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Subject[PATCH 3.16.y-ckt 109/126] xprtrdma: Re-arm after missed events
Date
3.16.7-ckt21 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Chuck Lever <chuck.lever@oracle.com>

commit 7b3d770c67bc07db5035999e4f864c5f2ff7b10e upstream.

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>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---
net/sunrpc/xprtrdma/verbs.c | 66 +++++++--------------------------------------
1 file changed, 10 insertions(+), 56 deletions(-)

diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
index 8467373e2ace..b456c8f09b60 100644
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -182,38 +182,17 @@ 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
@@ -272,42 +251,17 @@ rpcrdma_recvcq_poll(struct ib_cq *cq, struct rpcrdma_ep *ep)
return 0;
}

-/*
- * 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);
}

#ifdef RPC_DEBUG

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