/*
 * Copyright (C) 2015, SUSE
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 */


#include <linux/module.h>
#include <linux/kthread.h>
#include <linux/dlm.h>
#include <linux/sched.h>
#include <linux/raid/md_p.h>
#include "md.h"
#include "bitmap.h"
#include "md-cluster.h"

#define LVB_SIZE        64
#define NEW_DEV_TIMEOUT 5000

struct dlm_lock_resource {
        dlm_lockspace_t *ls;
        struct dlm_lksb lksb;
        char *name; /* lock name. */
        uint32_t flags; /* flags to pass to dlm_lock() */
        wait_queue_head_t sync_locking; /* wait queue for synchronized locking */
        bool sync_locking_done;
        void (*bast)(void *arg, int mode); /* blocking AST function pointer*/
        struct mddev *mddev; /* pointing back to mddev. */
        int mode;
};

struct suspend_info {
        int slot;
        sector_t lo;
        sector_t hi;
        struct list_head list;
};

struct resync_info {
        __le64 lo;
        __le64 hi;
};

/* md_cluster_info flags */
#define         MD_CLUSTER_WAITING_FOR_NEWDISK          1
#define         MD_CLUSTER_SUSPEND_READ_BALANCING       2
#define         MD_CLUSTER_BEGIN_JOIN_CLUSTER           3

/* Lock the send communication. This is done through
 * bit manipulation as opposed to a mutex in order to
 * accomodate lock and hold. See next comment.
 */
#define         MD_CLUSTER_SEND_LOCK                    4
/* If cluster operations (such as adding a disk) must lock the
 * communication channel, so as to perform extra operations
 * (update metadata) and no other operation is allowed on the
 * MD. Token needs to be locked and held until the operation
 * completes witha md_update_sb(), which would eventually release
 * the lock.
 */
#define         MD_CLUSTER_SEND_LOCKED_ALREADY          5
/* We should receive message after node joined cluster and
 * set up all the related infos such as bitmap and personality */
#define         MD_CLUSTER_ALREADY_IN_CLUSTER           6
#define         MD_CLUSTER_PENDING_RECV_EVENT           7


struct md_cluster_info {
        /* dlm lock space and resources for clustered raid. */
        dlm_lockspace_t *lockspace;
        int slot_number;
        struct completion completion;
        struct mutex recv_mutex;
        struct dlm_lock_resource *bitmap_lockres;
        struct dlm_lock_resource **other_bitmap_lockres;
        struct dlm_lock_resource *resync_lockres;
        struct list_head suspend_list;
        spinlock_t suspend_lock;
        struct md_thread *recovery_thread;
        unsigned long recovery_map;
        /* communication loc resources */
        struct dlm_lock_resource *ack_lockres;
        struct dlm_lock_resource *message_lockres;
        struct dlm_lock_resource *token_lockres;
        struct dlm_lock_resource *no_new_dev_lockres;
        struct md_thread *recv_thread;
        struct completion newdisk_completion;
        wait_queue_head_t wait;
        unsigned long state;
        /* record the region in RESYNCING message */
        sector_t sync_low;
        sector_t sync_hi;
};

enum msg_type {
        METADATA_UPDATED = 0,
        RESYNCING,
        NEWDISK,
        REMOVE,
        RE_ADD,
        BITMAP_NEEDS_SYNC,
};

struct cluster_msg {
        __le32 type;
        __le32 slot;
        /* TODO: Unionize this for smaller footprint */
        __le64 low;
        __le64 high;
        char uuid[16];
        __le32 raid_slot;
};

static void sync_ast(void *arg)
{
        struct dlm_lock_resource *res;

        res = arg;
        res->sync_locking_done = true;
        wake_up(&res->sync_locking);
}

static int dlm_lock_sync(struct dlm_lock_resource *res, int mode)
{
        int ret = 0;

        ret = dlm_lock(res->ls, mode, &res->lksb,
                        res->flags, res->name, strlen(res->name),
                        0, sync_ast, res, res->bast);
        if (ret)
                return ret;
        wait_event(res->sync_locking, res->sync_locking_done);
        res->sync_locking_done = false;
        if (res->lksb.sb_status == 0)
                res->mode = mode;
        return res->lksb.sb_status;
}

static int dlm_unlock_sync(struct dlm_lock_resource *res)
{
        return dlm_lock_sync(res, DLM_LOCK_NL);
}

/*
 * An variation of dlm_lock_sync, which make lock request could
 * be interrupted
 */
static int dlm_lock_sync_interruptible(struct dlm_lock_resource *res, int mode,
                                       struct mddev *mddev)
{
        int ret = 0;

        ret = dlm_lock(res->ls, mode, &res->lksb,
                        res->flags, res->name, strlen(res->name),
                        0, sync_ast, res, res->bast);
        if (ret)
                return ret;

        wait_event(res->sync_locking, res->sync_locking_done
                                      || kthread_should_stop()
                                      || test_bit(MD_CLOSING, &mddev->flags));
        if (!res->sync_locking_done) {
                /*
                 * the convert queue contains the lock request when request is
                 * interrupted, and sync_ast could still be run, so need to
                 * cancel the request and reset completion
                 */
                ret = dlm_unlock(res->ls, res->lksb.sb_lkid, DLM_LKF_CANCEL,
                        &res->lksb, res);
                res->sync_locking_done = false;
                if (unlikely(ret != 0))
                        pr_info("failed to cancel previous lock request "
                                 "%s return %d\n", res->name, ret);
                return -EPERM;
        } else
                res->sync_locking_done = false;
        if (res->lksb.sb_status == 0)
                res->mode = mode;
        return res->lksb.sb_status;
}

static struct dlm_lock_resource *lockres_init(struct mddev *mddev,
                char *name, void (*bastfn)(void *arg, int mode), int with_lvb)
{
        struct dlm_lock_resource *res = NULL;
        int ret, namelen;
        struct md_cluster_info *cinfo = mddev->cluster_info;

