[apple/xnu.git] / bsd / miscfs / devfs / devfs_tree.c

/*
 * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this
 * file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */

/*
 * Copyright 1997,1998 Julian Elischer.  All rights reserved.
 * julian@freebsd.org
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *  1. Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *  2. Redistributions in binary form must reproduce the above copyright notice,
 *     this list of conditions and the following disclaimer in the documentation
 *     and/or other materials provided with the distribution.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER ``AS IS'' AND ANY EXPRESS
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE HOLDER OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * 
 * devfs_tree.c
 */

/*
 * HISTORY
 *  Dieter Siegmund (dieter@apple.com) Thu Apr  8 14:08:19 PDT 1999
 *  - removed mounting of "hidden" mountpoint
 *  - fixed problem in which devnode->dn_vn pointer was not
 *    updated with the vnode returned from checkalias()
 *  - replaced devfs_vntodn() with a macro VTODN()
 *  - rewrote dev_finddir() to not use recursion
 *  - added locking to avoid data structure corruption (DEVFS_(UN)LOCK())
 *  Dieter Siegmund (dieter@apple.com) Wed Jul 14 13:37:59 PDT 1999
 *  - fixed problem with devfs_dntovn() checking the v_id against the
 *    value cached in the device node; a union mount on top of us causes
 *    the v_id to get incremented thus, we would end up returning a new
 *    vnode instead of the existing one that has the mounted_here
 *    field filled in; the net effect was that the filesystem mounted
 *    on top of us would never show up
 *  - added devfs_stats to store how many data structures are actually 
 *    allocated
 */

/* SPLIT_DEVS means each devfs uses a different devnode for the same device */
/* Otherwise the same device always ends up at the same vnode even if  */
/* reached througgh a different devfs instance. The practical difference */
/* is that with the same vnode, chmods and chowns show up on all instances of */
/* a device. (etc) */

#define SPLIT_DEVS 1 /* maybe make this an option */
/*#define SPLIT_DEVS 1*/

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/conf.h>
#include <sys/malloc.h>
#include <sys/mount_internal.h>
#include <sys/proc.h>
#include <sys/vnode.h>
#include <stdarg.h>

#include "devfs.h"
#include "devfsdefs.h"

static void     devfs_release_busy(devnode_t *);
static void     dev_free_hier(devdirent_t *);
static int      devfs_propogate(devdirent_t *, devdirent_t *);
static int      dev_finddir(char *, devnode_t *, int, devnode_t **);
static int      dev_dup_entry(devnode_t *, devdirent_t *, devdirent_t **, struct devfsmount *);


lck_grp_t       * devfs_lck_grp;
lck_grp_attr_t  * devfs_lck_grp_attr;
lck_attr_t      * devfs_lck_attr;
lck_mtx_t         devfs_mutex;

devdirent_t *           dev_root = NULL;        /* root of backing tree */
struct devfs_stats      devfs_stats;            /* hold stats */

#ifdef HIDDEN_MOUNTPOINT
static struct mount *devfs_hidden_mount;
#endif /* HIDDEN_MOINTPOINT */

static int devfs_ready = 0;

#define NOCREATE        FALSE
#define CREATE          TRUE

/*
 * Set up the root directory node in the backing plane
 * This is happenning before the vfs system has been
 * set up yet, so be careful about what we reference..
 * Notice that the ops are by indirection.. as they haven't
 * been set up yet!
 * DEVFS has a hidden mountpoint that is used as the anchor point
 * for the internal 'blueprint' version of the dev filesystem tree.
 */
/*proto*/
int
devfs_sinit(void)
{
        int error;

        devfs_lck_grp_attr = lck_grp_attr_alloc_init();
        lck_grp_attr_setstat(devfs_lck_grp_attr);
        devfs_lck_grp = lck_grp_alloc_init("devfs_lock", devfs_lck_grp_attr);

        devfs_lck_attr = lck_attr_alloc_init();
        //lck_attr_setdebug(devfs_lck_attr);

        lck_mtx_init(&devfs_mutex, devfs_lck_grp, devfs_lck_attr);

        DEVFS_LOCK();
        error = dev_add_entry("root", NULL, DEV_DIR, NULL, NULL, NULL, &dev_root);
        DEVFS_UNLOCK();

        if (error) {
            printf("devfs_sinit: dev_add_entry failed ");
            return (ENOTSUP);
        }
#ifdef HIDDEN_MOUNTPOINT
        MALLOC(devfs_hidden_mount, struct mount *, sizeof(struct mount),
               M_MOUNT, M_WAITOK);
        bzero(devfs_hidden_mount,sizeof(struct mount));
        mount_lock_init(devfs_hidden_mount);
        TAILQ_INIT(&devfs_hidden_mount->mnt_vnodelist);
        TAILQ_INIT(&devfs_hidden_mount->mnt_workerqueue);
        TAILQ_INIT(&devfs_hidden_mount->mnt_newvnodes);

