remove unnecessary offset_t casts of 0

[unleashed.git] / kernel / fs / specfs / specsubr.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 2009 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */
/*
 * Copyright (c) 2012 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/t_lock.h>
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/buf.h>
#include <sys/conf.h>
#include <sys/cred.h>
#include <sys/kmem.h>
#include <sys/sysmacros.h>
#include <sys/vfs.h>
#include <sys/vnode.h>
#include <sys/fs/snode.h>
#include <sys/fs/fifonode.h>
#include <sys/debug.h>
#include <sys/errno.h>
#include <sys/time.h>
#include <sys/file.h>
#include <sys/open.h>
#include <sys/user.h>
#include <sys/termios.h>
#include <sys/stream.h>
#include <sys/strsubr.h>
#include <sys/autoconf.h>
#include <sys/esunddi.h>
#include <sys/flock.h>
#include <sys/modctl.h>

struct vfs spec_vfs;
static dev_t specdev;
struct kmem_cache *snode_cache;
int spec_debug = 0;

static struct snode *sfind(dev_t, vtype_t, struct vnode *);
static struct vnode *get_cvp(dev_t, vtype_t, struct snode *, int *);
static void sinsert(struct snode *);

struct vnode *
specvp_devfs(
        struct vnode    *realvp,
        dev_t           dev,
        vtype_t         vtyp,
        struct cred     *cr,
        dev_info_t      *dip)
{
        struct vnode    *vp;

        ASSERT(realvp && dip);
        vp = specvp(realvp, dev, vtyp, cr);
        ASSERT(vp);

        /* associate a dip hold with the common snode's s_dip pointer */
        spec_assoc_vp_with_devi(vp, dip);
        return (vp);
}

/*
 * Return a shadow special vnode for the given dev.
 * If no snode exists for this dev create one and put it
 * in a table hashed by <dev, realvp>.  If the snode for
 * this dev is already in the table return it (ref count is
 * incremented by sfind).  The snode will be flushed from the
 * table when spec_inactive calls sdelete.
 *
 * The fsid is inherited from the real vnode so that clones
 * can be found.
 *
 */
struct vnode *
specvp(
        struct vnode    *vp,
        dev_t           dev,
        vtype_t         type,
        struct cred     *cr)
{
        struct snode *sp;
        struct snode *nsp;
        struct snode *csp;
        struct vnode *svp;
        struct vattr va;
        int     rc;
        int     used_csp = 0;           /* Did we use pre-allocated csp */

        if (vp == NULL)
                return (NULL);
        if (vp->v_type == VFIFO)
                return (fifovp(vp, cr));

        ASSERT(vp->v_type == type);
        ASSERT(vp->v_rdev == dev);

        /*
         * Pre-allocate snodes before holding any locks in case we block
         */
        nsp = kmem_cache_alloc(snode_cache, KM_SLEEP);
        csp = kmem_cache_alloc(snode_cache, KM_SLEEP);

        /*
         * Get the time attributes outside of the stable lock since
         * this operation may block. Unfortunately, it may not have
         * been required if the snode is in the cache.
         */
        va.va_mask = AT_FSID | AT_TIMES;
        rc = fop_getattr(vp, &va, 0, cr, NULL); /* XXX may block! */

        mutex_enter(&stable_lock);
        if ((sp = sfind(dev, type, vp)) == NULL) {
                struct vnode *cvp;

                sp = nsp;       /* Use pre-allocated snode */
                svp = STOV(sp);

