+static void disk_free_ptbl_rcu_cb(struct rcu_head *head)
+{
+ struct disk_part_tbl *ptbl =
+ container_of(head, struct disk_part_tbl, rcu_head);
+
+ kfree(ptbl);
+}
+
+/**
+ * disk_replace_part_tbl - replace disk->part_tbl in RCU-safe way
+ * @disk: disk to replace part_tbl for
+ * @new_ptbl: new part_tbl to install
+ *
+ * Replace disk->part_tbl with @new_ptbl in RCU-safe way. The
+ * original ptbl is freed using RCU callback.
+ *
+ * LOCKING:
+ * Matching bd_mutx locked.
+ */
+static void disk_replace_part_tbl(struct gendisk *disk,
+ struct disk_part_tbl *new_ptbl)
+{
+ struct disk_part_tbl *old_ptbl = disk->part_tbl;
+
+ rcu_assign_pointer(disk->part_tbl, new_ptbl);
+
+ if (old_ptbl) {
+ rcu_assign_pointer(old_ptbl->last_lookup, NULL);
+ call_rcu(&old_ptbl->rcu_head, disk_free_ptbl_rcu_cb);
+ }
+}
+
+/**
+ * disk_expand_part_tbl - expand disk->part_tbl
+ * @disk: disk to expand part_tbl for
+ * @partno: expand such that this partno can fit in
+ *
+ * Expand disk->part_tbl such that @partno can fit in. disk->part_tbl
+ * uses RCU to allow unlocked dereferencing for stats and other stuff.
+ *
+ * LOCKING:
+ * Matching bd_mutex locked, might sleep.
+ *
+ * RETURNS:
+ * 0 on success, -errno on failure.
+ */
+int disk_expand_part_tbl(struct gendisk *disk, int partno)
+{
+ struct disk_part_tbl *old_ptbl = disk->part_tbl;
+ struct disk_part_tbl *new_ptbl;
+ int len = old_ptbl ? old_ptbl->len : 0;
+ int target = partno + 1;
+ size_t size;
+ int i;
+
+ /* disk_max_parts() is zero during initialization, ignore if so */
+ if (disk_max_parts(disk) && target > disk_max_parts(disk))
+ return -EINVAL;
+
+ if (target <= len)
+ return 0;
+
+ size = sizeof(*new_ptbl) + target * sizeof(new_ptbl->part[0]);
+ new_ptbl = kzalloc_node(size, GFP_KERNEL, disk->node_id);
+ if (!new_ptbl)
+ return -ENOMEM;
+
+ INIT_RCU_HEAD(&new_ptbl->rcu_head);
+ new_ptbl->len = target;
+
+ for (i = 0; i < len; i++)
+ rcu_assign_pointer(new_ptbl->part[i], old_ptbl->part[i]);
+
+ disk_replace_part_tbl(disk, new_ptbl);
+ return 0;
+}
+