linux-kernel - Re: fs/notify/fanotify/fanotify.c:198:2: note: in expansion of macro 'pr_warn

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Date:   Thu, 14 Mar 2019 18:16:35 +0200
From:   Amir Goldstein <amir73il@...il.com>
To:     Ralf Baechle <ralf@...ux-mips.org>
Cc:     Jan Kara <jack@...e.cz>, kbuild-all@...org,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-mips@...r.kernel.org, Paul Burton <paul.burton@...s.com>,
        James Hogan <jhogan@...nel.org>
Subject: Re: fs/notify/fanotify/fanotify.c:198:2: note: in expansion of macro 'pr_warn_ratelimited'

On Thu, Mar 14, 2019 at 4:34 PM Ralf Baechle <ralf@...ux-mips.org> wrote:
>
> On Thu, Mar 14, 2019 at 01:38:11PM +0100, Jan Kara wrote:
>
> > On Thu 14-03-19 14:01:18, Amir Goldstein wrote:
> > > On Thu, Mar 14, 2019 at 10:37 AM Jan Kara <jack@...e.cz> wrote:
> > > >
> > > > AFAICS this is the known problem with weird mips definitions of
> > > > __kernel_fsid_t which uses long whereas all other architectures use int,
> > > > right? Seeing that mips can actually have 8-byte longs, I guess this
> > > > bogosity is just wired in the kernel API and we cannot easily fix it in
> > > > mips (mips guys, correct me if I'm wrong). So what if we just
> > > > unconditionally typed printed values to unsigned int to silence the
> > > > warning?
> > >
> > > I don't understand why. To me that sounds like papering over a bug.
> > >
> > > See this reply from mips developer Paul Burton:
> > > https://marc.info/?l=linux-fsdevel&m=154783680019904&w=2
> > > mips developers have not replied to the question why __kernel_fsid_t
> > > should use long.
> >
> > Ah, right. I've missed that mips defines __kernel_fsid_t only if
> > sizeof(long) == 4. OK, than fixing MIPS headers is definitely what we ought
> > to do. Mips guys, any reason why the patch from Ralf didn't get merged yet?
>
> Paul's patch :-)
>
> As for the reason why the definition is as it is - 32-bit MIPS was
> born using long, then in 2000 64-bit MIPS started off as arch/mips64
> using int.  Eventually the two ports were combined using:
>
> ypedef struct {
> #if (_MIPS_SZLONG == 32)
>         long    val[2];
> #endif
> #if (_MIPS_SZLONG == 64)
>         int     val[2];
> #endif
> } __kernel_fsid_t;
>
> A desparate attempt to use asm-generic where ever possible then resulted
> in the confusing definition we'e having today.
>
> Normally APIs are cast into stone not to be changed.  But fsid is used in
> struct statfs and the man page states "Nobody knows what f_fsid is supposed
> to contain (but see below)." and f_fsid is supposed to be opaque anyway so
> I'm wondering if something could break at all.  Researching that.
>

Its content is opaque, but its size must be equal to that of fsid_t
from glibc/toolchain headers. Do the mips32 glibc headers also
define fsid_t as long val[2], or do they define it as int val[2]?

Thanks,
Amir.