// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2017-2018 Christoph Hellwig.
 */

#include <linux/moduleparam.h>
#include <trace/events/block.h>
#include "nvme.h"

static bool multipath = true;
module_param(multipath, bool, 0444);
MODULE_PARM_DESC(multipath,
        "turn on native support for multiple controllers per subsystem");

inline bool nvme_ctrl_use_ana(struct nvme_ctrl *ctrl)
{
        return multipath && ctrl->subsys && (ctrl->subsys->cmic & (1 << 3));
}

/*
 * If multipathing is enabled we need to always use the subsystem instance
 * number for numbering our devices to avoid conflicts between subsystems that
 * have multiple controllers and thus use the multipath-aware subsystem node
 * and those that have a single controller and use the controller node
 * directly.
 */
void nvme_set_disk_name(char *disk_name, struct nvme_ns *ns,
                        struct nvme_ctrl *ctrl, int *flags)
{
        if (!multipath) {
                sprintf(disk_name, "nvme%dn%d", ctrl->instance, ns->head->instance);
        } else if (ns->head->disk) {
                sprintf(disk_name, "nvme%dc%dn%d", ctrl->subsys->instance,
                                ctrl->cntlid, ns->head->instance);
                *flags = GENHD_FL_HIDDEN;
        } else {
                sprintf(disk_name, "nvme%dn%d", ctrl->subsys->instance,
                                ns->head->instance);
        }
}

void nvme_failover_req(struct request *req)
{
        struct nvme_ns *ns = req->q->queuedata;
        u16 status = nvme_req(req)->status;
        unsigned long flags;

        spin_lock_irqsave(&ns->head->requeue_lock, flags);
        blk_steal_bios(&ns->head->requeue_list, req);
        spin_unlock_irqrestore(&ns->head->requeue_lock, flags);
        blk_mq_end_request(req, 0);

        switch (status & 0x7ff) {
        case NVME_SC_ANA_TRANSITION:
        case NVME_SC_ANA_INACCESSIBLE:
        case NVME_SC_ANA_PERSISTENT_LOSS:
                /*
                 * If we got back an ANA error we know the controller is alive,
                 * but not ready to serve this namespaces.  The spec suggests
                 * we should update our general state here, but due to the fact
                 * that the admin and I/O queues are not serialized that is
                 * fundamentally racy.  So instead just clear the current path,
                 * mark the the path as pending and kick of a re-read of the ANA
                 * log page ASAP.
                 */
                nvme_mpath_clear_current_path(ns);
                if (ns->ctrl->ana_log_buf) {
                        set_bit(NVME_NS_ANA_PENDING, &ns->flags);
                        queue_work(nvme_wq, &ns->ctrl->ana_work);
                }
                break;
        case NVME_SC_HOST_PATH_ERROR:
                /*
                 * Temporary transport disruption in talking to the controller.
                 * Try to send on a new path.
                 */
                nvme_mpath_clear_current_path(ns);
                break;
        default:
                /*
                 * Reset the controller for any non-ANA error as we don't know
                 * what caused the error.
                 */
                nvme_reset_ctrl(ns->ctrl);
                break;
        }

        kblockd_schedule_work(&ns->head->requeue_work);
}

void nvme_kick_requeue_lists(struct nvme_ctrl *ctrl)
{
        struct nvme_ns *ns;

        down_read(&ctrl->namespaces_rwsem);
        list_for_each_entry(ns, &ctrl->namespaces, list) {
                if (ns->head->disk)
                        kblockd_schedule_work(&ns->head->requeue_work);
        }
        up_read(&ctrl->namespaces_rwsem);
}

static const char *nvme_ana_state_names[] = {
        [0]                             = "invalid state",
        [NVME_ANA_OPTIMIZED]            = "optimized",
        [NVME_ANA_NONOPTIMIZED]         = "non-optimized",
        [NVME_ANA_INACCESSIBLE]         = "inaccessible",
        [NVME_ANA_PERSISTENT_LOSS]      = "persistent-loss",
        [NVME_ANA_CHANGE]               = "change",
};