                sp->s_realvp    = vp;
                VN_HOLD(vp);
                sp->s_commonvp  = NULL;
                sp->s_dev       = dev;
                sp->s_dip       = NULL;
                sp->s_nextr     = 0;
                sp->s_list      = NULL;
                sp->s_plcy      = NULL;
                sp->s_size      = 0;
                sp->s_flag      = 0;
                if (rc == 0) {
                        /*
                         * Set times in snode to those in the vnode.
                         */
                        sp->s_fsid = va.va_fsid;
                        sp->s_atime = va.va_atime.tv_sec;
                        sp->s_mtime = va.va_mtime.tv_sec;
                        sp->s_ctime = va.va_ctime.tv_sec;
                } else {
                        sp->s_fsid = specdev;
                        sp->s_atime = 0;
                        sp->s_mtime = 0;
                        sp->s_ctime = 0;
                }
                sp->s_count     = 0;
                sp->s_mapcnt    = 0;

                vn_reinit(svp);
                svp->v_flag     = (vp->v_flag & VROOT);
                svp->v_vfsp     = vp->v_vfsp;
                VFS_HOLD(svp->v_vfsp);
                svp->v_type     = type;
                svp->v_rdev     = dev;
                (void) vn_copypath(vp, svp);
                if (type == VBLK || type == VCHR) {
                        cvp = get_cvp(dev, type, csp, &used_csp);
                        svp->v_stream = cvp->v_stream;

                        sp->s_commonvp = cvp;
                }
                vn_exists(svp);
                sinsert(sp);
                mutex_exit(&stable_lock);
                if (used_csp == 0) {
                        /* Didn't use pre-allocated snode so free it */
                        kmem_cache_free(snode_cache, csp);
                }
        } else {
                mutex_exit(&stable_lock);
                /* free unused snode memory */
                kmem_cache_free(snode_cache, nsp);
                kmem_cache_free(snode_cache, csp);
        }
        return (STOV(sp));
}

/*
 * Return a special vnode for the given dev; no vnode is supplied
 * for it to shadow.  Always create a new snode and put it in the
 * table hashed by <dev, NULL>.  The snode will be flushed from the
 * table when spec_inactive() calls sdelete().  The association of
 * this node with a attached instance of hardware is not made until
 * spec_open time.
 *
 * N.B. Assumes caller takes on responsibility of making sure no one
 * else is creating a snode for (dev, type) at this time.
 */
struct vnode *
makespecvp(dev_t dev, vtype_t type)
{
        struct snode *sp;
        struct vnode *svp, *cvp;
        time_t now;

        sp = kmem_cache_alloc(snode_cache, KM_SLEEP);
        svp = STOV(sp);
        cvp = commonvp(dev, type);
        now = gethrestime_sec();

        sp->s_realvp    = NULL;
        sp->s_commonvp  = cvp;
        sp->s_dev       = dev;
        sp->s_dip       = NULL;
        sp->s_nextr     = 0;
        sp->s_list      = NULL;
        sp->s_plcy      = NULL;
        sp->s_size      = 0;
        sp->s_flag      = 0;
        sp->s_fsid      = specdev;
        sp->s_atime     = now;
        sp->s_mtime     = now;
        sp->s_ctime     = now;
        sp->s_count     = 0;
        sp->s_mapcnt    = 0;

        vn_reinit(svp);
        svp->v_vfsp     = &spec_vfs;
        svp->v_stream   = cvp->v_stream;
        svp->v_type     = type;
        svp->v_rdev     = dev;

        vn_exists(svp);
        mutex_enter(&stable_lock);
        sinsert(sp);
        mutex_exit(&stable_lock);

        return (svp);
}


/*
 * This function is called from spec_assoc_vp_with_devi(). That function
 * associates a "new" dip with a common snode, releasing (any) old dip
 * in the process. This function (spec_assoc_fence()) looks at the "new dip"
 * and determines whether the snode should be fenced of or not. As the table
 * below indicates, the value of old-dip is a don't care for all cases.
 *
 * old-dip      new-dip         common-snode
 * =========================================
 * Don't care   NULL            unfence
 * Don't care   retired         fence
 * Don't care   not-retired     unfence
 *
 * Since old-dip value is a "don't care", it is not passed into this function.
 */
static void
spec_assoc_fence(dev_info_t *ndip, vnode_t *vp)
{
        int             fence;
        struct snode    *csp;

