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 <[e-mail]>

block/blk-core.c

···
 		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
···
 			 * 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);
···
 		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

···
 		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

···
 			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);

fs/partitions/check.c

···
 	put_device(part_to_dev(part));
 }
 
-void __delete_partition(struct kref *ref)
+void __delete_partition(struct hd_struct *part)
 {
-	struct hd_struct *part = container_of(ref, struct hd_struct, ref);
-
 	call_rcu(&part->rcu_head, delete_partition_rcu_cb);
 }
 
···
 	kobject_put(part->holder_dir);
 	device_del(part_to_dev(part));
 
-	kref_put(&part->ref, __delete_partition);
+	hd_struct_put(part);
 }
 
 static ssize_t whole_disk_show(struct device *dev,
···
 	if (!dev_get_uevent_suppress(ddev))
 		kobject_uevent(&pdev->kobj, KOBJ_ADD);
 
-	kref_init(&p->ref);
+	hd_ref_init(p);
 	return p;
 
 out_free_info:

include/linux/genhd.h

···
 #else
 	struct disk_stats dkstats;
 #endif
+	atomic_t ref;
 	struct rcu_head rcu_head;
-	struct kref ref;
 };
 
 #define GENHD_FL_REMOVABLE			1
···
 						     sector_t len, int flags,
 						     struct partition_meta_info
 						       *info);
-extern void __delete_partition(struct kref *ref);
+extern void __delete_partition(struct hd_struct *);
 extern void delete_partition(struct gendisk *, int);
 extern void printk_all_partitions(void);
 
···
 			       struct device_attribute *attr,
 			       const char *buf, size_t count);
 #endif /* CONFIG_FAIL_MAKE_REQUEST */
+
+static inline void hd_ref_init(struct hd_struct *part)
+{
+	atomic_set(&part->ref, 1);
+	smp_mb();
+}
+
+static inline void hd_struct_get(struct hd_struct *part)
+{
+	atomic_inc(&part->ref);
+	smp_mb__after_atomic_inc();
+}
+
+static inline int hd_struct_try_get(struct hd_struct *part)
+{
+	return atomic_inc_not_zero(&part->ref);
+}
+
+static inline void hd_struct_put(struct hd_struct *part)
+{
+	if (atomic_dec_and_test(&part->ref))
+		__delete_partition(part);
+}
 
 #else /* CONFIG_BLOCK */
 

include/linux/kref.h

···
 
 void kref_init(struct kref *kref);
 void kref_get(struct kref *kref);
-int kref_test_and_get(struct kref *kref);
 int kref_put(struct kref *kref, void (*release) (struct kref *kref));
 
 #endif /* _KREF_H_ */

lib/kref.c

···
 }
 
 /**
- * kref_test_and_get - increment refcount for object only if refcount is not
- * zero.
- * @kref: object.
- *
- * Return non-zero if the refcount was incremented, 0 otherwise
- */
-int kref_test_and_get(struct kref *kref)
-{
-	return atomic_inc_not_zero(&kref->refcount);
-}
-
-/**
  * kref_put - decrement refcount for object.
  * @kref: object.
  * @release: pointer to the function that will clean up the object when the