/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2009-2010 The FreeBSD Foundation
 * Copyright (c) 2010 Pawel Jakub Dawidek <pjd@FreeBSD.org>
 * All rights reserved.
 *
 * This software was developed by Pawel Jakub Dawidek under sponsorship from
 * the FreeBSD Foundation.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/param.h>
#include <sys/time.h>
#include <sys/bio.h>
#include <sys/disk.h>
#include <sys/stat.h>

#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <libgeom.h>
#include <pthread.h>
#include <signal.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <sysexits.h>
#include <unistd.h>

#include <activemap.h>
#include <nv.h>
#include <pjdlog.h>

#include "control.h"
#include "event.h"
#include "hast.h"
#include "hast_proto.h"
#include "hastd.h"
#include "hooks.h"
#include "metadata.h"
#include "proto.h"
#include "subr.h"
#include "synch.h"

struct hio {
        uint64_t         hio_seq;
        int              hio_error;
        void            *hio_data;
        uint8_t          hio_cmd;
        uint64_t         hio_offset;
        uint64_t         hio_length;
        bool             hio_memsync;
        TAILQ_ENTRY(hio) hio_next;
};

static struct hast_resource *gres;

/*
 * Free list holds unused structures. When free list is empty, we have to wait
 * until some in-progress requests are freed.
 */
static TAILQ_HEAD(, hio) hio_free_list;
static size_t hio_free_list_size;
static pthread_mutex_t hio_free_list_lock;
static pthread_cond_t hio_free_list_cond;
/*
 * Disk thread (the one that does I/O requests) takes requests from this list.
 */
static TAILQ_HEAD(, hio) hio_disk_list;
static size_t hio_disk_list_size;
static pthread_mutex_t hio_disk_list_lock;
static pthread_cond_t hio_disk_list_cond;
/*
 * Thread that sends requests back to primary takes requests from this list.
 */
static TAILQ_HEAD(, hio) hio_send_list;
static size_t hio_send_list_size;
static pthread_mutex_t hio_send_list_lock;
static pthread_cond_t hio_send_list_cond;

/*
 * Maximum number of outstanding I/O requests.
 */
#define HAST_HIO_MAX    256

static void *recv_thread(void *arg);
static void *disk_thread(void *arg);
static void *send_thread(void *arg);

#define QUEUE_INSERT(name, hio) do {                                    \
        mtx_lock(&hio_##name##_list_lock);                              \
        if (TAILQ_EMPTY(&hio_##name##_list))                            \
                cv_broadcast(&hio_##name##_list_cond);                  \
        TAILQ_INSERT_TAIL(&hio_##name##_list, (hio), hio_next);         \
        hio_##name##_list_size++;                                       \
        mtx_unlock(&hio_##name##_list_lock);                            \
} while (0)
#define QUEUE_TAKE(name, hio)   do {                                    \
        mtx_lock(&hio_##name##_list_lock);                              \
        while (((hio) = TAILQ_FIRST(&hio_##name##_list)) == NULL) {     \
                cv_wait(&hio_##name##_list_cond,                        \
                    &hio_##name##_list_lock);                           \
        }                                                               \
        PJDLOG_ASSERT(hio_##name##_list_size != 0);                     \
        hio_##name##_list_size--;                                       \
        TAILQ_REMOVE(&hio_##name##_list, (hio), hio_next);              \
        mtx_unlock(&hio_##name##_list_lock);                            \
} while (0)

static void
output_status_aux(struct nv *nvout)
{

        nv_add_uint64(nvout, (uint64_t)hio_free_list_size, "idle_queue_size");
        nv_add_uint64(nvout, (uint64_t)hio_disk_list_size, "local_queue_size");
        nv_add_uint64(nvout, (uint64_t)hio_send_list_size, "send_queue_size");
}

static void
hio_clear(struct hio *hio)
{

        hio->hio_seq = 0;
        hio->hio_error = 0;
        hio->hio_cmd = HIO_UNDEF;
        hio->hio_offset = 0;
        hio->hio_length = 0;
        hio->hio_memsync = false;
}

static void
hio_copy(const struct hio *srchio, struct hio *dsthio)
{

        /*
         * We don't copy hio_error, hio_data and hio_next fields.
         */

        dsthio->hio_seq = srchio->hio_seq;
        dsthio->hio_cmd = srchio->hio_cmd;
        dsthio->hio_offset = srchio->hio_offset;
        dsthio->hio_length = srchio->hio_length;
        dsthio->hio_memsync = srchio->hio_memsync;
}

static void
init_environment(void)
{
        struct hio *hio;
        unsigned int ii;

