/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2009 The FreeBSD Foundation
 * Copyright (c) 2010-2011 Pawel Jakub Dawidek <pawel@dawidek.net>
 * 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/types.h>
#include <sys/time.h>
#include <sys/bio.h>
#include <sys/disk.h>
#include <sys/stat.h>

#include <geom/gate/g_gate.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 <rangelock.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 "pjdlog.h"
#include "refcnt.h"
#include "subr.h"
#include "synch.h"

/* The is only one remote component for now. */
#define ISREMOTE(no)    ((no) == 1)

struct hio {
        /*
         * Number of components we are still waiting for.
         * When this field goes to 0, we can send the request back to the
         * kernel. Each component has to decrease this counter by one
         * even on failure.
         */
        refcnt_t                 hio_countdown;
        /*
         * Each component has a place to store its own error.
         * Once the request is handled by all components we can decide if the
         * request overall is successful or not.
         */
        int                     *hio_errors;
        /*
         * Structure used to communicate with GEOM Gate class.
         */
        struct g_gate_ctl_io     hio_ggio;
        /*
         * Request was already confirmed to GEOM Gate.
         */
        bool                     hio_done;
        /*
         * Number of components we are still waiting before sending write
         * completion ack to GEOM Gate. Used for memsync.
         */
        refcnt_t                 hio_writecount;
        /*
         * Memsync request was acknowledged by remote.
         */
        bool                     hio_memsyncacked;
        /*
         * Remember replication from the time the request was initiated,
         * so we won't get confused when replication changes on reload.
         */
        int                      hio_replication;
        TAILQ_ENTRY(hio)        *hio_next;
};
#define hio_free_next   hio_next[0]
#define hio_done_next   hio_next[0]

/*
 * 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;
/*
 * There is one send list for every component. One requests is placed on all
 * send lists - each component gets the same request, but each component is
 * responsible for managing his own send 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;
#define hio_send_local_list_size        hio_send_list_size[0]
#define hio_send_remote_list_size       hio_send_list_size[1]
/*
 * There is one recv list for every component, although local components don't
 * use recv lists as local requests are done synchronously.
 */
static TAILQ_HEAD(, hio) *hio_recv_list;
static size_t *hio_recv_list_size;
static pthread_mutex_t *hio_recv_list_lock;
static pthread_cond_t *hio_recv_list_cond;
#define hio_recv_remote_list_size       hio_recv_list_size[1]
/*
 * Request is placed on done list by the slowest component (the one that
 * decreased hio_countdown from 1 to 0).
 */
static TAILQ_HEAD(, hio) hio_done_list;
static size_t hio_done_list_size;
static pthread_mutex_t hio_done_list_lock;
static pthread_cond_t hio_done_list_cond;
/*
 * Structure below are for interaction with sync thread.
 */
static bool sync_inprogress;
static pthread_mutex_t sync_lock;
static pthread_cond_t sync_cond;
/*
 * The lock below allows to synchornize access to remote connections.
 */
static pthread_rwlock_t *hio_remote_lock;

/*
 * Lock to synchronize metadata updates. Also synchronize access to
 * hr_primary_localcnt and hr_primary_remotecnt fields.
 */
static pthread_mutex_t metadata_lock;

/*
 * Maximum number of outstanding I/O requests.
 */
#define HAST_HIO_MAX    256
/*
 * Number of components. At this point there are only two components: local
 * and remote, but in the future it might be possible to use multiple local
 * and remote components.
 */
#define HAST_NCOMPONENTS        2

#define ISCONNECTED(res, no)    \
        ((res)->hr_remotein != NULL && (res)->hr_remoteout != NULL)

#define QUEUE_INSERT1(hio, name, ncomp) do {                            \
        mtx_lock(&hio_##name##_list_lock[(ncomp)]);                     \
        if (TAILQ_EMPTY(&hio_##name##_list[(ncomp)]))                   \
                cv_broadcast(&hio_##name##_list_cond[(ncomp)]);         \
        TAILQ_INSERT_TAIL(&hio_##name##_list[(ncomp)], (hio),           \
            hio_next[(ncomp)]);                                         \
        hio_##name##_list_size[(ncomp)]++;                              \
        mtx_unlock(&hio_##name##_list_lock[(ncomp)]);                   \
} while (0)
#define QUEUE_INSERT2(hio, name)        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_##name##_next);\
        hio_##name##_list_size++;                                       \
        mtx_unlock(&hio_##name##_list_lock);                            \
} while (0)
#define QUEUE_TAKE1(hio, name, ncomp, timeout)  do {                    \
        bool _last;                                                     \
                                                                        \
        mtx_lock(&hio_##name##_list_lock[(ncomp)]);                     \
        _last = false;                                                  \
        while (((hio) = TAILQ_FIRST(&hio_##name##_list[(ncomp)])) == NULL && !_last) { \
                cv_timedwait(&hio_##name##_list_cond[(ncomp)],          \
                    &hio_##name##_list_lock[(ncomp)], (timeout));       \
                if ((timeout) != 0)                                     \
                        _last = true;                                   \
        }                                                               \
        if (hio != NULL) {                                              \
                PJDLOG_ASSERT(hio_##name##_list_size[(ncomp)] != 0);    \
                hio_##name##_list_size[(ncomp)]--;                      \
                TAILQ_REMOVE(&hio_##name##_list[(ncomp)], (hio),        \
                    hio_next[(ncomp)]);                                 \
        }                                                               \
        mtx_unlock(&hio_##name##_list_lock[(ncomp)]);                   \
} while (0)
#define QUEUE_TAKE2(hio, name)  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_##name##_next);     \
        mtx_unlock(&hio_##name##_list_lock);                            \
} while (0)

#define ISFULLSYNC(hio) ((hio)->hio_replication == HAST_REPLICATION_FULLSYNC)
#define ISMEMSYNC(hio)  ((hio)->hio_replication == HAST_REPLICATION_MEMSYNC)
#define ISASYNC(hio)    ((hio)->hio_replication == HAST_REPLICATION_ASYNC)

#define SYNCREQ(hio)            do {                                    \
        (hio)->hio_ggio.gctl_unit = -1;                                 \
        (hio)->hio_ggio.gctl_seq = 1;                                   \
} while (0)
#define ISSYNCREQ(hio)          ((hio)->hio_ggio.gctl_unit == -1)
#define SYNCREQDONE(hio)        do { (hio)->hio_ggio.gctl_unit = -2; } while (0)
#define ISSYNCREQDONE(hio)      ((hio)->hio_ggio.gctl_unit == -2)

#define ISMEMSYNCWRITE(hio)     (ISMEMSYNC(hio) &&                      \
            (hio)->hio_ggio.gctl_cmd == BIO_WRITE && !ISSYNCREQ(hio))

static struct hast_resource *gres;

static pthread_mutex_t range_lock;
static struct rangelocks *range_regular;
static bool range_regular_wait;
static pthread_cond_t range_regular_cond;
static struct rangelocks *range_sync;
static bool range_sync_wait;
static pthread_cond_t range_sync_cond;
static bool fullystarted;

static void *ggate_recv_thread(void *arg);
static void *local_send_thread(void *arg);
static void *remote_send_thread(void *arg);
static void *remote_recv_thread(void *arg);
static void *ggate_send_thread(void *arg);
static void *sync_thread(void *arg);
static void *guard_thread(void *arg);

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_send_local_list_size,
            "local_queue_size");
        nv_add_uint64(nvout, (uint64_t)hio_send_remote_list_size,
            "send_queue_size");
        nv_add_uint64(nvout, (uint64_t)hio_recv_remote_list_size,
            "recv_queue_size");
        nv_add_uint64(nvout, (uint64_t)hio_done_list_size,
            "done_queue_size");
}

static void
cleanup(struct hast_resource *res)
{
        int rerrno;

        /* Remember errno. */
        rerrno = errno;

        /* Destroy ggate provider if we created one. */
        if (res->hr_ggateunit >= 0) {
                struct g_gate_ctl_destroy ggiod;

                bzero(&ggiod, sizeof(ggiod));
                ggiod.gctl_version = G_GATE_VERSION;
                ggiod.gctl_unit = res->hr_ggateunit;
                ggiod.gctl_force = 1;
                if (ioctl(res->hr_ggatefd, G_GATE_CMD_DESTROY, &ggiod) == -1) {
                        pjdlog_errno(LOG_WARNING,
                            "Unable to destroy hast/%s device",
                            res->hr_provname);
                }
                res->hr_ggateunit = -1;
        }

        /* Restore errno. */
        errno = rerrno;
}

static __dead2 void
primary_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);
        cleanup(gres);
        exit(exitcode);
}

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

        va_start(ap, fmt);
        pjdlogv(exitcode == EX_OK ? LOG_INFO : LOG_ERR, fmt, ap);
        va_end(ap);
        cleanup(gres);
        exit(exitcode);
}

static int
hast_activemap_flush(struct hast_resource *res) __unlocks(res->hr_amp_lock)
{
        const unsigned char *buf;
        size_t size;
        int ret;

        mtx_lock(&res->hr_amp_diskmap_lock);
        buf = activemap_bitmap(res->hr_amp, &size);
        mtx_unlock(&res->hr_amp_lock);
        PJDLOG_ASSERT(buf != NULL);
        PJDLOG_ASSERT((size % res->hr_local_sectorsize) == 0);
        ret = 0;
        if (pwrite(res->hr_localfd, buf, size, METADATA_SIZE) !=
            (ssize_t)size) {
                pjdlog_errno(LOG_ERR, "Unable to flush activemap to disk");
                res->hr_stat_activemap_write_error++;
                ret = -1;
        }
        if (ret == 0 && res->hr_metaflush == 1 &&
            g_flush(res->hr_localfd) == -1) {
                if (errno == EOPNOTSUPP) {
                        pjdlog_warning("The %s provider doesn't support flushing write cache. Disabling it.",
                            res->hr_localpath);
                        res->hr_metaflush = 0;
                } else {
                        pjdlog_errno(LOG_ERR,
                            "Unable to flush disk cache on activemap update");
                        res->hr_stat_activemap_flush_error++;
                        ret = -1;
                }
        }
        mtx_unlock(&res->hr_amp_diskmap_lock);
        return (ret);
}

static bool
real_remote(const struct hast_resource *res)
{

        return (strcmp(res->hr_remoteaddr, "none") != 0);
}

static void
init_environment(struct hast_resource *res __unused)
{
        struct hio *hio;
        unsigned int ii, ncomps;

        /*
         * In the future it might be per-resource value.
         */
        ncomps = HAST_NCOMPONENTS;

