// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *   Copyright (C) 2017, Microsoft Corporation.
 *
 *   Author(s): Long Li <longli@microsoft.com>
 */
#include <linux/module.h>
#include <linux/highmem.h>
#include "smbdirect.h"
#include "cifs_debug.h"
#include "cifsproto.h"
#include "smb2proto.h"

static struct smbd_response *get_empty_queue_buffer(
                struct smbd_connection *info);
static struct smbd_response *get_receive_buffer(
                struct smbd_connection *info);
static void put_receive_buffer(
                struct smbd_connection *info,
                struct smbd_response *response);
static int allocate_receive_buffers(struct smbd_connection *info, int num_buf);
static void destroy_receive_buffers(struct smbd_connection *info);

static void put_empty_packet(
                struct smbd_connection *info, struct smbd_response *response);
static void enqueue_reassembly(
                struct smbd_connection *info,
                struct smbd_response *response, int data_length);
static struct smbd_response *_get_first_reassembly(
                struct smbd_connection *info);

static int smbd_post_recv(
                struct smbd_connection *info,
                struct smbd_response *response);

static int smbd_post_send_empty(struct smbd_connection *info);
static int smbd_post_send_data(
                struct smbd_connection *info,
                struct kvec *iov, int n_vec, int remaining_data_length);
static int smbd_post_send_page(struct smbd_connection *info,
                struct page *page, unsigned long offset,
                size_t size, int remaining_data_length);

static void destroy_mr_list(struct smbd_connection *info);
static int allocate_mr_list(struct smbd_connection *info);

/* SMBD version number */
#define SMBD_V1 0x0100

/* Port numbers for SMBD transport */
#define SMB_PORT        445
#define SMBD_PORT       5445

/* Address lookup and resolve timeout in ms */
#define RDMA_RESOLVE_TIMEOUT    5000

/* SMBD negotiation timeout in seconds */
#define SMBD_NEGOTIATE_TIMEOUT  120

/* SMBD minimum receive size and fragmented sized defined in [MS-SMBD] */
#define SMBD_MIN_RECEIVE_SIZE           128
#define SMBD_MIN_FRAGMENTED_SIZE        131072

/*
 * Default maximum number of RDMA read/write outstanding on this connection
 * This value is possibly decreased during QP creation on hardware limit
 */
#define SMBD_CM_RESPONDER_RESOURCES     32

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

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

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

/* The maximum single message size can be sent to remote peer */
int smbd_max_send_size = 1364;

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

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

/* The timeout to initiate send of a keepalive message on idle */
int smbd_keep_alive_interval = 120;

/*
 * User configurable initial values for RDMA transport
 * The actual values used may be lower and are limited to hardware capabilities
 */
/* Default maximum number of SGEs in a RDMA write/read */
int smbd_max_frmr_depth = 2048;

/* If payload is less than this byte, use RDMA send/recv not read/write */
int rdma_readwrite_threshold = 4096;

/* Transport logging functions
 * Logging are defined as classes. They can be OR'ed to define the actual
 * logging level via module parameter smbd_logging_class
 * e.g. cifs.smbd_logging_class=0xa0 will log all log_rdma_recv() and
 * log_rdma_event()
 */
#define LOG_OUTGOING                    0x1
#define LOG_INCOMING                    0x2
#define LOG_READ                        0x4
#define LOG_WRITE                       0x8
#define LOG_RDMA_SEND                   0x10
#define LOG_RDMA_RECV                   0x20
#define LOG_KEEP_ALIVE                  0x40
#define LOG_RDMA_EVENT                  0x80
#define LOG_RDMA_MR                     0x100
static unsigned int smbd_logging_class;
module_param(smbd_logging_class, uint, 0644);
MODULE_PARM_DESC(smbd_logging_class,
        "Logging class for SMBD transport 0x0 to 0x100");

#define ERR             0x0
#define INFO            0x1
static unsigned int smbd_logging_level = ERR;
module_param(smbd_logging_level, uint, 0644);
MODULE_PARM_DESC(smbd_logging_level,
        "Logging level for SMBD transport, 0 (default): error, 1: info");

#define log_rdma(level, class, fmt, args...)                            \
do {                                                                    \
        if (level <= smbd_logging_level || class & smbd_logging_class)  \
                cifs_dbg(VFS, "%s:%d " fmt, __func__, __LINE__, ##args);\
} while (0)

#define log_outgoing(level, fmt, args...) \
                log_rdma(level, LOG_OUTGOING, fmt, ##args)
#define log_incoming(level, fmt, args...) \
                log_rdma(level, LOG_INCOMING, fmt, ##args)
#define log_read(level, fmt, args...)   log_rdma(level, LOG_READ, fmt, ##args)
#define log_write(level, fmt, args...)  log_rdma(level, LOG_WRITE, fmt, ##args)
#define log_rdma_send(level, fmt, args...) \
                log_rdma(level, LOG_RDMA_SEND, fmt, ##args)
#define log_rdma_recv(level, fmt, args...) \
                log_rdma(level, LOG_RDMA_RECV, fmt, ##args)
#define log_keep_alive(level, fmt, args...) \
                log_rdma(level, LOG_KEEP_ALIVE, fmt, ##args)
#define log_rdma_event(level, fmt, args...) \
                log_rdma(level, LOG_RDMA_EVENT, fmt, ##args)
#define log_rdma_mr(level, fmt, args...) \
                log_rdma(level, LOG_RDMA_MR, fmt, ##args)

static void smbd_disconnect_rdma_work(struct work_struct *work)
{
        struct smbd_connection *info =
                container_of(work, struct smbd_connection, disconnect_work);

        if (info->transport_status == SMBD_CONNECTED) {
                info->transport_status = SMBD_DISCONNECTING;
                rdma_disconnect(info->id);
        }
}

static void smbd_disconnect_rdma_connection(struct smbd_connection *info)
{
        queue_work(info->workqueue, &info->disconnect_work);
}

/* Upcall from RDMA CM */
static int smbd_conn_upcall(
                struct rdma_cm_id *id, struct rdma_cm_event *event)
{
        struct smbd_connection *info = id->context;

        log_rdma_event(INFO, "event=%d status=%d\n",
                event->event, event->status);

        switch (event->event) {
        case RDMA_CM_EVENT_ADDR_RESOLVED:
        case RDMA_CM_EVENT_ROUTE_RESOLVED:
                info->ri_rc = 0;
                complete(&info->ri_done);
                break;

        case RDMA_CM_EVENT_ADDR_ERROR:
                info->ri_rc = -EHOSTUNREACH;
                complete(&info->ri_done);
                break;

        case RDMA_CM_EVENT_ROUTE_ERROR:
                info->ri_rc = -ENETUNREACH;
                complete(&info->ri_done);
                break;

        case RDMA_CM_EVENT_ESTABLISHED:
                log_rdma_event(INFO, "connected event=%d\n", event->event);
                info->transport_status = SMBD_CONNECTED;
                wake_up_interruptible(&info->conn_wait);
                break;

        case RDMA_CM_EVENT_CONNECT_ERROR:
        case RDMA_CM_EVENT_UNREACHABLE:
        case RDMA_CM_EVENT_REJECTED:
                log_rdma_event(INFO, "connecting failed event=%d\n", event->event);
                info->transport_status = SMBD_DISCONNECTED;
                wake_up_interruptible(&info->conn_wait);
                break;

        case RDMA_CM_EVENT_DEVICE_REMOVAL:
        case RDMA_CM_EVENT_DISCONNECTED:
                /* This happenes when we fail the negotiation */
                if (info->transport_status == SMBD_NEGOTIATE_FAILED) {
                        info->transport_status = SMBD_DISCONNECTED;
                        wake_up(&info->conn_wait);
                        break;
                }

                info->transport_status = SMBD_DISCONNECTED;
                wake_up_interruptible(&info->disconn_wait);
                wake_up_interruptible(&info->wait_reassembly_queue);
                wake_up_interruptible_all(&info->wait_send_queue);
                break;

        default:
                break;
        }

        return 0;
}

/* Upcall from RDMA QP */
static void
smbd_qp_async_error_upcall(struct ib_event *event, void *context)
{
        struct smbd_connection *info = context;

        log_rdma_event(ERR, "%s on device %s info %p\n",
                ib_event_msg(event->event), event->device->name, info);

        switch (event->event) {
        case IB_EVENT_CQ_ERR:
        case IB_EVENT_QP_FATAL:
                smbd_disconnect_rdma_connection(info);

        default:
                break;
        }
}

static inline void *smbd_request_payload(struct smbd_request *request)
{
        return (void *)request->packet;
}

static inline void *smbd_response_payload(struct smbd_response *response)
{
        return (void *)response->packet;
}

/* Called when a RDMA send is done */
static void send_done(struct ib_cq *cq, struct ib_wc *wc)
{
        int i;
        struct smbd_request *request =
                container_of(wc->wr_cqe, struct smbd_request, cqe);

        log_rdma_send(INFO, "smbd_request %p completed wc->status=%d\n",
                request, wc->status);

        if (wc->status != IB_WC_SUCCESS || wc->opcode != IB_WC_SEND) {
                log_rdma_send(ERR, "wc->status=%d wc->opcode=%d\n",
                        wc->status, wc->opcode);
                smbd_disconnect_rdma_connection(request->info);
        }

        for (i = 0; i < request->num_sge; i++)
                ib_dma_unmap_single(request->info->id->device,
                        request->sge[i].addr,
                        request->sge[i].length,
                        DMA_TO_DEVICE);

        if (atomic_dec_and_test(&request->info->send_pending))
                wake_up(&request->info->wait_send_pending);

        wake_up(&request->info->wait_post_send);

        mempool_free(request, request->info->request_mempool);
}

static void dump_smbd_negotiate_resp(struct smbd_negotiate_resp *resp)
{
        log_rdma_event(INFO, "resp message min_version %u max_version %u negotiated_version %u credits_requested %u credits_granted %u status %u max_readwrite_size %u preferred_send_size %u max_receive_size %u max_fragmented_size %u\n",
                       resp->min_version, resp->max_version,
                       resp->negotiated_version, resp->credits_requested,
                       resp->credits_granted, resp->status,
                       resp->max_readwrite_size, resp->preferred_send_size,
                       resp->max_receive_size, resp->max_fragmented_size);
}

