fs/zfs/zfs_znode.c

	zfs_znode.c revision 893a6d32980d24be1349478f44169009d4801c25
/*
 * 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"

#ifdef _KERNEL
#include <sys/types.h>
#include <sys/param.h>
#include <sys/time.h>
#include <sys/systm.h>
#include <sys/sysmacros.h>
#include <sys/resource.h>
#include <sys/mntent.h>
#include <sys/mkdev.h>
#include <sys/vfs.h>
#include <sys/vnode.h>
#include <sys/file.h>
#include <sys/kmem.h>
#include <sys/cmn_err.h>
#include <sys/errno.h>
#include <sys/unistd.h>
#include <sys/mode.h>
#include <sys/atomic.h>
#include <vm/pvn.h>
#include "fs/fs_subr.h"
#include <sys/zfs_dir.h>
#include <sys/zfs_acl.h>
#include <sys/zfs_ioctl.h>
#include <sys/zfs_rlock.h>
#include <sys/fs/zfs.h>
#endif /* _KERNEL */

#include <sys/dmu.h>
#include <sys/refcount.h>
#include <sys/stat.h>
#include <sys/zap.h>
#include <sys/zfs_znode.h>

/*
 * Functions needed for userland (ie: libzpool) are not put under
 * #ifdef_KERNEL; the rest of the functions have dependencies
 * (such as VFS logic) that will not compile easily in userland.
 */
#ifdef _KERNEL
struct kmem_cache *znode_cache = NULL;

/*ARGSUSED*/
static void
znode_pageout_func(dmu_buf_t *dbuf, void *user_ptr)
{
    znode_t *zp = user_ptr;
    vnode_t *vp = ZTOV(zp);

    mutex_enter(&zp->z_lock);
    if (vp->v_count == 0) {
        mutex_exit(&zp->z_lock);
        vn_invalid(vp);
        zfs_znode_free(zp);
    } else {
        /* signal force unmount that this znode can be freed */
        zp->z_dbuf = NULL;
        mutex_exit(&zp->z_lock);
    }
}

/*ARGSUSED*/
static int
zfs_znode_cache_constructor(void *buf, void *cdrarg, int kmflags)
{
    znode_t *zp = buf;

    zp->z_vnode = vn_alloc(KM_SLEEP);
    zp->z_vnode->v_data = (caddr_t)zp;
    mutex_init(&zp->z_lock, NULL, MUTEX_DEFAULT, NULL);
    rw_init(&zp->z_map_lock, NULL, RW_DEFAULT, NULL);
    rw_init(&zp->z_parent_lock, NULL, RW_DEFAULT, NULL);
    mutex_init(&zp->z_acl_lock, NULL, MUTEX_DEFAULT, NULL);

    mutex_init(&zp->z_range_lock, NULL, MUTEX_DEFAULT, NULL);
    avl_create(&zp->z_range_avl, zfs_range_compare,
        sizeof (rl_t), offsetof(rl_t, r_node));

    zp->z_dbuf_held = 0;
    zp->z_dirlocks = 0;
    return (0);
}

/*ARGSUSED*/
static void
zfs_znode_cache_destructor(void *buf, void *cdarg)
{
    znode_t *zp = buf;

    ASSERT(zp->z_dirlocks == 0);
    mutex_destroy(&zp->z_lock);
    rw_destroy(&zp->z_map_lock);
    rw_destroy(&zp->z_parent_lock);
    mutex_destroy(&zp->z_acl_lock);
    avl_destroy(&zp->z_range_avl);

    ASSERT(zp->z_dbuf_held == 0);
    ASSERT(ZTOV(zp)->v_count == 0);
    vn_free(ZTOV(zp));
}

void
zfs_znode_init(void)
{
    /*
     * Initialize zcache
     */
    ASSERT(znode_cache == NULL);
    znode_cache = kmem_cache_create("zfs_znode_cache",
        sizeof (znode_t), 0, zfs_znode_cache_constructor,
        zfs_znode_cache_destructor, NULL, NULL, NULL, 0);
}

void
zfs_znode_fini(void)
{
    /*
     * Cleanup vfs & vnode ops
     */
    zfs_remove_op_tables();

    /*
     * Cleanup zcache
     */
    if (znode_cache)
        kmem_cache_destroy(znode_cache);
    znode_cache = NULL;
}

struct vnodeops *zfs_dvnodeops;
struct vnodeops *zfs_fvnodeops;
struct vnodeops *zfs_symvnodeops;
struct vnodeops *zfs_xdvnodeops;
struct vnodeops *zfs_evnodeops;

void
zfs_remove_op_tables()
{
    /*
     * Remove vfs ops
     */
    ASSERT(zfsfstype);
    (void) vfs_freevfsops_by_type(zfsfstype);
    zfsfstype = 0;

