mlock: fix unevictable_pgs event counts on THP

5.8 commit 5d91f31f ("mm: swap: fix vmstats for huge page") has
established that vm_events should count every subpage of a THP, including
unevictable_pgs_culled and unevictable_pgs_rescued; but
lru_cache_add_inactive_or_unevictable() was not doing so for
unevictable_pgs_mlocked, and mm/mlock.c was not doing so for
unevictable_pgs mlocked, munlocked, cleared and stranded.

Fix them; but THPs don't go the pagevec way in mlock.c, so no fixes needed
on that path.

Fixes: 5d91f31f ("mm: swap: fix vmstats for huge page")
Signed-off-by: NHugh Dickins <hughd@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Reviewed-by: NShakeel Butt <shakeelb@google.com>
Acked-by: NYang Shi <shy828301@gmail.com>
Cc: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Qian Cai <cai@lca.pw>
Link: http://lkml.kernel.org/r/alpine.LSU.2.11.2008301408230.5954@eggly.anvilsSigned-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/mlock.c

@@ -58,11 +58,14 @@ EXPORT_SYMBOL(can_do_mlock);
  */
 void clear_page_mlock(struct page *page)
 {
+	int nr_pages;
+
 	if (!TestClearPageMlocked(page))
 		return;
 
-	mod_zone_page_state(page_zone(page), NR_MLOCK, -thp_nr_pages(page));
-	count_vm_event(UNEVICTABLE_PGCLEARED);
+	nr_pages = thp_nr_pages(page);
+	mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages);
+	count_vm_events(UNEVICTABLE_PGCLEARED, nr_pages);
 	/*
 	 * The previous TestClearPageMlocked() corresponds to the smp_mb()
 	 * in __pagevec_lru_add_fn().
@@ -76,7 +79,7 @@ void clear_page_mlock(struct page *page)
 		 * We lost the race. the page already moved to evictable list.
 		 */
 		if (PageUnevictable(page))
-			count_vm_event(UNEVICTABLE_PGSTRANDED);
+			count_vm_events(UNEVICTABLE_PGSTRANDED, nr_pages);
 	}
 }
 
@@ -93,9 +96,10 @@ void mlock_vma_page(struct page *page)
 	VM_BUG_ON_PAGE(PageCompound(page) && PageDoubleMap(page), page);
 
 	if (!TestSetPageMlocked(page)) {
-		mod_zone_page_state(page_zone(page), NR_MLOCK,
-				    thp_nr_pages(page));
-		count_vm_event(UNEVICTABLE_PGMLOCKED);
+		int nr_pages = thp_nr_pages(page);
+
+		mod_zone_page_state(page_zone(page), NR_MLOCK, nr_pages);
+		count_vm_events(UNEVICTABLE_PGMLOCKED, nr_pages);
 		if (!isolate_lru_page(page))
 			putback_lru_page(page);
 	}
@@ -138,7 +142,7 @@ static void __munlock_isolated_page(struct page *page)
 
 	/* Did try_to_unlock() succeed or punt? */
 	if (!PageMlocked(page))
-		count_vm_event(UNEVICTABLE_PGMUNLOCKED);
+		count_vm_events(UNEVICTABLE_PGMUNLOCKED, thp_nr_pages(page));
 
 	putback_lru_page(page);
 }
@@ -154,10 +158,12 @@ static void __munlock_isolated_page(struct page *page)
  */
 static void __munlock_isolation_failed(struct page *page)
 {
+	int nr_pages = thp_nr_pages(page);
+
 	if (PageUnevictable(page))
-		__count_vm_event(UNEVICTABLE_PGSTRANDED);
+		__count_vm_events(UNEVICTABLE_PGSTRANDED, nr_pages);
 	else
-		__count_vm_event(UNEVICTABLE_PGMUNLOCKED);
+		__count_vm_events(UNEVICTABLE_PGMUNLOCKED, nr_pages);
 }
 
 /**

mm/swap.c

@@ -494,14 +494,14 @@ void lru_cache_add_inactive_or_unevictable(struct page *page,
 
 	unevictable = (vma->vm_flags & (VM_LOCKED | VM_SPECIAL)) == VM_LOCKED;
 	if (unlikely(unevictable) && !TestSetPageMlocked(page)) {
+		int nr_pages = thp_nr_pages(page);
 		/*
 		 * We use the irq-unsafe __mod_zone_page_stat because this
 		 * counter is not modified from interrupt context, and the pte
 		 * lock is held(spinlock), which implies preemption disabled.
 		 */
-		__mod_zone_page_state(page_zone(page), NR_MLOCK,
-				    thp_nr_pages(page));
-		count_vm_event(UNEVICTABLE_PGMLOCKED);
+		__mod_zone_page_state(page_zone(page), NR_MLOCK, nr_pages);
+		count_vm_events(UNEVICTABLE_PGMLOCKED, nr_pages);
 	}
 	lru_cache_add(page);
 }