        ASSERT(vp);
        ASSERT(vn_matchops(vp, spec_getvnodeops()));

        fence = 0;
        if (ndip != NULL) {
                mutex_enter(&DEVI(ndip)->devi_lock);
                if (DEVI(ndip)->devi_flags & DEVI_RETIRED)
                        fence = 1;
                mutex_exit(&DEVI(ndip)->devi_lock);
        }

        csp = VTOCS(vp);
        ASSERT(csp);

        /* SFENCED flag only set on common snode */
        mutex_enter(&csp->s_lock);
        if (fence)
                csp->s_flag |= SFENCED;
        else
                csp->s_flag &= ~SFENCED;
        mutex_exit(&csp->s_lock);

        FENDBG((CE_NOTE, "%sfenced common snode (%p) for new dip=%p",
            fence ? "" : "un", (void *)csp, (void *)ndip));
}

/*
 * Associate the common snode with a devinfo node.  This is called from:
 *
 *   1) specvp_devfs to associate a specfs node with the dip attached
 *      by devfs.
 *
 *   2) spec_open after path reconstruction and attach.
 *
 *   3) From dacf processing to associate a makespecvp node with
 *      the dip that dacf postattach processing is being performed on.
 *      This association is made prior to open to avoid recursion issues.
 *
 *   4) From ddi_assoc_queue_with_devi to change vnode association as part of
 *      DL_ATTACH/DL_DETACH processing (SDIPSET already set).  The call
 *      from ddi_assoc_queue_with_devi may specify a NULL dip.
 *
 * We put an extra hold on the devinfo node passed in as we establish it as
 * the new s_dip pointer.  Any hold associated with the prior s_dip pointer
 * is released. The new hold will stay active until another call to
 * spec_assoc_vp_with_devi or until the common snode is destroyed by
 * spec_inactive after the last VN_RELE of the common node. This devinfo hold
 * transfers across a clone open except in the clone_dev case, where the clone
 * driver is no longer required after open.
 *
 * When SDIPSET is set and s_dip is NULL, the vnode has an association with
 * the driver even though there is currently no association with a specific
 * hardware instance.
 */
void
spec_assoc_vp_with_devi(struct vnode *vp, dev_info_t *dip)
{
        struct snode    *csp;
        dev_info_t      *olddip;

        ASSERT(vp);

        /*
         * Don't establish a NULL association for a vnode associated with the
         * clone driver.  The qassociate(, -1) call from a streams driver's
         * open implementation to indicate support for qassociate has the
         * side-effect of this type of spec_assoc_vp_with_devi call. This
         * call should not change the the association of the pre-clone
         * vnode associated with the clone driver, the post-clone newdev
         * association will be established later by spec_clone().
         */
        if ((dip == NULL) && (getmajor(vp->v_rdev) == clone_major))
                return;

        /* hold the new */
        if (dip)
                e_ddi_hold_devi(dip);

        csp = VTOS(VTOS(vp)->s_commonvp);
        mutex_enter(&csp->s_lock);
        olddip = csp->s_dip;
        csp->s_dip = dip;
        csp->s_flag |= SDIPSET;

        /* If association changes then invalidate cached size */
        if (olddip != dip)
                csp->s_flag &= ~SSIZEVALID;
        mutex_exit(&csp->s_lock);

        spec_assoc_fence(dip, vp);

        /* release the old */
        if (olddip)
                ddi_release_devi(olddip);
}

/*
 * Return the held dip associated with the specified snode.
 */
dev_info_t *
spec_hold_devi_by_vp(struct vnode *vp)
{
        struct snode    *csp;
        dev_info_t      *dip;

        ASSERT(vn_matchops(vp, spec_getvnodeops()));

        csp = VTOS(VTOS(vp)->s_commonvp);
        dip = csp->s_dip;
        if (dip)
                e_ddi_hold_devi(dip);
        return (dip);
}

