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1/*
2 * fs/inotify.c - inode-based file event notifications
3 *
4 * Authors:
5 * John McCutchan <ttb@tentacle.dhs.org>
6 * Robert Love <rml@novell.com>
7 *
8 * Copyright (C) 2005 John McCutchan
9 *
10 * This program is free software; you can redistribute it and/or modify it
11 * under the terms of the GNU General Public License as published by the
12 * Free Software Foundation; either version 2, or (at your option) any
13 * later version.
14 *
15 * This program is distributed in the hope that it will be useful, but
16 * WITHOUT ANY WARRANTY; without even the implied warranty of
17 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
18 * General Public License for more details.
19 */
20
21#include <linux/module.h>
22#include <linux/kernel.h>
23#include <linux/sched.h>
24#include <linux/spinlock.h>
25#include <linux/idr.h>
26#include <linux/slab.h>
27#include <linux/fs.h>
28#include <linux/file.h>
29#include <linux/mount.h>
30#include <linux/namei.h>
31#include <linux/poll.h>
32#include <linux/init.h>
33#include <linux/list.h>
34#include <linux/writeback.h>
35#include <linux/inotify.h>
36
37#include <asm/ioctls.h>
38
39static atomic_t inotify_cookie;
40
41static kmem_cache_t *watch_cachep;
42static kmem_cache_t *event_cachep;
43
44static struct vfsmount *inotify_mnt;
45
46/* these are configurable via /proc/sys/fs/inotify/ */
47int inotify_max_user_instances;
48int inotify_max_user_watches;
49int inotify_max_queued_events;
50
51/*
52 * Lock ordering:
53 *
54 * dentry->d_lock (used to keep d_move() away from dentry->d_parent)
55 * iprune_sem (synchronize shrink_icache_memory())
56 * inode_lock (protects the super_block->s_inodes list)
57 * inode->inotify_sem (protects inode->inotify_watches and watches->i_list)
58 * inotify_dev->sem (protects inotify_device and watches->d_list)
59 */
60
61/*
62 * Lifetimes of the three main data structures--inotify_device, inode, and
63 * inotify_watch--are managed by reference count.
64 *
65 * inotify_device: Lifetime is from open until release. Additional references
66 * can bump the count via get_inotify_dev() and drop the count via
67 * put_inotify_dev().
68 *
69 * inotify_watch: Lifetime is from create_watch() to destory_watch().
70 * Additional references can bump the count via get_inotify_watch() and drop
71 * the count via put_inotify_watch().
72 *
73 * inode: Pinned so long as the inode is associated with a watch, from
74 * create_watch() to put_inotify_watch().
75 */
76
77/*
78 * struct inotify_device - represents an open instance of an inotify device
79 *
80 * This structure is protected by the semaphore 'sem'.
81 */
82struct inotify_device {
83 wait_queue_head_t wq; /* wait queue for i/o */
84 struct idr idr; /* idr mapping wd -> watch */
85 struct semaphore sem; /* protects this bad boy */
86 struct list_head events; /* list of queued events */
87 struct list_head watches; /* list of watches */
88 atomic_t count; /* reference count */
89 struct user_struct *user; /* user who opened this dev */
90 unsigned int queue_size; /* size of the queue (bytes) */
91 unsigned int event_count; /* number of pending events */
92 unsigned int max_events; /* maximum number of events */
93};
94
95/*
96 * struct inotify_kernel_event - An inotify event, originating from a watch and
97 * queued for user-space. A list of these is attached to each instance of the
98 * device. In read(), this list is walked and all events that can fit in the
99 * buffer are returned.
100 *
101 * Protected by dev->sem of the device in which we are queued.
102 */
103struct inotify_kernel_event {
104 struct inotify_event event; /* the user-space event */
105 struct list_head list; /* entry in inotify_device's list */
106 char *name; /* filename, if any */
107};
108
109/*
110 * struct inotify_watch - represents a watch request on a specific inode
111 *
112 * d_list is protected by dev->sem of the associated watch->dev.
113 * i_list and mask are protected by inode->inotify_sem of the associated inode.
114 * dev, inode, and wd are never written to once the watch is created.
