[PATCH] mm: Ensure that pfn_valid is called once per pageblock whenreserving pageblocks
From: Michal Hocko
Date: Tue Nov 29 2011 - 10:58:38 EST
setup_zone_migrate_reserve expects that zone->start_pfn starts
at pageblock_nr_pages aligned pfn otherwise we could access
beyond an existing memblock resulting in the following panic if
CONFIG_HOLES_IN_ZONE is not configured and we do not check pfn_valid:
IP: [<c02d331d>] setup_zone_migrate_reserve+0xcd/0x180
*pdpt = 0000000000000000 *pde = f000ff53f000ff53
Oops: 0000 [#1] SMP
Modules linked in:
Supported: Yes
Pid: 1, comm: swapper Not tainted 3.0.7-0.7-pae #1 VMware, Inc.
VMware Virtual Platform/440BX Desktop Reference Platform
EIP: 0060:[<c02d331d>] EFLAGS: 00010006 CPU: 0
EIP is at setup_zone_migrate_reserve+0xcd/0x180
EAX: 000c0000 EBX: f5801fc0 ECX: 000c0000 EDX: 00000000
ESI: 000c01fe EDI: 000c01fe EBP: 00140000 ESP: f2475f58
DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068
Process swapper (pid: 1, ti=f2474000 task=f2472cd0 task.ti=f2474000)
Stack:
f4000800 00000000 f4000800 000006b8 00000000 000c6cd5 c02d389c 000003b2
00036aa9 00000292 f4000830 c08cfe78 00000000 00000000 c08a76f5 c02d3a1f
c08a771c c08cfe78 c020111b 35310001 00000000 00000000 00000100 f24730c4
Call Trace:
[<c02d389c>] __setup_per_zone_wmarks+0xec/0x160
[<c02d3a1f>] setup_per_zone_wmarks+0xf/0x20
[<c08a771c>] init_per_zone_wmark_min+0x27/0x86
[<c020111b>] do_one_initcall+0x2b/0x160
[<c086639d>] kernel_init+0xbe/0x157
[<c05cae26>] kernel_thread_helper+0x6/0xd
Code: a5 39 f5 89 f7 0f 46 fd 39 cf 76 40 8b 03 f6 c4 08 74 32 eb 91 90 89 c8 c1 e8 0e 0f be 80 80 2f 86 c0 8b 14 85 60 2f 86 c0 89 c8 <2b> 82 b4 12 00 00 c1 e0 05 03 82 ac 12 00 00 8b 00 f6 c4 08 0f
EIP: [<c02d331d>] setup_zone_migrate_reserve+0xcd/0x180 SS:ESP 0068:f2475f58
CR2: 00000000000012b4
---[ end trace 93d72a36b9146f22 ]---
We crashed in pageblock_is_reserved() when accessing pfn 0xc0000 because
highstart_pfn = 0x36ffe.
Make sure that start_pfn is always aligned to pageblock_nr_pages to
ensure that pfn_valid s always called at the start of each pageblock.
Architectures with holes in pageblocks will be correctly handled by
pfn_valid_within in pageblock_is_reserved.
Signed-off-by: Michal Hocko <mhocko@xxxxxxx>
Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
Tested-by: Dang Bo <bdang@xxxxxxxxxx>
---
mm/page_alloc.c | 8 +++++++-
1 files changed, 7 insertions(+), 1 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 9dd443d..94ff20d 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3377,9 +3377,15 @@ static void setup_zone_migrate_reserve(struct zone *zone)
unsigned long block_migratetype;
int reserve;
- /* Get the start pfn, end pfn and the number of blocks to reserve */
+ /*
+ * Get the start pfn, end pfn and the number of blocks to reserve
+ * We have to be careful to be aligned to pageblock_nr_pages to
+ * make sure that we always check pfn_valid for the first page in
+ * the block.
+ */
start_pfn = zone->zone_start_pfn;
end_pfn = start_pfn + zone->spanned_pages;
+ start_pfn = roundup(start_pfn, pageblock_nr_pages);
reserve = roundup(min_wmark_pages(zone), pageblock_nr_pages) >>
pageblock_order;
--
1.7.7.3
--
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9
Czech Republic
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