/*
 * Find a special vnode that refers to the given device
 * of the given type.  Never return a "common" vnode.
 * Return NULL if a special vnode does not exist.
 * HOLD the vnode before returning it.
 */
struct vnode *
specfind(dev_t dev, vtype_t type)
{
        struct snode *st;
        struct vnode *nvp;

        mutex_enter(&stable_lock);
        st = stable[STABLEHASH(dev)];
        while (st != NULL) {
                if (st->s_dev == dev) {
                        nvp = STOV(st);
                        if (nvp->v_type == type && st->s_commonvp != nvp) {
                                VN_HOLD(nvp);
                                mutex_exit(&stable_lock);
                                return (nvp);
                        }
                }
                st = st->s_next;
        }
        mutex_exit(&stable_lock);
        return (NULL);
}

/*
 * Loop through the snode cache looking for snodes referencing dip.
 *
 * This function determines if a devinfo node is "BUSY" from the perspective
 * of having an active vnode associated with the device, which represents a
 * dependency on the device's services.  This function is needed because a
 * devinfo node can have a non-zero devi_ref and still NOT be "BUSY" when,
 * for instance, the framework is manipulating the node (has an open
 * ndi_hold_devi).
 *
 * Returns:
 *      DEVI_REFERENCED         - if dip is referenced
 *      DEVI_NOT_REFERENCED     - if dip is not referenced
 */
int
devi_stillreferenced(dev_info_t *dip)
{
        struct snode    *sp;
        int             i;

        /* if no hold then there can't be an snode with s_dip == dip */
        if (e_ddi_devi_holdcnt(dip) == 0)
                return (DEVI_NOT_REFERENCED);

        mutex_enter(&stable_lock);
        for (i = 0; i < STABLESIZE; i++) {
                for (sp = stable[i]; sp != NULL; sp = sp->s_next) {
                        if (sp->s_dip == dip) {
                                mutex_exit(&stable_lock);
                                return (DEVI_REFERENCED);
                        }
                }
        }
        mutex_exit(&stable_lock);
        return (DEVI_NOT_REFERENCED);
}

/*
 * Given an snode, returns the open count and the dip
 * associated with that snode
 * Assumes the caller holds the appropriate locks
 * to prevent snode and/or dip from going away.
 * Returns:
 *      -1      No associated dip
 *      >= 0    Number of opens.
 */
int
spec_devi_open_count(struct snode *sp, dev_info_t **dipp)
{
        dev_info_t *dip;
        uint_t count;
        struct vnode *vp;

        ASSERT(sp);
        ASSERT(dipp);

        vp = STOV(sp);

        *dipp = NULL;

        /*
         * We are only interested in common snodes. Only common snodes
         * get their s_count fields bumped up on opens.
         */
        if (sp->s_commonvp != vp || (dip = sp->s_dip) == NULL)
                return (-1);

        mutex_enter(&sp->s_lock);
        count = sp->s_count + sp->s_mapcnt;
        if (sp->s_flag & SLOCKED)
                count++;
        mutex_exit(&sp->s_lock);

        *dipp = dip;

        return (count);
}

/*
 * Given a device vnode, return the common
 * vnode associated with it.
 */
struct vnode *
common_specvp(struct vnode *vp)
{
        struct snode *sp;

        if ((vp->v_type != VBLK) && (vp->v_type != VCHR) ||
            !vn_matchops(vp, spec_getvnodeops()))
                return (vp);
        sp = VTOS(vp);
        return (sp->s_commonvp);
}

/*
 * Returns a special vnode for the given dev.  The vnode is the
 * one which is "common" to all the snodes which represent the
 * same device.
 * Similar to commonvp() but doesn't acquire the stable_lock, and
 * may use a pre-allocated snode provided by caller.
 */
static struct vnode *
get_cvp(
        dev_t           dev,
        vtype_t         type,
        struct snode    *nsp,           /* pre-allocated snode */
        int             *used_nsp)      /* flag indicating if we use nsp */
{
        struct snode *sp;
        struct vnode *svp;

