diff --git a/block/genhd.c b/block/genhd.c
index 0a2f16bd54b7..65b7386c26d8 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -54,10 +54,10 @@ struct hd_struct *disk_get_part(struct gendisk *disk, int partno)
 {
 	struct hd_struct *part;
 
-	if (unlikely(partno < 1 || partno > disk_max_parts(disk)))
+	if (unlikely(partno < 0 || partno >= disk_max_parts(disk)))
 		return NULL;
 	rcu_read_lock();
-	part = rcu_dereference(disk->__part[partno - 1]);
+	part = rcu_dereference(disk->__part[partno]);
 	if (part)
 		get_device(part_to_dev(part));
 	rcu_read_unlock();
@@ -85,8 +85,10 @@ void disk_part_iter_init(struct disk_part_iter *piter, struct gendisk *disk,
 
 	if (flags & DISK_PITER_REVERSE)
 		piter->idx = disk_max_parts(piter->disk) - 1;
-	else
+	else if (flags & DISK_PITER_INCL_PART0)
 		piter->idx = 0;
+	else
+		piter->idx = 1;
 
 	piter->flags = flags;
 }
@@ -114,7 +116,10 @@ struct hd_struct *disk_part_iter_next(struct disk_part_iter *piter)
 	/* determine iteration parameters */
 	if (piter->flags & DISK_PITER_REVERSE) {
 		inc = -1;
-		end = -1;
+		if (piter->flags & DISK_PITER_INCL_PART0)
+			end = -1;
+		else
+			end = 0;
 	} else {
 		inc = 1;
 		end = disk_max_parts(piter->disk);
@@ -177,7 +182,7 @@ struct hd_struct *disk_map_sector_rcu(struct gendisk *disk, sector_t sector)
 {
 	int i;
 
-	for (i = 0; i < disk_max_parts(disk); i++) {
+	for (i = 1; i < disk_max_parts(disk); i++) {
 		struct hd_struct *part = rcu_dereference(disk->__part[i]);
 
 		if (part && part->start_sect <= sector &&
@@ -669,7 +674,7 @@ static int show_partition(struct seq_file *seqf, void *v)
 	char buf[BDEVNAME_SIZE];
 
 	/* Don't show non-partitionable removeable devices or empty devices */
-	if (!get_capacity(sgp) || (!disk_max_parts(sgp) &&
+	if (!get_capacity(sgp) || (!disk_partitionable(sgp) &&
 				   (sgp->flags & GENHD_FL_REMOVABLE)))
 		return 0;
 	if (sgp->flags & GENHD_FL_SUPPRESS_PARTITION_INFO)
@@ -742,7 +747,7 @@ static ssize_t disk_ext_range_show(struct device *dev,
 {
 	struct gendisk *disk = dev_to_disk(dev);
 
-	return sprintf(buf, "%d\n", disk_max_parts(disk) + 1);
+	return sprintf(buf, "%d\n", disk_max_parts(disk));
 }
 
 static ssize_t disk_removable_show(struct device *dev,
@@ -998,7 +1003,7 @@ dev_t blk_lookup_devt(const char *name, int partno)
 
 		if (strcmp(dev->bus_id, name))
 			continue;
-		if (partno < 0 || partno > disk_max_parts(disk))
+		if (partno < 0 || partno >= disk_max_parts(disk))
 			continue;
 
 		if (partno == 0)
@@ -1045,21 +1050,22 @@ struct gendisk *alloc_disk_ext_node(int minors, int ext_minors, int node_id)
 				GFP_KERNEL | __GFP_ZERO, node_id);
 	if (disk) {
 		int tot_minors = minors + ext_minors;
+		int size = tot_minors * sizeof(struct hd_struct *);
 
 		if (!init_disk_stats(disk)) {
 			kfree(disk);
 			return NULL;
 		}
-		if (tot_minors > 1) {
-			int size = (tot_minors - 1) * sizeof(struct hd_struct *);
-			disk->__part = kmalloc_node(size,
-				GFP_KERNEL | __GFP_ZERO, node_id);
-			if (!disk->__part) {
-				free_disk_stats(disk);
-				kfree(disk);
-				return NULL;
-			}
+
+		disk->__part = kmalloc_node(size, GFP_KERNEL | __GFP_ZERO,
+					    node_id);
+		if (!disk->__part) {
+			free_disk_stats(disk);
+			kfree(disk);
+			return NULL;
 		}
+		disk->__part[0] = &disk->part0;
+
 		disk->minors = minors;
 		disk->ext_minors = ext_minors;
 		rand_initialize_disk(disk);
diff --git a/block/ioctl.c b/block/ioctl.c
index a5f672ad55f6..64e7c67a64b0 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -30,7 +30,7 @@ static int blkpg_ioctl(struct block_device *bdev, struct blkpg_ioctl_arg __user
 	if (bdev != bdev->bd_contains)
 		return -EINVAL;
 	partno = p.pno;
-	if (partno <= 0 || partno > disk_max_parts(disk))
+	if (partno <= 0 || partno >= disk_max_parts(disk))
 		return -EINVAL;
 	switch (a.op) {
 		case BLKPG_ADD_PARTITION:
@@ -102,7 +102,7 @@ static int blkdev_reread_part(struct block_device *bdev)
 	struct gendisk *disk = bdev->bd_disk;
 	int res;
 
