blob: 7bbed1b89825f8b37f4fa753201290d0002bf618 [file] [log] [blame]
Robert Love0eeca282005-07-12 17:06:03 -04001/*
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 *
Amy Griffis2d9048e2006-06-01 13:10:59 -07008 * Kernel API added by: Amy Griffis <amy.griffis@hp.com>
9 *
Robert Love0eeca282005-07-12 17:06:03 -040010 * Copyright (C) 2005 John McCutchan
Amy Griffis2d9048e2006-06-01 13:10:59 -070011 * Copyright 2006 Hewlett-Packard Development Company, L.P.
Robert Love0eeca282005-07-12 17:06:03 -040012 *
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
16 * later version.
17 *
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.
22 */
23
24#include <linux/module.h>
25#include <linux/kernel.h>
Robert Love0eeca282005-07-12 17:06:03 -040026#include <linux/spinlock.h>
27#include <linux/idr.h>
28#include <linux/slab.h>
29#include <linux/fs.h>
Al Viro914e2632006-10-18 13:55:46 -040030#include <linux/sched.h>
Robert Love0eeca282005-07-12 17:06:03 -040031#include <linux/init.h>
32#include <linux/list.h>
33#include <linux/writeback.h>
34#include <linux/inotify.h>
Robert Love0eeca282005-07-12 17:06:03 -040035
36static atomic_t inotify_cookie;
37
Robert Love0eeca282005-07-12 17:06:03 -040038/*
39 * Lock ordering:
40 *
41 * dentry->d_lock (used to keep d_move() away from dentry->d_parent)
Ingo Molnarf24075b2006-03-23 03:00:34 -080042 * iprune_mutex (synchronize shrink_icache_memory())
Robert Love0eeca282005-07-12 17:06:03 -040043 * inode_lock (protects the super_block->s_inodes list)
Ingo Molnard4f9af92006-03-23 03:00:30 -080044 * inode->inotify_mutex (protects inode->inotify_watches and watches->i_list)
Amy Griffis2d9048e2006-06-01 13:10:59 -070045 * inotify_handle->mutex (protects inotify_handle and watches->h_list)
46 *
47 * The inode->inotify_mutex and inotify_handle->mutex and held during execution
48 * of a caller's event handler. Thus, the caller must not hold any locks
49 * taken in their event handler while calling any of the published inotify
50 * interfaces.
Robert Love0eeca282005-07-12 17:06:03 -040051 */
52
53/*
Amy Griffis2d9048e2006-06-01 13:10:59 -070054 * Lifetimes of the three main data structures--inotify_handle, inode, and
Robert Love0eeca282005-07-12 17:06:03 -040055 * inotify_watch--are managed by reference count.
56 *
Amy Griffis2d9048e2006-06-01 13:10:59 -070057 * inotify_handle: Lifetime is from inotify_init() to inotify_destroy().
58 * Additional references can bump the count via get_inotify_handle() and drop
59 * the count via put_inotify_handle().
Robert Love0eeca282005-07-12 17:06:03 -040060 *
Amy Griffis2d9048e2006-06-01 13:10:59 -070061 * inotify_watch: for inotify's purposes, lifetime is from inotify_add_watch()
62 * to remove_watch_no_event(). Additional references can bump the count via
63 * get_inotify_watch() and drop the count via put_inotify_watch(). The caller
64 * is reponsible for the final put after receiving IN_IGNORED, or when using
65 * IN_ONESHOT after receiving the first event. Inotify does the final put if
66 * inotify_destroy() is called.
Robert Love0eeca282005-07-12 17:06:03 -040067 *
68 * inode: Pinned so long as the inode is associated with a watch, from
Amy Griffis2d9048e2006-06-01 13:10:59 -070069 * inotify_add_watch() to the final put_inotify_watch().
Robert Love0eeca282005-07-12 17:06:03 -040070 */
71
72/*
Amy Griffis2d9048e2006-06-01 13:10:59 -070073 * struct inotify_handle - represents an inotify instance
Robert Love0eeca282005-07-12 17:06:03 -040074 *
Ingo Molnard4f9af92006-03-23 03:00:30 -080075 * This structure is protected by the mutex 'mutex'.
Robert Love0eeca282005-07-12 17:06:03 -040076 */
Amy Griffis2d9048e2006-06-01 13:10:59 -070077struct inotify_handle {
Robert Love0eeca282005-07-12 17:06:03 -040078 struct idr idr; /* idr mapping wd -> watch */
Ingo Molnard4f9af92006-03-23 03:00:30 -080079 struct mutex mutex; /* protects this bad boy */
Robert Love0eeca282005-07-12 17:06:03 -040080 struct list_head watches; /* list of watches */
81 atomic_t count; /* reference count */
John McCutchanb9c55d22005-08-01 11:00:45 -040082 u32 last_wd; /* the last wd allocated */
Amy Griffis2d9048e2006-06-01 13:10:59 -070083 const struct inotify_operations *in_ops; /* inotify caller operations */
Robert Love0eeca282005-07-12 17:06:03 -040084};
85
Amy Griffis2d9048e2006-06-01 13:10:59 -070086static inline void get_inotify_handle(struct inotify_handle *ih)
Robert Love0eeca282005-07-12 17:06:03 -040087{
Amy Griffis2d9048e2006-06-01 13:10:59 -070088 atomic_inc(&ih->count);
Robert Love0eeca282005-07-12 17:06:03 -040089}
90
Amy Griffis2d9048e2006-06-01 13:10:59 -070091static inline void put_inotify_handle(struct inotify_handle *ih)
Robert Love0eeca282005-07-12 17:06:03 -040092{
Amy Griffis2d9048e2006-06-01 13:10:59 -070093 if (atomic_dec_and_test(&ih->count)) {
94 idr_destroy(&ih->idr);
95 kfree(ih);
Robert Love0eeca282005-07-12 17:06:03 -040096 }
97}
98
Amy Griffis2d9048e2006-06-01 13:10:59 -070099/**
100 * get_inotify_watch - grab a reference to an inotify_watch
101 * @watch: watch to grab
102 */
103void get_inotify_watch(struct inotify_watch *watch)
Robert Love0eeca282005-07-12 17:06:03 -0400104{
105 atomic_inc(&watch->count);
106}
Amy Griffis2d9048e2006-06-01 13:10:59 -0700107EXPORT_SYMBOL_GPL(get_inotify_watch);
Robert Love0eeca282005-07-12 17:06:03 -0400108
Al Viro8f7b0ba2008-11-15 01:15:43 +0000109int pin_inotify_watch(struct inotify_watch *watch)
110{
111 struct super_block *sb = watch->inode->i_sb;
112 spin_lock(&sb_lock);
113 if (sb->s_count >= S_BIAS) {
114 atomic_inc(&sb->s_active);
115 spin_unlock(&sb_lock);
116 atomic_inc(&watch->count);
117 return 1;
118 }
119 spin_unlock(&sb_lock);
120 return 0;
121}
122
Amy Griffis2d9048e2006-06-01 13:10:59 -0700123/**
Robert Love0eeca282005-07-12 17:06:03 -0400124 * put_inotify_watch - decrements the ref count on a given watch. cleans up
Amy Griffis2d9048e2006-06-01 13:10:59 -0700125 * watch references if the count reaches zero. inotify_watch is freed by
126 * inotify callers via the destroy_watch() op.
127 * @watch: watch to release
Robert Love0eeca282005-07-12 17:06:03 -0400128 */
Amy Griffis2d9048e2006-06-01 13:10:59 -0700129void put_inotify_watch(struct inotify_watch *watch)
Robert Love0eeca282005-07-12 17:06:03 -0400130{
131 if (atomic_dec_and_test(&watch->count)) {
Amy Griffis2d9048e2006-06-01 13:10:59 -0700132 struct inotify_handle *ih = watch->ih;
133
Robert Love0eeca282005-07-12 17:06:03 -0400134 iput(watch->inode);
Amy Griffis2d9048e2006-06-01 13:10:59 -0700135 ih->in_ops->destroy_watch(watch);
136 put_inotify_handle(ih);
Robert Love0eeca282005-07-12 17:06:03 -0400137 }
138}
Amy Griffis2d9048e2006-06-01 13:10:59 -0700139EXPORT_SYMBOL_GPL(put_inotify_watch);
Robert Love0eeca282005-07-12 17:06:03 -0400140
Al Viro8f7b0ba2008-11-15 01:15:43 +0000141void unpin_inotify_watch(struct inotify_watch *watch)
142{
143 struct super_block *sb = watch->inode->i_sb;
144 put_inotify_watch(watch);
145 deactivate_super(sb);
146}
147
Robert Love0eeca282005-07-12 17:06:03 -0400148/*
Amy Griffis2d9048e2006-06-01 13:10:59 -0700149 * inotify_handle_get_wd - returns the next WD for use by the given handle
Robert Love0eeca282005-07-12 17:06:03 -0400150 *
Amy Griffis2d9048e2006-06-01 13:10:59 -0700151 * Callers must hold ih->mutex. This function can sleep.
Robert Love0eeca282005-07-12 17:06:03 -0400152 */
Amy Griffis2d9048e2006-06-01 13:10:59 -0700153static int inotify_handle_get_wd(struct inotify_handle *ih,
154 struct inotify_watch *watch)
Robert Love0eeca282005-07-12 17:06:03 -0400155{
156 int ret;
157
158 do {
Amy Griffis2d9048e2006-06-01 13:10:59 -0700159 if (unlikely(!idr_pre_get(&ih->idr, GFP_KERNEL)))
Robert Love0eeca282005-07-12 17:06:03 -0400160 return -ENOSPC;
Amy Griffis2d9048e2006-06-01 13:10:59 -0700161 ret = idr_get_new_above(&ih->idr, watch, ih->last_wd+1, &watch->wd);
Robert Love0eeca282005-07-12 17:06:03 -0400162 } while (ret == -EAGAIN);
163
Amy Griffis2d9048e2006-06-01 13:10:59 -0700164 if (likely(!ret))
165 ih->last_wd = watch->wd;
166
Robert Love0eeca282005-07-12 17:06:03 -0400167 return ret;
168}
169
170/*
Nick Pigginc32ccd82006-03-25 03:07:09 -0800171 * inotify_inode_watched - returns nonzero if there are watches on this inode
172 * and zero otherwise. We call this lockless, we do not care if we race.
173 */
174static inline int inotify_inode_watched(struct inode *inode)
175{
176 return !list_empty(&inode->inotify_watches);
177}
178
179/*
180 * Get child dentry flag into synch with parent inode.
181 * Flag should always be clear for negative dentrys.
182 */
183static void set_dentry_child_flags(struct inode *inode, int watched)
184{
185 struct dentry *alias;
186
187 spin_lock(&dcache_lock);
188 list_for_each_entry(alias, &inode->i_dentry, d_alias) {
189 struct dentry *child;
190
191 list_for_each_entry(child, &alias->d_subdirs, d_u.d_child) {
Nick Piggin0d71bd52008-02-06 01:37:29 -0800192 if (!child->d_inode)
Nick Pigginc32ccd82006-03-25 03:07:09 -0800193 continue;
Nick Piggin0d71bd52008-02-06 01:37:29 -0800194
Nick Pigginc32ccd82006-03-25 03:07:09 -0800195 spin_lock(&child->d_lock);
Nick Piggin0d71bd52008-02-06 01:37:29 -0800196 if (watched)
Nick Pigginc32ccd82006-03-25 03:07:09 -0800197 child->d_flags |= DCACHE_INOTIFY_PARENT_WATCHED;
Nick Piggin0d71bd52008-02-06 01:37:29 -0800198 else
199 child->d_flags &=~DCACHE_INOTIFY_PARENT_WATCHED;
Nick Pigginc32ccd82006-03-25 03:07:09 -0800200 spin_unlock(&child->d_lock);
201 }
202 }
203 spin_unlock(&dcache_lock);
204}
205
206/*
Amy Griffis2d9048e2006-06-01 13:10:59 -0700207 * inotify_find_handle - find the watch associated with the given inode and
208 * handle
Robert Love0eeca282005-07-12 17:06:03 -0400209 *
Ingo Molnard4f9af92006-03-23 03:00:30 -0800210 * Callers must hold inode->inotify_mutex.
