inotify.c 26.4 KB
Newer Older
R
Robert Love 已提交
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39
/*
 * fs/inotify.c - inode-based file event notifications
 *
 * Authors:
 *	John McCutchan	<ttb@tentacle.dhs.org>
 *	Robert Love	<rml@novell.com>
 *
 * Copyright (C) 2005 John McCutchan
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2, or (at your option) any
 * later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/spinlock.h>
#include <linux/idr.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/poll.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/writeback.h>
#include <linux/inotify.h>

#include <asm/ioctls.h>

static atomic_t inotify_cookie;
J
John McCutchan 已提交
40
static atomic_t inotify_watches;
R
Robert Love 已提交
41 42 43 44 45 46

static kmem_cache_t *watch_cachep;
static kmem_cache_t *event_cachep;

static struct vfsmount *inotify_mnt;

R
Robert Love 已提交
47 48
/* these are configurable via /proc/sys/fs/inotify/ */
int inotify_max_user_instances;
R
Robert Love 已提交
49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
int inotify_max_user_watches;
int inotify_max_queued_events;

/*
 * Lock ordering:
 *
 * dentry->d_lock (used to keep d_move() away from dentry->d_parent)
 * iprune_sem (synchronize shrink_icache_memory())
 * 	inode_lock (protects the super_block->s_inodes list)
 * 	inode->inotify_sem (protects inode->inotify_watches and watches->i_list)
 * 		inotify_dev->sem (protects inotify_device and watches->d_list)
 */

/*
 * Lifetimes of the three main data structures--inotify_device, inode, and
 * inotify_watch--are managed by reference count.
 *
R
Robert Love 已提交
66 67
 * inotify_device: Lifetime is from inotify_init() until release.  Additional
 * references can bump the count via get_inotify_dev() and drop the count via
R
Robert Love 已提交
68 69 70 71 72 73 74 75 76 77 78
 * put_inotify_dev().
 *
 * inotify_watch: Lifetime is from create_watch() to destory_watch().
 * Additional references can bump the count via get_inotify_watch() and drop
 * the count via put_inotify_watch().
 *
 * inode: Pinned so long as the inode is associated with a watch, from
 * create_watch() to put_inotify_watch().
 */

/*
R
Robert Love 已提交
79
 * struct inotify_device - represents an inotify instance
R
Robert Love 已提交
80 81 82 83 84 85 86 87 88 89 90 91 92 93
 *
 * This structure is protected by the semaphore 'sem'.
 */
struct inotify_device {
	wait_queue_head_t 	wq;		/* wait queue for i/o */
	struct idr		idr;		/* idr mapping wd -> watch */
	struct semaphore	sem;		/* protects this bad boy */
	struct list_head 	events;		/* list of queued events */
	struct list_head	watches;	/* list of watches */
	atomic_t		count;		/* reference count */
	struct user_struct	*user;		/* user who opened this dev */
	unsigned int		queue_size;	/* size of the queue (bytes) */
	unsigned int		event_count;	/* number of pending events */
	unsigned int		max_events;	/* maximum number of events */
94
	u32			last_wd;	/* the last wd allocated */
R
Robert Love 已提交
95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127
};

/*
 * struct inotify_kernel_event - An inotify event, originating from a watch and
 * queued for user-space.  A list of these is attached to each instance of the
 * device.  In read(), this list is walked and all events that can fit in the
 * buffer are returned.
 *
 * Protected by dev->sem of the device in which we are queued.
 */
struct inotify_kernel_event {
	struct inotify_event	event;	/* the user-space event */
	struct list_head        list;	/* entry in inotify_device's list */
	char			*name;	/* filename, if any */
};

/*
 * struct inotify_watch - represents a watch request on a specific inode
 *
 * d_list is protected by dev->sem of the associated watch->dev.
 * i_list and mask are protected by inode->inotify_sem of the associated inode.
 * dev, inode, and wd are never written to once the watch is created.
 */
struct inotify_watch {
	struct list_head	d_list;	/* entry in inotify_device's list */
	struct list_head	i_list;	/* entry in inode's list */
	atomic_t		count;	/* reference count */
	struct inotify_device	*dev;	/* associated device */
	struct inode		*inode;	/* associated inode */
	s32 			wd;	/* watch descriptor */
	u32			mask;	/* event mask for this watch */
};

R
Robert Love 已提交
128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168
#ifdef CONFIG_SYSCTL