        ASSERT(MUTEX_HELD(&stable_lock));
        if ((sp = sfind(dev, type, NULL)) == NULL) {
                sp = nsp;               /* Use pre-allocated snode */
                *used_nsp = 1;          /* return value */
                svp = STOV(sp);

                sp->s_realvp    = NULL;
                sp->s_commonvp  = svp;          /* points to itself */
                sp->s_dev       = dev;
                sp->s_dip       = NULL;
                sp->s_nextr     = 0;
                sp->s_list      = NULL;
                sp->s_plcy      = NULL;
                sp->s_size      = UNKNOWN_SIZE;
                sp->s_flag      = 0;
                sp->s_fsid      = specdev;
                sp->s_atime     = 0;
                sp->s_mtime     = 0;
                sp->s_ctime     = 0;
                sp->s_count     = 0;
                sp->s_mapcnt    = 0;

                vn_reinit(svp);
                svp->v_vfsp     = &spec_vfs;
                svp->v_type     = type;
                svp->v_rdev     = dev;
                vn_exists(svp);
                sinsert(sp);
        } else
                *used_nsp = 0;
        return (STOV(sp));
}

/*
 * Returns a special vnode for the given dev.  The vnode is the
 * one which is "common" to all the snodes which represent the
 * same device.  For use ONLY by SPECFS.
 */
struct vnode *
commonvp(dev_t dev, vtype_t type)
{
        struct snode *sp, *nsp;
        struct vnode *svp;

        /* Pre-allocate snode in case we might block */
        nsp = kmem_cache_alloc(snode_cache, KM_SLEEP);

        mutex_enter(&stable_lock);
        if ((sp = sfind(dev, type, NULL)) == NULL) {
                sp = nsp;               /* Use pre-alloced snode */
                svp = STOV(sp);

                sp->s_realvp    = NULL;
                sp->s_commonvp  = svp;          /* points to itself */
                sp->s_dev       = dev;
                sp->s_dip       = NULL;
                sp->s_nextr     = 0;
                sp->s_list      = NULL;
                sp->s_plcy      = NULL;
                sp->s_size      = UNKNOWN_SIZE;
                sp->s_flag      = 0;
                sp->s_fsid      = specdev;
                sp->s_atime     = 0;
                sp->s_mtime     = 0;
                sp->s_ctime     = 0;
                sp->s_count     = 0;
                sp->s_mapcnt    = 0;

                vn_reinit(svp);
                svp->v_vfsp     = &spec_vfs;
                svp->v_type     = type;
                svp->v_rdev     = dev;
                vn_exists(svp);
                sinsert(sp);
                mutex_exit(&stable_lock);
        } else {
                mutex_exit(&stable_lock);
                /* Didn't need the pre-allocated snode */
                kmem_cache_free(snode_cache, nsp);
        }
        return (STOV(sp));
}

/*
 * Snode lookup stuff.
 * These routines maintain a table of snodes hashed by dev so
 * that the snode for an dev can be found if it already exists.
 */
struct snode *stable[STABLESIZE];
int             stablesz = STABLESIZE;
kmutex_t        stable_lock;

/*
 * Put a snode in the table.
 */
static void
sinsert(struct snode *sp)
{
        ASSERT(MUTEX_HELD(&stable_lock));
        sp->s_next = stable[STABLEHASH(sp->s_dev)];
        stable[STABLEHASH(sp->s_dev)] = sp;
}

/*
 * Remove an snode from the hash table.
 * The realvp is not released here because spec_inactive() still
 * needs it to do a spec_fsync().
 */
void
sdelete(struct snode *sp)
{
        struct snode *st;
        struct snode *stprev = NULL;