        /*
         * Initialize lists, their locks and theirs condition variables.
         */
        TAILQ_INIT(&hio_free_list);
        mtx_init(&hio_free_list_lock);
        cv_init(&hio_free_list_cond);
        TAILQ_INIT(&hio_disk_list);
        mtx_init(&hio_disk_list_lock);
        cv_init(&hio_disk_list_cond);
        TAILQ_INIT(&hio_send_list);
        mtx_init(&hio_send_list_lock);
        cv_init(&hio_send_list_cond);

        /*
         * Allocate requests pool and initialize requests.
         */
        for (ii = 0; ii < HAST_HIO_MAX; ii++) {
                hio = malloc(sizeof(*hio));
                if (hio == NULL) {
                        pjdlog_exitx(EX_TEMPFAIL,
                            "Unable to allocate memory (%zu bytes) for hio request.",
                            sizeof(*hio));
                }
                hio->hio_data = malloc(MAXPHYS);
                if (hio->hio_data == NULL) {
                        pjdlog_exitx(EX_TEMPFAIL,
                            "Unable to allocate memory (%zu bytes) for gctl_data.",
                            (size_t)MAXPHYS);
                }
                hio_clear(hio);
                TAILQ_INSERT_HEAD(&hio_free_list, hio, hio_next);
                hio_free_list_size++;
        }
}

static void
init_local(struct hast_resource *res)
{

        if (metadata_read(res, true) == -1)
                exit(EX_NOINPUT);
}

static void
init_remote(struct hast_resource *res, struct nv *nvin)
{
        uint64_t resuid;
        struct nv *nvout;
        unsigned char *map;
        size_t mapsize;

#ifdef notyet
        /* Setup direction. */
        if (proto_send(res->hr_remoteout, NULL, 0) == -1)
                pjdlog_errno(LOG_WARNING, "Unable to set connection direction");
#endif

