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

On Wed, Dec 02, 2020 at 12:42:08PM -0800, Linus Torvalds wrote:

On Tue, Dec 1, 2020 at 6:16 PM Ira Weiny [off-list ref] wrote:

quoted

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@intel.com/ (local)