rdma.h
@@ -138,6 +138,8 @@ struct svc_rdma_recv_ctxt {
 	unsigned int		rc_page_count;
 	unsigned int		rc_hdr_count;
 	u32			rc_inv_rkey;
+	__be32			*rc_write_list;
+	__be32			*rc_reply_chunk;
 	unsigned int		rc_read_payload_offset;
 	unsigned int		rc_read_payload_length;
 	struct page		*rc_pages[RPCSVC_MAXPAGES];
diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
index 7db151b7dfd3..f9a3c413491c 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
@@ -480,6 +480,7 @@ static bool xdr_check_write_list(struct svc_rdma_recv_ctxt *rctxt)
 	p = xdr_inline_decode(&rctxt->rc_stream, sizeof(*p));
 	if (!p)
 		return false;
+	rctxt->rc_write_list = p;
 	while (*p != xdr_zero) {
 		if (!xdr_check_write_chunk(rctxt, MAX_BYTES_WRITE_CHUNK))
 			return false;
@@ -488,6 +489,8 @@ static bool xdr_check_write_list(struct svc_rdma_recv_ctxt *rctxt)
 		if (!p)
 			return false;
 	}
+	if (!chcount)
+		rctxt->rc_write_list = NULL;
 	return chcount < 2;
 }
 
@@ -510,9 +513,12 @@ static bool xdr_check_reply_chunk(struct svc_rdma_recv_ctxt *rctxt)
 	p = xdr_inline_decode(&rctxt->rc_stream, sizeof(*p));
 	if (!p)
 		return false;
-	if (*p != xdr_zero)
+	rctxt->rc_reply_chunk = p;
+	if (*p != xdr_zero) {
 		if (!xdr_check_write_chunk(rctxt, MAX_BYTES_SPECIAL_CHUNK))
 			return false;
+	} else
+		rctxt->rc_reply_chunk = NULL;
 	return true;
 }
 
diff --git a/net/sunrpc/xprtrdma/svc_rdma_sendto.c b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
index 4add875277f8..94895635c007 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_sendto.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
@@ -449,36 +449,6 @@ static void svc_rdma_xdr_encode_reply_chunk(__be32 *rdma_resp, __be32 *rp_ch,
 	xdr_encode_write_chunk(p, rp_ch, consumed);
 }
 
-/* Parse the RPC Call's transport header.
- */
-static void svc_rdma_get_write_arrays(__be32 *rdma_argp,
-				      __be32 **write, __be32 **reply)
-{
-	__be32 *p;
-
-	p = rdma_argp + rpcrdma_fixed_maxsz;
-
-	/* Read list */
-	while (*p++ != xdr_zero)
-		p += 5;
-
-	/* Write list */
-	if (*p != xdr_zero) {
-		*write = p;
-		while (*p++ != xdr_zero)
-			p += 1 + be32_to_cpu(*p) * 4;
-	} else {
-		*write = NULL;
-		p++;
-	}
-
-	/* Reply chunk */
-	if (*p != xdr_zero)
-		*reply = p;
-	else
-		*reply = NULL;
-}
-
 static int svc_rdma_dma_map_page(struct svcxprt_rdma *rdma,
 				 struct svc_rdma_send_ctxt *ctxt,
 				 struct page *page,
@@ -813,14 +783,14 @@ int svc_rdma_sendto(struct svc_rqst *rqstp)
 	struct svcxprt_rdma *rdma =
 		container_of(xprt, struct svcxprt_rdma, sc_xprt);
 	struct svc_rdma_recv_ctxt *rctxt = rqstp->rq_xprt_ctxt;
-	__be32 *p, *rdma_argp, *rdma_resp, *wr_lst, *rp_ch;
+	__be32 *rdma_argp = rctxt->rc_recv_buf;
+	__be32 *wr_lst = rctxt->rc_write_list;
+	__be32 *rp_ch = rctxt->rc_reply_chunk;
 	struct xdr_buf *xdr = &rqstp->rq_res;
 	struct svc_rdma_send_ctxt *sctxt;
+	__be32 *p, *rdma_resp;
 	int ret;
 
-	rdma_argp = rctxt->rc_recv_buf;
-	svc_rdma_get_write_arrays(rdma_argp, &wr_lst, &rp_ch);
-
 	/* Create the RDMA response header. xprt->xpt_mutex,
 	 * acquired in svc_send(), serializes RPC replies. The
 	 * code path below that inserts the credit grant value

[PATCH v1 09/16] svcrdma: Update synopsis of svc_rdma_send_reply_chunk()

[Chuck Lever]

Preparing for subsequent patches, no behavior change expected.

Pass the RPC Call's svc_rdma_recv_ctxt deeper into the sendto()
path. This enables passing more information about Requester-
provided Write and Reply chunks into the lower-level send
functions.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 include/linux/sunrpc/svc_rdma.h       |    2 +-
 net/sunrpc/xprtrdma/svc_rdma_rw.c     |   12 ++++++------
 net/sunrpc/xprtrdma/svc_rdma_sendto.c |    2 +-
 3 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/include/linux/sunrpc/svc_rdma.h b/include/linux/sunrpc/svc_rdma.h
index e714e4d90ac5..42b68126cc60 100644
--- a/include/linux/sunrpc/svc_rdma.h
+++ b/include/linux/sunrpc/svc_rdma.h
@@ -179,7 +179,7 @@ extern int svc_rdma_send_write_chunk(struct svcxprt_rdma *rdma,
 				     unsigned int offset,
 				     unsigned long length);
 extern int svc_rdma_send_reply_chunk(struct svcxprt_rdma *rdma,
-				     __be32 *rp_ch, bool writelist,
+				     const struct svc_rdma_recv_ctxt *rctxt,
 				     struct xdr_buf *xdr);
 
 /* svc_rdma_sendto.c */
diff --git a/net/sunrpc/xprtrdma/svc_rdma_rw.c b/net/sunrpc/xprtrdma/svc_rdma_rw.c
index b0ac535c8728..9d854755d78d 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_rw.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_rw.c
@@ -545,8 +545,7 @@ int svc_rdma_send_write_chunk(struct svcxprt_rdma *rdma, __be32 *wr_ch,
 /**
  * svc_rdma_send_reply_chunk - Write all segments in the Reply chunk
  * @rdma: controlling RDMA transport
- * @rp_ch: Reply chunk provided by client
- * @writelist: true if client provided a Write list
+ * @rctxt: Write and Reply chunks from client
  * @xdr: xdr_buf containing an RPC Reply
  *
  * Returns a non-negative number of bytes the chunk consumed, or
@@ -556,13 +555,14 @@ int svc_rdma_send_write_chunk(struct svcxprt_rdma *rdma, __be32 *wr_ch,
  *	%-ENOTCONN if posting failed (connection is lost),
  *	%-EIO if rdma_rw initialization failed (DMA mapping, etc).
  */
-int svc_rdma_send_reply_chunk(struct svcxprt_rdma *rdma, __be32 *rp_ch,
-			      bool writelist, struct xdr_buf *xdr)
+int svc_rdma_send_reply_chunk(struct svcxprt_rdma *rdma,
+			      const struct svc_rdma_recv_ctxt *rctxt,
+			      struct xdr_buf *xdr)
 {
 	struct svc_rdma_write_info *info;
 	int consumed, ret;
 
-	info = svc_rdma_write_info_alloc(rdma, rp_ch);
+	info = svc_rdma_write_info_alloc(rdma, rctxt->rc_reply_chunk);
 	if (!info)
 		return -ENOMEM;
 
@@ -574,7 +574,7 @@ int svc_rdma_send_reply_chunk(struct svcxprt_rdma *rdma, __be32 *rp_ch,
 	/* Send the page list in the Reply chunk only if the
 	 * client did not provide Write chunks.
 	 */
-	if (!writelist && xdr->page_len) {
+	if (!rctxt->rc_write_list && xdr->page_len) {
 		ret = svc_rdma_send_xdr_pagelist(info, xdr,
 						 xdr->head[0].iov_len,
 						 xdr->page_len);
diff --git a/net/sunrpc/xprtrdma/svc_rdma_sendto.c b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
index 94895635c007..0b6ff55b1ab1 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_sendto.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
@@ -833,7 +833,7 @@ int svc_rdma_sendto(struct svc_rqst *rqstp)
 		svc_rdma_xdr_encode_write_list(rdma_resp, wr_lst, ret);
 	}
 	if (rp_ch) {
-		ret = svc_rdma_send_reply_chunk(rdma, rp_ch, wr_lst, xdr);
+		ret = svc_rdma_send_reply_chunk(rdma, rctxt, &rqstp->rq_res);
 		if (ret < 0)
 			goto err2;
 		svc_rdma_xdr_encode_reply_chunk(rdma_resp, rp_ch, ret);

[PATCH v1 10/16] svcrdma: Update synopsis of svc_rdma_map_reply_msg()

[Chuck Lever]

Preparing for subsequent patches, no behavior change expected.

