NFSv3: fix rpc receive buffer size for MOUNT call

Prior to commit e3d3ab64dd66 ("SUNRPC: Use au_rslack when
computing reply buffer size"), there was enough slack in the reply
buffer to commodate filehandles of size 60bytes. However, the real
problem was that the reply buffer size for the MOUNT operation was
not correctly calculated. Received buffer size used the filehandle
size for NFSv2 (32bytes) which is much smaller than the allowed
filehandle size for the v3 mounts.

Fix the reply buffer size (decode arguments size) for the MNT command.

Fixes: 2c94b8ec ("SUNRPC: Use au_rslack when computing reply buffer size")
Signed-off-by: Olga Kornievskaia <kolga@netapp.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

fs/nfs/mount_clnt.c

@@ -30,6 +30,7 @@
 #define encode_dirpath_sz	(1 + XDR_QUADLEN(MNTPATHLEN))
 #define MNT_status_sz		(1)
 #define MNT_fhandle_sz		XDR_QUADLEN(NFS2_FHSIZE)
+#define MNT_fhandlev3_sz	XDR_QUADLEN(NFS3_FHSIZE)
 #define MNT_authflav3_sz	(1 + NFS_MAX_SECFLAVORS)
 
 /*
@@ -37,7 +38,7 @@
  */
 #define MNT_enc_dirpath_sz	encode_dirpath_sz
 #define MNT_dec_mountres_sz	(MNT_status_sz + MNT_fhandle_sz)
-#define MNT_dec_mountres3_sz	(MNT_status_sz + MNT_fhandle_sz + \
+#define MNT_dec_mountres3_sz	(MNT_status_sz + MNT_fhandlev3_sz + \
 				 MNT_authflav3_sz)
 
 /*