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1/*
2 * Directory notifications for Linux.
3 *
4 * Copyright (C) 2000,2001,2002 Stephen Rothwell
5 *
6 * Copyright (C) 2009 Eric Paris <Red Hat Inc>
7 * dnotify was largly rewritten to use the new fsnotify infrastructure
8 *
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>
26#include <linux/fdtable.h>
27#include <linux/fsnotify_backend.h>
28
29int dir_notify_enable __read_mostly = 1;
30
31static struct kmem_cache *dnotify_struct_cache __read_mostly;
32static struct kmem_cache *dnotify_mark_cache __read_mostly;
33static struct fsnotify_group *dnotify_group __read_mostly;
34
35/*
36 * dnotify will attach one of these to each inode (i_fsnotify_marks) which
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 */
40struct dnotify_mark {
41 struct fsnotify_mark fsn_mark;
42 struct dnotify_struct *dn;
43};
44
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 */
53static void dnotify_recalc_inode_mask(struct fsnotify_mark *fsn_mark)
54{
55 __u32 new_mask = 0;
56 struct dnotify_struct *dn;
57 struct dnotify_mark *dn_mark = container_of(fsn_mark,
58 struct dnotify_mark,
59 fsn_mark);
60
61 assert_spin_locked(&fsn_mark->lock);
62
63 for (dn = dn_mark->dn; dn != NULL; dn = dn->dn_next)
64 new_mask |= (dn->dn_mask & ~FS_DN_MULTISHOT);
65 if (fsn_mark->mask == new_mask)
66 return;
67 fsn_mark->mask = new_mask;
68
69 fsnotify_recalc_mask(fsn_mark->connector);
70}
71
72/*
73 * Mains fsnotify call where events are delivered to dnotify.
74 * Find the dnotify mark on the relevant inode, run the list of dnotify structs
75 * on that mark and determine which of them has expressed interest in receiving
76 * events of this type. When found send the correct process and signal and
77 * destroy the dnotify struct if it was not registered to receive multiple
78 * events.
79 */
80static int dnotify_handle_event(struct fsnotify_group *group,
81 struct inode *inode,
82 struct fsnotify_mark *inode_mark,
83 struct fsnotify_mark *vfsmount_mark,
84 u32 mask, const void *data, int data_type,
85 const unsigned char *file_name, u32 cookie,
86 struct fsnotify_iter_info *iter_info)
87{
88 struct dnotify_mark *dn_mark;
89 struct dnotify_struct *dn;
90 struct dnotify_struct **prev;
91 struct fown_struct *fown;
92 __u32 test_mask = mask & ~FS_EVENT_ON_CHILD;
93
94 /* not a dir, dnotify doesn't care */
95 if (!S_ISDIR(inode->i_mode))
96 return 0;
97
98 BUG_ON(vfsmount_mark);
99
100 dn_mark = container_of(inode_mark, struct dnotify_mark, fsn_mark);
101
102 spin_lock(&inode_mark->lock);
103 prev = &dn_mark->dn;
104 while ((dn = *prev) != NULL) {
105 if ((dn->dn_mask & test_mask) == 0) {
106 prev = &dn->dn_next;
107 continue;
108 }
109 fown = &dn->dn_filp->f_owner;
110 send_sigio(fown, dn->dn_fd, POLL_MSG);
111 if (dn->dn_mask & FS_DN_MULTISHOT)
112 prev = &dn->dn_next;
113 else {
114 *prev = dn->dn_next;
115 kmem_cache_free(dnotify_struct_cache, dn);
116 dnotify_recalc_inode_mask(inode_mark);
117 }
118 }
119
120 spin_unlock(&inode_mark->lock);
121
122 return 0;
123}
124
125static void dnotify_free_mark(struct fsnotify_mark *fsn_mark)
126{
127 struct dnotify_mark *dn_mark = container_of(fsn_mark,
128 struct dnotify_mark,
129 fsn_mark);
130
131 BUG_ON(dn_mark->dn);
132
133 kmem_cache_free(dnotify_mark_cache, dn_mark);
134}
135
136static const struct fsnotify_ops dnotify_fsnotify_ops = {
137 .handle_event = dnotify_handle_event,
138 .free_mark = dnotify_free_mark,
139};
140
141/*
142 * Called every time a file is closed. Looks first for a dnotify mark on the
143 * inode. If one is found run all of the ->dn structures attached to that
144 * mark for one relevant to this process closing the file and remove that
145 * dnotify_struct. If that was the last dnotify_struct also remove the
146 * fsnotify_mark.
