[PATCH] truncate: dirty memory accounting fix

Only (un)account for IO and page-dirtying for devices which have real backing
store (ie: not tmpfs or ramdisks).

Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/mm/truncate.c b/mm/truncate.c
index 89a5c359b6e8..4a38dd1a4ce8 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -60,7 +60,8 @@ void cancel_dirty_page(struct page *page, unsigned int account_size)
                 WARN_ON(++warncount < 5);
         }
                 
-        if (TestClearPageDirty(page) && account_size) {
+        if (TestClearPageDirty(page) && account_size &&
+                        mapping_cap_account_dirty(page->mapping)) {
                 dec_zone_page_state(page, NR_FILE_DIRTY);
                 task_io_account_cancelled_write(account_size);
         }