block: add internal hd part table references

We can't use krefs since it's apparently restricted to very basic
reference counting.

This reverts commit e4a683c8.

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

block/blk-core.c

@@ -70,7 +70,7 @@ static void drive_stat_acct(struct request *rq, int new_io)
 		part_stat_inc(cpu, part, merges[rw]);
 	} else {
 		part = disk_map_sector_rcu(rq->rq_disk, blk_rq_pos(rq));
-		if (!kref_test_and_get(&part->ref)) {
+		if (!hd_struct_try_get(part)) {
 			/*
 			 * The partition is already being removed,
 			 * the request will be accounted on the disk only
@@ -80,7 +80,7 @@ static void drive_stat_acct(struct request *rq, int new_io)
 			 * it as any other partition.
 			 */
 			part = &rq->rq_disk->part0;
-			kref_get(&part->ref);
+			hd_struct_get(part);
 		}
 		part_round_stats(cpu, part);
 		part_inc_in_flight(part, rw);
@@ -1818,7 +1818,7 @@ static void blk_account_io_done(struct request *req)
 		part_round_stats(cpu, part);
 		part_dec_in_flight(part, rw);
 
-		kref_put(&part->ref, __delete_partition);
+		hd_struct_put(part);
 		part_stat_unlock();
 	}
 }

block/blk-merge.c

@@ -356,7 +356,7 @@ static void blk_account_io_merge(struct request *req)
 		part_round_stats(cpu, part);
 		part_dec_in_flight(part, rq_data_dir(req));
 
-		kref_put(&part->ref, __delete_partition);
+		hd_struct_put(part);
 		part_stat_unlock();
 	}
 }

block/genhd.c

@@ -1192,7 +1192,8 @@ struct gendisk *alloc_disk_node(int minors, int node_id)
 			return NULL;
 		}
 		disk->part_tbl->part[0] = &disk->part0;
-		kref_init(&disk->part0.ref);
+
+		hd_ref_init(&disk->part0);
 
 		disk->minors = minors;
 		rand_initialize_disk(disk);