mm: add comment on storage key dirty bit semantics

[can-eth-gw-linux.git] / mm / rmap.c

diff --git a/mm/rmap.c b/mm/rmap.c
index 46823fb0e801b599178f8bd548437fa03d87b8ef..cf7e99a87c32865c4e6cf5b6ed4f48f7f05aa9e0 100644 (file)
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1151,9 +1151,11 @@ void page_remove_rmap(struct page *page)
         * containing the swap entry, but page not yet written to swap.
         *
         * And we can skip it on file pages, so long as the filesystem
-        * participates in dirty tracking; but need to catch shm and tmpfs
-        * and ramfs pages which have been modified since creation by read
-        * fault.
+        * participates in dirty tracking (note that this is not only an
+        * optimization but also solves problems caused by dirty flag in
+        * storage key getting set by a write from inside kernel); but need to
+        * catch shm and tmpfs and ramfs pages which have been modified since
+        * creation by read fault.
         *
         * Note that mapping must be decided above, before decrementing
         * mapcount (which luckily provides a barrier): once page is unmapped,