        nvout = nv_alloc();
        nv_add_int64(nvout, (int64_t)res->hr_datasize, "datasize");
        nv_add_int32(nvout, (int32_t)res->hr_extentsize, "extentsize");
        resuid = nv_get_uint64(nvin, "resuid");
        res->hr_primary_localcnt = nv_get_uint64(nvin, "localcnt");
        res->hr_primary_remotecnt = nv_get_uint64(nvin, "remotecnt");
        nv_add_uint64(nvout, res->hr_secondary_localcnt, "localcnt");
        nv_add_uint64(nvout, res->hr_secondary_remotecnt, "remotecnt");
        mapsize = activemap_calc_ondisk_size(res->hr_local_mediasize -
            METADATA_SIZE, res->hr_extentsize, res->hr_local_sectorsize);
        map = malloc(mapsize);
        if (map == NULL) {
                pjdlog_exitx(EX_TEMPFAIL,
                    "Unable to allocate memory (%zu bytes) for activemap.",
                    mapsize);
        }
        /*
         * When we work as primary and secondary is missing we will increase
         * localcnt in our metadata. When secondary is connected and synced
         * we make localcnt be equal to remotecnt, which means nodes are more
         * or less in sync.
         * Split-brain condition is when both nodes are not able to communicate
         * and are both configured as primary nodes. In turn, they can both
         * make incompatible changes to the data and we have to detect that.
         * Under split-brain condition we will increase our localcnt on first
         * write and remote node will increase its localcnt on first write.
         * When we connect we can see that primary's localcnt is greater than
         * our remotecnt (primary was modified while we weren't watching) and
         * our localcnt is greater than primary's remotecnt (we were modified
         * while primary wasn't watching).
         * There are many possible combinations which are all gathered below.
         * Don't pay too much attention to exact numbers, the more important
         * is to compare them. We compare secondary's local with primary's
         * remote and secondary's remote with primary's local.
         * Note that every case where primary's localcnt is smaller than
         * secondary's remotecnt and where secondary's localcnt is smaller than
         * primary's remotecnt should be impossible in practise. We will perform
         * full synchronization then. Those cases are marked with an asterisk.
         * Regular synchronization means that only extents marked as dirty are
         * synchronized (regular synchronization).
         *
         * SECONDARY METADATA PRIMARY METADATA
         * local=3 remote=3   local=2 remote=2*  ?! Full sync from secondary.
         * local=3 remote=3   local=2 remote=3*  ?! Full sync from primary.
         * local=3 remote=3   local=2 remote=4*  ?! Full sync from primary.
         * local=3 remote=3   local=3 remote=2   Primary is out-of-date,
         *                                       regular sync from secondary.
         * local=3 remote=3   local=3 remote=3   Regular sync just in case.
         * local=3 remote=3   local=3 remote=4*  ?! Full sync from primary.
         * local=3 remote=3   local=4 remote=2   Split-brain condition.
         * local=3 remote=3   local=4 remote=3   Secondary out-of-date,
         *                                       regular sync from primary.
         * local=3 remote=3   local=4 remote=4*  ?! Full sync from primary.
         */
        if (res->hr_resuid == 0) {
                /*
                 * Provider is used for the first time. If primary node done no
                 * writes yet as well (we will find "virgin" argument) then
                 * there is no need to synchronize anything. If primary node
                 * done any writes already we have to synchronize everything.
                 */
                PJDLOG_ASSERT(res->hr_secondary_localcnt == 0);
                res->hr_resuid = resuid;
                if (metadata_write(res) == -1)
                        exit(EX_NOINPUT);
                if (nv_exists(nvin, "virgin")) {
                        free(map);
                        map = NULL;
                        mapsize = 0;
                } else {
                        memset(map, 0xff, mapsize);
                }
                nv_add_int8(nvout, 1, "virgin");
                nv_add_uint8(nvout, HAST_SYNCSRC_PRIMARY, "syncsrc");
        } else if (res->hr_resuid != resuid) {
                char errmsg[256];

