xprtrdma: Re-arm after missed events

ib_req_notify_cq(IB_CQ_REPORT_MISSED_EVENTS) returns a positive
value if WCs were added to a CQ after the last completion upcall
but before the CQ has been re-armed.

Commit 7f23f6f6e388 ("xprtrmda: Reduce lock contention in
completion handlers") assumed that when ib_req_notify_cq() returned
a positive RC, the CQ had also been successfully re-armed, making
it safe to return control to the provider without losing any
completion signals. That is an invalid assumption.

Change both completion handlers to continue polling while
ib_req_notify_cq() returns a positive value.

Fixes: 7f23f6f6e388 ("xprtrmda: Reduce lock contention in ...")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Reviewed-by: Devesh Sharma <devesh.sharma@avagotech.com>
Tested-By: Devesh Sharma <devesh.sharma@avagotech.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
index 5502d4dade74aa8646f89305b011d215294352e0..61eea73557fff0778a43acc0208f6c9cd57e5feb 100644 (file)
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -179,38 +179,17 @@ rpcrdma_sendcq_poll(struct ib_cq *cq, struct rpcrdma_ep *ep)
        return 0;
 }
 
-/*
- * Handle send, fast_reg_mr, and local_inv completions.
- *
- * Send events are typically suppressed and thus do not result
- * in an upcall. Occasionally one is signaled, however. This
- * prevents the provider's completion queue from wrapping and
- * losing a completion.
+/* Handle provider send completion upcalls.
  */
 static void
 rpcrdma_sendcq_upcall(struct ib_cq *cq, void *cq_context)
 {
        struct rpcrdma_ep *ep = (struct rpcrdma_ep *)cq_context;
-       int rc;
-
-       rc = rpcrdma_sendcq_poll(cq, ep);
-       if (rc) {
-               dprintk("RPC:       %s: ib_poll_cq failed: %i\n",
-                       __func__, rc);
-               return;
-       }
 
-       rc = ib_req_notify_cq(cq,
-                       IB_CQ_NEXT_COMP | IB_CQ_REPORT_MISSED_EVENTS);
-       if (rc == 0)
-               return;
-       if (rc < 0) {
-               dprintk("RPC:       %s: ib_req_notify_cq failed: %i\n",
-                       __func__, rc);
-               return;
-       }
-
-       rpcrdma_sendcq_poll(cq, ep);
+       do {
+               rpcrdma_sendcq_poll(cq, ep);
+       } while (ib_req_notify_cq(cq, IB_CQ_NEXT_COMP |
+                                 IB_CQ_REPORT_MISSED_EVENTS) > 0);
 }
 
 static void
@@ -274,42 +253,17 @@ out_schedule:
        return rc;
 }
 
-/*
- * Handle receive completions.
- *
- * It is reentrant but processes single events in order to maintain
- * ordering of receives to keep server credits.
- *
- * It is the responsibility of the scheduled tasklet to return
- * recv buffers to the pool. NOTE: this affects synchronization of
- * connection shutdown. That is, the structures required for
- * the completion of the reply handler must remain intact until
- * all memory has been reclaimed.
+/* Handle provider receive completion upcalls.
  */
 static void
 rpcrdma_recvcq_upcall(struct ib_cq *cq, void *cq_context)
 {
        struct rpcrdma_ep *ep = (struct rpcrdma_ep *)cq_context;
-       int rc;
-
-       rc = rpcrdma_recvcq_poll(cq, ep);
-       if (rc) {
-               dprintk("RPC:       %s: ib_poll_cq failed: %i\n",
-                       __func__, rc);
-               return;
-       }
 
-       rc = ib_req_notify_cq(cq,
-                       IB_CQ_NEXT_COMP | IB_CQ_REPORT_MISSED_EVENTS);
-       if (rc == 0)
-               return;
-       if (rc < 0) {
-               dprintk("RPC:       %s: ib_req_notify_cq failed: %i\n",
-                       __func__, rc);
-               return;
-       }
-
-       rpcrdma_recvcq_poll(cq, ep);
+       do {
+               rpcrdma_recvcq_poll(cq, ep);
+       } while (ib_req_notify_cq(cq, IB_CQ_NEXT_COMP |
+                                 IB_CQ_REPORT_MISSED_EVENTS) > 0);
 }
 
 static void