fsnotify: do not share events between notification groups
[deliverable/linux.git] / fs / notify / dnotify / dnotify.c
CommitLineData
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 29int dir_notify_enable __read_mostly = 1;
1da177e4 30
3c5119c0 31static struct kmem_cache *dnotify_struct_cache __read_mostly;
ef5e2b78 32static struct kmem_cache *dnotify_mark_cache __read_mostly;
3c5119c0 33static 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
40struct 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 53static 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
ef5e2b78
EP
72 if (fsn_mark->i.inode)
73 fsnotify_recalc_inode_mask(fsn_mark->i.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 */
84static 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
JK
88 u32 mask, void *data, int data_type,
89 const unsigned char *file_name)
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
ce8f76fb
EP
97 BUG_ON(vfsmount_mark);
98
ce8f76fb 99 dn_mark = container_of(inode_mark, struct dnotify_mark, fsn_mark);
3c5119c0 100
ce8f76fb 101 spin_lock(&inode_mark->lock);
ef5e2b78 102 prev = &dn_mark->dn;
3c5119c0 103 while ((dn = *prev) != NULL) {
94552684 104 if ((dn->dn_mask & test_mask) == 0) {
3c5119c0
EP
105 prev = &dn->dn_next;
106 continue;
107 }
108 fown = &dn->dn_filp->f_owner;
109 send_sigio(fown, dn->dn_fd, POLL_MSG);
110 if (dn->dn_mask & FS_DN_MULTISHOT)
111 prev = &dn->dn_next;
112 else {
113 *prev = dn->dn_next;
114 kmem_cache_free(dnotify_struct_cache, dn);
ce8f76fb 115 dnotify_recalc_inode_mask(inode_mark);
3c5119c0
EP
116 }
117 }
118
ce8f76fb 119 spin_unlock(&inode_mark->lock);
3c5119c0
EP
120
121 return 0;
122}
123
124/*
125 * Given an inode and mask determine if dnotify would be interested in sending
126 * userspace notification for that pair.
127 */
128static bool dnotify_should_send_event(struct fsnotify_group *group,
1968f5ee 129 struct inode *inode,
ce8f76fb
EP
130 struct fsnotify_mark *inode_mark,
131 struct fsnotify_mark *vfsmount_mark,
132 __u32 mask, void *data, int data_type)
3c5119c0 133{
3c5119c0
EP
134 /* not a dir, dnotify doesn't care */
135 if (!S_ISDIR(inode->i_mode))
136 return false;
137
2612abb5 138 return true;
3c5119c0
EP
139}
140
ef5e2b78 141static void dnotify_free_mark(struct fsnotify_mark *fsn_mark)
3c5119c0 142{
ef5e2b78
EP
143 struct dnotify_mark *dn_mark = container_of(fsn_mark,
144 struct dnotify_mark,
145 fsn_mark);
3c5119c0 146
ef5e2b78 147 BUG_ON(dn_mark->dn);
3c5119c0 148
ef5e2b78 149 kmem_cache_free(dnotify_mark_cache, dn_mark);
3c5119c0
EP
150}
151
152static struct fsnotify_ops dnotify_fsnotify_ops = {
153 .handle_event = dnotify_handle_event,
154 .should_send_event = dnotify_should_send_event,
155 .free_group_priv = NULL,
a092ee20 156 .freeing_mark = NULL,
7053aee2 157 .free_event = NULL,
3c5119c0
EP
158};
159
160/*
161 * Called every time a file is closed. Looks first for a dnotify mark on the
e61ce867 162 * inode. If one is found run all of the ->dn structures attached to that
3c5119c0
EP
163 * mark for one relevant to this process closing the file and remove that
164 * dnotify_struct. If that was the last dnotify_struct also remove the
e61ce867 165 * fsnotify_mark.
