Re: [PATCH 05/24] ibtrs: client: main functionality

[Sagi Grimberg <sagi@grimberg.me>]

Hi Roman,

> +static inline void ibtrs_clt_state_lock(void)
> +{
> +	rcu_read_lock();
> +}
> +
> +static inline void ibtrs_clt_state_unlock(void)
> +{
> +	rcu_read_unlock();
> +}

This looks rather pointless...

> +
> +#define cmpxchg_min(var, new) ({					\
> +	typeof(var) old;						\
> +									\
> +	do {								\
> +		old = var;						\
> +		new = (!old ? new : min_t(typeof(var), old, new));	\
> +	} while (cmpxchg(&var, old, new) != old);			\
> +})

Why is this sort of thing local to your driver?

> +/**
> + * struct ibtrs_fr_pool - pool of fast registration descriptors
> + *
> + * An entry is available for allocation if and only if it occurs in @free_list.
> + *
> + * @size:      Number of descriptors in this pool.
> + * @max_page_list_len: Maximum fast registration work request page list length.
> + * @lock:      Protects free_list.
> + * @free_list: List of free descriptors.
> + * @desc:      Fast registration descriptor pool.
> + */
> +struct ibtrs_fr_pool {
> +	int			size;
> +	int			max_page_list_len;
> +	spinlock_t		lock; /* protects free_list */
> +	struct list_head	free_list;
> +	struct ibtrs_fr_desc	desc[0];
> +};

We already have a per-qp fr list implementation, any specific reason to
implement it again?

> +static inline struct ibtrs_tag *
> +__ibtrs_get_tag(struct ibtrs_clt *clt, enum ibtrs_clt_con_type con_type)
> +{
> +	size_t max_depth = clt->queue_depth;
> +	struct ibtrs_tag *tag;
> +	int cpu, bit;
> +
> +	cpu = get_cpu();
> +	do {
> +		bit = find_first_zero_bit(clt->tags_map, max_depth);
> +		if (unlikely(bit >= max_depth)) {
> +			put_cpu();
> +			return NULL;
> +		}
> +
> +	} while (unlikely(test_and_set_bit_lock(bit, clt->tags_map)));
> +	put_cpu();
> +
> +	tag = GET_TAG(clt, bit);
> +	WARN_ON(tag->mem_id != bit);
> +	tag->cpu_id = cpu;
> +	tag->con_type = con_type;
> +
> +	return tag;
> +}
> +
> +static inline void __ibtrs_put_tag(struct ibtrs_clt *clt,
> +				   struct ibtrs_tag *tag)
> +{
> +	clear_bit_unlock(tag->mem_id, clt->tags_map);
> +}
> +
> +struct ibtrs_tag *ibtrs_clt_get_tag(struct ibtrs_clt *clt,
> +				    enum ibtrs_clt_con_type con_type,
> +				    int can_wait)
> +{
> +	struct ibtrs_tag *tag;
> +	DEFINE_WAIT(wait);
> +
> +	tag = __ibtrs_get_tag(clt, con_type);
> +	if (likely(tag) || !can_wait)
> +		return tag;
> +
> +	do {
> +		prepare_to_wait(&clt->tags_wait, &wait, TASK_UNINTERRUPTIBLE);
> +		tag = __ibtrs_get_tag(clt, con_type);
> +		if (likely(tag))
> +			break;
> +
> +		io_schedule();
> +	} while (1);
> +
> +	finish_wait(&clt->tags_wait, &wait);
> +
> +	return tag;
> +}
> +EXPORT_SYMBOL(ibtrs_clt_get_tag);
> +
> +void ibtrs_clt_put_tag(struct ibtrs_clt *clt, struct ibtrs_tag *tag)
> +{
> +	if (WARN_ON(!test_bit(tag->mem_id, clt->tags_map)))
> +		return;
> +
> +	__ibtrs_put_tag(clt, tag);
> +
> +	/*
> +	 * Putting a tag is a barrier, so we will observe
> +	 * new entry in the wait list, no worries.
> +	 */
> +	if (waitqueue_active(&clt->tags_wait))
> +		wake_up(&clt->tags_wait);
> +}
> +EXPORT_SYMBOL(ibtrs_clt_put_tag);

Again, the tags are not clear why they are needed...

> +/**
> + * ibtrs_destroy_fr_pool() - free the resources owned by a pool
> + * @pool: Fast registration pool to be destroyed.
> + */
> +static void ibtrs_destroy_fr_pool(struct ibtrs_fr_pool *pool)
> +{
> +	struct ibtrs_fr_desc *d;
> +	int i, err;
> +
> +	if (!pool)
> +		return;
> +
> +	for (i = 0, d = &pool->desc[0]; i < pool->size; i++, d++) {
> +		if (d->mr) {
> +			err = ib_dereg_mr(d->mr);
> +			if (err)
> +				pr_err("Failed to deregister memory region,"
> +				       " err: %d\n", err);
> +		}
> +	}
> +	kfree(pool);
> +}
> +
> +/**
> + * ibtrs_create_fr_pool() - allocate and initialize a pool for fast registration
> + * @device:            IB device to allocate fast registration descriptors for.
> + * @pd:                Protection domain associated with the FR descriptors.
> + * @pool_size:         Number of descriptors to allocate.
> + * @max_page_list_len: Maximum fast registration work request page list length.
> + */
> +static struct ibtrs_fr_pool *ibtrs_create_fr_pool(struct ib_device *device,
> +						  struct ib_pd *pd,
> +						  int pool_size,
> +						  int max_page_list_len)
> +{
> +	struct ibtrs_fr_pool *pool;
> +	struct ibtrs_fr_desc *d;
> +	struct ib_mr *mr;
> +	int i, ret;
> +
> +	if (pool_size <= 0) {
> +		pr_warn("Creating fr pool failed, invalid pool size %d\n",
> +			pool_size);
> +		ret = -EINVAL;
> +		goto err;
> +	}
> +
> +	pool = kzalloc(sizeof(*pool) + pool_size * sizeof(*d), GFP_KERNEL);
> +	if (!pool) {
> +		ret = -ENOMEM;
> +		goto err;
> +	}
> +
> +	pool->size = pool_size;
> +	pool->max_page_list_len = max_page_list_len;
> +	spin_lock_init(&pool->lock);
> +	INIT_LIST_HEAD(&pool->free_list);
> +
> +	for (i = 0, d = &pool->desc[0]; i < pool->size; i++, d++) {
> +		mr = ib_alloc_mr(pd, IB_MR_TYPE_MEM_REG, max_page_list_len);
> +		if (IS_ERR(mr)) {
> +			pr_warn("Failed to allocate fast region memory\n");
> +			ret = PTR_ERR(mr);
> +			goto destroy_pool;
> +		}
> +		d->mr = mr;
> +		list_add_tail(&d->entry, &pool->free_list);
> +	}
> +
> +	return pool;
> +
> +destroy_pool:
> +	ibtrs_destroy_fr_pool(pool);
> +err:
> +	return ERR_PTR(ret);
> +}
> +
> +/**
> + * ibtrs_fr_pool_get() - obtain a descriptor suitable for fast registration
> + * @pool: Pool to obtain descriptor from.
> + */
> +static struct ibtrs_fr_desc *ibtrs_fr_pool_get(struct ibtrs_fr_pool *pool)
> +{
> +	struct ibtrs_fr_desc *d = NULL;
> +
> +	spin_lock_bh(&pool->lock);
> +	if (!list_empty(&pool->free_list)) {
> +		d = list_first_entry(&pool->free_list, typeof(*d), entry);
> +		list_del(&d->entry);
> +	}
> +	spin_unlock_bh(&pool->lock);
> +
> +	return d;
> +}
> +
> +/**
> + * ibtrs_fr_pool_put() - put an FR descriptor back in the free list
> + * @pool: Pool the descriptor was allocated from.
> + * @desc: Pointer to an array of fast registration descriptor pointers.
> + * @n:    Number of descriptors to put back.
> + *
> + * Note: The caller must already have queued an invalidation request for
> + * desc->mr->rkey before calling this function.
> + */
> +static void ibtrs_fr_pool_put(struct ibtrs_fr_pool *pool,
> +			      struct ibtrs_fr_desc **desc, int n)
> +{
> +	int i;
> +
> +	spin_lock_bh(&pool->lock);
> +	for (i = 0; i < n; i++)
> +		list_add(&desc[i]->entry, &pool->free_list);
> +	spin_unlock_bh(&pool->lock);
> +}
> +
> +static void ibtrs_map_desc(struct ibtrs_map_state *state, dma_addr_t dma_addr,
> +			   u32 dma_len, u32 rkey, u32 max_desc)
> +{
> +	struct ibtrs_sg_desc *desc = state->desc;
> +
> +	pr_debug("dma_addr %llu, key %u, dma_len %u\n",
> +		 dma_addr, rkey, dma_len);
> +	desc->addr = cpu_to_le64(dma_addr);
> +	desc->key  = cpu_to_le32(rkey);
> +	desc->len  = cpu_to_le32(dma_len);
> +
> +	state->total_len += dma_len;
> +	if (state->ndesc < max_desc) {
> +		state->desc++;
> +		state->ndesc++;
> +	} else {
> +		state->ndesc = INT_MIN;
> +		pr_err("Could not fit S/G list into buffer descriptor %d.\n",
> +		       max_desc);
> +	}
> +}
> +
> +static int ibtrs_map_finish_fmr(struct ibtrs_map_state *state,
> +				struct ibtrs_clt_con *con)
> +{
> +	struct ibtrs_clt_sess *sess = to_clt_sess(con->c.sess);
> +	struct ib_pool_fmr *fmr;
> +	dma_addr_t dma_addr;
> +	u64 io_addr = 0;
> +
> +	fmr = ib_fmr_pool_map_phys(sess->fmr_pool, state->pages,
> +				   state->npages, io_addr);
> +	if (IS_ERR(fmr)) {
> +		ibtrs_wrn_rl(sess, "Failed to map FMR from FMR pool, "
> +			     "err: %ld\n", PTR_ERR(fmr));
> +		return PTR_ERR(fmr);
> +	}
> +
> +	*state->next_fmr++ = fmr;
> +	state->nmdesc++;
> +	dma_addr = state->base_dma_addr & ~sess->mr_page_mask;
> +	pr_debug("ndesc = %d, nmdesc = %d, npages = %d\n",
> +		 state->ndesc, state->nmdesc, state->npages);
> +	if (state->dir == DMA_TO_DEVICE)
> +		ibtrs_map_desc(state, dma_addr, state->dma_len, fmr->fmr->lkey,
> +			       sess->max_desc);
> +	else
> +		ibtrs_map_desc(state, dma_addr, state->dma_len, fmr->fmr->rkey,
> +			       sess->max_desc);
> +
> +	return 0;
> +}
> +
> +static void ibtrs_clt_fast_reg_done(struct ib_cq *cq, struct ib_wc *wc)
> +{
> +	struct ibtrs_clt_con *con = cq->cq_context;
> +	struct ibtrs_clt_sess *sess = to_clt_sess(con->c.sess);
> +
> +	if (unlikely(wc->status != IB_WC_SUCCESS)) {
> +		ibtrs_err(sess, "Failed IB_WR_REG_MR: %s\n",
> +			  ib_wc_status_msg(wc->status));
> +		ibtrs_rdma_error_recovery(con);
> +	}
> +}
> +
> +static struct ib_cqe fast_reg_cqe = {
> +	.done = ibtrs_clt_fast_reg_done
> +};
> +
> +/* TODO */
> +static int ibtrs_map_finish_fr(struct ibtrs_map_state *state,
> +			       struct ibtrs_clt_con *con, int sg_cnt,
> +			       unsigned int *sg_offset_p)
> +{
> +	struct ibtrs_clt_sess *sess = to_clt_sess(con->c.sess);
> +	struct ibtrs_fr_desc *desc;
> +	struct ib_send_wr *bad_wr;
> +	struct ib_reg_wr wr;
> +	struct ib_pd *pd;
> +	u32 rkey;
> +	int n;
> +
> +	pd = sess->s.ib_dev->pd;
> +	if (sg_cnt == 1 && (pd->flags & IB_PD_UNSAFE_GLOBAL_RKEY)) {
> +		unsigned int sg_offset = sg_offset_p ? *sg_offset_p : 0;
> +
> +		ibtrs_map_desc(state, sg_dma_address(state->sg) + sg_offset,
> +			       sg_dma_len(state->sg) - sg_offset,
> +			       pd->unsafe_global_rkey, sess->max_desc);
> +		if (sg_offset_p)
> +			*sg_offset_p = 0;
> +		return 1;
> +	}
> +
> +	desc = ibtrs_fr_pool_get(con->fr_pool);
> +	if (!desc) {
> +		ibtrs_wrn_rl(sess, "Failed to get descriptor from FR pool\n");
> +		return -ENOMEM;
> +	}
> +
> +	rkey = ib_inc_rkey(desc->mr->rkey);
> +	ib_update_fast_reg_key(desc->mr, rkey);
> +
> +	memset(&wr, 0, sizeof(wr));
> +	n = ib_map_mr_sg(desc->mr, state->sg, sg_cnt, sg_offset_p,
> +			 sess->mr_page_size);
> +	if (unlikely(n < 0)) {
> +		ibtrs_fr_pool_put(con->fr_pool, &desc, 1);
> +		return n;
> +	}
> +
> +	wr.wr.next = NULL;
> +	wr.wr.opcode = IB_WR_REG_MR;
> +	wr.wr.wr_cqe = &fast_reg_cqe;
> +	wr.wr.num_sge = 0;
> +	wr.wr.send_flags = 0;
> +	wr.mr = desc->mr;
> +	wr.key = desc->mr->rkey;
> +	wr.access = (IB_ACCESS_LOCAL_WRITE | IB_ACCESS_REMOTE_WRITE);

Do you actually ever have remote write access in your protocol?

