SUNRPC: Add XDR overflow trace event

This can help field troubleshooting without needing the overhead of
a full network capture (ie, tcpdump).

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

1 files changed, 17 insertions, 7 deletions

diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
index 345f08b634ee..6d0b615a02ae 100644
--- a/net/sunrpc/xdr.c
+++ b/net/sunrpc/xdr.c
@@ -16,6 +16,7 @@
 #include <linux/sunrpc/xdr.h>
 #include <linux/sunrpc/msg_prot.h>
 #include <linux/bvec.h>
+#include <trace/events/sunrpc.h>
 
 /*
  * XDR functions for basic NFS types
@@ -554,9 +555,9 @@ static __be32 *xdr_get_next_encode_buffer(struct xdr_stream *xdr,
 	int frag1bytes, frag2bytes;
 
 	if (nbytes > PAGE_SIZE)
-		return NULL; /* Bigger buffers require special handling */
+		goto out_overflow; /* Bigger buffers require special handling */
 	if (xdr->buf->len + nbytes > xdr->buf->buflen)
-		return NULL; /* Sorry, we're totally out of space */
+		goto out_overflow; /* Sorry, we're totally out of space */
 	frag1bytes = (xdr->end - xdr->p) << 2;
 	frag2bytes = nbytes - frag1bytes;
 	if (xdr->iov)
@@ -585,6 +586,9 @@ static __be32 *xdr_get_next_encode_buffer(struct xdr_stream *xdr,
 	xdr->buf->page_len += frag2bytes;
 	xdr->buf->len += nbytes;
 	return p;
+out_overflow:
+	trace_rpc_xdr_overflow(xdr, nbytes);
+	return NULL;
 }
 
 /**
@@ -902,20 +906,23 @@ static __be32 *xdr_copy_to_scratch(struct xdr_stream *xdr, size_t nbytes)
 	size_t cplen = (char *)xdr->end - (char *)xdr->p;
 
 	if (nbytes > xdr->scratch.iov_len)
-		return NULL;
+		goto out_overflow;
 	p = __xdr_inline_decode(xdr, cplen);
 	if (p == NULL)
 		return NULL;
 	memcpy(cpdest, p, cplen);
+	if (!xdr_set_next_buffer(xdr))
+		goto out_overflow;
 	cpdest += cplen;
 	nbytes -= cplen;
-	if (!xdr_set_next_buffer(xdr))
-		return NULL;
 	p = __xdr_inline_decode(xdr, nbytes);
 	if (p == NULL)
 		return NULL;
 	memcpy(cpdest, p, nbytes);
 	return xdr->scratch.iov_base;
+out_overflow:
+	trace_rpc_xdr_overflow(xdr, nbytes);
+	return NULL;
 }
 
 /**
@@ -932,14 +939,17 @@ __be32 * xdr_inline_decode(struct xdr_stream *xdr, size_t nbytes)
 {
 	__be32 *p;
 
-	if (nbytes == 0)
+	if (unlikely(nbytes == 0))
 		return xdr->p;
 	if (xdr->p == xdr->end && !xdr_set_next_buffer(xdr))
-		return NULL;
+		goto out_overflow;
 	p = __xdr_inline_decode(xdr, nbytes);
 	if (p != NULL)
 		return p;
 	return xdr_copy_to_scratch(xdr, nbytes);
+out_overflow:
+	trace_rpc_xdr_overflow(xdr, nbytes);
+	return NULL;
 }
 EXPORT_SYMBOL_GPL(xdr_inline_decode);