linux-kernel - [RFC PATCH v2 3/4] mm: use mapcount for identifying zbud pages

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-id: <1376043740-10576-4-git-send-email-k.kozlowski@samsung.com>
Date:	Fri, 09 Aug 2013 12:22:19 +0200
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Seth Jennings <sjenning@...ux.vnet.ibm.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Mel Gorman <mgorman@...e.de>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Dave Hansen <dave.hansen@...el.com>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>
Subject: [RFC PATCH v2 3/4] mm: use mapcount for identifying zbud pages

Currently zbud pages do not have any flags set so it is not possible to
identify them during migration or compaction.

Implement PageZbud() by comparing page->_mapcount to -127 to distinguish
pages allocated by zbud. Just like PageBuddy() is implemented.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
---
 include/linux/mm.h |   23 +++++++++++++++++++++++
 mm/zbud.c          |    4 ++++
 2 files changed, 27 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index f022460..b9ae6f2 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -440,6 +440,7 @@ static inline void init_page_count(struct page *page)
  * efficiently by most CPU architectures.
  */
 #define PAGE_BUDDY_MAPCOUNT_VALUE (-128)
+#define PAGE_ZBUD_MAPCOUNT_VALUE (-127)
 
 static inline int PageBuddy(struct page *page)
 {
@@ -458,6 +459,28 @@ static inline void __ClearPageBuddy(struct page *page)
 	atomic_set(&page->_mapcount, -1);
 }
 
+#ifdef CONFIG_ZBUD
+static inline int PageZbud(struct page *page)
+{
+	return atomic_read(&page->_mapcount) == PAGE_ZBUD_MAPCOUNT_VALUE;
+}
+
+static inline void SetPageZbud(struct page *page)
+{
+	VM_BUG_ON(atomic_read(&page->_mapcount) != -1);
+	atomic_set(&page->_mapcount, PAGE_ZBUD_MAPCOUNT_VALUE);
+}
+
+static inline void ClearPageZbud(struct page *page)
+{
+	VM_BUG_ON(!PageZbud(page));
+	atomic_set(&page->_mapcount, -1);
+}
+#else
+PAGEFLAG_FALSE(Zbud)
+#endif
+
+
 void put_page(struct page *page);
 void put_pages_list(struct list_head *pages);
 
diff --git a/mm/zbud.c b/mm/zbud.c
index 52f6ba1..24c9ba0 100644
--- a/mm/zbud.c
+++ b/mm/zbud.c
@@ -199,7 +199,10 @@ static void get_zbud_page(struct zbud_header *zhdr)
 static int put_zbud_page(struct zbud_pool *pool, struct zbud_header *zhdr)
 {
 	struct page *page = virt_to_page(zhdr);
+	BUG_ON(!PageZbud(page));
+
 	if (put_page_testzero(page)) {
+		ClearPageZbud(page);
 		free_hot_cold_page(page, 0);
 		pool->pages_nr--;
 		return 1;
@@ -310,6 +313,7 @@ int zbud_alloc(struct zbud_pool *pool, int size, gfp_t gfp,
 	 * don't increase the page count.
 	 */
 	zhdr = init_zbud_page(page);
+	SetPageZbud(page);
 	bud = FIRST;
 
 found:
-- 
1.7.9.5

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/