        res = kzalloc(sizeof(struct dlm_lock_resource), GFP_KERNEL);
        if (!res)
                return NULL;
        init_waitqueue_head(&res->sync_locking);
        res->sync_locking_done = false;
        res->ls = cinfo->lockspace;
        res->mddev = mddev;
        res->mode = DLM_LOCK_IV;
        namelen = strlen(name);
        res->name = kzalloc(namelen + 1, GFP_KERNEL);
        if (!res->name) {
                pr_err("md-cluster: Unable to allocate resource name for resource %s\n", name);
                goto out_err;
        }
        strlcpy(res->name, name, namelen + 1);
        if (with_lvb) {
                res->lksb.sb_lvbptr = kzalloc(LVB_SIZE, GFP_KERNEL);
                if (!res->lksb.sb_lvbptr) {
                        pr_err("md-cluster: Unable to allocate LVB for resource %s\n", name);
                        goto out_err;
                }
                res->flags = DLM_LKF_VALBLK;
        }

        if (bastfn)
                res->bast = bastfn;

        res->flags |= DLM_LKF_EXPEDITE;

        ret = dlm_lock_sync(res, DLM_LOCK_NL);
        if (ret) {
                pr_err("md-cluster: Unable to lock NL on new lock resource %s\n", name);
                goto out_err;
        }
        res->flags &= ~DLM_LKF_EXPEDITE;
        res->flags |= DLM_LKF_CONVERT;

        return res;
out_err:
        kfree(res->lksb.sb_lvbptr);
        kfree(res->name);
        kfree(res);
        return NULL;
}

static void lockres_free(struct dlm_lock_resource *res)
{
        int ret = 0;

        if (!res)
                return;

        /*
         * use FORCEUNLOCK flag, so we can unlock even the lock is on the
         * waiting or convert queue
         */
        ret = dlm_unlock(res->ls, res->lksb.sb_lkid, DLM_LKF_FORCEUNLOCK,
                &res->lksb, res);
        if (unlikely(ret != 0))
                pr_err("failed to unlock %s return %d\n", res->name, ret);
        else
                wait_event(res->sync_locking, res->sync_locking_done);

        kfree(res->name);
        kfree(res->lksb.sb_lvbptr);
        kfree(res);
}

static void add_resync_info(struct dlm_lock_resource *lockres,
                            sector_t lo, sector_t hi)
{
        struct resync_info *ri;

        ri = (struct resync_info *)lockres->lksb.sb_lvbptr;
        ri->lo = cpu_to_le64(lo);
        ri->hi = cpu_to_le64(hi);
}

static struct suspend_info *read_resync_info(struct mddev *mddev, struct dlm_lock_resource *lockres)
{
        struct resync_info ri;
        struct suspend_info *s = NULL;
        sector_t hi = 0;

        dlm_lock_sync(lockres, DLM_LOCK_CR);
        memcpy(&ri, lockres->lksb.sb_lvbptr, sizeof(struct resync_info));
        hi = le64_to_cpu(ri.hi);
        if (hi > 0) {
                s = kzalloc(sizeof(struct suspend_info), GFP_KERNEL);
                if (!s)
                        goto out;
                s->hi = hi;
                s->lo = le64_to_cpu(ri.lo);
        }
        dlm_unlock_sync(lockres);
out:
        return s;
}

static void recover_bitmaps(struct md_thread *thread)
{
        struct mddev *mddev = thread->mddev;
        struct md_cluster_info *cinfo = mddev->cluster_info;
        struct dlm_lock_resource *bm_lockres;
        char str[64];
        int slot, ret;
        struct suspend_info *s, *tmp;
        sector_t lo, hi;

        while (cinfo->recovery_map) {
                slot = fls64((u64)cinfo->recovery_map) - 1;

                /* Clear suspend_area associated with the bitmap */
                spin_lock_irq(&cinfo->suspend_lock);
                list_for_each_entry_safe(s, tmp, &cinfo->suspend_list, list)
                        if (slot == s->slot) {
                                list_del(&s->list);
                                kfree(s);
                        }
                spin_unlock_irq(&cinfo->suspend_lock);

                snprintf(str, 64, "bitmap%04d", slot);
                bm_lockres = lockres_init(mddev, str, NULL, 1);
                if (!bm_lockres) {
                        pr_err("md-cluster: Cannot initialize bitmaps\n");
                        goto clear_bit;
                }

                ret = dlm_lock_sync_interruptible(bm_lockres, DLM_LOCK_PW, mddev);
                if (ret) {
                        pr_err("md-cluster: Could not DLM lock %s: %d\n",
                                        str, ret);
                        goto clear_bit;
                }
                ret = bitmap_copy_from_slot(mddev, slot, &lo, &hi, true);
                if (ret) {
                        pr_err("md-cluster: Could not copy data from bitmap %d\n", slot);
                        goto clear_bit;
                }
                if (hi > 0) {
                        if (lo < mddev->recovery_cp)
                                mddev->recovery_cp = lo;
                        /* wake up thread to continue resync in case resync
                         * is not finished */
                        if (mddev->recovery_cp != MaxSector) {
                            set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
                            md_wakeup_thread(mddev->thread);
                        }
                }
clear_bit:
                lockres_free(bm_lockres);
                clear_bit(slot, &cinfo->recovery_map);
        }
}

static void recover_prep(void *arg)
{
        struct mddev *mddev = arg;
        struct md_cluster_info *cinfo = mddev->cluster_info;
        set_bit(MD_CLUSTER_SUSPEND_READ_BALANCING, &cinfo->state);
}

static void __recover_slot(struct mddev *mddev, int slot)
{
        struct md_cluster_info *cinfo = mddev->cluster_info;

        set_bit(slot, &cinfo->recovery_map);
        if (!cinfo->recovery_thread) {
                cinfo->recovery_thread = md_register_thread(recover_bitmaps,
                                mddev, "recover");
                if (!cinfo->recovery_thread) {
                        pr_warn("md-cluster: Could not create recovery thread\n");
                        return;
                }
        }
        md_wakeup_thread(cinfo->recovery_thread);
}