-	if (!disk_max_parts(disk) || bdev != bdev->bd_contains)
+	if (!disk_partitionable(disk) || bdev != bdev->bd_contains)
 		return -EINVAL;
 	if (!capable(CAP_SYS_ADMIN))
 		return -EACCES;
diff --git a/fs/block_dev.c b/fs/block_dev.c
index a02df22f37c3..c982a9107979 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -892,7 +892,7 @@ int check_disk_change(struct block_device *bdev)
 
 	if (bdops->revalidate_disk)
 		bdops->revalidate_disk(bdev->bd_disk);
-	if (disk_max_parts(bdev->bd_disk))
+	if (disk_partitionable(bdev->bd_disk))
 		bdev->bd_invalidated = 1;
 	return 1;
 }
diff --git a/fs/partitions/check.c b/fs/partitions/check.c
index ac0df3acdcda..b60699c271ac 100644
--- a/fs/partitions/check.c
+++ b/fs/partitions/check.c
@@ -173,7 +173,7 @@ check_partition(struct gendisk *hd, struct block_device *bdev)
 	if (isdigit(state->name[strlen(state->name)-1]))
 		sprintf(state->name, "p");
 
-	state->limit = disk_max_parts(hd) + 1;
+	state->limit = disk_max_parts(hd);
 	i = res = err = 0;
 	while (!res && check_part[i]) {
 		memset(&state->parts, 0, sizeof(state->parts));
@@ -329,12 +329,12 @@ void delete_partition(struct gendisk *disk, int partno)
 {
 	struct hd_struct *part;
 
-	part = disk->__part[partno-1];
+	part = disk->__part[partno];
 	if (!part)
 		return;
 
 	blk_free_devt(part_devt(part));
-	rcu_assign_pointer(disk->__part[partno-1], NULL);
+	rcu_assign_pointer(disk->__part[partno], NULL);
 	kobject_put(part->holder_dir);
 	device_del(part_to_dev(part));
 
@@ -359,7 +359,7 @@ int add_partition(struct gendisk *disk, int partno,
 	const char *dname;
 	int err;
 
-	if (disk->__part[partno - 1])
+	if (disk->__part[partno])
 		return -EBUSY;
 
 	p = kzalloc(sizeof(*p), GFP_KERNEL);
@@ -413,7 +413,7 @@ int add_partition(struct gendisk *disk, int partno,
 
 	/* everything is up and running, commence */
 	INIT_RCU_HEAD(&p->rcu_head);
-	rcu_assign_pointer(disk->__part[partno - 1], p);
+	rcu_assign_pointer(disk->__part[partno], p);
 
 	/* suppress uevent if the disk supresses it */
 	if (!ddev->uevent_suppress)
@@ -467,7 +467,7 @@ void register_disk(struct gendisk *disk)
 	disk_sysfs_add_subdirs(disk);
 
 	/* No minors to use for partitions */
-	if (!disk_max_parts(disk))
+	if (!disk_partitionable(disk))
 		goto exit;
 
 	/* No such device (e.g., media were just removed) */
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index e4e18c509ac5..9e866a2aee50 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -127,12 +127,13 @@ struct gendisk {
 
 	char disk_name[32];		/* name of major driver */
 
-	/* Array of pointers to partitions indexed by partno - 1.
+	/* Array of pointers to partitions indexed by partno.
 	 * Protected with matching bdev lock but stat and other
 	 * non-critical accesses use RCU.  Always access through
 	 * helpers.
 	 */
 	struct hd_struct **__part;
+	struct hd_struct part0;
 
 	struct block_device_operations *fops;
 	struct request_queue *queue;
@@ -171,7 +172,12 @@ static inline struct gendisk *part_to_disk(struct hd_struct *part)
 
 static inline int disk_max_parts(struct gendisk *disk)
 {
-	return disk->minors + disk->ext_minors - 1;
+	return disk->minors + disk->ext_minors;
+}
+
+static inline bool disk_partitionable(struct gendisk *disk)
+{
+	return disk_max_parts(disk) > 1;
 }
 
 static inline dev_t disk_devt(struct gendisk *disk)
@@ -197,6 +203,7 @@ static inline void disk_put_part(struct hd_struct *part)
  */
 #define DISK_PITER_REVERSE	(1 << 0) /* iterate in the reverse direction */
 #define DISK_PITER_INCL_EMPTY	(1 << 1) /* include 0-sized parts */
+#define DISK_PITER_INCL_PART0	(1 << 2) /* include partition 0 */
 
 struct disk_part_iter {
 	struct gendisk		*disk;