                free(map);
                (void)snprintf(errmsg, sizeof(errmsg),
                    "Resource unique ID mismatch (primary=%ju, secondary=%ju).",
                    (uintmax_t)resuid, (uintmax_t)res->hr_resuid);
                pjdlog_error("%s", errmsg);
                nv_add_string(nvout, errmsg, "errmsg");
                if (hast_proto_send(res, res->hr_remotein, nvout,
                    NULL, 0) == -1) {
                        pjdlog_exit(EX_TEMPFAIL,
                            "Unable to send response to %s",
                            res->hr_remoteaddr);
                }
                nv_free(nvout);
                exit(EX_CONFIG);
        } else if (
            /* Is primary out-of-date? */
            (res->hr_secondary_localcnt > res->hr_primary_remotecnt &&
             res->hr_secondary_remotecnt == res->hr_primary_localcnt) ||
            /* Are the nodes more or less in sync? */
            (res->hr_secondary_localcnt == res->hr_primary_remotecnt &&
             res->hr_secondary_remotecnt == res->hr_primary_localcnt) ||
            /* Is secondary out-of-date? */
            (res->hr_secondary_localcnt == res->hr_primary_remotecnt &&
             res->hr_secondary_remotecnt < res->hr_primary_localcnt)) {
                /*
                 * Nodes are more or less in sync or one of the nodes is
                 * out-of-date.
                 * It doesn't matter at this point which one, we just have to
                 * send out local bitmap to the remote node.
                 */
                if (pread(res->hr_localfd, map, mapsize, METADATA_SIZE) !=
                    (ssize_t)mapsize) {
                        pjdlog_exit(LOG_ERR, "Unable to read activemap");
                }
                if (res->hr_secondary_localcnt > res->hr_primary_remotecnt &&
                     res->hr_secondary_remotecnt == res->hr_primary_localcnt) {
                        /* Primary is out-of-date, sync from secondary. */
                        nv_add_uint8(nvout, HAST_SYNCSRC_SECONDARY, "syncsrc");
                } else {
                        /*
                         * Secondary is out-of-date or counts match.
                         * Sync from primary.
                         */
                        nv_add_uint8(nvout, HAST_SYNCSRC_PRIMARY, "syncsrc");
                }
        } else if (res->hr_secondary_localcnt > res->hr_primary_remotecnt &&
             res->hr_primary_localcnt > res->hr_secondary_remotecnt) {
                /*
                 * Not good, we have split-brain condition.
                 */
                free(map);
                pjdlog_error("Split-brain detected, exiting.");
                nv_add_string(nvout, "Split-brain condition!", "errmsg");
                if (hast_proto_send(res, res->hr_remotein, nvout,
                    NULL, 0) == -1) {
                        pjdlog_exit(EX_TEMPFAIL,
                            "Unable to send response to %s",
                            res->hr_remoteaddr);
                }
                nv_free(nvout);
                /* Exit on split-brain. */
                event_send(res, EVENT_SPLITBRAIN);
                exit(EX_CONFIG);
        } else /* if (res->hr_secondary_localcnt < res->hr_primary_remotecnt ||
            res->hr_primary_localcnt < res->hr_secondary_remotecnt) */ {
                /*
                 * This should never happen in practise, but we will perform
                 * full synchronization.
                 */
                PJDLOG_ASSERT(res->hr_secondary_localcnt < res->hr_primary_remotecnt ||
                    res->hr_primary_localcnt < res->hr_secondary_remotecnt);
                mapsize = activemap_calc_ondisk_size(res->hr_local_mediasize -
                    METADATA_SIZE, res->hr_extentsize,
                    res->hr_local_sectorsize);
                memset(map, 0xff, mapsize);
                if (res->hr_secondary_localcnt > res->hr_primary_remotecnt) {
                        /* In this one of five cases sync from secondary. */
                        nv_add_uint8(nvout, HAST_SYNCSRC_SECONDARY, "syncsrc");
                } else {
                        /* For the rest four cases sync from primary. */
                        nv_add_uint8(nvout, HAST_SYNCSRC_PRIMARY, "syncsrc");
                }
                pjdlog_warning("This should never happen, asking for full synchronization (primary(local=%ju, remote=%ju), secondary(local=%ju, remote=%ju)).",
                    (uintmax_t)res->hr_primary_localcnt,
                    (uintmax_t)res->hr_primary_remotecnt,
                    (uintmax_t)res->hr_secondary_localcnt,
                    (uintmax_t)res->hr_secondary_remotecnt);
        }
        nv_add_uint32(nvout, (uint32_t)mapsize, "mapsize");
        if (hast_proto_send(res, res->hr_remotein, nvout, map, mapsize) == -1) {
                pjdlog_exit(EX_TEMPFAIL, "Unable to send activemap to %s",
                    res->hr_remoteaddr);
        }
        if (map != NULL)
                free(map);
        nv_free(nvout);
#ifdef notyet
        /* Setup direction. */
        if (proto_recv(res->hr_remotein, NULL, 0) == -1)
                pjdlog_errno(LOG_WARNING, "Unable to set connection direction");
#endif
}

void
hastd_secondary(struct hast_resource *res, struct nv *nvin)
{
        sigset_t mask;
        pthread_t td;
        pid_t pid;
        int error, mode, debuglevel;

        /*
         * Create communication channel between parent and child.
         */
        if (proto_client(NULL, "socketpair://", &res->hr_ctrl) == -1) {
                KEEP_ERRNO((void)pidfile_remove(pfh));
                pjdlog_exit(EX_OSERR,
                    "Unable to create control sockets between parent and child");
        }
        /*
         * Create communication channel between child and parent.
         */
        if (proto_client(NULL, "socketpair://", &res->hr_event) == -1) {
                KEEP_ERRNO((void)pidfile_remove(pfh));
                pjdlog_exit(EX_OSERR,
                    "Unable to create event sockets between child and parent");
        }

        pid = fork();
        if (pid == -1) {
                KEEP_ERRNO((void)pidfile_remove(pfh));
                pjdlog_exit(EX_OSERR, "Unable to fork");
        }

        if (pid > 0) {
                /* This is parent. */
                proto_close(res->hr_remotein);
                res->hr_remotein = NULL;
                proto_close(res->hr_remoteout);
                res->hr_remoteout = NULL;
                /* Declare that we are receiver. */
                proto_recv(res->hr_event, NULL, 0);
                /* Declare that we are sender. */
                proto_send(res->hr_ctrl, NULL, 0);
                res->hr_workerpid = pid;
                return;
        }

        gres = res;
        res->output_status_aux = output_status_aux;
        mode = pjdlog_mode_get();
        debuglevel = pjdlog_debug_get();