Robert Love0eeca282005-07-12 17:06:03 -0400211 */
Amy Griffis2d9048e2006-06-01 13:10:59 -0700212static struct inotify_watch *inode_find_handle(struct inode *inode,
213 struct inotify_handle *ih)
Robert Love0eeca282005-07-12 17:06:03 -0400214{
215 struct inotify_watch *watch;
216
217 list_for_each_entry(watch, &inode->inotify_watches, i_list) {
Amy Griffis2d9048e2006-06-01 13:10:59 -0700218 if (watch->ih == ih)
Robert Love0eeca282005-07-12 17:06:03 -0400219 return watch;
220 }
221
222 return NULL;
223}
224
225/*
Amy Griffis3ca10062006-06-01 13:11:05 -0700226 * remove_watch_no_event - remove watch without the IN_IGNORED event.
Amy Griffis2d9048e2006-06-01 13:10:59 -0700227 *
228 * Callers must hold both inode->inotify_mutex and ih->mutex.
Robert Love0eeca282005-07-12 17:06:03 -0400229 */
230static void remove_watch_no_event(struct inotify_watch *watch,
Amy Griffis2d9048e2006-06-01 13:10:59 -0700231 struct inotify_handle *ih)
Robert Love0eeca282005-07-12 17:06:03 -0400232{
233 list_del(&watch->i_list);
Amy Griffis2d9048e2006-06-01 13:10:59 -0700234 list_del(&watch->h_list);
Robert Love0eeca282005-07-12 17:06:03 -0400235
Nick Pigginc32ccd82006-03-25 03:07:09 -0800236 if (!inotify_inode_watched(watch->inode))
237 set_dentry_child_flags(watch->inode, 0);
238
Amy Griffis2d9048e2006-06-01 13:10:59 -0700239 idr_remove(&ih->idr, watch->wd);
Robert Love0eeca282005-07-12 17:06:03 -0400240}
241
Amy Griffis3ca10062006-06-01 13:11:05 -0700242/**
243 * inotify_remove_watch_locked - Remove a watch from both the handle and the
244 * inode. Sends the IN_IGNORED event signifying that the inode is no longer
245 * watched. May be invoked from a caller's event handler.
246 * @ih: inotify handle associated with watch
247 * @watch: watch to remove
Robert Love0eeca282005-07-12 17:06:03 -0400248 *
Amy Griffis2d9048e2006-06-01 13:10:59 -0700249 * Callers must hold both inode->inotify_mutex and ih->mutex.
Robert Love0eeca282005-07-12 17:06:03 -0400250 */
Amy Griffis3ca10062006-06-01 13:11:05 -0700251void inotify_remove_watch_locked(struct inotify_handle *ih,
252 struct inotify_watch *watch)
Robert Love0eeca282005-07-12 17:06:03 -0400253{
Amy Griffis2d9048e2006-06-01 13:10:59 -0700254 remove_watch_no_event(watch, ih);
Amy Griffis7c297722006-06-01 13:11:01 -0700255 ih->in_ops->handle_event(watch, watch->wd, IN_IGNORED, 0, NULL, NULL);
Robert Love0eeca282005-07-12 17:06:03 -0400256}
Amy Griffis3ca10062006-06-01 13:11:05 -0700257EXPORT_SYMBOL_GPL(inotify_remove_watch_locked);
Robert Love0eeca282005-07-12 17:06:03 -0400258
Amy Griffis2d9048e2006-06-01 13:10:59 -0700259/* Kernel API for producing events */
Nick Pigginc32ccd82006-03-25 03:07:09 -0800260
Robert Love0eeca282005-07-12 17:06:03 -0400261/*
Nick Pigginc32ccd82006-03-25 03:07:09 -0800262 * inotify_d_instantiate - instantiate dcache entry for inode
Robert Love0eeca282005-07-12 17:06:03 -0400263 */
Nick Pigginc32ccd82006-03-25 03:07:09 -0800264void inotify_d_instantiate(struct dentry *entry, struct inode *inode)
Robert Love0eeca282005-07-12 17:06:03 -0400265{
Nick Pigginc32ccd82006-03-25 03:07:09 -0800266 struct dentry *parent;
267
268 if (!inode)
269 return;
270
Nick Pigginc32ccd82006-03-25 03:07:09 -0800271 spin_lock(&entry->d_lock);
272 parent = entry->d_parent;
Arnd Bergmann091e8812006-04-10 22:54:31 -0700273 if (parent->d_inode && inotify_inode_watched(parent->d_inode))
Nick Pigginc32ccd82006-03-25 03:07:09 -0800274 entry->d_flags |= DCACHE_INOTIFY_PARENT_WATCHED;
275 spin_unlock(&entry->d_lock);
Robert Love0eeca282005-07-12 17:06:03 -0400276}
277
Nick Pigginc32ccd82006-03-25 03:07:09 -0800278/*
279 * inotify_d_move - dcache entry has been moved
280 */
281void inotify_d_move(struct dentry *entry)
282{
283 struct dentry *parent;
284
285 parent = entry->d_parent;
286 if (inotify_inode_watched(parent->d_inode))
287 entry->d_flags |= DCACHE_INOTIFY_PARENT_WATCHED;
288 else
289 entry->d_flags &= ~DCACHE_INOTIFY_PARENT_WATCHED;
290}
Robert Love0eeca282005-07-12 17:06:03 -0400291
292/**
293 * inotify_inode_queue_event - queue an event to all watches on this inode
294 * @inode: inode event is originating from
295 * @mask: event mask describing this event
296 * @cookie: cookie for synchronization, or zero
297 * @name: filename, if any
Amy Griffis7c297722006-06-01 13:11:01 -0700298 * @n_inode: inode associated with name
Robert Love0eeca282005-07-12 17:06:03 -0400299 */
300void inotify_inode_queue_event(struct inode *inode, u32 mask, u32 cookie,
Amy Griffis7c297722006-06-01 13:11:01 -0700301 const char *name, struct inode *n_inode)
Robert Love0eeca282005-07-12 17:06:03 -0400302{
303 struct inotify_watch *watch, *next;
