xref: /linux/fs/smb/smbdirect/connection.c (revision 3a2c4d55e32ad65efebdb6de44eef3bfa08bb49d)

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *   Copyright (C) 2017, Microsoft Corporation.
 *   Copyright (c) 2025, Stefan Metzmacher
 */

#include "internal.h"
#include <linux/folio_queue.h>

struct smbdirect_map_sges {
	struct ib_sge *sge;
	size_t num_sge;
	size_t max_sge;
	struct ib_device *device;
	u32 local_dma_lkey;
	enum dma_data_direction direction;
};

static ssize_t smbdirect_map_sges_from_iter(struct iov_iter *iter, size_t len,
					    struct smbdirect_map_sges *state);

static void smbdirect_connection_recv_io_refill_work(struct work_struct *work);
static void smbdirect_connection_send_immediate_work(struct work_struct *work);

static void smbdirect_connection_qp_event_handler(struct ib_event *event, void *context)
{
	struct smbdirect_socket *sc = context;

	smbdirect_log_rdma_event(sc, SMBDIRECT_LOG_ERR,
		"%s on device %.*s socket %p (cm_id=%p) status %s first_error %1pe\n",
		ib_event_msg(event->event),
		IB_DEVICE_NAME_MAX,
		event->device->name,
		sc, sc->rdma.cm_id,
		smbdirect_socket_status_string(sc->status),
		SMBDIRECT_DEBUG_ERR_PTR(sc->first_error));

	switch (event->event) {
	case IB_EVENT_CQ_ERR:
	case IB_EVENT_QP_FATAL:
		smbdirect_socket_schedule_cleanup(sc, -ECONNABORTED);
		break;

	default:
		break;
	}
}

static int smbdirect_connection_rdma_event_handler(struct rdma_cm_id *id,
						   struct rdma_cm_event *event)
{
	struct smbdirect_socket *sc = id->context;
	int ret = -ECONNRESET;

	if (event->event == RDMA_CM_EVENT_DEVICE_REMOVAL)
		ret = -ENETDOWN;
	if (IS_ERR(SMBDIRECT_DEBUG_ERR_PTR(event->status)))
		ret = event->status;

	/*
	 * cma_cm_event_handler() has
	 * lockdep_assert_held(&id_priv->handler_mutex);
	 *
	 * Mutexes are not allowed in interrupts,
	 * and we rely on not being in an interrupt here.
	 */
	WARN_ON_ONCE(in_interrupt());

	if (event->event != sc->rdma.expected_event) {
		smbdirect_log_rdma_event(sc, SMBDIRECT_LOG_ERR,
			"%s (first_error=%1pe, expected=%s) => event=%s status=%d => ret=%1pe\n",
			smbdirect_socket_status_string(sc->status),
			SMBDIRECT_DEBUG_ERR_PTR(sc->first_error),
			rdma_event_msg(sc->rdma.expected_event),
			rdma_event_msg(event->event),
			event->status,
			SMBDIRECT_DEBUG_ERR_PTR(ret));

		/*
		 * If we get RDMA_CM_EVENT_DEVICE_REMOVAL,
		 * we should change to SMBDIRECT_SOCKET_DISCONNECTED,
		 * so that rdma_disconnect() is avoided later via
		 * smbdirect_socket_schedule_cleanup[_status]() =>
		 * smbdirect_socket_cleanup_work().
		 *
		 * As otherwise we'd set SMBDIRECT_SOCKET_DISCONNECTING,
		 * but never ever get RDMA_CM_EVENT_DISCONNECTED and
		 * never reach SMBDIRECT_SOCKET_DISCONNECTED.
		 */
		if (event->event == RDMA_CM_EVENT_DEVICE_REMOVAL)
			smbdirect_socket_schedule_cleanup_status(sc,
								 SMBDIRECT_LOG_ERR,
								 ret,
								 SMBDIRECT_SOCKET_DISCONNECTED);
		else
			smbdirect_socket_schedule_cleanup(sc, ret);
		if (sc->ib.qp)
			ib_drain_qp(sc->ib.qp);
		return 0;
	}

	smbdirect_log_rdma_event(sc, SMBDIRECT_LOG_INFO,
		"%s (first_error=%1pe) event=%s\n",
		smbdirect_socket_status_string(sc->status),
		SMBDIRECT_DEBUG_ERR_PTR(sc->first_error),
		rdma_event_msg(event->event));

	switch (event->event) {
	case RDMA_CM_EVENT_DISCONNECTED:
		/*
		 * We need to change to SMBDIRECT_SOCKET_DISCONNECTED,
		 * so that rdma_disconnect() is avoided later via
		 * smbdirect_socket_schedule_cleanup_status() =>
		 * smbdirect_socket_cleanup_work().
		 *
		 * As otherwise we'd set SMBDIRECT_SOCKET_DISCONNECTING,
		 * but never ever get RDMA_CM_EVENT_DISCONNECTED and
		 * never reach SMBDIRECT_SOCKET_DISCONNECTED.
		 *
		 * This is also a normal disconnect so
		 * SMBDIRECT_LOG_INFO should be good enough
		 * and avoids spamming the default logs.
		 */
		smbdirect_socket_schedule_cleanup_status(sc,
							 SMBDIRECT_LOG_INFO,
							 ret,
							 SMBDIRECT_SOCKET_DISCONNECTED);
		if (sc->ib.qp)
			ib_drain_qp(sc->ib.qp);
		return 0;

	default:
		break;
	}

	/*
	 * This is an internal error, should be handled above via
	 * event->event != sc->rdma.expected_event already.
	 */
	WARN_ON_ONCE(sc->rdma.expected_event != RDMA_CM_EVENT_DISCONNECTED);
	smbdirect_socket_schedule_cleanup(sc, -ECONNABORTED);
	return 0;
}

void smbdirect_connection_rdma_established(struct smbdirect_socket *sc)
{
	smbdirect_log_rdma_event(sc, SMBDIRECT_LOG_INFO,
		"rdma established: device: %.*s local: %pISpsfc remote: %pISpsfc\n",
		IB_DEVICE_NAME_MAX,
		sc->ib.dev->name,
		&sc->rdma.cm_id->route.addr.src_addr,
		&sc->rdma.cm_id->route.addr.dst_addr);

	sc->rdma.cm_id->event_handler = smbdirect_connection_rdma_event_handler;
	sc->rdma.expected_event = RDMA_CM_EVENT_DISCONNECTED;
}

void smbdirect_connection_negotiation_done(struct smbdirect_socket *sc)
{
	if (unlikely(sc->first_error))
		return;

	if (sc->status == SMBDIRECT_SOCKET_CONNECTED)
		/*
		 * This is the accept case where
		 * smbdirect_socket_accept() already sets
		 * SMBDIRECT_SOCKET_CONNECTED
		 */
		goto done;

	if (sc->status != SMBDIRECT_SOCKET_NEGOTIATE_RUNNING) {
		/*
		 * Something went wrong...
		 */
		smbdirect_log_rdma_event(sc, SMBDIRECT_LOG_ERR,
			"status=%s first_error=%1pe local: %pISpsfc remote: %pISpsfc\n",
			smbdirect_socket_status_string(sc->status),
			SMBDIRECT_DEBUG_ERR_PTR(sc->first_error),
			&sc->rdma.cm_id->route.addr.src_addr,
			&sc->rdma.cm_id->route.addr.dst_addr);
		return;
	}

	/*
	 * We are done, so we can wake up the waiter.
	 */
	WARN_ONCE(sc->status == SMBDIRECT_SOCKET_CONNECTED,
		  "status=%s first_error=%1pe",
		  smbdirect_socket_status_string(sc->status),
		  SMBDIRECT_DEBUG_ERR_PTR(sc->first_error));
	sc->status = SMBDIRECT_SOCKET_CONNECTED;

	/*
	 * We need to setup the refill and send immediate work
	 * in order to get a working connection.
	 */
done:
	INIT_WORK(&sc->recv_io.posted.refill_work, smbdirect_connection_recv_io_refill_work);
	INIT_WORK(&sc->idle.immediate_work, smbdirect_connection_send_immediate_work);

	smbdirect_log_rdma_event(sc, SMBDIRECT_LOG_INFO,
		"negotiated: local: %pISpsfc remote: %pISpsfc\n",
		&sc->rdma.cm_id->route.addr.src_addr,
		&sc->rdma.cm_id->route.addr.dst_addr);

	wake_up(&sc->status_wait);
}

static u32 smbdirect_rdma_rw_send_wrs(struct ib_device *dev,
				      const struct ib_qp_init_attr *attr)
{
	/*
	 * This could be split out of rdma_rw_init_qp()
	 * and be a helper function next to rdma_rw_mr_factor()
	 *
	 * We can't check unlikely(rdma_rw_force_mr) here,
	 * but that is most likely 0 anyway.
	 */
	u32 factor;

	WARN_ON_ONCE(attr->port_num == 0);

	/*
	 * Each context needs at least one RDMA READ or WRITE WR.
	 *
	 * For some hardware we might need more, eventually we should ask the
	 * HCA driver for a multiplier here.
	 */
	factor = 1;

	/*
	 * If the device needs MRs to perform RDMA READ or WRITE operations,
	 * we'll need two additional MRs for the registrations and the
	 * invalidation.
	 */
	if (rdma_protocol_iwarp(dev, attr->port_num) || dev->attrs.max_sgl_rd)
		factor += 2;	/* inv + reg */

	return factor * attr->cap.max_rdma_ctxs;
}

int smbdirect_connection_create_qp(struct smbdirect_socket *sc)
{
	const struct smbdirect_socket_parameters *sp = &sc->parameters;
	struct ib_qp_init_attr qp_attr;
	struct ib_qp_cap qp_cap;
	u32 rdma_send_wr;
	u32 max_send_wr;
	int ret;

