libzfs_core/common/libzfs_core.c

	libzfs_core.c revision bb6e70758d0c30c09f148026d6e686e21cfc8d18
/*
 * 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) 2012 by Delphix. All rights reserved.
 * Copyright (c) 2013 Steven Hartland. All rights reserved.
 */

/*
 * LibZFS_Core (lzc) is intended to replace most functionality in libzfs.
 * It has the following characteristics:
 *
 *  - Thread Safe.  libzfs_core is accessible concurrently from multiple
 *  threads.  This is accomplished primarily by avoiding global data
 *  (e.g. caching).  Since it's thread-safe, there is no reason for a
 *  process to have multiple libzfs "instances".  Therefore, we store
 *  our few pieces of data (e.g. the file descriptor) in global
 *  variables.  The fd is reference-counted so that the libzfs_core
 *  library can be "initialized" multiple times (e.g. by different
 *  consumers within the same process).
 *
 *  - Committed Interface.  The libzfs_core interface will be committed,
 *  therefore consumers can compile against it and be confident that
 *  their code will continue to work on future releases of this code.
 *  Currently, the interface is Evolving (not Committed), but we intend
 *  to commit to it once it is more complete and we determine that it
 *  meets the needs of all consumers.
 *
 *  - Programatic Error Handling.  libzfs_core communicates errors with
 *  defined error numbers, and doesn't print anything to stdout/stderr.
 *
 *  - Thin Layer.  libzfs_core is a thin layer, marshaling arguments
 *  to/from the kernel ioctls.  There is generally a 1:1 correspondence
 *  between libzfs_core functions and ioctls to /dev/zfs.
 *
 *  - Clear Atomicity.  Because libzfs_core functions are generally 1:1
 *  with kernel ioctls, and kernel ioctls are general atomic, each
 *  libzfs_core function is atomic.  For example, creating multiple
 *  snapshots with a single call to lzc_snapshot() is atomic -- it
 *  can't fail with only some of the requested snapshots created, even
 *  in the event of power loss or system crash.
 *
 *  - Continued libzfs Support.  Some higher-level operations (e.g.
 *  support for "zfs send -R") are too complicated to fit the scope of
 *  libzfs_core.  This functionality will continue to live in libzfs.
 *  Where appropriate, libzfs will use the underlying atomic operations
 *  of libzfs_core.  For example, libzfs may implement "zfs send -R |
 *  zfs receive" by using individual "send one snapshot", rename,
 *  destroy, and "receive one snapshot" operations in libzfs_core.
 *  /sbin/zfs and /zbin/zpool will link with both libzfs and
 *  libzfs_core.  Other consumers should aim to use only libzfs_core,
 *  since that will be the supported, stable interface going forwards.
 */

#include <libzfs_core.h>
#include <ctype.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <pthread.h>
#include <sys/nvpair.h>
#include <sys/param.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/zfs_ioctl.h>

static int g_fd;
static pthread_mutex_t g_lock = PTHREAD_MUTEX_INITIALIZER;
static int g_refcount;

int
libzfs_core_init(void)
{
    (void) pthread_mutex_lock(&g_lock);
    if (g_refcount == 0) {
        g_fd = open("/dev/zfs", O_RDWR);
        if (g_fd < 0) {
            (void) pthread_mutex_unlock(&g_lock);
            return (errno);
        }
    }
    g_refcount++;
    (void) pthread_mutex_unlock(&g_lock);
    return (0);
}

void
libzfs_core_fini(void)
{
    (void) pthread_mutex_lock(&g_lock);
    ASSERT3S(g_refcount, >, 0);
    g_refcount--;
    if (g_refcount == 0)
        (void) close(g_fd);
    (void) pthread_mutex_unlock(&g_lock);
}

static int
lzc_ioctl(zfs_ioc_t ioc, const char *name,
    nvlist_t *source, nvlist_t **resultp)
{
    zfs_cmd_t zc = { 0 };
    int error = 0;
    char *packed;
    size_t size;

    ASSERT3S(g_refcount, >, 0);

    (void) strlcpy(zc.zc_name, name, sizeof (zc.zc_name));

    packed = fnvlist_pack(source, &size);
    zc.zc_nvlist_src = (uint64_t)(uintptr_t)packed;
    zc.zc_nvlist_src_size = size;

    if (resultp != NULL) {
        *resultp = NULL;
        zc.zc_nvlist_dst_size = MAX(size * 2, 128 * 1024);
        zc.zc_nvlist_dst = (uint64_t)(uintptr_t)
            malloc(zc.zc_nvlist_dst_size);
        if (zc.zc_nvlist_dst == NULL) {
            error = ENOMEM;
            goto out;
        }
    }

