/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 2012, 2017 by Delphix. All rights reserved.
 * Copyright (c) 2013 Steven Hartland. All rights reserved.
 */

#include <sys/zfs_context.h>
#include <sys/dsl_userhold.h>
#include <sys/dsl_dataset.h>
#include <sys/dsl_destroy.h>
#include <sys/dsl_synctask.h>
#include <sys/dmu_tx.h>
#include <sys/zfs_onexit.h>
#include <sys/dsl_pool.h>
#include <sys/dsl_dir.h>
#include <sys/zfs_ioctl.h>
#include <sys/zap.h>

typedef struct dsl_dataset_user_hold_arg {
        nvlist_t *dduha_holds;
        nvlist_t *dduha_chkholds;
        nvlist_t *dduha_errlist;
        minor_t dduha_minor;
} dsl_dataset_user_hold_arg_t;

/*
 * If you add new checks here, you may need to add additional checks to the
 * "temporary" case in snapshot_check() in dmu_objset.c.
 */
int
dsl_dataset_user_hold_check_one(dsl_dataset_t *ds, const char *htag,
    boolean_t temphold, dmu_tx_t *tx)
{
        dsl_pool_t *dp = dmu_tx_pool(tx);
        objset_t *mos = dp->dp_meta_objset;
        int error = 0;

        ASSERT(dsl_pool_config_held(dp));

        if (strlen(htag) > MAXNAMELEN)
                return (SET_ERROR(E2BIG));
        /* Tempholds have a more restricted length */
        if (temphold && strlen(htag) + MAX_TAG_PREFIX_LEN >= MAXNAMELEN)
                return (SET_ERROR(E2BIG));

        /* tags must be unique (if ds already exists) */
        if (ds != NULL && dsl_dataset_phys(ds)->ds_userrefs_obj != 0) {
                uint64_t value;

                error = zap_lookup(mos, dsl_dataset_phys(ds)->ds_userrefs_obj,
                    htag, 8, 1, &value);
                if (error == 0)
                        error = SET_ERROR(EEXIST);
                else if (error == ENOENT)
                        error = 0;
        }

        return (error);
}

static int
dsl_dataset_user_hold_check(void *arg, dmu_tx_t *tx)
{
        dsl_dataset_user_hold_arg_t *dduha = arg;
        dsl_pool_t *dp = dmu_tx_pool(tx);
        nvlist_t *tmp_holds;

        if (spa_version(dp->dp_spa) < SPA_VERSION_USERREFS)
                return (SET_ERROR(ENOTSUP));

        if (!dmu_tx_is_syncing(tx))
                return (0);

        /*
         * Ensure the list has no duplicates by copying name/values from
         * non-unique dduha_holds to unique tmp_holds, and comparing counts.
         */
        tmp_holds = fnvlist_alloc();
        for (nvpair_t *pair = nvlist_next_nvpair(dduha->dduha_holds, NULL);
            pair != NULL; pair = nvlist_next_nvpair(dduha->dduha_holds, pair)) {
                size_t len = strlen(nvpair_name(pair)) +
                    strlen(fnvpair_value_string(pair));
                char *nameval = kmem_zalloc(len + 2, KM_SLEEP);
                (void) strcpy(nameval, nvpair_name(pair));
                (void) strcat(nameval, "@");
                (void) strcat(nameval, fnvpair_value_string(pair));
                fnvlist_add_string(tmp_holds, nameval, "");
                kmem_free(nameval, len + 2);
        }
        size_t tmp_count = fnvlist_num_pairs(tmp_holds);
        fnvlist_free(tmp_holds);
        if (tmp_count != fnvlist_num_pairs(dduha->dduha_holds))
                return (SET_ERROR(EEXIST));
        for (nvpair_t *pair = nvlist_next_nvpair(dduha->dduha_holds, NULL);
            pair != NULL; pair = nvlist_next_nvpair(dduha->dduha_holds, pair)) {
                dsl_dataset_t *ds;
                int error = 0;
                char *htag, *name;

