nfsd: be more systematic about selecting error codes for internal use.

Rather than using ad hoc values for internal errors (30000, 11000, ...)
use 'enum' to sequentially allocate numbers starting from the first
known available number - now visible as NFS4ERR_FIRST_FREE.

The goal is values that are distinct from all be32 error codes.  To get
those we must first select integers that are not already used, then
convert them with cpu_to_be32().
Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/nfsd.h

@@ -330,17 +330,31 @@ void		nfsd_lockd_shutdown(void);
 #define nfserr_xattr2big		cpu_to_be32(NFS4ERR_XATTR2BIG)
 #define nfserr_noxattr			cpu_to_be32(NFS4ERR_NOXATTR)
 
-/* error codes for internal use */
+/*
+ * Error codes for internal use.  We use enum to choose numbers that are
+ * not already assigned, then covert to be32 resulting in a number that
+ * cannot conflict with any existing be32 nfserr value.
+ */
+enum {
+	NFSERR_DROPIT = NFS4ERR_FIRST_FREE,
 /* if a request fails due to kmalloc failure, it gets dropped.
  *  Client should resend eventually
  */
-#define	nfserr_dropit		cpu_to_be32(30000)
+#define	nfserr_dropit		cpu_to_be32(NFSERR_DROPIT)
+
 /* end-of-file indicator in readdir */
-#define	nfserr_eof		cpu_to_be32(30001)
+	NFSERR_EOF,
+#define	nfserr_eof		cpu_to_be32(NFSERR_EOF)
+
 /* replay detected */
-#define	nfserr_replay_me	cpu_to_be32(11001)
+	NFSERR_REPLAY_ME,
+#define	nfserr_replay_me	cpu_to_be32(NFSERR_REPLAY_ME)
+
 /* nfs41 replay detected */
-#define	nfserr_replay_cache	cpu_to_be32(11002)
+	NFSERR_REPLAY_CACHE,
+#define	nfserr_replay_cache	cpu_to_be32(NFSERR_REPLAY_CACHE)
+
+};
 
 /* Check for dir entries '.' and '..' */
 #define isdotent(n, l)	(l < 3 && n[0] == '.' && (l == 1 || n[1] == '.'))

include/linux/nfs4.h

@@ -281,15 +281,18 @@ enum nfsstat4 {
 	/* nfs42 */
 	NFS4ERR_PARTNER_NOTSUPP	= 10088,
 	NFS4ERR_PARTNER_NO_AUTH	= 10089,
-	NFS4ERR_UNION_NOTSUPP = 10090,
-	NFS4ERR_OFFLOAD_DENIED = 10091,
-	NFS4ERR_WRONG_LFS = 10092,
-	NFS4ERR_BADLABEL = 10093,
-	NFS4ERR_OFFLOAD_NO_REQS = 10094,
+	NFS4ERR_UNION_NOTSUPP	= 10090,
+	NFS4ERR_OFFLOAD_DENIED	= 10091,
+	NFS4ERR_WRONG_LFS	= 10092,
+	NFS4ERR_BADLABEL	= 10093,
+	NFS4ERR_OFFLOAD_NO_REQS	= 10094,
 
 	/* xattr (RFC8276) */
-	NFS4ERR_NOXATTR        = 10095,
-	NFS4ERR_XATTR2BIG      = 10096,
+	NFS4ERR_NOXATTR		= 10095,
+	NFS4ERR_XATTR2BIG	= 10096,
+
+	/* can be used for internal errors */
+	NFS4ERR_FIRST_FREE
 };
 
 /* error codes for internal client use */