Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 3180 insertions, 0 deletions

diff --git a/drivers/infiniband/ulp/rtrs/rtrs-clt.c b/drivers/infiniband/ulp/rtrs/rtrs-clt.c
new file mode 100644
index 000000000..cc07c91f9
--- /dev/null
+++ b/drivers/infiniband/ulp/rtrs/rtrs-clt.c
@@ -0,0 +1,3180 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * RDMA Transport Layer
+ *
+ * Copyright (c) 2014 - 2018 ProfitBricks GmbH. All rights reserved.
+ * Copyright (c) 2018 - 2019 1&1 IONOS Cloud GmbH. All rights reserved.
+ * Copyright (c) 2019 - 2020 1&1 IONOS SE. All rights reserved.
+ */
+
+#undef pr_fmt
+#define pr_fmt(fmt) KBUILD_MODNAME " L" __stringify(__LINE__) ": " fmt
+
+#include <linux/module.h>
+#include <linux/rculist.h>
+#include <linux/random.h>
+
+#include "rtrs-clt.h"
+#include "rtrs-log.h"
+#include "rtrs-clt-trace.h"
+
+#define RTRS_CONNECT_TIMEOUT_MS 30000
+/*
+ * Wait a bit before trying to reconnect after a failure
+ * in order to give server time to finish clean up which
+ * leads to "false positives" failed reconnect attempts
+ */
+#define RTRS_RECONNECT_BACKOFF 1000
+/*
+ * Wait for additional random time between 0 and 8 seconds
+ * before starting to reconnect to avoid clients reconnecting
+ * all at once in case of a major network outage
+ */
+#define RTRS_RECONNECT_SEED 8
+
+#define FIRST_CONN 0x01
+/* limit to 128 * 4k = 512k max IO */
+#define RTRS_MAX_SEGMENTS          128
+
+MODULE_DESCRIPTION("RDMA Transport Client");
+MODULE_LICENSE("GPL");
+
+static const struct rtrs_rdma_dev_pd_ops dev_pd_ops;
+static struct rtrs_rdma_dev_pd dev_pd = {
+	.ops = &dev_pd_ops
+};
+
+static struct workqueue_struct *rtrs_wq;
+static struct class *rtrs_clt_dev_class;
+
+static inline bool rtrs_clt_is_connected(const struct rtrs_clt_sess *clt)
+{
+	struct rtrs_clt_path *clt_path;
+	bool connected = false;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(clt_path, &clt->paths_list, s.entry)
+		if (READ_ONCE(clt_path->state) == RTRS_CLT_CONNECTED) {
+			connected = true;
+			break;
+		}
+	rcu_read_unlock();
+
+	return connected;
+}
+
+static struct rtrs_permit *
+__rtrs_get_permit(struct rtrs_clt_sess *clt, enum rtrs_clt_con_type con_type)
+{
+	size_t max_depth = clt->queue_depth;
+	struct rtrs_permit *permit;
+	int bit;
+
+	/*
+	 * Adapted from null_blk get_tag(). Callers from different cpus may
+	 * grab the same bit, since find_first_zero_bit is not atomic.
+	 * But then the test_and_set_bit_lock will fail for all the
+	 * callers but one, so that they will loop again.
+	 * This way an explicit spinlock is not required.
+	 */
+	do {
+		bit = find_first_zero_bit(clt->permits_map, max_depth);
+		if (bit >= max_depth)
+			return NULL;
+	} while (test_and_set_bit_lock(bit, clt->permits_map));
+
+	permit = get_permit(clt, bit);
+	WARN_ON(permit->mem_id != bit);
+	permit->cpu_id = raw_smp_processor_id();
+	permit->con_type = con_type;
+
+	return permit;
+}
+
+static inline void __rtrs_put_permit(struct rtrs_clt_sess *clt,
+				      struct rtrs_permit *permit)
+{
+	clear_bit_unlock(permit->mem_id, clt->permits_map);
+}
+
+/**
+ * rtrs_clt_get_permit() - allocates permit for future RDMA operation
+ * @clt:	Current session
+ * @con_type:	Type of connection to use with the permit
+ * @can_wait:	Wait type
+ *
+ * Description:
+ *    Allocates permit for the following RDMA operation.  Permit is used
+ *    to preallocate all resources and to propagate memory pressure
+ *    up earlier.
+ *
+ * Context:
+ *    Can sleep if @wait == RTRS_PERMIT_WAIT
+ */
+struct rtrs_permit *rtrs_clt_get_permit(struct rtrs_clt_sess *clt,
+					  enum rtrs_clt_con_type con_type,
+					  enum wait_type can_wait)
+{
+	struct rtrs_permit *permit;
+	DEFINE_WAIT(wait);
+
+	permit = __rtrs_get_permit(clt, con_type);
+	if (permit || !can_wait)
+		return permit;
+
+	do {
+		prepare_to_wait(&clt->permits_wait, &wait,
+				TASK_UNINTERRUPTIBLE);
+		permit = __rtrs_get_permit(clt, con_type);
+		if (permit)
+			break;
+
+		io_schedule();
+	} while (1);
+
+	finish_wait(&clt->permits_wait, &wait);
+
+	return permit;
+}
+EXPORT_SYMBOL(rtrs_clt_get_permit);
+
+/**
+ * rtrs_clt_put_permit() - puts allocated permit
+ * @clt:	Current session
+ * @permit:	Permit to be freed
+ *
+ * Context:
+ *    Does not matter
+ */
+void rtrs_clt_put_permit(struct rtrs_clt_sess *clt,
+			 struct rtrs_permit *permit)
+{
+	if (WARN_ON(!test_bit(permit->mem_id, clt->permits_map)))
+		return;
+
+	__rtrs_put_permit(clt, permit);
+
+	/*
+	 * rtrs_clt_get_permit() adds itself to the &clt->permits_wait list
+	 * before calling schedule(). So if rtrs_clt_get_permit() is sleeping
+	 * it must have added itself to &clt->permits_wait before
+	 * __rtrs_put_permit() finished.
+	 * Hence it is safe to guard wake_up() with a waitqueue_active() test.
+	 */
+	if (waitqueue_active(&clt->permits_wait))
+		wake_up(&clt->permits_wait);
+}
+EXPORT_SYMBOL(rtrs_clt_put_permit);
+
+/**
+ * rtrs_permit_to_clt_con() - returns RDMA connection pointer by the permit
+ * @clt_path: client path pointer
+ * @permit: permit for the allocation of the RDMA buffer
+ * Note:
+ *     IO connection starts from 1.
+ *     0 connection is for user messages.
+ */
+static
+struct rtrs_clt_con *rtrs_permit_to_clt_con(struct rtrs_clt_path *clt_path,
+					    struct rtrs_permit *permit)
+{
+	int id = 0;
+
+	if (permit->con_type == RTRS_IO_CON)
+		id = (permit->cpu_id % (clt_path->s.irq_con_num - 1)) + 1;
+
+	return to_clt_con(clt_path->s.con[id]);
+}
+
+/**
+ * rtrs_clt_change_state() - change the session state through session state
+ * machine.
+ *
+ * @clt_path: client path to change the state of.
+ * @new_state: state to change to.
+ *
+ * returns true if sess's state is changed to new state, otherwise return false.
+ *
+ * Locks:
+ * state_wq lock must be hold.
+ */
+static bool rtrs_clt_change_state(struct rtrs_clt_path *clt_path,
+				     enum rtrs_clt_state new_state)
+{
+	enum rtrs_clt_state old_state;
+	bool changed = false;
+
+	lockdep_assert_held(&clt_path->state_wq.lock);
+
+	old_state = clt_path->state;
+	switch (new_state) {
+	case RTRS_CLT_CONNECTING:
+		switch (old_state) {
+		case RTRS_CLT_RECONNECTING:
+			changed = true;
+			fallthrough;
+		default:
+			break;
+		}
+		break;
+	case RTRS_CLT_RECONNECTING:
+		switch (old_state) {
+		case RTRS_CLT_CONNECTED:
+		case RTRS_CLT_CONNECTING_ERR:
+		case RTRS_CLT_CLOSED:
+			changed = true;
+			fallthrough;
+		default:
+			break;
+		}
+		break;
+	case RTRS_CLT_CONNECTED:
+		switch (old_state) {
+		case RTRS_CLT_CONNECTING:
+			changed = true;
+			fallthrough;
+		default:
+			break;
+		}
+		break;
+	case RTRS_CLT_CONNECTING_ERR:
+		switch (old_state) {
+		case RTRS_CLT_CONNECTING:
+			changed = true;
+			fallthrough;
+		default:
+			break;
+		}
+		break;
+	case RTRS_CLT_CLOSING:
+		switch (old_state) {
+		case RTRS_CLT_CONNECTING:
+		case RTRS_CLT_CONNECTING_ERR:
+		case RTRS_CLT_RECONNECTING:
+		case RTRS_CLT_CONNECTED:
+			changed = true;
+			fallthrough;
+		default:
+			break;
+		}
+		break;
+	case RTRS_CLT_CLOSED:
+		switch (old_state) {
+		case RTRS_CLT_CLOSING:
+			changed = true;
+			fallthrough;
+		default:
+			break;
+		}
+		break;
+	case RTRS_CLT_DEAD:
+		switch (old_state) {
+		case RTRS_CLT_CLOSED:
+			changed = true;
+			fallthrough;
+		default:
+			break;
+		}
+		break;
+	default:
+		break;
+	}
+	if (changed) {
+		clt_path->state = new_state;
+		wake_up_locked(&clt_path->state_wq);
+	}
+
+	return changed;
+}
+
+static bool rtrs_clt_change_state_from_to(struct rtrs_clt_path *clt_path,
+					   enum rtrs_clt_state old_state,
+					   enum rtrs_clt_state new_state)
+{
+	bool changed = false;
+
+	spin_lock_irq(&clt_path->state_wq.lock);
+	if (clt_path->state == old_state)
+		changed = rtrs_clt_change_state(clt_path, new_state);
+	spin_unlock_irq(&clt_path->state_wq.lock);
+
+	return changed;
+}
+
+static void rtrs_clt_stop_and_destroy_conns(struct rtrs_clt_path *clt_path);
+static void rtrs_rdma_error_recovery(struct rtrs_clt_con *con)
+{
+	struct rtrs_clt_path *clt_path = to_clt_path(con->c.path);
+
+	trace_rtrs_rdma_error_recovery(clt_path);
+
+	if (rtrs_clt_change_state_from_to(clt_path,
+					   RTRS_CLT_CONNECTED,
+					   RTRS_CLT_RECONNECTING)) {
+		queue_work(rtrs_wq, &clt_path->err_recovery_work);
+	} else {
+		/*
+		 * Error can happen just on establishing new connection,
+		 * so notify waiter with error state, waiter is responsible
+		 * for cleaning the rest and reconnect if needed.
+		 */
+		rtrs_clt_change_state_from_to(clt_path,
+					       RTRS_CLT_CONNECTING,
+					       RTRS_CLT_CONNECTING_ERR);
+	}
+}
+
+static void rtrs_clt_fast_reg_done(struct ib_cq *cq, struct ib_wc *wc)
+{
+	struct rtrs_clt_con *con = to_clt_con(wc->qp->qp_context);
+
+	if (wc->status != IB_WC_SUCCESS) {
+		rtrs_err(con->c.path, "Failed IB_WR_REG_MR: %s\n",
+			  ib_wc_status_msg(wc->status));
+		rtrs_rdma_error_recovery(con);
+	}
+}
+
+static struct ib_cqe fast_reg_cqe = {
+	.done = rtrs_clt_fast_reg_done
+};
+
+static void complete_rdma_req(struct rtrs_clt_io_req *req, int errno,
+			      bool notify, bool can_wait);
+
+static void rtrs_clt_inv_rkey_done(struct ib_cq *cq, struct ib_wc *wc)
+{
+	struct rtrs_clt_io_req *req =
+		container_of(wc->wr_cqe, typeof(*req), inv_cqe);
+	struct rtrs_clt_con *con = to_clt_con(wc->qp->qp_context);
+
+	if (wc->status != IB_WC_SUCCESS) {
+		rtrs_err(con->c.path, "Failed IB_WR_LOCAL_INV: %s\n",
+			  ib_wc_status_msg(wc->status));
+		rtrs_rdma_error_recovery(con);
+	}
+	req->need_inv = false;
+	if (req->need_inv_comp)
+		complete(&req->inv_comp);
+	else
+		/* Complete request from INV callback */
+		complete_rdma_req(req, req->inv_errno, true, false);
+}
+
+static int rtrs_inv_rkey(struct rtrs_clt_io_req *req)
+{
+	struct rtrs_clt_con *con = req->con;
+	struct ib_send_wr wr = {
+		.opcode		    = IB_WR_LOCAL_INV,
+		.wr_cqe		    = &req->inv_cqe,
+		.send_flags	    = IB_SEND_SIGNALED,
+		.ex.invalidate_rkey = req->mr->rkey,
+	};
+	req->inv_cqe.done = rtrs_clt_inv_rkey_done;
+
+	return ib_post_send(con->c.qp, &wr, NULL);
+}
+
+static void complete_rdma_req(struct rtrs_clt_io_req *req, int errno,
+			      bool notify, bool can_wait)
+{
+	struct rtrs_clt_con *con = req->con;
+	struct rtrs_clt_path *clt_path;
+	int err;
+
+	if (!req->in_use)
+		return;
+	if (WARN_ON(!req->con))
+		return;
+	clt_path = to_clt_path(con->c.path);
+
+	if (req->sg_cnt) {
+		if (req->dir == DMA_FROM_DEVICE && req->need_inv) {
+			/*
+			 * We are here to invalidate read requests
+			 * ourselves.  In normal scenario server should
+			 * send INV for all read requests, but
+			 * we are here, thus two things could happen:
+			 *
+			 *    1.  this is failover, when errno != 0
+			 *        and can_wait == 1,
+			 *
+			 *    2.  something totally bad happened and
+			 *        server forgot to send INV, so we
+			 *        should do that ourselves.
+			 */
+
+			if (can_wait) {
+				req->need_inv_comp = true;
+			} else {
+				/* This should be IO path, so always notify */
+				WARN_ON(!notify);
+				/* Save errno for INV callback */
+				req->inv_errno = errno;
+			}
+
+			refcount_inc(&req->ref);
+			err = rtrs_inv_rkey(req);
+			if (err) {
+				rtrs_err(con->c.path, "Send INV WR key=%#x: %d\n",
+					  req->mr->rkey, err);
+			} else if (can_wait) {
+				wait_for_completion(&req->inv_comp);
+			} else {
+				/*
+				 * Something went wrong, so request will be
+				 * completed from INV callback.