        /* Declare that we are sender. */
        proto_send(res->hr_event, NULL, 0);
        /* Declare that we are receiver. */
        proto_recv(res->hr_ctrl, NULL, 0);
        descriptors_cleanup(res);

        descriptors_assert(res, mode);

        pjdlog_init(mode);
        pjdlog_debug_set(debuglevel);
        pjdlog_prefix_set("[%s] (%s) ", res->hr_name, role2str(res->hr_role));
        setproctitle("%s (%s)", res->hr_name, role2str(res->hr_role));

        PJDLOG_VERIFY(sigemptyset(&mask) == 0);
        PJDLOG_VERIFY(sigprocmask(SIG_SETMASK, &mask, NULL) == 0);

        /* Error in setting timeout is not critical, but why should it fail? */
        if (proto_timeout(res->hr_remotein, 2 * HAST_KEEPALIVE) == -1)
                pjdlog_errno(LOG_WARNING, "Unable to set connection timeout");
        if (proto_timeout(res->hr_remoteout, res->hr_timeout) == -1)
                pjdlog_errno(LOG_WARNING, "Unable to set connection timeout");

        init_local(res);
        init_environment();

        if (drop_privs(res) != 0)
                exit(EX_CONFIG);
        pjdlog_info("Privileges successfully dropped.");

        /*
         * Create the control thread before sending any event to the parent,
         * as we can deadlock when parent sends control request to worker,
         * but worker has no control thread started yet, so parent waits.
         * In the meantime worker sends an event to the parent, but parent
         * is unable to handle the event, because it waits for control
         * request response.
         */
        error = pthread_create(&td, NULL, ctrl_thread, res);
        PJDLOG_ASSERT(error == 0);

        init_remote(res, nvin);
        event_send(res, EVENT_CONNECT);

        error = pthread_create(&td, NULL, recv_thread, res);
        PJDLOG_ASSERT(error == 0);
        error = pthread_create(&td, NULL, disk_thread, res);
        PJDLOG_ASSERT(error == 0);
        (void)send_thread(res);
}

static void
reqlog(int loglevel, int debuglevel, int error, struct hio *hio,
    const char *fmt, ...)
{
        char msg[1024];
        va_list ap;
        int len;

        va_start(ap, fmt);
        len = vsnprintf(msg, sizeof(msg), fmt, ap);
        va_end(ap);
        if ((size_t)len < sizeof(msg)) {
                switch (hio->hio_cmd) {
                case HIO_READ:
                        (void)snprintf(msg + len, sizeof(msg) - len,
                            "READ(%ju, %ju).", (uintmax_t)hio->hio_offset,
                            (uintmax_t)hio->hio_length);
                        break;
                case HIO_DELETE:
                        (void)snprintf(msg + len, sizeof(msg) - len,
                            "DELETE(%ju, %ju).", (uintmax_t)hio->hio_offset,
                            (uintmax_t)hio->hio_length);
                        break;
                case HIO_FLUSH:
                        (void)snprintf(msg + len, sizeof(msg) - len, "FLUSH.");
                        break;
                case HIO_WRITE:
                        (void)snprintf(msg + len, sizeof(msg) - len,
                            "WRITE(%ju, %ju).", (uintmax_t)hio->hio_offset,
                            (uintmax_t)hio->hio_length);
                        break;
                case HIO_KEEPALIVE:
                        (void)snprintf(msg + len, sizeof(msg) - len, "KEEPALIVE.");
                        break;
                default:
                        (void)snprintf(msg + len, sizeof(msg) - len,
                            "UNKNOWN(%u).", (unsigned int)hio->hio_cmd);
                        break;
                }
        }
        pjdlog_common(loglevel, debuglevel, error, "%s", msg);
}

