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Date: Tue, 24 May 2016 11:49:24 +0300
From: Vladimir Davydov <vdavydov@...tuozzo.com>
To: Andrew Morton <akpm@...ux-foundation.org>
CC: Johannes Weiner <hannes@...xchg.org>,
Michal Hocko <mhocko@...nel.org>, <linux-mm@...ck.org>,
<linux-fsdevel@...r.kernel.org>, <netdev@...r.kernel.org>,
<x86@...nel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH RESEND 2/8] 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.
Signed-off-by: Vladimir Davydov <vdavydov@...tuozzo.com>
---
include/linux/mm_types.h | 5 ++++
include/linux/page-flags.h | 73 ++++++++++++++++++++--------------------------
scripts/tags.sh | 3 ++
3 files changed, 40 insertions(+), 41 deletions(-)
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 3cc5977a9cab..16bdef7943e3 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -85,6 +85,11 @@ struct page {
/*
* 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 e5a32445f930..9940ade6a25e 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -593,54 +593,45 @@ TESTPAGEFLAG_FALSE(DoubleMap)
#endif
/*
- * 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.
+ * 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_BUDDY_MAPCOUNT_VALUE (-128)
-
-static inline int PageBuddy(struct page *page)
-{
- return atomic_read(&page->_mapcount) == PAGE_BUDDY_MAPCOUNT_VALUE;
+#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); \
}
-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);
-}
+/*
+ * PageBuddy() indicate that the page is free and in the buddy system
+ * (see mm/page_alloc.c).
+ */
+#define PAGE_BUDDY_MAPCOUNT_VALUE (-128)
+PAGE_MAPCOUNT_OPS(Buddy, BUDDY)
-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);
-}
-
/*
* If network-based swap is enabled, sl*b must keep track of whether pages
* were allocated from pfmemalloc reserves.
diff --git a/scripts/tags.sh b/scripts/tags.sh
index f72f48f638ae..ed7eef24ef89 100755
--- a/scripts/tags.sh
+++ b/scripts/tags.sh
@@ -185,6 +185,9 @@ regex_c=(
'/\<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/'
--
2.1.4
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