fs/zfs/zvol.c

	zvol.c revision 3a8a1de4a7950ac5cf7ca65f761e324145e7237b
/*
 * 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 2007 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

/*
 * 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 ZFS-specific devfsadm link generator.
 * Volumes are persistent through reboot.  No user command needs to be
 * run before opening and using a device.
 */

#include <sys/types.h>
#include <sys/param.h>
#include <sys/errno.h>
#include <sys/uio.h>
#include <sys/buf.h>
#include <sys/modctl.h>
#include <sys/open.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/zio.h>
#include <sys/dsl_prop.h>
#include <sys/dkio.h>
#include <sys/efi_partition.h>
#include <sys/byteorder.h>
#include <sys/pathname.h>
#include <sys/ddi.h>
#include <sys/sunddi.h>
#include <sys/crc32.h>
#include <sys/dirent.h>
#include <sys/policy.h>
#include <sys/fs/zfs.h>
#include <sys/zfs_ioctl.h>
#include <sys/mkdev.h>
#include <sys/zil.h>
#include <sys/refcount.h>
#include <sys/zfs_znode.h>
#include <sys/zfs_rlock.h>

#include "zfs_namecheck.h"

#define ZVOL_OBJ        1ULL
#define ZVOL_ZAP_OBJ        2ULL

static void *zvol_state;

/*
 * This lock protects the zvol_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.
 */
static kmutex_t zvol_state_lock;
static uint32_t zvol_minors;

/*
 * The in-core state of each volume.
 */
typedef struct zvol_state {
    char        zv_name[MAXPATHLEN]; /* pool/dd name */
    uint64_t    zv_volsize; /* amount of space we advertise */
    uint64_t    zv_volblocksize; /* volume block size */
    minor_t     zv_minor;   /* minor number */
    uint8_t     zv_min_bs;  /* minimum addressable block shift */
    uint8_t     zv_readonly;    /* hard readonly; like write-protect */
    objset_t    *zv_objset; /* objset handle */
    uint32_t    zv_mode;    /* DS_MODE_* flags at open time */
    uint32_t    zv_open_count[OTYPCNT]; /* open counts */
    uint32_t    zv_total_opens; /* total open count */
    zilog_t     *zv_zilog;  /* ZIL handle */
    uint64_t    zv_txg_assign;  /* txg to assign during ZIL replay */
    znode_t     zv_znode;   /* for range locking */
} zvol_state_t;

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

static int zvol_get_data(void *arg, lr_write_t *lr, char *buf, zio_t *zio);

static void
zvol_size_changed(zvol_state_t *zv, major_t maj)
{
    dev_t dev = makedevice(maj, zv->zv_minor);

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

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

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

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

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

    return (0);
}

static void
zvol_readonly_changed_cb(void *arg, uint64_t newval)
{
    zvol_state_t *zv = arg;

    zv->zv_readonly = (uint8_t)newval;
}

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);
}

/*
 * Find a free minor number.
 */
static minor_t
zvol_minor_alloc(void)
{
    minor_t minor;

    ASSERT(MUTEX_HELD(&zvol_state_lock));

    for (minor = 1; minor <= ZVOL_MAX_MINOR; minor++)
        if (ddi_get_soft_state(zvol_state, minor) == NULL)
            return (minor);

    return (0);
}

static zvol_state_t *
zvol_minor_lookup(const char *name)
{
    minor_t minor;
    zvol_state_t *zv;

    ASSERT(MUTEX_HELD(&zvol_state_lock));

    for (minor = 1; minor <= ZVOL_MAX_MINOR; minor++) {
        zv = ddi_get_soft_state(zvol_state, minor);
        if (zv == NULL)
            continue;
        if (strcmp(zv->zv_name, name) == 0)
            break;
    }

    return (zv);
}

/* ARGSUSED */
void
zvol_create_cb(objset_t *os, void *arg, cred_t *cr, dmu_tx_t *tx)
{
    nvlist_t *nvprops = arg;
    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 properites 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_WRITE ZIL transaction that didn't get committed
 * after a system failure
 */
static int
zvol_replay_write(zvol_state_t *zv, lr_write_t *lr, boolean_t byteswap)
{
    objset_t *os = zv->zv_objset;
    char *data = (char *)(lr + 1);  /* data follows lr_write_t */
    uint64_t off = lr->lr_offset;
    uint64_t len = lr->lr_length;
    dmu_tx_t *tx;
    int error;

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

    tx = dmu_tx_create(os);
    dmu_tx_hold_write(tx, ZVOL_OBJ, off, len);
    error = dmu_tx_assign(tx, zv->zv_txg_assign);
    if (error) {
        dmu_tx_abort(tx);
    } else {
        dmu_write(os, ZVOL_OBJ, off, len, data, tx);
        dmu_tx_commit(tx);
    }

    return (error);
}

/* ARGSUSED */
static int
zvol_replay_err(zvol_state_t *zv, lr_t *lr, boolean_t byteswap)
{
    return (ENOTSUP);
}

/*
 * Callback vectors for replaying records.
 * Only TX_WRITE is 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_err,    /* TX_TRUNCATE */
    zvol_replay_err,    /* TX_SETATTR */
    zvol_replay_err,    /* TX_ACL */
};

/*
 * Create a minor node for the specified volume.
 */
int
zvol_create_minor(const char *name, major_t maj)
{
    zvol_state_t *zv;
    objset_t *os;
    dmu_object_info_t doi;
    uint64_t volsize;
    minor_t minor = 0;
    struct pathname linkpath;
    int ds_mode = DS_MODE_PRIMARY;
    vnode_t *vp = NULL;
    char *devpath;
    size_t devpathlen = strlen(ZVOL_FULL_DEV_DIR) + 1 + strlen(name) + 1;
    char chrbuf[30], blkbuf[30];
    int error;

    mutex_enter(&zvol_state_lock);

    if ((zv = zvol_minor_lookup(name)) != NULL) {
        mutex_exit(&zvol_state_lock);
        return (EEXIST);
    }

    if (strchr(name, '@') != 0)
        ds_mode |= DS_MODE_READONLY;

    error = dmu_objset_open(name, DMU_OST_ZVOL, ds_mode, &os);

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

    error = zap_lookup(os, ZVOL_ZAP_OBJ, "size", 8, 1, &volsize);

    if (error) {
        dmu_objset_close(os);
        mutex_exit(&zvol_state_lock);
        return (error);
    }

    /*
     * If there's an existing /dev/zvol symlink, try to use the
     * same minor number we used last time.
     */
    devpath = kmem_alloc(devpathlen, KM_SLEEP);

    (void) sprintf(devpath, "%s/%s", ZVOL_FULL_DEV_DIR, name);

    error = lookupname(devpath, UIO_SYSSPACE, NO_FOLLOW, NULL, &vp);

    kmem_free(devpath, devpathlen);

    if (error == 0 && vp->v_type != VLNK)
        error = EINVAL;

    if (error == 0) {
        pn_alloc(&linkpath);
        error = pn_getsymlink(vp, &linkpath, kcred);
        if (error == 0) {
            char *ms = strstr(linkpath.pn_path, ZVOL_PSEUDO_DEV);
            if (ms != NULL) {
                ms += strlen(ZVOL_PSEUDO_DEV);
                minor = stoi(&ms);
            }
        }
        pn_free(&linkpath);
    }

    if (vp != NULL)
        VN_RELE(vp);

    /*
     * If we found a minor but it's already in use, we must pick a new one.
     */
    if (minor != 0 && ddi_get_soft_state(zvol_state, minor) != NULL)
        minor = 0;

    if (minor == 0)
        minor = zvol_minor_alloc();

    if (minor == 0) {
        dmu_objset_close(os);
        mutex_exit(&zvol_state_lock);
        return (ENXIO);
    }

    if (ddi_soft_state_zalloc(zvol_state, minor) != DDI_SUCCESS) {
        dmu_objset_close(os);
        mutex_exit(&zvol_state_lock);
        return (EAGAIN);
    }

    (void) ddi_prop_update_string(minor, zfs_dip, ZVOL_PROP_NAME,
        (char *)name);

    (void) sprintf(chrbuf, "%uc,raw", minor);

    if (ddi_create_minor_node(zfs_dip, chrbuf, S_IFCHR,
        minor, DDI_PSEUDO, 0) == DDI_FAILURE) {
        ddi_soft_state_free(zvol_state, minor);
        dmu_objset_close(os);
        mutex_exit(&zvol_state_lock);
        return (EAGAIN);
    }

    (void) sprintf(blkbuf, "%uc", 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(zvol_state, minor);
        dmu_objset_close(os);
        mutex_exit(&zvol_state_lock);
        return (EAGAIN);
    }

    zv = ddi_get_soft_state(zvol_state, minor);

    (void) strcpy(zv->zv_name, name);
    zv->zv_min_bs = DEV_BSHIFT;
    zv->zv_minor = minor;
    zv->zv_volsize = volsize;
    zv->zv_objset = os;
    zv->zv_mode = ds_mode;
    zv->zv_zilog = zil_open(os, zvol_get_data);
    mutex_init(&zv->zv_znode.z_range_lock, NULL, MUTEX_DEFAULT, NULL);
    avl_create(&zv->zv_znode.z_range_avl, zfs_range_compare,
        sizeof (rl_t), offsetof(rl_t, r_node));


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

    zil_replay(os, zv, &zv->zv_txg_assign, zvol_replay_vector);

    zvol_size_changed(zv, maj);

    /* XXX this should handle the possible i/o error */
    VERIFY(dsl_prop_register(dmu_objset_ds(zv->zv_objset),
        "readonly", zvol_readonly_changed_cb, zv) == 0);

    zvol_minors++;

    mutex_exit(&zvol_state_lock);

    return (0);
}

/*
 * Remove minor node for the specified volume.
 */
int
zvol_remove_minor(const char *name)
{
    zvol_state_t *zv;
    char namebuf[30];

    mutex_enter(&zvol_state_lock);

    if ((zv = zvol_minor_lookup(name)) == NULL) {
        mutex_exit(&zvol_state_lock);
        return (ENXIO);
    }

    if (zv->zv_total_opens != 0) {
        mutex_exit(&zvol_state_lock);
        return (EBUSY);
    }

    (void) sprintf(namebuf, "%uc,raw", zv->zv_minor);
    ddi_remove_minor_node(zfs_dip, namebuf);

    (void) sprintf(namebuf, "%uc", zv->zv_minor);
    ddi_remove_minor_node(zfs_dip, namebuf);

    VERIFY(dsl_prop_unregister(dmu_objset_ds(zv->zv_objset),
        "readonly", zvol_readonly_changed_cb, zv) == 0);

    zil_close(zv->zv_zilog);
    zv->zv_zilog = NULL;
    dmu_objset_close(zv->zv_objset);
    zv->zv_objset = NULL;
    avl_destroy(&zv->zv_znode.z_range_avl);
    mutex_destroy(&zv->zv_znode.z_range_lock);

    ddi_soft_state_free(zvol_state, zv->zv_minor);

    zvol_minors--;

    mutex_exit(&zvol_state_lock);

    return (0);
}

int
zvol_set_volsize(const char *name, major_t maj, uint64_t volsize)
{
    zvol_state_t *zv;
    dmu_tx_t *tx;
    int error;
    dmu_object_info_t doi;

    mutex_enter(&zvol_state_lock);

    if ((zv = zvol_minor_lookup(name)) == NULL) {
        mutex_exit(&zvol_state_lock);
        return (ENXIO);
    }

    if ((error = dmu_object_info(zv->zv_objset, ZVOL_OBJ, &doi)) != 0 ||
        (error = zvol_check_volsize(volsize,
        doi.doi_data_block_size)) != 0) {
        mutex_exit(&zvol_state_lock);
        return (error);
    }

    if (zv->zv_readonly || (zv->zv_mode & DS_MODE_READONLY)) {
        mutex_exit(&zvol_state_lock);
        return (EROFS);
    }

