Subject: + mm-correct-the-comment-about-the-value-for-buddy-_mapcount.patch added to -mm tree
To: shhuiw@xxxxxxxxx,mel@xxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Thu, 22 Aug 2013 15:28:48 -0700
The patch titled
Subject: mm: correct the comment about the value for buddy _mapcount
has been added to the -mm tree. Its filename is
mm-correct-the-comment-about-the-value-for-buddy-_mapcount.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-correct-the-comment-about-the-value-for-buddy-_mapcount.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-correct-the-comment-about-the-value-for-buddy-_mapcount.patch
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------------------------------------------------------
From: Wang Sheng-Hui <shhuiw@xxxxxxxxx>
Subject: mm: correct the comment about the value for buddy _mapcount
Set _mapcount PAGE_BUDDY_MAPCOUNT_VALUE to make the page buddy. Not the
magic number -2.
Signed-off-by: Wang Sheng-Hui <shhuiw@xxxxxxxxx>
Cc: Mel Gorman <mel@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
diff -puN mm/page_alloc.c~mm-correct-the-comment-about-the-value-for-buddy-_mapcount mm/page_alloc.c
--- a/mm/page_alloc.c~mm-correct-the-comment-about-the-value-for-buddy-_mapcount
+++ a/mm/page_alloc.c
@@ -489,8 +489,10 @@ __find_buddy_index(unsigned long page_id
* (c) a page and its buddy have the same order &&
* (d) a page and its buddy are in the same zone.
*
- * For recording whether a page is in the buddy system, we set ->_mapcount -2.
- * Setting, clearing, and testing _mapcount -2 is serialized by zone->lock.
+ * For recording whether a page is in the buddy system, we set ->_mapcount
+ * PAGE_BUDDY_MAPCOUNT_VALUE.
+ * Setting, clearing, and testing _mapcount PAGE_BUDDY_MAPCOUNT_VALUE is
+ * serialized by zone->lock.
*
* For recording page's order, we use page_private(page).
*/
@@ -528,8 +530,9 @@ static inline int page_is_buddy(struct p
* as necessary, plus some accounting needed to play nicely with other
* parts of the VM system.
* At each level, we keep a list of pages, which are heads of continuous
- * free pages of length of (1 << order) and marked with _mapcount -2. Page's
- * order is recorded in page_private(page) field.
+ * free pages of length of (1 << order) and marked with _mapcount
+ * PAGE_BUDDY_MAPCOUNT_VALUE. Page's order is recorded in page_private(page)
+ * field.
* So when we are allocating or freeing one, we can derive the state of the
* other. That is, if we allocate a small block, and both were
* free, the remainder of the region must be split into blocks.
_
Patches currently in -mm which might be from shhuiw@xxxxxxxxx are
mm-correct-the-comment-about-the-value-for-buddy-_mapcount.patch
linux-next.patch
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