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>

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 5c98df68a95354c226d7b87a1616ddf0583d0484..07ea89c167618d5ad2c71311ea983a2e9b7fcab5 100644 (file)
--- 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);
 

diff --git a/mm/rmap.c b/mm/rmap.c
index f5ad996a4a8f76615d1f383fde5e4a783375a7b7..0995a8f68866a5eb3e6d6404b69010b9a118356c 100644 (file)
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -314,7 +314,7 @@ void __init anon_vma_init(void)
  * Getting a lock on a stable anon_vma from a page off the LRU is
  * tricky: page_lock_anon_vma rely on RCU to guard against the races.
  */
-struct anon_vma *page_lock_anon_vma(struct page *page)
+struct anon_vma *__page_lock_anon_vma(struct page *page)
 {
        struct anon_vma *anon_vma, *root_anon_vma;
        unsigned long anon_mapping;
@@ -348,6 +348,8 @@ out:
 }
 
 void page_unlock_anon_vma(struct anon_vma *anon_vma)
+       __releases(&anon_vma->root->lock)
+       __releases(RCU)
 {
        anon_vma_unlock(anon_vma);
        rcu_read_unlock();