147 */
148void dnotify_flush(struct file *filp, fl_owner_t id)
149{
150 struct fsnotify_mark *fsn_mark;
151 struct dnotify_mark *dn_mark;
152 struct dnotify_struct *dn;
153 struct dnotify_struct **prev;
154 struct inode *inode;
155 bool free = false;
156
157 inode = file_inode(filp);
158 if (!S_ISDIR(inode->i_mode))
159 return;
160
161 fsn_mark = fsnotify_find_mark(&inode->i_fsnotify_marks, dnotify_group);
162 if (!fsn_mark)
163 return;
164 dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark);
165
166 mutex_lock(&dnotify_group->mark_mutex);
167
168 spin_lock(&fsn_mark->lock);
169 prev = &dn_mark->dn;
170 while ((dn = *prev) != NULL) {
171 if ((dn->dn_owner == id) && (dn->dn_filp == filp)) {
172 *prev = dn->dn_next;
173 kmem_cache_free(dnotify_struct_cache, dn);
174 dnotify_recalc_inode_mask(fsn_mark);
175 break;
176 }
177 prev = &dn->dn_next;
178 }
179
180 spin_unlock(&fsn_mark->lock);
181
182 /* nothing else could have found us thanks to the dnotify_groups
183 mark_mutex */
184 if (dn_mark->dn == NULL) {
185 fsnotify_detach_mark(fsn_mark);
186 free = true;
187 }
188
189 mutex_unlock(&dnotify_group->mark_mutex);
190
191 if (free)
192 fsnotify_free_mark(fsn_mark);
193 fsnotify_put_mark(fsn_mark);
194}
195
196/* this conversion is done only at watch creation */
197static __u32 convert_arg(unsigned long arg)
198{
199 __u32 new_mask = FS_EVENT_ON_CHILD;
200
201 if (arg & DN_MULTISHOT)
202 new_mask |= FS_DN_MULTISHOT;
203 if (arg & DN_DELETE)
204 new_mask |= (FS_DELETE | FS_MOVED_FROM);
205 if (arg & DN_MODIFY)
206 new_mask |= FS_MODIFY;
207 if (arg & DN_ACCESS)
208 new_mask |= FS_ACCESS;
209 if (arg & DN_ATTRIB)
210 new_mask |= FS_ATTRIB;
211 if (arg & DN_RENAME)
212 new_mask |= FS_DN_RENAME;
213 if (arg & DN_CREATE)
214 new_mask |= (FS_CREATE | FS_MOVED_TO);
215
216 return new_mask;
217}
218
219/*
220 * If multiple processes watch the same inode with dnotify there is only one
221 * dnotify mark in inode->i_fsnotify_marks but we chain a dnotify_struct
222 * onto that mark. This function either attaches the new dnotify_struct onto
223 * that list, or it |= the mask onto an existing dnofiy_struct.
224 */
225static int attach_dn(struct dnotify_struct *dn, struct dnotify_mark *dn_mark,
226 fl_owner_t id, int fd, struct file *filp, __u32 mask)
227{
228 struct dnotify_struct *odn;
229
230 odn = dn_mark->dn;
231 while (odn != NULL) {
232 /* adding more events to existing dnofiy_struct? */
233 if ((odn->dn_owner == id) && (odn->dn_filp == filp)) {
234 odn->dn_fd = fd;
235 odn->dn_mask |= mask;
236 return -EEXIST;
237 }
238 odn = odn->dn_next;
239 }
240
241 dn->dn_mask = mask;
242 dn->dn_fd = fd;
243 dn->dn_filp = filp;
244 dn->dn_owner = id;
245 dn->dn_next = dn_mark->dn;
246 dn_mark->dn = dn;
247
248 return 0;
249}
250
251/*
252 * When a process calls fcntl to attach a dnotify watch to a directory it ends
253 * up here. Allocate both a mark for fsnotify to add and a dnotify_struct to be
254 * attached to the fsnotify_mark.
