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[dm-devel] Re: [PATCH] IO Controller: Add per-device weight and ioprio_class handling

Gui Jianfeng wrote:
IKEDA, Munehiro wrote:
Hi Gui,

Gui Jianfeng wrote:
Hi Vivek,

This patch enables per-cgroup per-device weight and ioprio_class
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
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.

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.

 # 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 cn fujitsu com>
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);

It looks nicer and reasonable for me.

IKEDA, Munehiro
NEC Corporation of America
  m-ikeda ds jp nec com

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