ia64/linux-2.6.18-xen.hg

view fs/configfs/file.c @ 524:7f8b544237bf

netfront: Allow netfront in domain 0.

This is useful if your physical network device is in a utility domain.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
author Keir Fraser <keir.fraser@citrix.com>
date Tue Apr 15 15:18:58 2008 +0100 (2008-04-15)
parents 831230e53067
children
line source
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 */
27 #include <linux/fs.h>
28 #include <linux/module.h>
29 #include <linux/slab.h>
30 #include <asm/uaccess.h>
31 #include <asm/semaphore.h>
33 #include <linux/configfs.h>
34 #include "configfs_internal.h"
37 struct configfs_buffer {
38 size_t count;
39 loff_t pos;
40 char * page;
41 struct configfs_item_operations * ops;
42 struct semaphore sem;
43 int needs_read_fill;
44 };
47 /**
48 * fill_read_buffer - allocate and fill buffer from item.
49 * @dentry: dentry pointer.
50 * @buffer: data buffer for file.
51 *
52 * Allocate @buffer->page, if it hasn't been already, then call the
53 * config_item's show() method to fill the buffer with this attribute's
54 * data.
55 * This is called only once, on the file's first read.
56 */
57 static int fill_read_buffer(struct dentry * dentry, struct configfs_buffer * buffer)
58 {
59 struct configfs_attribute * attr = to_attr(dentry);
60 struct config_item * item = to_item(dentry->d_parent);
61 struct configfs_item_operations * ops = buffer->ops;
62 int ret = 0;
63 ssize_t count;
65 if (!buffer->page)
66 buffer->page = (char *) get_zeroed_page(GFP_KERNEL);
67 if (!buffer->page)
68 return -ENOMEM;
70 count = ops->show_attribute(item,attr,buffer->page);
71 buffer->needs_read_fill = 0;
72 BUG_ON(count > (ssize_t)PAGE_SIZE);
73 if (count >= 0)
74 buffer->count = count;
75 else
76 ret = count;
77 return ret;
78 }
81 /**
82 * flush_read_buffer - push buffer to userspace.
83 * @buffer: data buffer for file.
84 * @userbuf: user-passed buffer.
85 * @count: number of bytes requested.
86 * @ppos: file position.
87 *
88 * Copy the buffer we filled in fill_read_buffer() to userspace.
89 * This is done at the reader's leisure, copying and advancing
90 * the amount they specify each time.
91 * This may be called continuously until the buffer is empty.
92 */
93 static int flush_read_buffer(struct configfs_buffer * buffer, char __user * buf,
94 size_t count, loff_t * ppos)
95 {
96 int error;
98 if (*ppos > buffer->count)
99 return 0;
101 if (count > (buffer->count - *ppos))
102 count = buffer->count - *ppos;
104 error = copy_to_user(buf,buffer->page + *ppos,count);
105 if (!error)
106 *ppos += count;
107 return error ? -EFAULT : count;
108 }
110 /**
111 * configfs_read_file - read an attribute.
112 * @file: file pointer.
113 * @buf: buffer to fill.
114 * @count: number of bytes to read.
115 * @ppos: starting offset in file.
116 *
117 * Userspace wants to read an attribute file. The attribute descriptor
118 * is in the file's ->d_fsdata. The target item is in the directory's
119 * ->d_fsdata.
120 *
121 * We call fill_read_buffer() to allocate and fill the buffer from the
122 * item's show() method exactly once (if the read is happening from
123 * the beginning of the file). That should fill the entire buffer with
124 * all the data the item has to offer for that attribute.
125 * We then call flush_read_buffer() to copy the buffer to userspace
126 * in the increments specified.
127 */
129 static ssize_t
130 configfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos)
131 {
132 struct configfs_buffer * buffer = file->private_data;
133 ssize_t retval = 0;
135 down(&buffer->sem);
136 if (buffer->needs_read_fill) {
137 if ((retval = fill_read_buffer(file->f_dentry,buffer)))
138 goto out;
139 }
140 pr_debug("%s: count = %d, ppos = %lld, buf = %s\n",
141 __FUNCTION__,count,*ppos,buffer->page);
142 retval = flush_read_buffer(buffer,buf,count,ppos);
143 out:
144 up(&buffer->sem);
145 return retval;
146 }
149 /**
150 * fill_write_buffer - copy buffer from userspace.
151 * @buffer: data buffer for file.
152 * @buf: data from user.
153 * @count: number of bytes in @userbuf.
154 *
155 * Allocate @buffer->page if it hasn't been already, then
156 * copy the user-supplied buffer into it.
157 */
159 static int
160 fill_write_buffer(struct configfs_buffer * buffer, const char __user * buf, size_t count)
161 {
162 int error;
164 if (!buffer->page)
165 buffer->page = (char *)get_zeroed_page(GFP_KERNEL);
166 if (!buffer->page)
167 return -ENOMEM;
169 if (count > PAGE_SIZE)
170 count = PAGE_SIZE;
171 error = copy_from_user(buffer->page,buf,count);
172 buffer->needs_read_fill = 1;
173 return error ? -EFAULT : count;
174 }
177 /**
178 * flush_write_buffer - push buffer to config_item.
179 * @dentry: dentry to the attribute
180 * @buffer: data buffer for file.
181 * @count: number of bytes
182 *
183 * Get the correct pointers for the config_item and the attribute we're
184 * dealing with, then call the store() method for the attribute,
185 * passing the buffer that we acquired in fill_write_buffer().