/*
 * Process a negotiation response message, according to [MS-SMBD]3.1.5.7
 * response, packet_length: the negotiation response message
 * return value: true if negotiation is a success, false if failed
 */
static bool process_negotiation_response(
                struct smbd_response *response, int packet_length)
{
        struct smbd_connection *info = response->info;
        struct smbd_negotiate_resp *packet = smbd_response_payload(response);

        if (packet_length < sizeof(struct smbd_negotiate_resp)) {
                log_rdma_event(ERR,
                        "error: packet_length=%d\n", packet_length);
                return false;
        }

        if (le16_to_cpu(packet->negotiated_version) != SMBD_V1) {
                log_rdma_event(ERR, "error: negotiated_version=%x\n",
                        le16_to_cpu(packet->negotiated_version));
                return false;
        }
        info->protocol = le16_to_cpu(packet->negotiated_version);

        if (packet->credits_requested == 0) {
                log_rdma_event(ERR, "error: credits_requested==0\n");
                return false;
        }
        info->receive_credit_target = le16_to_cpu(packet->credits_requested);

        if (packet->credits_granted == 0) {
                log_rdma_event(ERR, "error: credits_granted==0\n");
                return false;
        }
        atomic_set(&info->send_credits, le16_to_cpu(packet->credits_granted));

        atomic_set(&info->receive_credits, 0);

        if (le32_to_cpu(packet->preferred_send_size) > info->max_receive_size) {
                log_rdma_event(ERR, "error: preferred_send_size=%d\n",
                        le32_to_cpu(packet->preferred_send_size));
                return false;
        }
        info->max_receive_size = le32_to_cpu(packet->preferred_send_size);

        if (le32_to_cpu(packet->max_receive_size) < SMBD_MIN_RECEIVE_SIZE) {
                log_rdma_event(ERR, "error: max_receive_size=%d\n",
                        le32_to_cpu(packet->max_receive_size));
                return false;
        }
        info->max_send_size = min_t(int, info->max_send_size,
                                        le32_to_cpu(packet->max_receive_size));

        if (le32_to_cpu(packet->max_fragmented_size) <
                        SMBD_MIN_FRAGMENTED_SIZE) {
                log_rdma_event(ERR, "error: max_fragmented_size=%d\n",
                        le32_to_cpu(packet->max_fragmented_size));
                return false;
        }
        info->max_fragmented_send_size =
                le32_to_cpu(packet->max_fragmented_size);
        info->rdma_readwrite_threshold =
                rdma_readwrite_threshold > info->max_fragmented_send_size ?
                info->max_fragmented_send_size :
                rdma_readwrite_threshold;


        info->max_readwrite_size = min_t(u32,
                        le32_to_cpu(packet->max_readwrite_size),
                        info->max_frmr_depth * PAGE_SIZE);
        info->max_frmr_depth = info->max_readwrite_size / PAGE_SIZE;

        return true;
}

static void smbd_post_send_credits(struct work_struct *work)
{
        int ret = 0;
        int use_receive_queue = 1;
        int rc;
        struct smbd_response *response;
        struct smbd_connection *info =
                container_of(work, struct smbd_connection,
                        post_send_credits_work);

        if (info->transport_status != SMBD_CONNECTED) {
                wake_up(&info->wait_receive_queues);
                return;
        }

        if (info->receive_credit_target >
                atomic_read(&info->receive_credits)) {
                while (true) {
                        if (use_receive_queue)
                                response = get_receive_buffer(info);
                        else
                                response = get_empty_queue_buffer(info);
                        if (!response) {
                                /* now switch to emtpy packet queue */
                                if (use_receive_queue) {
                                        use_receive_queue = 0;
                                        continue;
                                } else
                                        break;
                        }

                        response->type = SMBD_TRANSFER_DATA;
                        response->first_segment = false;
                        rc = smbd_post_recv(info, response);
                        if (rc) {
                                log_rdma_recv(ERR,
                                        "post_recv failed rc=%d\n", rc);
                                put_receive_buffer(info, response);
                                break;
                        }

                        ret++;
                }
        }

        spin_lock(&info->lock_new_credits_offered);
        info->new_credits_offered += ret;
        spin_unlock(&info->lock_new_credits_offered);

        /* Promptly send an immediate packet as defined in [MS-SMBD] 3.1.1.1 */
        info->send_immediate = true;
        if (atomic_read(&info->receive_credits) <
                info->receive_credit_target - 1) {
                if (info->keep_alive_requested == KEEP_ALIVE_PENDING ||
                    info->send_immediate) {
                        log_keep_alive(INFO, "send an empty message\n");
                        smbd_post_send_empty(info);
                }
        }
}

/* Called from softirq, when recv is done */
static void recv_done(struct ib_cq *cq, struct ib_wc *wc)
{
        struct smbd_data_transfer *data_transfer;
        struct smbd_response *response =
                container_of(wc->wr_cqe, struct smbd_response, cqe);
        struct smbd_connection *info = response->info;
        int data_length = 0;

        log_rdma_recv(INFO, "response=%p type=%d wc status=%d wc opcode %d byte_len=%d pkey_index=%x\n",
                      response, response->type, wc->status, wc->opcode,
                      wc->byte_len, wc->pkey_index);

        if (wc->status != IB_WC_SUCCESS || wc->opcode != IB_WC_RECV) {
                log_rdma_recv(INFO, "wc->status=%d opcode=%d\n",
                        wc->status, wc->opcode);
                smbd_disconnect_rdma_connection(info);
                goto error;
        }

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

        switch (response->type) {
        /* SMBD negotiation response */
        case SMBD_NEGOTIATE_RESP:
                dump_smbd_negotiate_resp(smbd_response_payload(response));
                info->full_packet_received = true;
                info->negotiate_done =
                        process_negotiation_response(response, wc->byte_len);
                complete(&info->negotiate_completion);
                break;

        /* SMBD data transfer packet */
        case SMBD_TRANSFER_DATA:
                data_transfer = smbd_response_payload(response);
                data_length = le32_to_cpu(data_transfer->data_length);

                /*
                 * If this is a packet with data playload place the data in
                 * reassembly queue and wake up the reading thread
                 */
                if (data_length) {
                        if (info->full_packet_received)
                                response->first_segment = true;

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

                        enqueue_reassembly(
                                info,
                                response,
                                data_length);
                } else
                        put_empty_packet(info, response);

                if (data_length)
                        wake_up_interruptible(&info->wait_reassembly_queue);

                atomic_dec(&info->receive_credits);
                info->receive_credit_target =
                        le16_to_cpu(data_transfer->credits_requested);
                if (le16_to_cpu(data_transfer->credits_granted)) {
                        atomic_add(le16_to_cpu(data_transfer->credits_granted),
                                &info->send_credits);
                        /*
                         * We have new send credits granted from remote peer
                         * If any sender is waiting for credits, unblock it
                         */
                        wake_up_interruptible(&info->wait_send_queue);
                }

                log_incoming(INFO, "data flags %d data_offset %d data_length %d remaining_data_length %d\n",
                             le16_to_cpu(data_transfer->flags),
                             le32_to_cpu(data_transfer->data_offset),
                             le32_to_cpu(data_transfer->data_length),
                             le32_to_cpu(data_transfer->remaining_data_length));

                /* Send a KEEP_ALIVE response right away if requested */
                info->keep_alive_requested = KEEP_ALIVE_NONE;
                if (le16_to_cpu(data_transfer->flags) &
                                SMB_DIRECT_RESPONSE_REQUESTED) {
                        info->keep_alive_requested = KEEP_ALIVE_PENDING;
                }

                return;

        default:
                log_rdma_recv(ERR,
                        "unexpected response type=%d\n", response->type);
        }

error:
        put_receive_buffer(info, response);
}

static struct rdma_cm_id *smbd_create_id(
                struct smbd_connection *info,
                struct sockaddr *dstaddr, int port)
{
        struct rdma_cm_id *id;
        int rc;
        __be16 *sport;

        id = rdma_create_id(&init_net, smbd_conn_upcall, info,
                RDMA_PS_TCP, IB_QPT_RC);
        if (IS_ERR(id)) {
                rc = PTR_ERR(id);
                log_rdma_event(ERR, "rdma_create_id() failed %i\n", rc);
                return id;
        }

        if (dstaddr->sa_family == AF_INET6)
                sport = &((struct sockaddr_in6 *)dstaddr)->sin6_port;
        else
                sport = &((struct sockaddr_in *)dstaddr)->sin_port;

        *sport = htons(port);

        init_completion(&info->ri_done);
        info->ri_rc = -ETIMEDOUT;

        rc = rdma_resolve_addr(id, NULL, (struct sockaddr *)dstaddr,
                RDMA_RESOLVE_TIMEOUT);
        if (rc) {
                log_rdma_event(ERR, "rdma_resolve_addr() failed %i\n", rc);
                goto out;
        }
        wait_for_completion_interruptible_timeout(
                &info->ri_done, msecs_to_jiffies(RDMA_RESOLVE_TIMEOUT));
        rc = info->ri_rc;
        if (rc) {
                log_rdma_event(ERR, "rdma_resolve_addr() completed %i\n", rc);
                goto out;
        }

        info->ri_rc = -ETIMEDOUT;
        rc = rdma_resolve_route(id, RDMA_RESOLVE_TIMEOUT);
        if (rc) {
                log_rdma_event(ERR, "rdma_resolve_route() failed %i\n", rc);
                goto out;
        }
        wait_for_completion_interruptible_timeout(
                &info->ri_done, msecs_to_jiffies(RDMA_RESOLVE_TIMEOUT));
        rc = info->ri_rc;
        if (rc) {
                log_rdma_event(ERR, "rdma_resolve_route() completed %i\n", rc);
                goto out;
        }

        return id;

out:
        rdma_destroy_id(id);
        return ERR_PTR(rc);
}

/*
 * Test if FRWR (Fast Registration Work Requests) is supported on the device
 * This implementation requries FRWR on RDMA read/write
 * return value: true if it is supported
 */
static bool 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 smbd_ia_open(
                struct smbd_connection *info,
                struct sockaddr *dstaddr, int port)
{
        int rc;

        info->id = smbd_create_id(info, dstaddr, port);
        if (IS_ERR(info->id)) {
                rc = PTR_ERR(info->id);
                goto out1;
        }

