1 files changed, 49 insertions, 14 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 277a36de11c1..f8e3dcd527b8 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1118,6 +1118,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 		int may_enter_fs;
 		enum page_references references = PAGEREF_RECLAIM_CLEAN;
 		bool dirty, writeback;
+		unsigned int nr_pages;
 
 		cond_resched();
 
@@ -1129,7 +1130,10 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 
 		VM_BUG_ON_PAGE(PageActive(page), page);
 
-		sc->nr_scanned++;
+		nr_pages = 1 << compound_order(page);
+
+		/* Account the number of base pages even though THP */
+		sc->nr_scanned += nr_pages;
 
 		if (unlikely(!page_evictable(page)))
 			goto activate_locked;
@@ -1250,7 +1254,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 		case PAGEREF_ACTIVATE:
 			goto activate_locked;
 		case PAGEREF_KEEP:
-			stat->nr_ref_keep++;
+			stat->nr_ref_keep += nr_pages;
 			goto keep_locked;
 		case PAGEREF_RECLAIM:
 		case PAGEREF_RECLAIM_CLEAN:
@@ -1282,7 +1286,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 				}
 				if (!add_to_swap(page)) {
 					if (!PageTransHuge(page))
-						goto activate_locked;
+						goto activate_locked_split;
 					/* Fallback to swap normal pages */
 					if (split_huge_page_to_list(page,
 								    page_list))
@@ -1291,7 +1295,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 					count_vm_event(THP_SWPOUT_FALLBACK);
 #endif
 					if (!add_to_swap(page))
-						goto activate_locked;
+						goto activate_locked_split;
 				}
 
 				may_enter_fs = 1;
@@ -1306,6 +1310,18 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 		}
 
 		/*
+		 * THP may get split above, need minus tail pages and update
+		 * nr_pages to avoid accounting tail pages twice.
+		 *
+		 * The tail pages that are added into swap cache successfully
+		 * reach here.
+		 */
+		if ((nr_pages > 1) && !PageTransHuge(page)) {
+			sc->nr_scanned -= (nr_pages - 1);
+			nr_pages = 1;
+		}
+
+		/*
 		 * The page is mapped into the page tables of one or more
 		 * processes. Try to unmap it here.
 		 */
@@ -1315,7 +1331,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 			if (unlikely(PageTransHuge(page)))
 				flags |= TTU_SPLIT_HUGE_PMD;
 			if (!try_to_unmap(page, flags)) {
-				stat->nr_unmap_fail++;
+				stat->nr_unmap_fail += nr_pages;
 				goto activate_locked;
 			}
 		}
@@ -1442,7 +1458,11 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 
 		unlock_page(page);
 free_it:
-		nr_reclaimed++;
+		/*
+		 * THP may get swapped out in a whole, need account
+		 * all base pages.
+		 */
+		nr_reclaimed += nr_pages;
 
 		/*
 		 * Is there need to periodically free_page_list? It would
@@ -1455,6 +1475,15 @@ free_it:
 			list_add(&page->lru, &free_pages);
 		continue;
 
+activate_locked_split:
+		/*
+		 * The tail pages that are failed to add into swap cache
+		 * reach here.  Fixup nr_scanned and nr_pages.
+		 */
+		if (nr_pages > 1) {
+			sc->nr_scanned -= (nr_pages - 1);
+			nr_pages = 1;
+		}
 activate_locked:
 		/* Not a candidate for swapping, so reclaim swap space. */
 		if (PageSwapCache(page) && (mem_cgroup_swap_full(page) ||
@@ -1464,8 +1493,7 @@ activate_locked:
 		if (!PageMlocked(page)) {
 			int type = page_is_file_cache(page);
 			SetPageActive(page);
-			pgactivate++;
-			stat->nr_activate[type] += hpage_nr_pages(page);
+			stat->nr_activate[type] += nr_pages;
 			count_memcg_page_event(page, PGACTIVATE);
 		}
 keep_locked:
@@ -1475,6 +1503,8 @@ keep:
 		VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page), page);
 	}
 
+	pgactivate = stat->nr_activate[0] + stat->nr_activate[1];
+
 	mem_cgroup_uncharge_list(&free_pages);
 	try_to_unmap_flush();
 	free_unref_page_list(&free_pages);
@@ -1646,10 +1676,9 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
 	LIST_HEAD(pages_skipped);
 	isolate_mode_t mode = (sc->may_unmap ? 0 : ISOLATE_UNMAPPED);
 
+	total_scan = 0;
 	scan = 0;
-	for (total_scan = 0;
-	     scan < nr_to_scan && nr_taken < nr_to_scan && !list_empty(src);
-	     total_scan++) {
+	while (scan < nr_to_scan && !list_empty(src)) {
 		struct page *page;
 
 		page = lru_to_page(src);
@@ -1657,9 +1686,12 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
 
 		VM_BUG_ON_PAGE(!PageLRU(page), page);
 
+		nr_pages = 1 << compound_order(page);
+		total_scan += nr_pages;
+
 		if (page_zonenum(page) > sc->reclaim_idx) {
 			list_move(&page->lru, &pages_skipped);
-			nr_skipped[page_zonenum(page)]++;
+			nr_skipped[page_zonenum(page)] += nr_pages;
 			continue;
 		}
 
@@ -1668,11 +1700,14 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
 		 * return with no isolated pages if the LRU mostly contains
 		 * ineligible pages.  This causes the VM to not reclaim any
 		 * pages, triggering a premature OOM.
+		 *
+		 * Account all tail pages of THP.  This would not cause
+		 * premature OOM since __isolate_lru_page() returns -EBUSY
+		 * only when the page is being freed somewhere else.
 		 */
-		scan++;
+		scan += nr_pages;
 		switch (__isolate_lru_page(page, mode)) {
 		case 0:
-			nr_pages = hpage_nr_pages(page);
 			nr_taken += nr_pages;
 			nr_zone_taken[page_zonenum(page)] += nr_pages;
 			list_move(&page->lru, dst);