mm: clean up non-standard page->_mapcount users
- Add a proper comment to page->_mapcount.
- Introduce a macro for generating helper functions.
- Place all special page->_mapcount values next to each other so that
readers can see all possible values and so we don't get duplicates.
Link: http://lkml.kernel.org/r/502f49000e0b63e6c62e338fac6b420bf34fb526.1464079537.git.vdavydov@virtuozzo.com
Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index a50ad73..79472b2 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -85,6 +85,11 @@
/*
* Count of ptes mapped in mms, to show when
* page is mapped & limit reverse map searches.
+ *
+ * Extra information about page type may be
+ * stored here for pages that are never mapped,
+ * in which case the value MUST BE <= -2.
+ * See page-flags.h for more details.
*/
atomic_t _mapcount;
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index f36dbb3..96084ee 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -604,54 +604,45 @@
#endif
/*
+ * For pages that are never mapped to userspace, page->mapcount may be
+ * used for storing extra information about page type. Any value used
+ * for this purpose must be <= -2, but it's better start not too close
+ * to -2 so that an underflow of the page_mapcount() won't be mistaken
+ * for a special page.
+ */
+#define PAGE_MAPCOUNT_OPS(uname, lname) \
+static __always_inline int Page##uname(struct page *page) \
+{ \
+ return atomic_read(&page->_mapcount) == \
+ PAGE_##lname##_MAPCOUNT_VALUE; \
+} \
+static __always_inline void __SetPage##uname(struct page *page) \
+{ \
+ VM_BUG_ON_PAGE(atomic_read(&page->_mapcount) != -1, page); \
+ atomic_set(&page->_mapcount, PAGE_##lname##_MAPCOUNT_VALUE); \
+} \
+static __always_inline void __ClearPage##uname(struct page *page) \
+{ \
+ VM_BUG_ON_PAGE(!Page##uname(page), page); \
+ atomic_set(&page->_mapcount, -1); \
+}
+
+/*
* PageBuddy() indicate that the page is free and in the buddy system
* (see mm/page_alloc.c).
- *
- * PAGE_BUDDY_MAPCOUNT_VALUE must be <= -2 but better not too close to
- * -2 so that an underflow of the page_mapcount() won't be mistaken
- * for a genuine PAGE_BUDDY_MAPCOUNT_VALUE. -128 can be created very
- * efficiently by most CPU architectures.
*/
-#define PAGE_BUDDY_MAPCOUNT_VALUE (-128)
+#define PAGE_BUDDY_MAPCOUNT_VALUE (-128)
+PAGE_MAPCOUNT_OPS(Buddy, BUDDY)
-static inline int PageBuddy(struct page *page)
-{
- return atomic_read(&page->_mapcount) == PAGE_BUDDY_MAPCOUNT_VALUE;
-}
-
-static inline void __SetPageBuddy(struct page *page)
-{
- VM_BUG_ON_PAGE(atomic_read(&page->_mapcount) != -1, page);
- atomic_set(&page->_mapcount, PAGE_BUDDY_MAPCOUNT_VALUE);
-}
-
-static inline void __ClearPageBuddy(struct page *page)
-{
- VM_BUG_ON_PAGE(!PageBuddy(page), page);
- atomic_set(&page->_mapcount, -1);
-}
+/*
+ * PageBalloon() is set on pages that are on the balloon page list
+ * (see mm/balloon_compaction.c).
+ */
+#define PAGE_BALLOON_MAPCOUNT_VALUE (-256)
+PAGE_MAPCOUNT_OPS(Balloon, BALLOON)
extern bool is_free_buddy_page(struct page *page);
-#define PAGE_BALLOON_MAPCOUNT_VALUE (-256)
-
-static inline int PageBalloon(struct page *page)
-{
- return atomic_read(&page->_mapcount) == PAGE_BALLOON_MAPCOUNT_VALUE;
-}
-
-static inline void __SetPageBalloon(struct page *page)
-{
- VM_BUG_ON_PAGE(atomic_read(&page->_mapcount) != -1, page);
- atomic_set(&page->_mapcount, PAGE_BALLOON_MAPCOUNT_VALUE);
-}
-
-static inline void __ClearPageBalloon(struct page *page)
-{
- VM_BUG_ON_PAGE(!PageBalloon(page), page);
- atomic_set(&page->_mapcount, -1);
-}
-
__PAGEFLAG(Isolated, isolated, PF_ANY);
/*
diff --git a/scripts/tags.sh b/scripts/tags.sh
index f72f48f..ed7eef2 100755
--- a/scripts/tags.sh
+++ b/scripts/tags.sh
@@ -185,6 +185,9 @@
'/\<CLEARPAGEFLAG_NOOP(\([[:alnum:]_]*\).*/ClearPage\1/'
'/\<__CLEARPAGEFLAG_NOOP(\([[:alnum:]_]*\).*/__ClearPage\1/'
'/\<TESTCLEARFLAG_FALSE(\([[:alnum:]_]*\).*/TestClearPage\1/'
+ '/^PAGE_MAPCOUNT_OPS(\([[:alnum:]_]*\).*/Page\1/'
+ '/^PAGE_MAPCOUNT_OPS(\([[:alnum:]_]*\).*/__SetPage\1/'
+ '/^PAGE_MAPCOUNT_OPS(\([[:alnum:]_]*\).*/__ClearPage\1/'
'/^TASK_PFA_TEST([^,]*, *\([[:alnum:]_]*\))/task_\1/'
'/^TASK_PFA_SET([^,]*, *\([[:alnum:]_]*\))/task_set_\1/'
'/^TASK_PFA_CLEAR([^,]*, *\([[:alnum:]_]*\))/task_clear_\1/'