Hi Chuck,
On 01/26/2017 12:56 PM, Chuck Lever wrote:
> Allow RPC-over-RDMA to send NULL pings even when the transport has
> hit its credit limit.
>
> One credit is reserved. It may be used only to send a keepalive
> ping.
>
> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> ---
> include/linux/sunrpc/sched.h | 2 ++
> net/sunrpc/xprt.c | 4 ++++
> net/sunrpc/xprtrdma/transport.c | 4 +++-
> net/sunrpc/xprtrdma/verbs.c | 13 ++++++++-----
> 4 files changed, 17 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/sunrpc/sched.h b/include/linux/sunrpc/sched.h
> index 7ba040c..a65278e 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_PRIORITY 0x8000 /* skip congestion control */
This file also defines various RPC_PRIORITY_<whatever> values that get used for the task->tk_priority field. I wonder if there is a better name for this flag that would help keep people from confusing the two later down the line, but I'm also struggling to come up with anything better.
Thoughts?
Anna
>
> #define RPC_IS_ASYNC(t) ((t)->tk_flags & RPC_TASK_ASYNC)
> #define RPC_IS_SWAPPER(t) ((t)->tk_flags & RPC_TASK_SWAPPER)
> @@ -135,6 +136,7 @@ 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_HAS_PRIORITY(t) ((t)->tk_flags & RPC_TASK_PRIORITY)
>
> #define RPC_TASK_RUNNING 0
> #define RPC_TASK_QUEUED 1
> diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
> index b530a28..e8b7b9f 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_HAS_PRIORITY(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 f97c851..e43cc85 100644
> --- a/net/sunrpc/xprtrdma/transport.c
> +++ b/net/sunrpc/xprtrdma/transport.c
> @@ -538,7 +538,9 @@ static void rpcrdma_keepalive_release(void *calldata)
>
> data = xprt_get(xprt);
> null_task = rpc_call_null_helper(task->tk_client, xprt, NULL,
> - RPC_TASK_SOFT | RPC_TASK_ASYNC,
> + RPC_TASK_SOFT |
> + RPC_TASK_ASYNC |
> + RPC_TASK_PRIORITY,
> &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 7e14b73..3e218dd 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);
> }
>
> @@ -914,6 +915,8 @@ 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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