                /* must be a snapshot */
                name = nvpair_name(pair);
                if (strchr(name, '@') == NULL)
                        error = SET_ERROR(EINVAL);

                if (error == 0)
                        error = nvpair_value_string(pair, &htag);

                if (error == 0)
                        error = dsl_dataset_hold(dp, name, FTAG, &ds);

                if (error == 0) {
                        error = dsl_dataset_user_hold_check_one(ds, htag,
                            dduha->dduha_minor != 0, tx);
                        dsl_dataset_rele(ds, FTAG);
                }

                if (error == 0) {
                        fnvlist_add_string(dduha->dduha_chkholds, name, htag);
                } else {
                        /*
                         * We register ENOENT errors so they can be correctly
                         * reported if needed, such as when all holds fail.
                         */
                        fnvlist_add_int32(dduha->dduha_errlist, name, error);
                        if (error != ENOENT)
                                return (error);
                }
        }

        return (0);
}


static void
dsl_dataset_user_hold_sync_one_impl(nvlist_t *tmpholds, dsl_dataset_t *ds,
    const char *htag, minor_t minor, uint64_t now, dmu_tx_t *tx)
{
        dsl_pool_t *dp = ds->ds_dir->dd_pool;
        objset_t *mos = dp->dp_meta_objset;
        uint64_t zapobj;

        ASSERT(RRW_WRITE_HELD(&dp->dp_config_rwlock));

        if (dsl_dataset_phys(ds)->ds_userrefs_obj == 0) {
                /*
                 * This is the first user hold for this dataset.  Create
                 * the userrefs zap object.
                 */
                dmu_buf_will_dirty(ds->ds_dbuf, tx);
                zapobj = dsl_dataset_phys(ds)->ds_userrefs_obj =
                    zap_create(mos, DMU_OT_USERREFS, DMU_OT_NONE, 0, tx);
        } else {
                zapobj = dsl_dataset_phys(ds)->ds_userrefs_obj;
        }
        ds->ds_userrefs++;

        VERIFY0(zap_add(mos, zapobj, htag, 8, 1, &now, tx));

        if (minor != 0) {
                char name[MAXNAMELEN];
                nvlist_t *tags;

                VERIFY0(dsl_pool_user_hold(dp, ds->ds_object,
                    htag, now, tx));
                (void) snprintf(name, sizeof (name), "%llx",
                    (u_longlong_t)ds->ds_object);

                if (nvlist_lookup_nvlist(tmpholds, name, &tags) != 0) {
                        tags = fnvlist_alloc();
                        fnvlist_add_boolean(tags, htag);
                        fnvlist_add_nvlist(tmpholds, name, tags);
                        fnvlist_free(tags);
                } else {
                        fnvlist_add_boolean(tags, htag);
                }
        }

        spa_history_log_internal_ds(ds, "hold", tx,
            "tag=%s temp=%d refs=%llu",
            htag, minor != 0, ds->ds_userrefs);
}

typedef struct zfs_hold_cleanup_arg {
        char zhca_spaname[ZFS_MAX_DATASET_NAME_LEN];
        uint64_t zhca_spa_load_guid;
        nvlist_t *zhca_holds;
} zfs_hold_cleanup_arg_t;

static void
dsl_dataset_user_release_onexit(void *arg)
{
        zfs_hold_cleanup_arg_t *ca = arg;
        spa_t *spa;
        int error;

        error = spa_open(ca->zhca_spaname, &spa, FTAG);
        if (error != 0) {
                zfs_dbgmsg("couldn't release holds on pool=%s "
                    "because pool is no longer loaded",
                    ca->zhca_spaname);
                return;
        }
        if (spa_load_guid(spa) != ca->zhca_spa_load_guid) {
                zfs_dbgmsg("couldn't release holds on pool=%s "
                    "because pool is no longer loaded (guid doesn't match)",
                    ca->zhca_spaname);
                spa_close(spa, FTAG);
                return;
        }

