memory hotplug: fix notifier's return value check

Even if notifier cannot find any pages, it doesn't mean no pages are
available...And, if there are no notifiers registered, this condition will
be always true and memory hotplug will show -EBUSY.

This is a bug but not critical.

In most case, a pageblock which will be offlined is MIGRATE_MOVABLE This
"notifier" is called only when the pageblock is _not_ MIGRATE_MOVABLE.
But if not MIGRATE_MOVABLE, it's common case that memory hotplug will
fail.  So, no one notice this bug.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 5faf876cfc3a1f58b7a392f89cf008b263148371..099790052bfe7d52e76be491e1c29bd9a0de6918 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5336,7 +5336,7 @@ int set_migratetype_isolate(struct page *page)
         */
        notifier_ret = memory_isolate_notify(MEM_ISOLATE_COUNT, &arg);
        notifier_ret = notifier_to_errno(notifier_ret);
-       if (notifier_ret || !arg.pages_found)
+       if (notifier_ret)
                goto out;
 
        for (iter = pfn; iter < (pfn + pageblock_nr_pages); iter++) {