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Subject[ 042/128] mm: compaction: fix echo 1 > compact_memory return error issue
3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jason Liu <r64343@freescale.com>

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@freescale.com>
Suggested-by: David Rientjes <rientjes@google.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
mm/compaction.c | 6 ++----
1 file 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;
}



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