        (void) dsl_dataset_user_release_tmp(spa_get_dsl(spa), ca->zhca_holds);
        fnvlist_free(ca->zhca_holds);
        kmem_free(ca, sizeof (zfs_hold_cleanup_arg_t));
        spa_close(spa, FTAG);
}

static void
dsl_onexit_hold_cleanup(spa_t *spa, nvlist_t *holds, minor_t minor)
{
        zfs_hold_cleanup_arg_t *ca;

        if (minor == 0 || nvlist_empty(holds)) {
                fnvlist_free(holds);
                return;
        }

        ASSERT(spa != NULL);
        ca = kmem_alloc(sizeof (*ca), KM_SLEEP);

        (void) strlcpy(ca->zhca_spaname, spa_name(spa),
            sizeof (ca->zhca_spaname));
        ca->zhca_spa_load_guid = spa_load_guid(spa);
        ca->zhca_holds = holds;
        VERIFY0(zfs_onexit_add_cb(minor,
            dsl_dataset_user_release_onexit, ca, NULL));
}

void
dsl_dataset_user_hold_sync_one(dsl_dataset_t *ds, const char *htag,
    minor_t minor, uint64_t now, dmu_tx_t *tx)
{
        nvlist_t *tmpholds;

        if (minor != 0)
                tmpholds = fnvlist_alloc();
        else
                tmpholds = NULL;
        dsl_dataset_user_hold_sync_one_impl(tmpholds, ds, htag, minor, now, tx);
        dsl_onexit_hold_cleanup(dsl_dataset_get_spa(ds), tmpholds, minor);
}

static void
dsl_dataset_user_hold_sync(void *arg, dmu_tx_t *tx)
{
        dsl_dataset_user_hold_arg_t *dduha = arg;
        dsl_pool_t *dp = dmu_tx_pool(tx);
        nvlist_t *tmpholds;
        uint64_t now = gethrestime_sec();

        if (dduha->dduha_minor != 0)
                tmpholds = fnvlist_alloc();
        else
                tmpholds = NULL;
        for (nvpair_t *pair = nvlist_next_nvpair(dduha->dduha_chkholds, NULL);
            pair != NULL;
            pair = nvlist_next_nvpair(dduha->dduha_chkholds, pair)) {
                dsl_dataset_t *ds;

                VERIFY0(dsl_dataset_hold(dp, nvpair_name(pair), FTAG, &ds));
                dsl_dataset_user_hold_sync_one_impl(tmpholds, ds,
                    fnvpair_value_string(pair), dduha->dduha_minor, now, tx);
                dsl_dataset_rele(ds, FTAG);
        }
        dsl_onexit_hold_cleanup(dp->dp_spa, tmpholds, dduha->dduha_minor);
}

/*
 * The full semantics of this function are described in the comment above
 * lzc_hold().
 *
 * To summarize:
 * holds is nvl of snapname -> holdname
 * errlist will be filled in with snapname -> error
 *
 * The snaphosts must all be in the same pool.
 *
 * Holds for snapshots that don't exist will be skipped.
 *
 * If none of the snapshots for requested holds exist then ENOENT will be
 * returned.
 *
 * If cleanup_minor is not 0, the holds will be temporary, which will be cleaned
 * up when the process exits.
 *
 * On success all the holds, for snapshots that existed, will be created and 0
 * will be returned.
 *
 * On failure no holds will be created, the errlist will be filled in,
 * and an errno will returned.
 *
 * In all cases the errlist will contain entries for holds where the snapshot
 * didn't exist.
 */
int
dsl_dataset_user_hold(nvlist_t *holds, minor_t cleanup_minor, nvlist_t *errlist)
{
        dsl_dataset_user_hold_arg_t dduha;
        nvpair_t *pair;
        int ret;

        pair = nvlist_next_nvpair(holds, NULL);
        if (pair == NULL)
                return (0);

        dduha.dduha_holds = holds;
        /* chkholds can have non-unique name */
        VERIFY(0 == nvlist_alloc(&dduha.dduha_chkholds, 0, KM_SLEEP));
        dduha.dduha_errlist = errlist;
        dduha.dduha_minor = cleanup_minor;

        ret = dsl_sync_task(nvpair_name(pair), dsl_dataset_user_hold_check,
            dsl_dataset_user_hold_sync, &dduha,
            fnvlist_num_pairs(holds), ZFS_SPACE_CHECK_RESERVED);
        fnvlist_free(dduha.dduha_chkholds);

        return (ret);
}

typedef int (dsl_holdfunc_t)(dsl_pool_t *dp, const char *name, void *tag,
    dsl_dataset_t **dsp);

typedef struct dsl_dataset_user_release_arg {
        dsl_holdfunc_t *ddura_holdfunc;
        nvlist_t *ddura_holds;
        nvlist_t *ddura_todelete;
        nvlist_t *ddura_errlist;
        nvlist_t *ddura_chkholds;
} dsl_dataset_user_release_arg_t;

