kernel - devfs - Fix deadlocks

[dragonfly.git] / sys / vfs / devfs / devfs_core.c

/*
 * Copyright (c) 2009 The DragonFly Project.  All rights reserved.
 *
 * This code is derived from software contributed to The DragonFly Project
 * by Alex Hornung <ahornung@gmail.com>
 *
 * 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.
 * 3. Neither the name of The DragonFly Project nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific, prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``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
 * COPYRIGHT HOLDERS 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.
 */
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/mount.h>
#include <sys/vnode.h>
#include <sys/types.h>
#include <sys/lock.h>
#include <sys/msgport.h>
#include <sys/msgport2.h>
#include <sys/spinlock2.h>
#include <sys/sysctl.h>
#include <sys/ucred.h>
#include <sys/param.h>
#include <sys/sysref2.h>
#include <sys/systm.h>
#include <sys/devfs.h>
#include <sys/devfs_rules.h>
#include <sys/hotplug.h>
#include <sys/udev.h>

MALLOC_DEFINE(M_DEVFS, "devfs", "Device File System (devfs) allocations");
DEVFS_DECLARE_CLONE_BITMAP(ops_id);
/*
 * SYSREF Integration - reference counting, allocation,
 * sysid and syslink integration.
 */
static void devfs_cdev_terminate(cdev_t dev);
static void devfs_cdev_lock(cdev_t dev);
static void devfs_cdev_unlock(cdev_t dev);
static struct sysref_class     cdev_sysref_class = {
        .name =         "cdev",
        .mtype =        M_DEVFS,
        .proto =        SYSREF_PROTO_DEV,
        .offset =       offsetof(struct cdev, si_sysref),
        .objsize =      sizeof(struct cdev),
        .mag_capacity = 32,
        .flags =        0,
        .ops =  {
                .terminate = (sysref_terminate_func_t)devfs_cdev_terminate,
                .lock = (sysref_lock_func_t)devfs_cdev_lock,
                .unlock = (sysref_unlock_func_t)devfs_cdev_unlock
        }
};

static struct objcache  *devfs_node_cache;
static struct objcache  *devfs_msg_cache;
static struct objcache  *devfs_dev_cache;

static struct objcache_malloc_args devfs_node_malloc_args = {
        sizeof(struct devfs_node), M_DEVFS };
struct objcache_malloc_args devfs_msg_malloc_args = {
        sizeof(struct devfs_msg), M_DEVFS };
struct objcache_malloc_args devfs_dev_malloc_args = {
        sizeof(struct cdev), M_DEVFS };

static struct devfs_dev_head devfs_dev_list =
                TAILQ_HEAD_INITIALIZER(devfs_dev_list);
static struct devfs_mnt_head devfs_mnt_list =
                TAILQ_HEAD_INITIALIZER(devfs_mnt_list);
static struct devfs_chandler_head devfs_chandler_list =
                TAILQ_HEAD_INITIALIZER(devfs_chandler_list);
static struct devfs_alias_head devfs_alias_list =
                TAILQ_HEAD_INITIALIZER(devfs_alias_list);
static struct devfs_dev_ops_head devfs_dev_ops_list =
                TAILQ_HEAD_INITIALIZER(devfs_dev_ops_list);

struct lock             devfs_lock;
static struct lwkt_port devfs_dispose_port;
static struct lwkt_port devfs_msg_port;
static struct thread    *td_core;

static struct spinlock  ino_lock;
static ino_t    d_ino;
static int      devfs_debug_enable;
static int      devfs_run;

static ino_t devfs_fetch_ino(void);
static int devfs_create_all_dev_worker(struct devfs_node *);
static int devfs_create_dev_worker(cdev_t, uid_t, gid_t, int);
static int devfs_destroy_dev_worker(cdev_t);
static int devfs_destroy_subnames_worker(char *);
static int devfs_destroy_dev_by_ops_worker(struct dev_ops *, int);
static int devfs_propagate_dev(cdev_t, int);
static int devfs_unlink_dev(cdev_t dev);
static void devfs_msg_exec(devfs_msg_t msg);

static int devfs_chandler_add_worker(const char *, d_clone_t *);
static int devfs_chandler_del_worker(const char *);

static void devfs_msg_autofree_reply(lwkt_port_t, lwkt_msg_t);
static void devfs_msg_core(void *);

static int devfs_find_device_by_name_worker(devfs_msg_t);
static int devfs_find_device_by_udev_worker(devfs_msg_t);

static int devfs_apply_reset_rules_caller(char *, int);

static int devfs_scan_callback_worker(devfs_scan_t *, void *);

static struct devfs_node *devfs_resolve_or_create_dir(struct devfs_node *,
                char *, size_t, int);

static int devfs_make_alias_worker(struct devfs_alias *);
static int devfs_alias_remove(cdev_t);
static int devfs_alias_reap(void);
static int devfs_alias_propagate(struct devfs_alias *);
static int devfs_alias_apply(struct devfs_node *, struct devfs_alias *);
static int devfs_alias_check_create(struct devfs_node *);

static int devfs_clr_subnames_flag_worker(char *, uint32_t);
static int devfs_destroy_subnames_without_flag_worker(char *, uint32_t);

static void *devfs_reaperp_callback(struct devfs_node *, void *);
static void *devfs_gc_dirs_callback(struct devfs_node *, void *);
static void *devfs_gc_links_callback(struct devfs_node *, struct devfs_node *);
static void *
devfs_inode_to_vnode_worker_callback(struct devfs_node *, ino_t *);

/* hotplug */
void (*devfs_node_added)(struct hotplug_device*) = NULL;
void (*devfs_node_removed)(struct hotplug_device*) = NULL;

/*
 * devfs_debug() is a SYSCTL and TUNABLE controlled debug output function
 * using kvprintf
 */
int
devfs_debug(int level, char *fmt, ...)
{
        __va_list ap;

        __va_start(ap, fmt);
        if (level <= devfs_debug_enable)
                kvprintf(fmt, ap);
        __va_end(ap);

        return 0;
}

/*
 * devfs_allocp() Allocates a new devfs node with the specified
 * parameters. The node is also automatically linked into the topology
 * if a parent is specified. It also calls the rule and alias stuff to
 * be applied on the new node
 */
struct devfs_node *
devfs_allocp(devfs_nodetype devfsnodetype, char *name,
             struct devfs_node *parent, struct mount *mp, cdev_t dev)
{
        struct devfs_node *node = NULL;
        size_t namlen = strlen(name);

        node = objcache_get(devfs_node_cache, M_WAITOK);
        bzero(node, sizeof(*node));

        atomic_add_long(&(DEVFS_MNTDATA(mp)->leak_count), 1);

        node->d_dev = NULL;
        node->nchildren = 1;
        node->mp = mp;
        node->d_dir.d_ino = devfs_fetch_ino();

        /*
         * Cookie jar for children. Leave 0 and 1 for '.' and '..' entries
         * respectively.
         */
        node->cookie_jar = 2;

        /*
         * Access Control members
         */
        node->mode = DEVFS_DEFAULT_MODE;
        node->uid = DEVFS_DEFAULT_UID;
        node->gid = DEVFS_DEFAULT_GID;

        switch (devfsnodetype) {
        case Proot:
                /*
                 * Ensure that we don't recycle the root vnode by marking it as
                 * linked into the topology.
                 */
                node->flags |= DEVFS_NODE_LINKED;
        case Pdir:
                TAILQ_INIT(DEVFS_DENODE_HEAD(node));
                node->d_dir.d_type = DT_DIR;
                node->nchildren = 2;
                break;

        case Plink:
                node->d_dir.d_type = DT_LNK;
                break;

        case Preg:
                node->d_dir.d_type = DT_REG;
                break;

        case Pdev:
                if (dev != NULL) {
                        node->d_dir.d_type = DT_CHR;
                        node->d_dev = dev;

                        node->mode = dev->si_perms;
                        node->uid = dev->si_uid;
                        node->gid = dev->si_gid;

                        devfs_alias_check_create(node);
                }
                break;

        default:
                panic("devfs_allocp: unknown node type");
        }

        node->v_node = NULL;
        node->node_type = devfsnodetype;

        /* Initialize the dirent structure of each devfs vnode */
        node->d_dir.d_namlen = namlen;
        node->d_dir.d_name = kmalloc(namlen+1, M_DEVFS, M_WAITOK);
        memcpy(node->d_dir.d_name, name, namlen);
        node->d_dir.d_name[namlen] = '\0';

        /* Initialize the parent node element */
        node->parent = parent;

        /* Apply rules */
        devfs_rule_check_apply(node, NULL);

        /* Initialize *time members */
        nanotime(&node->atime);
        node->mtime = node->ctime = node->atime;

        /*
         * Associate with parent as last step, clean out namecache
         * reference.
         */
        if ((parent != NULL) &&
            ((parent->node_type == Proot) || (parent->node_type == Pdir))) {
                parent->nchildren++;
                node->cookie = parent->cookie_jar++;
                node->flags |= DEVFS_NODE_LINKED;
                TAILQ_INSERT_TAIL(DEVFS_DENODE_HEAD(parent), node, link);