        /*
         * Allocate memory needed by lists.
         */
        hio_send_list = malloc(sizeof(hio_send_list[0]) * ncomps);
        if (hio_send_list == NULL) {
                primary_exitx(EX_TEMPFAIL,
                    "Unable to allocate %zu bytes of memory for send lists.",
                    sizeof(hio_send_list[0]) * ncomps);
        }
        hio_send_list_size = malloc(sizeof(hio_send_list_size[0]) * ncomps);
        if (hio_send_list_size == NULL) {
                primary_exitx(EX_TEMPFAIL,
                    "Unable to allocate %zu bytes of memory for send list counters.",
                    sizeof(hio_send_list_size[0]) * ncomps);
        }
        hio_send_list_lock = malloc(sizeof(hio_send_list_lock[0]) * ncomps);
        if (hio_send_list_lock == NULL) {
                primary_exitx(EX_TEMPFAIL,
                    "Unable to allocate %zu bytes of memory for send list locks.",
                    sizeof(hio_send_list_lock[0]) * ncomps);
        }
        hio_send_list_cond = malloc(sizeof(hio_send_list_cond[0]) * ncomps);
        if (hio_send_list_cond == NULL) {
                primary_exitx(EX_TEMPFAIL,
                    "Unable to allocate %zu bytes of memory for send list condition variables.",
                    sizeof(hio_send_list_cond[0]) * ncomps);
        }
        hio_recv_list = malloc(sizeof(hio_recv_list[0]) * ncomps);
        if (hio_recv_list == NULL) {
                primary_exitx(EX_TEMPFAIL,
                    "Unable to allocate %zu bytes of memory for recv lists.",
                    sizeof(hio_recv_list[0]) * ncomps);
        }
        hio_recv_list_size = malloc(sizeof(hio_recv_list_size[0]) * ncomps);
        if (hio_recv_list_size == NULL) {
                primary_exitx(EX_TEMPFAIL,
                    "Unable to allocate %zu bytes of memory for recv list counters.",
                    sizeof(hio_recv_list_size[0]) * ncomps);
        }
        hio_recv_list_lock = malloc(sizeof(hio_recv_list_lock[0]) * ncomps);
        if (hio_recv_list_lock == NULL) {
                primary_exitx(EX_TEMPFAIL,
                    "Unable to allocate %zu bytes of memory for recv list locks.",
                    sizeof(hio_recv_list_lock[0]) * ncomps);
        }
        hio_recv_list_cond = malloc(sizeof(hio_recv_list_cond[0]) * ncomps);
        if (hio_recv_list_cond == NULL) {
                primary_exitx(EX_TEMPFAIL,
                    "Unable to allocate %zu bytes of memory for recv list condition variables.",
                    sizeof(hio_recv_list_cond[0]) * ncomps);
        }
        hio_remote_lock = malloc(sizeof(hio_remote_lock[0]) * ncomps);
        if (hio_remote_lock == NULL) {
                primary_exitx(EX_TEMPFAIL,
                    "Unable to allocate %zu bytes of memory for remote connections locks.",
                    sizeof(hio_remote_lock[0]) * ncomps);
        }

        /*
         * Initialize lists, their counters, locks and condition variables.
         */
        TAILQ_INIT(&hio_free_list);
        mtx_init(&hio_free_list_lock);
        cv_init(&hio_free_list_cond);
        for (ii = 0; ii < HAST_NCOMPONENTS; ii++) {
                TAILQ_INIT(&hio_send_list[ii]);
                hio_send_list_size[ii] = 0;
                mtx_init(&hio_send_list_lock[ii]);
                cv_init(&hio_send_list_cond[ii]);
                TAILQ_INIT(&hio_recv_list[ii]);
                hio_recv_list_size[ii] = 0;
                mtx_init(&hio_recv_list_lock[ii]);
                cv_init(&hio_recv_list_cond[ii]);
                rw_init(&hio_remote_lock[ii]);
        }
        TAILQ_INIT(&hio_done_list);
        mtx_init(&hio_done_list_lock);
        cv_init(&hio_done_list_cond);
        mtx_init(&metadata_lock);

        /*
         * Allocate requests pool and initialize requests.
         */
        for (ii = 0; ii < HAST_HIO_MAX; ii++) {
                hio = malloc(sizeof(*hio));
                if (hio == NULL) {
                        primary_exitx(EX_TEMPFAIL,
                            "Unable to allocate %zu bytes of memory for hio request.",
                            sizeof(*hio));
                }
                refcnt_init(&hio->hio_countdown, 0);
                hio->hio_errors = malloc(sizeof(hio->hio_errors[0]) * ncomps);
                if (hio->hio_errors == NULL) {
                        primary_exitx(EX_TEMPFAIL,
                            "Unable allocate %zu bytes of memory for hio errors.",
                            sizeof(hio->hio_errors[0]) * ncomps);
                }
                hio->hio_next = malloc(sizeof(hio->hio_next[0]) * ncomps);
                if (hio->hio_next == NULL) {
                        primary_exitx(EX_TEMPFAIL,
                            "Unable allocate %zu bytes of memory for hio_next field.",
                            sizeof(hio->hio_next[0]) * ncomps);
                }
                hio->hio_ggio.gctl_version = G_GATE_VERSION;
                hio->hio_ggio.gctl_data = malloc(MAXPHYS);
                if (hio->hio_ggio.gctl_data == NULL) {
                        primary_exitx(EX_TEMPFAIL,
                            "Unable to allocate %zu bytes of memory for gctl_data.",
                            MAXPHYS);
                }
                hio->hio_ggio.gctl_length = MAXPHYS;
                hio->hio_ggio.gctl_error = 0;
                TAILQ_INSERT_HEAD(&hio_free_list, hio, hio_free_next);
                hio_free_list_size++;
        }
}

static bool
init_resuid(struct hast_resource *res)
{

        mtx_lock(&metadata_lock);
        if (res->hr_resuid != 0) {
                mtx_unlock(&metadata_lock);
                return (false);
        } else {
                /* Initialize unique resource identifier. */
                arc4random_buf(&res->hr_resuid, sizeof(res->hr_resuid));
                mtx_unlock(&metadata_lock);
                if (metadata_write(res) == -1)
                        exit(EX_NOINPUT);
                return (true);
        }
}

static void
init_local(struct hast_resource *res)
{
        unsigned char *buf;
        size_t mapsize;

        if (metadata_read(res, true) == -1)
                exit(EX_NOINPUT);
        mtx_init(&res->hr_amp_lock);
        if (activemap_init(&res->hr_amp, res->hr_datasize, res->hr_extentsize,
            res->hr_local_sectorsize, res->hr_keepdirty) == -1) {
                primary_exit(EX_TEMPFAIL, "Unable to create activemap");
        }
        mtx_init(&range_lock);
        cv_init(&range_regular_cond);
        if (rangelock_init(&range_regular) == -1)
                primary_exit(EX_TEMPFAIL, "Unable to create regular range lock");
        cv_init(&range_sync_cond);
        if (rangelock_init(&range_sync) == -1)
                primary_exit(EX_TEMPFAIL, "Unable to create sync range lock");
        mapsize = activemap_ondisk_size(res->hr_amp);
        buf = calloc(1, mapsize);
        if (buf == NULL) {
                primary_exitx(EX_TEMPFAIL,
                    "Unable to allocate buffer for activemap.");
        }
        if (pread(res->hr_localfd, buf, mapsize, METADATA_SIZE) !=
            (ssize_t)mapsize) {
                primary_exit(EX_NOINPUT, "Unable to read activemap");
        }
        activemap_copyin(res->hr_amp, buf, mapsize);
        free(buf);
        if (res->hr_resuid != 0)
                return;
        /*
         * We're using provider for the first time. Initialize local and remote
         * counters. We don't initialize resuid here, as we want to do it just
         * in time. The reason for this is that we want to inform secondary
         * that there were no writes yet, so there is no need to synchronize
         * anything.
         */
        res->hr_primary_localcnt = 0;
        res->hr_primary_remotecnt = 0;
        if (metadata_write(res) == -1)
                exit(EX_NOINPUT);
}

static int
primary_connect(struct hast_resource *res, struct proto_conn **connp)
{
        struct proto_conn *conn;
        int16_t val;

        val = 1;
        if (proto_send(res->hr_conn, &val, sizeof(val)) == -1) {
                primary_exit(EX_TEMPFAIL,
                    "Unable to send connection request to parent");
        }
        if (proto_recv(res->hr_conn, &val, sizeof(val)) == -1) {
                primary_exit(EX_TEMPFAIL,
                    "Unable to receive reply to connection request from parent");
        }
        if (val != 0) {
                errno = val;
                pjdlog_errno(LOG_WARNING, "Unable to connect to %s",
                    res->hr_remoteaddr);
                return (-1);
        }
        if (proto_connection_recv(res->hr_conn, true, &conn) == -1) {
                primary_exit(EX_TEMPFAIL,
                    "Unable to receive connection from parent");
        }
        if (proto_connect_wait(conn, res->hr_timeout) == -1) {
                pjdlog_errno(LOG_WARNING, "Unable to connect to %s",
                    res->hr_remoteaddr);
                proto_close(conn);
                return (-1);
        }
        /* Error in setting timeout is not critical, but why should it fail? */
        if (proto_timeout(conn, res->hr_timeout) == -1)
                pjdlog_errno(LOG_WARNING, "Unable to set connection timeout");

        *connp = conn;

        return (0);
}

/*
 * Function instructs GEOM_GATE to handle reads directly from within the kernel.
 */
static void
enable_direct_reads(struct hast_resource *res)
{
        struct g_gate_ctl_modify ggiomodify;

        bzero(&ggiomodify, sizeof(ggiomodify));
        ggiomodify.gctl_version = G_GATE_VERSION;
        ggiomodify.gctl_unit = res->hr_ggateunit;
        ggiomodify.gctl_modify = GG_MODIFY_READPROV | GG_MODIFY_READOFFSET;
        strlcpy(ggiomodify.gctl_readprov, res->hr_localpath,
            sizeof(ggiomodify.gctl_readprov));
        ggiomodify.gctl_readoffset = res->hr_localoff;
        if (ioctl(res->hr_ggatefd, G_GATE_CMD_MODIFY, &ggiomodify) == 0)
                pjdlog_debug(1, "Direct reads enabled.");
        else
                pjdlog_errno(LOG_WARNING, "Failed to enable direct reads");
}

static int
init_remote(struct hast_resource *res, struct proto_conn **inp,
    struct proto_conn **outp)
{
        struct proto_conn *in, *out;
        struct nv *nvout, *nvin;
        const unsigned char *token;
        unsigned char *map;
        const char *errmsg;
        int32_t extentsize;
        int64_t datasize;
        uint32_t mapsize;
        uint8_t version;
        size_t size;
        int error;

