mm: compaction: fix echo 1 > compact_memory return error issue

LiuHui-Jason · torvalds · commit 7964c06d66c7 · 2013-01-11T14:54:54.000-08:00
when run the folloing command under shell, it will return error

  sh/$ echo 1 &gt; /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 &lt;r64343@freescale.com&gt;
Suggested-by: David Rientjes &lt;rientjes@google.com&gt;
Acked-by: Mel Gorman &lt;mgorman@suse.de&gt;
Cc: Rik van Riel &lt;riel@redhat.com&gt;
Cc: Minchan Kim &lt;minchan@kernel.org&gt;
Cc: KAMEZAWA Hiroyuki &lt;kamezawa.hiroyu@jp.fujitsu.com&gt;
Acked-by: David Rientjes &lt;rientjes@google.com&gt;
Cc: &lt;stable@vger.kernel.org&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
diff --git 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;
 }

Original file line number	Diff line number	Diff line change
`@@ -1210,7 +1210,7 @@ static int compact_node(int nid)`
`1210`	`1210`	`}`
`1211`	`1211`
`1212`	`1212`	`/* Compact all nodes in the system */`
`1213`		`-static int compact_nodes(void)`
	`1213`	`+static void compact_nodes(void)`
`1214`	`1214`	`{`
`1215`	`1215`	`int nid;`
`1216`	`1216`
`@@ -1219,8 +1219,6 @@ static int compact_nodes(void)`
`1219`	`1219`
`1220`	`1220`	`for_each_online_node(nid)`
`1221`	`1221`	`compact_node(nid);`
`1222`		`-`
`1223`		`- return COMPACT_COMPLETE;`
`1224`	`1222`	`}`
`1225`	`1223`
`1226`	`1224`	`/* The written value is actually unused, all memory is compacted */`
`@@ -1231,7 +1229,7 @@ int sysctl_compaction_handler(struct ctl_table *table, int write,`
`1231`	`1229`	`void __user buffer, size_t length, loff_t *ppos)`
`1232`	`1230`	`{`
`1233`	`1231`	`if (write)`
`1234`		`- return compact_nodes();`
	`1232`	`+ compact_nodes();`
`1235`	`1233`
`1236`	`1234`	`return 0;`
`1237`	`1235`	`}`