115 */
116struct inotify_watch {
117 struct list_head d_list; /* entry in inotify_device's list */
118 struct list_head i_list; /* entry in inode's list */
119 atomic_t count; /* reference count */
120 struct inotify_device *dev; /* associated device */
121 struct inode *inode; /* associated inode */
122 s32 wd; /* watch descriptor */
123 u32 mask; /* event mask for this watch */
124};
125
126#ifdef CONFIG_SYSCTL
127
128#include <linux/sysctl.h>
129
130static int zero;
131
132ctl_table inotify_table[] = {
133 {
134 .ctl_name = INOTIFY_MAX_USER_INSTANCES,
135 .procname = "max_user_instances",
136 .data = &inotify_max_user_instances,
137 .maxlen = sizeof(int),
138 .mode = 0644,
139 .proc_handler = &proc_dointvec_minmax,
140 .strategy = &sysctl_intvec,
141 .extra1 = &zero,
142 },
143 {
144 .ctl_name = INOTIFY_MAX_USER_WATCHES,
145 .procname = "max_user_watches",
146 .data = &inotify_max_user_watches,
147 .maxlen = sizeof(int),
148 .mode = 0644,
149 .proc_handler = &proc_dointvec_minmax,
150 .strategy = &sysctl_intvec,
151 .extra1 = &zero,
152 },
153 {
154 .ctl_name = INOTIFY_MAX_QUEUED_EVENTS,
155 .procname = "max_queued_events",
156 .data = &inotify_max_queued_events,
157 .maxlen = sizeof(int),
158 .mode = 0644,
159 .proc_handler = &proc_dointvec_minmax,
160 .strategy = &sysctl_intvec,
161 .extra1 = &zero
162 },
163 { .ctl_name = 0 }
164};
165#endif /* CONFIG_SYSCTL */
166
167static inline void get_inotify_dev(struct inotify_device *dev)
168{
169 atomic_inc(&dev->count);
170}
171
172static inline void put_inotify_dev(struct inotify_device *dev)
173{
174 if (atomic_dec_and_test(&dev->count)) {
175 atomic_dec(&dev->user->inotify_devs);
176 free_uid(dev->user);
177 kfree(dev);
178 }
179}
180
181static inline void get_inotify_watch(struct inotify_watch *watch)
182{
183 atomic_inc(&watch->count);
184}
185
186/*
187 * put_inotify_watch - decrements the ref count on a given watch. cleans up
188 * the watch and its references if the count reaches zero.
189 */
190static inline void put_inotify_watch(struct inotify_watch *watch)
191{
192 if (atomic_dec_and_test(&watch->count)) {
193 put_inotify_dev(watch->dev);
194 iput(watch->inode);
195 kmem_cache_free(watch_cachep, watch);
196 }
197}
198
199/*
200 * kernel_event - create a new kernel event with the given parameters
201 *
202 * This function can sleep.
203 */
204static struct inotify_kernel_event * kernel_event(s32 wd, u32 mask, u32 cookie,
205 const char *name)
206{
207 struct inotify_kernel_event *kevent;
208
209 kevent = kmem_cache_alloc(event_cachep, GFP_KERNEL);
210 if (unlikely(!kevent))
211 return NULL;
212
213 /* we hand this out to user-space, so zero it just in case */
214 memset(&kevent->event, 0, sizeof(struct inotify_event));
215
216 kevent->event.wd = wd;
217 kevent->event.mask = mask;
218 kevent->event.cookie = cookie;
219
220 INIT_LIST_HEAD(&kevent->list);
221
222 if (name) {
223 size_t len, rem, event_size = sizeof(struct inotify_event);
224
225 /*
226 * We need to pad the filename so as to properly align an
227 * array of inotify_event structures. Because the structure is
228 * small and the common case is a small filename, we just round
229 * up to the next multiple of the structure's sizeof. This is
230 * simple and safe for all architectures.
231 */
232 len = strlen(name) + 1;
233 rem = event_size - len;
234 if (len > event_size) {
235 rem = event_size - (len % event_size);
236 if (len % event_size == 0)
237 rem = 0;
238 }
239
240 kevent->name = kmalloc(len + rem, GFP_KERNEL);
241 if (unlikely(!kevent->name)) {
242 kmem_cache_free(event_cachep, kevent);
243 return NULL;
244 }
245 memcpy(kevent->name, name, len);
246 if (rem)
247 memset(kevent->name + len, 0, rem);
248 kevent->event.len = len + rem;
249 } else {
250 kevent->event.len = 0;
251 kevent->name = NULL;
252 }
253
254 return kevent;
255}
256
257/*
258 * inotify_dev_get_event - return the next event in the given dev's queue
259 *
260 * Caller must hold dev->sem.
261 */
262static inline struct inotify_kernel_event *
263inotify_dev_get_event(struct inotify_device *dev)
264{
265 return list_entry(dev->events.next, struct inotify_kernel_event, list);
266}
267
268/*
269 * inotify_dev_queue_event - add a new event to the given device
270 *
271 * Caller must hold dev->sem. Can sleep (calls kernel_event()).
272 */
273static void inotify_dev_queue_event(struct inotify_device *dev,
274 struct inotify_watch *watch, u32 mask,
275 u32 cookie, const char *name)
276{
277 struct inotify_kernel_event *kevent, *last;
278
279 /* coalescing: drop this event if it is a dupe of the previous */
280 last = inotify_dev_get_event(dev);
281 if (last && last->event.mask == mask && last->event.wd == watch->wd &&
282 last->event.cookie == cookie) {
283 const char *lastname = last->name;
284
285 if (!name && !lastname)
286 return;
287 if (name && lastname && !strcmp(lastname, name))
288 return;
289 }
290
291 /* the queue overflowed and we already sent the Q_OVERFLOW event */
292 if (unlikely(dev->event_count > dev->max_events))
293 return;
294
295 /* if the queue overflows, we need to notify user space */
296 if (unlikely(dev->event_count == dev->max_events))
297 kevent = kernel_event(-1, IN_Q_OVERFLOW, cookie, NULL);
298 else
299 kevent = kernel_event(watch->wd, mask, cookie, name);
300
301 if (unlikely(!kevent))
302 return;
303
304 /* queue the event and wake up anyone waiting */
305 dev->event_count++;
306 dev->queue_size += sizeof(struct inotify_event) + kevent->event.len;
307 list_add_tail(&kevent->list, &dev->events);
308 wake_up_interruptible(&dev->wq);
309}
310
311/*
312 * remove_kevent - cleans up and ultimately frees the given kevent
313 *
314 * Caller must hold dev->sem.
315 */
316static void remove_kevent(struct inotify_device *dev,
317 struct inotify_kernel_event *kevent)
318{
319 list_del(&kevent->list);
320
321 dev->event_count--;
322 dev->queue_size -= sizeof(struct inotify_event) + kevent->event.len;
323
324 kfree(kevent->name);
325 kmem_cache_free(event_cachep, kevent);
326}
327
328/*
329 * inotify_dev_event_dequeue - destroy an event on the given device
330 *
331 * Caller must hold dev->sem.
332 */
333static void inotify_dev_event_dequeue(struct inotify_device *dev)
334{
335 if (!list_empty(&dev->events)) {
336 struct inotify_kernel_event *kevent;
337 kevent = inotify_dev_get_event(dev);
338 remove_kevent(dev, kevent);
339 }
340}
341
342/*
343 * inotify_dev_get_wd - returns the next WD for use by the given dev
344 *
345 * Callers must hold dev->sem. This function can sleep.
346 */
347static int inotify_dev_get_wd(struct inotify_device *dev,
348 struct inotify_watch *watch)
349{
350 int ret;
351
352 do {
353 if (unlikely(!idr_pre_get(&dev->idr, GFP_KERNEL)))
354 return -ENOSPC;
355 ret = idr_get_new(&dev->idr, watch, &watch->wd);
356 } while (ret == -EAGAIN);
357
358 return ret;
359}
360
361/*
362 * find_inode - resolve a user-given path to a specific inode and return a nd
363 */
364static int find_inode(const char __user *dirname, struct nameidata *nd)
365{
366 int error;
367
368 error = __user_walk(dirname, LOOKUP_FOLLOW, nd);
369 if (error)
370 return error;
371 /* you can only watch an inode if you have read permissions on it */
372 error = permission(nd->dentry->d_inode, MAY_READ, NULL);
373 if (error)
374 path_release (nd);
375 return error;
376}
377
378/*
379 * create_watch - creates a watch on the given device.