#include <linux/sysctl.h>

static int zero;

ctl_table inotify_table[] = {
	{
		.ctl_name	= INOTIFY_MAX_USER_INSTANCES,
		.procname	= "max_user_instances",
		.data		= &inotify_max_user_instances,
		.maxlen		= sizeof(int),
		.mode		= 0644,
		.proc_handler	= &proc_dointvec_minmax,
		.strategy	= &sysctl_intvec,
		.extra1		= &zero,
	},
	{
		.ctl_name	= INOTIFY_MAX_USER_WATCHES,
		.procname	= "max_user_watches",
		.data		= &inotify_max_user_watches,
		.maxlen		= sizeof(int),
		.mode		= 0644,
		.proc_handler	= &proc_dointvec_minmax,
		.strategy	= &sysctl_intvec,
		.extra1		= &zero, 
	},
	{
		.ctl_name	= INOTIFY_MAX_QUEUED_EVENTS,
		.procname	= "max_queued_events",
		.data		= &inotify_max_queued_events,
		.maxlen		= sizeof(int),
		.mode		= 0644, 
		.proc_handler	= &proc_dointvec_minmax,
		.strategy	= &sysctl_intvec, 
		.extra1		= &zero
	},
	{ .ctl_name = 0 }
};
#endif /* CONFIG_SYSCTL */

R
Robert Love 已提交
169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356
static inline void get_inotify_dev(struct inotify_device *dev)
{
	atomic_inc(&dev->count);
}

static inline void put_inotify_dev(struct inotify_device *dev)
{
	if (atomic_dec_and_test(&dev->count)) {
		atomic_dec(&dev->user->inotify_devs);
		free_uid(dev->user);
		kfree(dev);
	}
}

static inline void get_inotify_watch(struct inotify_watch *watch)
{
	atomic_inc(&watch->count);
}

/*
 * put_inotify_watch - decrements the ref count on a given watch.  cleans up
 * the watch and its references if the count reaches zero.
 */
static inline void put_inotify_watch(struct inotify_watch *watch)
{
	if (atomic_dec_and_test(&watch->count)) {
		put_inotify_dev(watch->dev);
		iput(watch->inode);
		kmem_cache_free(watch_cachep, watch);
	}
}

/*
 * kernel_event - create a new kernel event with the given parameters
 *
 * This function can sleep.
 */
static struct inotify_kernel_event * kernel_event(s32 wd, u32 mask, u32 cookie,
						  const char *name)
{
	struct inotify_kernel_event *kevent;

	kevent = kmem_cache_alloc(event_cachep, GFP_KERNEL);
	if (unlikely(!kevent))
		return NULL;

	/* we hand this out to user-space, so zero it just in case */
	memset(&kevent->event, 0, sizeof(struct inotify_event));

	kevent->event.wd = wd;
	kevent->event.mask = mask;
	kevent->event.cookie = cookie;

	INIT_LIST_HEAD(&kevent->list);

	if (name) {
		size_t len, rem, event_size = sizeof(struct inotify_event);

		/*
		 * We need to pad the filename so as to properly align an
		 * array of inotify_event structures.  Because the structure is
		 * small and the common case is a small filename, we just round
		 * up to the next multiple of the structure's sizeof.  This is
		 * simple and safe for all architectures.
		 */
		len = strlen(name) + 1;
		rem = event_size - len;
		if (len > event_size) {
			rem = event_size - (len % event_size);
			if (len % event_size == 0)
				rem = 0;
		}

		kevent->name = kmalloc(len + rem, GFP_KERNEL);
		if (unlikely(!kevent->name)) {
			kmem_cache_free(event_cachep, kevent);
			return NULL;
		}
		memcpy(kevent->name, name, len);
		if (rem)
			memset(kevent->name + len, 0, rem);		
		kevent->event.len = len + rem;
	} else {
		kevent->event.len = 0;
		kevent->name = NULL;
	}

	return kevent;
}

/*
 * inotify_dev_get_event - return the next event in the given dev's queue
 *
 * Caller must hold dev->sem.
 */
static inline struct inotify_kernel_event *
inotify_dev_get_event(struct inotify_device *dev)
{
	return list_entry(dev->events.next, struct inotify_kernel_event, list);
}

/*
 * inotify_dev_queue_event - add a new event to the given device
 *
 * Caller must hold dev->sem.  Can sleep (calls kernel_event()).
 */
static void inotify_dev_queue_event(struct inotify_device *dev,
				    struct inotify_watch *watch, u32 mask,
				    u32 cookie, const char *name)
{
	struct inotify_kernel_event *kevent, *last;

