On Thu, Mar 02, 2023 at 11:07:15AM +0100, Andreas Hindborg wrote: > > Ming Lei <ming.lei@xxxxxxxxxx> writes: > > > On Thu, Mar 2, 2023 at 5:02 PM Ming Lei <ming.lei@xxxxxxxxxx> wrote: > >> > >> On Thu, Mar 02, 2023 at 04:32:21PM +0800, Ming Lei wrote: > >> > On Thu, Mar 02, 2023 at 08:31:07AM +0100, Andreas Hindborg wrote: > >> > > > >> > >> ... > >> > >> > > > >> > > I agree about fetching more zones. However, it is no good to fetch up to > >> > > a max, since the requested zone report may less than max. I was > >> > > >> > Short read should always be supported, so the interface may need to > >> > return how many zones in single command, please refer to nvme_ns_report_zones(). > >> > >> blk_zone is part of uapi, maybe the short read can be figured out by > >> one all-zeroed 'blk_zone'? then no extra uapi data is needed for > >> reporting zones. > > > > oops, we have blk_zone_report data for reporting zones to userspace already, > > see blkdev_report_zones_ioctl(), then this way can be re-used for getting zone > > report from ublk server too, right? > > Yes that would be nice. But I did the report_zone command like a read > operation, so we are not currently copying any buffers to user space > when issuing the command, we just rely on the iod. What I meant is to reuse the format of blk_zone_report for returning multiple 'blk_zone' info in single command. The only change is that you need to allocate one bigger kernel buffer to hold more 'blk_zone' in single report zone request. > I think it would be > better to use the start_sectors and nr_sectors of the iod instead. Then > we don't have to copy the blk_zone_report. What do you think? For IN parameter of report zone command, you still can reuse blk_zone_report: struct blk_zone_report { __u64 sector; __u32 nr_zones; __u32 flags; }; Just by using the 1st two 64b words of iod for holding 'blk_zone_report', and keep the iod->addr field not touched. [1] https://lore.kernel.org/linux-block/20230301140611.163055-1-ming.lei@xxxxxxxxxx/T/#md36358552d45a7d563940632d4c779a99f72916d Thanks, Ming