    while (ioctl(g_fd, ioc, &zc) != 0) {
        if (errno == ENOMEM && resultp != NULL) {
            free((void *)(uintptr_t)zc.zc_nvlist_dst);
            zc.zc_nvlist_dst_size *= 2;
            zc.zc_nvlist_dst = (uint64_t)(uintptr_t)
                malloc(zc.zc_nvlist_dst_size);
            if (zc.zc_nvlist_dst == NULL) {
                error = ENOMEM;
                goto out;
            }
        } else {
            error = errno;
            break;
        }
    }
    if (zc.zc_nvlist_dst_filled) {
        *resultp = fnvlist_unpack((void *)(uintptr_t)zc.zc_nvlist_dst,
            zc.zc_nvlist_dst_size);
    }

out:
    fnvlist_pack_free(packed, size);
    free((void *)(uintptr_t)zc.zc_nvlist_dst);
    return (error);
}

int
lzc_create(const char *fsname, dmu_objset_type_t type, nvlist_t *props)
{
    int error;
    nvlist_t *args = fnvlist_alloc();
    fnvlist_add_int32(args, "type", type);
    if (props != NULL)
        fnvlist_add_nvlist(args, "props", props);
    error = lzc_ioctl(ZFS_IOC_CREATE, fsname, args, NULL);
    nvlist_free(args);
    return (error);
}

int
lzc_clone(const char *fsname, const char *origin,
    nvlist_t *props)
{
    int error;
    nvlist_t *args = fnvlist_alloc();
    fnvlist_add_string(args, "origin", origin);
    if (props != NULL)
        fnvlist_add_nvlist(args, "props", props);
    error = lzc_ioctl(ZFS_IOC_CLONE, fsname, args, NULL);
    nvlist_free(args);
    return (error);
}

/*
 * Creates snapshots.
 *
 * The keys in the snaps nvlist are the snapshots to be created.
 * They must all be in the same pool.
 *
 * The props nvlist is properties to set.  Currently only user properties
 * are supported.  { user:prop_name -> string value }
 *
 * The returned results nvlist will have an entry for each snapshot that failed.
 * The value will be the (int32) error code.
 *
 * The return value will be 0 if all snapshots were created, otherwise it will
 * be the errno of a (unspecified) snapshot that failed.
 */
int
lzc_snapshot(nvlist_t *snaps, nvlist_t *props, nvlist_t **errlist)
{
    nvpair_t *elem;
    nvlist_t *args;
    int error;
    char pool[MAXNAMELEN];

    *errlist = NULL;

    /* determine the pool name */
    elem = nvlist_next_nvpair(snaps, NULL);
    if (elem == NULL)
        return (0);
    (void) strlcpy(pool, nvpair_name(elem), sizeof (pool));
    pool[strcspn(pool, "/@")] = '\0';

    args = fnvlist_alloc();
    fnvlist_add_nvlist(args, "snaps", snaps);
    if (props != NULL)
        fnvlist_add_nvlist(args, "props", props);

    error = lzc_ioctl(ZFS_IOC_SNAPSHOT, pool, args, errlist);
    nvlist_free(args);

    return (error);
}

/*
 * Destroys snapshots.
 *
 * The keys in the snaps nvlist are the snapshots to be destroyed.
 * They must all be in the same pool.
 *
 * Snapshots that do not exist will be silently ignored.
 *
 * If 'defer' is not set, and a snapshot has user holds or clones, the
 * destroy operation will fail and none of the snapshots will be
 * destroyed.
 *
 * If 'defer' is set, and a snapshot has user holds or clones, it will be
 * marked for deferred destruction, and will be destroyed when the last hold
 * or clone is removed/destroyed.
 *
 * The return value will be 0 if all snapshots were destroyed (or marked for
 * later destruction if 'defer' is set) or didn't exist to begin with.
 *
 * Otherwise the return value will be the errno of a (unspecified) snapshot
 * that failed, no snapshots will be destroyed, and the errlist will have an
 * entry for each snapshot that failed.  The value in the errlist will be
 * the (int32) error code.
 */
int
lzc_destroy_snaps(nvlist_t *snaps, boolean_t defer, nvlist_t **errlist)
{
    nvpair_t *elem;
    nvlist_t *args;
    int error;
    char pool[MAXNAMELEN];

    /* determine the pool name */
    elem = nvlist_next_nvpair(snaps, NULL);
    if (elem == NULL)
        return (0);
    (void) strlcpy(pool, nvpair_name(elem), sizeof (pool));
    pool[strcspn(pool, "/@")] = '\0';

    args = fnvlist_alloc();
    fnvlist_add_nvlist(args, "snaps", snaps);
    if (defer)
        fnvlist_add_boolean(args, "defer");

    error = lzc_ioctl(ZFS_IOC_DESTROY_SNAPS, pool, args, errlist);
    nvlist_free(args);

    return (error);
}

int
lzc_snaprange_space(const char *firstsnap, const char *lastsnap,
    uint64_t *usedp)
{
    nvlist_t *args;
    nvlist_t *result;
    int err;
    char fs[MAXNAMELEN];
    char *atp;

