aboutsummaryrefslogtreecommitdiff
path: root/fs/sysfs/inode.c
blob: 3eab9c46a71b6f30a27b51d2f5c0521a9f3275c2 (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
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
/*
 * inode.c - basic inode and dentry operations.
 *
 * sysfs is Copyright (c) 2001-3 Patrick Mochel
 *
 * Please see Documentation/filesystems/sysfs.txt for more information.
 */

#undef DEBUG 

#include <linux/pagemap.h>
#include <linux/namei.h>
#include <linux/backing-dev.h>
#include <linux/capability.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <asm/semaphore.h>
#include "sysfs.h"

extern struct super_block * sysfs_sb;

static const struct address_space_operations sysfs_aops = {
	.readpage	= simple_readpage,
	.prepare_write	= simple_prepare_write,
	.commit_write	= simple_commit_write
};

static struct backing_dev_info sysfs_backing_dev_info = {
	.ra_pages	= 0,	/* No readahead */
	.capabilities	= BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
};

static const struct inode_operations sysfs_inode_operations ={
	.setattr	= sysfs_setattr,
};

void sysfs_delete_inode(struct inode *inode)
{
	/* Free the shadowed directory inode operations */
	if (sysfs_is_shadowed_inode(inode)) {
		kfree(inode->i_op);
		inode->i_op = NULL;
	}
	return generic_delete_inode(inode);
}

int sysfs_setattr(struct dentry * dentry, struct iattr * iattr)
{
	struct inode * inode = dentry->d_inode;
	struct sysfs_dirent * sd = dentry->d_fsdata;
	struct iattr * sd_iattr;
	unsigned int ia_valid = iattr->ia_valid;
	int error;

	if (!sd)
		return -EINVAL;

	sd_iattr = sd->s_iattr;

	error = inode_change_ok(inode, iattr);
	if (error)
		return error;

	error = inode_setattr(inode, iattr);
	if (error)
		return error;

	if (!sd_iattr) {
		/* setting attributes for the first time, allocate now */
		sd_iattr = kzalloc(sizeof(struct iattr), GFP_KERNEL);
		if (!sd_iattr)
			return -ENOMEM;
		/* assign default attributes */
		sd_iattr->ia_mode = sd->s_mode;
		sd_iattr->ia_uid = 0;
		sd_iattr->ia_gid = 0;
		sd_iattr->ia_atime = sd_iattr->ia_mtime = sd_iattr->ia_ctime = CURRENT_TIME;
		sd->s_iattr = sd_iattr;
	}

	/* attributes were changed atleast once in past */

	if (ia_valid & ATTR_UID)
		sd_iattr->ia_uid = iattr->ia_uid;
	if (ia_valid & ATTR_GID)
		sd_iattr->ia_gid = iattr->ia_gid;
	if (ia_valid & ATTR_ATIME)
		sd_iattr->ia_atime = timespec_trunc(iattr->ia_atime,
						inode->i_sb->s_time_gran);
	if (ia_valid & ATTR_MTIME)
		sd_iattr->ia_mtime = timespec_trunc(iattr->ia_mtime,
						inode->i_sb->s_time_gran);
	if (ia_valid & ATTR_CTIME)
		sd_iattr->ia_ctime = timespec_trunc(iattr->ia_ctime,
						inode->i_sb->s_time_gran);
	if (ia_valid & ATTR_MODE) {
		umode_t mode = iattr->ia_mode;

		if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
			mode &= ~S_ISGID;
		sd_iattr->ia_mode = sd->s_mode = mode;
	}

	return error;
}

static inline void set_default_inode_attr(struct inode * inode, mode_t mode)
{
	inode->i_mode = mode;
	inode->i_uid = 0;
	inode->i_gid = 0;
	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
}

static inline void set_inode_attr(struct inode * inode, struct iattr * iattr)
{
	inode->i_mode = iattr->ia_mode;
	inode->i_uid = iattr->ia_uid;
	inode->i_gid = iattr->ia_gid;
	inode->i_atime = iattr->ia_atime;
	inode->i_mtime = iattr->ia_mtime;
	inode->i_ctime = iattr->ia_ctime;
}


/*
 * sysfs has a different i_mutex lock order behavior for i_mutex than other
 * filesystems; sysfs i_mutex is called in many places with subsystem locks
 * held. At the same time, many of the VFS locking rules do not apply to
 * sysfs at all (cross directory rename for example). To untangle this mess
 * (which gives false positives in lockdep), we're giving sysfs inodes their
 * own class for i_mutex.
 */
static struct lock_class_key sysfs_inode_imutex_key;

void sysfs_init_inode(struct sysfs_dirent *sd, struct inode *inode)
{
	inode->i_blocks = 0;
	inode->i_mapping->a_ops = &sysfs_aops;
	inode->i_mapping->backing_dev_info = &sysfs_backing_dev_info;
	inode->i_op = &sysfs_inode_operations;
	inode->i_ino = sd->s_ino;
	lockdep_set_class(&inode->i_mutex, &sysfs_inode_imutex_key);

	if (sd->s_iattr) {
		/* sysfs_dirent has non-default attributes
		 * get them for the new inode from persistent copy
		 * in sysfs_dirent
		 */
		set_inode_attr(inode, sd->s_iattr);
	} else
		set_default_inode_attr(inode, sd->s_mode);
}