        PJDLOG_ASSERT((inp == NULL && outp == NULL) || (inp != NULL && outp != NULL));
        PJDLOG_ASSERT(real_remote(res));

        in = out = NULL;
        errmsg = NULL;

        if (primary_connect(res, &out) == -1)
                return (ECONNREFUSED);

        error = ECONNABORTED;

        /*
         * First handshake step.
         * Setup outgoing connection with remote node.
         */
        nvout = nv_alloc();
        nv_add_string(nvout, res->hr_name, "resource");
        nv_add_uint8(nvout, HAST_PROTO_VERSION, "version");
        if (nv_error(nvout) != 0) {
                pjdlog_common(LOG_WARNING, 0, nv_error(nvout),
                    "Unable to allocate header for connection with %s",
                    res->hr_remoteaddr);
                nv_free(nvout);
                goto close;
        }
        if (hast_proto_send(res, out, nvout, NULL, 0) == -1) {
                pjdlog_errno(LOG_WARNING,
                    "Unable to send handshake header to %s",
                    res->hr_remoteaddr);
                nv_free(nvout);
                goto close;
        }
        nv_free(nvout);
        if (hast_proto_recv_hdr(out, &nvin) == -1) {
                pjdlog_errno(LOG_WARNING,
                    "Unable to receive handshake header from %s",
                    res->hr_remoteaddr);
                goto close;
        }
        errmsg = nv_get_string(nvin, "errmsg");
        if (errmsg != NULL) {
                pjdlog_warning("%s", errmsg);
                if (nv_exists(nvin, "wait"))
                        error = EBUSY;
                nv_free(nvin);
                goto close;
        }
        version = nv_get_uint8(nvin, "version");
        if (version == 0) {
                /*
                 * If no version is sent, it means this is protocol version 1.
                 */
                version = 1;
        }
        if (version > HAST_PROTO_VERSION) {
                pjdlog_warning("Invalid version received (%hhu).", version);
                nv_free(nvin);
                goto close;
        }
        res->hr_version = version;
        pjdlog_debug(1, "Negotiated protocol version %d.", res->hr_version);
        token = nv_get_uint8_array(nvin, &size, "token");
        if (token == NULL) {
                pjdlog_warning("Handshake header from %s has no 'token' field.",
                    res->hr_remoteaddr);
                nv_free(nvin);
                goto close;
        }
        if (size != sizeof(res->hr_token)) {
                pjdlog_warning("Handshake header from %s contains 'token' of wrong size (got %zu, expected %zu).",
                    res->hr_remoteaddr, size, sizeof(res->hr_token));
                nv_free(nvin);
                goto close;
        }
        bcopy(token, res->hr_token, sizeof(res->hr_token));
        nv_free(nvin);

        /*
         * Second handshake step.
         * Setup incoming connection with remote node.
         */
        if (primary_connect(res, &in) == -1)
                goto close;

        nvout = nv_alloc();
        nv_add_string(nvout, res->hr_name, "resource");
        nv_add_uint8_array(nvout, res->hr_token, sizeof(res->hr_token),
            "token");
        if (res->hr_resuid == 0) {
                /*
                 * The resuid field was not yet initialized.
                 * Because we do synchronization inside init_resuid(), it is
                 * possible that someone already initialized it, the function
                 * will return false then, but if we successfully initialized
                 * it, we will get true. True means that there were no writes
                 * to this resource yet and we want to inform secondary that
                 * synchronization is not needed by sending "virgin" argument.
                 */
                if (init_resuid(res))
                        nv_add_int8(nvout, 1, "virgin");
        }
        nv_add_uint64(nvout, res->hr_resuid, "resuid");
        nv_add_uint64(nvout, res->hr_primary_localcnt, "localcnt");
        nv_add_uint64(nvout, res->hr_primary_remotecnt, "remotecnt");
        if (nv_error(nvout) != 0) {
                pjdlog_common(LOG_WARNING, 0, nv_error(nvout),
                    "Unable to allocate header for connection with %s",
                    res->hr_remoteaddr);
                nv_free(nvout);
                goto close;
        }
        if (hast_proto_send(res, in, nvout, NULL, 0) == -1) {
                pjdlog_errno(LOG_WARNING,
                    "Unable to send handshake header to %s",
                    res->hr_remoteaddr);
                nv_free(nvout);
                goto close;
        }
        nv_free(nvout);
        if (hast_proto_recv_hdr(out, &nvin) == -1) {
                pjdlog_errno(LOG_WARNING,
                    "Unable to receive handshake header from %s",
                    res->hr_remoteaddr);
                goto close;
        }
        errmsg = nv_get_string(nvin, "errmsg");
        if (errmsg != NULL) {
                pjdlog_warning("%s", errmsg);
                nv_free(nvin);
                goto close;
        }
        datasize = nv_get_int64(nvin, "datasize");
        if (datasize != res->hr_datasize) {
                pjdlog_warning("Data size differs between nodes (local=%jd, remote=%jd).",
                    (intmax_t)res->hr_datasize, (intmax_t)datasize);
                nv_free(nvin);
                goto close;
        }
        extentsize = nv_get_int32(nvin, "extentsize");
        if (extentsize != res->hr_extentsize) {
                pjdlog_warning("Extent size differs between nodes (local=%zd, remote=%zd).",
                    (ssize_t)res->hr_extentsize, (ssize_t)extentsize);
                nv_free(nvin);
                goto close;
        }
        res->hr_secondary_localcnt = nv_get_uint64(nvin, "localcnt");
        res->hr_secondary_remotecnt = nv_get_uint64(nvin, "remotecnt");
        res->hr_syncsrc = nv_get_uint8(nvin, "syncsrc");
        if (res->hr_syncsrc == HAST_SYNCSRC_PRIMARY)
                enable_direct_reads(res);
        if (nv_exists(nvin, "virgin")) {
                /*
                 * Secondary was reinitialized, bump localcnt if it is 0 as
                 * only we have the data.
                 */
                PJDLOG_ASSERT(res->hr_syncsrc == HAST_SYNCSRC_PRIMARY);
                PJDLOG_ASSERT(res->hr_secondary_localcnt == 0);

                if (res->hr_primary_localcnt == 0) {
                        PJDLOG_ASSERT(res->hr_secondary_remotecnt == 0);

                        mtx_lock(&metadata_lock);
                        res->hr_primary_localcnt++;
                        pjdlog_debug(1, "Increasing localcnt to %ju.",
                            (uintmax_t)res->hr_primary_localcnt);
                        (void)metadata_write(res);
                        mtx_unlock(&metadata_lock);
                }
        }
        map = NULL;
        mapsize = nv_get_uint32(nvin, "mapsize");
        if (mapsize > 0) {
                map = malloc(mapsize);
                if (map == NULL) {
                        pjdlog_error("Unable to allocate memory for remote activemap (mapsize=%ju).",
                            (uintmax_t)mapsize);
                        nv_free(nvin);
                        goto close;
                }
                /*
                 * Remote node have some dirty extents on its own, lets
                 * download its activemap.
                 */
                if (hast_proto_recv_data(res, out, nvin, map,
                    mapsize) == -1) {
                        pjdlog_errno(LOG_ERR,
                            "Unable to receive remote activemap");
                        nv_free(nvin);
                        free(map);
                        goto close;
                }
                mtx_lock(&res->hr_amp_lock);
                /*
                 * Merge local and remote bitmaps.
                 */
                activemap_merge(res->hr_amp, map, mapsize);
                free(map);
                /*
                 * Now that we merged bitmaps from both nodes, flush it to the
                 * disk before we start to synchronize.
                 */
                (void)hast_activemap_flush(res);
        }
        nv_free(nvin);
#ifdef notyet
        /* Setup directions. */
        if (proto_send(out, NULL, 0) == -1)
                pjdlog_errno(LOG_WARNING, "Unable to set connection direction");
        if (proto_recv(in, NULL, 0) == -1)
                pjdlog_errno(LOG_WARNING, "Unable to set connection direction");
#endif
        pjdlog_info("Connected to %s.", res->hr_remoteaddr);
        if (res->hr_original_replication == HAST_REPLICATION_MEMSYNC &&
            res->hr_version < 2) {
                pjdlog_warning("The 'memsync' replication mode is not supported by the remote node, falling back to 'fullsync' mode.");
                res->hr_replication = HAST_REPLICATION_FULLSYNC;
        } else if (res->hr_replication != res->hr_original_replication) {
                /*
                 * This is in case hastd disconnected and was upgraded.
                 */
                res->hr_replication = res->hr_original_replication;
        }
        if (inp != NULL && outp != NULL) {
                *inp = in;
                *outp = out;
        } else {
                res->hr_remotein = in;
                res->hr_remoteout = out;
        }
        event_send(res, EVENT_CONNECT);
        return (0);
close:
        if (errmsg != NULL && strcmp(errmsg, "Split-brain condition!") == 0)
                event_send(res, EVENT_SPLITBRAIN);
        proto_close(out);
        if (in != NULL)
                proto_close(in);
        return (error);
}

static void
sync_start(void)
{

        mtx_lock(&sync_lock);
        sync_inprogress = true;
        mtx_unlock(&sync_lock);
        cv_signal(&sync_cond);
}

static void
sync_stop(void)
{

        mtx_lock(&sync_lock);
        if (sync_inprogress)
                sync_inprogress = false;
        mtx_unlock(&sync_lock);
}

static void
init_ggate(struct hast_resource *res)
{
        struct g_gate_ctl_create ggiocreate;
        struct g_gate_ctl_cancel ggiocancel;

