3 files changed, 72 insertions, 36 deletions

diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 864035fb8f8..4307231bd22 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -70,6 +70,10 @@ extern void online_page(struct page *page);
 extern int online_pages(unsigned long, unsigned long);
 extern void __offline_isolated_pages(unsigned long, unsigned long);
 
+#ifdef CONFIG_MEMORY_HOTREMOVE
+extern bool is_pageblock_removable_nolock(struct page *page);
+#endif /* CONFIG_MEMORY_HOTREMOVE */
+
 /* reasonably generic interface to expand the physical pages in a zone  */
 extern int __add_pages(int nid, struct zone *zone, unsigned long start_pfn,
         unsigned long nr_pages);
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 4821338b4e4..b0dc6545297 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -602,27 +602,14 @@ static struct page *next_active_pageblock(struct page *page)
 /* Checks if this range of memory is likely to be hot-removable. */
 int is_mem_section_removable(unsigned long start_pfn, unsigned long nr_pages)
 {
-        int type;
         struct page *page = pfn_to_page(start_pfn);
         struct page *end_page = page + nr_pages;
 
         /* Check the starting page of each pageblock within the range */
         for (; page < end_page; page = next_active_pageblock(page)) {
-                type = get_pageblock_migratetype(page);
-
-                /*
-                 * A pageblock containing MOVABLE or free pages is considered
-                 * removable
-                 */
-                if (type != MIGRATE_MOVABLE && !pageblock_free(page))
-                        return 0;
-
-                /*
-                 * A pageblock starting with a PageReserved page is not
-                 * considered removable.
-                 */
-                if (PageReserved(page))
+                if (!is_pageblock_removable_nolock(page))
                         return 0;
+                cond_resched();
         }
 
         /* All pageblocks in the memory block are likely to be hot-removable */
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 099790052bf..6a683f81943 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5297,12 +5297,65 @@ void set_pageblock_flags_group(struct page *page, unsigned long flags,
  * page allocater never alloc memory from ISOLATE block.
  */
 
+static int
+__count_immobile_pages(struct zone *zone, struct page *page, int count)
+{
+        unsigned long pfn, iter, found;
+        /*
+         * For avoiding noise data, lru_add_drain_all() should be called
+         * If ZONE_MOVABLE, the zone never contains immobile pages
+         */
+        if (zone_idx(zone) == ZONE_MOVABLE)
+                return true;
+
+        if (get_pageblock_migratetype(page) == MIGRATE_MOVABLE)
+                return true;
+
+        pfn = page_to_pfn(page);
+        for (found = 0, iter = 0; iter < pageblock_nr_pages; iter++) {
+                unsigned long check = pfn + iter;
+
+                if (!pfn_valid_within(check)) {
+                        iter++;
+                        continue;
+                }
+                page = pfn_to_page(check);
+                if (!page_count(page)) {
+                        if (PageBuddy(page))
+                                iter += (1 << page_order(page)) - 1;
+                        continue;
+                }
+                if (!PageLRU(page))
+                        found++;
+                /*
+                 * If there are RECLAIMABLE pages, we need to check it.
+                 * But now, memory offline itself doesn't call shrink_slab()
+                 * and it still to be fixed.
+                 */
+                /*
+                 * If the page is not RAM, page_count()should be 0.
+                 * we don't need more check. This is an _used_ not-movable page.
+                 *
+                 * The problematic thing here is PG_reserved pages. PG_reserved
+                 * is set to both of a memory hole page and a _used_ kernel
+                 * page at boot.
+                 */
+                if (found > count)
+                        return false;
+        }
+        return true;
+}
+
+bool is_pageblock_removable_nolock(struct page *page)
+{
+        struct zone *zone = page_zone(page);
+        return __count_immobile_pages(zone, page, 0);
+}
+
 int set_migratetype_isolate(struct page *page)
 {
         struct zone *zone;
-        struct page *curr_page;
-        unsigned long flags, pfn, iter;
-        unsigned long immobile = 0;
+        unsigned long flags, pfn;
         struct memory_isolate_notify arg;
         int notifier_ret;
         int ret = -EBUSY;
@@ -5312,11 +5365,6 @@ int set_migratetype_isolate(struct page *page)
         zone_idx = zone_idx(zone);
 
         spin_lock_irqsave(&zone->lock, flags);
-        if (get_pageblock_migratetype(page) == MIGRATE_MOVABLE ||
-            zone_idx == ZONE_MOVABLE) {
-                ret = 0;
-                goto out;
-        }
 
         pfn = page_to_pfn(page);
         arg.start_pfn = pfn;
@@ -5338,21 +5386,18 @@ int set_migratetype_isolate(struct page *page)
         notifier_ret = notifier_to_errno(notifier_ret);
         if (notifier_ret)
                 goto out;
-
-        for (iter = pfn; iter < (pfn + pageblock_nr_pages); iter++) {
-                if (!pfn_valid_within(pfn))
-                        continue;
-
-                curr_page = pfn_to_page(iter);
-                if (!page_count(curr_page) || PageLRU(curr_page))
-                        continue;
-
-                immobile++;
-        }
-
-        if (arg.pages_found == immobile)
+        /*
+         * FIXME: Now, memory hotplug doesn't call shrink_slab() by itself.
+         * We just check MOVABLE pages.
+         */
+        if (__count_immobile_pages(zone, page, arg.pages_found))
                 ret = 0;
 
+        /*
+         * immobile means "not-on-lru" paes. If immobile is larger than
+         * removable-by-driver pages reported by notifier, we'll fail.
+         */
+
 out:
         if (!ret) {
                 set_pageblock_migratetype(page, MIGRATE_ISOLATE);