> +static void ibtrs_clt_inv_rkey_done(struct ib_cq *cq, struct ib_wc *wc)
> +{
> +	struct ibtrs_clt_con *con = cq->cq_context;
> +	struct ibtrs_clt_sess *sess = to_clt_sess(con->c.sess);
> +
> +	if (unlikely(wc->status != IB_WC_SUCCESS)) {
> +		ibtrs_err(sess, "Failed IB_WR_LOCAL_INV: %s\n",
> +			  ib_wc_status_msg(wc->status));
> +		ibtrs_rdma_error_recovery(con);
> +	}
> +}
> +
> +static struct ib_cqe local_inv_cqe = {
> +	.done = ibtrs_clt_inv_rkey_done
> +};
> +
> +static int ibtrs_inv_rkey(struct ibtrs_clt_con *con, u32 rkey)
> +{
> +	struct ib_send_wr *bad_wr;
> +	struct ib_send_wr wr = {
> +		.opcode		    = IB_WR_LOCAL_INV,
> +		.wr_cqe		    = &local_inv_cqe,
> +		.next		    = NULL,
> +		.num_sge	    = 0,
> +		.send_flags	    = 0,
> +		.ex.invalidate_rkey = rkey,
> +	};
> +
> +	return ib_post_send(con->c.qp, &wr, &bad_wr);
> +}

Is not signalling the local invalidate safe? A recent report
suggested that this is not safe in the presence of ack drops.

> +static int ibtrs_post_send_rdma(struct ibtrs_clt_con *con,
> +				struct ibtrs_clt_io_req *req,
> +				u64 addr, u32 off, u32 imm)
> +{
> +	struct ibtrs_clt_sess *sess = to_clt_sess(con->c.sess);
> +	enum ib_send_flags flags;
> +	struct ib_sge list[1];
> +
> +	if (unlikely(!req->sg_size)) {
> +		ibtrs_wrn(sess, "Doing RDMA Write failed, no data supplied\n");
> +		return -EINVAL;
> +	}
> +
> +	/* user data and user message in the first list element */
> +	list[0].addr   = req->iu->dma_addr;
> +	list[0].length = req->sg_size;
> +	list[0].lkey   = sess->s.ib_dev->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->io_cnt) % sess->queue_depth ?
> +			0 : IB_SEND_SIGNALED;
> +	return ibtrs_iu_post_rdma_write_imm(&con->c, req->iu, list, 1,
> +					    sess->srv_rdma_buf_rkey,
> +					    addr + off, imm, flags);
> +}
> +
> +static void ibtrs_set_sge_with_desc(struct ib_sge *list,
> +				    struct ibtrs_sg_desc *desc)
> +{
> +	list->addr   = le64_to_cpu(desc->addr);
> +	list->length = le32_to_cpu(desc->len);
> +	list->lkey   = le32_to_cpu(desc->key);
> +	pr_debug("dma_addr %llu, key %u, dma_len %u\n",
> +		 list->addr, list->lkey, list->length);
> +}
> +
> +static void ibtrs_set_rdma_desc_last(struct ibtrs_clt_con *con,
> +				     struct ib_sge *list,
> +				     struct ibtrs_clt_io_req *req,
> +				     struct ib_rdma_wr *wr, int offset,
> +				     struct ibtrs_sg_desc *desc, int m,
> +				     int n, u64 addr, u32 size, u32 imm)
> +{
> +	struct ibtrs_clt_sess *sess = to_clt_sess(con->c.sess);
> +	enum ib_send_flags flags;
> +	int i;
> +
> +	for (i = m; i < n; i++, desc++)
> +		ibtrs_set_sge_with_desc(&list[i], desc);
> +
> +	list[i].addr   = req->iu->dma_addr;
> +	list[i].length = size;
> +	list[i].lkey   = sess->s.ib_dev->lkey;
> +
> +	wr->wr.wr_cqe = &req->iu->cqe;
> +	wr->wr.sg_list = &list[m];
> +	wr->wr.num_sge = n - m + 1;
> +	wr->remote_addr	= addr + offset;
> +	wr->rkey = sess->srv_rdma_buf_rkey;
> +
> +	/*
> +	 * 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->io_cnt) % sess->queue_depth ?
> +			0 : IB_SEND_SIGNALED;
> +
> +	wr->wr.opcode = IB_WR_RDMA_WRITE_WITH_IMM;
> +	wr->wr.send_flags  = flags;
> +	wr->wr.ex.imm_data = cpu_to_be32(imm);
> +}
> +
> +static int ibtrs_post_send_rdma_desc_more(struct ibtrs_clt_con *con,
> +					  struct ib_sge *list,
> +					  struct ibtrs_clt_io_req *req,
> +					  struct ibtrs_sg_desc *desc, int n,
> +					  u64 addr, u32 size, u32 imm)
> +{
> +	struct ibtrs_clt_sess *sess = to_clt_sess(con->c.sess);
> +	size_t max_sge, num_sge, num_wr;
> +	struct ib_send_wr *bad_wr;
> +	struct ib_rdma_wr *wrs, *wr;
> +	int j = 0, k, offset = 0, len = 0;
> +	int m = 0;
> +	int ret;
> +
> +	max_sge = sess->max_sge;
> +	num_sge = 1 + n;
> +	num_wr = DIV_ROUND_UP(num_sge, max_sge);
> +
> +	wrs = kcalloc(num_wr, sizeof(*wrs), GFP_ATOMIC);
> +	if (!wrs)
> +		return -ENOMEM;
> +
> +	if (num_wr == 1)
> +		goto last_one;
> +
> +	for (; j < num_wr; j++) {
> +		wr = &wrs[j];
> +		for (k = 0; k < max_sge; k++, desc++) {
> +			m = k + j * max_sge;
> +			ibtrs_set_sge_with_desc(&list[m], desc);
> +			len += le32_to_cpu(desc->len);
> +		}
> +		wr->wr.wr_cqe = &req->iu->cqe;
> +		wr->wr.sg_list = &list[m];
> +		wr->wr.num_sge = max_sge;
> +		wr->remote_addr	= addr + offset;
> +		wr->rkey = sess->srv_rdma_buf_rkey;
> +
> +		offset += len;
> +		wr->wr.next = &wrs[j + 1].wr;
> +		wr->wr.opcode = IB_WR_RDMA_WRITE;
> +	}
> +
> +last_one:
> +	wr = &wrs[j];
> +
> +	ibtrs_set_rdma_desc_last(con, list, req, wr, offset,
> +				 desc, m, n, addr, size, imm);
> +
> +	ret = ib_post_send(con->c.qp, &wrs[0].wr, &bad_wr);
> +	if (unlikely(ret))
> +		ibtrs_err(sess, "Posting write request to QP failed,"
> +			  " err: %d\n", ret);
> +	kfree(wrs);
> +	return ret;
> +}
> +
> +static int ibtrs_post_send_rdma_desc(struct ibtrs_clt_con *con,
> +				     struct ibtrs_clt_io_req *req,
> +				     struct ibtrs_sg_desc *desc, int n,
> +				     u64 addr, u32 size, u32 imm)
> +{
> +	struct ibtrs_clt_sess *sess = to_clt_sess(con->c.sess);
> +	enum ib_send_flags flags;
> +	struct ib_sge *list;
> +	size_t num_sge;
> +	int ret, i;
> +
> +	num_sge = 1 + n;
> +	list = kmalloc_array(num_sge, sizeof(*list), GFP_ATOMIC);
> +	if (!list)
> +		return -ENOMEM;
> +
> +	if (num_sge < sess->max_sge) {
> +		for (i = 0; i < n; i++, desc++)
> +			ibtrs_set_sge_with_desc(&list[i], desc);
> +		list[i].addr   = req->iu->dma_addr;
> +		list[i].length = size;
> +		list[i].lkey   = sess->s.ib_dev->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->io_cnt) % sess->queue_depth ?
> +				0 : IB_SEND_SIGNALED;
> +		ret = ibtrs_iu_post_rdma_write_imm(&con->c, req->iu, list,
> +						   num_sge,
> +						   sess->srv_rdma_buf_rkey,
> +						   addr, imm, flags);
> +	} else {
> +		ret = ibtrs_post_send_rdma_desc_more(con, list, req, desc, n,
> +						     addr, size, imm);
> +	}
> +
> +	kfree(list);
> +	return ret;
> +}
> +
> +static int ibtrs_post_send_rdma_more(struct ibtrs_clt_con *con,
> +				     struct ibtrs_clt_io_req *req,
> +				     u64 addr, u32 size, u32 imm)
> +{
> +	struct ibtrs_clt_sess *sess = to_clt_sess(con->c.sess);
> +	struct ib_device *ibdev = sess->s.ib_dev->dev;
> +	enum ib_send_flags flags;
> +	struct scatterlist *sg;
> +	struct ib_sge *list;
> +	size_t num_sge;
> +	int i, ret;
> +
> +	num_sge = 1 + req->sg_cnt;
> +	list = kmalloc_array(num_sge, sizeof(*list), GFP_ATOMIC);
> +	if (!list)
> +		return -ENOMEM;
> +
> +	for_each_sg(req->sglist, sg, req->sg_cnt, i) {
> +		list[i].addr   = ib_sg_dma_address(ibdev, sg);
> +		list[i].length = ib_sg_dma_len(ibdev, sg);
> +		list[i].lkey   = sess->s.ib_dev->lkey;
> +	}
> +	list[i].addr   = req->iu->dma_addr;
> +	list[i].length = size;
> +	list[i].lkey   = sess->s.ib_dev->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->io_cnt) % sess->queue_depth ?
> +			0 : IB_SEND_SIGNALED;
> +	ret = ibtrs_iu_post_rdma_write_imm(&con->c, req->iu, list, num_sge,
> +					   sess->srv_rdma_buf_rkey,
> +					   addr, imm, flags);
> +	kfree(list);
> +
> +	return ret;
> +}

All these rdma halpers looks like that can be reused from the rdma rw
API if it was enhanced with immediate capabilities.

> +static inline unsigned long ibtrs_clt_get_raw_ms(void)
> +{
> +	struct timespec ts;
> +
> +	getrawmonotonic(&ts);
> +
> +	return timespec_to_ns(&ts) / NSEC_PER_MSEC;
> +}

Why is this local to your driver?

> +
> +static void complete_rdma_req(struct ibtrs_clt_io_req *req,
> +			      int errno, bool notify)
> +{
> +	struct ibtrs_clt_con *con = req->con;
> +	struct ibtrs_clt_sess *sess;
> +	enum dma_data_direction dir;
> +	struct ibtrs_clt *clt;
> +	void *priv;
> +
> +	if (WARN_ON(!req->in_use))
> +		return;
> +	if (WARN_ON(!req->con))
> +		return;
> +	sess = to_clt_sess(con->c.sess);
> +	clt = sess->clt;
> +
> +	if (req->sg_cnt > fmr_sg_cnt)
> +		ibtrs_unmap_fast_reg_data(req->con, req);
> +	if (req->sg_cnt)
> +		ib_dma_unmap_sg(sess->s.ib_dev->dev, req->sglist,
> +				req->sg_cnt, req->dir);
> +	if (sess->stats.enable_rdma_lat)
> +		ibtrs_clt_update_rdma_lat(&sess->stats,
> +					  req->dir == DMA_FROM_DEVICE,
> +					  ibtrs_clt_get_raw_ms() -
> +					  req->start_time);
> +	ibtrs_clt_decrease_inflight(&sess->stats);
> +
> +	req->in_use = false;
> +	req->con = NULL;
> +	priv = req->priv;
> +	dir = req->dir;
> +
> +	if (notify)
> +		req->conf(priv, errno);
> +}



> +
> +static void process_io_rsp(struct ibtrs_clt_sess *sess, u32 msg_id, s16 errno)
> +{
> +	if (WARN_ON(msg_id >= sess->queue_depth))
> +		return;
> +
> +	complete_rdma_req(&sess->reqs[msg_id], errno, true);
> +}
> +
> +static struct ib_cqe io_comp_cqe = {
> +	.done = ibtrs_clt_rdma_done
> +};
> +
> +static void ibtrs_clt_rdma_done(struct ib_cq *cq, struct ib_wc *wc)
> +{
> +	struct ibtrs_clt_con *con = cq->cq_context;
> +	struct ibtrs_clt_sess *sess = to_clt_sess(con->c.sess);
> +	u32 imm_type, imm_payload;
> +	int err;
> +
> +	if (unlikely(wc->status != IB_WC_SUCCESS)) {
> +		if (wc->status != IB_WC_WR_FLUSH_ERR) {
> +			ibtrs_err(sess, "RDMA failed: %s\n",
> +				  ib_wc_status_msg(wc->status));
> +			ibtrs_rdma_error_recovery(con);
> +		}
> +		return;
> +	}
> +	ibtrs_clt_update_wc_stats(con);
> +
> +	switch (wc->opcode) {
> +	case IB_WC_RDMA_WRITE:
> +		/*
> +		 * post_send() RDMA write completions of IO reqs (read/write)
> +		 * and hb
> +		 */
> +		break;
> +	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 != &io_comp_cqe))
> +			return;
> +		err = ibtrs_post_recv_empty(&con->c, &io_comp_cqe);
> +		if (unlikely(err)) {
> +			ibtrs_err(sess, "ibtrs_post_recv_empty(): %d\n", err);
> +			ibtrs_rdma_error_recovery(con);
> +			break;
> +		}
> +		ibtrs_from_imm(be32_to_cpu(wc->ex.imm_data),
> +			       &imm_type, &imm_payload);
> +		if (likely(imm_type == IBTRS_IO_RSP_IMM)) {
> +			u32 msg_id;
> +
> +			ibtrs_from_io_rsp_imm(imm_payload, &msg_id, &err);
> +			process_io_rsp(sess, msg_id, err);
> +		} else if (imm_type == IBTRS_HB_MSG_IMM) {
> +			WARN_ON(con->c.cid);
> +			ibtrs_send_hb_ack(&sess->s);
> +		} else if (imm_type == IBTRS_HB_ACK_IMM) {
> +			WARN_ON(con->c.cid);
> +			sess->s.hb_missed_cnt = 0;
> +		} else {
> +			ibtrs_wrn(sess, "Unknown IMM type %u\n", imm_type);
> +		}
> +		break;
> +	default:
> +		ibtrs_wrn(sess, "Unexpected WC type: %s\n",
> +			  ib_wc_opcode_str(wc->opcode));
> +		return;
> +	}

Is there a spec somewhere with the protocol information that explains
how this all works?

