bcachefs: Fix adding a device with a label

Device labels are represented as pointers in the member info section: we
need to get and then set the label for it to be kept correctly.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

fs/bcachefs/disk_groups.c

@@ -384,32 +384,34 @@ void bch2_disk_path_to_text(struct printbuf *out, struct bch_sb *sb, unsigned v)
 	prt_printf(out, "invalid label %u", v);
 }
 
-int bch2_dev_group_set(struct bch_fs *c, struct bch_dev *ca, const char *name)
+int __bch2_dev_group_set(struct bch_fs *c, struct bch_dev *ca, const char *name)
 {
 	struct bch_member *mi;
-	int v = -1;
-	int ret = 0;
-
-	mutex_lock(&c->sb_lock);
+	int ret, v = -1;
 
 	if (!strlen(name) || !strcmp(name, "none"))
-		goto write_sb;
+		return 0;
 
 	v = bch2_disk_path_find_or_create(&c->disk_sb, name);
-	if (v < 0) {
-		mutex_unlock(&c->sb_lock);
+	if (v < 0)
 		return v;
-	}
 
 	ret = bch2_sb_disk_groups_to_cpu(c);
 	if (ret)
-		goto unlock;
-write_sb:
+		return ret;
+
 	mi = &bch2_sb_get_members(c->disk_sb.sb)->members[ca->dev_idx];
 	SET_BCH_MEMBER_GROUP(mi, v + 1);
+	return 0;
+}
 
-	bch2_write_super(c);
-unlock:
+int bch2_dev_group_set(struct bch_fs *c, struct bch_dev *ca, const char *name)
+{
+	int ret;
+
+	mutex_lock(&c->sb_lock);
+	ret = __bch2_dev_group_set(c, ca, name) ?:
+		bch2_write_super(c);
 	mutex_unlock(&c->sb_lock);
 
 	return ret;

fs/bcachefs/disk_groups.h

@@ -82,6 +82,7 @@ void bch2_opt_target_to_text(struct printbuf *, struct bch_fs *, struct bch_sb *
 
 int bch2_sb_disk_groups_to_cpu(struct bch_fs *);
 
+int __bch2_dev_group_set(struct bch_fs *, struct bch_dev *, const char *);
 int bch2_dev_group_set(struct bch_fs *, struct bch_dev *, const char *);
 
 const char *bch2_sb_validate_disk_groups(struct bch_sb *,

fs/bcachefs/super.c

@@ -1522,6 +1522,7 @@ int bch2_dev_add(struct bch_fs *c, const char *path)
 	struct bch_member dev_mi;
 	unsigned dev_idx, nr_devices, u64s;
 	struct printbuf errbuf = PRINTBUF;
+	struct printbuf label = PRINTBUF;
 	int ret;
 
 	ret = bch2_read_super(path, &opts, &sb);
@@ -1532,6 +1533,14 @@ int bch2_dev_add(struct bch_fs *c, const char *path)
 
 	dev_mi = bch2_sb_get_members(sb.sb)->members[sb.sb->dev_idx];
 
+	if (BCH_MEMBER_GROUP(&dev_mi)) {
+		bch2_disk_path_to_text(&label, sb.sb, BCH_MEMBER_GROUP(&dev_mi) - 1);
+		if (label.allocation_failure) {
+			ret = -ENOMEM;
+			goto err;
+		}
+	}
+
 	err = bch2_dev_may_add(sb.sb, c);
 	if (err) {
 		bch_err(c, "device add error: %s", err);
@@ -1612,6 +1621,14 @@ int bch2_dev_add(struct bch_fs *c, const char *path)
 	ca->disk_sb.sb->dev_idx	= dev_idx;
 	bch2_dev_attach(c, ca, dev_idx);
 
+	if (BCH_MEMBER_GROUP(&dev_mi)) {
+		ret = __bch2_dev_group_set(c, ca, label.buf);
+		if (ret) {
+			bch_err(c, "device add error: error setting label");
+			goto err_unlock;
+		}
+	}
+
 	bch2_write_super(c);
 	mutex_unlock(&c->sb_lock);
 
@@ -1644,6 +1661,7 @@ int bch2_dev_add(struct bch_fs *c, const char *path)
 	if (ca)
 		bch2_dev_free(ca);
 	bch2_free_super(&sb);
+	printbuf_exit(&label);
 	printbuf_exit(&errbuf);
 	return ret;
 err_late: