base.c

来自「Linux Kernel 2.6.9 for OMAP1710」· C语言 代码 · 共 2,003 行 · 第 1/5 页

		}

		if ((de =
		     _devfs_descend(dir, name, namelen, &next_pos)) == NULL) {
			devfs_put(dir);
			return NULL;
		}
		if (S_ISLNK(de->mode) && traverse_symlink) {	/*  Need to follow the link: this is a stack chomper  */
			/* FIXME what if it puts outside of mounted tree? */
			link = _devfs_walk_path(dir, de->u.symlink.linkname,
						de->u.symlink.length, TRUE);
			devfs_put(de);
			if (!link) {
				devfs_put(dir);
				return NULL;
			}
			de = link;
		}
		devfs_put(dir);
		dir = de;
		if (name[next_pos] == '/')
			++next_pos;
	}
	return dir;
}				/*  End Function _devfs_walk_path  */

/**
 *	_devfs_find_entry - Find a devfs entry.
 *	@dir: The handle to the parent devfs directory entry. If this is %NULL the
 *		name is relative to the root of the devfs.
 *	@name: The name of the entry. This may be %NULL.
 *	@traverse_symlink: If %TRUE then symbolic links are traversed.
 *
 *	Returns the devfs_entry pointer on success, else %NULL. An implicit
 *	devfs_get() is performed.
 */

static struct devfs_entry *_devfs_find_entry(devfs_handle_t dir,
					     const char *name,
					     int traverse_symlink)
{
	unsigned int namelen = strlen(name);

	if (name[0] == '/') {
		/*  Skip leading pathname component  */
		if (namelen < 2) {
			PRINTK("(%s): too short\n", name);
			return NULL;
		}
		for (++name, --namelen; (*name != '/') && (namelen > 0);
		     ++name, --namelen) ;
		if (namelen < 2) {
			PRINTK("(%s): too short\n", name);
			return NULL;
		}
		++name;
		--namelen;
	}
	return _devfs_walk_path(dir, name, namelen, traverse_symlink);
}				/*  End Function _devfs_find_entry  */

static struct devfs_entry *get_devfs_entry_from_vfs_inode(struct inode *inode)
{
	if (inode == NULL)
		return NULL;
	VERIFY_ENTRY((struct devfs_entry *)inode->u.generic_ip);
	return inode->u.generic_ip;
}				/*  End Function get_devfs_entry_from_vfs_inode  */

/**
 *	free_dentry - Free the dentry for a device entry and invalidate inode.
 *	@de: The entry.
 *
 *	This must only be called after the entry has been unhooked from its
 *	 parent directory.
 */

static void free_dentry(struct devfs_entry *de)
{
	struct dentry *dentry = de->inode.dentry;

	if (!dentry)
		return;
	spin_lock(&dcache_lock);
	dget_locked(dentry);
	spin_unlock(&dcache_lock);
	/*  Forcefully remove the inode  */
	if (dentry->d_inode != NULL)
		dentry->d_inode->i_nlink = 0;
	d_drop(dentry);
	dput(dentry);
}				/*  End Function free_dentry  */

/**
 *	is_devfsd_or_child - Test if the current process is devfsd or one of its children.
 *	@fs_info: The filesystem information.
 *
 *	Returns %TRUE if devfsd or child, else %FALSE.
 */

static int is_devfsd_or_child(struct fs_info *fs_info)
{
	struct task_struct *p = current;

	if (p == fs_info->devfsd_task)
		return (TRUE);
	if (process_group(p) == fs_info->devfsd_pgrp)
		return (TRUE);
	read_lock(&tasklist_lock);
	for (; p != &init_task; p = p->real_parent) {
		if (p == fs_info->devfsd_task) {
			read_unlock(&tasklist_lock);
			return (TRUE);
		}
	}
	read_unlock(&tasklist_lock);
	return (FALSE);
}				/*  End Function is_devfsd_or_child  */

/**
 *	devfsd_queue_empty - Test if devfsd has work pending in its event queue.
 *	@fs_info: The filesystem information.
 *
 *	Returns %TRUE if the queue is empty, else %FALSE.
 */

static inline int devfsd_queue_empty(struct fs_info *fs_info)
{
	return (fs_info->devfsd_last_event) ? FALSE : TRUE;
}				/*  End Function devfsd_queue_empty  */

