From: Andrew Morton <akpm@osdl.org>

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 mm/page-writeback.c |    2 ++
 1 files changed, 2 insertions(+)

diff -puN mm/page-writeback.c~mm-tracking-shared-dirty-pages-checks mm/page-writeback.c
--- a/mm/page-writeback.c~mm-tracking-shared-dirty-pages-checks
+++ a/mm/page-writeback.c
@@ -717,6 +717,7 @@ int test_clear_page_dirty(struct page *p
 	struct address_space *mapping = page_mapping(page);
 	unsigned long flags;
 
+	WARN_ON_ONCE(!PageLocked(page));
 	if (mapping) {
 		write_lock_irqsave(&mapping->tree_lock, flags);
 		if (TestClearPageDirty(page)) {
@@ -759,6 +760,7 @@ int clear_page_dirty_for_io(struct page 
 {
 	struct address_space *mapping = page_mapping(page);
 
+	WARN_ON_ONCE(!PageLocked(page));
 	if (mapping) {
 		if (TestClearPageDirty(page)) {
 			if (mapping_cap_account_dirty(mapping)) {
_