        /* Initialize the default IO constraints */
        mp->mnt_maxreadcnt = mp->mnt_maxwritecnt = MAXPHYS;
        mp->mnt_segreadcnt = mp->mnt_segwritecnt = 32;

        devfs_mount(devfs_hidden_mount,"dummy",NULL,NULL,NULL);
        dev_root->de_dnp->dn_dvm 
            = (struct devfsmount *)devfs_hidden_mount->mnt_data;
#endif /* HIDDEN_MOUNTPOINT */
        devfs_ready = 1;
        return (0);
}

/***********************************************************************\
*************************************************************************
*       Routines used to find our way to a point in the tree            *
*************************************************************************
\***********************************************************************/



/***************************************************************
 * Search down the linked list off a dir to find "name"         
 * return the devnode_t * for that node.
 *
 * called with DEVFS_LOCK held
 ***************************************************************/
devdirent_t *
dev_findname(devnode_t * dir, char *name)
{
        devdirent_t * newfp;
        if (dir->dn_type != DEV_DIR) return 0;/*XXX*/ /* printf?*/

        if (name[0] == '.')
        {
                if(name[1] == 0)
                {
                        return dir->dn_typeinfo.Dir.myname;
                }
                if((name[1] == '.') && (name[2] == 0))
                {
                        /* for root, .. == . */
                        return dir->dn_typeinfo.Dir.parent->dn_typeinfo.Dir.myname;
                }
        }
        newfp = dir->dn_typeinfo.Dir.dirlist;

        while(newfp)
        {
                if(!(strcmp(name,newfp->de_name)))
                        return newfp;
                newfp = newfp->de_next;
        }
        return NULL;
}

/***********************************************************************
 * Given a starting node (0 for root) and a pathname, return the node   
 * for the end item on the path. It MUST BE A DIRECTORY. If the 'CREATE'
 * option is true, then create any missing nodes in the path and create
 * and return the final node as well.                                   
 * This is used to set up a directory, before making nodes in it..
 *
 * called with DEVFS_LOCK held
 ***********************************************************************/
static int
dev_finddir(char * path, 
            devnode_t * dirnode,
            int create, 
            devnode_t * * dn_pp)
{
        devnode_t *     dnp = NULL;
        int             error = 0;
        char *          scan;


        if (!dirnode) /* dirnode == NULL means start at root */
            dirnode = dev_root->de_dnp;

        if (dirnode->dn_type != DEV_DIR) 
            return ENOTDIR;

        if (strlen(path) > (DEVMAXPATHSIZE - 1)) 
            return ENAMETOOLONG;

        scan = path;

        while (*scan == '/') 
            scan++;

        *dn_pp = NULL;

        while (1) {
            char                component[DEVMAXPATHSIZE];
            devdirent_t *       dirent_p;
            char *              start;

            if (*scan == 0) { 
                /* we hit the end of the string, we're done */
                *dn_pp = dirnode;
                break;
            }
            start = scan;
            while (*scan != '/' && *scan)
                scan++;

            strncpy(component, start, scan - start);
                component[ scan - start ] = '\0';
            if (*scan == '/')
                scan++;

            dirent_p = dev_findname(dirnode, component);
            if (dirent_p) {
                dnp = dirent_p->de_dnp;
                if (dnp->dn_type != DEV_DIR) {
                    error = ENOTDIR;
                    break;
                }
            }
            else {
                if (!create) {
                    error = ENOENT;
                    break;
                }
                error = dev_add_entry(component, dirnode, 
                                       DEV_DIR, NULL, NULL, NULL, &dirent_p);
                if (error)
                    break;
                dnp = dirent_p->de_dnp;
                devfs_propogate(dirnode->dn_typeinfo.Dir.myname, dirent_p);
            }
            dirnode = dnp; /* continue relative to this directory */
        }
        return (error);
}


/***********************************************************************
 * Add a new NAME element to the devfs
 * If we're creating a root node, then dirname is NULL
 * Basically this creates a new namespace entry for the device node
 *
 * Creates a name node, and links it to the supplied node
 *
 * called with DEVFS_LOCK held
 ***********************************************************************/
int
dev_add_name(char * name, devnode_t * dirnode, __unused devdirent_t * back, 
    devnode_t * dnp, devdirent_t * *dirent_pp)
{
        devdirent_t *   dirent_p = NULL;

        if(dirnode != NULL ) {
                if(dirnode->dn_type != DEV_DIR) return(ENOTDIR);
        
                if( dev_findname(dirnode,name))
                        return(EEXIST);
        }
        /*
         * make sure the name is legal
         * slightly misleading in the case of NULL
         */
        if (!name || (strlen(name) > (DEVMAXNAMESIZE - 1)))
            return (ENAMETOOLONG);