	/*
	 * Note that {rdma,ib}_create_qp() will call
	 * rdma_rw_init_qp() if max_rdma_ctxs is not 0.
	 * It will adjust max_send_wr to the required
	 * number of additional WRs for the RDMA RW operations.
	 * It will cap max_send_wr to the device limit.
	 *
	 * We use allocate sp->responder_resources * 2 MRs
	 * and each MR needs WRs for REG and INV, so
	 * we use '* 4'.
	 *
	 * +1 for ib_drain_qp()
	 */
	memset(&qp_cap, 0, sizeof(qp_cap));
	qp_cap.max_send_wr = sp->send_credit_target + sp->responder_resources * 4 + 1;
	qp_cap.max_recv_wr = sp->recv_credit_max + 1;
	qp_cap.max_send_sge = SMBDIRECT_SEND_IO_MAX_SGE;
	qp_cap.max_recv_sge = SMBDIRECT_RECV_IO_MAX_SGE;
	qp_cap.max_inline_data = 0;
	qp_cap.max_rdma_ctxs = sc->rw_io.credits.max;

	/*
	 * Find out the number of max_send_wr
	 * after rdma_rw_init_qp() adjusted it.
	 *
	 * We only do it on a temporary variable,
	 * as rdma_create_qp() will trigger
	 * rdma_rw_init_qp() again.
	 */
	memset(&qp_attr, 0, sizeof(qp_attr));
	qp_attr.cap = qp_cap;
	qp_attr.port_num = sc->rdma.cm_id->port_num;
	rdma_send_wr = smbdirect_rdma_rw_send_wrs(sc->ib.dev, &qp_attr);
	max_send_wr = qp_cap.max_send_wr + rdma_send_wr;

	if (qp_cap.max_send_wr > sc->ib.dev->attrs.max_cqe ||
	    qp_cap.max_send_wr > sc->ib.dev->attrs.max_qp_wr) {
		pr_err("Possible CQE overrun: max_send_wr %d\n",
		       qp_cap.max_send_wr);
		pr_err("device %.*s reporting max_cqe %u max_qp_wr %u\n",
		       IB_DEVICE_NAME_MAX,
		       sc->ib.dev->name,
		       sc->ib.dev->attrs.max_cqe,
		       sc->ib.dev->attrs.max_qp_wr);
		pr_err("consider lowering send_credit_target = %d\n",
		       sp->send_credit_target);
		return -EINVAL;
	}

	if (qp_cap.max_rdma_ctxs &&
	    (max_send_wr >= sc->ib.dev->attrs.max_cqe ||
	     max_send_wr >= sc->ib.dev->attrs.max_qp_wr)) {
		pr_err("Possible CQE overrun: rdma_send_wr %d + max_send_wr %d = %d\n",
		       rdma_send_wr, qp_cap.max_send_wr, max_send_wr);
		pr_err("device %.*s reporting max_cqe %u max_qp_wr %u\n",
		       IB_DEVICE_NAME_MAX,
		       sc->ib.dev->name,
		       sc->ib.dev->attrs.max_cqe,
		       sc->ib.dev->attrs.max_qp_wr);
		pr_err("consider lowering send_credit_target = %d, max_rdma_ctxs = %d\n",
		       sp->send_credit_target, qp_cap.max_rdma_ctxs);
		return -EINVAL;
	}

	if (qp_cap.max_recv_wr > sc->ib.dev->attrs.max_cqe ||
	    qp_cap.max_recv_wr > sc->ib.dev->attrs.max_qp_wr) {
		pr_err("Possible CQE overrun: max_recv_wr %d\n",
		       qp_cap.max_recv_wr);
		pr_err("device %.*s reporting max_cqe %u max_qp_wr %u\n",
		       IB_DEVICE_NAME_MAX,
		       sc->ib.dev->name,
		       sc->ib.dev->attrs.max_cqe,
		       sc->ib.dev->attrs.max_qp_wr);
		pr_err("consider lowering receive_credit_max = %d\n",
		       sp->recv_credit_max);
		return -EINVAL;
	}

	if (qp_cap.max_send_sge > sc->ib.dev->attrs.max_send_sge ||
	    qp_cap.max_recv_sge > sc->ib.dev->attrs.max_recv_sge) {
		pr_err("device %.*s max_send_sge/max_recv_sge = %u/%u too small\n",
		       IB_DEVICE_NAME_MAX,
		       sc->ib.dev->name,
		       sc->ib.dev->attrs.max_send_sge,
		       sc->ib.dev->attrs.max_recv_sge);
		return -EINVAL;
	}

	sc->ib.pd = ib_alloc_pd(sc->ib.dev, 0);
	if (IS_ERR(sc->ib.pd)) {
		pr_err("Can't create RDMA PD: %1pe\n", sc->ib.pd);
		ret = PTR_ERR(sc->ib.pd);
		sc->ib.pd = NULL;
		return ret;
	}

	sc->ib.send_cq = ib_alloc_cq_any(sc->ib.dev, sc,
					 max_send_wr,
					 sc->ib.poll_ctx);
	if (IS_ERR(sc->ib.send_cq)) {
		pr_err("Can't create RDMA send CQ: %1pe\n", sc->ib.send_cq);
		ret = PTR_ERR(sc->ib.send_cq);
		sc->ib.send_cq = NULL;
		goto err;
	}

	sc->ib.recv_cq = ib_alloc_cq_any(sc->ib.dev, sc,
					 qp_cap.max_recv_wr,
					 sc->ib.poll_ctx);
	if (IS_ERR(sc->ib.recv_cq)) {
		pr_err("Can't create RDMA recv CQ: %1pe\n", sc->ib.recv_cq);
		ret = PTR_ERR(sc->ib.recv_cq);
		sc->ib.recv_cq = NULL;
		goto err;
	}

	/*
	 * We reset completely here!
	 * As the above use was just temporary
	 * to calc max_send_wr and rdma_send_wr.
	 *
	 * rdma_create_qp() will trigger rdma_rw_init_qp()
	 * again if max_rdma_ctxs is not 0.
	 */
	memset(&qp_attr, 0, sizeof(qp_attr));
	qp_attr.event_handler = smbdirect_connection_qp_event_handler;
	qp_attr.qp_context = sc;
	qp_attr.cap = qp_cap;
	qp_attr.sq_sig_type = IB_SIGNAL_REQ_WR;
	qp_attr.qp_type = IB_QPT_RC;
	qp_attr.send_cq = sc->ib.send_cq;
	qp_attr.recv_cq = sc->ib.recv_cq;
	qp_attr.port_num = ~0;

	ret = rdma_create_qp(sc->rdma.cm_id, sc->ib.pd, &qp_attr);
	if (ret) {
		pr_err("Can't create RDMA QP: %1pe\n",
		       SMBDIRECT_DEBUG_ERR_PTR(ret));
		goto err;
	}
	sc->ib.qp = sc->rdma.cm_id->qp;

	return 0;
err:
	smbdirect_connection_destroy_qp(sc);
	return ret;
}

void smbdirect_connection_destroy_qp(struct smbdirect_socket *sc)
{
	if (sc->ib.qp) {
		ib_drain_qp(sc->ib.qp);
		sc->ib.qp = NULL;
		rdma_destroy_qp(sc->rdma.cm_id);
	}
	/*
	 * These CQs were created with ib_alloc_cq_any(), which arms an internal
	 * completion handler (ib_cq_poll_work for IB_POLL_WORKQUEUE). They MUST be
	 * torn down with ib_free_cq(), which cancel_work_sync()es that poll work
	 * before freeing the CQ. ib_destroy_cq() skips that step, so a completion
	 * posted late by the (software) provider — e.g. rxe posting an RNR error
	 * from rxe_receiver after rdma_destroy_qp() — re-queues ib_cq_poll_work on
	 * an already-freed CQ (KASAN slab-use-after-free in ib_cq_poll_work).
	 */
	if (sc->ib.recv_cq) {
		ib_free_cq(sc->ib.recv_cq);
		sc->ib.recv_cq = NULL;
	}
	if (sc->ib.send_cq) {
		ib_free_cq(sc->ib.send_cq);
		sc->ib.send_cq = NULL;
	}
	if (sc->ib.pd) {
		ib_dealloc_pd(sc->ib.pd);
		sc->ib.pd = NULL;
	}
}

int smbdirect_connection_create_mem_pools(struct smbdirect_socket *sc)
{
	const struct smbdirect_socket_parameters *sp = &sc->parameters;
	char name[80];
	size_t i;

	/*
	 * We use sizeof(struct smbdirect_negotiate_resp) for the
	 * payload size as it is larger as
	 * sizeof(struct smbdirect_data_transfer).
	 *
	 * This will fit client and server usage for now.
	 */
	snprintf(name, sizeof(name), "smbdirect_send_io_cache_%p", sc);
	struct kmem_cache_args send_io_args = {
		.align		= __alignof__(struct smbdirect_send_io),
	};
	sc->send_io.mem.cache = kmem_cache_create(name,
						  sizeof(struct smbdirect_send_io) +
						  sizeof(struct smbdirect_negotiate_resp),
						  &send_io_args,
						  SLAB_HWCACHE_ALIGN);
	if (!sc->send_io.mem.cache)
		goto err;

	sc->send_io.mem.pool = mempool_create_slab_pool(sp->send_credit_target,
							sc->send_io.mem.cache);
	if (!sc->send_io.mem.pool)
		goto err;

