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Date:   Tue, 26 Nov 2019 10:34:49 -0500
From:   "J. Bruce Fields" <bfields@redhat.com>
To:     Doug Nazar <nazard@nazar.ca>
Cc:     linux-nfs@vger.kernel.org, Thomas Deutschmann <whissi@gentoo.org>,
        Steve Dickson <steved@redhat.com>
Subject: Re: nfs-utils: v3 mounts broken due to statx() returning EINVAL
Message-ID: <20191126153449.GA68204@pick.fieldses.org>
References: <20191011170709.GE19318@fieldses.org>
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On Tue, Nov 26, 2019 at 02:22:40AM -0500, Doug Nazar wrote:
> On Fri, Oct 11, 2019 at 17:07:09PM +0000, Bruce Fields wrote:
> >On Tue, Oct 08, 2019 at 10:23:56PM +0200, Thomas Deutschmann wrote:
> >> Hi,
> >>
> >> we have some user reporting that NFS v3 mounts are broken
> >> when using glibc-2.29 and linux-4.9.x (4.9.128) because
> >> statx() with mask=3DSTATX_BASIC_STATS returns EINVAL.
> >>
> >> Looks like this isn't happening with <nfs-utils-2.4.1 or
> >> newer kernels.
> >>
> >> The following workaround was confirmed to be working:
> >>
> >> --- a/support/misc/xstat.c=A0=A0=A0 2019-06-24 21:31:55.260371592 +020=
0
> >> +++ b/support/misc/xstat.c=A0=A0=A0 2019-06-24 21:32:29.098777436 +020=
0
> >> @@ -47,6 +47,8 @@
> >>=A0 =A0=A0=A0 =A0=A0=A0 =A0=A0=A0 statx_copy(statbuf, &stxbuf);
> >>=A0 =A0=A0=A0 =A0=A0=A0 =A0=A0=A0 return 0;
> >>=A0 =A0=A0=A0 =A0=A0=A0 }
> >> +=A0=A0=A0 =A0=A0=A0 if (errno =3D=3D EINVAL)
> >> +=A0=A0=A0 =A0=A0=A0 =A0=A0=A0 errno =3D ENOSYS;
> >>=A0 =A0=A0=A0 =A0=A0=A0 if (errno =3D=3D ENOSYS)
> >>=A0 =A0=A0=A0 =A0=A0=A0 =A0=A0=A0 statx_supported =3D 0;
> >>=A0 =A0=A0=A0 } else
> >>
> >>
> >> Bug: https://bugs.gentoo.org/688644
> >>
> >> At the moment I have no clue whether this is kernel/glibc or
> >> nfs-utils related; if the patch is safe to apply...
> >
> >Well, sounds like nfs-utils started using statx in 2.4.1.=A0 And just th=
e
> >fact that varying the kernel version makes it sound like there was a
> >kernel bug causing an EINVAL return in this case, and that bug got
> >fixed.
> >
> >One way to confirm might be running mount under strace and looking for
> >that EINVAL return.
>=20
> Just to provide an update on this issue, it was tracked down to glibc's
> statx emulation not supporting AT_STATX_DONT_SYNC and returning EINVAL.
>=20
> So on a kernel without statx support, but a new glibc with statx support,
> nfs-utils will always fail to stat any paths.
>=20
> Either this or a similar fix is required to support older kernels.

OK.  So maybe your patch is the best we can do.  I'd just add a comment
there documenting the situation.

--b.