My usual tmpfs swapping loads on recent mmotms have oddly aroused the OOM

killer after an hour or two.  Bisection led to
mm-return-boolean-from-page_is_file_cache.patch, but really it's the prior
mm-introduce-page_lru_base_type.patch that's at fault.

It converted page_lru() to use page_lru_base_type(), but forgot to convert
del_page_from_lru() - which then decremented the wrong stats once
page_is_file_cache() was changed to a boolean.

Fix that, move page_lru_base_type() before del_page_from_lru(), and mark
it "inline" like the other mm_inline.h functions.
Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/mm_inline.h

@@ -39,41 +39,41 @@ del_page_from_lru_list(struct zone *zone, struct page *page, enum lru_list l)
 	mem_cgroup_del_lru_list(page, l);
 }
 
+/**
+ * page_lru_base_type - which LRU list type should a page be on?
+ * @page: the page to test
+ *
+ * Used for LRU list index arithmetic.
+ *
+ * Returns the base LRU type - file or anon - @page should be on.
+ */
+static inline enum lru_list page_lru_base_type(struct page *page)
+{
+	if (page_is_file_cache(page))
+		return LRU_INACTIVE_FILE;
+	return LRU_INACTIVE_ANON;
+}
+
 static inline void
 del_page_from_lru(struct zone *zone, struct page *page)
 {
-	enum lru_list l = LRU_BASE;
+	enum lru_list l;
 
 	list_del(&page->lru);
 	if (PageUnevictable(page)) {
 		__ClearPageUnevictable(page);
 		l = LRU_UNEVICTABLE;
 	} else {
+		l = page_lru_base_type(page);
 		if (PageActive(page)) {
 			__ClearPageActive(page);
 			l += LRU_ACTIVE;
 		}
-		l += page_is_file_cache(page);
 	}
 	__dec_zone_state(zone, NR_LRU_BASE + l);
 	mem_cgroup_del_lru_list(page, l);
 }
 
-/**
- * page_lru_base_type - which LRU list type should a page be on?
- * @page: the page to test
- *
- * Used for LRU list index arithmetic.
- *
- * Returns the base LRU type - file or anon - @page should be on.
- */
-static enum lru_list page_lru_base_type(struct page *page)
-{
-	if (page_is_file_cache(page))
-		return LRU_INACTIVE_FILE;
-	return LRU_INACTIVE_ANON;
-}
-
 /**
  * page_lru - which LRU list should a page be on?
  * @page: the page to test