fs/dev/sdev_zvolops.c

	sdev_zvolops.c revision d65686849024838243515b5c40ae2c479460b4b5
/*
 * 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 2009 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 * Copyright 2013 Joyent, Inc.  All rights reserved.
 */

/* vnode ops for the /dev/zvol directory */

#include <sys/types.h>
#include <sys/param.h>
#include <sys/sysmacros.h>
#include <sys/ddi.h>
#include <sys/sunndi.h>
#include <sys/sunldi.h>
#include <fs/fs_subr.h>
#include <sys/fs/dv_node.h>
#include <sys/fs/sdev_impl.h>
#include <sys/zfs_ioctl.h>
#include <sys/policy.h>
#include <sys/stat.h>
#include <sys/vfs_opreg.h>

struct vnodeops *devzvol_vnodeops;
static uint64_t devzvol_gen = 0;
static uint64_t devzvol_zclist;
static size_t devzvol_zclist_size;
static ldi_ident_t devzvol_li;
static ldi_handle_t devzvol_lh;
static kmutex_t devzvol_mtx;
static boolean_t devzvol_isopen;
static major_t devzvol_major;

/*
 * we need to use ddi_mod* since fs/dev gets loaded early on in
 * startup(), and linking fs/dev to fs/zfs would drag in a lot of
 * other stuff (like drv/random) before the rest of the system is
 * ready to go
 */
ddi_modhandle_t zfs_mod;
int (*szcm)(char *);
int (*szn2m)(char *, minor_t *);

int
sdev_zvol_create_minor(char *dsname)
{
    if (szcm == NULL)
        return (-1);
    return ((*szcm)(dsname));
}

int
sdev_zvol_name2minor(char *dsname, minor_t *minor)
{
    if (szn2m == NULL)
        return (-1);
    return ((*szn2m)(dsname, minor));
}

int
devzvol_open_zfs()
{
    int rc;
    dev_t dv;

    devzvol_li = ldi_ident_from_anon();
    if (ldi_open_by_name("/dev/zfs", FREAD | FWRITE, kcred,
        &devzvol_lh, devzvol_li))
        return (-1);
    if (zfs_mod == NULL && ((zfs_mod = ddi_modopen("fs/zfs",
        KRTLD_MODE_FIRST, &rc)) == NULL)) {
        return (rc);
    }
    ASSERT(szcm == NULL && szn2m == NULL);
    if ((szcm = (int (*)(char *))
        ddi_modsym(zfs_mod, "zvol_create_minor", &rc)) == NULL) {
        cmn_err(CE_WARN, "couldn't resolve zvol_create_minor");
        return (rc);
    }
    if ((szn2m = (int(*)(char *, minor_t *))
        ddi_modsym(zfs_mod, "zvol_name2minor", &rc)) == NULL) {
        cmn_err(CE_WARN, "couldn't resolve zvol_name2minor");
        return (rc);
    }
    if (ldi_get_dev(devzvol_lh, &dv))
        return (-1);
    devzvol_major = getmajor(dv);
    return (0);
}

void
devzvol_close_zfs()
{
    szcm = NULL;
    szn2m = NULL;
    (void) ldi_close(devzvol_lh, FREAD|FWRITE, kcred);
    ldi_ident_release(devzvol_li);
    if (zfs_mod != NULL) {
        (void) ddi_modclose(zfs_mod);
        zfs_mod = NULL;
    }
}

int
devzvol_handle_ioctl(int cmd, zfs_cmd_t *zc, size_t *alloc_size)
{
    uint64_t cookie;
    int size = 8000;
    int unused;
    int rc;

    if (cmd != ZFS_IOC_POOL_CONFIGS)
        mutex_enter(&devzvol_mtx);
    if (!devzvol_isopen) {
        if ((rc = devzvol_open_zfs()) == 0) {
            devzvol_isopen = B_TRUE;
        } else {
            if (cmd != ZFS_IOC_POOL_CONFIGS)
                mutex_exit(&devzvol_mtx);
            return (ENXIO);
        }
    }
    cookie = zc->zc_cookie;
again:
    zc->zc_nvlist_dst = (uint64_t)(intptr_t)kmem_alloc(size,
        KM_SLEEP);
    zc->zc_nvlist_dst_size = size;
    rc = ldi_ioctl(devzvol_lh, cmd, (intptr_t)zc, FKIOCTL, kcred,
        &unused);
    if (rc == ENOMEM) {
        int newsize;
        newsize = zc->zc_nvlist_dst_size;
        ASSERT(newsize > size);
        kmem_free((void *)(uintptr_t)zc->zc_nvlist_dst, size);
        size = newsize;
        zc->zc_cookie = cookie;
        goto again;
    }
    if (alloc_size == NULL)
        kmem_free((void *)(uintptr_t)zc->zc_nvlist_dst, size);
    else
        *alloc_size = size;
    if (cmd != ZFS_IOC_POOL_CONFIGS)
        mutex_exit(&devzvol_mtx);
    return (rc);
}

/* figures out if the objset exists and returns its type */
int
devzvol_objset_check(char *dsname, dmu_objset_type_t *type)
{
    boolean_t   ispool;
    zfs_cmd_t   *zc;
    int rc;

    zc = kmem_zalloc(sizeof (zfs_cmd_t), KM_SLEEP);
    (void) strlcpy(zc->zc_name, dsname, MAXPATHLEN);

    ispool = (strchr(dsname, '/') == NULL) ? B_TRUE : B_FALSE;
    if (!ispool && sdev_zvol_name2minor(dsname, NULL) == 0) {
        sdcmn_err13(("found cached minor node"));
        if (type)
            *type = DMU_OST_ZVOL;
        kmem_free(zc, sizeof (zfs_cmd_t));
        return (0);
    }
    rc = devzvol_handle_ioctl(ispool ? ZFS_IOC_POOL_STATS :
        ZFS_IOC_OBJSET_STATS, zc, NULL);
    if (type && rc == 0)
        *type = (ispool) ? DMU_OST_ZFS :
            zc->zc_objset_stats.dds_type;
    kmem_free(zc, sizeof (zfs_cmd_t));
    return (rc);
}

/*
 * returns what the zfs dataset name should be, given the /dev/zvol
 * path and an optional name; otherwise NULL
 */
char *
devzvol_make_dsname(const char *path, const char *name)
{
    char *dsname;
    const char *ptr;
    int dslen;

    if (strcmp(path, ZVOL_DIR) == 0)
        return (NULL);
    if (name && (strcmp(name, ".") == 0 || strcmp(name, "..") == 0))
        return (NULL);
    ptr = path + strlen(ZVOL_DIR);
    if (strncmp(ptr, "/dsk", 4) == 0)
        ptr += strlen("/dsk");
    else if (strncmp(ptr, "/rdsk", 5) == 0)
        ptr += strlen("/rdsk");
    else
        return (NULL);
    if (*ptr == '/')
        ptr++;

    dslen = strlen(ptr);
    if (dslen)
        dslen++;            /* plus null */
    if (name)
        dslen += strlen(name) + 1;  /* plus slash */
    dsname = kmem_zalloc(dslen, KM_SLEEP);
    if (*ptr) {
        (void) strlcpy(dsname, ptr, dslen);
        if (name)
            (void) strlcat(dsname, "/", dslen);
    }
    if (name)
        (void) strlcat(dsname, name, dslen);
    return (dsname);
}

/*
 * check if the zvol's sdev_node is still valid, which means make
 * sure the zvol is still valid.  zvol minors aren't proactively
 * destroyed when the zvol is destroyed, so we use a validator to clean
 * these up (in other words, when such nodes are encountered during
 * subsequent lookup() and readdir() operations) so that only valid
 * nodes are returned.  The ordering between devname_lookup_func and
 * devzvol_validate is a little inefficient in the case of invalid
 * or stale nodes because devname_lookup_func calls
 * devzvol_create_{dir, link}, then the validator says it's invalid,
 * and then the node gets cleaned up.
 */
int
devzvol_validate(struct sdev_node *dv)
{
    dmu_objset_type_t do_type;
    char *dsname;
    char *nm = dv->sdev_name;
    int rc;

    sdcmn_err13(("validating ('%s' '%s')", dv->sdev_path, nm));
    /*
     * validate only READY nodes; if someone is sitting on the
     * directory of a dataset that just got destroyed we could
     * get a zombie node which we just skip.
     */
    if (dv->sdev_state != SDEV_READY) {
        sdcmn_err13(("skipping '%s'", nm));
        return (SDEV_VTOR_SKIP);
    }

