block: don't depend on consecutive minor space

* Implement disk_devt() and part_devt() and use them to directly
  access devt instead of computing it from ->major and ->first_minor.

  Note that all references to ->major and ->first_minor outside of
  block layer is used to determine devt of the disk (the part0) and as
  ->major and ->first_minor will continue to represent devt for the
  disk, converting these users aren't strictly necessary.  However,
  convert them for consistency.

* Implement disk_max_parts() to avoid directly deferencing
  genhd->minors.

* Update bdget_disk() such that it doesn't assume consecutive minor
  space.

* Move devt computation from register_disk() to add_disk() and make it
  the only one (all other usages use the initially determined value).

These changes clean up the code and will help disk->part dereference
fix and extended block device numbers.

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

1 files changed, 3 insertions, 3 deletions

diff --git a/block/ioctl.c b/block/ioctl.c
index d77f5e280a6e..403f7d7e0c28 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -29,7 +29,7 @@ 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->minors)
+        if (partno <= 0 || partno > disk_max_parts(disk))
                 return -EINVAL;
         switch (a.op) {
                 case BLKPG_ADD_PARTITION:
@@ -47,7 +47,7 @@ static int blkpg_ioctl(struct block_device *bdev, struct blkpg_ioctl_arg __user
                         mutex_lock(&bdev->bd_mutex);
 
                         /* overlap? */
-                        for (i = 0; i < disk->minors - 1; i++) {
+                        for (i = 0; i < disk_max_parts(disk); i++) {
                                 struct hd_struct *s = disk->part[i];
 
                                 if (!s)
@@ -96,7 +96,7 @@ static int blkdev_reread_part(struct block_device *bdev)
         struct gendisk *disk = bdev->bd_disk;
         int res;
 
-        if (disk->minors == 1 || bdev != bdev->bd_contains)
+        if (!disk_max_parts(disk) || bdev != bdev->bd_contains)
                 return -EINVAL;
         if (!capable(CAP_SYS_ADMIN))
                 return -EACCES;