Re: [PATCH 1/2] nfsd: fix version-setting regression on old kernels

J. Bruce Fields
2010-02-04T21:46:54Z

On Thu, Feb 04, 2010 at 04:37:52PM -0500, Steve Dickson wrote:
>
>
> On 01/27/2010 05:26 PM, J. Bruce Fields wrote:
> > /proc/fs/nfsd/versions was extended to allow turning on/off minor
> > versions by echoing "+4.1" or "-4.1" to /proc/fs/nsfd/versions.
> >
> > Unfortunately, pre-2.6.30 kernels just stop parsing at first non-digit,
> > so "-4.1" is interpreted as "-4". If new nfs-utils (on old kernel)
> > writes "+2", "+3", "+4", then "-4.1", result therefore is to turn off
> > 4.1.
> >
> > Given that historical behavior, it may have been a mistake to extend the
> > interface the way we did; but at this point we're probably stuck with
> > it. So, just reverse the order we write versions in.
> >
> > Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
> > ---
> > utils/nfsd/nfssvc.c | 10 +++++-----
> > 1 files changed, 5 insertions(+), 5 deletions(-)
> >
> > diff --git a/utils/nfsd/nfssvc.c b/utils/nfsd/nfssvc.c
> > index b8028bb..7bbbaba 100644
> > --- a/utils/nfsd/nfssvc.c
> > +++ b/utils/nfsd/nfssvc.c
> > @@ -238,17 +238,17 @@ nfssvc_setvers(unsigned int ctlbits, int minorvers4)
> > if (fd < 0)
> > return;
> >
> > + n = minorvers4 >= 0 ? minorvers4 : -minorvers4;
> > + if (n >= NFSD_MINMINORVERS4 && n <= NFSD_MAXMINORVERS4)
> > + off += snprintf(ptr+off, sizeof(buf) - off, "%c4.%d",
> There needs to be a space between the %d and ".
>
> But more importantly what problem is the patch fixing?? I've tested this
> on a 2.6.29 and 2.6.31 as well as a 2.6.33 kernel and I see no different
> in how the versions are ordered.

See the patch description. A test case:

- boot 2.6.29
- run 'nfsd -N4.1'
- try to mount v4.0.

See also https://bugzilla.redhat.com/show_bug.cgi?id=512377.

--b.

> Note, as you probably already know, the kernel will always display
> the versions in descending order...
>
> steved.
>
>