> +struct path_it {
> +	int i;
> +	struct list_head skip_list;
> +	struct ibtrs_clt *clt;
> +	struct ibtrs_clt_sess *(*next_path)(struct path_it *);
> +};
> +
> +#define do_each_path(path, clt, it) {					\
> +	path_it_init(it, clt);						\
> +	ibtrs_clt_state_lock();						\
> +	for ((it)->i = 0; ((path) = ((it)->next_path)(it)) &&		\
> +			  (it)->i < (it)->clt->paths_num;		\
> +	     (it)->i++)
> +
> +#define while_each_path(it)						\
> +	path_it_deinit(it);						\
> +	ibtrs_clt_state_unlock();					\
> +	}
> +
> +/**
> + * get_next_path_rr() - Returns path in round-robin fashion.
> + *
> + * Related to @MP_POLICY_RR
> + *
> + * Locks:
> + *    ibtrs_clt_state_lock() must be hold.
> + */
> +static struct ibtrs_clt_sess *get_next_path_rr(struct path_it *it)
> +{
> +	struct ibtrs_clt_sess __percpu * __rcu *ppcpu_path, *path;
> +	struct ibtrs_clt *clt = it->clt;
> +
> +	ppcpu_path = this_cpu_ptr(clt->pcpu_path);
> +	path = rcu_dereference(*ppcpu_path);
> +	if (unlikely(!path))
> +		path = list_first_or_null_rcu(&clt->paths_list,
> +					      typeof(*path), s.entry);
> +	else
> +		path = list_next_or_null_rcu_rr(path, &clt->paths_list,
> +						s.entry);
> +	rcu_assign_pointer(*ppcpu_path, path);
> +
> +	return path;
> +}
> +
> +/**
> + * get_next_path_min_inflight() - Returns path with minimal inflight count.
> + *
> + * Related to @MP_POLICY_MIN_INFLIGHT
> + *
> + * Locks:
> + *    ibtrs_clt_state_lock() must be hold.
> + */
> +static struct ibtrs_clt_sess *get_next_path_min_inflight(struct path_it *it)
> +{
> +	struct ibtrs_clt_sess *min_path = NULL;
> +	struct ibtrs_clt *clt = it->clt;
> +	struct ibtrs_clt_sess *sess;
> +	int min_inflight = INT_MAX;
> +	int inflight;
> +
> +	list_for_each_entry_rcu(sess, &clt->paths_list, s.entry) {
> +		if (unlikely(!list_empty(raw_cpu_ptr(sess->mp_skip_entry))))
> +			continue;
> +
> +		inflight = atomic_read(&sess->stats.inflight);
> +
> +		if (inflight < min_inflight) {
> +			min_inflight = inflight;
> +			min_path = sess;
> +		}
> +	}
> +
> +	/*
> +	 * 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 ibtrs_clt *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
> +		it->next_path = get_next_path_min_inflight;
> +}
> +
> +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 policy.
> +	 * 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);
> +}
> +
> +static inline void ibtrs_clt_init_req(struct ibtrs_clt_io_req *req,
> +				      struct ibtrs_clt_sess *sess,
> +				      ibtrs_conf_fn *conf,
> +				      struct ibtrs_tag *tag, void *priv,
> +				      const struct kvec *vec, size_t usr_len,
> +				      struct scatterlist *sg, size_t sg_cnt,
> +				      size_t data_len, int dir)
> +{
> +	req->tag = tag;
> +	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 = ibtrs_tag_to_clt_con(sess, tag);
> +	req->conf = conf;
> +	copy_from_kvec(req->iu->buf, vec, usr_len);
> +	if (sess->stats.enable_rdma_lat)
> +		req->start_time = ibtrs_clt_get_raw_ms();
> +}
> +
> +static inline struct ibtrs_clt_io_req *
> +ibtrs_clt_get_req(struct ibtrs_clt_sess *sess, ibtrs_conf_fn *conf,
> +		  struct ibtrs_tag *tag, void *priv,
> +		  const struct kvec *vec, size_t usr_len,
> +		  struct scatterlist *sg, size_t sg_cnt,
> +		  size_t data_len, int dir)
> +{
> +	struct ibtrs_clt_io_req *req;
> +
> +	req = &sess->reqs[tag->mem_id];
> +	ibtrs_clt_init_req(req, sess, conf, tag, priv, vec, usr_len,
> +			   sg, sg_cnt, data_len, dir);
> +	return req;
> +}
> +
> +static inline struct ibtrs_clt_io_req *
> +ibtrs_clt_get_copy_req(struct ibtrs_clt_sess *alive_sess,
> +		       struct ibtrs_clt_io_req *fail_req)
> +{
> +	struct ibtrs_clt_io_req *req;
> +	struct kvec vec = {
> +		.iov_base = fail_req->iu->buf,
> +		.iov_len  = fail_req->usr_len
> +	};
> +
> +	req = &alive_sess->reqs[fail_req->tag->mem_id];
> +	ibtrs_clt_init_req(req, alive_sess, fail_req->conf, fail_req->tag,
> +			   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 ibtrs_clt_write_req(struct ibtrs_clt_io_req *req);
> +static int ibtrs_clt_read_req(struct ibtrs_clt_io_req *req);
> +
> +static int ibtrs_clt_failover_req(struct ibtrs_clt *clt,
> +				  struct ibtrs_clt_io_req *fail_req)
> +{
> +	struct ibtrs_clt_sess *alive_sess;
> +	struct ibtrs_clt_io_req *req;
> +	int err = -ECONNABORTED;
> +	struct path_it it;
> +
> +	do_each_path(alive_sess, clt, &it) {
> +		if (unlikely(alive_sess->state != IBTRS_CLT_CONNECTED))
> +			continue;
> +		req = ibtrs_clt_get_copy_req(alive_sess, fail_req);
> +		if (req->dir == DMA_TO_DEVICE)
> +			err = ibtrs_clt_write_req(req);
> +		else
> +			err = ibtrs_clt_read_req(req);
> +		if (unlikely(err)) {
> +			req->in_use = false;
> +			continue;
> +		}
> +		/* Success path */
> +		ibtrs_clt_inc_failover_cnt(&alive_sess->stats);
> +		break;
> +	} while_each_path(&it);
> +
> +	return err;
> +}
> +
> +static void fail_all_outstanding_reqs(struct ibtrs_clt_sess *sess,
> +				      bool failover)
> +{
> +	struct ibtrs_clt *clt = sess->clt;
> +	struct ibtrs_clt_io_req *req;
> +	int i;
> +
> +	if (!sess->reqs)
> +		return;
> +	for (i = 0; i < sess->queue_depth; ++i) {
> +		bool notify;
> +		int err = 0;
> +
> +		req = &sess->reqs[i];
> +		if (!req->in_use)
> +			continue;
> +
> +		if (failover)
> +			err = ibtrs_clt_failover_req(clt, req);
> +
> +		notify = (!failover || err);
> +		complete_rdma_req(req, -ECONNABORTED, notify);
> +	}
> +}
> +
> +static void free_sess_reqs(struct ibtrs_clt_sess *sess)
> +{
> +	struct ibtrs_clt_io_req *req;
> +	int i;
> +
> +	if (!sess->reqs)
> +		return;
> +	for (i = 0; i < sess->queue_depth; ++i) {
> +		req = &sess->reqs[i];
> +		if (sess->fast_reg_mode == IBTRS_FAST_MEM_FR)
> +			kfree(req->fr_list);
> +		else if (sess->fast_reg_mode == IBTRS_FAST_MEM_FMR)
> +			kfree(req->fmr_list);
> +		kfree(req->map_page);
> +		ibtrs_iu_free(req->iu, DMA_TO_DEVICE,
> +			      sess->s.ib_dev->dev);
> +	}
> +	kfree(sess->reqs);
> +	sess->reqs = NULL;
> +}
> +
> +static int alloc_sess_reqs(struct ibtrs_clt_sess *sess)
> +{
> +	struct ibtrs_clt_io_req *req;
> +	void *mr_list;
> +	int i;
> +
> +	sess->reqs = kcalloc(sess->queue_depth, sizeof(*sess->reqs),
> +			     GFP_KERNEL);
> +	if (unlikely(!sess->reqs))
> +		return -ENOMEM;
> +
> +	for (i = 0; i < sess->queue_depth; ++i) {
> +		req = &sess->reqs[i];
> +		req->iu = ibtrs_iu_alloc(i, sess->max_req_size, GFP_KERNEL,
> +					 sess->s.ib_dev->dev, DMA_TO_DEVICE,
> +					 ibtrs_clt_rdma_done);
> +		if (unlikely(!req->iu))
> +			goto out;
> +		mr_list = kmalloc_array(sess->max_pages_per_mr,
> +					sizeof(void *), GFP_KERNEL);
> +		if (unlikely(!mr_list))
> +			goto out;
> +		if (sess->fast_reg_mode == IBTRS_FAST_MEM_FR)
> +			req->fr_list = mr_list;
> +		else if (sess->fast_reg_mode == IBTRS_FAST_MEM_FMR)
> +			req->fmr_list = mr_list;
> +
> +		req->map_page = kmalloc_array(sess->max_pages_per_mr,
> +					      sizeof(void *), GFP_KERNEL);
> +		if (unlikely(!req->map_page))
> +			goto out;
> +	}
> +
> +	return 0;
> +
> +out:
> +	free_sess_reqs(sess);
> +
> +	return -ENOMEM;
> +}
> +
> +static int alloc_tags(struct ibtrs_clt *clt)
> +{
> +	unsigned int chunk_bits;
> +	int err, i;
> +
> +	clt->tags_map = kcalloc(BITS_TO_LONGS(clt->queue_depth), sizeof(long),
> +				GFP_KERNEL);
> +	if (unlikely(!clt->tags_map)) {
> +		err = -ENOMEM;
> +		goto out_err;
> +	}
> +	clt->tags = kcalloc(clt->queue_depth, TAG_SIZE(clt), GFP_KERNEL);
> +	if (unlikely(!clt->tags)) {
> +		err = -ENOMEM;
> +		goto err_map;
> +	}
> +	chunk_bits = ilog2(clt->queue_depth - 1) + 1;
> +	for (i = 0; i < clt->queue_depth; i++) {
> +		struct ibtrs_tag *tag;
> +
> +		tag = GET_TAG(clt, i);
> +		tag->mem_id = i;
> +		tag->mem_off = i << (MAX_IMM_PAYL_BITS - chunk_bits);
> +	}
> +
> +	return 0;
> +
> +err_map:
> +	kfree(clt->tags_map);
> +	clt->tags_map = NULL;
> +out_err:
> +	return err;
> +}
> +
> +static void free_tags(struct ibtrs_clt *clt)
> +{
> +	kfree(clt->tags_map);
> +	clt->tags_map = NULL;
> +	kfree(clt->tags);
> +	clt->tags = NULL;
> +}
> +
> +static void query_fast_reg_mode(struct ibtrs_clt_sess *sess)
> +{
> +	struct ibtrs_ib_dev *ib_dev;
> +	u64 max_pages_per_mr;
> +	int mr_page_shift;
> +
> +	ib_dev = sess->s.ib_dev;
> +	if (ib_dev->dev->alloc_fmr && ib_dev->dev->dealloc_fmr &&
> +	    ib_dev->dev->map_phys_fmr && ib_dev->dev->unmap_fmr) {
> +		sess->fast_reg_mode = IBTRS_FAST_MEM_FMR;
> +		ibtrs_info(sess, "Device %s supports FMR\n", ib_dev->dev->name);
> +	}
> +	if (ib_dev->attrs.device_cap_flags & IB_DEVICE_MEM_MGT_EXTENSIONS &&
> +	    use_fr) {
> +		sess->fast_reg_mode = IBTRS_FAST_MEM_FR;
> +		ibtrs_info(sess, "Device %s supports FR\n", ib_dev->dev->name);
> +	}
> +
> +	/*
> +	 * 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);
> +	sess->mr_page_size = 1 << mr_page_shift;
> +	sess->max_sge      = ib_dev->attrs.max_sge;
> +	sess->mr_page_mask = ~((u64)sess->mr_page_size - 1);
> +	max_pages_per_mr   = ib_dev->attrs.max_mr_size;
> +	do_div(max_pages_per_mr, sess->mr_page_size);
> +	sess->max_pages_per_mr = min_t(u64, sess->max_pages_per_mr,
> +				       max_pages_per_mr);
> +	if (sess->fast_reg_mode == IBTRS_FAST_MEM_FR) {
> +		sess->max_pages_per_mr =
> +			min_t(u32, sess->max_pages_per_mr,
> +			      ib_dev->attrs.max_fast_reg_page_list_len);
> +	}
> +	sess->mr_max_size = sess->mr_page_size * sess->max_pages_per_mr;
> +}
> +
> +static int alloc_con_fast_pool(struct ibtrs_clt_con *con)
> +{
> +	struct ibtrs_clt_sess *sess = to_clt_sess(con->c.sess);
> +	struct ibtrs_fr_pool *fr_pool;
> +	int err = 0;
> +
> +	if (sess->fast_reg_mode == IBTRS_FAST_MEM_FR) {
> +		fr_pool = ibtrs_create_fr_pool(sess->s.ib_dev->dev,
> +					       sess->s.ib_dev->pd,
> +					       sess->queue_depth,
> +					       sess->max_pages_per_mr);
> +		if (unlikely(IS_ERR(fr_pool))) {
> +			err = PTR_ERR(fr_pool);
> +			ibtrs_err(sess, "FR pool allocation failed, err: %d\n",
> +				  err);
> +			return err;
> +		}
> +		con->fr_pool = fr_pool;
> +	}
> +
> +	return err;
> +}
> +
> +static void free_con_fast_pool(struct ibtrs_clt_con *con)
> +{
> +	if (con->fr_pool) {
> +		ibtrs_destroy_fr_pool(con->fr_pool);
> +		con->fr_pool = NULL;
> +	}
> +}
> +
> +static int alloc_sess_fast_pool(struct ibtrs_clt_sess *sess)
> +{
> +	struct ib_fmr_pool_param fmr_param;
> +	struct ib_fmr_pool *fmr_pool;
> +	int err = 0;