                /* This forces negative namecache lookups to clear */
                ++mp->mnt_namecache_gen;
        }

        ++DEVFS_MNTDATA(mp)->file_count;

        return node;
}

/*
 * devfs_allocv() allocates a new vnode based on a devfs node.
 */
int
devfs_allocv(struct vnode **vpp, struct devfs_node *node)
{
        struct vnode *vp;
        int error = 0;

        KKASSERT(node);

try_again:
        while ((vp = node->v_node) != NULL) {
                error = vget(vp, LK_EXCLUSIVE);
                if (error != ENOENT) {
                        *vpp = vp;
                        goto out;
                }
        }

        if ((error = getnewvnode(VT_DEVFS, node->mp, vpp, 0, 0)) != 0)
                goto out;

        vp = *vpp;

        if (node->v_node != NULL) {
                vp->v_type = VBAD;
                vx_put(vp);
                goto try_again;
        }

        vp->v_data = node;
        node->v_node = vp;

        switch (node->node_type) {
        case Proot:
                vsetflags(vp, VROOT);
                /* fall through */
        case Pdir:
                vp->v_type = VDIR;
                break;

        case Plink:
                vp->v_type = VLNK;
                break;

        case Preg:
                vp->v_type = VREG;
                break;

        case Pdev:
                vp->v_type = VCHR;
                KKASSERT(node->d_dev);

                vp->v_uminor = node->d_dev->si_uminor;
                vp->v_umajor = 0;

                v_associate_rdev(vp, node->d_dev);
                vp->v_ops = &node->mp->mnt_vn_spec_ops;
                break;

        default:
                panic("devfs_allocv: unknown node type");
        }

out:
        return error;
}

/*
 * devfs_allocvp allocates both a devfs node (with the given settings) and a vnode
 * based on the newly created devfs node.
 */
int
devfs_allocvp(struct mount *mp, struct vnode **vpp, devfs_nodetype devfsnodetype,
                char *name, struct devfs_node *parent, cdev_t dev)
{
        struct devfs_node *node;

        node = devfs_allocp(devfsnodetype, name, parent, mp, dev);

        if (node != NULL)
                devfs_allocv(vpp, node);
        else
                *vpp = NULL;

        return 0;
}

/*
 * Destroy the devfs_node.  The node must be unlinked from the topology.
 *
 * This function will also destroy any vnode association with the node
 * and device.
 *
 * The cdev_t itself remains intact.
 */
int
devfs_freep(struct devfs_node *node)
{
        struct vnode *vp;

        KKASSERT(node);
        KKASSERT(((node->flags & DEVFS_NODE_LINKED) == 0) ||
                 (node->node_type == Proot));

        /*
         * Protect against double frees
         */
        KKASSERT((node->flags & DEVFS_DESTROYED) == 0);
        node->flags |= DEVFS_DESTROYED;

        /*
         * Avoid deadlocks between devfs_lock and the vnode lock when
         * disassociating the vnode (stress2 pty vs ls -la /dev/pts).
         *
         * This also prevents the vnode reclaim code from double-freeing
         * the node.  The vget() is required to safely modified the vp
         * and cycle the refs to terminate an inactive vp.
         */
        lockmgr(&devfs_lock, LK_RELEASE);

        while ((vp = node->v_node) != NULL) {
                if (vget(vp, LK_EXCLUSIVE | LK_RETRY) != 0)
                        break;
                v_release_rdev(vp);
                vp->v_data = NULL;
                node->v_node = NULL;
                cache_inval_vp(vp, CINV_DESTROY);
                vput(vp);
        }
        lockmgr(&devfs_lock, LK_EXCLUSIVE);

        /*
         * Remaining cleanup
         */
        atomic_subtract_long(&(DEVFS_MNTDATA(node->mp)->leak_count), 1);
        if (node->symlink_name) {
                kfree(node->symlink_name, M_DEVFS);
                node->symlink_name = NULL;
        }

        /*
         * Remove the node from the orphan list if it is still on it.
         */
        if (node->flags & DEVFS_ORPHANED)
                devfs_tracer_del_orphan(node);

        if (node->d_dir.d_name) {
                kfree(node->d_dir.d_name, M_DEVFS);
                node->d_dir.d_name = NULL;
        }
        --DEVFS_MNTDATA(node->mp)->file_count;
        objcache_put(devfs_node_cache, node);

        return 0;
}

/*
 * Unlink the devfs node from the topology and add it to the orphan list.
 * The node will later be destroyed by freep.
 *
 * Any vnode association, including the v_rdev and v_data, remains intact
 * until the freep.
 */
int
devfs_unlinkp(struct devfs_node *node)
{
        struct devfs_node *parent;
        struct hotplug_device *hpdev;
        KKASSERT(node);

        /*
         * Add the node to the orphan list, so it is referenced somewhere, to
         * so we don't leak it.
         */
        devfs_tracer_add_orphan(node);

        parent = node->parent;

        /*
         * If the parent is known we can unlink the node out of the topology
         */
        if (parent)     {
                TAILQ_REMOVE(DEVFS_DENODE_HEAD(parent), node, link);
                parent->nchildren--;
                node->flags &= ~DEVFS_NODE_LINKED;
        }
        /* hotplug handler */
        if(devfs_node_removed) {
                hpdev = kmalloc(sizeof(struct hotplug_device), M_TEMP, M_WAITOK);
                hpdev->dev = node->d_dev;
                if(hpdev->dev)
                        hpdev->name = node->d_dev->si_name;
                devfs_node_removed(hpdev);
                kfree(hpdev, M_TEMP);
        }
        node->parent = NULL;
        return 0;
}

void *
devfs_iterate_topology(struct devfs_node *node,
                devfs_iterate_callback_t *callback, void *arg1)
{
        struct devfs_node *node1, *node2;
        void *ret = NULL;

        if ((node->node_type == Proot) || (node->node_type == Pdir)) {
                if (node->nchildren > 2) {
                        TAILQ_FOREACH_MUTABLE(node1, DEVFS_DENODE_HEAD(node),
                                                        link, node2) {
                                if ((ret = devfs_iterate_topology(node1, callback, arg1)))
                                        return ret;
                        }
                }
        }

        ret = callback(node, arg1);
        return ret;
}

/*
 * devfs_reaperp() is a recursive function that iterates through all the
 * topology, unlinking and freeing all devfs nodes.
 */
static void *
devfs_reaperp_callback(struct devfs_node *node, void *unused)
{
        devfs_unlinkp(node);
        devfs_freep(node);

        return NULL;
}

static void *
devfs_gc_dirs_callback(struct devfs_node *node, void *unused)
{
        if (node->node_type == Pdir) {
                if ((node->nchildren == 2) &&
                    !(node->flags & DEVFS_USER_CREATED)) {
                        devfs_unlinkp(node);
                        devfs_freep(node);
                }
        }

        return NULL;
}

static void *
devfs_gc_links_callback(struct devfs_node *node, struct devfs_node *target)
{
        if ((node->node_type == Plink) && (node->link_target == target)) {
                devfs_unlinkp(node);
                devfs_freep(node);
        }

        return NULL;
}

/*
 * devfs_gc() is devfs garbage collector. It takes care of unlinking and
 * freeing a node, but also removes empty directories and links that link
 * via devfs auto-link mechanism to the node being deleted.
 */
int
devfs_gc(struct devfs_node *node)
{
        struct devfs_node *root_node = DEVFS_MNTDATA(node->mp)->root_node;

        if (node->nlinks > 0)
                devfs_iterate_topology(root_node,
                                (devfs_iterate_callback_t *)devfs_gc_links_callback, node);

        devfs_unlinkp(node);
        devfs_iterate_topology(root_node,
                        (devfs_iterate_callback_t *)devfs_gc_dirs_callback, NULL);

        devfs_freep(node);

        return 0;
}

/*
 * devfs_create_dev() is the asynchronous entry point for device creation.
 * It just sends a message with the relevant details to the devfs core.
 *
 * This function will reference the passed device.  The reference is owned
 * by devfs and represents all of the device's node associations.
 */
int
devfs_create_dev(cdev_t dev, uid_t uid, gid_t gid, int perms)
{
        reference_dev(dev);
        devfs_msg_send_dev(DEVFS_DEVICE_CREATE, dev, uid, gid, perms);

        return 0;
}

/*
 * devfs_destroy_dev() is the asynchronous entry point for device destruction.
 * It just sends a message with the relevant details to the devfs core.
 */
int
devfs_destroy_dev(cdev_t dev)
{
        devfs_msg_send_dev(DEVFS_DEVICE_DESTROY, dev, 0, 0, 0);
        return 0;
}

