xref: /openbmc/linux/fs/inode.c (revision c21b37f6)
1 /*
2  * linux/fs/inode.c
3  *
4  * (C) 1997 Linus Torvalds
5  */
6 
7 #include <linux/fs.h>
8 #include <linux/mm.h>
9 #include <linux/dcache.h>
10 #include <linux/init.h>
11 #include <linux/quotaops.h>
12 #include <linux/slab.h>
13 #include <linux/writeback.h>
14 #include <linux/module.h>
15 #include <linux/backing-dev.h>
16 #include <linux/wait.h>
17 #include <linux/hash.h>
18 #include <linux/swap.h>
19 #include <linux/security.h>
20 #include <linux/pagemap.h>
21 #include <linux/cdev.h>
22 #include <linux/bootmem.h>
23 #include <linux/inotify.h>
24 #include <linux/mount.h>
25 
26 /*
27  * This is needed for the following functions:
28  *  - inode_has_buffers
29  *  - invalidate_inode_buffers
30  *  - invalidate_bdev
31  *
32  * FIXME: remove all knowledge of the buffer layer from this file
33  */
34 #include <linux/buffer_head.h>
35 
36 /*
37  * New inode.c implementation.
38  *
39  * This implementation has the basic premise of trying
40  * to be extremely low-overhead and SMP-safe, yet be
41  * simple enough to be "obviously correct".
42  *
43  * Famous last words.
44  */
45 
46 /* inode dynamic allocation 1999, Andrea Arcangeli <andrea@suse.de> */
47 
48 /* #define INODE_PARANOIA 1 */
49 /* #define INODE_DEBUG 1 */
50 
51 /*
52  * Inode lookup is no longer as critical as it used to be:
53  * most of the lookups are going to be through the dcache.
54  */
55 #define I_HASHBITS	i_hash_shift
56 #define I_HASHMASK	i_hash_mask
57 
58 static unsigned int i_hash_mask __read_mostly;
59 static unsigned int i_hash_shift __read_mostly;
60 
61 /*
62  * Each inode can be on two separate lists. One is
63  * the hash list of the inode, used for lookups. The
64  * other linked list is the "type" list:
65  *  "in_use" - valid inode, i_count > 0, i_nlink > 0
66  *  "dirty"  - as "in_use" but also dirty
67  *  "unused" - valid inode, i_count = 0
68  *
69  * A "dirty" list is maintained for each super block,
70  * allowing for low-overhead inode sync() operations.
71  */
72 
73 LIST_HEAD(inode_in_use);
74 LIST_HEAD(inode_unused);
75 static struct hlist_head *inode_hashtable __read_mostly;
76 
77 /*
78  * A simple spinlock to protect the list manipulations.
79  *
80  * NOTE! You also have to own the lock if you change
81  * the i_state of an inode while it is in use..
82  */
83 DEFINE_SPINLOCK(inode_lock);
84 
85 /*
86  * iprune_mutex provides exclusion between the kswapd or try_to_free_pages
87  * icache shrinking path, and the umount path.  Without this exclusion,
88  * by the time prune_icache calls iput for the inode whose pages it has
89  * been invalidating, or by the time it calls clear_inode & destroy_inode
90  * from its final dispose_list, the struct super_block they refer to
91  * (for inode->i_sb->s_op) may already have been freed and reused.
92  */
93 static DEFINE_MUTEX(iprune_mutex);
94 
95 /*
96  * Statistics gathering..