380 *
381 * Callers must hold dev->sem. Calls inotify_dev_get_wd() so may sleep.
382 * Both 'dev' and 'inode' (by way of nameidata) need to be pinned.
383 */
384static struct inotify_watch *create_watch(struct inotify_device *dev,
385 u32 mask, struct inode *inode)
386{
387 struct inotify_watch *watch;
388 int ret;
389
390 if (atomic_read(&dev->user->inotify_watches) >= inotify_max_user_watches)
391 return ERR_PTR(-ENOSPC);
392
393 watch = kmem_cache_alloc(watch_cachep, GFP_KERNEL);
394 if (unlikely(!watch))
395 return ERR_PTR(-ENOMEM);
396
397 ret = inotify_dev_get_wd(dev, watch);
398 if (unlikely(ret)) {
399 kmem_cache_free(watch_cachep, watch);
400 return ERR_PTR(ret);
401 }
402
403 watch->mask = mask;
404 atomic_set(&watch->count, 0);
405 INIT_LIST_HEAD(&watch->d_list);
406 INIT_LIST_HEAD(&watch->i_list);
407
408 /* save a reference to device and bump the count to make it official */
409 get_inotify_dev(dev);
410 watch->dev = dev;
411
412 /*
413 * Save a reference to the inode and bump the ref count to make it
414 * official. We hold a reference to nameidata, which makes this safe.
415 */
416 watch->inode = igrab(inode);
417
418 /* bump our own count, corresponding to our entry in dev->watches */
419 get_inotify_watch(watch);
420
421 atomic_inc(&dev->user->inotify_watches);
422
423 return watch;
424}
425
426/*
427 * inotify_find_dev - find the watch associated with the given inode and dev
428 *
429 * Callers must hold inode->inotify_sem.
430 */
431static struct inotify_watch *inode_find_dev(struct inode *inode,
432 struct inotify_device *dev)
433{
434 struct inotify_watch *watch;
435
436 list_for_each_entry(watch, &inode->inotify_watches, i_list) {
437 if (watch->dev == dev)
438 return watch;
439 }
440
441 return NULL;
442}
443
444/*
445 * remove_watch_no_event - remove_watch() without the IN_IGNORED event.
446 */
447static void remove_watch_no_event(struct inotify_watch *watch,
448 struct inotify_device *dev)
449{
450 list_del(&watch->i_list);
451 list_del(&watch->d_list);
452
453 atomic_dec(&dev->user->inotify_watches);
454 idr_remove(&dev->idr, watch->wd);
455 put_inotify_watch(watch);
456}
457
458/*
459 * remove_watch - Remove a watch from both the device and the inode. Sends
460 * the IN_IGNORED event to the given device signifying that the inode is no
461 * longer watched.
462 *
463 * Callers must hold both inode->inotify_sem and dev->sem. We drop a
464 * reference to the inode before returning.
465 *
466 * The inode is not iput() so as to remain atomic. If the inode needs to be
467 * iput(), the call returns one. Otherwise, it returns zero.
468 */
469static void remove_watch(struct inotify_watch *watch,struct inotify_device *dev)
470{
471 inotify_dev_queue_event(dev, watch, IN_IGNORED, 0, NULL);
472 remove_watch_no_event(watch, dev);
473}
474
475/*
476 * inotify_inode_watched - returns nonzero if there are watches on this inode
477 * and zero otherwise. We call this lockless, we do not care if we race.
