lockd: Introduce nlm__int__deadlock

The use of CONFIG_LOCKD_V4 in combination with a later cast_status()
in the NLMv3 code is difficult to reason about. Instead, replace the
use of nlm_deadlock with an implementation-defined status value that
version-specific code translates appropriately.

The new approach establishes a translation boundary: generic lockd
code returns nlm__int__deadlock when posix_lock_file() yields
-EDEADLK. Version-specific handlers (svc4proc.c for NLMv4,
svcproc.c for NLMv3) translate this internal status to the
appropriate wire protocol value. NLMv4 maps to nlm4_deadlock;
NLMv3 maps to nlm_lck_denied (since NLMv3 lacks a deadlock-specific
status code).

Later this modification will also remove the need to include NLMv4
headers in NLMv3 and generic code.

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

fs/lockd/svc4proc.c

@@ -148,10 +148,16 @@ __nlm4svc_proc_lock(struct svc_rqst *rqstp, struct nlm_res *resp)
 	resp->status = nlmsvc_lock(rqstp, file, host, &argp->lock,
 					argp->block, &argp->cookie,
 					argp->reclaim);
-	if (resp->status == nlm__int__drop_reply)
+	switch (resp->status) {
+	case nlm__int__drop_reply:
 		rc = rpc_drop_reply;
-	else
+		break;
+	case nlm__int__deadlock:
+		resp->status = nlm4_deadlock;
+		fallthrough;
+	default:
 		dprintk("lockd: LOCK         status %d\n", ntohl(resp->status));
+	}
 
 	nlmsvc_release_lockowner(&argp->lock);
 	nlmsvc_release_host(host);

fs/lockd/svclock.c

@@ -33,12 +33,6 @@
 
 #define NLMDBG_FACILITY		NLMDBG_SVCLOCK
 
-#ifdef CONFIG_LOCKD_V4
-#define nlm_deadlock	nlm4_deadlock
-#else
-#define nlm_deadlock	nlm_lck_denied
-#endif
-
 static void nlmsvc_release_block(struct nlm_block *block);
 static void	nlmsvc_insert_block(struct nlm_block *block, unsigned long);
 static void	nlmsvc_remove_block(struct nlm_block *block);
@@ -589,7 +583,7 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
 			goto out;
 		case -EDEADLK:
 			nlmsvc_remove_block(block);
-			ret = nlm_deadlock;
+			ret = nlm__int__deadlock;
 			goto out;
 		default:			/* includes ENOLCK */
 			nlmsvc_remove_block(block);

fs/lockd/svcproc.c

@@ -27,7 +27,7 @@ static inline __be32 cast_status(__be32 status)
 	case nlm_lck_denied_grace_period:
 	case nlm__int__drop_reply:
 		break;
-	case nlm4_deadlock:
+	case nlm__int__deadlock:
 		status = nlm_lck_denied;
 		break;
 	default:
@@ -39,6 +39,8 @@ static inline __be32 cast_status(__be32 status)
 #else
 static inline __be32 cast_status(__be32 status)
 {
+	if (status == nlm__int__deadlock)
+		status = nlm_lck_denied;
 	return status;
 }
 #endif

include/linux/lockd/lockd.h

@@ -43,6 +43,7 @@
  * Version handlers translate these to appropriate wire values.
  */
 #define nlm__int__drop_reply	cpu_to_be32(30000)
+#define nlm__int__deadlock	cpu_to_be32(30001)
 
 /*
  * Lockd host handle (used both by the client and server personality).