RDS: Implement atomic operations

Implement a CMSG-based interface to do FADD and CSWP ops.

Alter send routines to handle atomic ops.

Add atomic counters to stats.

Add xmit_atomic() to struct rds_transport

Inline rds_ib_send_unmap_rdma into unmap_rm

Signed-off-by: Andy Grover <andy.grover@oracle.com>

1 files changed, 124 insertions, 16 deletions

diff --git a/net/rds/ib_send.c b/net/rds/ib_send.c
index f0edfdb2866..b2bd164434a 100644
--- a/net/rds/ib_send.c
+++ b/net/rds/ib_send.c
@@ -62,15 +62,17 @@ static void rds_ib_send_rdma_complete(struct rds_message *rm,
 	rds_rdma_send_complete(rm, notify_status);
 }
 
-static void rds_ib_send_unmap_rdma(struct rds_ib_connection *ic,
-				   struct rds_rdma_op *op)
+static void rds_ib_send_atomic_complete(struct rds_message *rm,
+				      int wc_status)
 {
-	if (op->r_mapped) {
-		ib_dma_unmap_sg(ic->i_cm_id->device,
-			op->r_sg, op->r_nents,
-			op->r_write ? DMA_TO_DEVICE : DMA_FROM_DEVICE);
-		op->r_mapped = 0;
-	}
+	int notify_status;
+
+	if (wc_status != IB_WC_SUCCESS)
+		notify_status = RDS_RDMA_OTHER_ERROR;
+	else
+		notify_status = RDS_RDMA_SUCCESS;
+
+	rds_atomic_send_complete(rm, notify_status);
 }
 
 static void rds_ib_send_unmap_rm(struct rds_ib_connection *ic,
@@ -86,7 +88,14 @@ static void rds_ib_send_unmap_rm(struct rds_ib_connection *ic,
 			DMA_TO_DEVICE);
 
 	if (rm->rdma.m_rdma_op.r_active) {
-		rds_ib_send_unmap_rdma(ic, &rm->rdma.m_rdma_op);
+		struct rds_rdma_op *op = &rm->rdma.m_rdma_op;
+
+		if (op->r_mapped) {
+			ib_dma_unmap_sg(ic->i_cm_id->device,
+					op->r_sg, op->r_nents,
+					op->r_write ? DMA_TO_DEVICE : DMA_FROM_DEVICE);
+			op->r_mapped = 0;
+		}
 
 		/* If the user asked for a completion notification on this
 		 * message, we can implement three different semantics:
@@ -116,6 +125,24 @@ static void rds_ib_send_unmap_rm(struct rds_ib_connection *ic,
 			rds_stats_add(s_recv_rdma_bytes, rm->rdma.m_rdma_op.r_bytes);
 	}
 
+	if (rm->atomic.op_active) {
+		struct rm_atomic_op *op = &rm->atomic;
+
+		/* unmap atomic recvbuf */
+		if (op->op_mapped) {
+			ib_dma_unmap_sg(ic->i_cm_id->device, op->op_sg, 1,
+					DMA_FROM_DEVICE);
+			op->op_mapped = 0;
+		}
+
+		rds_ib_send_atomic_complete(rm, wc_status);
+
+		if (rm->atomic.op_type == RDS_ATOMIC_TYPE_CSWP)
+			rds_stats_inc(s_atomic_cswp);
+		else
+			rds_stats_inc(s_atomic_fadd);
+	}
+
 	/* If anyone waited for this message to get flushed out, wake
 	 * them up now */
 	rds_message_unmapped(rm);
@@ -158,12 +185,9 @@ void rds_ib_send_clear_ring(struct rds_ib_connection *ic)
 	u32 i;
 
 	for (i = 0, send = ic->i_sends; i < ic->i_send_ring.w_nr; i++, send++) {
-		if (send->s_wr.opcode == 0xdead)
+		if (!send->s_rm || send->s_wr.opcode == 0xdead)
 			continue;
-		if (send->s_rm)
-			rds_ib_send_unmap_rm(ic, send, IB_WC_WR_FLUSH_ERR);
-		if (send->s_op)
-			rds_ib_send_unmap_rdma(ic, send->s_op);
+		rds_ib_send_unmap_rm(ic, send, IB_WC_WR_FLUSH_ERR);
 	}
 }
 
