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    Subject[PATCH v2] cgroup:be able to remove the record of unplugged device
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    Hi Paul:
    How about this version?
    Thanks

    Write a record like:
    echo 8:0 1000 > blkio.throttle.read_bps_device
    to control the bps of the device.
    And then unplug this device without doing
    "8:0 0 > blkio.throttle.read_bps_device" to remove the record,
    it will not be removed until reboot, because if the device is removed,
    write some record will return "-ENODEV".

    With this patch, when the device is removed, then if we want to remove
    the record for this removed device, just write "0" then it'll not check
    if it is a present device, just remove the present record.

    Below is my test:
    1. Test native.
    [root@test ~]# mount -t cgroup -o blkio nodev /cgroup/
    [root@test ~]# cd /cgroup/
    [root@test cgroup]# ll /dev/sd*
    brw-rw---- 1 root disk 8, 0 Jul 25 13:27 /dev/sda
    brw-rw---- 1 root disk 8, 1 Jul 25 13:27 /dev/sda1
    [root@test cgroup]# cat blkio.throttle.read_bps_device
    [root@test cgroup]# echo 8:0 1000 > blkio.throttle.read_bps_device
    [root@test cgroup]# cat blkio.throttle.read_bps_device
    8:0 1000
    [root@test cgroup]# echo 8:0 0 > blkio.throttle.read_bps_device
    [root@test cgroup]# cat blkio.throttle.read_bps_device
    [root@test cgroup]# echo 8:0 1000 > blkio.throttle.read_bps_device
    [root@test cgroup]# cat blkio.throttle.read_bps_device
    8:0 1000
    [root@test cgroup]# ll /dev/sd*
    ls: cannot access /dev/sd*: No such file or directory
    [root@test cgroup]# cat blkio.throttle.read_bps_device
    8:0 1000
    [root@test cgroup]# echo 8:0 0 > blkio.throttle.read_bps_device
    -bash: echo: write error: No such device
    [root@test cgroup]# cat blkio.throttle.read_bps_device
    8:0 1000

    2.Test with this patch:

    [root@test ~]# mount -t cgroup -o blkio nodev /cgroup/
    [root@test ~]# ll /dev/sd*
    brw-rw---- 1 root disk 8, 0 Jul 25 13:11 /dev/sda
    brw-rw---- 1 root disk 8, 1 Jul 25 13:11 /dev/sda1
    [root@test ~]# cd /cgroup/
    [root@test cgroup]# echo 8:0 1000 > blkio.throttle.read_bps_device
    [root@test cgroup]# cat blkio.throttle.read_bps_device
    8:0 1000
    [root@test cgroup]# ll /dev/sd*
    brw-rw---- 1 root disk 8, 0 Jul 25 13:11 /dev/sda
    brw-rw---- 1 root disk 8, 1 Jul 25 13:11 /dev/sda1
    [root@test cgroup]# echo 8:0 0 > blkio.throttle.read_bps_device
    [root@test cgroup]# cat blkio.throttle.read_bps_device
    [root@test cgroup]# ll /dev/sd*
    brw-rw---- 1 root disk 8, 0 Jul 25 13:11 /dev/sda
    brw-rw---- 1 root disk 8, 1 Jul 25 13:11 /dev/sda1
    [root@test cgroup]# echo 8:0 2000 > blkio.throttle.read_bps_device
    [root@test cgroup]# cat blkio.throttle.read_bps_device
    8:0 2000

    [root@test cgroup]# ll /dev/sd*
    ls: cannot access /dev/sd*: No such file or directory
    [root@test cgroup]# cat blkio.throttle.read_bps_device
    8:0 2000
    [root@test cgroup]# echo 8:0 0 > blkio.throttle.read_bps_device
    [root@test cgroup]# cat blkio.throttle.read_bps_device
    [root@test cgroup]# echo 8:0 1000 > blkio.throttle.read_bps_device
    -bash: echo: write error: No such device
    [root@test cgroup]# echo 8:0 01100 > blkio.throttle.read_bps_device
    -bash: echo: write error: No such device
    [root@test cgroup]#

    Signed-off-by: Wanlong Gao <gaowanlong@cn.fujitsu.com>
    ---
    block/blk-cgroup.c | 12 ++++++------
    1 files changed, 6 insertions(+), 6 deletions(-)

    diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
    index bcaf16e..4e81170 100644
    --- a/block/blk-cgroup.c
    +++ b/block/blk-cgroup.c
    @@ -826,19 +826,19 @@ static int blkio_policy_parse_and_set(char *buf,

    dev = MKDEV(major, minor);

    - ret = blkio_check_dev_num(dev);
    + ret = strict_strtoul(s[1], 10, &temp);
    if (ret)
    + return -EINVAL;
    +
    + ret = blkio_check_dev_num(dev);
    + if (ret && (temp != 0))
    return ret;

    newpn->dev = dev;

    - if (s[1] == NULL)
    - return -EINVAL;
    -
    switch (plid) {
    case BLKIO_POLICY_PROP:
    - ret = strict_strtoul(s[1], 10, &temp);
    - if (ret || (temp < BLKIO_WEIGHT_MIN && temp > 0) ||
    + if ((temp < BLKIO_WEIGHT_MIN && temp > 0) ||
    temp > BLKIO_WEIGHT_MAX)
    return -EINVAL;

    --
    1.7.6


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