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[FreeBSD/FreeBSD.git] / sys / cddl / contrib / opensolaris / uts / common / fs / zfs / zvol.c

/*
 * 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) 2006-2010 Pawel Jakub Dawidek <pjd@FreeBSD.org>
 * All rights reserved.
 *
 * Portions Copyright 2010 Robert Milkowski
 *
 * Copyright 2017 Nexenta Systems, Inc.  All rights reserved.
 * Copyright (c) 2012, 2017 by Delphix. All rights reserved.
 * Copyright (c) 2013, Joyent, Inc. All rights reserved.
 * Copyright (c) 2014 Integros [integros.com]
 */

/* Portions Copyright 2011 Martin Matuska <mm@FreeBSD.org> */

/*
 * ZFS volume emulation driver.
 *
 * Makes a DMU object look like a volume of arbitrary size, up to 2^64 bytes.
 * Volumes are accessed through the symbolic links named:
 *
 * /dev/zvol/dsk/<pool_name>/<dataset_name>
 * /dev/zvol/rdsk/<pool_name>/<dataset_name>
 *
 * These links are created by the /dev filesystem (sdev_zvolops.c).
 * Volumes are persistent through reboot.  No user command needs to be
 * run before opening and using a device.
 *
 * FreeBSD notes.
 * On FreeBSD ZVOLs are simply GEOM providers like any other storage device
 * in the system.
 */

#include <sys/types.h>
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/errno.h>
#include <sys/uio.h>
#include <sys/bio.h>
#include <sys/buf.h>
#include <sys/kmem.h>
#include <sys/conf.h>
#include <sys/cmn_err.h>
#include <sys/stat.h>
#include <sys/zap.h>
#include <sys/spa.h>
#include <sys/spa_impl.h>
#include <sys/zio.h>
#include <sys/disk.h>
#include <sys/dmu_traverse.h>
#include <sys/dnode.h>
#include <sys/dsl_dataset.h>
#include <sys/dsl_prop.h>
#include <sys/dkio.h>
#include <sys/byteorder.h>
#include <sys/sunddi.h>
#include <sys/dirent.h>
#include <sys/policy.h>
#include <sys/queue.h>
#include <sys/fs/zfs.h>
#include <sys/zfs_ioctl.h>
#include <sys/zil.h>
#include <sys/refcount.h>
#include <sys/zfs_znode.h>
#include <sys/zfs_rlock.h>
#include <sys/vdev_impl.h>
#include <sys/vdev_raidz.h>
#include <sys/zvol.h>
#include <sys/zil_impl.h>
#include <sys/dbuf.h>
#include <sys/dmu_tx.h>
#include <sys/zfeature.h>
#include <sys/zio_checksum.h>
#include <sys/zil_impl.h>
#include <sys/filio.h>
#include <sys/zfs_rlock.h>

#include <geom/geom.h>

#include "zfs_namecheck.h"

#ifndef illumos
struct g_class zfs_zvol_class = {
        .name = "ZFS::ZVOL",
        .version = G_VERSION,
};

DECLARE_GEOM_CLASS(zfs_zvol_class, zfs_zvol);

#endif
void *zfsdev_state;
static char *zvol_tag = "zvol_tag";

#define ZVOL_DUMPSIZE           "dumpsize"

/*
 * This lock protects the zfsdev_state structure from being modified
 * while it's being used, e.g. an open that comes in before a create
 * finishes.  It also protects temporary opens of the dataset so that,
 * e.g., an open doesn't get a spurious EBUSY.
 */
#ifdef illumos
kmutex_t zfsdev_state_lock;
#else
/*
 * In FreeBSD we've replaced the upstream zfsdev_state_lock with the
 * spa_namespace_lock in the ZVOL code.
 */
#define zfsdev_state_lock spa_namespace_lock
#endif
static uint32_t zvol_minors;

#ifndef illumos
SYSCTL_DECL(_vfs_zfs);
SYSCTL_NODE(_vfs_zfs, OID_AUTO, vol, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
    "ZFS VOLUME");
static int      volmode = ZFS_VOLMODE_GEOM;
SYSCTL_INT(_vfs_zfs_vol, OID_AUTO, mode, CTLFLAG_RWTUN, &volmode, 0,
    "Expose as GEOM providers (1), device files (2) or neither");
static boolean_t zpool_on_zvol = B_FALSE;
SYSCTL_INT(_vfs_zfs_vol, OID_AUTO, recursive, CTLFLAG_RWTUN, &zpool_on_zvol, 0,
    "Allow zpools to use zvols as vdevs (DANGEROUS)");

#endif
typedef struct zvol_extent {
        list_node_t     ze_node;
        dva_t           ze_dva;         /* dva associated with this extent */
        uint64_t        ze_nblks;       /* number of blocks in extent */
} zvol_extent_t;

/*
 * The in-core state of each volume.
 */
typedef struct zvol_state {
#ifndef illumos
        LIST_ENTRY(zvol_state)  zv_links;
#endif
        char            zv_name[MAXPATHLEN]; /* pool/dd name */
        uint64_t        zv_volsize;     /* amount of space we advertise */
        uint64_t        zv_volblocksize; /* volume block size */
#ifdef illumos
        minor_t         zv_minor;       /* minor number */
#else
        struct cdev     *zv_dev;        /* non-GEOM device */
        struct g_provider *zv_provider; /* GEOM provider */
#endif
        uint8_t         zv_min_bs;      /* minimum addressable block shift */
        uint8_t         zv_flags;       /* readonly, dumpified, etc. */
        objset_t        *zv_objset;     /* objset handle */
#ifdef illumos
        uint32_t        zv_open_count[OTYPCNT]; /* open counts */
#endif
        uint32_t        zv_total_opens; /* total open count */
        uint32_t        zv_sync_cnt;    /* synchronous open count */
        zilog_t         *zv_zilog;      /* ZIL handle */
        list_t          zv_extents;     /* List of extents for dump */
        rangelock_t     zv_rangelock;
        dnode_t         *zv_dn;         /* dnode hold */
#ifndef illumos
        int             zv_state;
        int             zv_volmode;     /* Provide GEOM or cdev */
        struct bio_queue_head zv_queue;
        struct mtx      zv_queue_mtx;   /* zv_queue mutex */
#endif
} zvol_state_t;

#ifndef illumos
static LIST_HEAD(, zvol_state) all_zvols;
#endif
/*
 * zvol specific flags
 */
#define ZVOL_RDONLY     0x1
#define ZVOL_DUMPIFIED  0x2
#define ZVOL_EXCL       0x4
#define ZVOL_WCE        0x8

/*
 * zvol maximum transfer in one DMU tx.
 */
int zvol_maxphys = DMU_MAX_ACCESS/2;

/*
 * Toggle unmap functionality.
 */
boolean_t zvol_unmap_enabled = B_TRUE;

/*
 * If true, unmaps requested as synchronous are executed synchronously,
 * otherwise all unmaps are asynchronous.
 */
boolean_t zvol_unmap_sync_enabled = B_FALSE;

#ifndef illumos
SYSCTL_INT(_vfs_zfs_vol, OID_AUTO, unmap_enabled, CTLFLAG_RWTUN,
    &zvol_unmap_enabled, 0,
    "Enable UNMAP functionality");

SYSCTL_INT(_vfs_zfs_vol, OID_AUTO, unmap_sync_enabled, CTLFLAG_RWTUN,
    &zvol_unmap_sync_enabled, 0,
    "UNMAPs requested as sync are executed synchronously");

static d_open_t         zvol_d_open;
static d_close_t        zvol_d_close;
static d_read_t         zvol_read;
static d_write_t        zvol_write;
static d_ioctl_t        zvol_d_ioctl;
static d_strategy_t     zvol_strategy;

static struct cdevsw zvol_cdevsw = {
        .d_version =    D_VERSION,
        .d_open =       zvol_d_open,
        .d_close =      zvol_d_close,
        .d_read =       zvol_read,
        .d_write =      zvol_write,
        .d_ioctl =      zvol_d_ioctl,
        .d_strategy =   zvol_strategy,
        .d_name =       "zvol",
        .d_flags =      D_DISK | D_TRACKCLOSE,
};

static void zvol_geom_run(zvol_state_t *zv);
static void zvol_geom_destroy(zvol_state_t *zv);
static int zvol_geom_access(struct g_provider *pp, int acr, int acw, int ace);
static void zvol_geom_start(struct bio *bp);
static void zvol_geom_worker(void *arg);
static void zvol_log_truncate(zvol_state_t *zv, dmu_tx_t *tx, uint64_t off,
    uint64_t len, boolean_t sync);
#endif  /* !illumos */

extern int zfs_set_prop_nvlist(const char *, zprop_source_t,
    nvlist_t *, nvlist_t *);
static int zvol_remove_zv(zvol_state_t *);
static int zvol_get_data(void *arg, lr_write_t *lr, char *buf,
    struct lwb *lwb, zio_t *zio);
static int zvol_dumpify(zvol_state_t *zv);
static int zvol_dump_fini(zvol_state_t *zv);
static int zvol_dump_init(zvol_state_t *zv, boolean_t resize);

static void
zvol_size_changed(zvol_state_t *zv, uint64_t volsize)
{
#ifdef illumos
        dev_t dev = makedevice(ddi_driver_major(zfs_dip), zv->zv_minor);

        zv->zv_volsize = volsize;
        VERIFY(ddi_prop_update_int64(dev, zfs_dip,
            "Size", volsize) == DDI_SUCCESS);
        VERIFY(ddi_prop_update_int64(dev, zfs_dip,
            "Nblocks", lbtodb(volsize)) == DDI_SUCCESS);

        /* Notify specfs to invalidate the cached size */
        spec_size_invalidate(dev, VBLK);
        spec_size_invalidate(dev, VCHR);
#else   /* !illumos */
        zv->zv_volsize = volsize;
        if (zv->zv_volmode == ZFS_VOLMODE_GEOM) {
                struct g_provider *pp;

                pp = zv->zv_provider;
                if (pp == NULL)
                        return;
                g_topology_lock();

                /*
                 * Do not invoke resize event when initial size was zero.
                 * ZVOL initializes the size on first open, this is not
                 * real resizing.
                 */
                if (pp->mediasize == 0)
                        pp->mediasize = zv->zv_volsize;
                else
                        g_resize_provider(pp, zv->zv_volsize);
                g_topology_unlock();
        }
#endif  /* illumos */
}

int
zvol_check_volsize(uint64_t volsize, uint64_t blocksize)
{
        if (volsize == 0)
                return (SET_ERROR(EINVAL));

        if (volsize % blocksize != 0)
                return (SET_ERROR(EINVAL));

#ifdef _ILP32
        if (volsize - 1 > SPEC_MAXOFFSET_T)
                return (SET_ERROR(EOVERFLOW));
#endif
        return (0);
}

int
zvol_check_volblocksize(uint64_t volblocksize)
{
        if (volblocksize < SPA_MINBLOCKSIZE ||
            volblocksize > SPA_OLD_MAXBLOCKSIZE ||
            !ISP2(volblocksize))
                return (SET_ERROR(EDOM));

        return (0);
}

int
zvol_get_stats(objset_t *os, nvlist_t *nv)
{
        int error;
        dmu_object_info_t doi;
        uint64_t val;

        error = zap_lookup(os, ZVOL_ZAP_OBJ, "size", 8, 1, &val);
        if (error)
                return (error);

        dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_VOLSIZE, val);

        error = dmu_object_info(os, ZVOL_OBJ, &doi);

        if (error == 0) {
                dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_VOLBLOCKSIZE,
                    doi.doi_data_block_size);
        }

        return (error);
}

static zvol_state_t *
zvol_minor_lookup(const char *name)
{
#ifdef illumos
        minor_t minor;
#endif
        zvol_state_t *zv;

        ASSERT(MUTEX_HELD(&zfsdev_state_lock));

#ifdef illumos
        for (minor = 1; minor <= ZFSDEV_MAX_MINOR; minor++) {
                zv = zfsdev_get_soft_state(minor, ZSST_ZVOL);
                if (zv == NULL)
                        continue;
#else
        LIST_FOREACH(zv, &all_zvols, zv_links) {
#endif
                if (strcmp(zv->zv_name, name) == 0)
                        return (zv);
        }

        return (NULL);
}

/* extent mapping arg */
struct maparg {
        zvol_state_t    *ma_zv;
        uint64_t        ma_blks;
};

/*ARGSUSED*/
static int
zvol_map_block(spa_t *spa, zilog_t *zilog, const blkptr_t *bp,
    const zbookmark_phys_t *zb, const dnode_phys_t *dnp, void *arg)
{
        struct maparg *ma = arg;
        zvol_extent_t *ze;
        int bs = ma->ma_zv->zv_volblocksize;

        if (bp == NULL || BP_IS_HOLE(bp) ||
            zb->zb_object != ZVOL_OBJ || zb->zb_level != 0)
                return (0);

        VERIFY(!BP_IS_EMBEDDED(bp));

        VERIFY3U(ma->ma_blks, ==, zb->zb_blkid);
        ma->ma_blks++;

        /* Abort immediately if we have encountered gang blocks */
        if (BP_IS_GANG(bp))
                return (SET_ERROR(EFRAGS));

        /*
         * See if the block is at the end of the previous extent.
         */
        ze = list_tail(&ma->ma_zv->zv_extents);
        if (ze &&
            DVA_GET_VDEV(BP_IDENTITY(bp)) == DVA_GET_VDEV(&ze->ze_dva) &&
            DVA_GET_OFFSET(BP_IDENTITY(bp)) ==
            DVA_GET_OFFSET(&ze->ze_dva) + ze->ze_nblks * bs) {
                ze->ze_nblks++;
                return (0);
        }

        dprintf_bp(bp, "%s", "next blkptr:");