        /*
         * Allocate and fill out a new directory entry 
         */
        MALLOC(dirent_p, devdirent_t *, sizeof(devdirent_t), 
               M_DEVFSNAME, M_WAITOK);
        if (!dirent_p) {
            return ENOMEM;
        }
        bzero(dirent_p,sizeof(devdirent_t));

        /* inherrit our parent's mount info */ /*XXX*/
        /* a kludge but.... */
        if(dirnode && ( dnp->dn_dvm == NULL)) {
                dnp->dn_dvm = dirnode->dn_dvm;
                /* if(!dnp->dn_dvm) printf("parent had null dvm "); */
        }

        /*
         * Link the two together
         * include the implicit link in the count of links to the devnode..
         * this stops it from being accidentally freed later.
         */
        dirent_p->de_dnp = dnp;
        dnp->dn_links++ ; /* implicit from our own name-node */

        /* 
         * Make sure that we can find all the links that reference a node
         * so that we can get them all if we need to zap the node.
         */
        if(dnp->dn_linklist) {
                dirent_p->de_nextlink = dnp->dn_linklist;
                dirent_p->de_prevlinkp = dirent_p->de_nextlink->de_prevlinkp;
                dirent_p->de_nextlink->de_prevlinkp = &(dirent_p->de_nextlink);
                *dirent_p->de_prevlinkp = dirent_p;
        } else {
                dirent_p->de_nextlink = dirent_p;
                dirent_p->de_prevlinkp = &(dirent_p->de_nextlink);
        }
        dnp->dn_linklist = dirent_p;

        /*
         * If the node is a directory, then we need to handle the 
         * creation of the .. link.
         * A NULL dirnode indicates a root node, so point to ourself.
         */
        if(dnp->dn_type == DEV_DIR) {
                dnp->dn_typeinfo.Dir.myname = dirent_p;
                /*
                 * If we are unlinking from an old dir, decrement its links
                 * as we point our '..' elsewhere
                 * Note: it's up to the calling code to remove the 
                 * us from the original directory's list
                 */
                if(dnp->dn_typeinfo.Dir.parent) {
                        dnp->dn_typeinfo.Dir.parent->dn_links--;
                }
                if(dirnode) {
                        dnp->dn_typeinfo.Dir.parent = dirnode;
                } else {
                        dnp->dn_typeinfo.Dir.parent = dnp;
                }
                dnp->dn_typeinfo.Dir.parent->dn_links++; /* account for the new '..' */
        }

        /*
         * put the name into the directory entry.
         */
        strcpy(dirent_p->de_name, name);


        /*
         * Check if we are not making a root node..
         * (i.e. have parent)
         */
        if(dirnode) {
                /*
                 * Put it on the END of the linked list of directory entries
                 */
                dirent_p->de_parent = dirnode; /* null for root */
                dirent_p->de_prevp = dirnode->dn_typeinfo.Dir.dirlast;
                dirent_p->de_next = *(dirent_p->de_prevp); /* should be NULL */ 
                                                        /*right?*/
                *(dirent_p->de_prevp) = dirent_p;
                dirnode->dn_typeinfo.Dir.dirlast = &(dirent_p->de_next);
                dirnode->dn_typeinfo.Dir.entrycount++;
                dirnode->dn_len += strlen(name) + 8;/*ok, ok?*/
        }

        *dirent_pp = dirent_p;
        DEVFS_INCR_ENTRIES();
        return 0 ;
}


/***********************************************************************
 * Add a new element to the devfs plane.
 *
 * Creates a new dev_node to go with it if the prototype should not be
 * reused. (Is a DIR, or we select SPLIT_DEVS at compile time)
 * typeinfo gives us info to make our node if we don't have a prototype.
 * If typeinfo is null and proto exists, then the typeinfo field of
 * the proto is used intead in the CREATE case.
 * note the 'links' count is 0 (except if a dir)
 * but it is only cleared on a transition
 * so this is ok till we link it to something
 * Even in SPLIT_DEVS mode,
 * if the node already exists on the wanted plane, just return it
 *
 * called with DEVFS_LOCK held
***********************************************************************/
int
dev_add_node(int entrytype, devnode_type_t * typeinfo, devnode_t * proto,
             devnode_t * *dn_pp, struct devfsmount *dvm)
{
        devnode_t *     dnp = NULL;

#if defined SPLIT_DEVS
        /*
         * If we have a prototype, then check if there is already a sibling
         * on the mount plane we are looking at, if so, just return it.
         */
        if (proto) {
                dnp = proto->dn_nextsibling;
                while( dnp != proto) {
                        if (dnp->dn_dvm == dvm) {
                                *dn_pp = dnp;
                                return (0);
                        }
                        dnp = dnp->dn_nextsibling;
                }
                if (typeinfo == NULL)
                        typeinfo = &(proto->dn_typeinfo);
        }
#else   /* SPLIT_DEVS */
        if ( proto ) {
                switch (proto->type) {
                        case DEV_BDEV:
                        case DEV_CDEV:
                                *dn_pp = proto;
                                return 0;
                }
        }
#endif  /* SPLIT_DEVS */
        MALLOC(dnp, devnode_t *, sizeof(devnode_t), M_DEVFSNODE, M_WAITOK);
        if (!dnp) {
            return ENOMEM;
        }

