/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2010 Edward Tomasz Napierala <trasz@FreeBSD.org>
 * Copyright (c) 2004-2006 Pawel Jakub Dawidek <pjd@FreeBSD.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/bio.h>
#include <sys/disk.h>
#include <sys/eventhandler.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/module.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/sbuf.h>
#include <sys/sysctl.h>

#include <geom/geom.h>
#include <geom/geom_dbg.h>
#include <geom/mountver/g_mountver.h>

SYSCTL_DECL(_kern_geom);
static SYSCTL_NODE(_kern_geom, OID_AUTO, mountver, CTLFLAG_RW | CTLFLAG_MPSAFE,
    0, "GEOM_MOUNTVER stuff");
static u_int g_mountver_debug = 0;
static u_int g_mountver_check_ident = 1;
SYSCTL_UINT(_kern_geom_mountver, OID_AUTO, debug, CTLFLAG_RW,
    &g_mountver_debug, 0, "Debug level");
SYSCTL_UINT(_kern_geom_mountver, OID_AUTO, check_ident, CTLFLAG_RW,
    &g_mountver_check_ident, 0, "Check disk ident when reattaching");

static eventhandler_tag g_mountver_pre_sync = NULL;

static void g_mountver_queue(struct bio *bp);
static void g_mountver_orphan(struct g_consumer *cp);
static void g_mountver_resize(struct g_consumer *cp);
static int g_mountver_destroy(struct g_geom *gp, boolean_t force);
static g_taste_t g_mountver_taste;
static int g_mountver_destroy_geom(struct gctl_req *req, struct g_class *mp,
    struct g_geom *gp);
static void g_mountver_config(struct gctl_req *req, struct g_class *mp,
    const char *verb);
static void g_mountver_dumpconf(struct sbuf *sb, const char *indent,
    struct g_geom *gp, struct g_consumer *cp, struct g_provider *pp);
static void g_mountver_init(struct g_class *mp);
static void g_mountver_fini(struct g_class *mp);

struct g_class g_mountver_class = {
        .name = G_MOUNTVER_CLASS_NAME,
        .version = G_VERSION,
        .ctlreq = g_mountver_config,
        .taste = g_mountver_taste,
        .destroy_geom = g_mountver_destroy_geom,
        .init = g_mountver_init,
        .fini = g_mountver_fini
};

static void
g_mountver_detach(void *arg, int flags __unused)
{
        struct g_consumer *cp = arg;

        g_topology_assert();
        if (cp->acr > 0 || cp->acw > 0 || cp->ace > 0)
                g_access(cp, -cp->acr, -cp->acw, -cp->ace);
        g_detach(cp);
}

static void
g_mountver_done(struct bio *bp)
{
        struct g_mountver_softc *sc;
        struct g_geom *gp;
        struct g_consumer *cp;
        struct bio *pbp;

        cp = bp->bio_from;
        gp = cp->geom;
        if (bp->bio_error != ENXIO) {
                g_std_done(bp);
                goto done;
        }

        /*
         * When the device goes away, it's possible that few requests
         * will be completed with ENXIO before g_mountver_orphan()
         * gets called.  To work around that, we have to queue requests
         * that failed with ENXIO, in order to send them later.
         */
        pbp = bp->bio_parent;
        KASSERT(pbp->bio_to == LIST_FIRST(&gp->provider),
            ("parent request was for someone else"));
        g_destroy_bio(bp);
        pbp->bio_inbed++;
        g_mountver_queue(pbp);

done:
        sc = gp->softc;
        mtx_lock(&sc->sc_mtx);
        if (--cp->index == 0 && sc->sc_orphaned)
                g_post_event(g_mountver_detach, cp, M_NOWAIT, NULL);
        mtx_unlock(&sc->sc_mtx);
}

/*
 * Send the BIO down.  The function is called with sc_mtx held to cover
 * the race with orphan, but drops it before external calls.
 */
static void
g_mountver_send(struct g_geom *gp, struct bio *bp)
{
        struct g_mountver_softc *sc = gp->softc;
        struct g_consumer *cp;
        struct bio *cbp;

        mtx_assert(&sc->sc_mtx, MA_OWNED);
        cbp = g_clone_bio(bp);
        if (cbp == NULL) {
                mtx_unlock(&sc->sc_mtx);
                g_io_deliver(bp, ENOMEM);
                return;
        }
        cp = LIST_FIRST(&gp->consumer);
        cp->index++;
        mtx_unlock(&sc->sc_mtx);