478 */
479static inline int inotify_inode_watched(struct inode *inode)
480{
481 return !list_empty(&inode->inotify_watches);
482}
483
484/* Kernel API */
485
486/**
487 * inotify_inode_queue_event - queue an event to all watches on this inode
488 * @inode: inode event is originating from
489 * @mask: event mask describing this event
490 * @cookie: cookie for synchronization, or zero
491 * @name: filename, if any
492 */
493void inotify_inode_queue_event(struct inode *inode, u32 mask, u32 cookie,
494 const char *name)
495{
496 struct inotify_watch *watch, *next;
497
498 if (!inotify_inode_watched(inode))
499 return;
500
501 down(&inode->inotify_sem);
502 list_for_each_entry_safe(watch, next, &inode->inotify_watches, i_list) {
503 u32 watch_mask = watch->mask;
504 if (watch_mask & mask) {
505 struct inotify_device *dev = watch->dev;
506 get_inotify_watch(watch);
507 down(&dev->sem);
508 inotify_dev_queue_event(dev, watch, mask, cookie, name);
509 if (watch_mask & IN_ONESHOT)
510 remove_watch_no_event(watch, dev);
511 up(&dev->sem);
512 put_inotify_watch(watch);
513 }
514 }
515 up(&inode->inotify_sem);
516}
517EXPORT_SYMBOL_GPL(inotify_inode_queue_event);
518
519/**
520 * inotify_dentry_parent_queue_event - queue an event to a dentry's parent
521 * @dentry: the dentry in question, we queue against this dentry's parent
522 * @mask: event mask describing this event
523 * @cookie: cookie for synchronization, or zero
524 * @name: filename, if any
525 */
526void inotify_dentry_parent_queue_event(struct dentry *dentry, u32 mask,
527 u32 cookie, const char *name)
528{
529 struct dentry *parent;
530 struct inode *inode;
531
532 spin_lock(&dentry->d_lock);
533 parent = dentry->d_parent;
534 inode = parent->d_inode;
535
536 if (inotify_inode_watched(inode)) {
537 dget(parent);
538 spin_unlock(&dentry->d_lock);
539 inotify_inode_queue_event(inode, mask, cookie, name);
540 dput(parent);
541 } else
542 spin_unlock(&dentry->d_lock);
543}
544EXPORT_SYMBOL_GPL(inotify_dentry_parent_queue_event);
545
546/**
547 * inotify_get_cookie - return a unique cookie for use in synchronizing events.
548 */
549u32 inotify_get_cookie(void)
550{
551 return atomic_inc_return(&inotify_cookie);
552}
553EXPORT_SYMBOL_GPL(inotify_get_cookie);
554
555/**
556 * inotify_unmount_inodes - an sb is unmounting. handle any watched inodes.
557 * @list: list of inodes being unmounted (sb->s_inodes)
558 *
559 * Called with inode_lock held, protecting the unmounting super block's list
560 * of inodes, and with iprune_sem held, keeping shrink_icache_memory() at bay.
561 * We temporarily drop inode_lock, however, and CAN block.
562 */
563void inotify_unmount_inodes(struct list_head *list)
564{
565 struct inode *inode, *next_i, *need_iput = NULL;
566
567 list_for_each_entry_safe(inode, next_i, list, i_sb_list) {
568 struct inotify_watch *watch, *next_w;
569 struct inode *need_iput_tmp;
570 struct list_head *watches;
571
572 /*
573 * If i_count is zero, the inode cannot have any watches and
574 * doing an __iget/iput with MS_ACTIVE clear would actually
575 * evict all inodes with zero i_count from icache which is
576 * unnecessarily violent and may in fact be illegal to do.
577 */
578 if (!atomic_read(&inode->i_count))
579 continue;
580
581 /*
582 * We cannot __iget() an inode in state I_CLEAR, I_FREEING, or
583 * I_WILL_FREE which is fine because by that point the inode
584 * cannot have any associated watches.
585 */
586 if (inode->i_state & (I_CLEAR | I_FREEING | I_WILL_FREE))
587 continue;
588
589 need_iput_tmp = need_iput;
590 need_iput = NULL;
591 /* In case the remove_watch() drops a reference. */
592 if (inode != need_iput_tmp)
593 __iget(inode);
594 else
595 need_iput_tmp = NULL;
596 /* In case the dropping of a reference would nuke next_i. */
597 if ((&next_i->i_sb_list != list) &&
598 atomic_read(&next_i->i_count) &&
599 !(next_i->i_state & (I_CLEAR | I_FREEING |
600 I_WILL_FREE))) {
601 __iget(next_i);
602 need_iput = next_i;
603 }
604
605 /*
606 * We can safely drop inode_lock here because we hold
607 * references on both inode and next_i. Also no new inodes
608 * will be added since the umount has begun. Finally,
609 * iprune_sem keeps shrink_icache_memory() away.