        /* start a new extent */
        ze = kmem_zalloc(sizeof (zvol_extent_t), KM_SLEEP);
        ze->ze_dva = bp->blk_dva[0];    /* structure assignment */
        ze->ze_nblks = 1;
        list_insert_tail(&ma->ma_zv->zv_extents, ze);
        return (0);
}

static void
zvol_free_extents(zvol_state_t *zv)
{
        zvol_extent_t *ze;

        while (ze = list_head(&zv->zv_extents)) {
                list_remove(&zv->zv_extents, ze);
                kmem_free(ze, sizeof (zvol_extent_t));
        }
}

static int
zvol_get_lbas(zvol_state_t *zv)
{
        objset_t *os = zv->zv_objset;
        struct maparg   ma;
        int             err;

        ma.ma_zv = zv;
        ma.ma_blks = 0;
        zvol_free_extents(zv);

        /* commit any in-flight changes before traversing the dataset */
        txg_wait_synced(dmu_objset_pool(os), 0);
        err = traverse_dataset(dmu_objset_ds(os), 0,
            TRAVERSE_PRE | TRAVERSE_PREFETCH_METADATA, zvol_map_block, &ma);
        if (err || ma.ma_blks != (zv->zv_volsize / zv->zv_volblocksize)) {
                zvol_free_extents(zv);
                return (err ? err : EIO);
        }

        return (0);
}

/* ARGSUSED */
void
zvol_create_cb(objset_t *os, void *arg, cred_t *cr, dmu_tx_t *tx)
{
        zfs_creat_t *zct = arg;
        nvlist_t *nvprops = zct->zct_props;
        int error;
        uint64_t volblocksize, volsize;

        VERIFY(nvlist_lookup_uint64(nvprops,
            zfs_prop_to_name(ZFS_PROP_VOLSIZE), &volsize) == 0);
        if (nvlist_lookup_uint64(nvprops,
            zfs_prop_to_name(ZFS_PROP_VOLBLOCKSIZE), &volblocksize) != 0)
                volblocksize = zfs_prop_default_numeric(ZFS_PROP_VOLBLOCKSIZE);

        /*
         * These properties must be removed from the list so the generic
         * property setting step won't apply to them.
         */
        VERIFY(nvlist_remove_all(nvprops,
            zfs_prop_to_name(ZFS_PROP_VOLSIZE)) == 0);
        (void) nvlist_remove_all(nvprops,
            zfs_prop_to_name(ZFS_PROP_VOLBLOCKSIZE));

        error = dmu_object_claim(os, ZVOL_OBJ, DMU_OT_ZVOL, volblocksize,
            DMU_OT_NONE, 0, tx);
        ASSERT(error == 0);

        error = zap_create_claim(os, ZVOL_ZAP_OBJ, DMU_OT_ZVOL_PROP,
            DMU_OT_NONE, 0, tx);
        ASSERT(error == 0);

        error = zap_update(os, ZVOL_ZAP_OBJ, "size", 8, 1, &volsize, tx);
        ASSERT(error == 0);
}

/*
 * Replay a TX_TRUNCATE ZIL transaction if asked.  TX_TRUNCATE is how we
 * implement DKIOCFREE/free-long-range.
 */
static int
zvol_replay_truncate(void *arg1, void *arg2, boolean_t byteswap)
{
        zvol_state_t *zv = arg1;
        lr_truncate_t *lr = arg2;
        uint64_t offset, length;

        if (byteswap)
                byteswap_uint64_array(lr, sizeof (*lr));

        offset = lr->lr_offset;
        length = lr->lr_length;

        return (dmu_free_long_range(zv->zv_objset, ZVOL_OBJ, offset, length));
}

/*
 * Replay a TX_WRITE ZIL transaction that didn't get committed
 * after a system failure
 */
static int
zvol_replay_write(void *arg1, void *arg2, boolean_t byteswap)
{
        zvol_state_t *zv = arg1;
        lr_write_t *lr = arg2;
        objset_t *os = zv->zv_objset;
        char *data = (char *)(lr + 1);  /* data follows lr_write_t */
        uint64_t offset, length;
        dmu_tx_t *tx;
        int error;

        if (byteswap)
                byteswap_uint64_array(lr, sizeof (*lr));

        offset = lr->lr_offset;
        length = lr->lr_length;

        /* If it's a dmu_sync() block, write the whole block */
        if (lr->lr_common.lrc_reclen == sizeof (lr_write_t)) {
                uint64_t blocksize = BP_GET_LSIZE(&lr->lr_blkptr);
                if (length < blocksize) {
                        offset -= offset % blocksize;
                        length = blocksize;
                }
        }

        tx = dmu_tx_create(os);
        dmu_tx_hold_write(tx, ZVOL_OBJ, offset, length);
        error = dmu_tx_assign(tx, TXG_WAIT);
        if (error) {
                dmu_tx_abort(tx);
        } else {
                dmu_write(os, ZVOL_OBJ, offset, length, data, tx);
                dmu_tx_commit(tx);
        }

        return (error);
}

/* ARGSUSED */
static int
zvol_replay_err(void *arg1, void *arg2, boolean_t byteswap)
{
        return (SET_ERROR(ENOTSUP));
}

/*
 * Callback vectors for replaying records.
 * Only TX_WRITE and TX_TRUNCATE are needed for zvol.
 */
zil_replay_func_t *zvol_replay_vector[TX_MAX_TYPE] = {
        zvol_replay_err,        /* 0 no such transaction type */
        zvol_replay_err,        /* TX_CREATE */
        zvol_replay_err,        /* TX_MKDIR */
        zvol_replay_err,        /* TX_MKXATTR */
        zvol_replay_err,        /* TX_SYMLINK */
        zvol_replay_err,        /* TX_REMOVE */
        zvol_replay_err,        /* TX_RMDIR */
        zvol_replay_err,        /* TX_LINK */
        zvol_replay_err,        /* TX_RENAME */
        zvol_replay_write,      /* TX_WRITE */
        zvol_replay_truncate,   /* TX_TRUNCATE */
        zvol_replay_err,        /* TX_SETATTR */
        zvol_replay_err,        /* TX_ACL */
        zvol_replay_err,        /* TX_CREATE_ACL */
        zvol_replay_err,        /* TX_CREATE_ATTR */
        zvol_replay_err,        /* TX_CREATE_ACL_ATTR */
        zvol_replay_err,        /* TX_MKDIR_ACL */
        zvol_replay_err,        /* TX_MKDIR_ATTR */
        zvol_replay_err,        /* TX_MKDIR_ACL_ATTR */
        zvol_replay_err,        /* TX_WRITE2 */
};

#ifdef illumos
int
zvol_name2minor(const char *name, minor_t *minor)
{
        zvol_state_t *zv;

        mutex_enter(&zfsdev_state_lock);
        zv = zvol_minor_lookup(name);
        if (minor && zv)
                *minor = zv->zv_minor;
        mutex_exit(&zfsdev_state_lock);
        return (zv ? 0 : -1);
}
#endif  /* illumos */

/*
 * Create a minor node (plus a whole lot more) for the specified volume.
 */
int
zvol_create_minor(const char *name)
{
        zfs_soft_state_t *zs;
        zvol_state_t *zv;
        objset_t *os;
#ifdef illumos
        dmu_object_info_t doi;
        minor_t minor = 0;
        char chrbuf[30], blkbuf[30];
#else
        struct g_provider *pp;
        struct g_geom *gp;
        uint64_t mode;
#endif
        int error;

#ifndef illumos
        ZFS_LOG(1, "Creating ZVOL %s...", name);
#endif

        mutex_enter(&zfsdev_state_lock);

        if (zvol_minor_lookup(name) != NULL) {
                mutex_exit(&zfsdev_state_lock);
                return (SET_ERROR(EEXIST));
        }

        /* lie and say we're read-only */
        error = dmu_objset_own(name, DMU_OST_ZVOL, B_TRUE, FTAG, &os);

        if (error) {
                mutex_exit(&zfsdev_state_lock);
                return (error);
        }

#ifdef illumos
        if ((minor = zfsdev_minor_alloc()) == 0) {
                dmu_objset_disown(os, FTAG);
                mutex_exit(&zfsdev_state_lock);
                return (SET_ERROR(ENXIO));
        }

        if (ddi_soft_state_zalloc(zfsdev_state, minor) != DDI_SUCCESS) {
                dmu_objset_disown(os, FTAG);
                mutex_exit(&zfsdev_state_lock);
                return (SET_ERROR(EAGAIN));
        }
        (void) ddi_prop_update_string(minor, zfs_dip, ZVOL_PROP_NAME,
            (char *)name);

        (void) snprintf(chrbuf, sizeof (chrbuf), "%u,raw", minor);

        if (ddi_create_minor_node(zfs_dip, chrbuf, S_IFCHR,
            minor, DDI_PSEUDO, 0) == DDI_FAILURE) {
                ddi_soft_state_free(zfsdev_state, minor);
                dmu_objset_disown(os, FTAG);
                mutex_exit(&zfsdev_state_lock);
                return (SET_ERROR(EAGAIN));
        }

        (void) snprintf(blkbuf, sizeof (blkbuf), "%u", minor);

        if (ddi_create_minor_node(zfs_dip, blkbuf, S_IFBLK,
            minor, DDI_PSEUDO, 0) == DDI_FAILURE) {
                ddi_remove_minor_node(zfs_dip, chrbuf);
                ddi_soft_state_free(zfsdev_state, minor);
                dmu_objset_disown(os, FTAG);
                mutex_exit(&zfsdev_state_lock);
                return (SET_ERROR(EAGAIN));
        }

        zs = ddi_get_soft_state(zfsdev_state, minor);
        zs->zss_type = ZSST_ZVOL;
        zv = zs->zss_data = kmem_zalloc(sizeof (zvol_state_t), KM_SLEEP);
#else   /* !illumos */

        zv = kmem_zalloc(sizeof(*zv), KM_SLEEP);
        zv->zv_state = 0;
        error = dsl_prop_get_integer(name,
            zfs_prop_to_name(ZFS_PROP_VOLMODE), &mode, NULL);
        if (error != 0 || mode == ZFS_VOLMODE_DEFAULT)
                mode = volmode;

        DROP_GIANT();
        zv->zv_volmode = mode;
        if (zv->zv_volmode == ZFS_VOLMODE_GEOM) {
                g_topology_lock();
                gp = g_new_geomf(&zfs_zvol_class, "zfs::zvol::%s", name);
                gp->start = zvol_geom_start;
                gp->access = zvol_geom_access;
                pp = g_new_providerf(gp, "%s/%s", ZVOL_DRIVER, name);
                pp->flags |= G_PF_DIRECT_RECEIVE | G_PF_DIRECT_SEND;
                pp->sectorsize = DEV_BSIZE;
                pp->mediasize = 0;
                pp->private = zv;

                zv->zv_provider = pp;
                bioq_init(&zv->zv_queue);
                mtx_init(&zv->zv_queue_mtx, "zvol", NULL, MTX_DEF);
        } else if (zv->zv_volmode == ZFS_VOLMODE_DEV) {
                struct make_dev_args args;

                make_dev_args_init(&args);
                args.mda_flags = MAKEDEV_CHECKNAME | MAKEDEV_WAITOK;
                args.mda_devsw = &zvol_cdevsw;
                args.mda_cr = NULL;
                args.mda_uid = UID_ROOT;
                args.mda_gid = GID_OPERATOR;
                args.mda_mode = 0640;
                args.mda_si_drv2 = zv;
                error = make_dev_s(&args, &zv->zv_dev,
                    "%s/%s", ZVOL_DRIVER, name);
                if (error != 0) {
                        kmem_free(zv, sizeof(*zv));
                        dmu_objset_disown(os, FTAG);
                        mutex_exit(&zfsdev_state_lock);
                        return (error);
                }
                zv->zv_dev->si_iosize_max = MAXPHYS;
        }
        LIST_INSERT_HEAD(&all_zvols, zv, zv_links);
#endif  /* illumos */

        (void) strlcpy(zv->zv_name, name, MAXPATHLEN);
        zv->zv_min_bs = DEV_BSHIFT;
#ifdef illumos
        zv->zv_minor = minor;
#endif
        zv->zv_objset = os;
        if (dmu_objset_is_snapshot(os) || !spa_writeable(dmu_objset_spa(os)))
                zv->zv_flags |= ZVOL_RDONLY;
        rangelock_init(&zv->zv_rangelock, NULL, NULL);
        list_create(&zv->zv_extents, sizeof (zvol_extent_t),
            offsetof(zvol_extent_t, ze_node));
#ifdef illumos
        /* get and cache the blocksize */
        error = dmu_object_info(os, ZVOL_OBJ, &doi);
        ASSERT(error == 0);
        zv->zv_volblocksize = doi.doi_data_block_size;
#endif

        if (spa_writeable(dmu_objset_spa(os))) {
                if (zil_replay_disable)
                        zil_destroy(dmu_objset_zil(os), B_FALSE);
                else
                        zil_replay(os, zv, zvol_replay_vector);
        }
        dmu_objset_disown(os, FTAG);
        zv->zv_objset = NULL;

        zvol_minors++;

        mutex_exit(&zfsdev_state_lock);
#ifndef illumos
        if (zv->zv_volmode == ZFS_VOLMODE_GEOM) {
                zvol_geom_run(zv);
                g_topology_unlock();
        }
        PICKUP_GIANT();

        ZFS_LOG(1, "ZVOL %s created.", name);
#endif

        return (0);
}

/*
 * Remove minor node for the specified volume.
 */
static int
zvol_remove_zv(zvol_state_t *zv)
{
#ifdef illumos
        char nmbuf[20];
        minor_t minor = zv->zv_minor;
#endif

        ASSERT(MUTEX_HELD(&zfsdev_state_lock));
        if (zv->zv_total_opens != 0)
                return (SET_ERROR(EBUSY));

#ifdef illumos
        (void) snprintf(nmbuf, sizeof (nmbuf), "%u,raw", minor);
        ddi_remove_minor_node(zfs_dip, nmbuf);

        (void) snprintf(nmbuf, sizeof (nmbuf), "%u", minor);
        ddi_remove_minor_node(zfs_dip, nmbuf);
#else
        ZFS_LOG(1, "ZVOL %s destroyed.", zv->zv_name);

