[deliverable/linux.git] / fs / autofs4 / root.c

/* -*- c -*- --------------------------------------------------------------- *
 *
 * linux/fs/autofs/root.c
 *
 *  Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
 *  Copyright 1999-2000 Jeremy Fitzhardinge <jeremy@goop.org>
 *  Copyright 2001-2006 Ian Kent <raven@themaw.net>
 *
 * This file is part of the Linux kernel and is made available under
 * the terms of the GNU General Public License, version 2, or at your
 * option, any later version, incorporated herein by reference.
 *
 * ------------------------------------------------------------------------- */

#include <linux/capability.h>
#include <linux/errno.h>
#include <linux/stat.h>
#include <linux/slab.h>
#include <linux/param.h>
#include <linux/time.h>
#include <linux/compat.h>
#include <linux/mutex.h>

#include "autofs_i.h"

DEFINE_SPINLOCK(autofs4_lock);

static int autofs4_dir_symlink(struct inode *,struct dentry *,const char *);
static int autofs4_dir_unlink(struct inode *,struct dentry *);
static int autofs4_dir_rmdir(struct inode *,struct dentry *);
static int autofs4_dir_mkdir(struct inode *,struct dentry *,int);
static long autofs4_root_ioctl(struct file *,unsigned int,unsigned long);
#ifdef CONFIG_COMPAT
static long autofs4_root_compat_ioctl(struct file *,unsigned int,unsigned long);
#endif
static int autofs4_dir_open(struct inode *inode, struct file *file);
static struct dentry *autofs4_lookup(struct inode *,struct dentry *, struct nameidata *);
static struct vfsmount *autofs4_d_automount(struct path *);
static int autofs4_d_manage(struct dentry *, bool);
static void autofs4_dentry_release(struct dentry *);

const struct file_operations autofs4_root_operations = {
        .open           = dcache_dir_open,
        .release        = dcache_dir_close,
        .read           = generic_read_dir,
        .readdir        = dcache_readdir,
        .llseek         = dcache_dir_lseek,
        .unlocked_ioctl = autofs4_root_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl   = autofs4_root_compat_ioctl,
#endif
};

const struct file_operations autofs4_dir_operations = {
        .open           = autofs4_dir_open,
        .release        = dcache_dir_close,
        .read           = generic_read_dir,
        .readdir        = dcache_readdir,
        .llseek         = dcache_dir_lseek,
};

const struct inode_operations autofs4_dir_inode_operations = {
        .lookup         = autofs4_lookup,
        .unlink         = autofs4_dir_unlink,
        .symlink        = autofs4_dir_symlink,
        .mkdir          = autofs4_dir_mkdir,
        .rmdir          = autofs4_dir_rmdir,
};

const struct dentry_operations autofs4_dentry_operations = {
        .d_automount    = autofs4_d_automount,
        .d_manage       = autofs4_d_manage,
        .d_release      = autofs4_dentry_release,
};

static void autofs4_add_active(struct dentry *dentry)
{
        struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
        struct autofs_info *ino = autofs4_dentry_ino(dentry);
        if (ino) {
                spin_lock(&sbi->lookup_lock);
                if (!ino->active_count) {
                        if (list_empty(&ino->active))
                                list_add(&ino->active, &sbi->active_list);
                }
                ino->active_count++;
                spin_unlock(&sbi->lookup_lock);
        }
        return;
}

static void autofs4_del_active(struct dentry *dentry)
{
        struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
        struct autofs_info *ino = autofs4_dentry_ino(dentry);
        if (ino) {
                spin_lock(&sbi->lookup_lock);
                ino->active_count--;
                if (!ino->active_count) {
                        if (!list_empty(&ino->active))
                                list_del_init(&ino->active);
                }
                spin_unlock(&sbi->lookup_lock);
        }
        return;
}

static int autofs4_dir_open(struct inode *inode, struct file *file)
{
        struct dentry *dentry = file->f_path.dentry;
        struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);

        DPRINTK("file=%p dentry=%p %.*s",
                file, dentry, dentry->d_name.len, dentry->d_name.name);

        if (autofs4_oz_mode(sbi))
                goto out;