void nvme_mpath_clear_current_path(struct nvme_ns *ns)
{
        struct nvme_ns_head *head = ns->head;
        int node;

        if (!head)
                return;

        for_each_node(node) {
                if (ns == rcu_access_pointer(head->current_path[node]))
                        rcu_assign_pointer(head->current_path[node], NULL);
        }
}

static struct nvme_ns *__nvme_find_path(struct nvme_ns_head *head, int node)
{
        int found_distance = INT_MAX, fallback_distance = INT_MAX, distance;
        struct nvme_ns *found = NULL, *fallback = NULL, *ns;

        list_for_each_entry_rcu(ns, &head->list, siblings) {
                if (ns->ctrl->state != NVME_CTRL_LIVE ||
                    test_bit(NVME_NS_ANA_PENDING, &ns->flags))
                        continue;

                if (READ_ONCE(head->subsys->iopolicy) == NVME_IOPOLICY_NUMA)
                        distance = node_distance(node, ns->ctrl->numa_node);
                else
                        distance = LOCAL_DISTANCE;

                switch (ns->ana_state) {
                case NVME_ANA_OPTIMIZED:
                        if (distance < found_distance) {
                                found_distance = distance;
                                found = ns;
                        }
                        break;
                case NVME_ANA_NONOPTIMIZED:
                        if (distance < fallback_distance) {
                                fallback_distance = distance;
                                fallback = ns;
                        }
                        break;
                default:
                        break;
                }
        }

        if (!found)
                found = fallback;
        if (found)
                rcu_assign_pointer(head->current_path[node], found);
        return found;
}

static struct nvme_ns *nvme_next_ns(struct nvme_ns_head *head,
                struct nvme_ns *ns)
{
        ns = list_next_or_null_rcu(&head->list, &ns->siblings, struct nvme_ns,
                        siblings);
        if (ns)
                return ns;
        return list_first_or_null_rcu(&head->list, struct nvme_ns, siblings);
}

static struct nvme_ns *nvme_round_robin_path(struct nvme_ns_head *head,
                int node, struct nvme_ns *old)
{
        struct nvme_ns *ns, *found, *fallback = NULL;

        if (list_is_singular(&head->list))
                return old;

        for (ns = nvme_next_ns(head, old);
             ns != old;
             ns = nvme_next_ns(head, ns)) {
                if (ns->ctrl->state != NVME_CTRL_LIVE ||
                    test_bit(NVME_NS_ANA_PENDING, &ns->flags))
                        continue;

                if (ns->ana_state == NVME_ANA_OPTIMIZED) {
                        found = ns;
                        goto out;
                }
                if (ns->ana_state == NVME_ANA_NONOPTIMIZED)
                        fallback = ns;
        }

        if (!fallback)
                return NULL;
        found = fallback;
out:
        rcu_assign_pointer(head->current_path[node], found);
        return found;
}

static inline bool nvme_path_is_optimized(struct nvme_ns *ns)
{
        return ns->ctrl->state == NVME_CTRL_LIVE &&
                ns->ana_state == NVME_ANA_OPTIMIZED;
}

inline struct nvme_ns *nvme_find_path(struct nvme_ns_head *head)
{
        int node = numa_node_id();
        struct nvme_ns *ns;

        ns = srcu_dereference(head->current_path[node], &head->srcu);
        if (READ_ONCE(head->subsys->iopolicy) == NVME_IOPOLICY_RR && ns)
                ns = nvme_round_robin_path(head, node, ns);
        if (unlikely(!ns || !nvme_path_is_optimized(ns)))
                ns = __nvme_find_path(head, node);
        return ns;
}