        /*
         * If we have a proto, that means that we are duplicating some
         * other device, which can only happen if we are not at the back plane
         */
        if (proto) {
                bcopy(proto, dnp, sizeof(devnode_t));
                dnp->dn_links = 0;
                dnp->dn_linklist = NULL;
                dnp->dn_vn = NULL;
                dnp->dn_len = 0;
                /* add to END of siblings list */
                dnp->dn_prevsiblingp = proto->dn_prevsiblingp;
                *(dnp->dn_prevsiblingp) = dnp;
                dnp->dn_nextsibling = proto;
                proto->dn_prevsiblingp = &(dnp->dn_nextsibling);
        } else {
                struct timeval tv;

                /* 
                 * We have no prototype, so start off with a clean slate
                 */
                microtime(&tv);
                bzero(dnp, sizeof(devnode_t));
                dnp->dn_type = entrytype;
                dnp->dn_nextsibling = dnp;
                dnp->dn_prevsiblingp = &(dnp->dn_nextsibling);
                dnp->dn_atime.tv_sec = tv.tv_sec;
                dnp->dn_mtime.tv_sec = tv.tv_sec;
                dnp->dn_ctime.tv_sec = tv.tv_sec;
        }
        dnp->dn_dvm = dvm;

        /*
         * fill out the dev node according to type
         */
        switch(entrytype) {
        case DEV_DIR:
                /*
                 * As it's a directory, make sure
                 * it has a null entries list
                 */
                dnp->dn_typeinfo.Dir.dirlast = &(dnp->dn_typeinfo.Dir.dirlist);
                dnp->dn_typeinfo.Dir.dirlist = (devdirent_t *)0;
                dnp->dn_typeinfo.Dir.entrycount = 0;
                /*  until we know better, it has a null parent pointer*/
                dnp->dn_typeinfo.Dir.parent = NULL;
                dnp->dn_links++; /* for .*/
                dnp->dn_typeinfo.Dir.myname = NULL;
                /*
                 * make sure that the ops associated with it are the ops
                 * that we use (by default) for directories
                 */
                dnp->dn_ops = &devfs_vnodeop_p;
                dnp->dn_mode |= 0555;   /* default perms */
                break;
        case DEV_SLNK:
                /*
                 * As it's a symlink allocate and store the link info
                 * Symlinks should only ever be created by the user,
                 * so they are not on the back plane and should not be 
                 * propogated forward.. a bit like directories in that way..
                 * A symlink only exists on one plane and has its own
                 * node.. therefore we might be on any random plane.
                 */
                MALLOC(dnp->dn_typeinfo.Slnk.name, char *, 
                       typeinfo->Slnk.namelen+1,
                       M_DEVFSNODE, M_WAITOK);
                if (!dnp->dn_typeinfo.Slnk.name) {
                        FREE(dnp,M_DEVFSNODE);
                        return ENOMEM;
                }
                strncpy(dnp->dn_typeinfo.Slnk.name, typeinfo->Slnk.name,
                        typeinfo->Slnk.namelen);
                dnp->dn_typeinfo.Slnk.name[typeinfo->Slnk.namelen] = '\0';
                dnp->dn_typeinfo.Slnk.namelen = typeinfo->Slnk.namelen;
                DEVFS_INCR_STRINGSPACE(dnp->dn_typeinfo.Slnk.namelen + 1);
                dnp->dn_ops = &devfs_vnodeop_p;
                dnp->dn_mode |= 0555;   /* default perms */
                break;
        case DEV_CDEV:
        case DEV_BDEV:
                /*
                 * Make sure it has DEVICE type ops
                 * and device specific fields are correct
                 */
                dnp->dn_ops = &devfs_spec_vnodeop_p;
                dnp->dn_typeinfo.dev = typeinfo->dev;
                break;
        default:
                return EINVAL;
        }

        *dn_pp = dnp;
        DEVFS_INCR_NODES();
        return 0 ;
}


/***********************************************************************
 * called with DEVFS_LOCK held
 **********************************************************************/
void
devnode_free(devnode_t * dnp)
{
    if (dnp->dn_lflags & DN_BUSY) {
            dnp->dn_lflags |= DN_DELETE;
            return;
    }
    if (dnp->dn_type == DEV_SLNK) {
        DEVFS_DECR_STRINGSPACE(dnp->dn_typeinfo.Slnk.namelen + 1);
        FREE(dnp->dn_typeinfo.Slnk.name, M_DEVFSNODE);
    }
    DEVFS_DECR_NODES();
    FREE(dnp, M_DEVFSNODE);
}