610 */
611 spin_unlock(&inode_lock);
612
613 if (need_iput_tmp)
614 iput(need_iput_tmp);
615
616 /* for each watch, send IN_UNMOUNT and then remove it */
617 down(&inode->inotify_sem);
618 watches = &inode->inotify_watches;
619 list_for_each_entry_safe(watch, next_w, watches, i_list) {
620 struct inotify_device *dev = watch->dev;
621 down(&dev->sem);
622 inotify_dev_queue_event(dev, watch, IN_UNMOUNT,0,NULL);
623 remove_watch(watch, dev);
624 up(&dev->sem);
625 }
626 up(&inode->inotify_sem);
627 iput(inode);
628
629 spin_lock(&inode_lock);
630 }
631}
632EXPORT_SYMBOL_GPL(inotify_unmount_inodes);
633
634/**
635 * inotify_inode_is_dead - an inode has been deleted, cleanup any watches
636 * @inode: inode that is about to be removed
637 */
638void inotify_inode_is_dead(struct inode *inode)
639{
640 struct inotify_watch *watch, *next;
641
642 down(&inode->inotify_sem);
643 list_for_each_entry_safe(watch, next, &inode->inotify_watches, i_list) {
644 struct inotify_device *dev = watch->dev;
645 down(&dev->sem);
646 remove_watch(watch, dev);
647 up(&dev->sem);
648 }
649 up(&inode->inotify_sem);
650}
651EXPORT_SYMBOL_GPL(inotify_inode_is_dead);
652
653/* Device Interface */
654
655static unsigned int inotify_poll(struct file *file, poll_table *wait)
656{
657 struct inotify_device *dev = file->private_data;
658 int ret = 0;
659
660 poll_wait(file, &dev->wq, wait);
661 down(&dev->sem);
662 if (!list_empty(&dev->events))
663 ret = POLLIN | POLLRDNORM;
664 up(&dev->sem);
665
666 return ret;
667}
668
669static ssize_t inotify_read(struct file *file, char __user *buf,
670 size_t count, loff_t *pos)
671{
672 size_t event_size = sizeof (struct inotify_event);
673 struct inotify_device *dev;
674 char __user *start;
675 int ret;
676 DEFINE_WAIT(wait);
677
678 start = buf;
679 dev = file->private_data;
680
681 while (1) {
682 int events;
683
684 prepare_to_wait(&dev->wq, &wait, TASK_INTERRUPTIBLE);
685
686 down(&dev->sem);
687 events = !list_empty(&dev->events);
688 up(&dev->sem);
689 if (events) {
690 ret = 0;
691 break;
692 }
693
694 if (file->f_flags & O_NONBLOCK) {
695 ret = -EAGAIN;
696 break;
697 }
698
699 if (signal_pending(current)) {
700 ret = -EINTR;
701 break;
702 }
703
704 schedule();
705 }
706
707 finish_wait(&dev->wq, &wait);
708 if (ret)
709 return ret;
710
711 down(&dev->sem);
712 while (1) {
713 struct inotify_kernel_event *kevent;
714
715 ret = buf - start;
716 if (list_empty(&dev->events))
717 break;
718
719 kevent = inotify_dev_get_event(dev);
720 if (event_size + kevent->event.len > count)
721 break;
722
723 if (copy_to_user(buf, &kevent->event, event_size)) {
724 ret = -EFAULT;
725 break;
726 }
727 buf += event_size;
728 count -= event_size;
729
730 if (kevent->name) {
731 if (copy_to_user(buf, kevent->name, kevent->event.len)){
732 ret = -EFAULT;
733 break;
734 }
735 buf += kevent->event.len;
736 count -= kevent->event.len;
737 }
738
739 remove_kevent(dev, kevent);
740 }
741 up(&dev->sem);
742
743 return ret;
744}
745
746static int inotify_release(struct inode *ignored, struct file *file)
747{
748 struct inotify_device *dev = file->private_data;
749
750 /*
751 * Destroy all of the watches on this device. Unfortunately, not very
752 * pretty. We cannot do a simple iteration over the list, because we
753 * do not know the inode until we iterate to the watch. But we need to
754 * hold inode->inotify_sem before dev->sem. The following works.
