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Commit | Line | Data |
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1da177e4 LT |
1 | /* |
2 | * Directory notifications for Linux. | |
3 | * | |
4 | * Copyright (C) 2000,2001,2002 Stephen Rothwell | |
5 | * | |
3c5119c0 EP |
6 | * Copyright (C) 2009 Eric Paris <Red Hat Inc> |
7 | * dnotify was largly rewritten to use the new fsnotify infrastructure | |
8 | * | |
1da177e4 LT |
9 | * This program is free software; you can redistribute it and/or modify it |
10 | * under the terms of the GNU General Public License as published by the | |
11 | * Free Software Foundation; either version 2, or (at your option) any | |
12 | * later version. | |
13 | * | |
14 | * This program is distributed in the hope that it will be useful, but | |
15 | * WITHOUT ANY WARRANTY; without even the implied warranty of | |
16 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
17 | * General Public License for more details. | |
18 | */ | |
19 | #include <linux/fs.h> | |
20 | #include <linux/module.h> | |
21 | #include <linux/sched.h> | |
22 | #include <linux/dnotify.h> | |
23 | #include <linux/init.h> | |
24 | #include <linux/spinlock.h> | |
25 | #include <linux/slab.h> | |
9f3acc31 | 26 | #include <linux/fdtable.h> |
3c5119c0 | 27 | #include <linux/fsnotify_backend.h> |
1da177e4 | 28 | |
fa3536cc | 29 | int dir_notify_enable __read_mostly = 1; |
1da177e4 | 30 | |
3c5119c0 | 31 | static struct kmem_cache *dnotify_struct_cache __read_mostly; |
ef5e2b78 | 32 | static struct kmem_cache *dnotify_mark_cache __read_mostly; |
3c5119c0 | 33 | static struct fsnotify_group *dnotify_group __read_mostly; |
3c5119c0 EP |
34 | |
35 | /* | |
e61ce867 | 36 | * dnotify will attach one of these to each inode (i_fsnotify_marks) which |
3c5119c0 EP |
37 | * is being watched by dnotify. If multiple userspace applications are watching |
38 | * the same directory with dnotify their information is chained in dn | |
39 | */ | |
ef5e2b78 EP |
40 | struct dnotify_mark { |
41 | struct fsnotify_mark fsn_mark; | |
3c5119c0 EP |
42 | struct dnotify_struct *dn; |
43 | }; | |
1da177e4 | 44 | |
3c5119c0 EP |
45 | /* |
46 | * When a process starts or stops watching an inode the set of events which | |
47 | * dnotify cares about for that inode may change. This function runs the | |
48 | * list of everything receiving dnotify events about this directory and calculates | |
49 | * the set of all those events. After it updates what dnotify is interested in | |
50 | * it calls the fsnotify function so it can update the set of all events relevant | |
51 | * to this inode. | |
52 | */ | |
ef5e2b78 | 53 | static void dnotify_recalc_inode_mask(struct fsnotify_mark *fsn_mark) |
1da177e4 | 54 | { |
3c5119c0 | 55 | __u32 new_mask, old_mask; |
1da177e4 | 56 | struct dnotify_struct *dn; |
ef5e2b78 EP |
57 | struct dnotify_mark *dn_mark = container_of(fsn_mark, |
58 | struct dnotify_mark, | |
59 | fsn_mark); | |
3c5119c0 | 60 | |
ef5e2b78 | 61 | assert_spin_locked(&fsn_mark->lock); |
1da177e4 | 62 | |
ef5e2b78 | 63 | old_mask = fsn_mark->mask; |
1da177e4 | 64 | new_mask = 0; |
ef5e2b78 | 65 | for (dn = dn_mark->dn; dn != NULL; dn = dn->dn_next) |
3c5119c0 | 66 | new_mask |= (dn->dn_mask & ~FS_DN_MULTISHOT); |
90b1e7a5 | 67 | fsnotify_set_mark_mask_locked(fsn_mark, new_mask); |