    /*
     * Remove vnode ops
     */
    if (zfs_dvnodeops)
        vn_freevnodeops(zfs_dvnodeops);
    if (zfs_fvnodeops)
        vn_freevnodeops(zfs_fvnodeops);
    if (zfs_symvnodeops)
        vn_freevnodeops(zfs_symvnodeops);
    if (zfs_xdvnodeops)
        vn_freevnodeops(zfs_xdvnodeops);
    if (zfs_evnodeops)
        vn_freevnodeops(zfs_evnodeops);

    zfs_dvnodeops = NULL;
    zfs_fvnodeops = NULL;
    zfs_symvnodeops = NULL;
    zfs_xdvnodeops = NULL;
    zfs_evnodeops = NULL;
}

extern const fs_operation_def_t zfs_dvnodeops_template[];
extern const fs_operation_def_t zfs_fvnodeops_template[];
extern const fs_operation_def_t zfs_xdvnodeops_template[];
extern const fs_operation_def_t zfs_symvnodeops_template[];
extern const fs_operation_def_t zfs_evnodeops_template[];

int
zfs_create_op_tables()
{
    int error;

    /*
     * zfs_dvnodeops can be set if mod_remove() calls mod_installfs()
     * due to a failure to remove the the 2nd modlinkage (zfs_modldrv).
     * In this case we just return as the ops vectors are already set up.
     */
    if (zfs_dvnodeops)
        return (0);

    error = vn_make_ops(MNTTYPE_ZFS, zfs_dvnodeops_template,
        &zfs_dvnodeops);
    if (error)
        return (error);

    error = vn_make_ops(MNTTYPE_ZFS, zfs_fvnodeops_template,
        &zfs_fvnodeops);
    if (error)
        return (error);

    error = vn_make_ops(MNTTYPE_ZFS, zfs_symvnodeops_template,
        &zfs_symvnodeops);
    if (error)
        return (error);

    error = vn_make_ops(MNTTYPE_ZFS, zfs_xdvnodeops_template,
        &zfs_xdvnodeops);
    if (error)
        return (error);

    error = vn_make_ops(MNTTYPE_ZFS, zfs_evnodeops_template,
        &zfs_evnodeops);

    return (error);
}

/*
 * zfs_init_fs - Initialize the zfsvfs struct and the file system
 *  incore "master" object.  Verify version compatibility.
 */
int
zfs_init_fs(zfsvfs_t *zfsvfs, znode_t **zpp, cred_t *cr)
{
    extern int zfsfstype;

    objset_t    *os = zfsvfs->z_os;
    uint64_t    version = ZPL_VERSION;
    int     i, error;
    dmu_object_info_t doi;
    uint64_t fsid_guid;

    *zpp = NULL;

    /*
     * XXX - hack to auto-create the pool root filesystem at
     * the first attempted mount.
     */
    if (dmu_object_info(os, MASTER_NODE_OBJ, &doi) == ENOENT) {
        dmu_tx_t *tx = dmu_tx_create(os);

        dmu_tx_hold_zap(tx, DMU_NEW_OBJECT, TRUE, NULL); /* master */
        dmu_tx_hold_zap(tx, DMU_NEW_OBJECT, TRUE, NULL); /* del queue */
        dmu_tx_hold_bonus(tx, DMU_NEW_OBJECT); /* root node */
        error = dmu_tx_assign(tx, TXG_WAIT);
        ASSERT3U(error, ==, 0);
        zfs_create_fs(os, cr, tx);
        dmu_tx_commit(tx);
    }

    error = zap_lookup(os, MASTER_NODE_OBJ, ZPL_VERSION_OBJ, 8, 1,
        &version);
    if (error) {
        return (error);
    } else if (version != ZPL_VERSION) {
        (void) printf("Mismatched versions:  File system "
            "is version %lld on-disk format, which is "
            "incompatible with this software version %lld!",
            (u_longlong_t)version, ZPL_VERSION);
        return (ENOTSUP);
    }

    /*
     * The fsid is 64 bits, composed of an 8-bit fs type, which
     * separates our fsid from any other filesystem types, and a
     * 56-bit objset unique ID.  The objset unique ID is unique to
     * all objsets open on this system, provided by unique_create().
     * The 8-bit fs type must be put in the low bits of fsid[1]
     * because that's where other Solaris filesystems put it.
     */
    fsid_guid = dmu_objset_fsid_guid(os);
    ASSERT((fsid_guid & ~((1ULL<<56)-1)) == 0);
    zfsvfs->z_vfs->vfs_fsid.val[0] = fsid_guid;
    zfsvfs->z_vfs->vfs_fsid.val[1] = ((fsid_guid>>32) << 8) |
        zfsfstype & 0xFF;

    error = zap_lookup(os, MASTER_NODE_OBJ, ZFS_ROOT_OBJ, 8, 1,
        &zfsvfs->z_root);
    if (error)
        return (error);
    ASSERT(zfsvfs->z_root != 0);