        if (!frwr_is_supported(&info->id->device->attrs)) {
                log_rdma_event(ERR, "Fast Registration Work Requests (FRWR) is not supported\n");
                log_rdma_event(ERR, "Device capability flags = %llx max_fast_reg_page_list_len = %u\n",
                               info->id->device->attrs.device_cap_flags,
                               info->id->device->attrs.max_fast_reg_page_list_len);
                rc = -EPROTONOSUPPORT;
                goto out2;
        }
        info->max_frmr_depth = min_t(int,
                smbd_max_frmr_depth,
                info->id->device->attrs.max_fast_reg_page_list_len);
        info->mr_type = IB_MR_TYPE_MEM_REG;
        if (info->id->device->attrs.device_cap_flags & IB_DEVICE_SG_GAPS_REG)
                info->mr_type = IB_MR_TYPE_SG_GAPS;

        info->pd = ib_alloc_pd(info->id->device, 0);
        if (IS_ERR(info->pd)) {
                rc = PTR_ERR(info->pd);
                log_rdma_event(ERR, "ib_alloc_pd() returned %d\n", rc);
                goto out2;
        }

        return 0;

out2:
        rdma_destroy_id(info->id);
        info->id = NULL;

out1:
        return rc;
}

/*
 * Send a negotiation request message to the peer
 * The negotiation procedure is in [MS-SMBD] 3.1.5.2 and 3.1.5.3
 * After negotiation, the transport is connected and ready for
 * carrying upper layer SMB payload
 */
static int smbd_post_send_negotiate_req(struct smbd_connection *info)
{
        struct ib_send_wr send_wr;
        int rc = -ENOMEM;
        struct smbd_request *request;
        struct smbd_negotiate_req *packet;

        request = mempool_alloc(info->request_mempool, GFP_KERNEL);
        if (!request)
                return rc;

        request->info = info;

        packet = smbd_request_payload(request);
        packet->min_version = cpu_to_le16(SMBD_V1);
        packet->max_version = cpu_to_le16(SMBD_V1);
        packet->reserved = 0;
        packet->credits_requested = cpu_to_le16(info->send_credit_target);
        packet->preferred_send_size = cpu_to_le32(info->max_send_size);
        packet->max_receive_size = cpu_to_le32(info->max_receive_size);
        packet->max_fragmented_size =
                cpu_to_le32(info->max_fragmented_recv_size);

        request->num_sge = 1;
        request->sge[0].addr = ib_dma_map_single(
                                info->id->device, (void *)packet,
                                sizeof(*packet), DMA_TO_DEVICE);
        if (ib_dma_mapping_error(info->id->device, request->sge[0].addr)) {
                rc = -EIO;
                goto dma_mapping_failed;
        }

        request->sge[0].length = sizeof(*packet);
        request->sge[0].lkey = info->pd->local_dma_lkey;

        ib_dma_sync_single_for_device(
                info->id->device, request->sge[0].addr,
                request->sge[0].length, DMA_TO_DEVICE);

        request->cqe.done = send_done;

        send_wr.next = NULL;
        send_wr.wr_cqe = &request->cqe;
        send_wr.sg_list = request->sge;
        send_wr.num_sge = request->num_sge;
        send_wr.opcode = IB_WR_SEND;
        send_wr.send_flags = IB_SEND_SIGNALED;

        log_rdma_send(INFO, "sge addr=%llx length=%x lkey=%x\n",
                request->sge[0].addr,
                request->sge[0].length, request->sge[0].lkey);

        atomic_inc(&info->send_pending);
        rc = ib_post_send(info->id->qp, &send_wr, NULL);
        if (!rc)
                return 0;

        /* if we reach here, post send failed */
        log_rdma_send(ERR, "ib_post_send failed rc=%d\n", rc);
        atomic_dec(&info->send_pending);
        ib_dma_unmap_single(info->id->device, request->sge[0].addr,
                request->sge[0].length, DMA_TO_DEVICE);

        smbd_disconnect_rdma_connection(info);

dma_mapping_failed:
        mempool_free(request, info->request_mempool);
        return rc;
}

/*
 * Extend the credits to remote peer
 * This implements [MS-SMBD] 3.1.5.9
 * The idea is that we should extend credits to remote peer as quickly as
 * it's allowed, to maintain data flow. We allocate as much receive
 * buffer as possible, and extend the receive credits to remote peer
 * return value: the new credtis being granted.
 */
static int manage_credits_prior_sending(struct smbd_connection *info)
{
        int new_credits;

        spin_lock(&info->lock_new_credits_offered);
        new_credits = info->new_credits_offered;
        info->new_credits_offered = 0;
        spin_unlock(&info->lock_new_credits_offered);

        return new_credits;
}

/*
 * Check if we need to send a KEEP_ALIVE message
 * The idle connection timer triggers a KEEP_ALIVE message when expires
 * SMB_DIRECT_RESPONSE_REQUESTED is set in the message flag to have peer send
 * back a response.
 * return value:
 * 1 if SMB_DIRECT_RESPONSE_REQUESTED needs to be set
 * 0: otherwise
 */
static int manage_keep_alive_before_sending(struct smbd_connection *info)
{
        if (info->keep_alive_requested == KEEP_ALIVE_PENDING) {
                info->keep_alive_requested = KEEP_ALIVE_SENT;
                return 1;
        }
        return 0;
}

/* Post the send request */
static int smbd_post_send(struct smbd_connection *info,
                struct smbd_request *request)
{
        struct ib_send_wr send_wr;
        int rc, i;

        for (i = 0; i < request->num_sge; i++) {
                log_rdma_send(INFO,
                        "rdma_request sge[%d] addr=%llu length=%u\n",
                        i, request->sge[i].addr, request->sge[i].length);
                ib_dma_sync_single_for_device(
                        info->id->device,
                        request->sge[i].addr,
                        request->sge[i].length,
                        DMA_TO_DEVICE);
        }

        request->cqe.done = send_done;

        send_wr.next = NULL;
        send_wr.wr_cqe = &request->cqe;
        send_wr.sg_list = request->sge;
        send_wr.num_sge = request->num_sge;
        send_wr.opcode = IB_WR_SEND;
        send_wr.send_flags = IB_SEND_SIGNALED;

        rc = ib_post_send(info->id->qp, &send_wr, NULL);
        if (rc) {
                log_rdma_send(ERR, "ib_post_send failed rc=%d\n", rc);
                smbd_disconnect_rdma_connection(info);
                rc = -EAGAIN;
        } else
                /* Reset timer for idle connection after packet is sent */
                mod_delayed_work(info->workqueue, &info->idle_timer_work,
                        info->keep_alive_interval*HZ);

        return rc;
}

static int smbd_post_send_sgl(struct smbd_connection *info,
        struct scatterlist *sgl, int data_length, int remaining_data_length)
{
        int num_sgs;
        int i, rc;
        int header_length;
        struct smbd_request *request;
        struct smbd_data_transfer *packet;
        int new_credits;
        struct scatterlist *sg;

wait_credit:
        /* Wait for send credits. A SMBD packet needs one credit */
        rc = wait_event_interruptible(info->wait_send_queue,
                atomic_read(&info->send_credits) > 0 ||
                info->transport_status != SMBD_CONNECTED);
        if (rc)
                goto err_wait_credit;

        if (info->transport_status != SMBD_CONNECTED) {
                log_outgoing(ERR, "disconnected not sending on wait_credit\n");
                rc = -EAGAIN;
                goto err_wait_credit;
        }
        if (unlikely(atomic_dec_return(&info->send_credits) < 0)) {
                atomic_inc(&info->send_credits);
                goto wait_credit;
        }

wait_send_queue:
        wait_event(info->wait_post_send,
                atomic_read(&info->send_pending) < info->send_credit_target ||
                info->transport_status != SMBD_CONNECTED);

        if (info->transport_status != SMBD_CONNECTED) {
                log_outgoing(ERR, "disconnected not sending on wait_send_queue\n");
                rc = -EAGAIN;
                goto err_wait_send_queue;
        }

        if (unlikely(atomic_inc_return(&info->send_pending) >
                                info->send_credit_target)) {
                atomic_dec(&info->send_pending);
                goto wait_send_queue;
        }

        request = mempool_alloc(info->request_mempool, GFP_KERNEL);
        if (!request) {
                rc = -ENOMEM;
                goto err_alloc;
        }

        request->info = info;

        /* Fill in the packet header */
        packet = smbd_request_payload(request);
        packet->credits_requested = cpu_to_le16(info->send_credit_target);

        new_credits = manage_credits_prior_sending(info);
        atomic_add(new_credits, &info->receive_credits);
        packet->credits_granted = cpu_to_le16(new_credits);

        info->send_immediate = false;

        packet->flags = 0;
        if (manage_keep_alive_before_sending(info))
                packet->flags |= cpu_to_le16(SMB_DIRECT_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;

        log_outgoing(INFO, "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 smbd_data_transfer);
        /* If this is a packet without payload, don't send padding */
        if (!data_length)
                header_length = offsetof(struct smbd_data_transfer, padding);

        request->num_sge = 1;
        request->sge[0].addr = ib_dma_map_single(info->id->device,
                                                 (void *)packet,
                                                 header_length,
                                                 DMA_TO_DEVICE);
        if (ib_dma_mapping_error(info->id->device, request->sge[0].addr)) {
                rc = -EIO;
                request->sge[0].addr = 0;
                goto err_dma;
        }

        request->sge[0].length = header_length;
        request->sge[0].lkey = info->pd->local_dma_lkey;

        /* Fill in the packet data payload */
        num_sgs = sgl ? sg_nents(sgl) : 0;
        for_each_sg(sgl, sg, num_sgs, i) {
                request->sge[i+1].addr =
                        ib_dma_map_page(info->id->device, sg_page(sg),
                               sg->offset, sg->length, DMA_TO_DEVICE);
                if (ib_dma_mapping_error(
                                info->id->device, request->sge[i+1].addr)) {
                        rc = -EIO;
                        request->sge[i+1].addr = 0;
                        goto err_dma;
                }
                request->sge[i+1].length = sg->length;
                request->sge[i+1].lkey = info->pd->local_dma_lkey;
                request->num_sge++;
        }

        rc = smbd_post_send(info, request);
        if (!rc)
                return 0;

err_dma:
        for (i = 0; i < request->num_sge; i++)
                if (request->sge[i].addr)
                        ib_dma_unmap_single(info->id->device,
                                            request->sge[i].addr,
                                            request->sge[i].length,
                                            DMA_TO_DEVICE);
        mempool_free(request, info->request_mempool);

