Re: [PATCH] IO Controller: Add per-device weight and ioprio_classhandling

[IKEDA, Munehiro]

Gui Jianfeng wrote:
> IKEDA, Munehiro wrote:
> > Hi Gui,
> >
> > Gui Jianfeng wrote:
> > > Hi Vivek,
> > >
> > > This patch enables per-cgroup per-device weight and ioprio_class
> > > handling.
> > > A new cgroup interface "policy" is introduced. You can make use of
> > > this file to configure weight and ioprio_class for each device in a
> > > given cgroup.
> > > The original "weight" and "ioprio_class" files are still available. If
> > > you
> > > don't do special configuration for a particular device, "weight" and
> > > "ioprio_class" are used as default values in this device.
> > >
> > > You can use the following format to play with the new interface.
> > > #echo DEV:weight:ioprio_class > /patch/to/cgroup/policy
> > > weight=0 means removing the policy for DEV.
> > >
> > > Examples:
> > > Configure weight=300 ioprio_class=2 on /dev/hdb in this cgroup
> > > # echo /dev/hdb:300:2 > io.policy
> > > # cat io.policy
> > > dev weight class
> > > /dev/hdb 300 2
> > Users can specify a device file of a partition for io.policy.
> > In this case, io_policy_node::dev_name is set as a name of the
> > partition device like /dev/sda2.
> >
> > ex)
> >  # cd /mnt/cgroup
> >  # cat /dev/sda2:500:2 > io.policy
> >  # echo io.policy
> >    dev weight class
> >    /dev/sda2 500 2
> >
> > I believe io_policy_node::dev_name should be set a generic
> > device name like /dev/sda.
> > What do you think about it?
>
>   Hi Ikeda-san,
>
>   Sorry for the late reply. Thanks for pointing this out. 
>   yes, it does the right thing but shows a wrong name. 
>   IMHO, Inputing a sigle partition should not be allowed since the
>   policy is disk basis. So how about the following patch?
>
> Signed-off-by: Gui Jianfeng <guijianfeng@xxxxxxxxxxxxxx>
> ---
> diff --git a/block/elevator-fq.c b/block/elevator-fq.c
> index 1a0ca07..b620768 100644
> --- a/block/elevator-fq.c
> +++ b/block/elevator-fq.c
> @@ -1650,6 +1650,9 @@ static int devname_to_devnum(const char *buf, dev_t *dev)
>  		return -ENODEV;
>  
>  	disk = get_gendisk(bdev->bd_dev, &part);
> +	if (part)
> +		return -EINVAL;
> +
>  	*dev = MKDEV(disk->major, disk->first_minor);
>  	bdput(bdev);

It looks nicer and reasonable for me.
Thanks!



--
IKEDA, Munehiro
NEC Corporation of America
  m-ikeda@xxxxxxxxxxxxx


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