linux-kernel - Re: [PATCH v5] blk-cgroup:be able to remove the record of unplugged device

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Date:	Wed, 27 Jul 2011 10:11:42 -0400
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Wanlong Gao <gaowanlong@...fujitsu.com>
Cc:	Paul Menage <menage@...gle.com>, lizf@...fujitsu.com,
	axboe@...nel.dk, linux-kernel@...r.kernel.org,
	wanlong.gao@...il.com
Subject: Re: [PATCH v5] blk-cgroup:be able to remove the record of unplugged
 device

On Wed, Jul 27, 2011 at 08:11:48AM +0800, Wanlong Gao wrote:
> 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.
> 
> Thanks for the comments of Paul, Zefan, and Vivek.
> 
> Signed-off-by: Wanlong Gao <gaowanlong@...fujitsu.com>

Thanks. This looks good to me.

Acked-by: Vivek Goyal <vgoyal@...hat.com>

Vivek

> ---
>  block/blk-cgroup.c |   37 ++++++++++++++++---------------------
>  1 files changed, 16 insertions(+), 21 deletions(-)
> 
> diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
> index bcaf16e..b596e54 100644
> --- a/block/blk-cgroup.c
> +++ b/block/blk-cgroup.c
> @@ -785,10 +785,10 @@ 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;
>  	int i = 0;
>  	dev_t dev;
> -	u64 bps, iops;
> +	u64 temp;
>  
>  	memset(s, 0, sizeof(s));
>  
> @@ -826,20 +826,23 @@ static int blkio_policy_parse_and_set(char *buf,
>  
>  	dev = MKDEV(major, minor);
>  
> -	ret = blkio_check_dev_num(dev);
> +	ret = strict_strtoull(s[1], 10, &temp);
>  	if (ret)
> -		return ret;
> +		return -EINVAL;
>  
> -	newpn->dev = dev;
> +	/* For rule removal, do not check for device presence. */
> +	if (temp) {
> +		ret = blkio_check_dev_num(dev);
> +		if (ret)
> +			return ret;
> +	}
>  
> -	if (s[1] == NULL)
> -		return -EINVAL;
> +	newpn->dev = dev;
>  
>  	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 ((temp < BLKIO_WEIGHT_MIN && temp > 0) ||
> +		     temp > BLKIO_WEIGHT_MAX)
>  			return -EINVAL;
>  
>  		newpn->plid = plid;
> @@ -850,26 +853,18 @@ static int blkio_policy_parse_and_set(char *buf,
>  		switch(fileid) {
>  		case BLKIO_THROTL_read_bps_device:
>  		case BLKIO_THROTL_write_bps_device:
> -			ret = strict_strtoull(s[1], 10, &bps);
> -			if (ret)
> -				return -EINVAL;
> -
>  			newpn->plid = plid;
>  			newpn->fileid = fileid;
> -			newpn->val.bps = bps;
> +			newpn->val.bps = temp;
>  			break;
>  		case BLKIO_THROTL_read_iops_device:
>  		case BLKIO_THROTL_write_iops_device:
> -			ret = strict_strtoull(s[1], 10, &iops);
> -			if (ret)
> -				return -EINVAL;
> -
> -			if (iops > THROTL_IOPS_MAX)
> +			if (temp > THROTL_IOPS_MAX)
>  				return -EINVAL;
>  
>  			newpn->plid = plid;
>  			newpn->fileid = fileid;
> -			newpn->val.iops = (unsigned int)iops;
> +			newpn->val.iops = (unsigned int)temp;
>  			break;
>  		}
>  		break;
> -- 
> 1.7.6
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