mm: document is_page_cache_freeable()
authorJohannes Weiner <hannes@cmpxchg.org>
Tue, 22 Sep 2009 00:03:00 +0000 (17:03 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Tue, 22 Sep 2009 14:17:38 +0000 (07:17 -0700)
Enlighten the reader of this code about what reference count makes a page
cache page freeable.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Lameter <cl@linux-foundation.org>
Reviewed-by: Christoph Lameter <cl@linux-foundation.org>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/vmscan.c

index f5b5f029288c6028b61a38304c5d78149d849480..5be8107e77580d2fdb9506104c7527812edc206b 100644 (file)
@@ -286,6 +286,11 @@ static inline int page_mapping_inuse(struct page *page)
 
 static inline int is_page_cache_freeable(struct page *page)
 {
+       /*
+        * A freeable page cache page is referenced only by the caller
+        * that isolated the page, the page cache radix tree and
+        * optional buffer heads at page->private.
+        */
        return page_count(page) - page_has_private(page) == 2;
 }