Re: [PATCH] NFSD: fix deny mode logic in nfs4_upgrade_open

[Jeff Layton <jlayton@kernel.org>]

On Thu, 2023-02-02 at 19:41 +0000, Chuck Lever III wrote:
> 
> > On Feb 2, 2023, at 2:36 AM, Pumpkin <cc85nod@gmail.com> wrote:
> > 
> > If the upgrading deny mode is invalid or conflicts with other client, we
> > should try to resolve it, but the if-condition makes those error handling
> > cannot be executed.
> > 
> > Signed-off-by: Pumpkin <cc85nod@gmail.com>
> > ---
> > fs/nfsd/nfs4state.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> > index 4ef529379..ebdfaf0f9 100644
> > --- a/fs/nfsd/nfs4state.c
> > +++ b/fs/nfsd/nfs4state.c
> > @@ -5298,7 +5298,7 @@ nfs4_upgrade_open(struct svc_rqst *rqstp, struct nfs4_file *fp,
> > 	/* test and set deny mode */
> > 	spin_lock(&fp->fi_lock);
> > 	status = nfs4_file_check_deny(fp, open->op_share_deny);
> > -	if (status == nfs_ok) {
> > +	if (status != nfs_ok) {
> > 		if (status != nfserr_share_denied) {
> 
> if status == nfs_ok then status will definitely not equal
> share_denied. So this check is a bit nonsensical as it stands.
> 
> Usually I prefer "switch (status)" in situations like this
> because that avoids this kind of issue and I find it easier
> to read quickly.
> 
> Jeff, you are the original author of this function, and
> Dai, your commit is the last one to touch this area. Can
> you guys have a look? The one-liner looks correct, but I
> might be missing something.
> 

Yeah, that code is clearly broken and it looks like it was done in
3d69427151806 (NFSD: add support for share reservation conflict to
courteous server).

I don't believe that one-liner is correct though. If the result is
nfs_ok, then we want to set the deny mode here and that won't happen.

Something like this maybe? (completely untested):

---------------8<-------------------

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index c39e43742dd6..af22dfdc6fcc 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -5282,16 +5282,17 @@ nfs4_upgrade_open(struct svc_rqst *rqstp, struct nfs4_file *fp,
        /* test and set deny mode */
        spin_lock(&fp->fi_lock);
        status = nfs4_file_check_deny(fp, open->op_share_deny);
-       if (status == nfs_ok) {
-               if (status != nfserr_share_denied) {
-                       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;
-               }
+       switch (status) {
+       case nfs_ok:
+               set_deny(open->op_share_deny, stp);
+               fp->fi_share_deny |=
+                       (open->op_share_deny & NFS4_SHARE_DENY_BOTH);
+               break;
+       case nfserr_share_denied:
+               if (nfs4_resolve_deny_conflicts_locked(fp, false,
+                               stp, open->op_share_deny, false))
+                       status = nfserr_jukebox;
+               break;
        }
        spin_unlock(&fp->fi_lock);

-- 
Jeff Layton <jlayton@kernel.org>