        /* roll back receive credits and credits to be offered */
        spin_lock(&info->lock_new_credits_offered);
        info->new_credits_offered += new_credits;
        spin_unlock(&info->lock_new_credits_offered);
        atomic_sub(new_credits, &info->receive_credits);

err_alloc:
        if (atomic_dec_and_test(&info->send_pending))
                wake_up(&info->wait_send_pending);

err_wait_send_queue:
        /* roll back send credits and pending */
        atomic_inc(&info->send_credits);

err_wait_credit:
        return rc;
}

/*
 * Send a page
 * page: the page to send
 * offset: offset in the page to send
 * size: length in the page to send
 * remaining_data_length: remaining data to send in this payload
 */
static int smbd_post_send_page(struct smbd_connection *info, struct page *page,
                unsigned long offset, size_t size, int remaining_data_length)
{
        struct scatterlist sgl;

        sg_init_table(&sgl, 1);
        sg_set_page(&sgl, page, size, offset);

        return smbd_post_send_sgl(info, &sgl, size, remaining_data_length);
}

/*
 * Send an empty message
 * Empty message is used to extend credits to peer to for keep live
 * while there is no upper layer payload to send at the time
 */
static int smbd_post_send_empty(struct smbd_connection *info)
{
        info->count_send_empty++;
        return smbd_post_send_sgl(info, NULL, 0, 0);
}

/*
 * Send a data buffer
 * iov: the iov array describing the data buffers
 * n_vec: number of iov array
 * remaining_data_length: remaining data to send following this packet

 * in segmented SMBD packet
 */
static int smbd_post_send_data(
        struct smbd_connection *info, struct kvec *iov, int n_vec,
        int remaining_data_length)
{
        int i;
        u32 data_length = 0;
        struct scatterlist sgl[SMBDIRECT_MAX_SGE];

        if (n_vec > SMBDIRECT_MAX_SGE) {
                cifs_dbg(VFS, "Can't fit data to SGL, n_vec=%d\n", n_vec);
                return -EINVAL;
        }

        sg_init_table(sgl, n_vec);
        for (i = 0; i < n_vec; i++) {
                data_length += iov[i].iov_len;
                sg_set_buf(&sgl[i], iov[i].iov_base, iov[i].iov_len);
        }

        return smbd_post_send_sgl(info, sgl, data_length, remaining_data_length);
}

/*
 * Post a receive request to the transport
 * The remote peer can only send data when a receive request is posted
 * The interaction is controlled by send/receive credit system
 */
static int smbd_post_recv(
                struct smbd_connection *info, struct smbd_response *response)
{
        struct ib_recv_wr recv_wr;
        int rc = -EIO;

        response->sge.addr = ib_dma_map_single(
                                info->id->device, response->packet,
                                info->max_receive_size, DMA_FROM_DEVICE);
        if (ib_dma_mapping_error(info->id->device, response->sge.addr))
                return rc;

        response->sge.length = info->max_receive_size;
        response->sge.lkey = info->pd->local_dma_lkey;

        response->cqe.done = recv_done;

        recv_wr.wr_cqe = &response->cqe;
        recv_wr.next = NULL;
        recv_wr.sg_list = &response->sge;
        recv_wr.num_sge = 1;

        rc = ib_post_recv(info->id->qp, &recv_wr, NULL);
        if (rc) {
                ib_dma_unmap_single(info->id->device, response->sge.addr,
                                    response->sge.length, DMA_FROM_DEVICE);
                smbd_disconnect_rdma_connection(info);
                log_rdma_recv(ERR, "ib_post_recv failed rc=%d\n", rc);
        }

        return rc;
}

/* Perform SMBD negotiate according to [MS-SMBD] 3.1.5.2 */
static int smbd_negotiate(struct smbd_connection *info)
{
        int rc;
        struct smbd_response *response = get_receive_buffer(info);

        response->type = SMBD_NEGOTIATE_RESP;
        rc = smbd_post_recv(info, response);
        log_rdma_event(INFO, "smbd_post_recv rc=%d iov.addr=%llx iov.length=%x iov.lkey=%x\n",
                       rc, response->sge.addr,
                       response->sge.length, response->sge.lkey);
        if (rc)
                return rc;

        init_completion(&info->negotiate_completion);
        info->negotiate_done = false;
        rc = smbd_post_send_negotiate_req(info);
        if (rc)
                return rc;

        rc = wait_for_completion_interruptible_timeout(
                &info->negotiate_completion, SMBD_NEGOTIATE_TIMEOUT * HZ);
        log_rdma_event(INFO, "wait_for_completion_timeout rc=%d\n", rc);

        if (info->negotiate_done)
                return 0;

        if (rc == 0)
                rc = -ETIMEDOUT;
        else if (rc == -ERESTARTSYS)
                rc = -EINTR;
        else
                rc = -ENOTCONN;

        return rc;
}

static void put_empty_packet(
                struct smbd_connection *info, struct smbd_response *response)
{
        spin_lock(&info->empty_packet_queue_lock);
        list_add_tail(&response->list, &info->empty_packet_queue);
        info->count_empty_packet_queue++;
        spin_unlock(&info->empty_packet_queue_lock);

        queue_work(info->workqueue, &info->post_send_credits_work);
}

/*
 * Implement Connection.FragmentReassemblyBuffer defined in [MS-SMBD] 3.1.1.1
 * This is a queue for reassembling upper layer payload and present to upper
 * layer. All the inncoming payload go to the reassembly queue, regardless of
 * if reassembly is required. The uuper layer code reads from the queue for all
 * incoming payloads.
 * Put a received packet to the reassembly queue
 * response: the packet received
 * data_length: the size of payload in this packet
 */
static void enqueue_reassembly(
        struct smbd_connection *info,
        struct smbd_response *response,
        int data_length)
{
        spin_lock(&info->reassembly_queue_lock);
        list_add_tail(&response->list, &info->reassembly_queue);
        info->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();
        info->reassembly_data_length += data_length;
        spin_unlock(&info->reassembly_queue_lock);
        info->count_reassembly_queue++;
        info->count_enqueue_reassembly_queue++;
}

/*
 * Get the first entry at the front of reassembly queue
 * Caller is responsible for locking
 * return value: the first entry if any, NULL if queue is empty
 */
static struct smbd_response *_get_first_reassembly(struct smbd_connection *info)
{
        struct smbd_response *ret = NULL;

        if (!list_empty(&info->reassembly_queue)) {
                ret = list_first_entry(
                        &info->reassembly_queue,
                        struct smbd_response, list);
        }
        return ret;
}

static struct smbd_response *get_empty_queue_buffer(
                struct smbd_connection *info)
{
        struct smbd_response *ret = NULL;
        unsigned long flags;

        spin_lock_irqsave(&info->empty_packet_queue_lock, flags);
        if (!list_empty(&info->empty_packet_queue)) {
                ret = list_first_entry(
                        &info->empty_packet_queue,
                        struct smbd_response, list);
                list_del(&ret->list);
                info->count_empty_packet_queue--;
        }
        spin_unlock_irqrestore(&info->empty_packet_queue_lock, flags);

        return ret;
}

/*
 * Get a receive buffer
 * For each remote send, we need to post a receive. The receive buffers are
 * pre-allocated in advance.
 * return value: the receive buffer, NULL if none is available
 */
static struct smbd_response *get_receive_buffer(struct smbd_connection *info)
{
        struct smbd_response *ret = NULL;
        unsigned long flags;

        spin_lock_irqsave(&info->receive_queue_lock, flags);
        if (!list_empty(&info->receive_queue)) {
                ret = list_first_entry(
                        &info->receive_queue,
                        struct smbd_response, list);
                list_del(&ret->list);
                info->count_receive_queue--;
                info->count_get_receive_buffer++;
        }
        spin_unlock_irqrestore(&info->receive_queue_lock, flags);

        return ret;
}

/*
 * Return a receive buffer
 * Upon returning of a receive buffer, we can post new receive and extend
 * more receive credits to remote peer. This is done immediately after a
 * receive buffer is returned.
 */
static void put_receive_buffer(
        struct smbd_connection *info, struct smbd_response *response)
{
        unsigned long flags;

        ib_dma_unmap_single(info->id->device, response->sge.addr,
                response->sge.length, DMA_FROM_DEVICE);

        spin_lock_irqsave(&info->receive_queue_lock, flags);
        list_add_tail(&response->list, &info->receive_queue);
        info->count_receive_queue++;
        info->count_put_receive_buffer++;
        spin_unlock_irqrestore(&info->receive_queue_lock, flags);

        queue_work(info->workqueue, &info->post_send_credits_work);
}

/* Preallocate all receive buffer on transport establishment */
static int allocate_receive_buffers(struct smbd_connection *info, int num_buf)
{
        int i;
        struct smbd_response *response;

        INIT_LIST_HEAD(&info->reassembly_queue);
        spin_lock_init(&info->reassembly_queue_lock);
        info->reassembly_data_length = 0;
        info->reassembly_queue_length = 0;

        INIT_LIST_HEAD(&info->receive_queue);
        spin_lock_init(&info->receive_queue_lock);
        info->count_receive_queue = 0;

        INIT_LIST_HEAD(&info->empty_packet_queue);
        spin_lock_init(&info->empty_packet_queue_lock);
        info->count_empty_packet_queue = 0;

        init_waitqueue_head(&info->wait_receive_queues);

        for (i = 0; i < num_buf; i++) {
                response = mempool_alloc(info->response_mempool, GFP_KERNEL);
                if (!response)
                        goto allocate_failed;

                response->info = info;
                list_add_tail(&response->list, &info->receive_queue);
                info->count_receive_queue++;
        }

        return 0;

allocate_failed:
        while (!list_empty(&info->receive_queue)) {
                response = list_first_entry(
                                &info->receive_queue,
                                struct smbd_response, list);
                list_del(&response->list);
                info->count_receive_queue--;

                mempool_free(response, info->response_mempool);
        }
        return -ENOMEM;
}

static void destroy_receive_buffers(struct smbd_connection *info)
{
        struct smbd_response *response;

        while ((response = get_receive_buffer(info)))
                mempool_free(response, info->response_mempool);

        while ((response = get_empty_queue_buffer(info)))
                mempool_free(response, info->response_mempool);
}

