Merge commit 'ea01a15a654b9e1c7b37d958f4d1911882ed7781'

[unleashed.git] / kernel / fs / vnode.c

/*
 * 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) 1988, 2010, Oracle and/or its affiliates. All rights reserved.
 * Copyright 2017, Joyent, Inc.
 * Copyright 2016 Nexenta Systems, Inc.  All rights reserved.
 * Copyright (c) 2011, 2017 by Delphix. All rights reserved.
 */

/*      Copyright (c) 1983, 1984, 1985, 1986, 1987, 1988, 1989 AT&T     */
/*        All Rights Reserved   */

/*
 * University Copyright- Copyright (c) 1982, 1986, 1988
 * The Regents of the University of California
 * All Rights Reserved
 *
 * University Acknowledgment- Portions of this document are derived from
 * software developed by the University of California, Berkeley, and its
 * contributors.
 */

#include <sys/types.h>
#include <sys/param.h>
#include <sys/t_lock.h>
#include <sys/errno.h>
#include <sys/cred.h>
#include <sys/user.h>
#include <sys/uio.h>
#include <sys/file.h>
#include <sys/pathname.h>
#include <sys/vfs.h>
#include <sys/vnode.h>
#include <sys/vnode_dispatch.h>
#include <sys/rwstlock.h>
#include <sys/fem.h>
#include <sys/stat.h>
#include <sys/mode.h>
#include <sys/conf.h>
#include <sys/sysmacros.h>
#include <sys/cmn_err.h>
#include <sys/systm.h>
#include <sys/kmem.h>
#include <sys/debug.h>
#include <c2/audit.h>
#include <sys/acl.h>
#include <sys/nbmlock.h>
#include <sys/fcntl.h>
#include <sys/fs_subr.h>
#include <sys/taskq.h>
#include <sys/fs_reparse.h>
#include <sys/time.h>
#include <sys/sdt.h>

/* Determine if this vnode is a file that is read-only */
#define ISROFILE(vp)    \
        ((vp)->v_type != VCHR && (vp)->v_type != VBLK && \
            (vp)->v_type != VFIFO && vn_is_readonly(vp))

/* Tunable via /etc/system; used only by admin/install */
int nfs_global_client_only;

/*
 * Array of vopstats_t for per-FS-type vopstats.  This array has the same
 * number of entries as and parallel to the vfssw table.  (Arguably, it could
 * be part of the vfssw table.)  Once it's initialized, it's accessed using
 * the same fstype index that is used to index into the vfssw table.
 */
vopstats_t **vopstats_fstype;

/* vopstats initialization template used for fast initialization via bcopy() */
static vopstats_t *vs_templatep;

/* Kmem cache handle for vsk_anchor_t allocations */
kmem_cache_t *vsk_anchor_cache;

/* file events cleanup routine */
extern void free_fopdata(vnode_t *);

/*
 * Root of AVL tree for the kstats associated with vopstats.  Lock protects
 * updates to vsktat_tree.
 */
avl_tree_t      vskstat_tree;
kmutex_t        vskstat_tree_lock;

/* Global variable which enables/disables the vopstats collection */
int vopstats_enabled = 1;

/* Global used for empty/invalid v_path */
char *vn_vpath_empty = "";

/*
 * forward declarations for internal vnode specific data (vsd)
 */
static void *vsd_realloc(void *, size_t, size_t);

/*
 * forward declarations for reparse point functions
 */
static int fs_reparse_mark(char *target, vattr_t *vap, xvattr_t *xvattr);

/*
 * VSD -- VNODE SPECIFIC DATA
 * The v_data pointer is typically used by a file system to store a
 * pointer to the file system's private node (e.g. ufs inode, nfs rnode).
 * However, there are times when additional project private data needs
 * to be stored separately from the data (node) pointed to by v_data.
 * This additional data could be stored by the file system itself or
 * by a completely different kernel entity.  VSD provides a way for
 * callers to obtain a key and store a pointer to private data associated
 * with a vnode.
 *
 * Callers are responsible for protecting the vsd by holding v_vsd_lock
 * for calls to vsd_set() and vsd_get().
 */

/*
 * vsd_lock protects:
 *   vsd_nkeys - creation and deletion of vsd keys
 *   vsd_list - insertion and deletion of vsd_node in the vsd_list
 *   vsd_destructor - adding and removing destructors to the list
 */
static kmutex_t         vsd_lock;
static uint_t           vsd_nkeys;       /* size of destructor array */
/* list of vsd_node's */
static list_t *vsd_list = NULL;
/* per-key destructor funcs */
static void             (**vsd_destructor)(void *);

/*
 * The following is the common set of actions needed to update the
 * vopstats structure from a vnode op.  Both VOPSTATS_UPDATE() and
 * VOPSTATS_UPDATE_IO() do almost the same thing, except for the
 * recording of the bytes transferred.  Since the code is similar
 * but small, it is nearly a duplicate.  Consequently any changes
 * to one may need to be reflected in the other.
 * Rundown of the variables:
 * vp - Pointer to the vnode
 * counter - Partial name structure member to update in vopstats for counts
 * bytecounter - Partial name structure member to update in vopstats for bytes
 * bytesval - Value to update in vopstats for bytes
 * fstype - Index into vsanchor_fstype[], same as index into vfssw[]
 * vsp - Pointer to vopstats structure (either in vfs or vsanchor_fstype[i])
 */

#define VOPSTATS_UPDATE(vp, counter) {                                  \
        vfs_t *vfsp = (vp)->v_vfsp;                                     \
        if (vfsp && vfsp->vfs_implp &&                                  \
            (vfsp->vfs_flag & VFS_STATS) && (vp)->v_type != VBAD) {     \
                vopstats_t *vsp = &vfsp->vfs_vopstats;                  \
                uint64_t *stataddr = &(vsp->n##counter.value.ui64);     \
                extern void __dtrace_probe___fsinfo_##counter(vnode_t *, \
                    size_t, uint64_t *);                                \
                __dtrace_probe___fsinfo_##counter(vp, 0, stataddr);     \
                (*stataddr)++;                                          \
                if ((vsp = vfsp->vfs_fstypevsp) != NULL) {              \
                        vsp->n##counter.value.ui64++;                   \
                }                                                       \
        }                                                               \
}

#define VOPSTATS_UPDATE_IO(vp, counter, bytecounter, bytesval) {        \
        vfs_t *vfsp = (vp)->v_vfsp;                                     \
        if (vfsp && vfsp->vfs_implp &&                                  \
            (vfsp->vfs_flag & VFS_STATS) && (vp)->v_type != VBAD) {     \
                vopstats_t *vsp = &vfsp->vfs_vopstats;                  \
                uint64_t *stataddr = &(vsp->n##counter.value.ui64);     \
                extern void __dtrace_probe___fsinfo_##counter(vnode_t *, \
                    size_t, uint64_t *);                                \
                __dtrace_probe___fsinfo_##counter(vp, bytesval, stataddr); \
                (*stataddr)++;                                          \
                vsp->bytecounter.value.ui64 += bytesval;                \
                if ((vsp = vfsp->vfs_fstypevsp) != NULL) {              \
                        vsp->n##counter.value.ui64++;                   \
                        vsp->bytecounter.value.ui64 += bytesval;        \
                }                                                       \
        }                                                               \
}

/*
 * If the filesystem does not support XIDs map credential
 * If the vfsp is NULL, perhaps we should also map?
 */
#define VOPXID_MAP_CR(vp, cr)   {                                       \
        vfs_t *vfsp = (vp)->v_vfsp;                                     \
        if (vfsp != NULL && (vfsp->vfs_flag & VFS_XID) == 0)            \
                cr = crgetmapped(cr);                                   \
        }

/*
 * Convert stat(2) formats to vnode types and vice versa.  (Knows about
 * numerical order of S_IFMT and vnode types.)
 */
enum vtype iftovt_tab[] = {
        VNON, VFIFO, VCHR, VNON, VDIR, VNON, VBLK, VNON,
        VREG, VNON, VLNK, VNON, VSOCK, VNON, VNON, VNON
};

ushort_t vttoif_tab[] = {
        0, S_IFREG, S_IFDIR, S_IFBLK, S_IFCHR, S_IFLNK, S_IFIFO,
        S_IFDOOR, 0, S_IFSOCK, S_IFPORT, 0
};

/*
 * The system vnode cache.
 */

kmem_cache_t *vn_cache;


/* Extensible attribute (xva) routines. */

/*
 * Zero out the structure, set the size of the requested/returned bitmaps,
 * set AT_XVATTR in the embedded vattr_t's va_mask, and set up the pointer
 * to the returned attributes array.
 */
void
xva_init(xvattr_t *xvap)
{
        bzero(xvap, sizeof (xvattr_t));
        xvap->xva_mapsize = XVA_MAPSIZE;
        xvap->xva_magic = XVA_MAGIC;
        xvap->xva_vattr.va_mask = AT_XVATTR;
        xvap->xva_rtnattrmapp = &(xvap->xva_rtnattrmap)[0];
}

/*
 * If AT_XVATTR is set, returns a pointer to the embedded xoptattr_t
 * structure.  Otherwise, returns NULL.
 */
xoptattr_t *
xva_getxoptattr(xvattr_t *xvap)
{
        xoptattr_t *xoap = NULL;
        if (xvap->xva_vattr.va_mask & AT_XVATTR)
                xoap = &xvap->xva_xoptattrs;
        return (xoap);
}

/*
 * Used by the AVL routines to compare two vsk_anchor_t structures in the tree.
 * We use the f_fsid reported by VFS_STATVFS() since we use that for the
 * kstat name.
 */
static int
vska_compar(const void *n1, const void *n2)
{
        int ret;
        ulong_t p1 = ((vsk_anchor_t *)n1)->vsk_fsid;
        ulong_t p2 = ((vsk_anchor_t *)n2)->vsk_fsid;

        if (p1 < p2) {
                ret = -1;
        } else if (p1 > p2) {
                ret = 1;
        } else {
                ret = 0;
        }

        return (ret);
}

/*
 * Used to create a single template which will be bcopy()ed to a newly
 * allocated vsanchor_combo_t structure in new_vsanchor(), below.
 */
static vopstats_t *
create_vopstats_template()
{
        vopstats_t              *vsp;

        vsp = kmem_alloc(sizeof (vopstats_t), KM_SLEEP);
        bzero(vsp, sizeof (*vsp));      /* Start fresh */

        /* fop_open */
        kstat_named_init(&vsp->nopen, "nopen", KSTAT_DATA_UINT64);
        /* fop_close */
        kstat_named_init(&vsp->nclose, "nclose", KSTAT_DATA_UINT64);
        /* fop_read I/O */
        kstat_named_init(&vsp->nread, "nread", KSTAT_DATA_UINT64);
        kstat_named_init(&vsp->read_bytes, "read_bytes", KSTAT_DATA_UINT64);
        /* fop_write I/O */
        kstat_named_init(&vsp->nwrite, "nwrite", KSTAT_DATA_UINT64);
        kstat_named_init(&vsp->write_bytes, "write_bytes", KSTAT_DATA_UINT64);
        /* fop_ioctl */
        kstat_named_init(&vsp->nioctl, "nioctl", KSTAT_DATA_UINT64);
        /* fop_setfl */
        kstat_named_init(&vsp->nsetfl, "nsetfl", KSTAT_DATA_UINT64);
        /* fop_getattr */
        kstat_named_init(&vsp->ngetattr, "ngetattr", KSTAT_DATA_UINT64);
        /* fop_setattr */
        kstat_named_init(&vsp->nsetattr, "nsetattr", KSTAT_DATA_UINT64);
        /* fop_access */
        kstat_named_init(&vsp->naccess, "naccess", KSTAT_DATA_UINT64);
        /* fop_lookup */
        kstat_named_init(&vsp->nlookup, "nlookup", KSTAT_DATA_UINT64);
        /* fop_create */
        kstat_named_init(&vsp->ncreate, "ncreate", KSTAT_DATA_UINT64);
        /* fop_remove */
        kstat_named_init(&vsp->nremove, "nremove", KSTAT_DATA_UINT64);
        /* fop_link */
        kstat_named_init(&vsp->nlink, "nlink", KSTAT_DATA_UINT64);
        /* fop_rename */
        kstat_named_init(&vsp->nrename, "nrename", KSTAT_DATA_UINT64);
        /* fop_mkdir */
        kstat_named_init(&vsp->nmkdir, "nmkdir", KSTAT_DATA_UINT64);
        /* fop_rmdir */
        kstat_named_init(&vsp->nrmdir, "nrmdir", KSTAT_DATA_UINT64);
        /* fop_readdir I/O */
        kstat_named_init(&vsp->nreaddir, "nreaddir", KSTAT_DATA_UINT64);
        kstat_named_init(&vsp->readdir_bytes, "readdir_bytes",
            KSTAT_DATA_UINT64);
        /* fop_symlink */
        kstat_named_init(&vsp->nsymlink, "nsymlink", KSTAT_DATA_UINT64);
        /* fop_readlink */
        kstat_named_init(&vsp->nreadlink, "nreadlink", KSTAT_DATA_UINT64);
        /* fop_fsync */
        kstat_named_init(&vsp->nfsync, "nfsync", KSTAT_DATA_UINT64);
        /* fop_inactive */
        kstat_named_init(&vsp->ninactive, "ninactive", KSTAT_DATA_UINT64);
        /* fop_fid */
        kstat_named_init(&vsp->nfid, "nfid", KSTAT_DATA_UINT64);
        /* fop_rwlock */
        kstat_named_init(&vsp->nrwlock, "nrwlock", KSTAT_DATA_UINT64);
        /* fop_rwunlock */
        kstat_named_init(&vsp->nrwunlock, "nrwunlock", KSTAT_DATA_UINT64);
        /* fop_seek */
        kstat_named_init(&vsp->nseek, "nseek", KSTAT_DATA_UINT64);
        /* fop_cmp */
        kstat_named_init(&vsp->ncmp, "ncmp", KSTAT_DATA_UINT64);
        /* fop_frlock */
        kstat_named_init(&vsp->nfrlock, "nfrlock", KSTAT_DATA_UINT64);
        /* fop_space */
        kstat_named_init(&vsp->nspace, "nspace", KSTAT_DATA_UINT64);
        /* fop_realvp */
        kstat_named_init(&vsp->nrealvp, "nrealvp", KSTAT_DATA_UINT64);
        /* fop_getpage */
        kstat_named_init(&vsp->ngetpage, "ngetpage", KSTAT_DATA_UINT64);
        /* fop_putpage */
        kstat_named_init(&vsp->nputpage, "nputpage", KSTAT_DATA_UINT64);
        /* fop_map */
        kstat_named_init(&vsp->nmap, "nmap", KSTAT_DATA_UINT64);
        /* fop_addmap */
        kstat_named_init(&vsp->naddmap, "naddmap", KSTAT_DATA_UINT64);
        /* fop_delmap */
        kstat_named_init(&vsp->ndelmap, "ndelmap", KSTAT_DATA_UINT64);
        /* fop_poll */
        kstat_named_init(&vsp->npoll, "npoll", KSTAT_DATA_UINT64);
        /* fop_dump */
        kstat_named_init(&vsp->ndump, "ndump", KSTAT_DATA_UINT64);
        /* fop_pathconf */
        kstat_named_init(&vsp->npathconf, "npathconf", KSTAT_DATA_UINT64);
        /* fop_pageio */
        kstat_named_init(&vsp->npageio, "npageio", KSTAT_DATA_UINT64);
        /* fop_dumpctl */
        kstat_named_init(&vsp->ndumpctl, "ndumpctl", KSTAT_DATA_UINT64);
        /* fop_dispose */
        kstat_named_init(&vsp->ndispose, "ndispose", KSTAT_DATA_UINT64);
        /* fop_setsecattr */
        kstat_named_init(&vsp->nsetsecattr, "nsetsecattr", KSTAT_DATA_UINT64);
        /* fop_getsecattr */
        kstat_named_init(&vsp->ngetsecattr, "ngetsecattr", KSTAT_DATA_UINT64);
        /* fop_shrlock */
        kstat_named_init(&vsp->nshrlock, "nshrlock", KSTAT_DATA_UINT64);
        /* fop_vnevent */
        kstat_named_init(&vsp->nvnevent, "nvnevent", KSTAT_DATA_UINT64);
        /* fop_reqzcbuf */
        kstat_named_init(&vsp->nreqzcbuf, "nreqzcbuf", KSTAT_DATA_UINT64);
        /* fop_retzcbuf */
        kstat_named_init(&vsp->nretzcbuf, "nretzcbuf", KSTAT_DATA_UINT64);

        return (vsp);
}

/*
 * Creates a kstat structure associated with a vopstats structure.
 */
kstat_t *
new_vskstat(char *ksname, vopstats_t *vsp)
{
        kstat_t         *ksp;

        if (!vopstats_enabled) {
                return (NULL);
        }

        ksp = kstat_create("unix", 0, ksname, "misc", KSTAT_TYPE_NAMED,
            sizeof (vopstats_t)/sizeof (kstat_named_t),
            KSTAT_FLAG_VIRTUAL|KSTAT_FLAG_WRITABLE);
        if (ksp) {
                ksp->ks_data = vsp;
                kstat_install(ksp);
        }

        return (ksp);
}

/*
 * Called from vfsinit() to initialize the support mechanisms for vopstats
 */
void
vopstats_startup()
{
        if (!vopstats_enabled)
                return;

