bcachefs: bch2_disk_path_to_text() no longer takes sb_lock

We're going to be using bch2_target_to_text() ->
bch2_disk_path_to_text() from bch2_bkey_ptrs_to_text() and
bch2_bkey_ptrs_invalid(), which can be called in any context.

This patch adds the actual label to bch_disk_group_cpu so that it can be
used by bch2_disk_path_to_text, and splits out bch2_disk_path_to_text()
into two variants - like the previous patch, one for when we have a
running filesystem and another for when we only have a superblock.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/disk_groups.c

@@ -175,6 +175,7 @@ int bch2_sb_disk_groups_to_cpu(struct bch_fs *c)
 
 		dst->deleted	= BCH_GROUP_DELETED(src);
 		dst->parent	= BCH_GROUP_PARENT(src);
+		memcpy(dst->label, src->label, sizeof(dst->label));
 	}
 
 	for (i = 0; i < c->disk_sb.sb->nr_devices; i++) {
@@ -382,7 +383,57 @@ int bch2_disk_path_find_or_create(struct bch_sb_handle *sb, const char *name)
 	return v;
 }
 
-void bch2_disk_path_to_text(struct printbuf *out, struct bch_sb *sb, unsigned v)
+void bch2_disk_path_to_text(struct printbuf *out, struct bch_fs *c, unsigned v)
+{
+	struct bch_disk_groups_cpu *groups;
+	struct bch_disk_group_cpu *g;
+	unsigned nr = 0;
+	u16 path[32];
+
+	out->atomic++;
+	rcu_read_lock();
+	groups = rcu_dereference(c->disk_groups);
+	if (!groups)
+		goto invalid;
+
+	while (1) {
+		if (nr == ARRAY_SIZE(path))
+			goto invalid;
+
+		if (v >= groups->nr)
+			goto invalid;
+
+		g = groups->entries + v;
+
+		if (g->deleted)
+			goto invalid;
+
+		path[nr++] = v;
+
+		if (!g->parent)
+			break;
+
+		v = g->parent - 1;
+	}
+
+	while (nr) {
+		v = path[--nr];
+		g = groups->entries + v;
+
+		prt_printf(out, "%.*s", (int) sizeof(g->label), g->label);
+		if (nr)
+			prt_printf(out, ".");
+	}
+out:
+	rcu_read_unlock();
+	out->atomic--;
+	return;
+invalid:
+	prt_printf(out, "invalid label %u", v);
+	goto out;
+}
+
+void bch2_disk_path_to_text_sb(struct printbuf *out, struct bch_sb *sb, unsigned v)
 {
 	struct bch_sb_field_disk_groups *groups =
 		bch2_sb_field_get(sb, disk_groups);
@@ -522,9 +573,7 @@ void bch2_target_to_text(struct printbuf *out, struct bch_fs *c, unsigned v)
 		break;
 	}
 	case TARGET_GROUP:
-		mutex_lock(&c->sb_lock);
-		bch2_disk_path_to_text(out, c->disk_sb.sb, t.group);
-		mutex_unlock(&c->sb_lock);
+		bch2_disk_path_to_text(out, c, t.group);
 		break;
 	default:
 		BUG();
@@ -552,7 +601,7 @@ void bch2_target_to_text_sb(struct printbuf *out, struct bch_sb *sb, unsigned v)
 		break;
 	}
 	case TARGET_GROUP:
-		bch2_disk_path_to_text(out, sb, t.group);
+		bch2_disk_path_to_text_sb(out, sb, t.group);
 		break;
 	default:
 		BUG();

fs/bcachefs/disk_groups.h

@@ -85,7 +85,9 @@ int bch2_disk_path_find(struct bch_sb_handle *, const char *);
 /* Exported for userspace bcachefs-tools: */
 int bch2_disk_path_find_or_create(struct bch_sb_handle *, const char *);
 
-void bch2_disk_path_to_text(struct printbuf *, struct bch_sb *, unsigned);
+void bch2_disk_path_to_text(struct printbuf *, struct bch_fs *, unsigned);
+void bch2_disk_path_to_text_sb(struct printbuf *, struct bch_sb *, unsigned);
+
 void bch2_target_to_text(struct printbuf *out, struct bch_fs *, unsigned);
 
 int bch2_opt_target_parse(struct bch_fs *, const char *, u64 *, struct printbuf *);

fs/bcachefs/disk_groups_types.h

@@ -5,6 +5,7 @@
 struct bch_disk_group_cpu {
 	bool				deleted;
 	u16				parent;
+	u8				label[BCH_SB_LABEL_SIZE];
 	struct bch_devs_mask		devs;
 };
 

fs/bcachefs/super.c

@@ -1582,7 +1582,7 @@ int bch2_dev_add(struct bch_fs *c, const char *path)
 	dev_mi = bch2_sb_member_get(sb.sb, sb.sb->dev_idx);
 
 	if (BCH_MEMBER_GROUP(&dev_mi)) {
-		bch2_disk_path_to_text(&label, sb.sb, BCH_MEMBER_GROUP(&dev_mi) - 1);
+		bch2_disk_path_to_text_sb(&label, sb.sb, BCH_MEMBER_GROUP(&dev_mi) - 1);
 		if (label.allocation_failure) {
 			ret = -ENOMEM;
 			goto err;

fs/bcachefs/sysfs.c

@@ -910,13 +910,8 @@ SHOW(bch2_dev)
 	sysfs_print(discard,		ca->mi.discard);
 
 	if (attr == &sysfs_label) {
-		if (ca->mi.group) {
-			mutex_lock(&c->sb_lock);
-			bch2_disk_path_to_text(out, c->disk_sb.sb,
-					       ca->mi.group - 1);
-			mutex_unlock(&c->sb_lock);
-		}
-
+		if (ca->mi.group)
+			bch2_disk_path_to_text(out, c, ca->mi.group - 1);
 		prt_char(out, '\n');
 	}