block: remove GENHD_FL_EXT_DEVT

All modern drivers can support extra partitions using the extended
dev_t.  In fact except for the ioctl method drivers never even see
partitions in normal operation.

So remove the GENHD_FL_EXT_DEVT and allow extra partitions for all
block devices that do support partitions, and require those that
do not support partitions to explicit disallow them using
GENHD_FL_NO_PART.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20211122130625.1136848-12-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/genhd.c

@@ -376,7 +376,7 @@ int disk_scan_partitions(struct gendisk *disk, fmode_t mode)
 {
 	struct block_device *bdev;
 
-	if (!disk_part_scan_enabled(disk))
+	if (disk->flags & GENHD_FL_NO_PART)
 		return -EINVAL;
 	if (disk->open_partitions)
 		return -EBUSY;
@@ -438,7 +438,6 @@ int __must_check device_add_disk(struct device *parent, struct gendisk *disk,
 			return ret;
 		disk->major = BLOCK_EXT_MAJOR;
 		disk->first_minor = ret;
-		disk->flags |= GENHD_FL_EXT_DEVT;
 	}
 
 	ret = disk_alloc_events(disk);
@@ -872,7 +871,8 @@ static ssize_t disk_ext_range_show(struct device *dev,
 {
 	struct gendisk *disk = dev_to_disk(dev);
 
-	return sprintf(buf, "%d\n", disk_max_parts(disk));
+	return sprintf(buf, "%d\n",
+		(disk->flags & GENHD_FL_NO_PART) ? 1 : DISK_MAX_PARTS);
 }
 
 static ssize_t disk_removable_show(struct device *dev,

block/partitions/core.c

@@ -98,13 +98,12 @@ static void bdev_set_nr_sectors(struct block_device *bdev, sector_t sectors)
 static struct parsed_partitions *allocate_partitions(struct gendisk *hd)
 {
 	struct parsed_partitions *state;
-	int nr;
+	int nr = DISK_MAX_PARTS;
 
 	state = kzalloc(sizeof(*state), GFP_KERNEL);
 	if (!state)
 		return NULL;
 
-	nr = disk_max_parts(hd);
 	state->parts = vzalloc(array_size(nr, sizeof(state->parts[0])));
 	if (!state->parts) {
 		kfree(state);
@@ -326,7 +325,7 @@ static struct block_device *add_partition(struct gendisk *disk, int partno,
 
 	lockdep_assert_held(&disk->open_mutex);
 
-	if (partno >= disk_max_parts(disk))
+	if (partno >= DISK_MAX_PARTS)
 		return ERR_PTR(-EINVAL);
 
 	/*
@@ -604,7 +603,7 @@ static int blk_add_partitions(struct gendisk *disk)
 	struct parsed_partitions *state;
 	int ret = -EAGAIN, p;
 
-	if (!disk_part_scan_enabled(disk))
+	if (disk->flags & GENHD_FL_NO_PART)
 		return 0;
 
 	state = check_partition(disk);
@@ -687,7 +686,7 @@ int bdev_disk_changed(struct gendisk *disk, bool invalidate)
 	 * userspace for this particular setup.
 	 */
 	if (invalidate) {
-		if (disk_part_scan_enabled(disk) ||
+		if (!(disk->flags & GENHD_FL_NO_PART) ||
 		    !(disk->flags & GENHD_FL_REMOVABLE))
 			set_capacity(disk, 0);
 	}

drivers/block/amiflop.c

@@ -1790,6 +1790,7 @@ static int fd_alloc_disk(int drive, int system)
 	disk->first_minor = drive + system;
 	disk->minors = 1;
 	disk->fops = &floppy_fops;
+	disk->flags |= GENHD_FL_NO_PART;
 	disk->events = DISK_EVENT_MEDIA_CHANGE;
 	if (system)
 		sprintf(disk->disk_name, "fd%d_msdos", drive);

drivers/block/ataflop.c

@@ -2000,6 +2000,7 @@ static int ataflop_alloc_disk(unsigned int drive, unsigned int type)
 	disk->minors = 1;
 	sprintf(disk->disk_name, "fd%d", drive);
 	disk->fops = &floppy_fops;
+	disk->flags |= GENHD_FL_NO_PART;
 	disk->events = DISK_EVENT_MEDIA_CHANGE;
 	disk->private_data = &unit[drive];
 	set_capacity(disk, MAX_DISK_SIZE * 2);

