[126/181] mm/page_isolation: exit early when pageblock is isolated in set_migratetype_isolate()

Commit Message

Andrew Morton Oct. 13, 2020, 11:55 p.m. UTC

From: David Hildenbrand <[e-mail]>
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/[e-mail]
Signed-off-by: David Hildenbrand <[e-mail]>
Reviewed-by: Baoquan He <[e-mail]>
Reviewed-by: Pankaj Gupta <[e-mail]>
Acked-by: Mike Kravetz <[e-mail]>
Cc: Michal Hocko <[e-mail]>
Cc: Michael S. Tsirkin <[e-mail]>
Cc: Qian Cai <[e-mail]>
Cc: Jason Wang <[e-mail]>
Cc: Mike Rapoport <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/page_isolation.c |    9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

Patch

--- 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);