Re: [PATCH v6 1/4] openat2: new OPENAT2_REGULAR flag support

[Jori Koolstra]

> Op 16-04-2026 16:21 CEST schreef Dorjoy Chowdhury <dorjoychy111@xxxxxxxxx>:
> 
>  
> On Thu, Apr 16, 2026 at 7:52 PM Jori Koolstra <jkoolstra@xxxxxxxxx> wrote:
> >
> > On Sat, Mar 28, 2026 at 11:22:22PM +0600, Dorjoy Chowdhury wrote:
> > > diff --git a/arch/alpha/include/uapi/asm/fcntl.h b/arch/alpha/include/uapi/asm/fcntl.h
> > > index 50bdc8e8a271..fe488bf7c18e 100644
> > > --- a/arch/alpha/include/uapi/asm/fcntl.h
> > > +++ b/arch/alpha/include/uapi/asm/fcntl.h
> > > @@ -34,6 +34,7 @@
> > >
> > >  #define O_PATH               040000000
> > >  #define __O_TMPFILE  0100000000
> > > +#define OPENAT2_REGULAR      0200000000
> > >
> >
> > I don't quite understand why we are adding OPENAT2_REGULAR inside the
> > O_* flag range. Wasn't this supposed to be only supported for openat2()?
> > If so, I don't see the need to waste an O_* flag bit. But maybe I am
> > missing something.
> >
> 
> Yes, OPENAT2_REGULAR is only supported for openat2. I am not sure if I
> got a specific review to not add OPENAT2_REGULAR in the O_* flag 32
> bit range. But as far as I understand, for the old open system calls
> we can't easily add new O_* flags as the older codepaths don't strip
> off unknown bits which openat2 does. It's not easy to add new O_*
> flags for the old open system calls since that could break userspace
> programs.

If I recall correctly, Aleksa has suggested we might also want to add
O_EMPTYPATH to openat() instead of only allowing this for openat2().
I am waiting to see what Christian thinks of this.

I guess in that case it is relatively harmless to change UAPI
behavior because openat() with an empty path never works; so it
would be silly if there are userspace programs that make
this call, which always fails and does nothing, and somehow rely on
that.

> So I guess it's okay to add OPENAT2_REGULAR in the 32 bits
> range anyway? (Also lots of code paths take 32bit flags param right
> now and those would need changing to take uint64_t instead but this is
> of course not a reason to not add the new flag outside of the 32
> bits).
> 
> Regards,
> Dorjoy

Thanks,
Jori.