3c5119c0 166 */
1da177e4
LT
167void dnotify_flush(struct file *filp, fl_owner_t id)
168{
ef5e2b78
EP
169 struct fsnotify_mark *fsn_mark;
170 struct dnotify_mark *dn_mark;
1da177e4
LT
171 struct dnotify_struct *dn;
172 struct dnotify_struct **prev;
173 struct inode *inode;
174
496ad9aa 175 inode = file_inode(filp);
1da177e4
LT
176 if (!S_ISDIR(inode->i_mode))
177 return;
3c5119c0 178
5444e298 179 fsn_mark = fsnotify_find_inode_mark(dnotify_group, inode);
ef5e2b78 180 if (!fsn_mark)
3c5119c0 181 return;
ef5e2b78 182 dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark);
3c5119c0 183
52f85729 184 mutex_lock(&dnotify_group->mark_mutex);
3c5119c0 185
ef5e2b78
EP
186 spin_lock(&fsn_mark->lock);
187 prev = &dn_mark->dn;
1da177e4
LT
188 while ((dn = *prev) != NULL) {
189 if ((dn->dn_owner == id) && (dn->dn_filp == filp)) {
190 *prev = dn->dn_next;
3c5119c0 191 kmem_cache_free(dnotify_struct_cache, dn);
ef5e2b78 192 dnotify_recalc_inode_mask(fsn_mark);
1da177e4
LT
193 break;
194 }
195 prev = &dn->dn_next;
196 }
3c5119c0 197
ef5e2b78 198 spin_unlock(&fsn_mark->lock);
3c5119c0 199
52f85729
LS
200 /* nothing else could have found us thanks to the dnotify_groups
201 mark_mutex */
ef5e2b78 202 if (dn_mark->dn == NULL)
52f85729 203 fsnotify_destroy_mark_locked(fsn_mark, dnotify_group);
3c5119c0 204
52f85729 205 mutex_unlock(&dnotify_group->mark_mutex);
3c5119c0 206
ef5e2b78 207 fsnotify_put_mark(fsn_mark);
3c5119c0
EP
208}
209
210/* this conversion is done only at watch creation */
211static __u32 convert_arg(unsigned long arg)
212{
213 __u32 new_mask = FS_EVENT_ON_CHILD;
214
215 if (arg & DN_MULTISHOT)
216 new_mask |= FS_DN_MULTISHOT;
217 if (arg & DN_DELETE)
218 new_mask |= (FS_DELETE | FS_MOVED_FROM);
219 if (arg & DN_MODIFY)
220 new_mask |= FS_MODIFY;
221 if (arg & DN_ACCESS)
222 new_mask |= FS_ACCESS;
223 if (arg & DN_ATTRIB)
224 new_mask |= FS_ATTRIB;
225 if (arg & DN_RENAME)
226 new_mask |= FS_DN_RENAME;
227 if (arg & DN_CREATE)
228 new_mask |= (FS_CREATE | FS_MOVED_TO);
229
230 return new_mask;
1da177e4
LT
231}
232
3c5119c0
EP
233/*
234 * If multiple processes watch the same inode with dnotify there is only one
e61ce867 235 * dnotify mark in inode->i_fsnotify_marks but we chain a dnotify_struct
3c5119c0
EP
236 * onto that mark. This function either attaches the new dnotify_struct onto
237 * that list, or it |= the mask onto an existing dnofiy_struct.
238 */
ef5e2b78 239static int attach_dn(struct dnotify_struct *dn, struct dnotify_mark *dn_mark,
3c5119c0
EP
240 fl_owner_t id, int fd, struct file *filp, __u32 mask)
241{
242 struct dnotify_struct *odn;
243
ef5e2b78 244 odn = dn_mark->dn;
3c5119c0
EP
245 while (odn != NULL) {
246 /* adding more events to existing dnofiy_struct? */
247 if ((odn->dn_owner == id) && (odn->dn_filp == filp)) {
248 odn->dn_fd = fd;
249 odn->dn_mask |= mask;
250 return -EEXIST;
251 }
252 odn = odn->dn_next;
253 }
254
255 dn->dn_mask = mask;
256 dn->dn_fd = fd;
257 dn->dn_filp = filp;
258 dn->dn_owner = id;
ef5e2b78
EP
259 dn->dn_next = dn_mark->dn;
260 dn_mark->dn = dn;
3c5119c0
EP
261
262 return 0;
263}
264
265/*
266 * When a process calls fcntl to attach a dnotify watch to a directory it ends
267 * up here. Allocate both a mark for fsnotify to add and a dnotify_struct to be
268 * attached to the fsnotify_mark.
269 */
1da177e4
LT
270int fcntl_dirnotify(int fd, struct file *filp, unsigned long arg)
271{
ef5e2b78
EP
272 struct dnotify_mark *new_dn_mark, *dn_mark;
273 struct fsnotify_mark *new_fsn_mark, *fsn_mark;
1da177e4 274 struct dnotify_struct *dn;
1da177e4
LT
275 struct inode *inode;
276 fl_owner_t id = current->files;
214b7049 277 struct file *f;
3c5119c0
EP
278 int destroy = 0, error = 0;
279 __u32 mask;
280
281 /* we use these to tell if we need to kfree */
ef5e2b78 282 new_fsn_mark = NULL;
3c5119c0 283 dn = NULL;
1da177e4 284
3c5119c0
EP
285 if (!dir_notify_enable) {
286 error = -EINVAL;
287 goto out_err;
288 }
289
290 /* a 0 mask means we are explicitly removing the watch */
1da177e4
LT
291 if ((arg & ~DN_MULTISHOT) == 0) {
292 dnotify_flush(filp, id);
3c5119c0
EP
293 error = 0;
294 goto out_err;
1da177e4 295 }
3c5119c0
EP
296
297 /* dnotify only works on directories */
496ad9aa 298 inode = file_inode(filp);
3c5119c0
EP