/* Implement idle connection timer [MS-SMBD] 3.1.6.2 */
static void idle_connection_timer(struct work_struct *work)
{
        struct smbd_connection *info = container_of(
                                        work, struct smbd_connection,
                                        idle_timer_work.work);

        if (info->keep_alive_requested != KEEP_ALIVE_NONE) {
                log_keep_alive(ERR,
                        "error status info->keep_alive_requested=%d\n",
                        info->keep_alive_requested);
                smbd_disconnect_rdma_connection(info);
                return;
        }

        log_keep_alive(INFO, "about to send an empty idle message\n");
        smbd_post_send_empty(info);

        /* Setup the next idle timeout work */
        queue_delayed_work(info->workqueue, &info->idle_timer_work,
                        info->keep_alive_interval*HZ);
}

/*
 * Destroy the transport and related RDMA and memory resources
 * Need to go through all the pending counters and make sure on one is using
 * the transport while it is destroyed
 */
void smbd_destroy(struct TCP_Server_Info *server)
{
        struct smbd_connection *info = server->smbd_conn;
        struct smbd_response *response;
        unsigned long flags;

        if (!info) {
                log_rdma_event(INFO, "rdma session already destroyed\n");
                return;
        }

        log_rdma_event(INFO, "destroying rdma session\n");
        if (info->transport_status != SMBD_DISCONNECTED) {
                rdma_disconnect(server->smbd_conn->id);
                log_rdma_event(INFO, "wait for transport being disconnected\n");
                wait_event_interruptible(
                        info->disconn_wait,
                        info->transport_status == SMBD_DISCONNECTED);
        }

        log_rdma_event(INFO, "destroying qp\n");
        ib_drain_qp(info->id->qp);
        rdma_destroy_qp(info->id);

        log_rdma_event(INFO, "cancelling idle timer\n");
        cancel_delayed_work_sync(&info->idle_timer_work);

        log_rdma_event(INFO, "wait for all send posted to IB to finish\n");
        wait_event(info->wait_send_pending,
                atomic_read(&info->send_pending) == 0);

        /* It's not posssible for upper layer to get to reassembly */
        log_rdma_event(INFO, "drain the reassembly queue\n");
        do {
                spin_lock_irqsave(&info->reassembly_queue_lock, flags);
                response = _get_first_reassembly(info);
                if (response) {
                        list_del(&response->list);
                        spin_unlock_irqrestore(
                                &info->reassembly_queue_lock, flags);
                        put_receive_buffer(info, response);
                } else
                        spin_unlock_irqrestore(
                                &info->reassembly_queue_lock, flags);
        } while (response);
        info->reassembly_data_length = 0;

        log_rdma_event(INFO, "free receive buffers\n");
        wait_event(info->wait_receive_queues,
                info->count_receive_queue + info->count_empty_packet_queue
                        == info->receive_credit_max);
        destroy_receive_buffers(info);

        /*
         * For performance reasons, memory registration and deregistration
         * are not locked by srv_mutex. It is possible some processes are
         * blocked on transport srv_mutex while holding memory registration.
         * Release the transport srv_mutex to allow them to hit the failure
         * path when sending data, and then release memory registartions.
         */
        log_rdma_event(INFO, "freeing mr list\n");
        wake_up_interruptible_all(&info->wait_mr);
        while (atomic_read(&info->mr_used_count)) {
                mutex_unlock(&server->srv_mutex);
                msleep(1000);
                mutex_lock(&server->srv_mutex);
        }
        destroy_mr_list(info);

        ib_free_cq(info->send_cq);
        ib_free_cq(info->recv_cq);
        ib_dealloc_pd(info->pd);
        rdma_destroy_id(info->id);

        /* free mempools */
        mempool_destroy(info->request_mempool);
        kmem_cache_destroy(info->request_cache);

        mempool_destroy(info->response_mempool);
        kmem_cache_destroy(info->response_cache);

        info->transport_status = SMBD_DESTROYED;

        destroy_workqueue(info->workqueue);
        log_rdma_event(INFO,  "rdma session destroyed\n");
        kfree(info);
}

/*
 * Reconnect this SMBD connection, called from upper layer
 * return value: 0 on success, or actual error code
 */
int smbd_reconnect(struct TCP_Server_Info *server)
{
        log_rdma_event(INFO, "reconnecting rdma session\n");

        if (!server->smbd_conn) {
                log_rdma_event(INFO, "rdma session already destroyed\n");
                goto create_conn;
        }

        /*
         * This is possible if transport is disconnected and we haven't received
         * notification from RDMA, but upper layer has detected timeout
         */
        if (server->smbd_conn->transport_status == SMBD_CONNECTED) {
                log_rdma_event(INFO, "disconnecting transport\n");
                smbd_destroy(server);
        }

create_conn:
        log_rdma_event(INFO, "creating rdma session\n");
        server->smbd_conn = smbd_get_connection(
                server, (struct sockaddr *) &server->dstaddr);

        if (server->smbd_conn)
                cifs_dbg(VFS, "RDMA transport re-established\n");

        return server->smbd_conn ? 0 : -ENOENT;
}

static void destroy_caches_and_workqueue(struct smbd_connection *info)
{
        destroy_receive_buffers(info);
        destroy_workqueue(info->workqueue);
        mempool_destroy(info->response_mempool);
        kmem_cache_destroy(info->response_cache);
        mempool_destroy(info->request_mempool);
        kmem_cache_destroy(info->request_cache);
}

#define MAX_NAME_LEN    80
static int allocate_caches_and_workqueue(struct smbd_connection *info)
{
        char name[MAX_NAME_LEN];
        int rc;

        scnprintf(name, MAX_NAME_LEN, "smbd_request_%p", info);
        info->request_cache =
                kmem_cache_create(
                        name,
                        sizeof(struct smbd_request) +
                                sizeof(struct smbd_data_transfer),
                        0, SLAB_HWCACHE_ALIGN, NULL);
        if (!info->request_cache)
                return -ENOMEM;

        info->request_mempool =
                mempool_create(info->send_credit_target, mempool_alloc_slab,
                        mempool_free_slab, info->request_cache);
        if (!info->request_mempool)
                goto out1;

        scnprintf(name, MAX_NAME_LEN, "smbd_response_%p", info);
        info->response_cache =
                kmem_cache_create(
                        name,
                        sizeof(struct smbd_response) +
                                info->max_receive_size,
                        0, SLAB_HWCACHE_ALIGN, NULL);
        if (!info->response_cache)
                goto out2;

        info->response_mempool =
                mempool_create(info->receive_credit_max, mempool_alloc_slab,
                       mempool_free_slab, info->response_cache);
        if (!info->response_mempool)
                goto out3;

        scnprintf(name, MAX_NAME_LEN, "smbd_%p", info);
        info->workqueue = create_workqueue(name);
        if (!info->workqueue)
                goto out4;

        rc = allocate_receive_buffers(info, info->receive_credit_max);
        if (rc) {
                log_rdma_event(ERR, "failed to allocate receive buffers\n");
                goto out5;
        }

        return 0;

out5:
        destroy_workqueue(info->workqueue);
out4:
        mempool_destroy(info->response_mempool);
out3:
        kmem_cache_destroy(info->response_cache);
out2:
        mempool_destroy(info->request_mempool);
out1:
        kmem_cache_destroy(info->request_cache);
        return -ENOMEM;
}

/* Create a SMBD connection, called by upper layer */
static struct smbd_connection *_smbd_get_connection(
        struct TCP_Server_Info *server, struct sockaddr *dstaddr, int port)
{
        int rc;
        struct smbd_connection *info;
        struct rdma_conn_param conn_param;
        struct ib_qp_init_attr qp_attr;
        struct sockaddr_in *addr_in = (struct sockaddr_in *) dstaddr;
        struct ib_port_immutable port_immutable;
        u32 ird_ord_hdr[2];

        info = kzalloc(sizeof(struct smbd_connection), GFP_KERNEL);
        if (!info)
                return NULL;

        info->transport_status = SMBD_CONNECTING;
        rc = smbd_ia_open(info, dstaddr, port);
        if (rc) {
                log_rdma_event(INFO, "smbd_ia_open rc=%d\n", rc);
                goto create_id_failed;
        }

        if (smbd_send_credit_target > info->id->device->attrs.max_cqe ||
            smbd_send_credit_target > info->id->device->attrs.max_qp_wr) {
                log_rdma_event(ERR, "consider lowering send_credit_target = %d. Possible CQE overrun, device reporting max_cpe %d max_qp_wr %d\n",
                               smbd_send_credit_target,
                               info->id->device->attrs.max_cqe,
                               info->id->device->attrs.max_qp_wr);
                goto config_failed;
        }

        if (smbd_receive_credit_max > info->id->device->attrs.max_cqe ||
            smbd_receive_credit_max > info->id->device->attrs.max_qp_wr) {
                log_rdma_event(ERR, "consider lowering receive_credit_max = %d. Possible CQE overrun, device reporting max_cpe %d max_qp_wr %d\n",
                               smbd_receive_credit_max,
                               info->id->device->attrs.max_cqe,
                               info->id->device->attrs.max_qp_wr);
                goto config_failed;
        }

        info->receive_credit_max = smbd_receive_credit_max;
        info->send_credit_target = smbd_send_credit_target;
        info->max_send_size = smbd_max_send_size;
        info->max_fragmented_recv_size = smbd_max_fragmented_recv_size;
        info->max_receive_size = smbd_max_receive_size;
        info->keep_alive_interval = smbd_keep_alive_interval;

        if (info->id->device->attrs.max_send_sge < SMBDIRECT_MAX_SGE) {
                log_rdma_event(ERR,
                        "warning: device max_send_sge = %d too small\n",
                        info->id->device->attrs.max_send_sge);
                log_rdma_event(ERR, "Queue Pair creation may fail\n");
        }
        if (info->id->device->attrs.max_recv_sge < SMBDIRECT_MAX_SGE) {
                log_rdma_event(ERR,
                        "warning: device max_recv_sge = %d too small\n",
                        info->id->device->attrs.max_recv_sge);
                log_rdma_event(ERR, "Queue Pair creation may fail\n");
        }

        info->send_cq = NULL;
        info->recv_cq = NULL;
        info->send_cq =
                ib_alloc_cq_any(info->id->device, info,
                                info->send_credit_target, IB_POLL_SOFTIRQ);
        if (IS_ERR(info->send_cq)) {
                info->send_cq = NULL;
                goto alloc_cq_failed;
        }

        info->recv_cq =
                ib_alloc_cq_any(info->id->device, info,
                                info->receive_credit_max, IB_POLL_SOFTIRQ);
        if (IS_ERR(info->recv_cq)) {
                info->recv_cq = NULL;
                goto alloc_cq_failed;
        }

