+ mm-page_isolation-exit-early-when-pageblock-is-isolated-in-set_migratetype_isolate.patch added to -mm tree

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/page_isolation: exit early when pageblock is isolated in set_migratetype_isolate()
has been added to the -mm tree.  Its filename is
     mm-page_isolation-exit-early-when-pageblock-is-isolated-in-set_migratetype_isolate.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/mm-page_isolation-exit-early-when-pageblock-is-isolated-in-set_migratetype_isolate.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/mm-page_isolation-exit-early-when-pageblock-is-isolated-in-set_migratetype_isolate.patch

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------------------------------------------------------
From: David Hildenbrand <david@redhat.com>
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@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Baoquan He <bhe@redhat.com>
Reviewed-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Acked-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Qian Cai <cai@lca.pw>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Mike Rapoport <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 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);
_

Patches currently in -mm which might be from david@redhat.com are

mm-page_alloc-tweak-comments-in-has_unmovable_pages.patch
mm-page_isolation-exit-early-when-pageblock-is-isolated-in-set_migratetype_isolate.patch
mm-page_isolation-drop-warn_on_once-in-set_migratetype_isolate.patch
mm-page_isolation-cleanup-set_migratetype_isolate.patch
virtio-mem-dont-special-case-zone_movable.patch
mm-document-semantics-of-zone_movable.patch