From: David Hildenbrand <david@xxxxxxxxxx>
Subject: mm/page_isolation: exit early when pageblock is isolated in set_migratetype_isolate()
Right now, if we have two isolations racing on a pageblock that's in the
MOVABLE zone, we would trigger the WARN_ON_ONCE(). Let's just return
directly, simplifying error handling.
The change was introduced in commit 3d680bdf60a5 ("mm/page_isolation: fix
potential warning from user"). As far as I can see, we currently don't
have alloc_contig_range() users that use the ZONE_MOVABLE (anymore), so
it's currently more a cleanup and a preparation for the future than a fix.
Link: http://lkml.kernel.org/r/20200816125333.7434-3-david@xxxxxxxxxx
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Reviewed-by: Baoquan He <bhe@xxxxxxxxxx>
Reviewed-by: Pankaj Gupta <pankaj.gupta.linux@xxxxxxxxx>
Acked-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
Cc: Qian Cai <cai@xxxxxx>
Cc: Jason Wang <jasowang@xxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_isolation.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
--- a/mm/page_isolation.c~mm-page_isolation-exit-early-when-pageblock-is-isolated-in-set_migratetype_isolate
+++ a/mm/page_isolation.c
@@ -29,10 +29,12 @@ static int set_migratetype_isolate(struc
/*
* 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.
@@ -52,7 +54,6 @@ static int set_migratetype_isolate(struc
ret = 0;
}
-out:
spin_unlock_irqrestore(&zone->lock, flags);
if (!ret) {
drain_all_pages(zone);
_
