The patch titled
     Subject: mm: compaction: fix echo 1 > compact_memory return error issue
has been added to the -mm tree.  Its filename is
     mm-compaction-fix-echo-1-compact_memory-return-error-issue.patch

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------------------------------------------------------
From: Jason Liu <[email protected]>
Subject: mm: compaction: fix echo 1 > compact_memory return error issue

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 <[email protected]>
Suggested-by: David Rientjes <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: KAMEZAWA Hiroyuki <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---

 mm/compaction.c |    6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff -puN 
mm/compaction.c~mm-compaction-fix-echo-1-compact_memory-return-error-issue 
mm/compaction.c
--- a/mm/compaction.c~mm-compaction-fix-echo-1-compact_memory-return-error-issue
+++ a/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
                        void __user *buffer, size_t *length, loff_t *ppos)
 {
        if (write)
-               return compact_nodes();
+               compact_nodes();
 
        return 0;
 }
_

Patches currently in -mm which might be from [email protected] are

mm-compaction-fix-echo-1-compact_memory-return-error-issue.patch
mm-compaction-make-__compact_pgdat-and-compact_pgdat-return-void.patch

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