block: introduce partition 0

genhd and partition code handled disk and partitions separately.  All
information about the whole disk was in struct genhd and partitions in
struct hd_struct.  However, the whole disk (part0) and other
partitions have a lot in common and the data structures end up having
good number of common fields and thus separate code paths doing the
same thing.  Also, the partition array was indexed by partno - 1 which
gets pretty confusing at times.

This patch introduces partition 0 and makes the partition array
indexed by partno.  Following patches will unify the handling of disk
and parts piece-by-piece.

This patch also implements disk_partitionable() which tests whether a
disk is partitionable.  With coming dynamic partition array change,
the most common usage of disk_max_parts() will be testing whether a
disk is partitionable and the number of max partitions will become
much less important.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 6 insertions, 6 deletions

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) */