        /*
         * An empty directory in an autofs file system is always a
         * mount point. The daemon must have failed to mount this
         * during lookup so it doesn't exist. This can happen, for
         * example, if user space returns an incorrect status for a
         * mount request. Otherwise we're doing a readdir on the
         * autofs file system so just let the libfs routines handle
         * it.
         */
        spin_lock(&autofs4_lock);
        spin_lock(&dentry->d_lock);
        if (!d_mountpoint(dentry) && list_empty(&dentry->d_subdirs)) {
                spin_unlock(&dentry->d_lock);
                spin_unlock(&autofs4_lock);
                return -ENOENT;
        }
        spin_unlock(&dentry->d_lock);
        spin_unlock(&autofs4_lock);

out:
        return dcache_dir_open(inode, file);
}

static void autofs4_dentry_release(struct dentry *de)
{
        struct autofs_info *ino = autofs4_dentry_ino(de);
        struct autofs_sb_info *sbi = autofs4_sbi(de->d_sb);

        DPRINTK("releasing %p", de);

        if (!ino)
                return;

        if (sbi) {
                spin_lock(&sbi->lookup_lock);
                if (!list_empty(&ino->active))
                        list_del(&ino->active);
                if (!list_empty(&ino->expiring))
                        list_del(&ino->expiring);
                spin_unlock(&sbi->lookup_lock);
        }

        autofs4_free_ino(ino);
}

static struct dentry *autofs4_lookup_active(struct dentry *dentry)
{
        struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
        struct dentry *parent = dentry->d_parent;
        struct qstr *name = &dentry->d_name;
        unsigned int len = name->len;
        unsigned int hash = name->hash;
        const unsigned char *str = name->name;
        struct list_head *p, *head;

        spin_lock(&autofs4_lock);
        spin_lock(&sbi->lookup_lock);
        head = &sbi->active_list;
        list_for_each(p, head) {
                struct autofs_info *ino;
                struct dentry *active;
                struct qstr *qstr;

                ino = list_entry(p, struct autofs_info, active);
                active = ino->dentry;

                spin_lock(&active->d_lock);

                /* Already gone? */
                if (active->d_count == 0)
                        goto next;

                qstr = &active->d_name;

                if (active->d_name.hash != hash)
                        goto next;
                if (active->d_parent != parent)
                        goto next;

                if (qstr->len != len)
                        goto next;
                if (memcmp(qstr->name, str, len))
                        goto next;

                if (d_unhashed(active)) {
                        dget_dlock(active);
                        spin_unlock(&active->d_lock);
                        spin_unlock(&sbi->lookup_lock);
                        spin_unlock(&autofs4_lock);
                        return active;
                }
next:
                spin_unlock(&active->d_lock);
        }
        spin_unlock(&sbi->lookup_lock);
        spin_unlock(&autofs4_lock);

        return NULL;
}

static struct dentry *autofs4_lookup_expiring(struct dentry *dentry)
{
        struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
        struct dentry *parent = dentry->d_parent;
        struct qstr *name = &dentry->d_name;
        unsigned int len = name->len;
        unsigned int hash = name->hash;
        const unsigned char *str = name->name;
        struct list_head *p, *head;

        spin_lock(&autofs4_lock);
        spin_lock(&sbi->lookup_lock);
        head = &sbi->expiring_list;
        list_for_each(p, head) {
                struct autofs_info *ino;
                struct dentry *expiring;
                struct qstr *qstr;

                ino = list_entry(p, struct autofs_info, expiring);
                expiring = ino->dentry;

                spin_lock(&expiring->d_lock);

                /* Bad luck, we've already been dentry_iput */
                if (!expiring->d_inode)
                        goto next;

                qstr = &expiring->d_name;

                if (expiring->d_name.hash != hash)
                        goto next;
                if (expiring->d_parent != parent)
                        goto next;

                if (qstr->len != len)
                        goto next;
                if (memcmp(qstr->name, str, len))
                        goto next;

                if (d_unhashed(expiring)) {
                        dget_dlock(expiring);
                        spin_unlock(&expiring->d_lock);
                        spin_unlock(&sbi->lookup_lock);
                        spin_unlock(&autofs4_lock);
                        return expiring;
                }
next:
                spin_unlock(&expiring->d_lock);
        }
        spin_unlock(&sbi->lookup_lock);
        spin_unlock(&autofs4_lock);