    tx = dmu_tx_create(zv->zv_objset);
    dmu_tx_hold_zap(tx, ZVOL_ZAP_OBJ, TRUE, NULL);
    dmu_tx_hold_free(tx, ZVOL_OBJ, volsize, DMU_OBJECT_END);
    error = dmu_tx_assign(tx, TXG_WAIT);
    if (error) {
        dmu_tx_abort(tx);
        mutex_exit(&zvol_state_lock);
        return (error);
    }

    error = zap_update(zv->zv_objset, ZVOL_ZAP_OBJ, "size", 8, 1,
        &volsize, tx);
    if (error == 0) {
        error = dmu_free_range(zv->zv_objset, ZVOL_OBJ, volsize,
            DMU_OBJECT_END, tx);
    }

    dmu_tx_commit(tx);

    if (error == 0) {
        zv->zv_volsize = volsize;
        zvol_size_changed(zv, maj);
    }

    mutex_exit(&zvol_state_lock);

    return (error);
}

int
zvol_set_volblocksize(const char *name, uint64_t volblocksize)
{
    zvol_state_t *zv;
    dmu_tx_t *tx;
    int error;

    mutex_enter(&zvol_state_lock);

    if ((zv = zvol_minor_lookup(name)) == NULL) {
        mutex_exit(&zvol_state_lock);
        return (ENXIO);
    }

    if (zv->zv_readonly || (zv->zv_mode & DS_MODE_READONLY)) {
        mutex_exit(&zvol_state_lock);
        return (EROFS);
    }

    tx = dmu_tx_create(zv->zv_objset);
    dmu_tx_hold_bonus(tx, ZVOL_OBJ);
    error = dmu_tx_assign(tx, TXG_WAIT);
    if (error) {
        dmu_tx_abort(tx);
    } else {
        error = dmu_object_set_blocksize(zv->zv_objset, ZVOL_OBJ,
            volblocksize, 0, tx);
        if (error == ENOTSUP)
            error = EBUSY;
        dmu_tx_commit(tx);
    }

    mutex_exit(&zvol_state_lock);

    return (error);
}

/*ARGSUSED*/
int
zvol_open(dev_t *devp, int flag, int otyp, cred_t *cr)
{
    minor_t minor = getminor(*devp);
    zvol_state_t *zv;

    if (minor == 0)         /* This is the control device */
        return (0);

    mutex_enter(&zvol_state_lock);

    zv = ddi_get_soft_state(zvol_state, minor);
    if (zv == NULL) {
        mutex_exit(&zvol_state_lock);
        return (ENXIO);
    }

    ASSERT(zv->zv_objset != NULL);

    if ((flag & FWRITE) &&
        (zv->zv_readonly || (zv->zv_mode & DS_MODE_READONLY))) {
        mutex_exit(&zvol_state_lock);
        return (EROFS);
    }

    if (zv->zv_open_count[otyp] == 0 || otyp == OTYP_LYR) {
        zv->zv_open_count[otyp]++;
        zv->zv_total_opens++;
    }

    mutex_exit(&zvol_state_lock);

    return (0);
}

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

    if (minor == 0)     /* This is the control device */
        return (0);

    mutex_enter(&zvol_state_lock);

    zv = ddi_get_soft_state(zvol_state, minor);
    if (zv == NULL) {
        mutex_exit(&zvol_state_lock);
        return (ENXIO);
    }

    /*
     * The next statement is a workaround for the following DDI bug:
     * 6343604 specfs race: multiple "last-close" of the same device
     */
    if (zv->zv_total_opens == 0) {
        mutex_exit(&zvol_state_lock);
        return (0);
    }

