linux/fs/cifsd/transport_rdma.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *   Copyright (C) 2017, Microsoft Corporation.
 *   Copyright (C) 2018, LG Electronics.
 *
 *   Author(s): Long Li <longli@microsoft.com>,
 *		Hyunchul Lee <hyc.lee@gmail.com>
 *
 *   This program is free software;  you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY;  without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
 *   the GNU General Public License for more details.
 */

#define SUBMOD_NAME	"smb_direct"

#include <linux/kthread.h>
#include <linux/rwlock.h>
#include <linux/list.h>
#include <linux/mempool.h>
#include <linux/highmem.h>
#include <linux/scatterlist.h>
#include <rdma/ib_verbs.h>
#include <rdma/rdma_cm.h>
#include <rdma/rw.h>

#include "glob.h"
#include "connection.h"
#include "smb_common.h"
#include "smbstatus.h"
#include "buffer_pool.h"
#include "transport_rdma.h"

#define SMB_DIRECT_PORT	5445

#define SMB_DIRECT_VERSION_LE		cpu_to_le16(0x0100)

/* SMB_DIRECT negotiation timeout in seconds */
#define SMB_DIRECT_NEGOTIATE_TIMEOUT		120

#define SMB_DIRECT_MAX_SEND_SGES		8
#define SMB_DIRECT_MAX_RECV_SGES		1

/*
 * Default maximum number of RDMA read/write outstanding on this connection
 * This value is possibly decreased during QP creation on hardware limit
 */
#define SMB_DIRECT_CM_INITIATOR_DEPTH		8

/* Maximum number of retries on data transfer operations */
#define SMB_DIRECT_CM_RETRY			6
/* No need to retry on Receiver Not Ready since SMB_DIRECT manages credits */
#define SMB_DIRECT_CM_RNR_RETRY		0

/*
 * User configurable initial values per SMB_DIRECT transport connection
 * as defined in [MS-KSMBD] 3.1.1.1
 * Those may change after a SMB_DIRECT negotiation
 */
/* The local peer's maximum number of credits to grant to the peer */
static int smb_direct_receive_credit_max = 255;

/* The remote peer's credit request of local peer */
static int smb_direct_send_credit_target = 255;

/* The maximum single message size can be sent to remote peer */
static int smb_direct_max_send_size = 8192;

/*  The maximum fragmented upper-layer payload receive size supported */
static int smb_direct_max_fragmented_recv_size = 1024 * 1024;

/*  The maximum single-message size which can be received */
static int smb_direct_max_receive_size = 8192;

static int smb_direct_max_read_write_size = 1024 * 1024;

static int smb_direct_max_outstanding_rw_ops = 8;

static struct smb_direct_listener {
	struct rdma_cm_id	*cm_id;
} smb_direct_listener;

static struct workqueue_struct *smb_direct_wq;

enum smb_direct_status {
	SMB_DIRECT_CS_NEW = 0,
	SMB_DIRECT_CS_CONNECTED,
	SMB_DIRECT_CS_DISCONNECTING,
	SMB_DIRECT_CS_DISCONNECTED,
};

struct smb_direct_transport {
	struct ksmbd_transport	transport;

	enum smb_direct_status	status;
	bool			full_packet_received;
	wait_queue_head_t	wait_status;

	struct rdma_cm_id	*cm_id;
	struct ib_cq		*send_cq;
	struct ib_cq		*recv_cq;
	struct ib_pd		*pd;
	struct ib_qp		*qp;

	int			max_send_size;
	int			max_recv_size;
	int			max_fragmented_send_size;
	int			max_fragmented_recv_size;
	int			max_rdma_rw_size;

	spinlock_t		reassembly_queue_lock;
	struct list_head	reassembly_queue;
	int			reassembly_data_length;
	int			reassembly_queue_length;
	int			first_entry_offset;
	wait_queue_head_t	wait_reassembly_queue;

	spinlock_t		receive_credit_lock;
	int			recv_credits;
	int			count_avail_recvmsg;
	int			recv_credit_max;
	int			recv_credit_target;

	spinlock_t		recvmsg_queue_lock;
	struct list_head	recvmsg_queue;

	spinlock_t		empty_recvmsg_queue_lock;
	struct list_head	empty_recvmsg_queue;

	int			send_credit_target;
	atomic_t		send_credits;
	spinlock_t		lock_new_recv_credits;
	int			new_recv_credits;
	atomic_t		rw_avail_ops;

	wait_queue_head_t	wait_send_credits;
	wait_queue_head_t	wait_rw_avail_ops;

	mempool_t		*sendmsg_mempool;
	struct kmem_cache	*sendmsg_cache;
	mempool_t		*recvmsg_mempool;
	struct kmem_cache	*recvmsg_cache;

	wait_queue_head_t	wait_send_payload_pending;
	atomic_t		send_payload_pending;
	wait_queue_head_t	wait_send_pending;
	atomic_t		send_pending;

	struct delayed_work	post_recv_credits_work;
	struct work_struct	send_immediate_work;
	struct work_struct	disconnect_work;

	bool			negotiation_requested;
};

#define KSMBD_TRANS(t) ((struct ksmbd_transport *)&((t)->transport))
#define SMB_DIRECT_TRANS(t) ((struct smb_direct_transport *)container_of(t, \
				struct smb_direct_transport, transport))

enum {
	SMB_DIRECT_MSG_NEGOTIATE_REQ = 0,
	SMB_DIRECT_MSG_DATA_TRANSFER
};

static struct ksmbd_transport_ops ksmbd_smb_direct_transport_ops;

struct smb_direct_send_ctx {
	struct list_head	msg_list;
	int			wr_cnt;
	bool			need_invalidate_rkey;
	unsigned int		remote_key;
};

struct smb_direct_sendmsg {
	struct smb_direct_transport	*transport;
	struct ib_send_wr	wr;
	struct list_head	list;
	int			num_sge;
	struct ib_sge		sge[SMB_DIRECT_MAX_SEND_SGES];
	struct ib_cqe		cqe;
	u8			packet[];
};

struct smb_direct_recvmsg {
	struct smb_direct_transport	*transport;
	struct list_head	list;
	int			type;
	struct ib_sge		sge;
	struct ib_cqe		cqe;
	bool			first_segment;
	u8			packet[];
};

struct smb_direct_rdma_rw_msg {
	struct smb_direct_transport	*t;
	struct ib_cqe		cqe;
	struct completion	*completion;
	struct rdma_rw_ctx	rw_ctx;
	struct sg_table		sgt;
	struct scatterlist	sg_list[0];
};

#define BUFFER_NR_PAGES(buf, len)					\
		(DIV_ROUND_UP((unsigned long)(buf) + (len), PAGE_SIZE)	\
			- (unsigned long)(buf) / PAGE_SIZE)

static void smb_direct_destroy_pools(struct smb_direct_transport *transport);
static void smb_direct_post_recv_credits(struct work_struct *work);
static int smb_direct_post_send_data(struct smb_direct_transport *t,
		struct smb_direct_send_ctx *send_ctx,
		struct kvec *iov, int niov, int remaining_data_length);

static inline void
*smb_direct_recvmsg_payload(struct smb_direct_recvmsg *recvmsg)
{
	return (void *)recvmsg->packet;
}

static inline bool is_receive_credit_post_required(int receive_credits,
		int avail_recvmsg_count)
{
	return receive_credits <= (smb_direct_receive_credit_max >> 3) &&
		avail_recvmsg_count >= (receive_credits >> 2);
}

static struct
smb_direct_recvmsg *get_free_recvmsg(struct smb_direct_transport *t)
{
	struct smb_direct_recvmsg *recvmsg = NULL;

	spin_lock(&t->recvmsg_queue_lock);
	if (!list_empty(&t->recvmsg_queue)) {
		recvmsg = list_first_entry(&t->recvmsg_queue,
					   struct smb_direct_recvmsg,
					   list);
		list_del(&recvmsg->list);
	}
	spin_unlock(&t->recvmsg_queue_lock);
	return recvmsg;
}

static void put_recvmsg(struct smb_direct_transport *t,
		struct smb_direct_recvmsg *recvmsg)
{
	ib_dma_unmap_single(t->cm_id->device, recvmsg->sge.addr,
			recvmsg->sge.length, DMA_FROM_DEVICE);

	spin_lock(&t->recvmsg_queue_lock);
	list_add(&recvmsg->list, &t->recvmsg_queue);
	spin_unlock(&t->recvmsg_queue_lock);
}

static struct
smb_direct_recvmsg *get_empty_recvmsg(struct smb_direct_transport *t)
{
	struct smb_direct_recvmsg *recvmsg = NULL;

