[PATCH 2/3] mem-hwpoison: fix page refcount around isolate_lru_page()

[Konstantin Khlebnikov <khlebnikov@openvz.org>]

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>
---
 mm/memory-failure.c |   11 ++++++-----
 1 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 2b9a5ee..a17d31e 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);