2 * fs/inotify.c - inode-based file event notifications
5 * John McCutchan <ttb@tentacle.dhs.org>
6 * Robert Love <rml@novell.com>
8 * Kernel API added by: Amy Griffis <amy.griffis@hp.com>
10 * Copyright (C) 2005 John McCutchan
11 * Copyright 2006 Hewlett-Packard Development Company, L.P.
13 * This program is free software; you can redistribute it and/or modify it
14 * under the terms of the GNU General Public License as published by the
15 * Free Software Foundation; either version 2, or (at your option) any
18 * This program is distributed in the hope that it will be useful, but
19 * WITHOUT ANY WARRANTY; without even the implied warranty of
20 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
21 * General Public License for more details.
24 #include <linux/module.h>
25 #include <linux/kernel.h>
26 #include <linux/spinlock.h>
27 #include <linux/idr.h>
28 #include <linux/slab.h>
30 #include <linux/init.h>
31 #include <linux/list.h>
32 #include <linux/writeback.h>
33 #include <linux/inotify.h>
35 static atomic_t inotify_cookie
;
40 * dentry->d_lock (used to keep d_move() away from dentry->d_parent)
41 * iprune_mutex (synchronize shrink_icache_memory())
42 * inode_lock (protects the super_block->s_inodes list)
43 * inode->inotify_mutex (protects inode->inotify_watches and watches->i_list)
44 * inotify_handle->mutex (protects inotify_handle and watches->h_list)
46 * The inode->inotify_mutex and inotify_handle->mutex and held during execution
47 * of a caller's event handler. Thus, the caller must not hold any locks
48 * taken in their event handler while calling any of the published inotify
53 * Lifetimes of the three main data structures--inotify_handle, inode, and
54 * inotify_watch--are managed by reference count.
56 * inotify_handle: Lifetime is from inotify_init() to inotify_destroy().
57 * Additional references can bump the count via get_inotify_handle() and drop
58 * the count via put_inotify_handle().
60 * inotify_watch: for inotify's purposes, lifetime is from inotify_add_watch()
61 * to remove_watch_no_event(). Additional references can bump the count via
62 * get_inotify_watch() and drop the count via put_inotify_watch(). The caller
63 * is reponsible for the final put after receiving IN_IGNORED, or when using
64 * IN_ONESHOT after receiving the first event. Inotify does the final put if
65 * inotify_destroy() is called.
67 * inode: Pinned so long as the inode is associated with a watch, from
68 * inotify_add_watch() to the final put_inotify_watch().
72 * struct inotify_handle - represents an inotify instance
74 * This structure is protected by the mutex 'mutex'.
76 struct inotify_handle
{
77 struct idr idr
; /* idr mapping wd -> watch */
78 struct mutex mutex
; /* protects this bad boy */
79 struct list_head watches
; /* list of watches */
80 atomic_t count
; /* reference count */
81 u32 last_wd
; /* the last wd allocated */
82 const struct inotify_operations
*in_ops
; /* inotify caller operations */
85 static inline void get_inotify_handle(struct inotify_handle
*ih
)
87 atomic_inc(&ih
->count
);
90 static inline void put_inotify_handle(struct inotify_handle
*ih
)
92 if (atomic_dec_and_test(&ih
->count
)) {
93 idr_destroy(&ih
->idr
);
99 * get_inotify_watch - grab a reference to an inotify_watch
100 * @watch: watch to grab
102 void get_inotify_watch(struct inotify_watch
*watch
)
104 atomic_inc(&watch
->count
);
106 EXPORT_SYMBOL_GPL(get_inotify_watch
);
109 * put_inotify_watch - decrements the ref count on a given watch. cleans up
110 * watch references if the count reaches zero. inotify_watch is freed by
111 * inotify callers via the destroy_watch() op.
112 * @watch: watch to release
114 void put_inotify_watch(struct inotify_watch
*watch
)
116 if (atomic_dec_and_test(&watch
->count
)) {
117 struct inotify_handle
*ih
= watch
->ih
;
120 ih
->in_ops
->destroy_watch(watch
);
121 put_inotify_handle(ih
);
124 EXPORT_SYMBOL_GPL(put_inotify_watch
);
127 * inotify_handle_get_wd - returns the next WD for use by the given handle
129 * Callers must hold ih->mutex. This function can sleep.
