OSCL-LXR linux-6.0.1/​drivers/​infiniband/​ulp/​rtrs/​rtrs-clt.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // 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"
 
 #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)
         connected |= READ_ONCE(clt_path->state) == RTRS_CLT_CONNECTED;
     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);
 
     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 (WARN_ON(!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, READ, 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() %
                         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 * 3 + 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)
 {
     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;
 }
 
 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);
         goto destroy_cm;
     }
     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);
         goto destroy_cm;
     }
     /*
      * 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 */
         goto errr;
     }
     if (con->cm_err < 0) {
         err = con->cm_err;
         goto errr;
     }
     if (READ_ONCE(clt_path->state) != RTRS_CLT_CONNECTING) {
         /* Device removal */
         err = -ECONNABORTED;
         goto errr;
     }
 
     return 0;
 
 errr:
     stop_cm(con);
     mutex_lock(&con->con_mutex);
     destroy_con_cq_qp(con);
     mutex_unlock(&con->con_mutex);
 destroy_cm:
     destroy_cm(con);
 
     return err;
 }
 
 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 inline bool xchg_paths(struct rtrs_clt_path __rcu **rcu_ppcpu_path,
                   struct rtrs_clt_path *clt_path,
                   struct rtrs_clt_path *next)
 {
     struct rtrs_clt_path **ppcpu_path;
 
     /* Call cmpxchg() without sparse warnings */
     ppcpu_path = (typeof(ppcpu_path))rcu_ppcpu_path;
     return clt_path == cmpxchg(ppcpu_path, clt_path, next);
 }
 
 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 (xchg_paths(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;
 
     /*
      * 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) {
             destroy_con(to_clt_con(clt_path->s.con[cid]));
             goto destroy;
         }
     }
     err = alloc_path_reqs(clt_path);
     if (err)
         goto destroy;
 
     rtrs_start_hb(&clt_path->s);
 
     return 0;
 
 destroy:
     while (cid--) {
         struct rtrs_clt_con *con = to_clt_con(clt_path->s.con[cid]);
 
         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);
 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;
 
     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);