        /*
         * Creates the AVL tree which holds per-vfs vopstat anchors.  This
         * is necessary since we need to check if a kstat exists before we
         * attempt to create it.  Also, initialize its lock.
         */
        avl_create(&vskstat_tree, vska_compar, sizeof (vsk_anchor_t),
            offsetof(vsk_anchor_t, vsk_node));
        mutex_init(&vskstat_tree_lock, NULL, MUTEX_DEFAULT, NULL);

        vsk_anchor_cache = kmem_cache_create("vsk_anchor_cache",
            sizeof (vsk_anchor_t), sizeof (uintptr_t), NULL, NULL, NULL,
            NULL, NULL, 0);

        /*
         * Set up the array of pointers for the vopstats-by-FS-type.
         * The entries will be allocated/initialized as each file system
         * goes through modload/mod_installfs.
         */
        vopstats_fstype = (vopstats_t **)kmem_zalloc(
            (sizeof (vopstats_t *) * nfstype), KM_SLEEP);

        /* Set up the global vopstats initialization template */
        vs_templatep = create_vopstats_template();
}

/*
 * We need to have the all of the counters zeroed.
 * The initialization of the vopstats_t includes on the order of
 * 50 calls to kstat_named_init().  Rather that do that on every call,
 * we do it once in a template (vs_templatep) then bcopy it over.
 */
void
initialize_vopstats(vopstats_t *vsp)
{
        if (vsp == NULL)
                return;

        bcopy(vs_templatep, vsp, sizeof (vopstats_t));
}

/*
 * If possible, determine which vopstats by fstype to use and
 * return a pointer to the caller.
 */
vopstats_t *
get_fstype_vopstats(vfs_t *vfsp, struct vfssw *vswp)
{
        int             fstype = 0;     /* Index into vfssw[] */
        vopstats_t      *vsp = NULL;

        if (vfsp == NULL || (vfsp->vfs_flag & VFS_STATS) == 0 ||
            !vopstats_enabled)
                return (NULL);
        /*
         * Set up the fstype.  We go to so much trouble because all versions
         * of NFS use the same fstype in their vfs even though they have
         * distinct entries in the vfssw[] table.
         * NOTE: A special vfs (e.g., EIO_vfs) may not have an entry.
         */
        if (vswp) {
                fstype = vswp - vfssw;  /* Gets us the index */
        } else {
                fstype = vfsp->vfs_fstype;
        }

        /*
         * Point to the per-fstype vopstats. The only valid values are
         * non-zero positive values less than the number of vfssw[] table
         * entries.
         */
        if (fstype > 0 && fstype < nfstype) {
                vsp = vopstats_fstype[fstype];
        }

        return (vsp);
}

/*
 * Generate a kstat name, create the kstat structure, and allocate a
 * vsk_anchor_t to hold it together.  Return the pointer to the vsk_anchor_t
 * to the caller.  This must only be called from a mount.
 */
vsk_anchor_t *
get_vskstat_anchor(vfs_t *vfsp)
{
        char            kstatstr[KSTAT_STRLEN]; /* kstat name for vopstats */
        statvfs64_t     statvfsbuf;             /* Needed to find f_fsid */
        vsk_anchor_t    *vskp = NULL;           /* vfs <--> kstat anchor */
        kstat_t         *ksp;                   /* Ptr to new kstat */
        avl_index_t     where;                  /* Location in the AVL tree */

        if (vfsp == NULL || vfsp->vfs_implp == NULL ||
            (vfsp->vfs_flag & VFS_STATS) == 0 || !vopstats_enabled)
                return (NULL);

        /* Need to get the fsid to build a kstat name */
        if (VFS_STATVFS(vfsp, &statvfsbuf) == 0) {
                /* Create a name for our kstats based on fsid */
                (void) snprintf(kstatstr, KSTAT_STRLEN, "%s%lx",
                    VOPSTATS_STR, statvfsbuf.f_fsid);

                /* Allocate and initialize the vsk_anchor_t */
                vskp = kmem_cache_alloc(vsk_anchor_cache, KM_SLEEP);
                bzero(vskp, sizeof (*vskp));
                vskp->vsk_fsid = statvfsbuf.f_fsid;

                mutex_enter(&vskstat_tree_lock);
                if (avl_find(&vskstat_tree, vskp, &where) == NULL) {
                        avl_insert(&vskstat_tree, vskp, where);
                        mutex_exit(&vskstat_tree_lock);

                        /*
                         * Now that we've got the anchor in the AVL
                         * tree, we can create the kstat.
                         */
                        ksp = new_vskstat(kstatstr, &vfsp->vfs_vopstats);
                        if (ksp) {
                                vskp->vsk_ksp = ksp;
                        }
                } else {
                        /* Oops, found one! Release memory and lock. */
                        mutex_exit(&vskstat_tree_lock);
                        kmem_cache_free(vsk_anchor_cache, vskp);
                        vskp = NULL;
                }
        }
        return (vskp);
}

/*
 * We're in the process of tearing down the vfs and need to cleanup
 * the data structures associated with the vopstats. Must only be called
 * from dounmount().
 */
void
teardown_vopstats(vfs_t *vfsp)
{
        vsk_anchor_t    *vskap;
        avl_index_t     where;

        if (vfsp == NULL || vfsp->vfs_implp == NULL ||
            (vfsp->vfs_flag & VFS_STATS) == 0 || !vopstats_enabled)
                return;

        /* This is a safe check since VFS_STATS must be set (see above) */
        if ((vskap = vfsp->vfs_vskap) == NULL)
                return;

        /* Whack the pointer right away */
        vfsp->vfs_vskap = NULL;

        /* Lock the tree, remove the node, and delete the kstat */
        mutex_enter(&vskstat_tree_lock);
        if (avl_find(&vskstat_tree, vskap, &where)) {
                avl_remove(&vskstat_tree, vskap);
        }

        if (vskap->vsk_ksp) {
                kstat_delete(vskap->vsk_ksp);
        }
        mutex_exit(&vskstat_tree_lock);

        kmem_cache_free(vsk_anchor_cache, vskap);
}

/*
 * Read or write a vnode.  Called from kernel code.
 */
int
vn_rdwr(
        enum uio_rw rw,
        struct vnode *vp,
        caddr_t base,
        ssize_t len,
        offset_t offset,
        enum uio_seg seg,
        int ioflag,
        rlim64_t ulimit,        /* meaningful only if rw is UIO_WRITE */
        cred_t *cr,
        ssize_t *residp)
{
        struct uio uio;
        struct iovec iov;
        int error;
        int in_crit = 0;

        if (rw == UIO_WRITE && ISROFILE(vp))
                return (EROFS);

        if (len < 0)
                return (EIO);

        VOPXID_MAP_CR(vp, cr);

        iov.iov_base = base;
        iov.iov_len = len;
        uio.uio_iov = &iov;
        uio.uio_iovcnt = 1;
        uio.uio_loffset = offset;
        uio.uio_segflg = (short)seg;
        uio.uio_resid = len;
        uio.uio_llimit = ulimit;

        /*
         * We have to enter the critical region before calling fop_rwlock
         * to avoid a deadlock with ufs.
         */
        if (nbl_need_check(vp)) {
                int svmand;

                nbl_start_crit(vp, RW_READER);
                in_crit = 1;
                error = nbl_svmand(vp, cr, &svmand);
                if (error != 0)
                        goto done;
                if (nbl_conflict(vp, rw == UIO_WRITE ? NBL_WRITE : NBL_READ,
                    uio.uio_offset, uio.uio_resid, svmand, NULL)) {
                        error = EACCES;
                        goto done;
                }
        }

        (void) fop_rwlock(vp,
            rw == UIO_WRITE ? V_WRITELOCK_TRUE : V_WRITELOCK_FALSE, NULL);
        if (rw == UIO_WRITE) {
                uio.uio_fmode = FWRITE;
                uio.uio_extflg = UIO_COPY_DEFAULT;
                error = fop_write(vp, &uio, ioflag, cr, NULL);
        } else {
                uio.uio_fmode = FREAD;
                uio.uio_extflg = UIO_COPY_CACHED;
                error = fop_read(vp, &uio, ioflag, cr, NULL);
        }
        fop_rwunlock(vp,
            rw == UIO_WRITE ? V_WRITELOCK_TRUE : V_WRITELOCK_FALSE, NULL);
        if (residp)
                *residp = uio.uio_resid;
        else if (uio.uio_resid)
                error = EIO;

done:
        if (in_crit)
                nbl_end_crit(vp);
        return (error);
}

/*
 * Release a vnode.  Call fop_inactive on last reference or
 * decrement reference count.
 *
 * To avoid race conditions, the v_count is left at 1 for
 * the call to fop_inactive. This prevents another thread
 * from reclaiming and releasing the vnode *before* the
 * fop_inactive routine has a chance to destroy the vnode.
 * We can't have more than 1 thread calling fop_inactive
 * on a vnode.
 */
void
vn_rele(vnode_t *vp)
{
        VERIFY(vp->v_count > 0);
        mutex_enter(&vp->v_lock);
        if (vp->v_count == 1) {
                mutex_exit(&vp->v_lock);
                fop_inactive(vp, CRED(), NULL);
                return;
        }
        VN_RELE_LOCKED(vp);
        mutex_exit(&vp->v_lock);
}

/*
 * Release a vnode referenced by the DNLC. Multiple DNLC references are treated
 * as a single reference, so v_count is not decremented until the last DNLC hold
 * is released. This makes it possible to distinguish vnodes that are referenced
 * only by the DNLC.
 */
void
vn_rele_dnlc(vnode_t *vp)
{
        VERIFY((vp->v_count > 0) && (vp->v_count_dnlc > 0));
        mutex_enter(&vp->v_lock);
        if (--vp->v_count_dnlc == 0) {
                if (vp->v_count == 1) {
                        mutex_exit(&vp->v_lock);
                        fop_inactive(vp, CRED(), NULL);
                        return;
                }
                VN_RELE_LOCKED(vp);
        }
        mutex_exit(&vp->v_lock);
}

/*
 * Like vn_rele() except that it clears v_stream under v_lock.
 * This is used by sockfs when it dismantles the association between
 * the sockfs node and the vnode in the underlying file system.
 * v_lock has to be held to prevent a thread coming through the lookupname
 * path from accessing a stream head that is going away.
 */
void
vn_rele_stream(vnode_t *vp)
{
        VERIFY(vp->v_count > 0);
        mutex_enter(&vp->v_lock);
        vp->v_stream = NULL;
        if (vp->v_count == 1) {
                mutex_exit(&vp->v_lock);
                fop_inactive(vp, CRED(), NULL);
                return;
        }
        VN_RELE_LOCKED(vp);
        mutex_exit(&vp->v_lock);
}

static void
vn_rele_inactive(vnode_t *vp)
{
        fop_inactive(vp, CRED(), NULL);
}

/*
 * Like vn_rele() except if we are going to call fop_inactive() then do it
 * asynchronously using a taskq. This can avoid deadlocks caused by re-entering
 * the file system as a result of releasing the vnode. Note, file systems
 * already have to handle the race where the vnode is incremented before the
 * inactive routine is called and does its locking.
 *
 * Warning: Excessive use of this routine can lead to performance problems.
 * This is because taskqs throttle back allocation if too many are created.
 */
void
vn_rele_async(vnode_t *vp, taskq_t *taskq)
{
        VERIFY(vp->v_count > 0);
        mutex_enter(&vp->v_lock);
        if (vp->v_count == 1) {
                mutex_exit(&vp->v_lock);
                VERIFY(taskq_dispatch(taskq, (task_func_t *)vn_rele_inactive,
                    vp, TQ_SLEEP) != (uintptr_t)NULL);
                return;
        }
        VN_RELE_LOCKED(vp);
        mutex_exit(&vp->v_lock);
}

int
vn_open(
        char *pnamep,
        enum uio_seg seg,
        int filemode,
        int createmode,
        struct vnode **vpp,
        enum create crwhy,
        mode_t umask)
{
        return (vn_openat(pnamep, seg, filemode, createmode, vpp, crwhy,
            umask, NULL, -1));
}


/*
 * Open/create a vnode.
 * This may be callable by the kernel, the only known use
 * of user context being that the current user credentials
 * are used for permissions.  crwhy is defined iff filemode & FCREAT.
 */
int
vn_openat(
        char *pnamep,
        enum uio_seg seg,
        int filemode,
        int createmode,
        struct vnode **vpp,
        enum create crwhy,
        mode_t umask,
        struct vnode *startvp,
        int fd)
{
        struct vnode *vp;
        int mode;
        int accessflags;
        int error;
        int in_crit = 0;
        int open_done = 0;
        int shrlock_done = 0;
        struct vattr vattr;
        enum symfollow follow;
        int estale_retry = 0;
        struct shrlock shr;
        struct shr_locowner shr_own;

        if (filemode & FSEARCH)
                filemode |= FDIRECTORY;

        mode = 0;
        accessflags = 0;
        if (filemode & FREAD)
                mode |= VREAD;
        if (filemode & (FWRITE|FTRUNC))
                mode |= VWRITE;
        if (filemode & (FSEARCH|FEXEC|FXATTRDIROPEN))
                mode |= VEXEC;

        /* symlink interpretation */
        if (filemode & FNOFOLLOW)
                follow = NO_FOLLOW;
        else
                follow = FOLLOW;

        if (filemode & FAPPEND)
                accessflags |= V_APPEND;

top:
        if (filemode & FCREAT && !(filemode & FDIRECTORY)) {
                enum vcexcl excl;

                /* Wish to create a file. */
                vattr.va_type = VREG;
                vattr.va_mode = createmode;
                vattr.va_mask = AT_TYPE|AT_MODE;
                if (filemode & FTRUNC) {
                        vattr.va_size = 0;
                        vattr.va_mask |= AT_SIZE;
                }
                if (filemode & FEXCL)
                        excl = EXCL;
                else
                        excl = NONEXCL;

                if (error =
                    vn_createat(pnamep, seg, &vattr, excl, mode, &vp, crwhy,
                    (filemode & ~(FTRUNC|FEXCL)), umask, startvp))
                        return (error);
        } else {
                /* Wish to open a file.  Just look it up. */
                if (error = lookupnameat(pnamep, seg, follow,
                    NULLVPP, &vp, startvp)) {
                        if ((error == ESTALE) &&
                            fs_need_estale_retry(estale_retry++))
                                goto top;
                        return (error);
                }

                /*
                 * Get the attributes to check whether file is large.
                 * We do this only if the FOFFMAX flag is not set and
                 * only for regular files.
                 */

                if (!(filemode & FOFFMAX) && (vp->v_type == VREG)) {
                        vattr.va_mask = AT_SIZE;
                        if ((error = fop_getattr(vp, &vattr, 0,
                            CRED(), NULL))) {
                                goto out;
                        }
                        if (vattr.va_size > (uoff_t)MAXOFF32_T) {
                                /*
                                 * Large File API - regular open fails
                                 * if FOFFMAX flag is set in file mode
                                 */
                                error = EOVERFLOW;
                                goto out;
                        }
                }
                /*
                 * Can't write directories, active texts, or
                 * read-only filesystems.  Can't truncate files
                 * on which mandatory locking is in effect.
                 */
                if (filemode & (FWRITE|FTRUNC)) {
                        /*
                         * Allow writable directory if VDIROPEN flag is set.
                         */
                        if (vp->v_type == VDIR && !(vp->v_flag & VDIROPEN)) {
                                error = EISDIR;
                                goto out;
                        }
                        if (ISROFILE(vp)) {
                                error = EROFS;
                                goto out;
                        }
                        /*
                         * Can't truncate files on which
                         * sysv mandatory locking is in effect.
                         */
                        if (filemode & FTRUNC) {
                                vnode_t *rvp;

                                if (fop_realvp(vp, &rvp, NULL) != 0)
                                        rvp = vp;
                                if (rvp->v_filocks != NULL) {
                                        vattr.va_mask = AT_MODE;
                                        if ((error = fop_getattr(vp,
                                            &vattr, 0, CRED(), NULL)) == 0 &&
                                            MANDLOCK(vp, vattr.va_mode))
                                                error = EAGAIN;
                                }
                        }
                        if (error)
                                goto out;
                }
                /*
                 * Check permissions.
                 */
                if (error = fop_access(vp, mode, accessflags, CRED(), NULL))
                        goto out;
                /*
                 * Require FDIRECTORY to return a directory.
                 * Require FEXEC to return a regular file.
                 */
                if ((filemode & FDIRECTORY) && vp->v_type != VDIR) {
                        error = ENOTDIR;
                        goto out;
                }
                if ((filemode & FEXEC) && vp->v_type != VREG) {
                        error = ENOEXEC;        /* XXX: error code? */
                        goto out;
                }
        }

        /*
         * Do remaining checks for FNOFOLLOW and FNOLINKS.
         */
        if ((filemode & FNOFOLLOW) && vp->v_type == VLNK) {
                error = ELOOP;
                goto out;
        }
        if (filemode & FNOLINKS) {
                vattr.va_mask = AT_NLINK;
                if ((error = fop_getattr(vp, &vattr, 0, CRED(), NULL))) {
                        goto out;
                }
                if (vattr.va_nlink != 1) {
                        error = EMLINK;
                        goto out;
                }
        }

