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>

11 files changed, 20 insertions, 18 deletions

diff --git a/drivers/block/pktcdvd.c b/drivers/block/pktcdvd.c
index 29b7a64..e1a90bb 100644
--- a/drivers/block/pktcdvd.c
+++ b/drivers/block/pktcdvd.c
@@ -2911,7 +2911,7 @@ static int pkt_setup_dev(dev_t dev, dev_t* pkt_dev)
 	if (!disk->queue)
 		goto out_mem2;
 
-	pd->pkt_dev = MKDEV(disk->major, disk->first_minor);
+	pd->pkt_dev = MKDEV(pktdev_major, idx);
 	ret = pkt_new_dev(pd, dev);
 	if (ret)
 		goto out_new_dev;
diff --git a/drivers/block/ps3disk.c b/drivers/block/ps3disk.c
index 4b0d6c7..936466f 100644
--- a/drivers/block/ps3disk.c
+++ b/drivers/block/ps3disk.c
@@ -541,7 +541,7 @@ static int ps3disk_remove(struct ps3_system_bus_device *_dev)
 	struct ps3disk_private *priv = dev->sbd.core.driver_data;
 
 	mutex_lock(&ps3disk_mask_mutex);
-	__clear_bit(priv->gendisk->first_minor / PS3DISK_MINORS,
+	__clear_bit(MINOR(disk_devt(priv->gendisk)) / PS3DISK_MINORS,
 		    &ps3disk_mask);
 	mutex_unlock(&ps3disk_mask_mutex);
 	del_gendisk(priv->gendisk);
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 7ce1ac4..6af435b 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -661,10 +661,10 @@ void add_disk_randomness(struct gendisk *disk)
 	if (!disk || !disk->random)
 		return;
 	/* first major is 1, so we get >= 0x200 here */
-	DEBUG_ENT("disk event %d:%d\n", disk->major, disk->first_minor);
+	DEBUG_ENT("disk event %d:%d\n",
+		  MAJOR(disk_devt(disk)), MINOR(disk_devt(disk)));
 
-	add_timer_randomness(disk->random,
-			     0x100 + MKDEV(disk->major, disk->first_minor));
+	add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
 }
 #endif
 
diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index b262c00..c3de311 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -426,7 +426,7 @@ static int list_devices(struct dm_ioctl *param, size_t param_size)
 				old_nl->next = (uint32_t) ((void *) nl -
 							   (void *) old_nl);
 			disk = dm_disk(hc->md);
-			nl->dev = huge_encode_dev(MKDEV(disk->major, disk->first_minor));
+			nl->dev = huge_encode_dev(disk_devt(disk));
 			nl->next = 0;
 			strcpy(nl->name, hc->name);
 
@@ -539,7 +539,7 @@ static int __dev_status(struct mapped_device *md, struct dm_ioctl *param)
 	if (dm_suspended(md))
 		param->flags |= DM_SUSPEND_FLAG;
 
-	param->dev = huge_encode_dev(MKDEV(disk->major, disk->first_minor));
+	param->dev = huge_encode_dev(disk_devt(disk));
 
 	/*
 	 * Yes, this will be out of date by the time it gets back
diff --git a/drivers/md/dm-stripe.c b/drivers/md/dm-stripe.c
index 4de90ab..b745d8a 100644
--- a/drivers/md/dm-stripe.c
+++ b/drivers/md/dm-stripe.c
@@ -284,8 +284,8 @@ static int stripe_end_io(struct dm_target *ti, struct bio *bio,
 
 	memset(major_minor, 0, sizeof(major_minor));
 	sprintf(major_minor, "%d:%d",
-		bio->bi_bdev->bd_disk->major,
-		bio->bi_bdev->bd_disk->first_minor);
+		MAJOR(disk_devt(bio->bi_bdev->bd_disk)),
+		MINOR(disk_devt(bio->bi_bdev->bd_disk)));
 
 	/*
 	 * Test to see which stripe drive triggered the event
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index ace998c..a78caad 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1146,7 +1146,7 @@ static void unlock_fs(struct mapped_device *md);
 
 static void free_dev(struct mapped_device *md)
 {
-	int minor = md->disk->first_minor;
+	int minor = MINOR(disk_devt(md->disk));
 
 	if (md->suspended_bdev) {
 		unlock_fs(md);
@@ -1267,7 +1267,7 @@ static struct mapped_device *dm_find_md(dev_t dev)
 
 	md = idr_find(&_minor_idr, minor);
 	if (md && (md == MINOR_ALLOCED ||
-		   (dm_disk(md)->first_minor != minor) ||
+		   (MINOR(disk_devt(dm_disk(md))) != minor) ||
 		   test_bit(DMF_FREEING, &md->flags))) {
 		md = NULL;
 		goto out;
@@ -1318,7 +1318,8 @@ void dm_put(struct mapped_device *md)
 
 	if (atomic_dec_and_lock(&md->holders, &_minor_lock)) {
 		map = dm_get_table(md);
-		idr_replace(&_minor_idr, MINOR_ALLOCED, dm_disk(md)->first_minor);
+		idr_replace(&_minor_idr, MINOR_ALLOCED,
+			    MINOR(disk_devt(dm_disk(md))));
 		set_bit(DMF_FREEING, &md->flags);
 		spin_unlock(&_minor_lock);
 		if (!dm_suspended(md)) {
diff --git a/drivers/memstick/core/mspro_block.c b/drivers/memstick/core/mspro_block.c
index d2d2318..82bf649 100644
--- a/drivers/memstick/core/mspro_block.c
+++ b/drivers/memstick/core/mspro_block.c
@@ -197,7 +197,7 @@ static int mspro_block_bd_open(struct inode *inode, struct file *filp)
 static int mspro_block_disk_release(struct gendisk *disk)
 {
 	struct mspro_block_data *msb = disk->private_data;
-	int disk_id = disk->first_minor >> MSPRO_BLOCK_PART_SHIFT;
+	int disk_id = MINOR(disk_devt(disk)) >> MSPRO_BLOCK_PART_SHIFT;
 
 	mutex_lock(&mspro_block_disk_lock);
 
diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index ebc8b9d..97156b6 100644
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -83,7 +83,7 @@ static void mmc_blk_put(struct mmc_blk_data *md)
 	mutex_lock(&open_lock);
 	md->usage--;
 	if (md->usage == 0) {
-		int devidx = md->disk->first_minor >> MMC_SHIFT;
+		int devidx = MINOR(disk_devt(md->disk)) >> MMC_SHIFT;
 		__clear_bit(devidx, dev_use);
 
 		put_disk(md->disk);
diff --git a/drivers/s390/block/dasd_proc.c b/drivers/s390/block/dasd_proc.c
index 03c0e40..e3b5c4d 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 711b300..9481e4a 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)) {
diff --git a/drivers/scsi/sr.c b/drivers/scsi/sr.c
index 27f5bfd..8dbe379 100644
--- a/drivers/scsi/sr.c
+++ b/drivers/scsi/sr.c
@@ -878,7 +878,7 @@ static void sr_kref_release(struct kref *kref)
 	struct gendisk *disk = cd->disk;
 
 	spin_lock(&sr_index_lock);
-	clear_bit(disk->first_minor, sr_index_bits);
+	clear_bit(MINOR(disk_devt(disk)), sr_index_bits);
 	spin_unlock(&sr_index_lock);
 
 	unregister_cdrom(&cd->cdi);