/*
 * Common code for the NVMe target.
 * Copyright (c) 2015-2016 HGST, a Western Digital Company.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/random.h>
#include <linux/rculist.h>

#include "nvmet.h"

static struct nvmet_fabrics_ops *nvmet_transports[NVMF_TRTYPE_MAX];
static DEFINE_IDA(cntlid_ida);

/*
 * This read/write semaphore is used to synchronize access to configuration
 * information on a target system that will result in discovery log page
 * information change for at least one host.
 * The full list of resources to protected by this semaphore is:
 *
 *  - subsystems list
 *  - per-subsystem allowed hosts list
 *  - allow_any_host subsystem attribute
 *  - nvmet_genctr
 *  - the nvmet_transports array
 *
 * When updating any of those lists/structures write lock should be obtained,
 * while when reading (popolating discovery log page or checking host-subsystem
 * link) read lock is obtained to allow concurrent reads.
 */
DECLARE_RWSEM(nvmet_config_sem);

static struct nvmet_subsys *nvmet_find_get_subsys(struct nvmet_port *port,
                const char *subsysnqn);

u16 nvmet_copy_to_sgl(struct nvmet_req *req, off_t off, const void *buf,
                size_t len)
{
        if (sg_pcopy_from_buffer(req->sg, req->sg_cnt, buf, len, off) != len)
                return NVME_SC_SGL_INVALID_DATA | NVME_SC_DNR;
        return 0;
}

u16 nvmet_copy_from_sgl(struct nvmet_req *req, off_t off, void *buf, size_t len)
{
        if (sg_pcopy_to_buffer(req->sg, req->sg_cnt, buf, len, off) != len)
                return NVME_SC_SGL_INVALID_DATA | NVME_SC_DNR;
        return 0;
}

static unsigned int nvmet_max_nsid(struct nvmet_subsys *subsys)
{
        struct nvmet_ns *ns;

        if (list_empty(&subsys->namespaces))
                return 0;

        ns = list_last_entry(&subsys->namespaces, struct nvmet_ns, dev_link);
        return ns->nsid;
}

static u32 nvmet_async_event_result(struct nvmet_async_event *aen)
{
        return aen->event_type | (aen->event_info << 8) | (aen->log_page << 16);
}

static void nvmet_async_events_free(struct nvmet_ctrl *ctrl)
{
        struct nvmet_req *req;

        while (1) {
                mutex_lock(&ctrl->lock);
                if (!ctrl->nr_async_event_cmds) {
                        mutex_unlock(&ctrl->lock);
                        return;
                }

                req = ctrl->async_event_cmds[--ctrl->nr_async_event_cmds];
                mutex_unlock(&ctrl->lock);
                nvmet_req_complete(req, NVME_SC_INTERNAL | NVME_SC_DNR);
        }
}

static void nvmet_async_event_work(struct work_struct *work)
{
        struct nvmet_ctrl *ctrl =
                container_of(work, struct nvmet_ctrl, async_event_work);
        struct nvmet_async_event *aen;
        struct nvmet_req *req;

        while (1) {
                mutex_lock(&ctrl->lock);
                aen = list_first_entry_or_null(&ctrl->async_events,
                                struct nvmet_async_event, entry);
                if (!aen || !ctrl->nr_async_event_cmds) {
                        mutex_unlock(&ctrl->lock);
                        return;
                }

                req = ctrl->async_event_cmds[--ctrl->nr_async_event_cmds];
                nvmet_set_result(req, nvmet_async_event_result(aen));

                list_del(&aen->entry);
                kfree(aen);

                mutex_unlock(&ctrl->lock);
                nvmet_req_complete(req, 0);
        }
}

static void nvmet_add_async_event(struct nvmet_ctrl *ctrl, u8 event_type,
                u8 event_info, u8 log_page)
{
        struct nvmet_async_event *aen;

        aen = kmalloc(sizeof(*aen), GFP_KERNEL);
        if (!aen)
                return;

        aen->event_type = event_type;
        aen->event_info = event_info;
        aen->log_page = log_page;

        mutex_lock(&ctrl->lock);
        list_add_tail(&aen->entry, &ctrl->async_events);
        mutex_unlock(&ctrl->lock);

        schedule_work(&ctrl->async_event_work);
}

int nvmet_register_transport(struct nvmet_fabrics_ops *ops)
{
        int ret = 0;