/**
 *	sysfs_get_inode - get inode for sysfs_dirent
 *	@sd: sysfs_dirent to allocate inode for
 *
 *	Get inode for @sd.  If such inode doesn't exist, a new inode
 *	is allocated and basics are initialized.  New inode is
 *	returned locked.
 *
 *	LOCKING:
 *	Kernel thread context (may sleep).
 *
 *	RETURNS:
 *	Pointer to allocated inode on success, NULL on failure.
 */
struct inode * sysfs_get_inode(struct sysfs_dirent *sd)
{
	struct inode *inode;

	inode = iget_locked(sysfs_sb, sd->s_ino);
	if (inode && (inode->i_state & I_NEW))
		sysfs_init_inode(sd, inode);

	return inode;
}

/**
 *	sysfs_instantiate - instantiate dentry
 *	@dentry: dentry to be instantiated
 *	@inode: inode associated with @sd
 *
 *	Unlock @inode if locked and instantiate @dentry with @inode.
 *
 *	LOCKING:
 *	None.
 */
void sysfs_instantiate(struct dentry *dentry, struct inode *inode)
{
	BUG_ON(!dentry || dentry->d_inode);

	if (inode->i_state & I_NEW) {
		unlock_new_inode(inode);

		if (dentry->d_parent && dentry->d_parent->d_inode) {
			struct inode *p_inode = dentry->d_parent->d_inode;
			p_inode->i_mtime = p_inode->i_ctime = CURRENT_TIME;
		}
	}

	d_instantiate(dentry, inode);
}

/**
 *	sysfs_drop_dentry - drop dentry for the specified sysfs_dirent
 *	@sd: target sysfs_dirent
 *
 *	Drop dentry for @sd.  @sd must have been unlinked from its
 *	parent on entry to this function such that it can't be looked
 *	up anymore.
 *
 *	@sd->s_dentry which is protected with sysfs_lock points to the
 *	currently associated dentry but we're not holding a reference
 *	to it and racing with dput().  Grab dcache_lock and verify
 *	dentry before dropping it.  If @sd->s_dentry is NULL or dput()
 *	beats us, no need to bother.
 */
void sysfs_drop_dentry(struct sysfs_dirent *sd)
{
	struct dentry *dentry = NULL, *parent = NULL;
	struct inode *dir;
	struct timespec curtime;

	/* We're not holding a reference to ->s_dentry dentry but the
	 * field will stay valid as long as sysfs_lock is held.
	 */
	spin_lock(&sysfs_lock);
	spin_lock(&dcache_lock);

	if (sd->s_dentry && sd->s_dentry->d_inode) {
		/* get dentry if it's there and dput() didn't kill it yet */
		dentry = dget_locked(sd->s_dentry);
		parent = dentry->d_parent;
	} else if (sd->s_parent->s_dentry->d_inode) {
		/* We need to update the parent even if dentry for the
		 * victim itself doesn't exist.
		 */
		parent = dget_locked(sd->s_parent->s_dentry);
	}

	/* drop */
	if (dentry) {
		spin_lock(&dentry->d_lock);
		__d_drop(dentry);
		spin_unlock(&dentry->d_lock);
	}

	spin_unlock(&dcache_lock);
	spin_unlock(&sysfs_lock);

	/* nothing to do if the parent isn't in dcache */
	if (!parent)
		return;

	/* adjust nlink and update timestamp */
	dir = parent->d_inode;
	mutex_lock(&dir->i_mutex);

	curtime = CURRENT_TIME;

	dir->i_ctime = dir->i_mtime = curtime;

	if (dentry) {
		dentry->d_inode->i_ctime = curtime;
		drop_nlink(dentry->d_inode);
		if (sd->s_type & SYSFS_DIR) {
			drop_nlink(dentry->d_inode);
			drop_nlink(dir);
			/* XXX: unpin if directory, this will go away soon */
			dput(dentry);
		}
	}

	mutex_unlock(&dir->i_mutex);

	/* bye bye */
	if (dentry)
		dput(dentry);
	else
		dput(parent);
}

int sysfs_hash_and_remove(struct dentry * dir, const char * name)
{
	struct sysfs_dirent * sd;
	struct sysfs_dirent * parent_sd;
	int found = 0;

	if (!dir)
		return -ENOENT;

	if (dir->d_inode == NULL)
		/* no inode means this hasn't been made visible yet */
		return -ENOENT;

	parent_sd = dir->d_fsdata;
	mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_PARENT);
	list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
		if (!sd->s_type)
			continue;
		if (!strcmp(sd->s_name, name)) {
			list_del_init(&sd->s_sibling);
			found = 1;
			break;
		}
	}
	mutex_unlock(&dir->d_inode->i_mutex);

	if (!found)
		return -ENOENT;

	sysfs_drop_dentry(sd);
	sysfs_deactivate(sd);
	sysfs_put(sd);

	return 0;
}