linux-kernel - [PATCH 1/2] mm/page_idle.c: Skip offline pages

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Date:   Fri, 5 Jun 2020 11:25:01 +0200
From:   SeongJae Park <sjpark@...zon.com>
To:     <akpm@...ux-foundation.org>
CC:     <david@...hat.com>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>, SeongJae Park <sjpark@...zon.de>
Subject: [PATCH 1/2] mm/page_idle.c: Skip offline pages

From: SeongJae Park <sjpark@...zon.de>

'Idle page tracking' users can pass random pfn that might be mapped to
an offline page.  To avoid accessing such pages, this commit modifies
the 'page_idle_get_page()' to use 'pfn_to_online_page()' instead of
'pfn_valid()' and 'pfn_to_page()' combination, so that the pfn mapped to
an offline page can be skipped.

Signed-off-by: SeongJae Park <sjpark@...zon.de>
Reported-by: David Hildenbrand <david@...hat.com>
---
 mm/page_idle.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/mm/page_idle.c b/mm/page_idle.c
index 295512465065..057c61df12db 100644
--- a/mm/page_idle.c
+++ b/mm/page_idle.c
@@ -4,6 +4,7 @@
 #include <linux/fs.h>
 #include <linux/sysfs.h>
 #include <linux/kobject.h>
+#include <linux/memory_hotplug.h>
 #include <linux/mm.h>
 #include <linux/mmzone.h>
 #include <linux/pagemap.h>
@@ -30,13 +31,9 @@
  */
 static struct page *page_idle_get_page(unsigned long pfn)
 {
-	struct page *page;
+	struct page *page = pfn_to_online_page(pfn);
 	pg_data_t *pgdat;
 
-	if (!pfn_valid(pfn))
-		return NULL;
-
-	page = pfn_to_page(pfn);
 	if (!page || !PageLRU(page) ||
 	    !get_page_unless_zero(page))
 		return NULL;
-- 
2.17.1