static int
requnpack(struct hast_resource *res, struct hio *hio, struct nv *nv)
{

        hio->hio_cmd = nv_get_uint8(nv, "cmd");
        if (hio->hio_cmd == 0) {
                pjdlog_error("Header contains no 'cmd' field.");
                hio->hio_error = EINVAL;
                goto end;
        }
        if (hio->hio_cmd != HIO_KEEPALIVE) {
                hio->hio_seq = nv_get_uint64(nv, "seq");
                if (hio->hio_seq == 0) {
                        pjdlog_error("Header contains no 'seq' field.");
                        hio->hio_error = EINVAL;
                        goto end;
                }
        }
        switch (hio->hio_cmd) {
        case HIO_FLUSH:
        case HIO_KEEPALIVE:
                break;
        case HIO_WRITE:
                hio->hio_memsync = nv_exists(nv, "memsync");
                /* FALLTHROUGH */
        case HIO_READ:
        case HIO_DELETE:
                hio->hio_offset = nv_get_uint64(nv, "offset");
                if (nv_error(nv) != 0) {
                        pjdlog_error("Header is missing 'offset' field.");
                        hio->hio_error = EINVAL;
                        goto end;
                }
                hio->hio_length = nv_get_uint64(nv, "length");
                if (nv_error(nv) != 0) {
                        pjdlog_error("Header is missing 'length' field.");
                        hio->hio_error = EINVAL;
                        goto end;
                }
                if (hio->hio_length == 0) {
                        pjdlog_error("Data length is zero.");
                        hio->hio_error = EINVAL;
                        goto end;
                }
                if (hio->hio_cmd != HIO_DELETE && hio->hio_length > MAXPHYS) {
                        pjdlog_error("Data length is too large (%ju > %ju).",
                            (uintmax_t)hio->hio_length, (uintmax_t)MAXPHYS);
                        hio->hio_error = EINVAL;
                        goto end;
                }
                if ((hio->hio_offset % res->hr_local_sectorsize) != 0) {
                        pjdlog_error("Offset %ju is not multiple of sector size.",
                            (uintmax_t)hio->hio_offset);
                        hio->hio_error = EINVAL;
                        goto end;
                }
                if ((hio->hio_length % res->hr_local_sectorsize) != 0) {
                        pjdlog_error("Length %ju is not multiple of sector size.",
                            (uintmax_t)hio->hio_length);
                        hio->hio_error = EINVAL;
                        goto end;
                }
                if (hio->hio_offset + hio->hio_length >
                    (uint64_t)res->hr_datasize) {
                        pjdlog_error("Data offset is too large (%ju > %ju).",
                            (uintmax_t)(hio->hio_offset + hio->hio_length),
                            (uintmax_t)res->hr_datasize);
                        hio->hio_error = EINVAL;
                        goto end;
                }
                break;
        default:
                pjdlog_error("Header contains invalid 'cmd' (%hhu).",
                    hio->hio_cmd);
                hio->hio_error = EINVAL;
                goto end;
        }
        hio->hio_error = 0;
end:
        return (hio->hio_error);
}

static __dead2 void
secondary_exit(int exitcode, const char *fmt, ...)
{
        va_list ap;

        PJDLOG_ASSERT(exitcode != EX_OK);
        va_start(ap, fmt);
        pjdlogv_errno(LOG_ERR, fmt, ap);
        va_end(ap);
        event_send(gres, EVENT_DISCONNECT);
        exit(exitcode);
}

/*
 * Thread receives requests from the primary node.
 */
static void *
recv_thread(void *arg)
{
        struct hast_resource *res = arg;
        struct hio *hio, *mshio;
        struct nv *nv;

