Re: [PATCH] ublk_drv: set DMA alignment mask to 3

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

On Sat, May 11, 2024 at 08:40:57AM -0600, Jens Axboe wrote:
> By default, this will be 511, as that's the block layer default. But
> drivers these days can support memory alignments that aren't tied to
> the sector sizes, instead just being limited by what the DMA engine
> supports. An example is NVMe, where it's generally set to a 32-bit or
> 64-bit boundary. As ublk itself doesn't really care, just set it low
> enough that we don't run into issues with NVMe where the required
> O_DIRECT memory alignment is now more restrictive on ublk than it is
> on the underlying device.
> 
> This was triggered by spurious -EINVAL returns on O_DIRECT IO on a
> setup with ublk managing NVMe devices, which previously worked just
> fine on the NVMe device itself. With the alignment relaxed, the test
> works fine.
> 
> Signed-off-by: Jens Axboe <axboe@kernel.dk>

It should be triggered since DIO DMA alignment is relaxed:

Reviewed-by: Ming Lei <ming.lei@redhat.com>



Thanks, 
Ming