        return NULL;
}

static int autofs4_mount_wait(struct dentry *dentry)
{
        struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
        struct autofs_info *ino = autofs4_dentry_ino(dentry);
        int status = 0;

        if (ino->flags & AUTOFS_INF_PENDING) {
                DPRINTK("waiting for mount name=%.*s",
                        dentry->d_name.len, dentry->d_name.name);
                status = autofs4_wait(sbi, dentry, NFY_MOUNT);
                DPRINTK("mount wait done status=%d", status);
        }
        ino->last_used = jiffies;
        return status;
}

static int do_expire_wait(struct dentry *dentry)
{
        struct dentry *expiring;

        expiring = autofs4_lookup_expiring(dentry);
        if (!expiring)
                return autofs4_expire_wait(dentry);
        else {
                /*
                 * If we are racing with expire the request might not
                 * be quite complete, but the directory has been removed
                 * so it must have been successful, just wait for it.
                 */
                autofs4_expire_wait(expiring);
                autofs4_del_expiring(expiring);
                dput(expiring);
        }
        return 0;
}

static struct dentry *autofs4_mountpoint_changed(struct path *path)
{
        struct dentry *dentry = path->dentry;
        struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);

        /*
         * If this is an indirect mount the dentry could have gone away
         * as a result of an expire and a new one created.
         */
        if (autofs_type_indirect(sbi->type) && d_unhashed(dentry)) {
                struct dentry *parent = dentry->d_parent;
                struct autofs_info *ino;
                struct dentry *new = d_lookup(parent, &dentry->d_name);
                if (!new)
                        return NULL;
                ino = autofs4_dentry_ino(new);
                ino->last_used = jiffies;
                dput(path->dentry);
                path->dentry = new;
        }
        return path->dentry;
}

static struct vfsmount *autofs4_d_automount(struct path *path)
{
        struct dentry *dentry = path->dentry;
        struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
        struct autofs_info *ino = autofs4_dentry_ino(dentry);
        int status;

        DPRINTK("dentry=%p %.*s",
                dentry, dentry->d_name.len, dentry->d_name.name);

        /* The daemon never triggers a mount. */
        if (autofs4_oz_mode(sbi))
                return NULL;

        /*
         * If an expire request is pending everyone must wait.
         * If the expire fails we're still mounted so continue
         * the follow and return. A return of -EAGAIN (which only
         * happens with indirect mounts) means the expire completed
         * and the directory was removed, so just go ahead and try
         * the mount.
         */
        status = do_expire_wait(dentry);
        if (status && status != -EAGAIN)
                return NULL;

        /* Callback to the daemon to perform the mount or wait */
        spin_lock(&sbi->fs_lock);
        if (ino->flags & AUTOFS_INF_PENDING) {
                spin_unlock(&sbi->fs_lock);
                status = autofs4_mount_wait(dentry);
                if (status)
                        return ERR_PTR(status);
                spin_lock(&sbi->fs_lock);
                goto done;
        }

