Re: [PATCH V2 RFC 1/3] svcrdma: Transport and header file changes

["J. Bruce Fields" <bfields@fieldses.org>]

On Tue, May 06, 2014 at 12:46:27PM -0500, Steve Wise wrote:
> From: Tom Tucker <tom@opengridcomputing.com>
> 
> Change poll logic to grab up to 6 completions at a time.
> 
> RDMA write and send completions no longer deal with fastreg objects.
> 
> Set SVCRDMA_DEVCAP_FAST_REG and allocate a dma_mr based on the device
> capabilities.
> 
> Signed-off-by: Tom Tucker <tom@opengridcomputing.com>
> Signed-off-by: Steve Wise <swise@opengridcomputing.com>
> ---
> 
>  include/linux/sunrpc/svc_rdma.h          |    3 -
>  net/sunrpc/xprtrdma/svc_rdma_transport.c |   62 +++++++++++++++++-------------
>  2 files changed, 37 insertions(+), 28 deletions(-)
> 
> diff --git a/include/linux/sunrpc/svc_rdma.h b/include/linux/sunrpc/svc_rdma.h
> index 0b8e3e6..5cf99a0 100644
> --- a/include/linux/sunrpc/svc_rdma.h
> +++ b/include/linux/sunrpc/svc_rdma.h
> @@ -115,14 +115,13 @@ struct svc_rdma_fastreg_mr {
>  	struct list_head frmr_list;
>  };
>  struct svc_rdma_req_map {
> -	struct svc_rdma_fastreg_mr *frmr;
>  	unsigned long count;
>  	union {
>  		struct kvec sge[RPCSVC_MAXPAGES];
>  		struct svc_rdma_chunk_sge ch[RPCSVC_MAXPAGES];
> +		unsigned long lkey[RPCSVC_MAXPAGES];
>  	};
>  };
> -#define RDMACTXT_F_FAST_UNREG	1
>  #define RDMACTXT_F_LAST_CTXT	2
>  
>  #define	SVCRDMA_DEVCAP_FAST_REG		1	/* fast mr registration */
> diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c
> index 25688fa..2c5b201 100644
> --- a/net/sunrpc/xprtrdma/svc_rdma_transport.c
> +++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c
> @@ -1,4 +1,5 @@
>  /*
> + * Copyright (c) 2014 Open Grid Computing, Inc. All rights reserved.
>   * Copyright (c) 2005-2007 Network Appliance, Inc. All rights reserved.
>   *
>   * This software is available to you under a choice of one of two
> @@ -160,7 +161,6 @@ struct svc_rdma_req_map *svc_rdma_get_req_map(void)
>  		schedule_timeout_uninterruptible(msecs_to_jiffies(500));
>  	}
>  	map->count = 0;
> -	map->frmr = NULL;
>  	return map;
>  }
>  
> @@ -336,22 +336,21 @@ static void process_context(struct svcxprt_rdma *xprt,
>  
>  	switch (ctxt->wr_op) {
>  	case IB_WR_SEND:
> -		if (test_bit(RDMACTXT_F_FAST_UNREG, &ctxt->flags))
> -			svc_rdma_put_frmr(xprt, ctxt->frmr);
> +		BUG_ON(ctxt->frmr);
>  		svc_rdma_put_context(ctxt, 1);
>  		break;
>  
>  	case IB_WR_RDMA_WRITE:
> +		BUG_ON(ctxt->frmr);
>  		svc_rdma_put_context(ctxt, 0);
>  		break;
>  
>  	case IB_WR_RDMA_READ:
>  	case IB_WR_RDMA_READ_WITH_INV:
> +		svc_rdma_put_frmr(xprt, ctxt->frmr);
>  		if (test_bit(RDMACTXT_F_LAST_CTXT, &ctxt->flags)) {
>  			struct svc_rdma_op_ctxt *read_hdr = ctxt->read_hdr;
>  			BUG_ON(!read_hdr);
> -			if (test_bit(RDMACTXT_F_FAST_UNREG, &ctxt->flags))
> -				svc_rdma_put_frmr(xprt, ctxt->frmr);
>  			spin_lock_bh(&xprt->sc_rq_dto_lock);
>  			set_bit(XPT_DATA, &xprt->sc_xprt.xpt_flags);
>  			list_add_tail(&read_hdr->dto_q,
> @@ -363,6 +362,7 @@ static void process_context(struct svcxprt_rdma *xprt,
>  		break;
>  
>  	default:
> +		BUG_ON(1);
>  		printk(KERN_ERR "svcrdma: unexpected completion type, "
>  		       "opcode=%d\n",
>  		       ctxt->wr_op);

Note the printk's unreachable now.  Should some of these BUG_ON()'s be
WARN_ON()'s?

