Re: [PATCH v2 7/7] sunrpc: Allow keepalive ping on a credit-full transport

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> On Feb 1, 2017, at 9:50 AM, Anna Schumaker <schumaker.anna@xxxxxxxxx> wrote:
> 
> Hi Chuck,
> 
> On 01/31/2017 01:39 PM, Chuck Lever wrote:
>> 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 ++++++++-----
>> net/sunrpc/xprtrdma/xprt_rdma.h |    2 +-
>> 5 files changed, 17 insertions(+), 7 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);
>> diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
>> index 95c1e3d..dd1340f 100644
>> --- a/net/sunrpc/xprtrdma/xprt_rdma.h
>> +++ b/net/sunrpc/xprtrdma/xprt_rdma.h
>> @@ -77,8 +77,8 @@ struct rpcrdma_ia {
>> 	unsigned int		ri_max_send_sges;
>> 	bool			ri_reminv_expected;
>> 	bool			ri_implicit_roundup;
>> -	unsigned long		ri_flags;
>> 	enum ib_mr_type		ri_mrtype;
>> +	unsigned long		ri_flags;
> 
> Any reason for the reordering here?

I thought 7/7 added this field, but 6/7 actually does.
6/7 should have put the ri_flags field in the right place.

I can respin the series.


> Thanks,
> Anna
> 
>> 	struct ib_qp_attr	ri_qp_attr;
>> 	struct ib_qp_init_attr	ri_qp_init_attr;
>> };
>> 
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> --
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--
Chuck Lever



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