Pass the RPC Call's svc_rdma_recv_ctxt deeper into the sendto()
path. This enables passing more information about Requester-
provided Write and Reply chunks into those lower-level functions.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 include/linux/sunrpc/svc_rdma.h            |    5 +-
 net/sunrpc/xprtrdma/svc_rdma_backchannel.c |    2 -
 net/sunrpc/xprtrdma/svc_rdma_sendto.c      |   80 +++++++++++++++++-----------
 3 files changed, 52 insertions(+), 35 deletions(-)

diff --git a/include/linux/sunrpc/svc_rdma.h b/include/linux/sunrpc/svc_rdma.h
index 42b68126cc60..c506732886b3 100644
--- a/include/linux/sunrpc/svc_rdma.h
+++ b/include/linux/sunrpc/svc_rdma.h
@@ -193,8 +193,9 @@ extern void svc_rdma_sync_reply_hdr(struct svcxprt_rdma *rdma,
 				    struct svc_rdma_send_ctxt *ctxt,
 				    unsigned int len);
 extern int svc_rdma_map_reply_msg(struct svcxprt_rdma *rdma,
-				  struct svc_rdma_send_ctxt *ctxt,
-				  struct xdr_buf *xdr, __be32 *wr_lst);
+				  struct svc_rdma_send_ctxt *sctxt,
+				  const struct svc_rdma_recv_ctxt *rctxt,
+				  struct xdr_buf *xdr);
 extern int svc_rdma_sendto(struct svc_rqst *);
 extern int svc_rdma_read_payload(struct svc_rqst *rqstp, unsigned int offset,
 				 unsigned int length);
diff --git a/net/sunrpc/xprtrdma/svc_rdma_backchannel.c b/net/sunrpc/xprtrdma/svc_rdma_backchannel.c
index 908e78bb87c6..ce1a7a706f36 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_backchannel.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_backchannel.c
@@ -117,7 +117,7 @@ static int svc_rdma_bc_sendto(struct svcxprt_rdma *rdma,
 {
 	int ret;
 
-	ret = svc_rdma_map_reply_msg(rdma, ctxt, &rqst->rq_snd_buf, NULL);
+	ret = svc_rdma_map_reply_msg(rdma, ctxt, NULL, &rqst->rq_snd_buf);
 	if (ret < 0)
 		return -EIO;
 
diff --git a/net/sunrpc/xprtrdma/svc_rdma_sendto.c b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
index 0b6ff55b1ab1..bc8863342878 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_sendto.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
@@ -502,13 +502,19 @@ void svc_rdma_sync_reply_hdr(struct svcxprt_rdma *rdma,
 				      DMA_TO_DEVICE);
 }
 
-/* If the xdr_buf has more elements than the device can
- * transmit in a single RDMA Send, then the reply will
- * have to be copied into a bounce buffer.
+/**
+ * svc_rdma_pull_up_needed - Determine whether to use pull-up
+ * @rdma: controlling transport
+ * @rctxt: Write and Reply chunks provided by client
+ * @xdr: xdr_buf containing RPC message to transmit
+ *
+ * Returns:
+ *	%true if pull-up must be used
+ *	%false otherwise
  */
 static bool svc_rdma_pull_up_needed(struct svcxprt_rdma *rdma,
-				    struct xdr_buf *xdr,
-				    __be32 *wr_lst)
+				    const struct svc_rdma_recv_ctxt *rctxt,
+				    struct xdr_buf *xdr)
 {
 	int elements;
 
@@ -516,7 +522,7 @@ static bool svc_rdma_pull_up_needed(struct svcxprt_rdma *rdma,
 	elements = 1;
 
 	/* xdr->pages */
-	if (!wr_lst) {
+	if (!rctxt || !rctxt->rc_write_list) {
 		unsigned int remaining;
 		unsigned long pageoff;
 
@@ -538,26 +544,35 @@ static bool svc_rdma_pull_up_needed(struct svcxprt_rdma *rdma,
 	return elements >= rdma->sc_max_send_sges;
 }
 
-/* The device is not capable of sending the reply directly.
- * Assemble the elements of @xdr into the transport header
- * buffer.
+/**
+ * svc_rdma_pull_up_reply_msg - Copy Reply into a single buffer
+ * @rdma: controlling transport
+ * @sctxt: send_ctxt for the Send WR
+ * @rctxt: Write and Reply chunks provided by client
+ * @xdr: prepared xdr_buf containing RPC message
+ *
+ * The device is not capable of sending the reply directly.
+ * Assemble the elements of @xdr into the transport header buffer.
+ *
+ * Returns zero on success, or a negative errno on failure.
  */
 static int svc_rdma_pull_up_reply_msg(struct svcxprt_rdma *rdma,
-				      struct svc_rdma_send_ctxt *ctxt,
-				      struct xdr_buf *xdr, __be32 *wr_lst)
+				      struct svc_rdma_send_ctxt *sctxt,
+				      const struct svc_rdma_recv_ctxt *rctxt,
+				      struct xdr_buf *xdr)
 {
 	unsigned char *dst, *tailbase;
 	unsigned int taillen;
 
-	dst = ctxt->sc_xprt_buf;
-	dst += ctxt->sc_sges[0].length;
+	dst = sctxt->sc_xprt_buf;
+	dst += sctxt->sc_sges[0].length;
 
 	memcpy(dst, xdr->head[0].iov_base, xdr->head[0].iov_len);
 	dst += xdr->head[0].iov_len;
 
 	tailbase = xdr->tail[0].iov_base;
 	taillen = xdr->tail[0].iov_len;
-	if (wr_lst) {
+	if (rctxt && rctxt->rc_write_list) {
 		u32 xdrpad;
 
 		xdrpad = xdr_pad_size(xdr->page_len);
@@ -586,10 +601,10 @@ static int svc_rdma_pull_up_reply_msg(struct svcxprt_rdma *rdma,
 	if (taillen)
 		memcpy(dst, tailbase, taillen);
 
-	ctxt->sc_sges[0].length += xdr->len;
+	sctxt->sc_sges[0].length += xdr->len;
 	ib_dma_sync_single_for_device(rdma->sc_pd->device,
-				      ctxt->sc_sges[0].addr,
-				      ctxt->sc_sges[0].length,
+				      sctxt->sc_sges[0].addr,
+				      sctxt->sc_sges[0].length,
 				      DMA_TO_DEVICE);
 
 	return 0;
@@ -597,9 +612,9 @@ static int svc_rdma_pull_up_reply_msg(struct svcxprt_rdma *rdma,
 
 /* svc_rdma_map_reply_msg - Map the buffer holding RPC message
  * @rdma: controlling transport
- * @ctxt: send_ctxt for the Send WR
+ * @sctxt: send_ctxt for the Send WR
+ * @rctxt: Write and Reply chunks provided by client
  * @xdr: prepared xdr_buf containing RPC message
- * @wr_lst: pointer to Call header's Write list, or NULL
  *
  * Load the xdr_buf into the ctxt's sge array, and DMA map each
  * element as it is added.
@@ -607,8 +622,9 @@ static int svc_rdma_pull_up_reply_msg(struct svcxprt_rdma *rdma,
  * Returns zero on success, or a negative errno on failure.
  */
 int svc_rdma_map_reply_msg(struct svcxprt_rdma *rdma,
-			   struct svc_rdma_send_ctxt *ctxt,
-			   struct xdr_buf *xdr, __be32 *wr_lst)
+			   struct svc_rdma_send_ctxt *sctxt,
+			   const struct svc_rdma_recv_ctxt *rctxt,
+			   struct xdr_buf *xdr)
 {
 	unsigned int len, remaining;
 	unsigned long page_off;
@@ -617,11 +633,11 @@ int svc_rdma_map_reply_msg(struct svcxprt_rdma *rdma,
 	u32 xdr_pad;
 	int ret;
 
-	if (svc_rdma_pull_up_needed(rdma, xdr, wr_lst))
-		return svc_rdma_pull_up_reply_msg(rdma, ctxt, xdr, wr_lst);
+	if (svc_rdma_pull_up_needed(rdma, rctxt, xdr))
+		return svc_rdma_pull_up_reply_msg(rdma, sctxt, rctxt, xdr);
 
