SUNRPC: Don't truncate tail data unnecessarily in xdr_shrink_pagelen

If we have unused buffer space, then we should make use of that rather
than unnecessarily truncating the message.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 10 insertions, 1 deletions

diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
index 3317db3cb10..3bbef7f5f82 100644
--- a/net/sunrpc/xdr.c
+++ b/net/sunrpc/xdr.c
@@ -396,12 +396,21 @@ xdr_shrink_pagelen(struct xdr_buf *buf, size_t len)
         struct kvec *tail;
         size_t copy;
         unsigned int pglen = buf->page_len;
+        unsigned int tailbuf_len;
 
         tail = buf->tail;
         BUG_ON (len > pglen);
 
+        tailbuf_len = buf->buflen - buf->head->iov_len - buf->page_len;
+
         /* Shift the tail first */
-        if (tail->iov_len != 0) {
+        if (tailbuf_len != 0) {
+                unsigned int free_space = tailbuf_len - tail->iov_len;
+
+                if (len < free_space)
+                        free_space = len;
+                tail->iov_len += free_space;
+
                 copy = len;
                 if (tail->iov_len > len) {
                         char *p = (char *)tail->iov_base + len;