/*
 * devfs_mount_add() is the synchronous entry point for adding a new devfs
 * mount.  It sends a synchronous message with the relevant details to the
 * devfs core.
 */
int
devfs_mount_add(struct devfs_mnt_data *mnt)
{
        devfs_msg_t msg;

        msg = devfs_msg_get();
        msg->mdv_mnt = mnt;
        msg = devfs_msg_send_sync(DEVFS_MOUNT_ADD, msg);
        devfs_msg_put(msg);

        return 0;
}

/*
 * devfs_mount_del() is the synchronous entry point for removing a devfs mount.
 * It sends a synchronous message with the relevant details to the devfs core.
 */
int
devfs_mount_del(struct devfs_mnt_data *mnt)
{
        devfs_msg_t msg;

        msg = devfs_msg_get();
        msg->mdv_mnt = mnt;
        msg = devfs_msg_send_sync(DEVFS_MOUNT_DEL, msg);
        devfs_msg_put(msg);

        return 0;
}

/*
 * devfs_destroy_subnames() is the synchronous entry point for device
 * destruction by subname. It just sends a message with the relevant details to
 * the devfs core.
 */
int
devfs_destroy_subnames(char *name)
{
        devfs_msg_t msg;

        msg = devfs_msg_get();
        msg->mdv_load = name;
        msg = devfs_msg_send_sync(DEVFS_DESTROY_SUBNAMES, msg);
        devfs_msg_put(msg);
        return 0;
}

int
devfs_clr_subnames_flag(char *name, uint32_t flag)
{
        devfs_msg_t msg;

        msg = devfs_msg_get();
        msg->mdv_flags.name = name;
        msg->mdv_flags.flag = flag;
        msg = devfs_msg_send_sync(DEVFS_CLR_SUBNAMES_FLAG, msg);
        devfs_msg_put(msg);

        return 0;
}

int
devfs_destroy_subnames_without_flag(char *name, uint32_t flag)
{
        devfs_msg_t msg;

        msg = devfs_msg_get();
        msg->mdv_flags.name = name;
        msg->mdv_flags.flag = flag;
        msg = devfs_msg_send_sync(DEVFS_DESTROY_SUBNAMES_WO_FLAG, msg);
        devfs_msg_put(msg);

        return 0;
}

/*
 * devfs_create_all_dev is the asynchronous entry point to trigger device
 * node creation.  It just sends a message with the relevant details to
 * the devfs core.
 */
int
devfs_create_all_dev(struct devfs_node *root)
{
        devfs_msg_send_generic(DEVFS_CREATE_ALL_DEV, root);
        return 0;
}

/*
 * devfs_destroy_dev_by_ops is the asynchronous entry point to destroy all
 * devices with a specific set of dev_ops and minor.  It just sends a
 * message with the relevant details to the devfs core.
 */
int
devfs_destroy_dev_by_ops(struct dev_ops *ops, int minor)
{
        devfs_msg_send_ops(DEVFS_DESTROY_DEV_BY_OPS, ops, minor);
        return 0;
}

/*
 * devfs_clone_handler_add is the synchronous entry point to add a new
 * clone handler.  It just sends a message with the relevant details to
 * the devfs core.
 */
int
devfs_clone_handler_add(const char *name, d_clone_t *nhandler)
{
        devfs_msg_t msg;

        msg = devfs_msg_get();
        msg->mdv_chandler.name = name;
        msg->mdv_chandler.nhandler = nhandler;
        msg = devfs_msg_send_sync(DEVFS_CHANDLER_ADD, msg);
        devfs_msg_put(msg);
        return 0;
}

/*
 * devfs_clone_handler_del is the synchronous entry point to remove a
 * clone handler.  It just sends a message with the relevant details to
 * the devfs core.
 */
int
devfs_clone_handler_del(const char *name)
{
        devfs_msg_t msg;

        msg = devfs_msg_get();
        msg->mdv_chandler.name = name;
        msg->mdv_chandler.nhandler = NULL;
        msg = devfs_msg_send_sync(DEVFS_CHANDLER_DEL, msg);
        devfs_msg_put(msg);
        return 0;
}

/*
 * devfs_find_device_by_name is the synchronous entry point to find a
 * device given its name.  It sends a synchronous message with the
 * relevant details to the devfs core and returns the answer.
 */
cdev_t
devfs_find_device_by_name(const char *fmt, ...)
{
        cdev_t found = NULL;
        devfs_msg_t msg;
        char *target;
        __va_list ap;

        if (fmt == NULL)
                return NULL;

        __va_start(ap, fmt);
        kvasnrprintf(&target, PATH_MAX, 10, fmt, ap);
        __va_end(ap);

        msg = devfs_msg_get();
        msg->mdv_name = target;
        msg = devfs_msg_send_sync(DEVFS_FIND_DEVICE_BY_NAME, msg);
        found = msg->mdv_cdev;
        devfs_msg_put(msg);
        kvasfree(&target);

        return found;
}

/*
 * devfs_find_device_by_udev is the synchronous entry point to find a
 * device given its udev number.  It sends a synchronous message with
 * the relevant details to the devfs core and returns the answer.
 */
cdev_t
devfs_find_device_by_udev(udev_t udev)
{
        cdev_t found = NULL;
        devfs_msg_t msg;

        msg = devfs_msg_get();
        msg->mdv_udev = udev;
        msg = devfs_msg_send_sync(DEVFS_FIND_DEVICE_BY_UDEV, msg);
        found = msg->mdv_cdev;
        devfs_msg_put(msg);

        devfs_debug(DEVFS_DEBUG_DEBUG,
                    "devfs_find_device_by_udev found? %s  -end:3-\n",
                    ((found) ? found->si_name:"NO"));
        return found;
}

struct vnode *
devfs_inode_to_vnode(struct mount *mp, ino_t target)
{
        struct vnode *vp = NULL;
        devfs_msg_t msg;

        if (mp == NULL)
                return NULL;

        msg = devfs_msg_get();
        msg->mdv_ino.mp = mp;
        msg->mdv_ino.ino = target;
        msg = devfs_msg_send_sync(DEVFS_INODE_TO_VNODE, msg);
        vp = msg->mdv_ino.vp;
        vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
        devfs_msg_put(msg);

        return vp;
}

/*
 * devfs_make_alias is the asynchronous entry point to register an alias
 * for a device.  It just sends a message with the relevant details to the
 * devfs core.
 */
int
devfs_make_alias(const char *name, cdev_t dev_target)
{
        struct devfs_alias *alias;
        size_t len;

        len = strlen(name);

        alias = kmalloc(sizeof(struct devfs_alias), M_DEVFS, M_WAITOK);
        alias->name = kstrdup(name, M_DEVFS);
        alias->namlen = len;
        alias->dev_target = dev_target;

        devfs_msg_send_generic(DEVFS_MAKE_ALIAS, alias);
        return 0;
}

/*
 * devfs_apply_rules is the asynchronous entry point to trigger application
 * of all rules.  It just sends a message with the relevant details to the
 * devfs core.
 */
int
devfs_apply_rules(char *mntto)
{
        char *new_name;

        new_name = kstrdup(mntto, M_DEVFS);
        devfs_msg_send_name(DEVFS_APPLY_RULES, new_name);

        return 0;
}

/*
 * devfs_reset_rules is the asynchronous entry point to trigger reset of all
 * rules. It just sends a message with the relevant details to the devfs core.
 */
int
devfs_reset_rules(char *mntto)
{
        char *new_name;

        new_name = kstrdup(mntto, M_DEVFS);
        devfs_msg_send_name(DEVFS_RESET_RULES, new_name);

        return 0;
}


/*
 * devfs_scan_callback is the asynchronous entry point to call a callback
 * on all cdevs.
 * It just sends a message with the relevant details to the devfs core.
 */
int
devfs_scan_callback(devfs_scan_t *callback, void *arg)
{
        devfs_msg_t msg;

        KKASSERT(sizeof(callback) == sizeof(void *));

        msg = devfs_msg_get();
        msg->mdv_load = callback;
        msg->mdv_load2 = arg;
        msg = devfs_msg_send_sync(DEVFS_SCAN_CALLBACK, msg);
        devfs_msg_put(msg);

        return 0;
}


/*
 * Acts as a message drain. Any message that is replied to here gets destroyed
 * and the memory freed.
 */
static void
devfs_msg_autofree_reply(lwkt_port_t port, lwkt_msg_t msg)
{
        devfs_msg_put((devfs_msg_t)msg);
}

/*
 * devfs_msg_get allocates a new devfs msg and returns it.
 */
devfs_msg_t
devfs_msg_get(void)
{
        return objcache_get(devfs_msg_cache, M_WAITOK);
}

/*
 * devfs_msg_put deallocates a given devfs msg.
 */
int
devfs_msg_put(devfs_msg_t msg)
{
        objcache_put(devfs_msg_cache, msg);
        return 0;
}