        down_write(&nvmet_config_sem);
        if (nvmet_transports[ops->type])
                ret = -EINVAL;
        else
                nvmet_transports[ops->type] = ops;
        up_write(&nvmet_config_sem);

        return ret;
}
EXPORT_SYMBOL_GPL(nvmet_register_transport);

void nvmet_unregister_transport(struct nvmet_fabrics_ops *ops)
{
        down_write(&nvmet_config_sem);
        nvmet_transports[ops->type] = NULL;
        up_write(&nvmet_config_sem);
}
EXPORT_SYMBOL_GPL(nvmet_unregister_transport);

int nvmet_enable_port(struct nvmet_port *port)
{
        struct nvmet_fabrics_ops *ops;
        int ret;

        lockdep_assert_held(&nvmet_config_sem);

        ops = nvmet_transports[port->disc_addr.trtype];
        if (!ops) {
                up_write(&nvmet_config_sem);
                request_module("nvmet-transport-%d", port->disc_addr.trtype);
                down_write(&nvmet_config_sem);
                ops = nvmet_transports[port->disc_addr.trtype];
                if (!ops) {
                        pr_err("transport type %d not supported\n",
                                port->disc_addr.trtype);
                        return -EINVAL;
                }
        }

        if (!try_module_get(ops->owner))
                return -EINVAL;

        ret = ops->add_port(port);
        if (ret) {
                module_put(ops->owner);
                return ret;
        }

        port->enabled = true;
        return 0;
}

void nvmet_disable_port(struct nvmet_port *port)
{
        struct nvmet_fabrics_ops *ops;

        lockdep_assert_held(&nvmet_config_sem);

        port->enabled = false;

        ops = nvmet_transports[port->disc_addr.trtype];
        ops->remove_port(port);
        module_put(ops->owner);
}

static void nvmet_keep_alive_timer(struct work_struct *work)
{
        struct nvmet_ctrl *ctrl = container_of(to_delayed_work(work),
                        struct nvmet_ctrl, ka_work);

        pr_err("ctrl %d keep-alive timer (%d seconds) expired!\n",
                ctrl->cntlid, ctrl->kato);

        nvmet_ctrl_fatal_error(ctrl);
}

static void nvmet_start_keep_alive_timer(struct nvmet_ctrl *ctrl)
{
        pr_debug("ctrl %d start keep-alive timer for %d secs\n",
                ctrl->cntlid, ctrl->kato);

        INIT_DELAYED_WORK(&ctrl->ka_work, nvmet_keep_alive_timer);
        schedule_delayed_work(&ctrl->ka_work, ctrl->kato * HZ);
}

static void nvmet_stop_keep_alive_timer(struct nvmet_ctrl *ctrl)
{
        pr_debug("ctrl %d stop keep-alive\n", ctrl->cntlid);

        cancel_delayed_work_sync(&ctrl->ka_work);
}

static struct nvmet_ns *__nvmet_find_namespace(struct nvmet_ctrl *ctrl,
                __le32 nsid)
{
        struct nvmet_ns *ns;

        list_for_each_entry_rcu(ns, &ctrl->subsys->namespaces, dev_link) {
                if (ns->nsid == le32_to_cpu(nsid))
                        return ns;
        }

        return NULL;
}

struct nvmet_ns *nvmet_find_namespace(struct nvmet_ctrl *ctrl, __le32 nsid)
{
        struct nvmet_ns *ns;

        rcu_read_lock();
        ns = __nvmet_find_namespace(ctrl, nsid);
        if (ns)
                percpu_ref_get(&ns->ref);
        rcu_read_unlock();

        return ns;
}

static void nvmet_destroy_namespace(struct percpu_ref *ref)
{
        struct nvmet_ns *ns = container_of(ref, struct nvmet_ns, ref);

        complete(&ns->disable_done);
}

void nvmet_put_namespace(struct nvmet_ns *ns)
{
        percpu_ref_put(&ns->ref);
}

int nvmet_ns_enable(struct nvmet_ns *ns)
{
        struct nvmet_subsys *subsys = ns->subsys;
        struct nvmet_ctrl *ctrl;
        int ret = 0;

        mutex_lock(&subsys->lock);
        if (ns->enabled)
                goto out_unlock;

        ns->bdev = blkdev_get_by_path(ns->device_path, FMODE_READ | FMODE_WRITE,
                        NULL);
        if (IS_ERR(ns->bdev)) {
                pr_err("failed to open block device %s: (%ld)\n",
                       ns->device_path, PTR_ERR(ns->bdev));
                ret = PTR_ERR(ns->bdev);
                ns->bdev = NULL;
                goto out_unlock;
        }

        ns->size = i_size_read(ns->bdev->bd_inode);
        ns->blksize_shift = blksize_bits(bdev_logical_block_size(ns->bdev));

        ret = percpu_ref_init(&ns->ref, nvmet_destroy_namespace,
                                0, GFP_KERNEL);
        if (ret)
                goto out_blkdev_put;

        if (ns->nsid > subsys->max_nsid)
                subsys->max_nsid = ns->nsid;

