+/**
+ * bdget_disk - do bdget() by gendisk and partition number
+ * @disk: gendisk of interest
+ * @partno: partition number
+ *
+ * Find partition @partno from @disk, do bdget() on it.
+ *
+ * CONTEXT:
+ * Don't care.
+ *
+ * RETURNS:
+ * Resulting block_device on success, NULL on failure.
+ */
+extern struct block_device *bdget_disk(struct gendisk *disk, int partno)
+{
+ dev_t devt = MKDEV(0, 0);
+
+ if (partno == 0)
+ devt = disk_devt(disk);
+ else {
+ struct hd_struct *part = disk->part[partno - 1];
+
+ if (part && part->nr_sects)
+ devt = part_devt(part);
+ }
+
+ if (likely(devt != MKDEV(0, 0)))
+ return bdget(devt);
+ return NULL;
+}
+EXPORT_SYMBOL(bdget_disk);
+