304
305 if (!inotify_inode_watched(inode))
306 return;
307
Ingo Molnard4f9af92006-03-23 03:00:30 -0800308 mutex_lock(&inode->inotify_mutex);
Robert Love0eeca282005-07-12 17:06:03 -0400309 list_for_each_entry_safe(watch, next, &inode->inotify_watches, i_list) {
310 u32 watch_mask = watch->mask;
311 if (watch_mask & mask) {
Amy Griffis2d9048e2006-06-01 13:10:59 -0700312 struct inotify_handle *ih= watch->ih;
313 mutex_lock(&ih->mutex);
Robert Love0eeca282005-07-12 17:06:03 -0400314 if (watch_mask & IN_ONESHOT)
Amy Griffis2d9048e2006-06-01 13:10:59 -0700315 remove_watch_no_event(watch, ih);
Amy Griffis7c297722006-06-01 13:11:01 -0700316 ih->in_ops->handle_event(watch, watch->wd, mask, cookie,
317 name, n_inode);
Amy Griffis2d9048e2006-06-01 13:10:59 -0700318 mutex_unlock(&ih->mutex);
Robert Love0eeca282005-07-12 17:06:03 -0400319 }
320 }
Ingo Molnard4f9af92006-03-23 03:00:30 -0800321 mutex_unlock(&inode->inotify_mutex);
Robert Love0eeca282005-07-12 17:06:03 -0400322}
323EXPORT_SYMBOL_GPL(inotify_inode_queue_event);
324
325/**
326 * inotify_dentry_parent_queue_event - queue an event to a dentry's parent
327 * @dentry: the dentry in question, we queue against this dentry's parent
328 * @mask: event mask describing this event
329 * @cookie: cookie for synchronization, or zero
330 * @name: filename, if any
331 */
332void inotify_dentry_parent_queue_event(struct dentry *dentry, u32 mask,
333 u32 cookie, const char *name)
334{
335 struct dentry *parent;
336 struct inode *inode;
337
Nick Pigginc32ccd82006-03-25 03:07:09 -0800338 if (!(dentry->d_flags & DCACHE_INOTIFY_PARENT_WATCHED))
John McCutchan820249b2005-09-06 15:16:38 -0700339 return;
340
Robert Love0eeca282005-07-12 17:06:03 -0400341 spin_lock(&dentry->d_lock);
342 parent = dentry->d_parent;
343 inode = parent->d_inode;
344
345 if (inotify_inode_watched(inode)) {
346 dget(parent);
347 spin_unlock(&dentry->d_lock);
Amy Griffis7c297722006-06-01 13:11:01 -0700348 inotify_inode_queue_event(inode, mask, cookie, name,
349 dentry->d_inode);
Robert Love0eeca282005-07-12 17:06:03 -0400350 dput(parent);
351 } else
352 spin_unlock(&dentry->d_lock);
353}
354EXPORT_SYMBOL_GPL(inotify_dentry_parent_queue_event);
355
356/**
357 * inotify_get_cookie - return a unique cookie for use in synchronizing events.
358 */
359u32 inotify_get_cookie(void)
360{
361 return atomic_inc_return(&inotify_cookie);
362}
363EXPORT_SYMBOL_GPL(inotify_get_cookie);
364
365/**
366 * inotify_unmount_inodes - an sb is unmounting. handle any watched inodes.
367 * @list: list of inodes being unmounted (sb->s_inodes)
368 *
369 * Called with inode_lock held, protecting the unmounting super block's list
Ingo Molnarf24075b2006-03-23 03:00:34 -0800370 * of inodes, and with iprune_mutex held, keeping shrink_icache_memory() at bay.
Robert Love0eeca282005-07-12 17:06:03 -0400371 * We temporarily drop inode_lock, however, and CAN block.
372 */
373void inotify_unmount_inodes(struct list_head *list)
374{
375 struct inode *inode, *next_i, *need_iput = NULL;
376
377 list_for_each_entry_safe(inode, next_i, list, i_sb_list) {
378 struct inotify_watch *watch, *next_w;
379 struct inode *need_iput_tmp;
380 struct list_head *watches;
381
382 /*
383 * If i_count is zero, the inode cannot have any watches and
384 * doing an __iget/iput with MS_ACTIVE clear would actually
385 * evict all inodes with zero i_count from icache which is
386 * unnecessarily violent and may in fact be illegal to do.
387 */
388 if (!atomic_read(&inode->i_count))
389 continue;
390
391 /*
392 * We cannot __iget() an inode in state I_CLEAR, I_FREEING, or
393 * I_WILL_FREE which is fine because by that point the inode
394 * cannot have any associated watches.
395 */
396 if (inode->i_state & (I_CLEAR | I_FREEING | I_WILL_FREE))
397 continue;
398
399 need_iput_tmp = need_iput;
400 need_iput = NULL;
Amy Griffis3ca10062006-06-01 13:11:05 -0700401 /* In case inotify_remove_watch_locked() drops a reference. */
Robert Love0eeca282005-07-12 17:06:03 -0400402 if (inode != need_iput_tmp)
403 __iget(inode);
404 else
405 need_iput_tmp = NULL;
406 /* In case the dropping of a reference would nuke next_i. */
407 if ((&next_i->i_sb_list != list) &&
408 atomic_read(&next_i->i_count) &&
409 !(next_i->i_state & (I_CLEAR | I_FREEING |
410 I_WILL_FREE))) {
411 __iget(next_i);
412 need_iput = next_i;
413 }
414
415 /*
416 * We can safely drop inode_lock here because we hold
417 * references on both inode and next_i. Also no new inodes
418 * will be added since the umount has begun. Finally,
Ingo Molnarf24075b2006-03-23 03:00:34 -0800419 * iprune_mutex keeps shrink_icache_memory() away.