+				 */
+				WARN_ON_ONCE(1);
+
+				return;
+			}
+			if (!refcount_dec_and_test(&req->ref))
+				return;
+		}
+		ib_dma_unmap_sg(clt_path->s.dev->ib_dev, req->sglist,
+				req->sg_cnt, req->dir);
+	}
+	if (!refcount_dec_and_test(&req->ref))
+		return;
+	if (req->mp_policy == MP_POLICY_MIN_INFLIGHT)
+		atomic_dec(&clt_path->stats->inflight);
+
+	req->in_use = false;
+	req->con = NULL;
+
+	if (errno) {
+		rtrs_err_rl(con->c.path, "IO request failed: error=%d path=%s [%s:%u] notify=%d\n",
+			    errno, kobject_name(&clt_path->kobj), clt_path->hca_name,
+			    clt_path->hca_port, notify);
+	}
+
+	if (notify)
+		req->conf(req->priv, errno);
+}
+
+static int rtrs_post_send_rdma(struct rtrs_clt_con *con,
+				struct rtrs_clt_io_req *req,
+				struct rtrs_rbuf *rbuf, u32 off,
+				u32 imm, struct ib_send_wr *wr)
+{
+	struct rtrs_clt_path *clt_path = to_clt_path(con->c.path);
+	enum ib_send_flags flags;
+	struct ib_sge sge;
+
+	if (!req->sg_size) {
+		rtrs_wrn(con->c.path,
+			 "Doing RDMA Write failed, no data supplied\n");
+		return -EINVAL;
+	}
+
+	/* user data and user message in the first list element */
+	sge.addr   = req->iu->dma_addr;
+	sge.length = req->sg_size;
+	sge.lkey   = clt_path->s.dev->ib_pd->local_dma_lkey;
+
+	/*
+	 * From time to time we have to post signalled sends,
+	 * or send queue will fill up and only QP reset can help.
+	 */
+	flags = atomic_inc_return(&con->c.wr_cnt) % clt_path->s.signal_interval ?
+			0 : IB_SEND_SIGNALED;
+
+	ib_dma_sync_single_for_device(clt_path->s.dev->ib_dev,
+				      req->iu->dma_addr,
+				      req->sg_size, DMA_TO_DEVICE);
+
+	return rtrs_iu_post_rdma_write_imm(&con->c, req->iu, &sge, 1,
+					    rbuf->rkey, rbuf->addr + off,
+					    imm, flags, wr, NULL);
+}
+
+static void process_io_rsp(struct rtrs_clt_path *clt_path, u32 msg_id,
+			   s16 errno, bool w_inval)
+{
+	struct rtrs_clt_io_req *req;
+
+	if (WARN_ON(msg_id >= clt_path->queue_depth))
+		return;
+
+	req = &clt_path->reqs[msg_id];
+	/* Drop need_inv if server responded with send with invalidation */
+	req->need_inv &= !w_inval;
+	complete_rdma_req(req, errno, true, false);
+}
+
+static void rtrs_clt_recv_done(struct rtrs_clt_con *con, struct ib_wc *wc)
+{
+	struct rtrs_iu *iu;
+	int err;
+	struct rtrs_clt_path *clt_path = to_clt_path(con->c.path);
+
+	WARN_ON((clt_path->flags & RTRS_MSG_NEW_RKEY_F) == 0);
+	iu = container_of(wc->wr_cqe, struct rtrs_iu,
+			  cqe);
+	err = rtrs_iu_post_recv(&con->c, iu);
+	if (err) {
+		rtrs_err(con->c.path, "post iu failed %d\n", err);
+		rtrs_rdma_error_recovery(con);
+	}
+}
+
+static void rtrs_clt_rkey_rsp_done(struct rtrs_clt_con *con, struct ib_wc *wc)
+{
+	struct rtrs_clt_path *clt_path = to_clt_path(con->c.path);
+	struct rtrs_msg_rkey_rsp *msg;
+	u32 imm_type, imm_payload;
+	bool w_inval = false;
+	struct rtrs_iu *iu;
+	u32 buf_id;
+	int err;
+
+	WARN_ON((clt_path->flags & RTRS_MSG_NEW_RKEY_F) == 0);
+
+	iu = container_of(wc->wr_cqe, struct rtrs_iu, cqe);
+
+	if (wc->byte_len < sizeof(*msg)) {
+		rtrs_err(con->c.path, "rkey response is malformed: size %d\n",
+			  wc->byte_len);
+		goto out;
+	}
+	ib_dma_sync_single_for_cpu(clt_path->s.dev->ib_dev, iu->dma_addr,
+				   iu->size, DMA_FROM_DEVICE);
+	msg = iu->buf;
+	if (le16_to_cpu(msg->type) != RTRS_MSG_RKEY_RSP) {
+		rtrs_err(clt_path->clt,
+			  "rkey response is malformed: type %d\n",
+			  le16_to_cpu(msg->type));
+		goto out;
+	}
+	buf_id = le16_to_cpu(msg->buf_id);
+	if (WARN_ON(buf_id >= clt_path->queue_depth))
+		goto out;
+
+	rtrs_from_imm(be32_to_cpu(wc->ex.imm_data), &imm_type, &imm_payload);
+	if (imm_type == RTRS_IO_RSP_IMM ||
+	    imm_type == RTRS_IO_RSP_W_INV_IMM) {
+		u32 msg_id;
+
+		w_inval = (imm_type == RTRS_IO_RSP_W_INV_IMM);
+		rtrs_from_io_rsp_imm(imm_payload, &msg_id, &err);
+
+		if (WARN_ON(buf_id != msg_id))
+			goto out;
+		clt_path->rbufs[buf_id].rkey = le32_to_cpu(msg->rkey);
+		process_io_rsp(clt_path, msg_id, err, w_inval);
+	}
+	ib_dma_sync_single_for_device(clt_path->s.dev->ib_dev, iu->dma_addr,
+				      iu->size, DMA_FROM_DEVICE);
+	return rtrs_clt_recv_done(con, wc);
+out:
+	rtrs_rdma_error_recovery(con);
+}
+
+static void rtrs_clt_rdma_done(struct ib_cq *cq, struct ib_wc *wc);
+
+static struct ib_cqe io_comp_cqe = {
+	.done = rtrs_clt_rdma_done
+};
+
+/*
+ * Post x2 empty WRs: first is for this RDMA with IMM,
+ * second is for RECV with INV, which happened earlier.
+ */
+static int rtrs_post_recv_empty_x2(struct rtrs_con *con, struct ib_cqe *cqe)
+{
+	struct ib_recv_wr wr_arr[2], *wr;
+	int i;
+
+	memset(wr_arr, 0, sizeof(wr_arr));
+	for (i = 0; i < ARRAY_SIZE(wr_arr); i++) {
+		wr = &wr_arr[i];
+		wr->wr_cqe  = cqe;
+		if (i)
+			/* Chain backwards */
+			wr->next = &wr_arr[i - 1];
+	}
+
+	return ib_post_recv(con->qp, wr, NULL);
+}
+
+static void rtrs_clt_rdma_done(struct ib_cq *cq, struct ib_wc *wc)
+{
+	struct rtrs_clt_con *con = to_clt_con(wc->qp->qp_context);
+	struct rtrs_clt_path *clt_path = to_clt_path(con->c.path);
+	u32 imm_type, imm_payload;
+	bool w_inval = false;
+	int err;
+
+	if (wc->status != IB_WC_SUCCESS) {
+		if (wc->status != IB_WC_WR_FLUSH_ERR) {
+			rtrs_err(clt_path->clt, "RDMA failed: %s\n",
+				  ib_wc_status_msg(wc->status));
+			rtrs_rdma_error_recovery(con);
+		}
+		return;
+	}
+	rtrs_clt_update_wc_stats(con);
+
+	switch (wc->opcode) {
+	case IB_WC_RECV_RDMA_WITH_IMM:
+		/*
+		 * post_recv() RDMA write completions of IO reqs (read/write)
+		 * and hb
+		 */
+		if (WARN_ON(wc->wr_cqe->done != rtrs_clt_rdma_done))
+			return;
+		rtrs_from_imm(be32_to_cpu(wc->ex.imm_data),
+			       &imm_type, &imm_payload);
+		if (imm_type == RTRS_IO_RSP_IMM ||
+		    imm_type == RTRS_IO_RSP_W_INV_IMM) {
+			u32 msg_id;
+
+			w_inval = (imm_type == RTRS_IO_RSP_W_INV_IMM);
+			rtrs_from_io_rsp_imm(imm_payload, &msg_id, &err);
+
+			process_io_rsp(clt_path, msg_id, err, w_inval);
+		} else if (imm_type == RTRS_HB_MSG_IMM) {
+			WARN_ON(con->c.cid);
+			rtrs_send_hb_ack(&clt_path->s);
+			if (clt_path->flags & RTRS_MSG_NEW_RKEY_F)
+				return  rtrs_clt_recv_done(con, wc);
+		} else if (imm_type == RTRS_HB_ACK_IMM) {
+			WARN_ON(con->c.cid);
+			clt_path->s.hb_missed_cnt = 0;
+			clt_path->s.hb_cur_latency =
+				ktime_sub(ktime_get(), clt_path->s.hb_last_sent);
+			if (clt_path->flags & RTRS_MSG_NEW_RKEY_F)
+				return  rtrs_clt_recv_done(con, wc);
+		} else {
+			rtrs_wrn(con->c.path, "Unknown IMM type %u\n",
+				  imm_type);
+		}
+		if (w_inval)
+			/*
+			 * Post x2 empty WRs: first is for this RDMA with IMM,
+			 * second is for RECV with INV, which happened earlier.
+			 */
+			err = rtrs_post_recv_empty_x2(&con->c, &io_comp_cqe);
+		else
+			err = rtrs_post_recv_empty(&con->c, &io_comp_cqe);
+		if (err) {
+			rtrs_err(con->c.path, "rtrs_post_recv_empty(): %d\n",
+				  err);
+			rtrs_rdma_error_recovery(con);
+		}
+		break;
+	case IB_WC_RECV:
+		/*
+		 * Key invalidations from server side
+		 */
+		WARN_ON(!(wc->wc_flags & IB_WC_WITH_INVALIDATE ||
+			  wc->wc_flags & IB_WC_WITH_IMM));
+		WARN_ON(wc->wr_cqe->done != rtrs_clt_rdma_done);
+		if (clt_path->flags & RTRS_MSG_NEW_RKEY_F) {
+			if (wc->wc_flags & IB_WC_WITH_INVALIDATE)
+				return  rtrs_clt_recv_done(con, wc);
+
+			return  rtrs_clt_rkey_rsp_done(con, wc);
+		}
+		break;
+	case IB_WC_RDMA_WRITE:
+		/*
+		 * post_send() RDMA write completions of IO reqs (read/write)
+		 * and hb.
+		 */
+		break;
+
+	default:
+		rtrs_wrn(clt_path->clt, "Unexpected WC type: %d\n", wc->opcode);
+		return;
+	}
+}
+
+static int post_recv_io(struct rtrs_clt_con *con, size_t q_size)
+{
+	int err, i;
+	struct rtrs_clt_path *clt_path = to_clt_path(con->c.path);
+
+	for (i = 0; i < q_size; i++) {
+		if (clt_path->flags & RTRS_MSG_NEW_RKEY_F) {
+			struct rtrs_iu *iu = &con->rsp_ius[i];
+
+			err = rtrs_iu_post_recv(&con->c, iu);
+		} else {
+			err = rtrs_post_recv_empty(&con->c, &io_comp_cqe);
+		}
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+
+static int post_recv_path(struct rtrs_clt_path *clt_path)
+{
+	size_t q_size = 0;
+	int err, cid;
+
+	for (cid = 0; cid < clt_path->s.con_num; cid++) {
+		if (cid == 0)
+			q_size = SERVICE_CON_QUEUE_DEPTH;
+		else
+			q_size = clt_path->queue_depth;
+
+		/*
+		 * x2 for RDMA read responses + FR key invalidations,
+		 * RDMA writes do not require any FR registrations.
+		 */
+		q_size *= 2;
+
+		err = post_recv_io(to_clt_con(clt_path->s.con[cid]), q_size);
+		if (err) {
+			rtrs_err(clt_path->clt, "post_recv_io(), err: %d\n",
+				 err);
+			return err;
+		}
+	}
+
+	return 0;
+}
+
+struct path_it {
+	int i;
+	struct list_head skip_list;
+	struct rtrs_clt_sess *clt;
+	struct rtrs_clt_path *(*next_path)(struct path_it *it);
+};
+
+/*
+ * rtrs_clt_get_next_path_or_null - get clt path from the list or return NULL
+ * @head:	the head for the list.
+ * @clt_path:	The element to take the next clt_path from.
+ *
+ * Next clt path returned in round-robin fashion, i.e. head will be skipped,
+ * but if list is observed as empty, NULL will be returned.
+ *
+ * This function may safely run concurrently with the _rcu list-mutation
+ * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock().
+ */
+static inline struct rtrs_clt_path *
+rtrs_clt_get_next_path_or_null(struct list_head *head, struct rtrs_clt_path *clt_path)
+{
+	return list_next_or_null_rcu(head, &clt_path->s.entry, typeof(*clt_path), s.entry) ?:
+				     list_next_or_null_rcu(head,
+							   READ_ONCE((&clt_path->s.entry)->next),
+							   typeof(*clt_path), s.entry);
+}
+
+/**
+ * get_next_path_rr() - Returns path in round-robin fashion.
+ * @it:	the path pointer
+ *
+ * Related to @MP_POLICY_RR
+ *
+ * Locks:
+ *    rcu_read_lock() must be hold.
+ */
+static struct rtrs_clt_path *get_next_path_rr(struct path_it *it)
+{
+	struct rtrs_clt_path __rcu **ppcpu_path;
+	struct rtrs_clt_path *path;
+	struct rtrs_clt_sess *clt;
+
+	clt = it->clt;
+
+	/*
+	 * Here we use two RCU objects: @paths_list and @pcpu_path
+	 * pointer.  See rtrs_clt_remove_path_from_arr() for details
+	 * how that is handled.
+	 */
+
+	ppcpu_path = this_cpu_ptr(clt->pcpu_path);
+	path = rcu_dereference(*ppcpu_path);
+	if (!path)
+		path = list_first_or_null_rcu(&clt->paths_list,
+					      typeof(*path), s.entry);
+	else
+		path = rtrs_clt_get_next_path_or_null(&clt->paths_list, path);
+
+	rcu_assign_pointer(*ppcpu_path, path);
+
+	return path;
+}
+
+/**
+ * get_next_path_min_inflight() - Returns path with minimal inflight count.
+ * @it:	the path pointer
+ *
+ * Related to @MP_POLICY_MIN_INFLIGHT
+ *
+ * Locks:
+ *    rcu_read_lock() must be hold.
