From d7ab3672c3ff7b2a2be3f15fcee77414fd9c4d7a Mon Sep 17 00:00:00 2001
From: Michal Hocko <mhocko@suse.com>
Date: Wed, 15 Nov 2017 17:33:30 -0800
Subject: [PATCH 2/4] mm, page_alloc: fail has_unmovable_pages when seeing
 reserved pages
Git-commit: d7ab3672c3ff7b2a2be3f15fcee77414fd9c4d7a
Patch-mainline: v4.15-rc1
References: bnc#1051406

Reserved pages should be completely ignored by the core mm because they
have a special meaning for their owners.  has_unmovable_pages doesn't
check those so we rely on other tests (reference count, or PageLRU) to
fail on such pages.  Althought this happens to work it is safer to
simply check for those explicitly and do not rely on the owner of the
page to abuse those fields for special purposes.

Please note that this is more of a further fortification of the code
rahter than a fix of an existing issue.

Link: http://lkml.kernel.org/r/20171013120756.jeopthigbmm3c7bl@dhcp22.suse.cz
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Reza Arbab <arbab@linux.vnet.ibm.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Xishi Qiu <qiuxishi@huawei.com>
Cc: Yasuaki Ishimatsu <yasu.isimatu@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

---
 mm/page_alloc.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -7364,6 +7364,9 @@ bool has_unmovable_pages(struct zone *zo
 
 		page = pfn_to_page(check);
 
+		if (PageReserved(page))
+			return true;
+
 		/*
 		 * Hugepages are not in LRU lists, but they're movable.
 		 * We need not scan over tail pages bacause we don't