        /*
         * We communicate with ggate via /dev/ggctl. Open it.
         */
        res->hr_ggatefd = open("/dev/" G_GATE_CTL_NAME, O_RDWR);
        if (res->hr_ggatefd == -1)
                primary_exit(EX_OSFILE, "Unable to open /dev/" G_GATE_CTL_NAME);
        /*
         * Create provider before trying to connect, as connection failure
         * is not critical, but may take some time.
         */
        bzero(&ggiocreate, sizeof(ggiocreate));
        ggiocreate.gctl_version = G_GATE_VERSION;
        ggiocreate.gctl_mediasize = res->hr_datasize;
        ggiocreate.gctl_sectorsize = res->hr_local_sectorsize;
        ggiocreate.gctl_flags = 0;
        ggiocreate.gctl_maxcount = 0;
        ggiocreate.gctl_timeout = 0;
        ggiocreate.gctl_unit = G_GATE_NAME_GIVEN;
        snprintf(ggiocreate.gctl_name, sizeof(ggiocreate.gctl_name), "hast/%s",
            res->hr_provname);
        if (ioctl(res->hr_ggatefd, G_GATE_CMD_CREATE, &ggiocreate) == 0) {
                pjdlog_info("Device hast/%s created.", res->hr_provname);
                res->hr_ggateunit = ggiocreate.gctl_unit;
                return;
        }
        if (errno != EEXIST) {
                primary_exit(EX_OSERR, "Unable to create hast/%s device",
                    res->hr_provname);
        }
        pjdlog_debug(1,
            "Device hast/%s already exists, we will try to take it over.",
            res->hr_provname);
        /*
         * If we received EEXIST, we assume that the process who created the
         * provider died and didn't clean up. In that case we will start from
         * where he left of.
         */
        bzero(&ggiocancel, sizeof(ggiocancel));
        ggiocancel.gctl_version = G_GATE_VERSION;
        ggiocancel.gctl_unit = G_GATE_NAME_GIVEN;
        snprintf(ggiocancel.gctl_name, sizeof(ggiocancel.gctl_name), "hast/%s",
            res->hr_provname);
        if (ioctl(res->hr_ggatefd, G_GATE_CMD_CANCEL, &ggiocancel) == 0) {
                pjdlog_info("Device hast/%s recovered.", res->hr_provname);
                res->hr_ggateunit = ggiocancel.gctl_unit;
                return;
        }
        primary_exit(EX_OSERR, "Unable to take over hast/%s device",
            res->hr_provname);
}

void
hastd_primary(struct hast_resource *res)
{
        pthread_t td;
        pid_t pid;
        int error, mode, debuglevel;

        /*
         * Create communication channel for sending control commands from
         * parent to child.
         */
        if (proto_client(NULL, "socketpair://", &res->hr_ctrl) == -1) {
                /* TODO: There's no need for this to be fatal error. */
                KEEP_ERRNO((void)pidfile_remove(pfh));
                pjdlog_exit(EX_OSERR,
                    "Unable to create control sockets between parent and child");
        }
        /*
         * Create communication channel for sending events from child to parent.
         */
        if (proto_client(NULL, "socketpair://", &res->hr_event) == -1) {
                /* TODO: There's no need for this to be fatal error. */
                KEEP_ERRNO((void)pidfile_remove(pfh));
                pjdlog_exit(EX_OSERR,
                    "Unable to create event sockets between child and parent");
        }
        /*
         * Create communication channel for sending connection requests from
         * child to parent.
         */
        if (proto_client(NULL, "socketpair://", &res->hr_conn) == -1) {
                /* TODO: There's no need for this to be fatal error. */
                KEEP_ERRNO((void)pidfile_remove(pfh));
                pjdlog_exit(EX_OSERR,
                    "Unable to create connection sockets between child and parent");
        }

        pid = fork();
        if (pid == -1) {
                /* TODO: There's no need for this to be fatal error. */
                KEEP_ERRNO((void)pidfile_remove(pfh));
                pjdlog_exit(EX_TEMPFAIL, "Unable to fork");
        }

        if (pid > 0) {
                /* This is parent. */
                /* Declare that we are receiver. */
                proto_recv(res->hr_event, NULL, 0);
                proto_recv(res->hr_conn, 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);
        proto_send(res->hr_conn, 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));

        init_local(res);
        init_ggate(res);
        init_environment(res);

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

        /*
         * Create the guard thread first, so we can handle signals from the
         * very beginning.
         */
        error = pthread_create(&td, NULL, guard_thread, res);
        PJDLOG_ASSERT(error == 0);
        /*
         * 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);
        if (real_remote(res)) {
                error = init_remote(res, NULL, NULL);
                if (error == 0) {
                        sync_start();
                } else if (error == EBUSY) {
                        time_t start = time(NULL);

                        pjdlog_warning("Waiting for remote node to become %s for %ds.",
                            role2str(HAST_ROLE_SECONDARY),
                            res->hr_timeout);
                        for (;;) {
                                sleep(1);
                                error = init_remote(res, NULL, NULL);
                                if (error != EBUSY)
                                        break;
                                if (time(NULL) > start + res->hr_timeout)
                                        break;
                        }
                        if (error == EBUSY) {
                                pjdlog_warning("Remote node is still %s, starting anyway.",
                                    role2str(HAST_ROLE_PRIMARY));
                        }
                }
        }
        error = pthread_create(&td, NULL, ggate_recv_thread, res);
        PJDLOG_ASSERT(error == 0);
        error = pthread_create(&td, NULL, local_send_thread, res);
        PJDLOG_ASSERT(error == 0);
        error = pthread_create(&td, NULL, remote_send_thread, res);
        PJDLOG_ASSERT(error == 0);
        error = pthread_create(&td, NULL, remote_recv_thread, res);
        PJDLOG_ASSERT(error == 0);
        error = pthread_create(&td, NULL, ggate_send_thread, res);
        PJDLOG_ASSERT(error == 0);
        fullystarted = true;
        (void)sync_thread(res);
}

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

        va_start(ap, fmt);
        (void)vsnprintf(msg, sizeof(msg), fmt, ap);
        va_end(ap);
        switch (ggio->gctl_cmd) {
        case BIO_READ:
                (void)snprlcat(msg, sizeof(msg), "READ(%ju, %ju).",
                    (uintmax_t)ggio->gctl_offset, (uintmax_t)ggio->gctl_length);
                break;
        case BIO_DELETE:
                (void)snprlcat(msg, sizeof(msg), "DELETE(%ju, %ju).",
                    (uintmax_t)ggio->gctl_offset, (uintmax_t)ggio->gctl_length);
                break;
        case BIO_FLUSH:
                (void)snprlcat(msg, sizeof(msg), "FLUSH.");
                break;
        case BIO_WRITE:
                (void)snprlcat(msg, sizeof(msg), "WRITE(%ju, %ju).",
                    (uintmax_t)ggio->gctl_offset, (uintmax_t)ggio->gctl_length);
                break;
        default:
                (void)snprlcat(msg, sizeof(msg), "UNKNOWN(%u).",
                    (unsigned int)ggio->gctl_cmd);
                break;
        }
        pjdlog_common(loglevel, debuglevel, -1, "%s", msg);
}

static void
remote_close(struct hast_resource *res, int ncomp)
{

        rw_wlock(&hio_remote_lock[ncomp]);
        /*
         * Check for a race between dropping rlock and acquiring wlock -
         * another thread can close connection in-between.
         */
        if (!ISCONNECTED(res, ncomp)) {
                PJDLOG_ASSERT(res->hr_remotein == NULL);
                PJDLOG_ASSERT(res->hr_remoteout == NULL);
                rw_unlock(&hio_remote_lock[ncomp]);
                return;
        }

        PJDLOG_ASSERT(res->hr_remotein != NULL);
        PJDLOG_ASSERT(res->hr_remoteout != NULL);

        pjdlog_debug(2, "Closing incoming connection to %s.",
            res->hr_remoteaddr);
        proto_close(res->hr_remotein);
        res->hr_remotein = NULL;
        pjdlog_debug(2, "Closing outgoing connection to %s.",
            res->hr_remoteaddr);
        proto_close(res->hr_remoteout);
        res->hr_remoteout = NULL;

        rw_unlock(&hio_remote_lock[ncomp]);

        pjdlog_warning("Disconnected from %s.", res->hr_remoteaddr);

        /*
         * Stop synchronization if in-progress.
         */
        sync_stop();

        event_send(res, EVENT_DISCONNECT);
}

/*
 * Acknowledge write completion to the kernel, but don't update activemap yet.
 */
static void
write_complete(struct hast_resource *res, struct hio *hio)
{
        struct g_gate_ctl_io *ggio;
        unsigned int ncomp;

        PJDLOG_ASSERT(!hio->hio_done);

        ggio = &hio->hio_ggio;
        PJDLOG_ASSERT(ggio->gctl_cmd == BIO_WRITE);

        /*
         * Bump local count if this is first write after
         * connection failure with remote node.
         */
        ncomp = 1;
        rw_rlock(&hio_remote_lock[ncomp]);
        if (!ISCONNECTED(res, ncomp)) {
                mtx_lock(&metadata_lock);
                if (res->hr_primary_localcnt == res->hr_secondary_remotecnt) {
                        res->hr_primary_localcnt++;
                        pjdlog_debug(1, "Increasing localcnt to %ju.",
                            (uintmax_t)res->hr_primary_localcnt);
                        (void)metadata_write(res);
                }
                mtx_unlock(&metadata_lock);
        }
        rw_unlock(&hio_remote_lock[ncomp]);
        if (ioctl(res->hr_ggatefd, G_GATE_CMD_DONE, ggio) == -1)
                primary_exit(EX_OSERR, "G_GATE_CMD_DONE failed");
        hio->hio_done = true;
}

/*
 * Thread receives ggate I/O requests from the kernel and passes them to
 * appropriate threads:
 * WRITE - always goes to both local_send and remote_send threads
 * READ (when the block is up-to-date on local component) -
 *      only local_send thread
 * READ (when the block isn't up-to-date on local component) -
 *      only remote_send thread
 * DELETE - always goes to both local_send and remote_send threads
 * FLUSH - always goes to both local_send and remote_send threads
 */
static void *
ggate_recv_thread(void *arg)
{
        struct hast_resource *res = arg;
        struct g_gate_ctl_io *ggio;
        struct hio *hio;
        unsigned int ii, ncomp, ncomps;
        int error;

        for (;;) {
                pjdlog_debug(2, "ggate_recv: Taking free request.");
                QUEUE_TAKE2(hio, free);
                pjdlog_debug(2, "ggate_recv: (%p) Got free request.", hio);
                ggio = &hio->hio_ggio;
                ggio->gctl_unit = res->hr_ggateunit;
                ggio->gctl_length = MAXPHYS;
                ggio->gctl_error = 0;
                hio->hio_done = false;
                hio->hio_replication = res->hr_replication;
                pjdlog_debug(2,
                    "ggate_recv: (%p) Waiting for request from the kernel.",
                    hio);
                if (ioctl(res->hr_ggatefd, G_GATE_CMD_START, ggio) == -1) {
                        if (sigexit_received)
                                pthread_exit(NULL);
                        primary_exit(EX_OSERR, "G_GATE_CMD_START failed");
                }
                error = ggio->gctl_error;
                switch (error) {
                case 0:
                        break;
                case ECANCELED:
                        /* Exit gracefully. */
                        if (!sigexit_received) {
                                pjdlog_debug(2,
                                    "ggate_recv: (%p) Received cancel from the kernel.",
                                    hio);
                                pjdlog_info("Received cancel from the kernel, exiting.");
                        }
                        pthread_exit(NULL);
                case ENOMEM:
                        /*
                         * Buffer too small? Impossible, we allocate MAXPHYS
                         * bytes - request can't be bigger than that.
                         */
                        /* FALLTHROUGH */
                case ENXIO:
                default:
                        primary_exitx(EX_OSERR, "G_GATE_CMD_START failed: %s.",
                            strerror(error));
                }

                ncomp = 0;
                ncomps = HAST_NCOMPONENTS;

                for (ii = 0; ii < ncomps; ii++)
                        hio->hio_errors[ii] = EINVAL;
                reqlog(LOG_DEBUG, 2, ggio,
                    "ggate_recv: (%p) Request received from the kernel: ",
                    hio);

