mm: move enum vm_event_item into a standalone header file

enums are problematic because they cannot be forward-declared:

akpm2:/home/akpm> cat t.c

enum foo;

static inline void bar(enum foo f)
{
}
akpm2:/home/akpm> gcc -c t.c
t.c:4: error: parameter 1 ('f') has incomplete type

So move the enum's definition into a standalone header file which can be used
wherever its definition is needed.

Cc: Ying Han <[e-mail]>
Cc: KAMEZAWA Hiroyuki <[e-mail]>
Cc: KOSAKI Motohiro <[e-mail]>
Cc: Minchan Kim <[e-mail]>
Cc: Daisuke Nishimura <[e-mail]>
Cc: Balbir Singh <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

include/linux/vm_event_item.h

···
+#ifndef VM_EVENT_ITEM_H_INCLUDED
+#define VM_EVENT_ITEM_H_INCLUDED
+
+#ifdef CONFIG_ZONE_DMA
+#define DMA_ZONE(xx) xx##_DMA,
+#else
+#define DMA_ZONE(xx)
+#endif
+
+#ifdef CONFIG_ZONE_DMA32
+#define DMA32_ZONE(xx) xx##_DMA32,
+#else
+#define DMA32_ZONE(xx)
+#endif
+
+#ifdef CONFIG_HIGHMEM
+#define HIGHMEM_ZONE(xx) , xx##_HIGH
+#else
+#define HIGHMEM_ZONE(xx)
+#endif
+
+#define FOR_ALL_ZONES(xx) DMA_ZONE(xx) DMA32_ZONE(xx) xx##_NORMAL HIGHMEM_ZONE(xx) , xx##_MOVABLE
+
+enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
+		FOR_ALL_ZONES(PGALLOC),
+		PGFREE, PGACTIVATE, PGDEACTIVATE,
+		PGFAULT, PGMAJFAULT,
+		FOR_ALL_ZONES(PGREFILL),
+		FOR_ALL_ZONES(PGSTEAL),
+		FOR_ALL_ZONES(PGSCAN_KSWAPD),
+		FOR_ALL_ZONES(PGSCAN_DIRECT),
+#ifdef CONFIG_NUMA
+		PGSCAN_ZONE_RECLAIM_FAILED,
+#endif
+		PGINODESTEAL, SLABS_SCANNED, KSWAPD_STEAL, KSWAPD_INODESTEAL,
+		KSWAPD_LOW_WMARK_HIT_QUICKLY, KSWAPD_HIGH_WMARK_HIT_QUICKLY,
+		KSWAPD_SKIP_CONGESTION_WAIT,
+		PAGEOUTRUN, ALLOCSTALL, PGROTATED,
+#ifdef CONFIG_COMPACTION
+		COMPACTBLOCKS, COMPACTPAGES, COMPACTPAGEFAILED,
+		COMPACTSTALL, COMPACTFAIL, COMPACTSUCCESS,
+#endif
+#ifdef CONFIG_HUGETLB_PAGE
+		HTLB_BUDDY_PGALLOC, HTLB_BUDDY_PGALLOC_FAIL,
+#endif
+		UNEVICTABLE_PGCULLED,	/* culled to noreclaim list */
+		UNEVICTABLE_PGSCANNED,	/* scanned for reclaimability */
+		UNEVICTABLE_PGRESCUED,	/* rescued from noreclaim list */
+		UNEVICTABLE_PGMLOCKED,
+		UNEVICTABLE_PGMUNLOCKED,
+		UNEVICTABLE_PGCLEARED,	/* on COW, page truncate */
+		UNEVICTABLE_PGSTRANDED,	/* unable to isolate on unlock */
+		UNEVICTABLE_MLOCKFREED,
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+		THP_FAULT_ALLOC,
+		THP_FAULT_FALLBACK,
+		THP_COLLAPSE_ALLOC,
+		THP_COLLAPSE_ALLOC_FAILED,
+		THP_SPLIT,
+#endif
+		NR_VM_EVENT_ITEMS
+};
+
+#endif		/* VM_EVENT_ITEM_H_INCLUDED */

include/linux/vmstat.h

···
 #include <linux/percpu.h>
 #include <linux/mm.h>
 #include <linux/mmzone.h>
+#include <linux/vm_event_item.h>
 #include <asm/atomic.h>
-
-#ifdef CONFIG_ZONE_DMA
-#define DMA_ZONE(xx) xx##_DMA,
-#else
-#define DMA_ZONE(xx)
-#endif
-
-#ifdef CONFIG_ZONE_DMA32
-#define DMA32_ZONE(xx) xx##_DMA32,
-#else
-#define DMA32_ZONE(xx)
-#endif
-
-#ifdef CONFIG_HIGHMEM
-#define HIGHMEM_ZONE(xx) , xx##_HIGH
-#else
-#define HIGHMEM_ZONE(xx)
-#endif
-
-
-#define FOR_ALL_ZONES(xx) DMA_ZONE(xx) DMA32_ZONE(xx) xx##_NORMAL HIGHMEM_ZONE(xx) , xx##_MOVABLE
-
-enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
-		FOR_ALL_ZONES(PGALLOC),
-		PGFREE, PGACTIVATE, PGDEACTIVATE,
-		PGFAULT, PGMAJFAULT,
-		FOR_ALL_ZONES(PGREFILL),
-		FOR_ALL_ZONES(PGSTEAL),
-		FOR_ALL_ZONES(PGSCAN_KSWAPD),
-		FOR_ALL_ZONES(PGSCAN_DIRECT),
-#ifdef CONFIG_NUMA
-		PGSCAN_ZONE_RECLAIM_FAILED,
-#endif
-		PGINODESTEAL, SLABS_SCANNED, KSWAPD_STEAL, KSWAPD_INODESTEAL,
-		KSWAPD_LOW_WMARK_HIT_QUICKLY, KSWAPD_HIGH_WMARK_HIT_QUICKLY,
-		KSWAPD_SKIP_CONGESTION_WAIT,
-		PAGEOUTRUN, ALLOCSTALL, PGROTATED,
-#ifdef CONFIG_COMPACTION
-		COMPACTBLOCKS, COMPACTPAGES, COMPACTPAGEFAILED,
-		COMPACTSTALL, COMPACTFAIL, COMPACTSUCCESS,
-#endif
-#ifdef CONFIG_HUGETLB_PAGE
-		HTLB_BUDDY_PGALLOC, HTLB_BUDDY_PGALLOC_FAIL,
-#endif
-		UNEVICTABLE_PGCULLED,	/* culled to noreclaim list */
-		UNEVICTABLE_PGSCANNED,	/* scanned for reclaimability */
-		UNEVICTABLE_PGRESCUED,	/* rescued from noreclaim list */
-		UNEVICTABLE_PGMLOCKED,
-		UNEVICTABLE_PGMUNLOCKED,
-		UNEVICTABLE_PGCLEARED,	/* on COW, page truncate */
-		UNEVICTABLE_PGSTRANDED,	/* unable to isolate on unlock */
-		UNEVICTABLE_MLOCKFREED,
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
-		THP_FAULT_ALLOC,
-		THP_FAULT_FALLBACK,
-		THP_COLLAPSE_ALLOC,
-		THP_COLLAPSE_ALLOC_FAILED,
-		THP_SPLIT,
-#endif
-		NR_VM_EVENT_ITEMS
-};
 
 extern int sysctl_stat_interval;