        /*
         * The namespaces list needs to be sorted to simplify the implementation
         * of the Identify Namepace List subcommand.
         */
        if (list_empty(&subsys->namespaces)) {
                list_add_tail_rcu(&ns->dev_link, &subsys->namespaces);
        } else {
                struct nvmet_ns *old;

                list_for_each_entry_rcu(old, &subsys->namespaces, dev_link) {
                        BUG_ON(ns->nsid == old->nsid);
                        if (ns->nsid < old->nsid)
                                break;
                }

                list_add_tail_rcu(&ns->dev_link, &old->dev_link);
        }

        list_for_each_entry(ctrl, &subsys->ctrls, subsys_entry)
                nvmet_add_async_event(ctrl, NVME_AER_TYPE_NOTICE, 0, 0);

        ns->enabled = true;
        ret = 0;
out_unlock:
        mutex_unlock(&subsys->lock);
        return ret;
out_blkdev_put:
        blkdev_put(ns->bdev, FMODE_WRITE|FMODE_READ);
        ns->bdev = NULL;
        goto out_unlock;
}

void nvmet_ns_disable(struct nvmet_ns *ns)
{
        struct nvmet_subsys *subsys = ns->subsys;
        struct nvmet_ctrl *ctrl;

        mutex_lock(&subsys->lock);
        if (!ns->enabled)
                goto out_unlock;

        ns->enabled = false;
        list_del_rcu(&ns->dev_link);
        if (ns->nsid == subsys->max_nsid)
                subsys->max_nsid = nvmet_max_nsid(subsys);
        mutex_unlock(&subsys->lock);

        /*
         * Now that we removed the namespaces from the lookup list, we
         * can kill the per_cpu ref and wait for any remaining references
         * to be dropped, as well as a RCU grace period for anyone only
         * using the namepace under rcu_read_lock().  Note that we can't
         * use call_rcu here as we need to ensure the namespaces have
         * been fully destroyed before unloading the module.
         */
        percpu_ref_kill(&ns->ref);
        synchronize_rcu();
        wait_for_completion(&ns->disable_done);
        percpu_ref_exit(&ns->ref);

        mutex_lock(&subsys->lock);
        list_for_each_entry(ctrl, &subsys->ctrls, subsys_entry)
                nvmet_add_async_event(ctrl, NVME_AER_TYPE_NOTICE, 0, 0);

        if (ns->bdev)
                blkdev_put(ns->bdev, FMODE_WRITE|FMODE_READ);
out_unlock:
        mutex_unlock(&subsys->lock);
}

void nvmet_ns_free(struct nvmet_ns *ns)
{
        nvmet_ns_disable(ns);

        kfree(ns->device_path);
        kfree(ns);
}

struct nvmet_ns *nvmet_ns_alloc(struct nvmet_subsys *subsys, u32 nsid)
{
        struct nvmet_ns *ns;

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

        INIT_LIST_HEAD(&ns->dev_link);
        init_completion(&ns->disable_done);

        ns->nsid = nsid;
        ns->subsys = subsys;
        uuid_gen(&ns->uuid);

        return ns;
}

static void __nvmet_req_complete(struct nvmet_req *req, u16 status)
{
        u32 old_sqhd, new_sqhd;
        u16 sqhd;

        if (status)
                nvmet_set_status(req, status);

        if (req->sq->size) {
                do {
                        old_sqhd = req->sq->sqhd;
                        new_sqhd = (old_sqhd + 1) % req->sq->size;
                } while (cmpxchg(&req->sq->sqhd, old_sqhd, new_sqhd) !=
                                        old_sqhd);
        }
        sqhd = req->sq->sqhd & 0x0000FFFF;
        req->rsp->sq_head = cpu_to_le16(sqhd);
        req->rsp->sq_id = cpu_to_le16(req->sq->qid);
        req->rsp->command_id = req->cmd->common.command_id;