+ */
+static struct rtrs_clt_path *get_next_path_min_inflight(struct path_it *it)
+{
+	struct rtrs_clt_path *min_path = NULL;
+	struct rtrs_clt_sess *clt = it->clt;
+	struct rtrs_clt_path *clt_path;
+	int min_inflight = INT_MAX;
+	int inflight;
+
+	list_for_each_entry_rcu(clt_path, &clt->paths_list, s.entry) {
+		if (READ_ONCE(clt_path->state) != RTRS_CLT_CONNECTED)
+			continue;
+
+		if (!list_empty(raw_cpu_ptr(clt_path->mp_skip_entry)))
+			continue;
+
+		inflight = atomic_read(&clt_path->stats->inflight);
+
+		if (inflight < min_inflight) {
+			min_inflight = inflight;
+			min_path = clt_path;
+		}
+	}
+
+	/*
+	 * add the path to the skip list, so that next time we can get
+	 * a different one
+	 */
+	if (min_path)
+		list_add(raw_cpu_ptr(min_path->mp_skip_entry), &it->skip_list);
+
+	return min_path;
+}
+
+/**
+ * get_next_path_min_latency() - Returns path with minimal latency.
+ * @it:	the path pointer
+ *
+ * Return: a path with the lowest latency or NULL if all paths are tried
+ *
+ * Locks:
+ *    rcu_read_lock() must be hold.
+ *
+ * Related to @MP_POLICY_MIN_LATENCY
+ *
+ * This DOES skip an already-tried path.
+ * There is a skip-list to skip a path if the path has tried but failed.
+ * It will try the minimum latency path and then the second minimum latency
+ * path and so on. Finally it will return NULL if all paths are tried.
+ * Therefore the caller MUST check the returned
+ * path is NULL and trigger the IO error.
+ */
+static struct rtrs_clt_path *get_next_path_min_latency(struct path_it *it)
+{
+	struct rtrs_clt_path *min_path = NULL;
+	struct rtrs_clt_sess *clt = it->clt;
+	struct rtrs_clt_path *clt_path;
+	ktime_t min_latency = KTIME_MAX;
+	ktime_t latency;
+
+	list_for_each_entry_rcu(clt_path, &clt->paths_list, s.entry) {
+		if (READ_ONCE(clt_path->state) != RTRS_CLT_CONNECTED)
+			continue;
+
+		if (!list_empty(raw_cpu_ptr(clt_path->mp_skip_entry)))
+			continue;
+
+		latency = clt_path->s.hb_cur_latency;
+
+		if (latency < min_latency) {
+			min_latency = latency;
+			min_path = clt_path;
+		}
+	}
+
+	/*
+	 * add the path to the skip list, so that next time we can get
+	 * a different one
+	 */
+	if (min_path)
+		list_add(raw_cpu_ptr(min_path->mp_skip_entry), &it->skip_list);
+
+	return min_path;
+}
+
+static inline void path_it_init(struct path_it *it, struct rtrs_clt_sess *clt)
+{
+	INIT_LIST_HEAD(&it->skip_list);
+	it->clt = clt;
+	it->i = 0;
+
+	if (clt->mp_policy == MP_POLICY_RR)
+		it->next_path = get_next_path_rr;
+	else if (clt->mp_policy == MP_POLICY_MIN_INFLIGHT)
+		it->next_path = get_next_path_min_inflight;
+	else
+		it->next_path = get_next_path_min_latency;
+}
+
+static inline void path_it_deinit(struct path_it *it)
+{
+	struct list_head *skip, *tmp;
+	/*
+	 * The skip_list is used only for the MIN_INFLIGHT and MIN_LATENCY policies.
+	 * We need to remove paths from it, so that next IO can insert
+	 * paths (->mp_skip_entry) into a skip_list again.
+	 */
+	list_for_each_safe(skip, tmp, &it->skip_list)
+		list_del_init(skip);
+}
+
+/**
+ * rtrs_clt_init_req() - Initialize an rtrs_clt_io_req holding information
+ * about an inflight IO.
+ * The user buffer holding user control message (not data) is copied into
+ * the corresponding buffer of rtrs_iu (req->iu->buf), which later on will
+ * also hold the control message of rtrs.
+ * @req: an io request holding information about IO.
+ * @clt_path: client path
+ * @conf: conformation callback function to notify upper layer.
+ * @permit: permit for allocation of RDMA remote buffer
+ * @priv: private pointer
+ * @vec: kernel vector containing control message
+ * @usr_len: length of the user message
+ * @sg: scater list for IO data
+ * @sg_cnt: number of scater list entries
+ * @data_len: length of the IO data
+ * @dir: direction of the IO.
+ */
+static void rtrs_clt_init_req(struct rtrs_clt_io_req *req,
+			      struct rtrs_clt_path *clt_path,
+			      void (*conf)(void *priv, int errno),
+			      struct rtrs_permit *permit, void *priv,
+			      const struct kvec *vec, size_t usr_len,
+			      struct scatterlist *sg, size_t sg_cnt,
+			      size_t data_len, int dir)
+{
+	struct iov_iter iter;
+	size_t len;
+
+	req->permit = permit;
+	req->in_use = true;
+	req->usr_len = usr_len;
+	req->data_len = data_len;
+	req->sglist = sg;
+	req->sg_cnt = sg_cnt;
+	req->priv = priv;
+	req->dir = dir;
+	req->con = rtrs_permit_to_clt_con(clt_path, permit);
+	req->conf = conf;
+	req->need_inv = false;
+	req->need_inv_comp = false;
+	req->inv_errno = 0;
+	refcount_set(&req->ref, 1);
+	req->mp_policy = clt_path->clt->mp_policy;
+
+	iov_iter_kvec(&iter, ITER_SOURCE, vec, 1, usr_len);
+	len = _copy_from_iter(req->iu->buf, usr_len, &iter);
+	WARN_ON(len != usr_len);
+
+	reinit_completion(&req->inv_comp);
+}
+
+static struct rtrs_clt_io_req *
+rtrs_clt_get_req(struct rtrs_clt_path *clt_path,
+		 void (*conf)(void *priv, int errno),
+		 struct rtrs_permit *permit, void *priv,
+		 const struct kvec *vec, size_t usr_len,
+		 struct scatterlist *sg, size_t sg_cnt,
+		 size_t data_len, int dir)
+{
+	struct rtrs_clt_io_req *req;
+
+	req = &clt_path->reqs[permit->mem_id];
+	rtrs_clt_init_req(req, clt_path, conf, permit, priv, vec, usr_len,
+			   sg, sg_cnt, data_len, dir);
+	return req;
+}
+
+static struct rtrs_clt_io_req *
+rtrs_clt_get_copy_req(struct rtrs_clt_path *alive_path,
+		       struct rtrs_clt_io_req *fail_req)
+{
+	struct rtrs_clt_io_req *req;
+	struct kvec vec = {
+		.iov_base = fail_req->iu->buf,
+		.iov_len  = fail_req->usr_len
+	};
+
+	req = &alive_path->reqs[fail_req->permit->mem_id];
+	rtrs_clt_init_req(req, alive_path, fail_req->conf, fail_req->permit,
+			   fail_req->priv, &vec, fail_req->usr_len,
+			   fail_req->sglist, fail_req->sg_cnt,
+			   fail_req->data_len, fail_req->dir);
+	return req;
+}
+
+static int rtrs_post_rdma_write_sg(struct rtrs_clt_con *con,
+				   struct rtrs_clt_io_req *req,
+				   struct rtrs_rbuf *rbuf, bool fr_en,
+				   u32 count, u32 size, u32 imm,
+				   struct ib_send_wr *wr,
+				   struct ib_send_wr *tail)
+{
+	struct rtrs_clt_path *clt_path = to_clt_path(con->c.path);
+	struct ib_sge *sge = req->sge;
+	enum ib_send_flags flags;
+	struct scatterlist *sg;
+	size_t num_sge;
+	int i;
+	struct ib_send_wr *ptail = NULL;
+
+	if (fr_en) {
+		i = 0;
+		sge[i].addr   = req->mr->iova;
+		sge[i].length = req->mr->length;
+		sge[i].lkey   = req->mr->lkey;
+		i++;
+		num_sge = 2;
+		ptail = tail;
+	} else {
+		for_each_sg(req->sglist, sg, count, i) {
+			sge[i].addr   = sg_dma_address(sg);
+			sge[i].length = sg_dma_len(sg);
+			sge[i].lkey   = clt_path->s.dev->ib_pd->local_dma_lkey;
+		}
+		num_sge = 1 + count;
+	}
+	sge[i].addr   = req->iu->dma_addr;
+	sge[i].length = size;
+	sge[i].lkey   = clt_path->s.dev->ib_pd->local_dma_lkey;
+
+	/*
+	 * From time to time we have to post signalled sends,
+	 * or send queue will fill up and only QP reset can help.
+	 */
+	flags = atomic_inc_return(&con->c.wr_cnt) % clt_path->s.signal_interval ?
+			0 : IB_SEND_SIGNALED;
+
+	ib_dma_sync_single_for_device(clt_path->s.dev->ib_dev,
+				      req->iu->dma_addr,
+				      size, DMA_TO_DEVICE);
+
+	return rtrs_iu_post_rdma_write_imm(&con->c, req->iu, sge, num_sge,
+					    rbuf->rkey, rbuf->addr, imm,
+					    flags, wr, ptail);
+}
+
+static int rtrs_map_sg_fr(struct rtrs_clt_io_req *req, size_t count)
+{
+	int nr;
+
+	/* Align the MR to a 4K page size to match the block virt boundary */
+	nr = ib_map_mr_sg(req->mr, req->sglist, count, NULL, SZ_4K);
+	if (nr < 0)
+		return nr;
+	if (nr < req->sg_cnt)
+		return -EINVAL;
+	ib_update_fast_reg_key(req->mr, ib_inc_rkey(req->mr->rkey));
+
+	return nr;
+}
+
+static int rtrs_clt_write_req(struct rtrs_clt_io_req *req)
+{
+	struct rtrs_clt_con *con = req->con;
+	struct rtrs_path *s = con->c.path;
+	struct rtrs_clt_path *clt_path = to_clt_path(s);
+	struct rtrs_msg_rdma_write *msg;
+
+	struct rtrs_rbuf *rbuf;
+	int ret, count = 0;
+	u32 imm, buf_id;
+	struct ib_reg_wr rwr;
+	struct ib_send_wr inv_wr;
+	struct ib_send_wr *wr = NULL;
+	bool fr_en = false;
+
+	const size_t tsize = sizeof(*msg) + req->data_len + req->usr_len;
+
+	if (tsize > clt_path->chunk_size) {
+		rtrs_wrn(s, "Write request failed, size too big %zu > %d\n",
+			  tsize, clt_path->chunk_size);
+		return -EMSGSIZE;
+	}
+	if (req->sg_cnt) {
+		count = ib_dma_map_sg(clt_path->s.dev->ib_dev, req->sglist,
+				      req->sg_cnt, req->dir);
+		if (!count) {
+			rtrs_wrn(s, "Write request failed, map failed\n");
+			return -EINVAL;
+		}
+	}
+	/* put rtrs msg after sg and user message */
+	msg = req->iu->buf + req->usr_len;
+	msg->type = cpu_to_le16(RTRS_MSG_WRITE);
+	msg->usr_len = cpu_to_le16(req->usr_len);
+
+	/* rtrs message on server side will be after user data and message */
+	imm = req->permit->mem_off + req->data_len + req->usr_len;
+	imm = rtrs_to_io_req_imm(imm);
+	buf_id = req->permit->mem_id;
+	req->sg_size = tsize;
+	rbuf = &clt_path->rbufs[buf_id];
+
+	if (count) {
+		ret = rtrs_map_sg_fr(req, count);
+		if (ret < 0) {
+			rtrs_err_rl(s,
+				    "Write request failed, failed to map fast reg. data, err: %d\n",
+				    ret);
+			ib_dma_unmap_sg(clt_path->s.dev->ib_dev, req->sglist,
+					req->sg_cnt, req->dir);
+			return ret;
+		}
+		inv_wr = (struct ib_send_wr) {
+			.opcode		    = IB_WR_LOCAL_INV,
+			.wr_cqe		    = &req->inv_cqe,
+			.send_flags	    = IB_SEND_SIGNALED,
+			.ex.invalidate_rkey = req->mr->rkey,
+		};
+		req->inv_cqe.done = rtrs_clt_inv_rkey_done;
+		rwr = (struct ib_reg_wr) {
+			.wr.opcode = IB_WR_REG_MR,
+			.wr.wr_cqe = &fast_reg_cqe,
+			.mr = req->mr,
+			.key = req->mr->rkey,
+			.access = (IB_ACCESS_LOCAL_WRITE),
+		};
+		wr = &rwr.wr;
+		fr_en = true;
+		refcount_inc(&req->ref);
+	}
+	/*
+	 * Update stats now, after request is successfully sent it is not
+	 * safe anymore to touch it.
+	 */
+	rtrs_clt_update_all_stats(req, WRITE);
+
+	ret = rtrs_post_rdma_write_sg(req->con, req, rbuf, fr_en, count,
+				      req->usr_len + sizeof(*msg),
+				      imm, wr, &inv_wr);
+	if (ret) {
+		rtrs_err_rl(s,
+			    "Write request failed: error=%d path=%s [%s:%u]\n",
+			    ret, kobject_name(&clt_path->kobj), clt_path->hca_name,
+			    clt_path->hca_port);
+		if (req->mp_policy == MP_POLICY_MIN_INFLIGHT)
+			atomic_dec(&clt_path->stats->inflight);
+		if (req->sg_cnt)
+			ib_dma_unmap_sg(clt_path->s.dev->ib_dev, req->sglist,
+					req->sg_cnt, req->dir);
+	}
+
+	return ret;
+}
+
+static int rtrs_clt_read_req(struct rtrs_clt_io_req *req)
+{
+	struct rtrs_clt_con *con = req->con;
+	struct rtrs_path *s = con->c.path;
+	struct rtrs_clt_path *clt_path = to_clt_path(s);
+	struct rtrs_msg_rdma_read *msg;
+	struct rtrs_ib_dev *dev = clt_path->s.dev;
+
+	struct ib_reg_wr rwr;
+	struct ib_send_wr *wr = NULL;
+
+	int ret, count = 0;
+	u32 imm, buf_id;
+
+	const size_t tsize = sizeof(*msg) + req->data_len + req->usr_len;
+
+	if (tsize > clt_path->chunk_size) {
+		rtrs_wrn(s,
+			  "Read request failed, message size is %zu, bigger than CHUNK_SIZE %d\n",
+			  tsize, clt_path->chunk_size);
+		return -EMSGSIZE;
+	}
+
+	if (req->sg_cnt) {
+		count = ib_dma_map_sg(dev->ib_dev, req->sglist, req->sg_cnt,
+				      req->dir);
+		if (!count) {
+			rtrs_wrn(s,
+				  "Read request failed, dma map failed\n");
+			return -EINVAL;
+		}
+	}
+	/* put our message into req->buf after user message*/
+	msg = req->iu->buf + req->usr_len;
+	msg->type = cpu_to_le16(RTRS_MSG_READ);
+	msg->usr_len = cpu_to_le16(req->usr_len);
+
+	if (count) {
+		ret = rtrs_map_sg_fr(req, count);
+		if (ret < 0) {
+			rtrs_err_rl(s,
+				     "Read request failed, failed to map  fast reg. data, err: %d\n",
+				     ret);
+			ib_dma_unmap_sg(dev->ib_dev, req->sglist, req->sg_cnt,
+					req->dir);
+			return ret;
+		}
+		rwr = (struct ib_reg_wr) {
+			.wr.opcode = IB_WR_REG_MR,
+			.wr.wr_cqe = &fast_reg_cqe,
+			.mr = req->mr,
+			.key = req->mr->rkey,
+			.access = (IB_ACCESS_LOCAL_WRITE |
+				   IB_ACCESS_REMOTE_WRITE),
+		};
+		wr = &rwr.wr;
+
+		msg->sg_cnt = cpu_to_le16(1);
+		msg->flags = cpu_to_le16(RTRS_MSG_NEED_INVAL_F);
+
+		msg->desc[0].addr = cpu_to_le64(req->mr->iova);
+		msg->desc[0].key = cpu_to_le32(req->mr->rkey);
+		msg->desc[0].len = cpu_to_le32(req->mr->length);
+
+		/* Further invalidation is required */
+		req->need_inv = !!RTRS_MSG_NEED_INVAL_F;
+
+	} else {
+		msg->sg_cnt = 0;
+		msg->flags = 0;
+	}
+	/*
+	 * rtrs message will be after the space reserved for disk data and
+	 * user message
+	 */
+	imm = req->permit->mem_off + req->data_len + req->usr_len;
+	imm = rtrs_to_io_req_imm(imm);
+	buf_id = req->permit->mem_id;
+
+	req->sg_size  = sizeof(*msg);
+	req->sg_size += le16_to_cpu(msg->sg_cnt) * sizeof(struct rtrs_sg_desc);
+	req->sg_size += req->usr_len;
+
+	/*
+	 * Update stats now, after request is successfully sent it is not
+	 * safe anymore to touch it.
