SUNRPC: introduce cache_detail->cache_request callback

This callback will allow to simplify upcalls in further patches in this
series.

Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/fs/nfs/dns_resolve.c b/fs/nfs/dns_resolve.c
index 9cbc98a..55bc5d1 100644
--- a/fs/nfs/dns_resolve.c
+++ b/fs/nfs/dns_resolve.c
@@ -144,7 +144,7 @@
 
 	ret = nfs_cache_upcall(cd, key->hostname);
 	if (ret)
-		ret = sunrpc_cache_pipe_upcall(cd, ch, nfs_dns_request);
+		ret = sunrpc_cache_pipe_upcall(cd, ch, cd->cache_request);
 	return ret;
 }
 
@@ -359,6 +359,7 @@
 	.name		= "dns_resolve",
 	.cache_put	= nfs_dns_ent_put,
 	.cache_upcall	= nfs_dns_upcall,
+	.cache_request	= nfs_dns_request,
 	.cache_parse	= nfs_dns_parse,
 	.cache_show	= nfs_dns_show,
 	.match		= nfs_dns_match,