Commit | Line | Data |
---|---|---|
1da177e4 LT |
1 | /* |
2 | * dir.c - Operations for sysfs directories. | |
3 | */ | |
4 | ||
5 | #undef DEBUG | |
6 | ||
7 | #include <linux/fs.h> | |
8 | #include <linux/mount.h> | |
9 | #include <linux/module.h> | |
10 | #include <linux/kobject.h> | |
5f45f1a7 | 11 | #include <linux/namei.h> |
2b611bb7 | 12 | #include <linux/idr.h> |
8619f979 | 13 | #include <linux/completion.h> |
869512ab | 14 | #include <linux/mutex.h> |
1da177e4 LT |
15 | #include "sysfs.h" |
16 | ||
3007e997 | 17 | DEFINE_MUTEX(sysfs_mutex); |
5f995323 | 18 | spinlock_t sysfs_assoc_lock = SPIN_LOCK_UNLOCKED; |
1da177e4 | 19 | |
2b611bb7 TH |
20 | static spinlock_t sysfs_ino_lock = SPIN_LOCK_UNLOCKED; |
21 | static DEFINE_IDA(sysfs_ino_ida); | |
22 | ||
0c73f18b TH |
23 | /** |
24 | * sysfs_link_sibling - link sysfs_dirent into sibling list | |
25 | * @sd: sysfs_dirent of interest | |
26 | * | |
27 | * Link @sd into its sibling list which starts from | |
28 | * sd->s_parent->s_children. | |
29 | * | |
30 | * Locking: | |
3007e997 | 31 | * mutex_lock(sysfs_mutex) |
0c73f18b | 32 | */ |
fb6896da | 33 | void sysfs_link_sibling(struct sysfs_dirent *sd) |
0c73f18b TH |
34 | { |
35 | struct sysfs_dirent *parent_sd = sd->s_parent; | |
36 | ||
37 | BUG_ON(sd->s_sibling); | |
38 | sd->s_sibling = parent_sd->s_children; | |
39 | parent_sd->s_children = sd; | |
40 | } | |
41 | ||
42 | /** | |
43 | * sysfs_unlink_sibling - unlink sysfs_dirent from sibling list | |
44 | * @sd: sysfs_dirent of interest | |
45 | * | |
46 | * Unlink @sd from its sibling list which starts from | |
47 | * sd->s_parent->s_children. | |
48 | * | |
49 | * Locking: | |
3007e997 | 50 | * mutex_lock(sysfs_mutex) |
0c73f18b | 51 | */ |
fb6896da | 52 | void sysfs_unlink_sibling(struct sysfs_dirent *sd) |
0c73f18b TH |
53 | { |
54 | struct sysfs_dirent **pos; | |
55 | ||
56 | for (pos = &sd->s_parent->s_children; *pos; pos = &(*pos)->s_sibling) { | |
57 | if (*pos == sd) { | |
58 | *pos = sd->s_sibling; | |
59 | sd->s_sibling = NULL; | |
60 | break; | |
61 | } | |
62 | } | |
63 | } | |
64 | ||
53e0ae92 TH |
65 | /** |
66 | * sysfs_get_dentry - get dentry for the given sysfs_dirent | |
67 | * @sd: sysfs_dirent of interest | |
68 | * | |
69 | * Get dentry for @sd. Dentry is looked up if currently not | |
70 | * present. This function climbs sysfs_dirent tree till it | |
71 | * reaches a sysfs_dirent with valid dentry attached and descends | |
72 | * down from there looking up dentry for each step. | |
73 | * | |
74 | * LOCKING: | |
75 | * Kernel thread context (may sleep) | |
76 | * | |
77 | * RETURNS: | |
78 | * Pointer to found dentry on success, ERR_PTR() value on error. | |
79 | */ | |
80 | struct dentry *sysfs_get_dentry(struct sysfs_dirent *sd) | |
81 | { | |
82 | struct sysfs_dirent *cur; | |
83 | struct dentry *parent_dentry, *dentry; | |
84 | int i, depth; | |
85 | ||
86 | /* Find the first parent which has valid s_dentry and get the | |
87 | * dentry. | |
88 | */ | |
89 | mutex_lock(&sysfs_mutex); | |
90 | restart0: | |
91 | spin_lock(&sysfs_assoc_lock); | |
