[PATCH v2 3/5] mm: use mapcount for identifying zbud pages

Krzysztof Kozlowski
2013-09-11T08:59:21Z

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@samsung.com>
Reviewed-by: Seth Jennings <sjenning@linux.vnet.ibm.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 1d5b26b..9be160c 100644
--- a/mm/zbud.c
+++ b/mm/zbud.c
@@ -197,7 +197,10 @@ static void get_zbud_page(struct zbud_header *zhdr)
static int put_zbud_page(struct zbud_header *zhdr)
{
struct page *page = virt_to_page(zhdr);
+ VM_BUG_ON(!PageZbud(page));
+
if (put_page_testzero(page)) {
+ ClearPageZbud(page);
free_hot_cold_page(page, 0);
return 1;
}
@@ -307,6 +310,7 @@ 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