	/*
	 * A payload size of sp->max_recv_size should fit
	 * any message.
	 *
	 * For smbdirect_data_transfer messages the whole
	 * buffer might be exposed to userspace
	 * (currently on the client side...)
	 * The documentation says data_offset = 0 would be
	 * strange but valid.
	 */
	snprintf(name, sizeof(name), "smbdirect_recv_io_cache_%p", sc);
	struct kmem_cache_args recv_io_args = {
		.align		= __alignof__(struct smbdirect_recv_io),
		.useroffset	= sizeof(struct smbdirect_recv_io),
		.usersize	= sp->max_recv_size,
	};
	sc->recv_io.mem.cache = kmem_cache_create(name,
						  sizeof(struct smbdirect_recv_io) +
						  sp->max_recv_size,
						  &recv_io_args,
						  SLAB_HWCACHE_ALIGN);
	if (!sc->recv_io.mem.cache)
		goto err;

	sc->recv_io.mem.pool = mempool_create_slab_pool(sp->recv_credit_max,
							sc->recv_io.mem.cache);
	if (!sc->recv_io.mem.pool)
		goto err;

	for (i = 0; i < sp->recv_credit_max; i++) {
		struct smbdirect_recv_io *recv_io;

		recv_io = mempool_alloc(sc->recv_io.mem.pool,
					sc->recv_io.mem.gfp_mask);
		if (!recv_io)
			goto err;
		recv_io->socket = sc;
		recv_io->sge.length = 0;
		list_add_tail(&recv_io->list, &sc->recv_io.free.list);
	}

	return 0;
err:
	smbdirect_connection_destroy_mem_pools(sc);
	return -ENOMEM;
}

void smbdirect_connection_destroy_mem_pools(struct smbdirect_socket *sc)
{
	struct smbdirect_recv_io *recv_io, *next_io;

	list_for_each_entry_safe(recv_io, next_io, &sc->recv_io.free.list, list) {
		list_del(&recv_io->list);
		mempool_free(recv_io, sc->recv_io.mem.pool);
	}

	/*
	 * Note mempool_destroy() and kmem_cache_destroy()
	 * work fine with a NULL pointer
	 */

	mempool_destroy(sc->recv_io.mem.pool);
	sc->recv_io.mem.pool = NULL;

	kmem_cache_destroy(sc->recv_io.mem.cache);
	sc->recv_io.mem.cache = NULL;

	mempool_destroy(sc->send_io.mem.pool);
	sc->send_io.mem.pool = NULL;

	kmem_cache_destroy(sc->send_io.mem.cache);
	sc->send_io.mem.cache = NULL;
}

struct smbdirect_send_io *smbdirect_connection_alloc_send_io(struct smbdirect_socket *sc)
{
	struct smbdirect_send_io *msg;

	msg = mempool_alloc(sc->send_io.mem.pool, sc->send_io.mem.gfp_mask);
	if (!msg)
		return ERR_PTR(-ENOMEM);
	msg->socket = sc;
	INIT_LIST_HEAD(&msg->sibling_list);
	msg->num_sge = 0;

	return msg;
}

void smbdirect_connection_free_send_io(struct smbdirect_send_io *msg)
{
	struct smbdirect_socket *sc = msg->socket;
	size_t i;

	/*
	 * The list needs to be empty!
	 * The caller should take care of it.
	 */
	WARN_ON_ONCE(!list_empty(&msg->sibling_list));

	/*
	 * Note we call ib_dma_unmap_page(), even if some sges are mapped using
	 * ib_dma_map_single().
	 *
	 * The difference between _single() and _page() only matters for the
	 * ib_dma_map_*() case.
	 *
	 * For the ib_dma_unmap_*() case it does not matter as both take the
	 * dma_addr_t and dma_unmap_single_attrs() is just an alias to
	 * dma_unmap_page_attrs().
	 */
	for (i = 0; i < msg->num_sge; i++)
		ib_dma_unmap_page(sc->ib.dev,
				  msg->sge[i].addr,
				  msg->sge[i].length,
				  DMA_TO_DEVICE);

	mempool_free(msg, sc->send_io.mem.pool);
}

struct smbdirect_recv_io *smbdirect_connection_get_recv_io(struct smbdirect_socket *sc)
{
	struct smbdirect_recv_io *msg = NULL;
	unsigned long flags;

	spin_lock_irqsave(&sc->recv_io.free.lock, flags);
	if (likely(!sc->first_error))
		msg = list_first_entry_or_null(&sc->recv_io.free.list,
					       struct smbdirect_recv_io,
					       list);
	if (likely(msg)) {
		list_del(&msg->list);
		sc->statistics.get_receive_buffer++;
	}
	spin_unlock_irqrestore(&sc->recv_io.free.lock, flags);

	return msg;
}

void smbdirect_connection_put_recv_io(struct smbdirect_recv_io *msg)
{
	struct smbdirect_socket *sc = msg->socket;
	unsigned long flags;

	if (likely(msg->sge.length != 0)) {
		ib_dma_unmap_single(sc->ib.dev,
				    msg->sge.addr,
				    msg->sge.length,
				    DMA_FROM_DEVICE);
		msg->sge.length = 0;
	}

	spin_lock_irqsave(&sc->recv_io.free.lock, flags);
	list_add_tail(&msg->list, &sc->recv_io.free.list);
	sc->statistics.put_receive_buffer++;
	spin_unlock_irqrestore(&sc->recv_io.free.lock, flags);

	queue_work(sc->workqueues.refill, &sc->recv_io.posted.refill_work);
}

void smbdirect_connection_reassembly_append_recv_io(struct smbdirect_socket *sc,
						    struct smbdirect_recv_io *msg,
						    u32 data_length)
{
	unsigned long flags;

	spin_lock_irqsave(&sc->recv_io.reassembly.lock, flags);
	list_add_tail(&msg->list, &sc->recv_io.reassembly.list);
	sc->recv_io.reassembly.queue_length++;
	/*
	 * Make sure reassembly_data_length is updated after list and
	 * reassembly_queue_length are updated. On the dequeue side
	 * reassembly_data_length is checked without a lock to determine
	 * if reassembly_queue_length and list is up to date
	 */
	virt_wmb();
	sc->recv_io.reassembly.data_length += data_length;
	spin_unlock_irqrestore(&sc->recv_io.reassembly.lock, flags);
	sc->statistics.enqueue_reassembly_queue++;
}

struct smbdirect_recv_io *
smbdirect_connection_reassembly_first_recv_io(struct smbdirect_socket *sc)
{
	struct smbdirect_recv_io *msg;

	msg = list_first_entry_or_null(&sc->recv_io.reassembly.list,
				       struct smbdirect_recv_io,
				       list);

	return msg;
}

void smbdirect_connection_negotiate_rdma_resources(struct smbdirect_socket *sc,
						   u8 peer_initiator_depth,
						   u8 peer_responder_resources,
						   const struct rdma_conn_param *param)
{
	struct smbdirect_socket_parameters *sp = &sc->parameters;

	if (rdma_protocol_iwarp(sc->ib.dev, sc->rdma.cm_id->port_num) &&
	    param->private_data_len == 8) {
		/*
		 * Legacy clients with only iWarp MPA v1 support
		 * need a private blob in order to negotiate
		 * the IRD/ORD values.
		 */
		const __be32 *ird_ord_hdr = param->private_data;
		u32 ird32 = be32_to_cpu(ird_ord_hdr[0]);
		u32 ord32 = be32_to_cpu(ird_ord_hdr[1]);

		/*
		 * cifs.ko sends the legacy IRD/ORD negotiation
		 * event if iWarp MPA v2 was used.
		 *
		 * Here we check that the values match and only
		 * mark the client as legacy if they don't match.
		 */
		if ((u32)param->initiator_depth != ird32 ||
		    (u32)param->responder_resources != ord32) {
			/*
			 * There are broken clients (old cifs.ko)
			 * using little endian and also
			 * struct rdma_conn_param only uses u8
			 * for initiator_depth and responder_resources,
			 * so we truncate the value to U8_MAX.
			 *
			 * smb_direct_accept_client() will then
			 * do the real negotiation in order to
			 * select the minimum between client and
			 * server.
			 */
			ird32 = min_t(u32, ird32, U8_MAX);
			ord32 = min_t(u32, ord32, U8_MAX);

			sc->rdma.legacy_iwarp = true;
			peer_initiator_depth = (u8)ird32;
			peer_responder_resources = (u8)ord32;
		}
	}

	/*
	 * negotiate the value by using the minimum
	 * between client and server if the client provided
	 * non 0 values.
	 */
	if (peer_initiator_depth != 0)
		sp->initiator_depth = min_t(u8, sp->initiator_depth,
					    peer_initiator_depth);
	if (peer_responder_resources != 0)
		sp->responder_resources = min_t(u8, sp->responder_resources,
						peer_responder_resources);
}

bool smbdirect_connection_is_connected(struct smbdirect_socket *sc)
{
	if (unlikely(!sc || sc->first_error || sc->status != SMBDIRECT_SOCKET_CONNECTED))
		return false;
	return true;
}
EXPORT_SYMBOL_GPL(smbdirect_connection_is_connected);

int smbdirect_connection_wait_for_connected(struct smbdirect_socket *sc)
{
	const struct smbdirect_socket_parameters *sp = &sc->parameters;
	union {
		struct sockaddr sa;
		struct sockaddr_storage ss;
	} src_addr, dst_addr;
	const struct sockaddr *src = NULL;
	const struct sockaddr *dst = NULL;
	char _devname[IB_DEVICE_NAME_MAX] = { 0, };
	const char *devname = NULL;
	int ret;

	if (sc->rdma.cm_id) {
		src_addr.ss = sc->rdma.cm_id->route.addr.src_addr;
		if (src_addr.sa.sa_family != AF_UNSPEC)
			src = &src_addr.sa;
		dst_addr.ss = sc->rdma.cm_id->route.addr.dst_addr;
		if (dst_addr.sa.sa_family != AF_UNSPEC)
			dst = &dst_addr.sa;

		if (sc->ib.dev) {
			memcpy(_devname, sc->ib.dev->name, IB_DEVICE_NAME_MAX);
			devname = _devname;
		}
	}

	smbdirect_log_rdma_event(sc, SMBDIRECT_LOG_INFO,
		"waiting for connection: device: %.*s local: %pISpsfc remote: %pISpsfc\n",
		IB_DEVICE_NAME_MAX, devname, src, dst);

	ret = wait_event_interruptible_timeout(sc->status_wait,
					       sc->status == SMBDIRECT_SOCKET_CONNECTED ||
					       sc->first_error,
					       msecs_to_jiffies(sp->negotiate_timeout_msec));
	if (sc->rdma.cm_id) {
		/*
		 * Maybe src and dev are updated in the meantime.
		 */
		src_addr.ss = sc->rdma.cm_id->route.addr.src_addr;
		if (src_addr.sa.sa_family != AF_UNSPEC)
			src = &src_addr.sa;
		dst_addr.ss = sc->rdma.cm_id->route.addr.dst_addr;
		if (dst_addr.sa.sa_family != AF_UNSPEC)
			dst = &dst_addr.sa;