    /*
     * Create the per mount vop tables.
     */

    /*
     * Initialize zget mutex's
     */
    for (i = 0; i != ZFS_OBJ_MTX_SZ; i++)
        mutex_init(&zfsvfs->z_hold_mtx[i], NULL, MUTEX_DEFAULT, NULL);

    error = zfs_zget(zfsvfs, zfsvfs->z_root, zpp);
    if (error)
        return (error);
    ASSERT3U((*zpp)->z_id, ==, zfsvfs->z_root);

    error = zap_lookup(os, MASTER_NODE_OBJ, ZFS_UNLINKED_SET, 8, 1,
        &zfsvfs->z_unlinkedobj);
    if (error)
        return (error);

    return (0);
}

/*
 * define a couple of values we need available
 * for both 64 and 32 bit environments.
 */
#ifndef NBITSMINOR64
#define NBITSMINOR64    32
#endif
#ifndef MAXMAJ64
#define MAXMAJ64    0xffffffffUL
#endif
#ifndef MAXMIN64
#define MAXMIN64    0xffffffffUL
#endif

/*
 * Create special expldev for ZFS private use.
 * Can't use standard expldev since it doesn't do
 * what we want.  The standard expldev() takes a
 * dev32_t in LP64 and expands it to a long dev_t.
 * We need an interface that takes a dev32_t in ILP32
 * and expands it to a long dev_t.
 */
static uint64_t
zfs_expldev(dev_t dev)
{
#ifndef _LP64
    major_t major = (major_t)dev >> NBITSMINOR32 & MAXMAJ32;
    return (((uint64_t)major << NBITSMINOR64) |
        ((minor_t)dev & MAXMIN32));
#else
    return (dev);
#endif
}

/*
 * Special cmpldev for ZFS private use.
 * Can't use standard cmpldev since it takes
 * a long dev_t and compresses it to dev32_t in
 * LP64.  We need to do a compaction of a long dev_t
 * to a dev32_t in ILP32.
 */
dev_t
zfs_cmpldev(uint64_t dev)
{
#ifndef _LP64
    minor_t minor = (minor_t)dev & MAXMIN64;
    major_t major = (major_t)(dev >> NBITSMINOR64) & MAXMAJ64;

    if (major > MAXMAJ32 || minor > MAXMIN32)
        return (NODEV32);

    return (((dev32_t)major << NBITSMINOR32) | minor);
#else
    return (dev);
#endif
}

/*
 * Construct a new znode/vnode and intialize.
 *
 * This does not do a call to dmu_set_user() that is
 * up to the caller to do, in case you don't want to
 * return the znode
 */
static znode_t *
zfs_znode_alloc(zfsvfs_t *zfsvfs, dmu_buf_t *db, uint64_t obj_num, int blksz)
{
    znode_t *zp;
    vnode_t *vp;

    zp = kmem_cache_alloc(znode_cache, KM_SLEEP);

    ASSERT(zp->z_dirlocks == NULL);

    zp->z_phys = db->db_data;
    zp->z_zfsvfs = zfsvfs;
    zp->z_unlinked = 0;
    zp->z_atime_dirty = 0;
    zp->z_dbuf_held = 0;
    zp->z_mapcnt = 0;
    zp->z_last_itx = 0;
    zp->z_dbuf = db;
    zp->z_id = obj_num;
    zp->z_blksz = blksz;
    zp->z_seq = 0x7A4653;
    zp->z_sync_cnt = 0;

    mutex_enter(&zfsvfs->z_znodes_lock);
    list_insert_tail(&zfsvfs->z_all_znodes, zp);
    mutex_exit(&zfsvfs->z_znodes_lock);

    vp = ZTOV(zp);
    vn_reinit(vp);

    vp->v_vfsp = zfsvfs->z_parent->z_vfs;
    vp->v_type = IFTOVT((mode_t)zp->z_phys->zp_mode);

    switch (vp->v_type) {
    case VDIR:
        if (zp->z_phys->zp_flags & ZFS_XATTR) {
            vn_setops(vp, zfs_xdvnodeops);
            vp->v_flag |= V_XATTRDIR;
        } else
            vn_setops(vp, zfs_dvnodeops);
        zp->z_zn_prefetch = B_TRUE; /* z_prefetch default is enabled */
        break;
    case VBLK:
    case VCHR:
        vp->v_rdev = zfs_cmpldev(zp->z_phys->zp_rdev);
        /*FALLTHROUGH*/
    case VFIFO:
    case VSOCK:
    case VDOOR:
        vn_setops(vp, zfs_fvnodeops);
        break;
    case VREG:
        vp->v_flag |= VMODSORT;
        vn_setops(vp, zfs_fvnodeops);
        break;
    case VLNK:
        vn_setops(vp, zfs_symvnodeops);
        break;
    default:
        vn_setops(vp, zfs_evnodeops);
        break;
    }

    return (zp);
}

static void
zfs_znode_dmu_init(znode_t *zp)
{
    znode_t     *nzp;
    zfsvfs_t    *zfsvfs = zp->z_zfsvfs;
    dmu_buf_t   *db = zp->z_dbuf;

    mutex_enter(&zp->z_lock);

    nzp = dmu_buf_set_user(db, zp, &zp->z_phys, znode_pageout_func);

