2 files changed, 14 insertions, 83 deletions

diff --git a/include/trace/events/vmscan.h b/include/trace/events/vmscan.h
index bdaf32f8a874..82f693395ac5 100644
--- a/include/trace/events/vmscan.h
+++ b/include/trace/events/vmscan.h
@@ -13,7 +13,7 @@
 #define RECLAIM_WB_ANON         0x0001u
 #define RECLAIM_WB_FILE         0x0002u
 #define RECLAIM_WB_MIXED        0x0010u
-#define RECLAIM_WB_SYNC         0x0004u
+#define RECLAIM_WB_SYNC         0x0004u /* Unused, all reclaim async */
 #define RECLAIM_WB_ASYNC        0x0008u
 
 #define show_reclaim_flags(flags)                               \
@@ -27,13 +27,13 @@
 
 #define trace_reclaim_flags(page, sync) ( \
         (page_is_file_cache(page) ? RECLAIM_WB_FILE : RECLAIM_WB_ANON) | \
-        (sync & RECLAIM_MODE_SYNC ? RECLAIM_WB_SYNC : RECLAIM_WB_ASYNC)   \
+        (RECLAIM_WB_ASYNC) \
         )
 
-#define trace_shrink_flags(file, sync) ( \
-        (sync & RECLAIM_MODE_SYNC ? RECLAIM_WB_MIXED : \
-                        (file ? RECLAIM_WB_FILE : RECLAIM_WB_ANON)) |  \
-        (sync & RECLAIM_MODE_SYNC ? RECLAIM_WB_SYNC : RECLAIM_WB_ASYNC) \
+#define trace_shrink_flags(file, sync) \
+        ( \
+                (file ? RECLAIM_WB_FILE : RECLAIM_WB_ANON) | \
+                (RECLAIM_WB_ASYNC) \
         )
 
 TRACE_EVENT(mm_vmscan_kswapd_sleep,
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 546d02ce90ee..e27f27d4cc19 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -56,15 +56,11 @@
 /*
  * reclaim_mode determines how the inactive list is shrunk
  * RECLAIM_MODE_SINGLE: Reclaim only order-0 pages
- * RECLAIM_MODE_ASYNC:  Do not block
- * RECLAIM_MODE_SYNC:   Allow blocking e.g. call wait_on_page_writeback
  * RECLAIM_MODE_COMPACTION: For high-order allocations, reclaim a number of
  *                      order-0 pages and then compact the zone
  */
 typedef unsigned __bitwise__ reclaim_mode_t;
 #define RECLAIM_MODE_SINGLE             ((__force reclaim_mode_t)0x01u)
-#define RECLAIM_MODE_ASYNC              ((__force reclaim_mode_t)0x02u)
-#define RECLAIM_MODE_SYNC               ((__force reclaim_mode_t)0x04u)
 #define RECLAIM_MODE_COMPACTION         ((__force reclaim_mode_t)0x10u)
 
 struct scan_control {
@@ -360,12 +356,8 @@ out:
         return ret;
 }
 
-static void set_reclaim_mode(int priority, struct scan_control *sc,
-                                   bool sync)
+static void set_reclaim_mode(int priority, struct scan_control *sc)
 {
-        /* Sync reclaim used only for compaction */
-        reclaim_mode_t syncmode = sync ? RECLAIM_MODE_SYNC : RECLAIM_MODE_ASYNC;
-
         /*
          * Restrict reclaim/compaction to costly allocations or when
          * under memory pressure
@@ -373,14 +365,14 @@ static void set_reclaim_mode(int priority, struct scan_control *sc,
         if (COMPACTION_BUILD && sc->order &&
                         (sc->order > PAGE_ALLOC_COSTLY_ORDER ||
                          priority < DEF_PRIORITY - 2))
-                sc->reclaim_mode = RECLAIM_MODE_COMPACTION | syncmode;
+                sc->reclaim_mode = RECLAIM_MODE_COMPACTION;
         else
-                sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC;
+                sc->reclaim_mode = RECLAIM_MODE_SINGLE;
 }
 
