linux-kernel - Re: [PATCH 1/2] uapi: fix statx attribute value overlap for DAX & MOUNT

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Message-ID: <20201203024504.GA1563847@iweiny-DESK2.sc.intel.com>
Date:   Wed, 2 Dec 2020 18:45:04 -0800
From:   Ira Weiny <ira.weiny@...el.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Eric Sandeen <sandeen@...hat.com>,
        Miklos Szeredi <mszeredi@...hat.com>,
        David Howells <dhowells@...hat.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-man <linux-man@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        xfs <linux-xfs@...r.kernel.org>,
        Ext4 Developers List <linux-ext4@...r.kernel.org>,
        Xiaoli Feng <xifeng@...hat.com>
Subject: 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 <ira.weiny@...el.com> 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@intel.com/