		if (sc->ib.dev) {
			memcpy(_devname, sc->ib.dev->name, IB_DEVICE_NAME_MAX);
			devname = _devname;
		}
	}
	if (ret == 0)
		ret = -ETIMEDOUT;
	if (ret < 0)
		smbdirect_socket_schedule_cleanup(sc, ret);
	if (sc->first_error) {
		int lvl = SMBDIRECT_LOG_ERR;

		ret = sc->first_error;
		if (ret == -ENODEV)
			lvl = SMBDIRECT_LOG_INFO;

		smbdirect_log_rdma_event(sc, lvl,
			"connection failed %1pe device: %.*s local: %pISpsfc remote: %pISpsfc\n",
			SMBDIRECT_DEBUG_ERR_PTR(ret),
			IB_DEVICE_NAME_MAX, devname, src, dst);
		return ret;
	}

	return 0;
}
EXPORT_SYMBOL_GPL(smbdirect_connection_wait_for_connected);

void smbdirect_connection_idle_timer_work(struct work_struct *work)
{
	struct smbdirect_socket *sc =
		container_of(work, struct smbdirect_socket, idle.timer_work.work);
	const struct smbdirect_socket_parameters *sp = &sc->parameters;

	if (sc->idle.keepalive != SMBDIRECT_KEEPALIVE_NONE) {
		smbdirect_log_keep_alive(sc, SMBDIRECT_LOG_ERR,
			"%s => timeout sc->idle.keepalive=%s\n",
			smbdirect_socket_status_string(sc->status),
			sc->idle.keepalive == SMBDIRECT_KEEPALIVE_SENT ?
			"SENT" : "PENDING");
		smbdirect_socket_schedule_cleanup(sc, -ETIMEDOUT);
		return;
	}

	if (sc->status != SMBDIRECT_SOCKET_CONNECTED)
		return;

	/*
	 * Now use the keepalive timeout (instead of keepalive interval)
	 * in order to wait for a response
	 */
	sc->idle.keepalive = SMBDIRECT_KEEPALIVE_PENDING;
	mod_delayed_work(sc->workqueues.idle, &sc->idle.timer_work,
			 msecs_to_jiffies(sp->keepalive_timeout_msec));
	smbdirect_log_keep_alive(sc, SMBDIRECT_LOG_INFO,
		"schedule send of empty idle message\n");
	queue_work(sc->workqueues.immediate, &sc->idle.immediate_work);
}

u16 smbdirect_connection_grant_recv_credits(struct smbdirect_socket *sc)
{
	int missing;
	int available;
	int new_credits;

	if (atomic_read(&sc->recv_io.credits.count) >= sc->recv_io.credits.target)
		return 0;

	missing = (int)sc->recv_io.credits.target - atomic_read(&sc->recv_io.credits.count);
	available = atomic_xchg(&sc->recv_io.credits.available, 0);
	new_credits = min3((int)U16_MAX, missing, available);
	if (new_credits <= 0) {
		/*
		 * If credits are available, but not granted
		 * we need to re-add them again.
		 */
		if (available)
			atomic_add(available, &sc->recv_io.credits.available);
		return 0;
	}

	if (new_credits < available) {
		/*
		 * Readd the remaining available again.
		 */
		available -= new_credits;
		atomic_add(available, &sc->recv_io.credits.available);
	}

	/*
	 * Remember we granted the credits
	 */
	atomic_add(new_credits, &sc->recv_io.credits.count);
	return new_credits;
}

static bool smbdirect_connection_request_keep_alive(struct smbdirect_socket *sc)
{
	const struct smbdirect_socket_parameters *sp = &sc->parameters;

	if (sc->idle.keepalive == SMBDIRECT_KEEPALIVE_PENDING) {
		sc->idle.keepalive = SMBDIRECT_KEEPALIVE_SENT;
		/*
		 * Now use the keepalive timeout (instead of keepalive interval)
		 * in order to wait for a response
		 */
		mod_delayed_work(sc->workqueues.idle, &sc->idle.timer_work,
				 msecs_to_jiffies(sp->keepalive_timeout_msec));
		return true;
	}

	return false;
}

int smbdirect_connection_post_send_wr(struct smbdirect_socket *sc,
				      struct ib_send_wr *wr)
{
	int ret;

	if (unlikely(sc->first_error))
		return sc->first_error;

	atomic_inc(&sc->send_io.pending.count);
	ret = ib_post_send(sc->ib.qp, wr, NULL);
	if (ret) {
		atomic_dec(&sc->send_io.pending.count);
		smbdirect_log_rdma_send(sc, SMBDIRECT_LOG_ERR,
			"ib_post_send() failed %1pe\n",
			SMBDIRECT_DEBUG_ERR_PTR(ret));
		smbdirect_socket_schedule_cleanup(sc, ret);
	}

	return ret;
}

static void smbdirect_connection_send_batch_init(struct smbdirect_send_batch *batch,
						 bool need_invalidate_rkey,
						 unsigned int remote_key)
{
	INIT_LIST_HEAD(&batch->msg_list);
	batch->wr_cnt = 0;
	batch->need_invalidate_rkey = need_invalidate_rkey;
	batch->remote_key = remote_key;
	batch->credit = 0;
}

int smbdirect_connection_send_batch_flush(struct smbdirect_socket *sc,
					  struct smbdirect_send_batch *batch,
					  bool is_last)
{
	struct smbdirect_send_io *first, *last;
	int ret = 0;

	if (list_empty(&batch->msg_list))
		goto release_credit;

	first = list_first_entry(&batch->msg_list,
				 struct smbdirect_send_io,
				 sibling_list);
	last = list_last_entry(&batch->msg_list,
			       struct smbdirect_send_io,
			       sibling_list);

	if (batch->need_invalidate_rkey) {
		first->wr.opcode = IB_WR_SEND_WITH_INV;
		first->wr.ex.invalidate_rkey = batch->remote_key;
		batch->need_invalidate_rkey = false;
		batch->remote_key = 0;
	}

	last->wr.send_flags = IB_SEND_SIGNALED;
	last->wr.wr_cqe = &last->cqe;

	/*
	 * Remove last from send_ctx->msg_list
	 * and splice the rest of send_ctx->msg_list
	 * to last->sibling_list.
	 *
	 * send_ctx->msg_list is a valid empty list
	 * at the end.
	 */
	list_del_init(&last->sibling_list);
	list_splice_tail_init(&batch->msg_list, &last->sibling_list);
	batch->wr_cnt = 0;

	ret = smbdirect_connection_post_send_wr(sc, &first->wr);
	if (ret) {
		struct smbdirect_send_io *sibling, *next;

		list_for_each_entry_safe(sibling, next, &last->sibling_list, sibling_list) {
			list_del_init(&sibling->sibling_list);
			smbdirect_connection_free_send_io(sibling);
		}
		smbdirect_connection_free_send_io(last);
	}

release_credit:
	if (is_last && !ret && batch->credit) {
		atomic_add(batch->credit, &sc->send_io.bcredits.count);
		batch->credit = 0;
		wake_up(&sc->send_io.bcredits.wait_queue);
	}

	return ret;
}
EXPORT_SYMBOL_GPL(smbdirect_connection_send_batch_flush);

struct smbdirect_send_batch *
smbdirect_init_send_batch_storage(struct smbdirect_send_batch_storage *storage,
				  bool need_invalidate_rkey,
				  unsigned int remote_key)
{
	struct smbdirect_send_batch *batch = (struct smbdirect_send_batch *)storage;

	memset(storage, 0, sizeof(*storage));
	BUILD_BUG_ON(sizeof(*batch) > sizeof(*storage));

	smbdirect_connection_send_batch_init(batch,
					     need_invalidate_rkey,
					     remote_key);

	return batch;
}
EXPORT_SYMBOL_GPL(smbdirect_init_send_batch_storage);

static int smbdirect_connection_wait_for_send_bcredit(struct smbdirect_socket *sc,
						      struct smbdirect_send_batch *batch)
{
	int ret;

	if (batch->credit)
		return 0;

	ret = smbdirect_socket_wait_for_credits(sc,
						 SMBDIRECT_SOCKET_CONNECTED,
						 -ENOTCONN,
						 &sc->send_io.bcredits.wait_queue,
						 &sc->send_io.bcredits.count,
						 1);
	if (ret)
		return ret;

	batch->credit = 1;
	return 0;
}

static int smbdirect_connection_wait_for_send_lcredit(struct smbdirect_socket *sc,
						      struct smbdirect_send_batch *batch)
{
	if (batch && atomic_read(&sc->send_io.lcredits.count) <= 1) {
		int ret;

		ret = smbdirect_connection_send_batch_flush(sc, batch, false);
		if (ret)
			return ret;
	}

	return smbdirect_socket_wait_for_credits(sc,
						 SMBDIRECT_SOCKET_CONNECTED,
						 -ENOTCONN,
						 &sc->send_io.lcredits.wait_queue,
						 &sc->send_io.lcredits.count,
						 1);
}

static int smbdirect_connection_wait_for_send_credits(struct smbdirect_socket *sc,
						      struct smbdirect_send_batch *batch)
{
	if (batch && (batch->wr_cnt >= 16 || atomic_read(&sc->send_io.credits.count) <= 1)) {
		int ret;

		ret = smbdirect_connection_send_batch_flush(sc, batch, false);
		if (ret)
			return ret;
	}

	return smbdirect_socket_wait_for_credits(sc,
						 SMBDIRECT_SOCKET_CONNECTED,
						 -ENOTCONN,
						 &sc->send_io.credits.wait_queue,
						 &sc->send_io.credits.count,
						 1);
}

static void smbdirect_connection_send_io_done(struct ib_cq *cq, struct ib_wc *wc);

static int smbdirect_connection_post_send_io(struct smbdirect_socket *sc,
					     struct smbdirect_send_batch *batch,
					     struct smbdirect_send_io *msg)
{
	int i;