255 */
256int fcntl_dirnotify(int fd, struct file *filp, unsigned long arg)
257{
258 struct dnotify_mark *new_dn_mark, *dn_mark;
259 struct fsnotify_mark *new_fsn_mark, *fsn_mark;
260 struct dnotify_struct *dn;
261 struct inode *inode;
262 fl_owner_t id = current->files;
263 struct file *f;
264 int destroy = 0, error = 0;
265 __u32 mask;
266
267 /* we use these to tell if we need to kfree */
268 new_fsn_mark = NULL;
269 dn = NULL;
270
271 if (!dir_notify_enable) {
272 error = -EINVAL;
273 goto out_err;
274 }
275
276 /* a 0 mask means we are explicitly removing the watch */
277 if ((arg & ~DN_MULTISHOT) == 0) {
278 dnotify_flush(filp, id);
279 error = 0;
280 goto out_err;
281 }
282
283 /* dnotify only works on directories */
284 inode = file_inode(filp);
285 if (!S_ISDIR(inode->i_mode)) {
286 error = -ENOTDIR;
287 goto out_err;
288 }
289
290 /* expect most fcntl to add new rather than augment old */
291 dn = kmem_cache_alloc(dnotify_struct_cache, GFP_KERNEL);
292 if (!dn) {
293 error = -ENOMEM;
294 goto out_err;
295 }
296
297 /* new fsnotify mark, we expect most fcntl calls to add a new mark */
298 new_dn_mark = kmem_cache_alloc(dnotify_mark_cache, GFP_KERNEL);
299 if (!new_dn_mark) {
300 error = -ENOMEM;
301 goto out_err;
302 }
303
304 /* convert the userspace DN_* "arg" to the internal FS_* defines in fsnotify */
305 mask = convert_arg(arg);
306
307 /* set up the new_fsn_mark and new_dn_mark */
308 new_fsn_mark = &new_dn_mark->fsn_mark;
309 fsnotify_init_mark(new_fsn_mark, dnotify_group);
310 new_fsn_mark->mask = mask;
311 new_dn_mark->dn = NULL;
312
313 /* this is needed to prevent the fcntl/close race described below */
314 mutex_lock(&dnotify_group->mark_mutex);
315
316 /* add the new_fsn_mark or find an old one. */
317 fsn_mark = fsnotify_find_mark(&inode->i_fsnotify_marks, dnotify_group);
318 if (fsn_mark) {
319 dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark);
320 spin_lock(&fsn_mark->lock);
321 } else {
322 error = fsnotify_add_mark_locked(new_fsn_mark, inode, NULL, 0);
323 if (error) {
324 mutex_unlock(&dnotify_group->mark_mutex);
325 goto out_err;
326 }
327 spin_lock(&new_fsn_mark->lock);
328 fsn_mark = new_fsn_mark;
329 dn_mark = new_dn_mark;
330 /* we used new_fsn_mark, so don't free it */
331 new_fsn_mark = NULL;
332 }
333
334 rcu_read_lock();
335 f = fcheck(fd);
336 rcu_read_unlock();
337
338 /* if (f != filp) means that we lost a race and another task/thread
339 * actually closed the fd we are still playing with before we grabbed
340 * the dnotify_groups mark_mutex and fsn_mark->lock. Since closing the
341 * fd is the only time we clean up the marks we need to get our mark
342 * off the list. */
343 if (f != filp) {
344 /* if we added ourselves, shoot ourselves, it's possible that
345 * the flush actually did shoot this fsn_mark. That's fine too
346 * since multiple calls to destroy_mark is perfectly safe, if
347 * we found a dn_mark already attached to the inode, just sod
348 * off silently as the flush at close time dealt with it.