    if ((strcmp(dv->sdev_path, ZVOL_DIR "/dsk") == 0) ||
        (strcmp(dv->sdev_path, ZVOL_DIR "/rdsk") == 0))
        return (SDEV_VTOR_VALID);
    dsname = devzvol_make_dsname(dv->sdev_path, NULL);
    if (dsname == NULL)
        return (SDEV_VTOR_INVALID);

    rc = devzvol_objset_check(dsname, &do_type);
    sdcmn_err13(("  '%s' rc %d", dsname, rc));
    if (rc != 0) {
        kmem_free(dsname, strlen(dsname) + 1);
        return (SDEV_VTOR_INVALID);
    }
    sdcmn_err13(("  v_type %d do_type %d",
        SDEVTOV(dv)->v_type, do_type));
    if ((SDEVTOV(dv)->v_type == VLNK && do_type != DMU_OST_ZVOL) ||
        ((SDEVTOV(dv)->v_type == VBLK || SDEVTOV(dv)->v_type == VCHR) &&
        do_type != DMU_OST_ZVOL) ||
        (SDEVTOV(dv)->v_type == VDIR && do_type == DMU_OST_ZVOL)) {
        kmem_free(dsname, strlen(dsname) + 1);
        return (SDEV_VTOR_STALE);
    }
    if (SDEVTOV(dv)->v_type == VLNK) {
        char *ptr, *link;
        long val = 0;
        minor_t lminor, ominor;

        rc = sdev_getlink(SDEVTOV(dv), &link);
        ASSERT(rc == 0);

        ptr = strrchr(link, ':') + 1;
        rc = ddi_strtol(ptr, NULL, 10, &val);
        kmem_free(link, strlen(link) + 1);
        ASSERT(rc == 0 && val != 0);
        lminor = (minor_t)val;
        if (sdev_zvol_name2minor(dsname, &ominor) < 0 ||
            ominor != lminor) {
            kmem_free(dsname, strlen(dsname) + 1);
            return (SDEV_VTOR_STALE);
        }
    }
    kmem_free(dsname, strlen(dsname) + 1);
    return (SDEV_VTOR_VALID);
}

/*
 * creates directories as needed in response to a readdir
 */
void
devzvol_create_pool_dirs(struct vnode *dvp)
{
    zfs_cmd_t   *zc;
    nvlist_t *nv = NULL;
    nvpair_t *elem = NULL;
    size_t size;
    int pools = 0;
    int rc;

    sdcmn_err13(("devzvol_create_pool_dirs"));
    zc = kmem_zalloc(sizeof (zfs_cmd_t), KM_SLEEP);
    mutex_enter(&devzvol_mtx);
    zc->zc_cookie = devzvol_gen;

    rc = devzvol_handle_ioctl(ZFS_IOC_POOL_CONFIGS, zc, &size);
    switch (rc) {
        case 0:
            /* new generation */
            ASSERT(devzvol_gen != zc->zc_cookie);
            devzvol_gen = zc->zc_cookie;
            if (devzvol_zclist)
                kmem_free((void *)(uintptr_t)devzvol_zclist,
                    devzvol_zclist_size);
            devzvol_zclist = zc->zc_nvlist_dst;
            devzvol_zclist_size = size;
            break;
        case EEXIST:
            /*
             * no change in the configuration; still need
             * to do lookups in case we did a lookup in
             * zvol/rdsk but not zvol/dsk (or vice versa)
             */
            kmem_free((void *)(uintptr_t)zc->zc_nvlist_dst,
                size);
            break;
        default:
            kmem_free((void *)(uintptr_t)zc->zc_nvlist_dst,
                size);
            goto out;
    }
    rc = nvlist_unpack((char *)(uintptr_t)devzvol_zclist,
        devzvol_zclist_size, &nv, 0);
    if (rc) {
        ASSERT(rc == 0);
        kmem_free((void *)(uintptr_t)devzvol_zclist,
            devzvol_zclist_size);
        devzvol_gen = 0;
        devzvol_zclist = NULL;
        devzvol_zclist_size = 0;
        goto out;
    }
    mutex_exit(&devzvol_mtx);
    while ((elem = nvlist_next_nvpair(nv, elem)) != NULL) {
        struct vnode *vp;
        ASSERT(dvp->v_count > 0);
        rc = VOP_LOOKUP(dvp, nvpair_name(elem), &vp, NULL, 0,
            NULL, kcred, NULL, 0, NULL);
        /* should either work, or not be visible from a zone */
        ASSERT(rc == 0 || rc == ENOENT);
        if (rc == 0)
            VN_RELE(vp);
        pools++;
    }
    nvlist_free(nv);
    mutex_enter(&devzvol_mtx);
    if (devzvol_isopen && pools == 0) {
        /* clean up so zfs can be unloaded */
        devzvol_close_zfs();
        devzvol_isopen = B_FALSE;
    }
out:
    mutex_exit(&devzvol_mtx);
    kmem_free(zc, sizeof (zfs_cmd_t));
}

