libzfs/common/libzfs_mount.c

	libzfs_mount.c revision 99653d4ee642c6528e88224f12409a5f23060994
/*
 * 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 2006 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

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

/*
 * Routines to manage ZFS mounts.  We separate all the nasty routines that have
 * to deal with the OS.  The main entry points are:
 *
 *  zfs_is_mounted()
 *  zfs_mount()
 *  zfs_unmount()
 *  zfs_unmountall()
 *
 * These functions are used by mount and unmount, and when changing a
 * filesystem's mountpoint.  This file also contains the functions used to
 * manage sharing filesystems via NFS:
 *
 *  zfs_is_shared()
 *  zfs_share()
 *  zfs_unshare()
 *  zfs_unshareall()
 */

#include <dirent.h>
#include <errno.h>
#include <libgen.h>
#include <libintl.h>
#include <stdio.h>
#include <stdlib.h>
#include <strings.h>
#include <unistd.h>
#include <zone.h>
#include <sys/mntent.h>
#include <sys/mnttab.h>
#include <sys/mount.h>
#include <sys/stat.h>

#include <libzfs.h>

#include "libzfs_impl.h"

/*
 * Search the sharetab for the given mountpoint, returning true if it is found.
 */
static boolean_t
is_shared(libzfs_handle_t *hdl, const char *mountpoint)
{
    char buf[MAXPATHLEN], *tab;

    if (hdl->libzfs_sharetab == NULL)
        return (0);

    (void) fseek(hdl->libzfs_sharetab, 0, SEEK_SET);

    while (fgets(buf, sizeof (buf), hdl->libzfs_sharetab) != NULL) {

        /* the mountpoint is the first entry on each line */
        if ((tab = strchr(buf, '\t')) != NULL) {
            *tab = '\0';
            if (strcmp(buf, mountpoint) == 0)
                return (B_TRUE);
        }
    }

    return (B_FALSE);
}

/*
 * Returns true if the specified directory is empty.  If we can't open the
 * directory at all, return true so that the mount can fail with a more
 * informative error message.
 */
static boolean_t
dir_is_empty(const char *dirname)
{
    DIR *dirp;
    struct dirent64 *dp;

    if ((dirp = opendir(dirname)) == NULL)
        return (B_TRUE);

    while ((dp = readdir64(dirp)) != NULL) {

        if (strcmp(dp->d_name, ".") == 0 ||
            strcmp(dp->d_name, "..") == 0)
            continue;

        (void) closedir(dirp);
        return (B_FALSE);
    }

    (void) closedir(dirp);
    return (B_TRUE);
}

/*
 * Checks to see if the mount is active.  If the filesystem is mounted, we fill
 * in 'where' with the current mountpoint, and return 1.  Otherwise, we return
 * 0.
 */
boolean_t
zfs_is_mounted(zfs_handle_t *zhp, char **where)
{
    struct mnttab search = { 0 }, entry;

    /*
     * Search for the entry in /etc/mnttab.  We don't bother getting the
     * mountpoint, as we can just search for the special device.  This will
     * also let us find mounts when the mountpoint is 'legacy'.
     */
    search.mnt_special = (char *)zfs_get_name(zhp);
    search.mnt_fstype = MNTTYPE_ZFS;

    rewind(zhp->zfs_hdl->libzfs_mnttab);
    if (getmntany(zhp->zfs_hdl->libzfs_mnttab, &entry, &search) != 0)
        return (B_FALSE);

    if (where != NULL)
        *where = zfs_strdup(zhp->zfs_hdl, entry.mnt_mountp);

    return (B_TRUE);
}

/*
 * Mount the given filesystem.
 */
int
zfs_mount(zfs_handle_t *zhp, const char *options, int flags)
{
    struct stat buf;
    char mountpoint[ZFS_MAXPROPLEN];
    char mntopts[MNT_LINE_MAX];
    libzfs_handle_t *hdl = zhp->zfs_hdl;

    if (options == NULL)
        mntopts[0] = '\0';
    else
        (void) strlcpy(mntopts, options, sizeof (mntopts));

    /* ignore non-filesystems */
    if (zfs_prop_get(zhp, ZFS_PROP_MOUNTPOINT, mountpoint,
        sizeof (mountpoint), NULL, NULL, 0, B_FALSE) != 0)
        return (0);

