Re: [PATCH v4 03/19] nvme: Added a newsysfs attribute appid_store

[Hannes Reinecke <hare@suse.de>]

On 11/9/20 5:23 AM, Muneendra wrote:
> Added a new sysfs attribute appid_store under
> /sys/class/fc/fc_udev_device/*
> 
> With this new interface the user can set the application identfier
> in  the blkcg associted with cgroup id.
> 
> Once the application identifer has set with this interface it allows
> identification of traffic sources at an individual cgroup based
> Applications (ex:virtual machine (VM))level in both host and
> fabric infrastructure(FC).
> 
> Below is the interface provided to set the app_id
> 
> echo "<cgroupid>:<appid>" >> /sys/class/fc/fc_udev_device/appid_store
> echo "457E:100000109b521d27" >> /sys/class/fc/fc_udev_device/appid_store
> 
> Signed-off-by: Muneendra <muneendra.kumar@broadcom.com>
> 
> ---
> v4:
> No change
> 
> v3:
> Replaced blkcg_set_app_identifier function with blkcg_set_fc_appid
> 
> v2:
> New Patch
> ---
>   drivers/nvme/host/fc.c | 73 +++++++++++++++++++++++++++++++++++++++++-
>   1 file changed, 72 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/nvme/host/fc.c b/drivers/nvme/host/fc.c
> index eae43bb444e0..6d6cc06fd54a 100644
> --- a/drivers/nvme/host/fc.c
> +++ b/drivers/nvme/host/fc.c
> @@ -9,7 +9,7 @@
>   #include <uapi/scsi/fc/fc_els.h>
>   #include <linux/delay.h>
>   #include <linux/overflow.h>
> -
> +#include <linux/blk-cgroup.h>
>   #include "nvme.h"
>   #include "fabrics.h"
>   #include <linux/nvme-fc-driver.h>
> @@ -3768,10 +3768,81 @@ static ssize_t nvme_fc_nvme_discovery_store(struct device *dev,
>   
>   	return count;
>   }
> +
> +/*parse the Cgroup id from a buf and returns the length of cgrpid*/
> +static int fc_parse_cgrpid(const char *buf, u64 *id)
> +{
> +	char cgrp_id[16+1];
> +	int cgrpid_len, j;
> +
> +	memset(cgrp_id, 0x0, sizeof(cgrp_id));
> +	for (cgrpid_len = 0, j = 0; cgrpid_len < 17; cgrpid_len++) {
> +		if (buf[cgrpid_len] != ':')
> +			cgrp_id[cgrpid_len] = buf[cgrpid_len];
> +		else {
> +			j = 1;
> +			break;
> +		}
> +	}
> +	if (!j)
> +		return -EINVAL;
> +	if (kstrtou64(cgrp_id, 16, id) < 0)
> +		return -EINVAL;
> +	return cgrpid_len;
> +}
> +
> +/*
> + * fc_update_appid :parses and updates the appid in the blkcg associated with
> + * cgroupid.
> + * @buf: buf contains both cgrpid and appid info
> + * @count: size of the buffer
> + */
> +static int fc_update_appid(const char *buf, size_t count)
> +{
> +	u64 cgrp_id;
> +	int appid_len = 0;
> +	int cgrpid_len = 0;
> +	char app_id[APPID_LEN];
> +	int ret = 0;
> +
> +	if (buf[count-1] == '\n')
> +		count--;
> +
> +	if ((count > (16+1+APPID_LEN)) || (!strchr(buf, ':')))
> +		return -EINVAL;
> +
> +	cgrpid_len = fc_parse_cgrpid(buf, &cgrp_id);
> +	if (cgrpid_len < 0)
> +		return -EINVAL;
> +	/*appid len is count - cgrpid_len -1 (: + \n) */
> +	appid_len = count - cgrpid_len - 1;
> +	if (appid_len > APPID_LEN)
> +		return -EINVAL;
> +
> +	memset(app_id, 0x0, sizeof(app_id));
> +	memcpy(app_id, &buf[cgrpid_len+1], appid_len);
> +	ret = blkcg_set_app_identifier(app_id, cgrp_id, sizeof(app_id));
> +	if (ret < 0)
> +		return ret;
> +	return count;
> +}
> +
Right. So you _do_ allow for an arbitrary length for the app_id.
Which means the previous patch had a bug, and you need to allocate 
APPID_LEN + 1 for the 'app_id' entry.

> +static ssize_t fc_appid_store(struct device *dev,
> +		struct device_attribute *attr, const char *buf, size_t count)
> +{
> +	int ret  = 0;
> +
> +	ret = fc_update_appid(buf, count);
> +	if (ret < 0)
> +		return -EINVAL;
> +	return count;
> +}
>   static DEVICE_ATTR(nvme_discovery, 0200, NULL, nvme_fc_nvme_discovery_store);
> +static DEVICE_ATTR(appid_store, 0200, NULL, fc_appid_store);
>   
>   static struct attribute *nvme_fc_attrs[] = {
>   	&dev_attr_nvme_discovery.attr,
> +	&dev_attr_appid_store.attr,
>   	NULL
>   };
>   
> 

Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

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