        LIST_REMOVE(zv, zv_links);
        if (zv->zv_volmode == ZFS_VOLMODE_GEOM) {
                g_topology_lock();
                zvol_geom_destroy(zv);
                g_topology_unlock();
        } else if (zv->zv_volmode == ZFS_VOLMODE_DEV) {
                if (zv->zv_dev != NULL)
                        destroy_dev(zv->zv_dev);
        }
#endif

        rangelock_fini(&zv->zv_rangelock);

        kmem_free(zv, sizeof (zvol_state_t));
#ifdef illumos
        ddi_soft_state_free(zfsdev_state, minor);
#endif
        zvol_minors--;
        return (0);
}

int
zvol_remove_minor(const char *name)
{
        zvol_state_t *zv;
        int rc;

        mutex_enter(&zfsdev_state_lock);
        if ((zv = zvol_minor_lookup(name)) == NULL) {
                mutex_exit(&zfsdev_state_lock);
                return (SET_ERROR(ENXIO));
        }
        rc = zvol_remove_zv(zv);
        mutex_exit(&zfsdev_state_lock);
        return (rc);
}

int
zvol_first_open(zvol_state_t *zv)
{
        dmu_object_info_t doi;
        objset_t *os;
        uint64_t volsize;
        int error;
        uint64_t readonly;

        /* lie and say we're read-only */
        error = dmu_objset_own(zv->zv_name, DMU_OST_ZVOL, B_TRUE,
            zvol_tag, &os);
        if (error)
                return (error);

        zv->zv_objset = os;
        error = zap_lookup(os, ZVOL_ZAP_OBJ, "size", 8, 1, &volsize);
        if (error) {
                ASSERT(error == 0);
                dmu_objset_disown(os, zvol_tag);
                return (error);
        }

        /* get and cache the blocksize */
        error = dmu_object_info(os, ZVOL_OBJ, &doi);
        if (error) {
                ASSERT(error == 0);
                dmu_objset_disown(os, zvol_tag);
                return (error);
        }
        zv->zv_volblocksize = doi.doi_data_block_size;

        error = dnode_hold(os, ZVOL_OBJ, zvol_tag, &zv->zv_dn);
        if (error) {
                dmu_objset_disown(os, zvol_tag);
                return (error);
        }

        zvol_size_changed(zv, volsize);
        zv->zv_zilog = zil_open(os, zvol_get_data);

        VERIFY(dsl_prop_get_integer(zv->zv_name, "readonly", &readonly,
            NULL) == 0);
        if (readonly || dmu_objset_is_snapshot(os) ||
            !spa_writeable(dmu_objset_spa(os)))
                zv->zv_flags |= ZVOL_RDONLY;
        else
                zv->zv_flags &= ~ZVOL_RDONLY;
        return (error);
}

void
zvol_last_close(zvol_state_t *zv)
{
        zil_close(zv->zv_zilog);
        zv->zv_zilog = NULL;

        dnode_rele(zv->zv_dn, zvol_tag);
        zv->zv_dn = NULL;

        /*
         * Evict cached data
         */
        if (dsl_dataset_is_dirty(dmu_objset_ds(zv->zv_objset)) &&
            !(zv->zv_flags & ZVOL_RDONLY))
                txg_wait_synced(dmu_objset_pool(zv->zv_objset), 0);
        dmu_objset_evict_dbufs(zv->zv_objset);

        dmu_objset_disown(zv->zv_objset, zvol_tag);
        zv->zv_objset = NULL;
}

#ifdef illumos
int
zvol_prealloc(zvol_state_t *zv)
{
        objset_t *os = zv->zv_objset;
        dmu_tx_t *tx;
        uint64_t refd, avail, usedobjs, availobjs;
        uint64_t resid = zv->zv_volsize;
        uint64_t off = 0;

        /* Check the space usage before attempting to allocate the space */
        dmu_objset_space(os, &refd, &avail, &usedobjs, &availobjs);
        if (avail < zv->zv_volsize)
                return (SET_ERROR(ENOSPC));

        /* Free old extents if they exist */
        zvol_free_extents(zv);

        while (resid != 0) {
                int error;
                uint64_t bytes = MIN(resid, SPA_OLD_MAXBLOCKSIZE);

                tx = dmu_tx_create(os);
                dmu_tx_hold_write(tx, ZVOL_OBJ, off, bytes);
                error = dmu_tx_assign(tx, TXG_WAIT);
                if (error) {
                        dmu_tx_abort(tx);
                        (void) dmu_free_long_range(os, ZVOL_OBJ, 0, off);
                        return (error);
                }
                dmu_prealloc(os, ZVOL_OBJ, off, bytes, tx);
                dmu_tx_commit(tx);
                off += bytes;
                resid -= bytes;
        }
        txg_wait_synced(dmu_objset_pool(os), 0);

        return (0);
}
#endif  /* illumos */

static int
zvol_update_volsize(objset_t *os, uint64_t volsize)
{
        dmu_tx_t *tx;
        int error;

        ASSERT(MUTEX_HELD(&zfsdev_state_lock));

        tx = dmu_tx_create(os);
        dmu_tx_hold_zap(tx, ZVOL_ZAP_OBJ, TRUE, NULL);
        dmu_tx_mark_netfree(tx);
        error = dmu_tx_assign(tx, TXG_WAIT);
        if (error) {
                dmu_tx_abort(tx);
                return (error);
        }

        error = zap_update(os, ZVOL_ZAP_OBJ, "size", 8, 1,
            &volsize, tx);
        dmu_tx_commit(tx);

        if (error == 0)
                error = dmu_free_long_range(os,
                    ZVOL_OBJ, volsize, DMU_OBJECT_END);
        return (error);
}

void
zvol_remove_minors(const char *name)
{
#ifdef illumos
        zvol_state_t *zv;
        char *namebuf;
        minor_t minor;

        namebuf = kmem_zalloc(strlen(name) + 2, KM_SLEEP);
        (void) strncpy(namebuf, name, strlen(name));
        (void) strcat(namebuf, "/");
        mutex_enter(&zfsdev_state_lock);
        for (minor = 1; minor <= ZFSDEV_MAX_MINOR; minor++) {

                zv = zfsdev_get_soft_state(minor, ZSST_ZVOL);
                if (zv == NULL)
                        continue;
                if (strncmp(namebuf, zv->zv_name, strlen(namebuf)) == 0)
                        (void) zvol_remove_zv(zv);
        }
        kmem_free(namebuf, strlen(name) + 2);

        mutex_exit(&zfsdev_state_lock);
#else   /* !illumos */
        zvol_state_t *zv, *tzv;
        size_t namelen;

        namelen = strlen(name);

        DROP_GIANT();
        mutex_enter(&zfsdev_state_lock);

        LIST_FOREACH_SAFE(zv, &all_zvols, zv_links, tzv) {
                if (strcmp(zv->zv_name, name) == 0 ||
                    (strncmp(zv->zv_name, name, namelen) == 0 &&
                    strlen(zv->zv_name) > namelen && (zv->zv_name[namelen] == '/' ||
                    zv->zv_name[namelen] == '@'))) {
                        (void) zvol_remove_zv(zv);
                }
        }

        mutex_exit(&zfsdev_state_lock);
        PICKUP_GIANT();
#endif  /* illumos */
}

static int
zvol_update_live_volsize(zvol_state_t *zv, uint64_t volsize)
{
        uint64_t old_volsize = 0ULL;
        int error = 0;

        ASSERT(MUTEX_HELD(&zfsdev_state_lock));

        /*
         * Reinitialize the dump area to the new size. If we
         * failed to resize the dump area then restore it back to
         * its original size.  We must set the new volsize prior
         * to calling dumpvp_resize() to ensure that the devices'
         * size(9P) is not visible by the dump subsystem.
         */
        old_volsize = zv->zv_volsize;
        zvol_size_changed(zv, volsize);

#ifdef ZVOL_DUMP
        if (zv->zv_flags & ZVOL_DUMPIFIED) {
                if ((error = zvol_dumpify(zv)) != 0 ||
                    (error = dumpvp_resize()) != 0) {
                        int dumpify_error;

                        (void) zvol_update_volsize(zv->zv_objset, old_volsize);
                        zvol_size_changed(zv, old_volsize);
                        dumpify_error = zvol_dumpify(zv);
                        error = dumpify_error ? dumpify_error : error;
                }
        }
#endif  /* ZVOL_DUMP */

#ifdef illumos
        /*
         * Generate a LUN expansion event.
         */
        if (error == 0) {
                sysevent_id_t eid;
                nvlist_t *attr;
                char *physpath = kmem_zalloc(MAXPATHLEN, KM_SLEEP);

                (void) snprintf(physpath, MAXPATHLEN, "%s%u", ZVOL_PSEUDO_DEV,
                    zv->zv_minor);

                VERIFY(nvlist_alloc(&attr, NV_UNIQUE_NAME, KM_SLEEP) == 0);
                VERIFY(nvlist_add_string(attr, DEV_PHYS_PATH, physpath) == 0);

                (void) ddi_log_sysevent(zfs_dip, SUNW_VENDOR, EC_DEV_STATUS,
                    ESC_DEV_DLE, attr, &eid, DDI_SLEEP);

                nvlist_free(attr);
                kmem_free(physpath, MAXPATHLEN);
        }
#endif  /* illumos */
        return (error);
}

int
zvol_set_volsize(const char *name, uint64_t volsize)
{
        zvol_state_t *zv = NULL;
        objset_t *os;
        int error;
        dmu_object_info_t doi;
        uint64_t readonly;
        boolean_t owned = B_FALSE;

        error = dsl_prop_get_integer(name,
            zfs_prop_to_name(ZFS_PROP_READONLY), &readonly, NULL);
        if (error != 0)
                return (error);
        if (readonly)
                return (SET_ERROR(EROFS));

        mutex_enter(&zfsdev_state_lock);
        zv = zvol_minor_lookup(name);

        if (zv == NULL || zv->zv_objset == NULL) {
                if ((error = dmu_objset_own(name, DMU_OST_ZVOL, B_FALSE,
                    FTAG, &os)) != 0) {
                        mutex_exit(&zfsdev_state_lock);
                        return (error);
                }
                owned = B_TRUE;
                if (zv != NULL)
                        zv->zv_objset = os;
        } else {
                os = zv->zv_objset;
        }

        if ((error = dmu_object_info(os, ZVOL_OBJ, &doi)) != 0 ||
            (error = zvol_check_volsize(volsize, doi.doi_data_block_size)) != 0)
                goto out;

        error = zvol_update_volsize(os, volsize);

        if (error == 0 && zv != NULL)
                error = zvol_update_live_volsize(zv, volsize);
out:
        if (owned) {
                dmu_objset_disown(os, FTAG);
                if (zv != NULL)
                        zv->zv_objset = NULL;
        }
        mutex_exit(&zfsdev_state_lock);
        return (error);
}

/*ARGSUSED*/
#ifdef illumos
int
zvol_open(dev_t *devp, int flag, int otyp, cred_t *cr)
#else
static int
zvol_open(struct g_provider *pp, int flag, int count)
#endif
{
        zvol_state_t *zv;
        int err = 0;
#ifdef illumos

        mutex_enter(&zfsdev_state_lock);

        zv = zfsdev_get_soft_state(getminor(*devp), ZSST_ZVOL);
        if (zv == NULL) {
                mutex_exit(&zfsdev_state_lock);
                return (SET_ERROR(ENXIO));
        }

        if (zv->zv_total_opens == 0)
                err = zvol_first_open(zv);
        if (err) {
                mutex_exit(&zfsdev_state_lock);
                return (err);
        }
#else   /* !illumos */
        boolean_t locked = B_FALSE;

        if (!zpool_on_zvol && tsd_get(zfs_geom_probe_vdev_key) != NULL) {
                /*
                 * if zfs_geom_probe_vdev_key is set, that means that zfs is
                 * attempting to probe geom providers while looking for a
                 * replacement for a missing VDEV.  In this case, the
                 * spa_namespace_lock will not be held, but it is still illegal
                 * to use a zvol as a vdev.  Deadlocks can result if another
                 * thread has spa_namespace_lock
                 */
                return (EOPNOTSUPP);
        }
        /*
         * Protect against recursively entering spa_namespace_lock
         * when spa_open() is used for a pool on a (local) ZVOL(s).
         * This is needed since we replaced upstream zfsdev_state_lock
         * with spa_namespace_lock in the ZVOL code.
         * We are using the same trick as spa_open().
         * Note that calls in zvol_first_open which need to resolve
         * pool name to a spa object will enter spa_open()
         * recursively, but that function already has all the
         * necessary protection.
         */
        if (!MUTEX_HELD(&zfsdev_state_lock)) {
                mutex_enter(&zfsdev_state_lock);
                locked = B_TRUE;
        }

        zv = pp->private;
        if (zv == NULL) {
                if (locked)
                        mutex_exit(&zfsdev_state_lock);
                return (SET_ERROR(ENXIO));
        }

        if (zv->zv_total_opens == 0) {
                err = zvol_first_open(zv);
                if (err) {
                        if (locked)
                                mutex_exit(&zfsdev_state_lock);
                        return (err);
                }
                pp->mediasize = zv->zv_volsize;
                pp->stripeoffset = 0;
                pp->stripesize = zv->zv_volblocksize;
        }
#endif  /* illumos */
        if ((flag & FWRITE) && (zv->zv_flags & ZVOL_RDONLY)) {
                err = SET_ERROR(EROFS);
                goto out;
        }
        if (zv->zv_flags & ZVOL_EXCL) {
                err = SET_ERROR(EBUSY);
                goto out;
        }
#ifdef FEXCL
        if (flag & FEXCL) {
                if (zv->zv_total_opens != 0) {
                        err = SET_ERROR(EBUSY);
                        goto out;
                }
                zv->zv_flags |= ZVOL_EXCL;
        }
#endif

#ifdef illumos
        if (zv->zv_open_count[otyp] == 0 || otyp == OTYP_LYR) {
                zv->zv_open_count[otyp]++;
                zv->zv_total_opens++;
        }
        mutex_exit(&zfsdev_state_lock);
#else
        zv->zv_total_opens += count;
        if (locked)
                mutex_exit(&zfsdev_state_lock);
#endif

        return (err);
out:
        if (zv->zv_total_opens == 0)
                zvol_last_close(zv);
#ifdef illumos
        mutex_exit(&zfsdev_state_lock);
#else
        if (locked)
                mutex_exit(&zfsdev_state_lock);
#endif
        return (err);
}