> +
> +	if (sess->fast_reg_mode == IBTRS_FAST_MEM_FMR) {
> +		memset(&fmr_param, 0, sizeof(fmr_param));
> +		fmr_param.pool_size	    = sess->queue_depth *
> +					      sess->max_pages_per_mr;
> +		fmr_param.dirty_watermark   = fmr_param.pool_size / 4;
> +		fmr_param.cache		    = 0;
> +		fmr_param.max_pages_per_fmr = sess->max_pages_per_mr;
> +		fmr_param.page_shift	    = ilog2(sess->mr_page_size);
> +		fmr_param.access	    = (IB_ACCESS_LOCAL_WRITE |
> +					       IB_ACCESS_REMOTE_WRITE);
> +
> +		fmr_pool = ib_create_fmr_pool(sess->s.ib_dev->pd, &fmr_param);
> +		if (unlikely(IS_ERR(fmr_pool))) {
> +			err = PTR_ERR(fmr_pool);
> +			ibtrs_err(sess, "FMR pool allocation failed, err: %d\n",
> +				  err);
> +			return err;
> +		}
> +		sess->fmr_pool = fmr_pool;
> +	}
> +
> +	return err;
> +}
> +
> +static void free_sess_fast_pool(struct ibtrs_clt_sess *sess)
> +{
> +	if (sess->fmr_pool) {
> +		ib_destroy_fmr_pool(sess->fmr_pool);
> +		sess->fmr_pool = NULL;
> +	}
> +}
> +
> +static int alloc_sess_io_bufs(struct ibtrs_clt_sess *sess)
> +{
> +	int ret;
> +
> +	ret = alloc_sess_reqs(sess);
> +	if (unlikely(ret)) {
> +		ibtrs_err(sess, "alloc_sess_reqs(), err: %d\n", ret);
> +		return ret;
> +	}
> +	ret = alloc_sess_fast_pool(sess);
> +	if (unlikely(ret)) {
> +		ibtrs_err(sess, "alloc_sess_fast_pool(), err: %d\n", ret);
> +		goto free_reqs;
> +	}
> +
> +	return 0;
> +
> +free_reqs:
> +	free_sess_reqs(sess);
> +
> +	return ret;
> +}
> +
> +static void free_sess_io_bufs(struct ibtrs_clt_sess *sess)
> +{
> +	free_sess_reqs(sess);
> +	free_sess_fast_pool(sess);
> +}
> +
> +static bool __ibtrs_clt_change_state(struct ibtrs_clt_sess *sess,
> +				     enum ibtrs_clt_state new_state)
> +{
> +	enum ibtrs_clt_state old_state;
> +	bool changed = false;
> +
> +	old_state = sess->state;
> +	switch (new_state) {
> +	case IBTRS_CLT_CONNECTING:
> +		switch (old_state) {
> +		case IBTRS_CLT_RECONNECTING:
> +			changed = true;
> +			/* FALLTHRU */
> +		default:
> +			break;
> +		}
> +		break;
> +	case IBTRS_CLT_RECONNECTING:
> +		switch (old_state) {
> +		case IBTRS_CLT_CONNECTED:
> +		case IBTRS_CLT_CONNECTING_ERR:
> +		case IBTRS_CLT_CLOSED:
> +			changed = true;
> +			/* FALLTHRU */
> +		default:
> +			break;
> +		}
> +		break;
> +	case IBTRS_CLT_CONNECTED:
> +		switch (old_state) {
> +		case IBTRS_CLT_CONNECTING:
> +			changed = true;
> +			/* FALLTHRU */
> +		default:
> +			break;
> +		}
> +		break;
> +	case IBTRS_CLT_CONNECTING_ERR:
> +		switch (old_state) {
> +		case IBTRS_CLT_CONNECTING:
> +			changed = true;
> +			/* FALLTHRU */
> +		default:
> +			break;
> +		}
> +		break;
> +	case IBTRS_CLT_CLOSING:
> +		switch (old_state) {
> +		case IBTRS_CLT_CONNECTING:
> +		case IBTRS_CLT_CONNECTING_ERR:
> +		case IBTRS_CLT_RECONNECTING:
> +		case IBTRS_CLT_CONNECTED:
> +			changed = true;
> +			/* FALLTHRU */
> +		default:
> +			break;
> +		}
> +		break;
> +	case IBTRS_CLT_CLOSED:
> +		switch (old_state) {
> +		case IBTRS_CLT_CLOSING:
> +			changed = true;
> +			/* FALLTHRU */
> +		default:
> +			break;
> +		}
> +		break;
> +	case IBTRS_CLT_DEAD:
> +		switch (old_state) {
> +		case IBTRS_CLT_CLOSED:
> +			changed = true;
> +			/* FALLTHRU */
> +		default:
> +			break;
> +		}
> +		break;
> +	default:
> +		break;
> +	}
> +	if (changed) {
> +		sess->state = new_state;
> +		wake_up_locked(&sess->state_wq);
> +	}
> +
> +	return changed;
> +}
> +
> +static bool ibtrs_clt_change_state_from_to(struct ibtrs_clt_sess *sess,
> +					   enum ibtrs_clt_state old_state,
> +					   enum ibtrs_clt_state new_state)
> +{
> +	bool changed = false;
> +
> +	spin_lock_irq(&sess->state_wq.lock);
> +	if (sess->state == old_state)
> +		changed = __ibtrs_clt_change_state(sess, new_state);
> +	spin_unlock_irq(&sess->state_wq.lock);
> +
> +	return changed;
> +}
> +
> +static bool ibtrs_clt_change_state_get_old(struct ibtrs_clt_sess *sess,
> +					   enum ibtrs_clt_state new_state,
> +					   enum ibtrs_clt_state *old_state)
> +{
> +	bool changed;
> +
> +	spin_lock_irq(&sess->state_wq.lock);
> +	*old_state = sess->state;
> +	changed = __ibtrs_clt_change_state(sess, new_state);
> +	spin_unlock_irq(&sess->state_wq.lock);
> +
> +	return changed;
> +}
> +
> +static bool ibtrs_clt_change_state(struct ibtrs_clt_sess *sess,
> +				   enum ibtrs_clt_state new_state)
> +{
> +	enum ibtrs_clt_state old_state;
> +
> +	return ibtrs_clt_change_state_get_old(sess, new_state, &old_state);
> +}
> +
> +static enum ibtrs_clt_state ibtrs_clt_state(struct ibtrs_clt_sess *sess)
> +{
> +	enum ibtrs_clt_state state;
> +
> +	spin_lock_irq(&sess->state_wq.lock);
> +	state = sess->state;
> +	spin_unlock_irq(&sess->state_wq.lock);
> +
> +	return state;
> +}
> +
> +static void ibtrs_clt_hb_err_handler(struct ibtrs_con *c, int err)
> +{
> +	struct ibtrs_clt_con *con;
> +
> +	(void)err;
> +	con = container_of(c, typeof(*con), c);
> +	ibtrs_rdma_error_recovery(con);
> +}
> +
> +static void ibtrs_clt_init_hb(struct ibtrs_clt_sess *sess)
> +{
> +	ibtrs_init_hb(&sess->s, &io_comp_cqe,
> +		      IBTRS_HB_INTERVAL_MS,
> +		      IBTRS_HB_MISSED_MAX,
> +		      ibtrs_clt_hb_err_handler,
> +		      ibtrs_wq);
> +}
> +
> +static void ibtrs_clt_start_hb(struct ibtrs_clt_sess *sess)
> +{
> +	ibtrs_start_hb(&sess->s);
> +}
> +
> +static void ibtrs_clt_stop_hb(struct ibtrs_clt_sess *sess)
> +{
> +	ibtrs_stop_hb(&sess->s);
> +}
> +
> +static void ibtrs_clt_reconnect_work(struct work_struct *work);
> +static void ibtrs_clt_close_work(struct work_struct *work);
> +
> +static struct ibtrs_clt_sess *alloc_sess(struct ibtrs_clt *clt,
> +					 const struct ibtrs_addr *path,
> +					 size_t con_num, u16 max_segments)
> +{
> +	struct ibtrs_clt_sess *sess;
> +	int err = -ENOMEM;
> +	int cpu;
> +
> +	sess = kzalloc(sizeof(*sess), GFP_KERNEL);
> +	if (unlikely(!sess))
> +		goto err;
> +
> +	/* Extra connection for user messages */
> +	con_num += 1;
> +
> +	sess->s.con = kcalloc(con_num, sizeof(*sess->s.con), GFP_KERNEL);
> +	if (unlikely(!sess->s.con))
> +		goto err_free_sess;
> +
> +	mutex_init(&sess->init_mutex);
> +	uuid_gen(&sess->s.uuid);
> +	memcpy(&sess->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(&sess->s.src_addr, path->src,
> +		       rdma_addr_size((struct sockaddr *)path->src));
> +	strlcpy(sess->s.sessname, clt->sessname, sizeof(sess->s.sessname));
> +	sess->s.con_num = con_num;
> +	sess->clt = clt;
> +	sess->max_pages_per_mr = max_segments;
> +	init_waitqueue_head(&sess->state_wq);
> +	sess->state = IBTRS_CLT_CONNECTING;
> +	atomic_set(&sess->connected_cnt, 0);
> +	INIT_WORK(&sess->close_work, ibtrs_clt_close_work);
> +	INIT_DELAYED_WORK(&sess->reconnect_dwork, ibtrs_clt_reconnect_work);
> +	ibtrs_clt_init_hb(sess);
> +
> +	sess->mp_skip_entry = alloc_percpu(typeof(*sess->mp_skip_entry));
> +	if (unlikely(!sess->mp_skip_entry))
> +		goto err_free_con;
> +
> +	for_each_possible_cpu(cpu)
> +		INIT_LIST_HEAD(per_cpu_ptr(sess->mp_skip_entry, cpu));
> +
> +	err = ibtrs_clt_init_stats(&sess->stats);
> +	if (unlikely(err))
> +		goto err_free_percpu;
> +
> +	return sess;
> +
> +err_free_percpu:
> +	free_percpu(sess->mp_skip_entry);
> +err_free_con:
> +	kfree(sess->s.con);
> +err_free_sess:
> +	kfree(sess);
> +err:
> +	return ERR_PTR(err);
> +}
> +
> +static void free_sess(struct ibtrs_clt_sess *sess)
> +{
> +	ibtrs_clt_free_stats(&sess->stats);
> +	free_percpu(sess->mp_skip_entry);
> +	kfree(sess->s.con);
> +	kfree(sess->srv_rdma_addr);
> +	kfree(sess);
> +}
> +
> +static int create_con(struct ibtrs_clt_sess *sess, unsigned int cid)
> +{
> +	struct ibtrs_clt_con *con;
> +
> +	con = kzalloc(sizeof(*con), GFP_KERNEL);
> +	if (unlikely(!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.sess = &sess->s;
> +	atomic_set(&con->io_cnt, 0);
> +
> +	sess->s.con[cid] = &con->c;
> +
> +	return 0;
> +}
> +
> +static void destroy_con(struct ibtrs_clt_con *con)
> +{
> +	struct ibtrs_clt_sess *sess = to_clt_sess(con->c.sess);
> +
> +	sess->s.con[con->c.cid] = NULL;
> +	kfree(con);
> +}
> +
> +static int create_con_cq_qp(struct ibtrs_clt_con *con)
> +{
> +	struct ibtrs_clt_sess *sess = to_clt_sess(con->c.sess);
> +	u16 cq_size, wr_queue_size;
> +	int err, cq_vector;
> +
> +	/*
> +	 * This function can fail, but still destroy_con_cq_qp() should
> +	 * be called, this is because create_con_cq_qp() is called on cm
> +	 * event path, thus caller/waiter never knows: have we failed before
> +	 * create_con_cq_qp() or after.  To solve this dilemma without
> +	 * creating any additional flags just allow destroy_con_cq_qp() be
> +	 * called many times.
> +	 */
> +
> +	if (con->c.cid == 0) {
> +		cq_size = SERVICE_CON_QUEUE_DEPTH;
> +		/* + 2 for drain and heartbeat */
> +		wr_queue_size = SERVICE_CON_QUEUE_DEPTH + 2;
> +		/* We must be the first here */
> +		if (WARN_ON(sess->s.ib_dev))
> +			return -EINVAL;
> +
> +		/*
> +		 * The whole session uses device from user connection.
> +		 * Be careful not to close user connection before ib dev
> +		 * is gracefully put.
> +		 */
> +		sess->s.ib_dev = ibtrs_ib_dev_find_get(con->c.cm_id);
> +		if (unlikely(!sess->s.ib_dev)) {
> +			ibtrs_wrn(sess, "ibtrs_ib_dev_find_get(): no memory\n");
> +			return -ENOMEM;
> +		}
> +		sess->s.ib_dev_ref = 1;
> +		query_fast_reg_mode(sess);
> +	} else {
> +		int num_wr;
> +
> +		/*
> +		 * Here we assume that session members are correctly set.
> +		 * This is always true if user connection (cid == 0) is
> +		 * established first.
> +		 */
> +		if (WARN_ON(!sess->s.ib_dev))
> +			return -EINVAL;
> +		if (WARN_ON(!sess->queue_depth))
> +			return -EINVAL;
> +
> +		/* Shared between connections */
> +		sess->s.ib_dev_ref++;
> +		cq_size = sess->queue_depth;
> +		num_wr = DIV_ROUND_UP(sess->max_pages_per_mr, sess->max_sge);
> +		wr_queue_size = sess->s.ib_dev->attrs.max_qp_wr;
> +		wr_queue_size = min_t(int, wr_queue_size,
> +				      sess->queue_depth * num_wr *
> +				      (use_fr ? 3 : 2) + 1);
> +	}
> +	cq_vector = con->cpu % sess->s.ib_dev->dev->num_comp_vectors;
> +	err = ibtrs_cq_qp_create(&sess->s, &con->c, sess->max_sge,
> +				 cq_vector, cq_size, wr_queue_size,
> +				 IB_POLL_SOFTIRQ);
> +	/*
> +	 * In case of error we do not bother to clean previous allocations,
> +	 * since destroy_con_cq_qp() must be called.
> +	 */
> +
> +	if (unlikely(err))
> +		return err;
