Looks good
On Wed, Feb 3, 2016 at 9:22 PM, Chuck Lever <chuck.lever@xxxxxxxxxx> wrote:
> Calling ib_poll_cq() to sort through WCs during a completion is a
> common pattern amongst RDMA consumers. Since commit 14d3a3b2498e
> ("IB: add a proper completion queue abstraction"), WC sorting can
> be handled by the IB core.
>
> By converting to this new API, svcrdma is made a better neighbor to
> other RDMA consumers, as it allows the core to schedule the delivery
> of completions more fairly amongst all active consumers.
>
> Receive completions no longer use the dto_tasklet. Each polled
> Receive WC is now handled individually in soft IRQ context.
>
> The server transport's rdma_stat_rq_poll and rdma_stat_rq_prod
> metrics are no longer updated.
>
> As far as I can tell, ib_alloc_cq() does not enable a consumer to
> specify a callback for handling async CQ events. This may cause
> a problem with handling spurious connection loss, though I think
> Receive completion flushing should be enough to force the server
> to clean up properly anyway.
>
> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> ---
> include/linux/sunrpc/svc_rdma.h | 2
> net/sunrpc/xprtrdma/svc_rdma_transport.c | 130 +++++++++---------------------
> 2 files changed, 41 insertions(+), 91 deletions(-)
>
> diff --git a/include/linux/sunrpc/svc_rdma.h b/include/linux/sunrpc/svc_rdma.h
> index 4ce7b74..7de9cbb 100644
> --- a/include/linux/sunrpc/svc_rdma.h
> +++ b/include/linux/sunrpc/svc_rdma.h
> @@ -75,6 +75,7 @@ struct svc_rdma_op_ctxt {
> struct svc_rdma_fastreg_mr *frmr;
> int hdr_count;
> struct xdr_buf arg;
> + struct ib_cqe cqe;
> struct list_head dto_q;
> enum ib_wr_opcode wr_op;
> enum ib_wc_status wc_status;
> @@ -174,7 +175,6 @@ struct svcxprt_rdma {
> struct work_struct sc_work;
> };
> /* sc_flags */
> -#define RDMAXPRT_RQ_PENDING 1
> #define RDMAXPRT_SQ_PENDING 2
> #define RDMAXPRT_CONN_PENDING 3
>
> diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c
> index e7bda1e..316df77 100644
> --- a/net/sunrpc/xprtrdma/svc_rdma_transport.c
> +++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c
> @@ -68,7 +68,6 @@ static void svc_rdma_detach(struct svc_xprt *xprt);
> static void svc_rdma_free(struct svc_xprt *xprt);
> static int svc_rdma_has_wspace(struct svc_xprt *xprt);
> static int svc_rdma_secure_port(struct svc_rqst *);
> -static void rq_cq_reap(struct svcxprt_rdma *xprt);
> static void sq_cq_reap(struct svcxprt_rdma *xprt);
>
> static DECLARE_TASKLET(dto_tasklet, dto_tasklet_func, 0UL);
> @@ -413,7 +412,6 @@ static void dto_tasklet_func(unsigned long data)
> list_del_init(&xprt->sc_dto_q);
> spin_unlock_irqrestore(&dto_lock, flags);
>
> - rq_cq_reap(xprt);
> sq_cq_reap(xprt);
>
> svc_xprt_put(&xprt->sc_xprt);
> @@ -422,93 +420,49 @@ static void dto_tasklet_func(unsigned long data)
> spin_unlock_irqrestore(&dto_lock, flags);
> }
>
> -/*
> - * Receive Queue Completion Handler
> - *
> - * Since an RQ completion handler is called on interrupt context, we
> - * need to defer the handling of the I/O to a tasklet
> - */
> -static void rq_comp_handler(struct ib_cq *cq, void *cq_context)
> -{
> - struct svcxprt_rdma *xprt = cq_context;
> - unsigned long flags;
> -
> - /* Guard against unconditional flush call for destroyed QP */
> - if (atomic_read(&xprt->sc_xprt.xpt_ref.refcount)==0)
> - return;
> -
> - /*
> - * Set the bit regardless of whether or not it's on the list
> - * because it may be on the list already due to an SQ
> - * completion.