        memset(&qp_attr, 0, sizeof(qp_attr));
        qp_attr.event_handler = smbd_qp_async_error_upcall;
        qp_attr.qp_context = info;
        qp_attr.cap.max_send_wr = info->send_credit_target;
        qp_attr.cap.max_recv_wr = info->receive_credit_max;
        qp_attr.cap.max_send_sge = SMBDIRECT_MAX_SGE;
        qp_attr.cap.max_recv_sge = SMBDIRECT_MAX_SGE;
        qp_attr.cap.max_inline_data = 0;
        qp_attr.sq_sig_type = IB_SIGNAL_REQ_WR;
        qp_attr.qp_type = IB_QPT_RC;
        qp_attr.send_cq = info->send_cq;
        qp_attr.recv_cq = info->recv_cq;
        qp_attr.port_num = ~0;

        rc = rdma_create_qp(info->id, info->pd, &qp_attr);
        if (rc) {
                log_rdma_event(ERR, "rdma_create_qp failed %i\n", rc);
                goto create_qp_failed;
        }

        memset(&conn_param, 0, sizeof(conn_param));
        conn_param.initiator_depth = 0;

        conn_param.responder_resources =
                info->id->device->attrs.max_qp_rd_atom
                        < SMBD_CM_RESPONDER_RESOURCES ?
                info->id->device->attrs.max_qp_rd_atom :
                SMBD_CM_RESPONDER_RESOURCES;
        info->responder_resources = conn_param.responder_resources;
        log_rdma_mr(INFO, "responder_resources=%d\n",
                info->responder_resources);

        /* Need to send IRD/ORD in private data for iWARP */
        info->id->device->ops.get_port_immutable(
                info->id->device, info->id->port_num, &port_immutable);
        if (port_immutable.core_cap_flags & RDMA_CORE_PORT_IWARP) {
                ird_ord_hdr[0] = info->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 = SMBD_CM_RETRY;
        conn_param.rnr_retry_count = SMBD_CM_RNR_RETRY;
        conn_param.flow_control = 0;

        log_rdma_event(INFO, "connecting to IP %pI4 port %d\n",
                &addr_in->sin_addr, port);

        init_waitqueue_head(&info->conn_wait);
        init_waitqueue_head(&info->disconn_wait);
        init_waitqueue_head(&info->wait_reassembly_queue);
        rc = rdma_connect(info->id, &conn_param);
        if (rc) {
                log_rdma_event(ERR, "rdma_connect() failed with %i\n", rc);
                goto rdma_connect_failed;
        }

        wait_event_interruptible(
                info->conn_wait, info->transport_status != SMBD_CONNECTING);

        if (info->transport_status != SMBD_CONNECTED) {
                log_rdma_event(ERR, "rdma_connect failed port=%d\n", port);
                goto rdma_connect_failed;
        }

        log_rdma_event(INFO, "rdma_connect connected\n");

        rc = allocate_caches_and_workqueue(info);
        if (rc) {
                log_rdma_event(ERR, "cache allocation failed\n");
                goto allocate_cache_failed;
        }

        init_waitqueue_head(&info->wait_send_queue);
        INIT_DELAYED_WORK(&info->idle_timer_work, idle_connection_timer);
        queue_delayed_work(info->workqueue, &info->idle_timer_work,
                info->keep_alive_interval*HZ);

        init_waitqueue_head(&info->wait_send_pending);
        atomic_set(&info->send_pending, 0);

        init_waitqueue_head(&info->wait_post_send);

        INIT_WORK(&info->disconnect_work, smbd_disconnect_rdma_work);
        INIT_WORK(&info->post_send_credits_work, smbd_post_send_credits);
        info->new_credits_offered = 0;
        spin_lock_init(&info->lock_new_credits_offered);

        rc = smbd_negotiate(info);
        if (rc) {
                log_rdma_event(ERR, "smbd_negotiate rc=%d\n", rc);
                goto negotiation_failed;
        }

        rc = allocate_mr_list(info);
        if (rc) {
                log_rdma_mr(ERR, "memory registration allocation failed\n");
                goto allocate_mr_failed;
        }

        return info;

allocate_mr_failed:
        /* At this point, need to a full transport shutdown */
        smbd_destroy(server);
        return NULL;

negotiation_failed:
        cancel_delayed_work_sync(&info->idle_timer_work);
        destroy_caches_and_workqueue(info);
        info->transport_status = SMBD_NEGOTIATE_FAILED;
        init_waitqueue_head(&info->conn_wait);
        rdma_disconnect(info->id);
        wait_event(info->conn_wait,
                info->transport_status == SMBD_DISCONNECTED);

allocate_cache_failed:
rdma_connect_failed:
        rdma_destroy_qp(info->id);

create_qp_failed:
alloc_cq_failed:
        if (info->send_cq)
                ib_free_cq(info->send_cq);
        if (info->recv_cq)
                ib_free_cq(info->recv_cq);

config_failed:
        ib_dealloc_pd(info->pd);
        rdma_destroy_id(info->id);

create_id_failed:
        kfree(info);
        return NULL;
}

struct smbd_connection *smbd_get_connection(
        struct TCP_Server_Info *server, struct sockaddr *dstaddr)
{
        struct smbd_connection *ret;
        int port = SMBD_PORT;

try_again:
        ret = _smbd_get_connection(server, dstaddr, port);

        /* Try SMB_PORT if SMBD_PORT doesn't work */
        if (!ret && port == SMBD_PORT) {
                port = SMB_PORT;
                goto try_again;
        }
        return ret;
}

/*
 * Receive data from receive reassembly queue
 * All the incoming data packets are placed in reassembly queue
 * buf: the buffer to read data into
 * size: the length of data to read
 * return value: actual data read
 * Note: this implementation copies the data from reassebmly queue to receive
 * buffers used by upper layer. This is not the optimal code path. A better way
 * to do it is to not have upper layer allocate its receive buffers but rather
 * borrow the buffer from reassembly queue, and return it after data is
 * consumed. But this will require more changes to upper layer code, and also
 * need to consider packet boundaries while they still being reassembled.
 */
static int smbd_recv_buf(struct smbd_connection *info, char *buf,
                unsigned int size)
{
        struct smbd_response *response;
        struct smbd_data_transfer *data_transfer;
        int to_copy, to_read, data_read, offset;
        u32 data_length, remaining_data_length, data_offset;
        int rc;

again:
        /*
         * 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
         */
        log_read(INFO, "size=%d info->reassembly_data_length=%d\n", size,
                info->reassembly_data_length);
        if (info->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 = info->reassembly_queue_length;
                data_read = 0;
                to_read = size;
                offset = info->first_entry_offset;
                while (data_read < size) {
                        response = _get_first_reassembly(info);
                        data_transfer = smbd_response_payload(response);
                        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 *)buf) = cpu_to_be32(rfc1002_len);
                                data_read = 4;
                                response->first_segment = false;
                                log_read(INFO, "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(&response->list);
                                else {
                                        spin_lock_irq(
                                                &info->reassembly_queue_lock);
                                        list_del(&response->list);
                                        spin_unlock_irq(
                                                &info->reassembly_queue_lock);
                                }
                                queue_removed++;
                                info->count_reassembly_queue--;
                                info->count_dequeue_reassembly_queue++;
                                put_receive_buffer(info, response);
                                offset = 0;
                                log_read(INFO, "put_receive_buffer offset=0\n");
                        } else
                                offset += to_copy;

                        to_read -= to_copy;
                        data_read += to_copy;

                        log_read(INFO, "_get_first_reassembly memcpy %d bytes data_transfer_length-offset=%d after that to_read=%d data_read=%d offset=%d\n",
                                 to_copy, data_length - offset,
                                 to_read, data_read, offset);
                }

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

                info->first_entry_offset = offset;
                log_read(INFO, "returning to thread data_read=%d reassembly_data_length=%d first_entry_offset=%d\n",
                         data_read, info->reassembly_data_length,
                         info->first_entry_offset);
read_rfc1002_done:
                return data_read;
        }

        log_read(INFO, "wait_event on more data\n");
        rc = wait_event_interruptible(
                info->wait_reassembly_queue,
                info->reassembly_data_length >= size ||
                        info->transport_status != SMBD_CONNECTED);
        /* Don't return any data if interrupted */
        if (rc)
                return rc;

        if (info->transport_status != SMBD_CONNECTED) {
                log_read(ERR, "disconnected\n");
                return -ECONNABORTED;
        }

        goto again;
}

/*
 * Receive a page from receive reassembly queue
 * page: the page to read data into
 * to_read: the length of data to read
 * return value: actual data read
 */
static int smbd_recv_page(struct smbd_connection *info,
                struct page *page, unsigned int page_offset,
                unsigned int to_read)
{
        int ret;
        char *to_address;
        void *page_address;

        /* make sure we have the page ready for read */
        ret = wait_event_interruptible(
                info->wait_reassembly_queue,
                info->reassembly_data_length >= to_read ||
                        info->transport_status != SMBD_CONNECTED);
        if (ret)
                return ret;

        /* now we can read from reassembly queue and not sleep */
        page_address = kmap_atomic(page);
        to_address = (char *) page_address + page_offset;

        log_read(INFO, "reading from page=%p address=%p to_read=%d\n",
                page, to_address, to_read);

        ret = smbd_recv_buf(info, to_address, to_read);
        kunmap_atomic(page_address);

        return ret;
}

/*
 * Receive data from transport
 * msg: a msghdr point to the buffer, can be ITER_KVEC or ITER_BVEC
 * return: total bytes read, or 0. SMB Direct will not do partial read.
 */
int smbd_recv(struct smbd_connection *info, struct msghdr *msg)
{
        char *buf;
        struct page *page;
        unsigned int to_read, page_offset;
        int rc;

        if (iov_iter_rw(&msg->msg_iter) == WRITE) {
                /* It's a bug in upper layer to get there */
                cifs_dbg(VFS, "Invalid msg iter dir %u\n",
                         iov_iter_rw(&msg->msg_iter));
                rc = -EINVAL;
                goto out;
        }

        switch (iov_iter_type(&msg->msg_iter)) {
        case ITER_KVEC:
                buf = msg->msg_iter.kvec->iov_base;
                to_read = msg->msg_iter.kvec->iov_len;
                rc = smbd_recv_buf(info, buf, to_read);
                break;

        case ITER_BVEC:
                page = msg->msg_iter.bvec->bv_page;
                page_offset = msg->msg_iter.bvec->bv_offset;
                to_read = msg->msg_iter.bvec->bv_len;
                rc = smbd_recv_page(info, page, page_offset, to_read);
                break;

        default:
                /* It's a bug in upper layer to get there */
                cifs_dbg(VFS, "Invalid msg type %d\n",
                         iov_iter_type(&msg->msg_iter));
                rc = -EINVAL;
        }

out:
        /* SMBDirect will read it all or nothing */
        if (rc > 0)
                msg->msg_iter.count = 0;
        return rc;
}