static void recover_slot(void *arg, struct dlm_slot *slot)
{
        struct mddev *mddev = arg;
        struct md_cluster_info *cinfo = mddev->cluster_info;

        pr_info("md-cluster: %s Node %d/%d down. My slot: %d. Initiating recovery.\n",
                        mddev->bitmap_info.cluster_name,
                        slot->nodeid, slot->slot,
                        cinfo->slot_number);
        /* deduct one since dlm slot starts from one while the num of
         * cluster-md begins with 0 */
        __recover_slot(mddev, slot->slot - 1);
}

static void recover_done(void *arg, struct dlm_slot *slots,
                int num_slots, int our_slot,
                uint32_t generation)
{
        struct mddev *mddev = arg;
        struct md_cluster_info *cinfo = mddev->cluster_info;

        cinfo->slot_number = our_slot;
        /* completion is only need to be complete when node join cluster,
         * it doesn't need to run during another node's failure */
        if (test_bit(MD_CLUSTER_BEGIN_JOIN_CLUSTER, &cinfo->state)) {
                complete(&cinfo->completion);
                clear_bit(MD_CLUSTER_BEGIN_JOIN_CLUSTER, &cinfo->state);
        }
        clear_bit(MD_CLUSTER_SUSPEND_READ_BALANCING, &cinfo->state);
}

/* the ops is called when node join the cluster, and do lock recovery
 * if node failure occurs */
static const struct dlm_lockspace_ops md_ls_ops = {
        .recover_prep = recover_prep,
        .recover_slot = recover_slot,
        .recover_done = recover_done,
};

/*
 * The BAST function for the ack lock resource
 * This function wakes up the receive thread in
 * order to receive and process the message.
 */
static void ack_bast(void *arg, int mode)
{
        struct dlm_lock_resource *res = arg;
        struct md_cluster_info *cinfo = res->mddev->cluster_info;

        if (mode == DLM_LOCK_EX) {
                if (test_bit(MD_CLUSTER_ALREADY_IN_CLUSTER, &cinfo->state))
                        md_wakeup_thread(cinfo->recv_thread);
                else
                        set_bit(MD_CLUSTER_PENDING_RECV_EVENT, &cinfo->state);
        }
}

static void __remove_suspend_info(struct md_cluster_info *cinfo, int slot)
{
        struct suspend_info *s, *tmp;

        list_for_each_entry_safe(s, tmp, &cinfo->suspend_list, list)
                if (slot == s->slot) {
                        list_del(&s->list);
                        kfree(s);
                        break;
                }
}

static void remove_suspend_info(struct mddev *mddev, int slot)
{
        struct md_cluster_info *cinfo = mddev->cluster_info;
        spin_lock_irq(&cinfo->suspend_lock);
        __remove_suspend_info(cinfo, slot);
        spin_unlock_irq(&cinfo->suspend_lock);
        mddev->pers->quiesce(mddev, 2);
}


static void process_suspend_info(struct mddev *mddev,
                int slot, sector_t lo, sector_t hi)
{
        struct md_cluster_info *cinfo = mddev->cluster_info;
        struct suspend_info *s;

        if (!hi) {
                remove_suspend_info(mddev, slot);
                set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
                md_wakeup_thread(mddev->thread);
                return;
        }

        /*
         * The bitmaps are not same for different nodes
         * if RESYNCING is happening in one node, then
         * the node which received the RESYNCING message
         * probably will perform resync with the region
         * [lo, hi] again, so we could reduce resync time
         * a lot if we can ensure that the bitmaps among
         * different nodes are match up well.
         *
         * sync_low/hi is used to record the region which
         * arrived in the previous RESYNCING message,
         *
         * Call bitmap_sync_with_cluster to clear
         * NEEDED_MASK and set RESYNC_MASK since
         * resync thread is running in another node,
         * so we don't need to do the resync again
         * with the same section */
        bitmap_sync_with_cluster(mddev, cinfo->sync_low,
                                        cinfo->sync_hi,
                                        lo, hi);
        cinfo->sync_low = lo;
        cinfo->sync_hi = hi;

        s = kzalloc(sizeof(struct suspend_info), GFP_KERNEL);
        if (!s)
                return;
        s->slot = slot;
        s->lo = lo;
        s->hi = hi;
        mddev->pers->quiesce(mddev, 1);
        mddev->pers->quiesce(mddev, 0);
        spin_lock_irq(&cinfo->suspend_lock);
        /* Remove existing entry (if exists) before adding */
        __remove_suspend_info(cinfo, slot);
        list_add(&s->list, &cinfo->suspend_list);
        spin_unlock_irq(&cinfo->suspend_lock);
        mddev->pers->quiesce(mddev, 2);
}

static void process_add_new_disk(struct mddev *mddev, struct cluster_msg *cmsg)
{
        char disk_uuid[64];
        struct md_cluster_info *cinfo = mddev->cluster_info;
        char event_name[] = "EVENT=ADD_DEVICE";
        char raid_slot[16];
        char *envp[] = {event_name, disk_uuid, raid_slot, NULL};
        int len;

        len = snprintf(disk_uuid, 64, "DEVICE_UUID=");
        sprintf(disk_uuid + len, "%pU", cmsg->uuid);
        snprintf(raid_slot, 16, "RAID_DISK=%d", le32_to_cpu(cmsg->raid_slot));
        pr_info("%s:%d Sending kobject change with %s and %s\n", __func__, __LINE__, disk_uuid, raid_slot);
        init_completion(&cinfo->newdisk_completion);
        set_bit(MD_CLUSTER_WAITING_FOR_NEWDISK, &cinfo->state);
        kobject_uevent_env(&disk_to_dev(mddev->gendisk)->kobj, KOBJ_CHANGE, envp);
        wait_for_completion_timeout(&cinfo->newdisk_completion,
                        NEW_DEV_TIMEOUT);
        clear_bit(MD_CLUSTER_WAITING_FOR_NEWDISK, &cinfo->state);
}


