linux-kernel - Re: [PATCH] memory hotplug: missing zone->lock in test_pages

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Message-Id: <20081002142734.1dfac4c7.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Thu, 2 Oct 2008 14:27:34 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Gerald Schaefer <gerald.schaefer@...ibm.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	schwidefsky@...ibm.com, heiko.carstens@...ibm.com,
	Yasunori Goto <y-goto@...fujitsu.com>,
	Mel Gorman <mel@....ul.ie>, Andy Whitcroft <apw@...dowen.org>
Subject: Re: [PATCH] memory hotplug: missing zone->lock in
 test_pages_isolated()

On Wed, 01 Oct 2008 19:27:48 +0200
Gerald Schaefer <gerald.schaefer@...ibm.com> wrote:

> From: Gerald Schaefer <gerald.schaefer@...ibm.com>
> 
> __test_page_isolated_in_pageblock() in mm/page_isolation.c has a comment
> saying that the caller must hold zone->lock. But the only caller of that
> function, test_pages_isolated(), does not hold zone->lock and the lock is
> also not acquired anywhere before. This patch adds the missing zone->lock
> to test_pages_isolated().
> 
Hmmmm ? my bad..
Of course, zone->lock is necessary. Thank you for test.


> We reproducibly run into BUG_ON(!PageBuddy(page)) in __offline_isolated_pages()
> during memory hotplug stress test, see trace below. This patch fixes that
> problem, it would be good if we could have it in 2.6.27.
> 

I agree to 2.6.27.

Thanks
-Kame


> <2>kernel BUG at /home/autobuild/BUILD/linux-2.6.26-20080909/mm/page_alloc.c:4561!
> <4>illegal operation: 0001 [#1] PREEMPT SMP
> <4>Modules linked in: dm_multipath sunrpc bonding qeth_l3 dm_mod qeth ccwgroup vmur
> <4>CPU: 1 Not tainted 2.6.26-29.x.20080909-s390default #1
> <4>Process memory_loop_all (pid: 10025, task: 2f444028, ksp: 2b10dd28)
> <4>Krnl PSW : 040c0000 801727ea (__offline_isolated_pages+0x18e/0x1c4)
> <4> R:0 T:1 IO:0 EX:0 Key:0 M:1 W:0 P:0 AS:0 CC:0 PM:0
> <4>Krnl GPRS: 00000000 7e27fc00 00000000 7e27fc00
> <4> 00000000 00000400 00014000 7e27fc01
> <4> 00606f00 7e27fc00 00013fe0 2b10dd28
> <4> 00000005 80172662 801727b2 2b10dd28
> <4>Krnl Code: 801727de: 5810900c l %r1,12(%r9)
> <4> 801727e2: a7f4ffb3 brc 15,80172748
> <4> 801727e6: a7f40001 brc 15,801727e8
> <4> >801727ea: a7f4ffbc brc 15,80172762
> <4> 801727ee: a7f40001 brc 15,801727f0
> <4> 801727f2: a7f4ffaf brc 15,80172750
> <4> 801727f6: 0707 bcr 0,%r7
> <4> 801727f8: 0017 unknown
> <4>Call Trace:
> <4>([<0000000000172772>] __offline_isolated_pages+0x116/0x1c4)
> <4> [<00000000001953a2>] offline_isolated_pages_cb+0x22/0x34
> <4> [<000000000013164c>] walk_memory_resource+0xcc/0x11c
> <4> [<000000000019520e>] offline_pages+0x36a/0x498
> <4> [<00000000001004d6>] remove_memory+0x36/0x44
> <4> [<000000000028fb06>] memory_block_change_state+0x112/0x150
> <4> [<000000000028ffb8>] store_mem_state+0x90/0xe4
> <4> [<0000000000289c00>] sysdev_store+0x34/0x40
> <4> [<00000000001ee048>] sysfs_write_file+0xd0/0x178
> <4> [<000000000019b1a8>] vfs_write+0x74/0x118
> <4> [<000000000019b9ae>] sys_write+0x46/0x7c
> <4> [<000000000011160e>] sysc_do_restart+0x12/0x16
> <4> [<0000000077f3e8ca>] 0x77f3e8ca
> 
> Signed-off-by: Gerald Schaefer <gerald.schaefer@...ibm.com>
> 
> ---
>  mm/page_isolation.c |   12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> Index: linux-2.6/mm/page_isolation.c
> ===================================================================
> --- linux-2.6.orig/mm/page_isolation.c
> +++ linux-2.6/mm/page_isolation.c
> @@ -114,8 +114,10 @@ __test_page_isolated_in_pageblock(unsign
>  
>  int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn)
>  {
> -	unsigned long pfn;
> +	unsigned long pfn, flags;
>  	struct page *page;
> +	struct zone *zone;
> +	int ret;
>  
>  	pfn = start_pfn;
>  	/*
> @@ -131,7 +133,9 @@ int test_pages_isolated(unsigned long st
>  	if (pfn < end_pfn)
>  		return -EBUSY;
>  	/* Check all pages are free or Marked as ISOLATED */
> -	if (__test_page_isolated_in_pageblock(start_pfn, end_pfn))
> -		return 0;
> -	return -EBUSY;
> +	zone = page_zone(pfn_to_page(pfn));
> +	spin_lock_irqsave(&zone->lock, flags);
> +	ret = __test_page_isolated_in_pageblock(start_pfn, end_pfn);
> +	spin_unlock_irqrestore(&zone->lock, flags);
> +	return ret ? 0 : -EBUSY;
>  }
> 
> 
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