> - */
> - set_bit(RDMAXPRT_RQ_PENDING, &xprt->sc_flags);
> -
> - /*
> - * If this transport is not already on the DTO transport queue,
> - * add it
> - */
> - spin_lock_irqsave(&dto_lock, flags);
> - if (list_empty(&xprt->sc_dto_q)) {
> - svc_xprt_get(&xprt->sc_xprt);
> - list_add_tail(&xprt->sc_dto_q, &dto_xprt_q);
> - }
> - spin_unlock_irqrestore(&dto_lock, flags);
> -
> - /* Tasklet does all the work to avoid irqsave locks. */
> - tasklet_schedule(&dto_tasklet);
> -}
> -
> -/*
> - * rq_cq_reap - Process the RQ CQ.
> +/**
> + * svc_rdma_receive_wc - Invoked by RDMA provider for each polled Receive WC
> + * @cq: completion queue
> + * @wc: completed WR
> *
> - * Take all completing WC off the CQE and enqueue the associated DTO
> - * context on the dto_q for the transport.
> - *
> - * Note that caller must hold a transport reference.
> */
> -static void rq_cq_reap(struct svcxprt_rdma *xprt)
> +static void svc_rdma_receive_wc(struct ib_cq *cq, struct ib_wc *wc)
> {
> - int ret;
> - struct ib_wc wc;
> - struct svc_rdma_op_ctxt *ctxt = NULL;
> -
> - if (!test_and_clear_bit(RDMAXPRT_RQ_PENDING, &xprt->sc_flags))
> - return;
> + struct svcxprt_rdma *xprt = cq->cq_context;
> + struct ib_cqe *cqe = wc->wr_cqe;
> + struct svc_rdma_op_ctxt *ctxt;
>
> - ib_req_notify_cq(xprt->sc_rq_cq, IB_CQ_NEXT_COMP);
> - atomic_inc(&rdma_stat_rq_poll);
> + /* WARNING: Only wc->wr_cqe and wc->status *
> + * are reliable at this point. */
> + ctxt = container_of(cqe, struct svc_rdma_op_ctxt, cqe);
> + ctxt->wc_status = wc->status;
> + svc_rdma_unmap_dma(ctxt);
>
> - while ((ret = ib_poll_cq(xprt->sc_rq_cq, 1, &wc)) > 0) {
> - ctxt = (struct svc_rdma_op_ctxt *)(unsigned long)wc.wr_id;
> - ctxt->wc_status = wc.status;
> - ctxt->byte_len = wc.byte_len;
> - svc_rdma_unmap_dma(ctxt);
> - if (wc.status != IB_WC_SUCCESS) {
> - /* Close the transport */
> - dprintk("svcrdma: transport closing putting ctxt %p\n", ctxt);
> - set_bit(XPT_CLOSE, &xprt->sc_xprt.xpt_flags);
> - svc_rdma_put_context(ctxt, 1);
> - svc_xprt_put(&xprt->sc_xprt);
> - continue;
> - }
> - spin_lock_bh(&xprt->sc_rq_dto_lock);
> - list_add_tail(&ctxt->dto_q, &xprt->sc_rq_dto_q);
> - spin_unlock_bh(&xprt->sc_rq_dto_lock);
> - svc_xprt_put(&xprt->sc_xprt);
> - }
> + if (wc->status != IB_WC_SUCCESS)
> + goto flushed;
>
> - if (ctxt)
> - atomic_inc(&rdma_stat_rq_prod);
> + /* All wc fields are now known to be valid */
> + ctxt->byte_len = wc->byte_len;
> + spin_lock(&xprt->sc_rq_dto_lock);
> + list_add_tail(&ctxt->dto_q, &xprt->sc_rq_dto_q);
> + spin_unlock(&xprt->sc_rq_dto_lock);
>
> set_bit(XPT_DATA, &xprt->sc_xprt.xpt_flags);
> - /*
> - * If data arrived before established event,
> - * don't enqueue. This defers RPC I/O until the
> - * RDMA connection is complete.