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

    /*
     * You may get multiple opens, but only one close.
     */
    zv->zv_open_count[otyp]--;
    zv->zv_total_opens--;

    mutex_exit(&zvol_state_lock);

    return (0);
}

static void
zvol_get_done(dmu_buf_t *db, void *vzgd)
{
    zgd_t *zgd = (zgd_t *)vzgd;
    rl_t *rl = zgd->zgd_rl;

    dmu_buf_rele(db, vzgd);
    zfs_range_unlock(rl);
    zil_add_vdev(zgd->zgd_zilog, DVA_GET_VDEV(BP_IDENTITY(zgd->zgd_bp)));
    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, zio_t *zio)
{
    zvol_state_t *zv = arg;
    objset_t *os = zv->zv_objset;
    dmu_buf_t *db;
    rl_t *rl;
    zgd_t *zgd;
    uint64_t boff;          /* block starting offset */
    int dlen = lr->lr_length;   /* length of user data */
    int error;

    ASSERT(zio);
    ASSERT(dlen != 0);

    /*
     * 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 */
        return (dmu_read(os, ZVOL_OBJ, lr->lr_offset, dlen, buf));

    zgd = (zgd_t *)kmem_alloc(sizeof (zgd_t), KM_SLEEP);
    zgd->zgd_zilog = zv->zv_zilog;
    zgd->zgd_bp = &lr->lr_blkptr;

    /*
     * Lock the range of the block to ensure that when the data is
     * written out and it's checksum is being calculated that no other
     * thread can change the block.
     */
    boff = P2ALIGN_TYPED(lr->lr_offset, zv->zv_volblocksize, uint64_t);
    rl = zfs_range_lock(&zv->zv_znode, boff, zv->zv_volblocksize,
        RL_READER);
    zgd->zgd_rl = rl;

    VERIFY(0 == dmu_buf_hold(os, ZVOL_OBJ, lr->lr_offset, zgd, &db));
    error = dmu_sync(zio, db, &lr->lr_blkptr,
        lr->lr_common.lrc_txg, zvol_get_done, zgd);
    if (error == 0)
        zil_add_vdev(zv->zv_zilog,
            DVA_GET_VDEV(BP_IDENTITY(&lr->lr_blkptr)));
    /*
     * If we get EINPROGRESS, then we need to wait for a
     * write IO initiated by dmu_sync() to complete before
     * we can release this dbuf.  We will finish everything
     * up in the zvol_get_done() callback.
     */
    if (error == EINPROGRESS)
        return (0);
    dmu_buf_rele(db, zgd);
    zfs_range_unlock(rl);
    kmem_free(zgd, sizeof (zgd_t));
    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;

static void
zvol_log_write(zvol_state_t *zv, dmu_tx_t *tx, offset_t off, ssize_t len)
{
    uint32_t blocksize = zv->zv_volblocksize;
    lr_write_t *lr;

    while (len) {
        ssize_t nbytes = MIN(len, blocksize - P2PHASE(off, blocksize));
        itx_t *itx = zil_itx_create(TX_WRITE, sizeof (*lr));

        itx->itx_wr_state =
            len > zvol_immediate_write_sz ?  WR_INDIRECT : WR_NEED_COPY;
        itx->itx_private = zv;
        lr = (lr_write_t *)&itx->itx_lr;
        lr->lr_foid = ZVOL_OBJ;
        lr->lr_offset = off;
        lr->lr_length = nbytes;
        lr->lr_blkoff = off - P2ALIGN_TYPED(off, blocksize, uint64_t);
        BP_ZERO(&lr->lr_blkptr);

        (void) zil_itx_assign(zv->zv_zilog, itx, tx);
        len -= nbytes;
        off += nbytes;
    }
}

int
zvol_strategy(buf_t *bp)
{
    zvol_state_t *zv = ddi_get_soft_state(zvol_state, getminor(bp->b_edev));
    uint64_t off, volsize;
    size_t size, resid;
    char *addr;
    objset_t *os;
    rl_t *rl;
    int error = 0;
    boolean_t reading;

    if (zv == NULL) {
        bioerror(bp, ENXIO);
        biodone(bp);
        return (0);
    }

    if (getminor(bp->b_edev) == 0) {
        bioerror(bp, EINVAL);
        biodone(bp);
        return (0);
    }

    if ((zv->zv_readonly || (zv->zv_mode & DS_MODE_READONLY)) &&
        !(bp->b_flags & B_READ)) {
        bioerror(bp, EROFS);
        biodone(bp);
        return (0);
    }

    off = ldbtob(bp->b_blkno);
    volsize = zv->zv_volsize;

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

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

    /*
     * There must be no buffer changes when doing a dmu_sync() because
     * we can't change the data whilst calculating the checksum.
     */
    reading = bp->b_flags & B_READ;
    rl = zfs_range_lock(&zv->zv_znode, off, resid,
        reading ? RL_READER : RL_WRITER);

    while (resid != 0 && off < volsize) {

        size = MIN(resid, zvol_maxphys); /* zvol_maxphys per tx */

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

        if (reading) {
            error = dmu_read(os, ZVOL_OBJ, off, size, addr);
        } 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);
                dmu_tx_commit(tx);
            }
        }
        if (error)
            break;
        off += size;
        addr += size;
        resid -= size;
    }
    zfs_range_unlock(rl);

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

    if (!(bp->b_flags & B_ASYNC) && !reading && !zil_disable)
        zil_commit(zv->zv_zilog, UINT64_MAX, ZVOL_OBJ);

    biodone(bp);

    return (0);
}

/*
 * 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;
}

/*ARGSUSED*/
int
zvol_read(dev_t dev, uio_t *uio, cred_t *cr)
{
    minor_t minor = getminor(dev);
    zvol_state_t *zv;
    rl_t *rl;
    int error = 0;

    if (minor == 0)         /* This is the control device */
        return (ENXIO);

    zv = ddi_get_soft_state(zvol_state, minor);
    if (zv == NULL)
        return (ENXIO);

    rl = zfs_range_lock(&zv->zv_znode, uio->uio_loffset, uio->uio_resid,
        RL_READER);
    while (uio->uio_resid > 0) {
        uint64_t bytes = MIN(uio->uio_resid, DMU_MAX_ACCESS >> 1);

        error =  dmu_read_uio(zv->zv_objset, ZVOL_OBJ, uio, bytes);
        if (error)
            break;
    }
    zfs_range_unlock(rl);
    return (error);
}

/*ARGSUSED*/
int
zvol_write(dev_t dev, uio_t *uio, cred_t *cr)
{
    minor_t minor = getminor(dev);
    zvol_state_t *zv;
    rl_t *rl;
    int error = 0;

    if (minor == 0)         /* This is the control device */
        return (ENXIO);

    zv = ddi_get_soft_state(zvol_state, minor);
    if (zv == NULL)
        return (ENXIO);

    rl = zfs_range_lock(&zv->zv_znode, uio->uio_loffset, uio->uio_resid,
        RL_WRITER);
    while (uio->uio_resid > 0) {
        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);
        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(zv->zv_objset, ZVOL_OBJ, uio, bytes, tx);
        if (error == 0)
            zvol_log_write(zv, tx, off, bytes);
        dmu_tx_commit(tx);

        if (error)
            break;
    }
    zfs_range_unlock(rl);
    return (error);
}

/*
 * Dirtbag ioctls to support mkfs(1M) for UFS filesystems.  See dkio(7I).
 */
/*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_cinfo dki;
    struct dk_minfo dkm;
    dk_efi_t efi;
    struct dk_callback *dkc;
    struct uuid uuid = EFI_RESERVED;
    uint32_t crc;
    int error = 0;

    mutex_enter(&zvol_state_lock);

    zv = ddi_get_soft_state(zvol_state, getminor(dev));

    if (zv == NULL) {
        mutex_exit(&zvol_state_lock);
        return (ENXIO);
    }

    switch (cmd) {

    case DKIOCINFO:
        bzero(&dki, sizeof (dki));
        (void) strcpy(dki.dki_cname, "zvol");
        (void) strcpy(dki.dki_dname, "zvol");
        dki.dki_ctype = DKC_UNKNOWN;
        dki.dki_maxtransfer = 1 << (SPA_MAXBLOCKSHIFT - zv->zv_min_bs);
        mutex_exit(&zvol_state_lock);
        if (ddi_copyout(&dki, (void *)arg, sizeof (dki), flag))
            error = EFAULT;
        return (error);

    case DKIOCGMEDIAINFO:
        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(&zvol_state_lock);
        if (ddi_copyout(&dkm, (void *)arg, sizeof (dkm), flag))
            error = EFAULT;
        return (error);

    case DKIOCGETEFI:
        if (ddi_copyin((void *)arg, &efi, sizeof (dk_efi_t), flag)) {
            mutex_exit(&zvol_state_lock);
            return (EFAULT);
        }
        efi.dki_data = (void *)(uintptr_t)efi.dki_data_64;