Robert Love0eeca282005-07-12 17:06:03 -0400420 */
421 spin_unlock(&inode_lock);
422
423 if (need_iput_tmp)
424 iput(need_iput_tmp);
425
426 /* for each watch, send IN_UNMOUNT and then remove it */
Ingo Molnard4f9af92006-03-23 03:00:30 -0800427 mutex_lock(&inode->inotify_mutex);
Robert Love0eeca282005-07-12 17:06:03 -0400428 watches = &inode->inotify_watches;
429 list_for_each_entry_safe(watch, next_w, watches, i_list) {
Amy Griffis2d9048e2006-06-01 13:10:59 -0700430 struct inotify_handle *ih= watch->ih;
431 mutex_lock(&ih->mutex);
432 ih->in_ops->handle_event(watch, watch->wd, IN_UNMOUNT, 0,
Amy Griffis7c297722006-06-01 13:11:01 -0700433 NULL, NULL);
Amy Griffis3ca10062006-06-01 13:11:05 -0700434 inotify_remove_watch_locked(ih, watch);
Amy Griffis2d9048e2006-06-01 13:10:59 -0700435 mutex_unlock(&ih->mutex);
Robert Love0eeca282005-07-12 17:06:03 -0400436 }
Ingo Molnard4f9af92006-03-23 03:00:30 -0800437 mutex_unlock(&inode->inotify_mutex);
Robert Love0eeca282005-07-12 17:06:03 -0400438 iput(inode);
439
440 spin_lock(&inode_lock);
441 }
442}
443EXPORT_SYMBOL_GPL(inotify_unmount_inodes);
444
445/**
446 * inotify_inode_is_dead - an inode has been deleted, cleanup any watches
447 * @inode: inode that is about to be removed
448 */
449void inotify_inode_is_dead(struct inode *inode)
450{
451 struct inotify_watch *watch, *next;
452
Ingo Molnard4f9af92006-03-23 03:00:30 -0800453 mutex_lock(&inode->inotify_mutex);
Robert Love0eeca282005-07-12 17:06:03 -0400454 list_for_each_entry_safe(watch, next, &inode->inotify_watches, i_list) {
Amy Griffis2d9048e2006-06-01 13:10:59 -0700455 struct inotify_handle *ih = watch->ih;
456 mutex_lock(&ih->mutex);
Amy Griffis3ca10062006-06-01 13:11:05 -0700457 inotify_remove_watch_locked(ih, watch);
Amy Griffis2d9048e2006-06-01 13:10:59 -0700458 mutex_unlock(&ih->mutex);
Robert Love0eeca282005-07-12 17:06:03 -0400459 }
Ingo Molnard4f9af92006-03-23 03:00:30 -0800460 mutex_unlock(&inode->inotify_mutex);
Robert Love0eeca282005-07-12 17:06:03 -0400461}
462EXPORT_SYMBOL_GPL(inotify_inode_is_dead);
463
Amy Griffis2d9048e2006-06-01 13:10:59 -0700464/* Kernel Consumer API */
Robert Love0eeca282005-07-12 17:06:03 -0400465
Amy Griffis2d9048e2006-06-01 13:10:59 -0700466/**
467 * inotify_init - allocate and initialize an inotify instance
468 * @ops: caller's inotify operations
469 */
470struct inotify_handle *inotify_init(const struct inotify_operations *ops)
Robert Love0eeca282005-07-12 17:06:03 -0400471{
Amy Griffis2d9048e2006-06-01 13:10:59 -0700472 struct inotify_handle *ih;
Robert Love0eeca282005-07-12 17:06:03 -0400473
Amy Griffis2d9048e2006-06-01 13:10:59 -0700474 ih = kmalloc(sizeof(struct inotify_handle), GFP_KERNEL);
475 if (unlikely(!ih))
476 return ERR_PTR(-ENOMEM);
Robert Love0eeca282005-07-12 17:06:03 -0400477
Amy Griffis2d9048e2006-06-01 13:10:59 -0700478 idr_init(&ih->idr);
479 INIT_LIST_HEAD(&ih->watches);
480 mutex_init(&ih->mutex);
481 ih->last_wd = 0;
482 ih->in_ops = ops;
483 atomic_set(&ih->count, 0);
484 get_inotify_handle(ih);
485
486 return ih;
Robert Love0eeca282005-07-12 17:06:03 -0400487}
Amy Griffis2d9048e2006-06-01 13:10:59 -0700488EXPORT_SYMBOL_GPL(inotify_init);
Robert Love0eeca282005-07-12 17:06:03 -0400489
Amy Griffis2d9048e2006-06-01 13:10:59 -0700490/**
Amy Griffisa9dc9712006-06-01 13:11:03 -0700491 * inotify_init_watch - initialize an inotify watch
492 * @watch: watch to initialize
493 */
494void inotify_init_watch(struct inotify_watch *watch)
495{
496 INIT_LIST_HEAD(&watch->h_list);
497 INIT_LIST_HEAD(&watch->i_list);
498 atomic_set(&watch->count, 0);
499 get_inotify_watch(watch); /* initial get */
500}
501EXPORT_SYMBOL_GPL(inotify_init_watch);
502
Al Viro8f7b0ba2008-11-15 01:15:43 +0000503/*
504 * Watch removals suck violently. To kick the watch out we need (in this
505 * order) inode->inotify_mutex and ih->mutex. That's fine if we have
506 * a hold on inode; however, for all other cases we need to make damn sure
507 * we don't race with umount. We can *NOT* just grab a reference to a
508 * watch - inotify_unmount_inodes() will happily sail past it and we'll end
509 * with reference to inode potentially outliving its superblock. Ideally
510 * we just want to grab an active reference to superblock if we can; that
511 * will make sure we won't go into inotify_umount_inodes() until we are
512 * done. Cleanup is just deactivate_super(). However, that leaves a messy
513 * case - what if we *are* racing with umount() and active references to
514 * superblock can't be acquired anymore? We can bump ->s_count, grab
515 * ->s_umount, which will almost certainly wait until the superblock is shut
516 * down and the watch in question is pining for fjords. That's fine, but
517 * there is a problem - we might have hit the window between ->s_active
518 * getting to 0 / ->s_count - below S_BIAS (i.e. the moment when superblock
519 * is past the point of no return and is heading for shutdown) and the
520 * moment when deactivate_super() acquires ->s_umount. We could just do
521 * drop_super() yield() and retry, but that's rather antisocial and this
522 * stuff is luser-triggerable. OTOH, having grabbed ->s_umount and having
523 * found that we'd got there first (i.e. that ->s_root is non-NULL) we know
524 * that we won't race with inotify_umount_inodes(). So we could grab a
525 * reference to watch and do the rest as above, just with drop_super() instead
526 * of deactivate_super(), right? Wrong. We had to drop ih->mutex before we
527 * could grab ->s_umount. So the watch could've been gone already.