> - */
> - if (!test_bit(RDMAXPRT_CONN_PENDING, &xprt->sc_flags))
> - svc_xprt_enqueue(&xprt->sc_xprt);
> + if (test_bit(RDMAXPRT_CONN_PENDING, &xprt->sc_flags))
> + goto out;
> + svc_xprt_enqueue(&xprt->sc_xprt);
> + goto out;
> +
> +flushed:
> + if (wc->status != IB_WC_WR_FLUSH_ERR)
> + pr_warn("svcrdma: Recv completion: %s (%u, vendor %u)\n",
> + ib_wc_status_msg(wc->status),
> + wc->status, wc->vendor_err);
> + set_bit(XPT_CLOSE, &xprt->sc_xprt.xpt_flags);
> + svc_rdma_put_context(ctxt, 1);
> +
> +out:
> + svc_xprt_put(&xprt->sc_xprt);
> }
>
> /*
> @@ -681,6 +635,7 @@ int svc_rdma_post_recv(struct svcxprt_rdma *xprt, gfp_t flags)
> ctxt = svc_rdma_get_context(xprt);
> buflen = 0;
> ctxt->direction = DMA_FROM_DEVICE;
> + ctxt->cqe.done = svc_rdma_receive_wc;
> for (sge_no = 0; buflen < xprt->sc_max_req_size; sge_no++) {
> if (sge_no >= xprt->sc_max_sge) {
> pr_err("svcrdma: Too many sges (%d)\n", sge_no);
> @@ -705,7 +660,7 @@ int svc_rdma_post_recv(struct svcxprt_rdma *xprt, gfp_t flags)
> recv_wr.next = NULL;
> recv_wr.sg_list = &ctxt->sge[0];
> recv_wr.num_sge = ctxt->count;
> - recv_wr.wr_id = (u64)(unsigned long)ctxt;
> + recv_wr.wr_cqe = &ctxt->cqe;
>
> svc_xprt_get(&xprt->sc_xprt);
> ret = ib_post_recv(xprt->sc_qp, &recv_wr, &bad_recv_wr);
> @@ -1124,12 +1079,8 @@ static struct svc_xprt *svc_rdma_accept(struct svc_xprt *xprt)
> dprintk("svcrdma: error creating SQ CQ for connect request\n");
> goto errout;
> }
> - cq_attr.cqe = newxprt->sc_rq_depth;
> - newxprt->sc_rq_cq = ib_create_cq(dev,
> - rq_comp_handler,
> - cq_event_handler,
> - newxprt,
> - &cq_attr);
> + newxprt->sc_rq_cq = ib_alloc_cq(dev, newxprt, newxprt->sc_rq_depth,
> + 0, IB_POLL_SOFTIRQ);
> if (IS_ERR(newxprt->sc_rq_cq)) {
> dprintk("svcrdma: error creating RQ CQ for connect request\n");
> goto errout;
> @@ -1225,7 +1176,6 @@ static struct svc_xprt *svc_rdma_accept(struct svc_xprt *xprt)
> * miss the first message
> */
> ib_req_notify_cq(newxprt->sc_sq_cq, IB_CQ_NEXT_COMP);
> - ib_req_notify_cq(newxprt->sc_rq_cq, IB_CQ_NEXT_COMP);
>
> /* Accept Connection */
> set_bit(RDMAXPRT_CONN_PENDING, &newxprt->sc_flags);
> @@ -1369,7 +1319,7 @@ static void __svc_rdma_free(struct work_struct *work)
> ib_destroy_cq(rdma->sc_sq_cq);
>
> if (rdma->sc_rq_cq && !IS_ERR(rdma->sc_rq_cq))
> - ib_destroy_cq(rdma->sc_rq_cq);
> + ib_free_cq(rdma->sc_rq_cq);
>
> if (rdma->sc_pd && !IS_ERR(rdma->sc_pd))
> ib_dealloc_pd(rdma->sc_pd);
>
> --
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