mm, thp: fix mlock statistics

NR_MLOCK is only accounted in single page units: there's no logic to
handle transparent hugepages.  This patch checks the appropriate number of
pages to adjust the statistics by so that the correct amount of memory is
reflected.

Currently:

		$ grep Mlocked /proc/meminfo
		Mlocked:           19636 kB

	#define MAP_SIZE	(4 << 30)	/* 4GB */

	void *ptr = mmap(NULL, MAP_SIZE, PROT_READ | PROT_WRITE,
			 MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);
	mlock(ptr, MAP_SIZE);

		$ grep Mlocked /proc/meminfo
		Mlocked:           29844 kB

	munlock(ptr, MAP_SIZE);

		$ grep Mlocked /proc/meminfo
		Mlocked:           19636 kB

And with this patch:

		$ grep Mlock /proc/meminfo
		Mlocked:           19636 kB

	mlock(ptr, MAP_SIZE);

		$ grep Mlock /proc/meminfo
		Mlocked:         4213664 kB

	munlock(ptr, MAP_SIZE);

		$ grep Mlock /proc/meminfo
		Mlocked:           19636 kB

Signed-off-by: David Rientjes <rientjes@google.com>
Reported-by: Hugh Dickens <hughd@google.com>
Acked-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Michel Lespinasse <walken@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 3 deletions

diff --git a/mm/mlock.c b/mm/mlock.c
index de7321592897..f0b9ce572fc7 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -56,7 +56,8 @@ void clear_page_mlock(struct page *page)
         if (!TestClearPageMlocked(page))
                 return;
 
-        dec_zone_page_state(page, NR_MLOCK);
+        mod_zone_page_state(page_zone(page), NR_MLOCK,
+                            -hpage_nr_pages(page));
         count_vm_event(UNEVICTABLE_PGCLEARED);
         if (!isolate_lru_page(page)) {
                 putback_lru_page(page);
@@ -78,7 +79,8 @@ void mlock_vma_page(struct page *page)
         BUG_ON(!PageLocked(page));
 
         if (!TestSetPageMlocked(page)) {
-                inc_zone_page_state(page, NR_MLOCK);
+                mod_zone_page_state(page_zone(page), NR_MLOCK,
+                                    hpage_nr_pages(page));
                 count_vm_event(UNEVICTABLE_PGMLOCKED);
                 if (!isolate_lru_page(page))
                         putback_lru_page(page);
@@ -105,7 +107,8 @@ void munlock_vma_page(struct page *page)
         BUG_ON(!PageLocked(page));
 
         if (TestClearPageMlocked(page)) {
-                dec_zone_page_state(page, NR_MLOCK);
+                mod_zone_page_state(page_zone(page), NR_MLOCK,
+                                    -hpage_nr_pages(page));
                 if (!isolate_lru_page(page)) {
                         int ret = SWAP_AGAIN;