> +
> +	if (con->c.cid) {
> +		err = alloc_con_fast_pool(con);
> +		if (unlikely(err))
> +			ibtrs_cq_qp_destroy(&con->c);
> +	}
> +
> +	return err;
> +}
> +
> +static void destroy_con_cq_qp(struct ibtrs_clt_con *con)
> +{
> +	struct ibtrs_clt_sess *sess = to_clt_sess(con->c.sess);
> +
> +	/*
> +	 * Be careful here: destroy_con_cq_qp() can be called even
> +	 * create_con_cq_qp() failed, see comments there.
> +	 */
> +
> +	ibtrs_cq_qp_destroy(&con->c);
> +	if (con->c.cid != 0)
> +		free_con_fast_pool(con);
> +	if (sess->s.ib_dev_ref && !--sess->s.ib_dev_ref) {
> +		ibtrs_ib_dev_put(sess->s.ib_dev);
> +		sess->s.ib_dev = NULL;
> +	}
> +}
> +
> +static void stop_cm(struct ibtrs_clt_con *con)
> +{
> +	rdma_disconnect(con->c.cm_id);
> +	if (con->c.qp)
> +		ib_drain_qp(con->c.qp);
> +}
> +
> +static void destroy_cm(struct ibtrs_clt_con *con)
> +{
> +	rdma_destroy_id(con->c.cm_id);
> +	con->c.cm_id = NULL;
> +}
> +
> +static int ibtrs_clt_rdma_cm_handler(struct rdma_cm_id *cm_id,
> +				     struct rdma_cm_event *ev);
> +
> +static int create_cm(struct ibtrs_clt_con *con)
> +{
> +	struct ibtrs_clt_sess *sess = to_clt_sess(con->c.sess);
> +	struct rdma_cm_id *cm_id;
> +	int err;
> +
> +	cm_id = rdma_create_id(&init_net, ibtrs_clt_rdma_cm_handler, con,
> +			       sess->s.dst_addr.ss_family == AF_IB ?
> +			       RDMA_PS_IB : RDMA_PS_TCP, IB_QPT_RC);
> +	if (unlikely(IS_ERR(cm_id))) {
> +		err = PTR_ERR(cm_id);
> +		ibtrs_err(sess, "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) {
> +		ibtrs_err(sess, "Set address reuse failed, err: %d\n", err);
> +		goto destroy_cm;
> +	}
> +	err = rdma_resolve_addr(cm_id, (struct sockaddr *)&sess->s.src_addr,
> +				(struct sockaddr *)&sess->s.dst_addr,
> +				IBTRS_CONNECT_TIMEOUT_MS);
> +	if (unlikely(err)) {
> +		ibtrs_err(sess, "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(sess->state_wq,
> +			con->cm_err || sess->state != IBTRS_CLT_CONNECTING,
> +			msecs_to_jiffies(IBTRS_CONNECT_TIMEOUT_MS));
> +	if (unlikely(err == 0 || err == -ERESTARTSYS)) {
> +		if (err == 0)
> +			err = -ETIMEDOUT;
> +		/* Timedout or interrupted */
> +		goto errr;
> +	}
> +	if (unlikely(con->cm_err < 0)) {
> +		err = con->cm_err;
> +		goto errr;
> +	}
> +	if (unlikely(sess->state != IBTRS_CLT_CONNECTING)) {
> +		/* Device removal */
> +		err = -ECONNABORTED;
> +		goto errr;
> +	}
> +
> +	return 0;
> +
> +errr:
> +	stop_cm(con);
> +	/* Is safe to call destroy if cq_qp is not inited */
> +	destroy_con_cq_qp(con);
> +destroy_cm:
> +	destroy_cm(con);
> +
> +	return err;
> +}
> +
> +static void ibtrs_clt_sess_up(struct ibtrs_clt_sess *sess)
> +{
> +	struct ibtrs_clt *clt = sess->clt;
> +	int up;
> +
> +	/*
> +	 * We can fire RECONNECTED event only when all paths were
> +	 * connected on ibtrs_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 ibtrs_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, IBTRS_CLT_LINK_EV_RECONNECTED);
> +	mutex_unlock(&clt->paths_ev_mutex);
> +
> +	/* Mark session as established */
> +	sess->established = true;
> +	sess->reconnect_attempts = 0;
> +	sess->stats.reconnects.successful_cnt++;
> +}
> +
> +static void ibtrs_clt_sess_down(struct ibtrs_clt_sess *sess)
> +{
> +	struct ibtrs_clt *clt = sess->clt;
> +
> +	if (!sess->established)
> +		return;
> +
> +	sess->established = false;
> +	mutex_lock(&clt->paths_ev_mutex);
> +	WARN_ON(!clt->paths_up);
> +	if (--clt->paths_up == 0)
> +		clt->link_ev(clt->priv, IBTRS_CLT_LINK_EV_DISCONNECTED);
> +	mutex_unlock(&clt->paths_ev_mutex);
> +}
> +
> +static void ibtrs_clt_stop_and_destroy_conns(struct ibtrs_clt_sess *sess,
> +					     bool failover)
> +{
> +	struct ibtrs_clt_con *con;
> +	unsigned int cid;
> +
> +	WARN_ON(sess->state == IBTRS_CLT_CONNECTED);
> +
> +	/*
> +	 * Possible race with ibtrs_clt_open(), when DEVICE_REMOVAL comes
> +	 * exactly in between.  Start destroying after it finishes.
> +	 */
> +	mutex_lock(&sess->init_mutex);
> +	mutex_unlock(&sess->init_mutex);
> +
> +	/*
> +	 * All IO paths must observe !CONNECTED state before we
> +	 * free everything.
> +	 */
> +	synchronize_rcu();
> +
> +	ibtrs_clt_stop_hb(sess);
> +
> +	/*
> +	 * 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 < sess->s.con_num; cid++) {
> +		con = to_clt_con(sess->s.con[cid]);
> +		if (!con)
> +			break;
> +
> +		stop_cm(con);
> +	}
> +	fail_all_outstanding_reqs(sess, failover);
> +	free_sess_io_bufs(sess);
> +	ibtrs_clt_sess_down(sess);
> +
> +	/*
> +	 * 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(sess->state_wq, !atomic_read(&sess->connected_cnt),
> +			   msecs_to_jiffies(IBTRS_CONNECT_TIMEOUT_MS));
> +
> +	for (cid = 0; cid < sess->s.con_num; cid++) {
> +		con = to_clt_con(sess->s.con[cid]);
> +		if (!con)
> +			break;
> +
> +		destroy_con_cq_qp(con);
> +		destroy_cm(con);
> +		destroy_con(con);
> +	}
> +}
> +
> +static void ibtrs_clt_remove_path_from_arr(struct ibtrs_clt_sess *sess)
> +{
> +	struct ibtrs_clt *clt = sess->clt;
> +	struct ibtrs_clt_sess *next;
> +	int cpu;
> +
> +	mutex_lock(&clt->paths_mutex);
> +	list_del_rcu(&sess->s.entry);
> +
> +	/* Make sure everybody observes path removal. */
> +	synchronize_rcu();
> +
> +	/*
> +	 * 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():                ibtrs_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--;
> +
> +	next = list_next_or_null_rcu_rr(sess, &clt->paths_list, s.entry);
> +
> +	/*
> +	 * 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 ibtrs_clt_sess **ppcpu_path;
> +
> +		ppcpu_path = per_cpu_ptr(clt->pcpu_path, cpu);
> +		if (*ppcpu_path != sess)
> +			/*
> +			 * 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 override it.
> +		 */
> +		cmpxchg(ppcpu_path, sess, next);
> +	}
> +	mutex_unlock(&clt->paths_mutex);
> +}
> +
> +static inline bool __ibtrs_clt_path_exists(struct ibtrs_clt *clt,
> +					   struct ibtrs_addr *addr)
> +{
> +	struct ibtrs_clt_sess *sess;
> +
> +	list_for_each_entry(sess, &clt->paths_list, s.entry)
> +		if (!sockaddr_cmp((struct sockaddr *)&sess->s.dst_addr,
> +				  addr->dst))
> +			return true;
> +
> +	return false;
> +}
> +
> +static bool ibtrs_clt_path_exists(struct ibtrs_clt *clt,
> +				  struct ibtrs_addr *addr)
> +{
> +	bool res;
> +
> +	mutex_lock(&clt->paths_mutex);
> +	res = __ibtrs_clt_path_exists(clt, addr);
> +	mutex_unlock(&clt->paths_mutex);
> +
> +	return res;
> +}
> +
> +static int ibtrs_clt_add_path_to_arr(struct ibtrs_clt_sess *sess,
> +				     struct ibtrs_addr *addr)
> +{
> +	struct ibtrs_clt *clt = sess->clt;
> +	int err = 0;
> +
> +	mutex_lock(&clt->paths_mutex);
> +	if (!__ibtrs_clt_path_exists(clt, addr)) {
> +		list_add_tail_rcu(&sess->s.entry, &clt->paths_list);
> +		clt->paths_num++;
> +	} else
> +		err = -EEXIST;
> +	mutex_unlock(&clt->paths_mutex);
> +
> +	return err;
> +}
> +
> +static void ibtrs_clt_close_work(struct work_struct *work)
> +{
> +	struct ibtrs_clt_sess *sess;
> +	/*
> +	 * Always try to do a failover, if only single path remains,
> +	 * all requests will be completed with error.
> +	 */
> +	bool failover = true;
> +
> +	sess = container_of(work, struct ibtrs_clt_sess, close_work);
> +
> +	cancel_delayed_work_sync(&sess->reconnect_dwork);
> +	ibtrs_clt_stop_and_destroy_conns(sess, failover);
> +	/*
> +	 * Sounds stupid, huh?  No, it is not.  Consider this sequence:
> +	 *
> +	 *   #CPU0                              #CPU1
> +	 *   1.  CONNECTED->RECONNECTING
> +	 *   2.                                 RECONNECTING->CLOSING
> +	 *   3.  queue_work(&reconnect_dwork)
> +	 *   4.                                 queue_work(&close_work);
> +	 *   5.  reconnect_work();              close_work();
> +	 *
> +	 * To avoid that case do cancel twice: before and after.
> +	 */
> +	cancel_delayed_work_sync(&sess->reconnect_dwork);
> +	ibtrs_clt_change_state(sess, IBTRS_CLT_CLOSED);
> +}
> +
> +static void ibtrs_clt_close_conns(struct ibtrs_clt_sess *sess, bool wait)
> +{
> +	if (ibtrs_clt_change_state(sess, IBTRS_CLT_CLOSING))
> +		queue_work(ibtrs_wq, &sess->close_work);
> +	if (wait)
> +		flush_work(&sess->close_work);
> +}
> +
> +static int init_conns(struct ibtrs_clt_sess *sess)
> +{
> +	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.
> +	 */
> +	sess->s.recon_cnt++;
> +
> +	/* Establish all RDMA connections  */
> +	for (cid = 0; cid < sess->s.con_num; cid++) {
> +		err = create_con(sess, cid);
> +		if (unlikely(err))
> +			goto destroy;
> +
> +		err = create_cm(to_clt_con(sess->s.con[cid]));
> +		if (unlikely(err)) {
> +			destroy_con(to_clt_con(sess->s.con[cid]));
> +			goto destroy;
> +		}
> +	}
> +	/* Allocate all session related buffers */
> +	err = alloc_sess_io_bufs(sess);
> +	if (unlikely(err))
> +		goto destroy;
> +
> +	ibtrs_clt_start_hb(sess);
> +
> +	return 0;
> +
> +destroy:
> +	while (cid--) {
> +		struct ibtrs_clt_con *con = to_clt_con(sess->s.con[cid]);
> +
> +		stop_cm(con);
> +		destroy_con_cq_qp(con);
> +		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.
> +	 */
> +	ibtrs_clt_change_state(sess, IBTRS_CLT_CONNECTING_ERR);
> +
> +	return err;
> +}
> +
> +static int ibtrs_rdma_addr_resolved(struct ibtrs_clt_con *con)
> +{
> +	struct ibtrs_clt_sess *sess = to_clt_sess(con->c.sess);
> +	int err;
> +
> +	err = create_con_cq_qp(con);
> +	if (unlikely(err)) {
> +		ibtrs_err(sess, "create_con_cq_qp(), err: %d\n", err);
> +		return err;
> +	}
> +	err = rdma_resolve_route(con->c.cm_id, IBTRS_CONNECT_TIMEOUT_MS);
> +	if (unlikely(err)) {
> +		ibtrs_err(sess, "Resolving route failed, err: %d\n", err);
> +		destroy_con_cq_qp(con);
> +	}
> +
> +	return err;
> +}
> +
> +static int ibtrs_rdma_route_resolved(struct ibtrs_clt_con *con)
> +{
> +	struct ibtrs_clt_sess *sess = to_clt_sess(con->c.sess);
> +	struct ibtrs_clt *clt = sess->clt;
> +	struct ibtrs_msg_conn_req msg;
> +	struct rdma_conn_param param;
> +
> +	int err;
> +
> +	memset(&param, 0, sizeof(param));
> +	param.retry_count = retry_count;
> +	param.rnr_retry_count = 7;
> +	param.private_data = &msg;
> +	param.private_data_len = sizeof(msg);
> +
> +	/*
> +	 * Those two are the part of struct cma_hdr which is shared
> +	 * with private_data in case of AF_IB, so put zeroes to avoid
> +	 * wrong validation inside cma.c on receiver side.
> +	 */
> +	msg.__cma_version = 0;
> +	msg.__ip_version = 0;
> +	msg.magic = cpu_to_le16(IBTRS_MAGIC);
