+/**
+ * blk_alloc_devt - allocate a dev_t for a partition
+ * @part: partition to allocate dev_t for
+ * @gfp_mask: memory allocation flag
+ * @devt: out parameter for resulting dev_t
+ *
+ * Allocate a dev_t for block device.
+ *
+ * RETURNS:
+ * 0 on success, allocated dev_t is returned in *@devt. -errno on
+ * failure.
+ *
+ * CONTEXT:
+ * Might sleep.
+ */
+int blk_alloc_devt(struct hd_struct *part, dev_t *devt)
+{
+ struct gendisk *disk = part_to_disk(part);
+ int idx, rc;
+
+ /* in consecutive minor range? */
+ if (part->partno < disk->minors) {
+ *devt = MKDEV(disk->major, disk->first_minor + part->partno);
+ return 0;
+ }
+
+ /* allocate ext devt */
+ do {
+ if (!idr_pre_get(&ext_devt_idr, GFP_KERNEL))
+ return -ENOMEM;
+ rc = idr_get_new(&ext_devt_idr, part, &idx);
+ } while (rc == -EAGAIN);
+
+ if (rc)
+ return rc;
+
+ if (idx > MAX_EXT_DEVT) {
+ idr_remove(&ext_devt_idr, idx);
+ return -EBUSY;
+ }
+
+ *devt = MKDEV(BLOCK_EXT_MAJOR, idx);
+ return 0;
+}
+
+/**
+ * blk_free_devt - free a dev_t
+ * @devt: dev_t to free
+ *
+ * Free @devt which was allocated using blk_alloc_devt().
+ *
+ * CONTEXT:
+ * Might sleep.
+ */
+void blk_free_devt(dev_t devt)
+{
+ might_sleep();
+
+ if (devt == MKDEV(0, 0))
+ return;
+
+ if (MAJOR(devt) == BLOCK_EXT_MAJOR) {
+ mutex_lock(&ext_devt_mutex);
+ idr_remove(&ext_devt_idr, MINOR(devt));
+ mutex_unlock(&ext_devt_mutex);
+ }
+}
+