/*ARGSUSED3*/
static int
devzvol_create_dir(struct sdev_node *ddv, char *nm, void **arg,
    cred_t *cred, void *whatever, char *whichever)
{
    timestruc_t now;
    struct vattr *vap = (struct vattr *)arg;

    sdcmn_err13(("create_dir (%s) (%s) '%s'", ddv->sdev_name,
        ddv->sdev_path, nm));
    ASSERT(strncmp(ddv->sdev_path, ZVOL_DIR,
        strlen(ZVOL_DIR)) == 0);
    *vap = *sdev_getdefault_attr(VDIR);
    gethrestime(&now);
    vap->va_atime = now;
    vap->va_mtime = now;
    vap->va_ctime = now;
    return (0);
}

/*ARGSUSED3*/
static int
devzvol_create_link(struct sdev_node *ddv, char *nm,
    void **arg, cred_t *cred, void *whatever, char *whichever)
{
    minor_t minor;
    char *pathname = (char *)*arg;
    int rc;
    char *dsname;
    char *x;
    char str[MAXNAMELEN];
    sdcmn_err13(("create_link (%s) (%s) '%s'", ddv->sdev_name,
        ddv->sdev_path, nm));
    dsname = devzvol_make_dsname(ddv->sdev_path, nm);
    rc = sdev_zvol_create_minor(dsname);
    if ((rc != 0 && rc != EEXIST && rc != EBUSY) ||
        sdev_zvol_name2minor(dsname, &minor)) {
        sdcmn_err13(("devzvol_create_link %d", rc));
        kmem_free(dsname, strlen(dsname) + 1);
        return (-1);
    }
    kmem_free(dsname, strlen(dsname) + 1);

    /*
     * This is a valid zvol; create a symlink that points to the
     * minor which was created under /devices/pseudo/zfs@0
     */
    *pathname = '\0';
    for (x = ddv->sdev_path; x = strchr(x, '/'); x++)
        (void) strcat(pathname, "../");
    (void) snprintf(str, sizeof (str), ZVOL_PSEUDO_DEV "%u", minor);
    (void) strncat(pathname, str, MAXPATHLEN);
    if (strncmp(ddv->sdev_path, ZVOL_FULL_RDEV_DIR,
        strlen(ZVOL_FULL_RDEV_DIR)) == 0)
        (void) strcat(pathname, ",raw");
    return (0);
}

/* Clean zvol sdev_nodes that are no longer valid.  */
static void
devzvol_prunedir(struct sdev_node *ddv)
{
    struct sdev_node *dv;

    ASSERT(RW_READ_HELD(&ddv->sdev_contents));

    sdcmn_err13(("prunedir '%s'", ddv->sdev_name));
    ASSERT(strncmp(ddv->sdev_path, ZVOL_DIR, strlen(ZVOL_DIR)) == 0);
    if (rw_tryupgrade(&ddv->sdev_contents) == 0) {
        rw_exit(&ddv->sdev_contents);
        rw_enter(&ddv->sdev_contents, RW_WRITER);
    }

    dv = SDEV_FIRST_ENTRY(ddv);
    while (dv) {
        sdcmn_err13(("sdev_name '%s'", dv->sdev_name));

        switch (devzvol_validate(dv)) {
        case SDEV_VTOR_VALID:
        case SDEV_VTOR_SKIP:
            dv = SDEV_NEXT_ENTRY(ddv, dv);
            continue;
        case SDEV_VTOR_INVALID:
            sdcmn_err7(("prunedir: destroy invalid "
                "node: %s\n", dv->sdev_name));
            break;
        }

        if ((SDEVTOV(dv)->v_type == VDIR) &&
            (sdev_cleandir(dv, NULL, 0) != 0)) {
            dv = SDEV_NEXT_ENTRY(ddv, dv);
            continue;
        }
        SDEV_HOLD(dv);
        /* remove the cache node */
        sdev_cache_update(ddv, &dv, dv->sdev_name,
            SDEV_CACHE_DELETE);
        SDEV_RELE(dv);
        dv = SDEV_FIRST_ENTRY(ddv);
    }
    rw_downgrade(&ddv->sdev_contents);
}

/*
 * This function is used to create a dir or dev inside a zone's /dev when the
 * zone has a zvol that is dynamically created within the zone (i.e. inside
 * of a delegated dataset.  Since there is no /devices tree within a zone,
 * we create the chr/blk devices directly inside the zone's /dev instead of
 * making symlinks.
 */
static int
devzvol_mk_ngz_node(struct sdev_node *parent, char *nm)
{
    struct vattr vattr;
    timestruc_t now;
    enum vtype expected_type = VDIR;
    dmu_objset_type_t do_type;
    struct sdev_node *dv = NULL;
    int res;
    char *dsname;

    bzero(&vattr, sizeof (vattr));
    gethrestime(&now);
    vattr.va_mask = AT_TYPE|AT_MODE|AT_UID|AT_GID;
    vattr.va_uid = SDEV_UID_DEFAULT;
    vattr.va_gid = SDEV_GID_DEFAULT;
    vattr.va_type = VNON;
    vattr.va_atime = now;
    vattr.va_mtime = now;
    vattr.va_ctime = now;

    if ((dsname = devzvol_make_dsname(parent->sdev_path, nm)) == NULL)
        return (ENOENT);

    if (devzvol_objset_check(dsname, &do_type) != 0) {
        kmem_free(dsname, strlen(dsname) + 1);
        return (ENOENT);
    }
    if (do_type == DMU_OST_ZVOL)
        expected_type = VBLK;

    if (expected_type == VDIR) {
        vattr.va_type = VDIR;
        vattr.va_mode = SDEV_DIRMODE_DEFAULT;
    } else {
        minor_t minor;
        dev_t devnum;
        int rc;

        rc = sdev_zvol_create_minor(dsname);
        if ((rc != 0 && rc != EEXIST && rc != EBUSY) ||
            sdev_zvol_name2minor(dsname, &minor)) {
            kmem_free(dsname, strlen(dsname) + 1);
            return (ENOENT);
        }

        devnum = makedevice(devzvol_major, minor);
        vattr.va_rdev = devnum;

        if (strstr(parent->sdev_path, "/rdsk/") != NULL)
            vattr.va_type = VCHR;
        else
            vattr.va_type = VBLK;
        vattr.va_mode = SDEV_DEVMODE_DEFAULT;
    }
    kmem_free(dsname, strlen(dsname) + 1);

    rw_enter(&parent->sdev_contents, RW_WRITER);

    res = sdev_mknode(parent, nm, &dv, &vattr,
        NULL, NULL, kcred, SDEV_READY);
    rw_exit(&parent->sdev_contents);
    if (res != 0)
        return (ENOENT);

    SDEV_RELE(dv);
    return (0);
}

/*ARGSUSED*/
static int
devzvol_lookup(struct vnode *dvp, char *nm, struct vnode **vpp,
    struct pathname *pnp, int flags, struct vnode *rdir, struct cred *cred,
    caller_context_t *ct, int *direntflags, pathname_t *realpnp)
{
    enum vtype expected_type = VDIR;
    struct sdev_node *parent = VTOSDEV(dvp);
    char *dsname;
    dmu_objset_type_t do_type;
    int error;

    sdcmn_err13(("devzvol_lookup '%s' '%s'", parent->sdev_path, nm));
    *vpp = NULL;
    /* execute access is required to search the directory */
    if ((error = VOP_ACCESS(dvp, VEXEC, 0, cred, ct)) != 0)
        return (error);

    rw_enter(&parent->sdev_contents, RW_READER);
    if (SDEV_IS_GLOBAL(parent)) {
        /*
         * During iter_datasets, don't create GZ dev when running in
         * NGZ.  We can't return ENOENT here since that could
         * incorrectly trigger the creation of the dev from the
         * recursive call through prof_filldir during iter_datasets.
         */
        if (getzoneid() != GLOBAL_ZONEID) {
            rw_exit(&parent->sdev_contents);
            return (EPERM);
        }
    } else {
        int res;

        rw_exit(&parent->sdev_contents);