+	 */
+	rtrs_clt_update_all_stats(req, READ);
+
+	ret = rtrs_post_send_rdma(req->con, req, &clt_path->rbufs[buf_id],
+				   req->data_len, imm, wr);
+	if (ret) {
+		rtrs_err_rl(s,
+			    "Read request failed: error=%d path=%s [%s:%u]\n",
+			    ret, kobject_name(&clt_path->kobj), clt_path->hca_name,
+			    clt_path->hca_port);
+		if (req->mp_policy == MP_POLICY_MIN_INFLIGHT)
+			atomic_dec(&clt_path->stats->inflight);
+		req->need_inv = false;
+		if (req->sg_cnt)
+			ib_dma_unmap_sg(dev->ib_dev, req->sglist,
+					req->sg_cnt, req->dir);
+	}
+
+	return ret;
+}
+
+/**
+ * rtrs_clt_failover_req() - Try to find an active path for a failed request
+ * @clt: clt context
+ * @fail_req: a failed io request.
+ */
+static int rtrs_clt_failover_req(struct rtrs_clt_sess *clt,
+				 struct rtrs_clt_io_req *fail_req)
+{
+	struct rtrs_clt_path *alive_path;
+	struct rtrs_clt_io_req *req;
+	int err = -ECONNABORTED;
+	struct path_it it;
+
+	rcu_read_lock();
+	for (path_it_init(&it, clt);
+	     (alive_path = it.next_path(&it)) && it.i < it.clt->paths_num;
+	     it.i++) {
+		if (READ_ONCE(alive_path->state) != RTRS_CLT_CONNECTED)
+			continue;
+		req = rtrs_clt_get_copy_req(alive_path, fail_req);
+		if (req->dir == DMA_TO_DEVICE)
+			err = rtrs_clt_write_req(req);
+		else
+			err = rtrs_clt_read_req(req);
+		if (err) {
+			req->in_use = false;
+			continue;
+		}
+		/* Success path */
+		rtrs_clt_inc_failover_cnt(alive_path->stats);
+		break;
+	}
+	path_it_deinit(&it);
+	rcu_read_unlock();
+
+	return err;
+}
+
+static void fail_all_outstanding_reqs(struct rtrs_clt_path *clt_path)
+{
+	struct rtrs_clt_sess *clt = clt_path->clt;
+	struct rtrs_clt_io_req *req;
+	int i, err;
+
+	if (!clt_path->reqs)
+		return;
+	for (i = 0; i < clt_path->queue_depth; ++i) {
+		req = &clt_path->reqs[i];
+		if (!req->in_use)
+			continue;
+
+		/*
+		 * Safely (without notification) complete failed request.
+		 * After completion this request is still useble and can
+		 * be failovered to another path.
+		 */
+		complete_rdma_req(req, -ECONNABORTED, false, true);
+
+		err = rtrs_clt_failover_req(clt, req);
+		if (err)
+			/* Failover failed, notify anyway */
+			req->conf(req->priv, err);
+	}
+}
+
+static void free_path_reqs(struct rtrs_clt_path *clt_path)
+{
+	struct rtrs_clt_io_req *req;
+	int i;
+
+	if (!clt_path->reqs)
+		return;
+	for (i = 0; i < clt_path->queue_depth; ++i) {
+		req = &clt_path->reqs[i];
+		if (req->mr)
+			ib_dereg_mr(req->mr);
+		kfree(req->sge);
+		rtrs_iu_free(req->iu, clt_path->s.dev->ib_dev, 1);
+	}
+	kfree(clt_path->reqs);
+	clt_path->reqs = NULL;
+}
+
+static int alloc_path_reqs(struct rtrs_clt_path *clt_path)
+{
+	struct rtrs_clt_io_req *req;
+	int i, err = -ENOMEM;
+
+	clt_path->reqs = kcalloc(clt_path->queue_depth,
+				 sizeof(*clt_path->reqs),
+				 GFP_KERNEL);
+	if (!clt_path->reqs)
+		return -ENOMEM;
+
+	for (i = 0; i < clt_path->queue_depth; ++i) {
+		req = &clt_path->reqs[i];
+		req->iu = rtrs_iu_alloc(1, clt_path->max_hdr_size, GFP_KERNEL,
+					 clt_path->s.dev->ib_dev,
+					 DMA_TO_DEVICE,
+					 rtrs_clt_rdma_done);
+		if (!req->iu)
+			goto out;
+
+		req->sge = kcalloc(2, sizeof(*req->sge), GFP_KERNEL);
+		if (!req->sge)
+			goto out;
+
+		req->mr = ib_alloc_mr(clt_path->s.dev->ib_pd,
+				      IB_MR_TYPE_MEM_REG,
+				      clt_path->max_pages_per_mr);
+		if (IS_ERR(req->mr)) {
+			err = PTR_ERR(req->mr);
+			req->mr = NULL;
+			pr_err("Failed to alloc clt_path->max_pages_per_mr %d\n",
+			       clt_path->max_pages_per_mr);
+			goto out;
+		}
+
+		init_completion(&req->inv_comp);
+	}
+
+	return 0;
+
+out:
+	free_path_reqs(clt_path);
+
+	return err;
+}
+
+static int alloc_permits(struct rtrs_clt_sess *clt)
+{
+	unsigned int chunk_bits;
+	int err, i;
+
+	clt->permits_map = bitmap_zalloc(clt->queue_depth, GFP_KERNEL);
+	if (!clt->permits_map) {
+		err = -ENOMEM;
+		goto out_err;
+	}
+	clt->permits = kcalloc(clt->queue_depth, permit_size(clt), GFP_KERNEL);
+	if (!clt->permits) {
+		err = -ENOMEM;
+		goto err_map;
+	}
+	chunk_bits = ilog2(clt->queue_depth - 1) + 1;
+	for (i = 0; i < clt->queue_depth; i++) {
+		struct rtrs_permit *permit;
+
+		permit = get_permit(clt, i);
+		permit->mem_id = i;
+		permit->mem_off = i << (MAX_IMM_PAYL_BITS - chunk_bits);
+	}
+
+	return 0;
+
+err_map:
+	bitmap_free(clt->permits_map);
+	clt->permits_map = NULL;
+out_err:
+	return err;
+}
+
+static void free_permits(struct rtrs_clt_sess *clt)
+{
+	if (clt->permits_map)
+		wait_event(clt->permits_wait,
+			   bitmap_empty(clt->permits_map, clt->queue_depth));
+
+	bitmap_free(clt->permits_map);
+	clt->permits_map = NULL;
+	kfree(clt->permits);
+	clt->permits = NULL;
+}
+
+static void query_fast_reg_mode(struct rtrs_clt_path *clt_path)
+{
+	struct ib_device *ib_dev;
+	u64 max_pages_per_mr;
+	int mr_page_shift;
+
+	ib_dev = clt_path->s.dev->ib_dev;
+
+	/*
+	 * Use the smallest page size supported by the HCA, down to a
+	 * minimum of 4096 bytes. We're unlikely to build large sglists
+	 * out of smaller entries.
+	 */
+	mr_page_shift      = max(12, ffs(ib_dev->attrs.page_size_cap) - 1);
+	max_pages_per_mr   = ib_dev->attrs.max_mr_size;
+	do_div(max_pages_per_mr, (1ull << mr_page_shift));
+	clt_path->max_pages_per_mr =
+		min3(clt_path->max_pages_per_mr, (u32)max_pages_per_mr,
+		     ib_dev->attrs.max_fast_reg_page_list_len);
+	clt_path->clt->max_segments =
+		min(clt_path->max_pages_per_mr, clt_path->clt->max_segments);
+}
+
+static bool rtrs_clt_change_state_get_old(struct rtrs_clt_path *clt_path,
+					   enum rtrs_clt_state new_state,
+					   enum rtrs_clt_state *old_state)
+{
+	bool changed;
+
+	spin_lock_irq(&clt_path->state_wq.lock);
+	if (old_state)
+		*old_state = clt_path->state;
+	changed = rtrs_clt_change_state(clt_path, new_state);
+	spin_unlock_irq(&clt_path->state_wq.lock);
+
+	return changed;
+}
+
+static void rtrs_clt_hb_err_handler(struct rtrs_con *c)
+{
+	struct rtrs_clt_con *con = container_of(c, typeof(*con), c);
+
+	rtrs_rdma_error_recovery(con);
+}
+
+static void rtrs_clt_init_hb(struct rtrs_clt_path *clt_path)
+{
+	rtrs_init_hb(&clt_path->s, &io_comp_cqe,
+		      RTRS_HB_INTERVAL_MS,
+		      RTRS_HB_MISSED_MAX,
+		      rtrs_clt_hb_err_handler,
+		      rtrs_wq);
+}
+
+static void rtrs_clt_reconnect_work(struct work_struct *work);
+static void rtrs_clt_close_work(struct work_struct *work);
+
+static void rtrs_clt_err_recovery_work(struct work_struct *work)
+{
+	struct rtrs_clt_path *clt_path;
+	struct rtrs_clt_sess *clt;
+	int delay_ms;
+
+	clt_path = container_of(work, struct rtrs_clt_path, err_recovery_work);
+	clt = clt_path->clt;
+	delay_ms = clt->reconnect_delay_sec * 1000;
+	rtrs_clt_stop_and_destroy_conns(clt_path);
+	queue_delayed_work(rtrs_wq, &clt_path->reconnect_dwork,
+			   msecs_to_jiffies(delay_ms +
+					    prandom_u32_max(RTRS_RECONNECT_SEED)));
+}
+
+static struct rtrs_clt_path *alloc_path(struct rtrs_clt_sess *clt,
+					const struct rtrs_addr *path,
+					size_t con_num, u32 nr_poll_queues)
+{
+	struct rtrs_clt_path *clt_path;
+	int err = -ENOMEM;
+	int cpu;
+	size_t total_con;
+
+	clt_path = kzalloc(sizeof(*clt_path), GFP_KERNEL);
+	if (!clt_path)
+		goto err;
+
+	/*
+	 * irqmode and poll
+	 * +1: Extra connection for user messages
+	 */
+	total_con = con_num + nr_poll_queues + 1;
+	clt_path->s.con = kcalloc(total_con, sizeof(*clt_path->s.con),
+				  GFP_KERNEL);
+	if (!clt_path->s.con)
+		goto err_free_path;
+
+	clt_path->s.con_num = total_con;
+	clt_path->s.irq_con_num = con_num + 1;
+
+	clt_path->stats = kzalloc(sizeof(*clt_path->stats), GFP_KERNEL);
+	if (!clt_path->stats)
+		goto err_free_con;
+
+	mutex_init(&clt_path->init_mutex);
+	uuid_gen(&clt_path->s.uuid);
+	memcpy(&clt_path->s.dst_addr, path->dst,
+	       rdma_addr_size((struct sockaddr *)path->dst));
+
+	/*
+	 * rdma_resolve_addr() passes src_addr to cma_bind_addr, which
+	 * checks the sa_family to be non-zero. If user passed src_addr=NULL
+	 * the sess->src_addr will contain only zeros, which is then fine.
+	 */
+	if (path->src)
+		memcpy(&clt_path->s.src_addr, path->src,
+		       rdma_addr_size((struct sockaddr *)path->src));
+	strscpy(clt_path->s.sessname, clt->sessname,
+		sizeof(clt_path->s.sessname));
+	clt_path->clt = clt;
+	clt_path->max_pages_per_mr = RTRS_MAX_SEGMENTS;
+	init_waitqueue_head(&clt_path->state_wq);
+	clt_path->state = RTRS_CLT_CONNECTING;
+	atomic_set(&clt_path->connected_cnt, 0);
+	INIT_WORK(&clt_path->close_work, rtrs_clt_close_work);
+	INIT_WORK(&clt_path->err_recovery_work, rtrs_clt_err_recovery_work);
+	INIT_DELAYED_WORK(&clt_path->reconnect_dwork, rtrs_clt_reconnect_work);
+	rtrs_clt_init_hb(clt_path);
+
+	clt_path->mp_skip_entry = alloc_percpu(typeof(*clt_path->mp_skip_entry));
+	if (!clt_path->mp_skip_entry)
+		goto err_free_stats;
+
+	for_each_possible_cpu(cpu)
+		INIT_LIST_HEAD(per_cpu_ptr(clt_path->mp_skip_entry, cpu));
+
+	err = rtrs_clt_init_stats(clt_path->stats);
+	if (err)
+		goto err_free_percpu;
+
+	return clt_path;
+
+err_free_percpu:
+	free_percpu(clt_path->mp_skip_entry);
+err_free_stats:
+	kfree(clt_path->stats);
+err_free_con:
+	kfree(clt_path->s.con);
+err_free_path:
+	kfree(clt_path);
+err:
+	return ERR_PTR(err);
+}
+
+void free_path(struct rtrs_clt_path *clt_path)
+{
+	free_percpu(clt_path->mp_skip_entry);
+	mutex_destroy(&clt_path->init_mutex);
+	kfree(clt_path->s.con);
+	kfree(clt_path->rbufs);
+	kfree(clt_path);
+}
+
+static int create_con(struct rtrs_clt_path *clt_path, unsigned int cid)
+{
+	struct rtrs_clt_con *con;
+
+	con = kzalloc(sizeof(*con), GFP_KERNEL);
+	if (!con)
+		return -ENOMEM;
+
+	/* Map first two connections to the first CPU */
+	con->cpu  = (cid ? cid - 1 : 0) % nr_cpu_ids;
+	con->c.cid = cid;
+	con->c.path = &clt_path->s;
+	/* Align with srv, init as 1 */
+	atomic_set(&con->c.wr_cnt, 1);
+	mutex_init(&con->con_mutex);
+
+	clt_path->s.con[cid] = &con->c;
+
+	return 0;
+}
+
+static void destroy_con(struct rtrs_clt_con *con)
+{
+	struct rtrs_clt_path *clt_path = to_clt_path(con->c.path);
+
+	clt_path->s.con[con->c.cid] = NULL;
+	mutex_destroy(&con->con_mutex);
+	kfree(con);
+}
+
+static int create_con_cq_qp(struct rtrs_clt_con *con)
+{
+	struct rtrs_clt_path *clt_path = to_clt_path(con->c.path);
+	u32 max_send_wr, max_recv_wr, cq_num, max_send_sge, wr_limit;
+	int err, cq_vector;
+	struct rtrs_msg_rkey_rsp *rsp;
+
+	lockdep_assert_held(&con->con_mutex);
+	if (con->c.cid == 0) {
+		max_send_sge = 1;
+		/* We must be the first here */
+		if (WARN_ON(clt_path->s.dev))
+			return -EINVAL;
+
+		/*
+		 * The whole session uses device from user connection.
