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32 results

root.c

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  • root.c 23.77 KiB
    /*
     * 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"
    
    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,
    	.iterate	= 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,
    	.iterate	= 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;
    
    	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);
    	}
    }
    
    static void autofs4_del_active(struct dentry *dentry)
    {
    	struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
    	struct autofs_info *ino;
    
    	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);
    	}
    }
    
    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 %pd", file, dentry, dentry);
    
    	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);
    	if (!d_mountpoint(dentry) && simple_empty(dentry)) {
    		spin_unlock(&sbi->lookup_lock);
    		return -ENOENT;
    	}
    	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;
    
    	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;
    		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 *autofs4_lookup_expiring(struct dentry *dentry,
    					      bool rcu_walk)
    {
    	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;
    
    	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;
    		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 autofs4_mount_wait(struct dentry *dentry, bool rcu_walk)
    {
    	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) {
    		if (rcu_walk)
    			return -ECHILD;
    		DPRINTK("waiting for mount name=%pd", dentry);
    		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, bool rcu_walk)
    {
    	struct dentry *expiring;
    
    	expiring = autofs4_lookup_expiring(dentry, rcu_walk);
    	if (IS_ERR(expiring))
    		return PTR_ERR(expiring);
    	if (!expiring)
    		return autofs4_expire_wait(dentry, rcu_walk);
    	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, 0);
    		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;
    
    		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 %pd", dentry, dentry);
    
    	/* 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, 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 = autofs4_mount_wait(dentry, 0);
    		if (status)
    			return ERR_PTR(status);
    		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 (d_really_is_positive(dentry) && d_is_symlink(dentry)) {
    		spin_unlock(&sbi->fs_lock);
    		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 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)) {
    				spin_unlock(&sbi->fs_lock);
    				goto done;
    			}
    		} else {
    			if (!simple_empty(dentry)) {
    				spin_unlock(&sbi->fs_lock);
    				goto done;
    			}
    		}
    		ino->flags |= AUTOFS_INF_PENDING;
    		spin_unlock(&sbi->fs_lock);
    		status = autofs4_mount_wait(dentry, 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 = autofs4_mountpoint_changed(path);
    	if (!dentry)
    		return ERR_PTR(-ENOENT);
    
    	return NULL;
    }
    
    static int autofs4_d_manage(struct dentry *dentry, bool rcu_walk)
    {
    	struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
    	struct autofs_info *ino = autofs4_dentry_ino(dentry);
    	int status;
    
    	DPRINTK("dentry=%p %pd", dentry, dentry);
    
    	/* The daemon never waits. */
    	if (autofs4_oz_mode(sbi)) {
    		if (!d_mountpoint(dentry))
    			return -EISDIR;
    		return 0;
    	}
    
    	/* Wait for pending expires */
    	if (do_expire_wait(dentry, rcu_walk) == -ECHILD)
    		return -ECHILD;
    
    	/*
    	 * This dentry may be under construction so wait on mount
    	 * completion.
    	 */
    	status = autofs4_mount_wait(dentry, rcu_walk);
    	if (status)
    		return status;
    
    	if (rcu_walk) {
    		/* We don't need fs_lock in rcu_walk mode,
    		 * just testing 'AUTOFS_INFO_NO_RCU' is enough.
    		 * simple_empty() takes a spinlock, so leave it
    		 * to last.
    		 * We only return -EISDIR when certain this isn't
    		 * a mount-trap.
    		 */
    		struct inode *inode;
    
    		if (ino->flags & (AUTOFS_INF_EXPIRING | AUTOFS_INF_NO_RCU))
    			return 0;
    		if (d_mountpoint(dentry))
    			return 0;
    		inode = d_inode_rcu(dentry);
    		if (inode && S_ISLNK(inode->i_mode))
    			return -EISDIR;
    		if (list_empty(&dentry->d_subdirs))
    			return 0;
    		if (!simple_empty(dentry))
    			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 ((!d_mountpoint(dentry) && !simple_empty(dentry)) ||
    		    (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 *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 = %pd", dentry);
    
    	/* 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 (IS_ROOT(dentry->d_parent) &&
    		    autofs_type_indirect(sbi->type))
    			__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 <- %pd", symname, dentry);
    
    	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 && !IS_ROOT(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 -EPERM;
    
    	if (atomic_dec_and_test(&ino->count)) {
    		p_ino = autofs4_dentry_ino(dentry->d_parent);
    		if (p_ino && !IS_ROOT(dentry))
    			atomic_dec(&p_ino->count);
    	}
    	dput(ino->dentry);
    
    	d_inode(dentry)->i_size = 0;
    	clear_nlink(d_inode(dentry));
    
    	dir->i_mtime = CURRENT_TIME;
    
    	spin_lock(&sbi->lookup_lock);
    	__autofs4_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 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_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);
    }
    
    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 %pd", dentry, dentry);
    
    	if (!autofs4_oz_mode(sbi))
    		return -EACCES;
    
    	spin_lock(&sbi->lookup_lock);
    	if (!simple_empty(dentry)) {
    		spin_unlock(&sbi->lookup_lock);
    		return -ENOTEMPTY;
    	}
    	__autofs4_add_expiring(dentry);
    	d_drop(dentry);
    	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);
    	d_inode(dentry)->i_size = 0;
    	clear_nlink(d_inode(dentry));
    
    	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 %pd", dentry, dentry);
    
    	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 && !IS_ROOT(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)
    {
    	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 autofs4_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 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 && d_really_is_positive(dentry) &&
    		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 -EINVAL;
    	}
    }
    
    static long autofs4_root_ioctl(struct file *filp,
    			       unsigned int cmd, unsigned long arg)
    {
    	struct inode *inode = file_inode(filp);
    
    	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 = file_inode(filp);
    	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