Re: [RFC] errno.h: Provide EFSCORRUPTED for everybody

Dave Chinner
2019-11-01T21:38:52Z

On Fri, Nov 01, 2019 at 09:57:31PM +0100, Geert Uytterhoeven wrote:
> Hi Valdis,
>
> On Thu, Oct 31, 2019 at 2:11 AM Valdis Kletnieks
> <valdis.kletnieks@vt.edu> wrote:
> > Three questions: (a) ACK/NAK on this patch, (b) should it be all in one
> > patch, or one to add to errno.h and 6 patches for 6 filesystems?), and
> > (c) if one patch, who gets to shepherd it through?
> >
> > There's currently 6 filesystems that have the same #define. Move it
> > into errno.h so it's defined in just one place.
> >
> > Signed-off-by: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
>
> Thanks for your patch!
>
> > --- a/include/uapi/asm-generic/errno.h
> > +++ b/include/uapi/asm-generic/errno.h
> > @@ -98,6 +98,7 @@
> > #define EINPROGRESS 115 /* Operation now in progress */
> > #define ESTALE 116 /* Stale file handle */
> > #define EUCLEAN 117 /* Structure needs cleaning */
> > +#define EFSCORRUPTED EUCLEAN
>
> I have two questions:
> a) Why not use EUCLEAN everywhere instead?
> Having two different names for the same errno complicates grepping.

Because:
a) EUCLEAN is horrible for code documentation. EFSCORRUPTED
describes exactly the error being returned and/or checked for.

b) we've used EFSCORRUPTED in XFS since 1993. i.e. it was an
official, published error value on Irix, and we've kept it
in the linux code for the past ~20 years because of a)

c) Userspace programs that include filesystem specific
headers have already been exposed to and use EFSCORRUPTED,
so we can't remove/change it without breaking userspace.

d) EUCLEAN has a convenient userspace string description
that is appropriate for filesystem corruption: "Structure
needs cleaning" is precisely what needs to happen. Repair of
the filesystem (i.e. recovery to a clean state) is what is
required to fix the error....

> b) Perhaps both errors should use different values?

That horse bolted to userspace years ago - this is just formalising
the practice that has spread across multiple linux filesystems from
XFS over the past ~10 years..

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com