92 | restart1: | |
93 | spin_lock(&dcache_lock); | |
94 | ||
95 | dentry = NULL; | |
96 | depth = 0; | |
97 | cur = sd; | |
98 | while (!cur->s_dentry || !cur->s_dentry->d_inode) { | |
99 | if (cur->s_flags & SYSFS_FLAG_REMOVED) { | |
100 | dentry = ERR_PTR(-ENOENT); | |
101 | depth = 0; | |
102 | break; | |
103 | } | |
104 | cur = cur->s_parent; | |
105 | depth++; | |
106 | } | |
107 | if (!IS_ERR(dentry)) | |
108 | dentry = dget_locked(cur->s_dentry); | |
109 | ||
110 | spin_unlock(&dcache_lock); | |
111 | spin_unlock(&sysfs_assoc_lock); | |
112 | ||
113 | /* from the found dentry, look up depth times */ | |
114 | while (depth--) { | |
115 | /* find and get depth'th ancestor */ | |
116 | for (cur = sd, i = 0; cur && i < depth; i++) | |
117 | cur = cur->s_parent; | |
118 | ||
119 | /* This can happen if tree structure was modified due | |
120 | * to move/rename. Restart. | |
121 | */ | |
122 | if (i != depth) { | |
123 | dput(dentry); | |
124 | goto restart0; | |
125 | } | |
126 | ||
127 | sysfs_get(cur); | |
128 | ||
129 | mutex_unlock(&sysfs_mutex); | |
130 | ||
131 | /* look it up */ | |
132 | parent_dentry = dentry; | |
133 | dentry = lookup_one_len_kern(cur->s_name, parent_dentry, | |
134 | strlen(cur->s_name)); | |
135 | dput(parent_dentry); | |
136 | ||
137 | if (IS_ERR(dentry)) { | |
138 | sysfs_put(cur); | |
139 | return dentry; | |
140 | } | |
141 | ||
142 | mutex_lock(&sysfs_mutex); | |
143 | spin_lock(&sysfs_assoc_lock); | |
144 | ||
145 | /* This, again, can happen if tree structure has | |
146 | * changed and we looked up the wrong thing. Restart. | |
147 | */ | |
148 | if (cur->s_dentry != dentry) { | |
149 | dput(dentry); | |
150 | sysfs_put(cur); | |
151 | goto restart1; | |
152 | } | |
153 | ||
154 | spin_unlock(&sysfs_assoc_lock); | |
155 | ||
156 | sysfs_put(cur); | |
157 | } | |
158 | ||
159 | mutex_unlock(&sysfs_mutex); | |
160 | return dentry; | |
161 | } | |
162 | ||
b6b4a439 TH |
163 | /** |
164 | * sysfs_get_active - get an active reference to sysfs_dirent | |
165 | * @sd: sysfs_dirent to get an active reference to | |
166 | * | |
167 | * Get an active reference of @sd. This function is noop if @sd | |
168 | * is NULL. | |
169 | * | |
170 | * RETURNS: | |
171 | * Pointer to @sd on success, NULL on failure. | |
172 | */ | |
173 | struct sysfs_dirent *sysfs_get_active(struct sysfs_dirent *sd) | |
174 | { | |
8619f979 TH |
175 | if (unlikely(!sd)) |
176 | return NULL; | |
177 | ||
178 | while (1) { | |
179 | int v, t; | |
180 | ||
181 | v = atomic_read(&sd->s_active); | |
182 | if (unlikely(v < 0)) | |
183 | return NULL; | |
184 | ||
185 | t = atomic_cmpxchg(&sd->s_active, v, v + 1); | |
186 | if (likely(t == v)) | |
187 | return sd; | |
188 | if (t < 0) | |
189 | return NULL; | |
190 | ||
191 | cpu_relax(); | |
b6b4a439 | 192 | } |
b6b4a439 TH |
193 | } |
194 | ||
195 | /** | |
196 | * sysfs_put_active - put an active reference to sysfs_dirent | |
197 | * @sd: sysfs_dirent to put an active reference to | |
198 | * | |
199 | * Put an active reference to @sd. This function is noop if @sd | |