        /*
         * If the dentry is a symlink it's equivalent to a directory
         * having d_mountpoint() true, so there's no need to call back
         * to the daemon.
         */
        if (dentry->d_inode && S_ISLNK(dentry->d_inode->i_mode))
                goto done;
        if (!d_mountpoint(dentry)) {
                /*
                 * It's possible that user space hasn't removed directories
                 * after umounting a rootless multi-mount, although it
                 * should. For v5 have_submounts() is sufficient to handle
                 * this because the leaves of the directory tree under the
                 * mount never trigger mounts themselves (they have an autofs
                 * trigger mount mounted on them). But v4 pseudo direct mounts
                 * do need the leaves to to trigger mounts. In this case we
                 * have no choice but to use the list_empty() check and
                 * require user space behave.
                 */
                if (sbi->version > 4) {
                        if (have_submounts(dentry))
                                goto done;
                } else {
                        spin_lock(&dentry->d_lock);
                        if (!list_empty(&dentry->d_subdirs)) {
                                spin_unlock(&dentry->d_lock);
                                goto done;
                        }
                        spin_unlock(&dentry->d_lock);
                }
                ino->flags |= AUTOFS_INF_PENDING;
                spin_unlock(&sbi->fs_lock);
                status = autofs4_mount_wait(dentry);
                if (status)
                        return ERR_PTR(status);
                spin_lock(&sbi->fs_lock);
                ino->flags &= ~AUTOFS_INF_PENDING;
        }
done:
        if (!(ino->flags & AUTOFS_INF_EXPIRING)) {
                /*
                 * Any needed mounting has been completed and the path
                 * updated so clear DCACHE_NEED_AUTOMOUNT so we don't
                 * call ->d_automount() on rootless multi-mounts since
                 * it can lead to an incorrect ELOOP error return.
                 *
                 * Only clear DMANAGED_AUTOMOUNT for rootless multi-mounts and
                 * symlinks as in all other cases the dentry will be covered by
                 * an actual mount so ->d_automount() won't be called during
                 * the follow.
                 */
                spin_lock(&dentry->d_lock);
                if ((!d_mountpoint(dentry) &&
                    !list_empty(&dentry->d_subdirs)) ||
                    (dentry->d_inode && S_ISLNK(dentry->d_inode->i_mode)))
                        __managed_dentry_clear_automount(dentry);
                spin_unlock(&dentry->d_lock);
        }
        spin_unlock(&sbi->fs_lock);

        /* Mount succeeded, check if we ended up with a new dentry */
        dentry = autofs4_mountpoint_changed(path);
        if (!dentry)
                return ERR_PTR(-ENOENT);

        return NULL;
}

int autofs4_d_manage(struct dentry *dentry, bool rcu_walk)
{
        struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);

        DPRINTK("dentry=%p %.*s",
                dentry, dentry->d_name.len, dentry->d_name.name);

        /* The daemon never waits. */
        if (autofs4_oz_mode(sbi)) {
                if (!d_mountpoint(dentry))
                        return -EISDIR;
                return 0;
        }

        /* We need to sleep, so we need pathwalk to be in ref-mode */
        if (rcu_walk)
                return -ECHILD;

        /* Wait for pending expires */
        do_expire_wait(dentry);

        /*
         * This dentry may be under construction so wait on mount
         * completion.
         */
        return autofs4_mount_wait(dentry);
}

/* Lookups in the root directory */
static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
{
        struct autofs_sb_info *sbi;
        struct autofs_info *ino;
        struct dentry *active;

        DPRINTK("name = %.*s", dentry->d_name.len, dentry->d_name.name);

        /* File name too long to exist */
        if (dentry->d_name.len > NAME_MAX)
                return ERR_PTR(-ENAMETOOLONG);

        sbi = autofs4_sbi(dir->i_sb);

        DPRINTK("pid = %u, pgrp = %u, catatonic = %d, oz_mode = %d",
                current->pid, task_pgrp_nr(current), sbi->catatonic,
                autofs4_oz_mode(sbi));

        active = autofs4_lookup_active(dentry);
        if (active) {
                return active;
        } else {
                /*
                 * A dentry that is not within the root can never trigger a
                 * mount operation, unless the directory already exists, so we
                 * can return fail immediately.  The daemon however does need
                 * to create directories within the file system.
                 */
                if (!autofs4_oz_mode(sbi) && !IS_ROOT(dentry->d_parent))
                        return ERR_PTR(-ENOENT);

                /* Mark entries in the root as mount triggers */
                if (autofs_type_indirect(sbi->type) && IS_ROOT(dentry->d_parent))
                        __managed_dentry_set_managed(dentry);

                ino = autofs4_new_ino(sbi);
                if (!ino)
                        return ERR_PTR(-ENOMEM);

                dentry->d_fsdata = ino;
                ino->dentry = dentry;

                autofs4_add_active(dentry);

                d_instantiate(dentry, NULL);
        }
        return NULL;
}

static int autofs4_dir_symlink(struct inode *dir, 
                               struct dentry *dentry,
                               const char *symname)
{
        struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
        struct autofs_info *ino = autofs4_dentry_ino(dentry);
        struct autofs_info *p_ino;
        struct inode *inode;
        size_t size = strlen(symname);
        char *cp;

        DPRINTK("%s <- %.*s", symname,
                dentry->d_name.len, dentry->d_name.name);

        if (!autofs4_oz_mode(sbi))
                return -EACCES;