/*ARGSUSED*/
#ifdef illumos
int
zvol_close(dev_t dev, int flag, int otyp, cred_t *cr)
{
        minor_t minor = getminor(dev);
        zvol_state_t *zv;
        int error = 0;

        mutex_enter(&zfsdev_state_lock);

        zv = zfsdev_get_soft_state(minor, ZSST_ZVOL);
        if (zv == NULL) {
                mutex_exit(&zfsdev_state_lock);
#else   /* !illumos */
static int
zvol_close(struct g_provider *pp, int flag, int count)
{
        zvol_state_t *zv;
        int error = 0;
        boolean_t locked = B_FALSE;

        /* See comment in zvol_open(). */
        if (!MUTEX_HELD(&zfsdev_state_lock)) {
                mutex_enter(&zfsdev_state_lock);
                locked = B_TRUE;
        }

        zv = pp->private;
        if (zv == NULL) {
                if (locked)
                        mutex_exit(&zfsdev_state_lock);
#endif  /* illumos */
                return (SET_ERROR(ENXIO));
        }

        if (zv->zv_flags & ZVOL_EXCL) {
                ASSERT(zv->zv_total_opens == 1);
                zv->zv_flags &= ~ZVOL_EXCL;
        }

        /*
         * If the open count is zero, this is a spurious close.
         * That indicates a bug in the kernel / DDI framework.
         */
#ifdef illumos
        ASSERT(zv->zv_open_count[otyp] != 0);
#endif
        ASSERT(zv->zv_total_opens != 0);

        /*
         * You may get multiple opens, but only one close.
         */
#ifdef illumos
        zv->zv_open_count[otyp]--;
        zv->zv_total_opens--;
#else
        zv->zv_total_opens -= count;
#endif

        if (zv->zv_total_opens == 0)
                zvol_last_close(zv);

#ifdef illumos
        mutex_exit(&zfsdev_state_lock);
#else
        if (locked)
                mutex_exit(&zfsdev_state_lock);
#endif
        return (error);
}

/* ARGSUSED */
static void
zvol_get_done(zgd_t *zgd, int error)
{
        if (zgd->zgd_db)
                dmu_buf_rele(zgd->zgd_db, zgd);

        rangelock_exit(zgd->zgd_lr);

        kmem_free(zgd, sizeof (zgd_t));
}

/*
 * Get data to generate a TX_WRITE intent log record.
 */
static int
zvol_get_data(void *arg, lr_write_t *lr, char *buf, struct lwb *lwb, zio_t *zio)
{
        zvol_state_t *zv = arg;
        uint64_t offset = lr->lr_offset;
        uint64_t size = lr->lr_length;  /* length of user data */
        dmu_buf_t *db;
        zgd_t *zgd;
        int error;

        ASSERT3P(lwb, !=, NULL);
        ASSERT3P(zio, !=, NULL);
        ASSERT3U(size, !=, 0);

        zgd = kmem_zalloc(sizeof (zgd_t), KM_SLEEP);
        zgd->zgd_lwb = lwb;

        /*
         * Write records come in two flavors: immediate and indirect.
         * For small writes it's cheaper to store the data with the
         * log record (immediate); for large writes it's cheaper to
         * sync the data and get a pointer to it (indirect) so that
         * we don't have to write the data twice.
         */
        if (buf != NULL) { /* immediate write */
                zgd->zgd_lr = rangelock_enter(&zv->zv_rangelock, offset, size,
                    RL_READER);
                error = dmu_read_by_dnode(zv->zv_dn, offset, size, buf,
                    DMU_READ_NO_PREFETCH);
        } else { /* indirect write */
                /*
                 * Have to lock the whole block to ensure when it's written out
                 * and its checksum is being calculated that no one can change
                 * the data. Contrarily to zfs_get_data we need not re-check
                 * blocksize after we get the lock because it cannot be changed.
                 */
                size = zv->zv_volblocksize;
                offset = P2ALIGN(offset, size);
                zgd->zgd_lr = rangelock_enter(&zv->zv_rangelock, offset, size,
                    RL_READER);
                error = dmu_buf_hold_by_dnode(zv->zv_dn, offset, zgd, &db,
                    DMU_READ_NO_PREFETCH);
                if (error == 0) {
                        blkptr_t *bp = &lr->lr_blkptr;

                        zgd->zgd_db = db;
                        zgd->zgd_bp = bp;

                        ASSERT(db->db_offset == offset);
                        ASSERT(db->db_size == size);

                        error = dmu_sync(zio, lr->lr_common.lrc_txg,
                            zvol_get_done, zgd);

                        if (error == 0)
                                return (0);
                }
        }

        zvol_get_done(zgd, error);

        return (error);
}

/*
 * zvol_log_write() handles synchronous writes using TX_WRITE ZIL transactions.
 *
 * We store data in the log buffers if it's small enough.
 * Otherwise we will later flush the data out via dmu_sync().
 */
ssize_t zvol_immediate_write_sz = 32768;
#ifdef _KERNEL
SYSCTL_LONG(_vfs_zfs_vol, OID_AUTO, immediate_write_sz, CTLFLAG_RWTUN,
    &zvol_immediate_write_sz, 0, "Minimal size for indirect log write");
#endif

static void
zvol_log_write(zvol_state_t *zv, dmu_tx_t *tx, offset_t off, ssize_t resid,
    boolean_t sync)
{
        uint32_t blocksize = zv->zv_volblocksize;
        zilog_t *zilog = zv->zv_zilog;
        itx_wr_state_t write_state;

        if (zil_replaying(zilog, tx))
                return;

        if (zilog->zl_logbias == ZFS_LOGBIAS_THROUGHPUT)
                write_state = WR_INDIRECT;
        else if (!spa_has_slogs(zilog->zl_spa) &&
            resid >= blocksize && blocksize > zvol_immediate_write_sz)
                write_state = WR_INDIRECT;
        else if (sync)
                write_state = WR_COPIED;
        else
                write_state = WR_NEED_COPY;

        while (resid) {
                itx_t *itx;
                lr_write_t *lr;
                itx_wr_state_t wr_state = write_state;
                ssize_t len = resid;

                if (wr_state == WR_COPIED && resid > zil_max_copied_data(zilog))
                        wr_state = WR_NEED_COPY;
                else if (wr_state == WR_INDIRECT)
                        len = MIN(blocksize - P2PHASE(off, blocksize), resid);

                itx = zil_itx_create(TX_WRITE, sizeof (*lr) +
                    (wr_state == WR_COPIED ? len : 0));
                lr = (lr_write_t *)&itx->itx_lr;
                if (wr_state == WR_COPIED && dmu_read_by_dnode(zv->zv_dn,
                    off, len, lr + 1, DMU_READ_NO_PREFETCH) != 0) {
                        zil_itx_destroy(itx);
                        itx = zil_itx_create(TX_WRITE, sizeof (*lr));
                        lr = (lr_write_t *)&itx->itx_lr;
                        wr_state = WR_NEED_COPY;
                }

                itx->itx_wr_state = wr_state;
                lr->lr_foid = ZVOL_OBJ;
                lr->lr_offset = off;
                lr->lr_length = len;
                lr->lr_blkoff = 0;
                BP_ZERO(&lr->lr_blkptr);

                itx->itx_private = zv;

                if (!sync && (zv->zv_sync_cnt == 0))
                        itx->itx_sync = B_FALSE;

                zil_itx_assign(zilog, itx, tx);

                off += len;
                resid -= len;
        }
}

#ifdef illumos
static int
zvol_dumpio_vdev(vdev_t *vd, void *addr, uint64_t offset, uint64_t origoffset,
    uint64_t size, boolean_t doread, boolean_t isdump)
{
        vdev_disk_t *dvd;
        int c;
        int numerrors = 0;

        if (vd->vdev_ops == &vdev_mirror_ops ||
            vd->vdev_ops == &vdev_replacing_ops ||
            vd->vdev_ops == &vdev_spare_ops) {
                for (c = 0; c < vd->vdev_children; c++) {
                        int err = zvol_dumpio_vdev(vd->vdev_child[c],
                            addr, offset, origoffset, size, doread, isdump);
                        if (err != 0) {
                                numerrors++;
                        } else if (doread) {
                                break;
                        }
                }
        }

        if (!vd->vdev_ops->vdev_op_leaf && vd->vdev_ops != &vdev_raidz_ops)
                return (numerrors < vd->vdev_children ? 0 : EIO);

        if (doread && !vdev_readable(vd))
                return (SET_ERROR(EIO));
        else if (!doread && !vdev_writeable(vd))
                return (SET_ERROR(EIO));

        if (vd->vdev_ops == &vdev_raidz_ops) {
                return (vdev_raidz_physio(vd,
                    addr, size, offset, origoffset, doread, isdump));
        }

        offset += VDEV_LABEL_START_SIZE;

        if (ddi_in_panic() || isdump) {
                ASSERT(!doread);
                if (doread)
                        return (SET_ERROR(EIO));
                dvd = vd->vdev_tsd;
                ASSERT3P(dvd, !=, NULL);
                return (ldi_dump(dvd->vd_lh, addr, lbtodb(offset),
                    lbtodb(size)));
        } else {
                dvd = vd->vdev_tsd;
                ASSERT3P(dvd, !=, NULL);
                return (vdev_disk_ldi_physio(dvd->vd_lh, addr, size,
                    offset, doread ? B_READ : B_WRITE));
        }
}

static int
zvol_dumpio(zvol_state_t *zv, void *addr, uint64_t offset, uint64_t size,
    boolean_t doread, boolean_t isdump)
{
        vdev_t *vd;
        int error;
        zvol_extent_t *ze;
        spa_t *spa = dmu_objset_spa(zv->zv_objset);

        /* Must be sector aligned, and not stradle a block boundary. */
        if (P2PHASE(offset, DEV_BSIZE) || P2PHASE(size, DEV_BSIZE) ||
            P2BOUNDARY(offset, size, zv->zv_volblocksize)) {
                return (SET_ERROR(EINVAL));
        }
        ASSERT(size <= zv->zv_volblocksize);

        /* Locate the extent this belongs to */
        ze = list_head(&zv->zv_extents);
        while (offset >= ze->ze_nblks * zv->zv_volblocksize) {
                offset -= ze->ze_nblks * zv->zv_volblocksize;
                ze = list_next(&zv->zv_extents, ze);
        }

        if (ze == NULL)
                return (SET_ERROR(EINVAL));

        if (!ddi_in_panic())
                spa_config_enter(spa, SCL_STATE, FTAG, RW_READER);

        vd = vdev_lookup_top(spa, DVA_GET_VDEV(&ze->ze_dva));
        offset += DVA_GET_OFFSET(&ze->ze_dva);
        error = zvol_dumpio_vdev(vd, addr, offset, DVA_GET_OFFSET(&ze->ze_dva),
            size, doread, isdump);

        if (!ddi_in_panic())
                spa_config_exit(spa, SCL_STATE, FTAG);

        return (error);
}

int
zvol_strategy(buf_t *bp)
{
        zfs_soft_state_t *zs = NULL;
#else   /* !illumos */
void
zvol_strategy(struct bio *bp)
{
#endif  /* illumos */
        zvol_state_t *zv;
        uint64_t off, volsize;
        size_t resid;
        char *addr;
        objset_t *os;
        int error = 0;
#ifdef illumos
        boolean_t doread = bp->b_flags & B_READ;
#else
        boolean_t doread = 0;
#endif
        boolean_t is_dumpified;
        boolean_t sync;

#ifdef illumos
        if (getminor(bp->b_edev) == 0) {
                error = SET_ERROR(EINVAL);
        } else {
                zs = ddi_get_soft_state(zfsdev_state, getminor(bp->b_edev));
                if (zs == NULL)
                        error = SET_ERROR(ENXIO);
                else if (zs->zss_type != ZSST_ZVOL)
                        error = SET_ERROR(EINVAL);
        }

        if (error) {
                bioerror(bp, error);
                biodone(bp);
                return (0);
        }

        zv = zs->zss_data;

        if (!(bp->b_flags & B_READ) && (zv->zv_flags & ZVOL_RDONLY)) {
                bioerror(bp, EROFS);
                biodone(bp);
                return (0);
        }

        off = ldbtob(bp->b_blkno);
#else   /* !illumos */
        if (bp->bio_to)
                zv = bp->bio_to->private;
        else
                zv = bp->bio_dev->si_drv2;

        if (zv == NULL) {
                error = SET_ERROR(ENXIO);
                goto out;
        }

        if (bp->bio_cmd != BIO_READ && (zv->zv_flags & ZVOL_RDONLY)) {
                error = SET_ERROR(EROFS);
                goto out;
        }

        switch (bp->bio_cmd) {
        case BIO_FLUSH:
                goto sync;
        case BIO_READ:
                doread = 1;
        case BIO_WRITE:
        case BIO_DELETE:
                break;
        default:
                error = EOPNOTSUPP;
                goto out;
        }

        off = bp->bio_offset;
#endif  /* illumos */
        volsize = zv->zv_volsize;

        os = zv->zv_objset;
        ASSERT(os != NULL);

#ifdef illumos
        bp_mapin(bp);
        addr = bp->b_un.b_addr;
        resid = bp->b_bcount;

        if (resid > 0 && (off < 0 || off >= volsize)) {
                bioerror(bp, EIO);
                biodone(bp);
                return (0);
        }

        is_dumpified = zv->zv_flags & ZVOL_DUMPIFIED;
        sync = ((!(bp->b_flags & B_ASYNC) &&
            !(zv->zv_flags & ZVOL_WCE)) ||
            (zv->zv_objset->os_sync == ZFS_SYNC_ALWAYS)) &&
            !doread && !is_dumpified;
#else   /* !illumos */
        addr = bp->bio_data;
        resid = bp->bio_length;

        if (resid > 0 && (off < 0 || off >= volsize)) {
                error = SET_ERROR(EIO);
                goto out;
        }

        is_dumpified = B_FALSE;
        sync = !doread && !is_dumpified &&
            zv->zv_objset->os_sync == ZFS_SYNC_ALWAYS;
#endif  /* illumos */