        cbp->bio_done = g_mountver_done;
        g_io_request(cbp, cp);
}

static void
g_mountver_queue(struct bio *bp)
{
        struct g_mountver_softc *sc;
        struct g_geom *gp;

        gp = bp->bio_to->geom;
        sc = gp->softc;

        mtx_lock(&sc->sc_mtx);
        TAILQ_INSERT_TAIL(&sc->sc_queue, bp, bio_queue);
        mtx_unlock(&sc->sc_mtx);
}

static void
g_mountver_send_queued(struct g_geom *gp)
{
        struct g_mountver_softc *sc;
        struct bio *bp;

        sc = gp->softc;

        mtx_lock(&sc->sc_mtx);
        while ((bp = TAILQ_FIRST(&sc->sc_queue)) != NULL && !sc->sc_orphaned) {
                TAILQ_REMOVE(&sc->sc_queue, bp, bio_queue);
                G_MOUNTVER_LOGREQ(bp, "Sending queued request.");
                /* sc_mtx is dropped inside */
                g_mountver_send(gp, bp);
                mtx_lock(&sc->sc_mtx);
        }
        mtx_unlock(&sc->sc_mtx);
}

static void
g_mountver_discard_queued(struct g_geom *gp)
{
        struct g_mountver_softc *sc;
        struct bio *bp;

        sc = gp->softc;

        mtx_lock(&sc->sc_mtx);
        while ((bp = TAILQ_FIRST(&sc->sc_queue)) != NULL) {
                TAILQ_REMOVE(&sc->sc_queue, bp, bio_queue);
                mtx_unlock(&sc->sc_mtx);
                G_MOUNTVER_LOGREQ(bp, "Discarding queued request.");
                g_io_deliver(bp, ENXIO);
                mtx_lock(&sc->sc_mtx);
        }
        mtx_unlock(&sc->sc_mtx);
}

static void
g_mountver_start(struct bio *bp)
{
        struct g_mountver_softc *sc;
        struct g_geom *gp;

        gp = bp->bio_to->geom;
        sc = gp->softc;
        G_MOUNTVER_LOGREQ(bp, "Request received.");

        /*
         * It is possible that some bios were returned with ENXIO, even though
         * orphaning didn't happen yet.  In that case, queue all subsequent
         * requests in order to maintain ordering.
         */
        mtx_lock(&sc->sc_mtx);
        if (sc->sc_orphaned || !TAILQ_EMPTY(&sc->sc_queue)) {
                mtx_unlock(&sc->sc_mtx);
                if (sc->sc_shutting_down) {
                        G_MOUNTVER_LOGREQ(bp, "Discarding request due to shutdown.");
                        g_io_deliver(bp, ENXIO);
                        return;
                }
                G_MOUNTVER_LOGREQ(bp, "Queueing request.");
                g_mountver_queue(bp);
                if (!sc->sc_orphaned)
                        g_mountver_send_queued(gp);
        } else {
                G_MOUNTVER_LOGREQ(bp, "Sending request.");
                /* sc_mtx is dropped inside */
                g_mountver_send(gp, bp);
        }
}

static int
g_mountver_access(struct g_provider *pp, int dr, int dw, int de)
{
        struct g_mountver_softc *sc;
        struct g_geom *gp;
        struct g_consumer *cp;

        g_topology_assert();

        gp = pp->geom;
        cp = LIST_FIRST(&gp->consumer);
        sc = gp->softc;
        if (sc == NULL && dr <= 0 && dw <= 0 && de <= 0)
                return (0);
        KASSERT(sc != NULL, ("Trying to access withered provider \"%s\".", pp->name));

        sc->sc_access_r += dr;
        sc->sc_access_w += dw;
        sc->sc_access_e += de;

        if (sc->sc_orphaned)
                return (0);

        return (g_access(cp, dr, dw, de));
}

static int
g_mountver_create(struct gctl_req *req, struct g_class *mp, struct g_provider *pp)
{
        struct g_mountver_softc *sc;
        struct g_geom *gp;
        struct g_provider *newpp;
        struct g_consumer *cp;
        struct g_geom_alias *gap;
        char name[64];
        int error;
        int identsize = DISK_IDENT_SIZE;

        g_topology_assert();

        gp = NULL;
        newpp = NULL;
        cp = NULL;