        ASSERT(MUTEX_HELD(&stable_lock));
        st = stable[STABLEHASH(sp->s_dev)];
        while (st != NULL) {
                if (st == sp) {
                        if (stprev == NULL)
                                stable[STABLEHASH(sp->s_dev)] = st->s_next;
                        else
                                stprev->s_next = st->s_next;
                        break;
                }
                stprev = st;
                st = st->s_next;
        }
}

/*
 * Lookup an snode by <dev, type, vp>.
 * ONLY looks for snodes with non-NULL s_realvp members and
 * common snodes (with s_commonvp pointing to its vnode).
 *
 * If vp is NULL, only return commonvp. Otherwise return
 * shadow vp with both shadow and common vp's VN_HELD.
 */
static struct snode *
sfind(
        dev_t   dev,
        vtype_t type,
        struct vnode *vp)
{
        struct snode *st;
        struct vnode *svp;

        ASSERT(MUTEX_HELD(&stable_lock));
        st = stable[STABLEHASH(dev)];
        while (st != NULL) {
                svp = STOV(st);
                if (st->s_dev == dev && svp->v_type == type &&
                    VN_CMP(st->s_realvp, vp) &&
                    (vp != NULL || st->s_commonvp == svp) &&
                    (vp == NULL || st->s_realvp->v_vfsp == vp->v_vfsp)) {
                        VN_HOLD(svp);
                        return (st);
                }
                st = st->s_next;
        }
        return (NULL);
}

/*
 * Mark the accessed, updated, or changed times in an snode
 * with the current time.
 */
void
smark(struct snode *sp, int flag)
{
        time_t  now = gethrestime_sec();

        /* check for change to avoid unnecessary locking */
        ASSERT((flag & ~(SACC|SUPD|SCHG)) == 0);
        if (((flag & sp->s_flag) != flag) ||
            ((flag & SACC) && (sp->s_atime != now)) ||
            ((flag & SUPD) && (sp->s_mtime != now)) ||
            ((flag & SCHG) && (sp->s_ctime != now))) {
                /* lock and update */
                mutex_enter(&sp->s_lock);
                sp->s_flag |= flag;
                if (flag & SACC)
                        sp->s_atime = now;
                if (flag & SUPD)
                        sp->s_mtime = now;
                if (flag & SCHG)
                        sp->s_ctime = now;
                mutex_exit(&sp->s_lock);
        }
}

/*
 * Return the maximum file offset permitted for this device.
 * -1 means unrestricted.  SLOFFSET is associated with D_64BIT.
 *
 * On a 32-bit kernel this will limit:
 *   o  D_64BIT devices to SPEC_MAXOFFSET_T.
 *   o  non-D_64BIT character drivers to a 32-bit offset (MAXOFF_T).
 */
offset_t
spec_maxoffset(struct vnode *vp)
{
        struct snode *sp = VTOS(vp);
        struct snode *csp = VTOS(sp->s_commonvp);

        if (vp->v_stream)
                return ((offset_t)-1);
        else if (csp->s_flag & SANYOFFSET)      /* D_U64BIT */
                return ((offset_t)-1);
#ifdef _ILP32
        if (csp->s_flag & SLOFFSET)             /* D_64BIT */
                return (SPEC_MAXOFFSET_T);
#endif  /* _ILP32 */
        return (MAXOFF_T);
}

/*ARGSUSED*/
static int
snode_constructor(void *buf, void *cdrarg, int kmflags)
{
        struct snode *sp = buf;
        struct vnode *vp;

        vp = sp->s_vnode = vn_alloc(kmflags);
        if (vp == NULL) {
                return (-1);
        }
        vn_setops(vp, spec_getvnodeops());
        vp->v_data = sp;

        mutex_init(&sp->s_lock, NULL, MUTEX_DEFAULT, NULL);
        cv_init(&sp->s_cv, NULL, CV_DEFAULT, NULL);
        return (0);
}