-	++ctxt->sc_cur_sge_no;
-	ret = svc_rdma_dma_map_buf(rdma, ctxt,
+	++sctxt->sc_cur_sge_no;
+	ret = svc_rdma_dma_map_buf(rdma, sctxt,
 				   xdr->head[0].iov_base,
 				   xdr->head[0].iov_len);
 	if (ret < 0)
@@ -632,7 +648,7 @@ int svc_rdma_map_reply_msg(struct svcxprt_rdma *rdma,
 	 * have added XDR padding in the tail buffer, and that
 	 * should not be included inline.
 	 */
-	if (wr_lst) {
+	if (rctxt && rctxt->rc_write_list) {
 		base = xdr->tail[0].iov_base;
 		len = xdr->tail[0].iov_len;
 		xdr_pad = xdr_pad_size(xdr->page_len);
@@ -651,8 +667,8 @@ int svc_rdma_map_reply_msg(struct svcxprt_rdma *rdma,
 	while (remaining) {
 		len = min_t(u32, PAGE_SIZE - page_off, remaining);
 
-		++ctxt->sc_cur_sge_no;
-		ret = svc_rdma_dma_map_page(rdma, ctxt, *ppages++,
+		++sctxt->sc_cur_sge_no;
+		ret = svc_rdma_dma_map_page(rdma, sctxt, *ppages++,
 					    page_off, len);
 		if (ret < 0)
 			return ret;
@@ -665,8 +681,8 @@ int svc_rdma_map_reply_msg(struct svcxprt_rdma *rdma,
 	len = xdr->tail[0].iov_len;
 tail:
 	if (len) {
-		++ctxt->sc_cur_sge_no;
-		ret = svc_rdma_dma_map_buf(rdma, ctxt, base, len);
+		++sctxt->sc_cur_sge_no;
+		ret = svc_rdma_dma_map_buf(rdma, sctxt, base, len);
 		if (ret < 0)
 			return ret;
 	}
@@ -720,8 +736,8 @@ static int svc_rdma_send_reply_msg(struct svcxprt_rdma *rdma,
 	int ret;
 
 	if (!rp_ch) {
-		ret = svc_rdma_map_reply_msg(rdma, sctxt,
-					     &rqstp->rq_res, wr_lst);
+		ret = svc_rdma_map_reply_msg(rdma, sctxt, rctxt,
+					     &rqstp->rq_res);
 		if (ret < 0)
 			return ret;
 	}

[PATCH v1 11/16] svcrdma: Update synopsis of svc_rdma_send_reply_msg()

[Chuck Lever]

Preparing for subsequent patches, no behavior change expected.

Pass the RPC Call's svc_rdma_recv_ctxt deeper into the sendto()
path. This enables passing more information about Requester-
provided Write and Reply chunks into those lower-level functions.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 net/sunrpc/xprtrdma/svc_rdma_sendto.c |   10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/net/sunrpc/xprtrdma/svc_rdma_sendto.c b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
index bc8863342878..1035df3a3b5c 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_sendto.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
@@ -729,13 +729,12 @@ static void svc_rdma_save_io_pages(struct svc_rqst *rqstp,
  */
 static int svc_rdma_send_reply_msg(struct svcxprt_rdma *rdma,
 				   struct svc_rdma_send_ctxt *sctxt,
-				   struct svc_rdma_recv_ctxt *rctxt,
-				   struct svc_rqst *rqstp,
-				   __be32 *wr_lst, __be32 *rp_ch)
+				   const struct svc_rdma_recv_ctxt *rctxt,
+				   struct svc_rqst *rqstp)
 {
 	int ret;
 
-	if (!rp_ch) {
+	if (!rctxt->rc_reply_chunk) {
 		ret = svc_rdma_map_reply_msg(rdma, sctxt, rctxt,
 					     &rqstp->rq_res);
 		if (ret < 0)
@@ -856,8 +855,7 @@ int svc_rdma_sendto(struct svc_rqst *rqstp)
 	}
 
 	svc_rdma_sync_reply_hdr(rdma, sctxt, svc_rdma_reply_hdr_len(rdma_resp));
-	ret = svc_rdma_send_reply_msg(rdma, sctxt, rctxt, rqstp,
-				      wr_lst, rp_ch);
+	ret = svc_rdma_send_reply_msg(rdma, sctxt, rctxt, rqstp);
 	if (ret < 0)
 		goto err1;
 	ret = 0;

[PATCH v1 12/16] svcrdma: Rename svcrdma_encode trace points in send routines

[Chuck Lever]

These trace points are misnamed:

	trace_svcrdma_encode_wseg
	trace_svcrdma_encode_write
	trace_svcrdma_encode_reply
	trace_svcrdma_encode_rseg
	trace_svcrdma_encode_read
	trace_svcrdma_encode_pzr

Because they actually trace posting on the Send Queue. Let's rename
them so that I can add trace points in the chunk list encoders that
actually do trace chunk list encoding events.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 include/trace/events/rpcrdma.h    |   14 +++++++++-----
 net/sunrpc/xprtrdma/svc_rdma_rw.c |   13 +++++++------
 2 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/include/trace/events/rpcrdma.h b/include/trace/events/rpcrdma.h
index 814b73bd2cc7..74b68547eefb 100644
--- a/include/trace/events/rpcrdma.h
+++ b/include/trace/events/rpcrdma.h
@@ -1479,7 +1479,9 @@ DECLARE_EVENT_CLASS(svcrdma_segment_event,
 
 DEFINE_SEGMENT_EVENT(decode_wseg);
 DEFINE_SEGMENT_EVENT(encode_rseg);
+DEFINE_SEGMENT_EVENT(send_rseg);
 DEFINE_SEGMENT_EVENT(encode_wseg);
+DEFINE_SEGMENT_EVENT(send_wseg);
 
 DECLARE_EVENT_CLASS(svcrdma_chunk_event,
 	TP_PROTO(
@@ -1502,17 +1504,19 @@ DECLARE_EVENT_CLASS(svcrdma_chunk_event,
 );
 
 #define DEFINE_CHUNK_EVENT(name)					\
-		DEFINE_EVENT(svcrdma_chunk_event, svcrdma_encode_##name,\
+		DEFINE_EVENT(svcrdma_chunk_event, svcrdma_##name,	\
 				TP_PROTO(				\
 					u32 length			\
 				),					\
 				TP_ARGS(length))
 
-DEFINE_CHUNK_EVENT(pzr);
-DEFINE_CHUNK_EVENT(write);
-DEFINE_CHUNK_EVENT(reply);
+DEFINE_CHUNK_EVENT(send_pzr);
+DEFINE_CHUNK_EVENT(encode_write_chunk);
+DEFINE_CHUNK_EVENT(send_write_chunk);
+DEFINE_CHUNK_EVENT(encode_read_chunk);
+DEFINE_CHUNK_EVENT(send_reply_chunk);
 
-TRACE_EVENT(svcrdma_encode_read,
+TRACE_EVENT(svcrdma_send_read_chunk,
 	TP_PROTO(
 		u32 length,
 		u32 position
diff --git a/net/sunrpc/xprtrdma/svc_rdma_rw.c b/net/sunrpc/xprtrdma/svc_rdma_rw.c
index 9d854755d78d..a0e83a94beeb 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_rw.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_rw.c
@@ -439,7 +439,8 @@ svc_rdma_build_writes(struct svc_rdma_write_info *info,
 		if (ret < 0)
 			goto out_initerr;
 
-		trace_svcrdma_encode_wseg(seg_handle, write_len, seg_offset);
+		trace_svcrdma_send_wseg(seg_handle, write_len, seg_offset);
+
 		list_add(&ctxt->rw_list, &cc->cc_rwctxts);
 		cc->cc_sqecount += ret;
 		if (write_len == seg_length - info->wi_seg_off) {
@@ -534,7 +535,7 @@ int svc_rdma_send_write_chunk(struct svcxprt_rdma *rdma, __be32 *wr_ch,
 	if (ret < 0)
 		goto out_err;
 
-	trace_svcrdma_encode_write(xdr->page_len);
+	trace_svcrdma_send_write_chunk(xdr->page_len);
 	return length;
 
 out_err:
@@ -594,7 +595,7 @@ int svc_rdma_send_reply_chunk(struct svcxprt_rdma *rdma,
 	if (ret < 0)
 		goto out_err;
 