	spin_lock(&t->empty_recvmsg_queue_lock);
	if (!list_empty(&t->empty_recvmsg_queue)) {
		recvmsg = list_first_entry(&t->empty_recvmsg_queue,
			struct smb_direct_recvmsg, list);
		list_del(&recvmsg->list);
	}
	spin_unlock(&t->empty_recvmsg_queue_lock);
	return recvmsg;
}

static void put_empty_recvmsg(struct smb_direct_transport *t,
		struct smb_direct_recvmsg *recvmsg)
{
	ib_dma_unmap_single(t->cm_id->device, recvmsg->sge.addr,
			recvmsg->sge.length, DMA_FROM_DEVICE);

	spin_lock(&t->empty_recvmsg_queue_lock);
	list_add_tail(&recvmsg->list, &t->empty_recvmsg_queue);
	spin_unlock(&t->empty_recvmsg_queue_lock);
}

static void enqueue_reassembly(struct smb_direct_transport *t,
		struct smb_direct_recvmsg *recvmsg, int data_length)
{
	spin_lock(&t->reassembly_queue_lock);
	list_add_tail(&recvmsg->list, &t->reassembly_queue);
	t->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();
	t->reassembly_data_length += data_length;
	spin_unlock(&t->reassembly_queue_lock);
}

static struct smb_direct_recvmsg *get_first_reassembly(struct smb_direct_transport *t)
{
	if (!list_empty(&t->reassembly_queue))
		return list_first_entry(&t->reassembly_queue,
				struct smb_direct_recvmsg, list);
	else
		return NULL;
}

static void smb_direct_disconnect_rdma_work(struct work_struct *work)
{
	struct smb_direct_transport *t =
		container_of(work, struct smb_direct_transport,
			     disconnect_work);

	if (t->status == SMB_DIRECT_CS_CONNECTED) {
		t->status = SMB_DIRECT_CS_DISCONNECTING;
		rdma_disconnect(t->cm_id);
	}
}

static void
smb_direct_disconnect_rdma_connection(struct smb_direct_transport *t)
{
	queue_work(smb_direct_wq, &t->disconnect_work);
}

static void smb_direct_send_immediate_work(struct work_struct *work)
{
	struct smb_direct_transport *t = container_of(work,
			struct smb_direct_transport, send_immediate_work);

	if (t->status != SMB_DIRECT_CS_CONNECTED)
		return;

	smb_direct_post_send_data(t, NULL, NULL, 0, 0);
}

static struct smb_direct_transport *alloc_transport(struct rdma_cm_id *cm_id)
{
	struct smb_direct_transport *t;
	struct ksmbd_conn *conn;

	t = kzalloc(sizeof(*t), GFP_KERNEL);
	if (!t)
		return NULL;

	t->cm_id = cm_id;
	cm_id->context = t;

	t->status = SMB_DIRECT_CS_NEW;
	init_waitqueue_head(&t->wait_status);

	spin_lock_init(&t->reassembly_queue_lock);
	INIT_LIST_HEAD(&t->reassembly_queue);
	t->reassembly_data_length = 0;
	t->reassembly_queue_length = 0;
	init_waitqueue_head(&t->wait_reassembly_queue);
	init_waitqueue_head(&t->wait_send_credits);
	init_waitqueue_head(&t->wait_rw_avail_ops);

	spin_lock_init(&t->receive_credit_lock);
	spin_lock_init(&t->recvmsg_queue_lock);
	INIT_LIST_HEAD(&t->recvmsg_queue);

	spin_lock_init(&t->empty_recvmsg_queue_lock);
	INIT_LIST_HEAD(&t->empty_recvmsg_queue);

	init_waitqueue_head(&t->wait_send_payload_pending);
	atomic_set(&t->send_payload_pending, 0);
	init_waitqueue_head(&t->wait_send_pending);
	atomic_set(&t->send_pending, 0);

	spin_lock_init(&t->lock_new_recv_credits);

	INIT_DELAYED_WORK(&t->post_recv_credits_work,
			  smb_direct_post_recv_credits);
	INIT_WORK(&t->send_immediate_work, smb_direct_send_immediate_work);
	INIT_WORK(&t->disconnect_work, smb_direct_disconnect_rdma_work);

	conn = ksmbd_conn_alloc();
	if (!conn)
		goto err;
	conn->transport = KSMBD_TRANS(t);
	KSMBD_TRANS(t)->conn = conn;
	KSMBD_TRANS(t)->ops = &ksmbd_smb_direct_transport_ops;
	return t;
err:
	kfree(t);
	return NULL;
}

static void free_transport(struct smb_direct_transport *t)
{
	struct smb_direct_recvmsg *recvmsg;

	wake_up_interruptible(&t->wait_send_credits);

	ksmbd_debug(RDMA, "wait for all send posted to IB to finish\n");
	wait_event(t->wait_send_payload_pending,
		atomic_read(&t->send_payload_pending) == 0);
	wait_event(t->wait_send_pending,
		atomic_read(&t->send_pending) == 0);

	cancel_work_sync(&t->disconnect_work);
	cancel_delayed_work_sync(&t->post_recv_credits_work);
	cancel_work_sync(&t->send_immediate_work);

	if (t->qp) {
		ib_drain_qp(t->qp);
		ib_destroy_qp(t->qp);
	}

	ksmbd_debug(RDMA, "drain the reassembly queue\n");
	do {
		spin_lock(&t->reassembly_queue_lock);
		recvmsg = get_first_reassembly(t);
		if (recvmsg) {
			list_del(&recvmsg->list);
			spin_unlock(&t->reassembly_queue_lock);
			put_recvmsg(t, recvmsg);
		} else {
			spin_unlock(&t->reassembly_queue_lock);
		}
	} while (recvmsg);
	t->reassembly_data_length = 0;

	if (t->send_cq)
		ib_free_cq(t->send_cq);
	if (t->recv_cq)
		ib_free_cq(t->recv_cq);
	if (t->pd)
		ib_dealloc_pd(t->pd);
	if (t->cm_id)
		rdma_destroy_id(t->cm_id);

	smb_direct_destroy_pools(t);
	ksmbd_conn_free(KSMBD_TRANS(t)->conn);
	kfree(t);
}

static struct smb_direct_sendmsg
*smb_direct_alloc_sendmsg(struct smb_direct_transport *t)
{
	struct smb_direct_sendmsg *msg;

	msg = mempool_alloc(t->sendmsg_mempool, GFP_KERNEL);
	if (!msg)
		return ERR_PTR(-ENOMEM);
	msg->transport = t;
	INIT_LIST_HEAD(&msg->list);
	msg->num_sge = 0;
	return msg;
}

static void smb_direct_free_sendmsg(struct smb_direct_transport *t,
		struct smb_direct_sendmsg *msg)
{
	int i;

	if (msg->num_sge > 0) {
		ib_dma_unmap_single(t->cm_id->device,
				msg->sge[0].addr, msg->sge[0].length,
				DMA_TO_DEVICE);
		for (i = 1; i < msg->num_sge; i++)
			ib_dma_unmap_page(t->cm_id->device,
					msg->sge[i].addr, msg->sge[i].length,
					DMA_TO_DEVICE);
	}
	mempool_free(msg, t->sendmsg_mempool);
}

static int smb_direct_check_recvmsg(struct smb_direct_recvmsg *recvmsg)
{
	switch (recvmsg->type) {
	case SMB_DIRECT_MSG_DATA_TRANSFER: {
		struct smb_direct_data_transfer *req =
			(struct smb_direct_data_transfer *)recvmsg->packet;
		struct smb2_hdr *hdr = (struct smb2_hdr *)(recvmsg->packet
				+ le32_to_cpu(req->data_offset) - 4);
		ksmbd_debug(RDMA,
				"CreditGranted: %u, CreditRequested: %u, DataLength: %u, RemainingDataLength: %u, SMB: %x, Command: %u\n",
				le16_to_cpu(req->credits_granted),
				le16_to_cpu(req->credits_requested),
				req->data_length, req->remaining_data_length,
				hdr->ProtocolId, hdr->Command);
		break;
	}
	case SMB_DIRECT_MSG_NEGOTIATE_REQ: {
		struct smb_direct_negotiate_req *req =
			(struct smb_direct_negotiate_req *)recvmsg->packet;
		ksmbd_debug(RDMA,
			"MinVersion: %u, MaxVersion: %u, CreditRequested: %u, MaxSendSize: %u, MaxRecvSize: %u, MaxFragmentedSize: %u\n",
			le16_to_cpu(req->min_version),
			le16_to_cpu(req->max_version),
			le16_to_cpu(req->credits_requested),
			le32_to_cpu(req->preferred_send_size),
			le32_to_cpu(req->max_receive_size),
			le32_to_cpu(req->max_fragmented_size));
		if (le16_to_cpu(req->min_version) > 0x0100 ||
		    le16_to_cpu(req->max_version) < 0x0100)
			return -EOPNOTSUPP;
		if (le16_to_cpu(req->credits_requested) <= 0 ||
		    le32_to_cpu(req->max_receive_size) <= 128 ||
		    le32_to_cpu(req->max_fragmented_size) <=
					128 * 1024)
			return -ECONNABORTED;