        for (;;) {
                pjdlog_debug(2, "recv: Taking free request.");
                QUEUE_TAKE(free, hio);
                pjdlog_debug(2, "recv: (%p) Got request.", hio);
                if (hast_proto_recv_hdr(res->hr_remotein, &nv) == -1) {
                        secondary_exit(EX_TEMPFAIL,
                            "Unable to receive request header");
                }
                if (requnpack(res, hio, nv) != 0) {
                        nv_free(nv);
                        pjdlog_debug(2,
                            "recv: (%p) Moving request to the send queue.",
                            hio);
                        QUEUE_INSERT(send, hio);
                        continue;
                }
                switch (hio->hio_cmd) {
                case HIO_READ:
                        res->hr_stat_read++;
                        break;
                case HIO_WRITE:
                        res->hr_stat_write++;
                        break;
                case HIO_DELETE:
                        res->hr_stat_delete++;
                        break;
                case HIO_FLUSH:
                        res->hr_stat_flush++;
                        break;
                case HIO_KEEPALIVE:
                        break;
                default:
                        PJDLOG_ABORT("Unexpected command (cmd=%hhu).",
                            hio->hio_cmd);
                }
                reqlog(LOG_DEBUG, 2, -1, hio,
                    "recv: (%p) Got request header: ", hio);
                if (hio->hio_cmd == HIO_KEEPALIVE) {
                        nv_free(nv);
                        pjdlog_debug(2,
                            "recv: (%p) Moving request to the free queue.",
                            hio);
                        hio_clear(hio);
                        QUEUE_INSERT(free, hio);
                        continue;
                } else if (hio->hio_cmd == HIO_WRITE) {
                        if (hast_proto_recv_data(res, res->hr_remotein, nv,
                            hio->hio_data, MAXPHYS) == -1) {
                                secondary_exit(EX_TEMPFAIL,
                                    "Unable to receive request data");
                        }
                        if (hio->hio_memsync) {
                                /*
                                 * For memsync requests we expect two replies.
                                 * Clone the hio so we can handle both of them.
                                 */
                                pjdlog_debug(2, "recv: Taking free request.");
                                QUEUE_TAKE(free, mshio);
                                pjdlog_debug(2, "recv: (%p) Got request.",
                                    mshio);
                                hio_copy(hio, mshio);
                                mshio->hio_error = 0;
                                /*
                                 * We want to keep 'memsync' tag only on the
                                 * request going onto send queue (mshio).
                                 */
                                hio->hio_memsync = false;
                                pjdlog_debug(2,
                                    "recv: (%p) Moving memsync request to the send queue.",
                                    mshio);
                                QUEUE_INSERT(send, mshio);
                        }
                }
                nv_free(nv);
                pjdlog_debug(2, "recv: (%p) Moving request to the disk queue.",
                    hio);
                QUEUE_INSERT(disk, hio);
        }
        /* NOTREACHED */
        return (NULL);
}

/*
 * Thread reads from or writes to local component and also handles DELETE and
 * FLUSH requests.
 */
static void *
disk_thread(void *arg)
{
        struct hast_resource *res = arg;
        struct hio *hio;
        ssize_t ret;
        bool clear_activemap, logerror;

        clear_activemap = true;

        for (;;) {
                pjdlog_debug(2, "disk: Taking request.");
                QUEUE_TAKE(disk, hio);
                while (clear_activemap) {
                        unsigned char *map;
                        size_t mapsize;

