dm: export name and uuid

This patch adds a function to obtain a copy of a mapped device's name and uuid.

Signed-off-by: Mike Anderson <andmike@linux.vnet.ibm.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

2 files changed, 33 insertions, 0 deletions

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index 6af95f9b7b52..138200bf5e0b 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -1515,3 +1515,35 @@ void dm_interface_exit(void)
 
 	dm_hash_exit();
 }
+
+/**
+ * dm_copy_name_and_uuid - Copy mapped device name & uuid into supplied buffers
+ * @md: Pointer to mapped_device
+ * @name: Buffer (size DM_NAME_LEN) for name
+ * @uuid: Buffer (size DM_UUID_LEN) for uuid or empty string if uuid not defined
+ */
+int dm_copy_name_and_uuid(struct mapped_device *md, char *name, char *uuid)
+{
+	int r = 0;
+	struct hash_cell *hc;
+
+	if (!md)
+		return -ENXIO;
+
+	dm_get(md);
+	down_read(&_hash_lock);
+	hc = dm_get_mdptr(md);
+	if (!hc || hc->md != md) {
+		r = -ENXIO;
+		goto out;
+	}
+
+	strcpy(name, hc->name);
+	strcpy(uuid, hc->uuid ? : "");
+
+out:
+	up_read(&_hash_lock);
+	dm_put(md);
+
+	return r;
+}
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 499f5373e213..8b3c7cdc599c 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -188,6 +188,7 @@ int dm_wait_event(struct mapped_device *md, int event_nr);
  * Info functions.
  */
 const char *dm_device_name(struct mapped_device *md);
+int dm_copy_name_and_uuid(struct mapped_device *md, char *name, char *uuid);
 struct gendisk *dm_disk(struct mapped_device *md);
 int dm_suspended(struct mapped_device *md);
 int dm_noflush_suspending(struct dm_target *ti);