X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=mm%2Ftruncate.c;h=b40ac6d4e86e7ea7d1df670e709452948a1dcb74;hb=af8f38b3499f0d4a3c354df2435f0fb2dded250a;hp=232eb2736a79624eeccfc1387e9360e78fdb0404;hpb=ed8f37370d83e695c0a4fa5d5fc7a83ecb947526;p=firefly-linux-kernel-4.4.55.git

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)) {