/*ARGSUSED1*/
static void
snode_destructor(void *buf, void *cdrarg)
{
        struct snode *sp = buf;
        struct vnode *vp = STOV(sp);

        mutex_destroy(&sp->s_lock);
        cv_destroy(&sp->s_cv);

        vn_free(vp);
}

static const struct vfsops spec_vfsops = {
        .vfs_sync = spec_sync,
};

int
specinit(int fstype, char *name)
{
        int error;
        dev_t dev;

        /*
         * Associate vfs and vnode operations.
         */
        error = vfs_setfsops(fstype, &spec_vfsops);
        if (error != 0) {
                cmn_err(CE_WARN, "specinit: bad fstype");
                return (error);
        }

        mutex_init(&stable_lock, NULL, MUTEX_DEFAULT, NULL);
        mutex_init(&spec_syncbusy, NULL, MUTEX_DEFAULT, NULL);

        /*
         * Create snode cache
         */
        snode_cache = kmem_cache_create("snode_cache", sizeof (struct snode),
            0, snode_constructor, snode_destructor, NULL, NULL, NULL, 0);

        /*
         * Associate vfs operations with spec_vfs
         */
        VFS_INIT(&spec_vfs, &spec_vfsops, NULL);
        if ((dev = getudev()) == -1)
                dev = 0;
        specdev = makedevice(dev, 0);
        return (0);
}

int
device_close(struct vnode *vp, int flag, struct cred *cr)
{
        struct snode *sp = VTOS(vp);
        enum vtype type = vp->v_type;
        struct vnode *cvp;
        dev_t dev;
        int error;

        dev = sp->s_dev;
        cvp = sp->s_commonvp;

        switch (type) {

        case VCHR:
                if (vp->v_stream) {
                        if (cvp->v_stream != NULL)
                                error = strclose(cvp, flag, cr);
                        vp->v_stream = NULL;
                } else
                        error = dev_close(dev, flag, OTYP_CHR, cr);
                break;

        case VBLK:
                /*
                 * On last close a block device we must
                 * invalidate any in-core blocks so that we
                 * can, for example, change floppy disks.
                 */
                (void) spec_putpage(cvp, 0,
                    (size_t)0, B_INVAL|B_FORCE, cr, NULL);
                bflush(dev);
                binval(dev);
                error = dev_close(dev, flag, OTYP_BLK, cr);
                break;
        default:
                panic("device_close: not a device");
                /*NOTREACHED*/
        }

        return (error);
}

struct vnode *
makectty(vnode_t *ovp)
{
        vnode_t *vp;

        if (vp = makespecvp(ovp->v_rdev, VCHR)) {
                struct snode *sp;
                struct snode *csp;
                struct vnode *cvp;

                sp = VTOS(vp);
                cvp = sp->s_commonvp;
                csp = VTOS(cvp);
                mutex_enter(&csp->s_lock);
                csp->s_count++;
                mutex_exit(&csp->s_lock);
        }

        return (vp);
}

void
spec_snode_walk(int (*callback)(struct snode *sp, void *arg), void *arg)
{
        struct snode    *sp;
        int             i;

        ASSERT(callback);

        mutex_enter(&stable_lock);
        for (i = 0; i < STABLESIZE; i++) {
                for (sp = stable[i]; sp; sp = sp->s_next) {
                        if (callback(sp, arg) != DDI_WALK_CONTINUE)
                                goto out;
                }
        }
out:
        mutex_exit(&stable_lock);
}

int
spec_is_clone(vnode_t *vp)
{
        struct snode *sp;

        if (vn_matchops(vp, spec_getvnodeops())) {
                sp = VTOS(vp);
                return ((sp->s_flag & SCLONE) ? 1 : 0);
        }

        return (0);
}

int
spec_is_selfclone(vnode_t *vp)
{
        struct snode *sp;

        if (vn_matchops(vp, spec_getvnodeops())) {
                sp = VTOS(vp);
                return ((sp->s_flag & SSELFCLONE) ? 1 : 0);
        }

        return (0);
}

/*
 * We may be invoked with a NULL vp in which case we fence off
 * all snodes associated with dip
 */
int
spec_fence_snode(dev_info_t *dip, struct vnode *vp)
{
        struct snode    *sp;
        struct snode    *csp;
        int             retired;
        int             i;
        char            *path;
        int             emitted;