    /*
     * there should be no
     * concurrent zgets on this object.
     */
    ASSERT3P(nzp, ==, NULL);

    /*
     * Slap on VROOT if we are the root znode
     */
    if (zp->z_id == zfsvfs->z_root) {
        ZTOV(zp)->v_flag |= VROOT;
    }

    ASSERT(zp->z_dbuf_held == 0);
    zp->z_dbuf_held = 1;
    VFS_HOLD(zfsvfs->z_vfs);
    mutex_exit(&zp->z_lock);
    vn_exists(ZTOV(zp));
}

/*
 * Create a new DMU object to hold a zfs znode.
 *
 *  IN: dzp - parent directory for new znode
 *      vap - file attributes for new znode
 *      tx  - dmu transaction id for zap operations
 *      cr  - credentials of caller
 *      flag    - flags:
 *            IS_ROOT_NODE  - new object will be root
 *            IS_XATTR  - new object is an attribute
 *            IS_REPLAY - intent log replay
 *
 *  OUT:    oid - ID of created object
 *
 */
void
zfs_mknode(znode_t *dzp, vattr_t *vap, uint64_t *oid, dmu_tx_t *tx, cred_t *cr,
    uint_t flag, znode_t **zpp, int bonuslen)
{
    dmu_buf_t   *dbp;
    znode_phys_t    *pzp;
    znode_t     *zp;
    zfsvfs_t    *zfsvfs = dzp->z_zfsvfs;
    timestruc_t now;
    uint64_t    gen;
    int     err;

    ASSERT(vap && (vap->va_mask & (AT_TYPE|AT_MODE)) == (AT_TYPE|AT_MODE));

    if (zfsvfs->z_assign >= TXG_INITIAL) {      /* ZIL replay */
        *oid = vap->va_nodeid;
        flag |= IS_REPLAY;
        now = vap->va_ctime;        /* see zfs_replay_create() */
        gen = vap->va_nblocks;      /* ditto */
    } else {
        *oid = 0;
        gethrestime(&now);
        gen = dmu_tx_get_txg(tx);
    }

    /*
     * Create a new DMU object.
     */
    /*
     * There's currently no mechanism for pre-reading the blocks that will
     * be to needed allocate a new object, so we accept the small chance
     * that there will be an i/o error and we will fail one of the
     * assertions below.
     */
    if (vap->va_type == VDIR) {
        if (flag & IS_REPLAY) {
            err = zap_create_claim(zfsvfs->z_os, *oid,
                DMU_OT_DIRECTORY_CONTENTS,
                DMU_OT_ZNODE, sizeof (znode_phys_t) + bonuslen, tx);
            ASSERT3U(err, ==, 0);
        } else {
            *oid = zap_create(zfsvfs->z_os,
                DMU_OT_DIRECTORY_CONTENTS,
                DMU_OT_ZNODE, sizeof (znode_phys_t) + bonuslen, tx);
        }
    } else {
        if (flag & IS_REPLAY) {
            err = dmu_object_claim(zfsvfs->z_os, *oid,
                DMU_OT_PLAIN_FILE_CONTENTS, 0,
                DMU_OT_ZNODE, sizeof (znode_phys_t) + bonuslen, tx);
            ASSERT3U(err, ==, 0);
        } else {
            *oid = dmu_object_alloc(zfsvfs->z_os,
                DMU_OT_PLAIN_FILE_CONTENTS, 0,
                DMU_OT_ZNODE, sizeof (znode_phys_t) + bonuslen, tx);
        }
    }
    VERIFY(0 == dmu_bonus_hold(zfsvfs->z_os, *oid, NULL, &dbp));
    dmu_buf_will_dirty(dbp, tx);

    /*
     * Initialize the znode physical data to zero.
     */
    ASSERT(dbp->db_size >= sizeof (znode_phys_t));
    bzero(dbp->db_data, dbp->db_size);
    pzp = dbp->db_data;

    /*
     * If this is the root, fix up the half-initialized parent pointer
     * to reference the just-allocated physical data area.
     */
    if (flag & IS_ROOT_NODE) {
        dzp->z_phys = pzp;
        dzp->z_id = *oid;
    }

    /*
     * If parent is an xattr, so am I.
     */
    if (dzp->z_phys->zp_flags & ZFS_XATTR)
        flag |= IS_XATTR;

    if (vap->va_type == VBLK || vap->va_type == VCHR) {
        pzp->zp_rdev = zfs_expldev(vap->va_rdev);
    }

    if (vap->va_type == VDIR) {
        pzp->zp_size = 2;       /* contents ("." and "..") */
        pzp->zp_links = (flag & (IS_ROOT_NODE | IS_XATTR)) ? 2 : 1;
    }

    pzp->zp_parent = dzp->z_id;
    if (flag & IS_XATTR)
        pzp->zp_flags |= ZFS_XATTR;

    pzp->zp_gen = gen;

