On 2020/07/17 16:50, Ming Lei wrote: > On Fri, Jul 17, 2020 at 02:45:25AM +0000, Damien Le Moal wrote: >> On 2020/07/16 23:35, Christoph Hellwig wrote: >>> On Thu, Jul 16, 2020 at 07:09:33PM +0900, Johannes Thumshirn wrote: >>>> Max append sectors needs to be aligned to physical block size, otherwise >>>> we can end up in a situation where it's off by 1-3 sectors which would >>>> cause short writes with asynchronous zone append submissions from an FS. >>> >>> Huh? The physical block size is purely a hint. >> >> For ZBC/ZAC SMR drives, all writes must be aligned to the physical sector size. > > Then the physical block size should be same with logical block size. > The real workable limit for io request is aligned with logical block size. Yes, I know. This T10/T13 design is not the brightest thing they did... on 512e SMR drives, addressing is LBA=512B unit, but all writes in sequential zones must be 4K aligned (8 LBAs). > >> However, sd/sd_zbc does not change max_hw_sectors_kb to ensure alignment to 4K >> on 512e disks. There is also nullblk which uses the default max_hw_sectors_kb to >> 255 x 512B sectors, which is not 4K aligned if the nullb device is created with >> 4K block size. > > Actually the real limit is from max_sectors_kb which is <= max_hw_sectors_kb, and > both should be aligned with logical block size, IMO. Yes, agreed, but for nullblk device created with block size = 4K it is not. So one driver to patch for sure. However, I though having some forced alignment in blk_queue_max_hw_sectors() for limit->max_hw_sectors and limit->max_sectors would avoid tripping on weird values for weird drives... -- Damien Le Moal Western Digital Research