3c5119c0 EP |
68 | |
69 | if (old_mask == new_mask) | |
70 | return; | |
71 | ||
0809ab69 JK |
72 | if (fsn_mark->inode) |
73 | fsnotify_recalc_inode_mask(fsn_mark->inode); | |
1da177e4 LT |
74 | } |
75 | ||
3c5119c0 EP |
76 | /* |
77 | * Mains fsnotify call where events are delivered to dnotify. | |
78 | * Find the dnotify mark on the relevant inode, run the list of dnotify structs | |
79 | * on that mark and determine which of them has expressed interest in receiving | |
80 | * events of this type. When found send the correct process and signal and | |
81 | * destroy the dnotify struct if it was not registered to receive multiple | |
82 | * events. | |
83 | */ | |
84 | static int dnotify_handle_event(struct fsnotify_group *group, | |
7053aee2 | 85 | struct inode *inode, |
ce8f76fb EP |
86 | struct fsnotify_mark *inode_mark, |
87 | struct fsnotify_mark *vfsmount_mark, | |
7053aee2 | 88 | u32 mask, void *data, int data_type, |
45a22f4c | 89 | const unsigned char *file_name, u32 cookie) |
3c5119c0 | 90 | { |
ef5e2b78 | 91 | struct dnotify_mark *dn_mark; |
3c5119c0 EP |
92 | struct dnotify_struct *dn; |
93 | struct dnotify_struct **prev; | |
94 | struct fown_struct *fown; | |
7053aee2 | 95 | __u32 test_mask = mask & ~FS_EVENT_ON_CHILD; |
3c5119c0 | 96 | |
83c4c4b0 JK |
97 | /* not a dir, dnotify doesn't care */ |
98 | if (!S_ISDIR(inode->i_mode)) | |
99 | return 0; | |
100 | ||
ce8f76fb EP |
101 | BUG_ON(vfsmount_mark); |
102 | ||
ce8f76fb | 103 | dn_mark = container_of(inode_mark, struct dnotify_mark, fsn_mark); |
3c5119c0 | 104 | |
ce8f76fb | 105 | spin_lock(&inode_mark->lock); |
ef5e2b78 | 106 | prev = &dn_mark->dn; |
3c5119c0 | 107 | while ((dn = *prev) != NULL) { |
94552684 | 108 | if ((dn->dn_mask & test_mask) == 0) { |
3c5119c0 EP |
109 | prev = &dn->dn_next; |
110 | continue; | |
111 | } | |
112 | fown = &dn->dn_filp->f_owner; | |
113 | send_sigio(fown, dn->dn_fd, POLL_MSG); | |
114 | if (dn->dn_mask & FS_DN_MULTISHOT) | |
115 | prev = &dn->dn_next; | |
116 | else { | |
117 | *prev = dn->dn_next; | |
118 | kmem_cache_free(dnotify_struct_cache, dn); | |
ce8f76fb | 119 | dnotify_recalc_inode_mask(inode_mark); |
3c5119c0 EP |
120 | } |
121 | } | |
122 | ||
ce8f76fb | 123 | spin_unlock(&inode_mark->lock); |
3c5119c0 EP |
124 | |
125 | return 0; | |
126 | } | |
127 | ||
ef5e2b78 | 128 | static void dnotify_free_mark(struct fsnotify_mark *fsn_mark) |
3c5119c0 | 129 | { |
ef5e2b78 EP |
130 | struct dnotify_mark *dn_mark = container_of(fsn_mark, |
131 | struct dnotify_mark, | |
132 | fsn_mark); | |
3c5119c0 | 133 | |
ef5e2b78 | 134 | BUG_ON(dn_mark->dn); |
3c5119c0 | 135 | |
ef5e2b78 | 136 | kmem_cache_free(dnotify_mark_cache, dn_mark); |
3c5119c0 EP |
137 | } |
138 | ||
139 | static struct fsnotify_ops dnotify_fsnotify_ops = { | |
140 | .handle_event = dnotify_handle_event, | |
3c5119c0 EP |
141 | }; |
142 | ||
143 | /* | |
144 | * Called every time a file is closed. Looks first for a dnotify mark on the | |
e61ce867 | 145 | * inode. If one is found run all of the ->dn structures attached to that |
3c5119c0 EP |
146 | * mark for one relevant to this process closing the file and remove that |
147 | * dnotify_struct. If that was the last dnotify_struct also remove the | |
e61ce867 | 148 | * fsnotify_mark. |
