Re: [PATCH v3 1/7] bio: Introduce LightNVM payload

[Christoph Hellwig]

On Mon, May 11, 2015 at 01:58:51PM +0200, Matias Bj?rling wrote:
> >Can you explain why this needs to be done on a per-bio instead of a
> >per-request level?  I don't really think a low-level driver should add
> >fields to struct bio as that can be easily remapped.
> 
> When a bio is submitted through the block layer, it can be merged/splitted
> on going through the block layer. Thus, we don't know the number of physical
> addresses that must be mapped before its on the other side.

For any sort of passthrough bios that should not be the case.  It's not
for BLOCK_PC, it's not for my new pass through NVMe commands and I don't
think it should be in this case.
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