drivers/block/brd.c

@@ -405,7 +405,6 @@ static int brd_alloc(int i)
 	disk->minors		= max_part;
 	disk->fops		= &brd_fops;
 	disk->private_data	= brd;
-	disk->flags		= GENHD_FL_EXT_DEVT;
 	strlcpy(disk->disk_name, buf, DISK_NAME_LEN);
 	set_capacity(disk, rd_size * 2);
 	

drivers/block/drbd/drbd_main.c

@@ -2734,6 +2734,7 @@ enum drbd_ret_code drbd_create_device(struct drbd_config_context *adm_ctx, unsig
 	disk->first_minor = minor;
 	disk->minors = 1;
 	disk->fops = &drbd_ops;
+	disk->flags |= GENHD_FL_NO_PART;
 	sprintf(disk->disk_name, "drbd%d", minor);
 	disk->private_data = device;
 

drivers/block/floppy.c

@@ -4503,6 +4503,7 @@ static int floppy_alloc_disk(unsigned int drive, unsigned int type)
 	disk->first_minor = TOMINOR(drive) | (type << 2);
 	disk->minors = 1;
 	disk->fops = &floppy_fops;
+	disk->flags |= GENHD_FL_NO_PART;
 	disk->events = DISK_EVENT_MEDIA_CHANGE;
 	if (type)
 		sprintf(disk->disk_name, "fd%d_type%d", drive, type);

drivers/block/loop.c

@@ -2033,7 +2033,6 @@ static int loop_add(int i)
 	 */
 	if (!part_shift)
 		disk->flags |= GENHD_FL_NO_PART;
-	disk->flags |= GENHD_FL_EXT_DEVT;
 	atomic_set(&lo->lo_refcnt, 0);
 	mutex_init(&lo->lo_mutex);
 	lo->lo_number		= i;

drivers/block/null_blk/main.c

@@ -1850,7 +1850,6 @@ static int null_gendisk_register(struct nullb *nullb)
 
 	set_capacity(disk, size);
 
-	disk->flags |= GENHD_FL_EXT_DEVT;
 	disk->major		= null_major;
 	disk->first_minor	= nullb->index;
 	disk->minors		= 1;

drivers/block/paride/pcd.c

@@ -928,6 +928,7 @@ static int pcd_init_unit(struct pcd_unit *cd, bool autoprobe, int port,
 	disk->minors = 1;
 	strcpy(disk->disk_name, cd->name);	/* umm... */
 	disk->fops = &pcd_bdops;
+	disk->flags |= GENHD_FL_NO_PART;
 	disk->events = DISK_EVENT_MEDIA_CHANGE;
 	disk->event_flags = DISK_EVENT_FLAG_BLOCK_ON_EXCL_WRITE;
 

drivers/block/paride/pf.c

@@ -942,6 +942,7 @@ static int __init pf_init_unit(struct pf_unit *pf, bool autoprobe, int port,
 	disk->minors = 1;
 	strcpy(disk->disk_name, pf->name);
 	disk->fops = &pf_fops;
+	disk->flags |= GENHD_FL_NO_PART;
 	disk->events = DISK_EVENT_MEDIA_CHANGE;
 	disk->private_data = pf;
 

drivers/block/pktcdvd.c

@@ -2719,7 +2719,7 @@ static int pkt_setup_dev(dev_t dev, dev_t* pkt_dev)
 	disk->first_minor = idx;
 	disk->minors = 1;
 	disk->fops = &pktcdvd_ops;
-	disk->flags = GENHD_FL_REMOVABLE;
+	disk->flags = GENHD_FL_REMOVABLE | GENHD_FL_NO_PART;
 	strcpy(disk->disk_name, pd->name);
 	disk->private_data = pd;
 

drivers/block/ps3vram.c

@@ -742,6 +742,7 @@ static int ps3vram_probe(struct ps3_system_bus_device *dev)
 	priv->gendisk = gendisk;
 	gendisk->major = ps3vram_major;
 	gendisk->minors = 1;
+	gendisk->flags |= GENHD_FL_NO_PART;
 	gendisk->fops = &ps3vram_fops;
 	gendisk->private_data = dev;
 	strlcpy(gendisk->disk_name, DEVICE_NAME, sizeof(gendisk->disk_name));

