[mirror_ubuntu-artful-kernel.git] / fs / configfs / file.c

/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * file.c - operations for regular (text) files.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 *
 * Based on sysfs:
 * 	sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
 *
 * configfs Copyright (C) 2005 Oracle.  All rights reserved.
 */

#include <linux/fs.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/mutex.h>
#include <asm/uaccess.h>

#include <linux/configfs.h>
#include "configfs_internal.h"

/*
 * A simple attribute can only be 4096 characters.  Why 4k?  Because the
 * original code limited it to PAGE_SIZE.  That's a bad idea, though,
 * because an attribute of 16k on ia64 won't work on x86.  So we limit to
 * 4k, our minimum common page size.
 */
#define SIMPLE_ATTR_SIZE 4096

struct configfs_buffer {
	size_t			count;
	loff_t			pos;
	char			* page;
	struct configfs_item_operations	* ops;
	struct mutex		mutex;
	int			needs_read_fill;
};


/**
 *	fill_read_buffer - allocate and fill buffer from item.
 *	@dentry:	dentry pointer.
 *	@buffer:	data buffer for file.
 *
 *	Allocate @buffer->page, if it hasn't been already, then call the
 *	config_item's show() method to fill the buffer with this attribute's
 *	data.
 *	This is called only once, on the file's first read.
 */
static int fill_read_buffer(struct dentry * dentry, struct configfs_buffer * buffer)
{
	struct configfs_attribute * attr = to_attr(dentry);
	struct config_item * item = to_item(dentry->d_parent);
	int ret = 0;
	ssize_t count;

	if (!buffer->page)
		buffer->page = (char *) get_zeroed_page(GFP_KERNEL);
	if (!buffer->page)
		return -ENOMEM;

	count = attr->show(item, buffer->page);

	buffer->needs_read_fill = 0;
	BUG_ON(count > (ssize_t)SIMPLE_ATTR_SIZE);
	if (count >= 0)
		buffer->count = count;
	else
		ret = count;
	return ret;
}

/**
 *	configfs_read_file - read an attribute.
 *	@file:	file pointer.
 *	@buf:	buffer to fill.
 *	@count:	number of bytes to read.
 *	@ppos:	starting offset in file.
 *
 *	Userspace wants to read an attribute file. The attribute descriptor
 *	is in the file's ->d_fsdata. The target item is in the directory's
 *	->d_fsdata.
 *
 *	We call fill_read_buffer() to allocate and fill the buffer from the
 *	item's show() method exactly once (if the read is happening from
 *	the beginning of the file). That should fill the entire buffer with
 *	all the data the item has to offer for that attribute.
 *	We then call flush_read_buffer() to copy the buffer to userspace
 *	in the increments specified.
 */

static ssize_t
configfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
	struct configfs_buffer * buffer = file->private_data;
	ssize_t retval = 0;

	mutex_lock(&buffer->mutex);
	if (buffer->needs_read_fill) {
		if ((retval = fill_read_buffer(file->f_path.dentry,buffer)))
			goto out;
	}
	pr_debug("%s: count = %zd, ppos = %lld, buf = %s\n",
		 __func__, count, *ppos, buffer->page);
	retval = simple_read_from_buffer(buf, count, ppos, buffer->page,
					 buffer->count);
out:
	mutex_unlock(&buffer->mutex);
	return retval;
}


/**
 *	fill_write_buffer - copy buffer from userspace.
 *	@buffer:	data buffer for file.
 *	@buf:		data from user.
 *	@count:		number of bytes in @userbuf.
 *
 *	Allocate @buffer->page if it hasn't been already, then
 *	copy the user-supplied buffer into it.
 */

static int
fill_write_buffer(struct configfs_buffer * buffer, const char __user * buf, size_t count)
{
	int error;

	if (!buffer->page)
		buffer->page = (char *)__get_free_pages(GFP_KERNEL, 0);
	if (!buffer->page)
		return -ENOMEM;

	if (count >= SIMPLE_ATTR_SIZE)
		count = SIMPLE_ATTR_SIZE - 1;
	error = copy_from_user(buffer->page,buf,count);
	buffer->needs_read_fill = 1;
	/* if buf is assumed to contain a string, terminate it by \0,
	 * so e.g. sscanf() can scan the string easily */
	buffer->page[count] = 0;
	return error ? -EFAULT : count;
}


