[ 3.5.y.z extended stable ] Patch "mm: compaction: fix echo 1 > compact_memory return error" has been added to staging queue

[Herton Ronaldo Krzesinski]

This is a note to let you know that I have just added a patch titled

    mm: compaction: fix echo 1 > compact_memory return error

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Herton

------

>From f193218a52affc0a16118a8e92952958a80095c5 Mon Sep 17 00:00:00 2001
From: Jason Liu <r64343 at freescale.com>
Date: Fri, 11 Jan 2013 14:31:47 -0800
Subject: [PATCH] mm: compaction: fix echo 1 > compact_memory return error
 issue

commit 7964c06d66c76507d8b6b662bffea770c29ef0ce upstream.

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

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.

Signed-off-by: Jason Liu <r64343 at freescale.com>
Suggested-by: David Rientjes <rientjes at google.com>
Acked-by: Mel Gorman <mgorman at suse.de>
Cc: Rik van Riel <riel at redhat.com>
Cc: Minchan Kim <minchan at kernel.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu at jp.fujitsu.com>
Acked-by: David Rientjes <rientjes at google.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
---
 mm/compaction.c |    6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/mm/compaction.c b/mm/compaction.c
index 2f42d95..cf955bb 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -843,7 +843,7 @@ static int compact_node(int nid)
 }

 /* Compact all nodes in the system */
-static int compact_nodes(void)
+static void compact_nodes(void)
 {
 	int nid;

@@ -852,8 +852,6 @@ 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 */
@@ -864,7 +862,7 @@ 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;
 }
--
1.7.9.5