/*
 * devfs_msg_send is the generic asynchronous message sending facility
 * for devfs. By default the reply port is the automatic disposal port.
 *
 * If the current thread is the devfs_msg_port thread we execute the
 * operation synchronously.
 */
void
devfs_msg_send(uint32_t cmd, devfs_msg_t devfs_msg)
{
        lwkt_port_t port = &devfs_msg_port;

        lwkt_initmsg(&devfs_msg->hdr, &devfs_dispose_port, 0);

        devfs_msg->hdr.u.ms_result = cmd;

        if (port->mpu_td == curthread) {
                devfs_msg_exec(devfs_msg);
                lwkt_replymsg(&devfs_msg->hdr, 0);
        } else {
                lwkt_sendmsg(port, (lwkt_msg_t)devfs_msg);
        }
}

/*
 * devfs_msg_send_sync is the generic synchronous message sending
 * facility for devfs. It initializes a local reply port and waits
 * for the core's answer. This answer is then returned.
 */
devfs_msg_t
devfs_msg_send_sync(uint32_t cmd, devfs_msg_t devfs_msg)
{
        struct lwkt_port rep_port;
        devfs_msg_t     msg_incoming;
        lwkt_port_t port = &devfs_msg_port;

        lwkt_initport_thread(&rep_port, curthread);
        lwkt_initmsg(&devfs_msg->hdr, &rep_port, 0);

        devfs_msg->hdr.u.ms_result = cmd;

        lwkt_sendmsg(port, (lwkt_msg_t)devfs_msg);
        msg_incoming = lwkt_waitport(&rep_port, 0);

        return msg_incoming;
}

/*
 * sends a message with a generic argument.
 */
void
devfs_msg_send_generic(uint32_t cmd, void *load)
{
        devfs_msg_t devfs_msg = devfs_msg_get();

        devfs_msg->mdv_load = load;
        devfs_msg_send(cmd, devfs_msg);
}

/*
 * sends a message with a name argument.
 */
void
devfs_msg_send_name(uint32_t cmd, char *name)
{
        devfs_msg_t devfs_msg = devfs_msg_get();

        devfs_msg->mdv_name = name;
        devfs_msg_send(cmd, devfs_msg);
}

/*
 * sends a message with a mount argument.
 */
void
devfs_msg_send_mount(uint32_t cmd, struct devfs_mnt_data *mnt)
{
        devfs_msg_t devfs_msg = devfs_msg_get();

        devfs_msg->mdv_mnt = mnt;
        devfs_msg_send(cmd, devfs_msg);
}

/*
 * sends a message with an ops argument.
 */
void
devfs_msg_send_ops(uint32_t cmd, struct dev_ops *ops, int minor)
{
        devfs_msg_t devfs_msg = devfs_msg_get();

        devfs_msg->mdv_ops.ops = ops;
        devfs_msg->mdv_ops.minor = minor;
        devfs_msg_send(cmd, devfs_msg);
}

/*
 * sends a message with a clone handler argument.
 */
void
devfs_msg_send_chandler(uint32_t cmd, char *name, d_clone_t handler)
{
        devfs_msg_t devfs_msg = devfs_msg_get();

        devfs_msg->mdv_chandler.name = name;
        devfs_msg->mdv_chandler.nhandler = handler;
        devfs_msg_send(cmd, devfs_msg);
}

/*
 * sends a message with a device argument.
 */
void
devfs_msg_send_dev(uint32_t cmd, cdev_t dev, uid_t uid, gid_t gid, int perms)
{
        devfs_msg_t devfs_msg = devfs_msg_get();

        devfs_msg->mdv_dev.dev = dev;
        devfs_msg->mdv_dev.uid = uid;
        devfs_msg->mdv_dev.gid = gid;
        devfs_msg->mdv_dev.perms = perms;

        devfs_msg_send(cmd, devfs_msg);
}

/*
 * sends a message with a link argument.
 */
void
devfs_msg_send_link(uint32_t cmd, char *name, char *target, struct mount *mp)
{
        devfs_msg_t devfs_msg = devfs_msg_get();

        devfs_msg->mdv_link.name = name;
        devfs_msg->mdv_link.target = target;
        devfs_msg->mdv_link.mp = mp;
        devfs_msg_send(cmd, devfs_msg);
}

/*
 * devfs_msg_core is the main devfs thread. It handles all incoming messages
 * and calls the relevant worker functions. By using messages it's assured
 * that events occur in the correct order.
 */
static void
devfs_msg_core(void *arg)
{
        devfs_msg_t msg;

        devfs_run = 1;
        lwkt_initport_thread(&devfs_msg_port, curthread);
        wakeup(td_core);

        while (devfs_run) {
                msg = (devfs_msg_t)lwkt_waitport(&devfs_msg_port, 0);
                devfs_debug(DEVFS_DEBUG_DEBUG,
                                "devfs_msg_core, new msg: %x\n",
                                (unsigned int)msg->hdr.u.ms_result);
                devfs_msg_exec(msg);
                lwkt_replymsg(&msg->hdr, 0);
        }
        wakeup(td_core);
        lwkt_exit();
}

static void
devfs_msg_exec(devfs_msg_t msg)
{
        struct devfs_mnt_data *mnt;
        struct devfs_node *node;
        cdev_t  dev;

        /*
         * Acquire the devfs lock to ensure safety of all called functions
         */
        lockmgr(&devfs_lock, LK_EXCLUSIVE);

        switch (msg->hdr.u.ms_result) {
        case DEVFS_DEVICE_CREATE:
                dev = msg->mdv_dev.dev;
                devfs_create_dev_worker(dev,
                                        msg->mdv_dev.uid,
                                        msg->mdv_dev.gid,
                                        msg->mdv_dev.perms);
                break;
        case DEVFS_DEVICE_DESTROY:
                dev = msg->mdv_dev.dev;
                devfs_destroy_dev_worker(dev);
                break;
        case DEVFS_DESTROY_SUBNAMES:
                devfs_destroy_subnames_worker(msg->mdv_load);
                break;
        case DEVFS_DESTROY_DEV_BY_OPS:
                devfs_destroy_dev_by_ops_worker(msg->mdv_ops.ops,
                                                msg->mdv_ops.minor);
                break;
        case DEVFS_CREATE_ALL_DEV:
                node = (struct devfs_node *)msg->mdv_load;
                devfs_create_all_dev_worker(node);
                break;
        case DEVFS_MOUNT_ADD:
                mnt = msg->mdv_mnt;
                TAILQ_INSERT_TAIL(&devfs_mnt_list, mnt, link);
                devfs_create_all_dev_worker(mnt->root_node);
                break;
        case DEVFS_MOUNT_DEL:
                mnt = msg->mdv_mnt;
                TAILQ_REMOVE(&devfs_mnt_list, mnt, link);
                devfs_iterate_topology(mnt->root_node, devfs_reaperp_callback,
                                       NULL);
                if (mnt->leak_count) {
                        devfs_debug(DEVFS_DEBUG_SHOW,
                                    "Leaked %ld devfs_node elements!\n",
                                    mnt->leak_count);
                }
                break;
        case DEVFS_CHANDLER_ADD:
                devfs_chandler_add_worker(msg->mdv_chandler.name,
                                msg->mdv_chandler.nhandler);
                break;
        case DEVFS_CHANDLER_DEL:
                devfs_chandler_del_worker(msg->mdv_chandler.name);
                break;
        case DEVFS_FIND_DEVICE_BY_NAME:
                devfs_find_device_by_name_worker(msg);
                break;
        case DEVFS_FIND_DEVICE_BY_UDEV:
                devfs_find_device_by_udev_worker(msg);
                break;
        case DEVFS_MAKE_ALIAS:
                devfs_make_alias_worker((struct devfs_alias *)msg->mdv_load);
                break;
        case DEVFS_APPLY_RULES:
                devfs_apply_reset_rules_caller(msg->mdv_name, 1);
                break;
        case DEVFS_RESET_RULES:
                devfs_apply_reset_rules_caller(msg->mdv_name, 0);
                break;
        case DEVFS_SCAN_CALLBACK:
                devfs_scan_callback_worker((devfs_scan_t *)msg->mdv_load,
                        msg->mdv_load2);
                break;
        case DEVFS_CLR_SUBNAMES_FLAG:
                devfs_clr_subnames_flag_worker(msg->mdv_flags.name,
                                msg->mdv_flags.flag);
                break;
        case DEVFS_DESTROY_SUBNAMES_WO_FLAG:
                devfs_destroy_subnames_without_flag_worker(msg->mdv_flags.name,
                                msg->mdv_flags.flag);
                break;
        case DEVFS_INODE_TO_VNODE:
                msg->mdv_ino.vp = devfs_iterate_topology(
                        DEVFS_MNTDATA(msg->mdv_ino.mp)->root_node,
                        (devfs_iterate_callback_t *)devfs_inode_to_vnode_worker_callback,
                        &msg->mdv_ino.ino);
                break;
        case DEVFS_TERMINATE_CORE:
                devfs_run = 0;
                break;
        case DEVFS_SYNC:
                break;
        default:
                devfs_debug(DEVFS_DEBUG_WARNING,
                            "devfs_msg_core: unknown message "
                            "received at core\n");
                break;
        }
        lockmgr(&devfs_lock, LK_RELEASE);
}

