@@ -19,35 +19,6 @@
#undef RPCRDMA_BACKCHANNEL_DEBUG
-static int rpcrdma_bc_setup_reqs(struct rpcrdma_xprt *r_xprt,
- unsigned int count)
-{
- struct rpc_xprt *xprt = &r_xprt->rx_xprt;
- struct rpcrdma_req *req;
- struct rpc_rqst *rqst;
- unsigned int i;
-
- for (i = 0; i < (count << 1); i++) {
- size_t size;
-
- size = min_t(size_t, r_xprt->rx_data.inline_rsize, PAGE_SIZE);
- req = rpcrdma_req_create(r_xprt, size, GFP_KERNEL);
- if (!req)
- return -ENOMEM;
- rqst = &req->rl_slot;
-
- rqst->rq_xprt = xprt;
- INIT_LIST_HEAD(&rqst->rq_bc_list);
- __set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
- spin_lock(&xprt->bc_pa_lock);
- list_add(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
- spin_unlock(&xprt->bc_pa_lock);
- xdr_buf_init(&rqst->rq_snd_buf, rdmab_data(req->rl_sendbuf),
- size);
- }
- return 0;
-}
-
/**
* xprt_rdma_bc_setup - Pre-allocate resources for handling backchannel requests
* @xprt: transport associated with these backchannel resources
@@ -58,34 +29,10 @@ static int rpcrdma_bc_setup_reqs(struct rpcrdma_xprt *r_xprt,
int xprt_rdma_bc_setup(struct rpc_xprt *xprt, unsigned int reqs)
{
struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
- int rc;
-
- /* The backchannel reply path returns each rpc_rqst to the
- * bc_pa_list _after_ the reply is sent. If the server is
- * faster than the client, it can send another backward
- * direction request before the rpc_rqst is returned to the
- * list. The client rejects the request in this case.
- *
- * Twice as many rpc_rqsts are prepared to ensure there is
- * always an rpc_rqst available as soon as a reply is sent.
- */
- if (reqs > RPCRDMA_BACKWARD_WRS >> 1)
- goto out_err;
-
- rc = rpcrdma_bc_setup_reqs(r_xprt, reqs);
- if (rc)
- goto out_free;
- r_xprt->rx_buf.rb_bc_srv_max_requests = reqs;
+ r_xprt->rx_buf.rb_bc_srv_max_requests = RPCRDMA_BACKWARD_WRS >> 1;
trace_xprtrdma_cb_setup(r_xprt, reqs);
return 0;
-
-out_free:
- xprt_rdma_bc_destroy(xprt, reqs);
-
-out_err:
- pr_err("RPC: %s: setup backchannel transport failed\n", __func__);
- return -ENOMEM;
}
/**
@@ -213,6 +160,43 @@ void xprt_rdma_bc_free_rqst(struct rpc_rqst *rqst)
spin_unlock(&xprt->bc_pa_lock);
}
+static struct rpc_rqst *rpcrdma_bc_rqst_get(struct rpcrdma_xprt *r_xprt)
+{
+ struct rpc_xprt *xprt = &r_xprt->rx_xprt;
+ struct rpcrdma_req *req;
+ struct rpc_rqst *rqst;
+ size_t size;
+
+ spin_lock(&xprt->bc_pa_lock);
+ rqst = list_first_entry_or_null(&xprt->bc_pa_list, struct rpc_rqst,
+ rq_bc_pa_list);
+ if (!rqst)
+ goto create_req;
+ list_del(&rqst->rq_bc_pa_list);
+ spin_unlock(&xprt->bc_pa_lock);
+ return rqst;
+
+create_req:
+ spin_unlock(&xprt->bc_pa_lock);
+
+ /* Set a limit to prevent a remote from overrunning our resources.
+ */
+ if (xprt->bc_alloc_count >= RPCRDMA_BACKWARD_WRS)
+ return NULL;
+
+ size = min_t(size_t, r_xprt->rx_data.inline_rsize, PAGE_SIZE);
+ req = rpcrdma_req_create(r_xprt, size, GFP_KERNEL);
+ if (!req)
+ return NULL;
+
+ xprt->bc_alloc_count++;
+ rqst = &req->rl_slot;
+ rqst->rq_xprt = xprt;
+ __set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
+ xdr_buf_init(&rqst->rq_snd_buf, rdmab_data(req->rl_sendbuf), size);
+ return rqst;
+}
+
/**
* rpcrdma_bc_receive_call - Handle a backward direction call
* @r_xprt: transport receiving the call
@@ -244,18 +228,10 @@ void rpcrdma_bc_receive_call(struct rpcrdma_xprt *r_xprt,
pr_info("RPC: %s: %*ph\n", __func__, size, p);
#endif
- /* Grab a free bc rqst */
- spin_lock(&xprt->bc_pa_lock);
- if (list_empty(&xprt->bc_pa_list)) {
- spin_unlock(&xprt->bc_pa_lock);
+ rqst = rpcrdma_bc_rqst_get(r_xprt);
+ if (!rqst)
goto out_overflow;
- }
- rqst = list_first_entry(&xprt->bc_pa_list,
- struct rpc_rqst, rq_bc_pa_list);
- list_del(&rqst->rq_bc_pa_list);
- spin_unlock(&xprt->bc_pa_lock);
- /* Prepare rqst */
rqst->rq_reply_bytes_recvd = 0;
rqst->rq_xid = *p;
The Receive handler runs in process context, thus can use on-demand GFP_KERNEL allocations instead of pre-allocation. This makes the xprtrdma backchannel independent of the number of backchannel session slots provisioned by the Upper Layer protocol. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> --- net/sunrpc/xprtrdma/backchannel.c | 104 ++++++++++++++----------------------- 1 file changed, 40 insertions(+), 64 deletions(-)