        snprintf(name, sizeof(name), "%s%s", pp->name, G_MOUNTVER_SUFFIX);
        LIST_FOREACH(gp, &mp->geom, geom) {
                if (strcmp(gp->name, name) == 0) {
                        gctl_error(req, "Provider %s already exists.", name);
                        return (EEXIST);
                }
        }
        gp = g_new_geom(mp, name);
        sc = g_malloc(sizeof(*sc), M_WAITOK | M_ZERO);
        mtx_init(&sc->sc_mtx, "gmountver", NULL, MTX_DEF | MTX_RECURSE);
        TAILQ_INIT(&sc->sc_queue);
        sc->sc_provider_name = strdup(pp->name, M_GEOM);
        gp->softc = sc;
        gp->start = g_mountver_start;
        gp->orphan = g_mountver_orphan;
        gp->resize = g_mountver_resize;
        gp->access = g_mountver_access;
        gp->dumpconf = g_mountver_dumpconf;

        newpp = g_new_providerf(gp, "%s", gp->name);
        newpp->mediasize = pp->mediasize;
        newpp->sectorsize = pp->sectorsize;
        newpp->flags |= G_PF_DIRECT_SEND | G_PF_DIRECT_RECEIVE;
        LIST_FOREACH(gap, &pp->aliases, ga_next)
                g_provider_add_alias(newpp, "%s%s", gap->ga_alias, G_MOUNTVER_SUFFIX);

        if ((pp->flags & G_PF_ACCEPT_UNMAPPED) != 0) {
                G_MOUNTVER_DEBUG(0, "Unmapped supported for %s.", gp->name);
                newpp->flags |= G_PF_ACCEPT_UNMAPPED;
        } else {
                G_MOUNTVER_DEBUG(0, "Unmapped unsupported for %s.", gp->name);
                newpp->flags &= ~G_PF_ACCEPT_UNMAPPED;
        }

        cp = g_new_consumer(gp);
        cp->flags |= G_CF_DIRECT_SEND | G_CF_DIRECT_RECEIVE;
        error = g_attach(cp, pp);
        if (error != 0) {
                gctl_error(req, "Cannot attach to provider %s.", pp->name);
                goto fail;
        }
        error = g_access(cp, 1, 0, 0);
        if (error != 0) {
                gctl_error(req, "Cannot access provider %s.", pp->name);
                goto fail;
        }
        error = g_io_getattr("GEOM::ident", cp, &identsize, sc->sc_ident);
        g_access(cp, -1, 0, 0);
        if (error != 0) {
                if (g_mountver_check_ident) {
                        gctl_error(req, "Cannot get disk ident from %s; error = %d.", pp->name, error);
                        goto fail;
                }

                G_MOUNTVER_DEBUG(0, "Cannot get disk ident from %s; error = %d.", pp->name, error);
                sc->sc_ident[0] = '\0';
        }

        g_error_provider(newpp, 0);
        G_MOUNTVER_DEBUG(0, "Device %s created.", gp->name);
        return (0);
fail:
        g_free(sc->sc_provider_name);
        if (cp->provider != NULL)
                g_detach(cp);
        g_destroy_consumer(cp);
        g_destroy_provider(newpp);
        g_free(gp->softc);
        g_destroy_geom(gp);
        return (error);
}

static int
g_mountver_destroy(struct g_geom *gp, boolean_t force)
{
        struct g_mountver_softc *sc;
        struct g_provider *pp;

        g_topology_assert();
        if (gp->softc == NULL)
                return (ENXIO);
        sc = gp->softc;
        pp = LIST_FIRST(&gp->provider);
        if (pp != NULL && (pp->acr != 0 || pp->acw != 0 || pp->ace != 0)) {
                if (force) {
                        G_MOUNTVER_DEBUG(0, "Device %s is still open, so it "
                            "can't be definitely removed.", pp->name);
                } else {
                        G_MOUNTVER_DEBUG(1, "Device %s is still open (r%dw%de%d).",
                            pp->name, pp->acr, pp->acw, pp->ace);
                        return (EBUSY);
                }
        } else {
                G_MOUNTVER_DEBUG(0, "Device %s removed.", gp->name);
        }
        if (pp != NULL)
                g_wither_provider(pp, ENXIO);
        g_mountver_discard_queued(gp);
        g_free(sc->sc_provider_name);
        g_free(gp->softc);
        gp->softc = NULL;
        g_wither_geom(gp, ENXIO);

        return (0);
}

static int
g_mountver_destroy_geom(struct gctl_req *req, struct g_class *mp, struct g_geom *gp)
{

        return (g_mountver_destroy(gp, 0));
}

static void
g_mountver_ctl_create(struct gctl_req *req, struct g_class *mp)
{
        struct g_provider *pp;
        char param[16];
        int i, *nargs;

        g_topology_assert();

        nargs = gctl_get_paraml(req, "nargs", sizeof(*nargs));
        if (nargs == NULL) {
                gctl_error(req, "No '%s' argument", "nargs");
                return;
        }
        if (*nargs <= 0) {
                gctl_error(req, "Missing device(s).");
                return;
        }
        for (i = 0; i < *nargs; i++) {
                snprintf(param, sizeof(param), "arg%d", i);
                pp = gctl_get_provider(req, param);
                if (pp == NULL)
                        return;
                if (g_mountver_create(req, mp, pp) != 0)
                        return;
        }
}

static struct g_geom *
g_mountver_find_geom(struct g_class *mp, const char *name)
{
        struct g_geom *gp;