/**
 *	wait_for_devfsd_finished - Wait for devfsd to finish processing its event queue.
 *	@fs_info: The filesystem information.
 *
 *	Returns %TRUE if no more waiting will be required, else %FALSE.
 */

static int wait_for_devfsd_finished(struct fs_info *fs_info)
{
	DECLARE_WAITQUEUE(wait, current);

	if (fs_info->devfsd_task == NULL)
		return (TRUE);
	if (devfsd_queue_empty(fs_info) && fs_info->devfsd_sleeping)
		return TRUE;
	if (is_devfsd_or_child(fs_info))
		return (FALSE);
	set_current_state(TASK_UNINTERRUPTIBLE);
	add_wait_queue(&fs_info->revalidate_wait_queue, &wait);
	if (!devfsd_queue_empty(fs_info) || !fs_info->devfsd_sleeping)
		if (fs_info->devfsd_task)
			schedule();
	remove_wait_queue(&fs_info->revalidate_wait_queue, &wait);
	__set_current_state(TASK_RUNNING);
	return (TRUE);
}				/*  End Function wait_for_devfsd_finished  */

/**
 *	devfsd_notify_de - Notify the devfsd daemon of a change.
 *	@de: The devfs entry that has changed. This and all parent entries will
 *            have their reference counts incremented if the event was queued.
 *	@type: The type of change.
 *	@mode: The mode of the entry.
 *	@uid: The user ID.
 *	@gid: The group ID.
 *	@fs_info: The filesystem info.
 *
 *	Returns %TRUE if an event was queued and devfsd woken up, else %FALSE.
 */

static int devfsd_notify_de(struct devfs_entry *de,
			    unsigned short type, umode_t mode,
			    uid_t uid, gid_t gid, struct fs_info *fs_info)
{
	struct devfsd_buf_entry *entry;
	struct devfs_entry *curr;

	if (!(fs_info->devfsd_event_mask & (1 << type)))
		return (FALSE);
	if ((entry = kmem_cache_alloc(devfsd_buf_cache, SLAB_KERNEL)) == NULL) {
		atomic_inc(&fs_info->devfsd_overrun_count);
		return (FALSE);
	}
	for (curr = de; curr != NULL; curr = curr->parent)
		devfs_get(curr);
	entry->de = de;
	entry->type = type;
	entry->mode = mode;
	entry->uid = uid;
	entry->gid = gid;
	entry->next = NULL;
	spin_lock(&fs_info->devfsd_buffer_lock);
	if (!fs_info->devfsd_first_event)
		fs_info->devfsd_first_event = entry;
	if (fs_info->devfsd_last_event)
		fs_info->devfsd_last_event->next = entry;
	fs_info->devfsd_last_event = entry;
	spin_unlock(&fs_info->devfsd_buffer_lock);
	wake_up_interruptible(&fs_info->devfsd_wait_queue);
	return (TRUE);
}				/*  End Function devfsd_notify_de  */

/**
 *	devfsd_notify - Notify the devfsd daemon of a change.
 *	@de: The devfs entry that has changed.
 *	@type: The type of change event.
 *	@wait: If TRUE, the function waits for the daemon to finish processing
 *		the event.
 */

static void devfsd_notify(struct devfs_entry *de, unsigned short type)
{
	devfsd_notify_de(de, type, de->mode, current->euid,
			 current->egid, &fs_info);
}

static int devfs_mk_dev(dev_t dev, umode_t mode, const char *fmt, va_list args)
{
	struct devfs_entry *dir = NULL, *de;
	char buf[64];
	int error, n;

	n = vsnprintf(buf, sizeof(buf), fmt, args);
	if (n >= sizeof(buf) || !buf[0]) {
		printk(KERN_WARNING "%s: invalid format string %s\n",
		       __FUNCTION__, fmt);
		return -EINVAL;
	}

	de = _devfs_prepare_leaf(&dir, buf, mode);
	if (!de) {
		printk(KERN_WARNING "%s: could not prepare leaf for %s\n",
		       __FUNCTION__, buf);
		return -ENOMEM;	/* could be more accurate... */
	}

	de->u.dev = dev;

	error = _devfs_append_entry(dir, de, NULL);
	if (error) {
		printk(KERN_WARNING "%s: could not append to parent for %s\n",
		       __FUNCTION__, buf);
		goto out;
	}

	devfsd_notify(de, DEVFSD_NOTIFY_REGISTERED);
      out:
	devfs_put(dir);
	return error;
}

int devfs_mk_bdev(dev_t dev, umode_t mode, const char *fmt, ...)
{
	va_list args;

	if (!S_ISBLK(mode)) {
		printk(KERN_WARNING "%s: invalide mode (%u) for %s\n",
		       __FUNCTION__, mode, fmt);
		return -EINVAL;
	}

	va_start(args, fmt);
	return devfs_mk_dev(dev, mode, fmt, args);
}

EXPORT_SYMBOL(devfs_mk_bdev);

int devfs_mk_cdev(dev_t dev, umode_t mode, const char *fmt, ...)
{
	va_list args;

	if (!S_ISCHR(mode)) {
		printk(KERN_WARNING "%s: invalide mode (%u) for %s\n",
		       __FUNCTION__, mode, fmt);
		return -EINVAL;
	}

	va_start(args, fmt);
	return devfs_mk_dev(dev, mode, fmt, args);
}

EXPORT_SYMBOL(devfs_mk_cdev);

