1 files changed, 11 insertions, 0 deletions

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,