Allow RPC-over-RDMA to send NULL pings even when the transport has
hit its credit limit. One RPC-over-RDMA credit is reserved for
operations like keepalive.
For transports that convey NFSv4, it seems like lease renewal would
also be a candidate for using a priority transport slot. I'd like to
see a mechanism better than RPCRDMA_PRIORITY that can ensure only
one priority operation is in use at a time.
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
include/linux/sunrpc/sched.h | 2 ++
net/sunrpc/xprt.c | 4 ++++
net/sunrpc/xprtrdma/transport.c | 3 ++-
net/sunrpc/xprtrdma/verbs.c | 13 ++++++++-----
4 files changed, 16 insertions(+), 6 deletions(-)
diff --git a/include/linux/sunrpc/sched.h b/include/linux/sunrpc/sched.h
index 13822e6..fcea158 100644
--- a/include/linux/sunrpc/sched.h
+++ b/include/linux/sunrpc/sched.h
@@ -127,6 +127,7 @@ struct rpc_task_setup {
#define RPC_TASK_TIMEOUT 0x1000 /* fail with ETIMEDOUT on timeout */
#define RPC_TASK_NOCONNECT 0x2000 /* return ENOTCONN if not connected */
#define RPC_TASK_NO_RETRANS_TIMEOUT 0x4000 /* wait forever for a reply */
+#define RPC_TASK_NO_CONG 0x8000 /* skip congestion control */
#define RPC_TASK_SOFTPING (RPC_TASK_SOFT | RPC_TASK_SOFTCONN)
@@ -137,6 +138,7 @@ struct rpc_task_setup {
#define RPC_IS_SOFT(t) ((t)->tk_flags & (RPC_TASK_SOFT|RPC_TASK_TIMEOUT))
#define RPC_IS_SOFTCONN(t) ((t)->tk_flags & RPC_TASK_SOFTCONN)
#define RPC_WAS_SENT(t) ((t)->tk_flags & RPC_TASK_SENT)
+#define RPC_SKIP_CONG(t) ((t)->tk_flags & RPC_TASK_NO_CONG)
#define RPC_TASK_RUNNING 0
#define RPC_TASK_QUEUED 1
diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index b530a28..a477ee6 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -392,6 +392,10 @@ static inline void xprt_release_write(struct rpc_xprt *xprt, struct rpc_task *ta
{
struct rpc_rqst *req = task->tk_rqstp;
+ if (RPC_SKIP_CONG(task)) {
+ req->rq_cong = 0;
+ return 1;
+ }
if (req->rq_cong)
return 1;
dprintk("RPC: %5u xprt_cwnd_limited cong = %lu cwnd = %lu\n",
diff --git a/net/sunrpc/xprtrdma/transport.c b/net/sunrpc/xprtrdma/transport.c
index 3a5a805..073fecd 100644
--- a/net/sunrpc/xprtrdma/transport.c
+++ b/net/sunrpc/xprtrdma/transport.c
@@ -546,7 +546,8 @@ static void rpcrdma_keepalive_release(void *calldata)
data = xprt_get(xprt);
null_task = rpc_call_null_helper(task->tk_client, xprt, NULL,
- RPC_TASK_SOFTPING | RPC_TASK_ASYNC,
+ RPC_TASK_SOFTPING | RPC_TASK_ASYNC |
+ RPC_TASK_NO_CONG,
&rpcrdma_keepalive_call_ops, data);
if (!IS_ERR(null_task))
rpc_put_task(null_task);
diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
index 81cd31a..d9b5fa7 100644
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -136,19 +136,20 @@
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;
+ __be32 *p = rep->rr_rdmabuf->rg_base;
u32 credits;
if (rep->rr_len < RPCRDMA_HDRLEN_ERR)
return;
- credits = be32_to_cpu(rmsgp->rm_credit);
+ credits = be32_to_cpup(p + 2);
+ if (credits > buffer->rb_max_requests)
+ credits = buffer->rb_max_requests;
+ /* Reserve one credit for keepalive ping */
+ credits--;
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);
}
@@ -915,6 +916,8 @@ struct rpcrdma_rep *
struct rpcrdma_buffer *buf = &r_xprt->rx_buf;
int i, rc;
+ if (r_xprt->rx_data.max_requests < 2)
+ return -EINVAL;
buf->rb_max_requests = r_xprt->rx_data.max_requests;
buf->rb_bc_srv_max_requests = 0;
atomic_set(&buf->rb_credits, 1);
--
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