Re: [PATCH] NFSD: Fix the share reservation conflict to courteous server logic in nfs4_upgrade_open()

[dai . ngo]

On 10/30/22 8:26 AM, Chuck Lever III wrote:
> > On Oct 30, 2022, at 3:26 AM, Christophe JAILLET <christophe.jaillet@xxxxxxxxxx> wrote:
> >
> > 'status != nfserr_share_denied' is known to be true because we test
> > 'status == nfs_ok' the line just above.
> >
> > So nfs4_resolve_deny_conflicts_locked() can never be called.
> >
> > Fix the logic and avoid the dead code.
> >
> > Fixes: 3d6942715180 ("NFSD: add support for share reservation conflict to courteous server")
> > Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
> > ---
> > This patch is speculative.
> > It is compile tested only.
> >
> > REVIEW WITH CARE.
> > ---
> > fs/nfsd/nfs4state.c | 14 ++++++--------
> > 1 file changed, 6 insertions(+), 8 deletions(-)
> >
> > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> > index 1ded89235111..de0565e9485c 100644
> > --- a/fs/nfsd/nfs4state.c
> > +++ b/fs/nfsd/nfs4state.c
> > @@ -5260,15 +5260,13 @@ nfs4_upgrade_open(struct svc_rqst *rqstp, struct nfs4_file *fp,
> > 	spin_lock(&fp->fi_lock);
> > 	status = nfs4_file_check_deny(fp, open->op_share_deny);
> I agree there's dead code here. I believe the bug is the first check is
> supposed to be "if (status != nfs_ok)". I will let Dai have a look at
> this to confirm.

Yes, it's actually a bug when nfs4_file_check_deny returns
nfserr_share_denied we won't try to resolve the conflict at all.

Thanks for catching this!
-Dai

> But, in the fix, let's replace this logic with "switch (status) { }".
>
>
> > 	if (status == nfs_ok) {
> > -		if (status != nfserr_share_denied) {
> > -			set_deny(open->op_share_deny, stp);
> > -			fp->fi_share_deny |=
> > +		set_deny(open->op_share_deny, stp);
> > +		fp->fi_share_deny |=
> > 				(open->op_share_deny & NFS4_SHARE_DENY_BOTH);
> > -		} else {
> > -			if (nfs4_resolve_deny_conflicts_locked(fp, false,
> > -					stp, open->op_share_deny, false))
> > -				status = nfserr_jukebox;
> > -		}
> > +	} else if (status == nfserr_share_denied) {
> > +		if (nfs4_resolve_deny_conflicts_locked(fp, false, stp,
> > +				open->op_share_deny, false))
> > +			status = nfserr_jukebox;
> > 	}
> > 	spin_unlock(&fp->fi_lock);
> >
> > --
> > 2.34.1
> --
> Chuck Lever