1/*
2 * inode.c - basic inode and dentry operations.
3 *
4 * sysfs is Copyright (c) 2001-3 Patrick Mochel
5 *
6 * Please see Documentation/filesystems/sysfs.txt for more information.
7 */
8
9#undef DEBUG
10
11#include <linux/pagemap.h>
12#include <linux/namei.h>
13#include <linux/backing-dev.h>
14#include <linux/capability.h>
15#include <linux/errno.h>
16#include <linux/sched.h>
17#include <asm/semaphore.h>
18#include "sysfs.h"
19
20extern struct super_block * sysfs_sb;
21
22static const struct address_space_operations sysfs_aops = {
23	.readpage	= simple_readpage,
24	.prepare_write	= simple_prepare_write,
25	.commit_write	= simple_commit_write
26};
27
28static struct backing_dev_info sysfs_backing_dev_info = {
29	.ra_pages	= 0,	/* No readahead */
30	.capabilities	= BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
31};
32
33static const struct inode_operations sysfs_inode_operations ={
34	.setattr	= sysfs_setattr,
35};
36
37void sysfs_delete_inode(struct inode *inode)
38{
39	/* Free the shadowed directory inode operations */
40	if (sysfs_is_shadowed_inode(inode)) {
41		kfree(inode->i_op);
42		inode->i_op = NULL;
43	}
44	return generic_delete_inode(inode);
45}
46
47int sysfs_setattr(struct dentry * dentry, struct iattr * iattr)
48{
49	struct inode * inode = dentry->d_inode;
50	struct sysfs_dirent * sd = dentry->d_fsdata;
51	struct iattr * sd_iattr;
52	unsigned int ia_valid = iattr->ia_valid;
53	int error;
54
55	if (!sd)
56		return -EINVAL;
57
58	sd_iattr = sd->s_iattr;
59
60	error = inode_change_ok(inode, iattr);
61	if (error)
62		return error;
63
64	error = inode_setattr(inode, iattr);
65	if (error)
66		return error;
67
68	if (!sd_iattr) {
69		/* setting attributes for the first time, allocate now */
70		sd_iattr = kzalloc(sizeof(struct iattr), GFP_KERNEL);
71		if (!sd_iattr)
72			return -ENOMEM;
73		/* assign default attributes */
74		sd_iattr->ia_mode = sd->s_mode;
75		sd_iattr->ia_uid = 0;
76		sd_iattr->ia_gid = 0;
77		sd_iattr->ia_atime = sd_iattr->ia_mtime = sd_iattr->ia_ctime = CURRENT_TIME;
78		sd->s_iattr = sd_iattr;
79	}
80
81	/* attributes were changed atleast once in past */
82
83	if (ia_valid & ATTR_UID)
84		sd_iattr->ia_uid = iattr->ia_uid;
85	if (ia_valid & ATTR_GID)
86		sd_iattr->ia_gid = iattr->ia_gid;
87	if (ia_valid & ATTR_ATIME)
88		sd_iattr->ia_atime = timespec_trunc(iattr->ia_atime,
89						inode->i_sb->s_time_gran);
90	if (ia_valid & ATTR_MTIME)
91		sd_iattr->ia_mtime = timespec_trunc(iattr->ia_mtime,
92						inode->i_sb->s_time_gran);
93	if (ia_valid & ATTR_CTIME)
94		sd_iattr->ia_ctime = timespec_trunc(iattr->ia_ctime,
95						inode->i_sb->s_time_gran);
96	if (ia_valid & ATTR_MODE) {
97		umode_t mode = iattr->ia_mode;
98
99		if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
100			mode &= ~S_ISGID;
101		sd_iattr->ia_mode = sd->s_mode = mode;
102	}
103
104	return error;
105}
106
107static inline void set_default_inode_attr(struct inode * inode, mode_t mode)
108{
109	inode->i_mode = mode;
110	inode->i_uid = 0;
111	inode->i_gid = 0;
112	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
113}
114
115static inline void set_inode_attr(struct inode * inode, struct iattr * iattr)
116{
117	inode->i_mode = iattr->ia_mode;
118	inode->i_uid = iattr->ia_uid;
119	inode->i_gid = iattr->ia_gid;
120	inode->i_atime = iattr->ia_atime;
121	inode->i_mtime = iattr->ia_mtime;
122	inode->i_ctime = iattr->ia_ctime;
123}
124
125
126/*
127 * sysfs has a different i_mutex lock order behavior for i_mutex than other
128 * filesystems; sysfs i_mutex is called in many places with subsystem locks
129 * held. At the same time, many of the VFS locking rules do not apply to
130 * sysfs at all (cross directory rename for example). To untangle this mess
131 * (which gives false positives in lockdep), we're giving sysfs inodes their
132 * own class for i_mutex.
133 */
134static struct lock_class_key sysfs_inode_imutex_key;
135
136struct inode * sysfs_new_inode(mode_t mode, struct sysfs_dirent * sd)
137{
138	struct inode * inode = new_inode(sysfs_sb);
139	if (inode) {
140		inode->i_blocks = 0;
141		inode->i_mapping->a_ops = &sysfs_aops;
142		inode->i_mapping->backing_dev_info = &sysfs_backing_dev_info;
143		inode->i_op = &sysfs_inode_operations;
144		inode->i_ino = sd->s_ino;
145		lockdep_set_class(&inode->i_mutex, &sysfs_inode_imutex_key);
146
147		if (sd->s_iattr) {
148			/* sysfs_dirent has non-default attributes
149			 * get them for the new inode from persistent copy
150			 * in sysfs_dirent
151			 */
152			set_inode_attr(inode, sd->s_iattr);
153		} else
154			set_default_inode_attr(inode, mode);
155	}
156	return inode;
157}
158
159int sysfs_create(struct dentry * dentry, int mode, int (*init)(struct inode *))
160{
161	int error = 0;
162	struct inode * inode = NULL;
163	if (dentry) {
164		if (!dentry->d_inode) {
165			struct sysfs_dirent * sd = dentry->d_fsdata;
166			if ((inode = sysfs_new_inode(mode, sd))) {
167				if (dentry->d_parent && dentry->d_parent->d_inode) {
168					struct inode *p_inode = dentry->d_parent->d_inode;
169					p_inode->i_mtime = p_inode->i_ctime = CURRENT_TIME;
170				}
171				goto Proceed;
172			}
173			else
174				error = -ENOMEM;
175		} else
176			error = -EEXIST;
177	} else
178		error = -ENOENT;
179	goto Done;
180
181 Proceed:
182	if (init)
183		error = init(inode);
184	if (!error) {
185		d_instantiate(dentry, inode);
186		if (S_ISDIR(mode))
187			dget(dentry);  /* pin only directory dentry in core */
188	} else
189		iput(inode);
190 Done:
191	return error;
192}
193
194/*
195 * Get the name for corresponding element represented by the given sysfs_dirent
196 */
197const unsigned char * sysfs_get_name(struct sysfs_dirent *sd)
198{
199	struct attribute * attr;
200	struct bin_attribute * bin_attr;
201	struct sysfs_symlink  * sl;
202
203	BUG_ON(!sd || !sd->s_element);
204
205	switch (sd->s_type) {
206		case SYSFS_DIR:
207			/* Always have a dentry so use that */
208			return sd->s_dentry->d_name.name;
209
210		case SYSFS_KOBJ_ATTR:
211			attr = sd->s_element;
212			return attr->name;
213
214		case SYSFS_KOBJ_BIN_ATTR:
215			bin_attr = sd->s_element;
216			return bin_attr->attr.name;
217
218		case SYSFS_KOBJ_LINK:
219			sl = sd->s_element;
220			return sl->link_name;
221	}
222	return NULL;
223}
224
225static inline void orphan_all_buffers(struct inode *node)
226{
227	struct sysfs_buffer_collection *set;
228	struct sysfs_buffer *buf;
229
230	mutex_lock_nested(&node->i_mutex, I_MUTEX_CHILD);
231	set = node->i_private;
232	if (set) {
233		list_for_each_entry(buf, &set->associates, associates) {
234			down(&buf->sem);
235			buf->orphaned = 1;
236			up(&buf->sem);
237		}
238	}
239	mutex_unlock(&node->i_mutex);
240}
241
242
243/*
244 * Unhashes the dentry corresponding to given sysfs_dirent
245 * Called with parent inode's i_mutex held.
246 */
247void sysfs_drop_dentry(struct sysfs_dirent * sd, struct dentry * parent)
248{
249	struct dentry *dentry = NULL;
250	struct inode *inode;
251
252	/* We're not holding a reference to ->s_dentry dentry but the
253	 * field will stay valid as long as sysfs_lock is held.
254	 */
255	spin_lock(&sysfs_lock);
256	spin_lock(&dcache_lock);
257
258	/* dget dentry if it's still alive */
259	if (sd->s_dentry && sd->s_dentry->d_inode)
260		dentry = dget_locked(sd->s_dentry);
261
262	spin_unlock(&dcache_lock);
263	spin_unlock(&sysfs_lock);
264
265	/* drop dentry */
266	if (dentry) {
267		spin_lock(&dcache_lock);
268		spin_lock(&dentry->d_lock);
269		if (!d_unhashed(dentry) && dentry->d_inode) {
270			inode = dentry->d_inode;
271			spin_lock(&inode->i_lock);
272			__iget(inode);
273			spin_unlock(&inode->i_lock);
274			dget_locked(dentry);
275			__d_drop(dentry);
276			spin_unlock(&dentry->d_lock);
277			spin_unlock(&dcache_lock);
278			simple_unlink(parent->d_inode, dentry);
279			orphan_all_buffers(inode);
280			iput(inode);
281		} else {
282			spin_unlock(&dentry->d_lock);
283			spin_unlock(&dcache_lock);
284		}
285
286		dput(dentry);
287	}
288}
289
290int sysfs_hash_and_remove(struct dentry * dir, const char * name)
291{
292	struct sysfs_dirent * sd;
293	struct sysfs_dirent * parent_sd;
294	int found = 0;
295
296	if (!dir)
297		return -ENOENT;
298
299	if (dir->d_inode == NULL)
300		/* no inode means this hasn't been made visible yet */
301		return -ENOENT;
302
303	parent_sd = dir->d_fsdata;
304	mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_PARENT);
305	list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
306		if (!sd->s_element)
307			continue;
308		if (!strcmp(sysfs_get_name(sd), name)) {
309			list_del_init(&sd->s_sibling);
310			sysfs_drop_dentry(sd, dir);
311			sysfs_put(sd);
312			found = 1;
313			break;
314		}
315	}
316	mutex_unlock(&dir->d_inode->i_mutex);
317
318	return found ? 0 : -ENOENT;
319}
320