/* Place a dataset hold on the snapshot identified by passed dsobj string */
static int
dsl_dataset_hold_obj_string(dsl_pool_t *dp, const char *dsobj, void *tag,
    dsl_dataset_t **dsp)
{
        return (dsl_dataset_hold_obj(dp, zfs_strtonum(dsobj, NULL), tag, dsp));
}

static int
dsl_dataset_user_release_check_one(dsl_dataset_user_release_arg_t *ddura,
    dsl_dataset_t *ds, nvlist_t *holds, const char *snapname)
{
        uint64_t zapobj;
        nvlist_t *holds_found;
        objset_t *mos;
        int numholds;

        if (!ds->ds_is_snapshot)
                return (SET_ERROR(EINVAL));

        if (nvlist_empty(holds))
                return (0);

        numholds = 0;
        mos = ds->ds_dir->dd_pool->dp_meta_objset;
        zapobj = dsl_dataset_phys(ds)->ds_userrefs_obj;
        holds_found = fnvlist_alloc();

        for (nvpair_t *pair = nvlist_next_nvpair(holds, NULL); pair != NULL;
            pair = nvlist_next_nvpair(holds, pair)) {
                uint64_t tmp;
                int error;
                const char *holdname = nvpair_name(pair);

                if (zapobj != 0)
                        error = zap_lookup(mos, zapobj, holdname, 8, 1, &tmp);
                else
                        error = SET_ERROR(ENOENT);

                /*
                 * Non-existent holds are put on the errlist, but don't
                 * cause an overall failure.
                 */
                if (error == ENOENT) {
                        if (ddura->ddura_errlist != NULL) {
                                char *errtag = kmem_asprintf("%s#%s",
                                    snapname, holdname);
                                fnvlist_add_int32(ddura->ddura_errlist, errtag,
                                    ENOENT);
                                strfree(errtag);
                        }
                        continue;
                }

                if (error != 0) {
                        fnvlist_free(holds_found);
                        return (error);
                }

                fnvlist_add_boolean(holds_found, holdname);
                numholds++;
        }

        if (DS_IS_DEFER_DESTROY(ds) &&
            dsl_dataset_phys(ds)->ds_num_children == 1 &&
            ds->ds_userrefs == numholds) {
                /* we need to destroy the snapshot as well */
                if (dsl_dataset_long_held(ds)) {
                        fnvlist_free(holds_found);
                        return (SET_ERROR(EBUSY));
                }
                fnvlist_add_boolean(ddura->ddura_todelete, snapname);
        }

        if (numholds != 0) {
                fnvlist_add_nvlist(ddura->ddura_chkholds, snapname,
                    holds_found);
        }
        fnvlist_free(holds_found);

        return (0);
}

static int
dsl_dataset_user_release_check(void *arg, dmu_tx_t *tx)
{
        dsl_dataset_user_release_arg_t *ddura;
        dsl_holdfunc_t *holdfunc;
        dsl_pool_t *dp;

        if (!dmu_tx_is_syncing(tx))
                return (0);

        dp = dmu_tx_pool(tx);

        ASSERT(RRW_WRITE_HELD(&dp->dp_config_rwlock));

        ddura = arg;
        holdfunc = ddura->ddura_holdfunc;

        for (nvpair_t *pair = nvlist_next_nvpair(ddura->ddura_holds, NULL);
            pair != NULL; pair = nvlist_next_nvpair(ddura->ddura_holds, pair)) {
                int error;
                dsl_dataset_t *ds;
                nvlist_t *holds;
                const char *snapname = nvpair_name(pair);

                error = nvpair_value_nvlist(pair, &holds);
                if (error != 0)
                        error = (SET_ERROR(EINVAL));
                else
                        error = holdfunc(dp, snapname, FTAG, &ds);
                if (error == 0) {
                        error = dsl_dataset_user_release_check_one(ddura, ds,
                            holds, snapname);
                        dsl_dataset_rele(ds, FTAG);
                }
                if (error != 0) {
                        if (ddura->ddura_errlist != NULL) {
                                fnvlist_add_int32(ddura->ddura_errlist,
                                    snapname, error);
                        }
                        /*
                         * Non-existent snapshots are put on the errlist,
                         * but don't cause an overall failure.
                         */
                        if (error != ENOENT)
                                return (error);
                }
        }

        return (0);
}

static void
dsl_dataset_user_release_sync_one(dsl_dataset_t *ds, nvlist_t *holds,
    dmu_tx_t *tx)
{
        dsl_pool_t *dp = ds->ds_dir->dd_pool;
        objset_t *mos = dp->dp_meta_objset;

        for (nvpair_t *pair = nvlist_next_nvpair(holds, NULL); pair != NULL;
            pair = nvlist_next_nvpair(holds, pair)) {
                int error;
                const char *holdname = nvpair_name(pair);

                /* Remove temporary hold if one exists. */
                error = dsl_pool_user_release(dp, ds->ds_object, holdname, tx);
                VERIFY(error == 0 || error == ENOENT);

                VERIFY0(zap_remove(mos, dsl_dataset_phys(ds)->ds_userrefs_obj,
                    holdname, tx));
                ds->ds_userrefs--;

                spa_history_log_internal_ds(ds, "release", tx,
                    "tag=%s refs=%lld", holdname, (longlong_t)ds->ds_userrefs);
        }
}

static void
dsl_dataset_user_release_sync(void *arg, dmu_tx_t *tx)
{
        dsl_dataset_user_release_arg_t *ddura = arg;
        dsl_holdfunc_t *holdfunc = ddura->ddura_holdfunc;
        dsl_pool_t *dp = dmu_tx_pool(tx);

        ASSERT(RRW_WRITE_HELD(&dp->dp_config_rwlock));

        for (nvpair_t *pair = nvlist_next_nvpair(ddura->ddura_chkholds, NULL);
            pair != NULL; pair = nvlist_next_nvpair(ddura->ddura_chkholds,
            pair)) {
                dsl_dataset_t *ds;
                const char *name = nvpair_name(pair);

                VERIFY0(holdfunc(dp, name, FTAG, &ds));

                dsl_dataset_user_release_sync_one(ds,
                    fnvpair_value_nvlist(pair), tx);
                if (nvlist_exists(ddura->ddura_todelete, name)) {
                        ASSERT(ds->ds_userrefs == 0 &&
                            dsl_dataset_phys(ds)->ds_num_children == 1 &&
                            DS_IS_DEFER_DESTROY(ds));
                        dsl_destroy_snapshot_sync_impl(ds, B_FALSE, tx);
                }
                dsl_dataset_rele(ds, FTAG);
        }
}

/*
 * The full semantics of this function are described in the comment above
 * lzc_release().
 *
 * To summarize:
 * Releases holds specified in the nvl holds.
 *
 * holds is nvl of snapname -> { holdname, ... }
 * errlist will be filled in with snapname -> error
 *
 * If tmpdp is not NULL the names for holds should be the dsobj's of snapshots,
 * otherwise they should be the names of shapshots.
 *
 * As a release may cause snapshots to be destroyed this trys to ensure they
 * aren't mounted.
 *
 * The release of non-existent holds are skipped.
 *
 * At least one hold must have been released for the this function to succeed
 * and return 0.
 */
static int
dsl_dataset_user_release_impl(nvlist_t *holds, nvlist_t *errlist,
    dsl_pool_t *tmpdp)
{
        dsl_dataset_user_release_arg_t ddura;
        nvpair_t *pair;
        char *pool;
        int error;

        pair = nvlist_next_nvpair(holds, NULL);
        if (pair == NULL)
                return (0);