        BUG_ON(!ino);

        autofs4_clean_ino(ino);

        autofs4_del_active(dentry);

        cp = kmalloc(size + 1, GFP_KERNEL);
        if (!cp)
                return -ENOMEM;

        strcpy(cp, symname);

        inode = autofs4_get_inode(dir->i_sb, S_IFLNK | 0555);
        if (!inode) {
                kfree(cp);
                if (!dentry->d_fsdata)
                        kfree(ino);
                return -ENOMEM;
        }
        inode->i_private = cp;
        inode->i_size = size;
        d_add(dentry, inode);

        dget(dentry);
        atomic_inc(&ino->count);
        p_ino = autofs4_dentry_ino(dentry->d_parent);
        if (p_ino && dentry->d_parent != dentry)
                atomic_inc(&p_ino->count);

        dir->i_mtime = CURRENT_TIME;

        return 0;
}

/*
 * NOTE!
 *
 * Normal filesystems would do a "d_delete()" to tell the VFS dcache
 * that the file no longer exists. However, doing that means that the
 * VFS layer can turn the dentry into a negative dentry.  We don't want
 * this, because the unlink is probably the result of an expire.
 * We simply d_drop it and add it to a expiring list in the super block,
 * which allows the dentry lookup to check for an incomplete expire.
 *
 * If a process is blocked on the dentry waiting for the expire to finish,
 * it will invalidate the dentry and try to mount with a new one.
 *
 * Also see autofs4_dir_rmdir()..
 */
static int autofs4_dir_unlink(struct inode *dir, struct dentry *dentry)
{
        struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
        struct autofs_info *ino = autofs4_dentry_ino(dentry);
        struct autofs_info *p_ino;
        
        /* This allows root to remove symlinks */
        if (!autofs4_oz_mode(sbi) && !capable(CAP_SYS_ADMIN))
                return -EACCES;

        if (atomic_dec_and_test(&ino->count)) {
                p_ino = autofs4_dentry_ino(dentry->d_parent);
                if (p_ino && dentry->d_parent != dentry)
                        atomic_dec(&p_ino->count);
        }
        dput(ino->dentry);

        dentry->d_inode->i_size = 0;
        clear_nlink(dentry->d_inode);

        dir->i_mtime = CURRENT_TIME;

        spin_lock(&autofs4_lock);
        autofs4_add_expiring(dentry);
        spin_lock(&dentry->d_lock);
        __d_drop(dentry);
        spin_unlock(&dentry->d_lock);
        spin_unlock(&autofs4_lock);

        return 0;
}

/*
 * Version 4 of autofs provides a pseudo direct mount implementation
 * that relies on directories at the leaves of a directory tree under
 * an indirect mount to trigger mounts. To allow for this we need to
 * set the DMANAGED_AUTOMOUNT and DMANAGED_TRANSIT flags on the leaves
 * of the directory tree. There is no need to clear the automount flag
 * following a mount or restore it after an expire because these mounts
 * are always covered. However, it is neccessary to ensure that these
 * flags are clear on non-empty directories to avoid unnecessary calls
 * during path walks.
 */
static void autofs_set_leaf_automount_flags(struct dentry *dentry)
{
        struct dentry *parent;

        /* root and dentrys in the root are already handled */
        if (IS_ROOT(dentry->d_parent))
                return;

        managed_dentry_set_managed(dentry);

        parent = dentry->d_parent;
        /* only consider parents below dentrys in the root */
        if (IS_ROOT(parent->d_parent))
                return;
        managed_dentry_clear_managed(parent);
        return;
}

static void autofs_clear_leaf_automount_flags(struct dentry *dentry)
{
        struct list_head *d_child;
        struct dentry *parent;

        /* flags for dentrys in the root are handled elsewhere */
        if (IS_ROOT(dentry->d_parent))
                return;

        managed_dentry_clear_managed(dentry);

        parent = dentry->d_parent;
        /* only consider parents below dentrys in the root */
        if (IS_ROOT(parent->d_parent))
                return;
        d_child = &dentry->d_u.d_child;
        /* Set parent managed if it's becoming empty */
        if (d_child->next == &parent->d_subdirs &&
            d_child->prev == &parent->d_subdirs)
                managed_dentry_set_managed(parent);
        return;
}

static int autofs4_dir_rmdir(struct inode *dir, struct dentry *dentry)
{
        struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
        struct autofs_info *ino = autofs4_dentry_ino(dentry);
        struct autofs_info *p_ino;
        