/*
 * Worker function to insert a new dev into the dev list and initialize its
 * permissions. It also calls devfs_propagate_dev which in turn propagates
 * the change to all mount points.
 *
 * The passed dev is already referenced.  This reference is eaten by this
 * function and represents the dev's linkage into devfs_dev_list.
 */
static int
devfs_create_dev_worker(cdev_t dev, uid_t uid, gid_t gid, int perms)
{
        KKASSERT(dev);

        dev->si_uid = uid;
        dev->si_gid = gid;
        dev->si_perms = perms;

        devfs_link_dev(dev);
        devfs_propagate_dev(dev, 1);

        udev_event_attach(dev, NULL, 0);

        return 0;
}

/*
 * Worker function to delete a dev from the dev list and free the cdev.
 * It also calls devfs_propagate_dev which in turn propagates the change
 * to all mount points.
 */
static int
devfs_destroy_dev_worker(cdev_t dev)
{
        int error;

        KKASSERT(dev);
        KKASSERT((lockstatus(&devfs_lock, curthread)) == LK_EXCLUSIVE);

        error = devfs_unlink_dev(dev);
        devfs_propagate_dev(dev, 0);

        udev_event_detach(dev, NULL, 0);

        if (error == 0)
                release_dev(dev);       /* link ref */
        release_dev(dev);
        release_dev(dev);

        return 0;
}

/*
 * Worker function to destroy all devices with a certain basename.
 * Calls devfs_destroy_dev_worker for the actual destruction.
 */
static int
devfs_destroy_subnames_worker(char *name)
{
        cdev_t dev, dev1;
        size_t len = strlen(name);

        TAILQ_FOREACH_MUTABLE(dev, &devfs_dev_list, link, dev1) {
                if ((!strncmp(dev->si_name, name, len)) &&
                                (dev->si_name[len] != '\0')) {
                        devfs_destroy_dev_worker(dev);
                }
        }
        return 0;
}

static int
devfs_clr_subnames_flag_worker(char *name, uint32_t flag)
{
        cdev_t dev, dev1;
        size_t len = strlen(name);

        TAILQ_FOREACH_MUTABLE(dev, &devfs_dev_list, link, dev1) {
                if ((!strncmp(dev->si_name, name, len)) &&
                                (dev->si_name[len] != '\0')) {
                        dev->si_flags &= ~flag;
                }
        }

        return 0;
}

static int
devfs_destroy_subnames_without_flag_worker(char *name, uint32_t flag)
{
        cdev_t dev, dev1;
        size_t len = strlen(name);

        TAILQ_FOREACH_MUTABLE(dev, &devfs_dev_list, link, dev1) {
                if ((!strncmp(dev->si_name, name, len)) &&
                                (dev->si_name[len] != '\0')) {
                        if (!(dev->si_flags & flag)) {
                                devfs_destroy_dev_worker(dev);
                        }
                }
        }

        return 0;
}

/*
 * Worker function that creates all device nodes on top of a devfs
 * root node.
 */
static int
devfs_create_all_dev_worker(struct devfs_node *root)
{
        cdev_t dev;

        KKASSERT(root);

        TAILQ_FOREACH(dev, &devfs_dev_list, link) {
                devfs_create_device_node(root, dev, NULL, NULL);
        }

        return 0;
}

/*
 * Worker function that destroys all devices that match a specific
 * dev_ops and/or minor. If minor is less than 0, it is not matched
 * against. It also propagates all changes.
 */
static int
devfs_destroy_dev_by_ops_worker(struct dev_ops *ops, int minor)
{
        cdev_t dev, dev1;

        KKASSERT(ops);

        TAILQ_FOREACH_MUTABLE(dev, &devfs_dev_list, link, dev1) {
                if (dev->si_ops != ops)
                        continue;
                if ((minor < 0) || (dev->si_uminor == minor)) {
                        devfs_destroy_dev_worker(dev);
                }
        }

        return 0;
}

/*
 * Worker function that registers a new clone handler in devfs.
 */
static int
devfs_chandler_add_worker(const char *name, d_clone_t *nhandler)
{
        struct devfs_clone_handler *chandler = NULL;
        u_char len = strlen(name);

        if (len == 0)
                return 1;

        TAILQ_FOREACH(chandler, &devfs_chandler_list, link) {
                if (chandler->namlen != len)
                        continue;

                if (!memcmp(chandler->name, name, len)) {
                        /* Clonable basename already exists */
                        return 1;
                }
        }

        chandler = kmalloc(sizeof(*chandler), M_DEVFS, M_WAITOK | M_ZERO);
        chandler->name = kstrdup(name, M_DEVFS);
        chandler->namlen = len;
        chandler->nhandler = nhandler;

        TAILQ_INSERT_TAIL(&devfs_chandler_list, chandler, link);
        return 0;
}

/*
 * Worker function that removes a given clone handler from the
 * clone handler list.
 */
static int
devfs_chandler_del_worker(const char *name)
{
        struct devfs_clone_handler *chandler, *chandler2;
        u_char len = strlen(name);

        if (len == 0)
                return 1;

        TAILQ_FOREACH_MUTABLE(chandler, &devfs_chandler_list, link, chandler2) {
                if (chandler->namlen != len)
                        continue;
                if (memcmp(chandler->name, name, len))
                        continue;

                TAILQ_REMOVE(&devfs_chandler_list, chandler, link);
                kfree(chandler->name, M_DEVFS);
                kfree(chandler, M_DEVFS);
                break;
        }

        return 0;
}

/*
 * Worker function that finds a given device name and changes
 * the message received accordingly so that when replied to,
 * the answer is returned to the caller.
 */
static int
devfs_find_device_by_name_worker(devfs_msg_t devfs_msg)
{
        struct devfs_alias *alias;
        cdev_t dev;
        cdev_t found = NULL;

        TAILQ_FOREACH(dev, &devfs_dev_list, link) {
                if (strcmp(devfs_msg->mdv_name, dev->si_name) == 0) {
                        found = dev;
                        break;
                }
        }
        if (found == NULL) {
                TAILQ_FOREACH(alias, &devfs_alias_list, link) {
                        if (strcmp(devfs_msg->mdv_name, alias->name) == 0) {
                                found = alias->dev_target;
                                break;
                        }
                }
        }
        devfs_msg->mdv_cdev = found;

        return 0;
}

/*
 * Worker function that finds a given device udev and changes
 * the message received accordingly so that when replied to,
 * the answer is returned to the caller.
 */
static int
devfs_find_device_by_udev_worker(devfs_msg_t devfs_msg)
{
        cdev_t dev, dev1;
        cdev_t found = NULL;

        TAILQ_FOREACH_MUTABLE(dev, &devfs_dev_list, link, dev1) {
                if (((udev_t)dev->si_inode) == devfs_msg->mdv_udev) {
                        found = dev;
                        break;
                }
        }
        devfs_msg->mdv_cdev = found;

        return 0;
}

/*
 * Worker function that inserts a given alias into the
 * alias list, and propagates the alias to all mount
 * points.
 */
static int
devfs_make_alias_worker(struct devfs_alias *alias)
{
        struct devfs_alias *alias2;
        size_t len = strlen(alias->name);
        int found = 0;

        TAILQ_FOREACH(alias2, &devfs_alias_list, link) {
                if (len != alias2->namlen)
                        continue;

                if (!memcmp(alias->name, alias2->name, len)) {
                        found = 1;
                        break;
                }
        }

        if (!found) {
                /*
                 * The alias doesn't exist yet, so we add it to the alias list
                 */
                TAILQ_INSERT_TAIL(&devfs_alias_list, alias, link);
                devfs_alias_propagate(alias);
                udev_event_attach(alias->dev_target, alias->name, 1);
        } else {
                devfs_debug(DEVFS_DEBUG_WARNING,
                            "Warning: duplicate devfs_make_alias for %s\n",
                            alias->name);
                kfree(alias->name, M_DEVFS);
                kfree(alias, M_DEVFS);
        }

        return 0;
}

/*
 * Function that removes and frees all aliases.
 */
static int
devfs_alias_reap(void)
{
        struct devfs_alias *alias, *alias2;

        TAILQ_FOREACH_MUTABLE(alias, &devfs_alias_list, link, alias2) {
                TAILQ_REMOVE(&devfs_alias_list, alias, link);
                kfree(alias, M_DEVFS);
        }
        return 0;
}

/*
 * Function that removes an alias matching a specific cdev and frees
 * it accordingly.
 */
static int
devfs_alias_remove(cdev_t dev)
{
        struct devfs_alias *alias, *alias2;

        TAILQ_FOREACH_MUTABLE(alias, &devfs_alias_list, link, alias2) {
                if (alias->dev_target == dev) {
                        TAILQ_REMOVE(&devfs_alias_list, alias, link);
                        udev_event_detach(alias->dev_target, alias->name, 1);
                        kfree(alias, M_DEVFS);
                }
        }
        return 0;
}