        /*
         * Opening a socket corresponding to the AF_UNIX pathname
         * in the filesystem name space is not supported.
         * However, VSOCK nodes in namefs are supported in order
         * to make fattach work for sockets.
         *
         * XXX This uses fop_realvp to distinguish between
         * an unopened namefs node (where fop_realvp returns a
         * different VSOCK vnode) and a VSOCK created by vn_create
         * in some file system (where fop_realvp would never return
         * a different vnode).
         */
        if (vp->v_type == VSOCK) {
                struct vnode *nvp;

                error = fop_realvp(vp, &nvp, NULL);
                if (error != 0 || nvp == NULL || nvp == vp ||
                    nvp->v_type != VSOCK) {
                        error = EOPNOTSUPP;
                        goto out;
                }
        }

        if ((vp->v_type == VREG) && nbl_need_check(vp)) {
                /* get share reservation */
                shr.s_access = 0;
                if (filemode & FWRITE)
                        shr.s_access |= F_WRACC;
                if (filemode & FREAD)
                        shr.s_access |= F_RDACC;
                shr.s_deny = 0;
                shr.s_sysid = 0;
                shr.s_pid = ttoproc(curthread)->p_pid;
                shr_own.sl_pid = shr.s_pid;
                shr_own.sl_id = fd;
                shr.s_own_len = sizeof (shr_own);
                shr.s_owner = (caddr_t)&shr_own;
                error = fop_shrlock(vp, F_SHARE_NBMAND, &shr, filemode, CRED(),
                    NULL);
                if (error)
                        goto out;
                shrlock_done = 1;

                /* nbmand conflict check if truncating file */
                if ((filemode & FTRUNC) && !(filemode & FCREAT)) {
                        nbl_start_crit(vp, RW_READER);
                        in_crit = 1;

                        vattr.va_mask = AT_SIZE;
                        if (error = fop_getattr(vp, &vattr, 0, CRED(), NULL))
                                goto out;
                        if (nbl_conflict(vp, NBL_WRITE, 0, vattr.va_size, 0,
                            NULL)) {
                                error = EACCES;
                                goto out;
                        }
                }
        }

        /*
         * Do opening protocol.
         */
        error = fop_open(&vp, filemode, CRED(), NULL);
        if (error)
                goto out;
        open_done = 1;

        /*
         * Truncate if required.
         */
        if ((filemode & FTRUNC) && !(filemode & FCREAT)) {
                vattr.va_size = 0;
                vattr.va_mask = AT_SIZE;
                if ((error = fop_setattr(vp, &vattr, 0, CRED(), NULL)) != 0)
                        goto out;
        }
out:
        ASSERT(vp->v_count > 0);

        if (in_crit) {
                nbl_end_crit(vp);
                in_crit = 0;
        }
        if (error) {
                if (open_done) {
                        (void) fop_close(vp, filemode, 1, 0, CRED(),
                            NULL);
                        open_done = 0;
                        shrlock_done = 0;
                }
                if (shrlock_done) {
                        (void) fop_shrlock(vp, F_UNSHARE, &shr, 0, CRED(),
                            NULL);
                        shrlock_done = 0;
                }

                /*
                 * The following clause was added to handle a problem
                 * with NFS consistency.  It is possible that a lookup
                 * of the file to be opened succeeded, but the file
                 * itself doesn't actually exist on the server.  This
                 * is chiefly due to the DNLC containing an entry for
                 * the file which has been removed on the server.  In
                 * this case, we just start over.  If there was some
                 * other cause for the ESTALE error, then the lookup
                 * of the file will fail and the error will be returned
                 * above instead of looping around from here.
                 */
                VN_RELE(vp);
                if ((error == ESTALE) && fs_need_estale_retry(estale_retry++))
                        goto top;
        } else
                *vpp = vp;
        return (error);
}

/*
 * The following two accessor functions are for the NFSv4 server.  Since there
 * is no fop_open_UP/DOWNGRADE we need a way for the NFS server to keep the
 * vnode open counts correct when a client "upgrades" an open or does an
 * open_downgrade.  In NFS, an upgrade or downgrade can not only change the
 * open mode (add or subtract read or write), but also change the share/deny
 * modes.  However, share reservations are not integrated with OPEN, yet, so
 * we need to handle each separately.  These functions are cleaner than having
 * the NFS server manipulate the counts directly, however, nobody else should
 * use these functions.
 */
void
vn_open_upgrade(
        vnode_t *vp,
        int filemode)
{
        ASSERT(vp->v_type == VREG);

        if (filemode & FREAD)
                atomic_inc_32(&vp->v_rdcnt);
        if (filemode & FWRITE)
                atomic_inc_32(&vp->v_wrcnt);

}

void
vn_open_downgrade(
        vnode_t *vp,
        int filemode)
{
        ASSERT(vp->v_type == VREG);

        if (filemode & FREAD) {
                ASSERT(vp->v_rdcnt > 0);
                atomic_dec_32(&vp->v_rdcnt);
        }
        if (filemode & FWRITE) {
                ASSERT(vp->v_wrcnt > 0);
                atomic_dec_32(&vp->v_wrcnt);
        }

}

int
vn_create(
        char *pnamep,
        enum uio_seg seg,
        struct vattr *vap,
        enum vcexcl excl,
        int mode,
        struct vnode **vpp,
        enum create why,
        int flag,
        mode_t umask)
{
        return (vn_createat(pnamep, seg, vap, excl, mode, vpp, why, flag,
            umask, NULL));
}

/*
 * Create a vnode (makenode).
 */
int
vn_createat(
        char *pnamep,
        enum uio_seg seg,
        struct vattr *vap,
        enum vcexcl excl,
        int mode,
        struct vnode **vpp,
        enum create why,
        int flag,
        mode_t umask,
        struct vnode *startvp)
{
        struct vnode *dvp;      /* ptr to parent dir vnode */
        struct vnode *vp = NULL;
        struct pathname pn;
        int error;
        int in_crit = 0;
        struct vattr vattr;
        enum symfollow follow;
        int estale_retry = 0;
        uint32_t auditing = AU_AUDITING();

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

        /* symlink interpretation */
        if ((flag & FNOFOLLOW) || excl == EXCL)
                follow = NO_FOLLOW;
        else
                follow = FOLLOW;
        flag &= ~(FNOFOLLOW|FNOLINKS);

top:
        /*
         * Lookup directory.
         * If new object is a file, call lower level to create it.
         * Note that it is up to the lower level to enforce exclusive
         * creation, if the file is already there.
         * This allows the lower level to do whatever
         * locking or protocol that is needed to prevent races.
         * If the new object is directory call lower level to make
         * the new directory, with "." and "..".
         */
        if (error = pn_get(pnamep, seg, &pn))
                return (error);
        if (auditing)
                audit_vncreate_start();
        dvp = NULL;
        *vpp = NULL;
        /*
         * lookup will find the parent directory for the vnode.
         * When it is done the pn holds the name of the entry
         * in the directory.
         * If this is a non-exclusive create we also find the node itself.
         */
        error = lookuppnat(&pn, NULL, follow, &dvp,
            (excl == EXCL) ? NULLVPP : vpp, startvp);
        if (error) {
                pn_free(&pn);
                if ((error == ESTALE) && fs_need_estale_retry(estale_retry++))
                        goto top;
                if (why == CRMKDIR && error == EINVAL)
                        error = EEXIST;         /* SVID */
                return (error);
        }

        if (why != CRMKNOD)
                vap->va_mode &= ~VSVTX;

        /*
         * If default ACLs are defined for the directory don't apply the
         * umask if umask is passed.
         */

        if (umask) {

                vsecattr_t vsec;

                vsec.vsa_aclcnt = 0;
                vsec.vsa_aclentp = NULL;
                vsec.vsa_dfaclcnt = 0;
                vsec.vsa_dfaclentp = NULL;
                vsec.vsa_mask = VSA_DFACLCNT;
                error = fop_getsecattr(dvp, &vsec, 0, CRED(), NULL);
                /*
                 * If error is ENOSYS then treat it as no error
                 * Don't want to force all file systems to support
                 * aclent_t style of ACL's.
                 */
                if (error == ENOSYS)
                        error = 0;
                if (error) {
                        if (*vpp != NULL)
                                VN_RELE(*vpp);
                        goto out;
                } else {
                        /*
                         * Apply the umask if no default ACLs.
                         */
                        if (vsec.vsa_dfaclcnt == 0)
                                vap->va_mode &= ~umask;

                        /*
                         * fop_getsecattr() may have allocated memory for
                         * ACLs we didn't request, so double-check and
                         * free it if necessary.
                         */
                        if (vsec.vsa_aclcnt && vsec.vsa_aclentp != NULL)
                                kmem_free((caddr_t)vsec.vsa_aclentp,
                                    vsec.vsa_aclcnt * sizeof (aclent_t));
                        if (vsec.vsa_dfaclcnt && vsec.vsa_dfaclentp != NULL)
                                kmem_free((caddr_t)vsec.vsa_dfaclentp,
                                    vsec.vsa_dfaclcnt * sizeof (aclent_t));
                }
        }

        /*
         * In general we want to generate EROFS if the file system is
         * readonly.  However, POSIX (IEEE Std. 1003.1) section 5.3.1
         * documents the open system call, and it says that O_CREAT has no
         * effect if the file already exists.  Bug 1119649 states
         * that open(path, O_CREAT, ...) fails when attempting to open an
         * existing file on a read only file system.  Thus, the first part
         * of the following if statement has 3 checks:
         *      if the file exists &&
         *              it is being open with write access &&
         *              the file system is read only
         *      then generate EROFS
         */
        if ((*vpp != NULL && (mode & VWRITE) && ISROFILE(*vpp)) ||
            (*vpp == NULL && dvp->v_vfsp->vfs_flag & VFS_RDONLY)) {
                if (*vpp)
                        VN_RELE(*vpp);
                error = EROFS;
        } else if (excl == NONEXCL && *vpp != NULL) {
                vnode_t *rvp;

                /*
                 * File already exists.  If a mandatory lock has been
                 * applied, return error.
                 */
                vp = *vpp;
                if (fop_realvp(vp, &rvp, NULL) != 0)
                        rvp = vp;
                if ((vap->va_mask & AT_SIZE) && nbl_need_check(vp)) {
                        nbl_start_crit(vp, RW_READER);
                        in_crit = 1;
                }
                if (rvp->v_filocks != NULL || rvp->v_shrlocks != NULL) {
                        vattr.va_mask = AT_MODE|AT_SIZE;
                        if (error = fop_getattr(vp, &vattr, 0, CRED(), NULL)) {
                                goto out;
                        }
                        if (MANDLOCK(vp, vattr.va_mode)) {
                                error = EAGAIN;
                                goto out;
                        }
                        /*
                         * File cannot be truncated if non-blocking mandatory
                         * locks are currently on the file.
                         */
                        if ((vap->va_mask & AT_SIZE) && in_crit) {
                                uoff_t offset;
                                ssize_t length;

                                offset = vap->va_size > vattr.va_size ?
                                    vattr.va_size : vap->va_size;
                                length = vap->va_size > vattr.va_size ?
                                    vap->va_size - vattr.va_size :
                                    vattr.va_size - vap->va_size;
                                if (nbl_conflict(vp, NBL_WRITE, offset,
                                    length, 0, NULL)) {
                                        error = EACCES;
                                        goto out;
                                }
                        }
                }

                /*
                 * If the file is the root of a VFS, we've crossed a
                 * mount point and the "containing" directory that we
                 * acquired above (dvp) is irrelevant because it's in
                 * a different file system.  We apply fop_create to the
                 * target itself instead of to the containing directory
                 * and supply a null path name to indicate (conventionally)
                 * the node itself as the "component" of interest.
                 *
                 * The call to fop_create() is necessary to ensure
                 * that the appropriate permission checks are made,
                 * i.e. EISDIR, EACCES, etc.  We already know that vpp
                 * exists since we are in the else condition where this
                 * was checked.
                 */
                if (vp->v_flag & VROOT) {
                        ASSERT(why != CRMKDIR);
                        error = fop_create(vp, "", vap, excl, mode, vpp,
                            CRED(), flag, NULL, NULL);
                        /*
                         * If the create succeeded, it will have created a
                         * new reference on a new vnode (*vpp) in the child
                         * file system, so we want to drop our reference on
                         * the old (vp) upon exit.
                         */
                        goto out;
                }

                /*
                 * Large File API - non-large open (FOFFMAX flag not set)
                 * of regular file fails if the file size exceeds MAXOFF32_T.
                 */
                if (why != CRMKDIR &&
                    !(flag & FOFFMAX) &&
                    (vp->v_type == VREG)) {
                        vattr.va_mask = AT_SIZE;
                        if ((error = fop_getattr(vp, &vattr, 0,
                            CRED(), NULL))) {
                                goto out;
                        }
                        if ((vattr.va_size > (uoff_t)MAXOFF32_T)) {
                                error = EOVERFLOW;
                                goto out;
                        }
                }
        }

        if (error == 0) {
                /*
                 * Call mkdir() if specified, otherwise create().
                 */
                int must_be_dir = pn_fixslash(&pn);     /* trailing '/'? */

                if (why == CRMKDIR)
                        /*
                         * N.B., if vn_createat() ever requests
                         * case-insensitive behavior then it will need
                         * to be passed to fop_mkdir().  fop_create()
                         * will already get it via "flag"
                         */
                        error = fop_mkdir(dvp, pn.pn_path, vap, vpp, CRED(),
                            NULL, 0, NULL);
                else if (!must_be_dir)
                        error = fop_create(dvp, pn.pn_path, vap,
                            excl, mode, vpp, CRED(), flag, NULL, NULL);
                else
                        error = ENOTDIR;
        }

out:

        if (auditing)
                audit_vncreate_finish(*vpp, error);
        if (in_crit) {
                nbl_end_crit(vp);
                in_crit = 0;
        }
        if (vp != NULL) {
                VN_RELE(vp);
                vp = NULL;
        }
        pn_free(&pn);
        VN_RELE(dvp);
        /*
         * The following clause was added to handle a problem
         * with NFS consistency.  It is possible that a lookup
         * of the file to be created succeeded, but the file
         * itself doesn't actually exist on the server.  This
         * is chiefly due to the DNLC containing an entry for
         * the file which has been removed on the server.  In
         * this case, we just start over.  If there was some
         * other cause for the ESTALE error, then the lookup
         * of the file will fail and the error will be returned
         * above instead of looping around from here.
         */
        if ((error == ESTALE) && fs_need_estale_retry(estale_retry++))
                goto top;
        return (error);
}

int
vn_link(char *from, char *to, enum uio_seg seg)
{
        return (vn_linkat(NULL, from, NO_FOLLOW, NULL, to, seg));
}

int
vn_linkat(vnode_t *fstartvp, char *from, enum symfollow follow,
    vnode_t *tstartvp, char *to, enum uio_seg seg)
{
        struct vnode *fvp;              /* from vnode ptr */
        struct vnode *tdvp;             /* to directory vnode ptr */
        struct pathname pn;
        int error;
        struct vattr vattr;
        dev_t fsid;
        int estale_retry = 0;
        uint32_t auditing = AU_AUDITING();

top:
        fvp = tdvp = NULL;
        if (error = pn_get(to, seg, &pn))
                return (error);
        if (auditing && fstartvp != NULL)
                audit_setfsat_path(1);
        if (error = lookupnameat(from, seg, follow, NULLVPP, &fvp, fstartvp))
                goto out;
        if (auditing && tstartvp != NULL)
                audit_setfsat_path(3);
        if (error = lookuppnat(&pn, NULL, NO_FOLLOW, &tdvp, NULLVPP, tstartvp))
                goto out;
        /*
         * Make sure both source vnode and target directory vnode are
         * in the same vfs and that it is writeable.
         */
        vattr.va_mask = AT_FSID;
        if (error = fop_getattr(fvp, &vattr, 0, CRED(), NULL))
                goto out;
        fsid = vattr.va_fsid;
        vattr.va_mask = AT_FSID;
        if (error = fop_getattr(tdvp, &vattr, 0, CRED(), NULL))
                goto out;
        if (fsid != vattr.va_fsid) {
                error = EXDEV;
                goto out;
        }
        if (tdvp->v_vfsp->vfs_flag & VFS_RDONLY) {
                error = EROFS;
                goto out;
        }
        /*
         * Do the link.
         */
        (void) pn_fixslash(&pn);
        error = fop_link(tdvp, fvp, pn.pn_path, CRED(), NULL, 0);
out:
        pn_free(&pn);
        if (fvp)
                VN_RELE(fvp);
        if (tdvp)
                VN_RELE(tdvp);
        if ((error == ESTALE) && fs_need_estale_retry(estale_retry++))
                goto top;
        return (error);
}

int
vn_rename(char *from, char *to, enum uio_seg seg)
{
        return (vn_renameat(NULL, from, NULL, to, seg));
}

int
vn_renameat(vnode_t *fdvp, char *fname, vnode_t *tdvp,
    char *tname, enum uio_seg seg)
{
        int error;
        struct vattr vattr;
        struct pathname fpn;            /* from pathname */
        struct pathname tpn;            /* to pathname */
        dev_t fsid;
        int in_crit_src, in_crit_targ;
        vnode_t *fromvp, *fvp;
        vnode_t *tovp, *targvp;
        int estale_retry = 0;
        uint32_t auditing = AU_AUDITING();

top:
        fvp = fromvp = tovp = targvp = NULL;
        in_crit_src = in_crit_targ = 0;
        /*
         * Get to and from pathnames.
         */
        if (error = pn_get(fname, seg, &fpn))
                return (error);
        if (error = pn_get(tname, seg, &tpn)) {
                pn_free(&fpn);
                return (error);
        }