186 */
188 static int
189 flush_write_buffer(struct dentry * dentry, struct configfs_buffer * buffer, size_t count)
190 {
191 struct configfs_attribute * attr = to_attr(dentry);
192 struct config_item * item = to_item(dentry->d_parent);
193 struct configfs_item_operations * ops = buffer->ops;
195 return ops->store_attribute(item,attr,buffer->page,count);
196 }
199 /**
200 * configfs_write_file - write an attribute.
201 * @file: file pointer
202 * @buf: data to write
203 * @count: number of bytes
204 * @ppos: starting offset
205 *
206 * Similar to configfs_read_file(), though working in the opposite direction.
207 * We allocate and fill the data from the user in fill_write_buffer(),
208 * then push it to the config_item in flush_write_buffer().
209 * There is no easy way for us to know if userspace is only doing a partial
210 * write, so we don't support them. We expect the entire buffer to come
211 * on the first write.
212 * Hint: if you're writing a value, first read the file, modify only the
213 * the value you're changing, then write entire buffer back.
214 */
216 static ssize_t
217 configfs_write_file(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
218 {
219 struct configfs_buffer * buffer = file->private_data;
220 ssize_t len;
222 down(&buffer->sem);
223 len = fill_write_buffer(buffer, buf, count);
224 if (len > 0)
225 len = flush_write_buffer(file->f_dentry, buffer, count);
226 if (len > 0)
227 *ppos += len;
228 up(&buffer->sem);
229 return len;
230 }
232 static int check_perm(struct inode * inode, struct file * file)
233 {
234 struct config_item *item = configfs_get_config_item(file->f_dentry->d_parent);
235 struct configfs_attribute * attr = to_attr(file->f_dentry);
236 struct configfs_buffer * buffer;
237 struct configfs_item_operations * ops = NULL;
238 int error = 0;
240 if (!item || !attr)
241 goto Einval;
243 /* Grab the module reference for this attribute if we have one */
244 if (!try_module_get(attr->ca_owner)) {
245 error = -ENODEV;
246 goto Done;
247 }
249 if (item->ci_type)
250 ops = item->ci_type->ct_item_ops;
251 else
252 goto Eaccess;
254 /* File needs write support.
255 * The inode's perms must say it's ok,
256 * and we must have a store method.
257 */
258 if (file->f_mode & FMODE_WRITE) {
260 if (!(inode->i_mode & S_IWUGO) || !ops->store_attribute)
261 goto Eaccess;
263 }
265 /* File needs read support.
266 * The inode's perms must say it's ok, and we there
267 * must be a show method for it.
268 */
269 if (file->f_mode & FMODE_READ) {
270 if (!(inode->i_mode & S_IRUGO) || !ops->show_attribute)
271 goto Eaccess;
272 }
274 /* No error? Great, allocate a buffer for the file, and store it
275 * it in file->private_data for easy access.
276 */
277 buffer = kmalloc(sizeof(struct configfs_buffer),GFP_KERNEL);
278 if (buffer) {
279 memset(buffer,0,sizeof(struct configfs_buffer));
280 init_MUTEX(&buffer->sem);
281 buffer->needs_read_fill = 1;
282 buffer->ops = ops;
283 file->private_data = buffer;
284 } else
285 error = -ENOMEM;
286 goto Done;
288 Einval:
289 error = -EINVAL;
290 goto Done;
291 Eaccess:
292 error = -EACCES;
293 module_put(attr->ca_owner);
294 Done:
295 if (error && item)
296 config_item_put(item);
297 return error;
298 }
300 static int configfs_open_file(struct inode * inode, struct file * filp)
301 {
302 return check_perm(inode,filp);
303 }
305 static int configfs_release(struct inode * inode, struct file * filp)
306 {
307 struct config_item * item = to_item(filp->f_dentry->d_parent);
308 struct configfs_attribute * attr = to_attr(filp->f_dentry);
309 struct module * owner = attr->ca_owner;
310 struct configfs_buffer * buffer = filp->private_data;
312 if (item)
313 config_item_put(item);
314 /* After this point, attr should not be accessed. */
315 module_put(owner);
317 if (buffer) {
318 if (buffer->page)
319 free_page((unsigned long)buffer->page);
320 kfree(buffer);
321 }
322 return 0;
323 }
325 const struct file_operations configfs_file_operations = {
326 .read = configfs_read_file,
327 .write = configfs_write_file,
328 .llseek = generic_file_llseek,
329 .open = configfs_open_file,
330 .release = configfs_release,
331 };
334 int configfs_add_file(struct dentry * dir, const struct configfs_attribute * attr, int type)
335 {
336 struct configfs_dirent * parent_sd = dir->d_fsdata;
337 umode_t mode = (attr->ca_mode & S_IALLUGO) | S_IFREG;
338 int error = 0;
340 mutex_lock(&dir->d_inode->i_mutex);
341 error = configfs_make_dirent(parent_sd, NULL, (void *) attr, mode, type);
342 mutex_unlock(&dir->d_inode->i_mutex);
344 return error;
345 }
348 /**
349 * configfs_create_file - create an attribute file for an item.
350 * @item: item we're creating for.
351 * @attr: atrribute descriptor.
352 */
354 int configfs_create_file(struct config_item * item, const struct configfs_attribute * attr)
355 {
356 BUG_ON(!item || !item->ci_dentry || !attr);
358 return configfs_add_file(item->ci_dentry, attr,
359 CONFIGFS_ITEM_ATTR);
360 }