                /*
                 * Inform all components about new write request.
                 * For read request prefer local component unless the given
                 * range is out-of-date, then use remote component.
                 */
                switch (ggio->gctl_cmd) {
                case BIO_READ:
                        res->hr_stat_read++;
                        ncomps = 1;
                        mtx_lock(&metadata_lock);
                        if (res->hr_syncsrc == HAST_SYNCSRC_UNDEF ||
                            res->hr_syncsrc == HAST_SYNCSRC_PRIMARY) {
                                /*
                                 * This range is up-to-date on local component,
                                 * so handle request locally.
                                 */
                                 /* Local component is 0 for now. */
                                ncomp = 0;
                        } else /* if (res->hr_syncsrc ==
                            HAST_SYNCSRC_SECONDARY) */ {
                                PJDLOG_ASSERT(res->hr_syncsrc ==
                                    HAST_SYNCSRC_SECONDARY);
                                /*
                                 * This range is out-of-date on local component,
                                 * so send request to the remote node.
                                 */
                                 /* Remote component is 1 for now. */
                                ncomp = 1;
                        }
                        mtx_unlock(&metadata_lock);
                        break;
                case BIO_WRITE:
                        res->hr_stat_write++;
                        if (res->hr_resuid == 0 &&
                            res->hr_primary_localcnt == 0) {
                                /* This is first write. */
                                res->hr_primary_localcnt = 1;
                        }
                        for (;;) {
                                mtx_lock(&range_lock);
                                if (rangelock_islocked(range_sync,
                                    ggio->gctl_offset, ggio->gctl_length)) {
                                        pjdlog_debug(2,
                                            "regular: Range offset=%jd length=%zu locked.",
                                            (intmax_t)ggio->gctl_offset,
                                            (size_t)ggio->gctl_length);
                                        range_regular_wait = true;
                                        cv_wait(&range_regular_cond, &range_lock);
                                        range_regular_wait = false;
                                        mtx_unlock(&range_lock);
                                        continue;
                                }
                                if (rangelock_add(range_regular,
                                    ggio->gctl_offset, ggio->gctl_length) == -1) {
                                        mtx_unlock(&range_lock);
                                        pjdlog_debug(2,
                                            "regular: Range offset=%jd length=%zu is already locked, waiting.",
                                            (intmax_t)ggio->gctl_offset,
                                            (size_t)ggio->gctl_length);
                                        sleep(1);
                                        continue;
                                }
                                mtx_unlock(&range_lock);
                                break;
                        }
                        mtx_lock(&res->hr_amp_lock);
                        if (activemap_write_start(res->hr_amp,
                            ggio->gctl_offset, ggio->gctl_length)) {
                                res->hr_stat_activemap_update++;
                                (void)hast_activemap_flush(res);
                        } else {
                                mtx_unlock(&res->hr_amp_lock);
                        }
                        if (ISMEMSYNC(hio)) {
                                hio->hio_memsyncacked = false;
                                refcnt_init(&hio->hio_writecount, ncomps);
                        }
                        break;
                case BIO_DELETE:
                        res->hr_stat_delete++;
                        break;
                case BIO_FLUSH:
                        res->hr_stat_flush++;
                        break;
                }
                pjdlog_debug(2,
                    "ggate_recv: (%p) Moving request to the send queues.", hio);
                refcnt_init(&hio->hio_countdown, ncomps);
                for (ii = ncomp; ii < ncomps; ii++)
                        QUEUE_INSERT1(hio, send, ii);
        }
        /* NOTREACHED */
        return (NULL);
}

/*
 * Thread reads from or writes to local component.
 * If local read fails, it redirects it to remote_send thread.
 */
static void *
local_send_thread(void *arg)
{
        struct hast_resource *res = arg;
        struct g_gate_ctl_io *ggio;
        struct hio *hio;
        unsigned int ncomp, rncomp;
        ssize_t ret;

        /* Local component is 0 for now. */
        ncomp = 0;
        /* Remote component is 1 for now. */
        rncomp = 1;

        for (;;) {
                pjdlog_debug(2, "local_send: Taking request.");
                QUEUE_TAKE1(hio, send, ncomp, 0);
                pjdlog_debug(2, "local_send: (%p) Got request.", hio);
                ggio = &hio->hio_ggio;
                switch (ggio->gctl_cmd) {
                case BIO_READ:
                        ret = pread(res->hr_localfd, ggio->gctl_data,
                            ggio->gctl_length,
                            ggio->gctl_offset + res->hr_localoff);
                        if (ret == ggio->gctl_length)
                                hio->hio_errors[ncomp] = 0;
                        else if (!ISSYNCREQ(hio)) {
                                /*
                                 * If READ failed, try to read from remote node.
                                 */
                                if (ret == -1) {
                                        reqlog(LOG_WARNING, 0, ggio,
                                            "Local request failed (%s), trying remote node. ",
                                            strerror(errno));
                                } else if (ret != ggio->gctl_length) {
                                        reqlog(LOG_WARNING, 0, ggio,
                                            "Local request failed (%zd != %jd), trying remote node. ",
                                            ret, (intmax_t)ggio->gctl_length);
                                }
                                QUEUE_INSERT1(hio, send, rncomp);
                                continue;
                        }
                        break;
                case BIO_WRITE:
                        ret = pwrite(res->hr_localfd, ggio->gctl_data,
                            ggio->gctl_length,
                            ggio->gctl_offset + res->hr_localoff);
                        if (ret == -1) {
                                hio->hio_errors[ncomp] = errno;
                                reqlog(LOG_WARNING, 0, ggio,
                                    "Local request failed (%s): ",
                                    strerror(errno));
                        } else if (ret != ggio->gctl_length) {
                                hio->hio_errors[ncomp] = EIO;
                                reqlog(LOG_WARNING, 0, ggio,
                                    "Local request failed (%zd != %jd): ",
                                    ret, (intmax_t)ggio->gctl_length);
                        } else {
                                hio->hio_errors[ncomp] = 0;
                                if (ISASYNC(hio)) {
                                        ggio->gctl_error = 0;
                                        write_complete(res, hio);
                                }
                        }
                        break;
                case BIO_DELETE:
                        ret = g_delete(res->hr_localfd,
                            ggio->gctl_offset + res->hr_localoff,
                            ggio->gctl_length);
                        if (ret == -1) {
                                hio->hio_errors[ncomp] = errno;
                                reqlog(LOG_WARNING, 0, ggio,
                                    "Local request failed (%s): ",
                                    strerror(errno));
                        } else {
                                hio->hio_errors[ncomp] = 0;
                        }
                        break;
                case BIO_FLUSH:
                        if (!res->hr_localflush) {
                                ret = -1;
                                errno = EOPNOTSUPP;
                                break;
                        }
                        ret = g_flush(res->hr_localfd);
                        if (ret == -1) {
                                if (errno == EOPNOTSUPP)
                                        res->hr_localflush = false;
                                hio->hio_errors[ncomp] = errno;
                                reqlog(LOG_WARNING, 0, ggio,
                                    "Local request failed (%s): ",
                                    strerror(errno));
                        } else {
                                hio->hio_errors[ncomp] = 0;
                        }
                        break;
                }
                if (ISMEMSYNCWRITE(hio)) {
                        if (refcnt_release(&hio->hio_writecount) == 0) {
                                write_complete(res, hio);
                        }
                }
                if (refcnt_release(&hio->hio_countdown) > 0)
                        continue;
                if (ISSYNCREQ(hio)) {
                        mtx_lock(&sync_lock);
                        SYNCREQDONE(hio);
                        mtx_unlock(&sync_lock);
                        cv_signal(&sync_cond);
                } else {
                        pjdlog_debug(2,
                            "local_send: (%p) Moving request to the done queue.",
                            hio);
                        QUEUE_INSERT2(hio, done);
                }
        }
        /* NOTREACHED */
        return (NULL);
}

static void
keepalive_send(struct hast_resource *res, unsigned int ncomp)
{
        struct nv *nv;

        rw_rlock(&hio_remote_lock[ncomp]);

        if (!ISCONNECTED(res, ncomp)) {
                rw_unlock(&hio_remote_lock[ncomp]);
                return;
        }

        PJDLOG_ASSERT(res->hr_remotein != NULL);
        PJDLOG_ASSERT(res->hr_remoteout != NULL);

        nv = nv_alloc();
        nv_add_uint8(nv, HIO_KEEPALIVE, "cmd");
        if (nv_error(nv) != 0) {
                rw_unlock(&hio_remote_lock[ncomp]);
                nv_free(nv);
                pjdlog_debug(1,
                    "keepalive_send: Unable to prepare header to send.");
                return;
        }
        if (hast_proto_send(res, res->hr_remoteout, nv, NULL, 0) == -1) {
                rw_unlock(&hio_remote_lock[ncomp]);
                pjdlog_common(LOG_DEBUG, 1, errno,
                    "keepalive_send: Unable to send request");
                nv_free(nv);
                remote_close(res, ncomp);
                return;
        }

        rw_unlock(&hio_remote_lock[ncomp]);
        nv_free(nv);
        pjdlog_debug(2, "keepalive_send: Request sent.");
}

/*
 * Thread sends request to secondary node.
 */
static void *
remote_send_thread(void *arg)
{
        struct hast_resource *res = arg;
        struct g_gate_ctl_io *ggio;
        time_t lastcheck, now;
        struct hio *hio;
        struct nv *nv;
        unsigned int ncomp;
        bool wakeup;
        uint64_t offset, length;
        uint8_t cmd;
        void *data;