		break;
	}
	default:
		return -EINVAL;
	}
	return 0;
}

static void recv_done(struct ib_cq *cq, struct ib_wc *wc)
{
	struct smb_direct_recvmsg *recvmsg;
	struct smb_direct_transport *t;

	recvmsg = container_of(wc->wr_cqe, struct smb_direct_recvmsg, cqe);
	t = recvmsg->transport;

	if (wc->status != IB_WC_SUCCESS || wc->opcode != IB_WC_RECV) {
		if (wc->status != IB_WC_WR_FLUSH_ERR) {
			ksmbd_err("Recv error. status='%s (%d)' opcode=%d\n",
				ib_wc_status_msg(wc->status), wc->status,
				wc->opcode);
			smb_direct_disconnect_rdma_connection(t);
		}
		put_empty_recvmsg(t, recvmsg);
		return;
	}

	ksmbd_debug(RDMA, "Recv completed. status='%s (%d)', opcode=%d\n",
			ib_wc_status_msg(wc->status), wc->status,
			wc->opcode);

	ib_dma_sync_single_for_cpu(wc->qp->device, recvmsg->sge.addr,
			recvmsg->sge.length, DMA_FROM_DEVICE);

	switch (recvmsg->type) {
	case SMB_DIRECT_MSG_NEGOTIATE_REQ:
		t->negotiation_requested = true;
		t->full_packet_received = true;
		wake_up_interruptible(&t->wait_status);
		break;
	case SMB_DIRECT_MSG_DATA_TRANSFER: {
		struct smb_direct_data_transfer *data_transfer =
			(struct smb_direct_data_transfer *)recvmsg->packet;
		int data_length = le32_to_cpu(data_transfer->data_length);
		int avail_recvmsg_count, receive_credits;

		if (data_length) {
			if (t->full_packet_received)
				recvmsg->first_segment = true;

			if (le32_to_cpu(data_transfer->remaining_data_length))
				t->full_packet_received = false;
			else
				t->full_packet_received = true;

			enqueue_reassembly(t, recvmsg, data_length);
			wake_up_interruptible(&t->wait_reassembly_queue);

			spin_lock(&t->receive_credit_lock);
			receive_credits = --(t->recv_credits);
			avail_recvmsg_count = t->count_avail_recvmsg;
			spin_unlock(&t->receive_credit_lock);
		} else {
			put_empty_recvmsg(t, recvmsg);

			spin_lock(&t->receive_credit_lock);
			receive_credits = --(t->recv_credits);
			avail_recvmsg_count = ++(t->count_avail_recvmsg);
			spin_unlock(&t->receive_credit_lock);
		}

		t->recv_credit_target =
				le16_to_cpu(data_transfer->credits_requested);
		atomic_add(le16_to_cpu(data_transfer->credits_granted),
				&t->send_credits);

		if (le16_to_cpu(data_transfer->flags) &
				SMB_DIRECT_RESPONSE_REQUESTED)
			queue_work(smb_direct_wq, &t->send_immediate_work);

		if (atomic_read(&t->send_credits) > 0)
			wake_up_interruptible(&t->wait_send_credits);

		if (is_receive_credit_post_required(receive_credits, avail_recvmsg_count))
			mod_delayed_work(smb_direct_wq,
					&t->post_recv_credits_work, 0);
		break;
	}
	default:
		break;
	}
}

static int smb_direct_post_recv(struct smb_direct_transport *t,
		struct smb_direct_recvmsg *recvmsg)
{
	struct ib_recv_wr wr;
	int ret;

	recvmsg->sge.addr = ib_dma_map_single(t->cm_id->device,
			recvmsg->packet, t->max_recv_size,
			DMA_FROM_DEVICE);
	ret = ib_dma_mapping_error(t->cm_id->device, recvmsg->sge.addr);
	if (ret)
		return ret;
	recvmsg->sge.length = t->max_recv_size;
	recvmsg->sge.lkey = t->pd->local_dma_lkey;
	recvmsg->cqe.done = recv_done;

	wr.wr_cqe = &recvmsg->cqe;
	wr.next = NULL;
	wr.sg_list = &recvmsg->sge;
	wr.num_sge = 1;

	ret = ib_post_recv(t->qp, &wr, NULL);
	if (ret) {
		ksmbd_err("Can't post recv: %d\n", ret);
		ib_dma_unmap_single(t->cm_id->device,
			recvmsg->sge.addr, recvmsg->sge.length,
			DMA_FROM_DEVICE);
		smb_direct_disconnect_rdma_connection(t);
		return ret;
	}
	return ret;
}

static int smb_direct_read(struct ksmbd_transport *t, char *buf,
		unsigned int size)
{
	struct smb_direct_recvmsg *recvmsg;
	struct smb_direct_data_transfer *data_transfer;
	int to_copy, to_read, data_read, offset;
	u32 data_length, remaining_data_length, data_offset;
	int rc;
	struct smb_direct_transport *st = SMB_DIRECT_TRANS(t);

again:
	if (st->status != SMB_DIRECT_CS_CONNECTED) {
		ksmbd_err("disconnected\n");
		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
	 */
	if (st->reassembly_data_length >= size) {
		int queue_length;
		int queue_removed = 0;

		/*
		 * Need to make sure reassembly_data_length is read before
		 * reading reassembly_queue_length and calling
		 * get_first_reassembly. 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 = st->reassembly_queue_length;
		data_read = 0;
		to_read = size;
		offset = st->first_entry_offset;
		while (data_read < size) {
			recvmsg = get_first_reassembly(st);
			data_transfer = smb_direct_recvmsg_payload(recvmsg);
			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 (recvmsg->first_segment && size == 4) {
				unsigned int rfc1002_len =
					data_length + remaining_data_length;
				*((__be32 *)buf) = cpu_to_be32(rfc1002_len);
				data_read = 4;
				recvmsg->first_segment = false;
				ksmbd_debug(RDMA,
					"returning rfc1002 length %d\n",
					rfc1002_len);
				goto read_rfc1002_done;
			}

			to_copy = min_t(int, data_length - offset, to_read);
			memcpy(buf + data_read, (char *)data_transfer + data_offset + offset,
				to_copy);

			/* 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(&recvmsg->list);
				} else {
					spin_lock_irq(&st->reassembly_queue_lock);
					list_del(&recvmsg->list);
					spin_unlock_irq(&st->reassembly_queue_lock);
				}
				queue_removed++;
				put_recvmsg(st, recvmsg);
				offset = 0;
			} else {
				offset += to_copy;
			}

			to_read -= to_copy;
			data_read += to_copy;
		}

		spin_lock_irq(&st->reassembly_queue_lock);
		st->reassembly_data_length -= data_read;
		st->reassembly_queue_length -= queue_removed;
		spin_unlock_irq(&st->reassembly_queue_lock);

		spin_lock(&st->receive_credit_lock);
		st->count_avail_recvmsg += queue_removed;
		if (is_receive_credit_post_required(st->recv_credits, st->count_avail_recvmsg)) {
			spin_unlock(&st->receive_credit_lock);
			mod_delayed_work(smb_direct_wq,
					&st->post_recv_credits_work, 0);
		} else {
			spin_unlock(&st->receive_credit_lock);
		}

		st->first_entry_offset = offset;
		ksmbd_debug(RDMA,
			"returning to thread data_read=%d reassembly_data_length=%d first_entry_offset=%d\n",
			data_read, st->reassembly_data_length,
			st->first_entry_offset);
read_rfc1002_done:
		return data_read;
	}

	ksmbd_debug(RDMA, "wait_event on more data\n");
	rc = wait_event_interruptible(st->wait_reassembly_queue,
		st->reassembly_data_length >= size || st->status != SMB_DIRECT_CS_CONNECTED);
	if (rc)
		return -EINTR;

	goto again;
}

static void smb_direct_post_recv_credits(struct work_struct *work)
{
	struct smb_direct_transport *t = container_of(work,
		struct smb_direct_transport, post_recv_credits_work.work);
	struct smb_direct_recvmsg *recvmsg;
	int receive_credits, credits = 0;
	int ret;
	int use_free = 1;

	spin_lock(&t->receive_credit_lock);
	receive_credits = t->recv_credits;
	spin_unlock(&t->receive_credit_lock);