    /* return success if there is no mountpoint set */
    if (strcmp(mountpoint, ZFS_MOUNTPOINT_NONE) == 0 ||
        strcmp(mountpoint, ZFS_MOUNTPOINT_LEGACY) == 0)
        return (0);

    /*
     * If the 'zoned' property is set, and we're in the global zone, simply
     * return success.
     */
    if (zfs_prop_get_int(zhp, ZFS_PROP_ZONED) &&
        getzoneid() == GLOBAL_ZONEID)
        return (0);

    /* Create the directory if it doesn't already exist */
    if (lstat(mountpoint, &buf) != 0) {
        if (mkdirp(mountpoint, 0755) != 0) {
            zfs_error_aux(hdl, dgettext(TEXT_DOMAIN,
                "failed to create mountpoint"));
            return (zfs_error(hdl, EZFS_MOUNTFAILED,
                dgettext(TEXT_DOMAIN, "cannot mount '%s'"),
                mountpoint));
        }
    }

    /*
     * Determine if the mountpoint is empty.  If so, refuse to perform the
     * mount.  We don't perform this check if MS_OVERLAY is specified, which
     * would defeat the point.  We also avoid this check if 'remount' is
     * specified.
     */
    if ((flags & MS_OVERLAY) == 0 &&
        strstr(mntopts, MNTOPT_REMOUNT) == NULL &&
        !dir_is_empty(mountpoint)) {
        zfs_error_aux(hdl, dgettext(TEXT_DOMAIN,
            "directory is not empty"));
        return (zfs_error(hdl, EZFS_MOUNTFAILED,
            dgettext(TEXT_DOMAIN, "cannot mount '%s'"), mountpoint));
    }

    /* perform the mount */
    if (mount(zfs_get_name(zhp), mountpoint, MS_OPTIONSTR | flags,
        MNTTYPE_ZFS, NULL, 0, mntopts, sizeof (mntopts)) != 0) {
        /*
         * Generic errors are nasty, but there are just way too many
         * from mount(), and they're well-understood.  We pick a few
         * common ones to improve upon.
         */
        if (errno == EBUSY)
            zfs_error_aux(hdl, dgettext(TEXT_DOMAIN,
                "mountpoint or dataset is busy"));
        else
            zfs_error_aux(hdl, strerror(errno));

        return (zfs_error(hdl, EZFS_MOUNTFAILED,
            dgettext(TEXT_DOMAIN, "cannot mount '%s'"),
            zhp->zfs_name));
    }

    return (0);
}

/*
 * Unmount the given filesystem.
 */
int
zfs_unmount(zfs_handle_t *zhp, const char *mountpoint, int flags)
{
    struct mnttab search = { 0 }, entry;

    /* check to see if need to unmount the filesystem */
    search.mnt_special = (char *)zfs_get_name(zhp);
    search.mnt_fstype = MNTTYPE_ZFS;
    rewind(zhp->zfs_hdl->libzfs_mnttab);
    if (mountpoint != NULL || ((zfs_get_type(zhp) == ZFS_TYPE_FILESYSTEM) &&
        getmntany(zhp->zfs_hdl->libzfs_mnttab, &entry, &search) == 0)) {

        if (mountpoint == NULL)
            mountpoint = entry.mnt_mountp;

        /*
         * Always unshare the filesystem first.
         */
        if (zfs_unshare(zhp, mountpoint) != 0)
            return (-1);

        /*
         * Try to unmount the filesystem.  There is no reason to try a
         * forced unmount because the vnodes will still carry a
         * reference to the underlying dataset, so we can't destroy it
         * anyway.
         *
         * In the unmount case, we print out a slightly more informative
         * error message, though we'll be relying on the poor error
         * semantics from the kernel.
         */
        if (umount2(mountpoint, flags) != 0) {
            zfs_error_aux(zhp->zfs_hdl, strerror(errno));
            return (zfs_error(zhp->zfs_hdl, EZFS_UMOUNTFAILED,
                dgettext(TEXT_DOMAIN, "cannot unmount '%s'"),
                mountpoint));
        }