	for (i = 0; i < msg->num_sge; i++)
		ib_dma_sync_single_for_device(sc->ib.dev,
					      msg->sge[i].addr, msg->sge[i].length,
					      DMA_TO_DEVICE);

	msg->cqe.done = smbdirect_connection_send_io_done;
	msg->wr.wr_cqe = &msg->cqe;
	msg->wr.opcode = IB_WR_SEND;
	msg->wr.sg_list = &msg->sge[0];
	msg->wr.num_sge = msg->num_sge;
	msg->wr.next = NULL;

	if (batch) {
		msg->wr.send_flags = 0;
		if (!list_empty(&batch->msg_list)) {
			struct smbdirect_send_io *last;

			last = list_last_entry(&batch->msg_list,
					       struct smbdirect_send_io,
					       sibling_list);
			last->wr.next = &msg->wr;
		}
		list_add_tail(&msg->sibling_list, &batch->msg_list);
		batch->wr_cnt++;
		return 0;
	}

	msg->wr.send_flags = IB_SEND_SIGNALED;
	return smbdirect_connection_post_send_wr(sc, &msg->wr);
}

int smbdirect_connection_send_single_iter(struct smbdirect_socket *sc,
					  struct smbdirect_send_batch *batch,
					  struct iov_iter *iter,
					  unsigned int flags,
					  u32 remaining_data_length)
{
	const struct smbdirect_socket_parameters *sp = &sc->parameters;
	struct smbdirect_send_batch _batch;
	struct smbdirect_send_io *msg;
	struct smbdirect_data_transfer *packet;
	size_t header_length;
	u16 new_credits = 0;
	u32 data_length = 0;
	int ret;

	if (WARN_ON_ONCE(flags))
		return -EINVAL; /* no flags support for now */

	if (iter) {
		if (WARN_ON_ONCE(iov_iter_rw(iter) != ITER_SOURCE))
			return -EINVAL; /* It's a bug in upper layer to get there */

		header_length = sizeof(struct smbdirect_data_transfer);
		if (WARN_ON_ONCE(remaining_data_length == 0 ||
				 iov_iter_count(iter) > remaining_data_length))
			return -EINVAL;
	} else {
		/* If this is a packet without payload, don't send padding */
		header_length = offsetof(struct smbdirect_data_transfer, padding);
		if (WARN_ON_ONCE(remaining_data_length))
			return -EINVAL;
	}

	if (sc->status != SMBDIRECT_SOCKET_CONNECTED) {
		smbdirect_log_write(sc, SMBDIRECT_LOG_ERR,
			"status=%s first_error=%1pe => %1pe\n",
			smbdirect_socket_status_string(sc->status),
			SMBDIRECT_DEBUG_ERR_PTR(sc->first_error),
			SMBDIRECT_DEBUG_ERR_PTR(-ENOTCONN));
		return -ENOTCONN;
	}

	if (!batch) {
		smbdirect_connection_send_batch_init(&_batch, false, 0);
		batch = &_batch;
	}

	ret = smbdirect_connection_wait_for_send_bcredit(sc, batch);
	if (ret)
		goto bcredit_failed;

	ret = smbdirect_connection_wait_for_send_lcredit(sc, batch);
	if (ret)
		goto lcredit_failed;

	ret = smbdirect_connection_wait_for_send_credits(sc, batch);
	if (ret)
		goto credit_failed;

	new_credits = smbdirect_connection_grant_recv_credits(sc);
	if (new_credits == 0 &&
	    atomic_read(&sc->send_io.credits.count) == 0 &&
	    atomic_read(&sc->recv_io.credits.count) == 0) {
		/*
		 * queue the refill work in order to
		 * get some new recv credits we can grant to
		 * the peer.
		 */
		queue_work(sc->workqueues.refill, &sc->recv_io.posted.refill_work);

		/*
		 * wait until either the refill work or the peer
		 * granted new credits
		 */
		ret = wait_event_interruptible(sc->send_io.credits.wait_queue,
					       atomic_read(&sc->send_io.credits.count) >= 1 ||
					       atomic_read(&sc->recv_io.credits.available) >= 1 ||
					       sc->status != SMBDIRECT_SOCKET_CONNECTED);
		if (sc->status != SMBDIRECT_SOCKET_CONNECTED)
			ret = -ENOTCONN;
		if (ret < 0)
			goto credit_failed;

		new_credits = smbdirect_connection_grant_recv_credits(sc);
	}

	msg = smbdirect_connection_alloc_send_io(sc);
	if (IS_ERR(msg)) {
		ret = PTR_ERR(msg);
		goto alloc_failed;
	}

	/* Map the packet to DMA */
	msg->sge[0].addr = ib_dma_map_single(sc->ib.dev,
					     msg->packet,
					     header_length,
					     DMA_TO_DEVICE);
	ret = ib_dma_mapping_error(sc->ib.dev, msg->sge[0].addr);
	if (ret)
		goto err;

	msg->sge[0].length = header_length;
	msg->sge[0].lkey = sc->ib.pd->local_dma_lkey;
	msg->num_sge = 1;

	if (iter) {
		struct smbdirect_map_sges extract = {
			.num_sge	= msg->num_sge,
			.max_sge	= ARRAY_SIZE(msg->sge),
			.sge		= msg->sge,
			.device		= sc->ib.dev,
			.local_dma_lkey	= sc->ib.pd->local_dma_lkey,
			.direction	= DMA_TO_DEVICE,
		};
		size_t payload_len = umin(iov_iter_count(iter),
					  sp->max_send_size - sizeof(*packet));

		ret = smbdirect_map_sges_from_iter(iter, payload_len, &extract);
		if (ret < 0)
			goto err;
		data_length = ret;
		remaining_data_length -= data_length;
		msg->num_sge = extract.num_sge;
	}

	/* Fill in the packet header */
	packet = (struct smbdirect_data_transfer *)msg->packet;
	packet->credits_requested = cpu_to_le16(sp->send_credit_target);
	packet->credits_granted = cpu_to_le16(new_credits);

	packet->flags = 0;
	if (smbdirect_connection_request_keep_alive(sc))
		packet->flags |= cpu_to_le16(SMBDIRECT_FLAG_RESPONSE_REQUESTED);

	packet->reserved = 0;
	if (!data_length)
		packet->data_offset = 0;
	else
		packet->data_offset = cpu_to_le32(24);
	packet->data_length = cpu_to_le32(data_length);
	packet->remaining_data_length = cpu_to_le32(remaining_data_length);
	packet->padding = 0;

	smbdirect_log_outgoing(sc, SMBDIRECT_LOG_INFO,
		"DataOut: %s=%u, %s=%u, %s=0x%x, %s=%u, %s=%u, %s=%u\n",
		"CreditsRequested",
		le16_to_cpu(packet->credits_requested),
		"CreditsGranted",
		le16_to_cpu(packet->credits_granted),
		"Flags",
		le16_to_cpu(packet->flags),
		"RemainingDataLength",
		le32_to_cpu(packet->remaining_data_length),
		"DataOffset",
		le32_to_cpu(packet->data_offset),
		"DataLength",
		le32_to_cpu(packet->data_length));

	ret = smbdirect_connection_post_send_io(sc, batch, msg);
	if (ret)
		goto err;

	/*
	 * From here msg is moved to send_ctx
	 * and we should not free it explicitly.
	 */

	if (batch == &_batch) {
		ret = smbdirect_connection_send_batch_flush(sc, batch, true);
		if (ret)
			goto flush_failed;
	}

	return data_length;
err:
	smbdirect_connection_free_send_io(msg);
flush_failed:
alloc_failed:
	atomic_inc(&sc->send_io.credits.count);
credit_failed:
	atomic_inc(&sc->send_io.lcredits.count);
lcredit_failed:
	atomic_add(batch->credit, &sc->send_io.bcredits.count);
	batch->credit = 0;
bcredit_failed:
	return ret;
}
EXPORT_SYMBOL_GPL(smbdirect_connection_send_single_iter);

int smbdirect_connection_send_wait_zero_pending(struct smbdirect_socket *sc)
{
	/*
	 * As an optimization, we don't wait for individual I/O to finish
	 * before sending the next one.
	 * Send them all and wait for pending send count to get to 0
	 * that means all the I/Os have been out and we are good to return
	 */

	wait_event(sc->send_io.pending.zero_wait_queue,
		   atomic_read(&sc->send_io.pending.count) == 0 ||
		   sc->status != SMBDIRECT_SOCKET_CONNECTED);
	if (sc->status != SMBDIRECT_SOCKET_CONNECTED) {
		smbdirect_log_write(sc, SMBDIRECT_LOG_ERR,
			"status=%s first_error=%1pe => %1pe\n",
			smbdirect_socket_status_string(sc->status),
			SMBDIRECT_DEBUG_ERR_PTR(sc->first_error),
			SMBDIRECT_DEBUG_ERR_PTR(-ENOTCONN));
		return -ENOTCONN;
	}

	return 0;
}
EXPORT_SYMBOL_GPL(smbdirect_connection_send_wait_zero_pending);

int smbdirect_connection_send_iter(struct smbdirect_socket *sc,
				   struct iov_iter *iter,
				   unsigned int flags,
				   bool need_invalidate,
				   unsigned int remote_key)
{
	const struct smbdirect_socket_parameters *sp = &sc->parameters;
	struct smbdirect_send_batch batch;
	int total_count = iov_iter_count(iter);
	int ret;
	int error = 0;
	__be32 hdr;

	if (WARN_ONCE(flags, "unexpected flags=0x%x\n", flags))
		return -EINVAL; /* no flags support for now */

	if (WARN_ON_ONCE(iov_iter_rw(iter) != ITER_SOURCE))
		return -EINVAL; /* It's a bug in upper layer to get there */

	if (sc->status != SMBDIRECT_SOCKET_CONNECTED) {
		smbdirect_log_write(sc, SMBDIRECT_LOG_INFO,
			"status=%s first_error=%1pe => %1pe\n",
			smbdirect_socket_status_string(sc->status),
			SMBDIRECT_DEBUG_ERR_PTR(sc->first_error),
			SMBDIRECT_DEBUG_ERR_PTR(-ENOTCONN));
		return -ENOTCONN;
	}