3c5119c0 | 149 | */ |
1da177e4 LT |
150 | void dnotify_flush(struct file *filp, fl_owner_t id) |
151 | { | |
ef5e2b78 EP |
152 | struct fsnotify_mark *fsn_mark; |
153 | struct dnotify_mark *dn_mark; | |
1da177e4 LT |
154 | struct dnotify_struct *dn; |
155 | struct dnotify_struct **prev; | |
156 | struct inode *inode; | |
4712e722 | 157 | bool free = false; |
1da177e4 | 158 | |
496ad9aa | 159 | inode = file_inode(filp); |
1da177e4 LT |
160 | if (!S_ISDIR(inode->i_mode)) |
161 | return; | |
3c5119c0 | 162 | |
5444e298 | 163 | fsn_mark = fsnotify_find_inode_mark(dnotify_group, inode); |
ef5e2b78 | 164 | if (!fsn_mark) |
3c5119c0 | 165 | return; |
ef5e2b78 | 166 | dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark); |
3c5119c0 | 167 | |
52f85729 | 168 | mutex_lock(&dnotify_group->mark_mutex); |
3c5119c0 | 169 | |
ef5e2b78 EP |
170 | spin_lock(&fsn_mark->lock); |
171 | prev = &dn_mark->dn; | |
1da177e4 LT |
172 | while ((dn = *prev) != NULL) { |
173 | if ((dn->dn_owner == id) && (dn->dn_filp == filp)) { | |
174 | *prev = dn->dn_next; | |
3c5119c0 | 175 | kmem_cache_free(dnotify_struct_cache, dn); |
ef5e2b78 | 176 | dnotify_recalc_inode_mask(fsn_mark); |
1da177e4 LT |
177 | break; |
178 | } | |
179 | prev = &dn->dn_next; | |
180 | } | |
3c5119c0 | 181 | |
ef5e2b78 | 182 | spin_unlock(&fsn_mark->lock); |
3c5119c0 | 183 | |
52f85729 LS |
184 | /* nothing else could have found us thanks to the dnotify_groups |
185 | mark_mutex */ | |
4712e722 JK |
186 | if (dn_mark->dn == NULL) { |
187 | fsnotify_detach_mark(fsn_mark); | |
188 | free = true; | |
189 | } | |
3c5119c0 | 190 | |
52f85729 | 191 | mutex_unlock(&dnotify_group->mark_mutex); |
3c5119c0 | 192 | |
4712e722 JK |
193 | if (free) |
194 | fsnotify_free_mark(fsn_mark); | |
ef5e2b78 | 195 | fsnotify_put_mark(fsn_mark); |
3c5119c0 EP |
196 | } |
197 | ||
198 | /* this conversion is done only at watch creation */ | |
199 | static __u32 convert_arg(unsigned long arg) | |
200 | { | |
201 | __u32 new_mask = FS_EVENT_ON_CHILD; | |
202 | ||
203 | if (arg & DN_MULTISHOT) | |
204 | new_mask |= FS_DN_MULTISHOT; | |
205 | if (arg & DN_DELETE) | |
206 | new_mask |= (FS_DELETE | FS_MOVED_FROM); | |
207 | if (arg & DN_MODIFY) | |
208 | new_mask |= FS_MODIFY; | |
209 | if (arg & DN_ACCESS) | |
210 | new_mask |= FS_ACCESS; | |
211 | if (arg & DN_ATTRIB) | |
212 | new_mask |= FS_ATTRIB; | |
213 | if (arg & DN_RENAME) | |
214 | new_mask |= FS_DN_RENAME; | |
215 | if (arg & DN_CREATE) | |
216 | new_mask |= (FS_CREATE | FS_MOVED_TO); | |
217 | ||
218 | return new_mask; | |
1da177e4 LT |
219 | } |
220 | ||
3c5119c0 EP |
221 | /* |
222 | * If multiple processes watch the same inode with dnotify there is only one | |
e61ce867 | 223 | * dnotify mark in inode->i_fsnotify_marks but we chain a dnotify_struct |
3c5119c0 EP |
224 | * onto that mark. This function either attaches the new dnotify_struct onto |
225 | * that list, or it |= the mask onto an existing dnofiy_struct. | |
226 | */ | |
ef5e2b78 | 227 | static int attach_dn(struct dnotify_struct *dn, struct dnotify_mark *dn_mark, |
3c5119c0 EP |
228 | fl_owner_t id, int fd, struct file *filp, __u32 mask) |
229 | { | |
230 | struct dnotify_struct *odn; | |
231 | ||
ef5e2b78 | 232 | odn = dn_mark->dn; |
3c5119c0 EP |
233 | while (odn != NULL) { |