        DPRINTK("dentry %p, removing %.*s",
                dentry, dentry->d_name.len, dentry->d_name.name);

        if (!autofs4_oz_mode(sbi))
                return -EACCES;

        spin_lock(&autofs4_lock);
        spin_lock(&sbi->lookup_lock);
        spin_lock(&dentry->d_lock);
        if (!list_empty(&dentry->d_subdirs)) {
                spin_unlock(&dentry->d_lock);
                spin_unlock(&sbi->lookup_lock);
                spin_unlock(&autofs4_lock);
                return -ENOTEMPTY;
        }
        __autofs4_add_expiring(dentry);
        spin_unlock(&sbi->lookup_lock);
        __d_drop(dentry);
        spin_unlock(&dentry->d_lock);
        spin_unlock(&autofs4_lock);

        if (sbi->version < 5)
                autofs_clear_leaf_automount_flags(dentry);

        if (atomic_dec_and_test(&ino->count)) {
                p_ino = autofs4_dentry_ino(dentry->d_parent);
                if (p_ino && dentry->d_parent != dentry)
                        atomic_dec(&p_ino->count);
        }
        dput(ino->dentry);
        dentry->d_inode->i_size = 0;
        clear_nlink(dentry->d_inode);

        if (dir->i_nlink)
                drop_nlink(dir);

        return 0;
}

static int autofs4_dir_mkdir(struct inode *dir, struct dentry *dentry, int mode)
{
        struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
        struct autofs_info *ino = autofs4_dentry_ino(dentry);
        struct autofs_info *p_ino;
        struct inode *inode;

        if (!autofs4_oz_mode(sbi))
                return -EACCES;

        DPRINTK("dentry %p, creating %.*s",
                dentry, dentry->d_name.len, dentry->d_name.name);

        BUG_ON(!ino);

        autofs4_clean_ino(ino);

        autofs4_del_active(dentry);

        inode = autofs4_get_inode(dir->i_sb, S_IFDIR | 0555);
        if (!inode)
                return -ENOMEM;
        d_add(dentry, inode);

        if (sbi->version < 5)
                autofs_set_leaf_automount_flags(dentry);

        dget(dentry);
        atomic_inc(&ino->count);
        p_ino = autofs4_dentry_ino(dentry->d_parent);
        if (p_ino && dentry->d_parent != dentry)
                atomic_inc(&p_ino->count);
        inc_nlink(dir);
        dir->i_mtime = CURRENT_TIME;

        return 0;
}

/* Get/set timeout ioctl() operation */
#ifdef CONFIG_COMPAT
static inline int autofs4_compat_get_set_timeout(struct autofs_sb_info *sbi,
                                         compat_ulong_t __user *p)
{
        int rv;
        unsigned long ntimeout;

        if ((rv = get_user(ntimeout, p)) ||
             (rv = put_user(sbi->exp_timeout/HZ, p)))
                return rv;

        if (ntimeout > UINT_MAX/HZ)
                sbi->exp_timeout = 0;
        else
                sbi->exp_timeout = ntimeout * HZ;

        return 0;
}
#endif

static inline int autofs4_get_set_timeout(struct autofs_sb_info *sbi,
                                         unsigned long __user *p)
{
        int rv;
        unsigned long ntimeout;

        if ((rv = get_user(ntimeout, p)) ||
             (rv = put_user(sbi->exp_timeout/HZ, p)))
                return rv;

        if (ntimeout > ULONG_MAX/HZ)
                sbi->exp_timeout = 0;
        else
                sbi->exp_timeout = ntimeout * HZ;

        return 0;
}

/* Return protocol version */
static inline int autofs4_get_protover(struct autofs_sb_info *sbi, int __user *p)
{
        return put_user(sbi->version, p);
}

/* Return protocol sub version */
static inline int autofs4_get_protosubver(struct autofs_sb_info *sbi, int __user *p)
{
        return put_user(sbi->sub_version, p);
}

