On Thu, May 14, 2020 at 10:54:52AM +0900, Damien Le Moal wrote:
> Currently, a namespace io_opt queue limit is set by default to the
> physical sector size of the namespace and to the the write optimal
> size (NOWS) when the namespace reports this value. This causes problems
> with block limits stacking in blk_stack_limits() when a namespace block
> device is combined with an HDD which generally do not report any optimal
> transfer size (io_opt limit is 0). The code:
>
> /* Optimal I/O a multiple of the physical block size? */
> if (t->io_opt & (t->physical_block_size - 1)) {
> t->io_opt = 0;
> t->misaligned = 1;
> ret = -1;
> }
>
> results in blk_stack_limits() to return an error when the combined
> devices have different but compatible physical sector sizes (e.g. 512B
> sector SSD with 4KB sector disks).
>
> Fix this by not setting the optiomal IO size limit if the namespace does
> not report an optimal write size value.
Won't this continue to break if a controller does report NOWS that's not
a multiple of the physical block size of the device it's stacking with?
