hwpoison: always unset MIGRATE_ISOLATE before returning from soft_offline_page()

Soft offline code expects that MIGRATE_ISOLATE is set on the target page
only during soft offlining work.  But currenly it doesn't work as expected
when get_any_page() fails and returns negative value.  In the result, end
users can have unexpectedly isolated pages.  This patch just fixes it.
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Reviewed-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memory-failure.c

@@ -1553,7 +1553,7 @@ int soft_offline_page(struct page *page, int flags)
 
 	ret = get_any_page(page, pfn, flags);
 	if (ret < 0)
-		return ret;
+		goto unset;
 	if (ret) { /* for in-use pages */
 		if (PageHuge(page))
 			ret = soft_offline_huge_page(page, flags);
@@ -1570,6 +1570,7 @@ int soft_offline_page(struct page *page, int flags)
 			atomic_long_inc(&num_poisoned_pages);
 		}
 	}
+unset:
 	unset_migratetype_isolate(page, MIGRATE_MOVABLE);
 	return ret;
 }