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Date: Tue, 26 Jul 2011 10:23:25 +0800
From: Li Zefan <lizf@...fujitsu.com>
To: Wanlong Gao <gaowanlong@...fujitsu.com>
CC: menage@...gle.com, Vivek Goyal <vgoyal@...hat.com>,
axboe@...nel.dk, linux-kernel@...r.kernel.org,
wanlong.gao@...il.com
Subject: Re: [PATCH v3] blk-cgroup:be able to remove the record of unplugged
device
patch looks good to me, just some minor nits below..
09:56, Wanlong Gao wrote:
> 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@...t ~]# mount -t cgroup -o blkio nodev /cgroup/
> [root@...t ~]# cd /cgroup/
> [root@...t 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@...t cgroup]# cat blkio.throttle.read_bps_device
> [root@...t cgroup]# echo 8:0 1000 > blkio.throttle.read_bps_device
> [root@...t cgroup]# cat blkio.throttle.read_bps_device
> 8:0 1000
> [root@...t cgroup]# echo 8:0 0 > blkio.throttle.read_bps_device
> [root@...t cgroup]# cat blkio.throttle.read_bps_device
> [root@...t cgroup]# echo 8:0 1000 > blkio.throttle.read_bps_device
> [root@...t cgroup]# cat blkio.throttle.read_bps_device
> 8:0 1000
> [root@...t cgroup]# ll /dev/sd*
> ls: cannot access /dev/sd*: No such file or directory
> [root@...t cgroup]# cat blkio.throttle.read_bps_device
> 8:0 1000
> [root@...t cgroup]# echo 8:0 0 > blkio.throttle.read_bps_device
> -bash: echo: write error: No such device
> [root@...t cgroup]# cat blkio.throttle.read_bps_device
> 8:0 1000
>
> 2.Test with this patch:
>
> [root@...t ~]# mount -t cgroup -o blkio nodev /cgroup/
> [root@...t ~]# 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@...t ~]# cd /cgroup/
> [root@...t cgroup]# echo 8:0 1000 > blkio.throttle.read_bps_device
> [root@...t cgroup]# cat blkio.throttle.read_bps_device
> 8:0 1000
> [root@...t 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@...t cgroup]# echo 8:0 0 > blkio.throttle.read_bps_device
> [root@...t cgroup]# cat blkio.throttle.read_bps_device
> [root@...t 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@...t cgroup]# echo 8:0 2000 > blkio.throttle.read_bps_device
> [root@...t cgroup]# cat blkio.throttle.read_bps_device
> 8:0 2000
>
> [root@...t cgroup]# ll /dev/sd*
> ls: cannot access /dev/sd*: No such file or directory
> [root@...t cgroup]# cat blkio.throttle.read_bps_device
> 8:0 2000
> [root@...t cgroup]# echo 8:0 0 > blkio.throttle.read_bps_device
> [root@...t cgroup]# cat blkio.throttle.read_bps_device
> [root@...t cgroup]# echo 8:0 1000 > blkio.throttle.read_bps_device
> -bash: echo: write error: No such device
> [root@...t cgroup]# echo 8:0 01100 > blkio.throttle.read_bps_device
> -bash: echo: write error: No such device
> [root@...t cgroup]#
>
The changelog is too verbose. How about:
The bug is we're not able to remove the device from blkio cgroup's
per-device control files if it gets unplugged.
To reproduce the bug:
# mount -t cgroup -o blkio xxx /cgroup
# cd /cgroup
# echo "8:0 1000" > blkio.throttle.read_bps_device
# unplug the device
# cat blkio.throttle.read_bps_device
8:0 1000
# echo "8:0 0" > blkio.throttle.read_bps_device
-bash: echo: write error: No such device
After patching, the device removal will succeed.
> Signed-off-by: Wanlong Gao <gaowanlong@...fujitsu.com>
> ---
> block/blk-cgroup.c | 18 +++++++++---------
> 1 files changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
> index bcaf16e..246645c 100644
> --- a/block/blk-cgroup.c
> +++ b/block/blk-cgroup.c
> @@ -785,7 +785,7 @@ static int blkio_policy_parse_and_set(char *buf,
> {
> char *s[4], *p, *major_s = NULL, *minor_s = NULL;
> int ret;
> - unsigned long major, minor, temp;
> + unsigned long major, minor, weight;
> int i = 0;
> dev_t dev;
> u64 bps, iops;
> @@ -826,25 +826,25 @@ 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, &weight);
> if (ret)
> + return -EINVAL;
> +
> + ret = blkio_check_dev_num(dev);
> + if (ret && (weight != 0))
unnecessary parentheses.
if (ret && weight != 0)
or
if (ret && !weight)
> 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) ||
> - temp > BLKIO_WEIGHT_MAX)
> + if ((weight < BLKIO_WEIGHT_MIN && weight > 0) ||
> + weight > BLKIO_WEIGHT_MAX)
> return -EINVAL;
Normally we align the above lines this way:
if ((weight < BLKIO_WEIGHT_MIN && weight > 0) ||
weight > BLKIO_WEIGHT_MAX)
return -EINVAL;
>
> newpn->plid = plid;
> newpn->fileid = fileid;
> - newpn->val.weight = temp;
> + newpn->val.weight = weight;
> break;
> case BLKIO_POLICY_THROTL:
> switch(fileid) {
--
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