        /*
         * Some clients may attempt to request a PMBR for the
         * zvol.  Currently this interface will return ENOTTY to
         * such requests.  These requests could be supported by
         * adding a check for lba == 0 and consing up an appropriate
         * RMBR.
         */
        if (efi.dki_lba == 1) {
            efi_gpt_t gpt;
            efi_gpe_t gpe;

            bzero(&gpt, sizeof (gpt));
            bzero(&gpe, sizeof (gpe));

            if (efi.dki_length < sizeof (gpt)) {
                mutex_exit(&zvol_state_lock);
                return (EINVAL);
            }

            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_FirstUsableLBA = LE_64(34ULL);
            gpt.efi_gpt_LastUsableLBA =
                LE_64((zv->zv_volsize >> zv->zv_min_bs) - 1);
            gpt.efi_gpt_NumberOfPartitionEntries = LE_32(1);
            gpt.efi_gpt_PartitionEntryLBA = LE_64(2ULL);
            gpt.efi_gpt_SizeOfPartitionEntry = LE_32(sizeof (gpe));

            UUID_LE_CONVERT(gpe.efi_gpe_PartitionTypeGUID, uuid);
            gpe.efi_gpe_StartingLBA = gpt.efi_gpt_FirstUsableLBA;
            gpe.efi_gpe_EndingLBA = gpt.efi_gpt_LastUsableLBA;

            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);

            mutex_exit(&zvol_state_lock);
            if (ddi_copyout(&gpt, efi.dki_data, sizeof (gpt), flag))
                error = EFAULT;
        } else if (efi.dki_lba == 2) {
            efi_gpe_t gpe;

            bzero(&gpe, sizeof (gpe));

            if (efi.dki_length < sizeof (gpe)) {
                mutex_exit(&zvol_state_lock);
                return (EINVAL);
            }

            UUID_LE_CONVERT(gpe.efi_gpe_PartitionTypeGUID, uuid);
            gpe.efi_gpe_StartingLBA = LE_64(34ULL);
            gpe.efi_gpe_EndingLBA =
                LE_64((zv->zv_volsize >> zv->zv_min_bs) - 1);

            mutex_exit(&zvol_state_lock);
            if (ddi_copyout(&gpe, efi.dki_data, sizeof (gpe), flag))
                error = EFAULT;
        } else {
            mutex_exit(&zvol_state_lock);
            error = EINVAL;
        }
        return (error);

    case DKIOCFLUSHWRITECACHE:
        dkc = (struct dk_callback *)arg;
        zil_commit(zv->zv_zilog, UINT64_MAX, ZVOL_OBJ);
        if ((flag & FKIOCTL) && dkc != NULL && dkc->dkc_callback) {
            (*dkc->dkc_callback)(dkc->dkc_cookie, error);
            error = 0;
        }
        break;

    case DKIOCGGEOM:
    case DKIOCGVTOC:
        /* commands using these (like prtvtoc) expect ENOTSUP */
        error = ENOTSUP;
        break;

    default:
        error = ENOTTY;
        break;

    }
    mutex_exit(&zvol_state_lock);
    return (error);
}

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

void
zvol_init(void)
{
    VERIFY(ddi_soft_state_init(&zvol_state, sizeof (zvol_state_t), 1) == 0);
    mutex_init(&zvol_state_lock, NULL, MUTEX_DEFAULT, NULL);
}

void
zvol_fini(void)
{
    mutex_destroy(&zvol_state_lock);
    ddi_soft_state_fini(&zvol_state);
}