linux-kernel - [PATCH 03/14] mm: drop page_initialized check from get_nid_for

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Date:   Mon, 15 May 2017 10:58:16 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, Mel Gorman <mgorman@...e.de>,
        Vlastimil Babka <vbabka@...e.cz>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Jerome Glisse <jglisse@...hat.com>,
        Reza Arbab <arbab@...ux.vnet.ibm.com>,
        Yasuaki Ishimatsu <yasu.isimatu@...il.com>,
        qiuxishi@...wei.com, Kani Toshimitsu <toshi.kani@....com>,
        slaoub@...il.com, Joonsoo Kim <js1304@...il.com>,
        Andi Kleen <ak@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Daniel Kiper <daniel.kiper@...cle.com>,
        Igor Mammedov <imammedo@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Michal Hocko <mhocko@...e.com>
Subject: [PATCH 03/14] mm: drop page_initialized check from get_nid_for_pfn

From: Michal Hocko <mhocko@...e.com>

c04fc586c1a4 ("mm: show node to memory section relationship with
symlinks in sysfs") has added means to export memblock<->node
association into the sysfs. It has also introduced get_nid_for_pfn
which is a rather confusing counterpart of pfn_to_nid which checks also
whether the pfn page is already initialized (page_initialized).  This
is done by checking page::lru != NULL which doesn't make any sense at
all. Nothing in this path really relies on the lru list being used or
initialized. Just remove it because this will become a problem with
later patches.

Thanks to Reza Arbab for testing which revealed this to be a problem
(http://lkml.kernel.org/r/20170403202337.GA12482@dhcp22.suse.cz)

Acked-by: Vlastimil Babka <vbabka@...e.cz>
Signed-off-by: Michal Hocko <mhocko@...e.com>
---
 drivers/base/node.c | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/drivers/base/node.c b/drivers/base/node.c
index 5548f9686016..06294d69779b 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -368,21 +368,14 @@ int unregister_cpu_under_node(unsigned int cpu, unsigned int nid)
 }
 
 #ifdef CONFIG_MEMORY_HOTPLUG_SPARSE
-#define page_initialized(page)  (page->lru.next)
-
 static int __ref get_nid_for_pfn(unsigned long pfn)
 {
-	struct page *page;
-
 	if (!pfn_valid_within(pfn))
 		return -1;
 #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
 	if (system_state == SYSTEM_BOOTING)
 		return early_pfn_to_nid(pfn);
 #endif
-	page = pfn_to_page(pfn);
-	if (!page_initialized(page))
-		return -1;
 	return pfn_to_nid(pfn);
 }
 
-- 
2.11.0