mem-hwpoison: fix page refcount around isolate_lru_page()

Drop first page reference only after calling isolate_lru_page() to keep
page stable reference while isolating.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 5 deletions

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 12178ec32ab5..369b80e81416 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1440,16 +1440,12 @@ int soft_offline_page(struct page *page, int flags)
          */
         ret = invalidate_inode_page(page);
         unlock_page(page);
-
         /*
-         * Drop count because page migration doesn't like raised
-         * counts. The page could get re-allocated, but if it becomes
-         * LRU the isolation will just fail.
          * RED-PEN would be better to keep it isolated here, but we
          * would need to fix isolation locking first.
          */
-        put_page(page);
         if (ret == 1) {
+                put_page(page);
                 ret = 0;
                 pr_info("soft_offline: %#lx: invalidated\n", pfn);
                 goto done;
@@ -1461,6 +1457,11 @@ int soft_offline_page(struct page *page, int flags)
          * handles a large number of cases for us.
          */
         ret = isolate_lru_page(page);
+        /*
+         * Drop page reference which is came from get_any_page()
+         * successful isolate_lru_page() already took another one.
+         */
+        put_page(page);
         if (!ret) {
                 LIST_HEAD(pagelist);