	/* coalescing: drop this event if it is a dupe of the previous */
	last = inotify_dev_get_event(dev);
	if (last && last->event.mask == mask && last->event.wd == watch->wd &&
			last->event.cookie == cookie) {
		const char *lastname = last->name;

		if (!name && !lastname)
			return;
		if (name && lastname && !strcmp(lastname, name))
			return;
	}

	/* the queue overflowed and we already sent the Q_OVERFLOW event */
	if (unlikely(dev->event_count > dev->max_events))
		return;

	/* if the queue overflows, we need to notify user space */
	if (unlikely(dev->event_count == dev->max_events))
		kevent = kernel_event(-1, IN_Q_OVERFLOW, cookie, NULL);
	else
		kevent = kernel_event(watch->wd, mask, cookie, name);

	if (unlikely(!kevent))
		return;

	/* queue the event and wake up anyone waiting */
	dev->event_count++;
	dev->queue_size += sizeof(struct inotify_event) + kevent->event.len;
	list_add_tail(&kevent->list, &dev->events);
	wake_up_interruptible(&dev->wq);
}

/*
 * remove_kevent - cleans up and ultimately frees the given kevent
 *
 * Caller must hold dev->sem.
 */
static void remove_kevent(struct inotify_device *dev,
			  struct inotify_kernel_event *kevent)
{
	list_del(&kevent->list);

	dev->event_count--;
	dev->queue_size -= sizeof(struct inotify_event) + kevent->event.len;

	kfree(kevent->name);
	kmem_cache_free(event_cachep, kevent);
}

/*
 * inotify_dev_event_dequeue - destroy an event on the given device
 *
 * Caller must hold dev->sem.
 */
static void inotify_dev_event_dequeue(struct inotify_device *dev)
{
	if (!list_empty(&dev->events)) {
		struct inotify_kernel_event *kevent;
		kevent = inotify_dev_get_event(dev);
		remove_kevent(dev, kevent);
	}
}

/*
 * inotify_dev_get_wd - returns the next WD for use by the given dev
 *
 * Callers must hold dev->sem.  This function can sleep.
 */
static int inotify_dev_get_wd(struct inotify_device *dev,
			      struct inotify_watch *watch)
{
	int ret;

	do {
		if (unlikely(!idr_pre_get(&dev->idr, GFP_KERNEL)))
			return -ENOSPC;
357
		ret = idr_get_new_above(&dev->idr, watch, dev->last_wd+1, &watch->wd);
R
Robert Love 已提交
358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375
	} while (ret == -EAGAIN);

	return ret;
}

/*
 * find_inode - resolve a user-given path to a specific inode and return a nd
 */
static int find_inode(const char __user *dirname, struct nameidata *nd)
{
	int error;

	error = __user_walk(dirname, LOOKUP_FOLLOW, nd);
	if (error)
		return error;
	/* you can only watch an inode if you have read permissions on it */
	error = permission(nd->dentry->d_inode, MAY_READ, NULL);
	if (error) 
R
Robert Love 已提交
376
		path_release(nd);
R
Robert Love 已提交
377 378 379 380 381 382 383 384 385 386 387 388 389 390 391
	return error;
}

/*
 * create_watch - creates a watch on the given device.
 *
 * Callers must hold dev->sem.  Calls inotify_dev_get_wd() so may sleep.
 * Both 'dev' and 'inode' (by way of nameidata) need to be pinned.
 */
static struct inotify_watch *create_watch(struct inotify_device *dev,
					  u32 mask, struct inode *inode)
{
	struct inotify_watch *watch;
	int ret;

R
Robert Love 已提交
392 393
	if (atomic_read(&dev->user->inotify_watches) >=
			inotify_max_user_watches)
R
Robert Love 已提交
394 395 396 397 398 399 400 401 402 403 404 405
		return ERR_PTR(-ENOSPC);

	watch = kmem_cache_alloc(watch_cachep, GFP_KERNEL);
	if (unlikely(!watch))
		return ERR_PTR(-ENOMEM);

	ret = inotify_dev_get_wd(dev, watch);
	if (unlikely(ret)) {
		kmem_cache_free(watch_cachep, watch);
		return ERR_PTR(ret);
	}

