From 46acecf8d0ddcae9f9536491351dcaa37ddb056c Mon Sep 17 00:00:00 2001
From: Matthew Dillon <dillon@apollo.backplane.com>
Date: Wed, 27 Feb 2019 22:36:27 -0800
Subject: [PATCH] kernel - Add /dev/part-by-label

* The DragonFly disklabel has a 'label' field which accepts up to
  a 63 byte ascii label.

* When this field is not empty, the kernel will now create a
  "/dev/part-by-label/<label>.<part>" alias.

  For example, if the label is FUBAR and you create a label with
  partitions 'a', 'b', and 'd', then you will get:

  # ls /dev/part-by-label
  FUBAR.a      FUBAR.b      FUBAR.d

* WARNING!  Duplicate labels will replace each other, so the
  label that shows up will be non-deterministic.

Suggested-by: Aaron LI
---
 sys/kern/subr_disk.c        | 24 +++++++++++++++++++++++-
 sys/kern/subr_disklabel32.c | 19 +++++++++++++++++++
 sys/kern/subr_disklabel64.c | 19 +++++++++++++++++++
 sys/sys/disklabel.h         |  4 ++++
 4 files changed, 65 insertions(+), 1 deletion(-)

diff --git a/sys/kern/subr_disk.c b/sys/kern/subr_disk.c
index e5b64e72a5..fb67cebe88 100644
--- a/sys/kern/subr_disk.c
+++ b/sys/kern/subr_disk.c
@@ -208,14 +208,23 @@ disk_probe_slice(struct disk *dp, cdev_t dev, int slice, int reprobe)
 	}
 
 	if (msg == NULL) {
+		char packname[DISKLABEL_MAXPACKNAME];
+
 		if (slice != WHOLE_DISK_SLICE)
 			ops->op_adjust_label_reserved(dp->d_slice, slice, sp);
 		else
 			sp->ds_reserved = 0;
 
+		ops->op_getpackname(sp->ds_label, packname, sizeof(packname));
+
+		destroy_dev_alias(dev, "by-label/*");
+		if (packname[0])
+			make_dev_alias(dev, "by-label/%s", packname);
+
 		sp->ds_ops = ops;
 		for (i = 0; i < ops->op_getnumparts(sp->ds_label); i++) {
 			ops->op_loadpartinfo(sp->ds_label, i, &part);
+
 			if (part.fstype) {
 				if (reprobe &&
 				    (ndev = devfs_find_device_by_name("%s%c",
@@ -230,7 +239,10 @@ disk_probe_slice(struct disk *dp, cdev_t dev, int slice, int reprobe)
 					/*
 					 * Destroy old UUID alias
 					 */
-					destroy_dev_alias(ndev, "part-by-uuid/*");
+					destroy_dev_alias(ndev,
+							  "part-by-uuid/*");
+					destroy_dev_alias(ndev,
+							  "part-by-label/*");
 
 					/* Create UUID alias */
 					if (!kuuid_is_nil(&part.storage_uuid)) {
@@ -242,6 +254,11 @@ disk_probe_slice(struct disk *dp, cdev_t dev, int slice, int reprobe)
 						    uuid_buf);
 						udev_dict_set_cstr(ndev, "uuid", uuid_buf);
 					}
+					if (packname[0]) {
+						make_dev_alias(ndev,
+						    "part-by-label/%s.%c",
+						    packname, 'a' + i);
+					}
 				} else {
 					ndev = make_dev_covering(dops,
 						dp->d_rawdev->si_ops,
@@ -277,6 +294,11 @@ disk_probe_slice(struct disk *dp, cdev_t dev, int slice, int reprobe)
 						    uuid_buf);
 						udev_dict_set_cstr(ndev, "uuid", uuid_buf);
 					}
+					if (packname[0]) {
+						make_dev_alias(ndev,
+						    "part-by-label/%s.%c",
+						    packname, 'a' + i);
+					}
 					ndev->si_flags |= SI_REPROBE_TEST;
 				}
 			}
diff --git a/sys/kern/subr_disklabel32.c b/sys/kern/subr_disklabel32.c
index 3012137340..323bb02a9e 100644
--- a/sys/kern/subr_disklabel32.c
+++ b/sys/kern/subr_disklabel32.c
@@ -155,6 +155,24 @@ l32_getnumparts(disklabel_t lp)
 	return(lp.lab32->d_npartitions);
 }
 
