Merge branch 'akpm' (patches from Andrew)HEADmaster

Merge updates from Andrew Morton:

 - a few misc things

 - ocfs2 updates

 - v9fs updates

 - MM

 - procfs updates

 - lib/ updates

 - autofs updates

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (118 commits)
  autofs: small cleanup in autofs_getpath()
  autofs: clean up includes
  autofs: comment on selinux changes needed for module autoload
  autofs: update MAINTAINERS entry for autofs
  autofs: use autofs instead of autofs4 in documentation
  autofs: rename autofs documentation files
  autofs: create autofs Kconfig and Makefile
  autofs: delete fs/autofs4 source files
  autofs: update fs/autofs4/Makefile
  autofs: update fs/autofs4/Kconfig
  autofs: copy autofs4 to autofs
  autofs4: use autofs instead of autofs4 everywhere
  autofs4: merge auto_fs.h and auto_fs4.h
  fs/binfmt_misc.c: do not allow offset overflow
  checkpatch: improve patch recognition
  lib/ucs2_string.c: add MODULE_LICENSE()
  lib/mpi: headers cleanup
  lib/percpu_ida.c: use _irqsave() instead of local_irq_save() + spin_lock
  lib/idr.c: remove simple_ida_lock
  lib/bitmap.c: micro-optimization for __bitmap_complement()
  ...

1 files changed, 32 insertions, 19 deletions

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index e34a27727b9a7..901943e4754b3 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -642,49 +642,62 @@ PAGEFLAG_FALSE(DoubleMap)
 #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.
+ * For pages that are never mapped to userspace (and aren't PageSlab),
+ * page_type may be used.  Because it is initialised to -1, we invert the
+ * sense of the bit, so __SetPageFoo *clears* the bit used for PageFoo, and
+ * __ClearPageFoo *sets* the bit used for PageFoo.  We reserve a few high and
+ * low bits so that an underflow or overflow of page_mapcount() won't be
+ * mistaken for a page type value.
  */
-#define PAGE_MAPCOUNT_OPS(uname, lname)					\
+
+#define PAGE_TYPE_BASE	0xf0000000
+/* Reserve		0x0000007f to catch underflows of page_mapcount */
+#define PG_buddy	0x00000080
+#define PG_balloon	0x00000100
+#define PG_kmemcg	0x00000200
+#define PG_table	0x00000400
+
+#define PageType(page, flag)						\
+	((page->page_type & (PAGE_TYPE_BASE | flag)) == PAGE_TYPE_BASE)
+
+#define PAGE_TYPE_OPS(uname, lname)					\
 static __always_inline int Page##uname(struct page *page)		\
 {									\
-	return atomic_read(&page->_mapcount) ==				\
-				PAGE_##lname##_MAPCOUNT_VALUE;		\
+	return PageType(page, PG_##lname);				\
 }									\
 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);	\
+	VM_BUG_ON_PAGE(!PageType(page, 0), page);			\
+	page->page_type &= ~PG_##lname;					\
 }									\
 static __always_inline void __ClearPage##uname(struct page *page)	\
 {									\
 	VM_BUG_ON_PAGE(!Page##uname(page), page);			\
-	atomic_set(&page->_mapcount, -1);				\
+	page->page_type |= PG_##lname;					\
 }
 
 /*
- * PageBuddy() indicate that the page is free and in the buddy system
+ * PageBuddy() indicates 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)
+PAGE_TYPE_OPS(Buddy, buddy)
 
 /*
- * PageBalloon() is set on pages that are on the balloon page list
+ * PageBalloon() is true for pages that are on the balloon page list
  * (see mm/balloon_compaction.c).
  */
-#define PAGE_BALLOON_MAPCOUNT_VALUE		(-256)
-PAGE_MAPCOUNT_OPS(Balloon, BALLOON)
+PAGE_TYPE_OPS(Balloon, balloon)
 
 /*
  * If kmemcg is enabled, the buddy allocator will set PageKmemcg() on
  * pages allocated with __GFP_ACCOUNT. It gets cleared on page free.
  */
-#define PAGE_KMEMCG_MAPCOUNT_VALUE		(-512)
-PAGE_MAPCOUNT_OPS(Kmemcg, KMEMCG)
+PAGE_TYPE_OPS(Kmemcg, kmemcg)
+
+/*
+ * Marks pages in use as page tables.
+ */
+PAGE_TYPE_OPS(Table, table)
 
 extern bool is_free_buddy_page(struct page *page);