/***********************************************************************
 * called with DEVFS_LOCK held
 **********************************************************************/
static void
devfs_dn_free(devnode_t * dnp)
{
        if(--dnp->dn_links <= 0 ) /* can be -1 for initial free, on error */
        {
                /*probably need to do other cleanups XXX */
                if (dnp->dn_nextsibling != dnp) {
                        devnode_t * *   prevp = dnp->dn_prevsiblingp;
                        *prevp = dnp->dn_nextsibling;
                        dnp->dn_nextsibling->dn_prevsiblingp = prevp;
                        
                }
                if (dnp->dn_vn == NULL) {
                    devnode_free(dnp); /* no accesses/references */
                }
                else {
                    dnp->dn_delete = TRUE;
                }
        }
}

/***********************************************************************\
*       Front Node Operations                                           * 
*       Add or delete a chain of front nodes                            *
\***********************************************************************/


/***********************************************************************
 * Given a directory backing node, and a child backing node, add the
 * appropriate front nodes to the front nodes of the directory to
 * represent the child node to the user
 *
 * on failure, front nodes will either be correct or not exist for each
 * front dir, however dirs completed will not be stripped of completed
 * frontnodes on failure of a later frontnode
 *
 * This allows a new node to be propogated through all mounted planes
 *
 * called with DEVFS_LOCK held
 ***********************************************************************/
static int
devfs_propogate(devdirent_t * parent,devdirent_t * child)
{
        int     error;
        devdirent_t * newnmp;
        devnode_t *     dnp = child->de_dnp;
        devnode_t *     pdnp = parent->de_dnp;
        devnode_t *     adnp = parent->de_dnp;
        int type = child->de_dnp->dn_type;

        /***********************************************
         * Find the other instances of the parent node
         ***********************************************/
        for (adnp = pdnp->dn_nextsibling;
                adnp != pdnp;
                adnp = adnp->dn_nextsibling)
        {
                /*
                 * Make the node, using the original as a prototype)
                 * if the node already exists on that plane it won't be
                 * re-made..
                 */
                if ((error = dev_add_entry(child->de_name, adnp, type,
                                           NULL, dnp, adnp->dn_dvm, 
                                           &newnmp)) != 0) {
                        printf("duplicating %s failed\n",child->de_name);
                }
        }
        return 0;       /* for now always succeed */
}


/***********************************************************************
 * remove all instances of this devicename [for backing nodes..]
 * note.. if there is another link to the node (non dir nodes only)
 * then the devfs_node will still exist as the ref count will be non-0
 * removing a directory node will remove all sup-nodes on all planes (ZAP)
 *
 * Used by device drivers to remove nodes that are no longer relevant
 * The argument is the 'cookie' they were given when they created the node
 * this function is exported.. see devfs.h
 ***********************************************************************/
void
devfs_remove(void *dirent_p)
{
        devnode_t * dnp = ((devdirent_t *)dirent_p)->de_dnp;
        devnode_t * dnp2;
        boolean_t   lastlink;

        DEVFS_LOCK();

        if (!devfs_ready) {
                printf("devfs_remove: not ready for devices!\n");
                goto out;
        }

        /* keep removing the next sibling till only we exist. */
        while ((dnp2 = dnp->dn_nextsibling) != dnp) {

                /*
                 * Keep removing the next front node till no more exist
                 */
                dnp->dn_nextsibling = dnp2->dn_nextsibling; 
                dnp->dn_nextsibling->dn_prevsiblingp = &(dnp->dn_nextsibling);
                dnp2->dn_nextsibling = dnp2;
                dnp2->dn_prevsiblingp = &(dnp2->dn_nextsibling);
                if (dnp2->dn_linklist) {
                        do {
                                lastlink = (1 == dnp2->dn_links);
                                dev_free_name(dnp2->dn_linklist);
                        } while (!lastlink);
                }
        }

        /*
         * then free the main node
         * If we are not running in SPLIT_DEVS mode, then
         * THIS is what gets rid of the propogated nodes.
         */
        if (dnp->dn_linklist) {
                do {
                        lastlink = (1 == dnp->dn_links);
                        dev_free_name(dnp->dn_linklist);
                } while (!lastlink);
        }
out:
        DEVFS_UNLOCK();

        return ;
}



/***************************************************************
 * duplicate the backing tree into a tree of nodes hung off the
 * mount point given as the argument. Do this by
 * calling dev_dup_entry which recurses all the way
 * up the tree..
 *
 * called with DEVFS_LOCK held
 **************************************************************/
int
dev_dup_plane(struct devfsmount *devfs_mp_p)
{
        devdirent_t *   new;
        int             error = 0;

        if ((error = dev_dup_entry(NULL, dev_root, &new, devfs_mp_p)))
                return error;
        devfs_mp_p->plane_root = new;
        return error;
}