static void process_metadata_update(struct mddev *mddev, struct cluster_msg *msg)
{
        struct md_cluster_info *cinfo = mddev->cluster_info;
        mddev->good_device_nr = le32_to_cpu(msg->raid_slot);
        set_bit(MD_RELOAD_SB, &mddev->flags);
        dlm_lock_sync(cinfo->no_new_dev_lockres, DLM_LOCK_CR);
        md_wakeup_thread(mddev->thread);
}

static void process_remove_disk(struct mddev *mddev, struct cluster_msg *msg)
{
        struct md_rdev *rdev;

        rcu_read_lock();
        rdev = md_find_rdev_nr_rcu(mddev, le32_to_cpu(msg->raid_slot));
        if (rdev) {
                set_bit(ClusterRemove, &rdev->flags);
                set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
                md_wakeup_thread(mddev->thread);
        }
        else
                pr_warn("%s: %d Could not find disk(%d) to REMOVE\n",
                        __func__, __LINE__, le32_to_cpu(msg->raid_slot));
        rcu_read_unlock();
}

static void process_readd_disk(struct mddev *mddev, struct cluster_msg *msg)
{
        struct md_rdev *rdev;

        rcu_read_lock();
        rdev = md_find_rdev_nr_rcu(mddev, le32_to_cpu(msg->raid_slot));
        if (rdev && test_bit(Faulty, &rdev->flags))
                clear_bit(Faulty, &rdev->flags);
        else
                pr_warn("%s: %d Could not find disk(%d) which is faulty",
                        __func__, __LINE__, le32_to_cpu(msg->raid_slot));
        rcu_read_unlock();
}

static int process_recvd_msg(struct mddev *mddev, struct cluster_msg *msg)
{
        int ret = 0;

        if (WARN(mddev->cluster_info->slot_number - 1 == le32_to_cpu(msg->slot),
                "node %d received it's own msg\n", le32_to_cpu(msg->slot)))
                return -1;
        switch (le32_to_cpu(msg->type)) {
        case METADATA_UPDATED:
                process_metadata_update(mddev, msg);
                break;
        case RESYNCING:
                process_suspend_info(mddev, le32_to_cpu(msg->slot),
                                     le64_to_cpu(msg->low),
                                     le64_to_cpu(msg->high));
                break;
        case NEWDISK:
                process_add_new_disk(mddev, msg);
                break;
        case REMOVE:
                process_remove_disk(mddev, msg);
                break;
        case RE_ADD:
                process_readd_disk(mddev, msg);
                break;
        case BITMAP_NEEDS_SYNC:
                __recover_slot(mddev, le32_to_cpu(msg->slot));
                break;
        default:
                ret = -1;
                pr_warn("%s:%d Received unknown message from %d\n",
                        __func__, __LINE__, msg->slot);
        }
        return ret;
}

/*
 * thread for receiving message
 */
static void recv_daemon(struct md_thread *thread)
{
        struct md_cluster_info *cinfo = thread->mddev->cluster_info;
        struct dlm_lock_resource *ack_lockres = cinfo->ack_lockres;
        struct dlm_lock_resource *message_lockres = cinfo->message_lockres;
        struct cluster_msg msg;
        int ret;

        mutex_lock(&cinfo->recv_mutex);
        /*get CR on Message*/
        if (dlm_lock_sync(message_lockres, DLM_LOCK_CR)) {
                pr_err("md/raid1:failed to get CR on MESSAGE\n");
                mutex_unlock(&cinfo->recv_mutex);
                return;
        }

        /* read lvb and wake up thread to process this message_lockres */
        memcpy(&msg, message_lockres->lksb.sb_lvbptr, sizeof(struct cluster_msg));
        ret = process_recvd_msg(thread->mddev, &msg);
        if (ret)
                goto out;

        /*release CR on ack_lockres*/
        ret = dlm_unlock_sync(ack_lockres);
        if (unlikely(ret != 0))
                pr_info("unlock ack failed return %d\n", ret);
        /*up-convert to PR on message_lockres*/
        ret = dlm_lock_sync(message_lockres, DLM_LOCK_PR);
        if (unlikely(ret != 0))
                pr_info("lock PR on msg failed return %d\n", ret);
        /*get CR on ack_lockres again*/
        ret = dlm_lock_sync(ack_lockres, DLM_LOCK_CR);
        if (unlikely(ret != 0))
                pr_info("lock CR on ack failed return %d\n", ret);
out:
        /*release CR on message_lockres*/
        ret = dlm_unlock_sync(message_lockres);
        if (unlikely(ret != 0))
                pr_info("unlock msg failed return %d\n", ret);
        mutex_unlock(&cinfo->recv_mutex);
}

/* lock_token()
 * Takes the lock on the TOKEN lock resource so no other
 * node can communicate while the operation is underway.
 */
static int lock_token(struct md_cluster_info *cinfo)
{
        int error;

        error = dlm_lock_sync(cinfo->token_lockres, DLM_LOCK_EX);
        if (error)
                pr_err("md-cluster(%s:%d): failed to get EX on TOKEN (%d)\n",
                                __func__, __LINE__, error);

        /* Lock the receive sequence */
        mutex_lock(&cinfo->recv_mutex);
        return error;
}

/* lock_comm()
 * Sets the MD_CLUSTER_SEND_LOCK bit to lock the send channel.
 */
static int lock_comm(struct md_cluster_info *cinfo)
{
        wait_event(cinfo->wait,
                   !test_and_set_bit(MD_CLUSTER_SEND_LOCK, &cinfo->state));

        return lock_token(cinfo);
}

static void unlock_comm(struct md_cluster_info *cinfo)
{
        WARN_ON(cinfo->token_lockres->mode != DLM_LOCK_EX);
        mutex_unlock(&cinfo->recv_mutex);
        dlm_unlock_sync(cinfo->token_lockres);
        clear_bit(MD_CLUSTER_SEND_LOCK, &cinfo->state);
        wake_up(&cinfo->wait);
}