349 */
350 if (dn_mark == new_dn_mark)
351 destroy = 1;
352 error = 0;
353 goto out;
354 }
355
356 __f_setown(filp, task_pid(current), PIDTYPE_PID, 0);
357
358 error = attach_dn(dn, dn_mark, id, fd, filp, mask);
359 /* !error means that we attached the dn to the dn_mark, so don't free it */
360 if (!error)
361 dn = NULL;
362 /* -EEXIST means that we didn't add this new dn and used an old one.
363 * that isn't an error (and the unused dn should be freed) */
364 else if (error == -EEXIST)
365 error = 0;
366
367 dnotify_recalc_inode_mask(fsn_mark);
368out:
369 spin_unlock(&fsn_mark->lock);
370
371 if (destroy)
372 fsnotify_detach_mark(fsn_mark);
373 mutex_unlock(&dnotify_group->mark_mutex);
374 if (destroy)
375 fsnotify_free_mark(fsn_mark);
376 fsnotify_put_mark(fsn_mark);
377out_err:
378 if (new_fsn_mark)
379 fsnotify_put_mark(new_fsn_mark);
380 if (dn)
381 kmem_cache_free(dnotify_struct_cache, dn);
382 return error;
383}
384
385static int __init dnotify_init(void)
386{
387 dnotify_struct_cache = KMEM_CACHE(dnotify_struct, SLAB_PANIC);
388 dnotify_mark_cache = KMEM_CACHE(dnotify_mark, SLAB_PANIC);
389
390 dnotify_group = fsnotify_alloc_group(&dnotify_fsnotify_ops);
391 if (IS_ERR(dnotify_group))
392 panic("unable to allocate fsnotify group for dnotify\n");
393 return 0;
394}
395
396module_init(dnotify_init)
1/*
2 * Directory notifications for Linux.
3 *
4 * Copyright (C) 2000,2001,2002 Stephen Rothwell
5 *
6 * Copyright (C) 2009 Eric Paris <Red Hat Inc>
7 * dnotify was largly rewritten to use the new fsnotify infrastructure
8 *
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>
26#include <linux/fdtable.h>
27#include <linux/fsnotify_backend.h>
28
29int dir_notify_enable __read_mostly = 1;
30
31static struct kmem_cache *dnotify_struct_cache __read_mostly;
32static struct kmem_cache *dnotify_mark_cache __read_mostly;
33static struct fsnotify_group *dnotify_group __read_mostly;
34static DEFINE_MUTEX(dnotify_mark_mutex);
35
36/*
37 * dnotify will attach one of these to each inode (i_fsnotify_marks) which
38 * is being watched by dnotify. If multiple userspace applications are watching
39 * the same directory with dnotify their information is chained in dn
40 */
41struct dnotify_mark {
42 struct fsnotify_mark fsn_mark;
43 struct dnotify_struct *dn;
44};
45
46/*
47 * When a process starts or stops watching an inode the set of events which
48 * dnotify cares about for that inode may change. This function runs the
49 * list of everything receiving dnotify events about this directory and calculates
50 * the set of all those events. After it updates what dnotify is interested in
51 * it calls the fsnotify function so it can update the set of all events relevant
52 * to this inode.
53 */
54static void dnotify_recalc_inode_mask(struct fsnotify_mark *fsn_mark)
55{
56 __u32 new_mask, old_mask;
57 struct dnotify_struct *dn;
58 struct dnotify_mark *dn_mark = container_of(fsn_mark,
59 struct dnotify_mark,
60 fsn_mark);
61
62 assert_spin_locked(&fsn_mark->lock);
63
64 old_mask = fsn_mark->mask;
65 new_mask = 0;
66 for (dn = dn_mark->dn; dn != NULL; dn = dn->dn_next)
67 new_mask |= (dn->dn_mask & ~FS_DN_MULTISHOT);
68 fsnotify_set_mark_mask_locked(fsn_mark, new_mask);
69
70 if (old_mask == new_mask)
71 return;
72
73 if (fsn_mark->i.inode)
74 fsnotify_recalc_inode_mask(fsn_mark->i.inode);
75}
76
77/*
78 * Mains fsnotify call where events are delivered to dnotify.
