tracing: Use guard() rather than scoped_guard()

[drm/drm-misc.git] / fs / autofs / root.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
 * Copyright 1999-2000 Jeremy Fitzhardinge <jeremy@goop.org>
 * Copyright 2001-2006 Ian Kent <raven@themaw.net>
 */

#include <linux/capability.h>
#include <linux/compat.h>

#include "autofs_i.h"

static int autofs_dir_permission(struct mnt_idmap *, struct inode *, int);
static int autofs_dir_symlink(struct mnt_idmap *, struct inode *,
                              struct dentry *, const char *);
static int autofs_dir_unlink(struct inode *, struct dentry *);
static int autofs_dir_rmdir(struct inode *, struct dentry *);
static int autofs_dir_mkdir(struct mnt_idmap *, struct inode *,
                            struct dentry *, umode_t);
static long autofs_root_ioctl(struct file *, unsigned int, unsigned long);
#ifdef CONFIG_COMPAT
static long autofs_root_compat_ioctl(struct file *,
                                     unsigned int, unsigned long);
#endif
static int autofs_dir_open(struct inode *inode, struct file *file);
static struct dentry *autofs_lookup(struct inode *,
                                    struct dentry *, unsigned int);
static struct vfsmount *autofs_d_automount(struct path *);
static int autofs_d_manage(const struct path *, bool);
static void autofs_dentry_release(struct dentry *);

const struct file_operations autofs_root_operations = {
        .open           = dcache_dir_open,
        .release        = dcache_dir_close,
        .read           = generic_read_dir,
        .iterate_shared = dcache_readdir,
        .llseek         = dcache_dir_lseek,
        .unlocked_ioctl = autofs_root_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl   = autofs_root_compat_ioctl,
#endif
};

const struct file_operations autofs_dir_operations = {
        .open           = autofs_dir_open,
        .release        = dcache_dir_close,
        .read           = generic_read_dir,
        .iterate_shared = dcache_readdir,
        .llseek         = dcache_dir_lseek,
};

const struct inode_operations autofs_dir_inode_operations = {
        .lookup         = autofs_lookup,
        .permission     = autofs_dir_permission,
        .unlink         = autofs_dir_unlink,
        .symlink        = autofs_dir_symlink,
        .mkdir          = autofs_dir_mkdir,
        .rmdir          = autofs_dir_rmdir,
};

const struct dentry_operations autofs_dentry_operations = {
        .d_automount    = autofs_d_automount,
        .d_manage       = autofs_d_manage,
        .d_release      = autofs_dentry_release,
};

static void autofs_del_active(struct dentry *dentry)
{
        struct autofs_sb_info *sbi = autofs_sbi(dentry->d_sb);
        struct autofs_info *ino;

        ino = autofs_dentry_ino(dentry);
        spin_lock(&sbi->lookup_lock);
        list_del_init(&ino->active);
        spin_unlock(&sbi->lookup_lock);
}

static int autofs_dir_open(struct inode *inode, struct file *file)
{
        struct dentry *dentry = file->f_path.dentry;
        struct autofs_sb_info *sbi = autofs_sbi(dentry->d_sb);
        struct autofs_info *ino = autofs_dentry_ino(dentry);

        pr_debug("file=%p dentry=%p %pd\n", file, dentry, dentry);

        if (autofs_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(&sbi->lookup_lock);
        if (!path_is_mountpoint(&file->f_path) && autofs_empty(ino)) {
                spin_unlock(&sbi->lookup_lock);
                return -ENOENT;
        }
        spin_unlock(&sbi->lookup_lock);

out:
        return dcache_dir_open(inode, file);
}

static void autofs_dentry_release(struct dentry *de)
{
        struct autofs_info *ino = autofs_dentry_ino(de);
        struct autofs_sb_info *sbi = autofs_sbi(de->d_sb);

        pr_debug("releasing %p\n", 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);
        }

        autofs_free_ino(ino);
}

static struct dentry *autofs_lookup_active(struct dentry *dentry)
{
        struct autofs_sb_info *sbi = autofs_sbi(dentry->d_sb);
        struct dentry *parent = dentry->d_parent;
        const 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;

        head = &sbi->active_list;
        if (list_empty(head))
                return NULL;
        spin_lock(&sbi->lookup_lock);
        list_for_each(p, head) {
                struct autofs_info *ino;
                struct dentry *active;
                const struct qstr *qstr;