    ZFS_TIME_ENCODE(&now, pzp->zp_crtime);
    ZFS_TIME_ENCODE(&now, pzp->zp_ctime);

    if (vap->va_mask & AT_ATIME) {
        ZFS_TIME_ENCODE(&vap->va_atime, pzp->zp_atime);
    } else {
        ZFS_TIME_ENCODE(&now, pzp->zp_atime);
    }

    if (vap->va_mask & AT_MTIME) {
        ZFS_TIME_ENCODE(&vap->va_mtime, pzp->zp_mtime);
    } else {
        ZFS_TIME_ENCODE(&now, pzp->zp_mtime);
    }

    pzp->zp_mode = MAKEIMODE(vap->va_type, vap->va_mode);
    zp = zfs_znode_alloc(zfsvfs, dbp, *oid, 0);

    zfs_perm_init(zp, dzp, flag, vap, tx, cr);

    if (zpp) {
        kmutex_t *hash_mtx = ZFS_OBJ_MUTEX(zp);

        mutex_enter(hash_mtx);
        zfs_znode_dmu_init(zp);
        mutex_exit(hash_mtx);

        *zpp = zp;
    } else {
        ZTOV(zp)->v_count = 0;
        dmu_buf_rele(dbp, NULL);
        zfs_znode_free(zp);
    }
}

int
zfs_zget(zfsvfs_t *zfsvfs, uint64_t obj_num, znode_t **zpp)
{
    dmu_object_info_t doi;
    dmu_buf_t   *db;
    znode_t     *zp;
    int err;

    *zpp = NULL;

    ZFS_OBJ_HOLD_ENTER(zfsvfs, obj_num);

    err = dmu_bonus_hold(zfsvfs->z_os, obj_num, NULL, &db);
    if (err) {
        ZFS_OBJ_HOLD_EXIT(zfsvfs, obj_num);
        return (err);
    }

    dmu_object_info_from_db(db, &doi);
    if (doi.doi_bonus_type != DMU_OT_ZNODE ||
        doi.doi_bonus_size < sizeof (znode_phys_t)) {
        dmu_buf_rele(db, NULL);
        ZFS_OBJ_HOLD_EXIT(zfsvfs, obj_num);
        return (EINVAL);
    }

    ASSERT(db->db_object == obj_num);
    ASSERT(db->db_offset == -1);
    ASSERT(db->db_data != NULL);

    zp = dmu_buf_get_user(db);

    if (zp != NULL) {
        mutex_enter(&zp->z_lock);

        ASSERT3U(zp->z_id, ==, obj_num);
        if (zp->z_unlinked) {
            dmu_buf_rele(db, NULL);
            mutex_exit(&zp->z_lock);
            ZFS_OBJ_HOLD_EXIT(zfsvfs, obj_num);
            return (ENOENT);
        } else if (zp->z_dbuf_held) {
            dmu_buf_rele(db, NULL);
        } else {
            zp->z_dbuf_held = 1;
            VFS_HOLD(zfsvfs->z_vfs);
        }


        VN_HOLD(ZTOV(zp));
        mutex_exit(&zp->z_lock);
        ZFS_OBJ_HOLD_EXIT(zfsvfs, obj_num);
        *zpp = zp;
        return (0);
    }

    /*
     * Not found create new znode/vnode
     */
    zp = zfs_znode_alloc(zfsvfs, db, obj_num, doi.doi_data_block_size);
    ASSERT3U(zp->z_id, ==, obj_num);
    zfs_znode_dmu_init(zp);
    ZFS_OBJ_HOLD_EXIT(zfsvfs, obj_num);
    *zpp = zp;
    return (0);
}

void
zfs_znode_delete(znode_t *zp, dmu_tx_t *tx)
{
    zfsvfs_t *zfsvfs = zp->z_zfsvfs;
    int error;

    ZFS_OBJ_HOLD_ENTER(zfsvfs, zp->z_id);
    if (zp->z_phys->zp_acl.z_acl_extern_obj) {
        error = dmu_object_free(zfsvfs->z_os,
            zp->z_phys->zp_acl.z_acl_extern_obj, tx);
        ASSERT3U(error, ==, 0);
    }
    error = dmu_object_free(zfsvfs->z_os, zp->z_id, tx);
    ASSERT3U(error, ==, 0);
    zp->z_dbuf_held = 0;
    ZFS_OBJ_HOLD_EXIT(zfsvfs, zp->z_id);
    dmu_buf_rele(zp->z_dbuf, NULL);
}

void
zfs_zinactive(znode_t *zp)
{
    vnode_t *vp = ZTOV(zp);
    zfsvfs_t *zfsvfs = zp->z_zfsvfs;
    uint64_t z_id = zp->z_id;

    ASSERT(zp->z_dbuf_held && zp->z_phys);

