thp, mm: avoid PageUnevictable on active/inactive lru lists

active/inactive lru lists can contain unevicable pages (i.e.  ramfs pages
that have been placed on the LRU lists when first allocated), but these
pages must not have PageUnevictable set - otherwise shrink_[in]active_list
goes crazy:

kernel BUG at /home/space/kas/git/public/linux-next/mm/vmscan.c:1122!

1090 static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
1091                 struct lruvec *lruvec, struct list_head *dst,
1092                 unsigned long *nr_scanned, struct scan_control *sc,
1093                 isolate_mode_t mode, enum lru_list lru)
1094 {
...
1108                 switch (__isolate_lru_page(page, mode)) {
1109                 case 0:
...
1116                 case -EBUSY:
...
1121                 default:
1122                         BUG();
1123                 }
1124         }
...
1130 }

__isolate_lru_page() returns EINVAL for PageUnevictable(page).

For lru_add_page_tail(), it means we should not set PageUnevictable()
for tail pages unless we're sure that it will go to LRU_UNEVICTABLE.
Let's just copy PG_active and PG_unevictable from head page in
__split_huge_page_refcount(), it will simplify lru_add_page_tail().

This will fix one more bug in lru_add_page_tail(): if
page_evictable(page_tail) is false and PageLRU(page) is true, page_tail
will go to the same lru as page, but nobody cares to sync page_tail
active/inactive state with page.  So we can end up with inactive page on
active lru.  The patch will fix it as well since we copy PG_active from
head page.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 18 deletions

diff --git a/mm/swap.c b/mm/swap.c
index d3982c062629..62b78a6e224f 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -770,8 +770,6 @@ EXPORT_SYMBOL(__pagevec_release);
 void lru_add_page_tail(struct page *page, struct page *page_tail,
                        struct lruvec *lruvec, struct list_head *list)
 {
-        int uninitialized_var(active);
-        enum lru_list lru;
         const int file = 0;
 
         VM_BUG_ON(!PageHead(page));
@@ -783,20 +781,6 @@ void lru_add_page_tail(struct page *page, struct page *page_tail,
         if (!list)
                 SetPageLRU(page_tail);
 
-        if (page_evictable(page_tail)) {
-                if (PageActive(page)) {
-                        SetPageActive(page_tail);
-                        active = 1;
-                        lru = LRU_ACTIVE_ANON;
-                } else {
-                        active = 0;
-                        lru = LRU_INACTIVE_ANON;
-                }
-        } else {
-                SetPageUnevictable(page_tail);
-                lru = LRU_UNEVICTABLE;
-        }
-
         if (likely(PageLRU(page)))
                 list_add_tail(&page_tail->lru, &page->lru);
         else if (list) {
@@ -812,13 +796,13 @@ void lru_add_page_tail(struct page *page, struct page *page_tail,
                  * Use the standard add function to put page_tail on the list,
                  * but then correct its position so they all end up in order.
                  */
-                add_page_to_lru_list(page_tail, lruvec, lru);
+                add_page_to_lru_list(page_tail, lruvec, page_lru(page_tail));
                 list_head = page_tail->lru.prev;
                 list_move_tail(&page_tail->lru, list_head);
         }
 
         if (!PageUnevictable(page))
-                update_page_reclaim_stat(lruvec, file, active);
+                update_page_reclaim_stat(lruvec, file, PageActive(page_tail));
 }
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */