aboutsummaryrefslogtreecommitdiff
path: root/fs/configfs/symlink.c
blob: 50f5840521a93c0b91fda648a9f3fc9debc659d8 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * symlink.c - operations for configfs symlinks.
 *
 * 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/namei.h>

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

static int item_depth(struct config_item * item)
{
	struct config_item * p = item;
	int depth = 0;
	do { depth++; } while ((p = p->ci_parent) && !configfs_is_root(p));
	return depth;
}

static int item_path_length(struct config_item * item)
{
	struct config_item * p = item;
	int length = 1;
	do {
		length += strlen(config_item_name(p)) + 1;
		p = p->ci_parent;
	} while (p && !configfs_is_root(p));
	return length;
}

static void fill_item_path(struct config_item * item, char * buffer, int length)
{
	struct config_item * p;

	--length;
	for (p = item; p && !configfs_is_root(p); p = p->ci_parent) {
		int cur = strlen(config_item_name(p));

		/* back up enough to print this bus id with '/' */
		length -= cur;
		strncpy(buffer + length,config_item_name(p),cur);
		*(buffer + --length) = '/';
	}
}

static int create_link(struct config_item *parent_item,
 		       struct config_item *item,
		       struct dentry *dentry)
{
	struct configfs_dirent *target_sd = item->ci_dentry->d_fsdata;
	struct configfs_symlink *sl;
	int ret;

	ret = -ENOMEM;
	sl = kmalloc(sizeof(struct configfs_symlink), GFP_KERNEL);
	if (sl) {
		sl->sl_target = config_item_get(item);
		/* FIXME: needs a lock, I'd bet */
		list_add(&sl->sl_list, &target_sd->s_links);
		ret = configfs_create_link(sl, parent_item->ci_dentry,
					   dentry);
		if (ret) {
			list_del_init(&sl->sl_list);
			config_item_put(item);
			kfree(sl);
		}
	}

	return ret;
}


static int get_target(const char *symname, struct nameidata *nd,
		      struct config_item **target)
{
	int ret;

	ret = path_lookup(symname, LOOKUP_FOLLOW|LOOKUP_DIRECTORY, nd);
	if (!ret) {
		if (nd->dentry->d_sb == configfs_sb) {
			*target = configfs_get_config_item(nd->dentry);
			if (!*target) {
				ret = -ENOENT;
				path_release(nd);
			}
		} else
			ret = -EPERM;
	}

	return ret;
}


int configfs_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
{
	int ret;
	struct nameidata nd;
	struct config_item *parent_item;
	struct config_item *target_item;
	struct config_item_type *type;

	ret = -EPERM;  /* What lack-of-symlink returns */
	if (dentry->d_parent == configfs_sb->s_root)
		goto out;

	parent_item = configfs_get_config_item(dentry->d_parent);
	type = parent_item->ci_type;

	if (!type || !type->ct_item_ops ||
	    !type->ct_item_ops->allow_link)
		goto out_put;

	ret = get_target(symname, &nd, &target_item);
	if (ret)
		goto out_put;

	ret = type->ct_item_ops->allow_link(parent_item, target_item);
	if (!ret)
		ret = create_link(parent_item, target_item, dentry);

	config_item_put(target_item);
	path_release(&nd);

out_put:
	config_item_put(parent_item);

out:
	return ret;
}

int configfs_unlink(struct inode *dir, struct dentry *dentry)
{
	struct configfs_dirent *sd = dentry->d_fsdata;
	struct configfs_symlink *sl;
	struct config_item *parent_item;
	struct config_item_type *type;
	int ret;

	ret = -EPERM;  /* What lack-of-symlink returns */
	if (!(sd->s_type & CONFIGFS_ITEM_LINK))
		goto out;

	if (dentry->d_parent == configfs_sb->s_root)
		BUG();

	sl = sd->s_element;

	parent_item = configfs_get_config_item(dentry->d_parent);
	type = parent_item->ci_type;

	list_del_init(&sd->s_sibling);
	configfs_drop_dentry(sd, dentry->d_parent);
	dput(dentry);
	configfs_put(sd);

	/*
	 * drop_link() must be called before
	 * list_del_init(&sl->sl_list), so that the order of
	 * drop_link(this, target) and drop_item(target) is preserved.
	 */
	if (type && type->ct_item_ops &&
	    type->ct_item_ops->drop_link)
		type->ct_item_ops->drop_link(parent_item,
					       sl->sl_target);

	/* FIXME: Needs lock */
	list_del_init(&sl->sl_list);

	/* Put reference from create_link() */
	config_item_put(sl->sl_target);
	kfree(sl);

	config_item_put(parent_item);

	ret = 0;

out:
	return ret;
}

static int configfs_get_target_path(struct config_item * item, struct config_item * target,
				   char *path)
{
	char * s;
	int depth, size;

	depth = item_depth(item);
	size = item_path_length(target) + depth * 3 - 1;
	if (size > PATH_MAX)
		return -ENAMETOOLONG;

	pr_debug("%s: depth = %d, size = %d\n", __FUNCTION__, depth, size);

	for (s = path; depth--; s += 3)
		strcpy(s,"../");

	fill_item_path(target, path, size);
	pr_debug("%s: path = '%s'\n", __FUNCTION__, path);

	return 0;
}

static int configfs_getlink(struct dentry *dentry, char * path)
{
	struct config_item *item, *target_item;
	int error = 0;

	item = configfs_get_config_item(dentry->d_parent);
	if (!item)
		return -EINVAL;

	target_item = configfs_get_config_item(dentry);
	if (!target_item) {
		config_item_put(item);
		return -EINVAL;
	}

	down_read(&configfs_rename_sem);
	error = configfs_get_target_path(item, target_item, path);
	up_read(&configfs_rename_sem);

	config_item_put(item);
	config_item_put(target_item);
	return error;

}

static void *configfs_follow_link(struct dentry *dentry, struct nameidata *nd)
{
	int error = -ENOMEM;
	unsigned long page = get_zeroed_page(GFP_KERNEL);

	if (page) {
		error = configfs_getlink(dentry, (char *)page);
		if (!error) {
			nd_set_link(nd, (char *)page);
			return (void *)page;
		}
	}

	nd_set_link(nd, ERR_PTR(error));
	return NULL;
}

static void configfs_put_link(struct dentry *dentry, struct nameidata *nd,
			      void *cookie)
{
	if (cookie) {
		unsigned long page = (unsigned long)cookie;
		free_page(page);
	}
}

struct inode_operations configfs_symlink_inode_operations = {
	.follow_link = configfs_follow_link,
	.readlink = generic_readlink,
	.put_link = configfs_put_link,
};