	if (receive_credits < t->recv_credit_target) {
		while (true) {
			if (use_free)
				recvmsg = get_free_recvmsg(t);
			else
				recvmsg = get_empty_recvmsg(t);
			if (!recvmsg) {
				if (use_free) {
					use_free = 0;
					continue;
				} else {
					break;
				}
			}

			recvmsg->type = SMB_DIRECT_MSG_DATA_TRANSFER;
			recvmsg->first_segment = false;

			ret = smb_direct_post_recv(t, recvmsg);
			if (ret) {
				ksmbd_err("Can't post recv: %d\n", ret);
				put_recvmsg(t, recvmsg);
				break;
			}
			credits++;
		}
	}

	spin_lock(&t->receive_credit_lock);
	t->recv_credits += credits;
	t->count_avail_recvmsg -= credits;
	spin_unlock(&t->receive_credit_lock);

	spin_lock(&t->lock_new_recv_credits);
	t->new_recv_credits += credits;
	spin_unlock(&t->lock_new_recv_credits);

	if (credits)
		queue_work(smb_direct_wq, &t->send_immediate_work);
}

static void send_done(struct ib_cq *cq, struct ib_wc *wc)
{
	struct smb_direct_sendmsg *sendmsg, *sibling;
	struct smb_direct_transport *t;
	struct list_head *pos, *prev, *end;

	sendmsg = container_of(wc->wr_cqe, struct smb_direct_sendmsg, cqe);
	t = sendmsg->transport;

	ksmbd_debug(RDMA, "Send completed. status='%s (%d)', opcode=%d\n",
			ib_wc_status_msg(wc->status), wc->status,
			wc->opcode);

	if (wc->status != IB_WC_SUCCESS || wc->opcode != IB_WC_SEND) {
		ksmbd_err("Send error. status='%s (%d)', opcode=%d\n",
			ib_wc_status_msg(wc->status), wc->status,
			wc->opcode);
		smb_direct_disconnect_rdma_connection(t);
	}

	if (sendmsg->num_sge > 1) {
		if (atomic_dec_and_test(&t->send_payload_pending))
			wake_up(&t->wait_send_payload_pending);
	} else {
		if (atomic_dec_and_test(&t->send_pending))
			wake_up(&t->wait_send_pending);
	}

	/* iterate and free the list of messages in reverse. the list's head
	 * is invalid.
	 */
	for (pos = &sendmsg->list, prev = pos->prev, end = sendmsg->list.next;
			prev != end; pos = prev, prev = prev->prev) {
		sibling = container_of(pos, struct smb_direct_sendmsg, list);
		smb_direct_free_sendmsg(t, sibling);
	}

	sibling = container_of(pos, struct smb_direct_sendmsg, list);
	smb_direct_free_sendmsg(t, sibling);
}

static int manage_credits_prior_sending(struct smb_direct_transport *t)
{
	int new_credits;

	spin_lock(&t->lock_new_recv_credits);
	new_credits = t->new_recv_credits;
	t->new_recv_credits = 0;
	spin_unlock(&t->lock_new_recv_credits);

	return new_credits;
}

static int smb_direct_post_send(struct smb_direct_transport *t,
		struct ib_send_wr *wr)
{
	int ret;

	if (wr->num_sge > 1)
		atomic_inc(&t->send_payload_pending);
	else
		atomic_inc(&t->send_pending);

	ret = ib_post_send(t->qp, wr, NULL);
	if (ret) {
		ksmbd_err("failed to post send: %d\n", ret);
		if (wr->num_sge > 1) {
			if (atomic_dec_and_test(&t->send_payload_pending))
				wake_up(&t->wait_send_payload_pending);
		} else {
			if (atomic_dec_and_test(&t->send_pending))
				wake_up(&t->wait_send_pending);
		}
		smb_direct_disconnect_rdma_connection(t);
	}
	return ret;
}

static void smb_direct_send_ctx_init(struct smb_direct_transport *t,
		struct smb_direct_send_ctx *send_ctx,
		bool need_invalidate_rkey, unsigned int remote_key)
{
	INIT_LIST_HEAD(&send_ctx->msg_list);
	send_ctx->wr_cnt = 0;
	send_ctx->need_invalidate_rkey = need_invalidate_rkey;
	send_ctx->remote_key = remote_key;
}

static int smb_direct_flush_send_list(struct smb_direct_transport *t,
		struct smb_direct_send_ctx *send_ctx, bool is_last)
{
	struct smb_direct_sendmsg *first, *last;
	int ret;

	if (list_empty(&send_ctx->msg_list))
		return 0;

	first = list_first_entry(&send_ctx->msg_list,
				struct smb_direct_sendmsg,
				list);
	last = list_last_entry(&send_ctx->msg_list,
				struct smb_direct_sendmsg,
				list);

	last->wr.send_flags = IB_SEND_SIGNALED;
	last->wr.wr_cqe = &last->cqe;
	if (is_last && send_ctx->need_invalidate_rkey) {
		last->wr.opcode = IB_WR_SEND_WITH_INV;
		last->wr.ex.invalidate_rkey = send_ctx->remote_key;
	}

	ret = smb_direct_post_send(t, &first->wr);
	if (!ret) {
		smb_direct_send_ctx_init(t, send_ctx,
			send_ctx->need_invalidate_rkey, send_ctx->remote_key);
	} else {
		atomic_add(send_ctx->wr_cnt, &t->send_credits);
		wake_up(&t->wait_send_credits);
		list_for_each_entry_safe(first, last, &send_ctx->msg_list,
				list) {
			smb_direct_free_sendmsg(t, first);
		}
	}
	return ret;
}

static int wait_for_credits(struct smb_direct_transport *t,
		wait_queue_head_t *waitq, atomic_t *credits)
{
	int ret;

	do {
		if (atomic_dec_return(credits) >= 0)
			return 0;

		atomic_inc(credits);
		ret = wait_event_interruptible(*waitq,
				atomic_read(credits) > 0 ||
				t->status != SMB_DIRECT_CS_CONNECTED);

		if (t->status != SMB_DIRECT_CS_CONNECTED)
			return -ENOTCONN;
		else if (ret < 0)
			return ret;
	} while (true);
}

static int wait_for_send_credits(struct smb_direct_transport *t,
		struct smb_direct_send_ctx *send_ctx)
{
	int ret;

	if (send_ctx && (send_ctx->wr_cnt >= 16 ||
			 atomic_read(&t->send_credits) <= 1)) {
		ret = smb_direct_flush_send_list(t, send_ctx, false);
		if (ret)
			return ret;
	}

	return wait_for_credits(t, &t->wait_send_credits, &t->send_credits);
}

static int smb_direct_create_header(struct smb_direct_transport *t,
		int size, int remaining_data_length,
		struct smb_direct_sendmsg **sendmsg_out)
{
	struct smb_direct_sendmsg *sendmsg;
	struct smb_direct_data_transfer *packet;
	int header_length;
	int ret;

	sendmsg = smb_direct_alloc_sendmsg(t);
	if (IS_ERR(sendmsg))
		return PTR_ERR(sendmsg);

	/* Fill in the packet header */
	packet = (struct smb_direct_data_transfer *)sendmsg->packet;
	packet->credits_requested = cpu_to_le16(t->send_credit_target);
	packet->credits_granted = cpu_to_le16(manage_credits_prior_sending(t));

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

	ksmbd_debug(RDMA,
		"credits_requested=%d credits_granted=%d data_offset=%d data_length=%d remaining_data_length=%d\n",
		le16_to_cpu(packet->credits_requested),
		le16_to_cpu(packet->credits_granted),
		le32_to_cpu(packet->data_offset),
		le32_to_cpu(packet->data_length),
		le32_to_cpu(packet->remaining_data_length));

	/* Map the packet to DMA */
	header_length = sizeof(struct smb_direct_data_transfer);
	/* If this is a packet without payload, don't send padding */
	if (!size)
		header_length =
			offsetof(struct smb_direct_data_transfer, padding);

	sendmsg->sge[0].addr = ib_dma_map_single(t->cm_id->device,
						 (void *)packet,
						 header_length,
						 DMA_TO_DEVICE);
	ret = ib_dma_mapping_error(t->cm_id->device, sendmsg->sge[0].addr);
	if (ret) {
		smb_direct_free_sendmsg(t, sendmsg);
		return ret;
	}

	sendmsg->num_sge = 1;
	sendmsg->sge[0].length = header_length;
	sendmsg->sge[0].lkey = t->pd->local_dma_lkey;