static blk_qc_t nvme_ns_head_make_request(struct request_queue *q,
                struct bio *bio)
{
        struct nvme_ns_head *head = q->queuedata;
        struct device *dev = disk_to_dev(head->disk);
        struct nvme_ns *ns;
        blk_qc_t ret = BLK_QC_T_NONE;
        int srcu_idx;

        srcu_idx = srcu_read_lock(&head->srcu);
        ns = nvme_find_path(head);
        if (likely(ns)) {
                bio->bi_disk = ns->disk;
                bio->bi_opf |= REQ_NVME_MPATH;
                trace_block_bio_remap(bio->bi_disk->queue, bio,
                                      disk_devt(ns->head->disk),
                                      bio->bi_iter.bi_sector);
                ret = direct_make_request(bio);
        } else if (!list_empty_careful(&head->list)) {
                dev_warn_ratelimited(dev, "no path available - requeuing I/O\n");

                spin_lock_irq(&head->requeue_lock);
                bio_list_add(&head->requeue_list, bio);
                spin_unlock_irq(&head->requeue_lock);
        } else {
                dev_warn_ratelimited(dev, "no path - failing I/O\n");

                bio->bi_status = BLK_STS_IOERR;
                bio_endio(bio);
        }

        srcu_read_unlock(&head->srcu, srcu_idx);
        return ret;
}

static void nvme_requeue_work(struct work_struct *work)
{
        struct nvme_ns_head *head =
                container_of(work, struct nvme_ns_head, requeue_work);
        struct bio *bio, *next;

        spin_lock_irq(&head->requeue_lock);
        next = bio_list_get(&head->requeue_list);
        spin_unlock_irq(&head->requeue_lock);

        while ((bio = next) != NULL) {
                next = bio->bi_next;
                bio->bi_next = NULL;

                /*
                 * Reset disk to the mpath node and resubmit to select a new
                 * path.
                 */
                bio->bi_disk = head->disk;
                generic_make_request(bio);
        }
}

int nvme_mpath_alloc_disk(struct nvme_ctrl *ctrl, struct nvme_ns_head *head)
{
        struct request_queue *q;
        bool vwc = false;

        mutex_init(&head->lock);
        bio_list_init(&head->requeue_list);
        spin_lock_init(&head->requeue_lock);
        INIT_WORK(&head->requeue_work, nvme_requeue_work);

        /*
         * Add a multipath node if the subsystems supports multiple controllers.
         * We also do this for private namespaces as the namespace sharing data could
         * change after a rescan.
         */
        if (!(ctrl->subsys->cmic & (1 << 1)) || !multipath)
                return 0;

        q = blk_alloc_queue_node(GFP_KERNEL, ctrl->numa_node);
        if (!q)
                goto out;
        q->queuedata = head;
        blk_queue_make_request(q, nvme_ns_head_make_request);
        blk_queue_flag_set(QUEUE_FLAG_NONROT, q);
        /* set to a default value for 512 until disk is validated */
        blk_queue_logical_block_size(q, 512);
        blk_set_stacking_limits(&q->limits);

        /* we need to propagate up the VMC settings */
        if (ctrl->vwc & NVME_CTRL_VWC_PRESENT)
                vwc = true;
        blk_queue_write_cache(q, vwc, vwc);

        head->disk = alloc_disk(0);
        if (!head->disk)
                goto out_cleanup_queue;
        head->disk->fops = &nvme_ns_head_ops;
        head->disk->private_data = head;
        head->disk->queue = q;
        head->disk->flags = GENHD_FL_EXT_DEVT;
        sprintf(head->disk->disk_name, "nvme%dn%d",
                        ctrl->subsys->instance, head->instance);
        return 0;

out_cleanup_queue:
        blk_cleanup_queue(q);
out:
        return -ENOMEM;
}

static void nvme_mpath_set_live(struct nvme_ns *ns)
{
        struct nvme_ns_head *head = ns->head;

        lockdep_assert_held(&ns->head->lock);

        if (!head->disk)
                return;