755 */
756 while (1) {
757 struct inotify_watch *watch;
758 struct list_head *watches;
759 struct inode *inode;
760
761 down(&dev->sem);
762 watches = &dev->watches;
763 if (list_empty(watches)) {
764 up(&dev->sem);
765 break;
766 }
767 watch = list_entry(watches->next, struct inotify_watch, d_list);
768 get_inotify_watch(watch);
769 up(&dev->sem);
770
771 inode = watch->inode;
772 down(&inode->inotify_sem);
773 down(&dev->sem);
774 remove_watch_no_event(watch, dev);
775 up(&dev->sem);
776 up(&inode->inotify_sem);
777 put_inotify_watch(watch);
778 }
779
780 /* destroy all of the events on this device */
781 down(&dev->sem);
782 while (!list_empty(&dev->events))
783 inotify_dev_event_dequeue(dev);
784 up(&dev->sem);
785
786 /* free this device: the put matching the get in inotify_open() */
787 put_inotify_dev(dev);
788
789 return 0;
790}
791
792/*
793 * inotify_ignore - handle the INOTIFY_IGNORE ioctl, asking that a given wd be
794 * removed from the device.
795 *
796 * Can sleep.
797 */
798static int inotify_ignore(struct inotify_device *dev, s32 wd)
799{
800 struct inotify_watch *watch;
801 struct inode *inode;
802
803 down(&dev->sem);
804 watch = idr_find(&dev->idr, wd);
805 if (unlikely(!watch)) {
806 up(&dev->sem);
807 return -EINVAL;
808 }
809 get_inotify_watch(watch);
810 inode = watch->inode;
811 up(&dev->sem);
812
813 down(&inode->inotify_sem);
814 down(&dev->sem);
815
816 /* make sure that we did not race */
817 watch = idr_find(&dev->idr, wd);
818 if (likely(watch))
819 remove_watch(watch, dev);
820
821 up(&dev->sem);
822 up(&inode->inotify_sem);
823 put_inotify_watch(watch);
824
825 return 0;
826}
827
828static long inotify_ioctl(struct file *file, unsigned int cmd,
829 unsigned long arg)
830{
831 struct inotify_device *dev;
832 void __user *p;
833 int ret = -ENOTTY;
834
835 dev = file->private_data;
836 p = (void __user *) arg;
837
838 switch (cmd) {
839 case FIONREAD:
840 ret = put_user(dev->queue_size, (int __user *) p);
841 break;
842 }
843
844 return ret;
845}
846
847static struct file_operations inotify_fops = {
848 .poll = inotify_poll,
849 .read = inotify_read,
850 .release = inotify_release,
851 .unlocked_ioctl = inotify_ioctl,
852 .compat_ioctl = inotify_ioctl,
853};
854
855asmlinkage long sys_inotify_init(void)
856{
857 struct inotify_device *dev;
858 struct user_struct *user;
859 int ret = -ENOTTY;
860 int fd;
861 struct file *filp;
862
863 fd = get_unused_fd();
864 if (fd < 0) {
865 ret = fd;
866 goto out;
867 }
868
869 filp = get_empty_filp();
870 if (!filp) {
871 put_unused_fd(fd);
872 ret = -ENFILE;
873 goto out;
874 }
875 filp->f_op = &inotify_fops;
876 filp->f_vfsmnt = mntget(inotify_mnt);
877 filp->f_dentry = dget(inotify_mnt->mnt_root);
878 filp->f_mapping = filp->f_dentry->d_inode->i_mapping;
879 filp->f_mode = FMODE_READ;
880 filp->f_flags = O_RDONLY;
881
882 user = get_uid(current->user);
883
884 if (unlikely(atomic_read(&user->inotify_devs) >= inotify_max_user_instances)) {
885 ret = -EMFILE;
886 goto out_err;
887 }
888
889 dev = kmalloc(sizeof(struct inotify_device), GFP_KERNEL);
890 if (unlikely(!dev)) {
891 ret = -ENOMEM;
892 goto out_err;
893 }
894
895 idr_init(&dev->idr);
896 INIT_LIST_HEAD(&dev->events);
897 INIT_LIST_HEAD(&dev->watches);
898 init_waitqueue_head(&dev->wq);
899 sema_init(&dev->sem, 1);
900 dev->event_count = 0;
901 dev->queue_size = 0;