406
	dev->last_wd = watch->wd;
R
Robert Love 已提交
407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425
	watch->mask = mask;
	atomic_set(&watch->count, 0);
	INIT_LIST_HEAD(&watch->d_list);
	INIT_LIST_HEAD(&watch->i_list);

	/* save a reference to device and bump the count to make it official */
	get_inotify_dev(dev);
	watch->dev = dev;

	/*
	 * Save a reference to the inode and bump the ref count to make it
	 * official.  We hold a reference to nameidata, which makes this safe.
	 */
	watch->inode = igrab(inode);

	/* bump our own count, corresponding to our entry in dev->watches */
	get_inotify_watch(watch);

	atomic_inc(&dev->user->inotify_watches);
J
John McCutchan 已提交
426
	atomic_inc(&inotify_watches);
R
Robert Love 已提交
427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458

	return watch;
}

/*
 * inotify_find_dev - find the watch associated with the given inode and dev
 *
 * Callers must hold inode->inotify_sem.
 */
static struct inotify_watch *inode_find_dev(struct inode *inode,
					    struct inotify_device *dev)
{
	struct inotify_watch *watch;

	list_for_each_entry(watch, &inode->inotify_watches, i_list) {
		if (watch->dev == dev)
			return watch;
	}

	return NULL;
}

/*
 * remove_watch_no_event - remove_watch() without the IN_IGNORED event.
 */
static void remove_watch_no_event(struct inotify_watch *watch,
				  struct inotify_device *dev)
{
	list_del(&watch->i_list);
	list_del(&watch->d_list);

	atomic_dec(&dev->user->inotify_watches);
J
John McCutchan 已提交
459
	atomic_dec(&inotify_watches);
R
Robert Love 已提交
460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537
	idr_remove(&dev->idr, watch->wd);
	put_inotify_watch(watch);
}

/*
 * remove_watch - Remove a watch from both the device and the inode.  Sends
 * the IN_IGNORED event to the given device signifying that the inode is no
 * longer watched.
 *
 * Callers must hold both inode->inotify_sem and dev->sem.  We drop a
 * reference to the inode before returning.
 *
 * The inode is not iput() so as to remain atomic.  If the inode needs to be
 * iput(), the call returns one.  Otherwise, it returns zero.
 */
static void remove_watch(struct inotify_watch *watch,struct inotify_device *dev)
{
	inotify_dev_queue_event(dev, watch, IN_IGNORED, 0, NULL);
	remove_watch_no_event(watch, dev);
}

/*
 * inotify_inode_watched - returns nonzero if there are watches on this inode
 * and zero otherwise.  We call this lockless, we do not care if we race.
 */
static inline int inotify_inode_watched(struct inode *inode)
{
	return !list_empty(&inode->inotify_watches);
}

/* Kernel API */

/**
 * inotify_inode_queue_event - queue an event to all watches on this inode
 * @inode: inode event is originating from
 * @mask: event mask describing this event
 * @cookie: cookie for synchronization, or zero
 * @name: filename, if any
 */
void inotify_inode_queue_event(struct inode *inode, u32 mask, u32 cookie,
			       const char *name)
{
	struct inotify_watch *watch, *next;

	if (!inotify_inode_watched(inode))
		return;

	down(&inode->inotify_sem);
	list_for_each_entry_safe(watch, next, &inode->inotify_watches, i_list) {
		u32 watch_mask = watch->mask;
		if (watch_mask & mask) {
			struct inotify_device *dev = watch->dev;
			get_inotify_watch(watch);
			down(&dev->sem);
			inotify_dev_queue_event(dev, watch, mask, cookie, name);
			if (watch_mask & IN_ONESHOT)
				remove_watch_no_event(watch, dev);
			up(&dev->sem);
			put_inotify_watch(watch);
		}
	}
	up(&inode->inotify_sem);
}
EXPORT_SYMBOL_GPL(inotify_inode_queue_event);

/**
 * inotify_dentry_parent_queue_event - queue an event to a dentry's parent
 * @dentry: the dentry in question, we queue against this dentry's parent
 * @mask: event mask describing this event
 * @cookie: cookie for synchronization, or zero
 * @name: filename, if any
 */
void inotify_dentry_parent_queue_event(struct dentry *dentry, u32 mask,
				       u32 cookie, const char *name)
{
	struct dentry *parent;
	struct inode *inode;

J
John McCutchan 已提交
538 539 540
	if (!atomic_read (&inotify_watches))
		return;