        if (!(head->disk->flags & GENHD_FL_UP))
                device_add_disk(&head->subsys->dev, head->disk,
                                nvme_ns_id_attr_groups);

        if (nvme_path_is_optimized(ns)) {
                int node, srcu_idx;

                srcu_idx = srcu_read_lock(&head->srcu);
                for_each_node(node)
                        __nvme_find_path(head, node);
                srcu_read_unlock(&head->srcu, srcu_idx);
        }

        kblockd_schedule_work(&ns->head->requeue_work);
}

static int nvme_parse_ana_log(struct nvme_ctrl *ctrl, void *data,
                int (*cb)(struct nvme_ctrl *ctrl, struct nvme_ana_group_desc *,
                        void *))
{
        void *base = ctrl->ana_log_buf;
        size_t offset = sizeof(struct nvme_ana_rsp_hdr);
        int error, i;

        lockdep_assert_held(&ctrl->ana_lock);

        for (i = 0; i < le16_to_cpu(ctrl->ana_log_buf->ngrps); i++) {
                struct nvme_ana_group_desc *desc = base + offset;
                u32 nr_nsids = le32_to_cpu(desc->nnsids);
                size_t nsid_buf_size = nr_nsids * sizeof(__le32);

                if (WARN_ON_ONCE(desc->grpid == 0))
                        return -EINVAL;
                if (WARN_ON_ONCE(le32_to_cpu(desc->grpid) > ctrl->anagrpmax))
                        return -EINVAL;
                if (WARN_ON_ONCE(desc->state == 0))
                        return -EINVAL;
                if (WARN_ON_ONCE(desc->state > NVME_ANA_CHANGE))
                        return -EINVAL;

                offset += sizeof(*desc);
                if (WARN_ON_ONCE(offset > ctrl->ana_log_size - nsid_buf_size))
                        return -EINVAL;

                error = cb(ctrl, desc, data);
                if (error)
                        return error;

                offset += nsid_buf_size;
                if (WARN_ON_ONCE(offset > ctrl->ana_log_size - sizeof(*desc)))
                        return -EINVAL;
        }

        return 0;
}

static inline bool nvme_state_is_live(enum nvme_ana_state state)
{
        return state == NVME_ANA_OPTIMIZED || state == NVME_ANA_NONOPTIMIZED;
}

static void nvme_update_ns_ana_state(struct nvme_ana_group_desc *desc,
                struct nvme_ns *ns)
{
        mutex_lock(&ns->head->lock);
        ns->ana_grpid = le32_to_cpu(desc->grpid);
        ns->ana_state = desc->state;
        clear_bit(NVME_NS_ANA_PENDING, &ns->flags);

        if (nvme_state_is_live(ns->ana_state))
                nvme_mpath_set_live(ns);
        mutex_unlock(&ns->head->lock);
}

static int nvme_update_ana_state(struct nvme_ctrl *ctrl,
                struct nvme_ana_group_desc *desc, void *data)
{
        u32 nr_nsids = le32_to_cpu(desc->nnsids), n = 0;
        unsigned *nr_change_groups = data;
        struct nvme_ns *ns;

        dev_info(ctrl->device, "ANA group %d: %s.\n",
                        le32_to_cpu(desc->grpid),
                        nvme_ana_state_names[desc->state]);

        if (desc->state == NVME_ANA_CHANGE)
                (*nr_change_groups)++;

        if (!nr_nsids)
                return 0;

        down_write(&ctrl->namespaces_rwsem);
        list_for_each_entry(ns, &ctrl->namespaces, list) {
                if (ns->head->ns_id != le32_to_cpu(desc->nsids[n]))
                        continue;
                nvme_update_ns_ana_state(desc, ns);
                if (++n == nr_nsids)
                        break;
        }
        up_write(&ctrl->namespaces_rwsem);
        WARN_ON_ONCE(n < nr_nsids);
        return 0;
}