234 | /* adding more events to existing dnofiy_struct? */ | |
235 | if ((odn->dn_owner == id) && (odn->dn_filp == filp)) { | |
236 | odn->dn_fd = fd; | |
237 | odn->dn_mask |= mask; | |
238 | return -EEXIST; | |
239 | } | |
240 | odn = odn->dn_next; | |
241 | } | |
242 | ||
243 | dn->dn_mask = mask; | |
244 | dn->dn_fd = fd; | |
245 | dn->dn_filp = filp; | |
246 | dn->dn_owner = id; | |
ef5e2b78 EP |
247 | dn->dn_next = dn_mark->dn; |
248 | dn_mark->dn = dn; | |
3c5119c0 EP |
249 | |
250 | return 0; | |
251 | } | |
252 | ||
253 | /* | |
254 | * When a process calls fcntl to attach a dnotify watch to a directory it ends | |
255 | * up here. Allocate both a mark for fsnotify to add and a dnotify_struct to be | |
256 | * attached to the fsnotify_mark. | |
257 | */ | |
1da177e4 LT |
258 | int fcntl_dirnotify(int fd, struct file *filp, unsigned long arg) |
259 | { | |
ef5e2b78 EP |
260 | struct dnotify_mark *new_dn_mark, *dn_mark; |
261 | struct fsnotify_mark *new_fsn_mark, *fsn_mark; | |
1da177e4 | 262 | struct dnotify_struct *dn; |
1da177e4 LT |
263 | struct inode *inode; |
264 | fl_owner_t id = current->files; | |
214b7049 | 265 | struct file *f; |
3c5119c0 EP |
266 | int destroy = 0, error = 0; |
267 | __u32 mask; | |
268 | ||
269 | /* we use these to tell if we need to kfree */ | |
ef5e2b78 | 270 | new_fsn_mark = NULL; |
3c5119c0 | 271 | dn = NULL; |
1da177e4 | 272 | |
3c5119c0 EP |
273 | if (!dir_notify_enable) { |
274 | error = -EINVAL; | |
275 | goto out_err; | |
276 | } | |
277 | ||
278 | /* a 0 mask means we are explicitly removing the watch */ | |
1da177e4 LT |
279 | if ((arg & ~DN_MULTISHOT) == 0) { |
280 | dnotify_flush(filp, id); | |
3c5119c0 EP |
281 | error = 0; |
282 | goto out_err; | |
1da177e4 | 283 | } |
3c5119c0 EP |
284 | |
285 | /* dnotify only works on directories */ | |
496ad9aa | 286 | inode = file_inode(filp); |
3c5119c0 EP |
287 | if (!S_ISDIR(inode->i_mode)) { |
288 | error = -ENOTDIR; | |
289 | goto out_err; | |
1da177e4 LT |
290 | } |
291 | ||
3c5119c0 EP |
292 | /* expect most fcntl to add new rather than augment old */ |
293 | dn = kmem_cache_alloc(dnotify_struct_cache, GFP_KERNEL); | |
294 | if (!dn) { | |
295 | error = -ENOMEM; | |
296 | goto out_err; | |
297 | } | |
214b7049 | 298 | |
3c5119c0 | 299 | /* new fsnotify mark, we expect most fcntl calls to add a new mark */ |
ef5e2b78 EP |
300 | new_dn_mark = kmem_cache_alloc(dnotify_mark_cache, GFP_KERNEL); |
301 | if (!new_dn_mark) { | |
3c5119c0 EP |
302 | error = -ENOMEM; |
303 | goto out_err; | |
304 | } | |
1da177e4 | 305 | |
3c5119c0 EP |
306 | /* convert the userspace DN_* "arg" to the internal FS_* defines in fsnotify */ |
307 | mask = convert_arg(arg); | |
1da177e4 | 308 | |
ef5e2b78 EP |
309 | /* set up the new_fsn_mark and new_dn_mark */ |
310 | new_fsn_mark = &new_dn_mark->fsn_mark; | |
311 | fsnotify_init_mark(new_fsn_mark, dnotify_free_mark); | |
312 | new_fsn_mark->mask = mask; | |
313 | new_dn_mark->dn = NULL; | |
1da177e4 | 314 | |
3c5119c0 | 315 | /* this is needed to prevent the fcntl/close race described below */ |
52f85729 | 316 | mutex_lock(&dnotify_group->mark_mutex); |
1da177e4 | 317 | |
ef5e2b78 | 318 | /* add the new_fsn_mark or find an old one. */ |
5444e298 | 319 | fsn_mark = fsnotify_find_inode_mark(dnotify_group, inode); |