-	trace_svcrdma_encode_reply(consumed);
+	trace_svcrdma_send_reply_chunk(consumed);
 	return consumed;
 
 out_err:
@@ -697,7 +698,7 @@ static int svc_rdma_build_read_chunk(struct svc_rqst *rqstp,
 		if (ret < 0)
 			break;
 
-		trace_svcrdma_encode_rseg(rs_handle, rs_length, rs_offset);
+		trace_svcrdma_send_rseg(rs_handle, rs_length, rs_offset);
 		info->ri_chunklen += rs_length;
 	}
 
@@ -728,7 +729,7 @@ static int svc_rdma_build_normal_read_chunk(struct svc_rqst *rqstp,
 	if (ret < 0)
 		goto out;
 
-	trace_svcrdma_encode_read(info->ri_chunklen, info->ri_position);
+	trace_svcrdma_send_read_chunk(info->ri_chunklen, info->ri_position);
 
 	head->rc_hdr_count = 0;
 
@@ -784,7 +785,7 @@ static int svc_rdma_build_pz_read_chunk(struct svc_rqst *rqstp,
 	if (ret < 0)
 		goto out;
 
-	trace_svcrdma_encode_pzr(info->ri_chunklen);
+	trace_svcrdma_send_pzr(info->ri_chunklen);
 
 	head->rc_arg.len += info->ri_chunklen;
 	head->rc_arg.buflen += info->ri_chunklen;

[PATCH v1 13/16] SUNRPC: Add encoders for list item discriminators

[Chuck Lever]

Clean up. These are taken from the client-side RPC/RDMA transport
to a more global header file so they can be used elsewhere.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 include/linux/sunrpc/xdr.h     |   38 ++++++++++++++++++++++++++++++++++++++
 net/sunrpc/xprtrdma/rpc_rdma.c |   36 +++++-------------------------------
 2 files changed, 43 insertions(+), 31 deletions(-)

diff --git a/include/linux/sunrpc/xdr.h b/include/linux/sunrpc/xdr.h
index 80972512edfd..cddfab4a5440 100644
--- a/include/linux/sunrpc/xdr.h
+++ b/include/linux/sunrpc/xdr.h
@@ -316,6 +316,44 @@ xdr_pad_size(size_t n)
 	return xdr_align_size(n) - n;
 }
 
+/**
+ * xdr_stream_encode_item_present - Encode a "present" list item
+ * @xdr: pointer to xdr_stream
+ *
+ * Return values:
+ *   On success, returns length in bytes of XDR buffer consumed
+ *   %-EMSGSIZE on XDR buffer overflow
+ */
+static inline ssize_t xdr_stream_encode_item_present(struct xdr_stream *xdr)
+{
+	const size_t len = sizeof(__be32);
+	__be32 *p = xdr_reserve_space(xdr, len);
+
+	if (unlikely(!p))
+		return -EMSGSIZE;
+	*p = xdr_one;
+	return len;
+}
+
+/**
+ * xdr_stream_encode_item_absent - Encode a "not present" list item
+ * @xdr: pointer to xdr_stream
+ *
+ * Return values:
+ *   On success, returns length in bytes of XDR buffer consumed
+ *   %-EMSGSIZE on XDR buffer overflow
+ */
+static inline int xdr_stream_encode_item_absent(struct xdr_stream *xdr)
+{
+	const size_t len = sizeof(__be32);
+	__be32 *p = xdr_reserve_space(xdr, len);
+
+	if (unlikely(!p))
+		return -EMSGSIZE;
+	*p = xdr_zero;
+	return len;
+}
+
 /**
  * xdr_stream_encode_u32 - Encode a 32-bit integer
  * @xdr: pointer to xdr_stream
diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
index b51e92d43dfd..737a54c3ad53 100644
--- a/net/sunrpc/xprtrdma/rpc_rdma.c
+++ b/net/sunrpc/xprtrdma/rpc_rdma.c
@@ -275,32 +275,6 @@ rpcrdma_convert_iovs(struct rpcrdma_xprt *r_xprt, struct xdr_buf *xdrbuf,
 	return n;
 }
 
-static inline int
-encode_item_present(struct xdr_stream *xdr)
-{
-	__be32 *p;
-
-	p = xdr_reserve_space(xdr, sizeof(*p));
-	if (unlikely(!p))
-		return -EMSGSIZE;
-
-	*p = xdr_one;
-	return 0;
-}
-
-static inline int
-encode_item_not_present(struct xdr_stream *xdr)
-{
-	__be32 *p;
-
-	p = xdr_reserve_space(xdr, sizeof(*p));
-	if (unlikely(!p))
-		return -EMSGSIZE;
-
-	*p = xdr_zero;
-	return 0;
-}
-
 static void
 xdr_encode_rdma_segment(__be32 *iptr, struct rpcrdma_mr *mr)
 {
@@ -414,7 +388,7 @@ static int rpcrdma_encode_read_list(struct rpcrdma_xprt *r_xprt,
 	} while (nsegs);
 
 done:
-	return encode_item_not_present(xdr);
+	return xdr_stream_encode_item_absent(xdr);
 }
 
 /* Register and XDR encode the Write list. Supports encoding a list
@@ -453,7 +427,7 @@ static int rpcrdma_encode_write_list(struct rpcrdma_xprt *r_xprt,
 	if (nsegs < 0)
 		return nsegs;
 
-	if (encode_item_present(xdr) < 0)
+	if (xdr_stream_encode_item_present(xdr) < 0)
 		return -EMSGSIZE;
 	segcount = xdr_reserve_space(xdr, sizeof(*segcount));
 	if (unlikely(!segcount))
@@ -480,7 +454,7 @@ static int rpcrdma_encode_write_list(struct rpcrdma_xprt *r_xprt,
 	*segcount = cpu_to_be32(nchunks);
 
 done:
-	return encode_item_not_present(xdr);
+	return xdr_stream_encode_item_absent(xdr);
 }
 
 /* Register and XDR encode the Reply chunk. Supports encoding an array
@@ -507,14 +481,14 @@ static int rpcrdma_encode_reply_chunk(struct rpcrdma_xprt *r_xprt,
 	__be32 *segcount;
 
 	if (wtype != rpcrdma_replych)
-		return encode_item_not_present(xdr);
+		return xdr_stream_encode_item_absent(xdr);
 
 	seg = req->rl_segments;
 	nsegs = rpcrdma_convert_iovs(r_xprt, &rqst->rq_rcv_buf, 0, wtype, seg);
 	if (nsegs < 0)
 		return nsegs;
 
-	if (encode_item_present(xdr) < 0)
+	if (xdr_stream_encode_item_present(xdr) < 0)
 		return -EMSGSIZE;
 	segcount = xdr_reserve_space(xdr, sizeof(*segcount));
 	if (unlikely(!segcount))

[PATCH v1 14/16] svcrdma: Refactor chunk list encoders

[Chuck Lever]

Same idea as the receive-side changes I did a while back: use
xdr_stream helpers rather than open-coding the XDR chunk list
encoders. This builds the Reply transport header from beginning to
end without backtracking.

As additional clean-ups, fill in documenting comments for the XDR
encoders and sprinkle some trace points in the new encoding
functions.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 include/linux/sunrpc/svc_rdma.h            |    2 
 net/sunrpc/xprtrdma/svc_rdma_backchannel.c |   15 +-
 net/sunrpc/xprtrdma/svc_rdma_recvfrom.c    |   34 +++
 net/sunrpc/xprtrdma/svc_rdma_sendto.c      |  279 +++++++++++++++++-----------
 4 files changed, 209 insertions(+), 121 deletions(-)

diff --git a/include/linux/sunrpc/svc_rdma.h b/include/linux/sunrpc/svc_rdma.h
index c506732886b3..d001aac13c2f 100644
--- a/include/linux/sunrpc/svc_rdma.h
+++ b/include/linux/sunrpc/svc_rdma.h
@@ -149,6 +149,8 @@ struct svc_rdma_send_ctxt {
 	struct list_head	sc_list;
 	struct ib_send_wr	sc_send_wr;
 	struct ib_cqe		sc_cqe;
+	struct xdr_buf		sc_hdrbuf;
+	struct xdr_stream	sc_stream;
 	void			*sc_xprt_buf;
 	int			sc_page_count;
 	int			sc_cur_sge_no;
diff --git a/net/sunrpc/xprtrdma/svc_rdma_backchannel.c b/net/sunrpc/xprtrdma/svc_rdma_backchannel.c
index ce1a7a706f36..9830748c58d2 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_backchannel.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_backchannel.c
@@ -181,7 +181,9 @@ rpcrdma_bc_send_request(struct svcxprt_rdma *rdma, struct rpc_rqst *rqst)
 	if (!ctxt)
 		goto drop_connection;
 
