svcrdma: support Remote Invalidation

Support Remote Invalidation. A private message is exchanged with
the client upon RDMA transport connect that indicates whether
Send With Invalidation may be used by the server to send RPC
replies. The invalidate_rkey is arbitrarily chosen from among
rkeys present in the RPC-over-RDMA header's chunk lists.

Send With Invalidate improves performance only when clients can
recognize, while processing an RPC reply, that an rkey has already
been invalidated. That has been submitted as a separate change.

In the future, the RPC-over-RDMA protocol might support Remote
Invalidation properly. The protocol needs to enable signaling
between peers to indicate when Remote Invalidation can be used
for each individual RPC.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/sunrpc/svc_rdma.h b/include/linux/sunrpc/svc_rdma.h
index 3584bc8864c4..cc3ae16eac68 100644
--- a/include/linux/sunrpc/svc_rdma.h
+++ b/include/linux/sunrpc/svc_rdma.h
@@ -137,6 +137,7 @@ struct svcxprt_rdma {
         int                  sc_ord;            /* RDMA read limit */
         int                  sc_max_sge;
         int                  sc_max_sge_rd;     /* max sge for read target */
+        bool                 sc_snd_w_inv;      /* OK to use Send With Invalidate */
 
         atomic_t             sc_sq_count;       /* Number of SQ WR on queue */
         unsigned int         sc_sq_depth;       /* Depth of SQ */