R
Robert Love 已提交
541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794
	spin_lock(&dentry->d_lock);
	parent = dentry->d_parent;
	inode = parent->d_inode;

	if (inotify_inode_watched(inode)) {
		dget(parent);
		spin_unlock(&dentry->d_lock);
		inotify_inode_queue_event(inode, mask, cookie, name);
		dput(parent);
	} else
		spin_unlock(&dentry->d_lock);
}
EXPORT_SYMBOL_GPL(inotify_dentry_parent_queue_event);

/**
 * inotify_get_cookie - return a unique cookie for use in synchronizing events.
 */
u32 inotify_get_cookie(void)
{
	return atomic_inc_return(&inotify_cookie);
}
EXPORT_SYMBOL_GPL(inotify_get_cookie);

/**
 * inotify_unmount_inodes - an sb is unmounting.  handle any watched inodes.
 * @list: list of inodes being unmounted (sb->s_inodes)
 *
 * Called with inode_lock held, protecting the unmounting super block's list
 * of inodes, and with iprune_sem held, keeping shrink_icache_memory() at bay.
 * We temporarily drop inode_lock, however, and CAN block.
 */
void inotify_unmount_inodes(struct list_head *list)
{
	struct inode *inode, *next_i, *need_iput = NULL;

	list_for_each_entry_safe(inode, next_i, list, i_sb_list) {
		struct inotify_watch *watch, *next_w;
		struct inode *need_iput_tmp;
		struct list_head *watches;

		/*
		 * If i_count is zero, the inode cannot have any watches and
		 * doing an __iget/iput with MS_ACTIVE clear would actually
		 * evict all inodes with zero i_count from icache which is
		 * unnecessarily violent and may in fact be illegal to do.
		 */
		if (!atomic_read(&inode->i_count))
			continue;

		/*
		 * We cannot __iget() an inode in state I_CLEAR, I_FREEING, or
		 * I_WILL_FREE which is fine because by that point the inode
		 * cannot have any associated watches.
		 */
		if (inode->i_state & (I_CLEAR | I_FREEING | I_WILL_FREE))
			continue;

		need_iput_tmp = need_iput;
		need_iput = NULL;
		/* In case the remove_watch() drops a reference. */
		if (inode != need_iput_tmp)
			__iget(inode);
		else
			need_iput_tmp = NULL;
		/* In case the dropping of a reference would nuke next_i. */
		if ((&next_i->i_sb_list != list) &&
				atomic_read(&next_i->i_count) &&
				!(next_i->i_state & (I_CLEAR | I_FREEING |
					I_WILL_FREE))) {
			__iget(next_i);
			need_iput = next_i;
		}

		/*
		 * We can safely drop inode_lock here because we hold
		 * references on both inode and next_i.  Also no new inodes
		 * will be added since the umount has begun.  Finally,
		 * iprune_sem keeps shrink_icache_memory() away.
		 */
		spin_unlock(&inode_lock);

		if (need_iput_tmp)
			iput(need_iput_tmp);

		/* for each watch, send IN_UNMOUNT and then remove it */
		down(&inode->inotify_sem);
		watches = &inode->inotify_watches;
		list_for_each_entry_safe(watch, next_w, watches, i_list) {
			struct inotify_device *dev = watch->dev;
			down(&dev->sem);
			inotify_dev_queue_event(dev, watch, IN_UNMOUNT,0,NULL);
			remove_watch(watch, dev);
			up(&dev->sem);
		}
		up(&inode->inotify_sem);
		iput(inode);		

		spin_lock(&inode_lock);
	}
}
EXPORT_SYMBOL_GPL(inotify_unmount_inodes);

/**
 * inotify_inode_is_dead - an inode has been deleted, cleanup any watches
 * @inode: inode that is about to be removed
 */
void inotify_inode_is_dead(struct inode *inode)
{
	struct inotify_watch *watch, *next;

	down(&inode->inotify_sem);
	list_for_each_entry_safe(watch, next, &inode->inotify_watches, i_list) {
		struct inotify_device *dev = watch->dev;
		down(&dev->sem);
		remove_watch(watch, dev);
		up(&dev->sem);
	}
	up(&inode->inotify_sem);
}
EXPORT_SYMBOL_GPL(inotify_inode_is_dead);

