[PATCH v2 05/10] xprtrdma: Re-write rpcrdma_flush_cqs()

Chuck Lever
2014-11-09T01:14:47Z

Currently rpcrdma_flush_cqs() attempts to avoid code duplication,
and simply invokes rpcrdma_recvcq_upcall and rpcrdma_sendcq_upcall.

1. rpcrdma_flush_cqs() can run concurrently with provider upcalls.
Both flush_cqs() and the upcalls were invoking ib_poll_cq() in
different threads using the same wc buffers (ep->rep_recv_wcs
and ep->rep_send_wcs), added by commit 1c00dd077654 ("xprtrmda:
Reduce calls to ib_poll_cq() in completion handlers").

During transport disconnect processing, this sometimes resulted
in the same reply getting added to the rpcrdma_tasklets_g list
more than once, which corrupted the list.

2. The upcall functions drain only a limited number of CQEs,
thanks to the poll budget added by commit 8301a2c047cc
("xprtrdma: Limit work done by completion handler").

Fixes: a7bc211ac926 ("xprtrdma: On disconnect, don't ignore ... ")
BugLink: https://bugzilla.linux-nfs.org/show_bug.cgi?id=276
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
net/sunrpc/xprtrdma/verbs.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
index 478b2fd..e6ac964 100644
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -317,8 +317,15 @@ rpcrdma_recvcq_upcall(struct ib_cq *cq, void *cq_context)
static void
rpcrdma_flush_cqs(struct rpcrdma_ep *ep)
{
- rpcrdma_recvcq_upcall(ep->rep_attr.recv_cq, ep);
- rpcrdma_sendcq_upcall(ep->rep_attr.send_cq, ep);
+ struct ib_wc wc;
+ LIST_HEAD(sched_list);
+
+ while (ib_poll_cq(ep->rep_attr.recv_cq, 1, &wc) > 0)
+ rpcrdma_recvcq_process_wc(&wc, &sched_list);
+ if (!list_empty(&sched_list))
+ rpcrdma_schedule_tasklet(&sched_list);
+ while (ib_poll_cq(ep->rep_attr.send_cq, 1, &wc) > 0)
+ rpcrdma_sendcq_process_wc(&wc);
}

#ifdef RPC_DEBUG