        /*
         * If we're in the global zone and reach down into a non-global
         * zone's /dev/zvol then this action could trigger the creation
         * of all of the zvol devices for every zone into the non-global
         * zone's /dev tree. This could be a big security hole. To
         * prevent this, disallow the global zone from looking inside
         * a non-global zones /dev/zvol. This behavior is similar to
         * delegated datasets, which cannot be used by the global zone.
         */
        if (getzoneid() == GLOBAL_ZONEID)
            return (EPERM);

        res = prof_lookup(dvp, nm, vpp, cred);

        /*
         * We won't find a zvol that was dynamically created inside
         * a NGZ, within a delegated dataset, in the zone's dev profile
         * but prof_lookup will also find it via sdev_cache_lookup.
         */
        if (res == ENOENT) {
            /*
             * We have to create the sdev node for the dymamically
             * created zvol.
             */
            if (devzvol_mk_ngz_node(parent, nm) != 0)
                return (ENOENT);
            res = prof_lookup(dvp, nm, vpp, cred);
        }

        return (res);
    }

    dsname = devzvol_make_dsname(parent->sdev_path, nm);
    rw_exit(&parent->sdev_contents);
    sdcmn_err13(("rvp dsname %s", dsname ? dsname : "(null)"));
    if (dsname) {
        error = devzvol_objset_check(dsname, &do_type);
        if (error != 0) {
            error = ENOENT;
            goto out;
        }
        if (do_type == DMU_OST_ZVOL)
            expected_type = VLNK;
    }
    /*
     * the callbacks expect:
     *
     * parent->sdev_path           nm
     * /dev/zvol               {r}dsk
     * /dev/zvol/{r}dsk        <pool name>
     * /dev/zvol/{r}dsk/<dataset name> <last ds component>
     *
     * sdev_name is always last path component of sdev_path
     */
    if (expected_type == VDIR) {
        error = devname_lookup_func(parent, nm, vpp, cred,
            devzvol_create_dir, SDEV_VATTR);
    } else {
        error = devname_lookup_func(parent, nm, vpp, cred,
            devzvol_create_link, SDEV_VLINK);
    }
    sdcmn_err13(("devzvol_lookup %d %d", expected_type, error));
    ASSERT(error || ((*vpp)->v_type == expected_type));
out:
    if (dsname)
        kmem_free(dsname, strlen(dsname) + 1);
    sdcmn_err13(("devzvol_lookup %d", error));
    return (error);
}

/*
 * We allow create to find existing nodes
 *  - if the node doesn't exist - EROFS
 *  - creating an existing dir read-only succeeds, otherwise EISDIR
 *  - exclusive creates fail - EEXIST
 */
/*ARGSUSED2*/
static int
devzvol_create(struct vnode *dvp, char *nm, struct vattr *vap, vcexcl_t excl,
    int mode, struct vnode **vpp, struct cred *cred, int flag,
    caller_context_t *ct, vsecattr_t *vsecp)
{
    int error;
    struct vnode *vp;

    *vpp = NULL;

    error = devzvol_lookup(dvp, nm, &vp, NULL, 0, NULL, cred, ct, NULL,
        NULL);
    if (error == 0) {
        if (excl == EXCL)
            error = EEXIST;
        else if (vp->v_type == VDIR && (mode & VWRITE))
            error = EISDIR;
        else
            error = VOP_ACCESS(vp, mode, 0, cred, ct);

        if (error) {
            VN_RELE(vp);
        } else
            *vpp = vp;
    } else if (error == ENOENT) {
        error = EROFS;
    }

    return (error);
}

void sdev_iter_snapshots(struct vnode *dvp, char *name);

void
sdev_iter_datasets(struct vnode *dvp, int arg, char *name)
{
    zfs_cmd_t   *zc;
    int rc;