        /* Remote component is 1 for now. */
        ncomp = 1;
        lastcheck = time(NULL);

        for (;;) {
                pjdlog_debug(2, "remote_send: Taking request.");
                QUEUE_TAKE1(hio, send, ncomp, HAST_KEEPALIVE);
                if (hio == NULL) {
                        now = time(NULL);
                        if (lastcheck + HAST_KEEPALIVE <= now) {
                                keepalive_send(res, ncomp);
                                lastcheck = now;
                        }
                        continue;
                }
                pjdlog_debug(2, "remote_send: (%p) Got request.", hio);
                ggio = &hio->hio_ggio;
                switch (ggio->gctl_cmd) {
                case BIO_READ:
                        cmd = HIO_READ;
                        data = NULL;
                        offset = ggio->gctl_offset;
                        length = ggio->gctl_length;
                        break;
                case BIO_WRITE:
                        cmd = HIO_WRITE;
                        data = ggio->gctl_data;
                        offset = ggio->gctl_offset;
                        length = ggio->gctl_length;
                        break;
                case BIO_DELETE:
                        cmd = HIO_DELETE;
                        data = NULL;
                        offset = ggio->gctl_offset;
                        length = ggio->gctl_length;
                        break;
                case BIO_FLUSH:
                        cmd = HIO_FLUSH;
                        data = NULL;
                        offset = 0;
                        length = 0;
                        break;
                default:
                        PJDLOG_ABORT("invalid condition");
                }
                nv = nv_alloc();
                nv_add_uint8(nv, cmd, "cmd");
                nv_add_uint64(nv, (uint64_t)ggio->gctl_seq, "seq");
                nv_add_uint64(nv, offset, "offset");
                nv_add_uint64(nv, length, "length");
                if (ISMEMSYNCWRITE(hio))
                        nv_add_uint8(nv, 1, "memsync");
                if (nv_error(nv) != 0) {
                        hio->hio_errors[ncomp] = nv_error(nv);
                        pjdlog_debug(2,
                            "remote_send: (%p) Unable to prepare header to send.",
                            hio);
                        reqlog(LOG_ERR, 0, ggio,
                            "Unable to prepare header to send (%s): ",
                            strerror(nv_error(nv)));
                        /* Move failed request immediately to the done queue. */
                        goto done_queue;
                }
                /*
                 * Protect connection from disappearing.
                 */
                rw_rlock(&hio_remote_lock[ncomp]);
                if (!ISCONNECTED(res, ncomp)) {
                        rw_unlock(&hio_remote_lock[ncomp]);
                        hio->hio_errors[ncomp] = ENOTCONN;
                        goto done_queue;
                }
                /*
                 * Move the request to recv queue before sending it, because
                 * in different order we can get reply before we move request
                 * to recv queue.
                 */
                pjdlog_debug(2,
                    "remote_send: (%p) Moving request to the recv queue.",
                    hio);
                mtx_lock(&hio_recv_list_lock[ncomp]);
                wakeup = TAILQ_EMPTY(&hio_recv_list[ncomp]);
                TAILQ_INSERT_TAIL(&hio_recv_list[ncomp], hio, hio_next[ncomp]);
                hio_recv_list_size[ncomp]++;
                mtx_unlock(&hio_recv_list_lock[ncomp]);
                if (hast_proto_send(res, res->hr_remoteout, nv, data,
                    data != NULL ? length : 0) == -1) {
                        hio->hio_errors[ncomp] = errno;
                        rw_unlock(&hio_remote_lock[ncomp]);
                        pjdlog_debug(2,
                            "remote_send: (%p) Unable to send request.", hio);
                        reqlog(LOG_ERR, 0, ggio,
                            "Unable to send request (%s): ",
                            strerror(hio->hio_errors[ncomp]));
                        remote_close(res, ncomp);
                } else {
                        rw_unlock(&hio_remote_lock[ncomp]);
                }
                nv_free(nv);
                if (wakeup)
                        cv_signal(&hio_recv_list_cond[ncomp]);
                continue;
done_queue:
                nv_free(nv);
                if (ISSYNCREQ(hio)) {
                        if (refcnt_release(&hio->hio_countdown) > 0)
                                continue;
                        mtx_lock(&sync_lock);
                        SYNCREQDONE(hio);
                        mtx_unlock(&sync_lock);
                        cv_signal(&sync_cond);
                        continue;
                }
                if (ggio->gctl_cmd == BIO_WRITE) {
                        mtx_lock(&res->hr_amp_lock);
                        if (activemap_need_sync(res->hr_amp, ggio->gctl_offset,
                            ggio->gctl_length)) {
                                (void)hast_activemap_flush(res);
                        } else {
                                mtx_unlock(&res->hr_amp_lock);
                        }
                        if (ISMEMSYNCWRITE(hio)) {
                                if (refcnt_release(&hio->hio_writecount) == 0) {
                                        if (hio->hio_errors[0] == 0)
                                                write_complete(res, hio);
                                }
                        }
                }
                if (refcnt_release(&hio->hio_countdown) > 0)
                        continue;
                pjdlog_debug(2,
                    "remote_send: (%p) Moving request to the done queue.",
                    hio);
                QUEUE_INSERT2(hio, done);
        }
        /* NOTREACHED */
        return (NULL);
}

/*
 * Thread receives answer from secondary node and passes it to ggate_send
 * thread.
 */
static void *
remote_recv_thread(void *arg)
{
        struct hast_resource *res = arg;
        struct g_gate_ctl_io *ggio;
        struct hio *hio;
        struct nv *nv;
        unsigned int ncomp;
        uint64_t seq;
        bool memsyncack;
        int error;

        /* Remote component is 1 for now. */
        ncomp = 1;

        for (;;) {
                /* Wait until there is anything to receive. */
                mtx_lock(&hio_recv_list_lock[ncomp]);
                while (TAILQ_EMPTY(&hio_recv_list[ncomp])) {
                        pjdlog_debug(2, "remote_recv: No requests, waiting.");
                        cv_wait(&hio_recv_list_cond[ncomp],
                            &hio_recv_list_lock[ncomp]);
                }
                mtx_unlock(&hio_recv_list_lock[ncomp]);

                memsyncack = false;

                rw_rlock(&hio_remote_lock[ncomp]);
                if (!ISCONNECTED(res, ncomp)) {
                        rw_unlock(&hio_remote_lock[ncomp]);
                        /*
                         * Connection is dead, so move all pending requests to
                         * the done queue (one-by-one).
                         */
                        mtx_lock(&hio_recv_list_lock[ncomp]);
                        hio = TAILQ_FIRST(&hio_recv_list[ncomp]);
                        PJDLOG_ASSERT(hio != NULL);
                        TAILQ_REMOVE(&hio_recv_list[ncomp], hio,
                            hio_next[ncomp]);
                        hio_recv_list_size[ncomp]--;
                        mtx_unlock(&hio_recv_list_lock[ncomp]);
                        hio->hio_errors[ncomp] = ENOTCONN;
                        goto done_queue;
                }
                if (hast_proto_recv_hdr(res->hr_remotein, &nv) == -1) {
                        pjdlog_errno(LOG_ERR,
                            "Unable to receive reply header");
                        rw_unlock(&hio_remote_lock[ncomp]);
                        remote_close(res, ncomp);
                        continue;
                }
                rw_unlock(&hio_remote_lock[ncomp]);
                seq = nv_get_uint64(nv, "seq");
                if (seq == 0) {
                        pjdlog_error("Header contains no 'seq' field.");
                        nv_free(nv);
                        continue;
                }
                memsyncack = nv_exists(nv, "received");
                mtx_lock(&hio_recv_list_lock[ncomp]);
                TAILQ_FOREACH(hio, &hio_recv_list[ncomp], hio_next[ncomp]) {
                        if (hio->hio_ggio.gctl_seq == seq) {
                                TAILQ_REMOVE(&hio_recv_list[ncomp], hio,
                                    hio_next[ncomp]);
                                hio_recv_list_size[ncomp]--;
                                break;
                        }
                }
                mtx_unlock(&hio_recv_list_lock[ncomp]);
                if (hio == NULL) {
                        pjdlog_error("Found no request matching received 'seq' field (%ju).",
                            (uintmax_t)seq);
                        nv_free(nv);
                        continue;
                }
                ggio = &hio->hio_ggio;
                error = nv_get_int16(nv, "error");
                if (error != 0) {
                        /* Request failed on remote side. */
                        hio->hio_errors[ncomp] = error;
                        reqlog(LOG_WARNING, 0, ggio,
                            "Remote request failed (%s): ", strerror(error));
                        nv_free(nv);
                        goto done_queue;
                }
                switch (ggio->gctl_cmd) {
                case BIO_READ:
                        rw_rlock(&hio_remote_lock[ncomp]);
                        if (!ISCONNECTED(res, ncomp)) {
                                rw_unlock(&hio_remote_lock[ncomp]);
                                nv_free(nv);
                                goto done_queue;
                        }
                        if (hast_proto_recv_data(res, res->hr_remotein, nv,
                            ggio->gctl_data, ggio->gctl_length) == -1) {
                                hio->hio_errors[ncomp] = errno;
                                pjdlog_errno(LOG_ERR,
                                    "Unable to receive reply data");
                                rw_unlock(&hio_remote_lock[ncomp]);
                                nv_free(nv);
                                remote_close(res, ncomp);
                                goto done_queue;
                        }
                        rw_unlock(&hio_remote_lock[ncomp]);
                        break;
                case BIO_WRITE:
                case BIO_DELETE:
                case BIO_FLUSH:
                        break;
                default:
                        PJDLOG_ABORT("invalid condition");
                }
                hio->hio_errors[ncomp] = 0;
                nv_free(nv);
done_queue:
                if (ISMEMSYNCWRITE(hio)) {
                        if (!hio->hio_memsyncacked) {
                                PJDLOG_ASSERT(memsyncack ||
                                    hio->hio_errors[ncomp] != 0);
                                /* Remote ack arrived. */
                                if (refcnt_release(&hio->hio_writecount) == 0) {
                                        if (hio->hio_errors[0] == 0)
                                                write_complete(res, hio);
                                }
                                hio->hio_memsyncacked = true;
                                if (hio->hio_errors[ncomp] == 0) {
                                        pjdlog_debug(2,
                                            "remote_recv: (%p) Moving request "
                                            "back to the recv queue.", hio);
                                        mtx_lock(&hio_recv_list_lock[ncomp]);
                                        TAILQ_INSERT_TAIL(&hio_recv_list[ncomp],
                                            hio, hio_next[ncomp]);
                                        hio_recv_list_size[ncomp]++;
                                        mtx_unlock(&hio_recv_list_lock[ncomp]);
                                        continue;
                                }
                        } else {
                                PJDLOG_ASSERT(!memsyncack);
                                /* Remote final reply arrived. */
                        }
                }
                if (refcnt_release(&hio->hio_countdown) > 0)
                        continue;
                if (ISSYNCREQ(hio)) {
                        mtx_lock(&sync_lock);
                        SYNCREQDONE(hio);
                        mtx_unlock(&sync_lock);
                        cv_signal(&sync_cond);
                } else {
                        pjdlog_debug(2,
                            "remote_recv: (%p) Moving request to the done queue.",
                            hio);
                        QUEUE_INSERT2(hio, done);
                }
        }
        /* NOTREACHED */
        return (NULL);
}