        /*
         * First we need to resolve the correct directories
         * The passed in directories may only be a starting point,
         * but we need the real directories the file(s) live in.
         * For example the fname may be something like usr/lib/sparc
         * and we were passed in the / directory, but we need to
         * use the lib directory for the rename.
         */

        if (auditing && fdvp != NULL)
                audit_setfsat_path(1);
        /*
         * Lookup to and from directories.
         */
        if (error = lookuppnat(&fpn, NULL, NO_FOLLOW, &fromvp, &fvp, fdvp)) {
                goto out;
        }

        /*
         * Make sure there is an entry.
         */
        if (fvp == NULL) {
                error = ENOENT;
                goto out;
        }

        if (auditing && tdvp != NULL)
                audit_setfsat_path(3);
        if (error = lookuppnat(&tpn, NULL, NO_FOLLOW, &tovp, &targvp, tdvp)) {
                goto out;
        }

        /*
         * Make sure both the from vnode directory and the to directory
         * are in the same vfs and the to directory is writable.
         * We check fsid's, not vfs pointers, so loopback fs works.
         */
        if (fromvp != tovp) {
                vattr.va_mask = AT_FSID;
                if (error = fop_getattr(fromvp, &vattr, 0, CRED(), NULL))
                        goto out;
                fsid = vattr.va_fsid;
                vattr.va_mask = AT_FSID;
                if (error = fop_getattr(tovp, &vattr, 0, CRED(), NULL))
                        goto out;
                if (fsid != vattr.va_fsid) {
                        error = EXDEV;
                        goto out;
                }
        }

        if (tovp->v_vfsp->vfs_flag & VFS_RDONLY) {
                error = EROFS;
                goto out;
        }

        /*
         * Make sure "from" vp is not a mount point.
         * Note, lookup did traverse() already, so
         * we'll be looking at the mounted FS root.
         * (but allow files like mnttab)
         */
        if ((fvp->v_flag & VROOT) != 0 && fvp->v_type == VDIR) {
                error = EBUSY;
                goto out;
        }

        if (targvp && (fvp != targvp)) {
                nbl_start_crit(targvp, RW_READER);
                in_crit_targ = 1;
                if (nbl_conflict(targvp, NBL_REMOVE, 0, 0, 0, NULL)) {
                        error = EACCES;
                        goto out;
                }
        }

        if (nbl_need_check(fvp)) {
                nbl_start_crit(fvp, RW_READER);
                in_crit_src = 1;
                if (nbl_conflict(fvp, NBL_RENAME, 0, 0, 0, NULL)) {
                        error = EACCES;
                        goto out;
                }
        }

        /*
         * Do the rename.
         */
        (void) pn_fixslash(&tpn);
        error = fop_rename(fromvp, fpn.pn_path, tovp, tpn.pn_path, CRED(),
            NULL, 0);

out:
        pn_free(&fpn);
        pn_free(&tpn);
        if (in_crit_src)
                nbl_end_crit(fvp);
        if (in_crit_targ)
                nbl_end_crit(targvp);
        if (fromvp)
                VN_RELE(fromvp);
        if (tovp)
                VN_RELE(tovp);
        if (targvp)
                VN_RELE(targvp);
        if (fvp)
                VN_RELE(fvp);
        if ((error == ESTALE) && fs_need_estale_retry(estale_retry++))
                goto top;
        return (error);
}

/*
 * Remove a file or directory.
 */
int
vn_remove(char *fnamep, enum uio_seg seg, enum rm dirflag)
{
        return (vn_removeat(NULL, fnamep, seg, dirflag));
}

int
vn_removeat(vnode_t *startvp, char *fnamep, enum uio_seg seg, enum rm dirflag)
{
        struct vnode *vp;               /* entry vnode */
        struct vnode *dvp;              /* ptr to parent dir vnode */
        struct vnode *coveredvp;
        struct pathname pn;             /* name of entry */
        enum vtype vtype;
        int error;
        struct vfs *vfsp;
        struct vfs *dvfsp;      /* ptr to parent dir vfs */
        int in_crit = 0;
        int estale_retry = 0;

top:
        if (error = pn_get(fnamep, seg, &pn))
                return (error);
        dvp = vp = NULL;
        if (error = lookuppnat(&pn, NULL, NO_FOLLOW, &dvp, &vp, startvp)) {
                pn_free(&pn);
                if ((error == ESTALE) && fs_need_estale_retry(estale_retry++))
                        goto top;
                return (error);
        }

        /*
         * Make sure there is an entry.
         */
        if (vp == NULL) {
                error = ENOENT;
                goto out;
        }

        vfsp = vp->v_vfsp;
        dvfsp = dvp->v_vfsp;

        /*
         * If the named file is the root of a mounted filesystem, fail,
         * unless it's marked unlinkable.  In that case, unmount the
         * filesystem and proceed to unlink the covered vnode.  (If the
         * covered vnode is a directory, use rmdir instead of unlink,
         * to avoid file system corruption.)
         */
        if (vp->v_flag & VROOT) {
                if ((vfsp->vfs_flag & VFS_UNLINKABLE) == 0) {
                        error = EBUSY;
                        goto out;
                }

                /*
                 * Namefs specific code starts here.
                 */

                if (dirflag == RMDIRECTORY) {
                        /*
                         * User called rmdir(2) on a file that has
                         * been namefs mounted on top of.  Since
                         * namefs doesn't allow directories to
                         * be mounted on other files we know
                         * vp is not of type VDIR so fail to operation.
                         */
                        error = ENOTDIR;
                        goto out;
                }

                /*
                 * If VROOT is still set after grabbing vp->v_lock,
                 * noone has finished nm_unmount so far and coveredvp
                 * is valid.
                 * If we manage to grab vn_vfswlock(coveredvp) before releasing
                 * vp->v_lock, any race window is eliminated.
                 */

                mutex_enter(&vp->v_lock);
                if ((vp->v_flag & VROOT) == 0) {
                        /* Someone beat us to the unmount */
                        mutex_exit(&vp->v_lock);
                        error = EBUSY;
                        goto out;
                }
                vfsp = vp->v_vfsp;
                coveredvp = vfsp->vfs_vnodecovered;
                ASSERT(coveredvp);
                /*
                 * Note: Implementation of vn_vfswlock shows that ordering of
                 * v_lock / vn_vfswlock is not an issue here.
                 */
                error = vn_vfswlock(coveredvp);
                mutex_exit(&vp->v_lock);

                if (error)
                        goto out;

                VN_HOLD(coveredvp);
                VN_RELE(vp);
                error = dounmount(vfsp, 0, CRED());

                /*
                 * Unmounted the namefs file system; now get
                 * the object it was mounted over.
                 */
                vp = coveredvp;
                /*
                 * If namefs was mounted over a directory, then
                 * we want to use rmdir() instead of unlink().
                 */
                if (vp->v_type == VDIR)
                        dirflag = RMDIRECTORY;

                if (error)
                        goto out;
        }

        /*
         * Make sure filesystem is writeable.
         * We check the parent directory's vfs in case this is an lofs vnode.
         */
        if (dvfsp && dvfsp->vfs_flag & VFS_RDONLY) {
                error = EROFS;
                goto out;
        }

        vtype = vp->v_type;

        /*
         * If there is the possibility of an nbmand share reservation, make
         * sure it's okay to remove the file.  Keep a reference to the
         * vnode, so that we can exit the nbl critical region after
         * calling fop_remove.
         * If there is no possibility of an nbmand share reservation,
         * release the vnode reference now.  Filesystems like NFS may
         * behave differently if there is an extra reference, so get rid of
         * this one.  Fortunately, we can't have nbmand mounts on NFS
         * filesystems.
         */
        if (nbl_need_check(vp)) {
                nbl_start_crit(vp, RW_READER);
                in_crit = 1;
                if (nbl_conflict(vp, NBL_REMOVE, 0, 0, 0, NULL)) {
                        error = EACCES;
                        goto out;
                }
        } else {
                VN_RELE(vp);
                vp = NULL;
        }

        if (dirflag == RMDIRECTORY) {
                /*
                 * Caller is using rmdir(2), which can only be applied to
                 * directories.
                 */
                if (vtype != VDIR) {
                        error = ENOTDIR;
                } else {
                        vnode_t *cwd;
                        proc_t *pp = curproc;

                        mutex_enter(&pp->p_lock);
                        cwd = PTOU(pp)->u_cdir;
                        VN_HOLD(cwd);
                        mutex_exit(&pp->p_lock);
                        error = fop_rmdir(dvp, pn.pn_path, cwd, CRED(),
                            NULL, 0);
                        VN_RELE(cwd);
                }
        } else {
                /*
                 * Unlink(2) can be applied to anything.
                 */
                error = fop_remove(dvp, pn.pn_path, CRED(), NULL, 0);
        }

out:
        pn_free(&pn);
        if (in_crit) {
                nbl_end_crit(vp);
                in_crit = 0;
        }
        if (vp != NULL)
                VN_RELE(vp);
        if (dvp != NULL)
                VN_RELE(dvp);
        if ((error == ESTALE) && fs_need_estale_retry(estale_retry++))
                goto top;
        return (error);
}

/*
 * Utility function to compare equality of vnodes.
 * Compare the underlying real vnodes, if there are underlying vnodes.
 * This is a more thorough comparison than the VN_CMP() macro provides.
 */
int
vn_compare(vnode_t *vp1, vnode_t *vp2)
{
        vnode_t *realvp;

        if (vp1 != NULL && fop_realvp(vp1, &realvp, NULL) == 0)
                vp1 = realvp;
        if (vp2 != NULL && fop_realvp(vp2, &realvp, NULL) == 0)
                vp2 = realvp;
        return (VN_CMP(vp1, vp2));
}

/*
 * The number of locks to hash into.  This value must be a power
 * of 2 minus 1 and should probably also be prime.
 */
#define NUM_BUCKETS     1023

struct  vn_vfslocks_bucket {
        kmutex_t vb_lock;
        vn_vfslocks_entry_t *vb_list;
        char pad[64 - sizeof (kmutex_t) - sizeof (void *)];
};

/*
 * Total number of buckets will be NUM_BUCKETS + 1 .
 */

#pragma align   64(vn_vfslocks_buckets)
static  struct vn_vfslocks_bucket       vn_vfslocks_buckets[NUM_BUCKETS + 1];

#define VN_VFSLOCKS_SHIFT       9

#define VN_VFSLOCKS_HASH(vfsvpptr)      \
        ((((intptr_t)(vfsvpptr)) >> VN_VFSLOCKS_SHIFT) & NUM_BUCKETS)

/*
 * vn_vfslocks_getlock() uses an HASH scheme to generate
 * rwstlock using vfs/vnode pointer passed to it.
 *
 * vn_vfslocks_rele() releases a reference in the
 * HASH table which allows the entry allocated by
 * vn_vfslocks_getlock() to be freed at a later
 * stage when the refcount drops to zero.
 */

vn_vfslocks_entry_t *
vn_vfslocks_getlock(void *vfsvpptr)
{
        struct vn_vfslocks_bucket *bp;
        vn_vfslocks_entry_t *vep;
        vn_vfslocks_entry_t *tvep;

        ASSERT(vfsvpptr != NULL);
        bp = &vn_vfslocks_buckets[VN_VFSLOCKS_HASH(vfsvpptr)];

        mutex_enter(&bp->vb_lock);
        for (vep = bp->vb_list; vep != NULL; vep = vep->ve_next) {
                if (vep->ve_vpvfs == vfsvpptr) {
                        vep->ve_refcnt++;
                        mutex_exit(&bp->vb_lock);
                        return (vep);
                }
        }
        mutex_exit(&bp->vb_lock);
        vep = kmem_alloc(sizeof (*vep), KM_SLEEP);
        rwst_init(&vep->ve_lock, NULL, RW_DEFAULT, NULL);
        vep->ve_vpvfs = (char *)vfsvpptr;
        vep->ve_refcnt = 1;
        mutex_enter(&bp->vb_lock);
        for (tvep = bp->vb_list; tvep != NULL; tvep = tvep->ve_next) {
                if (tvep->ve_vpvfs == vfsvpptr) {
                        tvep->ve_refcnt++;
                        mutex_exit(&bp->vb_lock);

                        /*
                         * There is already an entry in the hash
                         * destroy what we just allocated.
                         */
                        rwst_destroy(&vep->ve_lock);
                        kmem_free(vep, sizeof (*vep));
                        return (tvep);
                }
        }
        vep->ve_next = bp->vb_list;
        bp->vb_list = vep;
        mutex_exit(&bp->vb_lock);
        return (vep);
}

void
vn_vfslocks_rele(vn_vfslocks_entry_t *vepent)
{
        struct vn_vfslocks_bucket *bp;
        vn_vfslocks_entry_t *vep;
        vn_vfslocks_entry_t *pvep;

        ASSERT(vepent != NULL);
        ASSERT(vepent->ve_vpvfs != NULL);

        bp = &vn_vfslocks_buckets[VN_VFSLOCKS_HASH(vepent->ve_vpvfs)];

        mutex_enter(&bp->vb_lock);
        vepent->ve_refcnt--;

        if ((int32_t)vepent->ve_refcnt < 0)
                cmn_err(CE_PANIC, "vn_vfslocks_rele: refcount negative");

        if (vepent->ve_refcnt == 0) {
                for (vep = bp->vb_list; vep != NULL; vep = vep->ve_next) {
                        if (vep->ve_vpvfs == vepent->ve_vpvfs) {
                                if (bp->vb_list == vep)
                                        bp->vb_list = vep->ve_next;
                                else {
                                        /* LINTED */
                                        pvep->ve_next = vep->ve_next;
                                }
                                mutex_exit(&bp->vb_lock);
                                rwst_destroy(&vep->ve_lock);
                                kmem_free(vep, sizeof (*vep));
                                return;
                        }
                        pvep = vep;
                }
                cmn_err(CE_PANIC, "vn_vfslocks_rele: vp/vfs not found");
        }
        mutex_exit(&bp->vb_lock);
}

/*
 * vn_vfswlock_wait is used to implement a lock which is logically a writers
 * lock protecting the v_vfsmountedhere field.
 * vn_vfswlock_wait has been modified to be similar to vn_vfswlock,
 * except that it blocks to acquire the lock VVFSLOCK.
 *
 * traverse() and routines re-implementing part of traverse (e.g. autofs)
 * need to hold this lock. mount(), vn_rename(), vn_remove() and so on
 * need the non-blocking version of the writers lock i.e. vn_vfswlock
 */
int
vn_vfswlock_wait(vnode_t *vp)
{
        int retval;
        vn_vfslocks_entry_t *vpvfsentry;
        ASSERT(vp != NULL);

        vpvfsentry = vn_vfslocks_getlock(vp);
        retval = rwst_enter_sig(&vpvfsentry->ve_lock, RW_WRITER);

        if (retval == EINTR) {
                vn_vfslocks_rele(vpvfsentry);
                return (EINTR);
        }
        return (retval);
}

int
vn_vfsrlock_wait(vnode_t *vp)
{
        int retval;
        vn_vfslocks_entry_t *vpvfsentry;
        ASSERT(vp != NULL);

        vpvfsentry = vn_vfslocks_getlock(vp);
        retval = rwst_enter_sig(&vpvfsentry->ve_lock, RW_READER);

        if (retval == EINTR) {
                vn_vfslocks_rele(vpvfsentry);
                return (EINTR);
        }

        return (retval);
}


/*
 * vn_vfswlock is used to implement a lock which is logically a writers lock
 * protecting the v_vfsmountedhere field.
 */
int
vn_vfswlock(vnode_t *vp)
{
        vn_vfslocks_entry_t *vpvfsentry;

        /*
         * If vp is NULL then somebody is trying to lock the covered vnode
         * of /.  (vfs_vnodecovered is NULL for /).  This situation will
         * only happen when unmounting /.  Since that operation will fail
         * anyway, return EBUSY here instead of in VFS_UNMOUNT.
         */
        if (vp == NULL)
                return (EBUSY);

        vpvfsentry = vn_vfslocks_getlock(vp);

        if (rwst_tryenter(&vpvfsentry->ve_lock, RW_WRITER))
                return (0);

        vn_vfslocks_rele(vpvfsentry);
        return (EBUSY);
}

int
vn_vfsrlock(vnode_t *vp)
{
        vn_vfslocks_entry_t *vpvfsentry;

        /*
         * If vp is NULL then somebody is trying to lock the covered vnode
         * of /.  (vfs_vnodecovered is NULL for /).  This situation will
         * only happen when unmounting /.  Since that operation will fail
         * anyway, return EBUSY here instead of in VFS_UNMOUNT.
         */
        if (vp == NULL)
                return (EBUSY);

        vpvfsentry = vn_vfslocks_getlock(vp);

        if (rwst_tryenter(&vpvfsentry->ve_lock, RW_READER))
                return (0);

        vn_vfslocks_rele(vpvfsentry);
        return (EBUSY);
}

void
vn_vfsunlock(vnode_t *vp)
{
        vn_vfslocks_entry_t *vpvfsentry;

