1 files changed, 8 insertions, 0 deletions

diff --git a/mm/truncate.c b/mm/truncate.c
index 232eb2736a79..b40ac6d4e86e 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -336,6 +336,14 @@ unsigned long invalidate_mapping_pages(struct address_space *mapping,
         unsigned long count = 0;
         int i;
 
+        /*
+         * Note: this function may get called on a shmem/tmpfs mapping:
+         * pagevec_lookup() might then return 0 prematurely (because it
+         * got a gangful of swap entries); but it's hardly worth worrying
+         * about - it can rarely have anything to free from such a mapping
+         * (most pages are dirty), and already skips over any difficulties.
+         */
+
         pagevec_init(&pvec, 0);
         while (index <= end && pagevec_lookup(&pvec, mapping, index,
                         min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {