lockd: Have nlm_fopen() return errno values

The nlm_fopen() function is part of the API between nfsd and lockd.

Currently its return value is an on-the-wire NLM status code. But
that forces NFSD to include NLM wire protocol definitions despite
having no other dependency on the NLM wire protocol.

In addition, a CONFIG_LOCKD_V4 Kconfig symbol appears in the middle
of NFSD source code.

Refactor: Let's not use on-the-wire values as part of a high-level
API between two Linux kernel modules. That's what we have errno for,
right?

And, instead of simply moving the CONFIG_LOCKD_V4 check, we can get
rid of it entirely and let the decision of what actual NLM status
code goes on the wire to be left up to NLM version-specific code.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/lockd/svc4proc.c

@@ -73,9 +73,21 @@ nlm4svc_retrieve_args(struct svc_rqst *rqstp, struct nlm_args *argp,
 
 no_locks:
 	nlmsvc_release_host(host);
- 	if (error)
-		return error;	
-	return nlm_lck_denied_nolocks;
+	switch (error) {
+	case nlm_granted:
+		return nlm_lck_denied_nolocks;
+	case nlm__int__stale_fh:
+		return nlm4_stale_fh;
+	case nlm__int__failed:
+		return nlm4_failed;
+	default:
+		if (be32_to_cpu(error) >= 30000) {
+			pr_warn_once("lockd: unhandled internal status %u\n",
+				     be32_to_cpu(error));
+			return nlm4_failed;
+		}
+		return error;
+	}
 }
 
 /*

fs/lockd/svcproc.c

@@ -39,8 +39,20 @@ static inline __be32 cast_status(__be32 status)
 #else
 static inline __be32 cast_status(__be32 status)
 {
-	if (status == nlm__int__deadlock)
+	switch (status) {
+	case nlm__int__deadlock:
 		status = nlm_lck_denied;
+		break;
+	case nlm__int__stale_fh:
+	case nlm__int__failed:
+		status = nlm_lck_denied_nolocks;
+		break;
+	default:
+		if (be32_to_cpu(status) >= 30000)
+			pr_warn_once("lockd: unhandled internal status %u\n",
+				     be32_to_cpu(status));
+		break;
+	}
 	return status;
 }
 #endif

fs/lockd/svcsubs.c

@@ -87,14 +87,29 @@ static __be32 nlm_do_fopen(struct svc_rqst *rqstp,
 			   struct nlm_file *file, int mode)
 {
 	struct file **fp = &file->f_file[mode];
-	__be32	nfserr;
+	__be32 nlmerr = nlm_granted;
+	int error;
 
 	if (*fp)
-		return 0;
-	nfserr = nlmsvc_ops->fopen(rqstp, &file->f_handle, fp, mode);
-	if (nfserr)
-		dprintk("lockd: open failed (error %d)\n", nfserr);
-	return nfserr;
+		return nlmerr;
+
+	error = nlmsvc_ops->fopen(rqstp, &file->f_handle, fp, mode);
+	if (error) {
+		dprintk("lockd: open failed (errno %d)\n", error);
+		switch (error) {
+		case -EWOULDBLOCK:
+			nlmerr = nlm__int__drop_reply;
+			break;
+		case -ESTALE:
+			nlmerr = nlm__int__stale_fh;
+			break;
+		default:
+			nlmerr = nlm__int__failed;
+			break;
+		}
+	}
+
+	return nlmerr;
 }
 
 /*

fs/nfsd/lockd.c

@@ -14,19 +14,20 @@
 
 #define NFSDDBG_FACILITY		NFSDDBG_LOCKD
 
-#ifdef CONFIG_LOCKD_V4
-#define nlm_stale_fh	nlm4_stale_fh
-#define nlm_failed	nlm4_failed
-#else
-#define nlm_stale_fh	nlm_lck_denied_nolocks
-#define nlm_failed	nlm_lck_denied_nolocks
-#endif
-/*
- * Note: we hold the dentry use count while the file is open.
+/**
+ * nlm_fopen - Open an NFSD file
+ * @rqstp: NLM RPC procedure execution context
+ * @f: NFS file handle to be opened
+ * @filp: OUT: an opened struct file
+ * @flags: the POSIX open flags to use
+ *
+ * nlm_fopen() holds the dentry reference until nlm_fclose() releases it.
+ *
+ * Returns zero on success or a negative errno value if the file
+ * cannot be opened.
  */
-static __be32
-nlm_fopen(struct svc_rqst *rqstp, struct nfs_fh *f, struct file **filp,
-		int mode)
+static int nlm_fopen(struct svc_rqst *rqstp, struct nfs_fh *f,
+		     struct file **filp, int flags)
 {
 	__be32		nfserr;
 	int		access;
@@ -47,18 +48,17 @@ nlm_fopen(struct svc_rqst *rqstp, struct nfs_fh *f, struct file **filp,
 	 * if NFSEXP_NOAUTHNLM is set.  Some older clients use AUTH_NULL
 	 * for NLM requests.
 	 */
-	access = (mode == O_WRONLY) ? NFSD_MAY_WRITE : NFSD_MAY_READ;
+	access = (flags == O_WRONLY) ? NFSD_MAY_WRITE : NFSD_MAY_READ;
 	access |= NFSD_MAY_NLM | NFSD_MAY_OWNER_OVERRIDE | NFSD_MAY_BYPASS_GSS;
 	nfserr = nfsd_open(rqstp, &fh, S_IFREG, access, filp);
 	fh_put(&fh);
-	/* We return nlm error codes as nlm doesn't know
-	 * about nfsd, but nfsd does know about nlm..
-	 */
+
 	switch (nfserr) {
 	case nfs_ok:
-		return 0;
+		break;
 	case nfserr_jukebox:
-		/* this error can indicate a presence of a conflicting
+		/*
+		 * This error can indicate a presence of a conflicting
 		 * delegation to an NLM lock request. Options are:
 		 * (1) For now, drop this request and make the client
 		 * retry. When delegation is returned, client's lock retry
@@ -66,19 +66,25 @@ nlm_fopen(struct svc_rqst *rqstp, struct nfs_fh *f, struct file **filp,
 		 * (2) NLM4_DENIED as per "spec" signals to the client
 		 * that the lock is unavailable now but client can retry.
 		 * Linux client implementation does not. It treats
-		 * NLM4_DENIED same as NLM4_FAILED and errors the request.
+		 * NLM4_DENIED same as NLM4_FAILED and fails the request.
 		 * (3) For the future, treat this as blocked lock and try
 		 * to callback when the delegation is returned but might
 		 * not have a proper lock request to block on.
 		 */
-		return nlm__int__drop_reply;
+		return -EWOULDBLOCK;
 	case nfserr_stale:
-		return nlm_stale_fh;
+		return -ESTALE;
 	default:
-		return nlm_failed;
+		return -ENOLCK;
 	}
+
+	return 0;
 }
 
+/**
+ * nlm_fclose - Close an NFSD file
+ * @filp: a struct file that was opened by nlm_fopen()
+ */
 static void
 nlm_fclose(struct file *filp)
 {

include/linux/lockd/bind.h

@@ -26,11 +26,9 @@ struct rpc_clnt;
  * This is the set of functions for lockd->nfsd communication
  */
 struct nlmsvc_binding {
-	__be32			(*fopen)(struct svc_rqst *,
-						struct nfs_fh *,
-						struct file **,
-						int mode);
-	void			(*fclose)(struct file *);
+	int		(*fopen)(struct svc_rqst *rqstp, struct nfs_fh *f,
+				 struct file **filp, int flags);
+	void		(*fclose)(struct file *filp);
 };
 
 extern const struct nlmsvc_binding *nlmsvc_ops;

include/linux/lockd/lockd.h

@@ -44,6 +44,8 @@
  */
 #define nlm__int__drop_reply	cpu_to_be32(30000)
 #define nlm__int__deadlock	cpu_to_be32(30001)
+#define nlm__int__stale_fh	cpu_to_be32(30002)
+#define nlm__int__failed	cpu_to_be32(30003)
 
 /*
  * Lockd host handle (used both by the client and server personality).