SUNRPC: Optimise away unnecessary data moves in xdr_align_pages

We only have to call xdr_shrink_pagelen() if the remaining RPC
message does not fit in the page buffer length that we supplied
to xdr_align_pages().

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

1 files changed, 13 insertions, 10 deletions

diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
index fbbd1c475b43..08f50afd5f2a 100644
--- a/net/sunrpc/xdr.c
+++ b/net/sunrpc/xdr.c
@@ -730,21 +730,24 @@ static unsigned int xdr_align_pages(struct xdr_stream *xdr, unsigned int len)
 
         if (xdr->nwords == 0)
                 return 0;
-        if (nwords > xdr->nwords) {
-                nwords = xdr->nwords;
-                len = nwords << 2;
-        }
         /* Realign pages to current pointer position */
         iov  = buf->head;
-        if (iov->iov_len > cur)
+        if (iov->iov_len > cur) {
                 xdr_shrink_bufhead(buf, iov->iov_len - cur);
+                xdr->nwords = XDR_QUADLEN(buf->len - cur);
+        }
 
-        /* Truncate page data and move it into the tail */
-        if (buf->page_len > len)
-                xdr_shrink_pagelen(buf, buf->page_len - len);
-        else
+        if (nwords > xdr->nwords) {
+                nwords = xdr->nwords;
+                len = nwords << 2;
+        }
+        if (buf->page_len <= len)
                 len = buf->page_len;
-        xdr->nwords = XDR_QUADLEN(buf->len - cur);
+        else if (nwords < xdr->nwords) {
+                /* Truncate page data and move it into the tail */
+                xdr_shrink_pagelen(buf, buf->page_len - len);
+                xdr->nwords = XDR_QUADLEN(buf->len - cur);
+        }
         return len;
 }