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, 12 insertions, 9 deletions

diff --git a/fs/block_dev.c b/fs/block_dev.c
index de0776cd721..72e0a2887cb 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 (bdev->bd_disk->minors > 1)
+        if (disk_max_parts(bdev->bd_disk))
                 bdev->bd_invalidated = 1;
         return 1;
 }
diff --git a/fs/partitions/check.c b/fs/partitions/check.c
index b86aab1b0df..e77fa144a07 100644
--- a/fs/partitions/check.c
+++ b/fs/partitions/check.c
@@ -134,7 +134,11 @@ char *disk_name(struct gendisk *hd, int partno, char *buf)
 
 const char *bdevname(struct block_device *bdev, char *buf)
 {
-        int partno = MINOR(bdev->bd_dev) - bdev->bd_disk->first_minor;
+        int partno = 0;
+
+        if (bdev->bd_part)
+                partno = bdev->bd_part->partno;
+
         return disk_name(bdev->bd_disk, partno, buf);
 }
 
@@ -169,7 +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 = hd->minors;
+        state->limit = disk_max_parts(hd) + 1;
         i = res = err = 0;
         while (!res && check_part[i]) {
                 memset(&state->parts, 0, sizeof(state->parts));
@@ -416,7 +420,6 @@ void register_disk(struct gendisk *disk)
         int err;
 
         disk->dev.parent = disk->driverfs_dev;
-        disk->dev.devt = MKDEV(disk->major, disk->first_minor);
 
         strlcpy(disk->dev.bus_id, disk->disk_name, BUS_ID_SIZE);
         /* ewww... some of these buggers have / in the name... */
@@ -440,7 +443,7 @@ void register_disk(struct gendisk *disk)
         disk_sysfs_add_subdirs(disk);
 
         /* No minors to use for partitions */
-        if (disk->minors == 1)
+        if (!disk_max_parts(disk))
                 goto exit;
 
         /* No such device (e.g., media were just removed) */
@@ -463,8 +466,8 @@ exit:
         kobject_uevent(&disk->dev.kobj, KOBJ_ADD);
 
         /* announce possible partitions */
-        for (i = 1; i < disk->minors; i++) {
-                p = disk->part[i-1];
+        for (i = 0; i < disk_max_parts(disk); i++) {
+                p = disk->part[i];
                 if (!p || !p->nr_sects)
                         continue;
                 kobject_uevent(&p->dev.kobj, KOBJ_ADD);
@@ -482,7 +485,7 @@ int rescan_partitions(struct gendisk *disk, struct block_device *bdev)
         if (res)
                 return res;
         bdev->bd_invalidated = 0;
-        for (p = 1; p < disk->minors; p++)
+        for (p = 1; p <= disk_max_parts(disk); p++)
                 delete_partition(disk, p);
         if (disk->fops->revalidate_disk)
                 disk->fops->revalidate_disk(disk);
@@ -545,7 +548,7 @@ void del_gendisk(struct gendisk *disk)
         int p;
 
         /* invalidate stuff */
-        for (p = disk->minors - 1; p > 0; p--) {
+        for (p = disk_max_parts(disk); p > 0; p--) {
                 invalidate_partition(disk, p);
                 delete_partition(disk, p);
         }