	*sendmsg_out = sendmsg;
	return 0;
}

static int get_sg_list(void *buf, int size, struct scatterlist *sg_list, int nentries)
{
	bool high = is_vmalloc_addr(buf);
	struct page *page;
	int offset, len;
	int i = 0;

	if (nentries < BUFFER_NR_PAGES(buf, size))
		return -EINVAL;

	offset = offset_in_page(buf);
	buf -= offset;
	while (size > 0) {
		len = min_t(int, PAGE_SIZE - offset, size);
		if (high)
			page = vmalloc_to_page(buf);
		else
			page = kmap_to_page(buf);

		if (!sg_list)
			return -EINVAL;
		sg_set_page(sg_list, page, len, offset);
		sg_list = sg_next(sg_list);

		buf += PAGE_SIZE;
		size -= len;
		offset = 0;
		i++;
	}
	return i;
}

static int get_mapped_sg_list(struct ib_device *device, void *buf, int size,
		struct scatterlist *sg_list, int nentries,
		enum dma_data_direction dir)
{
	int npages;

	npages = get_sg_list(buf, size, sg_list, nentries);
	if (npages <= 0)
		return -EINVAL;
	return ib_dma_map_sg(device, sg_list, npages, dir);
}

static int post_sendmsg(struct smb_direct_transport *t,
		struct smb_direct_send_ctx *send_ctx,
		struct smb_direct_sendmsg *msg)
{
	int i;

	for (i = 0; i < msg->num_sge; i++)
		ib_dma_sync_single_for_device(t->cm_id->device,
				msg->sge[i].addr, msg->sge[i].length,
				DMA_TO_DEVICE);

	msg->cqe.done = send_done;
	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 (send_ctx) {
		msg->wr.wr_cqe = NULL;
		msg->wr.send_flags = 0;
		if (!list_empty(&send_ctx->msg_list)) {
			struct smb_direct_sendmsg *last;

			last = list_last_entry(&send_ctx->msg_list,
					       struct smb_direct_sendmsg,
					       list);
			last->wr.next = &msg->wr;
		}
		list_add_tail(&msg->list, &send_ctx->msg_list);
		send_ctx->wr_cnt++;
		return 0;
	}

	msg->wr.wr_cqe = &msg->cqe;
	msg->wr.send_flags = IB_SEND_SIGNALED;
	return smb_direct_post_send(t, &msg->wr);
}

static int smb_direct_post_send_data(struct smb_direct_transport *t,
		struct smb_direct_send_ctx *send_ctx,
		struct kvec *iov, int niov, int remaining_data_length)
{
	int i, j, ret;
	struct smb_direct_sendmsg *msg;
	int data_length;
	struct scatterlist sg[SMB_DIRECT_MAX_SEND_SGES - 1];

	ret = wait_for_send_credits(t, send_ctx);
	if (ret)
		return ret;

	data_length = 0;
	for (i = 0; i < niov; i++)
		data_length += iov[i].iov_len;

	ret = smb_direct_create_header(t, data_length, remaining_data_length,
				       &msg);
	if (ret) {
		atomic_inc(&t->send_credits);
		return ret;
	}

	for (i = 0; i < niov; i++) {
		struct ib_sge *sge;
		int sg_cnt;

		sg_init_table(sg, SMB_DIRECT_MAX_SEND_SGES - 1);
		sg_cnt = get_mapped_sg_list(t->cm_id->device,
				iov[i].iov_base, iov[i].iov_len,
				sg, SMB_DIRECT_MAX_SEND_SGES - 1, DMA_TO_DEVICE);
		if (sg_cnt <= 0) {
			ksmbd_err("failed to map buffer\n");
			ret = -ENOMEM;
			goto err;
		} else if (sg_cnt + msg->num_sge > SMB_DIRECT_MAX_SEND_SGES - 1) {
			ksmbd_err("buffer not fitted into sges\n");
			ret = -E2BIG;
			ib_dma_unmap_sg(t->cm_id->device, sg, sg_cnt,
					DMA_TO_DEVICE);
			goto err;
		}

		for (j = 0; j < sg_cnt; j++) {
			sge = &msg->sge[msg->num_sge];
			sge->addr = sg_dma_address(&sg[j]);
			sge->length = sg_dma_len(&sg[j]);
			sge->lkey  = t->pd->local_dma_lkey;
			msg->num_sge++;
		}
	}

	ret = post_sendmsg(t, send_ctx, msg);
	if (ret)
		goto err;
	return 0;
err:
	smb_direct_free_sendmsg(t, msg);
	atomic_inc(&t->send_credits);
	return ret;
}

static int smb_direct_writev(struct ksmbd_transport *t,
		struct kvec *iov, int niovs, int buflen,
		bool need_invalidate, unsigned int remote_key)
{
	struct smb_direct_transport *st = SMB_DIRECT_TRANS(t);
	int remaining_data_length;
	int start, i, j;
	int max_iov_size = st->max_send_size -
			sizeof(struct smb_direct_data_transfer);
	int ret;
	struct kvec vec;
	struct smb_direct_send_ctx send_ctx;

	if (st->status != SMB_DIRECT_CS_CONNECTED) {
		ret = -ENOTCONN;
		goto done;
	}

	//FIXME: skip RFC1002 header..
	buflen -= 4;
	iov[0].iov_base += 4;
	iov[0].iov_len -= 4;

	remaining_data_length = buflen;
	ksmbd_debug(RDMA, "Sending smb (RDMA): smb_len=%u\n", buflen);

	smb_direct_send_ctx_init(st, &send_ctx, need_invalidate, remote_key);
	start = i = 0;
	buflen = 0;
	while (true) {
		buflen += iov[i].iov_len;
		if (buflen > max_iov_size) {
			if (i > start) {
				remaining_data_length -=
					(buflen - iov[i].iov_len);
				ret = smb_direct_post_send_data(st, &send_ctx,
						&iov[start], i - start,
						remaining_data_length);
				if (ret)
					goto done;
			} else {
				/* iov[start] is too big, break it */
				int nvec  = (buflen + max_iov_size - 1) /
						max_iov_size;

				for (j = 0; j < nvec; j++) {
					vec.iov_base =
						(char *)iov[start].iov_base +
						j * max_iov_size;
					vec.iov_len =
						min_t(int, max_iov_size,
						buflen - max_iov_size * j);
					remaining_data_length -= vec.iov_len;
					ret = smb_direct_post_send_data(st,
						&send_ctx, &vec, 1,
						remaining_data_length);
					if (ret)
						goto done;
				}
				i++;
				if (i == niovs)
					break;
			}
			start = i;
			buflen = 0;
		} else {
			i++;
			if (i == niovs) {
				/* send out all remaining vecs */
				remaining_data_length -= buflen;
				ret = smb_direct_post_send_data(st, &send_ctx,
					&iov[start], i - start,
					remaining_data_length);
				if (ret)
					goto done;
				break;
			}
		}
	}

done:
	ret = smb_direct_flush_send_list(st, &send_ctx, true);

	/*
	 * 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(st->wait_send_payload_pending,
		atomic_read(&st->send_payload_pending) == 0);
	return ret;
}

static void read_write_done(struct ib_cq *cq, struct ib_wc *wc,
		enum dma_data_direction dir)
{
	struct smb_direct_rdma_rw_msg *msg = container_of(wc->wr_cqe,
					struct smb_direct_rdma_rw_msg, cqe);
	struct smb_direct_transport *t = msg->t;

	if (wc->status != IB_WC_SUCCESS) {
		ksmbd_err("read/write error. opcode = %d, status = %s(%d)\n",
			wc->opcode, ib_wc_status_msg(wc->status), wc->status);
		smb_direct_disconnect_rdma_connection(t);
	}

	if (atomic_inc_return(&t->rw_avail_ops) > 0)
		wake_up(&t->wait_rw_avail_ops);

	rdma_rw_ctx_destroy(&msg->rw_ctx, t->qp, t->qp->port,
			msg->sg_list, msg->sgt.nents, dir);
	sg_free_table_chained(&msg->sgt, SG_CHUNK_SIZE);
	complete(msg->completion);
	kfree(msg);
}

static void read_done(struct ib_cq *cq, struct ib_wc *wc)
{
	read_write_done(cq, wc, DMA_FROM_DEVICE);
}

static void write_done(struct ib_cq *cq, struct ib_wc *wc)
{
	read_write_done(cq, wc, DMA_TO_DEVICE);
}

static int smb_direct_rdma_xmit(struct smb_direct_transport *t, void *buf,
		int buf_len, u32 remote_key, u64 remote_offset, u32 remote_len,
		bool is_read)
{
	struct smb_direct_rdma_rw_msg *msg;
	int ret;
	DECLARE_COMPLETION_ONSTACK(completion);
	struct ib_send_wr *first_wr = NULL;

	ret = wait_for_credits(t, &t->wait_rw_avail_ops, &t->rw_avail_ops);
	if (ret < 0)
		return ret;