        /*
         * Don't actually destroy the underlying directory
         */
    }

    return (0);
}

/*
 * Unmount this filesystem and any children inheriting the mountpoint property.
 * To do this, just act like we're changing the mountpoint property, but don't
 * remount the filesystems afterwards.
 */
int
zfs_unmountall(zfs_handle_t *zhp, int flags)
{
    prop_changelist_t *clp;
    int ret;

    clp = changelist_gather(zhp, ZFS_PROP_MOUNTPOINT, flags);
    if (clp == NULL)
        return (-1);

    ret = changelist_prefix(clp);
    changelist_free(clp);

    return (ret);
}

/*
 * Check to see if the filesystem is currently shared.
 */
boolean_t
zfs_is_shared(zfs_handle_t *zhp, char **where)
{
    char *mountpoint;

    if (!zfs_is_mounted(zhp, &mountpoint))
        return (B_FALSE);

    if (is_shared(zhp->zfs_hdl, mountpoint)) {
        if (where != NULL)
            *where = mountpoint;
        else
            free(mountpoint);
        return (B_TRUE);
    } else {
        free(mountpoint);
        return (B_FALSE);
    }
}

/*
 * Share the given filesystem according to the options in 'sharenfs'.  We rely
 * on share(1M) to the dirty work for us.
 */
int
zfs_share(zfs_handle_t *zhp)
{
    char mountpoint[ZFS_MAXPROPLEN];
    char shareopts[ZFS_MAXPROPLEN];
    char buf[MAXPATHLEN];
    FILE *fp;
    libzfs_handle_t *hdl = zhp->zfs_hdl;

    /* ignore non-filesystems */
    if (zfs_get_type(zhp) != ZFS_TYPE_FILESYSTEM)
        return (0);

    /* return success if there is no mountpoint set */
    if (zfs_prop_get(zhp, ZFS_PROP_MOUNTPOINT,
        mountpoint, sizeof (mountpoint), NULL, NULL, 0, B_FALSE) != 0 ||
        strcmp(mountpoint, ZFS_MOUNTPOINT_NONE) == 0 ||
        strcmp(mountpoint, ZFS_MOUNTPOINT_LEGACY) == 0)
        return (0);

    /* return success if there are no share options */
    if (zfs_prop_get(zhp, ZFS_PROP_SHARENFS, shareopts, sizeof (shareopts),
        NULL, NULL, 0, B_FALSE) != 0 ||
        strcmp(shareopts, "off") == 0)
        return (0);

    /*
     * If the 'zoned' property is set, simply return success since:
     * 1. in a global zone, a dataset should not be shared if it's
     *    managed in a local zone.
     * 2. in a local zone, NFS server is not available.
     */
    if (zfs_prop_get_int(zhp, ZFS_PROP_ZONED)) {
        return (0);
    }

    /*
     * Invoke the share(1M) command.  We always do this, even if it's
     * currently shared, as the options may have changed.
     */
    if (strcmp(shareopts, "on") == 0)
        (void) snprintf(buf, sizeof (buf), "/usr/sbin/share "
            "-F nfs \"%s\" 2>&1", mountpoint);
    else
        (void) snprintf(buf, sizeof (buf), "/usr/sbin/share "
            "-F nfs -o \"%s\" \"%s\" 2>&1", shareopts,
            mountpoint);

    if ((fp = popen(buf, "r")) == NULL)
        return (zfs_error(hdl, EZFS_SHAREFAILED,
            dgettext(TEXT_DOMAIN, "cannot share '%s'"),
            zfs_get_name(zhp)));

    /*
     * share(1M) should only produce output if there is some kind
     * of error.  All output begins with "share_nfs: ", so we trim
     * this off to get to the real error.
     */
    if (fgets(buf, sizeof (buf), fp) != NULL) {
        char *colon = strchr(buf, ':');

        while (buf[strlen(buf) - 1] == '\n')
            buf[strlen(buf) - 1] = '\0';

        if (colon != NULL)
            zfs_error_aux(hdl, colon + 2);