/*
 * This function propagates a new alias to all mount points.
 */
static int
devfs_alias_propagate(struct devfs_alias *alias)
{
        struct devfs_mnt_data *mnt;

        TAILQ_FOREACH(mnt, &devfs_mnt_list, link) {
                devfs_alias_apply(mnt->root_node, alias);
        }
        return 0;
}

/*
 * This function is a recursive function iterating through
 * all device nodes in the topology and, if applicable,
 * creating the relevant alias for a device node.
 */
static int
devfs_alias_apply(struct devfs_node *node, struct devfs_alias *alias)
{
        struct devfs_node *node1, *node2;

        KKASSERT(alias != NULL);

        if ((node->node_type == Proot) || (node->node_type == Pdir)) {
                if (node->nchildren > 2) {
                        TAILQ_FOREACH_MUTABLE(node1, DEVFS_DENODE_HEAD(node), link, node2) {
                                devfs_alias_apply(node1, alias);
                        }
                }
        } else {
                if (node->d_dev == alias->dev_target)
                        devfs_alias_create(alias->name, node, 0);
        }
        return 0;
}

/*
 * This function checks if any alias possibly is applicable
 * to the given node. If so, the alias is created.
 */
static int
devfs_alias_check_create(struct devfs_node *node)
{
        struct devfs_alias *alias;

        TAILQ_FOREACH(alias, &devfs_alias_list, link) {
                if (node->d_dev == alias->dev_target)
                        devfs_alias_create(alias->name, node, 0);
        }
        return 0;
}

/*
 * This function creates an alias with a given name
 * linking to a given devfs node. It also increments
 * the link count on the target node.
 */
int
devfs_alias_create(char *name_orig, struct devfs_node *target, int rule_based)
{
        struct mount *mp = target->mp;
        struct devfs_node *parent = DEVFS_MNTDATA(mp)->root_node;
        struct devfs_node *linknode;
        struct hotplug_device *hpdev;
        char *create_path = NULL;
        char *name;
        char *name_buf;
        int result = 0;

        KKASSERT((lockstatus(&devfs_lock, curthread)) == LK_EXCLUSIVE);

        name_buf = kmalloc(PATH_MAX, M_TEMP, M_WAITOK);
        devfs_resolve_name_path(name_orig, name_buf, &create_path, &name);

        if (create_path)
                parent = devfs_resolve_or_create_path(parent, create_path, 1);


        if (devfs_find_device_node_by_name(parent, name)) {
                devfs_debug(DEVFS_DEBUG_WARNING,
                            "Node already exists: %s "
                            "(devfs_make_alias_worker)!\n",
                            name);
                result = 1;
                goto done;
        }

        linknode = devfs_allocp(Plink, name, parent, mp, NULL);
        if (linknode == NULL) {
                result = 1;
                goto done;
        }

        linknode->link_target = target;
        target->nlinks++;

        if (rule_based)
                linknode->flags |= DEVFS_RULE_CREATED;

done:
        /* hotplug handler */
        if(devfs_node_added) {
                hpdev = kmalloc(sizeof(struct hotplug_device), M_TEMP, M_WAITOK);
                hpdev->dev = target->d_dev;
                hpdev->name = name_orig;
                devfs_node_added(hpdev);
                kfree(hpdev, M_TEMP);
        }
        kfree(name_buf, M_TEMP);
        return (result);
}

/*
 * This function is called by the core and handles mount point
 * strings. It either calls the relevant worker (devfs_apply_
 * reset_rules_worker) on all mountpoints or only a specific
 * one.
 */
static int
devfs_apply_reset_rules_caller(char *mountto, int apply)
{
        struct devfs_mnt_data *mnt;

        if (mountto[0] == '*') {
                TAILQ_FOREACH(mnt, &devfs_mnt_list, link) {
                        devfs_iterate_topology(mnt->root_node,
                                        (apply)?(devfs_rule_check_apply):(devfs_rule_reset_node),
                                        NULL);
                }
        } else {
                TAILQ_FOREACH(mnt, &devfs_mnt_list, link) {
                        if (!strcmp(mnt->mp->mnt_stat.f_mntonname, mountto)) {
                                devfs_iterate_topology(mnt->root_node,
                                        (apply)?(devfs_rule_check_apply):(devfs_rule_reset_node),
                                        NULL);
                                break;
                        }
                }
        }

        kfree(mountto, M_DEVFS);
        return 0;
}

/*
 * This function calls a given callback function for
 * every dev node in the devfs dev list.
 */
static int
devfs_scan_callback_worker(devfs_scan_t *callback, void *arg)
{
        cdev_t dev, dev1;

        TAILQ_FOREACH_MUTABLE(dev, &devfs_dev_list, link, dev1) {
                callback(dev, arg);
        }

        return 0;
}

/*
 * This function tries to resolve a given directory, or if not
 * found and creation requested, creates the given directory.
 */
static struct devfs_node *
devfs_resolve_or_create_dir(struct devfs_node *parent, char *dir_name,
                            size_t name_len, int create)
{
        struct devfs_node *node, *found = NULL;

        TAILQ_FOREACH(node, DEVFS_DENODE_HEAD(parent), link) {
                if (name_len != node->d_dir.d_namlen)
                        continue;

                if (!memcmp(dir_name, node->d_dir.d_name, name_len)) {
                        found = node;
                        break;
                }
        }

        if ((found == NULL) && (create)) {
                found = devfs_allocp(Pdir, dir_name, parent, parent->mp, NULL);
        }

        return found;
}

/*
 * This function tries to resolve a complete path. If creation is requested,
 * if a given part of the path cannot be resolved (because it doesn't exist),
 * it is created.
 */
struct devfs_node *
devfs_resolve_or_create_path(struct devfs_node *parent, char *path, int create)
{
        struct devfs_node *node = parent;
        char *buf;
        size_t idx = 0;

        if (path == NULL)
                return parent;

        buf = kmalloc(PATH_MAX, M_TEMP, M_WAITOK);

        while (*path && idx < PATH_MAX - 1) {
                if (*path != '/') {
                        buf[idx++] = *path;
                } else {
                        buf[idx] = '\0';
                        node = devfs_resolve_or_create_dir(node, buf, idx, create);
                        if (node == NULL) {
                                kfree(buf, M_TEMP);
                                return NULL;
                        }
                        idx = 0;
                }
                ++path;
        }
        buf[idx] = '\0';
        node = devfs_resolve_or_create_dir(node, buf, idx, create);
        kfree (buf, M_TEMP);
        return (node);
}

/*
 * Takes a full path and strips it into a directory path and a name.
 * For a/b/c/foo, it returns foo in namep and a/b/c in pathp. It
 * requires a working buffer with enough size to keep the whole
 * fullpath.
 */
int
devfs_resolve_name_path(char *fullpath, char *buf, char **pathp, char **namep)
{
        char *name = NULL;
        char *path = NULL;
        size_t len = strlen(fullpath) + 1;
        int i;

        KKASSERT((fullpath != NULL) && (buf != NULL));
        KKASSERT((pathp != NULL) && (namep != NULL));

        memcpy(buf, fullpath, len);

        for (i = len-1; i>= 0; i--) {
                if (buf[i] == '/') {
                        buf[i] = '\0';
                        name = &(buf[i+1]);
                        path = buf;
                        break;
                }
        }

        *pathp = path;

        if (name) {
                *namep = name;
        } else {
                *namep = buf;
        }

        return 0;
}

/*
 * This function creates a new devfs node for a given device.  It can
 * handle a complete path as device name, and accordingly creates
 * the path and the final device node.
 *
 * The reference count on the passed dev remains unchanged.
 */
struct devfs_node *
devfs_create_device_node(struct devfs_node *root, cdev_t dev,
                         char *dev_name, char *path_fmt, ...)
{
        struct devfs_node *parent, *node = NULL;
        struct hotplug_device *hpdev;
        char *path = NULL;
        char *name;
        char *name_buf;
        __va_list ap;
        int i, found;
        char *create_path = NULL;
        char *names = "pqrsPQRS";

        name_buf = kmalloc(PATH_MAX, M_TEMP, M_WAITOK);

        if (path_fmt != NULL) {
                __va_start(ap, path_fmt);
                kvasnrprintf(&path, PATH_MAX, 10, path_fmt, ap);
                __va_end(ap);
        }

        parent = devfs_resolve_or_create_path(root, path, 1);
        KKASSERT(parent);

        devfs_resolve_name_path(
                        ((dev_name == NULL) && (dev))?(dev->si_name):(dev_name),
                        name_buf, &create_path, &name);

        if (create_path)
                parent = devfs_resolve_or_create_path(parent, create_path, 1);


        if (devfs_find_device_node_by_name(parent, name)) {
                devfs_debug(DEVFS_DEBUG_WARNING, "devfs_create_device_node: "
                        "DEVICE %s ALREADY EXISTS!!! Ignoring creation request.\n", name);
                goto out;
        }

        node = devfs_allocp(Pdev, name, parent, parent->mp, dev);
        nanotime(&parent->mtime);