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

                spin_lock(&active->d_lock);

                /* Already gone? */
                if ((int) d_count(active) <= 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);
                        return active;
                }
next:
                spin_unlock(&active->d_lock);
        }
        spin_unlock(&sbi->lookup_lock);

        return NULL;
}

static struct dentry *autofs_lookup_expiring(struct dentry *dentry,
                                             bool rcu_walk)
{
        struct autofs_sb_info *sbi = autofs_sbi(dentry->d_sb);
        struct dentry *parent = dentry->d_parent;
        const 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;

        head = &sbi->expiring_list;
        if (list_empty(head))
                return NULL;
        spin_lock(&sbi->lookup_lock);
        list_for_each(p, head) {
                struct autofs_info *ino;
                struct dentry *expiring;
                const struct qstr *qstr;

                if (rcu_walk) {
                        spin_unlock(&sbi->lookup_lock);
                        return ERR_PTR(-ECHILD);
                }

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

                spin_lock(&expiring->d_lock);

                /* We've already been dentry_iput or unlinked */
                if (d_really_is_negative(expiring))
                        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);
                        return expiring;
                }
next:
                spin_unlock(&expiring->d_lock);
        }
        spin_unlock(&sbi->lookup_lock);

        return NULL;
}

static int autofs_mount_wait(const struct path *path, bool rcu_walk)
{
        struct autofs_sb_info *sbi = autofs_sbi(path->dentry->d_sb);
        struct autofs_info *ino = autofs_dentry_ino(path->dentry);
        int status = 0;

        if (ino->flags & AUTOFS_INF_PENDING) {
                if (rcu_walk)
                        return -ECHILD;
                pr_debug("waiting for mount name=%pd\n", path->dentry);
                status = autofs_wait(sbi, path, NFY_MOUNT);
                pr_debug("mount wait done status=%d\n", status);
                ino->last_used = jiffies;
                return status;
        }
        if (!(sbi->flags & AUTOFS_SBI_STRICTEXPIRE))
                ino->last_used = jiffies;
        return status;
}

static int do_expire_wait(const struct path *path, bool rcu_walk)
{
        struct dentry *dentry = path->dentry;
        struct dentry *expiring;

        expiring = autofs_lookup_expiring(dentry, rcu_walk);
        if (IS_ERR(expiring))
                return PTR_ERR(expiring);
        if (!expiring)
                return autofs_expire_wait(path, rcu_walk);
        else {
                const struct path this = { .mnt = path->mnt, .dentry = expiring };
                /*
                 * 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.
                 */
                autofs_expire_wait(&this, 0);
                autofs_del_expiring(expiring);
                dput(expiring);
        }
        return 0;
}

static struct dentry *autofs_mountpoint_changed(struct path *path)
{
        struct dentry *dentry = path->dentry;
        struct autofs_sb_info *sbi = autofs_sbi(dentry->d_sb);

        /* If this is an indirect mount the dentry could have gone away
         * and a new one created.
         *
         * This is unusual and I can't remember the case for which it
         * was originally added now. But an example of how this can
         * happen is an autofs indirect mount that has the "browse"
         * option set and also has the "symlink" option in the autofs
         * map entry. In this case the daemon will remove the browse
         * directory and create a symlink as the mount leaving the
         * struct path stale.
         *
         * Another not so obvious case is when a mount in an autofs
         * indirect mount that uses the "nobrowse" option is being
         * expired at the same time as a path walk. If the mount has
         * been umounted but the mount point directory seen before
         * becoming unhashed (during a lockless path walk) when a stat
         * family system call is made the mount won't be re-mounted as
         * it should. In this case the mount point that's been removed
         * (by the daemon) will be stale and the a new mount point
         * dentry created.
         */
        if (autofs_type_indirect(sbi->type) && d_unhashed(dentry)) {
                struct dentry *parent = dentry->d_parent;
                struct autofs_info *ino;
                struct dentry *new;

                new = d_lookup(parent, &dentry->d_name);
                if (!new)
                        return NULL;
                ino = autofs_dentry_ino(new);
                ino->last_used = jiffies;
                dput(path->dentry);
                path->dentry = new;
        }
        return path->dentry;
}

static struct vfsmount *autofs_d_automount(struct path *path)
{
        struct dentry *dentry = path->dentry;
        struct autofs_sb_info *sbi = autofs_sbi(dentry->d_sb);
        struct autofs_info *ino = autofs_dentry_ino(dentry);
        int status;

        pr_debug("dentry=%p %pd\n", dentry, dentry);