        /*
         * There must be no buffer changes when doing a dmu_sync() because
         * we can't change the data whilst calculating the checksum.
         */
        locked_range_t *lr = rangelock_enter(&zv->zv_rangelock, off, resid,
            doread ? RL_READER : RL_WRITER);

#ifndef illumos
        if (bp->bio_cmd == BIO_DELETE) {
                dmu_tx_t *tx = dmu_tx_create(zv->zv_objset);
                error = dmu_tx_assign(tx, TXG_WAIT);
                if (error != 0) {
                        dmu_tx_abort(tx);
                } else {
                        zvol_log_truncate(zv, tx, off, resid, sync);
                        dmu_tx_commit(tx);
                        error = dmu_free_long_range(zv->zv_objset, ZVOL_OBJ,
                            off, resid);
                        resid = 0;
                }
                goto unlock;
        }
#endif
        while (resid != 0 && off < volsize) {
                size_t size = MIN(resid, zvol_maxphys);
#ifdef illumos
                if (is_dumpified) {
                        size = MIN(size, P2END(off, zv->zv_volblocksize) - off);
                        error = zvol_dumpio(zv, addr, off, size,
                            doread, B_FALSE);
                } else if (doread) {
#else
                if (doread) {
#endif
                        error = dmu_read(os, ZVOL_OBJ, off, size, addr,
                            DMU_READ_PREFETCH);
                } else {
                        dmu_tx_t *tx = dmu_tx_create(os);
                        dmu_tx_hold_write(tx, ZVOL_OBJ, off, size);
                        error = dmu_tx_assign(tx, TXG_WAIT);
                        if (error) {
                                dmu_tx_abort(tx);
                        } else {
                                dmu_write(os, ZVOL_OBJ, off, size, addr, tx);
                                zvol_log_write(zv, tx, off, size, sync);
                                dmu_tx_commit(tx);
                        }
                }
                if (error) {
                        /* convert checksum errors into IO errors */
                        if (error == ECKSUM)
                                error = SET_ERROR(EIO);
                        break;
                }
                off += size;
                addr += size;
                resid -= size;
        }
#ifndef illumos
unlock:
#endif
        rangelock_exit(lr);

#ifdef illumos
        if ((bp->b_resid = resid) == bp->b_bcount)
                bioerror(bp, off > volsize ? EINVAL : error);

        if (sync)
                zil_commit(zv->zv_zilog, ZVOL_OBJ);
        biodone(bp);

        return (0);
#else   /* !illumos */
        bp->bio_completed = bp->bio_length - resid;
        if (bp->bio_completed < bp->bio_length && off > volsize)
                error = EINVAL;

        if (sync) {
sync:
                zil_commit(zv->zv_zilog, ZVOL_OBJ);
        }
out:
        if (bp->bio_to)
                g_io_deliver(bp, error);
        else
                biofinish(bp, NULL, error);
#endif  /* illumos */
}

#ifdef illumos
/*
 * Set the buffer count to the zvol maximum transfer.
 * Using our own routine instead of the default minphys()
 * means that for larger writes we write bigger buffers on X86
 * (128K instead of 56K) and flush the disk write cache less often
 * (every zvol_maxphys - currently 1MB) instead of minphys (currently
 * 56K on X86 and 128K on sparc).
 */
void
zvol_minphys(struct buf *bp)
{
        if (bp->b_bcount > zvol_maxphys)
                bp->b_bcount = zvol_maxphys;
}

int
zvol_dump(dev_t dev, caddr_t addr, daddr_t blkno, int nblocks)
{
        minor_t minor = getminor(dev);
        zvol_state_t *zv;
        int error = 0;
        uint64_t size;
        uint64_t boff;
        uint64_t resid;

        zv = zfsdev_get_soft_state(minor, ZSST_ZVOL);
        if (zv == NULL)
                return (SET_ERROR(ENXIO));

        if ((zv->zv_flags & ZVOL_DUMPIFIED) == 0)
                return (SET_ERROR(EINVAL));

        boff = ldbtob(blkno);
        resid = ldbtob(nblocks);

        VERIFY3U(boff + resid, <=, zv->zv_volsize);

        while (resid) {
                size = MIN(resid, P2END(boff, zv->zv_volblocksize) - boff);
                error = zvol_dumpio(zv, addr, boff, size, B_FALSE, B_TRUE);
                if (error)
                        break;
                boff += size;
                addr += size;
                resid -= size;
        }

        return (error);
}

/*ARGSUSED*/
int
zvol_read(dev_t dev, uio_t *uio, cred_t *cr)
{
        minor_t minor = getminor(dev);
#else   /* !illumos */
int
zvol_read(struct cdev *dev, struct uio *uio, int ioflag)
{
#endif  /* illumos */
        zvol_state_t *zv;
        uint64_t volsize;
        int error = 0;

#ifdef illumos
        zv = zfsdev_get_soft_state(minor, ZSST_ZVOL);
        if (zv == NULL)
                return (SET_ERROR(ENXIO));
#else
        zv = dev->si_drv2;
#endif

        volsize = zv->zv_volsize;
        /* uio_loffset == volsize isn't an error as its required for EOF processing. */
        if (uio->uio_resid > 0 &&
            (uio->uio_loffset < 0 || uio->uio_loffset > volsize))
                return (SET_ERROR(EIO));

#ifdef illumos
        if (zv->zv_flags & ZVOL_DUMPIFIED) {
                error = physio(zvol_strategy, NULL, dev, B_READ,
                    zvol_minphys, uio);
                return (error);
        }
#endif

        locked_range_t *lr = rangelock_enter(&zv->zv_rangelock,
            uio->uio_loffset, uio->uio_resid, RL_READER);
        while (uio->uio_resid > 0 && uio->uio_loffset < volsize) {
                uint64_t bytes = MIN(uio->uio_resid, DMU_MAX_ACCESS >> 1);

                /* don't read past the end */
                if (bytes > volsize - uio->uio_loffset)
                        bytes = volsize - uio->uio_loffset;

                error =  dmu_read_uio_dnode(zv->zv_dn, uio, bytes);
                if (error) {
                        /* convert checksum errors into IO errors */
                        if (error == ECKSUM)
                                error = SET_ERROR(EIO);
                        break;
                }
        }
        rangelock_exit(lr);

        return (error);
}

#ifdef illumos
/*ARGSUSED*/
int
zvol_write(dev_t dev, uio_t *uio, cred_t *cr)
{
        minor_t minor = getminor(dev);
#else   /* !illumos */
int
zvol_write(struct cdev *dev, struct uio *uio, int ioflag)
{
#endif  /* illumos */
        zvol_state_t *zv;
        uint64_t volsize;
        int error = 0;
        boolean_t sync;

#ifdef illumos
        zv = zfsdev_get_soft_state(minor, ZSST_ZVOL);
        if (zv == NULL)
                return (SET_ERROR(ENXIO));
#else
        zv = dev->si_drv2;
#endif

        volsize = zv->zv_volsize;
        /* uio_loffset == volsize isn't an error as its required for EOF processing. */
        if (uio->uio_resid > 0 &&
            (uio->uio_loffset < 0 || uio->uio_loffset > volsize))
                return (SET_ERROR(EIO));

#ifdef illumos
        if (zv->zv_flags & ZVOL_DUMPIFIED) {
                error = physio(zvol_strategy, NULL, dev, B_WRITE,
                    zvol_minphys, uio);
                return (error);
        }

        sync = !(zv->zv_flags & ZVOL_WCE) ||
#else
        sync = (ioflag & IO_SYNC) ||
#endif
            (zv->zv_objset->os_sync == ZFS_SYNC_ALWAYS);

        locked_range_t *lr = rangelock_enter(&zv->zv_rangelock,
            uio->uio_loffset, uio->uio_resid, RL_WRITER);
        while (uio->uio_resid > 0 && uio->uio_loffset < volsize) {
                uint64_t bytes = MIN(uio->uio_resid, DMU_MAX_ACCESS >> 1);
                uint64_t off = uio->uio_loffset;
                dmu_tx_t *tx = dmu_tx_create(zv->zv_objset);

                if (bytes > volsize - off)      /* don't write past the end */
                        bytes = volsize - off;

                dmu_tx_hold_write(tx, ZVOL_OBJ, off, bytes);
                error = dmu_tx_assign(tx, TXG_WAIT);
                if (error) {
                        dmu_tx_abort(tx);
                        break;
                }
                error = dmu_write_uio_dnode(zv->zv_dn, uio, bytes, tx);
                if (error == 0)
                        zvol_log_write(zv, tx, off, bytes, sync);
                dmu_tx_commit(tx);

                if (error)
                        break;
        }
        rangelock_exit(lr);

        if (sync)
                zil_commit(zv->zv_zilog, ZVOL_OBJ);
        return (error);
}

#ifdef illumos
int
zvol_getefi(void *arg, int flag, uint64_t vs, uint8_t bs)
{
        struct uuid uuid = EFI_RESERVED;
        efi_gpe_t gpe = { 0 };
        uint32_t crc;
        dk_efi_t efi;
        int length;
        char *ptr;

        if (ddi_copyin(arg, &efi, sizeof (dk_efi_t), flag))
                return (SET_ERROR(EFAULT));
        ptr = (char *)(uintptr_t)efi.dki_data_64;
        length = efi.dki_length;
        /*
         * Some clients may attempt to request a PMBR for the
         * zvol.  Currently this interface will return EINVAL to
         * such requests.  These requests could be supported by
         * adding a check for lba == 0 and consing up an appropriate
         * PMBR.
         */
        if (efi.dki_lba < 1 || efi.dki_lba > 2 || length <= 0)
                return (SET_ERROR(EINVAL));

        gpe.efi_gpe_StartingLBA = LE_64(34ULL);
        gpe.efi_gpe_EndingLBA = LE_64((vs >> bs) - 1);
        UUID_LE_CONVERT(gpe.efi_gpe_PartitionTypeGUID, uuid);

        if (efi.dki_lba == 1) {
                efi_gpt_t gpt = { 0 };

                gpt.efi_gpt_Signature = LE_64(EFI_SIGNATURE);
                gpt.efi_gpt_Revision = LE_32(EFI_VERSION_CURRENT);
                gpt.efi_gpt_HeaderSize = LE_32(sizeof (gpt));
                gpt.efi_gpt_MyLBA = LE_64(1ULL);
                gpt.efi_gpt_FirstUsableLBA = LE_64(34ULL);
                gpt.efi_gpt_LastUsableLBA = LE_64((vs >> bs) - 1);
                gpt.efi_gpt_PartitionEntryLBA = LE_64(2ULL);
                gpt.efi_gpt_NumberOfPartitionEntries = LE_32(1);
                gpt.efi_gpt_SizeOfPartitionEntry =
                    LE_32(sizeof (efi_gpe_t));
                CRC32(crc, &gpe, sizeof (gpe), -1U, crc32_table);
                gpt.efi_gpt_PartitionEntryArrayCRC32 = LE_32(~crc);
                CRC32(crc, &gpt, sizeof (gpt), -1U, crc32_table);
                gpt.efi_gpt_HeaderCRC32 = LE_32(~crc);
                if (ddi_copyout(&gpt, ptr, MIN(sizeof (gpt), length),
                    flag))
                        return (SET_ERROR(EFAULT));
                ptr += sizeof (gpt);
                length -= sizeof (gpt);
        }
        if (length > 0 && ddi_copyout(&gpe, ptr, MIN(sizeof (gpe),
            length), flag))
                return (SET_ERROR(EFAULT));
        return (0);
}

/*
 * BEGIN entry points to allow external callers access to the volume.
 */
/*
 * Return the volume parameters needed for access from an external caller.
 * These values are invariant as long as the volume is held open.
 */
int
zvol_get_volume_params(minor_t minor, uint64_t *blksize,
    uint64_t *max_xfer_len, void **minor_hdl, void **objset_hdl, void **zil_hdl,
    void **rl_hdl, void **dnode_hdl)
{
        zvol_state_t *zv;

        zv = zfsdev_get_soft_state(minor, ZSST_ZVOL);
        if (zv == NULL)
                return (SET_ERROR(ENXIO));
        if (zv->zv_flags & ZVOL_DUMPIFIED)
                return (SET_ERROR(ENXIO));

        ASSERT(blksize && max_xfer_len && minor_hdl &&
            objset_hdl && zil_hdl && rl_hdl && dnode_hdl);

        *blksize = zv->zv_volblocksize;
        *max_xfer_len = (uint64_t)zvol_maxphys;
        *minor_hdl = zv;
        *objset_hdl = zv->zv_objset;
        *zil_hdl = zv->zv_zilog;
        *rl_hdl = &zv->zv_rangelock;
        *dnode_hdl = zv->zv_dn;
        return (0);
}

/*
 * Return the current volume size to an external caller.
 * The size can change while the volume is open.
 */
uint64_t
zvol_get_volume_size(void *minor_hdl)
{
        zvol_state_t *zv = minor_hdl;

        return (zv->zv_volsize);
}

/*
 * Return the current WCE setting to an external caller.
 * The WCE setting can change while the volume is open.
 */
int
zvol_get_volume_wce(void *minor_hdl)
{
        zvol_state_t *zv = minor_hdl;

        return ((zv->zv_flags & ZVOL_WCE) ? 1 : 0);
}

/*
 * Entry point for external callers to zvol_log_write
 */
void
zvol_log_write_minor(void *minor_hdl, dmu_tx_t *tx, offset_t off, ssize_t resid,
    boolean_t sync)
{
        zvol_state_t *zv = minor_hdl;

        zvol_log_write(zv, tx, off, resid, sync);
}
/*
 * END entry points to allow external callers access to the volume.
 */
#endif  /* illumos */

/*
 * Log a DKIOCFREE/free-long-range to the ZIL with TX_TRUNCATE.
 */
static void
zvol_log_truncate(zvol_state_t *zv, dmu_tx_t *tx, uint64_t off, uint64_t len,
    boolean_t sync)
{
        itx_t *itx;
        lr_truncate_t *lr;
        zilog_t *zilog = zv->zv_zilog;

        if (zil_replaying(zilog, tx))
                return;

        itx = zil_itx_create(TX_TRUNCATE, sizeof (*lr));
        lr = (lr_truncate_t *)&itx->itx_lr;
        lr->lr_foid = ZVOL_OBJ;
        lr->lr_offset = off;
        lr->lr_length = len;

        itx->itx_sync = (sync || zv->zv_sync_cnt != 0);
        zil_itx_assign(zilog, itx, tx);
}

#ifdef illumos
/*
 * Dirtbag ioctls to support mkfs(1M) for UFS filesystems.  See dkio(7I).
 * Also a dirtbag dkio ioctl for unmap/free-block functionality.
 */
/*ARGSUSED*/
int
zvol_ioctl(dev_t dev, int cmd, intptr_t arg, int flag, cred_t *cr, int *rvalp)
{
        zvol_state_t *zv;
        struct dk_callback *dkc;
        int error = 0;
        locked_range_t *lr;

        mutex_enter(&zfsdev_state_lock);

        zv = zfsdev_get_soft_state(getminor(dev), ZSST_ZVOL);

        if (zv == NULL) {
                mutex_exit(&zfsdev_state_lock);
                return (SET_ERROR(ENXIO));
        }
        ASSERT(zv->zv_total_opens > 0);

        switch (cmd) {

        case DKIOCINFO:
        {
                struct dk_cinfo dki;

                bzero(&dki, sizeof (dki));
                (void) strcpy(dki.dki_cname, "zvol");
                (void) strcpy(dki.dki_dname, "zvol");
                dki.dki_ctype = DKC_UNKNOWN;
                dki.dki_unit = getminor(dev);
                dki.dki_maxtransfer =
                    1 << (SPA_OLD_MAXBLOCKSHIFT - zv->zv_min_bs);
                mutex_exit(&zfsdev_state_lock);
                if (ddi_copyout(&dki, (void *)arg, sizeof (dki), flag))
                        error = SET_ERROR(EFAULT);
                return (error);
        }

        case DKIOCGMEDIAINFO:
        {
                struct dk_minfo dkm;

                bzero(&dkm, sizeof (dkm));
                dkm.dki_lbsize = 1U << zv->zv_min_bs;
                dkm.dki_capacity = zv->zv_volsize >> zv->zv_min_bs;
                dkm.dki_media_type = DK_UNKNOWN;
                mutex_exit(&zfsdev_state_lock);
                if (ddi_copyout(&dkm, (void *)arg, sizeof (dkm), flag))
                        error = SET_ERROR(EFAULT);
                return (error);
        }

        case DKIOCGMEDIAINFOEXT:
        {
                struct dk_minfo_ext dkmext;

                bzero(&dkmext, sizeof (dkmext));
                dkmext.dki_lbsize = 1U << zv->zv_min_bs;
                dkmext.dki_pbsize = zv->zv_volblocksize;
                dkmext.dki_capacity = zv->zv_volsize >> zv->zv_min_bs;
                dkmext.dki_media_type = DK_UNKNOWN;
                mutex_exit(&zfsdev_state_lock);
                if (ddi_copyout(&dkmext, (void *)arg, sizeof (dkmext), flag))
                        error = SET_ERROR(EFAULT);
                return (error);
        }

        case DKIOCGETEFI:
        {
                uint64_t vs = zv->zv_volsize;
                uint8_t bs = zv->zv_min_bs;

                mutex_exit(&zfsdev_state_lock);
                error = zvol_getefi((void *)arg, flag, vs, bs);
                return (error);
        }

        case DKIOCFLUSHWRITECACHE:
                dkc = (struct dk_callback *)arg;
                mutex_exit(&zfsdev_state_lock);
                zil_commit(zv->zv_zilog, ZVOL_OBJ);
                if ((flag & FKIOCTL) && dkc != NULL && dkc->dkc_callback) {
                        (*dkc->dkc_callback)(dkc->dkc_cookie, error);
                        error = 0;
                }
                return (error);

        case DKIOCGETWCE:
        {
                int wce = (zv->zv_flags & ZVOL_WCE) ? 1 : 0;
                if (ddi_copyout(&wce, (void *)arg, sizeof (int),
                    flag))
                        error = SET_ERROR(EFAULT);
                break;
        }
        case DKIOCSETWCE:
        {
                int wce;
                if (ddi_copyin((void *)arg, &wce, sizeof (int),
                    flag)) {
                        error = SET_ERROR(EFAULT);
                        break;
                }
                if (wce) {
                        zv->zv_flags |= ZVOL_WCE;
                        mutex_exit(&zfsdev_state_lock);
                } else {
                        zv->zv_flags &= ~ZVOL_WCE;
                        mutex_exit(&zfsdev_state_lock);
                        zil_commit(zv->zv_zilog, ZVOL_OBJ);
                }
                return (0);
        }

        case DKIOCGGEOM:
        case DKIOCGVTOC:
                /*
                 * commands using these (like prtvtoc) expect ENOTSUP
                 * since we're emulating an EFI label
                 */
                error = SET_ERROR(ENOTSUP);
                break;

        case DKIOCDUMPINIT:
                lr = rangelock_enter(&zv->zv_rangelock, 0, zv->zv_volsize,
                    RL_WRITER);
                error = zvol_dumpify(zv);
                rangelock_exit(lr);
                break;

        case DKIOCDUMPFINI:
                if (!(zv->zv_flags & ZVOL_DUMPIFIED))
                        break;
                lr = rangelock_enter(&zv->zv_rangelock, 0, zv->zv_volsize,
                    RL_WRITER);
                error = zvol_dump_fini(zv);
                rangelock_exit(lr);
                break;

        case DKIOCFREE:
        {
                dkioc_free_list_t *dfl;
                dmu_tx_t *tx;

                if (!zvol_unmap_enabled)
                        break;

                if (!(flag & FKIOCTL)) {
                        error = dfl_copyin((void *)arg, &dfl, flag, KM_SLEEP);
                        if (error != 0)
                                break;
                } else {
                        dfl = (dkioc_free_list_t *)arg;
                        ASSERT3U(dfl->dfl_num_exts, <=, DFL_COPYIN_MAX_EXTS);
                        if (dfl->dfl_num_exts > DFL_COPYIN_MAX_EXTS) {
                                error = SET_ERROR(EINVAL);
                                break;
                        }
                }

                mutex_exit(&zfsdev_state_lock);

                for (int i = 0; i < dfl->dfl_num_exts; i++) {
                        uint64_t start = dfl->dfl_exts[i].dfle_start,
                            length = dfl->dfl_exts[i].dfle_length,
                            end = start + length;

                        /*
                         * Apply Postel's Law to length-checking.  If they
                         * overshoot, just blank out until the end, if there's
                         * a need to blank out anything.
                         */
                        if (start >= zv->zv_volsize)
                                continue;       /* No need to do anything... */
                        if (end > zv->zv_volsize) {
                                end = DMU_OBJECT_END;
                                length = end - start;
                        }

                        lr = rangelock_enter(&zv->zv_rangelock, start, length,
                            RL_WRITER);
                        tx = dmu_tx_create(zv->zv_objset);
                        error = dmu_tx_assign(tx, TXG_WAIT);
                        if (error != 0) {
                                dmu_tx_abort(tx);
                        } else {
                                zvol_log_truncate(zv, tx, start, length,
                                    B_TRUE);
                                dmu_tx_commit(tx);
                                error = dmu_free_long_range(zv->zv_objset,
                                    ZVOL_OBJ, start, length);
                        }

                        rangelock_exit(lr);

                        if (error != 0)
                                break;
                }

                /*
                 * If the write-cache is disabled, 'sync' property
                 * is set to 'always', or if the caller is asking for
                 * a synchronous free, commit this operation to the zil.
                 * This will sync any previous uncommitted writes to the
                 * zvol object.
                 * Can be overridden by the zvol_unmap_sync_enabled tunable.
                 */
                if ((error == 0) && zvol_unmap_sync_enabled &&
                    (!(zv->zv_flags & ZVOL_WCE) ||
                    (zv->zv_objset->os_sync == ZFS_SYNC_ALWAYS) ||
                    (dfl->dfl_flags & DF_WAIT_SYNC))) {
                        zil_commit(zv->zv_zilog, ZVOL_OBJ);
                }

                if (!(flag & FKIOCTL))
                        dfl_free(dfl);

                return (error);
        }

        default:
                error = SET_ERROR(ENOTTY);
                break;

        }
        mutex_exit(&zfsdev_state_lock);
        return (error);
}
#endif  /* illumos */

int
zvol_busy(void)
{
        return (zvol_minors != 0);
}

void
zvol_init(void)
{
        VERIFY(ddi_soft_state_init(&zfsdev_state, sizeof (zfs_soft_state_t),
            1) == 0);
#ifdef illumos
        mutex_init(&zfsdev_state_lock, NULL, MUTEX_DEFAULT, NULL);
#else
        ZFS_LOG(1, "ZVOL Initialized.");
#endif
}

void
zvol_fini(void)
{
#ifdef illumos
        mutex_destroy(&zfsdev_state_lock);
#endif
        ddi_soft_state_fini(&zfsdev_state);
        ZFS_LOG(1, "ZVOL Deinitialized.");
}

#ifdef illumos
/*ARGSUSED*/
static int
zfs_mvdev_dump_feature_check(void *arg, dmu_tx_t *tx)
{
        spa_t *spa = dmu_tx_pool(tx)->dp_spa;

        if (spa_feature_is_active(spa, SPA_FEATURE_MULTI_VDEV_CRASH_DUMP))
                return (1);
        return (0);
}

/*ARGSUSED*/
static void
zfs_mvdev_dump_activate_feature_sync(void *arg, dmu_tx_t *tx)
{
        spa_t *spa = dmu_tx_pool(tx)->dp_spa;

        spa_feature_incr(spa, SPA_FEATURE_MULTI_VDEV_CRASH_DUMP, tx);
}

static int
zvol_dump_init(zvol_state_t *zv, boolean_t resize)
{
        dmu_tx_t *tx;
        int error;
        objset_t *os = zv->zv_objset;
        spa_t *spa = dmu_objset_spa(os);
        vdev_t *vd = spa->spa_root_vdev;
        nvlist_t *nv = NULL;
        uint64_t version = spa_version(spa);
        uint64_t checksum, compress, refresrv, vbs, dedup;

        ASSERT(MUTEX_HELD(&zfsdev_state_lock));
        ASSERT(vd->vdev_ops == &vdev_root_ops);

        error = dmu_free_long_range(zv->zv_objset, ZVOL_OBJ, 0,
            DMU_OBJECT_END);
        if (error != 0)
                return (error);
        /* wait for dmu_free_long_range to actually free the blocks */
        txg_wait_synced(dmu_objset_pool(zv->zv_objset), 0);

        /*
         * If the pool on which the dump device is being initialized has more
         * than one child vdev, check that the MULTI_VDEV_CRASH_DUMP feature is
         * enabled.  If so, bump that feature's counter to indicate that the
         * feature is active. We also check the vdev type to handle the
         * following case:
         *   # zpool create test raidz disk1 disk2 disk3
         *   Now have spa_root_vdev->vdev_children == 1 (the raidz vdev),
         *   the raidz vdev itself has 3 children.
         */
        if (vd->vdev_children > 1 || vd->vdev_ops == &vdev_raidz_ops) {
                if (!spa_feature_is_enabled(spa,
                    SPA_FEATURE_MULTI_VDEV_CRASH_DUMP))
                        return (SET_ERROR(ENOTSUP));
                (void) dsl_sync_task(spa_name(spa),
                    zfs_mvdev_dump_feature_check,
                    zfs_mvdev_dump_activate_feature_sync, NULL,
                    2, ZFS_SPACE_CHECK_RESERVED);
        }

        if (!resize) {
                error = dsl_prop_get_integer(zv->zv_name,
                    zfs_prop_to_name(ZFS_PROP_COMPRESSION), &compress, NULL);
                if (error == 0) {
                        error = dsl_prop_get_integer(zv->zv_name,
                            zfs_prop_to_name(ZFS_PROP_CHECKSUM), &checksum,
                            NULL);
                }
                if (error == 0) {
                        error = dsl_prop_get_integer(zv->zv_name,
                            zfs_prop_to_name(ZFS_PROP_REFRESERVATION),
                            &refresrv, NULL);
                }
                if (error == 0) {
                        error = dsl_prop_get_integer(zv->zv_name,
                            zfs_prop_to_name(ZFS_PROP_VOLBLOCKSIZE), &vbs,
                            NULL);
                }
                if (version >= SPA_VERSION_DEDUP && error == 0) {
                        error = dsl_prop_get_integer(zv->zv_name,
                            zfs_prop_to_name(ZFS_PROP_DEDUP), &dedup, NULL);
                }
        }
        if (error != 0)
                return (error);

        tx = dmu_tx_create(os);
        dmu_tx_hold_zap(tx, ZVOL_ZAP_OBJ, TRUE, NULL);
        dmu_tx_hold_bonus(tx, ZVOL_OBJ);
        error = dmu_tx_assign(tx, TXG_WAIT);
        if (error != 0) {
                dmu_tx_abort(tx);
                return (error);
        }

        /*
         * If we are resizing the dump device then we only need to
         * update the refreservation to match the newly updated
         * zvolsize. Otherwise, we save off the original state of the
         * zvol so that we can restore them if the zvol is ever undumpified.
         */
        if (resize) {
                error = zap_update(os, ZVOL_ZAP_OBJ,
                    zfs_prop_to_name(ZFS_PROP_REFRESERVATION), 8, 1,
                    &zv->zv_volsize, tx);
        } else {
                error = zap_update(os, ZVOL_ZAP_OBJ,
                    zfs_prop_to_name(ZFS_PROP_COMPRESSION), 8, 1,
                    &compress, tx);
                if (error == 0) {
                        error = zap_update(os, ZVOL_ZAP_OBJ,
                            zfs_prop_to_name(ZFS_PROP_CHECKSUM), 8, 1,
                            &checksum, tx);
                }
                if (error == 0) {
                        error = zap_update(os, ZVOL_ZAP_OBJ,
                            zfs_prop_to_name(ZFS_PROP_REFRESERVATION), 8, 1,
                            &refresrv, tx);
                }
                if (error == 0) {
                        error = zap_update(os, ZVOL_ZAP_OBJ,
                            zfs_prop_to_name(ZFS_PROP_VOLBLOCKSIZE), 8, 1,
                            &vbs, tx);
                }
                if (error == 0) {
                        error = dmu_object_set_blocksize(
                            os, ZVOL_OBJ, SPA_OLD_MAXBLOCKSIZE, 0, tx);
                }
                if (version >= SPA_VERSION_DEDUP && error == 0) {
                        error = zap_update(os, ZVOL_ZAP_OBJ,
                            zfs_prop_to_name(ZFS_PROP_DEDUP), 8, 1,
                            &dedup, tx);
                }
                if (error == 0)
                        zv->zv_volblocksize = SPA_OLD_MAXBLOCKSIZE;
        }
        dmu_tx_commit(tx);

        /*
         * We only need update the zvol's property if we are initializing
         * the dump area for the first time.
         */
        if (error == 0 && !resize) {
                /*
                 * If MULTI_VDEV_CRASH_DUMP is active, use the NOPARITY checksum
                 * function.  Otherwise, use the old default -- OFF.
                 */
                checksum = spa_feature_is_active(spa,
                    SPA_FEATURE_MULTI_VDEV_CRASH_DUMP) ? ZIO_CHECKSUM_NOPARITY :
                    ZIO_CHECKSUM_OFF;

                VERIFY(nvlist_alloc(&nv, NV_UNIQUE_NAME, KM_SLEEP) == 0);
                VERIFY(nvlist_add_uint64(nv,
                    zfs_prop_to_name(ZFS_PROP_REFRESERVATION), 0) == 0);
                VERIFY(nvlist_add_uint64(nv,
                    zfs_prop_to_name(ZFS_PROP_COMPRESSION),
                    ZIO_COMPRESS_OFF) == 0);
                VERIFY(nvlist_add_uint64(nv,
                    zfs_prop_to_name(ZFS_PROP_CHECKSUM),
                    checksum) == 0);
                if (version >= SPA_VERSION_DEDUP) {
                        VERIFY(nvlist_add_uint64(nv,
                            zfs_prop_to_name(ZFS_PROP_DEDUP),
                            ZIO_CHECKSUM_OFF) == 0);
                }

                error = zfs_set_prop_nvlist(zv->zv_name, ZPROP_SRC_LOCAL,
                    nv, NULL);
                nvlist_free(nv);
        }

        /* Allocate the space for the dump */
        if (error == 0)
                error = zvol_prealloc(zv);
        return (error);
}

static int
zvol_dumpify(zvol_state_t *zv)
{
        int error = 0;
        uint64_t dumpsize = 0;
        dmu_tx_t *tx;
        objset_t *os = zv->zv_objset;

        if (zv->zv_flags & ZVOL_RDONLY)
                return (SET_ERROR(EROFS));

        if (zap_lookup(zv->zv_objset, ZVOL_ZAP_OBJ, ZVOL_DUMPSIZE,
            8, 1, &dumpsize) != 0 || dumpsize != zv->zv_volsize) {
                boolean_t resize = (dumpsize > 0);

                if ((error = zvol_dump_init(zv, resize)) != 0) {
                        (void) zvol_dump_fini(zv);
                        return (error);
                }
        }

        /*
         * Build up our lba mapping.
         */
        error = zvol_get_lbas(zv);
        if (error) {
                (void) zvol_dump_fini(zv);
                return (error);
        }

        tx = dmu_tx_create(os);
        dmu_tx_hold_zap(tx, ZVOL_ZAP_OBJ, TRUE, NULL);
        error = dmu_tx_assign(tx, TXG_WAIT);
        if (error) {
                dmu_tx_abort(tx);
                (void) zvol_dump_fini(zv);
                return (error);
        }

        zv->zv_flags |= ZVOL_DUMPIFIED;
        error = zap_update(os, ZVOL_ZAP_OBJ, ZVOL_DUMPSIZE, 8, 1,
            &zv->zv_volsize, tx);
        dmu_tx_commit(tx);

        if (error) {
                (void) zvol_dump_fini(zv);
                return (error);
        }

        txg_wait_synced(dmu_objset_pool(os), 0);
        return (0);
}

static int
zvol_dump_fini(zvol_state_t *zv)
{
        dmu_tx_t *tx;
        objset_t *os = zv->zv_objset;
        nvlist_t *nv;
        int error = 0;
        uint64_t checksum, compress, refresrv, vbs, dedup;
        uint64_t version = spa_version(dmu_objset_spa(zv->zv_objset));

        /*
         * Attempt to restore the zvol back to its pre-dumpified state.
         * This is a best-effort attempt as it's possible that not all
         * of these properties were initialized during the dumpify process
         * (i.e. error during zvol_dump_init).
         */

        tx = dmu_tx_create(os);
        dmu_tx_hold_zap(tx, ZVOL_ZAP_OBJ, TRUE, NULL);
        error = dmu_tx_assign(tx, TXG_WAIT);
        if (error) {
                dmu_tx_abort(tx);
                return (error);
        }
        (void) zap_remove(os, ZVOL_ZAP_OBJ, ZVOL_DUMPSIZE, tx);
        dmu_tx_commit(tx);

        (void) zap_lookup(zv->zv_objset, ZVOL_ZAP_OBJ,
            zfs_prop_to_name(ZFS_PROP_CHECKSUM), 8, 1, &checksum);
        (void) zap_lookup(zv->zv_objset, ZVOL_ZAP_OBJ,
            zfs_prop_to_name(ZFS_PROP_COMPRESSION), 8, 1, &compress);
        (void) zap_lookup(zv->zv_objset, ZVOL_ZAP_OBJ,
            zfs_prop_to_name(ZFS_PROP_REFRESERVATION), 8, 1, &refresrv);
        (void) zap_lookup(zv->zv_objset, ZVOL_ZAP_OBJ,
            zfs_prop_to_name(ZFS_PROP_VOLBLOCKSIZE), 8, 1, &vbs);

        VERIFY(nvlist_alloc(&nv, NV_UNIQUE_NAME, KM_SLEEP) == 0);
        (void) nvlist_add_uint64(nv,
            zfs_prop_to_name(ZFS_PROP_CHECKSUM), checksum);
        (void) nvlist_add_uint64(nv,
            zfs_prop_to_name(ZFS_PROP_COMPRESSION), compress);
        (void) nvlist_add_uint64(nv,
            zfs_prop_to_name(ZFS_PROP_REFRESERVATION), refresrv);
        if (version >= SPA_VERSION_DEDUP &&
            zap_lookup(zv->zv_objset, ZVOL_ZAP_OBJ,
            zfs_prop_to_name(ZFS_PROP_DEDUP), 8, 1, &dedup) == 0) {
                (void) nvlist_add_uint64(nv,
                    zfs_prop_to_name(ZFS_PROP_DEDUP), dedup);
        }
        (void) zfs_set_prop_nvlist(zv->zv_name, ZPROP_SRC_LOCAL,
            nv, NULL);
        nvlist_free(nv);

        zvol_free_extents(zv);
        zv->zv_flags &= ~ZVOL_DUMPIFIED;
        (void) dmu_free_long_range(os, ZVOL_OBJ, 0, DMU_OBJECT_END);
        /* wait for dmu_free_long_range to actually free the blocks */
        txg_wait_synced(dmu_objset_pool(zv->zv_objset), 0);
        tx = dmu_tx_create(os);
        dmu_tx_hold_bonus(tx, ZVOL_OBJ);
        error = dmu_tx_assign(tx, TXG_WAIT);
        if (error) {
                dmu_tx_abort(tx);
                return (error);
        }
        if (dmu_object_set_blocksize(os, ZVOL_OBJ, vbs, 0, tx) == 0)
                zv->zv_volblocksize = vbs;
        dmu_tx_commit(tx);

        return (0);
}
#else   /* !illumos */

static void
zvol_geom_run(zvol_state_t *zv)
{
        struct g_provider *pp;

        pp = zv->zv_provider;
        g_error_provider(pp, 0);

        kproc_kthread_add(zvol_geom_worker, zv, &system_proc, NULL, 0, 0,
            "zfskern", "zvol %s", pp->name + sizeof(ZVOL_DRIVER));
}

static void
zvol_geom_destroy(zvol_state_t *zv)
{
        struct g_provider *pp;

        g_topology_assert();

        mtx_lock(&zv->zv_queue_mtx);
        zv->zv_state = 1;
        wakeup_one(&zv->zv_queue);
        while (zv->zv_state != 2)
                msleep(&zv->zv_state, &zv->zv_queue_mtx, 0, "zvol:w", 0);
        mtx_destroy(&zv->zv_queue_mtx);

        pp = zv->zv_provider;
        zv->zv_provider = NULL;
        pp->private = NULL;
        g_wither_geom(pp->geom, ENXIO);
}

static int
zvol_geom_access(struct g_provider *pp, int acr, int acw, int ace)
{
        int count, error, flags;

        g_topology_assert();

        /*
         * To make it easier we expect either open or close, but not both
         * at the same time.
         */
        KASSERT((acr >= 0 && acw >= 0 && ace >= 0) ||
            (acr <= 0 && acw <= 0 && ace <= 0),
            ("Unsupported access request to %s (acr=%d, acw=%d, ace=%d).",
            pp->name, acr, acw, ace));

        if (pp->private == NULL) {
                if (acr <= 0 && acw <= 0 && ace <= 0)
                        return (0);
                return (pp->error);
        }

        /*
         * We don't pass FEXCL flag to zvol_open()/zvol_close() if ace != 0,
         * because GEOM already handles that and handles it a bit differently.
         * GEOM allows for multiple read/exclusive consumers and ZFS allows
         * only one exclusive consumer, no matter if it is reader or writer.
         * I like better the way GEOM works so I'll leave it for GEOM to
         * decide what to do.
         */

        count = acr + acw + ace;
        if (count == 0)
                return (0);

        flags = 0;
        if (acr != 0 || ace != 0)
                flags |= FREAD;
        if (acw != 0)
                flags |= FWRITE;

        g_topology_unlock();
        if (count > 0)
                error = zvol_open(pp, flags, count);
        else
                error = zvol_close(pp, flags, -count);
        g_topology_lock();
        return (error);
}

static void
zvol_geom_start(struct bio *bp)
{
        zvol_state_t *zv;
        boolean_t first;

        zv = bp->bio_to->private;
        ASSERT(zv != NULL);
        switch (bp->bio_cmd) {
        case BIO_FLUSH:
                if (!THREAD_CAN_SLEEP())
                        goto enqueue;
                zil_commit(zv->zv_zilog, ZVOL_OBJ);
                g_io_deliver(bp, 0);
                break;
        case BIO_READ:
        case BIO_WRITE:
        case BIO_DELETE:
                if (!THREAD_CAN_SLEEP())
                        goto enqueue;
                zvol_strategy(bp);
                break;
        case BIO_GETATTR: {
                spa_t *spa = dmu_objset_spa(zv->zv_objset);
                uint64_t refd, avail, usedobjs, availobjs, val;

                if (g_handleattr_int(bp, "GEOM::candelete", 1))
                        return;
                if (strcmp(bp->bio_attribute, "blocksavail") == 0) {
                        dmu_objset_space(zv->zv_objset, &refd, &avail,
                            &usedobjs, &availobjs);
                        if (g_handleattr_off_t(bp, "blocksavail",
                            avail / DEV_BSIZE))
                                return;
                } else if (strcmp(bp->bio_attribute, "blocksused") == 0) {
                        dmu_objset_space(zv->zv_objset, &refd, &avail,
                            &usedobjs, &availobjs);
                        if (g_handleattr_off_t(bp, "blocksused",
                            refd / DEV_BSIZE))
                                return;
                } else if (strcmp(bp->bio_attribute, "poolblocksavail") == 0) {
                        avail = metaslab_class_get_space(spa_normal_class(spa));
                        avail -= metaslab_class_get_alloc(spa_normal_class(spa));
                        if (g_handleattr_off_t(bp, "poolblocksavail",
                            avail / DEV_BSIZE))
                                return;
                } else if (strcmp(bp->bio_attribute, "poolblocksused") == 0) {
                        refd = metaslab_class_get_alloc(spa_normal_class(spa));
                        if (g_handleattr_off_t(bp, "poolblocksused",
                            refd / DEV_BSIZE))
                                return;
                }
                /* FALLTHROUGH */
        }
        default:
                g_io_deliver(bp, EOPNOTSUPP);
                break;
        }
        return;

enqueue:
        mtx_lock(&zv->zv_queue_mtx);
        first = (bioq_first(&zv->zv_queue) == NULL);
        bioq_insert_tail(&zv->zv_queue, bp);
        mtx_unlock(&zv->zv_queue_mtx);
        if (first)
                wakeup_one(&zv->zv_queue);
}

static void
zvol_geom_worker(void *arg)
{
        zvol_state_t *zv;
        struct bio *bp;

        thread_lock(curthread);
        sched_prio(curthread, PRIBIO);
        thread_unlock(curthread);

        zv = arg;
        for (;;) {
                mtx_lock(&zv->zv_queue_mtx);
                bp = bioq_takefirst(&zv->zv_queue);
                if (bp == NULL) {
                        if (zv->zv_state == 1) {
                                zv->zv_state = 2;
                                wakeup(&zv->zv_state);
                                mtx_unlock(&zv->zv_queue_mtx);
                                kthread_exit();
                        }
                        msleep(&zv->zv_queue, &zv->zv_queue_mtx, PRIBIO | PDROP,
                            "zvol:io", 0);
                        continue;
                }
                mtx_unlock(&zv->zv_queue_mtx);
                switch (bp->bio_cmd) {
                case BIO_FLUSH:
                        zil_commit(zv->zv_zilog, ZVOL_OBJ);
                        g_io_deliver(bp, 0);
                        break;
                case BIO_READ:
                case BIO_WRITE:
                case BIO_DELETE:
                        zvol_strategy(bp);
                        break;
                default:
                        g_io_deliver(bp, EOPNOTSUPP);
                        break;
                }
        }
}

extern boolean_t dataset_name_hidden(const char *name);

static int
zvol_create_snapshots(objset_t *os, const char *name)
{
        uint64_t cookie, obj;
        char *sname;
        int error, len;

        cookie = obj = 0;
        sname = kmem_alloc(MAXPATHLEN, KM_SLEEP);

#if 0
        (void) dmu_objset_find(name, dmu_objset_prefetch, NULL,
            DS_FIND_SNAPSHOTS);
#endif

        for (;;) {
                len = snprintf(sname, MAXPATHLEN, "%s@", name);
                if (len >= MAXPATHLEN) {
                        dmu_objset_rele(os, FTAG);
                        error = ENAMETOOLONG;
                        break;
                }

                dsl_pool_config_enter(dmu_objset_pool(os), FTAG);
                error = dmu_snapshot_list_next(os, MAXPATHLEN - len,
                    sname + len, &obj, &cookie, NULL);
                dsl_pool_config_exit(dmu_objset_pool(os), FTAG);
                if (error != 0) {
                        if (error == ENOENT)
                                error = 0;
                        break;
                }

                error = zvol_create_minor(sname);
                if (error != 0 && error != EEXIST) {
                        printf("ZFS WARNING: Unable to create ZVOL %s (error=%d).\n",
                            sname, error);
                        break;
                }
        }

        kmem_free(sname, MAXPATHLEN);
        return (error);
}

int
zvol_create_minors(const char *name)
{
        uint64_t cookie;
        objset_t *os;
        char *osname, *p;
        int error, len;

        if (dataset_name_hidden(name))
                return (0);

        if ((error = dmu_objset_hold(name, FTAG, &os)) != 0) {
                printf("ZFS WARNING: Unable to put hold on %s (error=%d).\n",
                    name, error);
                return (error);
        }
        if (dmu_objset_type(os) == DMU_OST_ZVOL) {
                dsl_dataset_long_hold(os->os_dsl_dataset, FTAG);
                dsl_pool_rele(dmu_objset_pool(os), FTAG);
                error = zvol_create_minor(name);
                if (error == 0 || error == EEXIST) {
                        error = zvol_create_snapshots(os, name);
                } else {
                        printf("ZFS WARNING: Unable to create ZVOL %s (error=%d).\n",
                            name, error);
                }
                dsl_dataset_long_rele(os->os_dsl_dataset, FTAG);
                dsl_dataset_rele(os->os_dsl_dataset, FTAG);
                return (error);
        }
        if (dmu_objset_type(os) != DMU_OST_ZFS) {
                dmu_objset_rele(os, FTAG);
                return (0);
        }

        osname = kmem_alloc(MAXPATHLEN, KM_SLEEP);
        if (snprintf(osname, MAXPATHLEN, "%s/", name) >= MAXPATHLEN) {
                dmu_objset_rele(os, FTAG);
                kmem_free(osname, MAXPATHLEN);
                return (ENOENT);
        }
        p = osname + strlen(osname);
        len = MAXPATHLEN - (p - osname);

#if 0
        /* Prefetch the datasets. */
        cookie = 0;
        while (dmu_dir_list_next(os, len, p, NULL, &cookie) == 0) {
                if (!dataset_name_hidden(osname))
                        (void) dmu_objset_prefetch(osname, NULL);
        }
#endif

        cookie = 0;
        while (dmu_dir_list_next(os, MAXPATHLEN - (p - osname), p, NULL,
            &cookie) == 0) {
                dmu_objset_rele(os, FTAG);
                (void)zvol_create_minors(osname);
                if ((error = dmu_objset_hold(name, FTAG, &os)) != 0) {
                        printf("ZFS WARNING: Unable to put hold on %s (error=%d).\n",
                            name, error);
                        return (error);
                }
        }

        dmu_objset_rele(os, FTAG);
        kmem_free(osname, MAXPATHLEN);
        return (0);
}

static void
zvol_rename_minor(zvol_state_t *zv, const char *newname)
{
        struct g_geom *gp;
        struct g_provider *pp;
        struct cdev *dev;

        ASSERT(MUTEX_HELD(&zfsdev_state_lock));

        if (zv->zv_volmode == ZFS_VOLMODE_GEOM) {
                g_topology_lock();
                pp = zv->zv_provider;
                ASSERT(pp != NULL);
                gp = pp->geom;
                ASSERT(gp != NULL);

                zv->zv_provider = NULL;
                g_wither_provider(pp, ENXIO);

                pp = g_new_providerf(gp, "%s/%s", ZVOL_DRIVER, newname);
                pp->flags |= G_PF_DIRECT_RECEIVE | G_PF_DIRECT_SEND;
                pp->sectorsize = DEV_BSIZE;
                pp->mediasize = zv->zv_volsize;
                pp->private = zv;
                zv->zv_provider = pp;
                g_error_provider(pp, 0);
                g_topology_unlock();
        } else if (zv->zv_volmode == ZFS_VOLMODE_DEV) {
                struct make_dev_args args;

                if ((dev = zv->zv_dev) != NULL) {
                        zv->zv_dev = NULL;
                        destroy_dev(dev);
                        if (zv->zv_total_opens > 0) {
                                zv->zv_flags &= ~ZVOL_EXCL;
                                zv->zv_total_opens = 0;
                                zvol_last_close(zv);
                        }
                }

                make_dev_args_init(&args);
                args.mda_flags = MAKEDEV_CHECKNAME | MAKEDEV_WAITOK;
                args.mda_devsw = &zvol_cdevsw;
                args.mda_cr = NULL;
                args.mda_uid = UID_ROOT;
                args.mda_gid = GID_OPERATOR;
                args.mda_mode = 0640;
                args.mda_si_drv2 = zv;
                if (make_dev_s(&args, &zv->zv_dev,
                    "%s/%s", ZVOL_DRIVER, newname) == 0)
                        zv->zv_dev->si_iosize_max = MAXPHYS;
        }
        strlcpy(zv->zv_name, newname, sizeof(zv->zv_name));
}

void
zvol_rename_minors(const char *oldname, const char *newname)
{
        char name[MAXPATHLEN];
        struct g_provider *pp;
        struct g_geom *gp;
        size_t oldnamelen, newnamelen;
        zvol_state_t *zv;
        char *namebuf;
        boolean_t locked = B_FALSE;

        oldnamelen = strlen(oldname);
        newnamelen = strlen(newname);

        DROP_GIANT();
        /* See comment in zvol_open(). */
        if (!MUTEX_HELD(&zfsdev_state_lock)) {
                mutex_enter(&zfsdev_state_lock);
                locked = B_TRUE;
        }

        LIST_FOREACH(zv, &all_zvols, zv_links) {
                if (strcmp(zv->zv_name, oldname) == 0) {
                        zvol_rename_minor(zv, newname);
                } else if (strncmp(zv->zv_name, oldname, oldnamelen) == 0 &&
                    (zv->zv_name[oldnamelen] == '/' ||
                     zv->zv_name[oldnamelen] == '@')) {
                        snprintf(name, sizeof(name), "%s%c%s", newname,
                            zv->zv_name[oldnamelen],
                            zv->zv_name + oldnamelen + 1);
                        zvol_rename_minor(zv, name);
                }
        }

        if (locked)
                mutex_exit(&zfsdev_state_lock);
        PICKUP_GIANT();
}

static int
zvol_d_open(struct cdev *dev, int flags, int fmt, struct thread *td)
{
        zvol_state_t *zv = dev->si_drv2;
        int err = 0;

        mutex_enter(&zfsdev_state_lock);
        if (zv->zv_total_opens == 0)
                err = zvol_first_open(zv);
        if (err) {
                mutex_exit(&zfsdev_state_lock);
                return (err);
        }
        if ((flags & FWRITE) && (zv->zv_flags & ZVOL_RDONLY)) {
                err = SET_ERROR(EROFS);
                goto out;
        }
        if (zv->zv_flags & ZVOL_EXCL) {
                err = SET_ERROR(EBUSY);
                goto out;
        }
#ifdef FEXCL
        if (flags & FEXCL) {
                if (zv->zv_total_opens != 0) {
                        err = SET_ERROR(EBUSY);
                        goto out;
                }
                zv->zv_flags |= ZVOL_EXCL;
        }
#endif

        zv->zv_total_opens++;
        if (flags & (FSYNC | FDSYNC)) {
                zv->zv_sync_cnt++;
                if (zv->zv_sync_cnt == 1)
                        zil_async_to_sync(zv->zv_zilog, ZVOL_OBJ);
        }
        mutex_exit(&zfsdev_state_lock);
        return (err);
out:
        if (zv->zv_total_opens == 0)
                zvol_last_close(zv);
        mutex_exit(&zfsdev_state_lock);
        return (err);
}

static int
zvol_d_close(struct cdev *dev, int flags, int fmt, struct thread *td)
{
        zvol_state_t *zv = dev->si_drv2;

        mutex_enter(&zfsdev_state_lock);
        if (zv->zv_flags & ZVOL_EXCL) {
                ASSERT(zv->zv_total_opens == 1);
                zv->zv_flags &= ~ZVOL_EXCL;
        }

        /*
         * If the open count is zero, this is a spurious close.
         * That indicates a bug in the kernel / DDI framework.
         */
        ASSERT(zv->zv_total_opens != 0);

        /*
         * You may get multiple opens, but only one close.
         */
        zv->zv_total_opens--;
        if (flags & (FSYNC | FDSYNC))
                zv->zv_sync_cnt--;

        if (zv->zv_total_opens == 0)
                zvol_last_close(zv);

        mutex_exit(&zfsdev_state_lock);
        return (0);
}

static int
zvol_d_ioctl(struct cdev *dev, u_long cmd, caddr_t data, int fflag, struct thread *td)
{
        zvol_state_t *zv;
        locked_range_t *lr;
        off_t offset, length;
        int i, error;
        boolean_t sync;

        zv = dev->si_drv2;

        error = 0;
        KASSERT(zv->zv_total_opens > 0,
            ("Device with zero access count in zvol_d_ioctl"));

        i = IOCPARM_LEN(cmd);
        switch (cmd) {
        case DIOCGSECTORSIZE:
                *(u_int *)data = DEV_BSIZE;
                break;
        case DIOCGMEDIASIZE:
                *(off_t *)data = zv->zv_volsize;
                break;
        case DIOCGFLUSH:
                zil_commit(zv->zv_zilog, ZVOL_OBJ);
                break;
        case DIOCGDELETE:
                if (!zvol_unmap_enabled)
                        break;

                offset = ((off_t *)data)[0];
                length = ((off_t *)data)[1];
                if ((offset % DEV_BSIZE) != 0 || (length % DEV_BSIZE) != 0 ||
                    offset < 0 || offset >= zv->zv_volsize ||
                    length <= 0) {
                        printf("%s: offset=%jd length=%jd\n", __func__, offset,
                            length);
                        error = EINVAL;
                        break;
                }

                lr = rangelock_enter(&zv->zv_rangelock, offset, length,
                    RL_WRITER);
                dmu_tx_t *tx = dmu_tx_create(zv->zv_objset);
                error = dmu_tx_assign(tx, TXG_WAIT);
                if (error != 0) {
                        sync = FALSE;
                        dmu_tx_abort(tx);
                } else {
                        sync = (zv->zv_objset->os_sync == ZFS_SYNC_ALWAYS);
                        zvol_log_truncate(zv, tx, offset, length, sync);
                        dmu_tx_commit(tx);
                        error = dmu_free_long_range(zv->zv_objset, ZVOL_OBJ,
                            offset, length);
                }
                rangelock_exit(lr);
                if (sync)
                        zil_commit(zv->zv_zilog, ZVOL_OBJ);
                break;
        case DIOCGSTRIPESIZE:
                *(off_t *)data = zv->zv_volblocksize;
                break;
        case DIOCGSTRIPEOFFSET:
                *(off_t *)data = 0;
                break;
        case DIOCGATTR: {
                spa_t *spa = dmu_objset_spa(zv->zv_objset);
                struct diocgattr_arg *arg = (struct diocgattr_arg *)data;
                uint64_t refd, avail, usedobjs, availobjs;

                if (strcmp(arg->name, "GEOM::candelete") == 0)
                        arg->value.i = 1;
                else if (strcmp(arg->name, "blocksavail") == 0) {
                        dmu_objset_space(zv->zv_objset, &refd, &avail,
                            &usedobjs, &availobjs);
                        arg->value.off = avail / DEV_BSIZE;
                } else if (strcmp(arg->name, "blocksused") == 0) {
                        dmu_objset_space(zv->zv_objset, &refd, &avail,
                            &usedobjs, &availobjs);
                        arg->value.off = refd / DEV_BSIZE;
                } else if (strcmp(arg->name, "poolblocksavail") == 0) {
                        avail = metaslab_class_get_space(spa_normal_class(spa));
                        avail -= metaslab_class_get_alloc(spa_normal_class(spa));
                        arg->value.off = avail / DEV_BSIZE;
                } else if (strcmp(arg->name, "poolblocksused") == 0) {
                        refd = metaslab_class_get_alloc(spa_normal_class(spa));
                        arg->value.off = refd / DEV_BSIZE;
                } else
                        error = ENOIOCTL;
                break;
        }
        case FIOSEEKHOLE:
        case FIOSEEKDATA: {
                off_t *off = (off_t *)data;
                uint64_t noff;
                boolean_t hole;

                hole = (cmd == FIOSEEKHOLE);
                noff = *off;
                error = dmu_offset_next(zv->zv_objset, ZVOL_OBJ, hole, &noff);
                *off = noff;
                break;
        }
        default:
                error = ENOIOCTL;
        }

        return (error);
}
#endif  /* illumos */