NFSv4.1: Select the "most recent locking state" for read/write/setattr stateids

Follow the practice described in section 8.2.2 of RFC5661: When sending a
read/write or setattr stateid, set the seqid field to zero in order to
signal that the NFS server should apply the most recent locking state.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/nfs4proc.c

@@ -6841,7 +6841,8 @@ static const struct nfs4_minor_version_ops nfs_v4_1_minor_ops = {
 	.init_caps = NFS_CAP_READDIRPLUS
 		| NFS_CAP_ATOMIC_OPEN
 		| NFS_CAP_CHANGE_ATTR
-		| NFS_CAP_POSIX_LOCK,
+		| NFS_CAP_POSIX_LOCK
+		| NFS_CAP_STATEID_NFSV41,
 	.call_sync = nfs4_call_sync_sequence,
 	.match_stateid = nfs41_match_stateid,
 	.find_root_sec = nfs41_find_root_sec,

fs/nfs/nfs4state.c

@@ -1053,6 +1053,8 @@ int nfs4_select_rw_stateid(nfs4_stateid *dst, struct nfs4_state *state,
 		goto out;
 	ret = nfs4_copy_open_stateid(dst, state);
 out:
+	if (nfs_server_capable(state->inode, NFS_CAP_STATEID_NFSV41))
+		dst->seqid = 0;
 	return ret;
 }
 

include/linux/nfs_fs_sb.h

@@ -197,5 +197,6 @@ struct nfs_server {
 #define NFS_CAP_MTIME		(1U << 13)
 #define NFS_CAP_POSIX_LOCK	(1U << 14)
 #define NFS_CAP_UIDGID_NOMAP	(1U << 15)
+#define NFS_CAP_STATEID_NFSV41	(1U << 16)
 
 #endif