diff --git a/mm/fadvise.c b/mm/fadvise.c
index b8024fa7101d..6c707bfe02fd 100644
--- a/mm/fadvise.c
+++ b/mm/fadvise.c
@@ -126,6 +126,17 @@ SYSCALL_DEFINE4(fadvise64_64, int, fd, loff_t, offset, loff_t, len, int, advice)
 		 */
 		start_index = (offset+(PAGE_SIZE-1)) >> PAGE_SHIFT;
 		end_index = (endbyte >> PAGE_SHIFT);
+		if ((endbyte & ~PAGE_MASK) != ~PAGE_MASK) {
+			/* First page is tricky as 0 - 1 = -1, but pgoff_t
+			 * is unsigned, so the end_index >= start_index
+			 * check below would be true and we'll discard the whole
+			 * file cache which is not what was asked.
+			 */
+			if (end_index == 0)
+				break;
+
+			end_index--;
+		}
 
 		if (end_index >= start_index) {
 			unsigned long count = invalidate_mapping_pages(mapping,