    /*
     * Don't allow a zfs_zget() while were trying to release this znode
     */
    ZFS_OBJ_HOLD_ENTER(zfsvfs, z_id);

    mutex_enter(&zp->z_lock);
    mutex_enter(&vp->v_lock);
    vp->v_count--;
    if (vp->v_count > 0 || vn_has_cached_data(vp)) {
        /*
         * If the hold count is greater than zero, somebody has
         * obtained a new reference on this znode while we were
         * processing it here, so we are done.  If we still have
         * mapped pages then we are also done, since we don't
         * want to inactivate the znode until the pages get pushed.
         *
         * XXX - if vn_has_cached_data(vp) is true, but count == 0,
         * this seems like it would leave the znode hanging with
         * no chance to go inactive...
         */
        mutex_exit(&vp->v_lock);
        mutex_exit(&zp->z_lock);
        ZFS_OBJ_HOLD_EXIT(zfsvfs, z_id);
        return;
    }
    mutex_exit(&vp->v_lock);

    /*
     * If this was the last reference to a file with no links,
     * remove the file from the file system.
     */
    if (zp->z_unlinked) {
        mutex_exit(&zp->z_lock);
        ZFS_OBJ_HOLD_EXIT(zfsvfs, z_id);
        zfs_rmnode(zp);
        VFS_RELE(zfsvfs->z_vfs);
        return;
    }
    ASSERT(zp->z_phys);
    ASSERT(zp->z_dbuf_held);

    zp->z_dbuf_held = 0;
    mutex_exit(&zp->z_lock);
    dmu_buf_rele(zp->z_dbuf, NULL);
    ZFS_OBJ_HOLD_EXIT(zfsvfs, z_id);
    VFS_RELE(zfsvfs->z_vfs);
}

void
zfs_znode_free(znode_t *zp)
{
    zfsvfs_t *zfsvfs = zp->z_zfsvfs;

    mutex_enter(&zfsvfs->z_znodes_lock);
    list_remove(&zfsvfs->z_all_znodes, zp);
    mutex_exit(&zfsvfs->z_znodes_lock);

    kmem_cache_free(znode_cache, zp);
}

void
zfs_time_stamper_locked(znode_t *zp, uint_t flag, dmu_tx_t *tx)
{
    timestruc_t now;

    ASSERT(MUTEX_HELD(&zp->z_lock));

    gethrestime(&now);

    if (tx) {
        dmu_buf_will_dirty(zp->z_dbuf, tx);
        zp->z_atime_dirty = 0;
        zp->z_seq++;
    } else {
        zp->z_atime_dirty = 1;
    }

    if (flag & AT_ATIME)
        ZFS_TIME_ENCODE(&now, zp->z_phys->zp_atime);

    if (flag & AT_MTIME)
        ZFS_TIME_ENCODE(&now, zp->z_phys->zp_mtime);

    if (flag & AT_CTIME)
        ZFS_TIME_ENCODE(&now, zp->z_phys->zp_ctime);
}

/*
 * Update the requested znode timestamps with the current time.
 * If we are in a transaction, then go ahead and mark the znode
 * dirty in the transaction so the timestamps will go to disk.
 * Otherwise, we will get pushed next time the znode is updated
 * in a transaction, or when this znode eventually goes inactive.
 *
 * Why is this OK?
 *  1 - Only the ACCESS time is ever updated outside of a transaction.
 *  2 - Multiple consecutive updates will be collapsed into a single
 *  znode update by the transaction grouping semantics of the DMU.
 */
void
zfs_time_stamper(znode_t *zp, uint_t flag, dmu_tx_t *tx)
{
    mutex_enter(&zp->z_lock);
    zfs_time_stamper_locked(zp, flag, tx);
    mutex_exit(&zp->z_lock);
}

/*
 * Grow the block size for a file.
 *
 *  IN: zp  - znode of file to free data in.
 *      size    - requested block size
 *      tx  - open transaction.
 *
 * NOTE: this function assumes that the znode is write locked.
 */
void
zfs_grow_blocksize(znode_t *zp, uint64_t size, dmu_tx_t *tx)
{
    int     error;
    u_longlong_t    dummy;

    if (size <= zp->z_blksz)
        return;
    /*
     * If the file size is already greater than the current blocksize,
     * we will not grow.  If there is more than one block in a file,
     * the blocksize cannot change.
     */
    if (zp->z_blksz && zp->z_phys->zp_size > zp->z_blksz)
        return;

    error = dmu_object_set_blocksize(zp->z_zfsvfs->z_os, zp->z_id,
        size, 0, tx);
    if (error == ENOTSUP)
        return;
    ASSERT3U(error, ==, 0);

    /* What blocksize did we actually get? */
    dmu_object_size_from_db(zp->z_dbuf, &zp->z_blksz, &dummy);
}

/*
 * This is a dummy interface used when pvn_vplist_dirty() should *not*
 * be calling back into the fs for a putpage().  E.g.: when truncating
 * a file, the pages being "thrown away* don't need to be written out.
 */
/* ARGSUSED */
static int
zfs_no_putpage(vnode_t *vp, page_t *pp, u_offset_t *offp, size_t *lenp,
    int flags, cred_t *cr)
{
    ASSERT(0);
    return (0);
}