	/* TODO: mempool */
	msg = kmalloc(offsetof(struct smb_direct_rdma_rw_msg, sg_list) +
		sizeof(struct scatterlist) * SG_CHUNK_SIZE, GFP_KERNEL);
	if (!msg) {
		atomic_inc(&t->rw_avail_ops);
		return -ENOMEM;
	}

	msg->sgt.sgl = &msg->sg_list[0];
	ret = sg_alloc_table_chained(&msg->sgt,
				BUFFER_NR_PAGES(buf, buf_len),
				msg->sg_list, SG_CHUNK_SIZE);
	if (ret) {
		atomic_inc(&t->rw_avail_ops);
		kfree(msg);
		return -ENOMEM;
	}

	ret = get_sg_list(buf, buf_len, msg->sgt.sgl, msg->sgt.orig_nents);
	if (ret <= 0) {
		ksmbd_err("failed to get pages\n");
		goto err;
	}

	ret = rdma_rw_ctx_init(&msg->rw_ctx, t->qp, t->qp->port,
			msg->sg_list, BUFFER_NR_PAGES(buf, buf_len),
			0, remote_offset, remote_key,
			is_read ? DMA_FROM_DEVICE : DMA_TO_DEVICE);
	if (ret < 0) {
		ksmbd_err("failed to init rdma_rw_ctx: %d\n", ret);
		goto err;
	}

	msg->t = t;
	msg->cqe.done = is_read ? read_done : write_done;
	msg->completion = &completion;
	first_wr = rdma_rw_ctx_wrs(&msg->rw_ctx, t->qp, t->qp->port,
				&msg->cqe, NULL);

	ret = ib_post_send(t->qp, first_wr, NULL);
	if (ret) {
		ksmbd_err("failed to post send wr: %d\n", ret);
		goto err;
	}

	wait_for_completion(&completion);
	return 0;

err:
	atomic_inc(&t->rw_avail_ops);
	if (first_wr)
		rdma_rw_ctx_destroy(&msg->rw_ctx, t->qp, t->qp->port,
				msg->sg_list, msg->sgt.nents,
				is_read ? DMA_FROM_DEVICE : DMA_TO_DEVICE);
	sg_free_table_chained(&msg->sgt, SG_CHUNK_SIZE);
	kfree(msg);
	return ret;
}

static int smb_direct_rdma_write(struct ksmbd_transport *t, void *buf,
		unsigned int buflen, u32 remote_key, u64 remote_offset,
		u32 remote_len)
{
	return smb_direct_rdma_xmit(SMB_DIRECT_TRANS(t), buf, buflen,
			remote_key, remote_offset,
			remote_len, false);
}

static int smb_direct_rdma_read(struct ksmbd_transport *t, void *buf,
		unsigned int buflen, u32 remote_key, u64 remote_offset,
		u32 remote_len)
{
	return smb_direct_rdma_xmit(SMB_DIRECT_TRANS(t), buf, buflen,
			remote_key, remote_offset,
			remote_len, true);
}

static void smb_direct_disconnect(struct ksmbd_transport *t)
{
	struct smb_direct_transport *st = SMB_DIRECT_TRANS(t);

	ksmbd_debug(RDMA, "Disconnecting cm_id=%p\n", st->cm_id);

	smb_direct_disconnect_rdma_connection(st);
	wait_event_interruptible(st->wait_status,
			st->status == SMB_DIRECT_CS_DISCONNECTED);
	free_transport(st);
}

static int smb_direct_cm_handler(struct rdma_cm_id *cm_id,
		struct rdma_cm_event *event)
{
	struct smb_direct_transport *t = cm_id->context;

	ksmbd_debug(RDMA, "RDMA CM event. cm_id=%p event=%s (%d)\n",
			cm_id, rdma_event_msg(event->event), event->event);

	switch (event->event) {
	case RDMA_CM_EVENT_ESTABLISHED: {
		t->status = SMB_DIRECT_CS_CONNECTED;
		wake_up_interruptible(&t->wait_status);
		break;
	}
	case RDMA_CM_EVENT_DEVICE_REMOVAL:
	case RDMA_CM_EVENT_DISCONNECTED: {
		t->status = SMB_DIRECT_CS_DISCONNECTED;
		wake_up_interruptible(&t->wait_status);
		wake_up_interruptible(&t->wait_reassembly_queue);
		wake_up(&t->wait_send_credits);
		break;
	}
	case RDMA_CM_EVENT_CONNECT_ERROR: {
		t->status = SMB_DIRECT_CS_DISCONNECTED;
		wake_up_interruptible(&t->wait_status);
		break;
	}
	default:
		ksmbd_err("Unexpected RDMA CM event. cm_id=%p, event=%s (%d)\n",
				cm_id, rdma_event_msg(event->event),
				event->event);
		break;
	}
	return 0;
}

static void smb_direct_qpair_handler(struct ib_event *event, void *context)
{
	struct smb_direct_transport *t = context;

	ksmbd_debug(RDMA, "Received QP event. cm_id=%p, event=%s (%d)\n",
			t->cm_id, ib_event_msg(event->event), event->event);

	switch (event->event) {
	case IB_EVENT_CQ_ERR:
	case IB_EVENT_QP_FATAL:
		smb_direct_disconnect_rdma_connection(t);
		break;
	default:
		break;
	}
}

static int smb_direct_send_negotiate_response(struct smb_direct_transport *t,
		int failed)
{
	struct smb_direct_sendmsg *sendmsg;
	struct smb_direct_negotiate_resp *resp;
	int ret;

	sendmsg = smb_direct_alloc_sendmsg(t);
	if (IS_ERR(sendmsg))
		return -ENOMEM;

	resp = (struct smb_direct_negotiate_resp *)sendmsg->packet;
	if (failed) {
		memset(resp, 0, sizeof(*resp));
		resp->min_version = cpu_to_le16(0x0100);
		resp->max_version = cpu_to_le16(0x0100);
		resp->status = STATUS_NOT_SUPPORTED;
	} else {
		resp->status = STATUS_SUCCESS;
		resp->min_version = SMB_DIRECT_VERSION_LE;
		resp->max_version = SMB_DIRECT_VERSION_LE;
		resp->negotiated_version = SMB_DIRECT_VERSION_LE;
		resp->reserved = 0;
		resp->credits_requested =
				cpu_to_le16(t->send_credit_target);
		resp->credits_granted = cpu_to_le16(manage_credits_prior_sending(t));
		resp->max_readwrite_size = cpu_to_le32(t->max_rdma_rw_size);
		resp->preferred_send_size = cpu_to_le32(t->max_send_size);
		resp->max_receive_size = cpu_to_le32(t->max_recv_size);
		resp->max_fragmented_size =
				cpu_to_le32(t->max_fragmented_recv_size);
	}

	sendmsg->sge[0].addr = ib_dma_map_single(t->cm_id->device,
				(void *)resp, sizeof(*resp), DMA_TO_DEVICE);
	ret = ib_dma_mapping_error(t->cm_id->device,
				sendmsg->sge[0].addr);
	if (ret) {
		smb_direct_free_sendmsg(t, sendmsg);
		return ret;
	}

	sendmsg->num_sge = 1;
	sendmsg->sge[0].length = sizeof(*resp);
	sendmsg->sge[0].lkey = t->pd->local_dma_lkey;

	ret = post_sendmsg(t, NULL, sendmsg);
	if (ret) {
		smb_direct_free_sendmsg(t, sendmsg);
		return ret;
	}

	wait_event(t->wait_send_pending,
			atomic_read(&t->send_pending) == 0);
	return 0;
}

static int smb_direct_accept_client(struct smb_direct_transport *t)
{
	struct rdma_conn_param conn_param;
	struct ib_port_immutable port_immutable;
	u32 ird_ord_hdr[2];
	int ret;

	memset(&conn_param, 0, sizeof(conn_param));
	conn_param.initiator_depth = min_t(u8,
				t->cm_id->device->attrs.max_qp_rd_atom,
				SMB_DIRECT_CM_INITIATOR_DEPTH);
	conn_param.responder_resources = 0;

	t->cm_id->device->ops.get_port_immutable(t->cm_id->device,
			t->cm_id->port_num, &port_immutable);
	if (port_immutable.core_cap_flags & RDMA_CORE_PORT_IWARP) {
		ird_ord_hdr[0] = conn_param.responder_resources;
		ird_ord_hdr[1] = 1;
		conn_param.private_data = ird_ord_hdr;
		conn_param.private_data_len = sizeof(ird_ord_hdr);
	} else {
		conn_param.private_data = NULL;
		conn_param.private_data_len = 0;
	}
	conn_param.retry_count = SMB_DIRECT_CM_RETRY;
	conn_param.rnr_retry_count = SMB_DIRECT_CM_RNR_RETRY;
	conn_param.flow_control = 0;