902 dev->max_events = inotify_max_queued_events;
903 dev->user = user;
904 atomic_set(&dev->count, 0);
905
906 get_inotify_dev(dev);
907 atomic_inc(&user->inotify_devs);
908
909 filp->private_data = dev;
910 fd_install (fd, filp);
911 return fd;
912out_err:
913 put_unused_fd (fd);
914 put_filp (filp);
915 free_uid(user);
916out:
917 return ret;
918}
919
920asmlinkage long sys_inotify_add_watch(int fd, const char *path, u32 mask)
921{
922 struct inotify_watch *watch, *old;
923 struct inode *inode;
924 struct inotify_device *dev;
925 struct nameidata nd;
926 struct file *filp;
927 int ret;
928
929 filp = fget(fd);
930 if (!filp)
931 return -EBADF;
932
933 dev = filp->private_data;
934
935 ret = find_inode((const char __user*) path, &nd);
936 if (ret)
937 goto fput_and_out;
938
939 /* Held in place by reference in nd */
940 inode = nd.dentry->d_inode;
941
942 down(&inode->inotify_sem);
943 down(&dev->sem);
944
945 /* don't let user-space set invalid bits: we don't want flags set */
946 mask &= IN_ALL_EVENTS;
947 if (!mask) {
948 ret = -EINVAL;
949 goto out;
950 }
951
952 /*
953 * Handle the case of re-adding a watch on an (inode,dev) pair that we
954 * are already watching. We just update the mask and return its wd.
955 */
956 old = inode_find_dev(inode, dev);
957 if (unlikely(old)) {
958 old->mask = mask;
959 ret = old->wd;
960 goto out;
961 }
962
963 watch = create_watch(dev, mask, inode);
964 if (unlikely(IS_ERR(watch))) {
965 ret = PTR_ERR(watch);
966 goto out;
967 }
968
969 /* Add the watch to the device's and the inode's list */
970 list_add(&watch->d_list, &dev->watches);
971 list_add(&watch->i_list, &inode->inotify_watches);
972 ret = watch->wd;
973out:
974 path_release (&nd);
975 up(&dev->sem);
976 up(&inode->inotify_sem);
977fput_and_out:
978 fput(filp);
979 return ret;
980}
981
982asmlinkage long sys_inotify_rm_watch(int fd, u32 wd)
983{
984 struct file *filp;
985 struct inotify_device *dev;
986 int ret;
987
988 filp = fget(fd);
989 if (!filp)
990 return -EBADF;
991 dev = filp->private_data;
992 ret = inotify_ignore(dev, wd);
993 fput(filp);
994
995 return ret;
996}
997
998static struct super_block *
999inotify_get_sb(struct file_system_type *fs_type, int flags,
1000 const char *dev_name, void *data)
1001{
1002 return get_sb_pseudo(fs_type, "inotify", NULL, 0xBAD1DEA);
1003}
1004
1005static struct file_system_type inotify_fs_type = {
1006 .name = "inotifyfs",
1007 .get_sb = inotify_get_sb,
1008 .kill_sb = kill_anon_super,
1009};
1010
1011/*
1012 * inotify_init - Our initialization function. Note that we cannnot return
1013 * error because we have compiled-in VFS hooks. So an (unlikely) failure here
1014 * must result in panic().
1015 */
1016static int __init inotify_init(void)
1017{
1018 register_filesystem(&inotify_fs_type);
1019 inotify_mnt = kern_mount(&inotify_fs_type);
1020
1021 inotify_max_queued_events = 8192;
1022 inotify_max_user_instances = 8;
1023 inotify_max_user_watches = 8192;
1024
1025 atomic_set(&inotify_cookie, 0);
1026
1027 watch_cachep = kmem_cache_create("inotify_watch_cache",
1028 sizeof(struct inotify_watch),
1029 0, SLAB_PANIC, NULL, NULL);
1030 event_cachep = kmem_cache_create("inotify_event_cache",
1031 sizeof(struct inotify_kernel_event),
1032 0, SLAB_PANIC, NULL, NULL);
1033
1034 return 0;
1035}
1036
1037module_init(inotify_init);
generated by cgit v1.2.2 (git 2.25.0) at 2025-11-02 17:43:41 -0500