        /*
         * Ugly unix98 pty magic, to hide pty master (ptm) devices and their
         * directory
         */
        if ((dev) && (strlen(dev->si_name) >= 4) &&
                        (!memcmp(dev->si_name, "ptm/", 4))) {
                node->parent->flags |= DEVFS_HIDDEN;
                node->flags |= DEVFS_HIDDEN;
        }

        /*
         * Ugly pty magic, to tag pty devices as such and hide them if needed.
         */
        if ((strlen(name) >= 3) && (!memcmp(name, "pty", 3)))
                node->flags |= (DEVFS_PTY | DEVFS_INVISIBLE);

        if ((strlen(name) >= 3) && (!memcmp(name, "tty", 3))) {
                found = 0;
                for (i = 0; i < strlen(names); i++) {
                        if (name[3] == names[i]) {
                                found = 1;
                                break;
                        }
                }
                if (found)
                        node->flags |= (DEVFS_PTY | DEVFS_INVISIBLE);
        }
        /* hotplug handler */
        if(devfs_node_added) {
                hpdev = kmalloc(sizeof(struct hotplug_device), M_TEMP, M_WAITOK);
                hpdev->dev = node->d_dev;
                hpdev->name = node->d_dev->si_name;
                devfs_node_added(hpdev);
                kfree(hpdev, M_TEMP);
        }

out:
        kfree(name_buf, M_TEMP);
        kvasfree(&path);
        return node;
}

/*
 * This function finds a given device node in the topology with a given
 * cdev.
 */
void *
devfs_find_device_node_callback(struct devfs_node *node, cdev_t target)
{
        if ((node->node_type == Pdev) && (node->d_dev == target)) {
                return node;
        }

        return NULL;
}

/*
 * This function finds a device node in the given parent directory by its
 * name and returns it.
 */
struct devfs_node *
devfs_find_device_node_by_name(struct devfs_node *parent, char *target)
{
        struct devfs_node *node, *found = NULL;
        size_t len = strlen(target);

        TAILQ_FOREACH(node, DEVFS_DENODE_HEAD(parent), link) {
                if (len != node->d_dir.d_namlen)
                        continue;

                if (!memcmp(node->d_dir.d_name, target, len)) {
                        found = node;
                        break;
                }
        }

        return found;
}

static void *
devfs_inode_to_vnode_worker_callback(struct devfs_node *node, ino_t *inop)
{
        struct vnode *vp = NULL;
        ino_t target = *inop;

        if (node->d_dir.d_ino == target) {
                if (node->v_node) {
                        vp = node->v_node;
                        vget(vp, LK_EXCLUSIVE | LK_RETRY);
                        vn_unlock(vp);
                } else {
                        devfs_allocv(&vp, node);
                        vn_unlock(vp);
                }
        }

        return vp;
}

/*
 * This function takes a cdev and removes its devfs node in the
 * given topology.  The cdev remains intact.
 */
int
devfs_destroy_device_node(struct devfs_node *root, cdev_t target)
{
        struct devfs_node *node, *parent;
        char *name;
        char *name_buf;
        char *create_path = NULL;

        KKASSERT(target);

        name_buf = kmalloc(PATH_MAX, M_TEMP, M_WAITOK);
        ksnprintf(name_buf, PATH_MAX, "%s", target->si_name);

        devfs_resolve_name_path(target->si_name, name_buf, &create_path, &name);

        if (create_path)
                parent = devfs_resolve_or_create_path(root, create_path, 0);
        else
                parent = root;

        if (parent == NULL) {
                kfree(name_buf, M_TEMP);
                return 1;
        }

        node = devfs_find_device_node_by_name(parent, name);

        if (node) {
                nanotime(&node->parent->mtime);
                devfs_gc(node);
        }

        kfree(name_buf, M_TEMP);

        return 0;
}

/*
 * Just set perms and ownership for given node.
 */
int
devfs_set_perms(struct devfs_node *node, uid_t uid, gid_t gid,
                u_short mode, u_long flags)
{
        node->mode = mode;
        node->uid = uid;
        node->gid = gid;

        return 0;
}

/*
 * Propagates a device attach/detach to all mount
 * points. Also takes care of automatic alias removal
 * for a deleted cdev.
 */
static int
devfs_propagate_dev(cdev_t dev, int attach)
{
        struct devfs_mnt_data *mnt;

        TAILQ_FOREACH(mnt, &devfs_mnt_list, link) {
                if (attach) {
                        /* Device is being attached */
                        devfs_create_device_node(mnt->root_node, dev,
                                                 NULL, NULL );
                } else {
                        /* Device is being detached */
                        devfs_alias_remove(dev);
                        devfs_destroy_device_node(mnt->root_node, dev);
                }
        }
        return 0;
}

/*
 * devfs_clone either returns a basename from a complete name by
 * returning the length of the name without trailing digits, or,
 * if clone != 0, calls the device's clone handler to get a new
 * device, which in turn is returned in devp.
 */
cdev_t
devfs_clone(cdev_t dev, const char *name, size_t len, int mode,
                struct ucred *cred)
{
        int error;
        struct devfs_clone_handler *chandler;
        struct dev_clone_args ap;

        TAILQ_FOREACH(chandler, &devfs_chandler_list, link) {
                if (chandler->namlen != len)
                        continue;
                if ((!memcmp(chandler->name, name, len)) && (chandler->nhandler)) {
                        lockmgr(&devfs_lock, LK_RELEASE);
                        devfs_config();
                        lockmgr(&devfs_lock, LK_EXCLUSIVE);

                        ap.a_head.a_dev = dev;
                        ap.a_dev = NULL;
                        ap.a_name = name;
                        ap.a_namelen = len;
                        ap.a_mode = mode;
                        ap.a_cred = cred;
                        error = (chandler->nhandler)(&ap);
                        if (error)
                                continue;

                        return ap.a_dev;
                }
        }

        return NULL;
}


/*
 * Registers a new orphan in the orphan list.
 */
void
devfs_tracer_add_orphan(struct devfs_node *node)
{
        struct devfs_orphan *orphan;

        KKASSERT(node);
        orphan = kmalloc(sizeof(struct devfs_orphan), M_DEVFS, M_WAITOK);
        orphan->node = node;

        KKASSERT((node->flags & DEVFS_ORPHANED) == 0);
        node->flags |= DEVFS_ORPHANED;
        TAILQ_INSERT_TAIL(DEVFS_ORPHANLIST(node->mp), orphan, link);
}

/*
 * Removes an orphan from the orphan list.
 */
void
devfs_tracer_del_orphan(struct devfs_node *node)
{
        struct devfs_orphan *orphan;

        KKASSERT(node);

        TAILQ_FOREACH(orphan, DEVFS_ORPHANLIST(node->mp), link) {
                if (orphan->node == node) {
                        node->flags &= ~DEVFS_ORPHANED;
                        TAILQ_REMOVE(DEVFS_ORPHANLIST(node->mp), orphan, link);
                        kfree(orphan, M_DEVFS);
                        break;
                }
        }
}

/*
 * Counts the orphans in the orphan list, and if cleanup
 * is specified, also frees the orphan and removes it from
 * the list.
 */
size_t
devfs_tracer_orphan_count(struct mount *mp, int cleanup)
{
        struct devfs_orphan *orphan, *orphan2;
        size_t count = 0;

        TAILQ_FOREACH_MUTABLE(orphan, DEVFS_ORPHANLIST(mp), link, orphan2)      {
                count++;
                /*
                 * If we are instructed to clean up, we do so.
                 */
                if (cleanup) {
                        TAILQ_REMOVE(DEVFS_ORPHANLIST(mp), orphan, link);
                        orphan->node->flags &= ~DEVFS_ORPHANED;
                        devfs_freep(orphan->node);
                        kfree(orphan, M_DEVFS);
                }
        }

        return count;
}

/*
 * Fetch an ino_t from the global d_ino by increasing it
 * while spinlocked.
 */
static ino_t
devfs_fetch_ino(void)
{
        ino_t   ret;

        spin_lock_wr(&ino_lock);
        ret = d_ino++;
        spin_unlock_wr(&ino_lock);

        return ret;
}

/*
 * Allocates a new cdev and initializes it's most basic
 * fields.
 */
cdev_t
devfs_new_cdev(struct dev_ops *ops, int minor, struct dev_ops *bops)
{
        cdev_t dev = sysref_alloc(&cdev_sysref_class);

        sysref_activate(&dev->si_sysref);
        reference_dev(dev);
        bzero(dev, offsetof(struct cdev, si_sysref));

        dev->si_uid = 0;
        dev->si_gid = 0;
        dev->si_perms = 0;
        dev->si_drv1 = NULL;
        dev->si_drv2 = NULL;
        dev->si_lastread = 0;           /* time_second */
        dev->si_lastwrite = 0;          /* time_second */

        dev->si_dict = NULL;
        dev->si_ops = ops;
        dev->si_flags = 0;
        dev->si_umajor = 0;
        dev->si_uminor = minor;
        dev->si_bops = bops;
        /* If there is a backing device, we reference its ops */
        dev->si_inode = makeudev(
                    devfs_reference_ops((bops)?(bops):(ops)),
                    minor );

        return dev;
}

static void
devfs_cdev_terminate(cdev_t dev)
{
        int locked = 0;