-	p = ctxt->sc_xprt_buf;
+	p = xdr_reserve_space(&ctxt->sc_stream, RPCRDMA_HDRLEN_MIN);
+	if (!p)
+		goto put_ctxt;
 	*p++ = rqst->rq_xid;
 	*p++ = rpcrdma_version;
 	*p++ = cpu_to_be32(r_xprt->rx_buf.rb_bc_max_requests);
@@ -189,7 +191,7 @@ rpcrdma_bc_send_request(struct svcxprt_rdma *rdma, struct rpc_rqst *rqst)
 	*p++ = xdr_zero;
 	*p++ = xdr_zero;
 	*p   = xdr_zero;
-	svc_rdma_sync_reply_hdr(rdma, ctxt, RPCRDMA_HDRLEN_MIN);
+	svc_rdma_sync_reply_hdr(rdma, ctxt, ctxt->sc_hdrbuf.len);
 
 #ifdef SVCRDMA_BACKCHANNEL_DEBUG
 	pr_info("%s: %*ph\n", __func__, 64, rqst->rq_buffer);
@@ -197,12 +199,13 @@ rpcrdma_bc_send_request(struct svcxprt_rdma *rdma, struct rpc_rqst *rqst)
 
 	rqst->rq_xtime = ktime_get();
 	rc = svc_rdma_bc_sendto(rdma, rqst, ctxt);
-	if (rc) {
-		svc_rdma_send_ctxt_put(rdma, ctxt);
-		goto drop_connection;
-	}
+	if (rc)
+		goto put_ctxt;
 	return 0;
 
+put_ctxt:
+	svc_rdma_send_ctxt_put(rdma, ctxt);
+
 drop_connection:
 	dprintk("svcrdma: failed to send bc call\n");
 	return -ENOTCONN;
diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
index f9a3c413491c..447060dbd6fd 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
@@ -698,7 +698,6 @@ static void svc_rdma_send_error(struct svcxprt_rdma *xprt,
 				__be32 *rdma_argp, int status)
 {
 	struct svc_rdma_send_ctxt *ctxt;
-	unsigned int length;
 	__be32 *p;
 	int ret;
 
@@ -706,29 +705,48 @@ static void svc_rdma_send_error(struct svcxprt_rdma *xprt,
 	if (!ctxt)
 		return;
 
-	p = ctxt->sc_xprt_buf;
+	p = xdr_reserve_space(&ctxt->sc_stream,
+			      rpcrdma_fixed_maxsz * sizeof(*p));
+	if (!p)
+		goto put_ctxt;
+
 	*p++ = *rdma_argp;
 	*p++ = *(rdma_argp + 1);
 	*p++ = xprt->sc_fc_credits;
-	*p++ = rdma_error;
+	*p = rdma_error;
+
 	switch (status) {
 	case -EPROTONOSUPPORT:
+		p = xdr_reserve_space(&ctxt->sc_stream,
+				      3 * sizeof(*p));
+		if (!p)
+			goto put_ctxt;
+
 		*p++ = err_vers;
 		*p++ = rpcrdma_version;
-		*p++ = rpcrdma_version;
+		*p = rpcrdma_version;
 		trace_svcrdma_err_vers(*rdma_argp);
 		break;
 	default:
-		*p++ = err_chunk;
+		p = xdr_reserve_space(&ctxt->sc_stream,
+				      sizeof(*p));
+		if (!p)
+			goto put_ctxt;
+
+		*p = err_chunk;
 		trace_svcrdma_err_chunk(*rdma_argp);
 	}
-	length = (unsigned long)p - (unsigned long)ctxt->sc_xprt_buf;
-	svc_rdma_sync_reply_hdr(xprt, ctxt, length);
+
+	svc_rdma_sync_reply_hdr(xprt, ctxt, ctxt->sc_hdrbuf.len);
 
 	ctxt->sc_send_wr.opcode = IB_WR_SEND;
 	ret = svc_rdma_send(xprt, &ctxt->sc_send_wr);
 	if (ret)
-		svc_rdma_send_ctxt_put(xprt, ctxt);
+		goto put_ctxt;
+	return;
+
+put_ctxt:
+	svc_rdma_send_ctxt_put(xprt, ctxt);
 }
 
 /* By convention, backchannel calls arrive via rdma_msg type
diff --git a/net/sunrpc/xprtrdma/svc_rdma_sendto.c b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
index 1035df3a3b5c..f557e1cc5694 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_sendto.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
@@ -151,6 +151,8 @@ svc_rdma_send_ctxt_alloc(struct svcxprt_rdma *rdma)
 	ctxt->sc_send_wr.send_flags = IB_SEND_SIGNALED;
 	ctxt->sc_cqe.done = svc_rdma_wc_send;
 	ctxt->sc_xprt_buf = buffer;
+	xdr_buf_init(&ctxt->sc_hdrbuf, ctxt->sc_xprt_buf,
+		     rdma->sc_max_req_size);
 	ctxt->sc_sges[0].addr = addr;
 
 	for (i = 0; i < rdma->sc_max_send_sges; i++)
@@ -204,6 +206,10 @@ struct svc_rdma_send_ctxt *svc_rdma_send_ctxt_get(struct svcxprt_rdma *rdma)
 	spin_unlock(&rdma->sc_send_lock);
 
 out:
+	rpcrdma_set_xdrlen(&ctxt->sc_hdrbuf, 0);
+	xdr_init_encode(&ctxt->sc_stream, &ctxt->sc_hdrbuf,
+			ctxt->sc_xprt_buf, NULL);
+
 	ctxt->sc_send_wr.num_sge = 0;
 	ctxt->sc_cur_sge_no = 0;
 	ctxt->sc_page_count = 0;
@@ -322,131 +328,171 @@ int svc_rdma_send(struct svcxprt_rdma *rdma, struct ib_send_wr *wr)
 	return ret;
 }
 
-/* Returns length of transport header, in bytes.
+/**
+ * svc_rdma_encode_read_list - Encode RPC Reply's Read chunk list
+ * @sctxt: Send context for the RPC Reply
+ *
+ * Return values:
+ *   On success, returns length in bytes of the Reply XDR buffer
+ *   that was consumed by the Reply Read list
+ *   %-EMSGSIZE on XDR buffer overflow
  */
-static unsigned int svc_rdma_reply_hdr_len(__be32 *rdma_resp)
+static ssize_t svc_rdma_encode_read_list(struct svc_rdma_send_ctxt *sctxt)
 {
-	unsigned int nsegs;
-	__be32 *p;
-
-	p = rdma_resp;
-
-	/* RPC-over-RDMA V1 replies never have a Read list. */
-	p += rpcrdma_fixed_maxsz + 1;
-
-	/* Skip Write list. */
-	while (*p++ != xdr_zero) {
-		nsegs = be32_to_cpup(p++);
-		p += nsegs * rpcrdma_segment_maxsz;
-	}
+	/* RPC-over-RDMA version 1 replies never have a Read list. */
+	return xdr_stream_encode_item_absent(&sctxt->sc_stream);
+}
 
-	/* Skip Reply chunk. */
-	if (*p++ != xdr_zero) {
-		nsegs = be32_to_cpup(p++);
-		p += nsegs * rpcrdma_segment_maxsz;
+/**
+ * svc_rdma_encode_write_segment - Encode one Write segment
+ * @src: matching Write chunk in the RPC Call header
+ * @sctxt: Send context for the RPC Reply
+ * @remaining: remaining bytes of the payload left in the Write chunk
+ *
+ * Return values:
+ *   On success, returns length in bytes of the Reply XDR buffer
+ *   that was consumed by the Write segment
+ *   %-EMSGSIZE on XDR buffer overflow
+ */
+static ssize_t svc_rdma_encode_write_segment(__be32 *src,
+					     struct svc_rdma_send_ctxt *sctxt,
+					     unsigned int *remaining)
+{
+	__be32 *p;
+	const size_t len = rpcrdma_segment_maxsz * sizeof(*p);
+	u32 handle, length;
+	u64 offset;
+
+	p = xdr_reserve_space(&sctxt->sc_stream, len);
+	if (!p)
+		return -EMSGSIZE;
+
+	handle = be32_to_cpup(src++);
+	length = be32_to_cpup(src++);
+	xdr_decode_hyper(src, &offset);
+
+	*p++ = cpu_to_be32(handle);
+	if (*remaining < length) {
+		/* segment only partly filled */
+		length = *remaining;
+		*remaining = 0;
+	} else {
+		/* entire segment was consumed */
+		*remaining -= length;
 	}
+	*p++ = cpu_to_be32(length);
+	xdr_encode_hyper(p, offset);
 
