The patch titled
Subject: mm: clean up non-standard page->_mapcount users
has been added to the -mm tree. Its filename is
mm-clean-up-non-standard-page-_mapcount-users.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-clean-up-non-standard-page-_mapcount-users.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-clean-up-non-standard-page-_mapcount-users.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
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------------------------------------------------------
From: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
Subject: 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@xxxxxxxxxxxxx
Signed-off-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Eric Dumazet <eric.dumazet@xxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/mm_types.h | 5 ++
include/linux/page-flags.h | 73 +++++++++++++++--------------------
scripts/tags.sh | 3 +
3 files changed, 40 insertions(+), 41 deletions(-)
diff -puN include/linux/mm_types.h~mm-clean-up-non-standard-page-_mapcount-users include/linux/mm_types.h
--- a/include/linux/mm_types.h~mm-clean-up-non-standard-page-_mapcount-users
+++ a/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 -puN include/linux/page-flags.h~mm-clean-up-non-standard-page-_mapcount-users include/linux/page-flags.h
--- a/include/linux/page-flags.h~mm-clean-up-non-standard-page-_mapcount-users
+++ a/include/linux/page-flags.h
@@ -604,54 +604,45 @@ 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);
-}
-
__PAGEFLAG(Isolated, isolated, PF_ANY);
/*
diff -puN scripts/tags.sh~mm-clean-up-non-standard-page-_mapcount-users scripts/tags.sh
--- a/scripts/tags.sh~mm-clean-up-non-standard-page-_mapcount-users
+++ a/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/'
_
Patches currently in -mm which might be from vdavydov@xxxxxxxxxxxxx are
mm-zap-zone_oom_locked.patch
mm-oom-add-memcg-to-oom_control.patch
mm-remove-pointless-struct-in-struct-page-definition.patch
mm-clean-up-non-standard-page-_mapcount-users.patch
mm-memcontrol-cleanup-kmem-charge-functions.patch
mm-charge-uncharge-kmemcg-from-generic-page-allocator-paths.patch
mm-memcontrol-teach-uncharge_list-to-deal-with-kmem-pages.patch
arch-x86-charge-page-tables-to-kmemcg.patch
pipe-account-to-kmemcg.patch
af_unix-charge-buffers-to-kmemcg.patch
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