NFSD: Use only RQ_DROPME to signal the need to drop a reply

Clean up: NFSv2 has the only two usages of rpc_drop_reply in the
NFSD code base. Since NFSv2 is going away at some point, replace
these in order to simplify the "drop this reply?" check in
nfsd_dispatch().
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>

fs/nfsd/nfsproc.c

@@ -211,7 +211,7 @@ nfsd_proc_read(struct svc_rqst *rqstp)
 	if (resp->status == nfs_ok)
 		resp->status = fh_getattr(&resp->fh, &resp->stat);
 	else if (resp->status == nfserr_jukebox)
-		return rpc_drop_reply;
+		__set_bit(RQ_DROPME, &rqstp->rq_flags);
 	return rpc_success;
 }
 
@@ -246,7 +246,7 @@ nfsd_proc_write(struct svc_rqst *rqstp)
 	if (resp->status == nfs_ok)
 		resp->status = fh_getattr(&resp->fh, &resp->stat);
 	else if (resp->status == nfserr_jukebox)
-		return rpc_drop_reply;
+		__set_bit(RQ_DROPME, &rqstp->rq_flags);
 	return rpc_success;
 }
 

fs/nfsd/nfssvc.c

@@ -1060,7 +1060,7 @@ int nfsd_dispatch(struct svc_rqst *rqstp, __be32 *statp)
 	svcxdr_init_encode(rqstp);
 
 	*statp = proc->pc_func(rqstp);
-	if (*statp == rpc_drop_reply || test_bit(RQ_DROPME, &rqstp->rq_flags))
+	if (test_bit(RQ_DROPME, &rqstp->rq_flags))
 		goto out_update_drop;
 
 	if (!proc->pc_encode(rqstp, &rqstp->rq_res_stream))