nvme-rdma: don't suppress send completions

The entire completions suppress mechanism is currently broken because the
HCA might retry a send operation (due to dropped ack) after the nvme
transaction has completed.

In order to handle this, we signal all send completions and introduce a
separate done handler for async events as they will be handled differently
(as they don't include in-capsule data by definition).

Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Max Gurtovoy <maxg@mellanox.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

diff --git a/drivers/nvme/host/rdma.c b/drivers/nvme/host/rdma.c
index 2c597105a6bf31e362d2a06a6289d4a0c1f28829..61511bed8acafb41852d804fc90b6c86bf8a40fe 100644 (file)
--- a/drivers/nvme/host/rdma.c
+++ b/drivers/nvme/host/rdma.c
@@ -77,7 +77,6 @@ enum nvme_rdma_queue_flags {
 
 struct nvme_rdma_queue {
        struct nvme_rdma_qe     *rsp_ring;
-       atomic_t                sig_count;
        int                     queue_size;
        size_t                  cmnd_capsule_len;
        struct nvme_rdma_ctrl   *ctrl;
@@ -510,7 +509,6 @@ static int nvme_rdma_alloc_queue(struct nvme_rdma_ctrl *ctrl,
                queue->cmnd_capsule_len = sizeof(struct nvme_command);
 
        queue->queue_size = queue_size;
-       atomic_set(&queue->sig_count, 0);
 
        queue->cm_id = rdma_create_id(&init_net, nvme_rdma_cm_handler, queue,
                        RDMA_PS_TCP, IB_QPT_RC);
@@ -1204,21 +1202,9 @@ static void nvme_rdma_send_done(struct ib_cq *cq, struct ib_wc *wc)
                nvme_rdma_wr_error(cq, wc, "SEND");
 }
 
-/*
- * We want to signal completion at least every queue depth/2.  This returns the
- * largest power of two that is not above half of (queue size + 1) to optimize
- * (avoid divisions).
- */
-static inline bool nvme_rdma_queue_sig_limit(struct nvme_rdma_queue *queue)
-{
-       int limit = 1 << ilog2((queue->queue_size + 1) / 2);
-
-       return (atomic_inc_return(&queue->sig_count) & (limit - 1)) == 0;
-}
-
 static int nvme_rdma_post_send(struct nvme_rdma_queue *queue,
                struct nvme_rdma_qe *qe, struct ib_sge *sge, u32 num_sge,
-               struct ib_send_wr *first, bool flush)
+               struct ib_send_wr *first)
 {
        struct ib_send_wr wr, *bad_wr;
        int ret;
@@ -1227,31 +1213,12 @@ static int nvme_rdma_post_send(struct nvme_rdma_queue *queue,
        sge->length = sizeof(struct nvme_command),
        sge->lkey   = queue->device->pd->local_dma_lkey;
 
-       qe->cqe.done = nvme_rdma_send_done;
-
        wr.next       = NULL;
        wr.wr_cqe     = &qe->cqe;
        wr.sg_list    = sge;
        wr.num_sge    = num_sge;
        wr.opcode     = IB_WR_SEND;
-       wr.send_flags = 0;
-
-       /*
-        * Unsignalled send completions are another giant desaster in the
-        * IB Verbs spec:  If we don't regularly post signalled sends
-        * the send queue will fill up and only a QP reset will rescue us.
-        * Would have been way to obvious to handle this in hardware or
-        * at least the RDMA stack..
-        *
-        * Always signal the flushes. The magic request used for the flush
-        * sequencer is not allocated in our driver's tagset and it's
-        * triggered to be freed by blk_cleanup_queue(). So we need to
-        * always mark it as signaled to ensure that the "wr_cqe", which is
-        * embedded in request's payload, is not freed when __ib_process_cq()
-        * calls wr_cqe->done().
-        */
-       if (nvme_rdma_queue_sig_limit(queue) || flush)
-               wr.send_flags |= IB_SEND_SIGNALED;
+       wr.send_flags = IB_SEND_SIGNALED;
 
        if (first)
                first->next = &wr;
@@ -1301,6 +1268,12 @@ static struct blk_mq_tags *nvme_rdma_tagset(struct nvme_rdma_queue *queue)
        return queue->ctrl->tag_set.tags[queue_idx - 1];
 }
 
+static void nvme_rdma_async_done(struct ib_cq *cq, struct ib_wc *wc)
+{
+       if (unlikely(wc->status != IB_WC_SUCCESS))
+               nvme_rdma_wr_error(cq, wc, "ASYNC");
+}
+
 static void nvme_rdma_submit_async_event(struct nvme_ctrl *arg)
 {
        struct nvme_rdma_ctrl *ctrl = to_rdma_ctrl(arg);
@@ -1319,10 +1292,12 @@ static void nvme_rdma_submit_async_event(struct nvme_ctrl *arg)
        cmd->common.flags |= NVME_CMD_SGL_METABUF;
        nvme_rdma_set_sg_null(cmd);
 
+       sqe->cqe.done = nvme_rdma_async_done;
+
        ib_dma_sync_single_for_device(dev, sqe->dma, sizeof(*cmd),
                        DMA_TO_DEVICE);
 
-       ret = nvme_rdma_post_send(queue, sqe, &sge, 1, NULL, false);
+       ret = nvme_rdma_post_send(queue, sqe, &sge, 1, NULL);
        WARN_ON_ONCE(ret);
 }
 
@@ -1607,7 +1582,6 @@ static blk_status_t nvme_rdma_queue_rq(struct blk_mq_hw_ctx *hctx,
        struct nvme_rdma_request *req = blk_mq_rq_to_pdu(rq);
        struct nvme_rdma_qe *sqe = &req->sqe;
        struct nvme_command *c = sqe->data;
-       bool flush = false;
        struct ib_device *dev;
        blk_status_t ret;
        int err;
@@ -1636,13 +1610,13 @@ static blk_status_t nvme_rdma_queue_rq(struct blk_mq_hw_ctx *hctx,
                goto err;
        }
 
+       sqe->cqe.done = nvme_rdma_send_done;
+
        ib_dma_sync_single_for_device(dev, sqe->dma,
                        sizeof(struct nvme_command), DMA_TO_DEVICE);
 
-       if (req_op(rq) == REQ_OP_FLUSH)
-               flush = true;
        err = nvme_rdma_post_send(queue, sqe, req->sge, req->num_sge,
-                       req->mr->need_inval ? &req->reg_wr.wr : NULL, flush);
+                       req->mr->need_inval ? &req->reg_wr.wr : NULL);
        if (unlikely(err)) {
                nvme_rdma_unmap_data(queue, rq);
                goto err;