        /*
         * ve_refcnt needs to be decremented twice.
         * 1. To release refernce after a call to vn_vfslocks_getlock()
         * 2. To release the reference from the locking routines like
         *    vn_vfsrlock/vn_vfswlock etc,.
         */
        vpvfsentry = vn_vfslocks_getlock(vp);
        vn_vfslocks_rele(vpvfsentry);

        rwst_exit(&vpvfsentry->ve_lock);
        vn_vfslocks_rele(vpvfsentry);
}

int
vn_vfswlock_held(vnode_t *vp)
{
        int held;
        vn_vfslocks_entry_t *vpvfsentry;

        ASSERT(vp != NULL);

        vpvfsentry = vn_vfslocks_getlock(vp);
        held = rwst_lock_held(&vpvfsentry->ve_lock, RW_WRITER);

        vn_vfslocks_rele(vpvfsentry);
        return (held);
}


/*
 * Vnode cache.
 */

/* ARGSUSED */
static int
vn_cache_constructor(void *buf, void *cdrarg, int kmflags)
{
        struct vnode *vp;

        vp = buf;

        mutex_init(&vp->v_lock, NULL, MUTEX_DEFAULT, NULL);
        mutex_init(&vp->v_vsd_lock, NULL, MUTEX_DEFAULT, NULL);
        cv_init(&vp->v_cv, NULL, CV_DEFAULT, NULL);
        rw_init(&vp->v_nbllock, NULL, RW_DEFAULT, NULL);
        vp->v_femhead = NULL;   /* Must be done before vn_reinit() */
        vp->v_path = vn_vpath_empty;
        vp->v_path_stamp = 0;
        vp->v_mpssdata = NULL;
        vp->v_vsd = NULL;
        vp->v_fopdata = NULL;

        vmobject_init(&vp->v_object, vp);

        return (0);
}

/* ARGSUSED */
static void
vn_cache_destructor(void *buf, void *cdrarg)
{
        struct vnode *vp;

        vp = buf;

        vmobject_fini(&vp->v_object);

        rw_destroy(&vp->v_nbllock);
        cv_destroy(&vp->v_cv);
        mutex_destroy(&vp->v_vsd_lock);
        mutex_destroy(&vp->v_lock);
}

void
vn_create_cache(void)
{
        /* LINTED */
        ASSERT((1 << VNODE_ALIGN_LOG2) ==
            P2ROUNDUP(sizeof (struct vnode), VNODE_ALIGN));
        vn_cache = kmem_cache_create("vn_cache", sizeof (struct vnode),
            VNODE_ALIGN, vn_cache_constructor, vn_cache_destructor, NULL, NULL,
            NULL, 0);
}

void
vn_destroy_cache(void)
{
        kmem_cache_destroy(vn_cache);
}

/*
 * Used by file systems when fs-specific nodes (e.g., ufs inodes) are
 * cached by the file system and vnodes remain associated.
 */
void
vn_recycle(vnode_t *vp)
{
        ASSERT(!vn_has_cached_data(vp));
        VERIFY(vp->v_path != NULL);

        /*
         * XXX - This really belongs in vn_reinit(), but we have some issues
         * with the counts.  Best to have it here for clean initialization.
         */
        vp->v_rdcnt = 0;
        vp->v_wrcnt = 0;
        vp->v_mmap_read = 0;
        vp->v_mmap_write = 0;

        /*
         * If FEM was in use, make sure everything gets cleaned up
         * NOTE: vp->v_femhead is initialized to NULL in the vnode
         * constructor.
         */
        if (vp->v_femhead) {
                /* XXX - There should be a free_femhead() that does all this */
                ASSERT(vp->v_femhead->femh_list == NULL);
                mutex_destroy(&vp->v_femhead->femh_lock);
                kmem_free(vp->v_femhead, sizeof (*(vp->v_femhead)));
                vp->v_femhead = NULL;
        }
        if (vp->v_path != vn_vpath_empty) {
                kmem_free(vp->v_path, strlen(vp->v_path) + 1);
                vp->v_path = vn_vpath_empty;
        }
        vp->v_path_stamp = 0;

        if (vp->v_fopdata != NULL) {
                free_fopdata(vp);
        }
        vp->v_mpssdata = NULL;
        vsd_free(vp);
}

/*
 * Used to reset the vnode fields including those that are directly accessible
 * as well as those which require an accessor function.
 *
 * Does not initialize:
 *      synchronization objects: v_lock, v_vsd_lock, v_nbllock, v_cv
 *      v_data (since FS-nodes and vnodes point to each other and should
 *              be updated simultaneously)
 *      v_op (in case someone needs to make a VOP call on this object)
 */
void
vn_reinit(vnode_t *vp)
{
        vp->v_count = 1;
        vp->v_count_dnlc = 0;
        vp->v_vfsp = NULL;
        vp->v_stream = NULL;
        vp->v_vfsmountedhere = NULL;
        vp->v_flag = 0;
        vp->v_type = VNON;
        vp->v_rdev = NODEV;

        vp->v_filocks = NULL;
        vp->v_shrlocks = NULL;
        VERIFY(!vn_has_cached_data(vp));

        vp->v_locality = NULL;
        vp->v_xattrdir = NULL;

        /*
         * In a few specific instances, vn_reinit() is used to initialize
         * locally defined vnode_t instances.  Lacking the construction offered
         * by vn_alloc(), these vnodes require v_path initialization.
         */
        if (vp->v_path == NULL) {
                vp->v_path = vn_vpath_empty;
        }

        /* Handles v_femhead, v_path, and the r/w/map counts */
        vn_recycle(vp);
}

vnode_t *
vn_alloc(int kmflag)
{
        vnode_t *vp;

        vp = kmem_cache_alloc(vn_cache, kmflag);

        if (vp != NULL) {
                vp->v_femhead = NULL;   /* Must be done before vn_reinit() */
                vp->v_fopdata = NULL;
                vn_reinit(vp);
        }

        return (vp);
}

void
vn_free(vnode_t *vp)
{
        ASSERT(vp->v_shrlocks == NULL);
        ASSERT(vp->v_filocks == NULL);

        /*
         * Some file systems call vn_free() with v_count of zero,
         * some with v_count of 1.  In any case, the value should
         * never be anything else.
         */
        ASSERT((vp->v_count == 0) || (vp->v_count == 1));
        ASSERT(vp->v_count_dnlc == 0);
        VERIFY(vp->v_path != NULL);
        if (vp->v_path != vn_vpath_empty) {
                kmem_free(vp->v_path, strlen(vp->v_path) + 1);
                vp->v_path = vn_vpath_empty;
        }

        /* If FEM was in use, make sure everything gets cleaned up */
        if (vp->v_femhead) {
                /* XXX - There should be a free_femhead() that does all this */
                ASSERT(vp->v_femhead->femh_list == NULL);
                mutex_destroy(&vp->v_femhead->femh_lock);
                kmem_free(vp->v_femhead, sizeof (*(vp->v_femhead)));
                vp->v_femhead = NULL;
        }

        if (vp->v_fopdata != NULL) {
                free_fopdata(vp);
        }
        vp->v_mpssdata = NULL;
        vsd_free(vp);
        kmem_cache_free(vn_cache, vp);
}

/*
 * vnode status changes, should define better states than 1, 0.
 */
void
vn_reclaim(vnode_t *vp)
{
        vfs_t   *vfsp = vp->v_vfsp;

        if (vfsp == NULL ||
            vfsp->vfs_implp == NULL || vfsp->vfs_femhead == NULL) {
                return;
        }
        (void) VFS_VNSTATE(vfsp, vp, VNTRANS_RECLAIMED);
}

void
vn_idle(vnode_t *vp)
{
        vfs_t   *vfsp = vp->v_vfsp;

        if (vfsp == NULL ||
            vfsp->vfs_implp == NULL || vfsp->vfs_femhead == NULL) {
                return;
        }
        (void) VFS_VNSTATE(vfsp, vp, VNTRANS_IDLED);
}
void
vn_exists(vnode_t *vp)
{
        vfs_t   *vfsp = vp->v_vfsp;

        if (vfsp == NULL ||
            vfsp->vfs_implp == NULL || vfsp->vfs_femhead == NULL) {
                return;
        }
        (void) VFS_VNSTATE(vfsp, vp, VNTRANS_EXISTS);
}

void
vn_invalid(vnode_t *vp)
{
        vfs_t   *vfsp = vp->v_vfsp;

        if (vfsp == NULL ||
            vfsp->vfs_implp == NULL || vfsp->vfs_femhead == NULL) {
                return;
        }
        (void) VFS_VNSTATE(vfsp, vp, VNTRANS_DESTROYED);
}

/* Vnode event notification */

int
vnevent_support(vnode_t *vp, caller_context_t *ct)
{
        if (vp == NULL)
                return (EINVAL);

        return (fop_vnevent(vp, VE_SUPPORT, NULL, NULL, ct));
}

void
vnevent_rename_src(vnode_t *vp, vnode_t *dvp, char *name, caller_context_t *ct)
{
        if (vp == NULL || vp->v_femhead == NULL) {
                return;
        }
        (void) fop_vnevent(vp, VE_RENAME_SRC, dvp, name, ct);
}

void
vnevent_rename_dest(vnode_t *vp, vnode_t *dvp, char *name,
    caller_context_t *ct)
{
        if (vp == NULL || vp->v_femhead == NULL) {
                return;
        }
        (void) fop_vnevent(vp, VE_RENAME_DEST, dvp, name, ct);
}

void
vnevent_rename_dest_dir(vnode_t *vp, caller_context_t *ct)
{
        if (vp == NULL || vp->v_femhead == NULL) {
                return;
        }
        (void) fop_vnevent(vp, VE_RENAME_DEST_DIR, NULL, NULL, ct);
}

void
vnevent_remove(vnode_t *vp, vnode_t *dvp, char *name, caller_context_t *ct)
{
        if (vp == NULL || vp->v_femhead == NULL) {
                return;
        }
        (void) fop_vnevent(vp, VE_REMOVE, dvp, name, ct);
}

void
vnevent_rmdir(vnode_t *vp, vnode_t *dvp, char *name, caller_context_t *ct)
{
        if (vp == NULL || vp->v_femhead == NULL) {
                return;
        }
        (void) fop_vnevent(vp, VE_RMDIR, dvp, name, ct);
}

void
vnevent_pre_rename_src(vnode_t *vp, vnode_t *dvp, char *name,
    caller_context_t *ct)
{
        if (vp == NULL || vp->v_femhead == NULL) {
                return;
        }
        (void) fop_vnevent(vp, VE_PRE_RENAME_SRC, dvp, name, ct);
}

void
vnevent_pre_rename_dest(vnode_t *vp, vnode_t *dvp, char *name,
    caller_context_t *ct)
{
        if (vp == NULL || vp->v_femhead == NULL) {
                return;
        }
        (void) fop_vnevent(vp, VE_PRE_RENAME_DEST, dvp, name, ct);
}

void
vnevent_pre_rename_dest_dir(vnode_t *vp, vnode_t *nvp, char *name,
    caller_context_t *ct)
{
        if (vp == NULL || vp->v_femhead == NULL) {
                return;
        }
        (void) fop_vnevent(vp, VE_PRE_RENAME_DEST_DIR, nvp, name, ct);
}

void
vnevent_create(vnode_t *vp, caller_context_t *ct)
{
        if (vp == NULL || vp->v_femhead == NULL) {
                return;
        }
        (void) fop_vnevent(vp, VE_CREATE, NULL, NULL, ct);
}

void
vnevent_link(vnode_t *vp, caller_context_t *ct)
{
        if (vp == NULL || vp->v_femhead == NULL) {
                return;
        }
        (void) fop_vnevent(vp, VE_LINK, NULL, NULL, ct);
}

void
vnevent_mountedover(vnode_t *vp, caller_context_t *ct)
{
        if (vp == NULL || vp->v_femhead == NULL) {
                return;
        }
        (void) fop_vnevent(vp, VE_MOUNTEDOVER, NULL, NULL, ct);
}

void
vnevent_truncate(vnode_t *vp, caller_context_t *ct)
{
        if (vp == NULL || vp->v_femhead == NULL) {
                return;
        }
        (void) fop_vnevent(vp, VE_TRUNCATE, NULL, NULL, ct);
}

/*
 * Vnode accessors.
 */

int
vn_is_readonly(vnode_t *vp)
{
        return (vp->v_vfsp->vfs_flag & VFS_RDONLY);
}

int
vn_has_flocks(vnode_t *vp)
{
        return (vp->v_filocks != NULL);
}

int
vn_has_mandatory_locks(vnode_t *vp, int mode)
{
        return ((vp->v_filocks != NULL) && (MANDLOCK(vp, mode)));
}

int
vn_has_cached_data(vnode_t *vp)
{
        return (!list_is_empty(&vp->v_object.list));
}

/*
 * Return 0 if the vnode in question shouldn't be permitted into a zone via
 * zone_enter(2).
 */
int
vn_can_change_zones(vnode_t *vp)
{
        struct vfssw *vswp;
        int allow = 1;
        vnode_t *rvp;

        if (nfs_global_client_only != 0)
                return (1);

        /*
         * We always want to look at the underlying vnode if there is one.
         */
        if (fop_realvp(vp, &rvp, NULL) != 0)
                rvp = vp;
        /*
         * Some pseudo filesystems (including doorfs) don't actually register
         * their vfsops_t, so the following may return NULL; we happily let
         * such vnodes switch zones.
         */
        vswp = vfs_getvfsswbyvfsops(vfs_getops(rvp->v_vfsp));
        if (vswp != NULL) {
                if (vswp->vsw_flag & VSW_NOTZONESAFE)
                        allow = 0;
                vfs_unrefvfssw(vswp);
        }
        return (allow);
}

/*
 * Return nonzero if the vnode is a mount point, zero if not.
 */
int
vn_ismntpt(vnode_t *vp)
{
        return (vp->v_vfsmountedhere != NULL);
}

/* Retrieve the vfs (if any) mounted on this vnode */
vfs_t *
vn_mountedvfs(vnode_t *vp)
{
        return (vp->v_vfsmountedhere);
}

/*
 * Return nonzero if the vnode is referenced by the dnlc, zero if not.
 */
int
vn_in_dnlc(vnode_t *vp)
{
        return (vp->v_count_dnlc > 0);
}

/*
 * vn_has_other_opens() checks whether a particular file is opened by more than
 * just the caller and whether the open is for read and/or write.
 * This routine is for calling after the caller has already called fop_open()
 * and the caller wishes to know if they are the only one with it open for
 * the mode(s) specified.
 *
 * Vnode counts are only kept on regular files (v_type=VREG).
 */
int
vn_has_other_opens(
        vnode_t *vp,
        v_mode_t mode)
{

        ASSERT(vp != NULL);

        switch (mode) {
        case V_WRITE:
                if (vp->v_wrcnt > 1)
                        return (V_TRUE);
                break;
        case V_RDORWR:
                if ((vp->v_rdcnt > 1) || (vp->v_wrcnt > 1))
                        return (V_TRUE);
                break;
        case V_RDANDWR:
                if ((vp->v_rdcnt > 1) && (vp->v_wrcnt > 1))
                        return (V_TRUE);
                break;
        case V_READ:
                if (vp->v_rdcnt > 1)
                        return (V_TRUE);
                break;
        }

        return (V_FALSE);
}

/*
 * vn_is_opened() checks whether a particular file is opened and
 * whether the open is for read and/or write.
 *
 * Vnode counts are only kept on regular files (v_type=VREG).
 */
int
vn_is_opened(
        vnode_t *vp,
        v_mode_t mode)
{

        ASSERT(vp != NULL);

        switch (mode) {
        case V_WRITE:
                if (vp->v_wrcnt)
                        return (V_TRUE);
                break;
        case V_RDANDWR:
                if (vp->v_rdcnt && vp->v_wrcnt)
                        return (V_TRUE);
                break;
        case V_RDORWR:
                if (vp->v_rdcnt || vp->v_wrcnt)
                        return (V_TRUE);
                break;
        case V_READ:
                if (vp->v_rdcnt)
                        return (V_TRUE);
                break;
        }

        return (V_FALSE);
}

/*
 * vn_is_mapped() checks whether a particular file is mapped and whether
 * the file is mapped read and/or write.
 */
int
vn_is_mapped(
        vnode_t *vp,
        v_mode_t mode)
{

        ASSERT(vp != NULL);

#if !defined(_LP64)
        switch (mode) {
        /*
         * The atomic_add_64_nv functions force atomicity in the
         * case of 32 bit architectures. Otherwise the 64 bit values
         * require two fetches. The value of the fields may be
         * (potentially) changed between the first fetch and the
         * second
         */
        case V_WRITE:
                if (atomic_add_64_nv((&(vp->v_mmap_write)), 0))
                        return (V_TRUE);
                break;
        case V_RDANDWR:
                if ((atomic_add_64_nv((&(vp->v_mmap_read)), 0)) &&
                    (atomic_add_64_nv((&(vp->v_mmap_write)), 0)))
                        return (V_TRUE);
                break;
        case V_RDORWR:
                if ((atomic_add_64_nv((&(vp->v_mmap_read)), 0)) ||
                    (atomic_add_64_nv((&(vp->v_mmap_write)), 0)))
                        return (V_TRUE);
                break;
        case V_READ:
                if (atomic_add_64_nv((&(vp->v_mmap_read)), 0))
                        return (V_TRUE);
                break;
        }
#else
        switch (mode) {
        case V_WRITE:
                if (vp->v_mmap_write)
                        return (V_TRUE);
                break;
        case V_RDANDWR:
                if (vp->v_mmap_read && vp->v_mmap_write)
                        return (V_TRUE);
                break;
        case V_RDORWR:
                if (vp->v_mmap_read || vp->v_mmap_write)
                        return (V_TRUE);
                break;
        case V_READ:
                if (vp->v_mmap_read)
                        return (V_TRUE);
                break;
        }
#endif

        return (V_FALSE);
}

/*
 * Set the operations vector for a vnode.
 */
void
vn_setops(struct vnode *vnode, const struct vnodeops *ops)
{
        vnode->v_op = ops;
}