/*
 * Thread sends answer to the kernel.
 */
static void *
ggate_send_thread(void *arg)
{
        struct hast_resource *res = arg;
        struct g_gate_ctl_io *ggio;
        struct hio *hio;
        unsigned int ii, ncomps;

        ncomps = HAST_NCOMPONENTS;

        for (;;) {
                pjdlog_debug(2, "ggate_send: Taking request.");
                QUEUE_TAKE2(hio, done);
                pjdlog_debug(2, "ggate_send: (%p) Got request.", hio);
                ggio = &hio->hio_ggio;
                for (ii = 0; ii < ncomps; ii++) {
                        if (hio->hio_errors[ii] == 0) {
                                /*
                                 * One successful request is enough to declare
                                 * success.
                                 */
                                ggio->gctl_error = 0;
                                break;
                        }
                }
                if (ii == ncomps) {
                        /*
                         * None of the requests were successful.
                         * Use the error from local component except the
                         * case when we did only remote request.
                         */
                        if (ggio->gctl_cmd == BIO_READ &&
                            res->hr_syncsrc == HAST_SYNCSRC_SECONDARY)
                                ggio->gctl_error = hio->hio_errors[1];
                        else
                                ggio->gctl_error = hio->hio_errors[0];
                }
                if (ggio->gctl_error == 0 && ggio->gctl_cmd == BIO_WRITE) {
                        mtx_lock(&res->hr_amp_lock);
                        if (activemap_write_complete(res->hr_amp,
                            ggio->gctl_offset, ggio->gctl_length)) {
                                res->hr_stat_activemap_update++;
                                (void)hast_activemap_flush(res);
                        } else {
                                mtx_unlock(&res->hr_amp_lock);
                        }
                }
                if (ggio->gctl_cmd == BIO_WRITE) {
                        /*
                         * Unlock range we locked.
                         */
                        mtx_lock(&range_lock);
                        rangelock_del(range_regular, ggio->gctl_offset,
                            ggio->gctl_length);
                        if (range_sync_wait)
                                cv_signal(&range_sync_cond);
                        mtx_unlock(&range_lock);
                        if (!hio->hio_done)
                                write_complete(res, hio);
                } else {
                        if (ioctl(res->hr_ggatefd, G_GATE_CMD_DONE, ggio) == -1) {
                                primary_exit(EX_OSERR,
                                    "G_GATE_CMD_DONE failed");
                        }
                }
                if (hio->hio_errors[0]) {
                        switch (ggio->gctl_cmd) {
                        case BIO_READ:
                                res->hr_stat_read_error++;
                                break;
                        case BIO_WRITE:
                                res->hr_stat_write_error++;
                                break;
                        case BIO_DELETE:
                                res->hr_stat_delete_error++;
                                break;
                        case BIO_FLUSH:
                                res->hr_stat_flush_error++;
                                break;
                        }
                }
                pjdlog_debug(2,
                    "ggate_send: (%p) Moving request to the free queue.", hio);
                QUEUE_INSERT2(hio, free);
        }
        /* NOTREACHED */
        return (NULL);
}

/*
 * Thread synchronize local and remote components.
 */
static void *
sync_thread(void *arg __unused)
{
        struct hast_resource *res = arg;
        struct hio *hio;
        struct g_gate_ctl_io *ggio;
        struct timeval tstart, tend, tdiff;
        unsigned int ii, ncomp, ncomps;
        off_t offset, length, synced;
        bool dorewind, directreads;
        int syncext;

        ncomps = HAST_NCOMPONENTS;
        dorewind = true;
        synced = 0;
        offset = -1;
        directreads = false;

        for (;;) {
                mtx_lock(&sync_lock);
                if (offset >= 0 && !sync_inprogress) {
                        gettimeofday(&tend, NULL);
                        timersub(&tend, &tstart, &tdiff);
                        pjdlog_info("Synchronization interrupted after %#.0T. "
                            "%NB synchronized so far.", &tdiff,
                            (intmax_t)synced);
                        event_send(res, EVENT_SYNCINTR);
                }
                while (!sync_inprogress) {
                        dorewind = true;
                        synced = 0;
                        cv_wait(&sync_cond, &sync_lock);
                }
                mtx_unlock(&sync_lock);
                /*
                 * Obtain offset at which we should synchronize.
                 * Rewind synchronization if needed.
                 */
                mtx_lock(&res->hr_amp_lock);
                if (dorewind)
                        activemap_sync_rewind(res->hr_amp);
                offset = activemap_sync_offset(res->hr_amp, &length, &syncext);
                if (syncext != -1) {
                        /*
                         * We synchronized entire syncext extent, we can mark
                         * it as clean now.
                         */
                        if (activemap_extent_complete(res->hr_amp, syncext))
                                (void)hast_activemap_flush(res);
                        else
                                mtx_unlock(&res->hr_amp_lock);
                } else {
                        mtx_unlock(&res->hr_amp_lock);
                }
                if (dorewind) {
                        dorewind = false;
                        if (offset == -1)
                                pjdlog_info("Nodes are in sync.");
                        else {
                                pjdlog_info("Synchronization started. %NB to go.",
                                    (intmax_t)(res->hr_extentsize *
                                    activemap_ndirty(res->hr_amp)));
                                event_send(res, EVENT_SYNCSTART);
                                gettimeofday(&tstart, NULL);
                        }
                }
                if (offset == -1) {
                        sync_stop();
                        pjdlog_debug(1, "Nothing to synchronize.");
                        /*
                         * Synchronization complete, make both localcnt and
                         * remotecnt equal.
                         */
                        ncomp = 1;
                        rw_rlock(&hio_remote_lock[ncomp]);
                        if (ISCONNECTED(res, ncomp)) {
                                if (synced > 0) {
                                        int64_t bps;

                                        gettimeofday(&tend, NULL);
                                        timersub(&tend, &tstart, &tdiff);
                                        bps = (int64_t)((double)synced /
                                            ((double)tdiff.tv_sec +
                                            (double)tdiff.tv_usec / 1000000));
                                        pjdlog_info("Synchronization complete. "
                                            "%NB synchronized in %#.0lT (%NB/sec).",
                                            (intmax_t)synced, &tdiff,
                                            (intmax_t)bps);
                                        event_send(res, EVENT_SYNCDONE);
                                }
                                mtx_lock(&metadata_lock);
                                if (res->hr_syncsrc == HAST_SYNCSRC_SECONDARY)
                                        directreads = true;
                                res->hr_syncsrc = HAST_SYNCSRC_UNDEF;
                                res->hr_primary_localcnt =
                                    res->hr_secondary_remotecnt;
                                res->hr_primary_remotecnt =
                                    res->hr_secondary_localcnt;
                                pjdlog_debug(1,
                                    "Setting localcnt to %ju and remotecnt to %ju.",
                                    (uintmax_t)res->hr_primary_localcnt,
                                    (uintmax_t)res->hr_primary_remotecnt);
                                (void)metadata_write(res);
                                mtx_unlock(&metadata_lock);
                        }
                        rw_unlock(&hio_remote_lock[ncomp]);
                        if (directreads) {
                                directreads = false;
                                enable_direct_reads(res);
                        }
                        continue;
                }
                pjdlog_debug(2, "sync: Taking free request.");
                QUEUE_TAKE2(hio, free);
                pjdlog_debug(2, "sync: (%p) Got free request.", hio);
                /*
                 * Lock the range we are going to synchronize. We don't want
                 * race where someone writes between our read and write.
                 */
                for (;;) {
                        mtx_lock(&range_lock);
                        if (rangelock_islocked(range_regular, offset, length)) {
                                pjdlog_debug(2,
                                    "sync: Range offset=%jd length=%jd locked.",
                                    (intmax_t)offset, (intmax_t)length);
                                range_sync_wait = true;
                                cv_wait(&range_sync_cond, &range_lock);
                                range_sync_wait = false;
                                mtx_unlock(&range_lock);
                                continue;
                        }
                        if (rangelock_add(range_sync, offset, length) == -1) {
                                mtx_unlock(&range_lock);
                                pjdlog_debug(2,
                                    "sync: Range offset=%jd length=%jd is already locked, waiting.",
                                    (intmax_t)offset, (intmax_t)length);
                                sleep(1);
                                continue;
                        }
                        mtx_unlock(&range_lock);
                        break;
                }
                /*
                 * First read the data from synchronization source.
                 */
                SYNCREQ(hio);
                ggio = &hio->hio_ggio;
                ggio->gctl_cmd = BIO_READ;
                ggio->gctl_offset = offset;
                ggio->gctl_length = length;
                ggio->gctl_error = 0;
                hio->hio_done = false;
                hio->hio_replication = res->hr_replication;
                for (ii = 0; ii < ncomps; ii++)
                        hio->hio_errors[ii] = EINVAL;
                reqlog(LOG_DEBUG, 2, ggio, "sync: (%p) Sending sync request: ",
                    hio);
                pjdlog_debug(2, "sync: (%p) Moving request to the send queue.",
                    hio);
                mtx_lock(&metadata_lock);
                if (res->hr_syncsrc == HAST_SYNCSRC_PRIMARY) {
                        /*
                         * This range is up-to-date on local component,
                         * so handle request locally.
                         */
                         /* Local component is 0 for now. */
                        ncomp = 0;
                } else /* if (res->hr_syncsrc == HAST_SYNCSRC_SECONDARY) */ {
                        PJDLOG_ASSERT(res->hr_syncsrc == HAST_SYNCSRC_SECONDARY);
                        /*
                         * This range is out-of-date on local component,
                         * so send request to the remote node.
                         */
                         /* Remote component is 1 for now. */
                        ncomp = 1;
                }
                mtx_unlock(&metadata_lock);
                refcnt_init(&hio->hio_countdown, 1);
                QUEUE_INSERT1(hio, send, ncomp);

                /*
                 * Let's wait for READ to finish.
                 */
                mtx_lock(&sync_lock);
                while (!ISSYNCREQDONE(hio))
                        cv_wait(&sync_cond, &sync_lock);
                mtx_unlock(&sync_lock);

                if (hio->hio_errors[ncomp] != 0) {
                        pjdlog_error("Unable to read synchronization data: %s.",
                            strerror(hio->hio_errors[ncomp]));
                        goto free_queue;
                }