/* Device Interface */

static unsigned int inotify_poll(struct file *file, poll_table *wait)
{
	struct inotify_device *dev = file->private_data;
	int ret = 0;

	poll_wait(file, &dev->wq, wait);
	down(&dev->sem);
	if (!list_empty(&dev->events))
		ret = POLLIN | POLLRDNORM;
	up(&dev->sem);

	return ret;
}

static ssize_t inotify_read(struct file *file, char __user *buf,
			    size_t count, loff_t *pos)
{
	size_t event_size = sizeof (struct inotify_event);
	struct inotify_device *dev;
	char __user *start;
	int ret;
	DEFINE_WAIT(wait);

	start = buf;
	dev = file->private_data;

	while (1) {
		int events;

		prepare_to_wait(&dev->wq, &wait, TASK_INTERRUPTIBLE);

		down(&dev->sem);
		events = !list_empty(&dev->events);
		up(&dev->sem);
		if (events) {
			ret = 0;
			break;
		}

		if (file->f_flags & O_NONBLOCK) {
			ret = -EAGAIN;
			break;
		}

		if (signal_pending(current)) {
			ret = -EINTR;
			break;
		}

		schedule();
	}

	finish_wait(&dev->wq, &wait);
	if (ret)
		return ret;

	down(&dev->sem);
	while (1) {
		struct inotify_kernel_event *kevent;

		ret = buf - start;
		if (list_empty(&dev->events))
			break;

		kevent = inotify_dev_get_event(dev);
		if (event_size + kevent->event.len > count)
			break;

		if (copy_to_user(buf, &kevent->event, event_size)) {
			ret = -EFAULT;
			break;
		}
		buf += event_size;
		count -= event_size;

		if (kevent->name) {
			if (copy_to_user(buf, kevent->name, kevent->event.len)){
				ret = -EFAULT;
				break;
			}
			buf += kevent->event.len;
			count -= kevent->event.len;
		}

		remove_kevent(dev, kevent);
	}
	up(&dev->sem);

	return ret;
}

static int inotify_release(struct inode *ignored, struct file *file)
{
	struct inotify_device *dev = file->private_data;

	/*
	 * Destroy all of the watches on this device.  Unfortunately, not very
	 * pretty.  We cannot do a simple iteration over the list, because we
	 * do not know the inode until we iterate to the watch.  But we need to
	 * hold inode->inotify_sem before dev->sem.  The following works.
	 */
	while (1) {
		struct inotify_watch *watch;
		struct list_head *watches;
		struct inode *inode;

		down(&dev->sem);
		watches = &dev->watches;
		if (list_empty(watches)) {
			up(&dev->sem);
			break;
		}
		watch = list_entry(watches->next, struct inotify_watch, d_list);
		get_inotify_watch(watch);
		up(&dev->sem);

		inode = watch->inode;
		down(&inode->inotify_sem);
		down(&dev->sem);
		remove_watch_no_event(watch, dev);
		up(&dev->sem);
		up(&inode->inotify_sem);
		put_inotify_watch(watch);
	}

	/* destroy all of the events on this device */
	down(&dev->sem);
	while (!list_empty(&dev->events))
		inotify_dev_event_dequeue(dev);
	up(&dev->sem);

R
Robert Love 已提交
795
	/* free this device: the put matching the get in inotify_init() */
R
Robert Love 已提交
796 797 798 799 800 801
	put_inotify_dev(dev);

	return 0;
}

/*
R
Robert Love 已提交
802
 * inotify_ignore - remove a given wd from this inotify instance.
R
Robert Love 已提交
803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866
 *
 * Can sleep.
 */
static int inotify_ignore(struct inotify_device *dev, s32 wd)
{
	struct inotify_watch *watch;
	struct inode *inode;

	down(&dev->sem);
	watch = idr_find(&dev->idr, wd);
	if (unlikely(!watch)) {
		up(&dev->sem);
		return -EINVAL;
	}
	get_inotify_watch(watch);
	inode = watch->inode;
	up(&dev->sem);

	down(&inode->inotify_sem);
	down(&dev->sem);

