[PATCH v2 12/20] xprtrdma: Dynamically allocate rpcrdma_reqs

[Chuck Lever <chuck.lever@oracle.com>]

rpcrdma_reps are dynamically allocated according to the server's
credit grant and the workload. rpcrdma_reqs can also be allocated
on demand. Having a number of these around means the transport can
handle minor bursts of RPC traffic easily.

Unlike TCP's dynamic slot allocator, these are not released by
->free_slot. This is because rpcrdma_reqs are large and have DMA
mapped buffers associated with them, and thus are costly to set up.

Instead, if the system needs memory, a shrinker can steal a few free
rpcrdma_reqs per transport. That can be added later if there is a
strong need.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 net/sunrpc/xprtrdma/transport.c |    1 +
 net/sunrpc/xprtrdma/verbs.c     |   12 ++++++++----
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/net/sunrpc/xprtrdma/transport.c b/net/sunrpc/xprtrdma/transport.c
index 3cbc9b7..254cb8c 100644
--- a/net/sunrpc/xprtrdma/transport.c
+++ b/net/sunrpc/xprtrdma/transport.c
@@ -450,6 +450,7 @@
 		xprt_clear_connected(xprt);
 		rpcrdma_ia_remove(ia);
 		clear_bit(RPCRDMA_IAF_REMOVING, &ia->ri_flags);
+		rpc_wake_up_next(&xprt->backlog);
 		return;
 	}
 	if (ep->rep_connected == -ENODEV)
diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
index 6308e60..73d5247 100644
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -1171,7 +1171,7 @@ struct rpcrdma_req *
 	INIT_LIST_HEAD(&buf->rb_allreqs);
 
 	rc = -ENOMEM;
-	for (i = 0; i < buf->rb_max_requests; i++) {
+	for (i = 0; i < RPCRDMA_MIN_SLOT_TABLE; i++) {
 		struct rpcrdma_req *req;
 
 		req = rpcrdma_req_create(buf, GFP_KERNEL);
@@ -1360,9 +1360,13 @@ struct rpcrdma_req *
 	spin_lock(&buffers->rb_lock);
 	req = list_first_entry_or_null(&buffers->rb_send_bufs,
 				       struct rpcrdma_req, rl_list);
-	if (req)
-		list_del_init(&req->rl_list);
-	spin_unlock(&buffers->rb_lock);
+	if (req) {
+		list_del(&req->rl_list);
+		spin_unlock(&buffers->rb_lock);
+	} else {
+		spin_unlock(&buffers->rb_lock);
+		req = rpcrdma_req_create(buffers, GFP_NOFS);
+	}
 	return req;
 }