	ret = rdma_accept(t->cm_id, &conn_param);
	if (ret) {
		ksmbd_err("error at rdma_accept: %d\n", ret);
		return ret;
	}

	wait_event_interruptible(t->wait_status,
				 t->status != SMB_DIRECT_CS_NEW);
	if (t->status != SMB_DIRECT_CS_CONNECTED)
		return -ENOTCONN;
	return 0;
}

static int smb_direct_negotiate(struct smb_direct_transport *t)
{
	int ret;
	struct smb_direct_recvmsg *recvmsg;
	struct smb_direct_negotiate_req *req;

	recvmsg = get_free_recvmsg(t);
	if (!recvmsg)
		return -ENOMEM;
	recvmsg->type = SMB_DIRECT_MSG_NEGOTIATE_REQ;

	ret = smb_direct_post_recv(t, recvmsg);
	if (ret) {
		ksmbd_err("Can't post recv: %d\n", ret);
		goto out;
	}

	t->negotiation_requested = false;
	ret = smb_direct_accept_client(t);
	if (ret) {
		ksmbd_err("Can't accept client\n");
		goto out;
	}

	smb_direct_post_recv_credits(&t->post_recv_credits_work.work);

	ksmbd_debug(RDMA, "Waiting for SMB_DIRECT negotiate request\n");
	ret = wait_event_interruptible_timeout(t->wait_status,
			t->negotiation_requested ||
			t->status == SMB_DIRECT_CS_DISCONNECTED,
			SMB_DIRECT_NEGOTIATE_TIMEOUT * HZ);
	if (ret <= 0 || t->status == SMB_DIRECT_CS_DISCONNECTED) {
		ret = ret < 0 ? ret : -ETIMEDOUT;
		goto out;
	}

	ret = smb_direct_check_recvmsg(recvmsg);
	if (ret == -ECONNABORTED)
		goto out;

	req = (struct smb_direct_negotiate_req *)recvmsg->packet;
	t->max_recv_size = min_t(int, t->max_recv_size,
			le32_to_cpu(req->preferred_send_size));
	t->max_send_size = min_t(int, t->max_send_size,
			le32_to_cpu(req->max_receive_size));
	t->max_fragmented_send_size =
			le32_to_cpu(req->max_fragmented_size);

	ret = smb_direct_send_negotiate_response(t, ret);
out:
	if (recvmsg)
		put_recvmsg(t, recvmsg);
	return ret;
}

static int smb_direct_init_params(struct smb_direct_transport *t,
		struct ib_qp_cap *cap)
{
	struct ib_device *device = t->cm_id->device;
	int max_send_sges, max_pages, max_rw_wrs, max_send_wrs;

	/* need 2 more sge. because a SMB_DIRECT header will be mapped,
	 * and maybe a send buffer could be not page aligned.
	 */
	t->max_send_size = smb_direct_max_send_size;
	max_send_sges = DIV_ROUND_UP(t->max_send_size, PAGE_SIZE) + 2;
	if (max_send_sges > SMB_DIRECT_MAX_SEND_SGES) {
		ksmbd_err("max_send_size %d is too large\n", t->max_send_size);
		return -EINVAL;
	}

	/*
	 * allow smb_direct_max_outstanding_rw_ops of in-flight RDMA
	 * read/writes. HCA guarantees at least max_send_sge of sges for
	 * a RDMA read/write work request, and if memory registration is used,
	 * we need reg_mr, local_inv wrs for each read/write.
	 */
	t->max_rdma_rw_size = smb_direct_max_read_write_size;
	max_pages = DIV_ROUND_UP(t->max_rdma_rw_size, PAGE_SIZE) + 1;
	max_rw_wrs = DIV_ROUND_UP(max_pages, SMB_DIRECT_MAX_SEND_SGES);
	max_rw_wrs += rdma_rw_mr_factor(device, t->cm_id->port_num,
			max_pages) * 2;
	max_rw_wrs *= smb_direct_max_outstanding_rw_ops;

	max_send_wrs = smb_direct_send_credit_target + max_rw_wrs;
	if (max_send_wrs > device->attrs.max_cqe ||
	    max_send_wrs > device->attrs.max_qp_wr) {
		ksmbd_err("consider lowering send_credit_target = %d, or max_outstanding_rw_ops = %d\n",
			smb_direct_send_credit_target,
			smb_direct_max_outstanding_rw_ops);
		ksmbd_err("Possible CQE overrun, device reporting max_cqe %d max_qp_wr %d\n",
			device->attrs.max_cqe, device->attrs.max_qp_wr);
		return -EINVAL;
	}

	if (smb_direct_receive_credit_max > device->attrs.max_cqe ||
	    smb_direct_receive_credit_max > device->attrs.max_qp_wr) {
		ksmbd_err("consider lowering receive_credit_max = %d\n",
			smb_direct_receive_credit_max);
		ksmbd_err("Possible CQE overrun, device reporting max_cpe %d max_qp_wr %d\n",
			device->attrs.max_cqe, device->attrs.max_qp_wr);
		return -EINVAL;
	}

	if (device->attrs.max_send_sge < SMB_DIRECT_MAX_SEND_SGES) {
		ksmbd_err("warning: device max_send_sge = %d too small\n",
			device->attrs.max_send_sge);
		return -EINVAL;
	}
	if (device->attrs.max_recv_sge < SMB_DIRECT_MAX_RECV_SGES) {
		ksmbd_err("warning: device max_recv_sge = %d too small\n",
			device->attrs.max_recv_sge);
		return -EINVAL;
	}

	t->recv_credits = 0;
	t->count_avail_recvmsg = 0;

	t->recv_credit_max = smb_direct_receive_credit_max;
	t->recv_credit_target = 10;
	t->new_recv_credits = 0;

	t->send_credit_target = smb_direct_send_credit_target;
	atomic_set(&t->send_credits, 0);
	atomic_set(&t->rw_avail_ops, smb_direct_max_outstanding_rw_ops);

	t->max_send_size = smb_direct_max_send_size;
	t->max_recv_size = smb_direct_max_receive_size;
	t->max_fragmented_recv_size = smb_direct_max_fragmented_recv_size;

	cap->max_send_wr = max_send_wrs;
	cap->max_recv_wr = t->recv_credit_max;
	cap->max_send_sge = SMB_DIRECT_MAX_SEND_SGES;
	cap->max_recv_sge = SMB_DIRECT_MAX_RECV_SGES;
	cap->max_inline_data = 0;
	cap->max_rdma_ctxs = 0;
	return 0;
}

static void smb_direct_destroy_pools(struct smb_direct_transport *t)
{
	struct smb_direct_recvmsg *recvmsg;

	while ((recvmsg = get_free_recvmsg(t)))
		mempool_free(recvmsg, t->recvmsg_mempool);
	while ((recvmsg = get_empty_recvmsg(t)))
		mempool_free(recvmsg, t->recvmsg_mempool);

	mempool_destroy(t->recvmsg_mempool);
	t->recvmsg_mempool = NULL;

	kmem_cache_destroy(t->recvmsg_cache);
	t->recvmsg_cache = NULL;

	mempool_destroy(t->sendmsg_mempool);
	t->sendmsg_mempool = NULL;

	kmem_cache_destroy(t->sendmsg_cache);
	t->sendmsg_cache = NULL;
}

static int smb_direct_create_pools(struct smb_direct_transport *t)
{
	char name[80];
	int i;
	struct smb_direct_recvmsg *recvmsg;

	snprintf(name, sizeof(name), "smb_direct_rqst_pool_%p", t);
	t->sendmsg_cache = kmem_cache_create(name,
			sizeof(struct smb_direct_sendmsg) +
			sizeof(struct smb_direct_negotiate_resp),
			0, SLAB_HWCACHE_ALIGN, NULL);
	if (!t->sendmsg_cache)
		return -ENOMEM;

	t->sendmsg_mempool = mempool_create(t->send_credit_target,
			mempool_alloc_slab, mempool_free_slab,
			t->sendmsg_cache);
	if (!t->sendmsg_mempool)
		goto err;

	snprintf(name, sizeof(name), "smb_direct_resp_%p", t);
	t->recvmsg_cache = kmem_cache_create(name,
			sizeof(struct smb_direct_recvmsg) +
			t->max_recv_size,
			0, SLAB_HWCACHE_ALIGN, NULL);
	if (!t->recvmsg_cache)
		goto err;

	t->recvmsg_mempool =
		mempool_create(t->recv_credit_max, mempool_alloc_slab,
		       mempool_free_slab, t->recvmsg_cache);
	if (!t->recvmsg_mempool)
		goto err;