> +	msg.version = cpu_to_le16(IBTRS_VERSION);
> +	msg.cid = cpu_to_le16(con->c.cid);
> +	msg.cid_num = cpu_to_le16(sess->s.con_num);
> +	msg.recon_cnt = cpu_to_le16(sess->s.recon_cnt);
> +	uuid_copy(&msg.sess_uuid, &sess->s.uuid);
> +	uuid_copy(&msg.paths_uuid, &clt->paths_uuid);
> +
> +	err = rdma_connect(con->c.cm_id, &param);
> +	if (err)
> +		ibtrs_err(sess, "rdma_connect(): %d\n", err);
> +
> +	return err;
> +}
> +
> +static int ibtrs_rdma_conn_established(struct ibtrs_clt_con *con,
> +				       struct rdma_cm_event *ev)
> +{
> +	struct ibtrs_clt_sess *sess = to_clt_sess(con->c.sess);
> +	const struct ibtrs_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 (unlikely(len < sizeof(*msg))) {
> +		ibtrs_err(sess, "Invalid IBTRS connection response");
> +		return -ECONNRESET;
> +	}
> +	if (unlikely(le16_to_cpu(msg->magic) != IBTRS_MAGIC)) {
> +		ibtrs_err(sess, "Invalid IBTRS magic");
> +		return -ECONNRESET;
> +	}
> +	version = le16_to_cpu(msg->version);
> +	if (unlikely(version >> 8 != IBTRS_VER_MAJOR)) {
> +		ibtrs_err(sess, "Unsupported major IBTRS version: %d",
> +			  version);
> +		return -ECONNRESET;
> +	}
> +	errno = le16_to_cpu(msg->errno);
> +	if (unlikely(errno)) {
> +		ibtrs_err(sess, "Invalid IBTRS message: errno %d",
> +			  errno);
> +		return -ECONNRESET;
> +	}
> +	if (con->c.cid == 0) {
> +		queue_depth = le16_to_cpu(msg->queue_depth);
> +
> +		if (queue_depth > MAX_SESS_QUEUE_DEPTH) {
> +			ibtrs_err(sess, "Invalid IBTRS message: queue=%d\n",
> +				  queue_depth);
> +			return -ECONNRESET;
> +		}
> +		if (!sess->srv_rdma_addr || sess->queue_depth < queue_depth) {
> +			kfree(sess->srv_rdma_addr);
> +			sess->srv_rdma_addr =
> +				kcalloc(queue_depth,
> +					sizeof(*sess->srv_rdma_addr),
> +					GFP_KERNEL);
> +			if (unlikely(!sess->srv_rdma_addr)) {
> +				ibtrs_err(sess, "Failed to allocate "
> +					  "queue_depth=%d\n", queue_depth);
> +				return -ENOMEM;
> +			}
> +		}
> +		sess->queue_depth = queue_depth;
> +		sess->srv_rdma_buf_rkey = le32_to_cpu(msg->rkey);
> +		sess->max_req_size = le32_to_cpu(msg->max_req_size);
> +		sess->max_io_size = le32_to_cpu(msg->max_io_size);
> +		sess->chunk_size = sess->max_io_size + sess->max_req_size;
> +		sess->max_desc  = sess->max_req_size;
> +		sess->max_desc -= sizeof(u32) + sizeof(u32) + IO_MSG_SIZE;
> +		sess->max_desc /= sizeof(struct ibtrs_sg_desc);
> +
> +		/*
> +		 * Global queue depth and is always a minimum.  If while a
> +		 * reconnection server sends us a value a bit higher -
> +		 * client does not care and uses cached minimum.
> +		 */
> +		ibtrs_clt_set_min_queue_depth(sess->clt, sess->queue_depth);
> +		ibtrs_clt_set_min_io_size(sess->clt, sess->max_io_size);
> +	}
> +
> +	return 0;
> +}
> +
> +static int ibtrs_rdma_conn_rejected(struct ibtrs_clt_con *con,
> +				    struct rdma_cm_event *ev)
> +{
> +	struct ibtrs_clt_sess *sess = to_clt_sess(con->c.sess);
> +	const struct ibtrs_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)
> +			ibtrs_err(sess,
> +				  "Previous session is still exists on the "
> +				  "server, please reconnect later\n");
> +		else
> +			ibtrs_err(sess,
> +				  "Connect rejected: status %d (%s), ibtrs "
> +				  "errno %d\n", status, rej_msg, errno);
> +	} else {
> +		ibtrs_err(sess,
> +			  "Connect rejected but with malformed message: "
> +			  "status %d (%s)\n", status, rej_msg);
> +	}
> +
> +	return -ECONNRESET;
> +}
> +
> +static void ibtrs_rdma_error_recovery(struct ibtrs_clt_con *con)
> +{
> +	struct ibtrs_clt_sess *sess = to_clt_sess(con->c.sess);
> +
> +	if (ibtrs_clt_change_state_from_to(sess,
> +					   IBTRS_CLT_CONNECTED,
> +					   IBTRS_CLT_RECONNECTING)) {
> +		/*
> +		 * Normal scenario, reconnect if we were successfully connected
> +		 */
> +		queue_delayed_work(ibtrs_wq, &sess->reconnect_dwork, 0);
> +	} 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.
> +		 */
> +		ibtrs_clt_change_state_from_to(sess,
> +					       IBTRS_CLT_CONNECTING,
> +					       IBTRS_CLT_CONNECTING_ERR);
> +	}
> +}
> +
> +static inline void flag_success_on_conn(struct ibtrs_clt_con *con)
> +{
> +	struct ibtrs_clt_sess *sess = to_clt_sess(con->c.sess);
> +
> +	atomic_inc(&sess->connected_cnt);
> +	con->cm_err = 1;
> +}
> +
> +static inline void flag_error_on_conn(struct ibtrs_clt_con *con, int cm_err)
> +{
> +	if (con->cm_err == 1) {
> +		struct ibtrs_clt_sess *sess;
> +
> +		sess = to_clt_sess(con->c.sess);
> +		if (atomic_dec_and_test(&sess->connected_cnt))
> +			wake_up(&sess->state_wq);
> +	}
> +	con->cm_err = cm_err;
> +}
> +
> +static int ibtrs_clt_rdma_cm_handler(struct rdma_cm_id *cm_id,
> +				     struct rdma_cm_event *ev)
> +{
> +	struct ibtrs_clt_con *con = cm_id->context;
> +	struct ibtrs_clt_sess *sess = to_clt_sess(con->c.sess);
> +	int cm_err = 0;
> +
> +	switch (ev->event) {
> +	case RDMA_CM_EVENT_ADDR_RESOLVED:
> +		cm_err = ibtrs_rdma_addr_resolved(con);
> +		break;
> +	case RDMA_CM_EVENT_ROUTE_RESOLVED:
> +		cm_err = ibtrs_rdma_route_resolved(con);
> +		break;
> +	case RDMA_CM_EVENT_ESTABLISHED:
> +		con->cm_err = ibtrs_rdma_conn_established(con, ev);
> +		if (likely(!con->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(&sess->state_wq);
> +			return 0;
> +		}
> +		break;
> +	case RDMA_CM_EVENT_REJECTED:
> +		cm_err = ibtrs_rdma_conn_rejected(con, ev);
> +		break;
> +	case RDMA_CM_EVENT_CONNECT_ERROR:
> +	case RDMA_CM_EVENT_UNREACHABLE:
> +		ibtrs_wrn(sess, "CM error event %d\n", ev->event);
> +		cm_err = -ECONNRESET;
> +		break;
> +	case RDMA_CM_EVENT_ADDR_ERROR:
> +	case RDMA_CM_EVENT_ROUTE_ERROR:
> +		cm_err = -EHOSTUNREACH;
> +		break;
> +	case RDMA_CM_EVENT_DISCONNECTED:
> +	case RDMA_CM_EVENT_ADDR_CHANGE:
> +	case RDMA_CM_EVENT_TIMEWAIT_EXIT:
> +		cm_err = -ECONNRESET;
> +		break;
> +	case RDMA_CM_EVENT_DEVICE_REMOVAL:
> +		/*
> +		 * Device removal is a special case.  Queue close and return 0.
> +		 */
> +		ibtrs_clt_close_conns(sess, false);
> +		return 0;
> +	default:
> +		ibtrs_err(sess, "Unexpected RDMA CM event (%d)\n", ev->event);
> +		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);
> +		ibtrs_rdma_error_recovery(con);
> +	}
> +
> +	return 0;
> +}
> +
> +static void ibtrs_clt_info_req_done(struct ib_cq *cq, struct ib_wc *wc)
> +{
> +	struct ibtrs_clt_con *con = cq->cq_context;
> +	struct ibtrs_clt_sess *sess = to_clt_sess(con->c.sess);
> +	struct ibtrs_iu *iu;
> +
> +	iu = container_of(wc->wr_cqe, struct ibtrs_iu, cqe);
> +	ibtrs_iu_free(iu, DMA_TO_DEVICE, sess->s.ib_dev->dev);
> +
> +	if (unlikely(wc->status != IB_WC_SUCCESS)) {
> +		ibtrs_err(sess, "Sess info request send failed: %s\n",
> +			  ib_wc_status_msg(wc->status));
> +		ibtrs_clt_change_state(sess, IBTRS_CLT_CONNECTING_ERR);
> +		return;
> +	}
> +
> +	ibtrs_clt_update_wc_stats(con);
> +}
> +
> +static int process_info_rsp(struct ibtrs_clt_sess *sess,
> +			    const struct ibtrs_msg_info_rsp *msg)
> +{
> +	unsigned int addr_num;
> +	int i;
> +
> +	addr_num = le16_to_cpu(msg->addr_num);
> +	/*
> +	 * Check if IB immediate data size is enough to hold the mem_id and
> +	 * the offset inside the memory chunk.
> +	 */
> +	if (unlikely(ilog2(addr_num - 1) + ilog2(sess->chunk_size - 1) >
> +		     MAX_IMM_PAYL_BITS)) {
> +		ibtrs_err(sess, "RDMA immediate size (%db) not enough to "
> +			  "encode %d buffers of size %dB\n",  MAX_IMM_PAYL_BITS,
> +			  addr_num, sess->chunk_size);
> +		return -EINVAL;
> +	}
> +	if (unlikely(addr_num > sess->queue_depth)) {
> +		ibtrs_err(sess, "Incorrect addr_num=%d\n", addr_num);
> +		return -EINVAL;
> +	}
> +	for (i = 0; i < msg->addr_num; i++)
> +		sess->srv_rdma_addr[i] = le64_to_cpu(msg->addr[i]);
> +
> +	return 0;
> +}
> +
> +static void ibtrs_clt_info_rsp_done(struct ib_cq *cq, struct ib_wc *wc)
> +{
> +	struct ibtrs_clt_con *con = cq->cq_context;
> +	struct ibtrs_clt_sess *sess = to_clt_sess(con->c.sess);
> +	struct ibtrs_msg_info_rsp *msg;
> +	enum ibtrs_clt_state state;
> +	struct ibtrs_iu *iu;
> +	size_t rx_sz;
> +	int err;
> +
> +	state = IBTRS_CLT_CONNECTING_ERR;
> +
> +	WARN_ON(con->c.cid);
> +	iu = container_of(wc->wr_cqe, struct ibtrs_iu, cqe);
> +	if (unlikely(wc->status != IB_WC_SUCCESS)) {
> +		ibtrs_err(sess, "Sess info response recv failed: %s\n",
> +			  ib_wc_status_msg(wc->status));
> +		goto out;
> +	}
> +	WARN_ON(wc->opcode != IB_WC_RECV);
> +
> +	if (unlikely(wc->byte_len < sizeof(*msg))) {
> +		ibtrs_err(sess, "Sess info response is malformed: size %d\n",
> +			  wc->byte_len);
> +		goto out;
> +	}
> +	msg = iu->buf;
> +	if (unlikely(le16_to_cpu(msg->type) != IBTRS_MSG_INFO_RSP)) {
> +		ibtrs_err(sess, "Sess info response is malformed: type %d\n",
> +			  le32_to_cpu(msg->type));
> +		goto out;
> +	}
> +	rx_sz  = sizeof(*msg);
> +	rx_sz += sizeof(msg->addr[0]) * le16_to_cpu(msg->addr_num);
> +	if (unlikely(wc->byte_len < rx_sz)) {
> +		ibtrs_err(sess, "Sess info response is malformed: size %d\n",
> +			  wc->byte_len);
> +		goto out;
> +	}
> +	err = process_info_rsp(sess, msg);
> +	if (unlikely(err))
> +		goto out;
> +
> +	err = post_recv_sess(sess);
> +	if (unlikely(err))
> +		goto out;
> +
> +	state = IBTRS_CLT_CONNECTED;
> +
> +out:
> +	ibtrs_clt_update_wc_stats(con);
> +	ibtrs_iu_free(iu, DMA_FROM_DEVICE, sess->s.ib_dev->dev);
> +	ibtrs_clt_change_state(sess, state);
> +}
> +
> +static int ibtrs_send_sess_info(struct ibtrs_clt_sess *sess)
> +{
> +	struct ibtrs_clt_con *usr_con = to_clt_con(sess->s.con[0]);
> +	struct ibtrs_msg_info_req *msg;
> +	struct ibtrs_iu *tx_iu, *rx_iu;
> +	size_t rx_sz;
> +	int err;
> +
> +	rx_sz  = sizeof(struct ibtrs_msg_info_rsp);
> +	rx_sz += sizeof(u64) * MAX_SESS_QUEUE_DEPTH;
> +
> +	tx_iu = ibtrs_iu_alloc(0, sizeof(struct ibtrs_msg_info_req), GFP_KERNEL,
> +			       sess->s.ib_dev->dev, DMA_TO_DEVICE,
> +			       ibtrs_clt_info_req_done);
> +	rx_iu = ibtrs_iu_alloc(0, rx_sz, GFP_KERNEL, sess->s.ib_dev->dev,
> +			       DMA_FROM_DEVICE, ibtrs_clt_info_rsp_done);
> +	if (unlikely(!tx_iu || !rx_iu)) {
> +		ibtrs_err(sess, "ibtrs_iu_alloc(): no memory\n");
> +		err = -ENOMEM;
> +		goto out;
> +	}
> +	/* Prepare for getting info response */
> +	err = ibtrs_iu_post_recv(&usr_con->c, rx_iu);
> +	if (unlikely(err)) {
> +		ibtrs_err(sess, "ibtrs_iu_post_recv(), err: %d\n", err);
> +		goto out;
> +	}
> +	rx_iu = NULL;
> +
