RE: [PATCH] mm: compaction: fix echo 1 > compact_memory return error issue

[Liu Hui-R64343 <r64343@freescale.com>]

>-----Original Message-----
>From: Simon Jeons [mailto:simon.jeons@gmail.com]
>Sent: Sunday, January 06, 2013 5:20 PM
>To: Liu Hui-R64343
>Cc: Wanpeng Li; linux-kernel@vger.kernel.org; mgorman@suse.de;
>akpm@linux-foundation.org; riel@redhat.com; minchan@kernel.org;
>kamezawa.hiroyu@jp.fujitsu.com; linux-mm@kvack.org
>Subject: Re: [PATCH] mm: compaction: fix echo 1 > compact_memory return
>error issue
>
>On Sun, 2013-01-06 at 08:48 +0000, Liu Hui-R64343 wrote:
>> >-----Original Message-----
>> >From: Wanpeng Li [mailto:liwanp@linux.vnet.ibm.com]
>> >Sent: Sunday, January 06, 2013 4:46 PM
>> >To: Liu Hui-R64343
>> >Cc: linux-kernel@vger.kernel.org; mgorman@suse.de; akpm@linux-
>> >foundation.org; riel@redhat.com; minchan@kernel.org;
>> >kamezawa.hiroyu@jp.fujitsu.com; linux-mm@kvack.org
>> >Subject: Re: [PATCH] mm: compaction: fix echo 1 > compact_memory
>> >return error issue
>> >
>> >On Sun, Jan 06, 2013 at 08:11:58AM +0000, Liu Hui-R64343 wrote:
>> >>>-----Original Message-----
>> >>>From: Wanpeng Li [mailto:liwanp@linux.vnet.ibm.com]
>> >>>Sent: Sunday, January 06, 2013 4:00 PM
>> >>>To: Liu Hui-R64343
>> >>>Cc: linux-kernel@vger.kernel.org; mgorman@suse.de; akpm@linux-
>> >>>foundation.org; riel@redhat.com; minchan@kernel.org;
>> >>>kamezawa.hiroyu@jp.fujitsu.com; linux-mm@kvack.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@freescale /$ 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
>> >>
>> >
>> >I test it on my desktop against latest 3.8-rc2, can't repoduce it. :)
>> >
>> >write(1, "1\n", 2)                      = 3
>>
>> Here it tells it.
>
>Why this value trouble you?

root@freescale /$strace echo 1 > /proc/sys/vm/compact_memory

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

root@freescale /$ sh


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

root@freescale /$  echo 1 > /proc/sys/vm/compact_memory
sh: write error: Bad address

>
>>
>> >close(1)                                = 0
>> >munmap(0xb779c000, 4096)                = 0
>> >close(2)                                = 0
>> >exit_group(0)                           = ?
>> >+++ exited with 0 +++
>> >
>> >Regards,
>> >Wanpeng Li
>> >
>> >>>
>> >>>Regards,
>> >>>Wanpeng Li
>> >>>
>> >>>>
>> >>>>Suggested-by:David Rientjes <rientjes@google.com> Cc:Mel Gorman
>> >>>><mgorman@suse.de> Cc:Andrew Morton <akpm@linux-
>foundation.org>
>> >>>Cc:Rik
>> >>>>van Riel <riel@redhat.com> Cc:Minchan Kim <minchan@kernel.org>
>> >>>>Cc:KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
>> >>>>Signed-off-by: Jason Liu <r64343@freescale.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@kvack.org.  For more info on Linux MM,
>> >>>>see: http://www.linux-mm.org/ .
>> >>>>Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
>> >>>
>> >>
>> >
>>
>>
>> --
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>
>