From: James Custer <jcuster@xxxxxxx>
Subject: mm: fix invalid use of pfn_valid_within in test_pages_in_a_zone
Offlining memory by 'echo 0 > /sys/devices/system/memory/memory#/online'
or reading valid_zones 'cat
/sys/devices/system/memory/memory#/valid_zones' causes BUG: unable to
handle kernel paging request due to invalid use of pfn_valid_within. This
is due to a bug in test_pages_in_a_zone.
In order to use pfn_valid_within within a MAX_ORDER_NR_PAGES block of
pages, a valid pfn within the block must first be found. There only needs
to be one valid pfn found in test_pages_in_a_zone in the first place. So
the fix is to replace pfn_valid_within with pfn_valid such that the first
valid pfn within the pageblock is found (if it exists). This works
independently of CONFIG_HOLES_IN_ZONE.
Signed-off-by: James Custer <jcuster@xxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: Russ Anderson <rja@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memory_hotplug.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff -puN mm/memory_hotplug.c~mm-fix-invalid-use-of-pfn_valid_within-in-test_pages_in_a_zone mm/memory_hotplug.c
--- a/mm/memory_hotplug.c~mm-fix-invalid-use-of-pfn_valid_within-in-test_pages_in_a_zone
+++ a/mm/memory_hotplug.c
@@ -1331,7 +1331,7 @@ int is_mem_section_removable(unsigned lo
}
/*
- * Confirm all pages in a range [start, end) is belongs to the same zone.
+ * Confirm all pages in a range [start, end) belong to the same zone.
*/
int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn)
{
@@ -1342,10 +1342,11 @@ int test_pages_in_a_zone(unsigned long s
for (pfn = start_pfn;
pfn < end_pfn;
pfn += MAX_ORDER_NR_PAGES) {
- i = 0;
- /* This is just a CONFIG_HOLES_IN_ZONE check.*/
- while ((i < MAX_ORDER_NR_PAGES) && !pfn_valid_within(pfn + i))
- i++;
+ /* Find the first valid pfn in this pageblock */
+ for (i = 0; i < MAX_ORDER_NR_PAGES; i++) {
+ if (pfn_valid(pfn + i))
+ break;
+ }
if (i == MAX_ORDER_NR_PAGES)
continue;
page = pfn_to_page(pfn + i);
_
--
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