97  */
98 struct inodes_stat_t inodes_stat;
99 
100 static struct kmem_cache * inode_cachep __read_mostly;
101 
102 static struct inode *alloc_inode(struct super_block *sb)
103 {
104 	static const struct address_space_operations empty_aops;
105 	static struct inode_operations empty_iops;
106 	static const struct file_operations empty_fops;
107 	struct inode *inode;
108 
109 	if (sb->s_op->alloc_inode)
110 		inode = sb->s_op->alloc_inode(sb);
111 	else
112 		inode = (struct inode *) kmem_cache_alloc(inode_cachep, GFP_KERNEL);
113 
114 	if (inode) {
115 		struct address_space * const mapping = &inode->i_data;
116 
117 		inode->i_sb = sb;
118 		inode->i_blkbits = sb->s_blocksize_bits;
119 		inode->i_flags = 0;
120 		atomic_set(&inode->i_count, 1);
121 		inode->i_op = &empty_iops;
122 		inode->i_fop = &empty_fops;
123 		inode->i_nlink = 1;
124 		atomic_set(&inode->i_writecount, 0);
125 		inode->i_size = 0;
126 		inode->i_blocks = 0;
127 		inode->i_bytes = 0;
128 		inode->i_generation = 0;
129 #ifdef CONFIG_QUOTA
130 		memset(&inode->i_dquot, 0, sizeof(inode->i_dquot));
131 #endif
132 		inode->i_pipe = NULL;
133 		inode->i_bdev = NULL;
134 		inode->i_cdev = NULL;
135 		inode->i_rdev = 0;
136 		inode->dirtied_when = 0;
137 		if (security_inode_alloc(inode)) {
138 			if (inode->i_sb->s_op->destroy_inode)
139 				inode->i_sb->s_op->destroy_inode(inode);
140 			else
141 				kmem_cache_free(inode_cachep, (inode));
142 			return NULL;
143 		}
144 
145 		mapping->a_ops = &empty_aops;
146  		mapping->host = inode;
147 		mapping->flags = 0;
148 		mapping_set_gfp_mask(mapping, GFP_HIGHUSER_PAGECACHE);
149 		mapping->assoc_mapping = NULL;
150 		mapping->backing_dev_info = &default_backing_dev_info;
151 
152 		/*
153 		 * If the block_device provides a backing_dev_info for client
154 		 * inodes then use that.  Otherwise the inode share the bdev's
155 		 * backing_dev_info.
156 		 */
157 		if (sb->s_bdev) {
158 			struct backing_dev_info *bdi;
159 
160 			bdi = sb->s_bdev->bd_inode_backing_dev_info;
161 			if (!bdi)
162 				bdi = sb->s_bdev->bd_inode->i_mapping->backing_dev_info;
163 			mapping->backing_dev_info = bdi;
164 		}
165 		inode->i_private = NULL;
166 		inode->i_mapping = mapping;
167 	}
168 	return inode;
169 }
170 
171 void destroy_inode(struct inode *inode)
172 {
173 	BUG_ON(inode_has_buffers(inode));
174 	security_inode_free(inode);
175 	if (inode->i_sb->s_op->destroy_inode)
176 		inode->i_sb->s_op->destroy_inode(inode);
177 	else
178 		kmem_cache_free(inode_cachep, (inode));
179 }
180 
181 
182 /*
183  * These are initializations that only need to be done
184  * once, because the fields are idempotent across use
185  * of the inode, so let the slab aware of that.
