Re: [PATCH v3 13/13] block: flag zoned disks with GENHD_FL_NO_PART

[Hannes Reinecke <hare@suse.de>]

On 8/11/26 12:58 PM, Damien Le Moal wrote:
> Zoned block devices do not support partitions. However, the partition
> table is nevertheless still inspected, and any partition found ignored
> with a warning in add_partition(). While this is generally not a problem,
> and in fact beneficial to the user as it indicates an invalid use of a
> zoned block device, scanning for a partition table on the device may
> result in issuing read operations to offline zones (e.g. after a disk head
> is depopulated for disks that support head management operations).
> 
> Since partitions are ignored anyway, completely disable partition scanning
> for zoned gendisks by setting the flag GENHD_FL_NO_PART in __add_disk().
> The existing check in add_partition() is left as-is to ensure that we
> still get a warning if for whatever reason, despite GENHD_FL_NO_PART, we
> still endup trying to add partitions.
> 
> Flagging zoned disks with GENHD_FL_NO_PART also has the benefit to expose
> through sysfs the ext_range attribute with the value of 1 instead of the
> default DISK_MAX_PARTS, thus correctly advertizing the fact that zoned
> disks do not support partitions.
> 
> Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
> Reviewed-by: Bart Van Assche <bvanassche@acm.org>
> ---
>   block/genhd.c | 7 +++++++
>   1 file changed, 7 insertions(+)
> 
> diff --git a/block/genhd.c b/block/genhd.c
> index e8ce0cabf392..34a64077ba02 100644
> --- a/block/genhd.c
> +++ b/block/genhd.c
> @@ -447,6 +447,13 @@ static int __add_disk(struct device *parent, struct gendisk *disk,
>   		bdev_set_flag(disk->part0, BD_HAS_SUBMIT_BIO);
>   	}
>   
> +	/*
> +	 * We do not support partitions with zoned block devices, so do not try
> +	 * to scan the partitions table.
> +	 */
> +	if (blk_queue_is_zoned(disk->queue))
> +		disk->flags |= GENHD_FL_NO_PART;
> +
>   	/*
>   	 * If the driver provides an explicit major number it also must provide
>   	 * the number of minors numbers supported, and those will be used to
Reviewed-by: Hannes Reinecke <hare@kernel.org>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@suse.de                                +49 911 74053 688
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