 static void reset_reclaim_mode(struct scan_control *sc)
 {
-        sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC;
+        sc->reclaim_mode = RECLAIM_MODE_SINGLE;
 }
 
 static inline int is_page_cache_freeable(struct page *page)
@@ -791,19 +783,8 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 
                 if (PageWriteback(page)) {
                         nr_writeback++;
-                        /*
-                         * Synchronous reclaim cannot queue pages for
-                         * writeback due to the possibility of stack overflow
-                         * but if it encounters a page under writeback, wait
-                         * for the IO to complete.
-                         */
-                        if ((sc->reclaim_mode & RECLAIM_MODE_SYNC) &&
-                            may_enter_fs)
-                                wait_on_page_writeback(page);
-                        else {
-                                unlock_page(page);
-                                goto keep_reclaim_mode;
-                        }
+                        unlock_page(page);
+                        goto keep;
                 }
 
                 references = page_check_references(page, mz, sc);
@@ -886,7 +867,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
                                 goto activate_locked;
                         case PAGE_SUCCESS:
                                 if (PageWriteback(page))
-                                        goto keep_reclaim_mode;
+                                        goto keep;
                                 if (PageDirty(page))
                                         goto keep;
 
@@ -985,8 +966,6 @@ activate_locked:
 keep_locked:
                 unlock_page(page);
 keep:
-                reset_reclaim_mode(sc);
-keep_reclaim_mode:
                 list_add(&page->lru, &ret_pages);
                 VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
         }
@@ -1342,47 +1321,6 @@ update_isolated_counts(struct mem_cgroup_zone *mz,
 }
 
 /*
- * Returns true if a direct reclaim should wait on pages under writeback.
- *
- * If we are direct reclaiming for contiguous pages and we do not reclaim
- * everything in the list, try again and wait for writeback IO to complete.
- * This will stall high-order allocations noticeably. Only do that when really
- * need to free the pages under high memory pressure.
- */
-static inline bool should_reclaim_stall(unsigned long nr_taken,
-                                        unsigned long nr_freed,
-                                        int priority,
-                                        struct scan_control *sc)
-{
-        int stall_priority;
-
-        /* kswapd should not stall on sync IO */
-        if (current_is_kswapd())
-                return false;
-
-        /* Only stall for memory compaction */
-        if (sc->reclaim_mode & RECLAIM_MODE_SINGLE)
-                return false;
-
-        /* If we have reclaimed everything on the isolated list, no stall */
-        if (nr_freed == nr_taken)
-                return false;
-
-        /*
-         * For high-order allocations, there are two stall thresholds.
-         * High-cost allocations stall immediately where as lower
-         * order allocations such as stacks require the scanning
-         * priority to be much higher before stalling.
-         */
-        if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
-                stall_priority = DEF_PRIORITY;
-        else
-                stall_priority = DEF_PRIORITY / 3;
-
-        return priority <= stall_priority;
-}
-
-/*
  * shrink_inactive_list() is a helper for shrink_zone().  It returns the number
  * of reclaimed pages
  */
@@ -1410,7 +1348,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct mem_cgroup_zone *mz,
                         return SWAP_CLUSTER_MAX;
         }
 
-        set_reclaim_mode(priority, sc, false);
+        set_reclaim_mode(priority, sc);
 
         lru_add_drain();
 
@@ -1442,13 +1380,6 @@ shrink_inactive_list(unsigned long nr_to_scan, struct mem_cgroup_zone *mz,
         nr_reclaimed = shrink_page_list(&page_list, mz, sc, priority,
                                                 &nr_dirty, &nr_writeback);
 
-        /* Check if we should syncronously wait for writeback */
-        if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) {
-                set_reclaim_mode(priority, sc, true);
-                nr_reclaimed += shrink_page_list(&page_list, mz, sc,
-                                        priority, &nr_dirty, &nr_writeback);
-        }
-
         spin_lock_irq(&zone->lru_lock);
 
         reclaim_stat->recent_scanned[0] += nr_anon;