186  */
187 void inode_init_once(struct inode *inode)
188 {
189 	memset(inode, 0, sizeof(*inode));
190 	INIT_HLIST_NODE(&inode->i_hash);
191 	INIT_LIST_HEAD(&inode->i_dentry);
192 	INIT_LIST_HEAD(&inode->i_devices);
193 	mutex_init(&inode->i_mutex);
194 	init_rwsem(&inode->i_alloc_sem);
195 	INIT_RADIX_TREE(&inode->i_data.page_tree, GFP_ATOMIC);
196 	rwlock_init(&inode->i_data.tree_lock);
197 	spin_lock_init(&inode->i_data.i_mmap_lock);
198 	INIT_LIST_HEAD(&inode->i_data.private_list);
199 	spin_lock_init(&inode->i_data.private_lock);
200 	INIT_RAW_PRIO_TREE_ROOT(&inode->i_data.i_mmap);
201 	INIT_LIST_HEAD(&inode->i_data.i_mmap_nonlinear);
202 	spin_lock_init(&inode->i_lock);
203 	i_size_ordered_init(inode);
204 #ifdef CONFIG_INOTIFY
205 	INIT_LIST_HEAD(&inode->inotify_watches);
206 	mutex_init(&inode->inotify_mutex);
207 #endif
208 }
209 
210 EXPORT_SYMBOL(inode_init_once);
211 
212 static void init_once(void * foo, struct kmem_cache * cachep, unsigned long flags)
213 {
214 	struct inode * inode = (struct inode *) foo;
215 
216 	inode_init_once(inode);
217 }
218 
219 /*
220  * inode_lock must be held
221  */
222 void __iget(struct inode * inode)
223 {
224 	if (atomic_read(&inode->i_count)) {
225 		atomic_inc(&inode->i_count);
226 		return;
227 	}
228 	atomic_inc(&inode->i_count);
229 	if (!(inode->i_state & (I_DIRTY|I_LOCK)))
230 		list_move(&inode->i_list, &inode_in_use);
231 	inodes_stat.nr_unused--;
232 }
233 
234 /**
235  * clear_inode - clear an inode
236  * @inode: inode to clear
237  *
238  * This is called by the filesystem to tell us
239  * that the inode is no longer useful. We just
240  * terminate it with extreme prejudice.
241  */
242 void clear_inode(struct inode *inode)
243 {
244 	might_sleep();
245 	invalidate_inode_buffers(inode);
246 
247 	BUG_ON(inode->i_data.nrpages);
248 	BUG_ON(!(inode->i_state & I_FREEING));
249 	BUG_ON(inode->i_state & I_CLEAR);
250 	wait_on_inode(inode);
251 	DQUOT_DROP(inode);
252 	if (inode->i_sb->s_op->clear_inode)
253 		inode->i_sb->s_op->clear_inode(inode);
254 	if (S_ISBLK(inode->i_mode) && inode->i_bdev)
255 		bd_forget(inode);
256 	if (S_ISCHR(inode->i_mode) && inode->i_cdev)
257 		cd_forget(inode);
258 	inode->i_state = I_CLEAR;
259 }
260 
261 EXPORT_SYMBOL(clear_inode);
262 
263 /*
264  * dispose_list - dispose of the contents of a local list
265  * @head: the head of the list to free
266  *
267  * Dispose-list gets a local list with local inodes in it, so it doesn't
268  * need to worry about list corruption and SMP locks.
269  */
270 static void dispose_list(struct list_head *head)
271 {
272 	int nr_disposed = 0;
273 
274 	while (!list_empty(head)) {
275 		struct inode *inode;
276 
277 		inode = list_first_entry(head, struct inode, i_list);
278 		list_del(&inode->i_list);
279 
280 		if (inode->i_data.nrpages)
281 			truncate_inode_pages(&inode->i_data, 0);
282 		clear_inode(inode);
283 
284 		spin_lock(&inode_lock);
285 		hlist_del_init(&inode->i_hash);
286 		list_del_init(&inode->i_sb_list);
287 		spin_unlock(&inode_lock);
288 
289 		wake_up_inode(inode);
290 		destroy_inode(inode);
291 		nr_disposed++;
292 	}
293 	spin_lock(&inode_lock);
294 	inodes_stat.nr_inodes -= nr_disposed;
295 	spin_unlock(&inode_lock);
296 }
297 
298 /*
299  * Invalidate all inodes for a device.
300  */
301 static int invalidate_list(struct list_head *head, struct list_head *dispose)
302 {
303 	struct list_head *next;
304 	int busy = 0, count = 0;
305 
306 	next = head->next;
307 	for (;;) {
308 		struct list_head * tmp = next;
309 		struct inode * inode;
310 
311 		/*
312 		 * We can reschedule here without worrying about the list's
313 		 * consistency because the per-sb list of inodes must not
314 		 * change during umount anymore, and because iprune_mutex keeps
315 		 * shrink_icache_memory() away.
