Commit | Line | Data |
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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> |
94bebf4d | 14 | #include <asm/semaphore.h> |
1da177e4 LT |
15 | #include "sysfs.h" |
16 | ||
17 | DECLARE_RWSEM(sysfs_rename_sem); | |
dd14cbc9 | 18 | spinlock_t sysfs_lock = SPIN_LOCK_UNLOCKED; |
aecdceda | 19 | spinlock_t kobj_sysfs_assoc_lock = SPIN_LOCK_UNLOCKED; |
1da177e4 | 20 | |
2b611bb7 TH |
21 | static spinlock_t sysfs_ino_lock = SPIN_LOCK_UNLOCKED; |
22 | static DEFINE_IDA(sysfs_ino_ida); | |
23 | ||
0c73f18b TH |
24 | /** |
25 | * sysfs_link_sibling - link sysfs_dirent into sibling list | |
26 | * @sd: sysfs_dirent of interest | |
27 | * | |
28 | * Link @sd into its sibling list which starts from | |
29 | * sd->s_parent->s_children. | |
30 | * | |
31 | * Locking: | |
32 | * mutex_lock(sd->s_parent->dentry->d_inode->i_mutex) | |
33 | */ | |
34 | static void sysfs_link_sibling(struct sysfs_dirent *sd) | |
35 | { | |
36 | struct sysfs_dirent *parent_sd = sd->s_parent; | |
37 | ||
38 | BUG_ON(sd->s_sibling); | |
39 | sd->s_sibling = parent_sd->s_children; | |
40 | parent_sd->s_children = sd; | |
41 | } | |
42 | ||
43 | /** | |
44 | * sysfs_unlink_sibling - unlink sysfs_dirent from sibling list | |
45 | * @sd: sysfs_dirent of interest | |
46 | * | |
47 | * Unlink @sd from its sibling list which starts from | |
48 | * sd->s_parent->s_children. | |
49 | * | |
50 | * Locking: | |
51 | * mutex_lock(sd->s_parent->dentry->d_inode->i_mutex) | |
52 | */ | |
53 | static void sysfs_unlink_sibling(struct sysfs_dirent *sd) | |
54 | { | |
55 | struct sysfs_dirent **pos; | |
56 | ||
57 | for (pos = &sd->s_parent->s_children; *pos; pos = &(*pos)->s_sibling) { | |
58 | if (*pos == sd) { | |
59 | *pos = sd->s_sibling; | |
60 | sd->s_sibling = NULL; | |
61 | break; | |
62 | } | |
63 | } | |
64 | } | |
65 | ||
b6b4a439 TH |
66 | /** |
67 | * sysfs_get_active - get an active reference to sysfs_dirent | |
68 | * @sd: sysfs_dirent to get an active reference to | |
69 | * | |
70 | * Get an active reference of @sd. This function is noop if @sd | |
71 | * is NULL. | |
72 | * | |
73 | * RETURNS: | |
74 | * Pointer to @sd on success, NULL on failure. | |
75 | */ | |
76 | struct sysfs_dirent *sysfs_get_active(struct sysfs_dirent *sd) | |
77 | { | |
8619f979 TH |
78 | if (unlikely(!sd)) |
79 | return NULL; | |
80 | ||
81 | while (1) { | |
82 | int v, t; | |
83 | ||
84 | v = atomic_read(&sd->s_active); | |
85 | if (unlikely(v < 0)) | |
86 | return NULL; | |
87 | ||
88 | t = atomic_cmpxchg(&sd->s_active, v, v + 1); | |
89 | if (likely(t == v)) | |
90 | return sd; | |
91 | if (t < 0) | |
92 | return NULL; | |
93 | ||
94 | cpu_relax(); | |
b6b4a439 | 95 | } |
b6b4a439 TH |
96 | } |
97 | ||
98 | /** | |
99 | * sysfs_put_active - put an active reference to sysfs_dirent | |
100 | * @sd: sysfs_dirent to put an active reference to | |
101 | * | |
102 | * Put an active reference to @sd. This function is noop if @sd | |