+		 * Be careful not to close user connection before ib dev
+		 * is gracefully put.
+		 */
+		clt_path->s.dev = rtrs_ib_dev_find_or_add(con->c.cm_id->device,
+						       &dev_pd);
+		if (!clt_path->s.dev) {
+			rtrs_wrn(clt_path->clt,
+				  "rtrs_ib_dev_find_get_or_add(): no memory\n");
+			return -ENOMEM;
+		}
+		clt_path->s.dev_ref = 1;
+		query_fast_reg_mode(clt_path);
+		wr_limit = clt_path->s.dev->ib_dev->attrs.max_qp_wr;
+		/*
+		 * Two (request + registration) completion for send
+		 * Two for recv if always_invalidate is set on server
+		 * or one for recv.
+		 * + 2 for drain and heartbeat
+		 * in case qp gets into error state.
+		 */
+		max_send_wr =
+			min_t(int, wr_limit, SERVICE_CON_QUEUE_DEPTH * 2 + 2);
+		max_recv_wr = max_send_wr;
+	} else {
+		/*
+		 * Here we assume that session members are correctly set.
+		 * This is always true if user connection (cid == 0) is
+		 * established first.
+		 */
+		if (WARN_ON(!clt_path->s.dev))
+			return -EINVAL;
+		if (WARN_ON(!clt_path->queue_depth))
+			return -EINVAL;
+
+		wr_limit = clt_path->s.dev->ib_dev->attrs.max_qp_wr;
+		/* Shared between connections */
+		clt_path->s.dev_ref++;
+		max_send_wr = min_t(int, wr_limit,
+			      /* QD * (REQ + RSP + FR REGS or INVS) + drain */
+			      clt_path->queue_depth * 4 + 1);
+		max_recv_wr = min_t(int, wr_limit,
+			      clt_path->queue_depth * 3 + 1);
+		max_send_sge = 2;
+	}
+	atomic_set(&con->c.sq_wr_avail, max_send_wr);
+	cq_num = max_send_wr + max_recv_wr;
+	/* alloc iu to recv new rkey reply when server reports flags set */
+	if (clt_path->flags & RTRS_MSG_NEW_RKEY_F || con->c.cid == 0) {
+		con->rsp_ius = rtrs_iu_alloc(cq_num, sizeof(*rsp),
+					      GFP_KERNEL,
+					      clt_path->s.dev->ib_dev,
+					      DMA_FROM_DEVICE,
+					      rtrs_clt_rdma_done);
+		if (!con->rsp_ius)
+			return -ENOMEM;
+		con->queue_num = cq_num;
+	}
+	cq_num = max_send_wr + max_recv_wr;
+	cq_vector = con->cpu % clt_path->s.dev->ib_dev->num_comp_vectors;
+	if (con->c.cid >= clt_path->s.irq_con_num)
+		err = rtrs_cq_qp_create(&clt_path->s, &con->c, max_send_sge,
+					cq_vector, cq_num, max_send_wr,
+					max_recv_wr, IB_POLL_DIRECT);
+	else
+		err = rtrs_cq_qp_create(&clt_path->s, &con->c, max_send_sge,
+					cq_vector, cq_num, max_send_wr,
+					max_recv_wr, IB_POLL_SOFTIRQ);
+	/*
+	 * In case of error we do not bother to clean previous allocations,
+	 * since destroy_con_cq_qp() must be called.
+	 */
+	return err;
+}
+
+static void destroy_con_cq_qp(struct rtrs_clt_con *con)
+{
+	struct rtrs_clt_path *clt_path = to_clt_path(con->c.path);
+
+	/*
+	 * Be careful here: destroy_con_cq_qp() can be called even
+	 * create_con_cq_qp() failed, see comments there.
+	 */
+	lockdep_assert_held(&con->con_mutex);
+	rtrs_cq_qp_destroy(&con->c);
+	if (con->rsp_ius) {
+		rtrs_iu_free(con->rsp_ius, clt_path->s.dev->ib_dev,
+			     con->queue_num);
+		con->rsp_ius = NULL;
+		con->queue_num = 0;
+	}
+	if (clt_path->s.dev_ref && !--clt_path->s.dev_ref) {
+		rtrs_ib_dev_put(clt_path->s.dev);
+		clt_path->s.dev = NULL;
+	}
+}
+
+static void stop_cm(struct rtrs_clt_con *con)
+{
+	rdma_disconnect(con->c.cm_id);
+	if (con->c.qp)
+		ib_drain_qp(con->c.qp);
+}
+
+static void destroy_cm(struct rtrs_clt_con *con)
+{
+	rdma_destroy_id(con->c.cm_id);
+	con->c.cm_id = NULL;
+}
+
+static int rtrs_rdma_addr_resolved(struct rtrs_clt_con *con)
+{
+	struct rtrs_path *s = con->c.path;
+	int err;
+
+	mutex_lock(&con->con_mutex);
+	err = create_con_cq_qp(con);
+	mutex_unlock(&con->con_mutex);
+	if (err) {
+		rtrs_err(s, "create_con_cq_qp(), err: %d\n", err);
+		return err;
+	}
+	err = rdma_resolve_route(con->c.cm_id, RTRS_CONNECT_TIMEOUT_MS);
+	if (err)
+		rtrs_err(s, "Resolving route failed, err: %d\n", err);
+
+	return err;
+}
+
+static int rtrs_rdma_route_resolved(struct rtrs_clt_con *con)
+{
+	struct rtrs_clt_path *clt_path = to_clt_path(con->c.path);
+	struct rtrs_clt_sess *clt = clt_path->clt;
+	struct rtrs_msg_conn_req msg;
+	struct rdma_conn_param param;
+
+	int err;
+
+	param = (struct rdma_conn_param) {
+		.retry_count = 7,
+		.rnr_retry_count = 7,
+		.private_data = &msg,
+		.private_data_len = sizeof(msg),
+	};
+
+	msg = (struct rtrs_msg_conn_req) {
+		.magic = cpu_to_le16(RTRS_MAGIC),
+		.version = cpu_to_le16(RTRS_PROTO_VER),
+		.cid = cpu_to_le16(con->c.cid),
+		.cid_num = cpu_to_le16(clt_path->s.con_num),
+		.recon_cnt = cpu_to_le16(clt_path->s.recon_cnt),
+	};
+	msg.first_conn = clt_path->for_new_clt ? FIRST_CONN : 0;
+	uuid_copy(&msg.sess_uuid, &clt_path->s.uuid);
+	uuid_copy(&msg.paths_uuid, &clt->paths_uuid);
+
+	err = rdma_connect_locked(con->c.cm_id, &param);
+	if (err)
+		rtrs_err(clt, "rdma_connect_locked(): %d\n", err);
+
+	return err;
+}
+
+static int rtrs_rdma_conn_established(struct rtrs_clt_con *con,
+				       struct rdma_cm_event *ev)
+{
+	struct rtrs_clt_path *clt_path = to_clt_path(con->c.path);
+	struct rtrs_clt_sess *clt = clt_path->clt;
+	const struct rtrs_msg_conn_rsp *msg;
+	u16 version, queue_depth;
+	int errno;
+	u8 len;
+
+	msg = ev->param.conn.private_data;
+	len = ev->param.conn.private_data_len;
+	if (len < sizeof(*msg)) {
+		rtrs_err(clt, "Invalid RTRS connection response\n");
+		return -ECONNRESET;
+	}
+	if (le16_to_cpu(msg->magic) != RTRS_MAGIC) {
+		rtrs_err(clt, "Invalid RTRS magic\n");
+		return -ECONNRESET;
+	}
+	version = le16_to_cpu(msg->version);
+	if (version >> 8 != RTRS_PROTO_VER_MAJOR) {
+		rtrs_err(clt, "Unsupported major RTRS version: %d, expected %d\n",
+			  version >> 8, RTRS_PROTO_VER_MAJOR);
+		return -ECONNRESET;
+	}
+	errno = le16_to_cpu(msg->errno);
+	if (errno) {
+		rtrs_err(clt, "Invalid RTRS message: errno %d\n",
+			  errno);
+		return -ECONNRESET;
+	}
+	if (con->c.cid == 0) {
+		queue_depth = le16_to_cpu(msg->queue_depth);
+
+		if (clt_path->queue_depth > 0 && queue_depth != clt_path->queue_depth) {
+			rtrs_err(clt, "Error: queue depth changed\n");
+
+			/*
+			 * Stop any more reconnection attempts
+			 */
+			clt_path->reconnect_attempts = -1;
+			rtrs_err(clt,
+				"Disabling auto-reconnect. Trigger a manual reconnect after issue is resolved\n");
+			return -ECONNRESET;
+		}
+
+		if (!clt_path->rbufs) {
+			clt_path->rbufs = kcalloc(queue_depth,
+						  sizeof(*clt_path->rbufs),
+						  GFP_KERNEL);
+			if (!clt_path->rbufs)
+				return -ENOMEM;
+		}
+		clt_path->queue_depth = queue_depth;
+		clt_path->s.signal_interval = min_not_zero(queue_depth,
+						(unsigned short) SERVICE_CON_QUEUE_DEPTH);
+		clt_path->max_hdr_size = le32_to_cpu(msg->max_hdr_size);
+		clt_path->max_io_size = le32_to_cpu(msg->max_io_size);
+		clt_path->flags = le32_to_cpu(msg->flags);
+		clt_path->chunk_size = clt_path->max_io_size + clt_path->max_hdr_size;
+
+		/*
+		 * Global IO size is always a minimum.
+		 * If while a reconnection server sends us a value a bit
+		 * higher - client does not care and uses cached minimum.
+		 *
+		 * Since we can have several sessions (paths) restablishing
+		 * connections in parallel, use lock.
+		 */
+		mutex_lock(&clt->paths_mutex);
+		clt->queue_depth = clt_path->queue_depth;
+		clt->max_io_size = min_not_zero(clt_path->max_io_size,
+						clt->max_io_size);
+		mutex_unlock(&clt->paths_mutex);
+
+		/*
+		 * Cache the hca_port and hca_name for sysfs
+		 */
+		clt_path->hca_port = con->c.cm_id->port_num;
+		scnprintf(clt_path->hca_name, sizeof(clt_path->hca_name),
+			  clt_path->s.dev->ib_dev->name);
+		clt_path->s.src_addr = con->c.cm_id->route.addr.src_addr;
+		/* set for_new_clt, to allow future reconnect on any path */
+		clt_path->for_new_clt = 1;
+	}
+
+	return 0;
+}
+
+static inline void flag_success_on_conn(struct rtrs_clt_con *con)
+{
+	struct rtrs_clt_path *clt_path = to_clt_path(con->c.path);
+
+	atomic_inc(&clt_path->connected_cnt);
+	con->cm_err = 1;
+}
+
+static int rtrs_rdma_conn_rejected(struct rtrs_clt_con *con,
+				    struct rdma_cm_event *ev)
+{
+	struct rtrs_path *s = con->c.path;
+	const struct rtrs_msg_conn_rsp *msg;
+	const char *rej_msg;
+	int status, errno;
+	u8 data_len;
+
+	status = ev->status;
+	rej_msg = rdma_reject_msg(con->c.cm_id, status);
+	msg = rdma_consumer_reject_data(con->c.cm_id, ev, &data_len);
+
+	if (msg && data_len >= sizeof(*msg)) {
+		errno = (int16_t)le16_to_cpu(msg->errno);
+		if (errno == -EBUSY)
+			rtrs_err(s,
+				  "Previous session is still exists on the server, please reconnect later\n");
+		else
+			rtrs_err(s,
+				  "Connect rejected: status %d (%s), rtrs errno %d\n",
+				  status, rej_msg, errno);
+	} else {
+		rtrs_err(s,
+			  "Connect rejected but with malformed message: status %d (%s)\n",
+			  status, rej_msg);
+	}
+
+	return -ECONNRESET;
+}
+
+void rtrs_clt_close_conns(struct rtrs_clt_path *clt_path, bool wait)
+{
+	trace_rtrs_clt_close_conns(clt_path);
+
+	if (rtrs_clt_change_state_get_old(clt_path, RTRS_CLT_CLOSING, NULL))
+		queue_work(rtrs_wq, &clt_path->close_work);
+	if (wait)
+		flush_work(&clt_path->close_work);
+}
+
+static inline void flag_error_on_conn(struct rtrs_clt_con *con, int cm_err)
+{
+	if (con->cm_err == 1) {
+		struct rtrs_clt_path *clt_path;
+
+		clt_path = to_clt_path(con->c.path);
+		if (atomic_dec_and_test(&clt_path->connected_cnt))
+
+			wake_up(&clt_path->state_wq);
+	}
+	con->cm_err = cm_err;
+}
+
+static int rtrs_clt_rdma_cm_handler(struct rdma_cm_id *cm_id,
+				     struct rdma_cm_event *ev)
+{
+	struct rtrs_clt_con *con = cm_id->context;
+	struct rtrs_path *s = con->c.path;
+	struct rtrs_clt_path *clt_path = to_clt_path(s);
+	int cm_err = 0;
+
+	switch (ev->event) {
+	case RDMA_CM_EVENT_ADDR_RESOLVED:
+		cm_err = rtrs_rdma_addr_resolved(con);
+		break;
+	case RDMA_CM_EVENT_ROUTE_RESOLVED:
+		cm_err = rtrs_rdma_route_resolved(con);
+		break;
+	case RDMA_CM_EVENT_ESTABLISHED:
+		cm_err = rtrs_rdma_conn_established(con, ev);
+		if (!cm_err) {
+			/*
+			 * Report success and wake up. Here we abuse state_wq,
+			 * i.e. wake up without state change, but we set cm_err.