> @@ -378,29 +378,42 @@ static void process_context(struct svcxprt_rdma *xprt,
>  static void sq_cq_reap(struct svcxprt_rdma *xprt)
>  {
>  	struct svc_rdma_op_ctxt *ctxt = NULL;
> -	struct ib_wc wc;
> +	struct ib_wc wc_a[6];
> +	struct ib_wc *wc;
>  	struct ib_cq *cq = xprt->sc_sq_cq;
>  	int ret;

May want to keep an eye on the stack usage here?

--b.

>  
> +	memset(wc_a, 0, sizeof(wc_a));
> +
>  	if (!test_and_clear_bit(RDMAXPRT_SQ_PENDING, &xprt->sc_flags))
>  		return;
>  
>  	ib_req_notify_cq(xprt->sc_sq_cq, IB_CQ_NEXT_COMP);
>  	atomic_inc(&rdma_stat_sq_poll);
> -	while ((ret = ib_poll_cq(cq, 1, &wc)) > 0) {
> -		if (wc.status != IB_WC_SUCCESS)
> -			/* Close the transport */
> -			set_bit(XPT_CLOSE, &xprt->sc_xprt.xpt_flags);
> +	while ((ret = ib_poll_cq(cq, ARRAY_SIZE(wc_a), wc_a)) > 0) {
> +		int i;
>  
> -		/* Decrement used SQ WR count */
> -		atomic_dec(&xprt->sc_sq_count);
> -		wake_up(&xprt->sc_send_wait);
> +		for (i = 0; i < ret; i++) {
> +			wc = &wc_a[i];
> +			if (wc->status != IB_WC_SUCCESS) {
> +				dprintk("svcrdma: sq wc err status %d\n",
> +					wc->status);
>  
> -		ctxt = (struct svc_rdma_op_ctxt *)(unsigned long)wc.wr_id;
> -		if (ctxt)
> -			process_context(xprt, ctxt);
> +				/* Close the transport */
> +				set_bit(XPT_CLOSE, &xprt->sc_xprt.xpt_flags);
> +			}
>  
> -		svc_xprt_put(&xprt->sc_xprt);
> +			/* Decrement used SQ WR count */
> +			atomic_dec(&xprt->sc_sq_count);
> +			wake_up(&xprt->sc_send_wait);
> +
> +			ctxt = (struct svc_rdma_op_ctxt *)
> +				(unsigned long)wc->wr_id;
> +			if (ctxt)
> +				process_context(xprt, ctxt);
> +
> +			svc_xprt_put(&xprt->sc_xprt);
> +		}
>  	}
>  
>  	if (ctxt)
> @@ -993,7 +1006,11 @@ static struct svc_xprt *svc_rdma_accept(struct svc_xprt *xprt)
>  			need_dma_mr = 0;
>  		break;
>  	case RDMA_TRANSPORT_IB:
> -		if (!(devattr.device_cap_flags & IB_DEVICE_LOCAL_DMA_LKEY)) {
> +		if (!(newxprt->sc_dev_caps & SVCRDMA_DEVCAP_FAST_REG)) {
> +			need_dma_mr = 1;
> +			dma_mr_acc = IB_ACCESS_LOCAL_WRITE;
> +		} else if (!(devattr.device_cap_flags &
> +			     IB_DEVICE_LOCAL_DMA_LKEY)) {
>  			need_dma_mr = 1;
>  			dma_mr_acc = IB_ACCESS_LOCAL_WRITE;
>  		} else
> @@ -1190,14 +1207,7 @@ static int svc_rdma_has_wspace(struct svc_xprt *xprt)
>  		container_of(xprt, struct svcxprt_rdma, sc_xprt);
>  
>  	/*
> -	 * If there are fewer SQ WR available than required to send a
> -	 * simple response, return false.
> -	 */
> -	if ((rdma->sc_sq_depth - atomic_read(&rdma->sc_sq_count) < 3))
> -		return 0;
> -
> -	/*
> -	 * ...or there are already waiters on the SQ,
> +	 * If there are already waiters on the SQ,
>  	 * return false.
>  	 */
>  	if (waitqueue_active(&rdma->sc_send_wait))
>