103 | * is NULL. | |
104 | */ | |
105 | void sysfs_put_active(struct sysfs_dirent *sd) | |
106 | { | |
8619f979 TH |
107 | struct completion *cmpl; |
108 | int v; | |
109 | ||
110 | if (unlikely(!sd)) | |
111 | return; | |
112 | ||
113 | v = atomic_dec_return(&sd->s_active); | |
114 | if (likely(v != SD_DEACTIVATED_BIAS)) | |
115 | return; | |
116 | ||
117 | /* atomic_dec_return() is a mb(), we'll always see the updated | |
0c73f18b | 118 | * sd->s_sibling. |
8619f979 | 119 | */ |
0c73f18b | 120 | cmpl = (void *)sd->s_sibling; |
8619f979 | 121 | complete(cmpl); |
b6b4a439 TH |
122 | } |
123 | ||
124 | /** | |
125 | * sysfs_get_active_two - get active references to sysfs_dirent and parent | |
126 | * @sd: sysfs_dirent of interest | |
127 | * | |
128 | * Get active reference to @sd and its parent. Parent's active | |
129 | * reference is grabbed first. This function is noop if @sd is | |
130 | * NULL. | |
131 | * | |
132 | * RETURNS: | |
133 | * Pointer to @sd on success, NULL on failure. | |
134 | */ | |
135 | struct sysfs_dirent *sysfs_get_active_two(struct sysfs_dirent *sd) | |
136 | { | |
137 | if (sd) { | |
138 | if (sd->s_parent && unlikely(!sysfs_get_active(sd->s_parent))) | |
139 | return NULL; | |
140 | if (unlikely(!sysfs_get_active(sd))) { | |
141 | sysfs_put_active(sd->s_parent); | |
142 | return NULL; | |
143 | } | |
144 | } | |
145 | return sd; | |
146 | } | |
147 | ||
148 | /** | |
149 | * sysfs_put_active_two - put active references to sysfs_dirent and parent | |
150 | * @sd: sysfs_dirent of interest | |
151 | * | |
152 | * Put active references to @sd and its parent. This function is | |
153 | * noop if @sd is NULL. | |
154 | */ | |
155 | void sysfs_put_active_two(struct sysfs_dirent *sd) | |
156 | { | |
157 | if (sd) { | |
158 | sysfs_put_active(sd); | |
159 | sysfs_put_active(sd->s_parent); | |
160 | } | |
161 | } | |
162 | ||
163 | /** | |
164 | * sysfs_deactivate - deactivate sysfs_dirent | |
165 | * @sd: sysfs_dirent to deactivate | |
166 | * | |
8619f979 | 167 | * Deny new active references and drain existing ones. |
b6b4a439 TH |
168 | */ |
169 | void sysfs_deactivate(struct sysfs_dirent *sd) | |
170 | { | |
8619f979 TH |
171 | DECLARE_COMPLETION_ONSTACK(wait); |
172 | int v; | |
b6b4a439 | 173 | |
380e6fbb | 174 | BUG_ON(sd->s_sibling || !(sd->s_flags & SYSFS_FLAG_REMOVED)); |
0c73f18b | 175 | sd->s_sibling = (void *)&wait; |
8619f979 TH |
176 | |
177 | /* atomic_add_return() is a mb(), put_active() will always see | |
0c73f18b | 178 | * the updated sd->s_sibling. |
b6b4a439 | 179 | */ |
8619f979 TH |
180 | v = atomic_add_return(SD_DEACTIVATED_BIAS, &sd->s_active); |
181 | ||
182 | if (v != SD_DEACTIVATED_BIAS) | |
183 | wait_for_completion(&wait); | |
184 | ||
0c73f18b | 185 | sd->s_sibling = NULL; |
b6b4a439 TH |
186 | } |
187 | ||
42b37df6 | 188 | static int sysfs_alloc_ino(ino_t *pino) |
2b611bb7 TH |
189 | { |
190 | int ino, rc; | |
191 | ||
192 | retry: | |