/**
 *	flush_write_buffer - push buffer to config_item.
 *	@dentry:	dentry to the attribute
 *	@buffer:	data buffer for file.
 *	@count:		number of bytes
 *
 *	Get the correct pointers for the config_item and the attribute we're
 *	dealing with, then call the store() method for the attribute,
 *	passing the buffer that we acquired in fill_write_buffer().
 */

static int
flush_write_buffer(struct dentry * dentry, struct configfs_buffer * buffer, size_t count)
{
	struct configfs_attribute * attr = to_attr(dentry);
	struct config_item * item = to_item(dentry->d_parent);

	return attr->store(item, buffer->page, count);
}


/**
 *	configfs_write_file - write an attribute.
 *	@file:	file pointer
 *	@buf:	data to write
 *	@count:	number of bytes
 *	@ppos:	starting offset
 *
 *	Similar to configfs_read_file(), though working in the opposite direction.
 *	We allocate and fill the data from the user in fill_write_buffer(),
 *	then push it to the config_item in flush_write_buffer().
 *	There is no easy way for us to know if userspace is only doing a partial
 *	write, so we don't support them. We expect the entire buffer to come
 *	on the first write.
 *	Hint: if you're writing a value, first read the file, modify only the
 *	the value you're changing, then write entire buffer back.
 */

static ssize_t
configfs_write_file(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
{
	struct configfs_buffer * buffer = file->private_data;
	ssize_t len;

	mutex_lock(&buffer->mutex);
	len = fill_write_buffer(buffer, buf, count);
	if (len > 0)
		len = flush_write_buffer(file->f_path.dentry, buffer, len);
	if (len > 0)
		*ppos += len;
	mutex_unlock(&buffer->mutex);
	return len;
}

static int check_perm(struct inode * inode, struct file * file)
{
	struct config_item *item = configfs_get_config_item(file->f_path.dentry->d_parent);
	struct configfs_attribute * attr = to_attr(file->f_path.dentry);
	struct configfs_buffer * buffer;
	struct configfs_item_operations * ops = NULL;
	int error = 0;

	if (!item || !attr)
		goto Einval;

	/* Grab the module reference for this attribute if we have one */
	if (!try_module_get(attr->ca_owner)) {
		error = -ENODEV;
		goto Done;
	}

	if (item->ci_type)
		ops = item->ci_type->ct_item_ops;
	else
		goto Eaccess;

	/* File needs write support.
	 * The inode's perms must say it's ok,
	 * and we must have a store method.
	 */
	if (file->f_mode & FMODE_WRITE) {
		if (!(inode->i_mode & S_IWUGO) || !attr->store)
			goto Eaccess;

	}

	/* File needs read support.
	 * The inode's perms must say it's ok, and we there
	 * must be a show method for it.
	 */
	if (file->f_mode & FMODE_READ) {
		if (!(inode->i_mode & S_IRUGO) || !attr->show)
			goto Eaccess;
	}

	/* No error? Great, allocate a buffer for the file, and store it
	 * it in file->private_data for easy access.
	 */
	buffer = kzalloc(sizeof(struct configfs_buffer),GFP_KERNEL);
	if (!buffer) {
		error = -ENOMEM;
		goto Enomem;
	}
	mutex_init(&buffer->mutex);
	buffer->needs_read_fill = 1;
	buffer->ops = ops;
	file->private_data = buffer;
	goto Done;

