On 2020/07/20 20:08, hch@xxxxxxxxxxxxx wrote: > On Fri, Jul 17, 2020 at 10:55:49AM +0000, Damien Le Moal wrote: >>> >>> 2) add one new limit for write on seq zone, such as: zone_write_block_size >>> >>> Then the two cases can be dealt with in same way, and physical block >>> size is usually a hint as Christoph mentioned, looks a bit weird to use >>> it in this way, or at least the story should be documented. >> >> Yeah, but zone_write_block_size would end up always being equal to the physical >> block size for SMR. For ZNS and nullblk, logical block size == physical block >> size, always, so it would not be useful. I do not think such change is necessary. > > I think we should add a write_block_size (or write_granularity) field. > There have been some early stage NVMe proposal to add that even for > conventional random/write namespaces. OK. We can add that easily enough. The default value will be the logical block size and only ZBC/ZAC SMR drives will need to set that to the physical block size. But for regular 4Kn drives, including all logical drives like null_blk, I think it would still be nice to have a max_hw_sectors and max_sectors aligned on 4K. We can enforce that generically in the block layer when setting these limits, or audit drivers and correct those setting weird values (like null_blk). Which approach do you think is better ? -- Damien Le Moal Western Digital Research