@@ -218,6 +242,8 @@ void rds_ib_send_cq_comp_handler(struct ib_cq *cq, void *context)
 				break;
 			case IB_WR_RDMA_WRITE:
 			case IB_WR_RDMA_READ:
+			case IB_WR_ATOMIC_FETCH_AND_ADD:
+			case IB_WR_ATOMIC_CMP_AND_SWP:
 				/* Nothing to be done - the SG list will be unmapped
 				 * when the SEND completes. */
 				break;
@@ -243,8 +269,7 @@ void rds_ib_send_cq_comp_handler(struct ib_cq *cq, void *context)
 
 				rm = rds_send_get_message(conn, send->s_op);
 				if (rm) {
-					if (rm->rdma.m_rdma_op.r_active)
-						rds_ib_send_unmap_rdma(ic, &rm->rdma.m_rdma_op);
+					rds_ib_send_unmap_rm(ic, send, wc.status);
 					rds_ib_send_rdma_complete(rm, wc.status);
 					rds_message_put(rm);
 				}
@@ -736,6 +761,89 @@ out:
 	return ret;
 }
 
+/*
+ * Issue atomic operation.
+ * A simplified version of the rdma case, we always map 1 SG, and
+ * only 8 bytes, for the return value from the atomic operation.
+ */
+int rds_ib_xmit_atomic(struct rds_connection *conn, struct rm_atomic_op *op)
+{
+	struct rds_ib_connection *ic = conn->c_transport_data;
+	struct rds_ib_send_work *send = NULL;
+	struct ib_send_wr *failed_wr;
+	struct rds_ib_device *rds_ibdev;
+	u32 pos;
+	u32 work_alloc;
+	int ret;
+
+	rds_ibdev = ib_get_client_data(ic->i_cm_id->device, &rds_ib_client);
+
+	work_alloc = rds_ib_ring_alloc(&ic->i_send_ring, 1, &pos);
+	if (work_alloc != 1) {
+		rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc);
+		rds_ib_stats_inc(s_ib_tx_ring_full);
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	/* address of send request in ring */
+	send = &ic->i_sends[pos];
+	send->s_queued = jiffies;
+
+	if (op->op_type == RDS_ATOMIC_TYPE_CSWP) {
+		send->s_wr.opcode = IB_WR_ATOMIC_CMP_AND_SWP;
+		send->s_wr.wr.atomic.compare_add = op->op_compare;
+		send->s_wr.wr.atomic.swap = op->op_swap_add;
+	} else { /* FADD */
+		send->s_wr.opcode = IB_WR_ATOMIC_FETCH_AND_ADD;
+		send->s_wr.wr.atomic.compare_add = op->op_swap_add;
+		send->s_wr.wr.atomic.swap = 0;
+	}
+	send->s_wr.send_flags = IB_SEND_SIGNALED;
+	send->s_wr.num_sge = 1;
+	send->s_wr.next = NULL;
+	send->s_wr.wr.atomic.remote_addr = op->op_remote_addr;
+	send->s_wr.wr.atomic.rkey = op->op_rkey;
+
+	/* map 8 byte retval buffer to the device */
+	ret = ib_dma_map_sg(ic->i_cm_id->device, op->op_sg, 1, DMA_FROM_DEVICE);
+	rdsdebug("ic %p mapping atomic op %p. mapped %d pg\n", ic, op, ret);
+	if (ret != 1) {
+		rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc);
+		rds_ib_stats_inc(s_ib_tx_sg_mapping_failure);
+		ret = -ENOMEM; /* XXX ? */
+		goto out;
+	}
+
+	/* Convert our struct scatterlist to struct ib_sge */
+	send->s_sge[0].addr = ib_sg_dma_address(ic->i_cm_id->device, op->op_sg);
+	send->s_sge[0].length = ib_sg_dma_len(ic->i_cm_id->device, op->op_sg);
+	send->s_sge[0].lkey = ic->i_mr->lkey;
+
+	rdsdebug("rva %Lx rpa %Lx len %u\n", op->op_remote_addr,
+		 send->s_sge[0].addr, send->s_sge[0].length);
+
+	failed_wr = &send->s_wr;
+	ret = ib_post_send(ic->i_cm_id->qp, &send->s_wr, &failed_wr);
+	rdsdebug("ic %p send %p (wr %p) ret %d wr %p\n", ic,
+		 send, &send->s_wr, ret, failed_wr);
+	BUG_ON(failed_wr != &send->s_wr);
+	if (ret) {
+		printk(KERN_WARNING "RDS/IB: atomic ib_post_send to %pI4 "
+		       "returned %d\n", &conn->c_faddr, ret);
+		rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc);
+		goto out;
+	}
+
+	if (unlikely(failed_wr != &send->s_wr)) {
+		printk(KERN_WARNING "RDS/IB: atomic ib_post_send() rc=%d, but failed_wqe updated!\n", ret);
+		BUG_ON(failed_wr != &send->s_wr);
+	}
+
+out:
+	return ret;
+}
+
 int rds_ib_xmit_rdma(struct rds_connection *conn, struct rds_rdma_op *op)
 {
 	struct rds_ib_connection *ic = conn->c_transport_data;