131 static int inotify_handle_get_wd(struct inotify_handle
*ih
,
132 struct inotify_watch
*watch
)
137 if (unlikely(!idr_pre_get(&ih
->idr
, GFP_KERNEL
)))
139 ret
= idr_get_new_above(&ih
->idr
, watch
, ih
->last_wd
+1, &watch
->wd
);
140 } while (ret
== -EAGAIN
);
143 ih
->last_wd
= watch
->wd
;
149 * inotify_inode_watched - returns nonzero if there are watches on this inode
150 * and zero otherwise. We call this lockless, we do not care if we race.
152 static inline int inotify_inode_watched(struct inode
*inode
)
154 return !list_empty(&inode
->inotify_watches
);
158 * Get child dentry flag into synch with parent inode.
159 * Flag should always be clear for negative dentrys.
161 static void set_dentry_child_flags(struct inode
*inode
, int watched
)
163 struct dentry
*alias
;
165 spin_lock(&dcache_lock
);
166 list_for_each_entry(alias
, &inode
->i_dentry
, d_alias
) {
167 struct dentry
*child
;
169 list_for_each_entry(child
, &alias
->d_subdirs
, d_u
.d_child
) {
170 if (!child
->d_inode
) {
171 WARN_ON(child
->d_flags
& DCACHE_INOTIFY_PARENT_WATCHED
);
174 spin_lock(&child
->d_lock
);
176 WARN_ON(child
->d_flags
&
177 DCACHE_INOTIFY_PARENT_WATCHED
);
178 child
->d_flags
|= DCACHE_INOTIFY_PARENT_WATCHED
;
180 WARN_ON(!(child
->d_flags
&
181 DCACHE_INOTIFY_PARENT_WATCHED
));
182 child
->d_flags
&=~DCACHE_INOTIFY_PARENT_WATCHED
;
184 spin_unlock(&child
->d_lock
);
187 spin_unlock(&dcache_lock
);
191 * inotify_find_handle - find the watch associated with the given inode and
194 * Callers must hold inode->inotify_mutex.
196 static struct inotify_watch
*inode_find_handle(struct inode
*inode
,
197 struct inotify_handle
*ih
)
199 struct inotify_watch
*watch
;
201 list_for_each_entry(watch
, &inode
->inotify_watches
, i_list
) {
210 * remove_watch_no_event - remove_watch() without the IN_IGNORED event.
212 * Callers must hold both inode->inotify_mutex and ih->mutex.
214 static void remove_watch_no_event(struct inotify_watch
*watch
,
215 struct inotify_handle
*ih
)
217 list_del(&watch
->i_list
);
218 list_del(&watch
->h_list
);
220 if (!inotify_inode_watched(watch
->inode
))
221 set_dentry_child_flags(watch
->inode
, 0);
223 idr_remove(&ih
->idr
, watch
->wd
);
227 * remove_watch - Remove a watch from both the handle and the inode. Sends
228 * the IN_IGNORED event signifying that the inode is no longer watched.
230 * Callers must hold both inode->inotify_mutex and ih->mutex.
232 static void remove_watch(struct inotify_watch
*watch
, struct inotify_handle
*ih
)
234 remove_watch_no_event(watch
, ih
);
235 ih
->in_ops
->handle_event(watch
, watch
->wd
, IN_IGNORED
, 0, NULL
, NULL
);
238 /* Kernel API for producing events */
241 * inotify_d_instantiate - instantiate dcache entry for inode
243 void inotify_d_instantiate(struct dentry
*entry
, struct inode
*inode
)
245 struct dentry
*parent
;
250 WARN_ON(entry
->d_flags
& DCACHE_INOTIFY_PARENT_WATCHED
);
251 spin_lock(&entry
->d_lock
);
252 parent
= entry
->d_parent
;
253 if (parent
->d_inode
&& inotify_inode_watched(parent
->d_inode
))
254 entry
->d_flags
|= DCACHE_INOTIFY_PARENT_WATCHED
;
255 spin_unlock(&entry
->d_lock
);
259 * inotify_d_move - dcache entry has been moved
261 void inotify_d_move(struct dentry
*entry
)
263 struct dentry
*parent
;
265 parent
= entry
->d_parent
;
266 if (inotify_inode_watched(parent
->d_inode
))
267 entry
->d_flags
|= DCACHE_INOTIFY_PARENT_WATCHED
;
269 entry
->d_flags
&= ~DCACHE_INOTIFY_PARENT_WATCHED
;
273 * inotify_inode_queue_event - queue an event to all watches on this inode
274 * @inode: inode event is originating from
275 * @mask: event mask describing this event