        if (req->ns)
                nvmet_put_namespace(req->ns);
        req->ops->queue_response(req);
}

void nvmet_req_complete(struct nvmet_req *req, u16 status)
{
        __nvmet_req_complete(req, status);
        percpu_ref_put(&req->sq->ref);
}
EXPORT_SYMBOL_GPL(nvmet_req_complete);

void nvmet_cq_setup(struct nvmet_ctrl *ctrl, struct nvmet_cq *cq,
                u16 qid, u16 size)
{
        cq->qid = qid;
        cq->size = size;

        ctrl->cqs[qid] = cq;
}

void nvmet_sq_setup(struct nvmet_ctrl *ctrl, struct nvmet_sq *sq,
                u16 qid, u16 size)
{
        sq->sqhd = 0;
        sq->qid = qid;
        sq->size = size;

        ctrl->sqs[qid] = sq;
}

static void nvmet_confirm_sq(struct percpu_ref *ref)
{
        struct nvmet_sq *sq = container_of(ref, struct nvmet_sq, ref);

        complete(&sq->confirm_done);
}

void nvmet_sq_destroy(struct nvmet_sq *sq)
{
        /*
         * If this is the admin queue, complete all AERs so that our
         * queue doesn't have outstanding requests on it.
         */
        if (sq->ctrl && sq->ctrl->sqs && sq->ctrl->sqs[0] == sq)
                nvmet_async_events_free(sq->ctrl);
        percpu_ref_kill_and_confirm(&sq->ref, nvmet_confirm_sq);
        wait_for_completion(&sq->confirm_done);
        wait_for_completion(&sq->free_done);
        percpu_ref_exit(&sq->ref);

        if (sq->ctrl) {
                nvmet_ctrl_put(sq->ctrl);
                sq->ctrl = NULL; /* allows reusing the queue later */
        }
}
EXPORT_SYMBOL_GPL(nvmet_sq_destroy);

static void nvmet_sq_free(struct percpu_ref *ref)
{
        struct nvmet_sq *sq = container_of(ref, struct nvmet_sq, ref);

        complete(&sq->free_done);
}

int nvmet_sq_init(struct nvmet_sq *sq)
{
        int ret;

        ret = percpu_ref_init(&sq->ref, nvmet_sq_free, 0, GFP_KERNEL);
        if (ret) {
                pr_err("percpu_ref init failed!\n");
                return ret;
        }
        init_completion(&sq->free_done);
        init_completion(&sq->confirm_done);

        return 0;
}
EXPORT_SYMBOL_GPL(nvmet_sq_init);

bool nvmet_req_init(struct nvmet_req *req, struct nvmet_cq *cq,
                struct nvmet_sq *sq, struct nvmet_fabrics_ops *ops)
{
        u8 flags = req->cmd->common.flags;
        u16 status;

        req->cq = cq;
        req->sq = sq;
        req->ops = ops;
        req->sg = NULL;
        req->sg_cnt = 0;
        req->transfer_len = 0;
        req->rsp->status = 0;
        req->ns = NULL;

        /* no support for fused commands yet */
        if (unlikely(flags & (NVME_CMD_FUSE_FIRST | NVME_CMD_FUSE_SECOND))) {
                status = NVME_SC_INVALID_FIELD | NVME_SC_DNR;
                goto fail;
        }

        /*
         * For fabrics, PSDT field shall describe metadata pointer (MPTR) that
         * contains an address of a single contiguous physical buffer that is
         * byte aligned.
         */
        if (unlikely((flags & NVME_CMD_SGL_ALL) != NVME_CMD_SGL_METABUF)) {
                status = NVME_SC_INVALID_FIELD | NVME_SC_DNR;
                goto fail;
        }

        if (unlikely(!req->sq->ctrl))
                /* will return an error for any Non-connect command: */
                status = nvmet_parse_connect_cmd(req);
        else if (likely(req->sq->qid != 0))
                status = nvmet_parse_io_cmd(req);
        else if (req->cmd->common.opcode == nvme_fabrics_command)
                status = nvmet_parse_fabrics_cmd(req);
        else if (req->sq->ctrl->subsys->type == NVME_NQN_DISC)
                status = nvmet_parse_discovery_cmd(req);
        else
                status = nvmet_parse_admin_cmd(req);

        if (status)
                goto fail;

        if (unlikely(!percpu_ref_tryget_live(&sq->ref))) {
                status = NVME_SC_INVALID_FIELD | NVME_SC_DNR;
                goto fail;
        }