+static int
+l32_getpackname(disklabel_t lp, char *buf, size_t bytes)
+{
+	size_t slen;
+
+	if (lp.lab32->d_packname[0] == 0) {
+		buf[0] = 0;
+		return -1;
+	}
+	slen = strnlen(lp.lab32->d_packname, sizeof(lp.lab32->d_packname));
+	if (slen >= bytes)
+		slen = bytes - 1;
+	bcopy(lp.lab32->d_packname, buf, slen);
+	buf[slen] = 0;
+
+	return 0;
+}
+
 static void
 l32_freedisklabel(disklabel_t *lpp)
 {
@@ -636,6 +654,7 @@ struct disklabel_ops disklabel32_ops = {
 	.op_loadpartinfo = l32_loadpartinfo,
 	.op_getnumparts = l32_getnumparts,
 	.op_makevirginlabel = l32_makevirginlabel,
+	.op_getpackname = l32_getpackname,
 	.op_freedisklabel = l32_freedisklabel
 };
 
diff --git a/sys/kern/subr_disklabel64.c b/sys/kern/subr_disklabel64.c
index fff9262005..d83743bd4b 100644
--- a/sys/kern/subr_disklabel64.c
+++ b/sys/kern/subr_disklabel64.c
@@ -110,6 +110,24 @@ l64_getnumparts(disklabel_t lp)
 	return(lp.lab64->d_npartitions);
 }
 
+static int
+l64_getpackname(disklabel_t lp, char *buf, size_t bytes)
+{
+	size_t slen;
+
+	if (lp.lab64->d_packname[0] == 0) {
+		buf[0] = 0;
+		return -1;
+	}
+	slen = strnlen(lp.lab64->d_packname, sizeof(lp.lab64->d_packname));
+	if (slen >= bytes)
+		slen = bytes - 1;
+	bcopy(lp.lab64->d_packname, buf, slen);
+	buf[slen] = 0;
+
+	return 0;
+}
+
 static void
 l64_freedisklabel(disklabel_t *lpp)
 {
@@ -517,6 +535,7 @@ struct disklabel_ops disklabel64_ops = {
 	.op_getpartbounds = l64_getpartbounds,
 	.op_loadpartinfo = l64_loadpartinfo,
 	.op_getnumparts = l64_getnumparts,
+	.op_getpackname = l64_getpackname,
 	.op_makevirginlabel = l64_makevirginlabel,
 	.op_freedisklabel = l64_freedisklabel
 };
diff --git a/sys/sys/disklabel.h b/sys/sys/disklabel.h
index 608165a53b..7b0bfbd1ad 100644
--- a/sys/sys/disklabel.h
+++ b/sys/sys/disklabel.h
@@ -62,6 +62,8 @@ struct diskslices;
 struct disk_info;
 struct partinfo;
 
+#define DISKLABEL_MAXPACKNAME	64
+
 struct disklabel_ops {
 	struct uuid type;	/* uuid specifies disklabel type */
 	int labelsize;		/* size of disklabel in bytes */
@@ -86,6 +88,8 @@ struct disklabel_ops {
 		    (disklabel_t, u_int32_t, struct partinfo *);
 	u_int32_t (*op_getnumparts)
 		    (disklabel_t);
+	int  (*op_getpackname)
+		    (disklabel_t, char *, size_t);
 	void (*op_makevirginlabel)
 		    (disklabel_t, struct diskslices *,
 		     struct diskslice *, struct disk_info *);
-- 
2.41.0