                /*
                 * We read the data from synchronization source, now write it
                 * to synchronization target.
                 */
                SYNCREQ(hio);
                ggio->gctl_cmd = BIO_WRITE;
                for (ii = 0; ii < ncomps; ii++)
                        hio->hio_errors[ii] = EINVAL;
                reqlog(LOG_DEBUG, 2, ggio, "sync: (%p) Sending sync request: ",
                    hio);
                pjdlog_debug(2, "sync: (%p) Moving request to the send queue.",
                    hio);
                mtx_lock(&metadata_lock);
                if (res->hr_syncsrc == HAST_SYNCSRC_PRIMARY) {
                        /*
                         * This range is up-to-date on local component,
                         * so we update remote component.
                         */
                         /* Remote component is 1 for now. */
                        ncomp = 1;
                } else /* if (res->hr_syncsrc == HAST_SYNCSRC_SECONDARY) */ {
                        PJDLOG_ASSERT(res->hr_syncsrc == HAST_SYNCSRC_SECONDARY);
                        /*
                         * This range is out-of-date on local component,
                         * so we update it.
                         */
                         /* Local component is 0 for now. */
                        ncomp = 0;
                }
                mtx_unlock(&metadata_lock);

                pjdlog_debug(2, "sync: (%p) Moving request to the send queue.",
                    hio);
                refcnt_init(&hio->hio_countdown, 1);
                QUEUE_INSERT1(hio, send, ncomp);

                /*
                 * Let's wait for WRITE to finish.
                 */
                mtx_lock(&sync_lock);
                while (!ISSYNCREQDONE(hio))
                        cv_wait(&sync_cond, &sync_lock);
                mtx_unlock(&sync_lock);

                if (hio->hio_errors[ncomp] != 0) {
                        pjdlog_error("Unable to write synchronization data: %s.",
                            strerror(hio->hio_errors[ncomp]));
                        goto free_queue;
                }

                synced += length;
free_queue:
                mtx_lock(&range_lock);
                rangelock_del(range_sync, offset, length);
                if (range_regular_wait)
                        cv_signal(&range_regular_cond);
                mtx_unlock(&range_lock);
                pjdlog_debug(2, "sync: (%p) Moving request to the free queue.",
                    hio);
                QUEUE_INSERT2(hio, free);
        }
        /* NOTREACHED */
        return (NULL);
}

void
primary_config_reload(struct hast_resource *res, struct nv *nv)
{
        unsigned int ii, ncomps;
        int modified, vint;
        const char *vstr;

        pjdlog_info("Reloading configuration...");

        PJDLOG_ASSERT(res->hr_role == HAST_ROLE_PRIMARY);
        PJDLOG_ASSERT(gres == res);
        nv_assert(nv, "remoteaddr");
        nv_assert(nv, "sourceaddr");
        nv_assert(nv, "replication");
        nv_assert(nv, "checksum");
        nv_assert(nv, "compression");
        nv_assert(nv, "timeout");
        nv_assert(nv, "exec");
        nv_assert(nv, "metaflush");

        ncomps = HAST_NCOMPONENTS;

#define MODIFIED_REMOTEADDR     0x01
#define MODIFIED_SOURCEADDR     0x02
#define MODIFIED_REPLICATION    0x04
#define MODIFIED_CHECKSUM       0x08
#define MODIFIED_COMPRESSION    0x10
#define MODIFIED_TIMEOUT        0x20
#define MODIFIED_EXEC           0x40
#define MODIFIED_METAFLUSH      0x80
        modified = 0;

        vstr = nv_get_string(nv, "remoteaddr");
        if (strcmp(gres->hr_remoteaddr, vstr) != 0) {
                /*
                 * Don't copy res->hr_remoteaddr to gres just yet.
                 * We want remote_close() to log disconnect from the old
                 * addresses, not from the new ones.
                 */
                modified |= MODIFIED_REMOTEADDR;
        }
        vstr = nv_get_string(nv, "sourceaddr");
        if (strcmp(gres->hr_sourceaddr, vstr) != 0) {
                strlcpy(gres->hr_sourceaddr, vstr, sizeof(gres->hr_sourceaddr));
                modified |= MODIFIED_SOURCEADDR;
        }
        vint = nv_get_int32(nv, "replication");
        if (gres->hr_replication != vint) {
                gres->hr_replication = vint;
                modified |= MODIFIED_REPLICATION;
        }
        vint = nv_get_int32(nv, "checksum");
        if (gres->hr_checksum != vint) {
                gres->hr_checksum = vint;
                modified |= MODIFIED_CHECKSUM;
        }
        vint = nv_get_int32(nv, "compression");
        if (gres->hr_compression != vint) {
                gres->hr_compression = vint;
                modified |= MODIFIED_COMPRESSION;
        }
        vint = nv_get_int32(nv, "timeout");
        if (gres->hr_timeout != vint) {
                gres->hr_timeout = vint;
                modified |= MODIFIED_TIMEOUT;
        }
        vstr = nv_get_string(nv, "exec");
        if (strcmp(gres->hr_exec, vstr) != 0) {
                strlcpy(gres->hr_exec, vstr, sizeof(gres->hr_exec));
                modified |= MODIFIED_EXEC;
        }
        vint = nv_get_int32(nv, "metaflush");
        if (gres->hr_metaflush != vint) {
                gres->hr_metaflush = vint;
                modified |= MODIFIED_METAFLUSH;
        }

        /*
         * Change timeout for connected sockets.
         * Don't bother if we need to reconnect.
         */
        if ((modified & MODIFIED_TIMEOUT) != 0 &&
            (modified & (MODIFIED_REMOTEADDR | MODIFIED_SOURCEADDR)) == 0) {
                for (ii = 0; ii < ncomps; ii++) {
                        if (!ISREMOTE(ii))
                                continue;
                        rw_rlock(&hio_remote_lock[ii]);
                        if (!ISCONNECTED(gres, ii)) {
                                rw_unlock(&hio_remote_lock[ii]);
                                continue;
                        }
                        rw_unlock(&hio_remote_lock[ii]);
                        if (proto_timeout(gres->hr_remotein,
                            gres->hr_timeout) == -1) {
                                pjdlog_errno(LOG_WARNING,
                                    "Unable to set connection timeout");
                        }
                        if (proto_timeout(gres->hr_remoteout,
                            gres->hr_timeout) == -1) {
                                pjdlog_errno(LOG_WARNING,
                                    "Unable to set connection timeout");
                        }
                }
        }
        if ((modified & (MODIFIED_REMOTEADDR | MODIFIED_SOURCEADDR)) != 0) {
                for (ii = 0; ii < ncomps; ii++) {
                        if (!ISREMOTE(ii))
                                continue;
                        remote_close(gres, ii);
                }
                if (modified & MODIFIED_REMOTEADDR) {
                        vstr = nv_get_string(nv, "remoteaddr");
                        strlcpy(gres->hr_remoteaddr, vstr,
                            sizeof(gres->hr_remoteaddr));
                }
        }
#undef  MODIFIED_REMOTEADDR
#undef  MODIFIED_SOURCEADDR
#undef  MODIFIED_REPLICATION
#undef  MODIFIED_CHECKSUM
#undef  MODIFIED_COMPRESSION
#undef  MODIFIED_TIMEOUT
#undef  MODIFIED_EXEC
#undef  MODIFIED_METAFLUSH

        pjdlog_info("Configuration reloaded successfully.");
}

static void
guard_one(struct hast_resource *res, unsigned int ncomp)
{
        struct proto_conn *in, *out;

        if (!ISREMOTE(ncomp))
                return;

        rw_rlock(&hio_remote_lock[ncomp]);

        if (!real_remote(res)) {
                rw_unlock(&hio_remote_lock[ncomp]);
                return;
        }

        if (ISCONNECTED(res, ncomp)) {
                PJDLOG_ASSERT(res->hr_remotein != NULL);
                PJDLOG_ASSERT(res->hr_remoteout != NULL);
                rw_unlock(&hio_remote_lock[ncomp]);
                pjdlog_debug(2, "remote_guard: Connection to %s is ok.",
                    res->hr_remoteaddr);
                return;
        }

        PJDLOG_ASSERT(res->hr_remotein == NULL);
        PJDLOG_ASSERT(res->hr_remoteout == NULL);
        /*
         * Upgrade the lock. It doesn't have to be atomic as no other thread
         * can change connection status from disconnected to connected.
         */
        rw_unlock(&hio_remote_lock[ncomp]);
        pjdlog_debug(2, "remote_guard: Reconnecting to %s.",
            res->hr_remoteaddr);
        in = out = NULL;
        if (init_remote(res, &in, &out) == 0) {
                rw_wlock(&hio_remote_lock[ncomp]);
                PJDLOG_ASSERT(res->hr_remotein == NULL);
                PJDLOG_ASSERT(res->hr_remoteout == NULL);
                PJDLOG_ASSERT(in != NULL && out != NULL);
                res->hr_remotein = in;
                res->hr_remoteout = out;
                rw_unlock(&hio_remote_lock[ncomp]);
                pjdlog_info("Successfully reconnected to %s.",
                    res->hr_remoteaddr);
                sync_start();
        } else {
                /* Both connections should be NULL. */
                PJDLOG_ASSERT(res->hr_remotein == NULL);
                PJDLOG_ASSERT(res->hr_remoteout == NULL);
                PJDLOG_ASSERT(in == NULL && out == NULL);
                pjdlog_debug(2, "remote_guard: Reconnect to %s failed.",
                    res->hr_remoteaddr);
        }
}

/*
 * Thread guards remote connections and reconnects when needed, handles
 * signals, etc.
 */
static void *
guard_thread(void *arg)
{
        struct hast_resource *res = arg;
        unsigned int ii, ncomps;
        struct timespec timeout;
        time_t lastcheck, now;
        sigset_t mask;
        int signo;

        ncomps = HAST_NCOMPONENTS;
        lastcheck = time(NULL);

        PJDLOG_VERIFY(sigemptyset(&mask) == 0);
        PJDLOG_VERIFY(sigaddset(&mask, SIGINT) == 0);
        PJDLOG_VERIFY(sigaddset(&mask, SIGTERM) == 0);

        timeout.tv_sec = HAST_KEEPALIVE;
        timeout.tv_nsec = 0;
        signo = -1;

        for (;;) {
                switch (signo) {
                case SIGINT:
                case SIGTERM:
                        sigexit_received = true;
                        primary_exitx(EX_OK,
                            "Termination signal received, exiting.");
                        break;
                default:
                        break;
                }

                /*
                 * Don't check connections until we fully started,
                 * as we may still be looping, waiting for remote node
                 * to switch from primary to secondary.
                 */
                if (fullystarted) {
                        pjdlog_debug(2, "remote_guard: Checking connections.");
                        now = time(NULL);
                        if (lastcheck + HAST_KEEPALIVE <= now) {
                                for (ii = 0; ii < ncomps; ii++)
                                        guard_one(res, ii);
                                lastcheck = now;
                        }
                }
                signo = sigtimedwait(&mask, NULL, &timeout);
        }
        /* NOTREACHED */
        return (NULL);
}