mm: remove SWAP_MLOCK in ttu

ttu doesn't need to return SWAP_MLOCK.  Instead, just return SWAP_FAIL
because it means the page is not-swappable so it should move to another
LRU list(active or unevictable).  putback friends will move it to right
list depending on the page's LRU flag.

Link: http://lkml.kernel.org/r/1489555493-14659-6-git-send-email-minchan@kernel.org
Signed-off-by: Minchan Kim <minchan@kernel.org>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/rmap.h

@@ -297,6 +297,5 @@ static inline int page_mkclean(struct page *page)
 #define SWAP_SUCCESS	0
 #define SWAP_AGAIN	1
 #define SWAP_FAIL	2
-#define SWAP_MLOCK	3
 
 #endif	/* _LINUX_RMAP_H */

mm/rmap.c

@@ -1329,7 +1329,7 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
 					 */
 					mlock_vma_page(page);
 				}
-				ret = SWAP_MLOCK;
+				ret = SWAP_FAIL;
 				page_vma_mapped_walk_done(&pvmw);
 				break;
 			}
@@ -1506,7 +1506,6 @@ static int page_mapcount_is_zero(struct page *page)
  * SWAP_SUCCESS	- we succeeded in removing all mappings
  * SWAP_AGAIN	- we missed a mapping, try again later
  * SWAP_FAIL	- the page is unswappable
- * SWAP_MLOCK	- page is mlocked.
  */
 int try_to_unmap(struct page *page, enum ttu_flags flags)
 {

mm/vmscan.c

@@ -987,7 +987,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 		sc->nr_scanned++;
 
 		if (unlikely(!page_evictable(page)))
-			goto cull_mlocked;
+			goto activate_locked;
 
 		if (!sc->may_unmap && page_mapped(page))
 			goto keep_locked;
@@ -1152,8 +1152,6 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 				goto activate_locked;
 			case SWAP_AGAIN:
 				goto keep_locked;
-			case SWAP_MLOCK:
-				goto cull_mlocked;
 			case SWAP_SUCCESS:
 				; /* try to free the page below */
 			}
@@ -1295,20 +1293,16 @@ free_it:
 		list_add(&page->lru, &free_pages);
 		continue;
 
-cull_mlocked:
-		if (PageSwapCache(page))
-			try_to_free_swap(page);
-		unlock_page(page);
-		list_add(&page->lru, &ret_pages);
-		continue;
-
 activate_locked:
 		/* Not a candidate for swapping, so reclaim swap space. */
-		if (PageSwapCache(page) && mem_cgroup_swap_full(page))
+		if (PageSwapCache(page) && (mem_cgroup_swap_full(page) ||
+						PageMlocked(page)))
 			try_to_free_swap(page);
 		VM_BUG_ON_PAGE(PageActive(page), page);
-		SetPageActive(page);
-		pgactivate++;
+		if (!PageMlocked(page)) {
+			SetPageActive(page);
+			pgactivate++;
+		}
 keep_locked:
 		unlock_page(page);
 keep: