xprtrdma: No direct data placement with krb5i and krb5p

Direct data placement is not allowed when using flavors that
guarantee integrity or privacy. When such security flavors are in
effect, don't allow the use of Read and Write chunks for moving
individual data items. All messages larger than the inline threshold
are sent via Long Call or Long Reply.

On my systems (CX-3 Pro on FDR), for small I/O operations, the use
of Long messages adds only around 5 usecs of latency in each
direction.

Note that when integrity or encryption is used, the host CPU touches
every byte in these messages. Even if it could be used, data
movement offload doesn't buy much in this case.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Tested-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/linux/sunrpc/auth.h b/include/linux/sunrpc/auth.h
index 899791573a40..3a40287b4d27 100644
--- a/include/linux/sunrpc/auth.h
+++ b/include/linux/sunrpc/auth.h
@@ -107,6 +107,9 @@ struct rpc_auth {
 	/* per-flavor data */
 };
 
+/* rpc_auth au_flags */
+#define RPCAUTH_AUTH_DATATOUCH	0x00000002
+
 struct rpc_auth_create_args {
 	rpc_authflavor_t pseudoflavor;
 	const char *target_name;