79 * Find the dnotify mark on the relevant inode, run the list of dnotify structs
80 * on that mark and determine which of them has expressed interest in receiving
81 * events of this type. When found send the correct process and signal and
82 * destroy the dnotify struct if it was not registered to receive multiple
83 * events.
84 */
85static int dnotify_handle_event(struct fsnotify_group *group,
86 struct fsnotify_mark *inode_mark,
87 struct fsnotify_mark *vfsmount_mark,
88 struct fsnotify_event *event)
89{
90 struct dnotify_mark *dn_mark;
91 struct inode *to_tell;
92 struct dnotify_struct *dn;
93 struct dnotify_struct **prev;
94 struct fown_struct *fown;
95 __u32 test_mask = event->mask & ~FS_EVENT_ON_CHILD;
96
97 BUG_ON(vfsmount_mark);
98
99 to_tell = event->to_tell;
100
101 dn_mark = container_of(inode_mark, struct dnotify_mark, fsn_mark);
102
103 spin_lock(&inode_mark->lock);
104 prev = &dn_mark->dn;
105 while ((dn = *prev) != NULL) {
106 if ((dn->dn_mask & test_mask) == 0) {
107 prev = &dn->dn_next;
108 continue;
109 }
110 fown = &dn->dn_filp->f_owner;
111 send_sigio(fown, dn->dn_fd, POLL_MSG);
112 if (dn->dn_mask & FS_DN_MULTISHOT)
113 prev = &dn->dn_next;
114 else {
115 *prev = dn->dn_next;
116 kmem_cache_free(dnotify_struct_cache, dn);
117 dnotify_recalc_inode_mask(inode_mark);
118 }
119 }
120
121 spin_unlock(&inode_mark->lock);
122
123 return 0;
124}
125
126/*
127 * Given an inode and mask determine if dnotify would be interested in sending
128 * userspace notification for that pair.
129 */
130static bool dnotify_should_send_event(struct fsnotify_group *group,
131 struct inode *inode,
132 struct fsnotify_mark *inode_mark,
133 struct fsnotify_mark *vfsmount_mark,
134 __u32 mask, void *data, int data_type)
135{
136 /* not a dir, dnotify doesn't care */
137 if (!S_ISDIR(inode->i_mode))
138 return false;
139
140 return true;
141}
142
143static void dnotify_free_mark(struct fsnotify_mark *fsn_mark)
144{
145 struct dnotify_mark *dn_mark = container_of(fsn_mark,
146 struct dnotify_mark,
147 fsn_mark);
148
149 BUG_ON(dn_mark->dn);
150
151 kmem_cache_free(dnotify_mark_cache, dn_mark);
152}
153
154static struct fsnotify_ops dnotify_fsnotify_ops = {
155 .handle_event = dnotify_handle_event,
156 .should_send_event = dnotify_should_send_event,
157 .free_group_priv = NULL,
158 .freeing_mark = NULL,
159 .free_event_priv = NULL,
160};
161
162/*
163 * Called every time a file is closed. Looks first for a dnotify mark on the
164 * inode. If one is found run all of the ->dn structures attached to that
165 * mark for one relevant to this process closing the file and remove that
166 * dnotify_struct. If that was the last dnotify_struct also remove the
167 * fsnotify_mark.
