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

This reverts commit a72c5e5eb738033938ab30d6a634b74d1d060f10.

The commit introduced alias for block devices which is intended to be
used during logging although actual usage hasn't been committed yet.
This approach adds very limited benefit (raw log might be easier to
follow) which can be trivially implemented in userland but has a lot
of problems.

It is much worse than netif renames because it doesn't rename the
actual device but just adds conveninence name which isn't used
universally or enforced. Everything internal including device lookup
and sysfs still uses the internal name and nothing prevents two
devices from using conflicting alias - ie. sda can have sdb as its
alias.

This has been nacked by people working on device driver core, block
layer and kernel-userland interface and shouldn't have been
upstreamed. Revert it.

http://thread.gmane.org/gmane.linux.kernel/1155104
http://thread.gmane.org/gmane.linux.scsi/68632
http://thread.gmane.org/gmane.linux.scsi/69776

Signed-off-by: Tejun Heo <[e-mail]>
Acked-by: Greg Kroah-Hartman <[e-mail]>
Acked-by: Kay Sievers <[e-mail]>
Cc: "James E.J. Bottomley" <[e-mail]>
Cc: Nao Nishijima <[e-mail]>
Cc: Alan Cox <[e-mail]>
Cc: Al Viro <[e-mail]>
Signed-off-by: Jens Axboe <[e-mail]>

Documentation/ABI/testing/sysfs-block

···
 		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 <[e-mail]>
-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

···
 #include <linux/mutex.h>
 #include <linux/idr.h>
 #include <linux/log2.h>
-#include <linux/ctype.h>
 
 #include "blk.h"
 
···
 
 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)
 {
···
 	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);
···
 #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

···
 #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;
···
 
 #define DISK_MAX_PARTS			256
 #define DISK_NAME_LEN			32
-#define ALIAS_LEN			256
 
 #include <linux/major.h>
 #include <linux/device.h>
···
                                          * 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 */