    /* determine the fs name */
    (void) strlcpy(fs, firstsnap, sizeof (fs));
    atp = strchr(fs, '@');
    if (atp == NULL)
        return (EINVAL);
    *atp = '\0';

    args = fnvlist_alloc();
    fnvlist_add_string(args, "firstsnap", firstsnap);

    err = lzc_ioctl(ZFS_IOC_SPACE_SNAPS, lastsnap, args, &result);
    nvlist_free(args);
    if (err == 0)
        *usedp = fnvlist_lookup_uint64(result, "used");
    fnvlist_free(result);

    return (err);
}

boolean_t
lzc_exists(const char *dataset)
{
    /*
     * The objset_stats ioctl is still legacy, so we need to construct our
     * own zfs_cmd_t rather than using zfsc_ioctl().
     */
    zfs_cmd_t zc = { 0 };

    (void) strlcpy(zc.zc_name, dataset, sizeof (zc.zc_name));
    return (ioctl(g_fd, ZFS_IOC_OBJSET_STATS, &zc) == 0);
}

/*
 * Create "user holds" on snapshots.  If there is a hold on a snapshot,
 * the snapshot can not be destroyed.  (However, it can be marked for deletion
 * by lzc_destroy_snaps(defer=B_TRUE).)
 *
 * The keys in the nvlist are snapshot names.
 * The snapshots must all be in the same pool.
 * The value is the name of the hold (string type).
 *
 * If cleanup_fd is not -1, it must be the result of open("/dev/zfs", O_EXCL).
 * In this case, when the cleanup_fd is closed (including on process
 * termination), the holds will be released.  If the system is shut down
 * uncleanly, the holds will be released when the pool is next opened
 * or imported.
 *
 * Holds for snapshots which don't exist will be skipped and have an entry
 * added to errlist, but will not cause an overall failure.
 *
 * The return value will be 0 if all holds, for snapshots that existed,
 * were succesfully created.
 *
 * Otherwise the return value will be the errno of a (unspecified) hold that
 * failed and no holds will be created.
 *
 * In all cases the errlist will have an entry for each hold that failed
 * (name = snapshot), with its value being the error code (int32).
 */
int
lzc_hold(nvlist_t *holds, int cleanup_fd, nvlist_t **errlist)
{
    char pool[MAXNAMELEN];
    nvlist_t *args;
    nvpair_t *elem;
    int error;

    /* determine the pool name */
    elem = nvlist_next_nvpair(holds, NULL);
    if (elem == NULL)
        return (0);
    (void) strlcpy(pool, nvpair_name(elem), sizeof (pool));
    pool[strcspn(pool, "/@")] = '\0';

    args = fnvlist_alloc();
    fnvlist_add_nvlist(args, "holds", holds);
    if (cleanup_fd != -1)
        fnvlist_add_int32(args, "cleanup_fd", cleanup_fd);

    error = lzc_ioctl(ZFS_IOC_HOLD, pool, args, errlist);
    nvlist_free(args);
    return (error);
}

/*
 * Release "user holds" on snapshots.  If the snapshot has been marked for
 * deferred destroy (by lzc_destroy_snaps(defer=B_TRUE)), it does not have
 * any clones, and all the user holds are removed, then the snapshot will be
 * destroyed.
 *
 * The keys in the nvlist are snapshot names.
 * The snapshots must all be in the same pool.
 * The value is a nvlist whose keys are the holds to remove.
 *
 * Holds which failed to release because they didn't exist will have an entry
 * added to errlist, but will not cause an overall failure.
 *
 * The return value will be 0 if the nvl holds was empty or all holds that
 * existed, were successfully removed.
 *
 * Otherwise the return value will be the errno of a (unspecified) hold that
 * failed to release and no holds will be released.
 *
 * In all cases the errlist will have an entry for each hold that failed to
 * to release.
 */
int
lzc_release(nvlist_t *holds, nvlist_t **errlist)
{
    char pool[MAXNAMELEN];
    nvpair_t *elem;

    /* determine the pool name */
    elem = nvlist_next_nvpair(holds, NULL);
    if (elem == NULL)
        return (0);
    (void) strlcpy(pool, nvpair_name(elem), sizeof (pool));
    pool[strcspn(pool, "/@")] = '\0';

    return (lzc_ioctl(ZFS_IOC_RELEASE, pool, holds, errlist));
}

/*
 * Retrieve list of user holds on the specified snapshot.
 *
 * On success, *holdsp will be set to a nvlist which the caller must free.
 * The keys are the names of the holds, and the value is the creation time
 * of the hold (uint64) in seconds since the epoch.
 */
int
lzc_get_holds(const char *snapname, nvlist_t **holdsp)
{
    int error;
    nvlist_t *innvl = fnvlist_alloc();
    error = lzc_ioctl(ZFS_IOC_GET_HOLDS, snapname, innvl, holdsp);
    fnvlist_free(innvl);
    return (error);
}

