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    Subject[PATCH] cgroup: alloc_css_id() increments hierarchy depth
    Date
    Child groups should have a greater depth than their parents.
    Prior to this change, the parent would incorrectly report zero
    memory usage for child cgroups when use_hierarchy is enabled.

    test script:
    mount -t cgroup none /cgroups -o memory
    cd /cgroups
    mkdir cg1

    echo 1 > cg1/memory.use_hierarchy
    mkdir cg1/cg11

    echo $$ > cg1/cg11/tasks
    dd if=/dev/zero of=/tmp/foo bs=1M count=1

    echo
    echo CHILD
    grep cache cg1/cg11/memory.stat

    echo
    echo PARENT
    grep cache cg1/memory.stat

    echo $$ > tasks
    rmdir cg1/cg11 cg1
    cd /
    umount /cgroups

    Using fae9c79, a recent patch that changed alloc_css_id() depth computation,
    the parent incorrectly reports zero usage:
    root@ubuntu:~# ./test
    1+0 records in
    1+0 records out
    1048576 bytes (1.0 MB) copied, 0.0151844 s, 69.1 MB/s

    CHILD
    cache 1048576
    total_cache 1048576

    PARENT
    cache 0
    total_cache 0

    With this patch, the parent correctly includes child usage:
    root@ubuntu:~# ./test
    1+0 records in
    1+0 records out
    1048576 bytes (1.0 MB) copied, 0.0136827 s, 76.6 MB/s

    CHILD
    cache 1052672
    total_cache 1052672

    PARENT
    cache 0
    total_cache 1052672

    Signed-off-by: Greg Thelen <gthelen@google.com>
    ---
    kernel/cgroup.c | 2 +-
    1 files changed, 1 insertions(+), 1 deletions(-)

    diff --git a/kernel/cgroup.c b/kernel/cgroup.c
    index 422cb19..3ac6f5b 100644
    --- a/kernel/cgroup.c
    +++ b/kernel/cgroup.c
    @@ -4598,7 +4598,7 @@ static int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *parent,
    parent_css = parent->subsys[subsys_id];
    child_css = child->subsys[subsys_id];
    parent_id = parent_css->id;
    - depth = parent_id->depth;
    + depth = parent_id->depth + 1;

    child_id = get_new_cssid(ss, depth);
    if (IS_ERR(child_id))
    --
    1.7.0.1


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