/*
 * Free space in a file.
 *
 *  IN: zp  - znode of file to free data in.
 *      off - start of section to free.
 *      len - length of section to free (0 => to EOF).
 *      flag    - current file open mode flags.
 *
 *  RETURN: 0 if success
 *      error code if failure
 */
int
zfs_freesp(znode_t *zp, uint64_t off, uint64_t len, int flag, boolean_t log)
{
    vnode_t *vp = ZTOV(zp);
    dmu_tx_t *tx;
    zfsvfs_t *zfsvfs = zp->z_zfsvfs;
    zilog_t *zilog = zfsvfs->z_log;
    rl_t *rl;
    uint64_t end = off + len;
    uint64_t size, new_blksz;
    int error;

    if (ZTOV(zp)->v_type == VFIFO)
        return (0);

    /*
     * If we will change zp_size then lock the whole file,
     * otherwise just lock the range being freed.
     */
    if (len == 0 || off + len > zp->z_phys->zp_size) {
        rl = zfs_range_lock(zp, 0, UINT64_MAX, RL_WRITER);
    } else {
        rl = zfs_range_lock(zp, off, len, RL_WRITER);
        /* recheck, in case zp_size changed */
        if (off + len > zp->z_phys->zp_size) {
            /* lost race: file size changed, lock whole file */
            zfs_range_unlock(rl);
            rl = zfs_range_lock(zp, 0, UINT64_MAX, RL_WRITER);
        }
    }

    /*
     * Nothing to do if file already at desired length.
     */
    size = zp->z_phys->zp_size;
    if (len == 0 && size == off) {
        zfs_range_unlock(rl);
        return (0);
    }

    /*
     * Check for any locks in the region to be freed.
     */
    if (MANDLOCK(vp, (mode_t)zp->z_phys->zp_mode)) {
        uint64_t start = off;
        uint64_t extent = len;

        if (off > size) {
            start = size;
            extent += off - size;
        } else if (len == 0) {
            extent = size - off;
        }
        if (error = chklock(vp, FWRITE, start, extent, flag, NULL)) {
            zfs_range_unlock(rl);
            return (error);
        }
    }

    tx = dmu_tx_create(zfsvfs->z_os);
    dmu_tx_hold_bonus(tx, zp->z_id);
    new_blksz = 0;
    if (end > size &&
        (!ISP2(zp->z_blksz) || zp->z_blksz < zfsvfs->z_max_blksz)) {
        /*
         * We are growing the file past the current block size.
         */
        if (zp->z_blksz > zp->z_zfsvfs->z_max_blksz) {
            ASSERT(!ISP2(zp->z_blksz));
            new_blksz = MIN(end, SPA_MAXBLOCKSIZE);
        } else {
            new_blksz = MIN(end, zp->z_zfsvfs->z_max_blksz);
        }
        dmu_tx_hold_write(tx, zp->z_id, 0, MIN(end, new_blksz));
    } else if (off < size) {
        /*
         * If len == 0, we are truncating the file.
         */
        dmu_tx_hold_free(tx, zp->z_id, off, len ? len : DMU_OBJECT_END);
    }

    error = dmu_tx_assign(tx, zfsvfs->z_assign);
    if (error) {
        if (error == ERESTART && zfsvfs->z_assign == TXG_NOWAIT)
            dmu_tx_wait(tx);
        dmu_tx_abort(tx);
        zfs_range_unlock(rl);
        return (error);
    }

    if (new_blksz)
        zfs_grow_blocksize(zp, new_blksz, tx);

    if (end > size || len == 0)
        zp->z_phys->zp_size = end;

    if (off < size) {
        objset_t *os = zfsvfs->z_os;
        uint64_t rlen = len;

        if (len == 0)
            rlen = -1;
        else if (end > size)
            rlen = size - off;
        VERIFY(0 == dmu_free_range(os, zp->z_id, off, rlen, tx));
    }

    if (log) {
        zfs_time_stamper(zp, CONTENT_MODIFIED, tx);
        zfs_log_truncate(zilog, tx, TX_TRUNCATE, zp, off, len);
    }

    zfs_range_unlock(rl);

    dmu_tx_commit(tx);

    /*
     * Clear any mapped pages in the truncated region.  This has to
     * happen outside of the transaction to avoid the possibility of
     * a deadlock with someone trying to push a page that we are
     * about to invalidate.
     */
    rw_enter(&zp->z_map_lock, RW_WRITER);
    if (off < size && vn_has_cached_data(vp)) {
        page_t *pp;
        uint64_t start = off & PAGEMASK;
        int poff = off & PAGEOFFSET;

        if (poff != 0 && (pp = page_lookup(vp, start, SE_SHARED))) {
            /*
             * We need to zero a partial page.
             */
            pagezero(pp, poff, PAGESIZE - poff);
            start += PAGESIZE;
            page_unlock(pp);
        }
        error = pvn_vplist_dirty(vp, start, zfs_no_putpage,
            B_INVAL | B_TRUNC, NULL);
        ASSERT(error == 0);
    }
    rw_exit(&zp->z_map_lock);

    return (0);
}

void
zfs_create_fs(objset_t *os, cred_t *cr, dmu_tx_t *tx)
{
    zfsvfs_t    zfsvfs;
    uint64_t    moid, doid, roid = 0;
    uint64_t    version = ZPL_VERSION;
    int     error;
    znode_t     *rootzp = NULL;
    vnode_t     *vp;
    vattr_t     vattr;