static int nvme_read_ana_log(struct nvme_ctrl *ctrl, bool groups_only)
{
        u32 nr_change_groups = 0;
        int error;

        mutex_lock(&ctrl->ana_lock);
        error = nvme_get_log(ctrl, NVME_NSID_ALL, NVME_LOG_ANA,
                        groups_only ? NVME_ANA_LOG_RGO : 0,
                        ctrl->ana_log_buf, ctrl->ana_log_size, 0);
        if (error) {
                dev_warn(ctrl->device, "Failed to get ANA log: %d\n", error);
                goto out_unlock;
        }

        error = nvme_parse_ana_log(ctrl, &nr_change_groups,
                        nvme_update_ana_state);
        if (error)
                goto out_unlock;

        /*
         * In theory we should have an ANATT timer per group as they might enter
         * the change state at different times.  But that is a lot of overhead
         * just to protect against a target that keeps entering new changes
         * states while never finishing previous ones.  But we'll still
         * eventually time out once all groups are in change state, so this
         * isn't a big deal.
         *
         * We also double the ANATT value to provide some slack for transports
         * or AEN processing overhead.
         */
        if (nr_change_groups)
                mod_timer(&ctrl->anatt_timer, ctrl->anatt * HZ * 2 + jiffies);
        else
                del_timer_sync(&ctrl->anatt_timer);
out_unlock:
        mutex_unlock(&ctrl->ana_lock);
        return error;
}

static void nvme_ana_work(struct work_struct *work)
{
        struct nvme_ctrl *ctrl = container_of(work, struct nvme_ctrl, ana_work);

        nvme_read_ana_log(ctrl, false);
}

static void nvme_anatt_timeout(struct timer_list *t)
{
        struct nvme_ctrl *ctrl = from_timer(ctrl, t, anatt_timer);

        dev_info(ctrl->device, "ANATT timeout, resetting controller.\n");
        nvme_reset_ctrl(ctrl);
}

void nvme_mpath_stop(struct nvme_ctrl *ctrl)
{
        if (!nvme_ctrl_use_ana(ctrl))
                return;
        del_timer_sync(&ctrl->anatt_timer);
        cancel_work_sync(&ctrl->ana_work);
}

#define SUBSYS_ATTR_RW(_name, _mode, _show, _store)  \
        struct device_attribute subsys_attr_##_name =   \
                __ATTR(_name, _mode, _show, _store)

static const char *nvme_iopolicy_names[] = {
        [NVME_IOPOLICY_NUMA]    = "numa",
        [NVME_IOPOLICY_RR]      = "round-robin",
};

static ssize_t nvme_subsys_iopolicy_show(struct device *dev,
                struct device_attribute *attr, char *buf)
{
        struct nvme_subsystem *subsys =
                container_of(dev, struct nvme_subsystem, dev);

        return sprintf(buf, "%s\n",
                        nvme_iopolicy_names[READ_ONCE(subsys->iopolicy)]);
}

static ssize_t nvme_subsys_iopolicy_store(struct device *dev,
                struct device_attribute *attr, const char *buf, size_t count)
{
        struct nvme_subsystem *subsys =
                container_of(dev, struct nvme_subsystem, dev);
        int i;

        for (i = 0; i < ARRAY_SIZE(nvme_iopolicy_names); i++) {
                if (sysfs_streq(buf, nvme_iopolicy_names[i])) {
                        WRITE_ONCE(subsys->iopolicy, i);
                        return count;
                }
        }

        return -EINVAL;
}
SUBSYS_ATTR_RW(iopolicy, S_IRUGO | S_IWUSR,
                      nvme_subsys_iopolicy_show, nvme_subsys_iopolicy_store);

static ssize_t ana_grpid_show(struct device *dev, struct device_attribute *attr,
                char *buf)
{
        return sprintf(buf, "%d\n", nvme_get_ns_from_dev(dev)->ana_grpid);
}
DEVICE_ATTR_RO(ana_grpid);