	INIT_LIST_HEAD(&t->recvmsg_queue);

	for (i = 0; i < t->recv_credit_max; i++) {
		recvmsg = mempool_alloc(t->recvmsg_mempool, GFP_KERNEL);
		if (!recvmsg)
			goto err;
		recvmsg->transport = t;
		list_add(&recvmsg->list, &t->recvmsg_queue);
	}
	t->count_avail_recvmsg = t->recv_credit_max;

	return 0;
err:
	smb_direct_destroy_pools(t);
	return -ENOMEM;
}

static int smb_direct_create_qpair(struct smb_direct_transport *t,
		struct ib_qp_cap *cap)
{
	int ret;
	struct ib_qp_init_attr qp_attr;

	t->pd = ib_alloc_pd(t->cm_id->device, 0);
	if (IS_ERR(t->pd)) {
		ksmbd_err("Can't create RDMA PD\n");
		ret = PTR_ERR(t->pd);
		t->pd = NULL;
		return ret;
	}

	t->send_cq = ib_alloc_cq(t->cm_id->device, t,
			t->send_credit_target, 0, IB_POLL_WORKQUEUE);
	if (IS_ERR(t->send_cq)) {
		ksmbd_err("Can't create RDMA send CQ\n");
		ret = PTR_ERR(t->send_cq);
		t->send_cq = NULL;
		goto err;
	}

	t->recv_cq = ib_alloc_cq(t->cm_id->device, t,
			cap->max_send_wr + cap->max_rdma_ctxs,
			0, IB_POLL_WORKQUEUE);
	if (IS_ERR(t->recv_cq)) {
		ksmbd_err("Can't create RDMA recv CQ\n");
		ret = PTR_ERR(t->recv_cq);
		t->recv_cq = NULL;
		goto err;
	}

	memset(&qp_attr, 0, sizeof(qp_attr));
	qp_attr.event_handler = smb_direct_qpair_handler;
	qp_attr.qp_context = t;
	qp_attr.cap = *cap;
	qp_attr.sq_sig_type = IB_SIGNAL_REQ_WR;
	qp_attr.qp_type = IB_QPT_RC;
	qp_attr.send_cq = t->send_cq;
	qp_attr.recv_cq = t->recv_cq;
	qp_attr.port_num = ~0;

	ret = rdma_create_qp(t->cm_id, t->pd, &qp_attr);
	if (ret) {
		ksmbd_err("Can't create RDMA QP: %d\n", ret);
		goto err;
	}

	t->qp = t->cm_id->qp;
	t->cm_id->event_handler = smb_direct_cm_handler;

	return 0;
err:
	if (t->qp) {
		ib_destroy_qp(t->qp);
		t->qp = NULL;
	}
	if (t->recv_cq) {
		ib_destroy_cq(t->recv_cq);
		t->recv_cq = NULL;
	}
	if (t->send_cq) {
		ib_destroy_cq(t->send_cq);
		t->send_cq = NULL;
	}
	if (t->pd) {
		ib_dealloc_pd(t->pd);
		t->pd = NULL;
	}
	return ret;
}

static int smb_direct_prepare(struct ksmbd_transport *t)
{
	struct smb_direct_transport *st = SMB_DIRECT_TRANS(t);
	int ret;
	struct ib_qp_cap qp_cap;

	ret = smb_direct_init_params(st, &qp_cap);
	if (ret) {
		ksmbd_err("Can't configure RDMA parameters\n");
		return ret;
	}

	ret = smb_direct_create_pools(st);
	if (ret) {
		ksmbd_err("Can't init RDMA pool: %d\n", ret);
		return ret;
	}

	ret = smb_direct_create_qpair(st, &qp_cap);
	if (ret) {
		ksmbd_err("Can't accept RDMA client: %d\n", ret);
		return ret;
	}

	ret = smb_direct_negotiate(st);
	if (ret) {
		ksmbd_err("Can't negotiate: %d\n", ret);
		return ret;
	}

	st->status = SMB_DIRECT_CS_CONNECTED;
	return 0;
}

static bool rdma_frwr_is_supported(struct ib_device_attr *attrs)
{
	if (!(attrs->device_cap_flags & IB_DEVICE_MEM_MGT_EXTENSIONS))
		return false;
	if (attrs->max_fast_reg_page_list_len == 0)
		return false;
	return true;
}

static int smb_direct_handle_connect_request(struct rdma_cm_id *new_cm_id)
{
	struct smb_direct_transport *t;

	if (!rdma_frwr_is_supported(&new_cm_id->device->attrs)) {
		ksmbd_debug(RDMA,
			"Fast Registration Work Requests is not supported. device capabilities=%llx\n",
			new_cm_id->device->attrs.device_cap_flags);
		return -EPROTONOSUPPORT;
	}

	t = alloc_transport(new_cm_id);
	if (!t)
		return -ENOMEM;

	KSMBD_TRANS(t)->handler = kthread_run(ksmbd_conn_handler_loop,
			KSMBD_TRANS(t)->conn, "ksmbd:r%u", SMB_DIRECT_PORT);
	if (IS_ERR(KSMBD_TRANS(t)->handler)) {
		int ret = PTR_ERR(KSMBD_TRANS(t)->handler);

		ksmbd_err("Can't start thread\n");
		free_transport(t);
		return ret;
	}

	return 0;
}

static int smb_direct_listen_handler(struct rdma_cm_id *cm_id,
		struct rdma_cm_event *event)
{
	switch (event->event) {
	case RDMA_CM_EVENT_CONNECT_REQUEST: {
		int ret = smb_direct_handle_connect_request(cm_id);

		if (ret) {
			ksmbd_err("Can't create transport: %d\n", ret);
			return ret;
		}

		ksmbd_debug(RDMA, "Received connection request. cm_id=%p\n",
			cm_id);
		break;
	}
	default:
		ksmbd_err("Unexpected listen event. cm_id=%p, event=%s (%d)\n",
				cm_id,
				rdma_event_msg(event->event), event->event);
		break;
	}
	return 0;
}

static int smb_direct_listen(int port)
{
	int ret;
	struct rdma_cm_id *cm_id;
	struct sockaddr_in sin = {
		.sin_family		= AF_INET,
		.sin_addr.s_addr	= htonl(INADDR_ANY),
		.sin_port		= htons(port),
	};

	cm_id = rdma_create_id(&init_net, smb_direct_listen_handler,
		&smb_direct_listener, RDMA_PS_TCP, IB_QPT_RC);
	if (IS_ERR(cm_id)) {
		ksmbd_err("Can't create cm id: %ld\n",
				PTR_ERR(cm_id));
		return PTR_ERR(cm_id);
	}

	ret = rdma_bind_addr(cm_id, (struct sockaddr *)&sin);
	if (ret) {
		ksmbd_err("Can't bind: %d\n", ret);
		goto err;
	}

	smb_direct_listener.cm_id = cm_id;

	ret = rdma_listen(cm_id, 10);
	if (ret) {
		ksmbd_err("Can't listen: %d\n", ret);
		goto err;
	}
	return 0;
err:
	smb_direct_listener.cm_id = NULL;
	rdma_destroy_id(cm_id);
	return ret;
}

int ksmbd_rdma_init(void)
{
	int ret;

	smb_direct_listener.cm_id = NULL;

	/* When a client is running out of send credits, the credits are
	 * granted by the server's sending a packet using this queue.
	 * This avoids the situation that a clients cannot send packets
	 * for lack of credits
	 */
	smb_direct_wq = alloc_workqueue("ksmbd-smb_direct-wq",
				WQ_HIGHPRI | WQ_MEM_RECLAIM, 0);
	if (!smb_direct_wq)
		return -ENOMEM;

	ret = smb_direct_listen(SMB_DIRECT_PORT);
	if (ret) {
		destroy_workqueue(smb_direct_wq);
		smb_direct_wq = NULL;
		ksmbd_err("Can't listen: %d\n", ret);
		return ret;
	}

	ksmbd_debug(RDMA, "init RDMA listener. cm_id=%p\n",
		smb_direct_listener.cm_id);
	return 0;
}

int ksmbd_rdma_destroy(void)
{
	if (smb_direct_listener.cm_id)
		rdma_destroy_id(smb_direct_listener.cm_id);
	smb_direct_listener.cm_id = NULL;

	if (smb_direct_wq) {
		flush_workqueue(smb_direct_wq);
		destroy_workqueue(smb_direct_wq);
		smb_direct_wq = NULL;
	}
	return 0;
}

static struct ksmbd_transport_ops ksmbd_smb_direct_transport_ops = {
	.prepare	= smb_direct_prepare,
	.disconnect	= smb_direct_disconnect,
	.writev		= smb_direct_writev,
	.read		= smb_direct_read,
	.rdma_read	= smb_direct_rdma_read,
	.rdma_write	= smb_direct_rdma_write,
};