linux-kernel - [PATCH] Check end_pfn in pageblock_is

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Date:	Tue,  3 May 2011 23:55:49 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-mm <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>,
	Minchan Kim <minchan.kim@...il.com>,
	John Stultz <john.stultz@...aro.org>,
	Arve Hjønnevåg <arve@...roid.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Mel Gorman <mel@....ul.ie>,
	Dave Hansen <dave@...ux.vnet.ibm.com>
Subject: [PATCH] Check end_pfn in pageblock_is_reserved

[mm-check-if-any-page-in-a-pageblock-is-reserved-before-marking-it-migrate_reserve]
added new function "pageblock_is_reserved". But it doesn't check end_pfn of system
so it meets following BUG in my system. This patch fixes it.

[    1.859574] type=2000 audit(1304330017.656:1): initialized
[    1.884130] BUG: unable to handle kernel paging request at f77fe000
[    1.890557] IP: [<c01dfe3f>] setup_per_zone_wmarks+0x17f/0x280
[    1.896493] *pde = 013fb067 *pte = 00000000
[    1.900921] Oops: 0000 [#1] SMP
[    1.904309] last sysfs file:
[    1.907324] Modules linked in:
[    1.910482]
[    1.912024] Pid: 1, comm: swapper Not tainted 2.6.39-rc5-mm1+ #49 SAMSUNG ELECTRONICS CO.,LTD Samsung DeskT
[    1.924756] EIP: 0060:[<c01dfe3f>] EFLAGS: 00010006 CPU: 0
[    1.930282] EIP is at setup_per_zone_wmarks+0x17f/0x280
[    1.935554] EAX: 00040080 EBX: 000403fe ECX: 00000000 EDX: f77fe000
[    1.941859] ESI: 00110000 EDI: f77fcfc0 EBP: f5077f88 ESP: f5077f50
[    1.948170]  DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068
[    1.953613] Process swapper (pid: 1, ti=f5076000 task=f5078000 task.ti=f5076000)
[    1.961056] Stack:
[    1.963116]  00000091 00000000 000003b5 00000286 c0803c80 c0803ca4 0003709b 00000000
[    1.971377]  006effe0 006effc0 00040000 00000000 f50783d8 00000001 f5077f94 c0846e40
[    1.979633]  00000000 f5077fc4 c0101125 00000000 000002c8 f50783d8 f5077fb0 c01a8b44
[    1.987890] Call Trace:
[    1.990386]  [<c0846e40>] init_per_zone_wmark_min+0x39/0x7c
[    1.996001]  [<c0101125>] do_one_initcall+0x35/0x170
[    2.001014]  [<c01a8b44>] ? irq_to_desc+0x14/0x20
[    2.005758]  [<c0846e07>] ? memmap_init_zone+0xca/0xca
[    2.010941]  [<c080c2bc>] kernel_init+0xbd/0x153
[    2.015606]  [<c080c1ff>] ? parse_early_options+0x25/0x25
[    2.021047]  [<c05e7542>] kernel_thread_helper+0x6/0x10
[    2.026318] Code: 76 33 8b 4d ec 39 c3 8b 15 80 62 e0 c0 8d 3c 0e 8d 3c 3a 76 67 8b 0f 80 e5 04 75 19 8b 4d
[    2.049095] EIP: [<c01dfe3f>] setup_per_zone_wmarks+0x17f/0x280 SS:ESP 0068:f5077f50
[    2.056996] CR2: 00000000f77fe000
[    2.060362] ---[ end trace 82bc55f036371117 ]---

Cc: John Stultz <john.stultz@...aro.org>
Cc: Arve Hjønnevåg <arve@...roid.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc: Mel Gorman <mel@....ul.ie>
Cc: Dave Hansen <dave@...ux.vnet.ibm.com>
Signed-off-by: Minchan Kim <minchan.kim@...il.com>
---
 mm/page_alloc.c |   11 ++++++-----
 1 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 8e4b80c..c5d06c0 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3344,14 +3344,14 @@ static inline unsigned long wait_table_bits(unsigned long size)
 /*
  * Check if a pageblock contains reserved pages
  */
-static int pageblock_is_reserved(unsigned long start_pfn)
+static int pageblock_is_reserved(unsigned long start_pfn, unsigned long end_pfn)
 {
-	unsigned long end_pfn = start_pfn + pageblock_nr_pages;
 	unsigned long pfn;
 
-	for (pfn = start_pfn; pfn < end_pfn; pfn++)
+	for (pfn = start_pfn; pfn < end_pfn; pfn++) {
 		if (!pfn_valid_within(pfn) || PageReserved(pfn_to_page(pfn)))
 			return 1;
+	}
 	return 0;
 }
 
@@ -3364,7 +3364,7 @@ static int pageblock_is_reserved(unsigned long start_pfn)
  */
 static void setup_zone_migrate_reserve(struct zone *zone)
 {
-	unsigned long start_pfn, pfn, end_pfn;
+	unsigned long start_pfn, pfn, end_pfn, block_end_pfn;
 	struct page *page;
 	unsigned long block_migratetype;
 	int reserve;
@@ -3394,7 +3394,8 @@ static void setup_zone_migrate_reserve(struct zone *zone)
 			continue;
 
 		/* Blocks with reserved pages will never free, skip them. */
-		if (pageblock_is_reserved(pfn))
+		block_end_pfn = min(pfn + pageblock_nr_pages, end_pfn);
+		if (pageblock_is_reserved(pfn, block_end_pfn))
 			continue;
 
 		block_migratetype = get_pageblock_migratetype(page);
-- 
1.7.1

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