        /*
         * The release may cause snapshots to be destroyed; make sure they
         * are not mounted.
         */
        if (tmpdp != NULL) {
                /* Temporary holds are specified by dsobj string. */
                ddura.ddura_holdfunc = dsl_dataset_hold_obj_string;
                pool = spa_name(tmpdp->dp_spa);
#ifdef _KERNEL
                for (pair = nvlist_next_nvpair(holds, NULL); pair != NULL;
                    pair = nvlist_next_nvpair(holds, pair)) {
                        dsl_dataset_t *ds;

                        dsl_pool_config_enter(tmpdp, FTAG);
                        error = dsl_dataset_hold_obj_string(tmpdp,
                            nvpair_name(pair), FTAG, &ds);
                        if (error == 0) {
                                char name[ZFS_MAX_DATASET_NAME_LEN];
                                dsl_dataset_name(ds, name);
                                dsl_pool_config_exit(tmpdp, FTAG);
                                dsl_dataset_rele(ds, FTAG);
                                (void) zfs_unmount_snap(name);
                        } else {
                                dsl_pool_config_exit(tmpdp, FTAG);
                        }
                }
#endif
        } else {
                /* Non-temporary holds are specified by name. */
                ddura.ddura_holdfunc = dsl_dataset_hold;
                pool = nvpair_name(pair);
#ifdef _KERNEL
                for (pair = nvlist_next_nvpair(holds, NULL); pair != NULL;
                    pair = nvlist_next_nvpair(holds, pair)) {
                        (void) zfs_unmount_snap(nvpair_name(pair));
                }
#endif
        }

        ddura.ddura_holds = holds;
        ddura.ddura_errlist = errlist;
        ddura.ddura_todelete = fnvlist_alloc();
        ddura.ddura_chkholds = fnvlist_alloc();

        error = dsl_sync_task(pool, dsl_dataset_user_release_check,
            dsl_dataset_user_release_sync, &ddura, 0,
            ZFS_SPACE_CHECK_EXTRA_RESERVED);
        fnvlist_free(ddura.ddura_todelete);
        fnvlist_free(ddura.ddura_chkholds);

        return (error);
}

/*
 * holds is nvl of snapname -> { holdname, ... }
 * errlist will be filled in with snapname -> error
 */
int
dsl_dataset_user_release(nvlist_t *holds, nvlist_t *errlist)
{
        return (dsl_dataset_user_release_impl(holds, errlist, NULL));
}

/*
 * holds is nvl of snapdsobj -> { holdname, ... }
 */
void
dsl_dataset_user_release_tmp(struct dsl_pool *dp, nvlist_t *holds)
{
        ASSERT(dp != NULL);
        (void) dsl_dataset_user_release_impl(holds, NULL, dp);
}

int
dsl_dataset_get_holds(const char *dsname, nvlist_t *nvl)
{
        dsl_pool_t *dp;
        dsl_dataset_t *ds;
        int err;

        err = dsl_pool_hold(dsname, FTAG, &dp);
        if (err != 0)
                return (err);
        err = dsl_dataset_hold(dp, dsname, FTAG, &ds);
        if (err != 0) {
                dsl_pool_rele(dp, FTAG);
                return (err);
        }

        if (dsl_dataset_phys(ds)->ds_userrefs_obj != 0) {
                zap_attribute_t *za;
                zap_cursor_t zc;

                za = kmem_alloc(sizeof (zap_attribute_t), KM_SLEEP);
                for (zap_cursor_init(&zc, ds->ds_dir->dd_pool->dp_meta_objset,
                    dsl_dataset_phys(ds)->ds_userrefs_obj);
                    zap_cursor_retrieve(&zc, za) == 0;
                    zap_cursor_advance(&zc)) {
                        fnvlist_add_uint64(nvl, za->za_name,
                            za->za_first_integer);
                }
                zap_cursor_fini(&zc);
                kmem_free(za, sizeof (zap_attribute_t));
        }
        dsl_dataset_rele(ds, FTAG);
        dsl_pool_rele(dp, FTAG);
        return (0);
}