 Einval:
	error = -EINVAL;
	goto Done;
 Eaccess:
	error = -EACCES;
 Enomem:
	module_put(attr->ca_owner);
 Done:
	if (error && item)
		config_item_put(item);
	return error;
}

static int configfs_open_file(struct inode * inode, struct file * filp)
{
	return check_perm(inode,filp);
}

static int configfs_release(struct inode * inode, struct file * filp)
{
	struct config_item * item = to_item(filp->f_path.dentry->d_parent);
	struct configfs_attribute * attr = to_attr(filp->f_path.dentry);
	struct module * owner = attr->ca_owner;
	struct configfs_buffer * buffer = filp->private_data;

	if (item)
		config_item_put(item);
	/* After this point, attr should not be accessed. */
	module_put(owner);

	if (buffer) {
		if (buffer->page)
			free_page((unsigned long)buffer->page);
		mutex_destroy(&buffer->mutex);
		kfree(buffer);
	}
	return 0;
}

const struct file_operations configfs_file_operations = {
	.read		= configfs_read_file,
	.write		= configfs_write_file,
	.llseek		= generic_file_llseek,
	.open		= configfs_open_file,
	.release	= configfs_release,
};

/**
 *	configfs_create_file - create an attribute file for an item.
 *	@item:	item we're creating for.
 *	@attr:	atrribute descriptor.
 */

int configfs_create_file(struct config_item * item, const struct configfs_attribute * attr)
{
	struct dentry *dir = item->ci_dentry;
	struct configfs_dirent *parent_sd = dir->d_fsdata;
	umode_t mode = (attr->ca_mode & S_IALLUGO) | S_IFREG;
	int error = 0;

	mutex_lock_nested(&d_inode(dir)->i_mutex, I_MUTEX_NORMAL);
	error = configfs_make_dirent(parent_sd, NULL, (void *) attr, mode,
				     CONFIGFS_ITEM_ATTR);
	mutex_unlock(&d_inode(dir)->i_mutex);