ef5e2b78 EP |
320 | if (fsn_mark) { |
321 | dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark); | |
322 | spin_lock(&fsn_mark->lock); | |
3c5119c0 | 323 | } else { |
52f85729 LS |
324 | fsnotify_add_mark_locked(new_fsn_mark, dnotify_group, inode, |
325 | NULL, 0); | |
ef5e2b78 EP |
326 | spin_lock(&new_fsn_mark->lock); |
327 | fsn_mark = new_fsn_mark; | |
328 | dn_mark = new_dn_mark; | |
329 | /* we used new_fsn_mark, so don't free it */ | |
330 | new_fsn_mark = NULL; | |
3c5119c0 | 331 | } |
1da177e4 | 332 | |
3c5119c0 EP |
333 | rcu_read_lock(); |
334 | f = fcheck(fd); | |
335 | rcu_read_unlock(); | |
1da177e4 | 336 | |
3c5119c0 EP |
337 | /* if (f != filp) means that we lost a race and another task/thread |
338 | * actually closed the fd we are still playing with before we grabbed | |
52f85729 LS |
339 | * the dnotify_groups mark_mutex and fsn_mark->lock. Since closing the |
340 | * fd is the only time we clean up the marks we need to get our mark | |
341 | * off the list. */ | |
3c5119c0 EP |
342 | if (f != filp) { |
343 | /* if we added ourselves, shoot ourselves, it's possible that | |
ef5e2b78 | 344 | * the flush actually did shoot this fsn_mark. That's fine too |
3c5119c0 | 345 | * since multiple calls to destroy_mark is perfectly safe, if |
ef5e2b78 | 346 | * we found a dn_mark already attached to the inode, just sod |
3c5119c0 EP |
347 | * off silently as the flush at close time dealt with it. |
348 | */ | |
ef5e2b78 | 349 | if (dn_mark == new_dn_mark) |
3c5119c0 EP |
350 | destroy = 1; |
351 | goto out; | |
352 | } | |
1da177e4 | 353 | |
e0b93edd | 354 | __f_setown(filp, task_pid(current), PIDTYPE_PID, 0); |
3c5119c0 | 355 | |
ef5e2b78 EP |
356 | error = attach_dn(dn, dn_mark, id, fd, filp, mask); |
357 | /* !error means that we attached the dn to the dn_mark, so don't free it */ | |
3c5119c0 EP |
358 | if (!error) |
359 | dn = NULL; | |
360 | /* -EEXIST means that we didn't add this new dn and used an old one. | |
361 | * that isn't an error (and the unused dn should be freed) */ | |
362 | else if (error == -EEXIST) | |
363 | error = 0; | |
364 | ||
ef5e2b78 | 365 | dnotify_recalc_inode_mask(fsn_mark); |
3c5119c0 | 366 | out: |
ef5e2b78 | 367 | spin_unlock(&fsn_mark->lock); |
3c5119c0 EP |
368 | |
369 | if (destroy) | |
4712e722 | 370 | fsnotify_detach_mark(fsn_mark); |
52f85729 | 371 | mutex_unlock(&dnotify_group->mark_mutex); |
4712e722 JK |
372 | if (destroy) |
373 | fsnotify_free_mark(fsn_mark); | |
ef5e2b78 | 374 | fsnotify_put_mark(fsn_mark); |
3c5119c0 | 375 | out_err: |
ef5e2b78 EP |
376 | if (new_fsn_mark) |
377 | fsnotify_put_mark(new_fsn_mark); | |
3c5119c0 EP |
378 | if (dn) |
379 | kmem_cache_free(dnotify_struct_cache, dn); | |
380 | return error; | |
1da177e4 | 381 | } |
1da177e4 LT |
382 | |
383 | static int __init dnotify_init(void) | |
384 | { | |
3c5119c0 | 385 | dnotify_struct_cache = KMEM_CACHE(dnotify_struct, SLAB_PANIC); |
ef5e2b78 | 386 | dnotify_mark_cache = KMEM_CACHE(dnotify_mark, SLAB_PANIC); |
3c5119c0 | 387 | |
0d2e2a1d | 388 | dnotify_group = fsnotify_alloc_group(&dnotify_fsnotify_ops); |
3c5119c0 EP |
389 | if (IS_ERR(dnotify_group)) |
390 | panic("unable to allocate fsnotify group for dnotify\n"); | |
1da177e4 LT |
391 | return 0; |
392 | } | |
393 | ||
394 | module_init(dnotify_init) |