Right now, if we have two isolations racing, we might trigger the
WARN_ON_ONCE() and to dump_page(NULL), dereferencing NULL. Let's just
return directly.

In the future, we might want to report -EAGAIN to the caller instead, as
this could indicate a temporary isolation failure only.

Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Michal Hocko <mho...@suse.com>
Cc: Michael S. Tsirkin <m...@redhat.com>
Signed-off-by: David Hildenbrand <da...@redhat.com>
 mm/page_isolation.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index f6d07c5f0d34d..553b49a34cf71 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -29,10 +29,12 @@ static int set_migratetype_isolate(struct page *page, int 
migratetype, int isol_
         * We assume the caller intended to SET migrate type to isolate.
         * If it is already set, then someone else must have raced and
-        * set it before us.  Return -EBUSY
+        * set it before us.
-       if (is_migrate_isolate_page(page))
-               goto out;
+       if (is_migrate_isolate_page(page)) {
+               spin_unlock_irqrestore(&zone->lock, flags);
+               return -EBUSY;
+       }
         * FIXME: Now, memory hotplug doesn't call shrink_slab() by itself.

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