        /* Check if it is locked already. if not, we acquire the devfs lock */
        if (!(lockstatus(&devfs_lock, curthread)) == LK_EXCLUSIVE) {
                lockmgr(&devfs_lock, LK_EXCLUSIVE);
                locked = 1;
        }

        /* Propagate destruction, just in case */
        devfs_propagate_dev(dev, 0);

        /* If we acquired the lock, we also get rid of it */
        if (locked)
                lockmgr(&devfs_lock, LK_RELEASE);

        /* If there is a backing device, we release the backing device's ops */
        devfs_release_ops((dev->si_bops)?(dev->si_bops):(dev->si_ops));

        /* Finally destroy the device */
        sysref_put(&dev->si_sysref);
}

/*
 * Dummies for now (individual locks for MPSAFE)
 */
static void
devfs_cdev_lock(cdev_t dev)
{
}

static void
devfs_cdev_unlock(cdev_t dev)
{
}

/*
 * Links a given cdev into the dev list.
 */
int
devfs_link_dev(cdev_t dev)
{
        KKASSERT((dev->si_flags & SI_DEVFS_LINKED) == 0);
        dev->si_flags |= SI_DEVFS_LINKED;
        TAILQ_INSERT_TAIL(&devfs_dev_list, dev, link);

        return 0;
}

/*
 * Removes a given cdev from the dev list.  The caller is responsible for
 * releasing the reference on the device associated with the linkage.
 *
 * Returns EALREADY if the dev has already been unlinked.
 */
static int
devfs_unlink_dev(cdev_t dev)
{
        if ((dev->si_flags & SI_DEVFS_LINKED)) {
                TAILQ_REMOVE(&devfs_dev_list, dev, link);
                dev->si_flags &= ~SI_DEVFS_LINKED;
                return (0);
        }
        return (EALREADY);
}

int
devfs_node_is_accessible(struct devfs_node *node)
{
        if ((node) && (!(node->flags & DEVFS_HIDDEN)))
                return 1;
        else
                return 0;
}

int
devfs_reference_ops(struct dev_ops *ops)
{
        int unit;
        struct devfs_dev_ops *found = NULL;
        struct devfs_dev_ops *devops;

        TAILQ_FOREACH(devops, &devfs_dev_ops_list, link) {
                if (devops->ops == ops) {
                        found = devops;
                        break;
                }
        }

        if (!found) {
                found = kmalloc(sizeof(struct devfs_dev_ops), M_DEVFS, M_WAITOK);
                found->ops = ops;
                found->ref_count = 0;
                TAILQ_INSERT_TAIL(&devfs_dev_ops_list, found, link);
        }

        KKASSERT(found);

        if (found->ref_count == 0) {
                found->id = devfs_clone_bitmap_get(&DEVFS_CLONE_BITMAP(ops_id), 255);
                if (found->id == -1) {
                        /* Ran out of unique ids */
                        devfs_debug(DEVFS_DEBUG_WARNING,
                                        "devfs_reference_ops: WARNING: ran out of unique ids\n");
                }
        }
        unit = found->id;
        ++found->ref_count;

        return unit;
}

void
devfs_release_ops(struct dev_ops *ops)
{
        struct devfs_dev_ops *found = NULL;
        struct devfs_dev_ops *devops;

        TAILQ_FOREACH(devops, &devfs_dev_ops_list, link) {
                if (devops->ops == ops) {
                        found = devops;
                        break;
                }
        }

        KKASSERT(found);

        --found->ref_count;

        if (found->ref_count == 0) {
                TAILQ_REMOVE(&devfs_dev_ops_list, found, link);
                devfs_clone_bitmap_put(&DEVFS_CLONE_BITMAP(ops_id), found->id);
                kfree(found, M_DEVFS);
        }
}

/*
 * Wait for asynchronous messages to complete in the devfs helper
 * thread, then return.  Do nothing if the helper thread is dead
 * (during reboot).
 */
void
devfs_config(void)
{
        devfs_msg_t msg;

        if (devfs_run) {
                msg = devfs_msg_get();
                msg = devfs_msg_send_sync(DEVFS_SYNC, msg);
                devfs_msg_put(msg);
        }
}

/*
 * Called on init of devfs; creates the objcaches and
 * spawns off the devfs core thread. Also initializes
 * locks.
 */
static void
devfs_init(void)
{
        devfs_debug(DEVFS_DEBUG_DEBUG, "devfs_init() called\n");
        /* Create objcaches for nodes, msgs and devs */
        devfs_node_cache = objcache_create("devfs-node-cache", 0, 0,
                                           NULL, NULL, NULL,
                                           objcache_malloc_alloc,
                                           objcache_malloc_free,
                                           &devfs_node_malloc_args );

        devfs_msg_cache = objcache_create("devfs-msg-cache", 0, 0,
                                          NULL, NULL, NULL,
                                          objcache_malloc_alloc,
                                          objcache_malloc_free,
                                          &devfs_msg_malloc_args );

        devfs_dev_cache = objcache_create("devfs-dev-cache", 0, 0,
                                          NULL, NULL, NULL,
                                          objcache_malloc_alloc,
                                          objcache_malloc_free,
                                          &devfs_dev_malloc_args );

        devfs_clone_bitmap_init(&DEVFS_CLONE_BITMAP(ops_id));

        /* Initialize the reply-only port which acts as a message drain */
        lwkt_initport_replyonly(&devfs_dispose_port, devfs_msg_autofree_reply);

        /* Initialize *THE* devfs lock */
        lockinit(&devfs_lock, "devfs_core lock", 0, 0);


        lwkt_create(devfs_msg_core, /*args*/NULL, &td_core, NULL,
                    0, 0, "devfs_msg_core");

        tsleep(td_core/*devfs_id*/, 0, "devfsc", 0);

        devfs_debug(DEVFS_DEBUG_DEBUG, "devfs_init finished\n");
}

/*
 * Called on unload of devfs; takes care of destroying the core
 * and the objcaches. Also removes aliases that are no longer needed.
 */
static void
devfs_uninit(void)
{
        devfs_debug(DEVFS_DEBUG_DEBUG, "devfs_uninit() called\n");

        devfs_msg_send(DEVFS_TERMINATE_CORE, NULL);

        tsleep(td_core/*devfs_id*/, 0, "devfsc", 0);
        tsleep(td_core/*devfs_id*/, 0, "devfsc", 10000);

        devfs_clone_bitmap_uninit(&DEVFS_CLONE_BITMAP(ops_id));

        /* Destroy the objcaches */
        objcache_destroy(devfs_msg_cache);
        objcache_destroy(devfs_node_cache);
        objcache_destroy(devfs_dev_cache);

        devfs_alias_reap();
}

/*
 * This is a sysctl handler to assist userland devname(3) to
 * find the device name for a given udev.
 */
static int
devfs_sysctl_devname_helper(SYSCTL_HANDLER_ARGS)
{
        udev_t  udev;
        cdev_t  found;
        int             error;


        if ((error = SYSCTL_IN(req, &udev, sizeof(udev_t))))
                return (error);

        devfs_debug(DEVFS_DEBUG_DEBUG, "devfs sysctl, received udev: %d\n", udev);

        if (udev == NOUDEV)
                return(EINVAL);

        if ((found = devfs_find_device_by_udev(udev)) == NULL)
                return(ENOENT);

        return(SYSCTL_OUT(req, found->si_name, strlen(found->si_name) + 1));
}


SYSCTL_PROC(_kern, OID_AUTO, devname, CTLTYPE_OPAQUE|CTLFLAG_RW|CTLFLAG_ANYBODY,
                        NULL, 0, devfs_sysctl_devname_helper, "", "helper for devname(3)");

SYSCTL_NODE(_vfs, OID_AUTO, devfs, CTLFLAG_RW, 0, "devfs");
TUNABLE_INT("vfs.devfs.debug", &devfs_debug_enable);
SYSCTL_INT(_vfs_devfs, OID_AUTO, debug, CTLFLAG_RW, &devfs_debug_enable,
                0, "Enable DevFS debugging");

SYSINIT(vfs_devfs_register, SI_SUB_PRE_DRIVERS, SI_ORDER_FIRST,
                devfs_init, NULL);
SYSUNINIT(vfs_devfs_register, SI_SUB_PRE_DRIVERS, SI_ORDER_ANY,
                devfs_uninit, NULL);