/***************************************************************
 * Free a whole plane
 *
 * called with DEVFS_LOCK held
 ***************************************************************/
void
devfs_free_plane(struct devfsmount *devfs_mp_p)
{
        devdirent_t * dirent_p;

        dirent_p = devfs_mp_p->plane_root;
        if (dirent_p) {
                dev_free_hier(dirent_p);
                dev_free_name(dirent_p);
        }
        devfs_mp_p->plane_root = NULL;
}


/***************************************************************
 * Create and link in a new front element..
 * Parent can be 0 for a root node
 * Not presently usable to make a symlink XXX
 * (Ok, symlinks don't propogate)
 * recursively will create subnodes corresponding to equivalent
 * child nodes in the base level
 *
 * called with DEVFS_LOCK held
 ***************************************************************/
static int
dev_dup_entry(devnode_t * parent, devdirent_t * back, devdirent_t * *dnm_pp,
              struct devfsmount *dvm)
{
        devdirent_t *   entry_p;
        devdirent_t *   newback;
        devdirent_t *   newfront;
        int     error;
        devnode_t *     dnp = back->de_dnp;
        int type = dnp->dn_type;

        /*
         * go get the node made (if we need to)
         * use the back one as a prototype
         */
        if ((error = dev_add_entry(back->de_name, parent, type,
                                NULL, dnp,
                                parent?parent->dn_dvm:dvm, &entry_p)) != 0) {
                printf("duplicating %s failed\n",back->de_name);
        }

        /*
         * If we have just made the root, then insert the pointer to the
         * mount information
         */
        if(dvm) {
                entry_p->de_dnp->dn_dvm = dvm;
        }

        /*
         * If it is a directory, then recurse down all the other
         * subnodes in it....
         * note that this time we don't pass on the mount info..
         */
        if (type == DEV_DIR)
        {
                for(newback = back->de_dnp->dn_typeinfo.Dir.dirlist;
                                newback; newback = newback->de_next)
                {
                        if((error = dev_dup_entry(entry_p->de_dnp,
                                            newback, &newfront, NULL)) != 0)
                        {
                                break; /* back out with an error */
                        }
                }
        }
        *dnm_pp = entry_p;
        return error;
}


/***************************************************************
 * Free a name node
 * remember that if there are other names pointing to the
 * dev_node then it may not get freed yet
 * can handle if there is no dnp
 *
 * called with DEVFS_LOCK held
 ***************************************************************/

int
dev_free_name(devdirent_t * dirent_p)
{
        devnode_t *     parent = dirent_p->de_parent;
        devnode_t *     dnp = dirent_p->de_dnp;

        if(dnp) {
                if(dnp->dn_type == DEV_DIR)
                {
                        devnode_t * p;

                        if(dnp->dn_typeinfo.Dir.dirlist)
                                return (ENOTEMPTY);
                        p = dnp->dn_typeinfo.Dir.parent;
                        devfs_dn_free(dnp);     /* account for '.' */
                        devfs_dn_free(p);       /* '..' */
                }
                /*
                 * unlink us from the list of links for this node
                 * If we are the only link, it's easy!
                 * if we are a DIR of course there should not be any
                 * other links.
                 */
                if(dirent_p->de_nextlink == dirent_p) {
                                dnp->dn_linklist = NULL;
                } else {
                        if(dnp->dn_linklist == dirent_p) {
                                dnp->dn_linklist = dirent_p->de_nextlink;
                        }
                        dirent_p->de_nextlink->de_prevlinkp 
                            = dirent_p->de_prevlinkp;
                        *dirent_p->de_prevlinkp = dirent_p->de_nextlink;
                }
                devfs_dn_free(dnp);
        }

        /*
         * unlink ourselves from the directory on this plane
         */
        if(parent) /* if not fs root */
        {
                if( (*dirent_p->de_prevp = dirent_p->de_next) )/* yes, assign */
                {
                        dirent_p->de_next->de_prevp = dirent_p->de_prevp;
                }
                else
                {
                        parent->dn_typeinfo.Dir.dirlast
                                = dirent_p->de_prevp;
                }
                parent->dn_typeinfo.Dir.entrycount--;
                parent->dn_len -= strlen(dirent_p->de_name) + 8;
        }

        DEVFS_DECR_ENTRIES();
        FREE(dirent_p, M_DEVFSNAME);
        return 0;
}


/***************************************************************
 * Free a hierarchy starting at a directory node name
 * remember that if there are other names pointing to the
 * dev_node then it may not get freed yet
 * can handle if there is no dnp
 * leave the node itself allocated.
 *
 * called with DEVFS_LOCK held
 ***************************************************************/

static void
dev_free_hier(devdirent_t * dirent_p)
{
        devnode_t *     dnp = dirent_p->de_dnp;

        if(dnp) {
                if(dnp->dn_type == DEV_DIR)
                {
                        while(dnp->dn_typeinfo.Dir.dirlist)
                        {
                                dev_free_hier(dnp->dn_typeinfo.Dir.dirlist);
                                dev_free_name(dnp->dn_typeinfo.Dir.dirlist);
                        }
                }
        }
}