    /*
     * First attempt to create master node.
     */
    /*
     * In an empty objset, there are no blocks to read and thus
     * there can be no i/o errors (which we assert below).
     */
    moid = MASTER_NODE_OBJ;
    error = zap_create_claim(os, moid, DMU_OT_MASTER_NODE,
        DMU_OT_NONE, 0, tx);
    ASSERT(error == 0);

    /*
     * Set starting attributes.
     */

    error = zap_update(os, moid, ZPL_VERSION_OBJ, 8, 1, &version, tx);
    ASSERT(error == 0);

    /*
     * Create a delete queue.
     */
    doid = zap_create(os, DMU_OT_UNLINKED_SET, DMU_OT_NONE, 0, tx);

    error = zap_add(os, moid, ZFS_UNLINKED_SET, 8, 1, &doid, tx);
    ASSERT(error == 0);

    /*
     * Create root znode.  Create minimal znode/vnode/zfsvfs
     * to allow zfs_mknode to work.
     */
    vattr.va_mask = AT_MODE|AT_UID|AT_GID|AT_TYPE;
    vattr.va_type = VDIR;
    vattr.va_mode = S_IFDIR|0755;
    vattr.va_uid = 0;
    vattr.va_gid = 3;

    rootzp = kmem_cache_alloc(znode_cache, KM_SLEEP);
    rootzp->z_zfsvfs = &zfsvfs;
    rootzp->z_unlinked = 0;
    rootzp->z_atime_dirty = 0;
    rootzp->z_dbuf_held = 0;

    vp = ZTOV(rootzp);
    vn_reinit(vp);
    vp->v_type = VDIR;

    bzero(&zfsvfs, sizeof (zfsvfs_t));

    zfsvfs.z_os = os;
    zfsvfs.z_assign = TXG_NOWAIT;
    zfsvfs.z_parent = &zfsvfs;

    mutex_init(&zfsvfs.z_znodes_lock, NULL, MUTEX_DEFAULT, NULL);
    list_create(&zfsvfs.z_all_znodes, sizeof (znode_t),
        offsetof(znode_t, z_link_node));

    zfs_mknode(rootzp, &vattr, &roid, tx, cr, IS_ROOT_NODE, NULL, 0);
    ASSERT3U(rootzp->z_id, ==, roid);
    error = zap_add(os, moid, ZFS_ROOT_OBJ, 8, 1, &roid, tx);
    ASSERT(error == 0);

    ZTOV(rootzp)->v_count = 0;
    kmem_cache_free(znode_cache, rootzp);
}
#endif /* _KERNEL */

/*
 * Given an object number, return its parent object number and whether
 * or not the object is an extended attribute directory.
 */
static int
zfs_obj_to_pobj(objset_t *osp, uint64_t obj, uint64_t *pobjp, int *is_xattrdir)
{
    dmu_buf_t *db;
    dmu_object_info_t doi;
    znode_phys_t *zp;
    int error;

    if ((error = dmu_bonus_hold(osp, obj, FTAG, &db)) != 0)
        return (error);

    dmu_object_info_from_db(db, &doi);
    if (doi.doi_bonus_type != DMU_OT_ZNODE ||
        doi.doi_bonus_size < sizeof (znode_phys_t)) {
        dmu_buf_rele(db, FTAG);
        return (EINVAL);
    }

    zp = db->db_data;
    *pobjp = zp->zp_parent;
    *is_xattrdir = ((zp->zp_flags & ZFS_XATTR) != 0) &&
        S_ISDIR(zp->zp_mode);
    dmu_buf_rele(db, FTAG);

    return (0);
}

int
zfs_obj_to_path(objset_t *osp, uint64_t obj, char *buf, int len)
{
    char *path = buf + len - 1;
    int error;

    *path = '\0';

    for (;;) {
        uint64_t pobj;
        char component[MAXNAMELEN + 2];
        size_t complen;
        int is_xattrdir;

        if ((error = zfs_obj_to_pobj(osp, obj, &pobj,
            &is_xattrdir)) != 0)
            break;

        if (pobj == obj) {
            if (path[0] != '/')
                *--path = '/';
            break;
        }

        component[0] = '/';
        if (is_xattrdir) {
            (void) sprintf(component + 1, "<xattrdir>");
        } else {
            error = zap_value_search(osp, pobj, obj, component + 1);
            if (error != 0)
                break;
        }

        complen = strlen(component);
        path -= complen;
        ASSERT(path >= buf);
        bcopy(component, path, complen);
        obj = pobj;
    }

    if (error == 0)
        (void) memmove(buf, path, buf + len - path);
    return (error);
}