/*
 * Retrieve the operations vector for a vnode
 */
const struct vnodeops *
vn_getops(struct vnode *vnode)
{
        return vnode->v_op;
}

/*
 * Returns non-zero (1) if the vnodeops matches that of the vnode.
 * Returns zero (0) if not.
 */
int
vn_matchops(struct vnode *vp, const struct vnodeops *vnodeops)
{
        return (vn_getops(vp) == vnodeops);
}

/*
 * fs_new_caller_id() needs to return a unique ID on a given local system.
 * The IDs do not need to survive across reboots.  These are primarily
 * used so that (FEM) monitors can detect particular callers (such as
 * the NFS server) to a given vnode/vfs operation.
 */
u_longlong_t
fs_new_caller_id()
{
        static uint64_t next_caller_id = 0LL; /* First call returns 1 */

        return ((u_longlong_t)atomic_inc_64_nv(&next_caller_id));
}

/*
 * The value stored in v_path is relative to rootdir, located in the global
 * zone.  Zones or chroot environments which reside deeper inside the VFS
 * hierarchy will have a relative view of MAXPATHLEN since they are unaware of
 * what lies below their perceived root.  In order to keep v_path usable for
 * these child environments, its allocations are allowed to exceed MAXPATHLEN.
 *
 * An upper bound of max_vnode_path is placed upon v_path allocations to
 * prevent the system from going too wild at the behest of pathological
 * behavior from the operator.
 */
size_t max_vnode_path = 4 * MAXPATHLEN;


void
vn_clearpath(vnode_t *vp, hrtime_t compare_stamp)
{
        char *buf;

        mutex_enter(&vp->v_lock);
        /*
         * If the snapshot of v_path_stamp passed in via compare_stamp does not
         * match the present value on the vnode, it indicates that subsequent
         * changes have occurred.  The v_path value is not cleared in this case
         * since the new value may be valid.
         */
        if (compare_stamp != 0 && vp->v_path_stamp != compare_stamp) {
                mutex_exit(&vp->v_lock);
                return;
        }
        buf = vp->v_path;
        vp->v_path = vn_vpath_empty;
        vp->v_path_stamp = 0;
        mutex_exit(&vp->v_lock);
        if (buf != vn_vpath_empty) {
                kmem_free(buf, strlen(buf) + 1);
        }
}

static void
vn_setpath_common(vnode_t *pvp, vnode_t *vp, const char *name, size_t len,
    boolean_t is_rename)
{
        char *buf, *oldbuf;
        hrtime_t pstamp;
        size_t baselen, buflen = 0;

        /* Handle the vn_setpath_str case. */
        if (pvp == NULL) {
                if (len + 1 > max_vnode_path) {
                        DTRACE_PROBE4(vn__setpath__too__long, vnode_t *, pvp,
                            vnode_t *, vp, char *, name, size_t, len + 1);
                        return;
                }
                buf = kmem_alloc(len + 1, KM_SLEEP);
                bcopy(name, buf, len);
                buf[len] = '\0';

                mutex_enter(&vp->v_lock);
                oldbuf = vp->v_path;
                vp->v_path = buf;
                vp->v_path_stamp = gethrtime();
                mutex_exit(&vp->v_lock);
                if (oldbuf != vn_vpath_empty) {
                        kmem_free(oldbuf, strlen(oldbuf) + 1);
                }
                return;
        }

        /* Take snapshot of parent dir */
        mutex_enter(&pvp->v_lock);

        if ((pvp->v_flag & VTRAVERSE) != 0) {
                /*
                 * When the parent vnode has VTRAVERSE set in its flags, normal
                 * assumptions about v_path calculation no longer apply.  The
                 * primary situation where this occurs is via the VFS tricks
                 * which procfs plays in order to allow /proc/PID/(root|cwd) to
                 * yield meaningful results.
                 *
                 * When this flag is set, v_path on the child must not be
                 * updated since the calculated value is likely to be
                 * incorrect, given the current context.
                 */
                mutex_exit(&pvp->v_lock);
                return;
        }

retrybuf:
        if (pvp->v_path == vn_vpath_empty) {
                /*
                 * Without v_path from the parent directory, generating a child
                 * path from the name is impossible.
                 */
                if (len > 0) {
                        pstamp = pvp->v_path_stamp;
                        mutex_exit(&pvp->v_lock);
                        vn_clearpath(vp, pstamp);
                        return;
                }

                /*
                 * The only feasible case here is where a NUL lookup is being
                 * performed on rootdir prior to its v_path being populated.
                 */
                ASSERT(pvp->v_path_stamp == 0);
                baselen = 0;
                pstamp = 0;
        } else {
                pstamp = pvp->v_path_stamp;
                baselen = strlen(pvp->v_path);
                /* ignore a trailing slash if present */
                if (pvp->v_path[baselen - 1] == '/') {
                        /* This should only the be case for rootdir */
                        ASSERT(baselen == 1 && pvp == rootdir);
                        baselen--;
                }
        }
        mutex_exit(&pvp->v_lock);

        if (buflen != 0) {
                /* Free the existing (mis-sized) buffer in case of retry */
                kmem_free(buf, buflen);
        }
        /* base, '/', name and trailing NUL */
        buflen = baselen + len + 2;
        if (buflen > max_vnode_path) {
                DTRACE_PROBE4(vn__setpath_too__long, vnode_t *, pvp,
                    vnode_t *, vp, char *, name, size_t, buflen);
                return;
        }
        buf = kmem_alloc(buflen, KM_SLEEP);

        mutex_enter(&pvp->v_lock);
        if (pvp->v_path_stamp != pstamp) {
                size_t vlen;

                /*
                 * Since v_path_stamp changed on the parent, it is likely that
                 * v_path has been altered as well.  If the length does not
                 * exactly match what was previously measured, the buffer
                 * allocation must be repeated for proper sizing.
                 */
                if (pvp->v_path == vn_vpath_empty) {
                        /* Give up if parent lack v_path */
                        mutex_exit(&pvp->v_lock);
                        kmem_free(buf, buflen);
                        return;
                }
                vlen = strlen(pvp->v_path);
                if (pvp->v_path[vlen - 1] == '/') {
                        vlen--;
                }
                if (vlen != baselen) {
                        goto retrybuf;
                }
        }
        bcopy(pvp->v_path, buf, baselen);
        mutex_exit(&pvp->v_lock);

        buf[baselen] = '/';
        baselen++;
        bcopy(name, &buf[baselen], len + 1);

        mutex_enter(&vp->v_lock);
        if (vp->v_path_stamp == 0) {
                /* never-visited vnode can inherit stamp from parent */
                ASSERT(vp->v_path == vn_vpath_empty);
                vp->v_path_stamp = pstamp;
                vp->v_path = buf;
                mutex_exit(&vp->v_lock);
        } else if (vp->v_path_stamp < pstamp || is_rename) {
                /*
                 * Install the updated path and stamp, ensuring that the v_path
                 * pointer is valid at all times for dtrace.
                 */
                oldbuf = vp->v_path;
                vp->v_path = buf;
                vp->v_path_stamp = gethrtime();
                mutex_exit(&vp->v_lock);
                kmem_free(oldbuf, strlen(oldbuf) + 1);
        } else {
                /*
                 * If the timestamp matches or is greater, it means another
                 * thread performed the update first while locks were dropped
                 * here to make the allocation.  We defer to the newer value.
                 */
                mutex_exit(&vp->v_lock);
                kmem_free(buf, buflen);
        }
        ASSERT(MUTEX_NOT_HELD(&vp->v_lock));
}

void
vn_updatepath(vnode_t *pvp, vnode_t *vp, const char *name)
{
        size_t len;

        /*
         * If the parent is older or empty, there's nothing further to do.
         */
        if (pvp->v_path == vn_vpath_empty ||
            pvp->v_path_stamp <= vp->v_path_stamp) {
                return;
        }

        /*
         * Given the lack of appropriate context, meaningful updates to v_path
         * cannot be made for during lookups for the '.' or '..' entries.
         */
        len = strlen(name);
        if (len == 0 || (len == 1 && name[0] == '.') ||
            (len == 2 && name[0] == '.' && name[1] == '.')) {
                return;
        }

        vn_setpath_common(pvp, vp, name, len, B_FALSE);
}

/*
 * Given a starting vnode and a path, updates the path in the target vnode in
 * a safe manner.  If the vnode already has path information embedded, then the
 * cached path is left untouched.
 */
/* ARGSUSED */
void
vn_setpath(vnode_t *rootvp, vnode_t *pvp, vnode_t *vp, const char *name,
    size_t len)
{
        vn_setpath_common(pvp, vp, name, len, B_FALSE);
}

/*
 * Sets the path to the vnode to be the given string, regardless of current
 * context.  The string must be a complete path from rootdir.  This is only used
 * by fsop_root() for setting the path based on the mountpoint.
 */
void
vn_setpath_str(vnode_t *vp, const char *str, size_t len)
{
        vn_setpath_common(NULL, vp, str, len, B_FALSE);
}

/*
 * Called from within filesystem's vop_rename() to handle renames once the
 * target vnode is available.
 */
void
vn_renamepath(vnode_t *pvp, vnode_t *vp, const char *name, size_t len)
{
        vn_setpath_common(pvp, vp, name, len, B_TRUE);
}

/*
 * Similar to vn_setpath_str(), this function sets the path of the destination
 * vnode to the be the same as the source vnode.
 */
void
vn_copypath(struct vnode *src, struct vnode *dst)
{
        char *buf;
        hrtime_t stamp;
        size_t buflen;

        mutex_enter(&src->v_lock);
        if (src->v_path == vn_vpath_empty) {
                mutex_exit(&src->v_lock);
                return;
        }
        buflen = strlen(src->v_path) + 1;
        mutex_exit(&src->v_lock);

        buf = kmem_alloc(buflen, KM_SLEEP);

        mutex_enter(&src->v_lock);
        if (src->v_path == vn_vpath_empty ||
            strlen(src->v_path) + 1 != buflen) {
                mutex_exit(&src->v_lock);
                kmem_free(buf, buflen);
                return;
        }
        bcopy(src->v_path, buf, buflen);
        stamp = src->v_path_stamp;
        mutex_exit(&src->v_lock);

        mutex_enter(&dst->v_lock);
        if (dst->v_path != vn_vpath_empty) {
                mutex_exit(&dst->v_lock);
                kmem_free(buf, buflen);
                return;
        }
        dst->v_path = buf;
        dst->v_path_stamp = stamp;
        mutex_exit(&dst->v_lock);
}


/*
 * XXX Private interface for segvn routines that handle vnode
 * large page segments.
 *
 * return 1 if vp's file system fop_pageio() implementation
 * can be safely used instead of fop_getpage() for handling
 * pagefaults against regular non swap files. fop_pageio()
 * interface is considered safe here if its implementation
 * is very close to fop_getpage() implementation.
 * e.g. It zero's out the part of the page beyond EOF. Doesn't
 * panic if there're file holes but instead returns an error.
 * Doesn't assume file won't be changed by user writes, etc.
 *
 * return 0 otherwise.
 *
 * For now allow segvn to only use fop_pageio() with ufs and nfs.
 */
int
vn_vmpss_usepageio(vnode_t *vp)
{
        vfs_t   *vfsp = vp->v_vfsp;
        char *fsname = vfssw[vfsp->vfs_fstype].vsw_name;
        char *pageio_ok_fss[] = {"ufs", "nfs", NULL};
        char **fsok = pageio_ok_fss;

        if (fsname == NULL) {
                return (0);
        }

        for (; *fsok; fsok++) {
                if (strcmp(*fsok, fsname) == 0) {
                        return (1);
                }
        }
        return (0);
}

/* VOP_XXX() macros call the corresponding fop_xxx() function */

int
fop_open(
        vnode_t **vpp,
        int mode,
        cred_t *cr,
        caller_context_t *ct)
{
        int ret;
        vnode_t *vp = *vpp;

        VN_HOLD(vp);
        /*
         * Adding to the vnode counts before calling open
         * avoids the need for a mutex. It circumvents a race
         * condition where a query made on the vnode counts results in a
         * false negative. The inquirer goes away believing the file is
         * not open when there is an open on the file already under way.
         *
         * The counts are meant to prevent NFS from granting a delegation
         * when it would be dangerous to do so.
         *
         * The vnode counts are only kept on regular files
         */
        if ((*vpp)->v_type == VREG) {
                if (mode & FREAD)
                        atomic_inc_32(&(*vpp)->v_rdcnt);
                if (mode & FWRITE)
                        atomic_inc_32(&(*vpp)->v_wrcnt);
        }

        VOPXID_MAP_CR(vp, cr);

        ret = fop_open_dispatch(vpp, mode, cr, ct, true);

        if (ret) {
                /*
                 * Use the saved vp just in case the vnode ptr got trashed
                 * by the error.
                 */
                VOPSTATS_UPDATE(vp, open);
                if ((vp->v_type == VREG) && (mode & FREAD))
                        atomic_dec_32(&vp->v_rdcnt);
                if ((vp->v_type == VREG) && (mode & FWRITE))
                        atomic_dec_32(&vp->v_wrcnt);
        } else {
                /*
                 * Some filesystems will return a different vnode,
                 * but the same path was still used to open it.
                 * So if we do change the vnode and need to
                 * copy over the path, do so here, rather than special
                 * casing each filesystem. Adjust the vnode counts to
                 * reflect the vnode switch.
                 */
                VOPSTATS_UPDATE(*vpp, open);
                if (*vpp != vp && *vpp != NULL) {
                        vn_copypath(vp, *vpp);
                        if (((*vpp)->v_type == VREG) && (mode & FREAD))
                                atomic_inc_32(&(*vpp)->v_rdcnt);
                        if ((vp->v_type == VREG) && (mode & FREAD))
                                atomic_dec_32(&vp->v_rdcnt);
                        if (((*vpp)->v_type == VREG) && (mode & FWRITE))
                                atomic_inc_32(&(*vpp)->v_wrcnt);
                        if ((vp->v_type == VREG) && (mode & FWRITE))
                                atomic_dec_32(&vp->v_wrcnt);
                }
        }
        VN_RELE(vp);
        return (ret);
}

int
fop_close(
        vnode_t *vp,
        int flag,
        int count,
        offset_t offset,
        cred_t *cr,
        caller_context_t *ct)
{
        int err;

        VOPXID_MAP_CR(vp, cr);

        err = fop_close_dispatch(vp, flag, count, offset, cr, ct, true);

        VOPSTATS_UPDATE(vp, close);
        /*
         * Check passed in count to handle possible dups. Vnode counts are only
         * kept on regular files
         */
        if ((vp->v_type == VREG) && (count == 1))  {
                if (flag & FREAD) {
                        ASSERT(vp->v_rdcnt > 0);
                        atomic_dec_32(&vp->v_rdcnt);
                }
                if (flag & FWRITE) {
                        ASSERT(vp->v_wrcnt > 0);
                        atomic_dec_32(&vp->v_wrcnt);
                }
        }
        return (err);
}

int
fop_read(
        vnode_t *vp,
        uio_t *uiop,
        int ioflag,
        cred_t *cr,
        caller_context_t *ct)
{
        int     err;
        ssize_t resid_start = uiop->uio_resid;

        VOPXID_MAP_CR(vp, cr);

        err = fop_read_dispatch(vp, uiop, ioflag, cr, ct, true);

        VOPSTATS_UPDATE_IO(vp, read,
            read_bytes, (resid_start - uiop->uio_resid));
        return (err);
}

int
fop_write(
        vnode_t *vp,
        uio_t *uiop,
        int ioflag,
        cred_t *cr,
        caller_context_t *ct)
{
        int     err;
        ssize_t resid_start = uiop->uio_resid;

        VOPXID_MAP_CR(vp, cr);

        err = fop_write_dispatch(vp, uiop, ioflag, cr, ct, true);

        VOPSTATS_UPDATE_IO(vp, write,
            write_bytes, (resid_start - uiop->uio_resid));
        return (err);
}

int
fop_ioctl(
        vnode_t *vp,
        int cmd,
        intptr_t arg,
        int flag,
        cred_t *cr,
        int *rvalp,
        caller_context_t *ct)
{
        int     err;

        VOPXID_MAP_CR(vp, cr);

        err = fop_ioctl_dispatch(vp, cmd, arg, flag, cr, rvalp, ct, true);

        VOPSTATS_UPDATE(vp, ioctl);
        return (err);
}

int
fop_setfl(
        vnode_t *vp,
        int oflags,
        int nflags,
        cred_t *cr,
        caller_context_t *ct)
{
        int     err;

