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Tsirkin" , Qian Cai Subject: [PATCH v2 1/6] mm/page_isolation: don't dump_page(NULL) in set_migratetype_isolate() Date: Thu, 30 Jul 2020 11:34:11 +0200 Message-Id: <20200730093416.36210-2-david@redhat.com> In-Reply-To: <20200730093416.36210-1-david@redhat.com> References: <20200730093416.36210-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Rspamd-Queue-Id: 5B9FD180AD802 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam01 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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 Reviewed-by: Pankaj Gupta Acked-by: Mike Kravetz Fixes: 4a55c0474a92 ("mm/hotplug: silence a lockdep splat with printk()") Cc: Andrew Morton Cc: Michal Hocko Cc: Michael S. Tsirkin Cc: Qian Cai Signed-off-by: David Hildenbrand --- 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; + } =20 /* * FIXME: Now, memory hotplug doesn't call shrink_slab() by itself. @@ -52,7 +54,6 @@ static int set_migratetype_isolate(struct page *page, i= nt migratetype, int isol_ ret =3D 0; } =20 -out: spin_unlock_irqrestore(&zone->lock, flags); if (!ret) { drain_all_pages(zone); --=20 2.26.2