Re: [PATCH v2 11/15] block: introduce BLKREPORTZONESV2 ioctl

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

On 11/4/25 00:17, Johannes Thumshirn wrote:
> On 11/3/25 2:38 PM, Damien Le Moal wrote:
>> Introduce the new BLKREPORTZONESV2 ioctl command to allow user
>> applications access to the fast zone report implemented by
>> blkdev_report_zones_cached(). This new ioctl is defined as number 142
>> and is documented in include/uapi/linux/fs.h.
>>
>> Unlike the existing BLKREPORTZONES ioctl, this new ioctl uses the flags
>> field of struct blk_zone_report also as an input. If the user sets the
>> BLK_ZONE_REP_CACHED flag as an input, then blkdev_report_zones_cached()
>> is used to generate the zone report using cached zone information. If
>> this flag is not set, then BLKREPORTZONESV2 behaves in the same manner
>> as BLKREPORTZONES and the zone report is generated by accessing the
>> zoned device.
> 
> 
> Is there a downside to always do the caching? A.k.a do we need the new 
> ioctl or can we keep using the old one and cache the report zones reply?

The old one is needed to allow getting the precise imp open, exp open, closed
conditions, if the user cares about these. E.g. Zonefs does because of the
(optional) explicit zone open done on file open.

And we cannot break existing user space anyway (e.g. sysutils blkzone), so we
must return the "legacy" report unless asked otherwise.


-- 
Damien Le Moal
Western Digital Research