drivers/block/rbd.c

@@ -4924,12 +4924,10 @@ static int rbd_init_disk(struct rbd_device *rbd_dev)
 		 rbd_dev->dev_id);
 	disk->major = rbd_dev->major;
 	disk->first_minor = rbd_dev->minor;
-	if (single_major) {
+	if (single_major)
 		disk->minors = (1 << RBD_SINGLE_MAJOR_PART_SHIFT);
-		disk->flags |= GENHD_FL_EXT_DEVT;
-	} else {
+	else
 		disk->minors = RBD_MINORS_PER_MAJOR;
-	}
 	disk->fops = &rbd_bd_ops;
 	disk->private_data = rbd_dev;
 

drivers/block/swim.c

@@ -840,6 +840,7 @@ static int swim_floppy_init(struct swim_priv *swd)
 		swd->unit[drive].disk->minors = 1;
 		sprintf(swd->unit[drive].disk->disk_name, "fd%d", drive);
 		swd->unit[drive].disk->fops = &floppy_fops;
+		swd->unit[drive].disk->flags |= GENHD_FL_NO_PART;
 		swd->unit[drive].disk->events = DISK_EVENT_MEDIA_CHANGE;
 		swd->unit[drive].disk->private_data = &swd->unit[drive];
 		set_capacity(swd->unit[drive].disk, 2880);

drivers/block/swim3.c

@@ -1227,7 +1227,7 @@ static int swim3_attach(struct macio_dev *mdev,
 	disk->fops = &floppy_fops;
 	disk->private_data = fs;
 	disk->events = DISK_EVENT_MEDIA_CHANGE;
-	disk->flags |= GENHD_FL_REMOVABLE;
+	disk->flags |= GENHD_FL_REMOVABLE | GENHD_FL_NO_PART;
 	sprintf(disk->disk_name, "fd%d", floppy_count);
 	set_capacity(disk, 2880);
 	rc = add_disk(disk);

drivers/block/virtio_blk.c

@@ -843,7 +843,6 @@ static int virtblk_probe(struct virtio_device *vdev)
 	vblk->disk->minors = 1 << PART_BITS;
 	vblk->disk->private_data = vblk;
 	vblk->disk->fops = &virtblk_fops;
-	vblk->disk->flags |= GENHD_FL_EXT_DEVT;
 	vblk->index = index;
 
 	/* configure queue flush support */

drivers/block/z2ram.c

@@ -327,6 +327,7 @@ static int z2ram_register_disk(int minor)
 	disk->major = Z2RAM_MAJOR;
 	disk->first_minor = minor;
 	disk->minors = 1;
+	disk->flags |= GENHD_FL_NO_PART;
 	disk->fops = &z2_fops;
 	if (minor)
 		sprintf(disk->disk_name, "z2ram%d", minor);

drivers/block/zram/zram_drv.c

@@ -1947,6 +1947,7 @@ static int zram_add(void)
 	zram->disk->major = zram_major;
 	zram->disk->first_minor = device_id;
 	zram->disk->minors = 1;
+	zram->disk->flags |= GENHD_FL_NO_PART;
 	zram->disk->fops = &zram_devops;
 	zram->disk->private_data = zram;
 	snprintf(zram->disk->disk_name, 16, "zram%d", device_id);

drivers/cdrom/gdrom.c

@@ -719,6 +719,7 @@ static void probe_gdrom_setupdisk(void)
 	gd.disk->major = gdrom_major;
 	gd.disk->first_minor = 1;
 	gd.disk->minors = 1;
+	gd.disk->flags |= GENHD_FL_NO_PART;
 	strcpy(gd.disk->disk_name, GDROM_DEV_NAME);
 }
 

drivers/md/dm.c

@@ -1778,6 +1778,7 @@ static struct mapped_device *alloc_dev(int minor)
 	md->disk->major = _major;
 	md->disk->first_minor = minor;
 	md->disk->minors = 1;
+	md->disk->flags |= GENHD_FL_NO_PART;
 	md->disk->fops = &dm_blk_dops;
 	md->disk->queue = md->queue;
 	md->disk->private_data = md;

drivers/md/md.c

@@ -5707,11 +5707,6 @@ static int md_alloc(dev_t dev, char *name)
 	mddev->queue = disk->queue;
 	blk_set_stacking_limits(&mddev->queue->limits);
 	blk_queue_write_cache(mddev->queue, true, true);
-	/* Allow extended partitions.  This makes the
-	 * 'mdp' device redundant, but we can't really
-	 * remove it now.
-	 */
-	disk->flags |= GENHD_FL_EXT_DEVT;
 	disk->events |= DISK_EVENT_MEDIA_CHANGE;
 	mddev->gendisk = disk;
 	error = add_disk(disk);

