[PATCH] nvme: set physical block size to value discovered in Identify Namespace

[Christoph Hellwig]

On Wed, Sep 20, 2017 at 01:48:42PM -0400, Keith Busch wrote:
> I think what you're wanting to say is:
> 
>   The physical block size will default to the logical block size unless
>   otherwise specified. While NVMe doesn't provide a way to discover the
>   physical block size, the format with best relative performance is a
>   good indicator as to the underlying block size.

I don't like this at all.  It's a really nasty guesswork.  If you need
this to get reasonable performance out of a specific device please
quirk it.

NVMe doesn't have the legacy issues that require 4k physical sectors
and 512 logical like ATA, so if a device really prefers 4k sectors
it should skip with 4k format by default instead of doing the logical /
physical dance.  Especially that a "physical" blocksize that Linux
could actually deal with (<= 4k) is a complete lie for flash anyway.