Re: [PATCHv2 1/7] block: check for valid bio while splitting

[Keith Busch <kbusch@kernel.org>]

On Wed, Aug 13, 2025 at 01:41:49PM -0700, Bart Van Assche wrote:
> On 8/13/25 1:06 PM, Keith Busch wrote:
> > But I can't make that change because many scsi devices don't set the dma
> > alignment and get the default 511 value. This is fine for the memory
> > address offset, but the lengths sent for various inquriy commands are
> > much smaller, like 4 and 32 byte lengths. That length wouldn't pass the
> > dma alignment granularity, so I think the default value is far too
> > conservative. Does the address start size need to be a different limit
> > than minimum length? I feel like they should be the same, but maybe
> > that's just an nvme thing.
> 
> Hi Keith,
> 
> Maybe I misunderstood your question. It seems to me that the SCSI core
> sets the DMA alignment by default to four bytes. From
> drivers/scsi/hosts.c:

Thanks, I think you got my meaning. 

I'm using the AHCI driver. It looks like ata_scsi_dev_config() overrides
the dma_alignment to sector_size - 1, and that pattern goes way back,
almost 20 years ago, so maybe I can't change it.