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    Subject[ 010/171] mm: compaction: fix echo 1 > compact_memory return error issue
    Date
    3.4-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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

    --- a/mm/compaction.c
    +++ b/mm/compaction.c
    @@ -736,7 +736,7 @@ static int compact_node(int nid)
    }

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

    @@ -745,8 +745,6 @@ 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 */
    @@ -757,7 +755,7 @@ int sysctl_compaction_handler(struct ctl
    void __user *buffer, size_t *length, loff_t *ppos)
    {
    if (write)
    - return compact_nodes();
    + compact_nodes();

    return 0;
    }



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