Re: [PATCH] fs: nfsd:xdr4.h: add missing conditional group CONFIG_NFSD_V3

[Guenter Roeck]

On 02/13/2015 06:51 AM, J. Bruce Fields wrote:
> On Thu, Feb 12, 2015 at 03:02:01PM -0800, Guenter Roeck wrote:
> > On Thu, Feb 12, 2015 at 11:09:13PM +0100, Bas Peters wrote:
> > > This patch adds a missing conditional group that has been causing build
> > > breakages due to undefined struct members being referenced when
> > > CONFIG_NFSD_v3 is not set.
> > >
> > > This patch applies against linux-next.
> > >
> > > Signed-off-by: Bas Peters <baspeters93@xxxxxxxxx>
> > > ---
> > >   fs/nfsd/xdr4.h | 6 ++++--
> > >   1 file changed, 4 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h
> > > index 0bda93e..5d1597f 100644
> > > --- a/fs/nfsd/xdr4.h
> > > +++ b/fs/nfsd/xdr4.h
> > > @@ -630,9 +630,11 @@ void warn_on_nonidempotent_op(struct nfsd4_op *op);
> > >   static inline void
> > >   set_change_info(struct nfsd4_change_info *cinfo, struct svc_fh *fhp)
> > >   {
> > > +	cinfo->change_supported = IS_I_VERSION(fhp->fh_dentry->d_inode);
> > > +
> > > +#ifdef CONFIG_NFSD_V3
> > >   	BUG_ON(!fhp->fh_pre_saved);
> > >   	cinfo->atomic = fhp->fh_post_saved;
> > > -	cinfo->change_supported = IS_I_VERSION(fhp->fh_dentry->d_inode);
> > >
> > >   	cinfo->before_change = fhp->fh_pre_change;
> > >   	cinfo->after_change = fhp->fh_post_change;
> > > @@ -640,7 +642,7 @@ set_change_info(struct nfsd4_change_info *cinfo, struct svc_fh *fhp)
> > >   	cinfo->before_ctime_nsec = fhp->fh_pre_ctime.tv_nsec;
> > >   	cinfo->after_ctime_sec = fhp->fh_post_attr.ctime.tv_sec;
> > >   	cinfo->after_ctime_nsec = fhp->fh_post_attr.ctime.tv_nsec;
> > > -
> > > +#endif
> > >   }
> >
> > You'll want to include and example of the build failure in the description,
> > bisect results after the '---' line, and a Fixes: line pointing to the patch
> > breaking the build.
> >
> > In this case, I am not sure if the above really fixes the problem,
> > or if it just hides it behind an #ifdef. To determine that, it will
> > probably be necessary to know which patch actually caused the problem.
> > This even more true since the code in question was not changed since
> > around 2010, so making it conditional looks really suspicious.
> >
> > In the curent case, I suspect that the problem may have been introduced by
> > commit 9cf514ccfac ("nfsd: implement pNFS operations"). That is just a guess,
> > though; I didn't run bisect myself. The key really is to figure out why the
> > code now fails to build, and not just to comment out the code that is causing
> > the failure.
>
> Yeah, when Jim Davis reported this I took a quick look at the history,
> didn't see an obvious explanation, and figured well maybe this is just
> the first time anyone's hit that particular config in a while.  Sounds
> like this actually is a recent regression?

It was intruduced by 9cf514ccfac. Problem is that xdr4.h is only supposed to
be used and included by NFSv4 code but is now included even if NFSv3 and/or
NFSv4 are not configured. The variables in fhp accessed above do not exist
unless NFSv3 is configured.

The patch here is therefore really just a kludge, though I don't really know
an easy real fix.

If you ask me, I'd say that 9cf514ccfac was rushed into mainline a bit.
It showed up in next on Feb 10 and pushed into mainline just a day or two
later. Result is that every build with NFS configured but not NSFv3 is
now broken.

Guenter

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