/* __sendmsg()
 * This function performs the actual sending of the message. This function is
 * usually called after performing the encompassing operation
 * The function:
 * 1. Grabs the message lockresource in EX mode
 * 2. Copies the message to the message LVB
 * 3. Downconverts message lockresource to CW
 * 4. Upconverts ack lock resource from CR to EX. This forces the BAST on other nodes
 *    and the other nodes read the message. The thread will wait here until all other
 *    nodes have released ack lock resource.
 * 5. Downconvert ack lockresource to CR
 */
static int __sendmsg(struct md_cluster_info *cinfo, struct cluster_msg *cmsg)
{
        int error;
        int slot = cinfo->slot_number - 1;

        cmsg->slot = cpu_to_le32(slot);
        /*get EX on Message*/
        error = dlm_lock_sync(cinfo->message_lockres, DLM_LOCK_EX);
        if (error) {
                pr_err("md-cluster: failed to get EX on MESSAGE (%d)\n", error);
                goto failed_message;
        }

        memcpy(cinfo->message_lockres->lksb.sb_lvbptr, (void *)cmsg,
                        sizeof(struct cluster_msg));
        /*down-convert EX to CW on Message*/
        error = dlm_lock_sync(cinfo->message_lockres, DLM_LOCK_CW);
        if (error) {
                pr_err("md-cluster: failed to convert EX to CW on MESSAGE(%d)\n",
                                error);
                goto failed_ack;
        }

        /*up-convert CR to EX on Ack*/
        error = dlm_lock_sync(cinfo->ack_lockres, DLM_LOCK_EX);
        if (error) {
                pr_err("md-cluster: failed to convert CR to EX on ACK(%d)\n",
                                error);
                goto failed_ack;
        }

        /*down-convert EX to CR on Ack*/
        error = dlm_lock_sync(cinfo->ack_lockres, DLM_LOCK_CR);
        if (error) {
                pr_err("md-cluster: failed to convert EX to CR on ACK(%d)\n",
                                error);
                goto failed_ack;
        }

failed_ack:
        error = dlm_unlock_sync(cinfo->message_lockres);
        if (unlikely(error != 0)) {
                pr_err("md-cluster: failed convert to NL on MESSAGE(%d)\n",
                        error);
                /* in case the message can't be released due to some reason */
                goto failed_ack;
        }
failed_message:
        return error;
}

static int sendmsg(struct md_cluster_info *cinfo, struct cluster_msg *cmsg)
{
        int ret;

        lock_comm(cinfo);
        ret = __sendmsg(cinfo, cmsg);
        unlock_comm(cinfo);
        return ret;
}

static int gather_all_resync_info(struct mddev *mddev, int total_slots)
{
        struct md_cluster_info *cinfo = mddev->cluster_info;
        int i, ret = 0;
        struct dlm_lock_resource *bm_lockres;
        struct suspend_info *s;
        char str[64];
        sector_t lo, hi;


        for (i = 0; i < total_slots; i++) {
                memset(str, '\0', 64);
                snprintf(str, 64, "bitmap%04d", i);
                bm_lockres = lockres_init(mddev, str, NULL, 1);
                if (!bm_lockres)
                        return -ENOMEM;
                if (i == (cinfo->slot_number - 1)) {
                        lockres_free(bm_lockres);
                        continue;
                }

                bm_lockres->flags |= DLM_LKF_NOQUEUE;
                ret = dlm_lock_sync(bm_lockres, DLM_LOCK_PW);
                if (ret == -EAGAIN) {
                        s = read_resync_info(mddev, bm_lockres);
                        if (s) {
                                pr_info("%s:%d Resync[%llu..%llu] in progress on %d\n",
                                                __func__, __LINE__,
                                                (unsigned long long) s->lo,
                                                (unsigned long long) s->hi, i);
                                spin_lock_irq(&cinfo->suspend_lock);
                                s->slot = i;
                                list_add(&s->list, &cinfo->suspend_list);
                                spin_unlock_irq(&cinfo->suspend_lock);
                        }
                        ret = 0;
                        lockres_free(bm_lockres);
                        continue;
                }
                if (ret) {
                        lockres_free(bm_lockres);
                        goto out;
                }

                /* Read the disk bitmap sb and check if it needs recovery */
                ret = bitmap_copy_from_slot(mddev, i, &lo, &hi, false);
                if (ret) {
                        pr_warn("md-cluster: Could not gather bitmaps from slot %d", i);
                        lockres_free(bm_lockres);
                        continue;
                }
                if ((hi > 0) && (lo < mddev->recovery_cp)) {
                        set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
                        mddev->recovery_cp = lo;
                        md_check_recovery(mddev);
                }

                lockres_free(bm_lockres);
        }
out:
        return ret;
}

static int join(struct mddev *mddev, int nodes)
{
        struct md_cluster_info *cinfo;
        int ret, ops_rv;
        char str[64];

        cinfo = kzalloc(sizeof(struct md_cluster_info), GFP_KERNEL);
        if (!cinfo)
                return -ENOMEM;