-	return (unsigned long)p - (unsigned long)rdma_resp;
+	trace_svcrdma_encode_wseg(handle, length, offset);
+	return len;
 }
 
-/* One Write chunk is copied from Call transport header to Reply
- * transport header. Each segment's length field is updated to
- * reflect number of bytes consumed in the segment.
- *
- * Returns number of segments in this chunk.
+/**
+ * svc_rdma_encode_write_chunk - Encode one Write chunk
+ * @src: matching Write chunk in the RPC Call header
+ * @sctxt: Send context for the RPC Reply
+ * @remaining: size in bytes of the payload in the Write chunk
+ *
+ * Copy a Write chunk from the Call transport header to the
+ * Reply transport header. Update each segment's length field
+ * to reflect the number of bytes written in that segment.
+ *
+ * Return values:
+ *   On success, returns length in bytes of the Reply XDR buffer
+ *   that was consumed by the Write chunk
+ *   %-EMSGSIZE on XDR buffer overflow
  */
-static unsigned int xdr_encode_write_chunk(__be32 *dst, __be32 *src,
+static ssize_t svc_rdma_encode_write_chunk(__be32 *src,
+					   struct svc_rdma_send_ctxt *sctxt,
 					   unsigned int remaining)
 {
 	unsigned int i, nsegs;
-	u32 seg_len;
+	ssize_t len, ret;
 
-	/* Write list discriminator */
-	*dst++ = *src++;
+	len = 0;
+	trace_svcrdma_encode_write_chunk(remaining);
 
-	/* number of segments in this chunk */
-	nsegs = be32_to_cpup(src);
-	*dst++ = *src++;
+	src++;
+	ret = xdr_stream_encode_item_present(&sctxt->sc_stream);
+	if (ret < 0)
+		return -EMSGSIZE;
+	len += ret;
 
-	for (i = nsegs; i; i--) {
-		/* segment's RDMA handle */
-		*dst++ = *src++;
-
-		/* bytes returned in this segment */
-		seg_len = be32_to_cpu(*src);
-		if (remaining >= seg_len) {
-			/* entire segment was consumed */
-			*dst = *src;
-			remaining -= seg_len;
-		} else {
-			/* segment only partly filled */
-			*dst = cpu_to_be32(remaining);
-			remaining = 0;
-		}
-		dst++; src++;
+	nsegs = be32_to_cpup(src++);
+	ret = xdr_stream_encode_u32(&sctxt->sc_stream, nsegs);
+	if (ret < 0)
+		return -EMSGSIZE;
+	len += ret;
 
-		/* segment's RDMA offset */
-		*dst++ = *src++;
-		*dst++ = *src++;
+	for (i = nsegs; i; i--) {
+		ret = svc_rdma_encode_write_segment(src, sctxt, &remaining);
+		if (ret < 0)
+			return -EMSGSIZE;
+		src += rpcrdma_segment_maxsz;
+		len += ret;
 	}
 
-	return nsegs;
+	return len;
 }
 
-/* The client provided a Write list in the Call message. Fill in
- * the segments in the first Write chunk in the Reply's transport
+/**
+ * svc_rdma_encode_write_list - Encode RPC Reply's Write chunk list
+ * @rctxt: Reply context with information about the RPC Call
+ * @sctxt: Send context for the RPC Reply
+ * @length: size in bytes of the payload in the first Write chunk
+ *
+ * The client provides a Write chunk list in the Call message. Fill
+ * in the segments in the first Write chunk in the Reply's transport
  * header with the number of bytes consumed in each segment.
  * Remaining chunks are returned unused.
  *
  * Assumptions:
  *  - Client has provided only one Write chunk
+ *
+ * Return values:
+ *   On success, returns length in bytes of the Reply XDR buffer
+ *   that was consumed by the Reply's Write list
+ *   %-EMSGSIZE on XDR buffer overflow
  */
-static void svc_rdma_xdr_encode_write_list(__be32 *rdma_resp, __be32 *wr_ch,
-					   unsigned int consumed)
+static ssize_t svc_rdma_encode_write_list(const struct svc_rdma_recv_ctxt *rctxt,
+					  struct svc_rdma_send_ctxt *sctxt,
+					  unsigned int length)
 {
-	unsigned int nsegs;
-	__be32 *p, *q;
-
-	/* RPC-over-RDMA V1 replies never have a Read list. */
-	p = rdma_resp + rpcrdma_fixed_maxsz + 1;
-
-	q = wr_ch;
-	while (*q != xdr_zero) {
-		nsegs = xdr_encode_write_chunk(p, q, consumed);
-		q += 2 + nsegs * rpcrdma_segment_maxsz;
-		p += 2 + nsegs * rpcrdma_segment_maxsz;
-		consumed = 0;
-	}
+	ssize_t len, ret;
 
-	/* Terminate Write list */
-	*p++ = xdr_zero;
+	ret = svc_rdma_encode_write_chunk(rctxt->rc_write_list, sctxt, length);
+	if (ret < 0)
+		return ret;
+	len = ret;
 
-	/* Reply chunk discriminator; may be replaced later */
-	*p = xdr_zero;
+	/* Terminate the Write list */
+	ret = xdr_stream_encode_item_absent(&sctxt->sc_stream);
+	if (ret < 0)
+		return ret;
+
+	return len + ret;
 }
 
-/* The client provided a Reply chunk in the Call message. Fill in
- * the segments in the Reply chunk in the Reply message with the
- * number of bytes consumed in each segment.
+/**
+ * svc_rdma_encode_reply_chunk - Encode RPC Reply's Reply chunk
+ * @rctxt: Reply context with information about the RPC Call
+ * @sctxt: Send context for the RPC Reply
+ * @length: size in bytes of the payload in the Reply chunk
  *
  * Assumptions:
- * - Reply can always fit in the provided Reply chunk
+ * - Reply can always fit in the client-provided Reply chunk
+ *
+ * Return values:
+ *   On success, returns length in bytes of the Reply XDR buffer
+ *   that was consumed by the Reply's Reply chunk
+ *   %-EMSGSIZE on XDR buffer overflow
  */
-static void svc_rdma_xdr_encode_reply_chunk(__be32 *rdma_resp, __be32 *rp_ch,
-					    unsigned int consumed)
+static ssize_t svc_rdma_encode_reply_chunk(const struct svc_rdma_recv_ctxt *rctxt,
+					   struct svc_rdma_send_ctxt *sctxt,
+					   unsigned int length)
 {
-	__be32 *p;
-
-	/* Find the Reply chunk in the Reply's xprt header.
-	 * RPC-over-RDMA V1 replies never have a Read list.
-	 */
-	p = rdma_resp + rpcrdma_fixed_maxsz + 1;
-
-	/* Skip past Write list */
-	while (*p++ != xdr_zero)
-		p += 1 + be32_to_cpup(p) * rpcrdma_segment_maxsz;
-
-	xdr_encode_write_chunk(p, rp_ch, consumed);
+	return svc_rdma_encode_write_chunk(rctxt->rc_reply_chunk, sctxt,
+					   length);
 }
 
 static int svc_rdma_dma_map_page(struct svcxprt_rdma *rdma,
@@ -765,14 +811,26 @@ static int svc_rdma_send_error_msg(struct svcxprt_rdma *rdma,
 				   struct svc_rdma_send_ctxt *ctxt,
 				   struct svc_rqst *rqstp)
 {
+	struct svc_rdma_recv_ctxt *rctxt = rqstp->rq_xprt_ctxt;
+	__be32 *rdma_argp = rctxt->rc_recv_buf;
 	__be32 *p;
 