	/* make sure that we did not race */
	watch = idr_find(&dev->idr, wd);
	if (likely(watch))
		remove_watch(watch, dev);

	up(&dev->sem);
	up(&inode->inotify_sem);
	put_inotify_watch(watch);

	return 0;
}

static long inotify_ioctl(struct file *file, unsigned int cmd,
			  unsigned long arg)
{
	struct inotify_device *dev;
	void __user *p;
	int ret = -ENOTTY;

	dev = file->private_data;
	p = (void __user *) arg;

	switch (cmd) {
	case FIONREAD:
		ret = put_user(dev->queue_size, (int __user *) p);
		break;
	}

	return ret;
}

static struct file_operations inotify_fops = {
	.poll           = inotify_poll,
	.read           = inotify_read,
	.release        = inotify_release,
	.unlocked_ioctl = inotify_ioctl,
	.compat_ioctl	= inotify_ioctl,
};

asmlinkage long sys_inotify_init(void)
{
	struct inotify_device *dev;
	struct user_struct *user;
R
Robert Love 已提交
867 868
	struct file *filp;	
	int fd, ret;
R
Robert Love 已提交
869 870

	fd = get_unused_fd();
R
Robert Love 已提交
871 872
	if (fd < 0)
		return fd;
R
Robert Love 已提交
873 874 875 876

	filp = get_empty_filp();
	if (!filp) {
		ret = -ENFILE;
877
		goto out_put_fd;
R
Robert Love 已提交
878 879 880
	}

	user = get_uid(current->user);
R
Robert Love 已提交
881 882
	if (unlikely(atomic_read(&user->inotify_devs) >=
			inotify_max_user_instances)) {
R
Robert Love 已提交
883
		ret = -EMFILE;
884
		goto out_free_uid;
R
Robert Love 已提交
885 886 887 888 889
	}

	dev = kmalloc(sizeof(struct inotify_device), GFP_KERNEL);
	if (unlikely(!dev)) {
		ret = -ENOMEM;
890
		goto out_free_uid;
R
Robert Love 已提交
891 892
	}

R
Robert Love 已提交
893 894 895 896 897 898 899 900
	filp->f_op = &inotify_fops;
	filp->f_vfsmnt = mntget(inotify_mnt);
	filp->f_dentry = dget(inotify_mnt->mnt_root);
	filp->f_mapping = filp->f_dentry->d_inode->i_mapping;
	filp->f_mode = FMODE_READ;
	filp->f_flags = O_RDONLY;
	filp->private_data = dev;

R
Robert Love 已提交
901 902 903 904 905 906 907 908 909
	idr_init(&dev->idr);
	INIT_LIST_HEAD(&dev->events);
	INIT_LIST_HEAD(&dev->watches);
	init_waitqueue_head(&dev->wq);
	sema_init(&dev->sem, 1);
	dev->event_count = 0;
	dev->queue_size = 0;
	dev->max_events = inotify_max_queued_events;
	dev->user = user;
910
	dev->last_wd = 0;
R
Robert Love 已提交
911 912 913 914
	atomic_set(&dev->count, 0);

	get_inotify_dev(dev);
	atomic_inc(&user->inotify_devs);
R
Robert Love 已提交
915
	fd_install(fd, filp);
R
Robert Love 已提交
916 917

	return fd;
918
out_free_uid:
R
Robert Love 已提交
919
	free_uid(user);
920 921 922
	put_filp(filp);
out_put_fd:
	put_unused_fd(fd);
R
Robert Love 已提交
923 924 925
	return ret;
}

R
Robert Love 已提交
926
asmlinkage long sys_inotify_add_watch(int fd, const char __user *path, u32 mask)
R
Robert Love 已提交
927 928 929 930 931 932
{
	struct inotify_watch *watch, *old;
	struct inode *inode;
	struct inotify_device *dev;
	struct nameidata nd;
	struct file *filp;
R
Robert Love 已提交
933
	int ret, fput_needed;
R
Robert Love 已提交
934

R
Robert Love 已提交
935 936
	filp = fget_light(fd, &fput_needed);
	if (unlikely(!filp))
R
Robert Love 已提交
937 938
		return -EBADF;

R
Robert Love 已提交
939 940 941 942 943 944
	/* verify that this is indeed an inotify instance */
	if (unlikely(filp->f_op != &inotify_fops)) {
		ret = -EINVAL;
		goto fput_and_out;
	}

R
Robert Love 已提交
945 946
	ret = find_inode(path, &nd);
	if (unlikely(ret))
R
Robert Love 已提交
947 948
		goto fput_and_out;

R
Robert Love 已提交
949
	/* inode held in place by reference to nd; dev by fget on fd */
R
Robert Love 已提交
950
	inode = nd.dentry->d_inode;
R
Robert Love 已提交
951
	dev = filp->private_data;
R
Robert Love 已提交
952 953 954 955 956 957

	down(&inode->inotify_sem);
	down(&dev->sem);