        INIT_LIST_HEAD(&cinfo->suspend_list);
        spin_lock_init(&cinfo->suspend_lock);
        init_completion(&cinfo->completion);
        set_bit(MD_CLUSTER_BEGIN_JOIN_CLUSTER, &cinfo->state);
        init_waitqueue_head(&cinfo->wait);
        mutex_init(&cinfo->recv_mutex);

        mddev->cluster_info = cinfo;

        memset(str, 0, 64);
        sprintf(str, "%pU", mddev->uuid);
        ret = dlm_new_lockspace(str, mddev->bitmap_info.cluster_name,
                                DLM_LSFL_FS, LVB_SIZE,
                                &md_ls_ops, mddev, &ops_rv, &cinfo->lockspace);
        if (ret)
                goto err;
        wait_for_completion(&cinfo->completion);
        if (nodes < cinfo->slot_number) {
                pr_err("md-cluster: Slot allotted(%d) is greater than available slots(%d).",
                        cinfo->slot_number, nodes);
                ret = -ERANGE;
                goto err;
        }
        /* Initiate the communication resources */
        ret = -ENOMEM;
        cinfo->recv_thread = md_register_thread(recv_daemon, mddev, "cluster_recv");
        if (!cinfo->recv_thread) {
                pr_err("md-cluster: cannot allocate memory for recv_thread!\n");
                goto err;
        }
        cinfo->message_lockres = lockres_init(mddev, "message", NULL, 1);
        if (!cinfo->message_lockres)
                goto err;
        cinfo->token_lockres = lockres_init(mddev, "token", NULL, 0);
        if (!cinfo->token_lockres)
                goto err;
        cinfo->no_new_dev_lockres = lockres_init(mddev, "no-new-dev", NULL, 0);
        if (!cinfo->no_new_dev_lockres)
                goto err;

        ret = dlm_lock_sync(cinfo->token_lockres, DLM_LOCK_EX);
        if (ret) {
                ret = -EAGAIN;
                pr_err("md-cluster: can't join cluster to avoid lock issue\n");
                goto err;
        }
        cinfo->ack_lockres = lockres_init(mddev, "ack", ack_bast, 0);
        if (!cinfo->ack_lockres) {
                ret = -ENOMEM;
                goto err;
        }
        /* get sync CR lock on ACK. */
        if (dlm_lock_sync(cinfo->ack_lockres, DLM_LOCK_CR))
                pr_err("md-cluster: failed to get a sync CR lock on ACK!(%d)\n",
                                ret);
        dlm_unlock_sync(cinfo->token_lockres);
        /* get sync CR lock on no-new-dev. */
        if (dlm_lock_sync(cinfo->no_new_dev_lockres, DLM_LOCK_CR))
                pr_err("md-cluster: failed to get a sync CR lock on no-new-dev!(%d)\n", ret);


        pr_info("md-cluster: Joined cluster %s slot %d\n", str, cinfo->slot_number);
        snprintf(str, 64, "bitmap%04d", cinfo->slot_number - 1);
        cinfo->bitmap_lockres = lockres_init(mddev, str, NULL, 1);
        if (!cinfo->bitmap_lockres) {
                ret = -ENOMEM;
                goto err;
        }
        if (dlm_lock_sync(cinfo->bitmap_lockres, DLM_LOCK_PW)) {
                pr_err("Failed to get bitmap lock\n");
                ret = -EINVAL;
                goto err;
        }

        cinfo->resync_lockres = lockres_init(mddev, "resync", NULL, 0);
        if (!cinfo->resync_lockres) {
                ret = -ENOMEM;
                goto err;
        }

        return 0;
err:
        md_unregister_thread(&cinfo->recovery_thread);
        md_unregister_thread(&cinfo->recv_thread);
        lockres_free(cinfo->message_lockres);
        lockres_free(cinfo->token_lockres);
        lockres_free(cinfo->ack_lockres);
        lockres_free(cinfo->no_new_dev_lockres);
        lockres_free(cinfo->resync_lockres);
        lockres_free(cinfo->bitmap_lockres);
        if (cinfo->lockspace)
                dlm_release_lockspace(cinfo->lockspace, 2);
        mddev->cluster_info = NULL;
        kfree(cinfo);
        return ret;
}

static void load_bitmaps(struct mddev *mddev, int total_slots)
{
        struct md_cluster_info *cinfo = mddev->cluster_info;

        /* load all the node's bitmap info for resync */
        if (gather_all_resync_info(mddev, total_slots))
                pr_err("md-cluster: failed to gather all resyn infos\n");
        set_bit(MD_CLUSTER_ALREADY_IN_CLUSTER, &cinfo->state);
        /* wake up recv thread in case something need to be handled */
        if (test_and_clear_bit(MD_CLUSTER_PENDING_RECV_EVENT, &cinfo->state))
                md_wakeup_thread(cinfo->recv_thread);
}

static void resync_bitmap(struct mddev *mddev)
{
        struct md_cluster_info *cinfo = mddev->cluster_info;
        struct cluster_msg cmsg = {0};
        int err;

        cmsg.type = cpu_to_le32(BITMAP_NEEDS_SYNC);
        err = sendmsg(cinfo, &cmsg);
        if (err)
                pr_err("%s:%d: failed to send BITMAP_NEEDS_SYNC message (%d)\n",
                        __func__, __LINE__, err);
}

static void unlock_all_bitmaps(struct mddev *mddev);
static int leave(struct mddev *mddev)
{
        struct md_cluster_info *cinfo = mddev->cluster_info;

        if (!cinfo)
                return 0;

        /* BITMAP_NEEDS_SYNC message should be sent when node
         * is leaving the cluster with dirty bitmap, also we
         * can only deliver it when dlm connection is available */
        if (cinfo->slot_number > 0 && mddev->recovery_cp != MaxSector)
                resync_bitmap(mddev);

        md_unregister_thread(&cinfo->recovery_thread);
        md_unregister_thread(&cinfo->recv_thread);
        lockres_free(cinfo->message_lockres);
        lockres_free(cinfo->token_lockres);
        lockres_free(cinfo->ack_lockres);
        lockres_free(cinfo->no_new_dev_lockres);
        lockres_free(cinfo->resync_lockres);
        lockres_free(cinfo->bitmap_lockres);
        unlock_all_bitmaps(mddev);
        dlm_release_lockspace(cinfo->lockspace, 2);
        kfree(cinfo);
        return 0;
}

