diff --git a/mm/filemap.c b/mm/filemap.c
index 1d33fec..4a2fee2 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1968,6 +1968,7 @@
 	do {
 		unsigned long index;
 		unsigned long offset;
+		unsigned long maxlen;
 		size_t copied;
 
 		offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */
@@ -1982,7 +1983,10 @@
 		 * same page as we're writing to, without it being marked
 		 * up-to-date.
 		 */
-		fault_in_pages_readable(buf, bytes);
+		maxlen = cur_iov->iov_len - iov_base;
+		if (maxlen > bytes)
+			maxlen = bytes;
+		fault_in_pages_readable(buf, maxlen);
 
 		page = __grab_cache_page(mapping,index,&cached_page,&lru_pvec);
 		if (!page) {
@@ -2024,6 +2028,8 @@
 					filemap_set_next_iovec(&cur_iov,
 							&iov_base, status);
 					buf = cur_iov->iov_base + iov_base;
+				} else {
+					iov_base += status;
 				}
 			}
 		}