Re: [PATCH v4 13/13] block: flag zoned disks with GENHD_FL_NO_PART

[Damien Le Moal <dlemoal@kernel.org>]

On 8/14/26 17:12, Christoph Hellwig wrote:
> On Fri, Aug 14, 2026 at 03:32:01PM +0900, 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>
>> Reviewed-by: Hannes Reinecke <hare@kernel.org>
> 
> This really should get a Fixes for my original patch that skipped
> partitions and go to -stable (and into 7.3 even if Jens won't take
> the whole series) as it causes totally pointless I/O.  I also suspect
> the partition scanning and blkid interaction might be related to some
> of the weirdo xfstests failure I see where blkid doesn't detect
> xfs file systems in synthetic devices.
> 
> Reviewed-by: Christoph Hellwig <hch@lst.de>

Will add the fixes tag.

-- 
Damien Le Moal
Western Digital Research