Re: [PATCH 1/2] uapi: fix statx attribute value overlap for DAX & MOUNT_ROOT

[Ira Weiny]

On Wed, Dec 02, 2020 at 12:42:08PM -0800, Linus Torvalds wrote:
> On Tue, Dec 1, 2020 at 6:16 PM Ira Weiny <ira.weiny@xxxxxxxxx> wrote:
> >
> > This will force a change to xfstests at a minimum.  And I do know of users who
> > have been using this value.  But I have gotten inquires about using the feature
> > so there are users out there.
> 
> If it's only a few tests that fail, I wouldn't worry about it, and the
> tests should just be updated.

Done[1]

> 
> But if there are real user concerns, we may need to have some kind of
> compat code. Because of the whole "no regressions" thing.
> 
> What would the typical failure cases be in practice?

The failure will be a user not seeing their file operating in DAX mode when
they expect it to.

I discussed this with Dan Williams today.  He and I agreed the flag is new
enough that we don't think users have any released code to the API just yet.
So I think we will be ok.

Also, after learning what the other flag was for I agree with Christoph that
the impact is going to be minimal since users are not typically operating on
the root inode.

So I think we are ok with just making the change and getting it into stable
quickly.

Thanks,
Ira

[1] https://lore.kernel.org/lkml/20201202214629.1563760-1-ira.weiny@xxxxxxxxx/