	return error;
}
Commit	Line	Data
7063fbf2 JB	1	/* -- mode: c; c-basic-offset: 8; --
	2	* vim: noexpandtab sw=8 ts=8 sts=0:
	3	*
	4	* file.c - operations for regular (text) files.
	5	*
	6	* This program is free software; you can redistribute it and/or
	7	* modify it under the terms of the GNU General Public
	8	* License as published by the Free Software Foundation; either
	9	* version 2 of the License, or (at your option) any later version.
	10	*
	11	* This program is distributed in the hope that it will be useful,
	12	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	13	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	14	* General Public License for more details.
	15	*
	16	* You should have received a copy of the GNU General Public
	17	* License along with this program; if not, write to the
	18	* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
	19	* Boston, MA 021110-1307, USA.
	20	*
	21	* Based on sysfs:
	22	* sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
	23	*
	24	* configfs Copyright (C) 2005 Oracle. All rights reserved.
	25	*/
	26
	27	#include <linux/fs.h>
	28	#include <linux/module.h>
7063fbf2	29	#include <linux/slab.h>
6d748924	30	#include <linux/mutex.h>
7063fbf2	31	#include <asm/uaccess.h>
7063fbf2 JB	32
	33	#include <linux/configfs.h>
	34	#include "configfs_internal.h"
	35
b23cdde4 JB	36	/*
	37	* A simple attribute can only be 4096 characters. Why 4k? Because the
	38	* original code limited it to PAGE_SIZE. That's a bad idea, though,
	39	* because an attribute of 16k on ia64 won't work on x86. So we limit to
	40	* 4k, our minimum common page size.
	41	*/
	42	#define SIMPLE_ATTR_SIZE 4096
7063fbf2 JB	43
	44	struct configfs_buffer {
	45	size_t count;
	46	loff_t pos;
	47	char * page;
	48	struct configfs_item_operations * ops;
6d748924	49	struct mutex mutex;
7063fbf2 JB	50	int needs_read_fill;
	51	};
	52
	53
	54	/**
	55	* fill_read_buffer - allocate and fill buffer from item.
	56	* @dentry: dentry pointer.
	57	* @buffer: data buffer for file.
	58	*
	59	* Allocate @buffer->page, if it hasn't been already, then call the
	60	* config_item's show() method to fill the buffer with this attribute's
	61	* data.
	62	* This is called only once, on the file's first read.
	63	*/
	64	static int fill_read_buffer(struct dentry * dentry, struct configfs_buffer * buffer)
	65	{
	66	struct configfs_attribute * attr = to_attr(dentry);
	67	struct config_item * item = to_item(dentry->d_parent);
7063fbf2 JB	68	int ret = 0;
	69	ssize_t count;
	70
	71	if (!buffer->page)
	72	buffer->page = (char *) get_zeroed_page(GFP_KERNEL);
	73	if (!buffer->page)
	74	return -ENOMEM;
	75
51798222	76	count = attr->show(item, buffer->page);
870823e6	77
7063fbf2	78	buffer->needs_read_fill = 0;
b23cdde4	79	BUG_ON(count > (ssize_t)SIMPLE_ATTR_SIZE);
7063fbf2 JB	80	if (count >= 0)
	81	buffer->count = count;
	82	else
	83	ret = count;
	84	return ret;
	85	}
	86
7063fbf2 JB	87	/**
	88	* configfs_read_file - read an attribute.
	89	* @file: file pointer.
	90	* @buf: buffer to fill.
	91	* @count: number of bytes to read.
	92	* @ppos: starting offset in file.
	93	*
	94	* Userspace wants to read an attribute file. The attribute descriptor
	95	* is in the file's ->d_fsdata. The target item is in the directory's
	96	* ->d_fsdata.
	97	*
	98	* We call fill_read_buffer() to allocate and fill the buffer from the
	99	* item's show() method exactly once (if the read is happening from
	100	* the beginning of the file). That should fill the entire buffer with
	101	* all the data the item has to offer for that attribute.
	102	* We then call flush_read_buffer() to copy the buffer to userspace
	103	* in the increments specified.
	104	*/
	105
	106	static ssize_t
	107	configfs_read_file(struct file file, char __user buf, size_t count, loff_t *ppos)
	108	{