/*
 * If fromsnap is NULL, a full (non-incremental) stream will be sent.
 */
int
lzc_send(const char *snapname, const char *fromsnap, int fd)
{
    nvlist_t *args;
    int err;

    args = fnvlist_alloc();
    fnvlist_add_int32(args, "fd", fd);
    if (fromsnap != NULL)
        fnvlist_add_string(args, "fromsnap", fromsnap);
    err = lzc_ioctl(ZFS_IOC_SEND_NEW, snapname, args, NULL);
    nvlist_free(args);
    return (err);
}

/*
 * If fromsnap is NULL, a full (non-incremental) stream will be estimated.
 */
int
lzc_send_space(const char *snapname, const char *fromsnap, uint64_t *spacep)
{
    nvlist_t *args;
    nvlist_t *result;
    int err;

    args = fnvlist_alloc();
    if (fromsnap != NULL)
        fnvlist_add_string(args, "fromsnap", fromsnap);
    err = lzc_ioctl(ZFS_IOC_SEND_SPACE, snapname, args, &result);
    nvlist_free(args);
    if (err == 0)
        *spacep = fnvlist_lookup_uint64(result, "space");
    nvlist_free(result);
    return (err);
}

static int
recv_read(int fd, void *buf, int ilen)
{
    char *cp = buf;
    int rv;
    int len = ilen;

    do {
        rv = read(fd, cp, len);
        cp += rv;
        len -= rv;
    } while (rv > 0);

    if (rv < 0 || len != 0)
        return (EIO);

    return (0);
}

/*
 * The simplest receive case: receive from the specified fd, creating the
 * specified snapshot.  Apply the specified properties a "received" properties
 * (which can be overridden by locally-set properties).  If the stream is a
 * clone, its origin snapshot must be specified by 'origin'.  The 'force'
 * flag will cause the target filesystem to be rolled back or destroyed if
 * necessary to receive.
 *
 * Return 0 on success or an errno on failure.
 *
 * Note: this interface does not work on dedup'd streams
 * (those with DMU_BACKUP_FEATURE_DEDUP).
 */
int
lzc_receive(const char *snapname, nvlist_t *props, const char *origin,
    boolean_t force, int fd)
{
    /*
     * The receive ioctl is still legacy, so we need to construct our own
     * zfs_cmd_t rather than using zfsc_ioctl().
     */
    zfs_cmd_t zc = { 0 };
    char *atp;
    char *packed = NULL;
    size_t size;
    dmu_replay_record_t drr;
    int error;

    ASSERT3S(g_refcount, >, 0);

    /* zc_name is name of containing filesystem */
    (void) strlcpy(zc.zc_name, snapname, sizeof (zc.zc_name));
    atp = strchr(zc.zc_name, '@');
    if (atp == NULL)
        return (EINVAL);
    *atp = '\0';

    /* if the fs does not exist, try its parent. */
    if (!lzc_exists(zc.zc_name)) {
        char *slashp = strrchr(zc.zc_name, '/');
        if (slashp == NULL)
            return (ENOENT);
        *slashp = '\0';

    }

    /* zc_value is full name of the snapshot to create */
    (void) strlcpy(zc.zc_value, snapname, sizeof (zc.zc_value));

    if (props != NULL) {
        /* zc_nvlist_src is props to set */
        packed = fnvlist_pack(props, &size);
        zc.zc_nvlist_src = (uint64_t)(uintptr_t)packed;
        zc.zc_nvlist_src_size = size;
    }

    /* zc_string is name of clone origin (if DRR_FLAG_CLONE) */
    if (origin != NULL)
        (void) strlcpy(zc.zc_string, origin, sizeof (zc.zc_string));

    /* zc_begin_record is non-byteswapped BEGIN record */
    error = recv_read(fd, &drr, sizeof (drr));
    if (error != 0)
        goto out;
    zc.zc_begin_record = drr.drr_u.drr_begin;

    /* zc_cookie is fd to read from */
    zc.zc_cookie = fd;

    /* zc guid is force flag */
    zc.zc_guid = force;

    /* zc_cleanup_fd is unused */
    zc.zc_cleanup_fd = -1;

    error = ioctl(g_fd, ZFS_IOC_RECV, &zc);
    if (error != 0)
        error = errno;

out:
    if (packed != NULL)
        fnvlist_pack_free(packed, size);
    free((void*)(uintptr_t)zc.zc_nvlist_dst);
    return (error);
}