static ssize_t ana_state_show(struct device *dev, struct device_attribute *attr,
                char *buf)
{
        struct nvme_ns *ns = nvme_get_ns_from_dev(dev);

        return sprintf(buf, "%s\n", nvme_ana_state_names[ns->ana_state]);
}
DEVICE_ATTR_RO(ana_state);

static int nvme_set_ns_ana_state(struct nvme_ctrl *ctrl,
                struct nvme_ana_group_desc *desc, void *data)
{
        struct nvme_ns *ns = data;

        if (ns->ana_grpid == le32_to_cpu(desc->grpid)) {
                nvme_update_ns_ana_state(desc, ns);
                return -ENXIO; /* just break out of the loop */
        }

        return 0;
}

void nvme_mpath_add_disk(struct nvme_ns *ns, struct nvme_id_ns *id)
{
        if (nvme_ctrl_use_ana(ns->ctrl)) {
                mutex_lock(&ns->ctrl->ana_lock);
                ns->ana_grpid = le32_to_cpu(id->anagrpid);
                nvme_parse_ana_log(ns->ctrl, ns, nvme_set_ns_ana_state);
                mutex_unlock(&ns->ctrl->ana_lock);
        } else {
                mutex_lock(&ns->head->lock);
                ns->ana_state = NVME_ANA_OPTIMIZED; 
                nvme_mpath_set_live(ns);
                mutex_unlock(&ns->head->lock);
        }
}

void nvme_mpath_remove_disk(struct nvme_ns_head *head)
{
        if (!head->disk)
                return;
        if (head->disk->flags & GENHD_FL_UP)
                del_gendisk(head->disk);
        blk_set_queue_dying(head->disk->queue);
        /* make sure all pending bios are cleaned up */
        kblockd_schedule_work(&head->requeue_work);
        flush_work(&head->requeue_work);
        blk_cleanup_queue(head->disk->queue);
        put_disk(head->disk);
}

int nvme_mpath_init(struct nvme_ctrl *ctrl, struct nvme_id_ctrl *id)
{
        int error;

        if (!nvme_ctrl_use_ana(ctrl))
                return 0;

        ctrl->anacap = id->anacap;
        ctrl->anatt = id->anatt;
        ctrl->nanagrpid = le32_to_cpu(id->nanagrpid);
        ctrl->anagrpmax = le32_to_cpu(id->anagrpmax);

        mutex_init(&ctrl->ana_lock);
        timer_setup(&ctrl->anatt_timer, nvme_anatt_timeout, 0);
        ctrl->ana_log_size = sizeof(struct nvme_ana_rsp_hdr) +
                ctrl->nanagrpid * sizeof(struct nvme_ana_group_desc);
        ctrl->ana_log_size += ctrl->max_namespaces * sizeof(__le32);

        if (ctrl->ana_log_size > ctrl->max_hw_sectors << SECTOR_SHIFT) {
                dev_err(ctrl->device,
                        "ANA log page size (%zd) larger than MDTS (%d).\n",
                        ctrl->ana_log_size,
                        ctrl->max_hw_sectors << SECTOR_SHIFT);
                dev_err(ctrl->device, "disabling ANA support.\n");
                return 0;
        }

        INIT_WORK(&ctrl->ana_work, nvme_ana_work);
        ctrl->ana_log_buf = kmalloc(ctrl->ana_log_size, GFP_KERNEL);
        if (!ctrl->ana_log_buf) {
                error = -ENOMEM;
                goto out;
        }

        error = nvme_read_ana_log(ctrl, true);
        if (error)
                goto out_free_ana_log_buf;
        return 0;
out_free_ana_log_buf:
        kfree(ctrl->ana_log_buf);
        ctrl->ana_log_buf = NULL;
out:
        return error;
}

void nvme_mpath_uninit(struct nvme_ctrl *ctrl)
{
        kfree(ctrl->ana_log_buf);
        ctrl->ana_log_buf = NULL;
}