    sdcmn_err13(("iter name is '%s' (arg %x)", name, arg));
    zc = kmem_zalloc(sizeof (zfs_cmd_t), KM_SLEEP);
    (void) strcpy(zc->zc_name, name);

    while ((rc = devzvol_handle_ioctl(arg, zc, B_FALSE)) == 0) {
        struct vnode *vpp;
        char *ptr;

        sdcmn_err13(("  name %s", zc->zc_name));
        if (strchr(zc->zc_name, '$') || strchr(zc->zc_name, '%'))
            goto skip;
        ptr = strrchr(zc->zc_name, '/') + 1;
        rc = devzvol_lookup(dvp, ptr, &vpp, NULL, 0, NULL,
            kcred, NULL, NULL, NULL);
        if (rc == 0) {
            VN_RELE(vpp);
        } else if (rc == ENOENT) {
            goto skip;
        } else {
            /*
             * EBUSY == problem with zvols's dmu holds?
             * EPERM when in a NGZ and traversing up and out.
             */
            goto skip;
        }
        if (arg == ZFS_IOC_DATASET_LIST_NEXT &&
            zc->zc_objset_stats.dds_type != DMU_OST_ZFS)
            sdev_iter_snapshots(dvp, zc->zc_name);
skip:
        (void) strcpy(zc->zc_name, name);
    }
    kmem_free(zc, sizeof (zfs_cmd_t));
}

void
sdev_iter_snapshots(struct vnode *dvp, char *name)
{
    sdev_iter_datasets(dvp, ZFS_IOC_SNAPSHOT_LIST_NEXT, name);
}

/*ARGSUSED4*/
static int
devzvol_readdir(struct vnode *dvp, struct uio *uiop, struct cred *cred,
    int *eofp, caller_context_t *ct_unused, int flags_unused)
{
    struct sdev_node *sdvp = VTOSDEV(dvp);
    char *ptr;

    sdcmn_err13(("zv readdir of '%s' %s'", sdvp->sdev_path,
        sdvp->sdev_name));

    if (strcmp(sdvp->sdev_path, ZVOL_DIR) == 0) {
        struct vnode *vp;

        rw_exit(&sdvp->sdev_contents);
        (void) devname_lookup_func(sdvp, "dsk", &vp, cred,
            devzvol_create_dir, SDEV_VATTR);
        VN_RELE(vp);
        (void) devname_lookup_func(sdvp, "rdsk", &vp, cred,
            devzvol_create_dir, SDEV_VATTR);
        VN_RELE(vp);
        rw_enter(&sdvp->sdev_contents, RW_READER);
        return (devname_readdir_func(dvp, uiop, cred, eofp, 0));
    }
    if (uiop->uio_offset == 0)
        devzvol_prunedir(sdvp);
    ptr = sdvp->sdev_path + strlen(ZVOL_DIR);
    if ((strcmp(ptr, "/dsk") == 0) || (strcmp(ptr, "/rdsk") == 0)) {
        rw_exit(&sdvp->sdev_contents);
        devzvol_create_pool_dirs(dvp);
        rw_enter(&sdvp->sdev_contents, RW_READER);
        return (devname_readdir_func(dvp, uiop, cred, eofp, 0));
    }

    ptr = strchr(ptr + 1, '/');
    if (ptr == NULL)
        return (ENOENT);
    ptr++;
    rw_exit(&sdvp->sdev_contents);
    sdev_iter_datasets(dvp, ZFS_IOC_DATASET_LIST_NEXT, ptr);
    rw_enter(&sdvp->sdev_contents, RW_READER);
    return (devname_readdir_func(dvp, uiop, cred, eofp, 0));
}

const fs_operation_def_t devzvol_vnodeops_tbl[] = {
    VOPNAME_READDIR,    { .vop_readdir = devzvol_readdir },
    VOPNAME_LOOKUP,     { .vop_lookup = devzvol_lookup },
    VOPNAME_CREATE,     { .vop_create = devzvol_create },
    VOPNAME_RENAME,     { .error = fs_nosys },
    VOPNAME_MKDIR,      { .error = fs_nosys },
    VOPNAME_RMDIR,      { .error = fs_nosys },
    VOPNAME_REMOVE,     { .error = fs_nosys },
    VOPNAME_SYMLINK,    { .error = fs_nosys },
    NULL,           NULL
};