                        /*
                         * When first request is received, it means that primary
                         * already received our activemap, merged it and stored
                         * locally. We can now safely clear our activemap.
                         */
                        mapsize =
                            activemap_calc_ondisk_size(res->hr_local_mediasize -
                            METADATA_SIZE, res->hr_extentsize,
                            res->hr_local_sectorsize);
                        map = calloc(1, mapsize);
                        if (map == NULL) {
                                pjdlog_warning("Unable to allocate memory to clear local activemap.");
                                break;
                        }
                        if (pwrite(res->hr_localfd, map, mapsize,
                            METADATA_SIZE) != (ssize_t)mapsize) {
                                pjdlog_errno(LOG_WARNING,
                                    "Unable to store cleared activemap");
                                free(map);
                                res->hr_stat_activemap_write_error++;
                                break;
                        }
                        free(map);
                        clear_activemap = false;
                        pjdlog_debug(1, "Local activemap cleared.");
                        break;
                }
                reqlog(LOG_DEBUG, 2, -1, hio, "disk: (%p) Got request: ", hio);
                logerror = true;
                /* Handle the actual request. */
                switch (hio->hio_cmd) {
                case HIO_READ:
                        ret = pread(res->hr_localfd, hio->hio_data,
                            hio->hio_length,
                            hio->hio_offset + res->hr_localoff);
                        if (ret == -1)
                                hio->hio_error = errno;
                        else if (ret != (int64_t)hio->hio_length)
                                hio->hio_error = EIO;
                        else
                                hio->hio_error = 0;
                        break;
                case HIO_WRITE:
                        ret = pwrite(res->hr_localfd, hio->hio_data,
                            hio->hio_length,
                            hio->hio_offset + res->hr_localoff);
                        if (ret == -1)
                                hio->hio_error = errno;
                        else if (ret != (int64_t)hio->hio_length)
                                hio->hio_error = EIO;
                        else
                                hio->hio_error = 0;
                        break;
                case HIO_DELETE:
                        ret = g_delete(res->hr_localfd,
                            hio->hio_offset + res->hr_localoff,
                            hio->hio_length);
                        if (ret == -1)
                                hio->hio_error = errno;
                        else
                                hio->hio_error = 0;
                        break;
                case HIO_FLUSH:
                        if (!res->hr_localflush) {
                                ret = -1;
                                hio->hio_error = EOPNOTSUPP;
                                logerror = false;
                                break;
                        }
                        ret = g_flush(res->hr_localfd);
                        if (ret == -1) {
                                if (errno == EOPNOTSUPP)
                                        res->hr_localflush = false;
                                hio->hio_error = errno;
                        } else {
                                hio->hio_error = 0;
                        }
                        break;
                default:
                        PJDLOG_ABORT("Unexpected command (cmd=%hhu).",
                            hio->hio_cmd);
                }
                if (logerror && hio->hio_error != 0) {
                        reqlog(LOG_ERR, 0, hio->hio_error, hio,
                            "Request failed: ");
                }
                pjdlog_debug(2, "disk: (%p) Moving request to the send queue.",
                    hio);
                QUEUE_INSERT(send, hio);
        }
        /* NOTREACHED */
        return (NULL);
}

/*
 * Thread sends requests back to primary node.
 */
static void *
send_thread(void *arg)
{
        struct hast_resource *res = arg;
        struct nv *nvout;
        struct hio *hio;
        void *data;
        size_t length;

        for (;;) {
                pjdlog_debug(2, "send: Taking request.");
                QUEUE_TAKE(send, hio);
                reqlog(LOG_DEBUG, 2, -1, hio, "send: (%p) Got request: ", hio);
                nvout = nv_alloc();
                /* Copy sequence number. */
                nv_add_uint64(nvout, hio->hio_seq, "seq");
                if (hio->hio_memsync) {
                        PJDLOG_ASSERT(hio->hio_cmd == HIO_WRITE);
                        nv_add_int8(nvout, 1, "received");
                }
                switch (hio->hio_cmd) {
                case HIO_READ:
                        if (hio->hio_error == 0) {
                                data = hio->hio_data;
                                length = hio->hio_length;
                                break;
                        }
                        /*
                         * We send no data in case of an error.
                         */
                        /* FALLTHROUGH */
                case HIO_DELETE:
                case HIO_FLUSH:
                case HIO_WRITE:
                        data = NULL;
                        length = 0;
                        break;
                default:
                        PJDLOG_ABORT("Unexpected command (cmd=%hhu).",
                            hio->hio_cmd);
                }
                if (hio->hio_error != 0) {
                        switch (hio->hio_cmd) {
                        case HIO_READ:
                                res->hr_stat_read_error++;
                                break;
                        case HIO_WRITE:
                                res->hr_stat_write_error++;
                                break;
                        case HIO_DELETE:
                                res->hr_stat_delete_error++;
                                break;
                        case HIO_FLUSH:
                                res->hr_stat_flush_error++;
                                break;
                        }
                        nv_add_int16(nvout, hio->hio_error, "error");
                }
                if (hast_proto_send(res, res->hr_remoteout, nvout, data,
                    length) == -1) {
                        secondary_exit(EX_TEMPFAIL, "Unable to send reply");
                }
                nv_free(nvout);
                pjdlog_debug(2, "send: (%p) Moving request to the free queue.",
                    hio);
                hio_clear(hio);
                QUEUE_INSERT(free, hio);
        }
        /* NOTREACHED */
        return (NULL);
}