1 files changed, 65 insertions, 41 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 5a610804cd06..1838c15ca4fd 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -443,6 +443,10 @@ static int shrink_list(struct list_head *page_list, struct scan_control *sc)
                 BUG_ON(PageActive(page));
 
                 sc->nr_scanned++;
+
+                if (!sc->may_swap && page_mapped(page))
+                        goto keep_locked;
+
                 /* Double the slab pressure for mapped and swapcache pages */
                 if (page_mapped(page) || PageSwapCache(page))
                         sc->nr_scanned++;
@@ -632,7 +636,7 @@ static int swap_page(struct page *page)
         struct address_space *mapping = page_mapping(page);
 
         if (page_mapped(page) && mapping)
-                if (try_to_unmap(page, 0) != SWAP_SUCCESS)
+                if (try_to_unmap(page, 1) != SWAP_SUCCESS)
                         goto unlock_retry;
 
         if (PageDirty(page)) {
@@ -839,7 +843,7 @@ EXPORT_SYMBOL(migrate_page);
  * pages are swapped out.
  *
  * The function returns after 10 attempts or if no pages
- * are movable anymore because t has become empty
+ * are movable anymore because to has become empty
  * or no retryable pages exist anymore.
  *
  * Return: Number of pages not migrated when "to" ran empty.
@@ -928,12 +932,21 @@ redo:
                         goto unlock_both;
 
                 if (mapping->a_ops->migratepage) {
+                        /*
+                         * Most pages have a mapping and most filesystems
+                         * should provide a migration function. Anonymous
+                         * pages are part of swap space which also has its
+                         * own migration function. This is the most common
+                         * path for page migration.
+                         */
                         rc = mapping->a_ops->migratepage(newpage, page);
                         goto unlock_both;
                 }
 
                 /*
-                 * Trigger writeout if page is dirty
+                 * Default handling if a filesystem does not provide
+                 * a migration function. We can only migrate clean
+                 * pages so try to write out any dirty pages first.
                  */
                 if (PageDirty(page)) {
                         switch (pageout(page, mapping)) {
@@ -949,9 +962,10 @@ redo:
                                 ; /* try to migrate the page below */
                         }
                 }
+
                 /*
-                 * If we have no buffer or can release the buffer
-                 * then do a simple migration.
+                 * Buffers are managed in a filesystem specific way.
+                 * We must have no buffers or drop them.
                  */
                 if (!page_has_buffers(page) ||
                     try_to_release_page(page, GFP_KERNEL)) {
@@ -966,6 +980,11 @@ redo:
                  * swap them out.
                  */
                 if (pass > 4) {
+                        /*
+                         * Persistently unable to drop buffers..... As a
+                         * measure of last resort we fall back to
+                         * swap_page().
+                         */
                         unlock_page(newpage);
                         newpage = NULL;
                         rc = swap_page(page);
@@ -1176,9 +1195,47 @@ refill_inactive_zone(struct zone *zone, struct scan_control *sc)
         struct page *page;
         struct pagevec pvec;
         int reclaim_mapped = 0;
-        long mapped_ratio;
-        long distress;
-        long swap_tendency;
+
+        if (unlikely(sc->may_swap)) {
+                long mapped_ratio;
+                long distress;
+                long swap_tendency;
+
+                /*
+                 * `distress' is a measure of how much trouble we're having
+                 * reclaiming pages.  0 -> no problems.  100 -> great trouble.
+                 */
+                distress = 100 >> zone->prev_priority;
+
+                /*
+                 * The point of this algorithm is to decide when to start
+                 * reclaiming mapped memory instead of just pagecache.  Work out
+                 * how much memory
+                 * is mapped.
+                 */
+                mapped_ratio = (sc->nr_mapped * 100) / total_memory;
+
+                /*
+                 * Now decide how much we really want to unmap some pages.  The
+                 * mapped ratio is downgraded - just because there's a lot of
+                 * mapped memory doesn't necessarily mean that page reclaim
+                 * isn't succeeding.
+                 *
+                 * The distress ratio is important - we don't want to start
+                 * going oom.
+                 *
+                 * A 100% value of vm_swappiness overrides this algorithm
+                 * altogether.
+                 */
+                swap_tendency = mapped_ratio / 2 + distress + vm_swappiness;
+
+                /*
+                 * Now use this metric to decide whether to start moving mapped
+                 * memory onto the inactive list.
+                 */
+                if (swap_tendency >= 100)
+                        reclaim_mapped = 1;
+        }
 
         lru_add_drain();
         spin_lock_irq(&zone->lru_lock);
@@ -1188,37 +1245,6 @@ refill_inactive_zone(struct zone *zone, struct scan_control *sc)
         zone->nr_active -= pgmoved;
         spin_unlock_irq(&zone->lru_lock);
 
-        /*
-         * `distress' is a measure of how much trouble we're having reclaiming
-         * pages.  0 -> no problems.  100 -> great trouble.
-         */
-        distress = 100 >> zone->prev_priority;
-
-        /*
-         * The point of this algorithm is to decide when to start reclaiming
-         * mapped memory instead of just pagecache.  Work out how much memory
-         * is mapped.
-         */
-        mapped_ratio = (sc->nr_mapped * 100) / total_memory;
-
-        /*
-         * Now decide how much we really want to unmap some pages.  The mapped
-         * ratio is downgraded - just because there's a lot of mapped memory
-         * doesn't necessarily mean that page reclaim isn't succeeding.
-         *
-         * The distress ratio is important - we don't want to start going oom.
-         *
-         * A 100% value of vm_swappiness overrides this algorithm altogether.
-         */
-        swap_tendency = mapped_ratio / 2 + distress + vm_swappiness;
-
-        /*
-         * Now use this metric to decide whether to start moving mapped memory
-         * onto the inactive list.
-         */
-        if (swap_tendency >= 100)
-                reclaim_mapped = 1;
-
         while (!list_empty(&l_hold)) {
                 cond_resched();
                 page = lru_to_page(&l_hold);
@@ -1595,9 +1621,7 @@ scan:
                         sc.nr_reclaimed = 0;
                         sc.priority = priority;
                         sc.swap_cluster_max = nr_pages? nr_pages : SWAP_CLUSTER_MAX;
-                        atomic_inc(&zone->reclaim_in_progress);
                         shrink_zone(zone, &sc);
-                        atomic_dec(&zone->reclaim_in_progress);
                         reclaim_state->reclaimed_slab = 0;
                         nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
                                                 lru_pages);