/*
* Tells the daemon whether it can umount the autofs mount.
*/
static inline int autofs4_ask_umount(struct vfsmount *mnt, int __user *p)
{
        int status = 0;

        if (may_umount(mnt))
                status = 1;

        DPRINTK("returning %d", status);

        status = put_user(status, p);

        return status;
}

/* Identify autofs4_dentries - this is so we can tell if there's
   an extra dentry refcount or not.  We only hold a refcount on the
   dentry if its non-negative (ie, d_inode != NULL)
*/
int is_autofs4_dentry(struct dentry *dentry)
{
        return dentry && dentry->d_inode &&
                dentry->d_op == &autofs4_dentry_operations &&
                dentry->d_fsdata != NULL;
}

/*
 * ioctl()'s on the root directory is the chief method for the daemon to
 * generate kernel reactions
 */
static int autofs4_root_ioctl_unlocked(struct inode *inode, struct file *filp,
                                       unsigned int cmd, unsigned long arg)
{
        struct autofs_sb_info *sbi = autofs4_sbi(inode->i_sb);
        void __user *p = (void __user *)arg;

        DPRINTK("cmd = 0x%08x, arg = 0x%08lx, sbi = %p, pgrp = %u",
                cmd,arg,sbi,task_pgrp_nr(current));

        if (_IOC_TYPE(cmd) != _IOC_TYPE(AUTOFS_IOC_FIRST) ||
             _IOC_NR(cmd) - _IOC_NR(AUTOFS_IOC_FIRST) >= AUTOFS_IOC_COUNT)
                return -ENOTTY;
        
        if (!autofs4_oz_mode(sbi) && !capable(CAP_SYS_ADMIN))
                return -EPERM;
        
        switch(cmd) {
        case AUTOFS_IOC_READY:  /* Wait queue: go ahead and retry */
                return autofs4_wait_release(sbi,(autofs_wqt_t)arg,0);
        case AUTOFS_IOC_FAIL:   /* Wait queue: fail with ENOENT */
                return autofs4_wait_release(sbi,(autofs_wqt_t)arg,-ENOENT);
        case AUTOFS_IOC_CATATONIC: /* Enter catatonic mode (daemon shutdown) */
                autofs4_catatonic_mode(sbi);
                return 0;
        case AUTOFS_IOC_PROTOVER: /* Get protocol version */
                return autofs4_get_protover(sbi, p);
        case AUTOFS_IOC_PROTOSUBVER: /* Get protocol sub version */
                return autofs4_get_protosubver(sbi, p);
        case AUTOFS_IOC_SETTIMEOUT:
                return autofs4_get_set_timeout(sbi, p);
#ifdef CONFIG_COMPAT
        case AUTOFS_IOC_SETTIMEOUT32:
                return autofs4_compat_get_set_timeout(sbi, p);
#endif

        case AUTOFS_IOC_ASKUMOUNT:
                return autofs4_ask_umount(filp->f_path.mnt, p);

        /* return a single thing to expire */
        case AUTOFS_IOC_EXPIRE:
                return autofs4_expire_run(inode->i_sb,filp->f_path.mnt,sbi, p);
        /* same as above, but can send multiple expires through pipe */
        case AUTOFS_IOC_EXPIRE_MULTI:
                return autofs4_expire_multi(inode->i_sb,filp->f_path.mnt,sbi, p);

        default:
                return -ENOSYS;
        }
}

static long autofs4_root_ioctl(struct file *filp,
                               unsigned int cmd, unsigned long arg)
{
        struct inode *inode = filp->f_dentry->d_inode;
        return autofs4_root_ioctl_unlocked(inode, filp, cmd, arg);
}

#ifdef CONFIG_COMPAT
static long autofs4_root_compat_ioctl(struct file *filp,
                             unsigned int cmd, unsigned long arg)
{
        struct inode *inode = filp->f_path.dentry->d_inode;
        int ret;

        if (cmd == AUTOFS_IOC_READY || cmd == AUTOFS_IOC_FAIL)
                ret = autofs4_root_ioctl_unlocked(inode, filp, cmd, arg);
        else
                ret = autofs4_root_ioctl_unlocked(inode, filp, cmd,
                        (unsigned long)compat_ptr(arg));

        return ret;
}
#endif