-	p = ctxt->sc_xprt_buf;
-	trace_svcrdma_err_chunk(*p);
-	p += 3;
+	rpcrdma_set_xdrlen(&ctxt->sc_hdrbuf, 0);
+	xdr_init_encode(&ctxt->sc_stream, &ctxt->sc_hdrbuf,
+			ctxt->sc_xprt_buf, NULL);
+
+	p = xdr_reserve_space(&ctxt->sc_stream, RPCRDMA_HDRLEN_ERR);
+	if (!p)
+		return -ENOMSG;
+
+	*p++ = *rdma_argp;
+	*p++ = *(rdma_argp + 1);
+	*p++ = rdma->sc_fc_credits;
 	*p++ = rdma_error;
 	*p   = err_chunk;
-	svc_rdma_sync_reply_hdr(rdma, ctxt, RPCRDMA_HDRLEN_ERR);
+	trace_svcrdma_err_chunk(*rdma_argp);
+
+	svc_rdma_sync_reply_hdr(rdma, ctxt, ctxt->sc_hdrbuf.len);
 
 	svc_rdma_save_io_pages(rqstp, ctxt);
 
@@ -803,7 +861,7 @@ int svc_rdma_sendto(struct svc_rqst *rqstp)
 	__be32 *rp_ch = rctxt->rc_reply_chunk;
 	struct xdr_buf *xdr = &rqstp->rq_res;
 	struct svc_rdma_send_ctxt *sctxt;
-	__be32 *p, *rdma_resp;
+	__be32 *p;
 	int ret;
 
 	/* Create the RDMA response header. xprt->xpt_mutex,
@@ -816,19 +874,18 @@ int svc_rdma_sendto(struct svc_rqst *rqstp)
 	sctxt = svc_rdma_send_ctxt_get(rdma);
 	if (!sctxt)
 		goto err0;
-	rdma_resp = sctxt->sc_xprt_buf;
 
-	p = rdma_resp;
+	p = xdr_reserve_space(&sctxt->sc_stream,
+			      rpcrdma_fixed_maxsz * sizeof(*p));
+	if (!p)
+		goto err0;
 	*p++ = *rdma_argp;
 	*p++ = *(rdma_argp + 1);
 	*p++ = rdma->sc_fc_credits;
-	*p++ = rp_ch ? rdma_nomsg : rdma_msg;
-
-	/* Start with empty chunks */
-	*p++ = xdr_zero;
-	*p++ = xdr_zero;
-	*p   = xdr_zero;
+	*p   = rp_ch ? rdma_nomsg : rdma_msg;
 
+	if (svc_rdma_encode_read_list(sctxt) < 0)
+		goto err0;
 	if (wr_lst) {
 		/* XXX: Presume the client sent only one Write chunk */
 		unsigned long offset;
@@ -845,16 +902,24 @@ int svc_rdma_sendto(struct svc_rqst *rqstp)
 						length);
 		if (ret < 0)
 			goto err2;
-		svc_rdma_xdr_encode_write_list(rdma_resp, wr_lst, ret);
+		if (svc_rdma_encode_write_list(rctxt, sctxt, length) < 0)
+			goto err0;
+	} else {
+		if (xdr_stream_encode_item_absent(&sctxt->sc_stream) < 0)
+			goto err0;
 	}
 	if (rp_ch) {
 		ret = svc_rdma_send_reply_chunk(rdma, rctxt, &rqstp->rq_res);
 		if (ret < 0)
 			goto err2;
-		svc_rdma_xdr_encode_reply_chunk(rdma_resp, rp_ch, ret);
+		if (svc_rdma_encode_reply_chunk(rctxt, sctxt, ret) < 0)
+			goto err0;
+	} else {
+		if (xdr_stream_encode_item_absent(&sctxt->sc_stream) < 0)
+			goto err0;
 	}
 
-	svc_rdma_sync_reply_hdr(rdma, sctxt, svc_rdma_reply_hdr_len(rdma_resp));
+	svc_rdma_sync_reply_hdr(rdma, sctxt, sctxt->sc_hdrbuf.len);
 	ret = svc_rdma_send_reply_msg(rdma, sctxt, rctxt, rqstp);
 	if (ret < 0)
 		goto err1;

[PATCH v1 15/16] svcrdma: Fix double sync of transport header buffer

[Chuck Lever]

Performance optimization: Avoid syncing the transport buffer twice
when Reply buffer pull-up is necessary.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 include/linux/sunrpc/svc_rdma.h            |    3 -
 net/sunrpc/xprtrdma/svc_rdma_backchannel.c |    1 
 net/sunrpc/xprtrdma/svc_rdma_recvfrom.c    |    4 +-
 net/sunrpc/xprtrdma/svc_rdma_sendto.c      |   58 ++++++++++------------------
 4 files changed, 22 insertions(+), 44 deletions(-)

diff --git a/include/linux/sunrpc/svc_rdma.h b/include/linux/sunrpc/svc_rdma.h
index d001aac13c2f..a3fa5b4fa2e4 100644
--- a/include/linux/sunrpc/svc_rdma.h
+++ b/include/linux/sunrpc/svc_rdma.h
@@ -191,9 +191,6 @@ extern struct svc_rdma_send_ctxt *
 extern void svc_rdma_send_ctxt_put(struct svcxprt_rdma *rdma,
 				   struct svc_rdma_send_ctxt *ctxt);
 extern int svc_rdma_send(struct svcxprt_rdma *rdma, struct ib_send_wr *wr);
-extern void svc_rdma_sync_reply_hdr(struct svcxprt_rdma *rdma,
-				    struct svc_rdma_send_ctxt *ctxt,
-				    unsigned int len);
 extern int svc_rdma_map_reply_msg(struct svcxprt_rdma *rdma,
 				  struct svc_rdma_send_ctxt *sctxt,
 				  const struct svc_rdma_recv_ctxt *rctxt,
diff --git a/net/sunrpc/xprtrdma/svc_rdma_backchannel.c b/net/sunrpc/xprtrdma/svc_rdma_backchannel.c
index 9830748c58d2..46b59e91d34a 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_backchannel.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_backchannel.c
@@ -191,7 +191,6 @@ rpcrdma_bc_send_request(struct svcxprt_rdma *rdma, struct rpc_rqst *rqst)
 	*p++ = xdr_zero;
 	*p++ = xdr_zero;
 	*p   = xdr_zero;
-	svc_rdma_sync_reply_hdr(rdma, ctxt, ctxt->sc_hdrbuf.len);
 
 #ifdef SVCRDMA_BACKCHANNEL_DEBUG
 	pr_info("%s: %*ph\n", __func__, 64, rqst->rq_buffer);
diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
index 447060dbd6fd..2fb1de40613c 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
@@ -737,9 +737,9 @@ static void svc_rdma_send_error(struct svcxprt_rdma *xprt,
 		trace_svcrdma_err_chunk(*rdma_argp);
 	}
 
-	svc_rdma_sync_reply_hdr(xprt, ctxt, ctxt->sc_hdrbuf.len);
-
+	ctxt->sc_send_wr.num_sge = 1;
 	ctxt->sc_send_wr.opcode = IB_WR_SEND;
+	ctxt->sc_sges[0].length = ctxt->sc_hdrbuf.len;
 	ret = svc_rdma_send(xprt, &ctxt->sc_send_wr);
 	if (ret)
 		goto put_ctxt;
diff --git a/net/sunrpc/xprtrdma/svc_rdma_sendto.c b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
index f557e1cc5694..9a7317bc54c9 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_sendto.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
@@ -301,6 +301,12 @@ int svc_rdma_send(struct svcxprt_rdma *rdma, struct ib_send_wr *wr)
 
 	might_sleep();
 
+	/* Sync the transport header buffer */
+	ib_dma_sync_single_for_device(rdma->sc_pd->device,
+				      wr->sg_list[0].addr,
+				      wr->sg_list[0].length,
+				      DMA_TO_DEVICE);
+
 	/* If the SQ is full, wait until an SQ entry is available */
 	while (1) {
 		if ((atomic_dec_return(&rdma->sc_sq_avail) < 0)) {
@@ -530,24 +536,6 @@ static int svc_rdma_dma_map_buf(struct svcxprt_rdma *rdma,
 				     offset_in_page(base), len);
 }
 
-/**
- * svc_rdma_sync_reply_hdr - DMA sync the transport header buffer
- * @rdma: controlling transport
- * @ctxt: send_ctxt for the Send WR
- * @len: length of transport header
- *
- */
-void svc_rdma_sync_reply_hdr(struct svcxprt_rdma *rdma,
-			     struct svc_rdma_send_ctxt *ctxt,
-			     unsigned int len)
-{
-	ctxt->sc_sges[0].length = len;
-	ctxt->sc_send_wr.num_sge++;
-	ib_dma_sync_single_for_device(rdma->sc_pd->device,
-				      ctxt->sc_sges[0].addr, len,
-				      DMA_TO_DEVICE);
-}
-
 /**
  * svc_rdma_pull_up_needed - Determine whether to use pull-up
  * @rdma: controlling transport
@@ -610,9 +598,7 @@ static int svc_rdma_pull_up_reply_msg(struct svcxprt_rdma *rdma,
 	unsigned char *dst, *tailbase;
 	unsigned int taillen;
 