        VOPXID_MAP_CR(vp, cr);

        err = fop_setfl_dispatch(vp, oflags, nflags, cr, ct, true);

        VOPSTATS_UPDATE(vp, setfl);
        return (err);
}

int
fop_getattr(
        vnode_t *vp,
        vattr_t *vap,
        int flags,
        cred_t *cr,
        caller_context_t *ct)
{
        int     err;

        VOPXID_MAP_CR(vp, cr);

        /*
         * If this file system doesn't understand the xvattr extensions
         * then turn off the xvattr bit.
         */
        if (vfs_has_feature(vp->v_vfsp, VFSFT_XVATTR) == 0) {
                vap->va_mask &= ~AT_XVATTR;
        }

        /*
         * We're only allowed to skip the ACL check iff we used a 32 bit
         * ACE mask with fop_access() to determine permissions.
         */
        if ((flags & ATTR_NOACLCHECK) &&
            vfs_has_feature(vp->v_vfsp, VFSFT_ACEMASKONACCESS) == 0)
                return (EINVAL);

        err = fop_getattr_dispatch(vp, vap, flags, cr, ct, true);

        VOPSTATS_UPDATE(vp, getattr);
        return (err);
}

int
fop_setattr(
        vnode_t *vp,
        vattr_t *vap,
        int flags,
        cred_t *cr,
        caller_context_t *ct)
{
        int     err;

        VOPXID_MAP_CR(vp, cr);

        /*
         * If this file system doesn't understand the xvattr extensions
         * then turn off the xvattr bit.
         */
        if (vfs_has_feature(vp->v_vfsp, VFSFT_XVATTR) == 0) {
                vap->va_mask &= ~AT_XVATTR;
        }

        /*
         * We're only allowed to skip the ACL check iff we used a 32 bit
         * ACE mask with fop_access() to determine permissions.
         */
        if ((flags & ATTR_NOACLCHECK) &&
            vfs_has_feature(vp->v_vfsp, VFSFT_ACEMASKONACCESS) == 0)
                return (EINVAL);

        err = fop_setattr_dispatch(vp, vap, flags, cr, ct, true);

        VOPSTATS_UPDATE(vp, setattr);
        return (err);
}

int
fop_access(
        vnode_t *vp,
        int mode,
        int flags,
        cred_t *cr,
        caller_context_t *ct)
{
        int     err;

        if ((flags & V_ACE_MASK) &&
            vfs_has_feature(vp->v_vfsp, VFSFT_ACEMASKONACCESS) == 0) {
                return (EINVAL);
        }

        VOPXID_MAP_CR(vp, cr);

        err = fop_access_dispatch(vp, mode, flags, cr, ct, true);

        VOPSTATS_UPDATE(vp, access);
        return (err);
}

int
fop_lookup(
        vnode_t *dvp,
        char *nm,
        vnode_t **vpp,
        pathname_t *pnp,
        int flags,
        vnode_t *rdir,
        cred_t *cr,
        caller_context_t *ct,
        int *deflags,           /* Returned per-dirent flags */
        pathname_t *ppnp)       /* Returned case-preserved name in directory */
{
        int ret;

        /*
         * If this file system doesn't support case-insensitive access
         * and said access is requested, fail quickly.  It is required
         * that if the vfs supports case-insensitive lookup, it also
         * supports extended dirent flags.
         */
        if (flags & FIGNORECASE &&
            (vfs_has_feature(dvp->v_vfsp, VFSFT_CASEINSENSITIVE) == 0 &&
            vfs_has_feature(dvp->v_vfsp, VFSFT_NOCASESENSITIVE) == 0))
                return (EINVAL);

        VOPXID_MAP_CR(dvp, cr);

        if ((flags & LOOKUP_XATTR) && (flags & LOOKUP_HAVE_SYSATTR_DIR) == 0) {
                ret = xattr_dir_lookup(dvp, vpp, flags, cr);
        } else {
                ret = fop_lookup_dispatch(dvp, nm, vpp, pnp, flags, rdir, cr,
                                          ct, deflags, ppnp, true);
        }

        if (ret == 0 && *vpp) {
                VOPSTATS_UPDATE(*vpp, lookup);
                vn_updatepath(dvp, *vpp, nm);
        }

        return (ret);
}

int
fop_create(
        vnode_t *dvp,
        char *name,
        vattr_t *vap,
        vcexcl_t excl,
        int mode,
        vnode_t **vpp,
        cred_t *cr,
        int flags,
        caller_context_t *ct,
        vsecattr_t *vsecp)      /* ACL to set during create */
{
        int ret;

        if (vsecp != NULL &&
            vfs_has_feature(dvp->v_vfsp, VFSFT_ACLONCREATE) == 0) {
                return (EINVAL);
        }
        /*
         * If this file system doesn't support case-insensitive access
         * and said access is requested, fail quickly.
         */
        if (flags & FIGNORECASE &&
            (vfs_has_feature(dvp->v_vfsp, VFSFT_CASEINSENSITIVE) == 0 &&
            vfs_has_feature(dvp->v_vfsp, VFSFT_NOCASESENSITIVE) == 0))
                return (EINVAL);

        VOPXID_MAP_CR(dvp, cr);

        ret = fop_create_dispatch(dvp, name, vap, excl, mode, vpp, cr, flags,
                                  ct, vsecp, true);

        if (ret == 0 && *vpp) {
                VOPSTATS_UPDATE(*vpp, create);
                vn_updatepath(dvp, *vpp, name);
        }

        return (ret);
}

int
fop_remove(
        vnode_t *dvp,
        char *nm,
        cred_t *cr,
        caller_context_t *ct,
        int flags)
{
        int     err;

        /*
         * If this file system doesn't support case-insensitive access
         * and said access is requested, fail quickly.
         */
        if (flags & FIGNORECASE &&
            (vfs_has_feature(dvp->v_vfsp, VFSFT_CASEINSENSITIVE) == 0 &&
            vfs_has_feature(dvp->v_vfsp, VFSFT_NOCASESENSITIVE) == 0))
                return (EINVAL);

        VOPXID_MAP_CR(dvp, cr);

        err = fop_remove_dispatch(dvp, nm, cr, ct, flags, true);

        VOPSTATS_UPDATE(dvp, remove);
        return (err);
}

int
fop_link(
        vnode_t *tdvp,
        vnode_t *svp,
        char *tnm,
        cred_t *cr,
        caller_context_t *ct,
        int flags)
{
        int     err;

        /*
         * If the target file system doesn't support case-insensitive access
         * and said access is requested, fail quickly.
         */
        if (flags & FIGNORECASE &&
            (vfs_has_feature(tdvp->v_vfsp, VFSFT_CASEINSENSITIVE) == 0 &&
            vfs_has_feature(tdvp->v_vfsp, VFSFT_NOCASESENSITIVE) == 0))
                return (EINVAL);

        VOPXID_MAP_CR(tdvp, cr);

        err = fop_link_dispatch(tdvp, svp, tnm, cr, ct, flags, true);

        VOPSTATS_UPDATE(tdvp, link);
        return (err);
}

int
fop_rename(
        vnode_t *sdvp,
        char *snm,
        vnode_t *tdvp,
        char *tnm,
        cred_t *cr,
        caller_context_t *ct,
        int flags)
{
        int     err;

        /*
         * If the file system involved does not support
         * case-insensitive access and said access is requested, fail
         * quickly.
         */
        if (flags & FIGNORECASE &&
            ((vfs_has_feature(sdvp->v_vfsp, VFSFT_CASEINSENSITIVE) == 0 &&
            vfs_has_feature(sdvp->v_vfsp, VFSFT_NOCASESENSITIVE) == 0)))
                return (EINVAL);

        VOPXID_MAP_CR(tdvp, cr);

        err = fop_rename_dispatch(sdvp, snm, tdvp, tnm, cr, ct, flags, true);

        VOPSTATS_UPDATE(sdvp, rename);
        return (err);
}

int
fop_mkdir(
        vnode_t *dvp,
        char *dirname,
        vattr_t *vap,
        vnode_t **vpp,
        cred_t *cr,
        caller_context_t *ct,
        int flags,
        vsecattr_t *vsecp)      /* ACL to set during create */
{
        int ret;

        if (vsecp != NULL &&
            vfs_has_feature(dvp->v_vfsp, VFSFT_ACLONCREATE) == 0) {
                return (EINVAL);
        }
        /*
         * If this file system doesn't support case-insensitive access
         * and said access is requested, fail quickly.
         */
        if (flags & FIGNORECASE &&
            (vfs_has_feature(dvp->v_vfsp, VFSFT_CASEINSENSITIVE) == 0 &&
            vfs_has_feature(dvp->v_vfsp, VFSFT_NOCASESENSITIVE) == 0))
                return (EINVAL);

        VOPXID_MAP_CR(dvp, cr);

        ret = fop_mkdir_dispatch(dvp, dirname, vap, vpp, cr, ct, flags, vsecp,
                                 true);

        if (ret == 0 && *vpp) {
                VOPSTATS_UPDATE(*vpp, mkdir);
                vn_updatepath(dvp, *vpp, dirname);
        }

        return (ret);
}

int
fop_rmdir(
        vnode_t *dvp,
        char *nm,
        vnode_t *cdir,
        cred_t *cr,
        caller_context_t *ct,
        int flags)
{
        int     err;

        /*
         * If this file system doesn't support case-insensitive access
         * and said access is requested, fail quickly.
         */
        if (flags & FIGNORECASE &&
            (vfs_has_feature(dvp->v_vfsp, VFSFT_CASEINSENSITIVE) == 0 &&
            vfs_has_feature(dvp->v_vfsp, VFSFT_NOCASESENSITIVE) == 0))
                return (EINVAL);

        VOPXID_MAP_CR(dvp, cr);

        err = fop_rmdir_dispatch(dvp, nm, cdir, cr, ct, flags, true);

        VOPSTATS_UPDATE(dvp, rmdir);
        return (err);
}

int
fop_readdir(
        vnode_t *vp,
        uio_t *uiop,
        cred_t *cr,
        int *eofp,
        caller_context_t *ct,
        int flags)
{
        int     err;
        ssize_t resid_start = uiop->uio_resid;

        /*
         * If this file system doesn't support retrieving directory
         * entry flags and said access is requested, fail quickly.
         */
        if (flags & V_RDDIR_ENTFLAGS &&
            vfs_has_feature(vp->v_vfsp, VFSFT_DIRENTFLAGS) == 0)
                return (EINVAL);

        VOPXID_MAP_CR(vp, cr);

        err = fop_readdir_dispatch(vp, uiop, cr, eofp, ct, flags, true);

        VOPSTATS_UPDATE_IO(vp, readdir,
            readdir_bytes, (resid_start - uiop->uio_resid));
        return (err);
}

int
fop_symlink(
        vnode_t *dvp,
        char *linkname,
        vattr_t *vap,
        char *target,
        cred_t *cr,
        caller_context_t *ct,
        int flags)
{
        int     err;
        xvattr_t xvattr;

        /*
         * If this file system doesn't support case-insensitive access
         * and said access is requested, fail quickly.
         */
        if (flags & FIGNORECASE &&
            (vfs_has_feature(dvp->v_vfsp, VFSFT_CASEINSENSITIVE) == 0 &&
            vfs_has_feature(dvp->v_vfsp, VFSFT_NOCASESENSITIVE) == 0))
                return (EINVAL);

        VOPXID_MAP_CR(dvp, cr);

        /* check for reparse point */
        if ((vfs_has_feature(dvp->v_vfsp, VFSFT_REPARSE)) &&
            (strncmp(target, FS_REPARSE_TAG_STR,
            strlen(FS_REPARSE_TAG_STR)) == 0)) {
                if (!fs_reparse_mark(target, vap, &xvattr))
                        vap = (vattr_t *)&xvattr;
        }

        err = fop_symlink_dispatch(dvp, linkname, vap, target, cr, ct, flags,
                                   true);

        VOPSTATS_UPDATE(dvp, symlink);
        return (err);
}

int
fop_readlink(
        vnode_t *vp,
        uio_t *uiop,
        cred_t *cr,
        caller_context_t *ct)
{
        int     err;

        VOPXID_MAP_CR(vp, cr);

        err = fop_readlink_dispatch(vp, uiop, cr, ct, true);

        VOPSTATS_UPDATE(vp, readlink);
        return (err);
}

int
fop_fsync(
        vnode_t *vp,
        int syncflag,
        cred_t *cr,
        caller_context_t *ct)
{
        int     err;

        VOPXID_MAP_CR(vp, cr);

        err = fop_fsync_dispatch(vp, syncflag, cr, ct, true);

        VOPSTATS_UPDATE(vp, fsync);
        return (err);
}

void
fop_inactive(
        vnode_t *vp,
        cred_t *cr,
        caller_context_t *ct)
{
        /* Need to update stats before vop call since we may lose the vnode */
        VOPSTATS_UPDATE(vp, inactive);

        VOPXID_MAP_CR(vp, cr);

        fop_inactive_dispatch(vp, cr, ct, true);
}

int
fop_fid(
        vnode_t *vp,
        fid_t *fidp,
        caller_context_t *ct)
{
        int     err;

        err = fop_fid_dispatch(vp, fidp, ct, true);

        VOPSTATS_UPDATE(vp, fid);
        return (err);
}

int
fop_rwlock(
        vnode_t *vp,
        int write_lock,
        caller_context_t *ct)
{
        int     ret;

        ret = fop_rwlock_dispatch(vp, write_lock, ct, true);

        VOPSTATS_UPDATE(vp, rwlock);
        return (ret);
}

void
fop_rwunlock(
        vnode_t *vp,
        int write_lock,
        caller_context_t *ct)
{
        fop_rwunlock_dispatch(vp, write_lock, ct, true);

        VOPSTATS_UPDATE(vp, rwunlock);
}

int
fop_seek(
        vnode_t *vp,
        offset_t ooff,
        offset_t *noffp,
        caller_context_t *ct)
{
        int     err;

        err = fop_seek_dispatch(vp, ooff, noffp, ct, true);

        VOPSTATS_UPDATE(vp, seek);
        return (err);
}

int
fop_cmp(
        vnode_t *vp1,
        vnode_t *vp2,
        caller_context_t *ct)
{
        int     err;

        err = fop_cmp_dispatch(vp1, vp2, ct, true);

        VOPSTATS_UPDATE(vp1, cmp);
        return (err);
}

int
fop_frlock(
        vnode_t *vp,
        int cmd,
        flock64_t *bfp,
        int flag,
        offset_t offset,
        struct flk_callback *flk_cbp,
        cred_t *cr,
        caller_context_t *ct)
{
        int     err;

        VOPXID_MAP_CR(vp, cr);

        err = fop_frlock_dispatch(vp, cmd, bfp, flag, offset, flk_cbp, cr,
                                  ct, true);

        VOPSTATS_UPDATE(vp, frlock);
        return (err);
}

int
fop_space(
        vnode_t *vp,
        int cmd,
        flock64_t *bfp,
        int flag,
        offset_t offset,
        cred_t *cr,
        caller_context_t *ct)
{
        int     err;

        VOPXID_MAP_CR(vp, cr);

        err = fop_space_dispatch(vp, cmd, bfp, flag, offset, cr, ct, true);

        VOPSTATS_UPDATE(vp, space);
        return (err);
}

int
fop_realvp(
        vnode_t *vp,
        vnode_t **vpp,
        caller_context_t *ct)
{
        int     err;

        err = fop_realvp_dispatch(vp, vpp, ct, true);

        VOPSTATS_UPDATE(vp, realvp);
        return (err);
}

int
fop_getpage(
        vnode_t *vp,
        offset_t off,
        size_t len,
        uint_t *protp,
        page_t **plarr,
        size_t plsz,
        struct seg *seg,
        caddr_t addr,
        enum seg_rw rw,
        cred_t *cr,
        caller_context_t *ct)
{
        int     err;

        VOPXID_MAP_CR(vp, cr);

        err = fop_getpage_dispatch(vp, off, len, protp, plarr, plsz, seg,
            addr, rw, cr, ct, true);

        VOPSTATS_UPDATE(vp, getpage);
        return (err);
}

int
fop_putpage(
        vnode_t *vp,
        offset_t off,
        size_t len,
        int flags,
        cred_t *cr,
        caller_context_t *ct)
{
        int     err;

        VOPXID_MAP_CR(vp, cr);

        err = fop_putpage_dispatch(vp, off, len, flags, cr, ct, true);

        VOPSTATS_UPDATE(vp, putpage);
        return (err);
}

int
fop_map(
        vnode_t *vp,
        offset_t off,
        struct as *as,
        caddr_t *addrp,
        size_t len,
        uchar_t prot,
        uchar_t maxprot,
        uint_t flags,
        cred_t *cr,
        caller_context_t *ct)
{
        int     err;

        VOPXID_MAP_CR(vp, cr);

        err = fop_map_dispatch(vp, off, as, addrp, len, prot, maxprot,
            flags, cr, ct, true);

        VOPSTATS_UPDATE(vp, map);
        return (err);
}

int
fop_addmap(
        vnode_t *vp,
        offset_t off,
        struct as *as,
        caddr_t addr,
        size_t len,
        uchar_t prot,
        uchar_t maxprot,
        uint_t flags,
        cred_t *cr,
        caller_context_t *ct)
{
        int error;
        u_longlong_t delta;