528 *
529 * That still can be dealt with - we need to save watch->wd, do idr_find()
530 * and compare its result with our pointer. If they match, we either have
531 * the damn thing still alive or we'd lost not one but two races at once,
532 * the watch had been killed and a new one got created with the same ->wd
533 * at the same address. That couldn't have happened in inotify_destroy(),
534 * but inotify_rm_wd() could run into that. Still, "new one got created"
535 * is not a problem - we have every right to kill it or leave it alone,
536 * whatever's more convenient.
537 *
538 * So we can use idr_find(...) == watch && watch->inode->i_sb == sb as
539 * "grab it and kill it" check. If it's been our original watch, we are
540 * fine, if it's a newcomer - nevermind, just pretend that we'd won the
541 * race and kill the fscker anyway; we are safe since we know that its
542 * superblock won't be going away.
543 *
544 * And yes, this is far beyond mere "not very pretty"; so's the entire
545 * concept of inotify to start with.
546 */
547
548/**
549 * pin_to_kill - pin the watch down for removal
550 * @ih: inotify handle
551 * @watch: watch to kill
552 *
553 * Called with ih->mutex held, drops it. Possible return values:
554 * 0 - nothing to do, it has died
555 * 1 - remove it, drop the reference and deactivate_super()
556 * 2 - remove it, drop the reference and drop_super(); we tried hard to avoid
557 * that variant, since it involved a lot of PITA, but that's the best that
558 * could've been done.
559 */
560static int pin_to_kill(struct inotify_handle *ih, struct inotify_watch *watch)
561{
562 struct super_block *sb = watch->inode->i_sb;
563 s32 wd = watch->wd;
564
565 spin_lock(&sb_lock);
566 if (sb->s_count >= S_BIAS) {
567 atomic_inc(&sb->s_active);
568 spin_unlock(&sb_lock);
569 get_inotify_watch(watch);
570 mutex_unlock(&ih->mutex);
571 return 1; /* the best outcome */
572 }
573 sb->s_count++;
574 spin_unlock(&sb_lock);
575 mutex_unlock(&ih->mutex); /* can't grab ->s_umount under it */
576 down_read(&sb->s_umount);
577 if (likely(!sb->s_root)) {
578 /* fs is already shut down; the watch is dead */
579 drop_super(sb);
580 return 0;
581 }
582 /* raced with the final deactivate_super() */
583 mutex_lock(&ih->mutex);
584 if (idr_find(&ih->idr, wd) != watch || watch->inode->i_sb != sb) {
585 /* the watch is dead */
586 mutex_unlock(&ih->mutex);
587 drop_super(sb);
588 return 0;
589 }
590 /* still alive or freed and reused with the same sb and wd; kill */
591 get_inotify_watch(watch);
592 mutex_unlock(&ih->mutex);
593 return 2;
594}
595
596static void unpin_and_kill(struct inotify_watch *watch, int how)
597{
598 struct super_block *sb = watch->inode->i_sb;
599 put_inotify_watch(watch);
600 switch (how) {
601 case 1:
602 deactivate_super(sb);
603 break;
604 case 2:
605 drop_super(sb);
606 }
607}
608
Amy Griffisa9dc9712006-06-01 13:11:03 -0700609/**
Amy Griffis2d9048e2006-06-01 13:10:59 -0700610 * inotify_destroy - clean up and destroy an inotify instance
611 * @ih: inotify handle
612 */
613void inotify_destroy(struct inotify_handle *ih)
Robert Love0eeca282005-07-12 17:06:03 -0400614{
Robert Love0eeca282005-07-12 17:06:03 -0400615 /*
Amy Griffis2d9048e2006-06-01 13:10:59 -0700616 * Destroy all of the watches for this handle. Unfortunately, not very
Robert Love0eeca282005-07-12 17:06:03 -0400617 * pretty. We cannot do a simple iteration over the list, because we
618 * do not know the inode until we iterate to the watch. But we need to
Amy Griffis2d9048e2006-06-01 13:10:59 -0700619 * hold inode->inotify_mutex before ih->mutex. The following works.
Al Viro8f7b0ba2008-11-15 01:15:43 +0000620 *
621 * AV: it had to become even uglier to start working ;-/
Robert Love0eeca282005-07-12 17:06:03 -0400622 */
623 while (1) {
624 struct inotify_watch *watch;
625 struct list_head *watches;
Al Viro8f7b0ba2008-11-15 01:15:43 +0000626 struct super_block *sb;
Robert Love0eeca282005-07-12 17:06:03 -0400627 struct inode *inode;
Al Viro8f7b0ba2008-11-15 01:15:43 +0000628 int how;
Robert Love0eeca282005-07-12 17:06:03 -0400629
Amy Griffis2d9048e2006-06-01 13:10:59 -0700630 mutex_lock(&ih->mutex);
631 watches = &ih->watches;
Robert Love0eeca282005-07-12 17:06:03 -0400632 if (list_empty(watches)) {
Amy Griffis2d9048e2006-06-01 13:10:59 -0700633 mutex_unlock(&ih->mutex);
Robert Love0eeca282005-07-12 17:06:03 -0400634 break;
635 }
Pavel Emelianovb5e61812007-05-08 00:30:19 -0700636 watch = list_first_entry(watches, struct inotify_watch, h_list);
Al Viro8f7b0ba2008-11-15 01:15:43 +0000637 sb = watch->inode->i_sb;
638 how = pin_to_kill(ih, watch);
639 if (!how)
640 continue;
Robert Love0eeca282005-07-12 17:06:03 -0400641
642 inode = watch->inode;
Ingo Molnard4f9af92006-03-23 03:00:30 -0800643 mutex_lock(&inode->inotify_mutex);
Amy Griffis2d9048e2006-06-01 13:10:59 -0700644 mutex_lock(&ih->mutex);
Amy Griffis66055a42006-05-20 15:00:06 -0700645
646 /* make sure we didn't race with another list removal */
Amy Griffis2d9048e2006-06-01 13:10:59 -0700647 if (likely(idr_find(&ih->idr, watch->wd))) {
648 remove_watch_no_event(watch, ih);
649 put_inotify_watch(watch);
650 }
Amy Griffis66055a42006-05-20 15:00:06 -0700651
Amy Griffis2d9048e2006-06-01 13:10:59 -0700652 mutex_unlock(&ih->mutex);
Ingo Molnard4f9af92006-03-23 03:00:30 -0800653 mutex_unlock(&inode->inotify_mutex);
Al Viro8f7b0ba2008-11-15 01:15:43 +0000654 unpin_and_kill(watch, how);
Robert Love0eeca282005-07-12 17:06:03 -0400655 }
656
Amy Griffis2d9048e2006-06-01 13:10:59 -0700657 /* free this handle: the put matching the get in inotify_init() */
658 put_inotify_handle(ih);
Robert Love0eeca282005-07-12 17:06:03 -0400659}
Amy Griffis2d9048e2006-06-01 13:10:59 -0700660EXPORT_SYMBOL_GPL(inotify_destroy);
Robert Love0eeca282005-07-12 17:06:03 -0400661
Amy Griffis2d9048e2006-06-01 13:10:59 -0700662/**
Amy Griffisa9dc9712006-06-01 13:11:03 -0700663 * inotify_find_watch - find an existing watch for an (ih,inode) pair
664 * @ih: inotify handle
665 * @inode: inode to watch
666 * @watchp: pointer to existing inotify_watch
667 *
668 * Caller must pin given inode (via nameidata).
