[PATCH] nvme: module parameter to disable pi checks

[Keith Busch]

On Thu, Oct 24, 2024 at 07:02:39AM +0200, Christoph Hellwig wrote:
> On Wed, Oct 23, 2024 at 08:50:48AM -0700, Keith Busch wrote:
> > From: Keith Busch <kbusch at kernel.org>
> > 
> > A recent commit enables integrity checks for formats the previous kernel
> > versions registered with the "nop" integrity profile. This means
> > namespaces using that format become unreadable when upgrading the kernel
> > past that commit.
> > 
> > Introduce a module parameter to restore the "nop" integrity profile so
> > that storage can be readable once again. This could be a boot device, so
> > the setting needs to happen at module load time.
> 
> Not exactly a fan of module option, especially with such broad scope.
> This will actually disable PI entirely as far as I can tell and not just
> for the PI at the end of metadata formats.

I don't like using module parameters for either, but I think I'm stuck
with no better option here.
 
> Can we at least restrict it to those formats?  And maybe add a few
> comments in the code why we have all this.

Yes, that's a good idea. Come to think of it, if you had a mix of
formats, some with pi at the beginning others at the end, the
"beginning" formats that were previously working would get incorrect PI
on subsequent writes.