	/*
	 * For now we expect the iter to have the full
	 * message, including a 4 byte length header.
	 */
	if (iov_iter_count(iter) <= 4)
		return -EINVAL;
	if (!copy_from_iter_full(&hdr, sizeof(hdr), iter))
		return -EFAULT;
	if (iov_iter_count(iter) != be32_to_cpu(hdr))
		return -EINVAL;

	/*
	 * The size must fit into the negotiated
	 * fragmented send size.
	 */
	if (iov_iter_count(iter) > sp->max_fragmented_send_size)
		return -EMSGSIZE;

	smbdirect_log_write(sc, SMBDIRECT_LOG_INFO,
		"Sending (RDMA): length=%zu\n",
		iov_iter_count(iter));

	smbdirect_connection_send_batch_init(&batch, need_invalidate, remote_key);
	while (iov_iter_count(iter)) {
		ret = smbdirect_connection_send_single_iter(sc,
							    &batch,
							    iter,
							    flags,
							    iov_iter_count(iter));
		if (unlikely(ret < 0)) {
			error = ret;
			break;
		}
	}

	ret = smbdirect_connection_send_batch_flush(sc, &batch, true);
	if (unlikely(ret && !error))
		error = ret;

	/*
	 * As an optimization, we don't wait for individual I/O to finish
	 * before sending the next one.
	 * Send them all and wait for pending send count to get to 0
	 * that means all the I/Os have been out and we are good to return
	 */

	ret = smbdirect_connection_send_wait_zero_pending(sc);
	if (unlikely(ret && !error))
		error = ret;

	if (unlikely(error))
		return error;

	return total_count;
}
EXPORT_SYMBOL_GPL(smbdirect_connection_send_iter);

static void smbdirect_connection_send_io_done(struct ib_cq *cq, struct ib_wc *wc)
{
	struct smbdirect_send_io *msg =
		container_of(wc->wr_cqe, struct smbdirect_send_io, cqe);
	struct smbdirect_socket *sc = msg->socket;
	struct smbdirect_send_io *sibling, *next;
	int lcredits = 0;

	smbdirect_log_rdma_send(sc, SMBDIRECT_LOG_INFO,
		"smbdirect_send_io completed. status='%s (%d)', opcode=%d\n",
		ib_wc_status_msg(wc->status), wc->status, wc->opcode);

	if (unlikely(!(msg->wr.send_flags & IB_SEND_SIGNALED))) {
		/*
		 * This happens when smbdirect_send_io is a sibling
		 * before the final message, it is signaled on
		 * error anyway, so we need to skip
		 * smbdirect_connection_free_send_io here,
		 * otherwise is will destroy the memory
		 * of the siblings too, which will cause
		 * use after free problems for the others
		 * triggered from ib_drain_qp().
		 */
		if (wc->status != IB_WC_SUCCESS)
			goto skip_free;

		/*
		 * This should not happen!
		 * But we better just close the
		 * connection...
		 */
		smbdirect_log_rdma_send(sc, SMBDIRECT_LOG_ERR,
			"unexpected send completion wc->status=%s (%d) wc->opcode=%d\n",
			ib_wc_status_msg(wc->status), wc->status, wc->opcode);
		smbdirect_socket_schedule_cleanup(sc, -ECONNABORTED);
		return;
	}

	/*
	 * Free possible siblings and then the main send_io
	 */
	list_for_each_entry_safe(sibling, next, &msg->sibling_list, sibling_list) {
		list_del_init(&sibling->sibling_list);
		smbdirect_connection_free_send_io(sibling);
		lcredits += 1;
	}
	/* Note this frees wc->wr_cqe, but not wc */
	smbdirect_connection_free_send_io(msg);
	lcredits += 1;

	if (unlikely(wc->status != IB_WC_SUCCESS || WARN_ON_ONCE(wc->opcode != IB_WC_SEND))) {
skip_free:
		if (wc->status != IB_WC_WR_FLUSH_ERR)
			smbdirect_log_rdma_send(sc, SMBDIRECT_LOG_ERR,
				"wc->status=%s (%d) wc->opcode=%d\n",
				ib_wc_status_msg(wc->status), wc->status, wc->opcode);
		smbdirect_socket_schedule_cleanup(sc, -ECONNABORTED);
		return;
	}

	atomic_add(lcredits, &sc->send_io.lcredits.count);
	wake_up(&sc->send_io.lcredits.wait_queue);

	if (atomic_dec_and_test(&sc->send_io.pending.count))
		wake_up(&sc->send_io.pending.zero_wait_queue);
}

static void smbdirect_connection_send_immediate_work(struct work_struct *work)
{
	struct smbdirect_socket *sc =
		container_of(work, struct smbdirect_socket, idle.immediate_work);
	int ret;

	if (sc->status != SMBDIRECT_SOCKET_CONNECTED)
		return;

	smbdirect_log_keep_alive(sc, SMBDIRECT_LOG_INFO,
		"send an empty message\n");
	sc->statistics.send_empty++;
	ret = smbdirect_connection_send_single_iter(sc, NULL, NULL, 0, 0);
	if (ret < 0) {
		smbdirect_log_write(sc, SMBDIRECT_LOG_ERR,
			"smbdirect_connection_send_single_iter ret=%1pe\n",
			SMBDIRECT_DEBUG_ERR_PTR(ret));
		smbdirect_socket_schedule_cleanup(sc, ret);
	}
}

int smbdirect_connection_post_recv_io(struct smbdirect_recv_io *msg)
{
	struct smbdirect_socket *sc = msg->socket;
	const struct smbdirect_socket_parameters *sp = &sc->parameters;
	struct ib_recv_wr recv_wr = {
		.wr_cqe = &msg->cqe,
		.sg_list = &msg->sge,
		.num_sge = 1,
	};
	int ret;

	if (unlikely(sc->first_error))
		return sc->first_error;

	msg->sge.addr = ib_dma_map_single(sc->ib.dev,
					  msg->packet,
					  sp->max_recv_size,
					  DMA_FROM_DEVICE);
	ret = ib_dma_mapping_error(sc->ib.dev, msg->sge.addr);
	if (ret)
		return ret;

	msg->sge.length = sp->max_recv_size;
	msg->sge.lkey = sc->ib.pd->local_dma_lkey;

	ret = ib_post_recv(sc->ib.qp, &recv_wr, NULL);
	if (ret) {
		smbdirect_log_rdma_recv(sc, SMBDIRECT_LOG_ERR,
			"ib_post_recv failed ret=%d (%1pe)\n",
			ret, SMBDIRECT_DEBUG_ERR_PTR(ret));
		ib_dma_unmap_single(sc->ib.dev,
				    msg->sge.addr,
				    msg->sge.length,
				    DMA_FROM_DEVICE);
		msg->sge.length = 0;
		smbdirect_socket_schedule_cleanup(sc, ret);
	}

	return ret;
}

void smbdirect_connection_recv_io_done(struct ib_cq *cq, struct ib_wc *wc)
{
	struct smbdirect_recv_io *recv_io =
		container_of(wc->wr_cqe, struct smbdirect_recv_io, cqe);
	struct smbdirect_socket *sc = recv_io->socket;
	const struct smbdirect_socket_parameters *sp = &sc->parameters;
	struct smbdirect_data_transfer *data_transfer;
	int current_recv_credits;
	u16 old_recv_credit_target;
	u16 credits_requested;
	u16 credits_granted;
	u16 flags;
	u32 data_offset;
	u32 data_length;
	u32 remaining_data_length;

	if (unlikely(wc->status != IB_WC_SUCCESS || WARN_ON_ONCE(wc->opcode != IB_WC_RECV))) {
		if (wc->status != IB_WC_WR_FLUSH_ERR)
			smbdirect_log_rdma_recv(sc, SMBDIRECT_LOG_ERR,
				"wc->status=%s (%d) wc->opcode=%d\n",
				ib_wc_status_msg(wc->status), wc->status, wc->opcode);
		goto error;
	}

	smbdirect_log_rdma_recv(sc, SMBDIRECT_LOG_INFO,
		"recv_io=0x%p type=%d wc status=%s wc opcode %d byte_len=%d pkey_index=%u\n",
		recv_io, sc->recv_io.expected,
		ib_wc_status_msg(wc->status), wc->opcode,
		wc->byte_len, wc->pkey_index);

	/*
	 * Reset timer to the keepalive interval in
	 * order to trigger our next keepalive message.
	 */
	sc->idle.keepalive = SMBDIRECT_KEEPALIVE_NONE;
	mod_delayed_work(sc->workqueues.idle, &sc->idle.timer_work,
			 msecs_to_jiffies(sp->keepalive_interval_msec));

	ib_dma_sync_single_for_cpu(sc->ib.dev,
				   recv_io->sge.addr,
				   recv_io->sge.length,
				   DMA_FROM_DEVICE);

	if (unlikely(wc->byte_len <
	    offsetof(struct smbdirect_data_transfer, padding))) {
		smbdirect_log_rdma_event(sc, SMBDIRECT_LOG_ERR,
			"wc->byte_len=%u < %zu\n",
			wc->byte_len,
			offsetof(struct smbdirect_data_transfer, padding));
		goto error;
	}

	data_transfer = (struct smbdirect_data_transfer *)recv_io->packet;
	credits_requested = le16_to_cpu(data_transfer->credits_requested);
	credits_granted = le16_to_cpu(data_transfer->credits_granted);
	flags = le16_to_cpu(data_transfer->flags);
	remaining_data_length = le32_to_cpu(data_transfer->remaining_data_length);
	data_offset = le32_to_cpu(data_transfer->data_offset);
	data_length = le32_to_cpu(data_transfer->data_length);

	smbdirect_log_incoming(sc, SMBDIRECT_LOG_INFO,
		"DataIn: %s=%u, %s=%u, %s=0x%x, %s=%u, %s=%u, %s=%u\n",
		"CreditsRequested",
		credits_requested,
		"CreditsGranted",
		credits_granted,
		"Flags",
		flags,
		"RemainingDataLength",
		remaining_data_length,
		"DataOffset",
		data_offset,
		"DataLength",
		data_length);