200 | * is NULL. | |
201 | */ | |
202 | void sysfs_put_active(struct sysfs_dirent *sd) | |
203 | { | |
8619f979 TH |
204 | struct completion *cmpl; |
205 | int v; | |
206 | ||
207 | if (unlikely(!sd)) | |
208 | return; | |
209 | ||
210 | v = atomic_dec_return(&sd->s_active); | |
211 | if (likely(v != SD_DEACTIVATED_BIAS)) | |
212 | return; | |
213 | ||
214 | /* atomic_dec_return() is a mb(), we'll always see the updated | |
0c73f18b | 215 | * sd->s_sibling. |
8619f979 | 216 | */ |
0c73f18b | 217 | cmpl = (void *)sd->s_sibling; |
8619f979 | 218 | complete(cmpl); |
b6b4a439 TH |
219 | } |
220 | ||
221 | /** | |
222 | * sysfs_get_active_two - get active references to sysfs_dirent and parent | |
223 | * @sd: sysfs_dirent of interest | |
224 | * | |
225 | * Get active reference to @sd and its parent. Parent's active | |
226 | * reference is grabbed first. This function is noop if @sd is | |
227 | * NULL. | |
228 | * | |
229 | * RETURNS: | |
230 | * Pointer to @sd on success, NULL on failure. | |
231 | */ | |
232 | struct sysfs_dirent *sysfs_get_active_two(struct sysfs_dirent *sd) | |
233 | { | |
234 | if (sd) { | |
235 | if (sd->s_parent && unlikely(!sysfs_get_active(sd->s_parent))) | |
236 | return NULL; | |
237 | if (unlikely(!sysfs_get_active(sd))) { | |
238 | sysfs_put_active(sd->s_parent); | |
239 | return NULL; | |
240 | } | |
241 | } | |
242 | return sd; | |
243 | } | |
244 | ||
245 | /** | |
246 | * sysfs_put_active_two - put active references to sysfs_dirent and parent | |
247 | * @sd: sysfs_dirent of interest | |
248 | * | |
249 | * Put active references to @sd and its parent. This function is | |
250 | * noop if @sd is NULL. | |
251 | */ | |
252 | void sysfs_put_active_two(struct sysfs_dirent *sd) | |
253 | { | |
254 | if (sd) { | |
255 | sysfs_put_active(sd); | |
256 | sysfs_put_active(sd->s_parent); | |
257 | } | |
258 | } | |
259 | ||
260 | /** | |
261 | * sysfs_deactivate - deactivate sysfs_dirent | |
262 | * @sd: sysfs_dirent to deactivate | |
263 | * | |
8619f979 | 264 | * Deny new active references and drain existing ones. |
b6b4a439 | 265 | */ |
fb6896da | 266 | static void sysfs_deactivate(struct sysfs_dirent *sd) |
b6b4a439 | 267 | { |
8619f979 TH |
268 | DECLARE_COMPLETION_ONSTACK(wait); |
269 | int v; | |
b6b4a439 | 270 | |
380e6fbb | 271 | BUG_ON(sd->s_sibling || !(sd->s_flags & SYSFS_FLAG_REMOVED)); |
0c73f18b | 272 | sd->s_sibling = (void *)&wait; |
8619f979 TH |
273 | |
274 | /* atomic_add_return() is a mb(), put_active() will always see | |
0c73f18b | 275 | * the updated sd->s_sibling. |
b6b4a439 | 276 | */ |
8619f979 TH |
277 | v = atomic_add_return(SD_DEACTIVATED_BIAS, &sd->s_active); |
278 | ||
279 | if (v != SD_DEACTIVATED_BIAS) | |
280 | wait_for_completion(&wait); | |
281 | ||
0c73f18b | 282 | sd->s_sibling = NULL; |
b6b4a439 TH |
283 | } |
284 | ||
42b37df6 | 285 | static int sysfs_alloc_ino(ino_t *pino) |
2b611bb7 TH |
286 | { |
287 | int ino, rc; | |
288 | ||
289 | retry: | |
290 | spin_lock(&sysfs_ino_lock); | |
291 | rc = ida_get_new_above(&sysfs_ino_ida, 2, &ino); | |
292 | spin_unlock(&sysfs_ino_lock); | |