276 * @cookie: cookie for synchronization, or zero
277 * @name: filename, if any
278 * @n_inode: inode associated with name
280 void inotify_inode_queue_event(struct inode
*inode
, u32 mask
, u32 cookie
,
281 const char *name
, struct inode
*n_inode
)
283 struct inotify_watch
*watch
, *next
;
285 if (!inotify_inode_watched(inode
))
288 mutex_lock(&inode
->inotify_mutex
);
289 list_for_each_entry_safe(watch
, next
, &inode
->inotify_watches
, i_list
) {
290 u32 watch_mask
= watch
->mask
;
291 if (watch_mask
& mask
) {
292 struct inotify_handle
*ih
= watch
->ih
;
293 mutex_lock(&ih
->mutex
);
294 if (watch_mask
& IN_ONESHOT
)
295 remove_watch_no_event(watch
, ih
);
296 ih
->in_ops
->handle_event(watch
, watch
->wd
, mask
, cookie
,
298 mutex_unlock(&ih
->mutex
);
301 mutex_unlock(&inode
->inotify_mutex
);
303 EXPORT_SYMBOL_GPL(inotify_inode_queue_event
);
306 * inotify_dentry_parent_queue_event - queue an event to a dentry's parent
307 * @dentry: the dentry in question, we queue against this dentry's parent
308 * @mask: event mask describing this event
309 * @cookie: cookie for synchronization, or zero
310 * @name: filename, if any
312 void inotify_dentry_parent_queue_event(struct dentry
*dentry
, u32 mask
,
313 u32 cookie
, const char *name
)
315 struct dentry
*parent
;
318 if (!(dentry
->d_flags
& DCACHE_INOTIFY_PARENT_WATCHED
))
321 spin_lock(&dentry
->d_lock
);
322 parent
= dentry
->d_parent
;
323 inode
= parent
->d_inode
;
325 if (inotify_inode_watched(inode
)) {
327 spin_unlock(&dentry
->d_lock
);
328 inotify_inode_queue_event(inode
, mask
, cookie
, name
,
332 spin_unlock(&dentry
->d_lock
);
334 EXPORT_SYMBOL_GPL(inotify_dentry_parent_queue_event
);
337 * inotify_get_cookie - return a unique cookie for use in synchronizing events.
339 u32
inotify_get_cookie(void)
341 return atomic_inc_return(&inotify_cookie
);
343 EXPORT_SYMBOL_GPL(inotify_get_cookie
);
346 * inotify_unmount_inodes - an sb is unmounting. handle any watched inodes.
347 * @list: list of inodes being unmounted (sb->s_inodes)
349 * Called with inode_lock held, protecting the unmounting super block's list
350 * of inodes, and with iprune_mutex held, keeping shrink_icache_memory() at bay.
351 * We temporarily drop inode_lock, however, and CAN block.
353 void inotify_unmount_inodes(struct list_head
*list
)
355 struct inode
*inode
, *next_i
, *need_iput
= NULL
;
357 list_for_each_entry_safe(inode
, next_i
, list
, i_sb_list
) {
358 struct inotify_watch
*watch
, *next_w
;
359 struct inode
*need_iput_tmp
;
360 struct list_head
*watches
;
363 * If i_count is zero, the inode cannot have any watches and
364 * doing an __iget/iput with MS_ACTIVE clear would actually
365 * evict all inodes with zero i_count from icache which is
366 * unnecessarily violent and may in fact be illegal to do.
368 if (!atomic_read(&inode
->i_count
))
372 * We cannot __iget() an inode in state I_CLEAR, I_FREEING, or
373 * I_WILL_FREE which is fine because by that point the inode
374 * cannot have any associated watches.
376 if (inode
->i_state
& (I_CLEAR
| I_FREEING
| I_WILL_FREE
))
379 need_iput_tmp
= need_iput
;
381 /* In case the remove_watch() drops a reference. */
382 if (inode
!= need_iput_tmp
)
385 need_iput_tmp
= NULL
;
386 /* In case the dropping of a reference would nuke next_i. */
387 if ((&next_i
->i_sb_list
!= list
) &&
388 atomic_read(&next_i
->i_count
) &&
389 !(next_i
->i_state
& (I_CLEAR
| I_FREEING
|
396 * We can safely drop inode_lock here because we hold
397 * references on both inode and next_i. Also no new inodes
398 * will be added since the umount has begun. Finally,
399 * iprune_mutex keeps shrink_icache_memory() away.
