Re: [PATCH] block: align max append sectors to physical block size

[Ming Lei <ming.lei@redhat.com>]

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.

> 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.


Thanks, 
Ming