/*
 * Send data to transport
 * Each rqst is transported as a SMBDirect payload
 * rqst: the data to write
 * return value: 0 if successfully write, otherwise error code
 */
int smbd_send(struct TCP_Server_Info *server,
        int num_rqst, struct smb_rqst *rqst_array)
{
        struct smbd_connection *info = server->smbd_conn;
        struct kvec vec;
        int nvecs;
        int size;
        unsigned int buflen, remaining_data_length;
        int start, i, j;
        int max_iov_size =
                info->max_send_size - sizeof(struct smbd_data_transfer);
        struct kvec *iov;
        int rc;
        struct smb_rqst *rqst;
        int rqst_idx;

        if (info->transport_status != SMBD_CONNECTED) {
                rc = -EAGAIN;
                goto done;
        }

        /*
         * Add in the page array if there is one. The caller needs to set
         * rq_tailsz to PAGE_SIZE when the buffer has multiple pages and
         * ends at page boundary
         */
        remaining_data_length = 0;

        for (i = 0; i < num_rqst; i++)
                remaining_data_length += smb_rqst_len(server, &rqst_array[i]);

        if (remaining_data_length > info->max_fragmented_send_size) {
                log_write(ERR, "payload size %d > max size %d\n",
                        remaining_data_length, info->max_fragmented_send_size);
                rc = -EINVAL;
                goto done;
        }

        log_write(INFO, "num_rqst=%d total length=%u\n",
                        num_rqst, remaining_data_length);

        rqst_idx = 0;
next_rqst:
        rqst = &rqst_array[rqst_idx];
        iov = rqst->rq_iov;

        cifs_dbg(FYI, "Sending smb (RDMA): idx=%d smb_len=%lu\n",
                rqst_idx, smb_rqst_len(server, rqst));
        for (i = 0; i < rqst->rq_nvec; i++)
                dump_smb(iov[i].iov_base, iov[i].iov_len);


        log_write(INFO, "rqst_idx=%d nvec=%d rqst->rq_npages=%d rq_pagesz=%d rq_tailsz=%d buflen=%lu\n",
                  rqst_idx, rqst->rq_nvec, rqst->rq_npages, rqst->rq_pagesz,
                  rqst->rq_tailsz, smb_rqst_len(server, rqst));

        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);
                                log_write(INFO, "sending iov[] from start=%d i=%d nvecs=%d remaining_data_length=%d\n",
                                          start, i, i - start,
                                          remaining_data_length);
                                rc = smbd_post_send_data(
                                        info, &iov[start], i-start,
                                        remaining_data_length);
                                if (rc)
                                        goto done;
                        } else {
                                /* iov[start] is too big, break it */
                                nvecs = (buflen+max_iov_size-1)/max_iov_size;
                                log_write(INFO, "iov[%d] iov_base=%p buflen=%d break to %d vectors\n",
                                          start, iov[start].iov_base,
                                          buflen, nvecs);
                                for (j = 0; j < nvecs; j++) {
                                        vec.iov_base =
                                                (char *)iov[start].iov_base +
                                                j*max_iov_size;
                                        vec.iov_len = max_iov_size;
                                        if (j == nvecs-1)
                                                vec.iov_len =
                                                        buflen -
                                                        max_iov_size*(nvecs-1);
                                        remaining_data_length -= vec.iov_len;
                                        log_write(INFO,
                                                "sending vec j=%d iov_base=%p iov_len=%zu remaining_data_length=%d\n",
                                                  j, vec.iov_base, vec.iov_len,
                                                  remaining_data_length);
                                        rc = smbd_post_send_data(
                                                info, &vec, 1,
                                                remaining_data_length);
                                        if (rc)
                                                goto done;
                                }
                                i++;
                                if (i == rqst->rq_nvec)
                                        break;
                        }
                        start = i;
                        buflen = 0;
                } else {
                        i++;
                        if (i == rqst->rq_nvec) {
                                /* send out all remaining vecs */
                                remaining_data_length -= buflen;
                                log_write(INFO, "sending iov[] from start=%d i=%d nvecs=%d remaining_data_length=%d\n",
                                          start, i, i - start,
                                          remaining_data_length);
                                rc = smbd_post_send_data(info, &iov[start],
                                        i-start, remaining_data_length);
                                if (rc)
                                        goto done;
                                break;
                        }
                }
                log_write(INFO, "looping i=%d buflen=%d\n", i, buflen);
        }

        /* now sending pages if there are any */
        for (i = 0; i < rqst->rq_npages; i++) {
                unsigned int offset;

                rqst_page_get_length(rqst, i, &buflen, &offset);
                nvecs = (buflen + max_iov_size - 1) / max_iov_size;
                log_write(INFO, "sending pages buflen=%d nvecs=%d\n",
                        buflen, nvecs);
                for (j = 0; j < nvecs; j++) {
                        size = max_iov_size;
                        if (j == nvecs-1)
                                size = buflen - j*max_iov_size;
                        remaining_data_length -= size;
                        log_write(INFO, "sending pages i=%d offset=%d size=%d remaining_data_length=%d\n",
                                  i, j * max_iov_size + offset, size,
                                  remaining_data_length);
                        rc = smbd_post_send_page(
                                info, rqst->rq_pages[i],
                                j*max_iov_size + offset,
                                size, remaining_data_length);
                        if (rc)
                                goto done;
                }
        }

        rqst_idx++;
        if (rqst_idx < num_rqst)
                goto next_rqst;

done:
        /*
         * 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(info->wait_send_pending,
                atomic_read(&info->send_pending) == 0);

        return rc;
}

static void register_mr_done(struct ib_cq *cq, struct ib_wc *wc)
{
        struct smbd_mr *mr;
        struct ib_cqe *cqe;

        if (wc->status) {
                log_rdma_mr(ERR, "status=%d\n", wc->status);
                cqe = wc->wr_cqe;
                mr = container_of(cqe, struct smbd_mr, cqe);
                smbd_disconnect_rdma_connection(mr->conn);
        }
}

/*
 * The work queue function that recovers MRs
 * We need to call ib_dereg_mr() and ib_alloc_mr() before this MR can be used
 * again. Both calls are slow, so finish them in a workqueue. This will not
 * block I/O path.
 * There is one workqueue that recovers MRs, there is no need to lock as the
 * I/O requests calling smbd_register_mr will never update the links in the
 * mr_list.
 */
static void smbd_mr_recovery_work(struct work_struct *work)
{
        struct smbd_connection *info =
                container_of(work, struct smbd_connection, mr_recovery_work);
        struct smbd_mr *smbdirect_mr;
        int rc;

        list_for_each_entry(smbdirect_mr, &info->mr_list, list) {
                if (smbdirect_mr->state == MR_ERROR) {

                        /* recover this MR entry */
                        rc = ib_dereg_mr(smbdirect_mr->mr);
                        if (rc) {
                                log_rdma_mr(ERR,
                                        "ib_dereg_mr failed rc=%x\n",
                                        rc);
                                smbd_disconnect_rdma_connection(info);
                                continue;
                        }

                        smbdirect_mr->mr = ib_alloc_mr(
                                info->pd, info->mr_type,
                                info->max_frmr_depth);
                        if (IS_ERR(smbdirect_mr->mr)) {
                                log_rdma_mr(ERR, "ib_alloc_mr failed mr_type=%x max_frmr_depth=%x\n",
                                            info->mr_type,
                                            info->max_frmr_depth);
                                smbd_disconnect_rdma_connection(info);
                                continue;
                        }
                } else
                        /* This MR is being used, don't recover it */
                        continue;

                smbdirect_mr->state = MR_READY;

                /* smbdirect_mr->state is updated by this function
                 * and is read and updated by I/O issuing CPUs trying
                 * to get a MR, the call to atomic_inc_return
                 * implicates a memory barrier and guarantees this
                 * value is updated before waking up any calls to
                 * get_mr() from the I/O issuing CPUs
                 */
                if (atomic_inc_return(&info->mr_ready_count) == 1)
                        wake_up_interruptible(&info->wait_mr);
        }
}

static void destroy_mr_list(struct smbd_connection *info)
{
        struct smbd_mr *mr, *tmp;

        cancel_work_sync(&info->mr_recovery_work);
        list_for_each_entry_safe(mr, tmp, &info->mr_list, list) {
                if (mr->state == MR_INVALIDATED)
                        ib_dma_unmap_sg(info->id->device, mr->sgl,
                                mr->sgl_count, mr->dir);
                ib_dereg_mr(mr->mr);
                kfree(mr->sgl);
                kfree(mr);
        }
}

/*
 * Allocate MRs used for RDMA read/write
 * The number of MRs will not exceed hardware capability in responder_resources
 * All MRs are kept in mr_list. The MR can be recovered after it's used
 * Recovery is done in smbd_mr_recovery_work. The content of list entry changes
 * as MRs are used and recovered for I/O, but the list links will not change
 */
static int allocate_mr_list(struct smbd_connection *info)
{
        int i;
        struct smbd_mr *smbdirect_mr, *tmp;