/***************************************************************
 * given a dev_node, find the appropriate vnode if one is already
 * associated, or get a new one and associate it with the dev_node
 *
 * called with DEVFS_LOCK held
 ***************************************************************/
int
devfs_dntovn(devnode_t * dnp, struct vnode **vn_pp, __unused struct proc * p)
{
        struct vnode *vn_p;
        int error = 0;
        struct vnode_fsparam vfsp;
        enum vtype vtype = 0;
        int markroot = 0;

retry:
        *vn_pp = NULL;
        vn_p = dnp->dn_vn;

        dnp->dn_lflags |= DN_BUSY;

        if (vn_p) { /* already has a vnode */
                uint32_t vid;
                
                vid = vnode_vid(vn_p);

                DEVFS_UNLOCK();

                error = vnode_getwithvid(vn_p, vid);

                DEVFS_LOCK();

                if (dnp->dn_lflags & DN_DELETE) {
                        /*
                         * our BUSY node got marked for
                         * deletion while the DEVFS lock
                         * was dropped...
                         */
                        if (error == 0) {
                                /*
                                 * vnode_getwithvid returned a valid ref
                                 * which we need to drop
                                 */
                                vnode_put(vn_p);
                        }
                        /*
                         * set the error to EAGAIN
                         * which will cause devfs_lookup
                         * to retry this node
                         */
                        error = EAGAIN;
                }
                if ( !error)
                        *vn_pp = vn_p;

                devfs_release_busy(dnp);

                return error;
        }

        if (dnp->dn_lflags & DN_CREATE) {
                dnp->dn_lflags |= DN_CREATEWAIT;
                msleep(&dnp->dn_lflags, &devfs_mutex, PRIBIO, 0 , 0);
                goto retry;
        }

        dnp->dn_lflags |= DN_CREATE;

        switch (dnp->dn_type) {
                case    DEV_SLNK:
                        vtype = VLNK;
                        break;
                case    DEV_DIR:
                        if (dnp->dn_typeinfo.Dir.parent == dnp) {
                                markroot = 1;
                        }
                        vtype = VDIR;
                        break;
                case    DEV_BDEV:
                case    DEV_CDEV:
                        vtype = (dnp->dn_type == DEV_BDEV) ? VBLK : VCHR;
                        break;
        }
        vfsp.vnfs_mp = dnp->dn_dvm->mount;
        vfsp.vnfs_vtype = vtype;
        vfsp.vnfs_str = "devfs";
        vfsp.vnfs_dvp = 0;
        vfsp.vnfs_fsnode = dnp;
        vfsp.vnfs_cnp = 0;
        vfsp.vnfs_vops = *(dnp->dn_ops);
                
        if (vtype == VBLK || vtype == VCHR)
                vfsp.vnfs_rdev = dnp->dn_typeinfo.dev;
        else
                vfsp.vnfs_rdev = 0;
        vfsp.vnfs_filesize = 0;
        vfsp.vnfs_flags = VNFS_NOCACHE | VNFS_CANTCACHE;
        /* Tag system files */
        vfsp.vnfs_marksystem = 0;
        vfsp.vnfs_markroot = markroot;

        DEVFS_UNLOCK();

        error = vnode_create(VNCREATE_FLAVOR, VCREATESIZE, &vfsp, &vn_p);

        DEVFS_LOCK();

        if (error == 0) {
                if ((dnp->dn_vn)) {
                        panic("devnode already has a vnode?");
                } else {
                        dnp->dn_vn = vn_p;
                        *vn_pp = vn_p;
                        vnode_settag(vn_p, VT_DEVFS);
                }
        }

        dnp->dn_lflags &= ~DN_CREATE;

        if (dnp->dn_lflags & DN_CREATEWAIT) {
                dnp->dn_lflags &= ~DN_CREATEWAIT;
                wakeup(&dnp->dn_lflags);
        }

        devfs_release_busy(dnp);

        return error;
}


/***********************************************************************
 * called with DEVFS_LOCK held
 ***********************************************************************/
static void
devfs_release_busy(devnode_t *dnp) {

        dnp->dn_lflags &= ~DN_BUSY;

        if (dnp->dn_lflags & DN_DELETE)
                devnode_free(dnp);
}

/***********************************************************************
 * add a whole device, with no prototype.. make name element and node
 * Used for adding the original device entries
 *
 * called with DEVFS_LOCK held
 ***********************************************************************/
int
dev_add_entry(char *name, devnode_t * parent, int type, devnode_type_t * typeinfo,
              devnode_t * proto, struct devfsmount *dvm, devdirent_t * *nm_pp)
{
        devnode_t *     dnp;
        int     error = 0;