401 spin_unlock(&inode_lock
);
406 /* for each watch, send IN_UNMOUNT and then remove it */
407 mutex_lock(&inode
->inotify_mutex
);
408 watches
= &inode
->inotify_watches
;
409 list_for_each_entry_safe(watch
, next_w
, watches
, i_list
) {
410 struct inotify_handle
*ih
= watch
->ih
;
411 mutex_lock(&ih
->mutex
);
412 ih
->in_ops
->handle_event(watch
, watch
->wd
, IN_UNMOUNT
, 0,
414 remove_watch(watch
, ih
);
415 mutex_unlock(&ih
->mutex
);
417 mutex_unlock(&inode
->inotify_mutex
);
420 spin_lock(&inode_lock
);
423 EXPORT_SYMBOL_GPL(inotify_unmount_inodes
);
426 * inotify_inode_is_dead - an inode has been deleted, cleanup any watches
427 * @inode: inode that is about to be removed
429 void inotify_inode_is_dead(struct inode
*inode
)
431 struct inotify_watch
*watch
, *next
;
433 mutex_lock(&inode
->inotify_mutex
);
434 list_for_each_entry_safe(watch
, next
, &inode
->inotify_watches
, i_list
) {
435 struct inotify_handle
*ih
= watch
->ih
;
436 mutex_lock(&ih
->mutex
);
437 remove_watch(watch
, ih
);
438 mutex_unlock(&ih
->mutex
);
440 mutex_unlock(&inode
->inotify_mutex
);
442 EXPORT_SYMBOL_GPL(inotify_inode_is_dead
);
444 /* Kernel Consumer API */
447 * inotify_init - allocate and initialize an inotify instance
448 * @ops: caller's inotify operations
450 struct inotify_handle
*inotify_init(const struct inotify_operations
*ops
)
452 struct inotify_handle
*ih
;
454 ih
= kmalloc(sizeof(struct inotify_handle
), GFP_KERNEL
);
456 return ERR_PTR(-ENOMEM
);
459 INIT_LIST_HEAD(&ih
->watches
);
460 mutex_init(&ih
->mutex
);
463 atomic_set(&ih
->count
, 0);
464 get_inotify_handle(ih
);
468 EXPORT_SYMBOL_GPL(inotify_init
);
471 * inotify_init_watch - initialize an inotify watch
472 * @watch: watch to initialize
474 void inotify_init_watch(struct inotify_watch
*watch
)
476 INIT_LIST_HEAD(&watch
->h_list
);
477 INIT_LIST_HEAD(&watch
->i_list
);
478 atomic_set(&watch
->count
, 0);
479 get_inotify_watch(watch
); /* initial get */
481 EXPORT_SYMBOL_GPL(inotify_init_watch
);
484 * inotify_destroy - clean up and destroy an inotify instance
485 * @ih: inotify handle
487 void inotify_destroy(struct inotify_handle
*ih
)
490 * Destroy all of the watches for this handle. Unfortunately, not very
491 * pretty. We cannot do a simple iteration over the list, because we
492 * do not know the inode until we iterate to the watch. But we need to
493 * hold inode->inotify_mutex before ih->mutex. The following works.
496 struct inotify_watch
*watch
;
497 struct list_head
*watches
;
500 mutex_lock(&ih
->mutex
);
501 watches
= &ih
->watches
;
502 if (list_empty(watches
)) {
503 mutex_unlock(&ih
->mutex
);
506 watch
= list_entry(watches
->next
, struct inotify_watch
, h_list
);
507 get_inotify_watch(watch
);
508 mutex_unlock(&ih
->mutex
);
510 inode
= watch
->inode
;
511 mutex_lock(&inode
->inotify_mutex
);
512 mutex_lock(&ih
->mutex
);
514 /* make sure we didn't race with another list removal */
515 if (likely(idr_find(&ih
->idr
, watch
->wd
))) {
516 remove_watch_no_event(watch
, ih
);
517 put_inotify_watch(watch
);
520 mutex_unlock(&ih
->mutex
);
521 mutex_unlock(&inode
->inotify_mutex
);
522 put_inotify_watch(watch
);
525 /* free this handle: the put matching the get in inotify_init() */
526 put_inotify_handle(ih
);
528 EXPORT_SYMBOL_GPL(inotify_destroy
);
531 * inotify_find_watch - find an existing watch for an (ih,inode) pair
532 * @ih: inotify handle
533 * @inode: inode to watch
534 * @watchp: pointer to existing inotify_watch
536 * Caller must pin given inode (via nameidata).
538 s32
inotify_find_watch(struct inotify_handle
*ih
, struct inode
*inode
,
539 struct inotify_watch
**watchp
)
541 struct inotify_watch
*old
;
544 mutex_lock(&inode
->inotify_mutex
);
545 mutex_lock(&ih
->mutex
);
547 old
= inode_find_handle(inode
, ih
);
549 get_inotify_watch(old
); /* caller must put watch */
554 mutex_unlock(&ih
->mutex
);
555 mutex_unlock(&inode
->inotify_mutex
);
559 EXPORT_SYMBOL_GPL(inotify_find_watch
);
562 * inotify_find_update_watch - find and update the mask of an existing watch
563 * @ih: inotify handle
564 * @inode: inode's watch to update
565 * @mask: mask of events to watch
567 * Caller must pin given inode (via nameidata).