299 if (!S_ISDIR(inode->i_mode)) {
300 error = -ENOTDIR;
301 goto out_err;
1da177e4
LT
302 }
303
3c5119c0
EP
304 /* expect most fcntl to add new rather than augment old */
305 dn = kmem_cache_alloc(dnotify_struct_cache, GFP_KERNEL);
306 if (!dn) {
307 error = -ENOMEM;
308 goto out_err;
309 }
214b7049 310
3c5119c0 311 /* new fsnotify mark, we expect most fcntl calls to add a new mark */
ef5e2b78
EP
312 new_dn_mark = kmem_cache_alloc(dnotify_mark_cache, GFP_KERNEL);
313 if (!new_dn_mark) {
3c5119c0
EP
314 error = -ENOMEM;
315 goto out_err;
316 }
1da177e4 317
3c5119c0
EP
318 /* convert the userspace DN_* "arg" to the internal FS_* defines in fsnotify */
319 mask = convert_arg(arg);
1da177e4 320
ef5e2b78
EP
321 /* set up the new_fsn_mark and new_dn_mark */
322 new_fsn_mark = &new_dn_mark->fsn_mark;
323 fsnotify_init_mark(new_fsn_mark, dnotify_free_mark);
324 new_fsn_mark->mask = mask;
325 new_dn_mark->dn = NULL;
1da177e4 326
3c5119c0 327 /* this is needed to prevent the fcntl/close race described below */
52f85729 328 mutex_lock(&dnotify_group->mark_mutex);
1da177e4 329
ef5e2b78 330 /* add the new_fsn_mark or find an old one. */
5444e298 331 fsn_mark = fsnotify_find_inode_mark(dnotify_group, inode);
ef5e2b78
EP
332 if (fsn_mark) {
333 dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark);
334 spin_lock(&fsn_mark->lock);
3c5119c0 335 } else {
52f85729
LS
336 fsnotify_add_mark_locked(new_fsn_mark, dnotify_group, inode,
337 NULL, 0);
ef5e2b78
EP
338 spin_lock(&new_fsn_mark->lock);
339 fsn_mark = new_fsn_mark;
340 dn_mark = new_dn_mark;
341 /* we used new_fsn_mark, so don't free it */
342 new_fsn_mark = NULL;
3c5119c0 343 }
1da177e4 344
3c5119c0
EP
345 rcu_read_lock();
346 f = fcheck(fd);
347 rcu_read_unlock();
1da177e4 348
3c5119c0
EP
349 /* if (f != filp) means that we lost a race and another task/thread
350 * actually closed the fd we are still playing with before we grabbed
52f85729
LS
351 * the dnotify_groups mark_mutex and fsn_mark->lock. Since closing the
352 * fd is the only time we clean up the marks we need to get our mark
353 * off the list. */
3c5119c0
EP
354 if (f != filp) {
355 /* if we added ourselves, shoot ourselves, it's possible that
ef5e2b78 356 * the flush actually did shoot this fsn_mark. That's fine too
3c5119c0 357 * since multiple calls to destroy_mark is perfectly safe, if
ef5e2b78 358 * we found a dn_mark already attached to the inode, just sod
3c5119c0
EP
359 * off silently as the flush at close time dealt with it.
360 */
ef5e2b78 361 if (dn_mark == new_dn_mark)
3c5119c0
EP
362 destroy = 1;
363 goto out;
364 }
1da177e4 365
3c5119c0
EP
366 error = __f_setown(filp, task_pid(current), PIDTYPE_PID, 0);
367 if (error) {
368 /* if we added, we must shoot */
ef5e2b78 369 if (dn_mark == new_dn_mark)
3c5119c0
EP
370 destroy = 1;
371 goto out;
1da177e4 372 }
3c5119c0 373
ef5e2b78
EP
374 error = attach_dn(dn, dn_mark, id, fd, filp, mask);
375 /* !error means that we attached the dn to the dn_mark, so don't free it */
3c5119c0
EP
376 if (!error)
377 dn = NULL;
378 /* -EEXIST means that we didn't add this new dn and used an old one.
379 * that isn't an error (and the unused dn should be freed) */
380 else if (error == -EEXIST)
381 error = 0;
382
ef5e2b78 383 dnotify_recalc_inode_mask(fsn_mark);
3c5119c0 384out:
ef5e2b78 385 spin_unlock(&fsn_mark->lock);
3c5119c0
EP
386
387 if (destroy)
52f85729 388 fsnotify_destroy_mark_locked(fsn_mark, dnotify_group);
3c5119c0 389
52f85729 390 mutex_unlock(&dnotify_group->mark_mutex);
ef5e2b78 391 fsnotify_put_mark(fsn_mark);
3c5119c0 392out_err:
ef5e2b78
EP
393 if (new_fsn_mark)
394 fsnotify_put_mark(new_fsn_mark);
3c5119c0
EP
395 if (dn)
396 kmem_cache_free(dnotify_struct_cache, dn);
397 return error;
1da177e4 398}
1da177e4
LT
399
400static int __init dnotify_init(void)
401{
3c5119c0 402 dnotify_struct_cache = KMEM_CACHE(dnotify_struct, SLAB_PANIC);
ef5e2b78 403 dnotify_mark_cache = KMEM_CACHE(dnotify_mark, SLAB_PANIC);
3c5119c0 404
0d2e2a1d 405 dnotify_group = fsnotify_alloc_group(&dnotify_fsnotify_ops);
3c5119c0
EP
406 if (IS_ERR(dnotify_group))
407 panic("unable to allocate fsnotify group for dnotify\n");
1da177e4
LT
408 return 0;
409}
410
411module_init(dnotify_init)
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