-	dst = sctxt->sc_xprt_buf;
-	dst += sctxt->sc_sges[0].length;
-
+	dst = sctxt->sc_xprt_buf + sctxt->sc_hdrbuf.len;
 	memcpy(dst, xdr->head[0].iov_base, xdr->head[0].iov_len);
 	dst += xdr->head[0].iov_len;
 
@@ -648,11 +634,6 @@ static int svc_rdma_pull_up_reply_msg(struct svcxprt_rdma *rdma,
 		memcpy(dst, tailbase, taillen);
 
 	sctxt->sc_sges[0].length += xdr->len;
-	ib_dma_sync_single_for_device(rdma->sc_pd->device,
-				      sctxt->sc_sges[0].addr,
-				      sctxt->sc_sges[0].length,
-				      DMA_TO_DEVICE);
-
 	return 0;
 }
 
@@ -663,7 +644,7 @@ static int svc_rdma_pull_up_reply_msg(struct svcxprt_rdma *rdma,
  * @xdr: prepared xdr_buf containing RPC message
  *
  * Load the xdr_buf into the ctxt's sge array, and DMA map each
- * element as it is added.
+ * element as it is added. The Send WR's num_sge field is set.
  *
  * Returns zero on success, or a negative errno on failure.
  */
@@ -679,6 +660,13 @@ int svc_rdma_map_reply_msg(struct svcxprt_rdma *rdma,
 	u32 xdr_pad;
 	int ret;
 
+	/* Set up the (persistently-mapped) transport header SGE */
+	sctxt->sc_send_wr.num_sge = 1;
+	sctxt->sc_sges[0].length = sctxt->sc_hdrbuf.len;
+
+	if (rctxt && rctxt->rc_reply_chunk)
+		return 0;
+
 	if (svc_rdma_pull_up_needed(rdma, rctxt, xdr))
 		return svc_rdma_pull_up_reply_msg(rdma, sctxt, rctxt, xdr);
 
@@ -780,12 +768,9 @@ static int svc_rdma_send_reply_msg(struct svcxprt_rdma *rdma,
 {
 	int ret;
 
-	if (!rctxt->rc_reply_chunk) {
-		ret = svc_rdma_map_reply_msg(rdma, sctxt, rctxt,
-					     &rqstp->rq_res);
-		if (ret < 0)
-			return ret;
-	}
+	ret = svc_rdma_map_reply_msg(rdma, sctxt, rctxt, &rqstp->rq_res);
+	if (ret < 0)
+		return ret;
 
 	svc_rdma_save_io_pages(rqstp, sctxt);
 
@@ -795,8 +780,6 @@ static int svc_rdma_send_reply_msg(struct svcxprt_rdma *rdma,
 	} else {
 		sctxt->sc_send_wr.opcode = IB_WR_SEND;
 	}
-	dprintk("svcrdma: posting Send WR with %u sge(s)\n",
-		sctxt->sc_send_wr.num_sge);
 	return svc_rdma_send(rdma, &sctxt->sc_send_wr);
 }
 
@@ -830,11 +813,11 @@ static int svc_rdma_send_error_msg(struct svcxprt_rdma *rdma,
 	*p   = err_chunk;
 	trace_svcrdma_err_chunk(*rdma_argp);
 
-	svc_rdma_sync_reply_hdr(rdma, ctxt, ctxt->sc_hdrbuf.len);
-
 	svc_rdma_save_io_pages(rqstp, ctxt);
 
+	ctxt->sc_send_wr.num_sge = 1;
 	ctxt->sc_send_wr.opcode = IB_WR_SEND;
+	ctxt->sc_sges[0].length = ctxt->sc_hdrbuf.len;
 	return svc_rdma_send(rdma, &ctxt->sc_send_wr);
 }
 
@@ -919,7 +902,6 @@ int svc_rdma_sendto(struct svc_rqst *rqstp)
 			goto err0;
 	}
 
-	svc_rdma_sync_reply_hdr(rdma, sctxt, sctxt->sc_hdrbuf.len);
 	ret = svc_rdma_send_reply_msg(rdma, sctxt, rctxt, rqstp);
 	if (ret < 0)
 		goto err1;

[PATCH v1 16/16] svcrdma: Avoid DMA mapping small RPC Replies

[Chuck Lever]

On some platforms, DMA mapping part of a page is more costly than
copying bytes. Indeed, not involving the I/O MMU can help the
RPC/RDMA transport scale better for tiny I/Os across more RDMA
devices. This is because interaction with the I/O MMU is eliminated
for each of these small I/Os. Without the explicit unmapping, the
NIC no longer needs to do a costly internal TLB shoot down for
buffers that are just a handful of bytes.

Since pull-up is now a more a frequent operation, I've introduced a
trace point in the pull-up path. It can be used for debugging or
user-space tools that count pull-up frequency.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 include/trace/events/rpcrdma.h        |   18 ++++++++++++++++++
 net/sunrpc/xprtrdma/svc_rdma_sendto.c |   15 ++++++++++++++-
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/include/trace/events/rpcrdma.h b/include/trace/events/rpcrdma.h
index 74b68547eefb..9238d233f8cf 100644
--- a/include/trace/events/rpcrdma.h
+++ b/include/trace/events/rpcrdma.h
@@ -1639,6 +1639,24 @@ TRACE_EVENT(svcrdma_dma_map_rwctx,
 	)
 );
 
+TRACE_EVENT(svcrdma_send_pullup,
+	TP_PROTO(
+		unsigned int len
+	),
+
+	TP_ARGS(len),
+
+	TP_STRUCT__entry(
+		__field(unsigned int, len)
+	),
+
+	TP_fast_assign(
+		__entry->len = len;
+	),
+
+	TP_printk("len=%u", __entry->len)
+);
+
 TRACE_EVENT(svcrdma_send_failed,
 	TP_PROTO(
 		const struct svc_rqst *rqst,
diff --git a/net/sunrpc/xprtrdma/svc_rdma_sendto.c b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
index 9a7317bc54c9..3669a41bf8b6 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_sendto.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
@@ -539,6 +539,7 @@ static int svc_rdma_dma_map_buf(struct svcxprt_rdma *rdma,
 /**
  * svc_rdma_pull_up_needed - Determine whether to use pull-up
  * @rdma: controlling transport
+ * @sctxt: send_ctxt for the Send WR
  * @rctxt: Write and Reply chunks provided by client
  * @xdr: xdr_buf containing RPC message to transmit
  *
@@ -547,11 +548,22 @@ static int svc_rdma_dma_map_buf(struct svcxprt_rdma *rdma,
  *	%false otherwise
  */
 static bool svc_rdma_pull_up_needed(struct svcxprt_rdma *rdma,
+				    struct svc_rdma_send_ctxt *sctxt,
 				    const struct svc_rdma_recv_ctxt *rctxt,
 				    struct xdr_buf *xdr)
 {
 	int elements;
 
+	/* For small messages, copying bytes is cheaper than DMA
+	 * mapping.
+	 */
+	if (sctxt->sc_hdrbuf.len + xdr->len <
+	    RPCRDMA_V1_DEF_INLINE_SIZE >> 1)
+		return true;
+
+	/* Check whether the xdr_buf has more elements than can
+	 * fit in a single RDMA Send.
+	 */
 	/* xdr->head */
 	elements = 1;
 
@@ -634,6 +646,7 @@ static int svc_rdma_pull_up_reply_msg(struct svcxprt_rdma *rdma,
 		memcpy(dst, tailbase, taillen);
 
 	sctxt->sc_sges[0].length += xdr->len;
+	trace_svcrdma_send_pullup(sctxt->sc_sges[0].length);
 	return 0;
 }
 
@@ -667,7 +680,7 @@ int svc_rdma_map_reply_msg(struct svcxprt_rdma *rdma,
 	if (rctxt && rctxt->rc_reply_chunk)
 		return 0;
 
-	if (svc_rdma_pull_up_needed(rdma, rctxt, xdr))
+	if (svc_rdma_pull_up_needed(rdma, sctxt, rctxt, xdr))
 		return svc_rdma_pull_up_reply_msg(rdma, sctxt, rctxt, xdr);
 
 	++sctxt->sc_cur_sge_no;