316 		 */
317 		cond_resched_lock(&inode_lock);
318 
319 		next = next->next;
320 		if (tmp == head)
321 			break;
322 		inode = list_entry(tmp, struct inode, i_sb_list);
323 		invalidate_inode_buffers(inode);
324 		if (!atomic_read(&inode->i_count)) {
325 			list_move(&inode->i_list, dispose);
326 			inode->i_state |= I_FREEING;
327 			count++;
328 			continue;
329 		}
330 		busy = 1;
331 	}
332 	/* only unused inodes may be cached with i_count zero */
333 	inodes_stat.nr_unused -= count;
334 	return busy;
335 }
336 
337 /**
338  *	invalidate_inodes	- discard the inodes on a device
339  *	@sb: superblock
340  *
341  *	Discard all of the inodes for a given superblock. If the discard
342  *	fails because there are busy inodes then a non zero value is returned.
343  *	If the discard is successful all the inodes have been discarded.
344  */
345 int invalidate_inodes(struct super_block * sb)
346 {
347 	int busy;
348 	LIST_HEAD(throw_away);
349 
350 	mutex_lock(&iprune_mutex);
351 	spin_lock(&inode_lock);
352 	inotify_unmount_inodes(&sb->s_inodes);
353 	busy = invalidate_list(&sb->s_inodes, &throw_away);
354 	spin_unlock(&inode_lock);
355 
356 	dispose_list(&throw_away);
357 	mutex_unlock(&iprune_mutex);
358 
359 	return busy;
360 }
361 
362 EXPORT_SYMBOL(invalidate_inodes);
363 
364 static int can_unuse(struct inode *inode)
365 {
366 	if (inode->i_state)
367 		return 0;
368 	if (inode_has_buffers(inode))
369 		return 0;
370 	if (atomic_read(&inode->i_count))
371 		return 0;
372 	if (inode->i_data.nrpages)
373 		return 0;
374 	return 1;
375 }
376 
377 /*
378  * Scan `goal' inodes on the unused list for freeable ones. They are moved to
379  * a temporary list and then are freed outside inode_lock by dispose_list().
380  *
381  * Any inodes which are pinned purely because of attached pagecache have their
382  * pagecache removed.  We expect the final iput() on that inode to add it to
383  * the front of the inode_unused list.  So look for it there and if the
384  * inode is still freeable, proceed.  The right inode is found 99.9% of the
385  * time in testing on a 4-way.
386  *
387  * If the inode has metadata buffers attached to mapping->private_list then
388  * try to remove them.
389  */
390 static void prune_icache(int nr_to_scan)
391 {
392 	LIST_HEAD(freeable);
393 	int nr_pruned = 0;
394 	int nr_scanned;
395 	unsigned long reap = 0;
396 
397 	mutex_lock(&iprune_mutex);
398 	spin_lock(&inode_lock);
399 	for (nr_scanned = 0; nr_scanned < nr_to_scan; nr_scanned++) {
400 		struct inode *inode;
401 
402 		if (list_empty(&inode_unused))
403 			break;
404 
405 		inode = list_entry(inode_unused.prev, struct inode, i_list);
406 
407 		if (inode->i_state || atomic_read(&inode->i_count)) {
408 			list_move(&inode->i_list, &inode_unused);
409 			continue;
410 		}
411 		if (inode_has_buffers(inode) || inode->i_data.nrpages) {
412 			__iget(inode);
413 			spin_unlock(&inode_lock);
414 			if (remove_inode_buffers(inode))
415 				reap += invalidate_mapping_pages(&inode->i_data,
416 								0, -1);
417 			iput(inode);
418 			spin_lock(&inode_lock);
419 
420 			if (inode != list_entry(inode_unused.next,
421 						struct inode, i_list))
422 				continue;	/* wrong inode or list_empty */
423 			if (!can_unuse(inode))
424 				continue;
425 		}
426 		list_move(&inode->i_list, &freeable);
427 		inode->i_state |= I_FREEING;
428 		nr_pruned++;
429 	}
430 	inodes_stat.nr_unused -= nr_pruned;
431 	if (current_is_kswapd())
432 		__count_vm_events(KSWAPD_INODESTEAL, reap);
433 	else
434 		__count_vm_events(PGINODESTEAL, reap);
435 	spin_unlock(&inode_lock);
436 
437 	dispose_list(&freeable);
438 	mutex_unlock(&iprune_mutex);
439 }
440 
441 /*
442  * shrink_icache_memory() will attempt to reclaim some unused inodes.  Here,
443  * "unused" means that no dentries are referring to the inodes: the files are
444  * not open and the dcache references to those inodes have already been
445  * reclaimed.