+			 */
+			flag_success_on_conn(con);
+			wake_up(&clt_path->state_wq);
+			return 0;
+		}
+		break;
+	case RDMA_CM_EVENT_REJECTED:
+		cm_err = rtrs_rdma_conn_rejected(con, ev);
+		break;
+	case RDMA_CM_EVENT_DISCONNECTED:
+		/* No message for disconnecting */
+		cm_err = -ECONNRESET;
+		break;
+	case RDMA_CM_EVENT_CONNECT_ERROR:
+	case RDMA_CM_EVENT_UNREACHABLE:
+	case RDMA_CM_EVENT_ADDR_CHANGE:
+	case RDMA_CM_EVENT_TIMEWAIT_EXIT:
+		rtrs_wrn(s, "CM error (CM event: %s, err: %d)\n",
+			 rdma_event_msg(ev->event), ev->status);
+		cm_err = -ECONNRESET;
+		break;
+	case RDMA_CM_EVENT_ADDR_ERROR:
+	case RDMA_CM_EVENT_ROUTE_ERROR:
+		rtrs_wrn(s, "CM error (CM event: %s, err: %d)\n",
+			 rdma_event_msg(ev->event), ev->status);
+		cm_err = -EHOSTUNREACH;
+		break;
+	case RDMA_CM_EVENT_DEVICE_REMOVAL:
+		/*
+		 * Device removal is a special case.  Queue close and return 0.
+		 */
+		rtrs_clt_close_conns(clt_path, false);
+		return 0;
+	default:
+		rtrs_err(s, "Unexpected RDMA CM error (CM event: %s, err: %d)\n",
+			 rdma_event_msg(ev->event), ev->status);
+		cm_err = -ECONNRESET;
+		break;
+	}
+
+	if (cm_err) {
+		/*
+		 * cm error makes sense only on connection establishing,
+		 * in other cases we rely on normal procedure of reconnecting.
+		 */
+		flag_error_on_conn(con, cm_err);
+		rtrs_rdma_error_recovery(con);
+	}
+
+	return 0;
+}
+
+/* The caller should do the cleanup in case of error */
+static int create_cm(struct rtrs_clt_con *con)
+{
+	struct rtrs_path *s = con->c.path;
+	struct rtrs_clt_path *clt_path = to_clt_path(s);
+	struct rdma_cm_id *cm_id;
+	int err;
+
+	cm_id = rdma_create_id(&init_net, rtrs_clt_rdma_cm_handler, con,
+			       clt_path->s.dst_addr.ss_family == AF_IB ?
+			       RDMA_PS_IB : RDMA_PS_TCP, IB_QPT_RC);
+	if (IS_ERR(cm_id)) {
+		err = PTR_ERR(cm_id);
+		rtrs_err(s, "Failed to create CM ID, err: %d\n", err);
+
+		return err;
+	}
+	con->c.cm_id = cm_id;
+	con->cm_err = 0;
+	/* allow the port to be reused */
+	err = rdma_set_reuseaddr(cm_id, 1);
+	if (err != 0) {
+		rtrs_err(s, "Set address reuse failed, err: %d\n", err);
+		return err;
+	}
+	err = rdma_resolve_addr(cm_id, (struct sockaddr *)&clt_path->s.src_addr,
+				(struct sockaddr *)&clt_path->s.dst_addr,
+				RTRS_CONNECT_TIMEOUT_MS);
+	if (err) {
+		rtrs_err(s, "Failed to resolve address, err: %d\n", err);
+		return err;
+	}
+	/*
+	 * Combine connection status and session events. This is needed
+	 * for waiting two possible cases: cm_err has something meaningful
+	 * or session state was really changed to error by device removal.
+	 */
+	err = wait_event_interruptible_timeout(
+			clt_path->state_wq,
+			con->cm_err || clt_path->state != RTRS_CLT_CONNECTING,
+			msecs_to_jiffies(RTRS_CONNECT_TIMEOUT_MS));
+	if (err == 0 || err == -ERESTARTSYS) {
+		if (err == 0)
+			err = -ETIMEDOUT;
+		/* Timedout or interrupted */
+		return err;
+	}
+	if (con->cm_err < 0)
+		return con->cm_err;
+	if (READ_ONCE(clt_path->state) != RTRS_CLT_CONNECTING)
+		/* Device removal */
+		return -ECONNABORTED;
+
+	return 0;
+}
+
+static void rtrs_clt_path_up(struct rtrs_clt_path *clt_path)
+{
+	struct rtrs_clt_sess *clt = clt_path->clt;
+	int up;
+
+	/*
+	 * We can fire RECONNECTED event only when all paths were
+	 * connected on rtrs_clt_open(), then each was disconnected
+	 * and the first one connected again.  That's why this nasty
+	 * game with counter value.
+	 */
+
+	mutex_lock(&clt->paths_ev_mutex);
+	up = ++clt->paths_up;
+	/*
+	 * Here it is safe to access paths num directly since up counter
+	 * is greater than MAX_PATHS_NUM only while rtrs_clt_open() is
+	 * in progress, thus paths removals are impossible.
+	 */
+	if (up > MAX_PATHS_NUM && up == MAX_PATHS_NUM + clt->paths_num)
+		clt->paths_up = clt->paths_num;
+	else if (up == 1)
+		clt->link_ev(clt->priv, RTRS_CLT_LINK_EV_RECONNECTED);
+	mutex_unlock(&clt->paths_ev_mutex);
+
+	/* Mark session as established */
+	clt_path->established = true;
+	clt_path->reconnect_attempts = 0;
+	clt_path->stats->reconnects.successful_cnt++;
+}
+
+static void rtrs_clt_path_down(struct rtrs_clt_path *clt_path)
+{
+	struct rtrs_clt_sess *clt = clt_path->clt;
+
+	if (!clt_path->established)
+		return;
+
+	clt_path->established = false;
+	mutex_lock(&clt->paths_ev_mutex);
+	WARN_ON(!clt->paths_up);
+	if (--clt->paths_up == 0)
+		clt->link_ev(clt->priv, RTRS_CLT_LINK_EV_DISCONNECTED);
+	mutex_unlock(&clt->paths_ev_mutex);
+}
+
+static void rtrs_clt_stop_and_destroy_conns(struct rtrs_clt_path *clt_path)
+{
+	struct rtrs_clt_con *con;
+	unsigned int cid;
+
+	WARN_ON(READ_ONCE(clt_path->state) == RTRS_CLT_CONNECTED);
+
+	/*
+	 * Possible race with rtrs_clt_open(), when DEVICE_REMOVAL comes
+	 * exactly in between.  Start destroying after it finishes.
+	 */
+	mutex_lock(&clt_path->init_mutex);
+	mutex_unlock(&clt_path->init_mutex);
+
+	/*
+	 * All IO paths must observe !CONNECTED state before we
+	 * free everything.
+	 */
+	synchronize_rcu();
+
+	rtrs_stop_hb(&clt_path->s);
+
+	/*
+	 * The order it utterly crucial: firstly disconnect and complete all
+	 * rdma requests with error (thus set in_use=false for requests),
+	 * then fail outstanding requests checking in_use for each, and
+	 * eventually notify upper layer about session disconnection.
+	 */
+
+	for (cid = 0; cid < clt_path->s.con_num; cid++) {
+		if (!clt_path->s.con[cid])
+			break;
+		con = to_clt_con(clt_path->s.con[cid]);
+		stop_cm(con);
+	}
+	fail_all_outstanding_reqs(clt_path);
+	free_path_reqs(clt_path);
+	rtrs_clt_path_down(clt_path);
+
+	/*
+	 * Wait for graceful shutdown, namely when peer side invokes
+	 * rdma_disconnect(). 'connected_cnt' is decremented only on
+	 * CM events, thus if other side had crashed and hb has detected
+	 * something is wrong, here we will stuck for exactly timeout ms,
+	 * since CM does not fire anything.  That is fine, we are not in
+	 * hurry.
+	 */
+	wait_event_timeout(clt_path->state_wq,
+			   !atomic_read(&clt_path->connected_cnt),
+			   msecs_to_jiffies(RTRS_CONNECT_TIMEOUT_MS));
+
+	for (cid = 0; cid < clt_path->s.con_num; cid++) {
+		if (!clt_path->s.con[cid])
+			break;
+		con = to_clt_con(clt_path->s.con[cid]);
+		mutex_lock(&con->con_mutex);
+		destroy_con_cq_qp(con);
+		mutex_unlock(&con->con_mutex);
+		destroy_cm(con);
+		destroy_con(con);
+	}
+}
+
+static void rtrs_clt_remove_path_from_arr(struct rtrs_clt_path *clt_path)
+{
+	struct rtrs_clt_sess *clt = clt_path->clt;
+	struct rtrs_clt_path *next;
+	bool wait_for_grace = false;
+	int cpu;
+
+	mutex_lock(&clt->paths_mutex);
+	list_del_rcu(&clt_path->s.entry);
+
+	/* Make sure everybody observes path removal. */
+	synchronize_rcu();
+
+	/*
+	 * At this point nobody sees @sess in the list, but still we have
+	 * dangling pointer @pcpu_path which _can_ point to @sess.  Since
+	 * nobody can observe @sess in the list, we guarantee that IO path
+	 * will not assign @sess to @pcpu_path, i.e. @pcpu_path can be equal
+	 * to @sess, but can never again become @sess.
+	 */
+
+	/*
+	 * Decrement paths number only after grace period, because
+	 * caller of do_each_path() must firstly observe list without
+	 * path and only then decremented paths number.
+	 *
+	 * Otherwise there can be the following situation:
+	 *    o Two paths exist and IO is coming.
+	 *    o One path is removed:
+	 *      CPU#0                          CPU#1
+	 *      do_each_path():                rtrs_clt_remove_path_from_arr():
+	 *          path = get_next_path()
+	 *          ^^^                            list_del_rcu(path)
+	 *          [!CONNECTED path]              clt->paths_num--
+	 *                                              ^^^^^^^^^
+	 *          load clt->paths_num                 from 2 to 1
+	 *                    ^^^^^^^^^
+	 *                    sees 1
+	 *
+	 *      path is observed as !CONNECTED, but do_each_path() loop
+	 *      ends, because expression i < clt->paths_num is false.
+	 */
+	clt->paths_num--;
+
+	/*
+	 * Get @next connection from current @sess which is going to be
+	 * removed.  If @sess is the last element, then @next is NULL.
+	 */
+	rcu_read_lock();
+	next = rtrs_clt_get_next_path_or_null(&clt->paths_list, clt_path);
+	rcu_read_unlock();
+
+	/*
+	 * @pcpu paths can still point to the path which is going to be
+	 * removed, so change the pointer manually.
+	 */
+	for_each_possible_cpu(cpu) {
+		struct rtrs_clt_path __rcu **ppcpu_path;
+
+		ppcpu_path = per_cpu_ptr(clt->pcpu_path, cpu);
+		if (rcu_dereference_protected(*ppcpu_path,
+			lockdep_is_held(&clt->paths_mutex)) != clt_path)
+			/*
+			 * synchronize_rcu() was called just after deleting
+			 * entry from the list, thus IO code path cannot
+			 * change pointer back to the pointer which is going
+			 * to be removed, we are safe here.
+			 */
+			continue;
+
+		/*
+		 * We race with IO code path, which also changes pointer,
+		 * thus we have to be careful not to overwrite it.
+		 */
+		if (try_cmpxchg((struct rtrs_clt_path **)ppcpu_path, &clt_path,
+				next))
+			/*
+			 * @ppcpu_path was successfully replaced with @next,
+			 * that means that someone could also pick up the
+			 * @sess and dereferencing it right now, so wait for
+			 * a grace period is required.
+			 */
+			wait_for_grace = true;
+	}
+	if (wait_for_grace)
+		synchronize_rcu();
+
+	mutex_unlock(&clt->paths_mutex);
+}
+
+static void rtrs_clt_add_path_to_arr(struct rtrs_clt_path *clt_path)
+{
+	struct rtrs_clt_sess *clt = clt_path->clt;
+
+	mutex_lock(&clt->paths_mutex);
+	clt->paths_num++;
+
+	list_add_tail_rcu(&clt_path->s.entry, &clt->paths_list);
+	mutex_unlock(&clt->paths_mutex);
+}
+
+static void rtrs_clt_close_work(struct work_struct *work)
+{
+	struct rtrs_clt_path *clt_path;
+
+	clt_path = container_of(work, struct rtrs_clt_path, close_work);
+
+	cancel_work_sync(&clt_path->err_recovery_work);
+	cancel_delayed_work_sync(&clt_path->reconnect_dwork);
+	rtrs_clt_stop_and_destroy_conns(clt_path);
+	rtrs_clt_change_state_get_old(clt_path, RTRS_CLT_CLOSED, NULL);
+}
+
+static int init_conns(struct rtrs_clt_path *clt_path)
+{
+	unsigned int cid;
+	int err, i;
+
+	/*
+	 * On every new session connections increase reconnect counter
+	 * to avoid clashes with previous sessions not yet closed
+	 * sessions on a server side.
+	 */
+	clt_path->s.recon_cnt++;
+
+	/* Establish all RDMA connections  */
+	for (cid = 0; cid < clt_path->s.con_num; cid++) {
+		err = create_con(clt_path, cid);
+		if (err)
+			goto destroy;
+
+		err = create_cm(to_clt_con(clt_path->s.con[cid]));
+		if (err)
+			goto destroy;
+	}
+	err = alloc_path_reqs(clt_path);
+	if (err)
+		goto destroy;
+
+	return 0;
+
+destroy:
+	/* Make sure we do the cleanup in the order they are created */
+	for (i = 0; i <= cid; i++) {
+		struct rtrs_clt_con *con;
+
+		if (!clt_path->s.con[i])
+			break;
+
+		con = to_clt_con(clt_path->s.con[i]);
+		if (con->c.cm_id) {
+			stop_cm(con);
+			mutex_lock(&con->con_mutex);
+			destroy_con_cq_qp(con);
+			mutex_unlock(&con->con_mutex);
+			destroy_cm(con);
+		}
+		destroy_con(con);
+	}
+	/*
+	 * If we've never taken async path and got an error, say,
+	 * doing rdma_resolve_addr(), switch to CONNECTION_ERR state
+	 * manually to keep reconnecting.