	if (unlikely(credits_requested == 0)) {
		smbdirect_log_rdma_event(sc, SMBDIRECT_LOG_ERR,
			"invalid: credits_requested == 0\n");
		goto error;
	}

	if (unlikely(data_offset % 8 != 0)) {
		smbdirect_log_rdma_event(sc, SMBDIRECT_LOG_ERR,
			"invalid: data_offset=%u (0x%x) not aligned to 8\n",
			data_offset, data_offset);
		goto error;
	}

	if (unlikely(wc->byte_len < data_offset ||
	    (u64)wc->byte_len < (u64)data_offset + data_length)) {
		smbdirect_log_rdma_event(sc, SMBDIRECT_LOG_ERR,
			"wc->byte_len=%u < date_offset=%u + data_length=%u\n",
			wc->byte_len, data_offset, data_length);
		goto error;
	}

	if (unlikely(remaining_data_length > sp->max_fragmented_recv_size ||
	    data_length > sp->max_fragmented_recv_size ||
	    (u64)remaining_data_length + (u64)data_length > (u64)sp->max_fragmented_recv_size)) {
		smbdirect_log_rdma_event(sc, SMBDIRECT_LOG_ERR,
			"remaining_data_length=%u + data_length=%u > max_fragmented=%u\n",
			remaining_data_length, data_length, sp->max_fragmented_recv_size);
		goto error;
	}

	if (data_length) {
		if (sc->recv_io.reassembly.full_packet_received)
			recv_io->first_segment = true;

		if (remaining_data_length)
			sc->recv_io.reassembly.full_packet_received = false;
		else
			sc->recv_io.reassembly.full_packet_received = true;
	}

	atomic_dec(&sc->recv_io.posted.count);
	current_recv_credits = atomic_dec_return(&sc->recv_io.credits.count);

	/*
	 * We take the value from the peer, which is checked to be higher than 0,
	 * but we limit it to the max value we support in order to have
	 * the main logic simpler.
	 */
	old_recv_credit_target = sc->recv_io.credits.target;
	sc->recv_io.credits.target = credits_requested;
	sc->recv_io.credits.target = min_t(u16, sc->recv_io.credits.target,
					   sp->recv_credit_max);
	if (credits_granted) {
		atomic_add(credits_granted, &sc->send_io.credits.count);
		/*
		 * We have new send credits granted from remote peer
		 * If any sender is waiting for credits, unblock it
		 */
		wake_up(&sc->send_io.credits.wait_queue);
	}

	/* Send an immediate response right away if requested */
	if (flags & SMBDIRECT_FLAG_RESPONSE_REQUESTED) {
		smbdirect_log_keep_alive(sc, SMBDIRECT_LOG_INFO,
			"schedule send of immediate response\n");
		queue_work(sc->workqueues.immediate, &sc->idle.immediate_work);
	}

	/*
	 * If this is a packet with data playload place the data in
	 * reassembly queue and wake up the reading thread
	 */
	if (data_length) {
		if (current_recv_credits <= (sc->recv_io.credits.target / 4) ||
		    sc->recv_io.credits.target > old_recv_credit_target)
			queue_work(sc->workqueues.refill, &sc->recv_io.posted.refill_work);

		smbdirect_connection_reassembly_append_recv_io(sc, recv_io, data_length);
		wake_up(&sc->recv_io.reassembly.wait_queue);
	} else
		smbdirect_connection_put_recv_io(recv_io);

	return;

error:
	/*
	 * Make sure smbdirect_connection_put_recv_io() does not
	 * start recv_io.posted.refill_work.
	 */
	disable_work(&sc->recv_io.posted.refill_work);
	smbdirect_connection_put_recv_io(recv_io);
	smbdirect_socket_schedule_cleanup(sc, -ECONNABORTED);
}

int smbdirect_connection_recv_io_refill(struct smbdirect_socket *sc)
{
	int missing;
	int posted = 0;

	if (unlikely(sc->first_error))
		return sc->first_error;

	/*
	 * Find out how much smbdirect_recv_io buffers we should post.
	 *
	 * Note that sc->recv_io.credits.target is the value
	 * from the peer and it can in theory change over time,
	 * but it is forced to be at least 1 and at max
	 * sp->recv_credit_max.
	 *
	 * So it can happen that missing will be lower than 0,
	 * which means the peer has recently lowered its desired
	 * target, while be already granted a higher number of credits.
	 *
	 * Note 'posted' is the number of smbdirect_recv_io buffers
	 * posted within this function, while sc->recv_io.posted.count
	 * is the overall value of posted smbdirect_recv_io buffers.
	 *
	 * We try to post as much buffers as missing, but
	 * this is limited if a lot of smbdirect_recv_io buffers
	 * are still in the sc->recv_io.reassembly.list instead of
	 * the sc->recv_io.free.list.
	 *
	 */
	missing = (int)sc->recv_io.credits.target - atomic_read(&sc->recv_io.posted.count);
	while (posted < missing) {
		struct smbdirect_recv_io *recv_io;
		int ret;

		/*
		 * It's ok if smbdirect_connection_get_recv_io()
		 * returns NULL, it means smbdirect_recv_io structures
		 * are still be in the reassembly.list.
		 */
		recv_io = smbdirect_connection_get_recv_io(sc);
		if (!recv_io)
			break;

		recv_io->first_segment = false;

		ret = smbdirect_connection_post_recv_io(recv_io);
		if (ret) {
			smbdirect_log_rdma_recv(sc, SMBDIRECT_LOG_ERR,
				"smbdirect_connection_post_recv_io failed rc=%d (%1pe)\n",
				ret, SMBDIRECT_DEBUG_ERR_PTR(ret));
			smbdirect_connection_put_recv_io(recv_io);
			return ret;
		}

		atomic_inc(&sc->recv_io.posted.count);
		posted += 1;
	}

	/* If nothing was posted we're done */
	if (posted == 0)
		return 0;

	atomic_add(posted, &sc->recv_io.credits.available);

	/*
	 * If the last send credit is waiting for credits
	 * it can grant we need to wake it up
	 */
	if (atomic_read(&sc->send_io.bcredits.count) == 0 &&
	    atomic_read(&sc->send_io.credits.count) == 0)
		wake_up(&sc->send_io.credits.wait_queue);

	/*
	 * If we posted at least one smbdirect_recv_io buffer,
	 * we need to inform the peer about it and grant
	 * additional credits.
	 *
	 * However there is one case where we don't want to
	 * do that.
	 *
	 * If only a single credit was missing before
	 * reaching the requested target, we should not
	 * post an immediate send, as that would cause
	 * endless ping pong once a keep alive exchange
	 * is started.
	 *
	 * However if sc->recv_io.credits.target is only 1,
	 * the peer has no credit left and we need to
	 * grant the credit anyway.
	 */
	if (missing == 1 && sc->recv_io.credits.target != 1)
		return 0;

	return posted;
}

static void smbdirect_connection_recv_io_refill_work(struct work_struct *work)
{
	struct smbdirect_socket *sc =
		container_of(work, struct smbdirect_socket, recv_io.posted.refill_work);
	int posted;

	posted = smbdirect_connection_recv_io_refill(sc);
	if (unlikely(posted < 0)) {
		smbdirect_socket_schedule_cleanup(sc, posted);
		return;
	}
	if (posted > 0) {
		smbdirect_log_keep_alive(sc, SMBDIRECT_LOG_INFO,
			"schedule send of an empty message\n");
		queue_work(sc->workqueues.immediate, &sc->idle.immediate_work);
	}
}

int smbdirect_connection_recvmsg(struct smbdirect_socket *sc,
				 struct msghdr *msg,
				 unsigned int flags)
{
	struct smbdirect_recv_io *response;
	struct smbdirect_data_transfer *data_transfer;
	size_t size = iov_iter_count(&msg->msg_iter);
	int to_copy, to_read, data_read, offset;
	u32 data_length, remaining_data_length, data_offset;
	int ret;

	if (WARN_ONCE(flags, "unexpected flags=0x%x\n", flags))
		return -EINVAL; /* no flags support for now */

	if (WARN_ON_ONCE(iov_iter_rw(&msg->msg_iter) != ITER_DEST))
		return -EINVAL; /* It's a bug in upper layer to get there */

again:
	if (sc->status != SMBDIRECT_SOCKET_CONNECTED) {
		smbdirect_log_read(sc, SMBDIRECT_LOG_INFO,
			"status=%s first_error=%1pe => %1pe\n",
			smbdirect_socket_status_string(sc->status),
			SMBDIRECT_DEBUG_ERR_PTR(sc->first_error),
			SMBDIRECT_DEBUG_ERR_PTR(-ENOTCONN));
		return -ENOTCONN;
	}

	/*
	 * No need to hold the reassembly queue lock all the time as we are
	 * the only one reading from the front of the queue. The transport
	 * may add more entries to the back of the queue at the same time
	 */
	smbdirect_log_read(sc, SMBDIRECT_LOG_INFO,
		"size=%zd sc->recv_io.reassembly.data_length=%d\n",
		size, sc->recv_io.reassembly.data_length);
	if (sc->recv_io.reassembly.data_length >= size) {
		int queue_length;
		int queue_removed = 0;
		unsigned long flags;

		/*
		 * Need to make sure reassembly_data_length is read before
		 * reading reassembly_queue_length and calling
		 * smbdirect_connection_reassembly_first_recv_io. This call is lock free
		 * as we never read at the end of the queue which are being
		 * updated in SOFTIRQ as more data is received
		 */
		virt_rmb();
		queue_length = sc->recv_io.reassembly.queue_length;
		data_read = 0;
		to_read = size;
		offset = sc->recv_io.reassembly.first_entry_offset;
		while (data_read < size) {
			response = smbdirect_connection_reassembly_first_recv_io(sc);
			data_transfer = (void *)response->packet;
			data_length = le32_to_cpu(data_transfer->data_length);
			remaining_data_length =
				le32_to_cpu(
					data_transfer->remaining_data_length);
			data_offset = le32_to_cpu(data_transfer->data_offset);