569 s32
inotify_find_update_watch(struct inotify_handle
*ih
, struct inode
*inode
,
572 struct inotify_watch
*old
;
576 if (mask
& IN_MASK_ADD
)
579 /* don't allow invalid bits: we don't want flags set */
580 mask
&= IN_ALL_EVENTS
| IN_ONESHOT
;
584 mutex_lock(&inode
->inotify_mutex
);
585 mutex_lock(&ih
->mutex
);
588 * Handle the case of re-adding a watch on an (inode,ih) pair that we
589 * are already watching. We just update the mask and return its wd.
591 old
= inode_find_handle(inode
, ih
);
592 if (unlikely(!old
)) {
603 mutex_unlock(&ih
->mutex
);
604 mutex_unlock(&inode
->inotify_mutex
);
607 EXPORT_SYMBOL_GPL(inotify_find_update_watch
);
610 * inotify_add_watch - add a watch to an inotify instance
611 * @ih: inotify handle
612 * @watch: caller allocated watch structure
613 * @inode: inode to watch
614 * @mask: mask of events to watch
616 * Caller must pin given inode (via nameidata).
617 * Caller must ensure it only calls inotify_add_watch() once per watch.
618 * Calls inotify_handle_get_wd() so may sleep.
620 s32
inotify_add_watch(struct inotify_handle
*ih
, struct inotify_watch
*watch
,
621 struct inode
*inode
, u32 mask
)
625 /* don't allow invalid bits: we don't want flags set */
626 mask
&= IN_ALL_EVENTS
| IN_ONESHOT
;
631 mutex_lock(&inode
->inotify_mutex
);
632 mutex_lock(&ih
->mutex
);
634 /* Initialize a new watch */
635 ret
= inotify_handle_get_wd(ih
, watch
);
640 /* save a reference to handle and bump the count to make it official */
641 get_inotify_handle(ih
);
645 * Save a reference to the inode and bump the ref count to make it
646 * official. We hold a reference to nameidata, which makes this safe.
648 watch
->inode
= igrab(inode
);
650 if (!inotify_inode_watched(inode
))
651 set_dentry_child_flags(inode
, 1);
653 /* Add the watch to the handle's and the inode's list */
654 list_add(&watch
->h_list
, &ih
->watches
);
655 list_add(&watch
->i_list
, &inode
->inotify_watches
);
657 mutex_unlock(&ih
->mutex
);
658 mutex_unlock(&inode
->inotify_mutex
);
661 EXPORT_SYMBOL_GPL(inotify_add_watch
);
664 * inotify_rm_wd - remove a watch from an inotify instance
665 * @ih: inotify handle
666 * @wd: watch descriptor to remove
670 int inotify_rm_wd(struct inotify_handle
*ih
, u32 wd
)
672 struct inotify_watch
*watch
;
675 mutex_lock(&ih
->mutex
);
676 watch
= idr_find(&ih
->idr
, wd
);
677 if (unlikely(!watch
)) {
678 mutex_unlock(&ih
->mutex
);
681 get_inotify_watch(watch
);
682 inode
= watch
->inode
;
683 mutex_unlock(&ih
->mutex
);
685 mutex_lock(&inode
->inotify_mutex
);
686 mutex_lock(&ih
->mutex
);
688 /* make sure that we did not race */
689 if (likely(idr_find(&ih
->idr
, wd
) == watch
))
690 remove_watch(watch
, ih
);
692 mutex_unlock(&ih
->mutex
);
693 mutex_unlock(&inode
->inotify_mutex
);
694 put_inotify_watch(watch
);
698 EXPORT_SYMBOL_GPL(inotify_rm_wd
);
701 * inotify_rm_watch - remove a watch from an inotify instance
702 * @ih: inotify handle
703 * @watch: watch to remove
707 int inotify_rm_watch(struct inotify_handle
*ih
,
708 struct inotify_watch
*watch
)
710 return inotify_rm_wd(ih
, watch
->wd
);
712 EXPORT_SYMBOL_GPL(inotify_rm_watch
);
715 * inotify_setup - core initialization function
717 static int __init
inotify_setup(void)
719 atomic_set(&inotify_cookie
, 0);
724 module_init(inotify_setup
);