        /* The daemon never triggers a mount. */
        if (autofs_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(path, 0);
        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 = autofs_mount_wait(path, 0);
                if (status)
                        return ERR_PTR(status);
                goto done;
        }

        /*
         * If the dentry is a symlink it's equivalent to a directory
         * having path_is_mountpoint() true, so there's no need to call
         * back to the daemon.
         */
        if (d_really_is_positive(dentry) && d_is_symlink(dentry)) {
                spin_unlock(&sbi->fs_lock);
                goto done;
        }

        if (!path_is_mountpoint(path)) {
                /*
                 * It's possible that user space hasn't removed directories
                 * after umounting a rootless multi-mount, although it
                 * should. For v5 path_has_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 trigger mounts. In this case
                 * we have no choice but to use the autofs_empty() check and
                 * require user space behave.
                 */
                if (sbi->version > 4) {
                        if (path_has_submounts(path)) {
                                spin_unlock(&sbi->fs_lock);
                                goto done;
                        }
                } else {
                        if (!autofs_empty(ino)) {
                                spin_unlock(&sbi->fs_lock);
                                goto done;
                        }
                }
                ino->flags |= AUTOFS_INF_PENDING;
                spin_unlock(&sbi->fs_lock);
                status = autofs_mount_wait(path, 0);
                spin_lock(&sbi->fs_lock);
                ino->flags &= ~AUTOFS_INF_PENDING;
                if (status) {
                        spin_unlock(&sbi->fs_lock);
                        return ERR_PTR(status);
                }
        }
        spin_unlock(&sbi->fs_lock);
done:
        /* Mount succeeded, check if we ended up with a new dentry */
        dentry = autofs_mountpoint_changed(path);
        if (!dentry)
                return ERR_PTR(-ENOENT);

        return NULL;
}

static int autofs_d_manage(const struct path *path, bool rcu_walk)
{
        struct dentry *dentry = path->dentry;
        struct autofs_sb_info *sbi = autofs_sbi(dentry->d_sb);
        struct autofs_info *ino = autofs_dentry_ino(dentry);
        int status;

        pr_debug("dentry=%p %pd\n", dentry, dentry);

        /* The daemon never waits. */
        if (autofs_oz_mode(sbi)) {
                if (!path_is_mountpoint(path))
                        return -EISDIR;
                return 0;
        }

        /* Wait for pending expires */
        if (do_expire_wait(path, rcu_walk) == -ECHILD)
                return -ECHILD;

        /*
         * This dentry may be under construction so wait on mount
         * completion.
         */
        status = autofs_mount_wait(path, rcu_walk);
        if (status)
                return status;

        if (rcu_walk) {
                /* We don't need fs_lock in rcu_walk mode,
                 * just testing 'AUTOFS_INF_WANT_EXPIRE' is enough.
                 *
                 * We only return -EISDIR when certain this isn't
                 * a mount-trap.
                 */
                struct inode *inode;

                if (ino->flags & AUTOFS_INF_WANT_EXPIRE)
                        return 0;
                if (path_is_mountpoint(path))
                        return 0;
                inode = d_inode_rcu(dentry);
                if (inode && S_ISLNK(inode->i_mode))
                        return -EISDIR;
                if (!autofs_empty(ino))
                        return -EISDIR;
                return 0;
        }