drivers/mmc/core/block.c

@@ -2395,7 +2395,6 @@ static struct mmc_blk_data *mmc_blk_alloc_req(struct mmc_card *card,
 	md->disk->private_data = md;
 	md->parent = parent;
 	set_disk_ro(md->disk, md->read_only || default_ro);
-	md->disk->flags = GENHD_FL_EXT_DEVT;
 	if (area_type & (MMC_BLK_DATA_AREA_RPMB | MMC_BLK_DATA_AREA_BOOT))
 		md->disk->flags |= GENHD_FL_NO_PART;
 

drivers/mtd/ubi/block.c

@@ -430,6 +430,7 @@ int ubiblock_create(struct ubi_volume_info *vi)
 		ret = -ENODEV;
 		goto out_cleanup_disk;
 	}
+	gd->flags |= GENHD_FL_NO_PART;
 	gd->private_data = dev;
 	sprintf(gd->disk_name, "ubiblock%d_%d", dev->ubi_num, dev->vol_id);
 	set_capacity(gd, disk_capacity);

drivers/scsi/sd.c

@@ -3566,7 +3566,6 @@ static int sd_probe(struct device *dev)
 
 	sd_revalidate_disk(gd);
 
-	gd->flags = GENHD_FL_EXT_DEVT;
 	if (sdp->removable) {
 		gd->flags |= GENHD_FL_REMOVABLE;
 		gd->events |= DISK_EVENT_MEDIA_CHANGE;

drivers/scsi/sr.c

@@ -684,6 +684,7 @@ static int sr_probe(struct device *dev)
 	disk->minors = 1;
 	sprintf(disk->disk_name, "sr%d", minor);
 	disk->fops = &sr_bdops;
+	disk->flags |= GENHD_FL_NO_PART;
 	disk->events = DISK_EVENT_MEDIA_CHANGE | DISK_EVENT_EJECT_REQUEST;
 	disk->event_flags = DISK_EVENT_FLAG_POLL | DISK_EVENT_FLAG_UEVENT |
 				DISK_EVENT_FLAG_BLOCK_ON_EXCL_WRITE;

include/linux/genhd.h

@@ -46,11 +46,6 @@ struct partition_meta_info {
  * Must not be set for devices which are removed entirely when the
  * media is removed.
  *
- * ``GENHD_FL_EXT_DEVT`` (0x0040): the driver supports extended
- * dynamic ``dev_t``, i.e. it wants extended device numbers
- * (``BLOCK_EXT_MAJOR``).
- * This affects the maximum number of partitions.
- *
  * ``GENHD_FL_NO_PART`` (0x0200): partition support is disabled.
  * The kernel will not scan for partitions from add_disk, and users
  * can't add partitions manually.
@@ -64,7 +59,6 @@ struct partition_meta_info {
 #define GENHD_FL_REMOVABLE			0x0001
 /* 2 is unused (used to be GENHD_FL_DRIVERFS) */
 /* 4 is unused (used to be GENHD_FL_MEDIA_CHANGE_NOTIFY) */
-#define GENHD_FL_EXT_DEVT			0x0040
 #define GENHD_FL_NO_PART			0x0200
 #define GENHD_FL_HIDDEN				0x0400
 
@@ -94,13 +88,13 @@ struct blk_integrity {
 };
 
 struct gendisk {
-	/* major, first_minor and minors are input parameters only,
-	 * don't use directly.  Use disk_devt() and disk_max_parts().
+	/*
+	 * major/first_minor/minors should not be set by any new driver, the
+	 * block core will take care of allocating them automatically.
 	 */
-	int major;			/* major number of driver */
+	int major;
 	int first_minor;
-	int minors;                     /* maximum number of minors, =1 for
-                                         * disks that can't be partitioned. */
+	int minors;
 
 	char disk_name[DISK_NAME_LEN];	/* name of major driver */
 
@@ -164,18 +158,6 @@ static inline bool disk_live(struct gendisk *disk)
 #define disk_to_cdi(disk)	NULL
 #endif
 
-static inline int disk_max_parts(struct gendisk *disk)
-{
-	if (disk->flags & GENHD_FL_EXT_DEVT)
-		return DISK_MAX_PARTS;
-	return disk->minors;
-}
-
-static inline bool disk_part_scan_enabled(struct gendisk *disk)
-{
-	return disk_max_parts(disk) > 1 && !(disk->flags & GENHD_FL_NO_PART);
-}
-
 static inline dev_t disk_devt(struct gendisk *disk)
 {
 	return MKDEV(disk->major, disk->first_minor);