/* slot_number(): Returns the MD slot number to use
 * DLM starts the slot numbers from 1, wheras cluster-md
 * wants the number to be from zero, so we deduct one
 */
static int slot_number(struct mddev *mddev)
{
        struct md_cluster_info *cinfo = mddev->cluster_info;

        return cinfo->slot_number - 1;
}

/*
 * Check if the communication is already locked, else lock the communication
 * channel.
 * If it is already locked, token is in EX mode, and hence lock_token()
 * should not be called.
 */
static int metadata_update_start(struct mddev *mddev)
{
        struct md_cluster_info *cinfo = mddev->cluster_info;

        wait_event(cinfo->wait,
                   !test_and_set_bit(MD_CLUSTER_SEND_LOCK, &cinfo->state) ||
                   test_and_clear_bit(MD_CLUSTER_SEND_LOCKED_ALREADY, &cinfo->state));

        /* If token is already locked, return 0 */
        if (cinfo->token_lockres->mode == DLM_LOCK_EX)
                return 0;

        return lock_token(cinfo);
}

static int metadata_update_finish(struct mddev *mddev)
{
        struct md_cluster_info *cinfo = mddev->cluster_info;
        struct cluster_msg cmsg;
        struct md_rdev *rdev;
        int ret = 0;
        int raid_slot = -1;

        memset(&cmsg, 0, sizeof(cmsg));
        cmsg.type = cpu_to_le32(METADATA_UPDATED);
        /* Pick up a good active device number to send.
         */
        rdev_for_each(rdev, mddev)
                if (rdev->raid_disk > -1 && !test_bit(Faulty, &rdev->flags)) {
                        raid_slot = rdev->desc_nr;
                        break;
                }
        if (raid_slot >= 0) {
                cmsg.raid_slot = cpu_to_le32(raid_slot);
                ret = __sendmsg(cinfo, &cmsg);
        } else
                pr_warn("md-cluster: No good device id found to send\n");
        clear_bit(MD_CLUSTER_SEND_LOCKED_ALREADY, &cinfo->state);
        unlock_comm(cinfo);
        return ret;
}

static void metadata_update_cancel(struct mddev *mddev)
{
        struct md_cluster_info *cinfo = mddev->cluster_info;
        clear_bit(MD_CLUSTER_SEND_LOCKED_ALREADY, &cinfo->state);
        unlock_comm(cinfo);
}

static int resync_start(struct mddev *mddev)
{
        struct md_cluster_info *cinfo = mddev->cluster_info;
        return dlm_lock_sync_interruptible(cinfo->resync_lockres, DLM_LOCK_EX, mddev);
}

static int resync_info_update(struct mddev *mddev, sector_t lo, sector_t hi)
{
        struct md_cluster_info *cinfo = mddev->cluster_info;
        struct resync_info ri;
        struct cluster_msg cmsg = {0};

        /* do not send zero again, if we have sent before */
        if (hi == 0) {
                memcpy(&ri, cinfo->bitmap_lockres->lksb.sb_lvbptr, sizeof(struct resync_info));
                if (le64_to_cpu(ri.hi) == 0)
                        return 0;
        }

        add_resync_info(cinfo->bitmap_lockres, lo, hi);
        /* Re-acquire the lock to refresh LVB */
        dlm_lock_sync(cinfo->bitmap_lockres, DLM_LOCK_PW);
        cmsg.type = cpu_to_le32(RESYNCING);
        cmsg.low = cpu_to_le64(lo);
        cmsg.high = cpu_to_le64(hi);

        return sendmsg(cinfo, &cmsg);
}

static int resync_finish(struct mddev *mddev)
{
        struct md_cluster_info *cinfo = mddev->cluster_info;
        dlm_unlock_sync(cinfo->resync_lockres);
        return resync_info_update(mddev, 0, 0);
}

static int area_resyncing(struct mddev *mddev, int direction,
                sector_t lo, sector_t hi)
{
        struct md_cluster_info *cinfo = mddev->cluster_info;
        int ret = 0;
        struct suspend_info *s;

        if ((direction == READ) &&
                test_bit(MD_CLUSTER_SUSPEND_READ_BALANCING, &cinfo->state))
                return 1;

        spin_lock_irq(&cinfo->suspend_lock);
        if (list_empty(&cinfo->suspend_list))
                goto out;
        list_for_each_entry(s, &cinfo->suspend_list, list)
                if (hi > s->lo && lo < s->hi) {
                        ret = 1;
                        break;
                }
out:
        spin_unlock_irq(&cinfo->suspend_lock);
        return ret;
}

/* add_new_disk() - initiates a disk add
 * However, if this fails before writing md_update_sb(),
 * add_new_disk_cancel() must be called to release token lock
 */
static int add_new_disk(struct mddev *mddev, struct md_rdev *rdev)
{
        struct md_cluster_info *cinfo = mddev->cluster_info;
        struct cluster_msg cmsg;
        int ret = 0;
        struct mdp_superblock_1 *sb = page_address(rdev->sb_page);
        char *uuid = sb->device_uuid;

        memset(&cmsg, 0, sizeof(cmsg));
        cmsg.type = cpu_to_le32(NEWDISK);
        memcpy(cmsg.uuid, uuid, 16);
        cmsg.raid_slot = cpu_to_le32(rdev->desc_nr);
        lock_comm(cinfo);
        ret = __sendmsg(cinfo, &cmsg);
        if (ret)
                return ret;
        cinfo->no_new_dev_lockres->flags |= DLM_LKF_NOQUEUE;
        ret = dlm_lock_sync(cinfo->no_new_dev_lockres, DLM_LOCK_EX);
        cinfo->no_new_dev_lockres->flags &= ~DLM_LKF_NOQUEUE;
        /* Some node does not "see" the device */
        if (ret == -EAGAIN)
                ret = -ENOENT;
        if (ret)
                unlock_comm(cinfo);
        else {
                dlm_lock_sync(cinfo->no_new_dev_lockres, DLM_LOCK_CR);
                /* Since MD_CHANGE_DEVS will be set in add_bound_rdev which
                 * will run soon after add_new_disk, the below path will be
                 * invoked:
                 *   md_wakeup_thread(mddev->thread)
                 *      -> conf->thread (raid1d)
                 *      -> md_check_recovery -> md_update_sb
                 *      -> metadata_update_start/finish
                 * MD_CLUSTER_SEND_LOCKED_ALREADY will be cleared eventually.
                 *
                 * For other failure cases, metadata_update_cancel and
                 * add_new_disk_cancel also clear below bit as well.
                 * */
                set_bit(MD_CLUSTER_SEND_LOCKED_ALREADY, &cinfo->state);
                wake_up(&cinfo->wait);
        }
        return ret;
}