	109	struct configfs_buffer * buffer = file->private_data;
	110	ssize_t retval = 0;
	111
6d748924	112	mutex_lock(&buffer->mutex);
7063fbf2	113	if (buffer->needs_read_fill) {
867fa491	114	if ((retval = fill_read_buffer(file->f_path.dentry,buffer)))
7063fbf2 JB	115	goto out;
7063fbf2 JB	116	}
4779efca	117	pr_debug("%s: count = %zd, ppos = %lld, buf = %s\n",
8e24eea7	118	__func__, count, *ppos, buffer->page);
92f4c701 AM	119	retval = simple_read_from_buffer(buf, count, ppos, buffer->page,
92f4c701 AM	120	buffer->count);
7063fbf2	121	out:
6d748924	122	mutex_unlock(&buffer->mutex);
7063fbf2 JB	123	return retval;
	124	}
	125
	126
	127	/**
	128	* fill_write_buffer - copy buffer from userspace.
	129	* @buffer: data buffer for file.
3d0f89bb	130	* @buf: data from user.
7063fbf2 JB	131	* @count: number of bytes in @userbuf.
	132	*
	133	* Allocate @buffer->page if it hasn't been already, then
	134	* copy the user-supplied buffer into it.
	135	*/
	136
	137	static int
	138	fill_write_buffer(struct configfs_buffer * buffer, const char __user * buf, size_t count)
	139	{
	140	int error;
	141
	142	if (!buffer->page)
ff05d1c4	143	buffer->page = (char *)__get_free_pages(GFP_KERNEL, 0);
7063fbf2 JB	144	if (!buffer->page)
	145	return -ENOMEM;
	146
b23cdde4 JB	147	if (count >= SIMPLE_ATTR_SIZE)
b23cdde4 JB	148	count = SIMPLE_ATTR_SIZE - 1;
7063fbf2 JB	149	error = copy_from_user(buffer->page,buf,count);
7063fbf2 JB	150	buffer->needs_read_fill = 1;
ff05d1c4 JB	151	/* if buf is assumed to contain a string, terminate it by \0,
	152	* so e.g. sscanf() can scan the string easily */
	153	buffer->page[count] = 0;
7063fbf2 JB	154	return error ? -EFAULT : count;
	155	}
	156
	157
	158	/**
	159	* flush_write_buffer - push buffer to config_item.
3d0f89bb	160	* @dentry: dentry to the attribute
7063fbf2	161	* @buffer: data buffer for file.
3d0f89bb	162	* @count: number of bytes
7063fbf2 JB	163	*
	164	* Get the correct pointers for the config_item and the attribute we're
	165	* dealing with, then call the store() method for the attribute,
	166	* passing the buffer that we acquired in fill_write_buffer().
	167	*/
	168
	169	static int
	170	flush_write_buffer(struct dentry * dentry, struct configfs_buffer * buffer, size_t count)
	171	{
	172	struct configfs_attribute * attr = to_attr(dentry);
	173	struct config_item * item = to_item(dentry->d_parent);
7063fbf2	174
870823e6	175	return attr->store(item, buffer->page, count);
7063fbf2 JB	176	}
	177
	178
	179	/**
	180	* configfs_write_file - write an attribute.
	181	* @file: file pointer
	182	* @buf: data to write
	183	* @count: number of bytes
	184	* @ppos: starting offset
	185	*
	186	* Similar to configfs_read_file(), though working in the opposite direction.
	187	* We allocate and fill the data from the user in fill_write_buffer(),
	188	* then push it to the config_item in flush_write_buffer().
	189	* There is no easy way for us to know if userspace is only doing a partial
	190	* write, so we don't support them. We expect the entire buffer to come
	191	* on the first write.
	192	* Hint: if you're writing a value, first read the file, modify only the
	193	* the value you're changing, then write entire buffer back.
	194	*/
	195
	196	static ssize_t
	197	configfs_write_file(struct file file, const char __user buf, size_t count, loff_t *ppos)
	198	{
	199	struct configfs_buffer * buffer = file->private_data;
3d0f89bb	200	ssize_t len;
7063fbf2	201
6d748924	202	mutex_lock(&buffer->mutex);
3d0f89bb JB	203	len = fill_write_buffer(buffer, buf, count);
3d0f89bb JB	204	if (len > 0)
7121064b	205	len = flush_write_buffer(file->f_path.dentry, buffer, len);
3d0f89bb JB	206	if (len > 0)
3d0f89bb JB	207	*ppos += len;
6d748924	208	mutex_unlock(&buffer->mutex);
3d0f89bb	209	return len;
7063fbf2 JB	210	}
	211
	212	static int check_perm(struct inode * inode, struct file * file)