        INIT_LIST_HEAD(&info->mr_list);
        init_waitqueue_head(&info->wait_mr);
        spin_lock_init(&info->mr_list_lock);
        atomic_set(&info->mr_ready_count, 0);
        atomic_set(&info->mr_used_count, 0);
        init_waitqueue_head(&info->wait_for_mr_cleanup);
        /* Allocate more MRs (2x) than hardware responder_resources */
        for (i = 0; i < info->responder_resources * 2; i++) {
                smbdirect_mr = kzalloc(sizeof(*smbdirect_mr), GFP_KERNEL);
                if (!smbdirect_mr)
                        goto out;
                smbdirect_mr->mr = ib_alloc_mr(info->pd, info->mr_type,
                                        info->max_frmr_depth);
                if (IS_ERR(smbdirect_mr->mr)) {
                        log_rdma_mr(ERR, "ib_alloc_mr failed mr_type=%x max_frmr_depth=%x\n",
                                    info->mr_type, info->max_frmr_depth);
                        goto out;
                }
                smbdirect_mr->sgl = kcalloc(
                                        info->max_frmr_depth,
                                        sizeof(struct scatterlist),
                                        GFP_KERNEL);
                if (!smbdirect_mr->sgl) {
                        log_rdma_mr(ERR, "failed to allocate sgl\n");
                        ib_dereg_mr(smbdirect_mr->mr);
                        goto out;
                }
                smbdirect_mr->state = MR_READY;
                smbdirect_mr->conn = info;

                list_add_tail(&smbdirect_mr->list, &info->mr_list);
                atomic_inc(&info->mr_ready_count);
        }
        INIT_WORK(&info->mr_recovery_work, smbd_mr_recovery_work);
        return 0;

out:
        kfree(smbdirect_mr);

        list_for_each_entry_safe(smbdirect_mr, tmp, &info->mr_list, list) {
                ib_dereg_mr(smbdirect_mr->mr);
                kfree(smbdirect_mr->sgl);
                kfree(smbdirect_mr);
        }
        return -ENOMEM;
}

/*
 * Get a MR from mr_list. This function waits until there is at least one
 * MR available in the list. It may access the list while the
 * smbd_mr_recovery_work is recovering the MR list. This doesn't need a lock
 * as they never modify the same places. However, there may be several CPUs
 * issueing I/O trying to get MR at the same time, mr_list_lock is used to
 * protect this situation.
 */
static struct smbd_mr *get_mr(struct smbd_connection *info)
{
        struct smbd_mr *ret;
        int rc;
again:
        rc = wait_event_interruptible(info->wait_mr,
                atomic_read(&info->mr_ready_count) ||
                info->transport_status != SMBD_CONNECTED);
        if (rc) {
                log_rdma_mr(ERR, "wait_event_interruptible rc=%x\n", rc);
                return NULL;
        }

        if (info->transport_status != SMBD_CONNECTED) {
                log_rdma_mr(ERR, "info->transport_status=%x\n",
                        info->transport_status);
                return NULL;
        }

        spin_lock(&info->mr_list_lock);
        list_for_each_entry(ret, &info->mr_list, list) {
                if (ret->state == MR_READY) {
                        ret->state = MR_REGISTERED;
                        spin_unlock(&info->mr_list_lock);
                        atomic_dec(&info->mr_ready_count);
                        atomic_inc(&info->mr_used_count);
                        return ret;
                }
        }

        spin_unlock(&info->mr_list_lock);
        /*
         * It is possible that we could fail to get MR because other processes may
         * try to acquire a MR at the same time. If this is the case, retry it.
         */
        goto again;
}

/*
 * Register memory for RDMA read/write
 * pages[]: the list of pages to register memory with
 * num_pages: the number of pages to register
 * tailsz: if non-zero, the bytes to register in the last page
 * writing: true if this is a RDMA write (SMB read), false for RDMA read
 * need_invalidate: true if this MR needs to be locally invalidated after I/O
 * return value: the MR registered, NULL if failed.
 */
struct smbd_mr *smbd_register_mr(
        struct smbd_connection *info, struct page *pages[], int num_pages,
        int offset, int tailsz, bool writing, bool need_invalidate)
{
        struct smbd_mr *smbdirect_mr;
        int rc, i;
        enum dma_data_direction dir;
        struct ib_reg_wr *reg_wr;

        if (num_pages > info->max_frmr_depth) {
                log_rdma_mr(ERR, "num_pages=%d max_frmr_depth=%d\n",
                        num_pages, info->max_frmr_depth);
                return NULL;
        }

        smbdirect_mr = get_mr(info);
        if (!smbdirect_mr) {
                log_rdma_mr(ERR, "get_mr returning NULL\n");
                return NULL;
        }
        smbdirect_mr->need_invalidate = need_invalidate;
        smbdirect_mr->sgl_count = num_pages;
        sg_init_table(smbdirect_mr->sgl, num_pages);

        log_rdma_mr(INFO, "num_pages=0x%x offset=0x%x tailsz=0x%x\n",
                        num_pages, offset, tailsz);

        if (num_pages == 1) {
                sg_set_page(&smbdirect_mr->sgl[0], pages[0], tailsz, offset);
                goto skip_multiple_pages;
        }

        /* We have at least two pages to register */
        sg_set_page(
                &smbdirect_mr->sgl[0], pages[0], PAGE_SIZE - offset, offset);
        i = 1;
        while (i < num_pages - 1) {
                sg_set_page(&smbdirect_mr->sgl[i], pages[i], PAGE_SIZE, 0);
                i++;
        }
        sg_set_page(&smbdirect_mr->sgl[i], pages[i],
                tailsz ? tailsz : PAGE_SIZE, 0);

skip_multiple_pages:
        dir = writing ? DMA_FROM_DEVICE : DMA_TO_DEVICE;
        smbdirect_mr->dir = dir;
        rc = ib_dma_map_sg(info->id->device, smbdirect_mr->sgl, num_pages, dir);
        if (!rc) {
                log_rdma_mr(ERR, "ib_dma_map_sg num_pages=%x dir=%x rc=%x\n",
                        num_pages, dir, rc);
                goto dma_map_error;
        }

        rc = ib_map_mr_sg(smbdirect_mr->mr, smbdirect_mr->sgl, num_pages,
                NULL, PAGE_SIZE);
        if (rc != num_pages) {
                log_rdma_mr(ERR,
                        "ib_map_mr_sg failed rc = %d num_pages = %x\n",
                        rc, num_pages);
                goto map_mr_error;
        }

        ib_update_fast_reg_key(smbdirect_mr->mr,
                ib_inc_rkey(smbdirect_mr->mr->rkey));
        reg_wr = &smbdirect_mr->wr;
        reg_wr->wr.opcode = IB_WR_REG_MR;
        smbdirect_mr->cqe.done = register_mr_done;
        reg_wr->wr.wr_cqe = &smbdirect_mr->cqe;
        reg_wr->wr.num_sge = 0;
        reg_wr->wr.send_flags = IB_SEND_SIGNALED;
        reg_wr->mr = smbdirect_mr->mr;
        reg_wr->key = smbdirect_mr->mr->rkey;
        reg_wr->access = writing ?
                        IB_ACCESS_REMOTE_WRITE | IB_ACCESS_LOCAL_WRITE :
                        IB_ACCESS_REMOTE_READ;

        /*
         * There is no need for waiting for complemtion on ib_post_send
         * on IB_WR_REG_MR. Hardware enforces a barrier and order of execution
         * on the next ib_post_send when we actaully send I/O to remote peer
         */
        rc = ib_post_send(info->id->qp, &reg_wr->wr, NULL);
        if (!rc)
                return smbdirect_mr;

        log_rdma_mr(ERR, "ib_post_send failed rc=%x reg_wr->key=%x\n",
                rc, reg_wr->key);

        /* If all failed, attempt to recover this MR by setting it MR_ERROR*/
map_mr_error:
        ib_dma_unmap_sg(info->id->device, smbdirect_mr->sgl,
                smbdirect_mr->sgl_count, smbdirect_mr->dir);

dma_map_error:
        smbdirect_mr->state = MR_ERROR;
        if (atomic_dec_and_test(&info->mr_used_count))
                wake_up(&info->wait_for_mr_cleanup);

        smbd_disconnect_rdma_connection(info);

        return NULL;
}

static void local_inv_done(struct ib_cq *cq, struct ib_wc *wc)
{
        struct smbd_mr *smbdirect_mr;
        struct ib_cqe *cqe;

        cqe = wc->wr_cqe;
        smbdirect_mr = container_of(cqe, struct smbd_mr, cqe);
        smbdirect_mr->state = MR_INVALIDATED;
        if (wc->status != IB_WC_SUCCESS) {
                log_rdma_mr(ERR, "invalidate failed status=%x\n", wc->status);
                smbdirect_mr->state = MR_ERROR;
        }
        complete(&smbdirect_mr->invalidate_done);
}

/*
 * Deregister a MR after I/O is done
 * This function may wait if remote invalidation is not used
 * and we have to locally invalidate the buffer to prevent data is being
 * modified by remote peer after upper layer consumes it
 */
int smbd_deregister_mr(struct smbd_mr *smbdirect_mr)
{
        struct ib_send_wr *wr;
        struct smbd_connection *info = smbdirect_mr->conn;
        int rc = 0;

        if (smbdirect_mr->need_invalidate) {
                /* Need to finish local invalidation before returning */
                wr = &smbdirect_mr->inv_wr;
                wr->opcode = IB_WR_LOCAL_INV;
                smbdirect_mr->cqe.done = local_inv_done;
                wr->wr_cqe = &smbdirect_mr->cqe;
                wr->num_sge = 0;
                wr->ex.invalidate_rkey = smbdirect_mr->mr->rkey;
                wr->send_flags = IB_SEND_SIGNALED;

                init_completion(&smbdirect_mr->invalidate_done);
                rc = ib_post_send(info->id->qp, wr, NULL);
                if (rc) {
                        log_rdma_mr(ERR, "ib_post_send failed rc=%x\n", rc);
                        smbd_disconnect_rdma_connection(info);
                        goto done;
                }
                wait_for_completion(&smbdirect_mr->invalidate_done);
                smbdirect_mr->need_invalidate = false;
        } else
                /*
                 * For remote invalidation, just set it to MR_INVALIDATED
                 * and defer to mr_recovery_work to recover the MR for next use
                 */
                smbdirect_mr->state = MR_INVALIDATED;

        if (smbdirect_mr->state == MR_INVALIDATED) {
                ib_dma_unmap_sg(
                        info->id->device, smbdirect_mr->sgl,
                        smbdirect_mr->sgl_count,
                        smbdirect_mr->dir);
                smbdirect_mr->state = MR_READY;
                if (atomic_inc_return(&info->mr_ready_count) == 1)
                        wake_up_interruptible(&info->wait_mr);
        } else
                /*
                 * Schedule the work to do MR recovery for future I/Os MR
                 * recovery is slow and don't want it to block current I/O
                 */
                queue_work(info->workqueue, &info->mr_recovery_work);

done:
        if (atomic_dec_and_test(&info->mr_used_count))
                wake_up(&info->wait_for_mr_cleanup);

        return rc;
}