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Date: Tue, 4 Aug 2020 21:41:37 +0200 From: David Hildenbrand <david@...hat.com> To: linux-kernel@...r.kernel.org Cc: virtualization@...ts.linux-foundation.org, linux-mm@...ck.org, David Hildenbrand <david@...hat.com>, Baoquan He <bhe@...hat.com>, Pankaj Gupta <pankaj.gupta.linux@...il.com>, Mike Kravetz <mike.kravetz@...cle.com>, Andrew Morton <akpm@...ux-foundation.org>, Michal Hocko <mhocko@...e.com>, "Michael S . Tsirkin" <mst@...hat.com>, Qian Cai <cai@....pw> Subject: [PATCH v4 1/6] mm/page_isolation: don't dump_page(NULL) in set_migratetype_isolate() 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. Reviewed-by: Baoquan He <bhe@...hat.com> Reviewed-by: Pankaj Gupta <pankaj.gupta.linux@...il.com> Acked-by: Mike Kravetz <mike.kravetz@...cle.com> Fixes: 4a55c0474a92 ("mm/hotplug: silence a lockdep splat with printk()") Cc: Andrew Morton <akpm@...ux-foundation.org> Cc: Michal Hocko <mhocko@...e.com> Cc: Michael S. Tsirkin <mst@...hat.com> Cc: Qian Cai <cai@....pw> Signed-off-by: David Hildenbrand <david@...hat.com> --- mm/page_isolation.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/mm/page_isolation.c b/mm/page_isolation.c index f6d07c5f0d34d..7d7d263ce7f4b 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. @@ -52,7 +54,6 @@ static int set_migratetype_isolate(struct page *page, int migratetype, int isol_ ret = 0; } -out: spin_unlock_irqrestore(&zone->lock, flags); if (!ret) { drain_all_pages(zone); -- 2.26.2
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