> +	msg = tx_iu->buf;
> +	msg->type = cpu_to_le16(IBTRS_MSG_INFO_REQ);
> +	memcpy(msg->sessname, sess->s.sessname, sizeof(msg->sessname));
> +
> +	/* Send info request */
> +	err = ibtrs_iu_post_send(&usr_con->c, tx_iu, sizeof(*msg));
> +	if (unlikely(err)) {
> +		ibtrs_err(sess, "ibtrs_iu_post_send(), err: %d\n", err);
> +		goto out;
> +	}
> +	tx_iu = NULL;
> +
> +	/* Wait for state change */
> +	wait_event_interruptible_timeout(sess->state_wq,
> +				sess->state != IBTRS_CLT_CONNECTING,
> +				msecs_to_jiffies(IBTRS_CONNECT_TIMEOUT_MS));
> +	if (unlikely(sess->state != IBTRS_CLT_CONNECTED)) {
> +		if (sess->state == IBTRS_CLT_CONNECTING_ERR)
> +			err = -ECONNRESET;
> +		else
> +			err = -ETIMEDOUT;
> +		goto out;
> +	}
> +
> +out:
> +	if (tx_iu)
> +		ibtrs_iu_free(tx_iu, DMA_TO_DEVICE, sess->s.ib_dev->dev);
> +	if (rx_iu)
> +		ibtrs_iu_free(rx_iu, DMA_FROM_DEVICE, sess->s.ib_dev->dev);
> +	if (unlikely(err))
> +		/* If we've never taken async path because of malloc problems */
> +		ibtrs_clt_change_state(sess, IBTRS_CLT_CONNECTING_ERR);
> +
> +	return err;
> +}
> +
> +/**
> + * init_sess() - establishes all session connections and does handshake
> + *
> + * In case of error full close or reconnect procedure should be taken,
> + * because reconnect or close async works can be started.
> + */
> +static int init_sess(struct ibtrs_clt_sess *sess)
> +{
> +	int err;
> +
> +	mutex_lock(&sess->init_mutex);
> +	err = init_conns(sess);
> +	if (unlikely(err)) {
> +		ibtrs_err(sess, "init_conns(), err: %d\n", err);
> +		goto out;
> +	}
> +	err = ibtrs_send_sess_info(sess);
> +	if (unlikely(err)) {
> +		ibtrs_err(sess, "ibtrs_send_sess_info(), err: %d\n", err);
> +		goto out;
> +	}
> +	ibtrs_clt_sess_up(sess);
> +out:
> +	mutex_unlock(&sess->init_mutex);
> +
> +	return err;
> +}
> +
> +static void ibtrs_clt_reconnect_work(struct work_struct *work)
> +{
> +	struct ibtrs_clt_sess *sess;
> +	struct ibtrs_clt *clt;
> +	unsigned int delay_ms;
> +	int err;
> +
> +	sess = container_of(to_delayed_work(work), struct ibtrs_clt_sess,
> +			    reconnect_dwork);
> +	clt = sess->clt;
> +
> +	if (ibtrs_clt_state(sess) == IBTRS_CLT_CLOSING)
> +		/* User requested closing */
> +		return;
> +
> +	if (sess->reconnect_attempts >= clt->max_reconnect_attempts) {
> +		/* Close a session completely if max attempts is reached */
> +		ibtrs_clt_close_conns(sess, false);
> +		return;
> +	}
> +	sess->reconnect_attempts++;
> +
> +	/* Stop everything */
> +	ibtrs_clt_stop_and_destroy_conns(sess, true);
> +	ibtrs_clt_change_state(sess, IBTRS_CLT_CONNECTING);
> +
> +	err = init_sess(sess);
> +	if (unlikely(err))
> +		goto reconnect_again;
> +
> +	return;
> +
> +reconnect_again:
> +	if (ibtrs_clt_change_state(sess, IBTRS_CLT_RECONNECTING)) {
> +		sess->stats.reconnects.fail_cnt++;
> +		delay_ms = clt->reconnect_delay_sec * 1000;
> +		queue_delayed_work(ibtrs_wq, &sess->reconnect_dwork,
> +				   msecs_to_jiffies(delay_ms));
> +	}
> +}
> +
> +static struct ibtrs_clt *alloc_clt(const char *sessname, size_t paths_num,
> +				   short port, size_t pdu_sz,
> +				   void *priv, link_clt_ev_fn *link_ev,
> +				   unsigned int max_segments,
> +				   unsigned int reconnect_delay_sec,
> +				   unsigned int max_reconnect_attempts)
> +{
> +	struct ibtrs_clt *clt;
> +	int err;
> +
> +	if (unlikely(!paths_num || paths_num > MAX_PATHS_NUM))
> +		return ERR_PTR(-EINVAL);
> +
> +	if (unlikely(strlen(sessname) >= sizeof(clt->sessname)))
> +		return ERR_PTR(-EINVAL);
> +
> +	clt = kzalloc(sizeof(*clt), GFP_KERNEL);
> +	if (unlikely(!clt))
> +		return ERR_PTR(-ENOMEM);
> +
> +	clt->pcpu_path = alloc_percpu(typeof(*clt->pcpu_path));
> +	if (unlikely(!clt->pcpu_path)) {
> +		kfree(clt);
> +		return ERR_PTR(-ENOMEM);
> +	}
> +
> +	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 = 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;
> +	strlcpy(clt->sessname, sessname, sizeof(clt->sessname));
> +	init_waitqueue_head(&clt->tags_wait);
> +	mutex_init(&clt->paths_ev_mutex);
> +	mutex_init(&clt->paths_mutex);
> +
> +	err = ibtrs_clt_create_sysfs_root_folders(clt);
> +	if (unlikely(err)) {
> +		free_percpu(clt->pcpu_path);
> +		kfree(clt);
> +		return ERR_PTR(err);
> +	}
> +
> +	return clt;
> +}
> +
> +static void wait_for_inflight_tags(struct ibtrs_clt *clt)
> +{
> +	if (clt->tags_map) {
> +		size_t sz = clt->queue_depth;
> +
> +		wait_event(clt->tags_wait,
> +			   find_first_bit(clt->tags_map, sz) >= sz);
> +	}
> +}
> +
> +static void free_clt(struct ibtrs_clt *clt)
> +{
> +	ibtrs_clt_destroy_sysfs_root_folders(clt);
> +	wait_for_inflight_tags(clt);
> +	free_tags(clt);
> +	free_percpu(clt->pcpu_path);
> +	kfree(clt);
> +}
> +
> +struct ibtrs_clt *ibtrs_clt_open(void *priv, link_clt_ev_fn *link_ev,
> +				 const char *sessname,
> +				 const struct ibtrs_addr *paths,
> +				 size_t paths_num,
> +				 short port,
> +				 size_t pdu_sz, u8 reconnect_delay_sec,
> +				 u16 max_segments,
> +				 s16 max_reconnect_attempts)
> +{
> +	struct ibtrs_clt_sess *sess, *tmp;
> +	struct ibtrs_clt *clt;
> +	int err, i;
> +
> +	clt = alloc_clt(sessname, paths_num, port, pdu_sz, priv, link_ev,
> +			max_segments, reconnect_delay_sec,
> +			max_reconnect_attempts);
> +	if (unlikely(IS_ERR(clt))) {
> +		err = PTR_ERR(clt);
> +		goto out;
> +	}
> +	for (i = 0; i < paths_num; i++) {
> +		struct ibtrs_clt_sess *sess;
> +
> +		sess = alloc_sess(clt, &paths[i], nr_cons_per_session,
> +				  max_segments);
> +		if (unlikely(IS_ERR(sess))) {
> +			err = PTR_ERR(sess);
> +			ibtrs_err(clt, "alloc_sess(), err: %d\n", err);
> +			goto close_all_sess;
> +		}
> +		list_add_tail_rcu(&sess->s.entry, &clt->paths_list);
> +
> +		err = init_sess(sess);
> +		if (unlikely(err))
> +			goto close_all_sess;
> +
> +		err = ibtrs_clt_create_sess_files(sess);
> +		if (unlikely(err))
> +			goto close_all_sess;
> +	}
> +	err = alloc_tags(clt);
> +	if (unlikely(err)) {
> +		ibtrs_err(clt, "alloc_tags(), err: %d\n", err);
> +		goto close_all_sess;
> +	}
> +	err = ibtrs_clt_create_sysfs_root_files(clt);
> +	if (unlikely(err))
> +		goto close_all_sess;
> +
> +	/*
> +	 * There is a race if someone decides to completely remove just
> +	 * newly created path using sysfs entry.  To avoid the race we
> +	 * use simple 'opened' flag, see ibtrs_clt_remove_path_from_sysfs().
> +	 */
> +	clt->opened = true;
> +
> +	/* Do not let module be unloaded if client is alive */
> +	__module_get(THIS_MODULE);
> +
> +	return clt;
> +
> +close_all_sess:
> +	list_for_each_entry_safe(sess, tmp, &clt->paths_list, s.entry) {
> +		ibtrs_clt_destroy_sess_files(sess, NULL);
> +		ibtrs_clt_close_conns(sess, true);
> +		free_sess(sess);
> +	}
> +	free_clt(clt);
> +
> +out:
> +	return ERR_PTR(err);
> +}
> +EXPORT_SYMBOL(ibtrs_clt_open);
> +
> +void ibtrs_clt_close(struct ibtrs_clt *clt)
> +{
> +	struct ibtrs_clt_sess *sess, *tmp;
> +
> +	/* Firstly forbid sysfs access */
> +	ibtrs_clt_destroy_sysfs_root_files(clt);
> +	ibtrs_clt_destroy_sysfs_root_folders(clt);
> +
> +	/* Now it is safe to iterate over all paths without locks */
> +	list_for_each_entry_safe(sess, tmp, &clt->paths_list, s.entry) {
> +		ibtrs_clt_destroy_sess_files(sess, NULL);
> +		ibtrs_clt_close_conns(sess, true);
> +		free_sess(sess);
> +	}
> +	free_clt(clt);
> +	module_put(THIS_MODULE);
> +}
> +EXPORT_SYMBOL(ibtrs_clt_close);
> +
> +int ibtrs_clt_reconnect_from_sysfs(struct ibtrs_clt_sess *sess)
> +{
> +	enum ibtrs_clt_state old_state;
> +	int err = -EBUSY;
> +	bool changed;
> +
> +	changed = ibtrs_clt_change_state_get_old(sess, IBTRS_CLT_RECONNECTING,
> +						 &old_state);
> +	if (changed) {
> +		sess->reconnect_attempts = 0;
> +		queue_delayed_work(ibtrs_wq, &sess->reconnect_dwork, 0);
> +	}
> +	if (changed || old_state == IBTRS_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(&sess->reconnect_dwork);
> +		err = ibtrs_clt_sess_is_connected(sess) ? 0 : -ENOTCONN;
> +	}
> +
> +	return err;
> +}
> +
> +int ibtrs_clt_disconnect_from_sysfs(struct ibtrs_clt_sess *sess)
> +{
> +	ibtrs_clt_close_conns(sess, true);
> +
> +	return 0;
> +}
> +
> +int ibtrs_clt_remove_path_from_sysfs(struct ibtrs_clt_sess *sess,
> +				     const struct attribute *sysfs_self)
> +{
> +	struct ibtrs_clt *clt = sess->clt;
> +	enum ibtrs_clt_state old_state;
> +	bool changed;
> +
> +	/*
> +	 * That can happen only when userspace tries to remove path
> +	 * very early, when ibtrs_clt_open() is not yet finished.
> +	 */
> +	if (unlikely(!clt->opened))
> +		return -EBUSY;
> +
> +	/*
> +	 * 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 ibtrs_clt_reconnect(), which can again start
> +	 *    reconnecting.
> +	 * 2. State was observed as DEAD - we have someone in parallel
> +	 *    removing the path.
> +	 */
> +	do {
> +		ibtrs_clt_close_conns(sess, true);
> +	} while (!(changed = ibtrs_clt_change_state_get_old(sess,
> +							    IBTRS_CLT_DEAD,
> +							    &old_state)) &&
> +		   old_state != IBTRS_CLT_DEAD);
> +
> +	/*
> +	 * If state was successfully changed to DEAD, commit suicide.
> +	 */
> +	if (likely(changed)) {
> +		ibtrs_clt_destroy_sess_files(sess, sysfs_self);
> +		ibtrs_clt_remove_path_from_arr(sess);
> +		free_sess(sess);
> +	}
> +
> +	return 0;
> +}
> +
> +void ibtrs_clt_set_max_reconnect_attempts(struct ibtrs_clt *clt, int value)
> +{
> +	clt->max_reconnect_attempts = (unsigned int)value;
> +}
> +
> +int ibtrs_clt_get_max_reconnect_attempts(const struct ibtrs_clt *clt)
> +{
> +	return (int)clt->max_reconnect_attempts;
> +}
> +
> +static int ibtrs_clt_rdma_write_desc(struct ibtrs_clt_con *con,
> +				     struct ibtrs_clt_io_req *req, u64 buf,
> +				     size_t u_msg_len, u32 imm,
> +				     struct ibtrs_msg_rdma_write *msg)
> +{
> +	struct ibtrs_clt_sess *sess = to_clt_sess(con->c.sess);
> +	struct ibtrs_sg_desc *desc;
> +	int ret;
> +
> +	desc = kmalloc_array(sess->max_pages_per_mr, sizeof(*desc), GFP_ATOMIC);
> +	if (unlikely(!desc))
> +		return -ENOMEM;
> +
> +	ret = ibtrs_fast_reg_map_data(con, desc, req);
> +	if (unlikely(ret < 0)) {
> +		ibtrs_err_rl(sess,
> +			     "Write request failed, fast reg. data mapping"
> +			     " failed, err: %d\n", ret);
> +		kfree(desc);
> +		return ret;
> +	}
> +	ret = ibtrs_post_send_rdma_desc(con, req, desc, ret, buf,
> +					u_msg_len + sizeof(*msg), imm);
> +	if (unlikely(ret)) {