        VOPXID_MAP_CR(vp, cr);

        error = fop_addmap_dispatch(vp, off, as, addr, len, prot, maxprot,
            flags, cr, ct, true);

        if ((!error) && (vp->v_type == VREG)) {
                delta = (u_longlong_t)btopr(len);
                /*
                 * If file is declared MAP_PRIVATE, it can't be written back
                 * even if open for write. Handle as read.
                 */
                if (flags & MAP_PRIVATE) {
                        atomic_add_64((uint64_t *)(&(vp->v_mmap_read)),
                            (int64_t)delta);
                } else {
                        /*
                         * atomic_add_64 forces the fetch of a 64 bit value to
                         * be atomic on 32 bit machines
                         */
                        if (maxprot & PROT_WRITE)
                                atomic_add_64((uint64_t *)(&(vp->v_mmap_write)),
                                    (int64_t)delta);
                        if (maxprot & PROT_READ)
                                atomic_add_64((uint64_t *)(&(vp->v_mmap_read)),
                                    (int64_t)delta);
                        if (maxprot & PROT_EXEC)
                                atomic_add_64((uint64_t *)(&(vp->v_mmap_read)),
                                    (int64_t)delta);
                }
        }
        VOPSTATS_UPDATE(vp, addmap);
        return (error);
}

int
fop_delmap(
        vnode_t *vp,
        offset_t off,
        struct as *as,
        caddr_t addr,
        size_t len,
        uint_t prot,
        uint_t maxprot,
        uint_t flags,
        cred_t *cr,
        caller_context_t *ct)
{
        int error;
        u_longlong_t delta;

        VOPXID_MAP_CR(vp, cr);

        error = fop_delmap_dispatch(vp, off, as, addr, len, prot, maxprot,
            flags, cr, ct, true);

        /*
         * NFS calls into delmap twice, the first time
         * it simply establishes a callback mechanism and returns EAGAIN
         * while the real work is being done upon the second invocation.
         * We have to detect this here and only decrement the counts upon
         * the second delmap request.
         */
        if ((error != EAGAIN) && (vp->v_type == VREG)) {

                delta = (u_longlong_t)btopr(len);

                if (flags & MAP_PRIVATE) {
                        atomic_add_64((uint64_t *)(&(vp->v_mmap_read)),
                            (int64_t)(-delta));
                } else {
                        /*
                         * atomic_add_64 forces the fetch of a 64 bit value
                         * to be atomic on 32 bit machines
                         */
                        if (maxprot & PROT_WRITE)
                                atomic_add_64((uint64_t *)(&(vp->v_mmap_write)),
                                    (int64_t)(-delta));
                        if (maxprot & PROT_READ)
                                atomic_add_64((uint64_t *)(&(vp->v_mmap_read)),
                                    (int64_t)(-delta));
                        if (maxprot & PROT_EXEC)
                                atomic_add_64((uint64_t *)(&(vp->v_mmap_read)),
                                    (int64_t)(-delta));
                }
        }
        VOPSTATS_UPDATE(vp, delmap);
        return (error);
}


int
fop_poll(
        vnode_t *vp,
        short events,
        int anyyet,
        short *reventsp,
        struct pollhead **phpp,
        caller_context_t *ct)
{
        int     err;

        err = fop_poll_dispatch(vp, events, anyyet, reventsp, phpp, ct, true);

        VOPSTATS_UPDATE(vp, poll);
        return (err);
}

int
fop_dump(
        vnode_t *vp,
        caddr_t addr,
        offset_t lbdn,
        offset_t dblks,
        caller_context_t *ct)
{
        int     err;

        /* ensure lbdn and dblks can be passed safely to bdev_dump */
        if ((lbdn != (daddr_t)lbdn) || (dblks != (int)dblks))
                return (EIO);

        err = fop_dump_dispatch(vp, addr, lbdn, dblks, ct, true);

        VOPSTATS_UPDATE(vp, dump);
        return (err);
}

int
fop_pathconf(
        vnode_t *vp,
        int cmd,
        ulong_t *valp,
        cred_t *cr,
        caller_context_t *ct)
{
        int     err;

        VOPXID_MAP_CR(vp, cr);

        err = fop_pathconf_dispatch(vp, cmd, valp, cr, ct, true);

        VOPSTATS_UPDATE(vp, pathconf);
        return (err);
}

int
fop_pageio(
        vnode_t *vp,
        struct page *pp,
        uoff_t io_off,
        size_t io_len,
        int flags,
        cred_t *cr,
        caller_context_t *ct)
{
        int     err;

        VOPXID_MAP_CR(vp, cr);

        err = fop_pageio_dispatch(vp, pp, io_off, io_len, flags, cr, ct, true);

        VOPSTATS_UPDATE(vp, pageio);
        return (err);
}

int
fop_dumpctl(
        vnode_t *vp,
        int action,
        offset_t *blkp,
        caller_context_t *ct)
{
        int     err;

        err = fop_dumpctl_dispatch(vp, action, blkp, ct, true);

        VOPSTATS_UPDATE(vp, dumpctl);
        return (err);
}

void
fop_dispose(
        vnode_t *vp,
        page_t *pp,
        int flag,
        int dn,
        cred_t *cr,
        caller_context_t *ct)
{
        /* Must do stats first since it's possible to lose the vnode */
        VOPSTATS_UPDATE(vp, dispose);

        VOPXID_MAP_CR(vp, cr);

        fop_dispose_dispatch(vp, pp, flag, dn, cr, ct, true);
}

int
fop_setsecattr(
        vnode_t *vp,
        vsecattr_t *vsap,
        int flag,
        cred_t *cr,
        caller_context_t *ct)
{
        int     err;

        VOPXID_MAP_CR(vp, cr);

        /*
         * We're only allowed to skip the ACL check iff we used a 32 bit
         * ACE mask with fop_access() to determine permissions.
         */
        if ((flag & ATTR_NOACLCHECK) &&
            vfs_has_feature(vp->v_vfsp, VFSFT_ACEMASKONACCESS) == 0) {
                return (EINVAL);
        }

        err = fop_setsecattr_dispatch(vp, vsap, flag, cr, ct, true);

        VOPSTATS_UPDATE(vp, setsecattr);
        return (err);
}

int
fop_getsecattr(
        vnode_t *vp,
        vsecattr_t *vsap,
        int flag,
        cred_t *cr,
        caller_context_t *ct)
{
        int     err;

        /*
         * We're only allowed to skip the ACL check iff we used a 32 bit
         * ACE mask with fop_access() to determine permissions.
         */
        if ((flag & ATTR_NOACLCHECK) &&
            vfs_has_feature(vp->v_vfsp, VFSFT_ACEMASKONACCESS) == 0) {
                return (EINVAL);
        }

        VOPXID_MAP_CR(vp, cr);

        err = fop_getsecattr_dispatch(vp, vsap, flag, cr, ct, true);

        VOPSTATS_UPDATE(vp, getsecattr);
        return (err);
}

int
fop_shrlock(
        vnode_t *vp,
        int cmd,
        struct shrlock *shr,
        int flag,
        cred_t *cr,
        caller_context_t *ct)
{
        int     err;

        VOPXID_MAP_CR(vp, cr);

        err = fop_shrlock_dispatch(vp, cmd, shr, flag, cr, ct, true);

        VOPSTATS_UPDATE(vp, shrlock);
        return (err);
}

int
fop_vnevent(vnode_t *vp, vnevent_t vnevent, vnode_t *dvp, char *fnm,
    caller_context_t *ct)
{
        int     err;

        err = fop_vnevent_dispatch(vp, vnevent, dvp, fnm, ct, true);

        VOPSTATS_UPDATE(vp, vnevent);
        return (err);
}

int
fop_reqzcbuf(vnode_t *vp, enum uio_rw ioflag, xuio_t *uiop, cred_t *cr,
    caller_context_t *ct)
{
        int err;

        if (vfs_has_feature(vp->v_vfsp, VFSFT_ZEROCOPY_SUPPORTED) == 0)
                return (ENOTSUP);

        err = fop_reqzcbuf_dispatch(vp, ioflag, uiop, cr, ct, true);

        VOPSTATS_UPDATE(vp, reqzcbuf);
        return (err);
}

int
fop_retzcbuf(vnode_t *vp, xuio_t *uiop, cred_t *cr, caller_context_t *ct)
{
        int err;

        if (vfs_has_feature(vp->v_vfsp, VFSFT_ZEROCOPY_SUPPORTED) == 0)
                return (ENOTSUP);

        err = fop_retzcbuf_dispatch(vp, uiop, cr, ct, true);

        VOPSTATS_UPDATE(vp, retzcbuf);
        return (err);
}

/*
 * Default destructor
 *      Needed because NULL destructor means that the key is unused
 */
/* ARGSUSED */
void
vsd_defaultdestructor(void *value)
{}

/*
 * Create a key (index into per vnode array)
 *      Locks out vsd_create, vsd_destroy, and vsd_free
 *      May allocate memory with lock held
 */
void
vsd_create(uint_t *keyp, void (*destructor)(void *))
{
        int     i;
        uint_t  nkeys;

        /*
         * if key is allocated, do nothing
         */
        mutex_enter(&vsd_lock);
        if (*keyp) {
                mutex_exit(&vsd_lock);
                return;
        }
        /*
         * find an unused key
         */
        if (destructor == NULL)
                destructor = vsd_defaultdestructor;

        for (i = 0; i < vsd_nkeys; ++i)
                if (vsd_destructor[i] == NULL)
                        break;

        /*
         * if no unused keys, increase the size of the destructor array
         */
        if (i == vsd_nkeys) {
                if ((nkeys = (vsd_nkeys << 1)) == 0)
                        nkeys = 1;
                vsd_destructor =
                    (void (**)(void *))vsd_realloc((void *)vsd_destructor,
                    (size_t)(vsd_nkeys * sizeof (void (*)(void *))),
                    (size_t)(nkeys * sizeof (void (*)(void *))));
                vsd_nkeys = nkeys;
        }

        /*
         * allocate the next available unused key
         */
        vsd_destructor[i] = destructor;
        *keyp = i + 1;

        /* create vsd_list, if it doesn't exist */
        if (vsd_list == NULL) {
                vsd_list = kmem_alloc(sizeof (list_t), KM_SLEEP);
                list_create(vsd_list, sizeof (struct vsd_node),
                    offsetof(struct vsd_node, vs_nodes));
        }

        mutex_exit(&vsd_lock);
}

/*
 * Destroy a key
 *
 * Assumes that the caller is preventing vsd_set and vsd_get
 * Locks out vsd_create, vsd_destroy, and vsd_free
 * May free memory with lock held
 */
void
vsd_destroy(uint_t *keyp)
{
        uint_t key;
        struct vsd_node *vsd;

        /*
         * protect the key namespace and our destructor lists
         */
        mutex_enter(&vsd_lock);
        key = *keyp;
        *keyp = 0;

        ASSERT(key <= vsd_nkeys);

        /*
         * if the key is valid
         */
        if (key != 0) {
                uint_t k = key - 1;
                /*
                 * for every vnode with VSD, call key's destructor
                 */
                for (vsd = list_head(vsd_list); vsd != NULL;
                    vsd = list_next(vsd_list, vsd)) {
                        /*
                         * no VSD for key in this vnode
                         */
                        if (key > vsd->vs_nkeys)
                                continue;
                        /*
                         * call destructor for key
                         */
                        if (vsd->vs_value[k] && vsd_destructor[k])
                                (*vsd_destructor[k])(vsd->vs_value[k]);
                        /*
                         * reset value for key
                         */
                        vsd->vs_value[k] = NULL;
                }
                /*
                 * actually free the key (NULL destructor == unused)
                 */
                vsd_destructor[k] = NULL;
        }

        mutex_exit(&vsd_lock);
}

/*
 * Quickly return the per vnode value that was stored with the specified key
 * Assumes the caller is protecting key from vsd_create and vsd_destroy
 * Assumes the caller is holding v_vsd_lock to protect the vsd.
 */
void *
vsd_get(vnode_t *vp, uint_t key)
{
        struct vsd_node *vsd;

        ASSERT(vp != NULL);
        ASSERT(mutex_owned(&vp->v_vsd_lock));

        vsd = vp->v_vsd;

        if (key && vsd != NULL && key <= vsd->vs_nkeys)
                return (vsd->vs_value[key - 1]);
        return (NULL);
}

/*
 * Set a per vnode value indexed with the specified key
 * Assumes the caller is holding v_vsd_lock to protect the vsd.
 */
int
vsd_set(vnode_t *vp, uint_t key, void *value)
{
        struct vsd_node *vsd;

        ASSERT(vp != NULL);
        ASSERT(mutex_owned(&vp->v_vsd_lock));

        if (key == 0)
                return (EINVAL);

        vsd = vp->v_vsd;
        if (vsd == NULL)
                vsd = vp->v_vsd = kmem_zalloc(sizeof (*vsd), KM_SLEEP);

        /*
         * If the vsd was just allocated, vs_nkeys will be 0, so the following
         * code won't happen and we will continue down and allocate space for
         * the vs_value array.
         * If the caller is replacing one value with another, then it is up
         * to the caller to free/rele/destroy the previous value (if needed).
         */
        if (key <= vsd->vs_nkeys) {
                vsd->vs_value[key - 1] = value;
                return (0);
        }

        ASSERT(key <= vsd_nkeys);

        if (vsd->vs_nkeys == 0) {
                mutex_enter(&vsd_lock); /* lock out vsd_destroy() */
                /*
                 * Link onto list of all VSD nodes.
                 */
                list_insert_head(vsd_list, vsd);
                mutex_exit(&vsd_lock);
        }

        /*
         * Allocate vnode local storage and set the value for key
         */
        vsd->vs_value = vsd_realloc(vsd->vs_value,
            vsd->vs_nkeys * sizeof (void *),
            key * sizeof (void *));
        vsd->vs_nkeys = key;
        vsd->vs_value[key - 1] = value;

        return (0);
}

/*
 * Called from vn_free() to run the destructor function for each vsd
 *      Locks out vsd_create and vsd_destroy
 *      Assumes that the destructor *DOES NOT* use vsd
 */
void
vsd_free(vnode_t *vp)
{
        int i;
        struct vsd_node *vsd = vp->v_vsd;

        if (vsd == NULL)
                return;

        if (vsd->vs_nkeys == 0) {
                kmem_free(vsd, sizeof (*vsd));
                vp->v_vsd = NULL;
                return;
        }

        /*
         * lock out vsd_create and vsd_destroy, call
         * the destructor, and mark the value as destroyed.
         */
        mutex_enter(&vsd_lock);

        for (i = 0; i < vsd->vs_nkeys; i++) {
                if (vsd->vs_value[i] && vsd_destructor[i])
                        (*vsd_destructor[i])(vsd->vs_value[i]);
                vsd->vs_value[i] = NULL;
        }

        /*
         * remove from linked list of VSD nodes
         */
        list_remove(vsd_list, vsd);

        mutex_exit(&vsd_lock);

        /*
         * free up the VSD
         */
        kmem_free(vsd->vs_value, vsd->vs_nkeys * sizeof (void *));
        kmem_free(vsd, sizeof (struct vsd_node));
        vp->v_vsd = NULL;
}

/*
 * realloc
 */
static void *
vsd_realloc(void *old, size_t osize, size_t nsize)
{
        void *new;

        new = kmem_zalloc(nsize, KM_SLEEP);
        if (old) {
                bcopy(old, new, osize);
                kmem_free(old, osize);
        }
        return (new);
}

/*
 * Setup the extensible system attribute for creating a reparse point.
 * The symlink data 'target' is validated for proper format of a reparse
 * string and a check also made to make sure the symlink data does not
 * point to an existing file.
 *
 * return 0 if ok else -1.
 */
static int
fs_reparse_mark(char *target, vattr_t *vap, xvattr_t *xvattr)
{
        xoptattr_t *xoap;

        if ((!target) || (!vap) || (!xvattr))
                return (-1);

        /* validate reparse string */
        if (reparse_validate((const char *)target))
                return (-1);

        xva_init(xvattr);
        xvattr->xva_vattr = *vap;
        xvattr->xva_vattr.va_mask |= AT_XVATTR;
        xoap = xva_getxoptattr(xvattr);
        ASSERT(xoap);
        XVA_SET_REQ(xvattr, XAT_REPARSE);
        xoap->xoa_reparse = 1;

        return (0);
}

/*
 * Function to check whether a symlink is a reparse point.
 * Return B_TRUE if it is a reparse point, else return B_FALSE
 */
boolean_t
vn_is_reparse(vnode_t *vp, cred_t *cr, caller_context_t *ct)
{
        xvattr_t xvattr;
        xoptattr_t *xoap;

        if ((vp->v_type != VLNK) ||
            !(vfs_has_feature(vp->v_vfsp, VFSFT_XVATTR)))
                return (B_FALSE);

        xva_init(&xvattr);
        xoap = xva_getxoptattr(&xvattr);
        ASSERT(xoap);
        XVA_SET_REQ(&xvattr, XAT_REPARSE);

        if (fop_getattr(vp, &xvattr.xva_vattr, 0, cr, ct))
                return (B_FALSE);

        if ((!(xvattr.xva_vattr.va_mask & AT_XVATTR)) ||
            (!(XVA_ISSET_RTN(&xvattr, XAT_REPARSE))))
                return (B_FALSE);

        return (xoap->xoa_reparse ? B_TRUE : B_FALSE);
}