193 | spin_lock(&sysfs_ino_lock); | |
194 | rc = ida_get_new_above(&sysfs_ino_ida, 2, &ino); | |
195 | spin_unlock(&sysfs_ino_lock); | |
196 | ||
197 | if (rc == -EAGAIN) { | |
198 | if (ida_pre_get(&sysfs_ino_ida, GFP_KERNEL)) | |
199 | goto retry; | |
200 | rc = -ENOMEM; | |
201 | } | |
202 | ||
203 | *pino = ino; | |
204 | return rc; | |
205 | } | |
206 | ||
207 | static void sysfs_free_ino(ino_t ino) | |
208 | { | |
209 | spin_lock(&sysfs_ino_lock); | |
210 | ida_remove(&sysfs_ino_ida, ino); | |
211 | spin_unlock(&sysfs_ino_lock); | |
212 | } | |
213 | ||
fa7f912a TH |
214 | void release_sysfs_dirent(struct sysfs_dirent * sd) |
215 | { | |
13b3086d TH |
216 | struct sysfs_dirent *parent_sd; |
217 | ||
218 | repeat: | |
219 | parent_sd = sd->s_parent; | |
220 | ||
b402d72c | 221 | if (sysfs_type(sd) == SYSFS_KOBJ_LINK) |
2b29ac25 | 222 | sysfs_put(sd->s_elem.symlink.target_sd); |
b402d72c | 223 | if (sysfs_type(sd) & SYSFS_COPY_NAME) |
0c096b50 | 224 | kfree(sd->s_name); |
fa7f912a | 225 | kfree(sd->s_iattr); |
2b611bb7 | 226 | sysfs_free_ino(sd->s_ino); |
fa7f912a | 227 | kmem_cache_free(sysfs_dir_cachep, sd); |
13b3086d TH |
228 | |
229 | sd = parent_sd; | |
230 | if (sd && atomic_dec_and_test(&sd->s_count)) | |
231 | goto repeat; | |
fa7f912a TH |
232 | } |
233 | ||
1da177e4 LT |
234 | static void sysfs_d_iput(struct dentry * dentry, struct inode * inode) |
235 | { | |
236 | struct sysfs_dirent * sd = dentry->d_fsdata; | |
237 | ||
238 | if (sd) { | |
dd14cbc9 TH |
239 | /* sd->s_dentry is protected with sysfs_lock. This |
240 | * allows sysfs_drop_dentry() to dereference it. | |
241 | */ | |
242 | spin_lock(&sysfs_lock); | |
243 | ||
244 | /* The dentry might have been deleted or another | |
245 | * lookup could have happened updating sd->s_dentry to | |
246 | * point the new dentry. Ignore if it isn't pointing | |
247 | * to this dentry. | |
248 | */ | |
249 | if (sd->s_dentry == dentry) | |
250 | sd->s_dentry = NULL; | |
251 | spin_unlock(&sysfs_lock); | |
1da177e4 LT |
252 | sysfs_put(sd); |
253 | } | |
254 | iput(inode); | |
255 | } | |
256 | ||
257 | static struct dentry_operations sysfs_dentry_ops = { | |
258 | .d_iput = sysfs_d_iput, | |
259 | }; | |
260 | ||
3e519038 | 261 | struct sysfs_dirent *sysfs_new_dirent(const char *name, umode_t mode, int type) |
1da177e4 | 262 | { |
0c096b50 TH |
263 | char *dup_name = NULL; |
264 | struct sysfs_dirent *sd = NULL; | |
265 | ||
266 | if (type & SYSFS_COPY_NAME) { | |
267 | name = dup_name = kstrdup(name, GFP_KERNEL); | |
268 | if (!name) | |
269 | goto err_out; | |
270 | } | |
1da177e4 | 271 | |
c3762229 | 272 | sd = kmem_cache_zalloc(sysfs_dir_cachep, GFP_KERNEL); |
1da177e4 | 273 | if (!sd) |
0c096b50 | 274 | goto err_out; |
1da177e4 | 275 | |
0c096b50 TH |
276 | if (sysfs_alloc_ino(&sd->s_ino)) |
277 | goto err_out; | |
2b611bb7 | 278 | |
1da177e4 | 279 | atomic_set(&sd->s_count, 1); |
8619f979 | 280 | atomic_set(&sd->s_active, 0); |