	213	{
867fa491 JJS	214	struct config_item *item = configfs_get_config_item(file->f_path.dentry->d_parent);
867fa491 JJS	215	struct configfs_attribute * attr = to_attr(file->f_path.dentry);
7063fbf2 JB	216	struct configfs_buffer * buffer;
	217	struct configfs_item_operations * ops = NULL;
	218	int error = 0;
	219
	220	if (!item \|\| !attr)
	221	goto Einval;
	222
	223	/* Grab the module reference for this attribute if we have one */
	224	if (!try_module_get(attr->ca_owner)) {
	225	error = -ENODEV;
	226	goto Done;
	227	}
	228
	229	if (item->ci_type)
	230	ops = item->ci_type->ct_item_ops;
	231	else
	232	goto Eaccess;
	233
	234	/* File needs write support.
	235	* The inode's perms must say it's ok,
	236	* and we must have a store method.
	237	*/
	238	if (file->f_mode & FMODE_WRITE) {
51798222	239	if (!(inode->i_mode & S_IWUGO) \|\| !attr->store)
7063fbf2 JB	240	goto Eaccess;
	241
	242	}
	243
	244	/* File needs read support.
	245	* The inode's perms must say it's ok, and we there
	246	* must be a show method for it.
	247	*/
	248	if (file->f_mode & FMODE_READ) {
51798222	249	if (!(inode->i_mode & S_IRUGO) \|\| !attr->show)
7063fbf2 JB	250	goto Eaccess;
	251	}
	252
	253	/* No error? Great, allocate a buffer for the file, and store it
	254	* it in file->private_data for easy access.
	255	*/
f8314dc6	256	buffer = kzalloc(sizeof(struct configfs_buffer),GFP_KERNEL);
559c9ac3	257	if (!buffer) {
7063fbf2	258	error = -ENOMEM;
559c9ac3 CS	259	goto Enomem;
559c9ac3 CS	260	}
6d748924	261	mutex_init(&buffer->mutex);
559c9ac3 CS	262	buffer->needs_read_fill = 1;
	263	buffer->ops = ops;
	264	file->private_data = buffer;
7063fbf2 JB	265	goto Done;
	266
	267	Einval:
	268	error = -EINVAL;
	269	goto Done;
	270	Eaccess:
	271	error = -EACCES;
559c9ac3	272	Enomem:
7063fbf2 JB	273	module_put(attr->ca_owner);
	274	Done:
	275	if (error && item)
	276	config_item_put(item);
	277	return error;
	278	}
	279
	280	static int configfs_open_file(struct inode * inode, struct file * filp)
	281	{
	282	return check_perm(inode,filp);
	283	}
	284
	285	static int configfs_release(struct inode * inode, struct file * filp)
	286	{
867fa491 JJS	287	struct config_item * item = to_item(filp->f_path.dentry->d_parent);
867fa491 JJS	288	struct configfs_attribute * attr = to_attr(filp->f_path.dentry);
7063fbf2 JB	289	struct module * owner = attr->ca_owner;
	290	struct configfs_buffer * buffer = filp->private_data;
	291
	292	if (item)
	293	config_item_put(item);
	294	/* After this point, attr should not be accessed. */
	295	module_put(owner);
	296
	297	if (buffer) {
	298	if (buffer->page)
	299	free_page((unsigned long)buffer->page);
6d748924	300	mutex_destroy(&buffer->mutex);
7063fbf2 JB	301	kfree(buffer);
	302	}
	303	return 0;
	304	}
	305
4b6f5d20	306	const struct file_operations configfs_file_operations = {
7063fbf2 JB	307	.read = configfs_read_file,
	308	.write = configfs_write_file,
	309	.llseek = generic_file_llseek,
	310	.open = configfs_open_file,
	311	.release = configfs_release,
	312	};
	313
7063fbf2 JB	314	/**
	315	* configfs_create_file - create an attribute file for an item.
	316	* @item: item we're creating for.
	317	* @attr: atrribute descriptor.
	318	*/
	319
	320	int configfs_create_file(struct config_item * item, const struct configfs_attribute * attr)
	321	{
28444a2b AV	322	struct dentry *dir = item->ci_dentry;
	323	struct configfs_dirent *parent_sd = dir->d_fsdata;
	324	umode_t mode = (attr->ca_mode & S_IALLUGO) \| S_IFREG;
	325	int error = 0;
7063fbf2	326
2b0143b5	327	mutex_lock_nested(&d_inode(dir)->i_mutex, I_MUTEX_NORMAL);
28444a2b AV	328	error = configfs_make_dirent(parent_sd, NULL, (void *) attr, mode,
28444a2b AV	329	CONFIGFS_ITEM_ATTR);
2b0143b5	330	mutex_unlock(&d_inode(dir)->i_mutex);
28444a2b AV	331
28444a2b AV	332	return error;
7063fbf2 JB	333	}
7063fbf2 JB	334