        LIST_FOREACH(gp, &mp->geom, geom) {
                if (strcmp(gp->name, name) == 0)
                        return (gp);
        }
        return (NULL);
}

static void
g_mountver_ctl_destroy(struct gctl_req *req, struct g_class *mp)
{
        int *nargs, *force, error, i;
        struct g_geom *gp;
        const char *name;
        char param[16];

        g_topology_assert();

        nargs = gctl_get_paraml(req, "nargs", sizeof(*nargs));
        if (nargs == NULL) {
                gctl_error(req, "No '%s' argument", "nargs");
                return;
        }
        if (*nargs <= 0) {
                gctl_error(req, "Missing device(s).");
                return;
        }
        force = gctl_get_paraml(req, "force", sizeof(*force));
        if (force == NULL) {
                gctl_error(req, "No 'force' argument");
                return;
        }

        for (i = 0; i < *nargs; i++) {
                snprintf(param, sizeof(param), "arg%d", i);
                name = gctl_get_asciiparam(req, param);
                if (name == NULL) {
                        gctl_error(req, "No 'arg%d' argument", i);
                        return;
                }
                if (strncmp(name, _PATH_DEV, strlen(_PATH_DEV)) == 0)
                        name += strlen(_PATH_DEV);
                gp = g_mountver_find_geom(mp, name);
                if (gp == NULL) {
                        G_MOUNTVER_DEBUG(1, "Device %s is invalid.", name);
                        gctl_error(req, "Device %s is invalid.", name);
                        return;
                }
                error = g_mountver_destroy(gp, *force);
                if (error != 0) {
                        gctl_error(req, "Cannot destroy device %s (error=%d).",
                            gp->name, error);
                        return;
                }
        }
}

static void
g_mountver_orphan(struct g_consumer *cp)
{
        struct g_mountver_softc *sc;
        int done;

        g_topology_assert();

        sc = cp->geom->softc;
        mtx_lock(&sc->sc_mtx);
        sc->sc_orphaned = 1;
        done = (cp->index == 0);
        mtx_unlock(&sc->sc_mtx);
        if (done)
                g_mountver_detach(cp, 0);
        G_MOUNTVER_DEBUG(0, "%s is offline.  Mount verification in progress.", sc->sc_provider_name);
}

static void
g_mountver_resize(struct g_consumer *cp)
{
        struct g_geom *gp;
        struct g_provider *pp;

        gp = cp->geom;

        LIST_FOREACH(pp, &gp->provider, provider)
                g_resize_provider(pp, cp->provider->mediasize);
}

static int
g_mountver_ident_matches(struct g_geom *gp)
{
        struct g_consumer *cp;
        struct g_mountver_softc *sc;
        char ident[DISK_IDENT_SIZE];
        int error, identsize = DISK_IDENT_SIZE;

        sc = gp->softc;
        cp = LIST_FIRST(&gp->consumer);

        if (g_mountver_check_ident == 0)
                return (0);

        error = g_access(cp, 1, 0, 0);
        if (error != 0) {
                G_MOUNTVER_DEBUG(0, "Cannot access %s; "
                    "not attaching; error = %d.", gp->name, error);
                return (1);
        }
        error = g_io_getattr("GEOM::ident", cp, &identsize, ident);
        g_access(cp, -1, 0, 0);
        if (error != 0) {
                G_MOUNTVER_DEBUG(0, "Cannot get disk ident for %s; "
                    "not attaching; error = %d.", gp->name, error);
                return (1);
        }
        if (strcmp(ident, sc->sc_ident) != 0) {
                G_MOUNTVER_DEBUG(1, "Disk ident for %s (\"%s\") is different "
                    "from expected \"%s\", not attaching.", gp->name, ident,
                    sc->sc_ident);
                return (1);
        }

        return (0);
}

static struct g_geom *
g_mountver_taste(struct g_class *mp, struct g_provider *pp, int flags __unused)
{
        struct g_mountver_softc *sc;
        struct g_consumer *cp;
        struct g_geom *gp;
        int error;

        g_topology_assert();
        g_trace(G_T_TOPOLOGY, "%s(%s, %s)", __func__, mp->name, pp->name);
        G_MOUNTVER_DEBUG(2, "Tasting %s.", pp->name);