669 */
670s32 inotify_find_watch(struct inotify_handle *ih, struct inode *inode,
671 struct inotify_watch **watchp)
672{
673 struct inotify_watch *old;
674 int ret = -ENOENT;
675
676 mutex_lock(&inode->inotify_mutex);
677 mutex_lock(&ih->mutex);
678
679 old = inode_find_handle(inode, ih);
680 if (unlikely(old)) {
681 get_inotify_watch(old); /* caller must put watch */
682 *watchp = old;
683 ret = old->wd;
684 }
685
686 mutex_unlock(&ih->mutex);
687 mutex_unlock(&inode->inotify_mutex);
688
689 return ret;
690}
691EXPORT_SYMBOL_GPL(inotify_find_watch);
692
693/**
Amy Griffis2d9048e2006-06-01 13:10:59 -0700694 * inotify_find_update_watch - find and update the mask of an existing watch
695 * @ih: inotify handle
696 * @inode: inode's watch to update
697 * @mask: mask of events to watch
698 *
699 * Caller must pin given inode (via nameidata).
700 */
701s32 inotify_find_update_watch(struct inotify_handle *ih, struct inode *inode,
702 u32 mask)
703{
704 struct inotify_watch *old;
705 int mask_add = 0;
706 int ret;
707
708 if (mask & IN_MASK_ADD)
709 mask_add = 1;
710
711 /* don't allow invalid bits: we don't want flags set */
712 mask &= IN_ALL_EVENTS | IN_ONESHOT;
713 if (unlikely(!mask))
714 return -EINVAL;
715
716 mutex_lock(&inode->inotify_mutex);
717 mutex_lock(&ih->mutex);
718
719 /*
720 * Handle the case of re-adding a watch on an (inode,ih) pair that we
721 * are already watching. We just update the mask and return its wd.
722 */
723 old = inode_find_handle(inode, ih);
724 if (unlikely(!old)) {
725 ret = -ENOENT;
726 goto out;
727 }
728
729 if (mask_add)
730 old->mask |= mask;
731 else
732 old->mask = mask;
733 ret = old->wd;
734out:
735 mutex_unlock(&ih->mutex);
736 mutex_unlock(&inode->inotify_mutex);
737 return ret;
738}
739EXPORT_SYMBOL_GPL(inotify_find_update_watch);
740
741/**
742 * inotify_add_watch - add a watch to an inotify instance
743 * @ih: inotify handle
744 * @watch: caller allocated watch structure
745 * @inode: inode to watch
746 * @mask: mask of events to watch
747 *
748 * Caller must pin given inode (via nameidata).
749 * Caller must ensure it only calls inotify_add_watch() once per watch.
750 * Calls inotify_handle_get_wd() so may sleep.
751 */
752s32 inotify_add_watch(struct inotify_handle *ih, struct inotify_watch *watch,
753 struct inode *inode, u32 mask)
754{
755 int ret = 0;
Nick Piggind599e362008-02-06 01:37:28 -0800756 int newly_watched;
Amy Griffis2d9048e2006-06-01 13:10:59 -0700757
758 /* don't allow invalid bits: we don't want flags set */
759 mask &= IN_ALL_EVENTS | IN_ONESHOT;
760 if (unlikely(!mask))
761 return -EINVAL;
762 watch->mask = mask;
763
764 mutex_lock(&inode->inotify_mutex);
765 mutex_lock(&ih->mutex);
766
767 /* Initialize a new watch */
768 ret = inotify_handle_get_wd(ih, watch);
769 if (unlikely(ret))
770 goto out;
771 ret = watch->wd;
772
Amy Griffis2d9048e2006-06-01 13:10:59 -0700773 /* save a reference to handle and bump the count to make it official */
774 get_inotify_handle(ih);
775 watch->ih = ih;
776
777 /*
778 * Save a reference to the inode and bump the ref count to make it
779 * official. We hold a reference to nameidata, which makes this safe.
780 */
781 watch->inode = igrab(inode);
782
Amy Griffis2d9048e2006-06-01 13:10:59 -0700783 /* Add the watch to the handle's and the inode's list */
Nick Piggind599e362008-02-06 01:37:28 -0800784 newly_watched = !inotify_inode_watched(inode);
Amy Griffis2d9048e2006-06-01 13:10:59 -0700785 list_add(&watch->h_list, &ih->watches);
786 list_add(&watch->i_list, &inode->inotify_watches);
Nick Piggind599e362008-02-06 01:37:28 -0800787 /*
788 * Set child flags _after_ adding the watch, so there is no race
789 * windows where newly instantiated children could miss their parent's
790 * watched flag.