        if ((error = dev_add_node(type, typeinfo, proto, &dnp, 
                        (parent?parent->dn_dvm:dvm))) != 0)
        {
                printf("devfs: %s: base node allocation failed (Errno=%d)\n",
                        name,error);
                return error;
        }
        if ((error = dev_add_name(name ,parent ,NULL, dnp, nm_pp)) != 0)
        {
                devfs_dn_free(dnp); /* 1->0 for dir, 0->(-1) for other */
                printf("devfs: %s: name slot allocation failed (Errno=%d)\n",
                       name,error);
                
        }
        return error;
}


/*
 * Function: devfs_make_node
 *
 * Purpose
 *   Create a device node with the given pathname in the devfs namespace.
 *
 * Parameters:
 *   dev        - the dev_t value to associate
 *   chrblk     - block or character device (DEVFS_CHAR or DEVFS_BLOCK)
 *   uid, gid   - ownership
 *   perms      - permissions
 *   fmt, ...   - path format string with printf args to format the path name
 * Returns:
 *   A handle to a device node if successful, NULL otherwise.
 */
void *
devfs_make_node(dev_t dev, int chrblk, uid_t uid,
                gid_t gid, int perms, const char *fmt, ...)
{
        devdirent_t *   new_dev = NULL;
        devnode_t *     dnp;    /* devnode for parent directory */
        devnode_type_t  typeinfo;

        char *name, *path, buf[256]; /* XXX */
        int i;
        va_list ap;


        DEVFS_LOCK();

        if (!devfs_ready) {
                printf("devfs_make_node: not ready for devices!\n");
                goto out;
        }
        if (chrblk != DEVFS_CHAR && chrblk != DEVFS_BLOCK)
                goto out;

        DEVFS_UNLOCK();

        va_start(ap, fmt);
        vsnprintf(buf, sizeof(buf), fmt, ap);
        va_end(ap);

        name = NULL;

        for(i=strlen(buf); i>0; i--)
                if(buf[i] == '/') {
                        name=&buf[i];
                        buf[i]=0;
                        break;
                }

        if (name) {
                *name++ = '\0';
                path = buf;
        } else {
                name = buf;
                path = "/";
        }
        DEVFS_LOCK();

        /* find/create directory path ie. mkdir -p */
        if (dev_finddir(path, NULL, CREATE, &dnp) == 0) {
            typeinfo.dev = dev;
            if (dev_add_entry(name, dnp, 
                              (chrblk == DEVFS_CHAR) ? DEV_CDEV : DEV_BDEV, 
                              &typeinfo, NULL, NULL, &new_dev) == 0) {
                new_dev->de_dnp->dn_gid = gid;
                new_dev->de_dnp->dn_uid = uid;
                new_dev->de_dnp->dn_mode |= perms;
                devfs_propogate(dnp->dn_typeinfo.Dir.myname, new_dev);
            }
        }
out:
        DEVFS_UNLOCK();

        return new_dev;
}

/*
 * Function: devfs_make_link
 *
 * Purpose:
 *   Create a link to a previously created device node.
 *
 * Returns:
 *   0 if successful, -1 if failed
 */
int
devfs_make_link(void *original, char *fmt, ...)
{
        devdirent_t *   new_dev = NULL;
        devdirent_t *   orig = (devdirent_t *) original;
        devnode_t *     dirnode;        /* devnode for parent directory */

        va_list ap;
        char *p, buf[256]; /* XXX */
        int i;

        DEVFS_LOCK();

        if (!devfs_ready) {
                printf("devfs_make_link: not ready for devices!\n");
                goto out;
        }
        DEVFS_UNLOCK();

        va_start(ap, fmt);
        vsnprintf(buf, sizeof(buf), fmt, ap);
        va_end(ap);

        p = NULL;

        for(i=strlen(buf); i>0; i--) {
                if(buf[i] == '/') {
                                p=&buf[i];
                                buf[i]=0;
                                break;
                }
        }
        DEVFS_LOCK();

        if (p) {
                *p++ = '\0';

                if (dev_finddir(buf, NULL, CREATE, &dirnode)
                    || dev_add_name(p, dirnode, NULL, orig->de_dnp, &new_dev))
                        goto fail;
        } else {
                if (dev_finddir("", NULL, CREATE, &dirnode)
                    || dev_add_name(buf, dirnode, NULL, orig->de_dnp, &new_dev))
                        goto fail;
        }
        devfs_propogate(dirnode->dn_typeinfo.Dir.myname, new_dev);
fail:
out:
        DEVFS_UNLOCK();

        return ((new_dev != NULL) ? 0 : -1);
}