5 files changed, 41 insertions, 28 deletions

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;