[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: James Bottomley <James.Bottomley@HansenPartnership.com>
Suggested-by: Jon Masters <jcm@redhat.com>
Signed-off-by: Nao Nishijima <nao.nishijima.xt@hitachi.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

1 files changed, 71 insertions, 0 deletions

diff --git a/block/genhd.c b/block/genhd.c
index e2f6790..94855a9 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -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,