168 */
169void dnotify_flush(struct file *filp, fl_owner_t id)
170{
171 struct fsnotify_mark *fsn_mark;
172 struct dnotify_mark *dn_mark;
173 struct dnotify_struct *dn;
174 struct dnotify_struct **prev;
175 struct inode *inode;
176
177 inode = filp->f_path.dentry->d_inode;
178 if (!S_ISDIR(inode->i_mode))
179 return;
180
181 fsn_mark = fsnotify_find_inode_mark(dnotify_group, inode);
182 if (!fsn_mark)
183 return;
184 dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark);
185
186 mutex_lock(&dnotify_mark_mutex);
187
188 spin_lock(&fsn_mark->lock);
189 prev = &dn_mark->dn;
190 while ((dn = *prev) != NULL) {
191 if ((dn->dn_owner == id) && (dn->dn_filp == filp)) {
192 *prev = dn->dn_next;
193 kmem_cache_free(dnotify_struct_cache, dn);
194 dnotify_recalc_inode_mask(fsn_mark);
195 break;
196 }
197 prev = &dn->dn_next;
198 }
199
200 spin_unlock(&fsn_mark->lock);
201
202 /* nothing else could have found us thanks to the dnotify_mark_mutex */
203 if (dn_mark->dn == NULL)
204 fsnotify_destroy_mark(fsn_mark);
205
206 mutex_unlock(&dnotify_mark_mutex);
207
208 fsnotify_put_mark(fsn_mark);
209}
210
211/* this conversion is done only at watch creation */
212static __u32 convert_arg(unsigned long arg)
213{
214 __u32 new_mask = FS_EVENT_ON_CHILD;
215
216 if (arg & DN_MULTISHOT)
217 new_mask |= FS_DN_MULTISHOT;
218 if (arg & DN_DELETE)
219 new_mask |= (FS_DELETE | FS_MOVED_FROM);
220 if (arg & DN_MODIFY)
221 new_mask |= FS_MODIFY;
222 if (arg & DN_ACCESS)
223 new_mask |= FS_ACCESS;
224 if (arg & DN_ATTRIB)
225 new_mask |= FS_ATTRIB;
226 if (arg & DN_RENAME)
227 new_mask |= FS_DN_RENAME;
228 if (arg & DN_CREATE)
229 new_mask |= (FS_CREATE | FS_MOVED_TO);
230
231 return new_mask;
232}
233
234/*
235 * If multiple processes watch the same inode with dnotify there is only one
236 * dnotify mark in inode->i_fsnotify_marks but we chain a dnotify_struct
237 * onto that mark. This function either attaches the new dnotify_struct onto
238 * that list, or it |= the mask onto an existing dnofiy_struct.
239 */
240static int attach_dn(struct dnotify_struct *dn, struct dnotify_mark *dn_mark,
241 fl_owner_t id, int fd, struct file *filp, __u32 mask)
242{
243 struct dnotify_struct *odn;
244
245 odn = dn_mark->dn;
246 while (odn != NULL) {
247 /* adding more events to existing dnofiy_struct? */
248 if ((odn->dn_owner == id) && (odn->dn_filp == filp)) {
249 odn->dn_fd = fd;
250 odn->dn_mask |= mask;
251 return -EEXIST;
252 }
253 odn = odn->dn_next;
254 }
255
256 dn->dn_mask = mask;
257 dn->dn_fd = fd;
258 dn->dn_filp = filp;
259 dn->dn_owner = id;
260 dn->dn_next = dn_mark->dn;
261 dn_mark->dn = dn;
262
263 return 0;
264}
265
266/*
267 * When a process calls fcntl to attach a dnotify watch to a directory it ends
268 * up here. Allocate both a mark for fsnotify to add and a dnotify_struct to be
269 * attached to the fsnotify_mark.
270 */
271int fcntl_dirnotify(int fd, struct file *filp, unsigned long arg)
272{
273 struct dnotify_mark *new_dn_mark, *dn_mark;
274 struct fsnotify_mark *new_fsn_mark, *fsn_mark;
275 struct dnotify_struct *dn;
276 struct inode *inode;
277 fl_owner_t id = current->files;
278 struct file *f;
279 int destroy = 0, error = 0;
280 __u32 mask;
281
282 /* we use these to tell if we need to kfree */
283 new_fsn_mark = NULL;
284 dn = NULL;
285
286 if (!dir_notify_enable) {
287 error = -EINVAL;
288 goto out_err;
289 }
290
291 /* a 0 mask means we are explicitly removing the watch */
292 if ((arg & ~DN_MULTISHOT) == 0) {
293 dnotify_flush(filp, id);
294 error = 0;
295 goto out_err;
296 }
297
298 /* dnotify only works on directories */
299 inode = filp->f_path.dentry->d_inode;
300 if (!S_ISDIR(inode->i_mode)) {
301 error = -ENOTDIR;
302 goto out_err;
303 }
304
305 /* expect most fcntl to add new rather than augment old */
306 dn = kmem_cache_alloc(dnotify_struct_cache, GFP_KERNEL);
307 if (!dn) {
308 error = -ENOMEM;
309 goto out_err;
310 }
311
312 /* new fsnotify mark, we expect most fcntl calls to add a new mark */
313 new_dn_mark = kmem_cache_alloc(dnotify_mark_cache, GFP_KERNEL);
314 if (!new_dn_mark) {
315 error = -ENOMEM;
316 goto out_err;
317 }
318
319 /* convert the userspace DN_* "arg" to the internal FS_* defines in fsnotify */
320 mask = convert_arg(arg);
321
322 /* set up the new_fsn_mark and new_dn_mark */
323 new_fsn_mark = &new_dn_mark->fsn_mark;
324 fsnotify_init_mark(new_fsn_mark, dnotify_free_mark);
325 new_fsn_mark->mask = mask;
326 new_dn_mark->dn = NULL;
327
328 /* this is needed to prevent the fcntl/close race described below */
329 mutex_lock(&dnotify_mark_mutex);
330
331 /* add the new_fsn_mark or find an old one. */
332 fsn_mark = fsnotify_find_inode_mark(dnotify_group, inode);
333 if (fsn_mark) {
334 dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark);
335 spin_lock(&fsn_mark->lock);
336 } else {
337 fsnotify_add_mark(new_fsn_mark, dnotify_group, inode, NULL, 0);
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;
343 }
344
345 rcu_read_lock();
346 f = fcheck(fd);
347 rcu_read_unlock();
348
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
351 * the dnotify_mark_mutex and fsn_mark->lock. Since closing the fd is the
352 * only time we clean up the marks we need to get our mark off
353 * the list. */
354 if (f != filp) {
355 /* if we added ourselves, shoot ourselves, it's possible that
356 * the flush actually did shoot this fsn_mark. That's fine too
357 * since multiple calls to destroy_mark is perfectly safe, if
358 * we found a dn_mark already attached to the inode, just sod
359 * off silently as the flush at close time dealt with it.
360 */
361 if (dn_mark == new_dn_mark)
362 destroy = 1;
363 goto out;
364 }
365
366 error = __f_setown(filp, task_pid(current), PIDTYPE_PID, 0);
367 if (error) {
368 /* if we added, we must shoot */
369 if (dn_mark == new_dn_mark)
370 destroy = 1;
371 goto out;
372 }
373
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 */
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
383 dnotify_recalc_inode_mask(fsn_mark);
384out:
385 spin_unlock(&fsn_mark->lock);
386
387 if (destroy)
388 fsnotify_destroy_mark(fsn_mark);
389
390 mutex_unlock(&dnotify_mark_mutex);
391 fsnotify_put_mark(fsn_mark);
392out_err:
393 if (new_fsn_mark)
394 fsnotify_put_mark(new_fsn_mark);
395 if (dn)
396 kmem_cache_free(dnotify_struct_cache, dn);
397 return error;
398}
399
400static int __init dnotify_init(void)
401{
402 dnotify_struct_cache = KMEM_CACHE(dnotify_struct, SLAB_PANIC);
403 dnotify_mark_cache = KMEM_CACHE(dnotify_mark, SLAB_PANIC);
404
405 dnotify_group = fsnotify_alloc_group(&dnotify_fsnotify_ops);
406 if (IS_ERR(dnotify_group))
407 panic("unable to allocate fsnotify group for dnotify\n");
408 return 0;
409}
410
411module_init(dnotify_init)