	/* don't let user-space set invalid bits: we don't want flags set */
	mask &= IN_ALL_EVENTS;
R
Robert Love 已提交
958
	if (unlikely(!mask)) {
R
Robert Love 已提交
959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986
		ret = -EINVAL;
		goto out;
	}

	/*
	 * Handle the case of re-adding a watch on an (inode,dev) pair that we
	 * are already watching.  We just update the mask and return its wd.
	 */
	old = inode_find_dev(inode, dev);
	if (unlikely(old)) {
		old->mask = mask;
		ret = old->wd;
		goto out;
	}

	watch = create_watch(dev, mask, inode);
	if (unlikely(IS_ERR(watch))) {
		ret = PTR_ERR(watch);
		goto out;
	}

	/* Add the watch to the device's and the inode's list */
	list_add(&watch->d_list, &dev->watches);
	list_add(&watch->i_list, &inode->inotify_watches);
	ret = watch->wd;
out:
	up(&dev->sem);
	up(&inode->inotify_sem);
987
	path_release(&nd);
R
Robert Love 已提交
988
fput_and_out:
R
Robert Love 已提交
989
	fput_light(filp, fput_needed);
R
Robert Love 已提交
990 991 992 993 994 995 996
	return ret;
}

asmlinkage long sys_inotify_rm_watch(int fd, u32 wd)
{
	struct file *filp;
	struct inotify_device *dev;
R
Robert Love 已提交
997
	int ret, fput_needed;
R
Robert Love 已提交
998

R
Robert Love 已提交
999 1000
	filp = fget_light(fd, &fput_needed);
	if (unlikely(!filp))
R
Robert Love 已提交
1001
		return -EBADF;
R
Robert Love 已提交
1002 1003 1004 1005 1006 1007 1008

	/* verify that this is indeed an inotify instance */
	if (unlikely(filp->f_op != &inotify_fops)) {
		ret = -EINVAL;
		goto out;
	}

R
Robert Love 已提交
1009
	dev = filp->private_data;
R
Robert Love 已提交
1010 1011
	ret = inotify_ignore(dev, wd);

R
Robert Love 已提交
1012 1013
out:
	fput_light(filp, fput_needed);
R
Robert Love 已提交
1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030
	return ret;
}

static struct super_block *
inotify_get_sb(struct file_system_type *fs_type, int flags,
	       const char *dev_name, void *data)
{
    return get_sb_pseudo(fs_type, "inotify", NULL, 0xBAD1DEA);
}

static struct file_system_type inotify_fs_type = {
    .name           = "inotifyfs",
    .get_sb         = inotify_get_sb,
    .kill_sb        = kill_anon_super,
};

/*
R
Robert Love 已提交
1031
 * inotify_setup - Our initialization function.  Note that we cannnot return
R
Robert Love 已提交
1032 1033 1034
 * error because we have compiled-in VFS hooks.  So an (unlikely) failure here
 * must result in panic().
 */
R
Robert Love 已提交
1035
static int __init inotify_setup(void)
R
Robert Love 已提交
1036
{
1037 1038 1039 1040 1041 1042
	int ret;

	ret = register_filesystem(&inotify_fs_type);
	if (unlikely(ret))
		panic("inotify: register_filesystem returned %d!\n", ret);

R
Robert Love 已提交
1043
	inotify_mnt = kern_mount(&inotify_fs_type);
A
Andrew Morton 已提交
1044
	if (IS_ERR(inotify_mnt))
1045
		panic("inotify: kern_mount ret %ld!\n", PTR_ERR(inotify_mnt));
R
Robert Love 已提交
1046

1047 1048
	inotify_max_queued_events = 16384;
	inotify_max_user_instances = 128;
R
Robert Love 已提交
1049 1050 1051
	inotify_max_user_watches = 8192;

	atomic_set(&inotify_cookie, 0);
J
John McCutchan 已提交
1052
	atomic_set(&inotify_watches, 0);
R
Robert Love 已提交
1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063

	watch_cachep = kmem_cache_create("inotify_watch_cache",
					 sizeof(struct inotify_watch),
					 0, SLAB_PANIC, NULL, NULL);
	event_cachep = kmem_cache_create("inotify_event_cache",
					 sizeof(struct inotify_kernel_event),
					 0, SLAB_PANIC, NULL, NULL);

	return 0;
}

R
Robert Love 已提交
1064
module_init(inotify_setup);