        ASSERT(dip);

        retired = 0;
        mutex_enter(&DEVI(dip)->devi_lock);
        if (DEVI(dip)->devi_flags & DEVI_RETIRED)
                retired = 1;
        mutex_exit(&DEVI(dip)->devi_lock);

        if (!retired)
                return (0);

        path = kmem_alloc(MAXPATHLEN, KM_SLEEP);
        (void) ddi_pathname(dip, path);


        if (vp != NULL) {
                ASSERT(vn_matchops(vp, spec_getvnodeops()));
                csp = VTOCS(vp);
                ASSERT(csp);
                mutex_enter(&csp->s_lock);
                csp->s_flag |= SFENCED;
                mutex_exit(&csp->s_lock);
                FENDBG((CE_NOTE, "fenced off snode(%p) for dip: %s",
                    (void *)csp, path));
                kmem_free(path, MAXPATHLEN);
                return (0);
        }

        emitted = 0;
        mutex_enter(&stable_lock);
        for (i = 0; i < STABLESIZE; i++) {
                for (sp = stable[i]; sp != NULL; sp = sp->s_next) {
                        ASSERT(sp->s_commonvp);
                        csp = VTOS(sp->s_commonvp);
                        if (csp->s_dip == dip) {
                                /* fence off the common snode */
                                mutex_enter(&csp->s_lock);
                                csp->s_flag |= SFENCED;
                                mutex_exit(&csp->s_lock);
                                if (!emitted) {
                                        FENDBG((CE_NOTE, "fenced 1 of N"));
                                        emitted++;
                                }
                        }
                }
        }
        mutex_exit(&stable_lock);

        FENDBG((CE_NOTE, "fenced off all snodes for dip: %s", path));
        kmem_free(path, MAXPATHLEN);

        return (0);
}


int
spec_unfence_snode(dev_info_t *dip)
{
        struct snode    *sp;
        struct snode    *csp;
        int             i;
        char            *path;
        int             emitted;

        ASSERT(dip);

        path = kmem_alloc(MAXPATHLEN, KM_SLEEP);
        (void) ddi_pathname(dip, path);

        emitted = 0;
        mutex_enter(&stable_lock);
        for (i = 0; i < STABLESIZE; i++) {
                for (sp = stable[i]; sp != NULL; sp = sp->s_next) {
                        ASSERT(sp->s_commonvp);
                        csp = VTOS(sp->s_commonvp);
                        ASSERT(csp);
                        if (csp->s_dip == dip) {
                                /* unfence the common snode */
                                mutex_enter(&csp->s_lock);
                                csp->s_flag &= ~SFENCED;
                                mutex_exit(&csp->s_lock);
                                if (!emitted) {
                                        FENDBG((CE_NOTE, "unfenced 1 of N"));
                                        emitted++;
                                }
                        }
                }
        }
        mutex_exit(&stable_lock);

        FENDBG((CE_NOTE, "unfenced all snodes for dip: %s", path));
        kmem_free(path, MAXPATHLEN);

        return (0);
}

void
spec_size_invalidate(dev_t dev, vtype_t type)
{

        struct snode *csp;

        mutex_enter(&stable_lock);
        if ((csp = sfind(dev, type, NULL)) != NULL) {
                mutex_enter(&csp->s_lock);
                csp->s_flag &= ~SSIZEVALID;
                VN_RELE_ASYNC(STOV(csp), system_taskq);
                mutex_exit(&csp->s_lock);
        }
        mutex_exit(&stable_lock);
}