Re: [PATCH 2/2] block: fix the length of a smaller last zone in blkdev_get_zone_info()

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

On 2026/10/12 14:29, shashank Jain wrote:
> On Mon, Oct 12, 2026, Christoph Hellwig wrote:
>> Can you add this to blktests as a reproducer?
> 
> Will do. I'll send a blktests test under tests/zbd/ that sets up a zoned
> null_blk device with a smaller last zone and checks that BLKREPORTZONEV2
> without BLK_ZONE_REP_CACHED matches BLKREPORTZONE, and that the cached
> report's last-zone length does not extend past the device. I'll post it
> to the blktests project separately and reference this series.

How do you plan to issue a BLK_ZONE_REP_CACHED report? "blkzone report" does not
have that yet. I am planning to send a patch for it.

> 
> Thanks,
> Shashank
> 
> On Mon, Oct 12, 2026 at 5:51 PM Christoph Hellwig <hch@lst.de> wrote:
>>
>> On Sun, Oct 11, 2026 at 10:49:06AM +0530, Shashank Mohan Jain wrote:
>>> blkdev_get_zone_info() sets the length of every zone to the zone size
>>> of the device. The last zone of a zoned block device may be smaller
>>> than the others: blk_revalidate_zone_cb() accepts that and remembers
>>> the capacity of that zone in disk->last_zone_capacity. For such a zone
>>> the length reported from the cached information is too large, and
>>> start + len is beyond the end of the device. A conventional last zone
>>> is also given the capacity of a full zone.
>>>
>>> Example with a zoned null_blk device of 10 MiB (20480 sectors) with
>>> 4 MiB zones, last zone:
>>>
>>>   BLKREPORTZONE:       start 16384 len 4096 capacity 4096
>>>   BLKREPORTZONEV2 with
>>>   BLK_ZONE_REP_CACHED: start 16384 len 8192 capacity 4096
>>
>> Can you add this to blktests as a reproducer?
>>
>> The patch looks good:
>>
>>
>> Reviewed-by: Christoph Hellwig <hch@lst.de>


-- 
Damien Le Moal
Western Digital Research