+	 */
+	rtrs_clt_change_state_get_old(clt_path, RTRS_CLT_CONNECTING_ERR, NULL);
+
+	return err;
+}
+
+static void rtrs_clt_info_req_done(struct ib_cq *cq, struct ib_wc *wc)
+{
+	struct rtrs_clt_con *con = to_clt_con(wc->qp->qp_context);
+	struct rtrs_clt_path *clt_path = to_clt_path(con->c.path);
+	struct rtrs_iu *iu;
+
+	iu = container_of(wc->wr_cqe, struct rtrs_iu, cqe);
+	rtrs_iu_free(iu, clt_path->s.dev->ib_dev, 1);
+
+	if (wc->status != IB_WC_SUCCESS) {
+		rtrs_err(clt_path->clt, "Path info request send failed: %s\n",
+			  ib_wc_status_msg(wc->status));
+		rtrs_clt_change_state_get_old(clt_path, RTRS_CLT_CONNECTING_ERR, NULL);
+		return;
+	}
+
+	rtrs_clt_update_wc_stats(con);
+}
+
+static int process_info_rsp(struct rtrs_clt_path *clt_path,
+			    const struct rtrs_msg_info_rsp *msg)
+{
+	unsigned int sg_cnt, total_len;
+	int i, sgi;
+
+	sg_cnt = le16_to_cpu(msg->sg_cnt);
+	if (!sg_cnt || (clt_path->queue_depth % sg_cnt)) {
+		rtrs_err(clt_path->clt,
+			  "Incorrect sg_cnt %d, is not multiple\n",
+			  sg_cnt);
+		return -EINVAL;
+	}
+
+	/*
+	 * Check if IB immediate data size is enough to hold the mem_id and
+	 * the offset inside the memory chunk.
+	 */
+	if ((ilog2(sg_cnt - 1) + 1) + (ilog2(clt_path->chunk_size - 1) + 1) >
+	    MAX_IMM_PAYL_BITS) {
+		rtrs_err(clt_path->clt,
+			  "RDMA immediate size (%db) not enough to encode %d buffers of size %dB\n",
+			  MAX_IMM_PAYL_BITS, sg_cnt, clt_path->chunk_size);
+		return -EINVAL;
+	}
+	total_len = 0;
+	for (sgi = 0, i = 0; sgi < sg_cnt && i < clt_path->queue_depth; sgi++) {
+		const struct rtrs_sg_desc *desc = &msg->desc[sgi];
+		u32 len, rkey;
+		u64 addr;
+
+		addr = le64_to_cpu(desc->addr);
+		rkey = le32_to_cpu(desc->key);
+		len  = le32_to_cpu(desc->len);
+
+		total_len += len;
+
+		if (!len || (len % clt_path->chunk_size)) {
+			rtrs_err(clt_path->clt, "Incorrect [%d].len %d\n",
+				  sgi,
+				  len);
+			return -EINVAL;
+		}
+		for ( ; len && i < clt_path->queue_depth; i++) {
+			clt_path->rbufs[i].addr = addr;
+			clt_path->rbufs[i].rkey = rkey;
+
+			len  -= clt_path->chunk_size;
+			addr += clt_path->chunk_size;
+		}
+	}
+	/* Sanity check */
+	if (sgi != sg_cnt || i != clt_path->queue_depth) {
+		rtrs_err(clt_path->clt,
+			 "Incorrect sg vector, not fully mapped\n");
+		return -EINVAL;
+	}
+	if (total_len != clt_path->chunk_size * clt_path->queue_depth) {
+		rtrs_err(clt_path->clt, "Incorrect total_len %d\n", total_len);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static void rtrs_clt_info_rsp_done(struct ib_cq *cq, struct ib_wc *wc)
+{
+	struct rtrs_clt_con *con = to_clt_con(wc->qp->qp_context);
+	struct rtrs_clt_path *clt_path = to_clt_path(con->c.path);
+	struct rtrs_msg_info_rsp *msg;
+	enum rtrs_clt_state state;
+	struct rtrs_iu *iu;
+	size_t rx_sz;
+	int err;
+
+	state = RTRS_CLT_CONNECTING_ERR;
+
+	WARN_ON(con->c.cid);
+	iu = container_of(wc->wr_cqe, struct rtrs_iu, cqe);
+	if (wc->status != IB_WC_SUCCESS) {
+		rtrs_err(clt_path->clt, "Path info response recv failed: %s\n",
+			  ib_wc_status_msg(wc->status));
+		goto out;
+	}
+	WARN_ON(wc->opcode != IB_WC_RECV);
+
+	if (wc->byte_len < sizeof(*msg)) {
+		rtrs_err(clt_path->clt, "Path info response is malformed: size %d\n",
+			  wc->byte_len);
+		goto out;
+	}
+	ib_dma_sync_single_for_cpu(clt_path->s.dev->ib_dev, iu->dma_addr,
+				   iu->size, DMA_FROM_DEVICE);
+	msg = iu->buf;
+	if (le16_to_cpu(msg->type) != RTRS_MSG_INFO_RSP) {
+		rtrs_err(clt_path->clt, "Path info response is malformed: type %d\n",
+			  le16_to_cpu(msg->type));
+		goto out;
+	}
+	rx_sz  = sizeof(*msg);
+	rx_sz += sizeof(msg->desc[0]) * le16_to_cpu(msg->sg_cnt);
+	if (wc->byte_len < rx_sz) {
+		rtrs_err(clt_path->clt, "Path info response is malformed: size %d\n",
+			  wc->byte_len);
+		goto out;
+	}
+	err = process_info_rsp(clt_path, msg);
+	if (err)
+		goto out;
+
+	err = post_recv_path(clt_path);
+	if (err)
+		goto out;
+
+	state = RTRS_CLT_CONNECTED;
+
+out:
+	rtrs_clt_update_wc_stats(con);
+	rtrs_iu_free(iu, clt_path->s.dev->ib_dev, 1);
+	rtrs_clt_change_state_get_old(clt_path, state, NULL);
+}
+
+static int rtrs_send_path_info(struct rtrs_clt_path *clt_path)
+{
+	struct rtrs_clt_con *usr_con = to_clt_con(clt_path->s.con[0]);
+	struct rtrs_msg_info_req *msg;
+	struct rtrs_iu *tx_iu, *rx_iu;
+	size_t rx_sz;
+	int err;
+
+	rx_sz  = sizeof(struct rtrs_msg_info_rsp);
+	rx_sz += sizeof(struct rtrs_sg_desc) * clt_path->queue_depth;
+
+	tx_iu = rtrs_iu_alloc(1, sizeof(struct rtrs_msg_info_req), GFP_KERNEL,
+			       clt_path->s.dev->ib_dev, DMA_TO_DEVICE,
+			       rtrs_clt_info_req_done);
+	rx_iu = rtrs_iu_alloc(1, rx_sz, GFP_KERNEL, clt_path->s.dev->ib_dev,
+			       DMA_FROM_DEVICE, rtrs_clt_info_rsp_done);
+	if (!tx_iu || !rx_iu) {
+		err = -ENOMEM;
+		goto out;
+	}
+	/* Prepare for getting info response */
+	err = rtrs_iu_post_recv(&usr_con->c, rx_iu);
+	if (err) {
+		rtrs_err(clt_path->clt, "rtrs_iu_post_recv(), err: %d\n", err);
+		goto out;
+	}
+	rx_iu = NULL;
+
+	msg = tx_iu->buf;
+	msg->type = cpu_to_le16(RTRS_MSG_INFO_REQ);
+	memcpy(msg->pathname, clt_path->s.sessname, sizeof(msg->pathname));
+
+	ib_dma_sync_single_for_device(clt_path->s.dev->ib_dev,
+				      tx_iu->dma_addr,
+				      tx_iu->size, DMA_TO_DEVICE);
+
+	/* Send info request */
+	err = rtrs_iu_post_send(&usr_con->c, tx_iu, sizeof(*msg), NULL);
+	if (err) {
+		rtrs_err(clt_path->clt, "rtrs_iu_post_send(), err: %d\n", err);
+		goto out;
+	}
+	tx_iu = NULL;
+
+	/* Wait for state change */
+	wait_event_interruptible_timeout(clt_path->state_wq,
+					 clt_path->state != RTRS_CLT_CONNECTING,
+					 msecs_to_jiffies(
+						 RTRS_CONNECT_TIMEOUT_MS));
+	if (READ_ONCE(clt_path->state) != RTRS_CLT_CONNECTED) {
+		if (READ_ONCE(clt_path->state) == RTRS_CLT_CONNECTING_ERR)
+			err = -ECONNRESET;
+		else
+			err = -ETIMEDOUT;
+	}
+
+out:
+	if (tx_iu)
+		rtrs_iu_free(tx_iu, clt_path->s.dev->ib_dev, 1);
+	if (rx_iu)
+		rtrs_iu_free(rx_iu, clt_path->s.dev->ib_dev, 1);
+	if (err)
+		/* If we've never taken async path because of malloc problems */
+		rtrs_clt_change_state_get_old(clt_path,
+					      RTRS_CLT_CONNECTING_ERR, NULL);
+
+	return err;
+}
+
+/**
+ * init_path() - establishes all path connections and does handshake
+ * @clt_path: client path.
+ * In case of error full close or reconnect procedure should be taken,
+ * because reconnect or close async works can be started.
+ */
+static int init_path(struct rtrs_clt_path *clt_path)
+{
+	int err;
+	char str[NAME_MAX];
+	struct rtrs_addr path = {
+		.src = &clt_path->s.src_addr,
+		.dst = &clt_path->s.dst_addr,
+	};
+
+	rtrs_addr_to_str(&path, str, sizeof(str));
+
+	mutex_lock(&clt_path->init_mutex);
+	err = init_conns(clt_path);
+	if (err) {
+		rtrs_err(clt_path->clt,
+			 "init_conns() failed: err=%d path=%s [%s:%u]\n", err,
+			 str, clt_path->hca_name, clt_path->hca_port);
+		goto out;
+	}
+	err = rtrs_send_path_info(clt_path);
+	if (err) {
+		rtrs_err(clt_path->clt,
+			 "rtrs_send_path_info() failed: err=%d path=%s [%s:%u]\n",
+			 err, str, clt_path->hca_name, clt_path->hca_port);
+		goto out;
+	}
+	rtrs_clt_path_up(clt_path);
+	rtrs_start_hb(&clt_path->s);
+out:
+	mutex_unlock(&clt_path->init_mutex);
+
+	return err;
+}
+
+static void rtrs_clt_reconnect_work(struct work_struct *work)
+{
+	struct rtrs_clt_path *clt_path;
+	struct rtrs_clt_sess *clt;
+	int err;
+
+	clt_path = container_of(to_delayed_work(work), struct rtrs_clt_path,
+				reconnect_dwork);
+	clt = clt_path->clt;
+
+	trace_rtrs_clt_reconnect_work(clt_path);
+
+	if (READ_ONCE(clt_path->state) != RTRS_CLT_RECONNECTING)
+		return;
+
+	if (clt_path->reconnect_attempts >= clt->max_reconnect_attempts) {
+		/* Close a path completely if max attempts is reached */
+		rtrs_clt_close_conns(clt_path, false);
+		return;
+	}
+	clt_path->reconnect_attempts++;
+
+	msleep(RTRS_RECONNECT_BACKOFF);
+	if (rtrs_clt_change_state_get_old(clt_path, RTRS_CLT_CONNECTING, NULL)) {
+		err = init_path(clt_path);
+		if (err)
+			goto reconnect_again;
+	}
+
+	return;
+
+reconnect_again:
+	if (rtrs_clt_change_state_get_old(clt_path, RTRS_CLT_RECONNECTING, NULL)) {
+		clt_path->stats->reconnects.fail_cnt++;
+		queue_work(rtrs_wq, &clt_path->err_recovery_work);
+	}
+}
+
+static void rtrs_clt_dev_release(struct device *dev)
+{
+	struct rtrs_clt_sess *clt = container_of(dev, struct rtrs_clt_sess,
+						 dev);
+
+	mutex_destroy(&clt->paths_ev_mutex);
+	mutex_destroy(&clt->paths_mutex);
+	kfree(clt);
+}
+
+static struct rtrs_clt_sess *alloc_clt(const char *sessname, size_t paths_num,
+				  u16 port, size_t pdu_sz, void *priv,
+				  void	(*link_ev)(void *priv,
+						   enum rtrs_clt_link_ev ev),
+				  unsigned int reconnect_delay_sec,
+				  unsigned int max_reconnect_attempts)
+{
+	struct rtrs_clt_sess *clt;
+	int err;
+
+	if (!paths_num || paths_num > MAX_PATHS_NUM)
+		return ERR_PTR(-EINVAL);
+
+	if (strlen(sessname) >= sizeof(clt->sessname))
+		return ERR_PTR(-EINVAL);
+
+	clt = kzalloc(sizeof(*clt), GFP_KERNEL);
+	if (!clt)
+		return ERR_PTR(-ENOMEM);
+
+	clt->pcpu_path = alloc_percpu(typeof(*clt->pcpu_path));
+	if (!clt->pcpu_path) {
+		kfree(clt);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	clt->dev.class = rtrs_clt_dev_class;
+	clt->dev.release = rtrs_clt_dev_release;
+	uuid_gen(&clt->paths_uuid);
+	INIT_LIST_HEAD_RCU(&clt->paths_list);
+	clt->paths_num = paths_num;
+	clt->paths_up = MAX_PATHS_NUM;
+	clt->port = port;
+	clt->pdu_sz = pdu_sz;
+	clt->max_segments = RTRS_MAX_SEGMENTS;
+	clt->reconnect_delay_sec = reconnect_delay_sec;
+	clt->max_reconnect_attempts = max_reconnect_attempts;
+	clt->priv = priv;
+	clt->link_ev = link_ev;
+	clt->mp_policy = MP_POLICY_MIN_INFLIGHT;
+	strscpy(clt->sessname, sessname, sizeof(clt->sessname));
+	init_waitqueue_head(&clt->permits_wait);
+	mutex_init(&clt->paths_ev_mutex);
+	mutex_init(&clt->paths_mutex);
+	device_initialize(&clt->dev);
+
+	err = dev_set_name(&clt->dev, "%s", sessname);
+	if (err)
+		goto err_put;
+
+	/*
+	 * Suppress user space notification until
+	 * sysfs files are created
+	 */
+	dev_set_uevent_suppress(&clt->dev, true);
+	err = device_add(&clt->dev);
+	if (err)
+		goto err_put;
+
+	clt->kobj_paths = kobject_create_and_add("paths", &clt->dev.kobj);
+	if (!clt->kobj_paths) {
+		err = -ENOMEM;
+		goto err_del;
+	}
+	err = rtrs_clt_create_sysfs_root_files(clt);
+	if (err) {
+		kobject_del(clt->kobj_paths);
+		kobject_put(clt->kobj_paths);
+		goto err_del;
+	}
+	dev_set_uevent_suppress(&clt->dev, false);
+	kobject_uevent(&clt->dev.kobj, KOBJ_ADD);
+
+	return clt;
+err_del:
+	device_del(&clt->dev);
+err_put:
+	free_percpu(clt->pcpu_path);
+	put_device(&clt->dev);
+	return ERR_PTR(err);
+}
+
+static void free_clt(struct rtrs_clt_sess *clt)
+{
+	free_percpu(clt->pcpu_path);
+
+	/*
+	 * release callback will free clt and destroy mutexes in last put
+	 */
+	device_unregister(&clt->dev);
+}
+
+/**
+ * rtrs_clt_open() - Open a path to an RTRS server
+ * @ops: holds the link event callback and the private pointer.