791 */
792 if (newly_watched)
793 set_dentry_child_flags(inode, 1);
794
Amy Griffis2d9048e2006-06-01 13:10:59 -0700795out:
796 mutex_unlock(&ih->mutex);
797 mutex_unlock(&inode->inotify_mutex);
798 return ret;
799}
800EXPORT_SYMBOL_GPL(inotify_add_watch);
801
802/**
Al Virob9efe8a2007-06-07 12:21:44 -0400803 * inotify_clone_watch - put the watch next to existing one
804 * @old: already installed watch
805 * @new: new watch
806 *
807 * Caller must hold the inotify_mutex of inode we are dealing with;
808 * it is expected to remove the old watch before unlocking the inode.
809 */
810s32 inotify_clone_watch(struct inotify_watch *old, struct inotify_watch *new)
811{
812 struct inotify_handle *ih = old->ih;
813 int ret = 0;
814
815 new->mask = old->mask;
816 new->ih = ih;
817
818 mutex_lock(&ih->mutex);
819
820 /* Initialize a new watch */
821 ret = inotify_handle_get_wd(ih, new);
822 if (unlikely(ret))
823 goto out;
824 ret = new->wd;
825
826 get_inotify_handle(ih);
827
828 new->inode = igrab(old->inode);
829
830 list_add(&new->h_list, &ih->watches);
831 list_add(&new->i_list, &old->inode->inotify_watches);
832out:
833 mutex_unlock(&ih->mutex);
834 return ret;
835}
836
Al Viro455434d2007-06-07 12:22:59 -0400837void inotify_evict_watch(struct inotify_watch *watch)
838{
839 get_inotify_watch(watch);
840 mutex_lock(&watch->ih->mutex);
841 inotify_remove_watch_locked(watch->ih, watch);
842 mutex_unlock(&watch->ih->mutex);
843}
844
Al Virob9efe8a2007-06-07 12:21:44 -0400845/**
Amy Griffis2d9048e2006-06-01 13:10:59 -0700846 * inotify_rm_wd - remove a watch from an inotify instance
847 * @ih: inotify handle
848 * @wd: watch descriptor to remove
Robert Love0eeca282005-07-12 17:06:03 -0400849 *
850 * Can sleep.
851 */
Amy Griffis2d9048e2006-06-01 13:10:59 -0700852int inotify_rm_wd(struct inotify_handle *ih, u32 wd)
Robert Love0eeca282005-07-12 17:06:03 -0400853{
854 struct inotify_watch *watch;
Al Viro8f7b0ba2008-11-15 01:15:43 +0000855 struct super_block *sb;
Robert Love0eeca282005-07-12 17:06:03 -0400856 struct inode *inode;
Al Viro8f7b0ba2008-11-15 01:15:43 +0000857 int how;
Robert Love0eeca282005-07-12 17:06:03 -0400858
Amy Griffis2d9048e2006-06-01 13:10:59 -0700859 mutex_lock(&ih->mutex);
860 watch = idr_find(&ih->idr, wd);
Robert Love0eeca282005-07-12 17:06:03 -0400861 if (unlikely(!watch)) {
Amy Griffis2d9048e2006-06-01 13:10:59 -0700862 mutex_unlock(&ih->mutex);
Robert Love0eeca282005-07-12 17:06:03 -0400863 return -EINVAL;
864 }
Al Viro8f7b0ba2008-11-15 01:15:43 +0000865 sb = watch->inode->i_sb;
866 how = pin_to_kill(ih, watch);
867 if (!how)
868 return 0;
869
Robert Love0eeca282005-07-12 17:06:03 -0400870 inode = watch->inode;
Robert Love0eeca282005-07-12 17:06:03 -0400871
Ingo Molnard4f9af92006-03-23 03:00:30 -0800872 mutex_lock(&inode->inotify_mutex);
Amy Griffis2d9048e2006-06-01 13:10:59 -0700873 mutex_lock(&ih->mutex);
Robert Love0eeca282005-07-12 17:06:03 -0400874
875 /* make sure that we did not race */
Amy Griffis2d9048e2006-06-01 13:10:59 -0700876 if (likely(idr_find(&ih->idr, wd) == watch))
Amy Griffis3ca10062006-06-01 13:11:05 -0700877 inotify_remove_watch_locked(ih, watch);
Robert Love0eeca282005-07-12 17:06:03 -0400878
Amy Griffis2d9048e2006-06-01 13:10:59 -0700879 mutex_unlock(&ih->mutex);
Ingo Molnard4f9af92006-03-23 03:00:30 -0800880 mutex_unlock(&inode->inotify_mutex);
Al Viro8f7b0ba2008-11-15 01:15:43 +0000881 unpin_and_kill(watch, how);
Robert Love0eeca282005-07-12 17:06:03 -0400882
883 return 0;
884}
Amy Griffis2d9048e2006-06-01 13:10:59 -0700885EXPORT_SYMBOL_GPL(inotify_rm_wd);
Robert Love0eeca282005-07-12 17:06:03 -0400886
Amy Griffisa9dc9712006-06-01 13:11:03 -0700887/**
888 * inotify_rm_watch - remove a watch from an inotify instance
889 * @ih: inotify handle
890 * @watch: watch to remove
891 *
892 * Can sleep.
893 */
894int inotify_rm_watch(struct inotify_handle *ih,
895 struct inotify_watch *watch)
896{
897 return inotify_rm_wd(ih, watch->wd);
898}
899EXPORT_SYMBOL_GPL(inotify_rm_watch);
900
Robert Love0eeca282005-07-12 17:06:03 -0400901/*
Amy Griffis2d9048e2006-06-01 13:10:59 -0700902 * inotify_setup - core initialization function
Robert Love0eeca282005-07-12 17:06:03 -0400903 */
Robert Loveb6807162005-07-25 15:07:13 -0400904static int __init inotify_setup(void)
Robert Love0eeca282005-07-12 17:06:03 -0400905{
Robert Love0eeca282005-07-12 17:06:03 -0400906 atomic_set(&inotify_cookie, 0);
907
Robert Love0eeca282005-07-12 17:06:03 -0400908 return 0;
909}
910
Robert Loveb6807162005-07-25 15:07:13 -0400911module_init(inotify_setup);