/**
 *	_devfs_unhook - Unhook a device entry from its parents list
 *	@de: The entry to unhook.
 *
 *	Returns %TRUE if the entry was unhooked, else %FALSE if it was
 *		previously unhooked.
 *	The caller must have a write lock on the parent directory.
 */

static int _devfs_unhook(struct devfs_entry *de)
{
	struct devfs_entry *parent;

	if (!de || (de->prev == de))
		return FALSE;
	parent = de->parent;
	if (de->prev == NULL)
		parent->u.dir.first = de->next;
	else
		de->prev->next = de->next;
	if (de->next == NULL)
		parent->u.dir.last = de->prev;
	else
		de->next->prev = de->prev;
	de->prev = de;		/*  Indicate we're unhooked                      */
	de->next = NULL;	/*  Force early termination for <devfs_readdir>  */
	return TRUE;
}				/*  End Function _devfs_unhook  */

/**
 *	_devfs_unregister - Unregister a device entry from its parent.
 *	@dir: The parent directory.
 *	@de: The entry to unregister.
 *
 *	The caller must have a write lock on the parent directory, which is
 *	unlocked by this function.
 */

static void _devfs_unregister(struct devfs_entry *dir, struct devfs_entry *de)
{
	int unhooked = _devfs_unhook(de);

	write_unlock(&dir->u.dir.lock);
	if (!unhooked)
		return;
	devfs_get(dir);
	devfsd_notify(de, DEVFSD_NOTIFY_UNREGISTERED);
	free_dentry(de);
	devfs_put(dir);
	if (!S_ISDIR(de->mode))
		return;
	while (TRUE) {		/*  Recursively unregister: this is a stack chomper  */
		struct devfs_entry *child;

		write_lock(&de->u.dir.lock);
		de->u.dir.no_more_additions = TRUE;
		child = de->u.dir.first;
		VERIFY_ENTRY(child);
		_devfs_unregister(de, child);
		if (!child)
			break;
		DPRINTK(DEBUG_UNREGISTER, "(%s): child: %p  refcount: %d\n",
			child->name, child, atomic_read(&child->refcount));
		devfs_put(child);
	}
}				/*  End Function _devfs_unregister  */

static int devfs_do_symlink(devfs_handle_t dir, const char *name,
			    const char *link, devfs_handle_t * handle)
{
	int err;
	unsigned int linklength;
	char *newlink;
	struct devfs_entry *de;

	if (handle != NULL)
		*handle = NULL;
	if (name == NULL) {
		PRINTK("(): NULL name pointer\n");
		return -EINVAL;
	}
	if (link == NULL) {
		PRINTK("(%s): NULL link pointer\n", name);
		return -EINVAL;
	}
	linklength = strlen(link);
	if ((newlink = kmalloc(linklength + 1, GFP_KERNEL)) == NULL)
		return -ENOMEM;
	memcpy(newlink, link, linklength);
	newlink[linklength] = '\0';
	if ((de = _devfs_prepare_leaf(&dir, name, S_IFLNK | S_IRUGO | S_IXUGO))
	    == NULL) {
		PRINTK("(%s): could not prepare leaf\n", name);
		kfree(newlink);
		return -ENOTDIR;
	}
	de->info = NULL;
	de->u.symlink.linkname = newlink;
	de->u.symlink.length = linklength;
	if ((err = _devfs_append_entry(dir, de, NULL)) != 0) {
		PRINTK("(%s): could not append to parent, err: %d\n", name,
		       err);
		devfs_put(dir);
		return err;
	}
	devfs_put(dir);
#ifdef CONFIG_DEVFS_DEBUG
	spin_lock(&stat_lock);
	stat_num_bytes += linklength + 1;
	spin_unlock(&stat_lock);
#endif
	if (handle != NULL)
		*handle = de;
	return 0;
}				/*  End Function devfs_do_symlink  */

/**