Revert "mm: batch activate_page() to reduce lock contention"

This reverts commit 744ed1442757767ffede5008bb13e0805085902e.

Chris Mason ended up chasing down some page allocation errors and pages
stuck waiting on the IO scheduler, and was able to narrow it down to two
commits: commit 744ed1442757 ("mm: batch activate_page() to reduce lock
contention") and d8505dee1a87 ("mm: simplify code of swap.c").

This reverts the first of them.

Reported-and-debugged-by: Chris Mason <[e-mail]>
Cc: Mel Gorman <[e-mail]>
Cc: Andrew Morton <[e-mail]>
Cc: Jens Axboe <[e-mail]>
Cc: linux-mm <[e-mail]>
Cc: KAMEZAWA Hiroyuki <[e-mail]>
Cc: Andrea Arcangeli <[e-mail]>
Cc: Shaohua Li <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

mm/internal.h

···
 
 extern unsigned long highest_memmap_pfn;
 
-#ifdef CONFIG_SMP
-extern int putback_active_lru_page(struct zone *zone, struct page *page);
-#else
-static inline int putback_active_lru_page(struct zone *zone, struct page *page)
-{
-	return 0;
-}
-#endif
-
 /*
  * in mm/vmscan.c:
  */

mm/swap.c

···
 }
 
 /*
- * A page will go to active list either by activate_page or putback_lru_page.
- * In the activate_page case, the page hasn't active bit set. The page might
- * not in LRU list because it's isolated before it gets a chance to be moved to
- * active list. The window is small because pagevec just stores several pages.
- * For such case, we do nothing for such page.
- * In the putback_lru_page case, the page isn't in lru list but has active
- * bit set
+ * FIXME: speed this up?
  */
-static void __activate_page(struct page *page, void *arg)
-{
-	struct zone *zone = page_zone(page);
-	int file = page_is_file_cache(page);
-	int lru = page_lru_base_type(page);
-	bool putback = !PageLRU(page);
-
-	/* The page is isolated before it's moved to active list */
-	if (!PageLRU(page) && !PageActive(page))
-		return;
-	if ((PageLRU(page) && PageActive(page)) || PageUnevictable(page))
-		return;
-
-	if (!putback)
-		del_page_from_lru_list(zone, page, lru);
-	else
-		SetPageLRU(page);
-
-	SetPageActive(page);
-	lru += LRU_ACTIVE;
-	add_page_to_lru_list(zone, page, lru);
-
-	if (putback)
-		return;
-	__count_vm_event(PGACTIVATE);
-	update_page_reclaim_stat(zone, page, file, 1);
-}
-
-#ifdef CONFIG_SMP
-static DEFINE_PER_CPU(struct pagevec, activate_page_pvecs);
-
-static void activate_page_drain(int cpu)
-{
-	struct pagevec *pvec = &per_cpu(activate_page_pvecs, cpu);
-
-	if (pagevec_count(pvec))
-		pagevec_lru_move_fn(pvec, __activate_page, NULL);
-}
-
-void activate_page(struct page *page)
-{
-	if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
-		struct pagevec *pvec = &get_cpu_var(activate_page_pvecs);
-
-		page_cache_get(page);
-		if (!pagevec_add(pvec, page))
-			pagevec_lru_move_fn(pvec, __activate_page, NULL);
-		put_cpu_var(activate_page_pvecs);
-	}
-}
-
-/* Caller should hold zone->lru_lock */
-int putback_active_lru_page(struct zone *zone, struct page *page)
-{
-	struct pagevec *pvec = &get_cpu_var(activate_page_pvecs);
-
-	if (!pagevec_add(pvec, page)) {
-		spin_unlock_irq(&zone->lru_lock);
-		pagevec_lru_move_fn(pvec, __activate_page, NULL);
-		spin_lock_irq(&zone->lru_lock);
-	}
-	put_cpu_var(activate_page_pvecs);
-	return 1;
-}
-
-#else
-static inline void activate_page_drain(int cpu)
-{
-}
-
 void activate_page(struct page *page)
 {
 	struct zone *zone = page_zone(page);
 
 	spin_lock_irq(&zone->lru_lock);
-	if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page))
-		__activate_page(page, NULL);
+	if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
+		int file = page_is_file_cache(page);
+		int lru = page_lru_base_type(page);
+		del_page_from_lru_list(zone, page, lru);
+
+		SetPageActive(page);
+		lru += LRU_ACTIVE;
+		add_page_to_lru_list(zone, page, lru);
+		__count_vm_event(PGACTIVATE);
+
+		update_page_reclaim_stat(zone, page, file, 1);
+	}
 	spin_unlock_irq(&zone->lru_lock);
 }
-#endif
 
 /*
  * Mark a page as having seen activity.
···
 		pagevec_move_tail(pvec);
 		local_irq_restore(flags);
 	}
-	activate_page_drain(cpu);
 }
 
 void lru_add_drain(void)

mm/vmscan.c

···
 			spin_lock_irq(&zone->lru_lock);
 			continue;
 		}
+		SetPageLRU(page);
 		lru = page_lru(page);
+		add_page_to_lru_list(zone, page, lru);
 		if (is_active_lru(lru)) {
 			int file = is_file_lru(lru);
 			int numpages = hpage_nr_pages(page);
 			reclaim_stat->recent_rotated[file] += numpages;
-			if (putback_active_lru_page(zone, page))
-				continue;
 		}
-		SetPageLRU(page);
-		add_page_to_lru_list(zone, page, lru);
 		if (!pagevec_add(&pvec, page)) {
 			spin_unlock_irq(&zone->lru_lock);
 			__pagevec_release(&pvec);