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>

2 files changed, 4 insertions, 3 deletions

diff --git a/drivers/s390/block/dasd_proc.c b/drivers/s390/block/dasd_proc.c
index 03c0e40a92ff..e3b5c4d3036e 100644
--- a/drivers/s390/block/dasd_proc.c
+++ b/drivers/s390/block/dasd_proc.c
@@ -76,7 +76,8 @@ dasd_devices_show(struct seq_file *m, void *v)
         /* Print kdev. */
         if (block->gdp)
                 seq_printf(m, " at (%3d:%6d)",
-                           block->gdp->major, block->gdp->first_minor);
+                           MAJOR(disk_devt(block->gdp)),
+                           MINOR(disk_devt(block->gdp)));
         else
                 seq_printf(m, "  at (???:??????)");
         /* Print device name. */
diff --git a/drivers/s390/block/dcssblk.c b/drivers/s390/block/dcssblk.c
index 711b3004b3e6..9481e4a3f76e 100644
--- a/drivers/s390/block/dcssblk.c
+++ b/drivers/s390/block/dcssblk.c
@@ -114,7 +114,7 @@ dcssblk_assign_free_minor(struct dcssblk_dev_info *dev_info)
                 found = 0;
                 // test if minor available
                 list_for_each_entry(entry, &dcssblk_devices, lh)
-                        if (minor == entry->gd->first_minor)
+                        if (minor == MINOR(disk_devt(entry->gd)))
                                 found++;
                 if (!found) break; // got unused minor
         }
@@ -397,7 +397,7 @@ dcssblk_add_store(struct device *dev, struct device_attribute *attr, const char
                 goto unload_seg;
         }
         sprintf(dev_info->gd->disk_name, "dcssblk%d",
-                dev_info->gd->first_minor);
+                MINOR(disk_devt(dev_info->gd)));
         list_add_tail(&dev_info->lh, &dcssblk_devices);
 
         if (!try_module_get(THIS_MODULE)) {