Linux kernel & device driver programming

Cross-Referenced Linux and Device Driver Code

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Version: [ 2.6.11.8 ] [ 2.6.25 ] [ 2.6.25.8 ] [ 2.6.31.13 ] Architecture: [ i386 ]
  1 /* -*- mode: c; c-basic-offset: 8; -*-
  2  * vim: noexpandtab sw=8 ts=8 sts=0:
  3  *
  4  * symlink.c - operations for configfs symlinks.
  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>
 29 #include <linux/namei.h>
 30 
 31 #include <linux/configfs.h>
 32 #include "configfs_internal.h"
 33 
 34 static int item_depth(struct config_item * item)
 35 {
 36         struct config_item * p = item;
 37         int depth = 0;
 38         do { depth++; } while ((p = p->ci_parent) && !configfs_is_root(p));
 39         return depth;
 40 }
 41 
 42 static int item_path_length(struct config_item * item)
 43 {
 44         struct config_item * p = item;
 45         int length = 1;
 46         do {
 47                 length += strlen(config_item_name(p)) + 1;
 48                 p = p->ci_parent;
 49         } while (p && !configfs_is_root(p));
 50         return length;
 51 }
 52 
 53 static void fill_item_path(struct config_item * item, char * buffer, int length)
 54 {
 55         struct config_item * p;
 56 
 57         --length;
 58         for (p = item; p && !configfs_is_root(p); p = p->ci_parent) {
 59                 int cur = strlen(config_item_name(p));
 60 
 61                 /* back up enough to print this bus id with '/' */
 62                 length -= cur;
 63                 strncpy(buffer + length,config_item_name(p),cur);
 64                 *(buffer + --length) = '/';
 65         }
 66 }
 67 
 68 static int create_link(struct config_item *parent_item,
 69                        struct config_item *item,
 70                        struct dentry *dentry)
 71 {
 72         struct configfs_dirent *target_sd = item->ci_dentry->d_fsdata;
 73         struct configfs_symlink *sl;
 74         int ret;
 75 
 76         ret = -ENOMEM;
 77         sl = kmalloc(sizeof(struct configfs_symlink), GFP_KERNEL);
 78         if (sl) {
 79                 sl->sl_target = config_item_get(item);
 80                 /* FIXME: needs a lock, I'd bet */
 81                 list_add(&sl->sl_list, &target_sd->s_links);
 82                 ret = configfs_create_link(sl, parent_item->ci_dentry,
 83                                            dentry);
 84                 if (ret) {
 85                         list_del_init(&sl->sl_list);
 86                         config_item_put(item);
 87                         kfree(sl);
 88                 }
 89         }
 90 
 91         return ret;
 92 }
 93 
 94 
 95 static int get_target(const char *symname, struct nameidata *nd,
 96                       struct config_item **target)
 97 {
 98         int ret;
 99 
100         ret = path_lookup(symname, LOOKUP_FOLLOW|LOOKUP_DIRECTORY, nd);
101         if (!ret) {
102                 if (nd->path.dentry->d_sb == configfs_sb) {
103                         *target = configfs_get_config_item(nd->path.dentry);
104                         if (!*target) {
105                                 ret = -ENOENT;
106                                 path_put(&nd->path);
107                         }
108                 } else
109                         ret = -EPERM;
110         }
111 
112         return ret;
113 }
114 
115 
116 int configfs_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
117 {
118         int ret;
119         struct nameidata nd;
120         struct config_item *parent_item;
121         struct config_item *target_item;
122         struct config_item_type *type;
123 
124         ret = -EPERM;  /* What lack-of-symlink returns */
125         if (dentry->d_parent == configfs_sb->s_root)
126                 goto out;
127 
128         parent_item = configfs_get_config_item(dentry->d_parent);
129         type = parent_item->ci_type;
130 
131         if (!type || !type->ct_item_ops ||
132             !type->ct_item_ops->allow_link)
133                 goto out_put;
134 
135         ret = get_target(symname, &nd, &target_item);
136         if (ret)
137                 goto out_put;
138 
139         ret = type->ct_item_ops->allow_link(parent_item, target_item);
140         if (!ret)
141                 ret = create_link(parent_item, target_item, dentry);
142 
143         config_item_put(target_item);
144         path_put(&nd.path);
145 
146 out_put:
147         config_item_put(parent_item);
148 
149 out:
150         return ret;
151 }
152 
153 int configfs_unlink(struct inode *dir, struct dentry *dentry)
154 {
155         struct configfs_dirent *sd = dentry->d_fsdata;
156         struct configfs_symlink *sl;
157         struct config_item *parent_item;
158         struct config_item_type *type;
159         int ret;
160 
161         ret = -EPERM;  /* What lack-of-symlink returns */
162         if (!(sd->s_type & CONFIGFS_ITEM_LINK))
163                 goto out;
164 
165         BUG_ON(dentry->d_parent == configfs_sb->s_root);
166 
167         sl = sd->s_element;
168 
169         parent_item = configfs_get_config_item(dentry->d_parent);
170         type = parent_item->ci_type;
171 
172         list_del_init(&sd->s_sibling);
173         configfs_drop_dentry(sd, dentry->d_parent);
174         dput(dentry);
175         configfs_put(sd);
176 
177         /*
178          * drop_link() must be called before
179          * list_del_init(&sl->sl_list), so that the order of
180          * drop_link(this, target) and drop_item(target) is preserved.
