Commit a72c5e5e authored by Nao Nishijima's avatar Nao Nishijima Committed by James Bottomley
Browse files

[SCSI] genhd: add a new attribute "alias" in gendisk 



This patch allows the user to set an "alias" of the disk via sysfs interface.

This patch only adds a new attribute "alias" in gendisk structure.
To show the alias instead of the device name in kernel messages,
we need to revise printk messages and use alias_name() in them.

Example:
(current) printk("disk name is %s\n", disk->disk_name);
(new)     printk("disk name is %s\n", alias_name(disk));

Users can use alphabets, numbers, '-' and '_' in "alias" attribute. A disk can
have an "alias" which length is up to 255 bytes. This attribute is write-once.

Suggested-by: default avatarJames Bottomley <James.Bottomley@HansenPartnership.com>
Suggested-by: default avatarJon Masters <jcm@redhat.com>
Signed-off-by: default avatarNao Nishijima <nao.nishijima.xt@hitachi.com>
Signed-off-by: default avatarJames Bottomley <JBottomley@Parallels.com>
parent 76e4e12f

Documentation/ABI/testing/sysfs-block

+13 −0
Original line number Diff line number Diff line
@@ -206,3 +206,16 @@ Description: 
		when a discarded area is read the discard_zeroes_data

		parameter will be set to one. Otherwise it will be 0 and

		the result of reading a discarded area is undefined.

What:		/sys/block/<disk>/alias

Date:		Aug 2011

Contact:	Nao Nishijima <nao.nishijima.xt@hitachi.com>

Description:

		A raw device name of a disk does not always point a same disk

		each boot-up time. Therefore, users have to use persistent

		device names, which udev creates when the kernel finds a disk,

		instead of raw device name. However, kernel doesn't show those

		persistent names on its messages (e.g. dmesg).

		This file can store an alias of the disk and it would be

		appeared in kernel messages if it is set. A disk can have an

		alias which length is up to 255bytes. Users can use alphabets,

		numbers, "-" and "_" in alias name. This file is writeonce.

block/genhd.c

+71 −0
Original line number Diff line number Diff line
@@ -19,6 +19,7 @@ 
#include <linux/mutex.h>

#include <linux/idr.h>

#include <linux/log2.h>

#include <linux/ctype.h>



#include "blk.h"
@@ -909,6 +910,74 @@ static int __init genhd_device_init(void) 


subsys_initcall(genhd_device_init);



static ssize_t alias_show(struct device *dev,

			       struct device_attribute *attr, char *buf)

{

	struct gendisk *disk = dev_to_disk(dev);

	ssize_t ret = 0;



	if (disk->alias)

		ret = snprintf(buf, ALIAS_LEN, "%s\n", disk->alias);

	return ret;

}



static ssize_t alias_store(struct device *dev, struct device_attribute *attr,

			   const char *buf, size_t count)

{

	struct gendisk *disk = dev_to_disk(dev);

	char *alias;

	char *envp[] = { NULL, NULL };

	unsigned char c;

	int i;

	ssize_t ret = count;



	if (!count)

		return -EINVAL;



	if (count >= ALIAS_LEN) {

		printk(KERN_ERR "alias: alias is too long\n");

		return -EINVAL;

	}



	/* Validation check */

	for (i = 0; i < count; i++) {

		c = buf[i];

		if (i == count - 1 && c == '\n')

			break;

		if (!isalnum(c) && c != '_' && c != '-') {

			printk(KERN_ERR "alias: invalid alias\n");

			return -EINVAL;

		}

	}



	if (disk->alias) {

		printk(KERN_INFO "alias: %s is already assigned (%s)\n",

		       disk->disk_name, disk->alias);

		return -EINVAL;

	}



	alias = kasprintf(GFP_KERNEL, "%s", buf);

	if (!alias)

		return -ENOMEM;



	if (alias[count - 1] == '\n')

		alias[count - 1] = '\0';



	envp[0] = kasprintf(GFP_KERNEL, "ALIAS=%s", alias);

	if (!envp[0]) {

		kfree(alias);

		return -ENOMEM;

	}



	disk->alias = alias;

	printk(KERN_INFO "alias: assigned %s to %s\n", alias, disk->disk_name);



	kobject_uevent_env(&dev->kobj, KOBJ_ADD, envp);



	kfree(envp[0]);

	return ret;

}



static ssize_t disk_range_show(struct device *dev,

			       struct device_attribute *attr, char *buf)

{
@@ -968,6 +1037,7 @@ static ssize_t disk_discard_alignment_show(struct device *dev, 
	return sprintf(buf, "%d\n", queue_discard_alignment(disk->queue));

}



static DEVICE_ATTR(alias, S_IRUGO|S_IWUSR, alias_show, alias_store);

static DEVICE_ATTR(range, S_IRUGO, disk_range_show, NULL);

static DEVICE_ATTR(ext_range, S_IRUGO, disk_ext_range_show, NULL);

static DEVICE_ATTR(removable, S_IRUGO, disk_removable_show, NULL);
@@ -990,6 +1060,7 @@ static struct device_attribute dev_attr_fail_timeout = 
#endif



static struct attribute *disk_attrs[] = {

	&dev_attr_alias.attr,

	&dev_attr_range.attr,

	&dev_attr_ext_range.attr,

	&dev_attr_removable.attr,

include/linux/genhd.h

+4 −0
Original line number Diff line number Diff line
@@ -21,6 +21,8 @@ 
#define dev_to_part(device)	container_of((device), struct hd_struct, __dev)

#define disk_to_dev(disk)	(&(disk)->part0.__dev)

#define part_to_dev(part)	(&((part)->__dev))

#define alias_name(disk)	((disk)->alias ? (disk)->alias : \

						 (disk)->disk_name)



extern struct device_type part_type;

extern struct kobject *block_depr;
@@ -58,6 +60,7 @@ enum { 


#define DISK_MAX_PARTS			256

#define DISK_NAME_LEN			32

#define ALIAS_LEN			256



#include <linux/major.h>

#include <linux/device.h>
@@ -162,6 +165,7 @@ struct gendisk { 
                                         * disks that can't be partitioned. */



	char disk_name[DISK_NAME_LEN];	/* name of major driver */

	char *alias;			/* alias name of disk */

	char *(*devnode)(struct gendisk *gd, mode_t *mode);



	unsigned int events;		/* supported events */

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