exofs: Add option to mount by osdname

If /dev/osd* devices are shuffled because more devices
where added, and/or login order has changed. It is hard to
mount the FS you want.

Add an option to mount by osdname. osdname is any osd-device's
osdname as specified to the mkfs.exofs command when formatting
the osd-devices.
The new mount format is:
OPT="osdname=$UUID0,pid=$PID,_netdev"
mount -t exofs -o $OPT $DEV_OSD0 $MOUNTDIR

if "osdname=" is specified in options above $DEV_OSD0 is
ignored and can be empty.

Also while at it: Removed some old unused Opt_* enums.

Signed-off-by: Boaz Harrosh <[e-mail]>

Documentation/filesystems/exofs.txt

···
     exofs specific options: Options are separated by commas (,)
 		pid=<integer> - The partition number to mount/create as
                                 container of the filesystem.
-                                This option is mandatory.
+                                This option is mandatory. integer can be
+                                Hex by pre-pending an 0x to the number.
+		osdname=<id>  - Mount by a device's osdname.
+                                osdname is usually a 36 character uuid of the
+                                form "d2683732-c906-4ee1-9dbd-c10c27bb40df".
+                                It is one of the device's uuid specified in the
+                                mkfs.exofs format command.
+                                If this option is specified then the /dev/osdX
+                                above can be empty and is ignored.
                 to=<integer>  - Timeout in ticks for a single command.
                                 default is (60 * HZ) [for debugging only]
 

fs/exofs/super.c

···
  * struct to hold what we get from mount options
  */
 struct exofs_mountopt {
+	bool is_osdname;
 	const char *dev_name;
 	uint64_t pid;
 	int timeout;
···
 /*
  * exofs-specific mount-time options.
  */
-enum { Opt_pid, Opt_to, Opt_mkfs, Opt_format, Opt_err };
+enum { Opt_name, Opt_pid, Opt_to, Opt_err };
 
 /*
  * Our mount-time options.  These should ideally be 64-bit unsigned, but the
···
  * sufficient for most applications now.
  */
 static match_table_t tokens = {
+	{Opt_name, "osdname=%s"},
 	{Opt_pid, "pid=%u"},
 	{Opt_to, "to=%u"},
 	{Opt_err, NULL}
···
 
 		token = match_token(p, tokens, args);
 		switch (token) {
+		case Opt_name:
+			opts->dev_name = match_strdup(&args[0]);
+			if (unlikely(!opts->dev_name)) {
+				EXOFS_ERR("Error allocating dev_name");
+				return -ENOMEM;
+			}
+			opts->is_osdname = true;
+			break;
 		case Opt_pid:
 			if (0 == match_strlcpy(str, &args[0], sizeof(str)))
 				return -EINVAL;
···
 		goto free_bdi;
 
 	/* use mount options to fill superblock */
-	od = osduld_path_lookup(opts->dev_name);
+	if (opts->is_osdname) {
+		struct osd_dev_info odi = {.systemid_len = 0};
+
+		odi.osdname_len = strlen(opts->dev_name);
+		odi.osdname = (u8 *)opts->dev_name;
+		od = osduld_info_lookup(&odi);
+	} else {
+		od = osduld_path_lookup(opts->dev_name);
+	}
 	if (IS_ERR(od)) {
-		ret = PTR_ERR(od);
+		ret = -EINVAL;
 		goto free_sbi;
 	}
 
···
 
 	_exofs_print_device("Mounting", opts->dev_name, sbi->layout.s_ods[0],
 			    sbi->layout.s_pid);
+	if (opts->is_osdname)
+		kfree(opts->dev_name);
 	return 0;
 
 free_sbi:
···
 	EXOFS_ERR("Unable to mount exofs on %s pid=0x%llx err=%d\n",
 		  opts->dev_name, sbi->layout.s_pid, ret);
 	exofs_free_sbi(sbi);
+	if (opts->is_osdname)
+		kfree(opts->dev_name);
 	return ret;
 }
 
···
 	if (ret)
 		return ERR_PTR(ret);
 
-	opts.dev_name = dev_name;
+	if (!opts.dev_name)
+		opts.dev_name = dev_name;
 	return mount_nodev(type, flags, &opts, exofs_fill_super);
 }