			/*
			 * The upper layer expects RFC1002 length at the
			 * beginning of the payload. Return it to indicate
			 * the total length of the packet. This minimize the
			 * change to upper layer packet processing logic. This
			 * will be eventually remove when an intermediate
			 * transport layer is added
			 */
			if (response->first_segment && size == 4) {
				unsigned int rfc1002_len =
					data_length + remaining_data_length;
				__be32 rfc1002_hdr = cpu_to_be32(rfc1002_len);

				if (copy_to_iter(&rfc1002_hdr, sizeof(rfc1002_hdr),
						 &msg->msg_iter) != sizeof(rfc1002_hdr))
					return -EFAULT;
				data_read = 4;
				response->first_segment = false;
				smbdirect_log_read(sc, SMBDIRECT_LOG_INFO,
					"returning rfc1002 length %d\n",
					rfc1002_len);
				goto read_rfc1002_done;
			}

			to_copy = min_t(int, data_length - offset, to_read);
			if (copy_to_iter((u8 *)data_transfer + data_offset + offset,
					 to_copy, &msg->msg_iter) != to_copy)
				return -EFAULT;

			/* move on to the next buffer? */
			if (to_copy == data_length - offset) {
				queue_length--;
				/*
				 * No need to lock if we are not at the
				 * end of the queue
				 */
				if (queue_length)
					list_del(&response->list);
				else {
					spin_lock_irqsave(
						&sc->recv_io.reassembly.lock, flags);
					list_del(&response->list);
					spin_unlock_irqrestore(
						&sc->recv_io.reassembly.lock, flags);
				}
				queue_removed++;
				sc->statistics.dequeue_reassembly_queue++;
				smbdirect_connection_put_recv_io(response);
				offset = 0;
				smbdirect_log_read(sc, SMBDIRECT_LOG_INFO,
					"smbdirect_connection_put_recv_io offset=0\n");
			} else
				offset += to_copy;

			to_read -= to_copy;
			data_read += to_copy;

			smbdirect_log_read(sc, SMBDIRECT_LOG_INFO,
				 "memcpy %d bytes len-ofs=%u => todo=%u done=%u ofs=%u\n",
				 to_copy, data_length - offset,
				 to_read, data_read, offset);
		}

		spin_lock_irqsave(&sc->recv_io.reassembly.lock, flags);
		sc->recv_io.reassembly.data_length -= data_read;
		sc->recv_io.reassembly.queue_length -= queue_removed;
		spin_unlock_irqrestore(&sc->recv_io.reassembly.lock, flags);

		sc->recv_io.reassembly.first_entry_offset = offset;
		smbdirect_log_read(sc, SMBDIRECT_LOG_INFO,
			 "returning data_read=%d reassembly_length=%d first_ofs=%u\n",
			 data_read, sc->recv_io.reassembly.data_length,
			 sc->recv_io.reassembly.first_entry_offset);
read_rfc1002_done:
		return data_read;
	}

	smbdirect_log_read(sc, SMBDIRECT_LOG_INFO,
		"wait_event on more data\n");
	ret = wait_event_interruptible(sc->recv_io.reassembly.wait_queue,
				       sc->recv_io.reassembly.data_length >= size ||
				       sc->status != SMBDIRECT_SOCKET_CONNECTED);
	/* Don't return any data if interrupted */
	if (ret)
		return ret;

	goto again;
}
EXPORT_SYMBOL_GPL(smbdirect_connection_recvmsg);

static bool smbdirect_map_sges_single_page(struct smbdirect_map_sges *state,
					   struct page *page, size_t off, size_t len)
{
	struct ib_sge *sge;
	u64 addr;

	if (state->num_sge >= state->max_sge)
		return false;

	addr = ib_dma_map_page(state->device, page,
			       off, len, state->direction);
	if (ib_dma_mapping_error(state->device, addr))
		return false;

	sge = &state->sge[state->num_sge++];
	sge->addr   = addr;
	sge->length = len;
	sge->lkey   = state->local_dma_lkey;

	return true;
}

/*
 * Extract page fragments from a BVEC-class iterator and add them to an ib_sge
 * list.  The pages are not pinned.
 */
static ssize_t smbdirect_map_sges_from_bvec(struct iov_iter *iter,
					    struct smbdirect_map_sges *state,
					    ssize_t maxsize)
{
	const struct bio_vec *bv = iter->bvec;
	unsigned long start = iter->iov_offset;
	unsigned int i;
	ssize_t ret = 0;

	for (i = 0; i < iter->nr_segs; i++) {
		size_t off, len;
		bool ok;

		len = bv[i].bv_len;
		if (start >= len) {
			start -= len;
			continue;
		}

		len = min_t(size_t, maxsize, len - start);
		off = bv[i].bv_offset + start;

		ok = smbdirect_map_sges_single_page(state,
						    bv[i].bv_page,
						    off,
						    len);
		if (!ok)
			return -EIO;

		ret += len;
		maxsize -= len;
		if (state->num_sge >= state->max_sge || maxsize <= 0)
			break;
		start = 0;
	}

	if (ret > 0)
		iov_iter_advance(iter, ret);
	return ret;
}

/*
 * Extract fragments from a KVEC-class iterator and add them to an ib_sge list.
 * This can deal with vmalloc'd buffers as well as kmalloc'd or static buffers.
 * The pages are not pinned.
 */
static ssize_t smbdirect_map_sges_from_kvec(struct iov_iter *iter,
					    struct smbdirect_map_sges *state,
					    ssize_t maxsize)
{
	const struct kvec *kv = iter->kvec;
	unsigned long start = iter->iov_offset;
	unsigned int i;
	ssize_t ret = 0;

	for (i = 0; i < iter->nr_segs; i++) {
		struct page *page;
		unsigned long kaddr;
		size_t off, len, seg;

		len = kv[i].iov_len;
		if (start >= len) {
			start -= len;
			continue;
		}

		kaddr = (unsigned long)kv[i].iov_base + start;
		off = kaddr & ~PAGE_MASK;
		len = min_t(size_t, maxsize, len - start);
		kaddr &= PAGE_MASK;

		maxsize -= len;
		do {
			bool ok;

			seg = min_t(size_t, len, PAGE_SIZE - off);

			if (is_vmalloc_or_module_addr((void *)kaddr))
				page = vmalloc_to_page((void *)kaddr);
			else
				page = virt_to_page((void *)kaddr);

			ok = smbdirect_map_sges_single_page(state, page, off, seg);
			if (!ok)
				return -EIO;

			ret += seg;
			len -= seg;
			kaddr += PAGE_SIZE;
			off = 0;
		} while (len > 0 && state->num_sge < state->max_sge);

		if (state->num_sge >= state->max_sge || maxsize <= 0)
			break;
		start = 0;
	}

	if (ret > 0)
		iov_iter_advance(iter, ret);
	return ret;
}

/*
 * Extract folio fragments from a FOLIOQ-class iterator and add them to an
 * ib_sge list.  The folios are not pinned.
 */
static ssize_t smbdirect_map_sges_from_folioq(struct iov_iter *iter,
					      struct smbdirect_map_sges *state,
					      ssize_t maxsize)
{
	const struct folio_queue *folioq = iter->folioq;
	unsigned int slot = iter->folioq_slot;
	ssize_t ret = 0;
	size_t offset = iter->iov_offset;

	if (WARN_ON_ONCE(!folioq))
		return -EIO;

	if (slot >= folioq_nr_slots(folioq)) {
		folioq = folioq->next;
		if (WARN_ON_ONCE(!folioq))
			return -EIO;
		slot = 0;
	}

	do {
		struct folio *folio = folioq_folio(folioq, slot);
		size_t fsize = folioq_folio_size(folioq, slot);

		if (offset < fsize) {
			size_t part = umin(maxsize, fsize - offset);
			bool ok;

			ok = smbdirect_map_sges_single_page(state,
							    folio_page(folio, 0),
							    offset,
							    part);
			if (!ok)
				return -EIO;

			offset += part;
			ret += part;
			maxsize -= part;
		}

		if (offset >= fsize) {
			offset = 0;
			slot++;
			if (slot >= folioq_nr_slots(folioq)) {
				if (!folioq->next) {
					WARN_ON_ONCE(ret < iter->count);
					break;
				}
				folioq = folioq->next;
				slot = 0;
			}
		}
	} while (state->num_sge < state->max_sge && maxsize > 0);

	iter->folioq = folioq;
	iter->folioq_slot = slot;
	iter->iov_offset = offset;
	iter->count -= ret;
	return ret;
}

/*
 * Extract page fragments from up to the given amount of the source iterator
 * and build up an ib_sge list that refers to all of those bits.  The ib_sge list
 * is appended to, up to the maximum number of elements set in the parameter
 * block.
 *
 * The extracted page fragments are not pinned or ref'd in any way; if an
 * IOVEC/UBUF-type iterator is to be used, it should be converted to a
 * BVEC-type iterator and the pages pinned, ref'd or otherwise held in some
 * way.
 */
static ssize_t smbdirect_map_sges_from_iter(struct iov_iter *iter, size_t len,
					    struct smbdirect_map_sges *state)
{
	ssize_t ret;
	size_t before = state->num_sge;

	if (WARN_ON_ONCE(iov_iter_rw(iter) != ITER_SOURCE))
		return -EIO;

	switch (iov_iter_type(iter)) {
	case ITER_BVEC:
		ret = smbdirect_map_sges_from_bvec(iter, state, len);
		break;
	case ITER_KVEC:
		ret = smbdirect_map_sges_from_kvec(iter, state, len);
		break;
	case ITER_FOLIOQ:
		ret = smbdirect_map_sges_from_folioq(iter, state, len);
		break;
	default:
		WARN_ONCE(1, "iov_iter_type[%u]\n", iov_iter_type(iter));
		return -EIO;
	}

	if (ret < 0) {
		while (state->num_sge > before) {
			struct ib_sge *sge = &state->sge[--state->num_sge];

			ib_dma_unmap_page(state->device,
					  sge->addr,
					  sge->length,
					  state->direction);
		}
	}

	return ret;
}