        /*
         * Let's check if device already exists.
         */
        LIST_FOREACH(gp, &mp->geom, geom) {
                sc = gp->softc;
                if (sc == NULL)
                        continue;

                /* Already attached? */
                if (pp == LIST_FIRST(&gp->provider))
                        return (NULL);

                if (sc->sc_orphaned && strcmp(pp->name, sc->sc_provider_name) == 0)
                        break;
        }
        if (gp == NULL)
                return (NULL);

        cp = LIST_FIRST(&gp->consumer);
        error = g_attach(cp, pp);
        if (error != 0) {
                G_MOUNTVER_DEBUG(0, "Cannot attach to %s; error = %d.", pp->name, error);
                return (NULL);
        }

        error = g_mountver_ident_matches(gp);
        if (error != 0) {
                g_detach(cp);
                return (NULL);
        }
        if (sc->sc_access_r > 0 || sc->sc_access_w > 0 || sc->sc_access_e > 0) {
                error = g_access(cp, sc->sc_access_r, sc->sc_access_w, sc->sc_access_e);
                if (error != 0) {
                        G_MOUNTVER_DEBUG(0, "Cannot access %s; error = %d.", pp->name, error);
                        g_detach(cp);
                        return (NULL);
                }
        }
        sc->sc_orphaned = 0;
        g_mountver_send_queued(gp);
        G_MOUNTVER_DEBUG(0, "%s has completed mount verification.", sc->sc_provider_name);

        return (gp);
}

static void
g_mountver_config(struct gctl_req *req, struct g_class *mp, const char *verb)
{
        uint32_t *version;

        g_topology_assert();

        version = gctl_get_paraml(req, "version", sizeof(*version));
        if (version == NULL) {
                gctl_error(req, "No '%s' argument.", "version");
                return;
        }
        if (*version != G_MOUNTVER_VERSION) {
                gctl_error(req, "Userland and kernel parts are out of sync.");
                return;
        }

        if (strcmp(verb, "create") == 0) {
                g_mountver_ctl_create(req, mp);
                return;
        } else if (strcmp(verb, "destroy") == 0) {
                g_mountver_ctl_destroy(req, mp);
                return;
        }

        gctl_error(req, "Unknown verb.");
}

static void
g_mountver_dumpconf(struct sbuf *sb, const char *indent, struct g_geom *gp,
    struct g_consumer *cp, struct g_provider *pp)
{
        struct g_mountver_softc *sc;

        if (pp != NULL || cp != NULL)
                return;

        sc = gp->softc;
        sbuf_printf(sb, "%s<State>%s</State>\n", indent,
            sc->sc_orphaned ? "OFFLINE" : "ONLINE");
        sbuf_printf(sb, "%s<Provider-Name>%s</Provider-Name>\n", indent, sc->sc_provider_name);
        sbuf_printf(sb, "%s<Disk-Ident>%s</Disk-Ident>\n", indent, sc->sc_ident);
}

static void
g_mountver_shutdown_pre_sync(void *arg, int howto)
{
        struct g_mountver_softc *sc;
        struct g_class *mp;
        struct g_geom *gp, *gp2;

        mp = arg;
        g_topology_lock();
        LIST_FOREACH_SAFE(gp, &mp->geom, geom, gp2) {
                if (gp->softc == NULL)
                        continue;
                sc = gp->softc;
                sc->sc_shutting_down = 1;
                if (sc->sc_orphaned)
                        g_mountver_destroy(gp, 1);
        }
        g_topology_unlock();
}

static void
g_mountver_init(struct g_class *mp)
{

        g_mountver_pre_sync = EVENTHANDLER_REGISTER(shutdown_pre_sync,
            g_mountver_shutdown_pre_sync, mp, SHUTDOWN_PRI_FIRST);
        if (g_mountver_pre_sync == NULL)
                G_MOUNTVER_DEBUG(0, "Warning! Cannot register shutdown event.");
}

static void
g_mountver_fini(struct g_class *mp)
{

        if (g_mountver_pre_sync != NULL)
                EVENTHANDLER_DEREGISTER(shutdown_pre_sync, g_mountver_pre_sync);
}

DECLARE_GEOM_CLASS(g_mountver_class, g_mountver);
MODULE_VERSION(geom_mountver, 0);