Commit fe97b47cd623 ("xprtrdma: Use workqueue to process RPC/RDMA
replies") replaced the reply tasklet with a workqueue that allows
RPC replies to be processed in parallel. Thus the credit values in
RPC-over-RDMA replies can applied in a different order than in
which the server sent them.
To fix this, revert commit eba8ff660b2d ("xprtrdma: Move credit
update to RPC reply handler"). Done by hand to accommodate code
changes that have occurred since then.
Fixes: fe97b47cd623 ("xprtrdma: Use workqueue to process . . .")
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
net/sunrpc/xprtrdma/rpc_rdma.c | 9 +--------
net/sunrpc/xprtrdma/verbs.c | 27 ++++++++++++++++++++++++++-
net/sunrpc/xprtrdma/xprt_rdma.h | 1 +
3 files changed, 28 insertions(+), 9 deletions(-)
diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
index c341225..0c45288 100644
--- a/net/sunrpc/xprtrdma/rpc_rdma.c
+++ b/net/sunrpc/xprtrdma/rpc_rdma.c
@@ -797,7 +797,6 @@ rpcrdma_reply_handler(struct rpcrdma_rep *rep)
__be32 *iptr;
int rdmalen, status, rmerr;
unsigned long cwnd;
- u32 credits;
dprintk("RPC: %s: incoming rep %p\n", __func__, rep);
@@ -930,15 +929,9 @@ out:
if (req->rl_nchunks)
r_xprt->rx_ia.ri_ops->ro_unmap_sync(r_xprt, req);
- credits = be32_to_cpu(headerp->rm_credit);
- if (credits == 0)
- credits = 1; /* don't deadlock */
- else if (credits > r_xprt->rx_buf.rb_max_requests)
- credits = r_xprt->rx_buf.rb_max_requests;
-
spin_lock_bh(&xprt->transport_lock);
cwnd = xprt->cwnd;
- xprt->cwnd = credits << RPC_CWNDSHIFT;
+ xprt->cwnd = atomic_read(&r_xprt->rx_buf.rb_credits) << RPC_CWNDSHIFT;
if (xprt->cwnd > cwnd)
xprt_release_rqst_cong(rqst->rq_task);
diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
index 878f1bf..fc1ef5f 100644
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -190,6 +190,28 @@ rpcrdma_receive_worker(struct work_struct *work)
rpcrdma_reply_handler(rep);
}
+/* Perform basic sanity checking to avoid using garbage
+ * to update the credit grant value.
+ */
+static void
+rpcrdma_update_granted_credits(struct rpcrdma_rep *rep)
+{
+ struct rpcrdma_msg *rmsgp = rdmab_to_msg(rep->rr_rdmabuf);
+ struct rpcrdma_buffer *buffer = &rep->rr_rxprt->rx_buf;
+ u32 credits;
+
+ if (rep->rr_len < RPCRDMA_HDRLEN_ERR)
+ return;
+
+ credits = be32_to_cpu(rmsgp->rm_credit);
+ if (credits == 0)
+ credits = 1; /* don't deadlock */
+ else if (credits > buffer->rb_max_requests)
+ credits = buffer->rb_max_requests;
+
+ atomic_set(&buffer->rb_credits, credits);
+}
+
static void
rpcrdma_recvcq_process_wc(struct ib_wc *wc)
{
@@ -211,7 +233,8 @@ rpcrdma_recvcq_process_wc(struct ib_wc *wc)
ib_dma_sync_single_for_cpu(rep->rr_device,
rdmab_addr(rep->rr_rdmabuf),
rep->rr_len, DMA_FROM_DEVICE);
- prefetch(rdmab_to_msg(rep->rr_rdmabuf));
+
+ rpcrdma_update_granted_credits(rep);
out_schedule:
queue_work(rpcrdma_receive_wq, &rep->rr_work);
@@ -330,6 +353,7 @@ rpcrdma_conn_upcall(struct rdma_cm_id *id, struct rdma_cm_event *event)
connected:
dprintk("RPC: %s: %sconnected\n",
__func__, connstate > 0 ? "" : "dis");
+ atomic_set(&xprt->rx_buf.rb_credits, 1);
ep->rep_connected = connstate;
rpcrdma_conn_func(ep);
wake_up_all(&ep->rep_connect_wait);
@@ -943,6 +967,7 @@ rpcrdma_buffer_create(struct rpcrdma_xprt *r_xprt)
buf->rb_max_requests = r_xprt->rx_data.max_requests;
buf->rb_bc_srv_max_requests = 0;
spin_lock_init(&buf->rb_lock);
+ atomic_set(&buf->rb_credits, 1);
rc = ia->ri_ops->ro_init(r_xprt);
if (rc)
diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
index bf98c67..efd6fa7 100644
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -312,6 +312,7 @@ struct rpcrdma_buffer {
struct list_head rb_send_bufs;
struct list_head rb_recv_bufs;
u32 rb_max_requests;
+ atomic_t rb_credits; /* most recent credit grant */
u32 rb_bc_srv_max_requests;
spinlock_t rb_reqslock; /* protect rb_allreqs */
--
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