        spin_lock(&sbi->fs_lock);
        /*
         * If the dentry has been selected for expire while we slept
         * on the lock then it might go away. We'll deal with that in
         * ->d_automount() and wait on a new mount if the expire
         * succeeds or return here if it doesn't (since there's no
         * mount to follow with a rootless multi-mount).
         */
        if (!(ino->flags & AUTOFS_INF_EXPIRING)) {
                /*
                 * Any needed mounting has been completed and the path
                 * updated so check if this is a rootless multi-mount so
                 * we can avoid needless calls ->d_automount() and avoid
                 * an incorrect ELOOP error return.
                 */
                if ((!path_is_mountpoint(path) && !autofs_empty(ino)) ||
                    (d_really_is_positive(dentry) && d_is_symlink(dentry)))
                        status = -EISDIR;
        }
        spin_unlock(&sbi->fs_lock);

        return status;
}

/* Lookups in the root directory */
static struct dentry *autofs_lookup(struct inode *dir,
                                    struct dentry *dentry, unsigned int flags)
{
        struct autofs_sb_info *sbi;
        struct autofs_info *ino;
        struct dentry *active;

        pr_debug("name = %pd\n", dentry);

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

        sbi = autofs_sbi(dir->i_sb);

        pr_debug("pid = %u, pgrp = %u, catatonic = %d, oz_mode = %d\n",
                 current->pid, task_pgrp_nr(current),
                 sbi->flags & AUTOFS_SBI_CATATONIC,
                 autofs_oz_mode(sbi));

        active = autofs_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 (!autofs_oz_mode(sbi) && !IS_ROOT(dentry->d_parent))
                        return ERR_PTR(-ENOENT);

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

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

                list_add(&ino->active, &sbi->active_list);
                spin_unlock(&sbi->lookup_lock);
                spin_unlock(&dentry->d_lock);
        }
        return NULL;
}

static int autofs_dir_permission(struct mnt_idmap *idmap,
                                 struct inode *inode, int mask)
{
        if (mask & MAY_WRITE) {
                struct autofs_sb_info *sbi = autofs_sbi(inode->i_sb);

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

                /* autofs_oz_mode() needs to allow path walks when the
                 * autofs mount is catatonic but the state of an autofs
                 * file system needs to be preserved over restarts.
                 */
                if (sbi->flags & AUTOFS_SBI_CATATONIC)
                        return -EACCES;
        }

        return generic_permission(idmap, inode, mask);
}

static int autofs_dir_symlink(struct mnt_idmap *idmap,
                              struct inode *dir, struct dentry *dentry,
                              const char *symname)
{
        struct autofs_info *ino = autofs_dentry_ino(dentry);
        struct autofs_info *p_ino;
        struct inode *inode;
        size_t size = strlen(symname);
        char *cp;

        pr_debug("%s <- %pd\n", symname, dentry);

        BUG_ON(!ino);

        autofs_clean_ino(ino);

        autofs_del_active(dentry);

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

        strcpy(cp, symname);

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

        dget(dentry);
        p_ino = autofs_dentry_ino(dentry->d_parent);
        p_ino->count++;

        inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));

        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 autofs_dir_rmdir()..
 */
static int autofs_dir_unlink(struct inode *dir, struct dentry *dentry)
{
        struct autofs_sb_info *sbi = autofs_sbi(dir->i_sb);
        struct autofs_info *ino = autofs_dentry_ino(dentry);
        struct autofs_info *p_ino;

        p_ino = autofs_dentry_ino(dentry->d_parent);
        p_ino->count--;
        dput(ino->dentry);

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

        inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));

        spin_lock(&sbi->lookup_lock);
        __autofs_add_expiring(dentry);
        d_drop(dentry);
        spin_unlock(&sbi->lookup_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 necessary 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);
}

static void autofs_clear_leaf_automount_flags(struct dentry *dentry)
{
        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;
        if (autofs_dentry_ino(parent)->count == 2)
                managed_dentry_set_managed(parent);
}

static int autofs_dir_rmdir(struct inode *dir, struct dentry *dentry)
{
        struct autofs_sb_info *sbi = autofs_sbi(dir->i_sb);
        struct autofs_info *ino = autofs_dentry_ino(dentry);
        struct autofs_info *p_ino;

        pr_debug("dentry %p, removing %pd\n", dentry, dentry);

        if (ino->count != 1)
                return -ENOTEMPTY;

        spin_lock(&sbi->lookup_lock);
        __autofs_add_expiring(dentry);
        d_drop(dentry);
        spin_unlock(&sbi->lookup_lock);