        return true;

fail:
        __nvmet_req_complete(req, status);
        return false;
}
EXPORT_SYMBOL_GPL(nvmet_req_init);

void nvmet_req_uninit(struct nvmet_req *req)
{
        percpu_ref_put(&req->sq->ref);
        if (req->ns)
                nvmet_put_namespace(req->ns);
}
EXPORT_SYMBOL_GPL(nvmet_req_uninit);

void nvmet_req_execute(struct nvmet_req *req)
{
        if (unlikely(req->data_len != req->transfer_len))
                nvmet_req_complete(req, NVME_SC_SGL_INVALID_DATA | NVME_SC_DNR);
        else
                req->execute(req);
}
EXPORT_SYMBOL_GPL(nvmet_req_execute);

static inline bool nvmet_cc_en(u32 cc)
{
        return (cc >> NVME_CC_EN_SHIFT) & 0x1;
}

static inline u8 nvmet_cc_css(u32 cc)
{
        return (cc >> NVME_CC_CSS_SHIFT) & 0x7;
}

static inline u8 nvmet_cc_mps(u32 cc)
{
        return (cc >> NVME_CC_MPS_SHIFT) & 0xf;
}

static inline u8 nvmet_cc_ams(u32 cc)
{
        return (cc >> NVME_CC_AMS_SHIFT) & 0x7;
}

static inline u8 nvmet_cc_shn(u32 cc)
{
        return (cc >> NVME_CC_SHN_SHIFT) & 0x3;
}

static inline u8 nvmet_cc_iosqes(u32 cc)
{
        return (cc >> NVME_CC_IOSQES_SHIFT) & 0xf;
}

static inline u8 nvmet_cc_iocqes(u32 cc)
{
        return (cc >> NVME_CC_IOCQES_SHIFT) & 0xf;
}

static void nvmet_start_ctrl(struct nvmet_ctrl *ctrl)
{
        lockdep_assert_held(&ctrl->lock);

        if (nvmet_cc_iosqes(ctrl->cc) != NVME_NVM_IOSQES ||
            nvmet_cc_iocqes(ctrl->cc) != NVME_NVM_IOCQES ||
            nvmet_cc_mps(ctrl->cc) != 0 ||
            nvmet_cc_ams(ctrl->cc) != 0 ||
            nvmet_cc_css(ctrl->cc) != 0) {
                ctrl->csts = NVME_CSTS_CFS;
                return;
        }

        ctrl->csts = NVME_CSTS_RDY;
}

static void nvmet_clear_ctrl(struct nvmet_ctrl *ctrl)
{
        lockdep_assert_held(&ctrl->lock);

        /* XXX: tear down queues? */
        ctrl->csts &= ~NVME_CSTS_RDY;
        ctrl->cc = 0;
}

void nvmet_update_cc(struct nvmet_ctrl *ctrl, u32 new)
{
        u32 old;

        mutex_lock(&ctrl->lock);
        old = ctrl->cc;
        ctrl->cc = new;

        if (nvmet_cc_en(new) && !nvmet_cc_en(old))
                nvmet_start_ctrl(ctrl);
        if (!nvmet_cc_en(new) && nvmet_cc_en(old))
                nvmet_clear_ctrl(ctrl);
        if (nvmet_cc_shn(new) && !nvmet_cc_shn(old)) {
                nvmet_clear_ctrl(ctrl);
                ctrl->csts |= NVME_CSTS_SHST_CMPLT;
        }
        if (!nvmet_cc_shn(new) && nvmet_cc_shn(old))
                ctrl->csts &= ~NVME_CSTS_SHST_CMPLT;
        mutex_unlock(&ctrl->lock);
}

static void nvmet_init_cap(struct nvmet_ctrl *ctrl)
{
        /* command sets supported: NVMe command set: */
        ctrl->cap = (1ULL << 37);
        /* CC.EN timeout in 500msec units: */
        ctrl->cap |= (15ULL << 24);
        /* maximum queue entries supported: */
        ctrl->cap |= NVMET_QUEUE_SIZE - 1;
}

u16 nvmet_ctrl_find_get(const char *subsysnqn, const char *hostnqn, u16 cntlid,
                struct nvmet_req *req, struct nvmet_ctrl **ret)
{
        struct nvmet_subsys *subsys;
        struct nvmet_ctrl *ctrl;
        u16 status = 0;