+ * @pathname: name of the path to an RTRS server
+ * @paths: Paths to be established defined by their src and dst addresses
+ * @paths_num: Number of elements in the @paths array
+ * @port: port to be used by the RTRS session
+ * @pdu_sz: Size of extra payload which can be accessed after permit allocation.
+ * @reconnect_delay_sec: time between reconnect tries
+ * @max_reconnect_attempts: Number of times to reconnect on error before giving
+ *			    up, 0 for * disabled, -1 for forever
+ * @nr_poll_queues: number of polling mode connection using IB_POLL_DIRECT flag
+ *
+ * Starts session establishment with the rtrs_server. The function can block
+ * up to ~2000ms before it returns.
+ *
+ * Return a valid pointer on success otherwise PTR_ERR.
+ */
+struct rtrs_clt_sess *rtrs_clt_open(struct rtrs_clt_ops *ops,
+				 const char *pathname,
+				 const struct rtrs_addr *paths,
+				 size_t paths_num, u16 port,
+				 size_t pdu_sz, u8 reconnect_delay_sec,
+				 s16 max_reconnect_attempts, u32 nr_poll_queues)
+{
+	struct rtrs_clt_path *clt_path, *tmp;
+	struct rtrs_clt_sess *clt;
+	int err, i;
+
+	if (strchr(pathname, '/') || strchr(pathname, '.')) {
+		pr_err("pathname cannot contain / and .\n");
+		err = -EINVAL;
+		goto out;
+	}
+
+	clt = alloc_clt(pathname, paths_num, port, pdu_sz, ops->priv,
+			ops->link_ev,
+			reconnect_delay_sec,
+			max_reconnect_attempts);
+	if (IS_ERR(clt)) {
+		err = PTR_ERR(clt);
+		goto out;
+	}
+	for (i = 0; i < paths_num; i++) {
+		struct rtrs_clt_path *clt_path;
+
+		clt_path = alloc_path(clt, &paths[i], nr_cpu_ids,
+				  nr_poll_queues);
+		if (IS_ERR(clt_path)) {
+			err = PTR_ERR(clt_path);
+			goto close_all_path;
+		}
+		if (!i)
+			clt_path->for_new_clt = 1;
+		list_add_tail_rcu(&clt_path->s.entry, &clt->paths_list);
+
+		err = init_path(clt_path);
+		if (err) {
+			list_del_rcu(&clt_path->s.entry);
+			rtrs_clt_close_conns(clt_path, true);
+			free_percpu(clt_path->stats->pcpu_stats);
+			kfree(clt_path->stats);
+			free_path(clt_path);
+			goto close_all_path;
+		}
+
+		err = rtrs_clt_create_path_files(clt_path);
+		if (err) {
+			list_del_rcu(&clt_path->s.entry);
+			rtrs_clt_close_conns(clt_path, true);
+			free_percpu(clt_path->stats->pcpu_stats);
+			kfree(clt_path->stats);
+			free_path(clt_path);
+			goto close_all_path;
+		}
+	}
+	err = alloc_permits(clt);
+	if (err)
+		goto close_all_path;
+
+	return clt;
+
+close_all_path:
+	list_for_each_entry_safe(clt_path, tmp, &clt->paths_list, s.entry) {
+		rtrs_clt_destroy_path_files(clt_path, NULL);
+		rtrs_clt_close_conns(clt_path, true);
+		kobject_put(&clt_path->kobj);
+	}
+	rtrs_clt_destroy_sysfs_root(clt);
+	free_clt(clt);
+
+out:
+	return ERR_PTR(err);
+}
+EXPORT_SYMBOL(rtrs_clt_open);
+
+/**
+ * rtrs_clt_close() - Close a path
+ * @clt: Session handle. Session is freed upon return.
+ */
+void rtrs_clt_close(struct rtrs_clt_sess *clt)
+{
+	struct rtrs_clt_path *clt_path, *tmp;
+
+	/* Firstly forbid sysfs access */
+	rtrs_clt_destroy_sysfs_root(clt);
+
+	/* Now it is safe to iterate over all paths without locks */
+	list_for_each_entry_safe(clt_path, tmp, &clt->paths_list, s.entry) {
+		rtrs_clt_close_conns(clt_path, true);
+		rtrs_clt_destroy_path_files(clt_path, NULL);
+		kobject_put(&clt_path->kobj);
+	}
+	free_permits(clt);
+	free_clt(clt);
+}
+EXPORT_SYMBOL(rtrs_clt_close);
+
+int rtrs_clt_reconnect_from_sysfs(struct rtrs_clt_path *clt_path)
+{
+	enum rtrs_clt_state old_state;
+	int err = -EBUSY;
+	bool changed;
+
+	changed = rtrs_clt_change_state_get_old(clt_path,
+						 RTRS_CLT_RECONNECTING,
+						 &old_state);
+	if (changed) {
+		clt_path->reconnect_attempts = 0;
+		rtrs_clt_stop_and_destroy_conns(clt_path);
+		queue_delayed_work(rtrs_wq, &clt_path->reconnect_dwork, 0);
+	}
+	if (changed || old_state == RTRS_CLT_RECONNECTING) {
+		/*
+		 * flush_delayed_work() queues pending work for immediate
+		 * execution, so do the flush if we have queued something
+		 * right now or work is pending.
+		 */
+		flush_delayed_work(&clt_path->reconnect_dwork);
+		err = (READ_ONCE(clt_path->state) ==
+		       RTRS_CLT_CONNECTED ? 0 : -ENOTCONN);
+	}
+
+	return err;
+}
+
+int rtrs_clt_remove_path_from_sysfs(struct rtrs_clt_path *clt_path,
+				     const struct attribute *sysfs_self)
+{
+	enum rtrs_clt_state old_state;
+	bool changed;
+
+	/*
+	 * Continue stopping path till state was changed to DEAD or
+	 * state was observed as DEAD:
+	 * 1. State was changed to DEAD - we were fast and nobody
+	 *    invoked rtrs_clt_reconnect(), which can again start
+	 *    reconnecting.
+	 * 2. State was observed as DEAD - we have someone in parallel
+	 *    removing the path.
+	 */
+	do {
+		rtrs_clt_close_conns(clt_path, true);
+		changed = rtrs_clt_change_state_get_old(clt_path,
+							RTRS_CLT_DEAD,
+							&old_state);
+	} while (!changed && old_state != RTRS_CLT_DEAD);
+
+	if (changed) {
+		rtrs_clt_remove_path_from_arr(clt_path);
+		rtrs_clt_destroy_path_files(clt_path, sysfs_self);
+		kobject_put(&clt_path->kobj);
+	}
+
+	return 0;
+}
+
+void rtrs_clt_set_max_reconnect_attempts(struct rtrs_clt_sess *clt, int value)
+{
+	clt->max_reconnect_attempts = (unsigned int)value;
+}
+
+int rtrs_clt_get_max_reconnect_attempts(const struct rtrs_clt_sess *clt)
+{
+	return (int)clt->max_reconnect_attempts;
+}
+
+/**
+ * rtrs_clt_request() - Request data transfer to/from server via RDMA.
+ *
+ * @dir:	READ/WRITE
+ * @ops:	callback function to be called as confirmation, and the pointer.
+ * @clt:	Session
+ * @permit:	Preallocated permit
+ * @vec:	Message that is sent to server together with the request.
+ *		Sum of len of all @vec elements limited to <= IO_MSG_SIZE.
+ *		Since the msg is copied internally it can be allocated on stack.
+ * @nr:		Number of elements in @vec.
+ * @data_len:	length of data sent to/from server
+ * @sg:		Pages to be sent/received to/from server.
+ * @sg_cnt:	Number of elements in the @sg
+ *
+ * Return:
+ * 0:		Success
+ * <0:		Error
+ *
+ * On dir=READ rtrs client will request a data transfer from Server to client.
+ * The data that the server will respond with will be stored in @sg when
+ * the user receives an %RTRS_CLT_RDMA_EV_RDMA_REQUEST_WRITE_COMPL event.
+ * On dir=WRITE rtrs client will rdma write data in sg to server side.
+ */
+int rtrs_clt_request(int dir, struct rtrs_clt_req_ops *ops,
+		     struct rtrs_clt_sess *clt, struct rtrs_permit *permit,
+		     const struct kvec *vec, size_t nr, size_t data_len,
+		     struct scatterlist *sg, unsigned int sg_cnt)
+{
+	struct rtrs_clt_io_req *req;
+	struct rtrs_clt_path *clt_path;
+
+	enum dma_data_direction dma_dir;
+	int err = -ECONNABORTED, i;
+	size_t usr_len, hdr_len;
+	struct path_it it;
+
+	/* Get kvec length */
+	for (i = 0, usr_len = 0; i < nr; i++)
+		usr_len += vec[i].iov_len;
+
+	if (dir == READ) {
+		hdr_len = sizeof(struct rtrs_msg_rdma_read) +
+			  sg_cnt * sizeof(struct rtrs_sg_desc);
+		dma_dir = DMA_FROM_DEVICE;
+	} else {
+		hdr_len = sizeof(struct rtrs_msg_rdma_write);
+		dma_dir = DMA_TO_DEVICE;
+	}
+
+	rcu_read_lock();
+	for (path_it_init(&it, clt);
+	     (clt_path = it.next_path(&it)) && it.i < it.clt->paths_num; it.i++) {
+		if (READ_ONCE(clt_path->state) != RTRS_CLT_CONNECTED)
+			continue;
+
+		if (usr_len + hdr_len > clt_path->max_hdr_size) {
+			rtrs_wrn_rl(clt_path->clt,
+				     "%s request failed, user message size is %zu and header length %zu, but max size is %u\n",
+				     dir == READ ? "Read" : "Write",
+				     usr_len, hdr_len, clt_path->max_hdr_size);
+			err = -EMSGSIZE;
+			break;
+		}
+		req = rtrs_clt_get_req(clt_path, ops->conf_fn, permit, ops->priv,
+				       vec, usr_len, sg, sg_cnt, data_len,
+				       dma_dir);
+		if (dir == READ)
+			err = rtrs_clt_read_req(req);
+		else
+			err = rtrs_clt_write_req(req);
+		if (err) {
+			req->in_use = false;
+			continue;
+		}
+		/* Success path */
+		break;
+	}
+	path_it_deinit(&it);
+	rcu_read_unlock();
+
+	return err;
+}
+EXPORT_SYMBOL(rtrs_clt_request);
+
+int rtrs_clt_rdma_cq_direct(struct rtrs_clt_sess *clt, unsigned int index)
+{
+	/* If no path, return -1 for block layer not to try again */
+	int cnt = -1;
+	struct rtrs_con *con;
+	struct rtrs_clt_path *clt_path;
+	struct path_it it;
+
+	rcu_read_lock();
+	for (path_it_init(&it, clt);
+	     (clt_path = it.next_path(&it)) && it.i < it.clt->paths_num; it.i++) {
+		if (READ_ONCE(clt_path->state) != RTRS_CLT_CONNECTED)
+			continue;
+
+		con = clt_path->s.con[index + 1];
+		cnt = ib_process_cq_direct(con->cq, -1);
+		if (cnt)
+			break;
+	}
+	path_it_deinit(&it);
+	rcu_read_unlock();
+
+	return cnt;
+}
+EXPORT_SYMBOL(rtrs_clt_rdma_cq_direct);
+
+/**
+ * rtrs_clt_query() - queries RTRS session attributes
+ *@clt: session pointer
+ *@attr: query results for session attributes.
+ * Returns:
+ *    0 on success
+ *    -ECOMM		no connection to the server
+ */
+int rtrs_clt_query(struct rtrs_clt_sess *clt, struct rtrs_attrs *attr)
+{
+	if (!rtrs_clt_is_connected(clt))
+		return -ECOMM;
+
+	attr->queue_depth      = clt->queue_depth;
+	attr->max_segments     = clt->max_segments;
+	/* Cap max_io_size to min of remote buffer size and the fr pages */
+	attr->max_io_size = min_t(int, clt->max_io_size,
+				  clt->max_segments * SZ_4K);
+
+	return 0;
+}
+EXPORT_SYMBOL(rtrs_clt_query);
+
+int rtrs_clt_create_path_from_sysfs(struct rtrs_clt_sess *clt,
+				     struct rtrs_addr *addr)
+{
+	struct rtrs_clt_path *clt_path;
+	int err;
+
+	clt_path = alloc_path(clt, addr, nr_cpu_ids, 0);
+	if (IS_ERR(clt_path))
+		return PTR_ERR(clt_path);
+
+	mutex_lock(&clt->paths_mutex);
+	if (clt->paths_num == 0) {
+		/*
+		 * When all the paths are removed for a session,
+		 * the addition of the first path is like a new session for
+		 * the storage server
+		 */
+		clt_path->for_new_clt = 1;
+	}
+
+	mutex_unlock(&clt->paths_mutex);
+
+	/*
+	 * It is totally safe to add path in CONNECTING state: coming
+	 * IO will never grab it.  Also it is very important to add
+	 * path before init, since init fires LINK_CONNECTED event.
+	 */
+	rtrs_clt_add_path_to_arr(clt_path);
+
+	err = init_path(clt_path);
+	if (err)
+		goto close_path;
+
+	err = rtrs_clt_create_path_files(clt_path);
+	if (err)
+		goto close_path;
+
+	return 0;
+
+close_path:
+	rtrs_clt_remove_path_from_arr(clt_path);
+	rtrs_clt_close_conns(clt_path, true);
+	free_percpu(clt_path->stats->pcpu_stats);
+	kfree(clt_path->stats);
+	free_path(clt_path);
+
+	return err;
+}
+
+static int rtrs_clt_ib_dev_init(struct rtrs_ib_dev *dev)
+{
+	if (!(dev->ib_dev->attrs.device_cap_flags &
+	      IB_DEVICE_MEM_MGT_EXTENSIONS)) {
+		pr_err("Memory registrations not supported.\n");
+		return -ENOTSUPP;
+	}
+
+	return 0;
+}
+
+static const struct rtrs_rdma_dev_pd_ops dev_pd_ops = {
+	.init = rtrs_clt_ib_dev_init
+};
+
+static int __init rtrs_client_init(void)
+{
+	rtrs_rdma_dev_pd_init(0, &dev_pd);
+
+	rtrs_clt_dev_class = class_create(THIS_MODULE, "rtrs-client");
+	if (IS_ERR(rtrs_clt_dev_class)) {
+		pr_err("Failed to create rtrs-client dev class\n");
+		return PTR_ERR(rtrs_clt_dev_class);
+	}
+	rtrs_wq = alloc_workqueue("rtrs_client_wq", 0, 0);
+	if (!rtrs_wq) {
+		class_destroy(rtrs_clt_dev_class);
+		return -ENOMEM;
+	}
+
+	return 0;
+}
+
+static void __exit rtrs_client_exit(void)
+{
+	destroy_workqueue(rtrs_wq);
+	class_destroy(rtrs_clt_dev_class);
+	rtrs_rdma_dev_pd_deinit(&dev_pd);
+}
+
+module_init(rtrs_client_init);
+module_exit(rtrs_client_exit);