rmap: annotate lock context change on page_[un]lock_anon_vma()

The page_lock_anon_vma() conditionally grabs RCU and anon_vma lock but
page_unlock_anon_vma() releases them unconditionally.  This leads sparse
to complain about context imbalance.  Annotate them.

Signed-off-by: Namhyung Kim <namhyung@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 14 insertions, 1 deletions

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 5c98df68a953..07ea89c16761 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -230,7 +230,20 @@ int try_to_munlock(struct page *);
 /*
  * Called by memory-failure.c to kill processes.
  */
-struct anon_vma *page_lock_anon_vma(struct page *page);
+struct anon_vma *__page_lock_anon_vma(struct page *page);
+
+static inline struct anon_vma *page_lock_anon_vma(struct page *page)
+{
+        struct anon_vma *anon_vma;
+
+        __cond_lock(RCU, anon_vma = __page_lock_anon_vma(page));
+
+        /* (void) is needed to make gcc happy */
+        (void) __cond_lock(&anon_vma->root->lock, anon_vma);
+
+        return anon_vma;
+}
+
 void page_unlock_anon_vma(struct anon_vma *anon_vma);
 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);