Re: [PATCH 11/14] block: remove GENHD_FL_EXT_DEVT

Ming Lei
2022-05-25T14:36:17Z

Hi Christoph,

On Mon, Nov 22, 2021 at 02:06:22PM +0100, Christoph Hellwig wrote:
> 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>
> ---
> block/genhd.c | 6 +++---
> block/partitions/core.c | 9 ++++-----
> drivers/block/amiflop.c | 1 +
> drivers/block/ataflop.c | 1 +
> drivers/block/brd.c | 1 -
> drivers/block/drbd/drbd_main.c | 1 +
> drivers/block/floppy.c | 1 +
> drivers/block/loop.c | 1 -
> drivers/block/null_blk/main.c | 1 -
> drivers/block/paride/pcd.c | 1 +
> drivers/block/paride/pf.c | 1 +
> drivers/block/pktcdvd.c | 2 +-
> drivers/block/ps3vram.c | 1 +
> drivers/block/rbd.c | 6 ++----
> drivers/block/swim.c | 1 +
> drivers/block/swim3.c | 2 +-
> drivers/block/virtio_blk.c | 1 -
> drivers/block/z2ram.c | 1 +
> drivers/block/zram/zram_drv.c | 1 +
> drivers/cdrom/gdrom.c | 1 +
> drivers/md/dm.c | 1 +
> drivers/md/md.c | 5 -----
> drivers/mmc/core/block.c | 1 -
> drivers/mtd/ubi/block.c | 1 +
> drivers/scsi/sd.c | 1 -
> drivers/scsi/sr.c | 1 +
> include/linux/genhd.h | 28 +++++-----------------------
> 27 files changed, 30 insertions(+), 48 deletions(-)
>
> diff --git a/block/genhd.c b/block/genhd.c
> index 09abd41249fd4..e9346fae48ad4 100644
> --- a/block/genhd.c
> +++ b/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);

The above change breaks parted on loop, which reads 'ext_range' to add
partitions.

Follows the test case:

fallocate -l 4096M loop0.img
losetup /dev/loop0 loop0.img
parted -s /dev/loop0 mklabel MSDOS
parted -s /dev/loop0 mkpart pri 1 1248

Since this patch is merged, /dev/loop0p1 can't be created any more
by above script.

Thanks,
Ming