thp, vmstats: add counters for huge file pages

THP_FILE_ALLOC: how many times huge page was allocated and put page
cache.

THP_FILE_MAPPED: how many times file huge page was mapped.

Link: http://lkml.kernel.org/r/1466021202-61880-13-git-send-email-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/vm_event_item.h

diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
index ec08432..4260417 100644
--- a/include/linux/vm_event_item.h
+++ b/include/linux/vm_event_item.h
@@ -70,6 +70,8 @@
 		THP_FAULT_FALLBACK,
 		THP_COLLAPSE_ALLOC,
 		THP_COLLAPSE_ALLOC_FAILED,
+		THP_FILE_ALLOC,
+		THP_FILE_MAPPED,
 		THP_SPLIT_PAGE,
 		THP_SPLIT_PAGE_FAILED,
 		THP_DEFERRED_SPLIT_PAGE,
@@ -100,4 +102,9 @@
 		NR_VM_EVENT_ITEMS
 };
 
+#ifndef CONFIG_TRANSPARENT_HUGEPAGE
+#define THP_FILE_ALLOC ({ BUILD_BUG(); 0; })
+#define THP_FILE_MAPPED ({ BUILD_BUG(); 0; })
+#endif
+
 #endif		/* VM_EVENT_ITEM_H_INCLUDED */

mm/memory.c

diff --git a/mm/memory.c b/mm/memory.c
index 650622a..10a424e 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2968,6 +2968,7 @@
 
 	/* fault is handled */
 	ret = 0;
+	count_vm_event(THP_FILE_MAPPED);
 out:
 	spin_unlock(fe->ptl);
 	return ret;

mm/vmstat.c

diff --git a/mm/vmstat.c b/mm/vmstat.c
index 2a0f26b..cff2f4e 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -817,6 +817,8 @@
 	"thp_fault_fallback",
 	"thp_collapse_alloc",
 	"thp_collapse_alloc_failed",
+	"thp_file_alloc",
+	"thp_file_mapped",
 	"thp_split_page",
 	"thp_split_page_failed",
 	"thp_deferred_split_page",