        (void) zfs_error(hdl, EZFS_SHAREFAILED,
            dgettext(TEXT_DOMAIN, "cannot share '%s'"));

        verify(pclose(fp) != 0);
        return (-1);
    }

    verify(pclose(fp) == 0);

    return (0);
}

/*
 * Unshare the given filesystem.
 */
int
zfs_unshare(zfs_handle_t *zhp, const char *mountpoint)
{
    char buf[MAXPATHLEN];
    struct mnttab search = { 0 }, entry;
    libzfs_handle_t *hdl = zhp->zfs_hdl;

    /* check to see if need to unmount the filesystem */
    search.mnt_special = (char *)zfs_get_name(zhp);
    search.mnt_fstype = MNTTYPE_ZFS;
    rewind(zhp->zfs_hdl->libzfs_mnttab);
    if (mountpoint != NULL || ((zfs_get_type(zhp) == ZFS_TYPE_FILESYSTEM) &&
        getmntany(zhp->zfs_hdl->libzfs_mnttab, &entry, &search) == 0)) {

        if (mountpoint == NULL)
            mountpoint = entry.mnt_mountp;

        if (is_shared(zhp->zfs_hdl, mountpoint)) {
            FILE *fp;

            (void) snprintf(buf, sizeof (buf),
                "/usr/sbin/unshare  \"%s\" 2>&1",
                mountpoint);

            if ((fp = popen(buf, "r")) == NULL)
                return (zfs_error(hdl, EZFS_UNSHAREFAILED,
                    dgettext(TEXT_DOMAIN,
                    "cannot unshare '%s'"), zfs_get_name(zhp)));

            /*
             * unshare(1M) should only produce output if there is
             * some kind of error.  All output begins with "unshare
             * nfs: ", so we trim this off to get to the real error.
             */
            if (fgets(buf, sizeof (buf), fp) != NULL) {
                char *colon = strchr(buf, ':');

                while (buf[strlen(buf) - 1] == '\n')
                    buf[strlen(buf) - 1] = '\0';

                if (colon != NULL)
                    zfs_error_aux(hdl, colon + 2);

                verify(pclose(fp) != 0);

                return (zfs_error(hdl, EZFS_UNSHAREFAILED,
                    dgettext(TEXT_DOMAIN,
                    "cannot unshare '%s'"), zfs_get_name(zhp)));
            }

            verify(pclose(fp) == 0);
        }
    }

    return (0);
}

/*
 * Same as zfs_unmountall(), but for unshares.
 */
int
zfs_unshareall(zfs_handle_t *zhp)
{
    prop_changelist_t *clp;
    int ret;

    clp = changelist_gather(zhp, ZFS_PROP_SHARENFS, 0);
    if (clp == NULL)
        return (-1);

    ret = changelist_unshare(clp);
    changelist_free(clp);

    return (ret);
}

/*
 * Remove the mountpoint associated with the current dataset, if necessary.
 * We only remove the underlying directory if:
 *
 *  - The mountpoint is not 'none' or 'legacy'
 *  - The mountpoint is non-empty
 *  - The mountpoint is the default or inherited
 *  - The 'zoned' property is set, or we're in a local zone
 *
 * Any other directories we leave alone.
 */
void
remove_mountpoint(zfs_handle_t *zhp)
{
    char mountpoint[ZFS_MAXPROPLEN];
    char source[ZFS_MAXNAMELEN];
    zfs_source_t sourcetype;
    int zoneid = getzoneid();

    /* ignore non-filesystems */
    if (zfs_prop_get(zhp, ZFS_PROP_MOUNTPOINT, mountpoint,
        sizeof (mountpoint), &sourcetype, source, sizeof (source),
        B_FALSE) != 0)
        return;

    if (strcmp(mountpoint, ZFS_MOUNTPOINT_NONE) != 0 &&
        strcmp(mountpoint, ZFS_MOUNTPOINT_LEGACY) != 0 &&
        (sourcetype == ZFS_SRC_DEFAULT ||
        sourcetype == ZFS_SRC_INHERITED) &&
        (!zfs_prop_get_int(zhp, ZFS_PROP_ZONED) ||
        zoneid != GLOBAL_ZONEID)) {

        /*
         * Try to remove the directory, silently ignoring any errors.
         * The filesystem may have since been removed or moved around,
         * and this isn't really useful to the administrator in any
         * way.
         */
        (void) rmdir(mountpoint);
    }
}