        subsys = nvmet_find_get_subsys(req->port, subsysnqn);
        if (!subsys) {
                pr_warn("connect request for invalid subsystem %s!\n",
                        subsysnqn);
                req->rsp->result.u32 = IPO_IATTR_CONNECT_DATA(subsysnqn);
                return NVME_SC_CONNECT_INVALID_PARAM | NVME_SC_DNR;
        }

        mutex_lock(&subsys->lock);
        list_for_each_entry(ctrl, &subsys->ctrls, subsys_entry) {
                if (ctrl->cntlid == cntlid) {
                        if (strncmp(hostnqn, ctrl->hostnqn, NVMF_NQN_SIZE)) {
                                pr_warn("hostnqn mismatch.\n");
                                continue;
                        }
                        if (!kref_get_unless_zero(&ctrl->ref))
                                continue;

                        *ret = ctrl;
                        goto out;
                }
        }

        pr_warn("could not find controller %d for subsys %s / host %s\n",
                cntlid, subsysnqn, hostnqn);
        req->rsp->result.u32 = IPO_IATTR_CONNECT_DATA(cntlid);
        status = NVME_SC_CONNECT_INVALID_PARAM | NVME_SC_DNR;

out:
        mutex_unlock(&subsys->lock);
        nvmet_subsys_put(subsys);
        return status;
}

u16 nvmet_check_ctrl_status(struct nvmet_req *req, struct nvme_command *cmd)
{
        if (unlikely(!(req->sq->ctrl->cc & NVME_CC_ENABLE))) {
                pr_err("got io cmd %d while CC.EN == 0 on qid = %d\n",
                       cmd->common.opcode, req->sq->qid);
                return NVME_SC_CMD_SEQ_ERROR | NVME_SC_DNR;
        }

        if (unlikely(!(req->sq->ctrl->csts & NVME_CSTS_RDY))) {
                pr_err("got io cmd %d while CSTS.RDY == 0 on qid = %d\n",
                       cmd->common.opcode, req->sq->qid);
                req->ns = NULL;
                return NVME_SC_CMD_SEQ_ERROR | NVME_SC_DNR;
        }
        return 0;
}

static bool __nvmet_host_allowed(struct nvmet_subsys *subsys,
                const char *hostnqn)
{
        struct nvmet_host_link *p;

        if (subsys->allow_any_host)
                return true;

        list_for_each_entry(p, &subsys->hosts, entry) {
                if (!strcmp(nvmet_host_name(p->host), hostnqn))
                        return true;
        }

        return false;
}

static bool nvmet_host_discovery_allowed(struct nvmet_req *req,
                const char *hostnqn)
{
        struct nvmet_subsys_link *s;

        list_for_each_entry(s, &req->port->subsystems, entry) {
                if (__nvmet_host_allowed(s->subsys, hostnqn))
                        return true;
        }

        return false;
}

bool nvmet_host_allowed(struct nvmet_req *req, struct nvmet_subsys *subsys,
                const char *hostnqn)
{
        lockdep_assert_held(&nvmet_config_sem);

        if (subsys->type == NVME_NQN_DISC)
                return nvmet_host_discovery_allowed(req, hostnqn);
        else
                return __nvmet_host_allowed(subsys, hostnqn);
}

u16 nvmet_alloc_ctrl(const char *subsysnqn, const char *hostnqn,
                struct nvmet_req *req, u32 kato, struct nvmet_ctrl **ctrlp)
{
        struct nvmet_subsys *subsys;
        struct nvmet_ctrl *ctrl;
        int ret;
        u16 status;

        status = NVME_SC_CONNECT_INVALID_PARAM | NVME_SC_DNR;
        subsys = nvmet_find_get_subsys(req->port, subsysnqn);
        if (!subsys) {
                pr_warn("connect request for invalid subsystem %s!\n",
                        subsysnqn);
                req->rsp->result.u32 = IPO_IATTR_CONNECT_DATA(subsysnqn);
                goto out;
        }

        status = NVME_SC_CONNECT_INVALID_PARAM | NVME_SC_DNR;
        down_read(&nvmet_config_sem);
        if (!nvmet_host_allowed(req, subsys, hostnqn)) {
                pr_info("connect by host %s for subsystem %s not allowed\n",
                        hostnqn, subsysnqn);
                req->rsp->result.u32 = IPO_IATTR_CONNECT_DATA(hostnqn);
                up_read(&nvmet_config_sem);
                status = NVME_SC_CONNECT_INVALID_HOST | NVME_SC_DNR;
                goto out_put_subsystem;
        }
        up_read(&nvmet_config_sem);

        status = NVME_SC_INTERNAL;
        ctrl = kzalloc(sizeof(*ctrl), GFP_KERNEL);
        if (!ctrl)
                goto out_put_subsystem;
        mutex_init(&ctrl->lock);

        nvmet_init_cap(ctrl);