181          */
182         if (type && type->ct_item_ops &&
183             type->ct_item_ops->drop_link)
184                 type->ct_item_ops->drop_link(parent_item,
185                                                sl->sl_target);
186 
187         /* FIXME: Needs lock */
188         list_del_init(&sl->sl_list);
189 
190         /* Put reference from create_link() */
191         config_item_put(sl->sl_target);
192         kfree(sl);
193 
194         config_item_put(parent_item);
195 
196         ret = 0;
197 
198 out:
199         return ret;
200 }
201 
202 static int configfs_get_target_path(struct config_item * item, struct config_item * target,
203                                    char *path)
204 {
205         char * s;
206         int depth, size;
207 
208         depth = item_depth(item);
209         size = item_path_length(target) + depth * 3 - 1;
210         if (size > PATH_MAX)
211                 return -ENAMETOOLONG;
212 
213         pr_debug("%s: depth = %d, size = %d\n", __FUNCTION__, depth, size);
214 
215         for (s = path; depth--; s += 3)
216                 strcpy(s,"../");
217 
218         fill_item_path(target, path, size);
219         pr_debug("%s: path = '%s'\n", __FUNCTION__, path);
220 
221         return 0;
222 }
223 
224 static int configfs_getlink(struct dentry *dentry, char * path)
225 {
226         struct config_item *item, *target_item;
227         int error = 0;
228 
229         item = configfs_get_config_item(dentry->d_parent);
230         if (!item)
231                 return -EINVAL;
232 
233         target_item = configfs_get_config_item(dentry);
234         if (!target_item) {
235                 config_item_put(item);
236                 return -EINVAL;
237         }
238 
239         down_read(&configfs_rename_sem);
240         error = configfs_get_target_path(item, target_item, path);
241         up_read(&configfs_rename_sem);
242 
243         config_item_put(item);
244         config_item_put(target_item);
245         return error;
246 
247 }
248 
249 static void *configfs_follow_link(struct dentry *dentry, struct nameidata *nd)
250 {
251         int error = -ENOMEM;
252         unsigned long page = get_zeroed_page(GFP_KERNEL);
253 
254         if (page) {
255                 error = configfs_getlink(dentry, (char *)page);
256                 if (!error) {
257                         nd_set_link(nd, (char *)page);
258                         return (void *)page;
259                 }
260         }
261 
262         nd_set_link(nd, ERR_PTR(error));
263         return NULL;
264 }
265 
266 static void configfs_put_link(struct dentry *dentry, struct nameidata *nd,
267                               void *cookie)
268 {
269         if (cookie) {
270                 unsigned long page = (unsigned long)cookie;
271                 free_page(page);
272         }
273 }
274 
275 const struct inode_operations configfs_symlink_inode_operations = {
276         .follow_link = configfs_follow_link,
277         .readlink = generic_readlink,
278         .put_link = configfs_put_link,
279         .setattr = configfs_setattr,
280 };
281 
282 
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