static void add_new_disk_cancel(struct mddev *mddev)
{
        struct md_cluster_info *cinfo = mddev->cluster_info;
        clear_bit(MD_CLUSTER_SEND_LOCKED_ALREADY, &cinfo->state);
        unlock_comm(cinfo);
}

static int new_disk_ack(struct mddev *mddev, bool ack)
{
        struct md_cluster_info *cinfo = mddev->cluster_info;

        if (!test_bit(MD_CLUSTER_WAITING_FOR_NEWDISK, &cinfo->state)) {
                pr_warn("md-cluster(%s): Spurious cluster confirmation\n", mdname(mddev));
                return -EINVAL;
        }

        if (ack)
                dlm_unlock_sync(cinfo->no_new_dev_lockres);
        complete(&cinfo->newdisk_completion);
        return 0;
}

static int remove_disk(struct mddev *mddev, struct md_rdev *rdev)
{
        struct cluster_msg cmsg = {0};
        struct md_cluster_info *cinfo = mddev->cluster_info;
        cmsg.type = cpu_to_le32(REMOVE);
        cmsg.raid_slot = cpu_to_le32(rdev->desc_nr);
        return sendmsg(cinfo, &cmsg);
}

static int lock_all_bitmaps(struct mddev *mddev)
{
        int slot, my_slot, ret, held = 1, i = 0;
        char str[64];
        struct md_cluster_info *cinfo = mddev->cluster_info;

        cinfo->other_bitmap_lockres = kzalloc((mddev->bitmap_info.nodes - 1) *
                                             sizeof(struct dlm_lock_resource *),
                                             GFP_KERNEL);
        if (!cinfo->other_bitmap_lockres) {
                pr_err("md: can't alloc mem for other bitmap locks\n");
                return 0;
        }

        my_slot = slot_number(mddev);
        for (slot = 0; slot < mddev->bitmap_info.nodes; slot++) {
                if (slot == my_slot)
                        continue;

                memset(str, '\0', 64);
                snprintf(str, 64, "bitmap%04d", slot);
                cinfo->other_bitmap_lockres[i] = lockres_init(mddev, str, NULL, 1);
                if (!cinfo->other_bitmap_lockres[i])
                        return -ENOMEM;

                cinfo->other_bitmap_lockres[i]->flags |= DLM_LKF_NOQUEUE;
                ret = dlm_lock_sync(cinfo->other_bitmap_lockres[i], DLM_LOCK_PW);
                if (ret)
                        held = -1;
                i++;
        }

        return held;
}

static void unlock_all_bitmaps(struct mddev *mddev)
{
        struct md_cluster_info *cinfo = mddev->cluster_info;
        int i;

        /* release other node's bitmap lock if they are existed */
        if (cinfo->other_bitmap_lockres) {
                for (i = 0; i < mddev->bitmap_info.nodes - 1; i++) {
                        if (cinfo->other_bitmap_lockres[i]) {
                                lockres_free(cinfo->other_bitmap_lockres[i]);
                        }
                }
                kfree(cinfo->other_bitmap_lockres);
        }
}

static int gather_bitmaps(struct md_rdev *rdev)
{
        int sn, err;
        sector_t lo, hi;
        struct cluster_msg cmsg = {0};
        struct mddev *mddev = rdev->mddev;
        struct md_cluster_info *cinfo = mddev->cluster_info;

        cmsg.type = cpu_to_le32(RE_ADD);
        cmsg.raid_slot = cpu_to_le32(rdev->desc_nr);
        err = sendmsg(cinfo, &cmsg);
        if (err)
                goto out;

        for (sn = 0; sn < mddev->bitmap_info.nodes; sn++) {
                if (sn == (cinfo->slot_number - 1))
                        continue;
                err = bitmap_copy_from_slot(mddev, sn, &lo, &hi, false);
                if (err) {
                        pr_warn("md-cluster: Could not gather bitmaps from slot %d", sn);
                        goto out;
                }
                if ((hi > 0) && (lo < mddev->recovery_cp))
                        mddev->recovery_cp = lo;
        }
out:
        return err;
}

static struct md_cluster_operations cluster_ops = {
        .join   = join,
        .leave  = leave,
        .slot_number = slot_number,
        .resync_start = resync_start,
        .resync_finish = resync_finish,
        .resync_info_update = resync_info_update,
        .metadata_update_start = metadata_update_start,
        .metadata_update_finish = metadata_update_finish,
        .metadata_update_cancel = metadata_update_cancel,
        .area_resyncing = area_resyncing,
        .add_new_disk = add_new_disk,
        .add_new_disk_cancel = add_new_disk_cancel,
        .new_disk_ack = new_disk_ack,
        .remove_disk = remove_disk,
        .load_bitmaps = load_bitmaps,
        .gather_bitmaps = gather_bitmaps,
        .lock_all_bitmaps = lock_all_bitmaps,
        .unlock_all_bitmaps = unlock_all_bitmaps,
};

static int __init cluster_init(void)
{
        pr_warn("md-cluster: EXPERIMENTAL. Use with caution\n");
        pr_info("Registering Cluster MD functions\n");
        register_md_cluster_operations(&cluster_ops, THIS_MODULE);
        return 0;
}

static void cluster_exit(void)
{
        unregister_md_cluster_operations();
}

module_init(cluster_init);
module_exit(cluster_exit);
MODULE_AUTHOR("SUSE");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Clustering support for MD");