        INIT_WORK(&ctrl->async_event_work, nvmet_async_event_work);
        INIT_LIST_HEAD(&ctrl->async_events);

        memcpy(ctrl->subsysnqn, subsysnqn, NVMF_NQN_SIZE);
        memcpy(ctrl->hostnqn, hostnqn, NVMF_NQN_SIZE);

        kref_init(&ctrl->ref);
        ctrl->subsys = subsys;

        ctrl->cqs = kcalloc(subsys->max_qid + 1,
                        sizeof(struct nvmet_cq *),
                        GFP_KERNEL);
        if (!ctrl->cqs)
                goto out_free_ctrl;

        ctrl->sqs = kcalloc(subsys->max_qid + 1,
                        sizeof(struct nvmet_sq *),
                        GFP_KERNEL);
        if (!ctrl->sqs)
                goto out_free_cqs;

        ret = ida_simple_get(&cntlid_ida,
                             NVME_CNTLID_MIN, NVME_CNTLID_MAX,
                             GFP_KERNEL);
        if (ret < 0) {
                status = NVME_SC_CONNECT_CTRL_BUSY | NVME_SC_DNR;
                goto out_free_sqs;
        }
        ctrl->cntlid = ret;

        ctrl->ops = req->ops;
        if (ctrl->subsys->type == NVME_NQN_DISC) {
                /* Don't accept keep-alive timeout for discovery controllers */
                if (kato) {
                        status = NVME_SC_INVALID_FIELD | NVME_SC_DNR;
                        goto out_remove_ida;
                }

                /*
                 * Discovery controllers use some arbitrary high value in order
                 * to cleanup stale discovery sessions
                 *
                 * From the latest base diff RC:
                 * "The Keep Alive command is not supported by
                 * Discovery controllers. A transport may specify a
                 * fixed Discovery controller activity timeout value
                 * (e.g., 2 minutes).  If no commands are received
                 * by a Discovery controller within that time
                 * period, the controller may perform the
                 * actions for Keep Alive Timer expiration".
                 */
                ctrl->kato = NVMET_DISC_KATO;
        } else {
                /* keep-alive timeout in seconds */
                ctrl->kato = DIV_ROUND_UP(kato, 1000);
        }
        nvmet_start_keep_alive_timer(ctrl);

        mutex_lock(&subsys->lock);
        list_add_tail(&ctrl->subsys_entry, &subsys->ctrls);
        mutex_unlock(&subsys->lock);

        *ctrlp = ctrl;
        return 0;

out_remove_ida:
        ida_simple_remove(&cntlid_ida, ctrl->cntlid);
out_free_sqs:
        kfree(ctrl->sqs);
out_free_cqs:
        kfree(ctrl->cqs);
out_free_ctrl:
        kfree(ctrl);
out_put_subsystem:
        nvmet_subsys_put(subsys);
out:
        return status;
}

static void nvmet_ctrl_free(struct kref *ref)
{
        struct nvmet_ctrl *ctrl = container_of(ref, struct nvmet_ctrl, ref);
        struct nvmet_subsys *subsys = ctrl->subsys;

        mutex_lock(&subsys->lock);
        list_del(&ctrl->subsys_entry);
        mutex_unlock(&subsys->lock);

        nvmet_stop_keep_alive_timer(ctrl);

        flush_work(&ctrl->async_event_work);
        cancel_work_sync(&ctrl->fatal_err_work);

        ida_simple_remove(&cntlid_ida, ctrl->cntlid);

        kfree(ctrl->sqs);
        kfree(ctrl->cqs);
        kfree(ctrl);

        nvmet_subsys_put(subsys);
}

void nvmet_ctrl_put(struct nvmet_ctrl *ctrl)
{
        kref_put(&ctrl->ref, nvmet_ctrl_free);
}

static void nvmet_fatal_error_handler(struct work_struct *work)
{
        struct nvmet_ctrl *ctrl =
                        container_of(work, struct nvmet_ctrl, fatal_err_work);

        pr_err("ctrl %d fatal error occurred!\n", ctrl->cntlid);
        ctrl->ops->delete_ctrl(ctrl);
}