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

        p_ino = autofs_dentry_ino(dentry->d_parent);
        p_ino->count--;
        dput(ino->dentry);
        d_inode(dentry)->i_size = 0;
        clear_nlink(d_inode(dentry));

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

        return 0;
}

static int autofs_dir_mkdir(struct mnt_idmap *idmap,
                            struct inode *dir, struct dentry *dentry,
                            umode_t mode)
{
        struct autofs_sb_info *sbi = autofs_sbi(dir->i_sb);
        struct autofs_info *ino = autofs_dentry_ino(dentry);
        struct autofs_info *p_ino;
        struct inode *inode;

        pr_debug("dentry %p, creating %pd\n", dentry, dentry);

        BUG_ON(!ino);

        autofs_clean_ino(ino);

        autofs_del_active(dentry);

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

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

        dget(dentry);
        p_ino = autofs_dentry_ino(dentry->d_parent);
        p_ino->count++;
        inc_nlink(dir);
        inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));

        return 0;
}

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

        rv = get_user(ntimeout, p);
        if (rv)
                goto error;

        rv = put_user(sbi->exp_timeout/HZ, p);
        if (rv)
                goto error;

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

        return 0;
error:
        return rv;
}
#endif

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

        rv = get_user(ntimeout, p);
        if (rv)
                goto error;

        rv = put_user(sbi->exp_timeout/HZ, p);
        if (rv)
                goto error;

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

        return 0;
error:
        return rv;
}

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

/* Return protocol sub version */
static inline int autofs_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 autofs_ask_umount(struct vfsmount *mnt, int __user *p)
{
        int status = 0;

        if (may_umount(mnt))
                status = 1;

        pr_debug("may umount %d\n", status);

        status = put_user(status, p);

        return status;
}

/* Identify autofs_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_autofs_dentry(struct dentry *dentry)
{
        return dentry && d_really_is_positive(dentry) &&
                dentry->d_op == &autofs_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 autofs_root_ioctl_unlocked(struct inode *inode, struct file *filp,
                                       unsigned int cmd, unsigned long arg)
{
        struct autofs_sb_info *sbi = autofs_sbi(inode->i_sb);
        void __user *p = (void __user *)arg;

        pr_debug("cmd = 0x%08x, arg = 0x%08lx, sbi = %p, pgrp = %u\n",
                 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 (!autofs_oz_mode(sbi) && !capable(CAP_SYS_ADMIN))
                return -EPERM;

        switch (cmd) {
        case AUTOFS_IOC_READY:  /* Wait queue: go ahead and retry */
                return autofs_wait_release(sbi, (autofs_wqt_t) arg, 0);
        case AUTOFS_IOC_FAIL:   /* Wait queue: fail with ENOENT */
                return autofs_wait_release(sbi, (autofs_wqt_t) arg, -ENOENT);
        case AUTOFS_IOC_CATATONIC: /* Enter catatonic mode (daemon shutdown) */
                autofs_catatonic_mode(sbi);
                return 0;
        case AUTOFS_IOC_PROTOVER: /* Get protocol version */
                return autofs_get_protover(sbi, p);
        case AUTOFS_IOC_PROTOSUBVER: /* Get protocol sub version */
                return autofs_get_protosubver(sbi, p);
        case AUTOFS_IOC_SETTIMEOUT:
                return autofs_get_set_timeout(sbi, p);
#ifdef CONFIG_COMPAT
        case AUTOFS_IOC_SETTIMEOUT32:
                return autofs_compat_get_set_timeout(sbi, p);
#endif

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

        /* return a single thing to expire */
        case AUTOFS_IOC_EXPIRE:
                return autofs_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 autofs_expire_multi(inode->i_sb,
                                           filp->f_path.mnt, sbi, p);

        default:
                return -EINVAL;
        }
}

static long autofs_root_ioctl(struct file *filp,
                               unsigned int cmd, unsigned long arg)
{
        struct inode *inode = file_inode(filp);

        return autofs_root_ioctl_unlocked(inode, filp, cmd, arg);
}

#ifdef CONFIG_COMPAT
static long autofs_root_compat_ioctl(struct file *filp,
                                      unsigned int cmd, unsigned long arg)
{
        struct inode *inode = file_inode(filp);
        int ret;

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

        return ret;
}
#endif