root.c

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/* -*- c -*- --------------------------------------------------------------- *
 *
 * linux/fs/autofs/root.c
 *
 *  Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
 *  Copyright 1999-2000 Jeremy Fitzhardinge <[email protected]>
 *  Copyright 2001-2006 Ian Kent <[email protected]>
 *
 * 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"

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 *,umode_t);
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 *, unsigned int);
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(&sbi->lookup_lock);
    spin_lock(&dentry->d_lock);
    if (!d_mountpoint(dentry) && list_empty(&dentry->d_subdirs)) {
        spin_unlock(&dentry->d_lock);
        spin_unlock(&sbi->lookup_lock);
        return -ENOENT;
    }
    spin_unlock(&dentry->d_lock);
    spin_unlock(&sbi->lookup_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(&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);
            return active;
        }
next:
        spin_unlock(&active->d_lock);
    }
    spin_unlock(&sbi->lookup_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(&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);
            return expiring;
        }
next:
        spin_unlock(&expiring->d_lock);
    }
    spin_unlock(&sbi->lookup_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);
        spin_lock(&sbi->fs_lock);
        ino->flags &= ~AUTOFS_INF_PENDING;
        if (status) {
            spin_unlock(&sbi->fs_lock);
            return ERR_PTR(status);
        }
    }
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 (rcu_walk)
            return 0;
        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, unsigned int flags)
{
    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(&sbi->lookup_lock);
    __autofs4_add_expiring(dentry);
    spin_lock(&dentry->d_lock);
    __d_drop(dentry);
    spin_unlock(&dentry->d_lock);
    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);
    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(&sbi->lookup_lock);
    spin_lock(&dentry->d_lock);
    if (!list_empty(&dentry->d_subdirs)) {
        spin_unlock(&dentry->d_lock);
        spin_unlock(&sbi->lookup_lock);
        return -ENOTEMPTY;
    }
    __autofs4_add_expiring(dentry);
    __d_drop(dentry);
    spin_unlock(&dentry->d_lock);
    spin_unlock(&sbi->lookup_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, umode_t 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