293 | ||
294 | if (rc == -EAGAIN) { | |
295 | if (ida_pre_get(&sysfs_ino_ida, GFP_KERNEL)) | |
296 | goto retry; | |
297 | rc = -ENOMEM; | |
298 | } | |
299 | ||
300 | *pino = ino; | |
301 | return rc; | |
302 | } | |
303 | ||
304 | static void sysfs_free_ino(ino_t ino) | |
305 | { | |
306 | spin_lock(&sysfs_ino_lock); | |
307 | ida_remove(&sysfs_ino_ida, ino); | |
308 | spin_unlock(&sysfs_ino_lock); | |
309 | } | |
310 | ||
fa7f912a TH |
311 | void release_sysfs_dirent(struct sysfs_dirent * sd) |
312 | { | |
13b3086d TH |
313 | struct sysfs_dirent *parent_sd; |
314 | ||
315 | repeat: | |
3007e997 TH |
316 | /* Moving/renaming is always done while holding reference. |
317 | * sd->s_parent won't change beneath us. | |
318 | */ | |
13b3086d TH |
319 | parent_sd = sd->s_parent; |
320 | ||
b402d72c | 321 | if (sysfs_type(sd) == SYSFS_KOBJ_LINK) |
2b29ac25 | 322 | sysfs_put(sd->s_elem.symlink.target_sd); |
b402d72c | 323 | if (sysfs_type(sd) & SYSFS_COPY_NAME) |
0c096b50 | 324 | kfree(sd->s_name); |
fa7f912a | 325 | kfree(sd->s_iattr); |
2b611bb7 | 326 | sysfs_free_ino(sd->s_ino); |
fa7f912a | 327 | kmem_cache_free(sysfs_dir_cachep, sd); |
13b3086d TH |
328 | |
329 | sd = parent_sd; | |
330 | if (sd && atomic_dec_and_test(&sd->s_count)) | |
331 | goto repeat; | |
fa7f912a TH |
332 | } |
333 | ||
1da177e4 LT |
334 | static void sysfs_d_iput(struct dentry * dentry, struct inode * inode) |
335 | { | |
336 | struct sysfs_dirent * sd = dentry->d_fsdata; | |
337 | ||
338 | if (sd) { | |
5f995323 TH |
339 | /* sd->s_dentry is protected with sysfs_assoc_lock. |
340 | * This allows sysfs_drop_dentry() to dereference it. | |
dd14cbc9 | 341 | */ |
5f995323 | 342 | spin_lock(&sysfs_assoc_lock); |
dd14cbc9 TH |
343 | |
344 | /* The dentry might have been deleted or another | |
345 | * lookup could have happened updating sd->s_dentry to | |
346 | * point the new dentry. Ignore if it isn't pointing | |
347 | * to this dentry. | |
348 | */ | |
349 | if (sd->s_dentry == dentry) | |
350 | sd->s_dentry = NULL; | |
5f995323 | 351 | spin_unlock(&sysfs_assoc_lock); |
1da177e4 LT |
352 | sysfs_put(sd); |
353 | } | |
354 | iput(inode); | |
355 | } | |
356 | ||
357 | static struct dentry_operations sysfs_dentry_ops = { | |
358 | .d_iput = sysfs_d_iput, | |
359 | }; | |
360 | ||
3e519038 | 361 | struct sysfs_dirent *sysfs_new_dirent(const char *name, umode_t mode, int type) |
1da177e4 | 362 | { |
0c096b50 | 363 | char *dup_name = NULL; |
01da2425 | 364 | struct sysfs_dirent *sd; |
0c096b50 TH |
365 | |
366 | if (type & SYSFS_COPY_NAME) { | |
367 | name = dup_name = kstrdup(name, GFP_KERNEL); | |
368 | if (!name) | |
01da2425 | 369 | return NULL; |
0c096b50 | 370 | } |
1da177e4 | 371 | |
c3762229 | 372 | sd = kmem_cache_zalloc(sysfs_dir_cachep, GFP_KERNEL); |
1da177e4 | 373 | if (!sd) |
01da2425 | 374 | goto err_out1; |
1da177e4 | 375 | |
0c096b50 | 376 | if (sysfs_alloc_ino(&sd->s_ino)) |
01da2425 | 377 | goto err_out2; |
2b611bb7 | 378 | |
1da177e4 | 379 | atomic_set(&sd->s_count, 1); |
8619f979 | 380 | atomic_set(&sd->s_active, 0); |