linux-kernel - RE: [PATCH] mm: compaction: fix echo 1 > compact

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Message-ID: <AD13664F485EE54694E29A7F9D5BE1AF4E5BCD@039-SN2MPN1-021.039d.mgd.msft.net>
Date:	Sun, 6 Jan 2013 08:11:58 +0000
From:	Liu Hui-R64343 <r64343@...escale.com>
To:	Wanpeng Li <liwanp@...ux.vnet.ibm.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"mgorman@...e.de" <mgorman@...e.de>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"riel@...hat.com" <riel@...hat.com>,
	"minchan@...nel.org" <minchan@...nel.org>,
	"kamezawa.hiroyu@...fujitsu.com" <kamezawa.hiroyu@...fujitsu.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: RE: [PATCH] mm: compaction: fix echo 1 > compact_memory return
 error issue

>-----Original Message-----
>From: Wanpeng Li [mailto:liwanp@...ux.vnet.ibm.com]
>Sent: Sunday, January 06, 2013 4:00 PM
>To: Liu Hui-R64343
>Cc: linux-kernel@...r.kernel.org; mgorman@...e.de; akpm@...ux-
>foundation.org; riel@...hat.com; minchan@...nel.org;
>kamezawa.hiroyu@...fujitsu.com; linux-mm@...ck.org
>Subject: Re: [PATCH] mm: compaction: fix echo 1 > compact_memory return
>error issue
>
>On Sun, Jan 06, 2013 at 03:44:33PM +0800, Jason Liu wrote:
>
>Hi Jason,
>
>>when run the folloing command under shell, it will return error sh/$
>>echo 1 > /proc/sys/vm/compact_memory sh/$ sh: write error: Bad address
>>
>
>How can you modify the value through none privileged user since the mode
>== 0200?

I write it through privileged user(root). I'm using the GNOME_Mobile rootfs.

>
>>After strace, I found the following log:
>>...
>>write(1, "1\n", 2)               = 3
>>write(1, "", 4294967295)         = -1 EFAULT (Bad address)
>>write(2, "echo: write error: Bad address\n", 31echo: write error: Bad
>>address
>>) = 31
>>
>>This tells system return 3(COMPACT_COMPLETE) after write data to
>compact_memory.
>>
>>The fix is to make the system just return 0 instead 3(COMPACT_COMPLETE)
>>from sysctl_compaction_handler after compaction_nodes finished.
>
>What's the special scenario you are in? I couldn't figure out the similar error
>against latest 3.8-rc2, how could you reproduce it?

I'm using the BusyBox v1.20.2 () built-in shell (ash), it reproduces the issue: 100%.

root@...escale /$ sh


BusyBox v1.20.2 () built-in shell (ash)
Enter 'help' for a list of built-in commands.

Could you run strace and see the log:  strace echo 1 > /proc/sys/vm/compact_memory

>
>Regards,
>Wanpeng Li
>
>>
>>Suggested-by:David Rientjes <rientjes@...gle.com> Cc:Mel Gorman
>><mgorman@...e.de> Cc:Andrew Morton <akpm@...ux-foundation.org>
>Cc:Rik
>>van Riel <riel@...hat.com> Cc:Minchan Kim <minchan@...nel.org>
>>Cc:KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
>>Signed-off-by: Jason Liu <r64343@...escale.com>
>>---
>> mm/compaction.c |    6 ++----
>> 1 files changed, 2 insertions(+), 4 deletions(-)
>>
>>diff --git a/mm/compaction.c b/mm/compaction.c index 6b807e4..f8f5c11
>>100644
>>--- a/mm/compaction.c
>>+++ b/mm/compaction.c
>>@@ -1210,7 +1210,7 @@ static int compact_node(int nid)  }
>>
>> /* Compact all nodes in the system */
>>-static int compact_nodes(void)
>>+static void compact_nodes(void)
>> {
>> 	int nid;
>>
>>@@ -1219,8 +1219,6 @@ static int compact_nodes(void)
>>
>> 	for_each_online_node(nid)
>> 		compact_node(nid);
>>-
>>-	return COMPACT_COMPLETE;
>> }
>>
>> /* The written value is actually unused, all memory is compacted */ @@
>>-1231,7 +1229,7 @@ int sysctl_compaction_handler(struct ctl_table *table,
>int write,
>> 			void __user *buffer, size_t *length, loff_t *ppos)  {
>> 	if (write)
>>-		return compact_nodes();
>>+		compact_nodes();
>>
>> 	return 0;
>> }
>>--
>>1.7.5.4
>>
>>
>>--
>>To unsubscribe, send a message with 'unsubscribe linux-mm' in the body
>>to majordomo@...ck.org.  For more info on Linux MM,
>>see: http://www.linux-mm.org/ .
>>Don't email: <a href=mailto:"dont@...ck.org"> email@...ck.org </a>
>


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