Merge back earlier powercap material for v4.8.

[cascardo/linux.git] / mm / fadvise.c

diff --git a/mm/fadvise.c b/mm/fadvise.c
index b8024fa..6c707bf 100644 (file)
--- 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,