> +		ibtrs_err(sess, "Write request failed, posting work"
> +			  " request failed, err: %d\n", ret);
> +		ibtrs_unmap_fast_reg_data(con, req);
> +	}
> +	kfree(desc);
> +	return ret;
> +}
> +
> +static int ibtrs_clt_write_req(struct ibtrs_clt_io_req *req)
> +{
> +	struct ibtrs_clt_con *con = req->con;
> +	struct ibtrs_clt_sess *sess = to_clt_sess(con->c.sess);
> +	struct ibtrs_msg_rdma_write *msg;
> +
> +	int ret, count = 0;
> +	u32 imm, buf_id;
> +	u64 buf;
> +
> +	const size_t tsize = sizeof(*msg) + req->data_len + req->usr_len;
> +
> +	if (unlikely(tsize > sess->chunk_size)) {
> +		ibtrs_wrn(sess, "Write request failed, size too big %zu > %d\n",
> +			  tsize, sess->chunk_size);
> +		return -EMSGSIZE;
> +	}
> +	if (req->sg_cnt) {
> +		count = ib_dma_map_sg(sess->s.ib_dev->dev, req->sglist,
> +				      req->sg_cnt, req->dir);
> +		if (unlikely(!count)) {
> +			ibtrs_wrn(sess, "Write request failed, map failed\n");
> +			return -EINVAL;
> +		}
> +	}
> +	/* put ibtrs msg after sg and user message */
> +	msg = req->iu->buf + req->usr_len;
> +	msg->type = cpu_to_le16(IBTRS_MSG_WRITE);
> +	msg->usr_len = cpu_to_le16(req->usr_len);
> +
> +	/* ibtrs message on server side will be after user data and message */
> +	imm = req->tag->mem_off + req->data_len + req->usr_len;
> +	imm = ibtrs_to_io_req_imm(imm);
> +	buf_id = req->tag->mem_id;
> +	req->sg_size = tsize;
> +	buf = sess->srv_rdma_addr[buf_id];
> +
> +	/*
> +	 * Update stats now, after request is successfully sent it is not
> +	 * safe anymore to touch it.
> +	 */
> +	ibtrs_clt_update_all_stats(req, WRITE);
> +
> +	if (count > fmr_sg_cnt)
> +		ret = ibtrs_clt_rdma_write_desc(req->con, req, buf,
> +						req->usr_len, imm, msg);
> +	else
> +		ret = ibtrs_post_send_rdma_more(req->con, req, buf,
> +						req->usr_len + sizeof(*msg),
> +						imm);
> +	if (unlikely(ret)) {
> +		ibtrs_err(sess, "Write request failed: %d\n", ret);
> +		ibtrs_clt_decrease_inflight(&sess->stats);
> +		if (req->sg_cnt)
> +			ib_dma_unmap_sg(sess->s.ib_dev->dev, req->sglist,
> +					req->sg_cnt, req->dir);
> +	}
> +
> +	return ret;
> +}
> +
> +int ibtrs_clt_write(struct ibtrs_clt *clt, ibtrs_conf_fn *conf,
> +		    struct ibtrs_tag *tag, void *priv, const struct kvec *vec,
> +		    size_t nr, size_t data_len, struct scatterlist *sg,
> +		    unsigned int sg_cnt)
> +{
> +	struct ibtrs_clt_io_req *req;
> +	struct ibtrs_clt_sess *sess;
> +
> +	int err = -ECONNABORTED;
> +	struct path_it it;
> +	size_t usr_len;
> +
> +	usr_len = kvec_length(vec, nr);
> +	do_each_path(sess, clt, &it) {
> +		if (unlikely(sess->state != IBTRS_CLT_CONNECTED))
> +			continue;
> +
> +		if (unlikely(usr_len > IO_MSG_SIZE)) {
> +			ibtrs_wrn_rl(sess, "Write request failed, user message"
> +				     " size is %zu B big, max size is %d B\n",
> +				     usr_len, IO_MSG_SIZE);
> +			err = -EMSGSIZE;
> +			break;
> +		}
> +		req = ibtrs_clt_get_req(sess, conf, tag, priv, vec, usr_len,
> +					sg, sg_cnt, data_len, DMA_TO_DEVICE);
> +		err = ibtrs_clt_write_req(req);
> +		if (unlikely(err)) {
> +			req->in_use = false;
> +			continue;
> +		}
> +		/* Success path */
> +		break;
> +	} while_each_path(&it);
> +
> +	return err;
> +}
> +
> +static int ibtrs_clt_read_req(struct ibtrs_clt_io_req *req)
> +{
> +	struct ibtrs_clt_con *con = req->con;
> +	struct ibtrs_clt_sess *sess = to_clt_sess(con->c.sess);
> +	struct ibtrs_msg_rdma_read *msg;
> +	struct ibtrs_ib_dev *ibdev;
> +	struct scatterlist *sg;
> +
> +	int i, ret, count = 0;
> +	u32 imm, buf_id;
> +
> +	const size_t tsize = sizeof(*msg) + req->data_len + req->usr_len;
> +
> +	ibdev = sess->s.ib_dev;
> +
> +	if (unlikely(tsize > sess->chunk_size)) {
> +		ibtrs_wrn(sess, "Read request failed, message size is"
> +			  " %zu, bigger than CHUNK_SIZE %d\n", tsize,
> +			  sess->chunk_size);
> +		return -EMSGSIZE;
> +	}
> +
> +	if (req->sg_cnt) {
> +		count = ib_dma_map_sg(ibdev->dev, req->sglist, req->sg_cnt,
> +				      req->dir);
> +		if (unlikely(!count)) {
> +			ibtrs_wrn(sess, "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(IBTRS_MSG_READ);
> +	msg->sg_cnt = cpu_to_le32(count);
> +	msg->usr_len = cpu_to_le16(req->usr_len);
> +
> +	if (count > fmr_sg_cnt) {
> +		ret = ibtrs_fast_reg_map_data(req->con, msg->desc, req);
> +		if (ret < 0) {
> +			ibtrs_err_rl(sess,
> +				     "Read request failed, failed to map "
> +				     " fast reg. data, err: %d\n", ret);
> +			ib_dma_unmap_sg(ibdev->dev, req->sglist, req->sg_cnt,
> +					req->dir);
> +			return ret;
> +		}
> +		msg->sg_cnt = cpu_to_le32(ret);
> +	} else {
> +		for_each_sg(req->sglist, sg, req->sg_cnt, i) {
> +			msg->desc[i].addr =
> +				cpu_to_le64(ib_sg_dma_address(ibdev->dev, sg));
> +			msg->desc[i].key =
> +				cpu_to_le32(ibdev->rkey);
> +			msg->desc[i].len =
> +				cpu_to_le32(ib_sg_dma_len(ibdev->dev, sg));
> +		}
> +		req->nmdesc = 0;
> +	}
> +	/*
> +	 * ibtrs message will be after the space reserved for disk data and
> +	 * user message
> +	 */
> +	imm = req->tag->mem_off + req->data_len + req->usr_len;
> +	imm = ibtrs_to_io_req_imm(imm);
> +	buf_id = req->tag->mem_id;
> +
> +	req->sg_size  = sizeof(*msg);
> +	req->sg_size += le32_to_cpu(msg->sg_cnt) * sizeof(struct ibtrs_sg_desc);
> +	req->sg_size += req->usr_len;
> +
> +	/*
> +	 * Update stats now, after request is successfully sent it is not
> +	 * safe anymore to touch it.
> +	 */
> +	ibtrs_clt_update_all_stats(req, READ);
> +
> +	ret = ibtrs_post_send_rdma(req->con, req, sess->srv_rdma_addr[buf_id],
> +				   req->data_len, imm);
> +	if (unlikely(ret)) {
> +		ibtrs_err(sess, "Read request failed: %d\n", ret);
> +		ibtrs_clt_decrease_inflight(&sess->stats);
> +		if (unlikely(count > fmr_sg_cnt))
> +			ibtrs_unmap_fast_reg_data(req->con, req);
> +		if (req->sg_cnt)
> +			ib_dma_unmap_sg(ibdev->dev, req->sglist,
> +					req->sg_cnt, req->dir);
> +	}
> +
> +	return ret;
> +}
> +
> +int ibtrs_clt_read(struct ibtrs_clt *clt, ibtrs_conf_fn *conf,
> +		   struct ibtrs_tag *tag, void *priv, const struct kvec *vec,
> +		   size_t nr, size_t data_len, struct scatterlist *sg,
> +		   unsigned int sg_cnt)
> +{
> +	struct ibtrs_clt_io_req *req;
> +	struct ibtrs_clt_sess *sess;
> +
> +	int err = -ECONNABORTED;
> +	struct path_it it;
> +	size_t usr_len;
> +
> +	usr_len = kvec_length(vec, nr);
> +	do_each_path(sess, clt, &it) {
> +		if (unlikely(sess->state != IBTRS_CLT_CONNECTED))
> +			continue;
> +
> +		if (unlikely(usr_len > IO_MSG_SIZE ||
> +			     sizeof(struct ibtrs_msg_rdma_read) +
> +			     sg_cnt * sizeof(struct ibtrs_sg_desc) >
> +			     sess->max_req_size)) {
> +			ibtrs_wrn_rl(sess, "Read request failed, user message"
> +				     " size is %zu B big, max size is %d B\n",
> +				     usr_len, IO_MSG_SIZE);
> +			err = -EMSGSIZE;
> +			break;
> +		}
> +		req = ibtrs_clt_get_req(sess, conf, tag, priv, vec, usr_len,
> +					sg, sg_cnt, data_len, DMA_FROM_DEVICE);
> +		err = ibtrs_clt_read_req(req);
> +		if (unlikely(err)) {
> +			req->in_use = false;
> +			continue;
> +		}
> +		/* Success path */
> +		break;
> +	} while_each_path(&it);
> +
> +	return err;
> +}
> +
> +int ibtrs_clt_request(int dir, ibtrs_conf_fn *conf, struct ibtrs_clt *clt,
> +		      struct ibtrs_tag *tag, void *priv, const struct kvec *vec,
> +		      size_t nr, size_t len, struct scatterlist *sg,
> +		      unsigned int sg_len)
> +{
> +	if (dir == READ)
> +		return ibtrs_clt_read(clt, conf, tag, priv, vec, nr, len, sg,
> +				      sg_len);
> +	else
> +		return ibtrs_clt_write(clt, conf, tag, priv, vec, nr, len, sg,
> +				       sg_len);
> +}
> +EXPORT_SYMBOL(ibtrs_clt_request);
> +
> +int ibtrs_clt_query(struct ibtrs_clt *clt, struct ibtrs_attrs *attr)
> +{
> +	if (unlikely(!ibtrs_clt_is_connected(clt)))
> +		return -ECOMM;
> +
> +	attr->queue_depth      = clt->queue_depth;
> +	attr->max_io_size      = clt->max_io_size;
> +	strlcpy(attr->sessname, clt->sessname, sizeof(attr->sessname));
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL(ibtrs_clt_query);
> +
> +int ibtrs_clt_create_path_from_sysfs(struct ibtrs_clt *clt,
> +				     struct ibtrs_addr *addr)
> +{
> +	struct ibtrs_clt_sess *sess;
> +	int err;
> +
> +	if (ibtrs_clt_path_exists(clt, addr))
> +		return -EEXIST;
> +
> +	sess = alloc_sess(clt, addr, nr_cons_per_session, clt->max_segments);
> +	if (unlikely(IS_ERR(sess)))
> +		return PTR_ERR(sess);
> +
> +	/*
> +	 * 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.
> +	 */
> +	err = ibtrs_clt_add_path_to_arr(sess, addr);
> +	if (unlikely(err))
> +		goto free_sess;
> +
> +	err = init_sess(sess);
> +	if (unlikely(err))
> +		goto close_sess;
> +
> +	err = ibtrs_clt_create_sess_files(sess);
> +	if (unlikely(err))
> +		goto close_sess;
> +
> +	return 0;
> +
> +close_sess:
> +	ibtrs_clt_remove_path_from_arr(sess);
> +	ibtrs_clt_close_conns(sess, true);
> +free_sess:
> +	free_sess(sess);
> +
> +	return err;
> +}
> +
> +static int check_module_params(void)
> +{
> +	if (fmr_sg_cnt > MAX_SEGMENTS || fmr_sg_cnt < 0) {
> +		pr_err("invalid fmr_sg_cnt values\n");
> +		return -EINVAL;
> +	}
> +	if (nr_cons_per_session == 0)
> +		nr_cons_per_session = min_t(unsigned int, nr_cpu_ids, U16_MAX);
> +
> +	return 0;
> +}
> +
> +static int __init ibtrs_client_init(void)
> +{
> +	int err;
> +
> +	pr_info("Loading module %s, version: %s "
> +		"(use_fr: %d, retry_count: %d, "
> +		"fmr_sg_cnt: %d)\n",
> +		KBUILD_MODNAME, IBTRS_VER_STRING,
> +		use_fr,	retry_count, fmr_sg_cnt);
> +	err = check_module_params();
> +	if (err) {
> +		pr_err("Failed to load module, invalid module parameters,"
> +		       " err: %d\n", err);
> +		return err;
> +	}
> +	ibtrs_wq = alloc_workqueue("ibtrs_client_wq", WQ_MEM_RECLAIM, 0);
> +	if (!ibtrs_wq) {
> +		pr_err("Failed to load module, alloc ibtrs_client_wq failed\n");
> +		return -ENOMEM;
> +	}
> +	err = ibtrs_clt_create_sysfs_module_files();
> +	if (err) {
> +		pr_err("Failed to load module, can't create sysfs files,"
> +		       " err: %d\n", err);
> +		goto out_ibtrs_wq;
> +	}
> +
> +	return 0;
> +
> +out_ibtrs_wq:
> +	destroy_workqueue(ibtrs_wq);
> +
> +	return err;
> +}
> +
> +static void __exit ibtrs_client_exit(void)
> +{
> +	ibtrs_clt_destroy_sysfs_module_files();
> +	destroy_workqueue(ibtrs_wq);
> +}
> +
> +module_init(ibtrs_client_init);
> +module_exit(ibtrs_client_exit);
>