void nvmet_ctrl_fatal_error(struct nvmet_ctrl *ctrl)
{
        mutex_lock(&ctrl->lock);
        if (!(ctrl->csts & NVME_CSTS_CFS)) {
                ctrl->csts |= NVME_CSTS_CFS;
                INIT_WORK(&ctrl->fatal_err_work, nvmet_fatal_error_handler);
                schedule_work(&ctrl->fatal_err_work);
        }
        mutex_unlock(&ctrl->lock);
}
EXPORT_SYMBOL_GPL(nvmet_ctrl_fatal_error);

static struct nvmet_subsys *nvmet_find_get_subsys(struct nvmet_port *port,
                const char *subsysnqn)
{
        struct nvmet_subsys_link *p;

        if (!port)
                return NULL;

        if (!strncmp(NVME_DISC_SUBSYS_NAME, subsysnqn,
                        NVMF_NQN_SIZE)) {
                if (!kref_get_unless_zero(&nvmet_disc_subsys->ref))
                        return NULL;
                return nvmet_disc_subsys;
        }

        down_read(&nvmet_config_sem);
        list_for_each_entry(p, &port->subsystems, entry) {
                if (!strncmp(p->subsys->subsysnqn, subsysnqn,
                                NVMF_NQN_SIZE)) {
                        if (!kref_get_unless_zero(&p->subsys->ref))
                                break;
                        up_read(&nvmet_config_sem);
                        return p->subsys;
                }
        }
        up_read(&nvmet_config_sem);
        return NULL;
}

struct nvmet_subsys *nvmet_subsys_alloc(const char *subsysnqn,
                enum nvme_subsys_type type)
{
        struct nvmet_subsys *subsys;

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

        subsys->ver = NVME_VS(1, 3, 0); /* NVMe 1.3.0 */
        /* generate a random serial number as our controllers are ephemeral: */
        get_random_bytes(&subsys->serial, sizeof(subsys->serial));

        switch (type) {
        case NVME_NQN_NVME:
                subsys->max_qid = NVMET_NR_QUEUES;
                break;
        case NVME_NQN_DISC:
                subsys->max_qid = 0;
                break;
        default:
                pr_err("%s: Unknown Subsystem type - %d\n", __func__, type);
                kfree(subsys);
                return NULL;
        }
        subsys->type = type;
        subsys->subsysnqn = kstrndup(subsysnqn, NVMF_NQN_SIZE,
                        GFP_KERNEL);
        if (!subsys->subsysnqn) {
                kfree(subsys);
                return NULL;
        }

        kref_init(&subsys->ref);

        mutex_init(&subsys->lock);
        INIT_LIST_HEAD(&subsys->namespaces);
        INIT_LIST_HEAD(&subsys->ctrls);
        INIT_LIST_HEAD(&subsys->hosts);

        return subsys;
}

static void nvmet_subsys_free(struct kref *ref)
{
        struct nvmet_subsys *subsys =
                container_of(ref, struct nvmet_subsys, ref);

        WARN_ON_ONCE(!list_empty(&subsys->namespaces));

        kfree(subsys->subsysnqn);
        kfree(subsys);
}

void nvmet_subsys_del_ctrls(struct nvmet_subsys *subsys)
{
        struct nvmet_ctrl *ctrl;

        mutex_lock(&subsys->lock);
        list_for_each_entry(ctrl, &subsys->ctrls, subsys_entry)
                ctrl->ops->delete_ctrl(ctrl);
        mutex_unlock(&subsys->lock);
}

void nvmet_subsys_put(struct nvmet_subsys *subsys)
{
        kref_put(&subsys->ref, nvmet_subsys_free);
}

static int __init nvmet_init(void)
{
        int error;

        error = nvmet_init_discovery();
        if (error)
                goto out;

        error = nvmet_init_configfs();
        if (error)
                goto out_exit_discovery;
        return 0;

out_exit_discovery:
        nvmet_exit_discovery();
out:
        return error;
}

static void __exit nvmet_exit(void)
{
        nvmet_exit_configfs();
        nvmet_exit_discovery();
        ida_destroy(&cntlid_ida);

        BUILD_BUG_ON(sizeof(struct nvmf_disc_rsp_page_entry) != 1024);
        BUILD_BUG_ON(sizeof(struct nvmf_disc_rsp_page_hdr) != 1024);
}

module_init(nvmet_init);
module_exit(nvmet_exit);

MODULE_LICENSE("GPL v2");