446  *
447  * This function is passed the number of inodes to scan, and it returns the
448  * total number of remaining possibly-reclaimable inodes.
449  */
450 static int shrink_icache_memory(int nr, gfp_t gfp_mask)
451 {
452 	if (nr) {
453 		/*
454 		 * Nasty deadlock avoidance.  We may hold various FS locks,
455 		 * and we don't want to recurse into the FS that called us
456 		 * in clear_inode() and friends..
457 	 	 */
458 		if (!(gfp_mask & __GFP_FS))
459 			return -1;
460 		prune_icache(nr);
461 	}
462 	return (inodes_stat.nr_unused / 100) * sysctl_vfs_cache_pressure;
463 }
464 
465 static struct shrinker icache_shrinker = {
466 	.shrink = shrink_icache_memory,
467 	.seeks = DEFAULT_SEEKS,
468 };
469 
470 static void __wait_on_freeing_inode(struct inode *inode);
471 /*
472  * Called with the inode lock held.
473  * NOTE: we are not increasing the inode-refcount, you must call __iget()
474  * by hand after calling find_inode now! This simplifies iunique and won't
475  * add any additional branch in the common code.
476  */
477 static struct inode * find_inode(struct super_block * sb, struct hlist_head *head, int (*test)(struct inode *, void *), void *data)
478 {
479 	struct hlist_node *node;
480 	struct inode * inode = NULL;
481 
482 repeat:
483 	hlist_for_each (node, head) {
484 		inode = hlist_entry(node, struct inode, i_hash);
485 		if (inode->i_sb != sb)
486 			continue;
487 		if (!test(inode, data))
488 			continue;
489 		if (inode->i_state & (I_FREEING|I_CLEAR|I_WILL_FREE)) {
490 			__wait_on_freeing_inode(inode);
491 			goto repeat;
492 		}
493 		break;
494 	}
495 	return node ? inode : NULL;
496 }
497 
498 /*
499  * find_inode_fast is the fast path version of find_inode, see the comment at
500  * iget_locked for details.
501  */
502 static struct inode * find_inode_fast(struct super_block * sb, struct hlist_head *head, unsigned long ino)
503 {
504 	struct hlist_node *node;
505 	struct inode * inode = NULL;
506 
507 repeat:
508 	hlist_for_each (node, head) {
509 		inode = hlist_entry(node, struct inode, i_hash);
510 		if (inode->i_ino != ino)
511 			continue;
512 		if (inode->i_sb != sb)
513 			continue;
514 		if (inode->i_state & (I_FREEING|I_CLEAR|I_WILL_FREE)) {
515 			__wait_on_freeing_inode(inode);
516 			goto repeat;
517 		}
518 		break;
519 	}
520 	return node ? inode : NULL;
521 }
522 
523 /**
524  *	new_inode 	- obtain an inode
525  *	@sb: superblock
526  *
527  *	Allocates a new inode for given superblock. The default gfp_mask
528  *	for allocations related to inode->i_mapping is GFP_HIGHUSER_PAGECACHE.
529  *	If HIGHMEM pages are unsuitable or it is known that pages allocated
530  *	for the page cache are not reclaimable or migratable,
531  *	mapping_set_gfp_mask() must be called with suitable flags on the
532  *	newly created inode's mapping
533  *
534  */
535 struct inode *new_inode(struct super_block *sb)
536 {
537 	/*
538 	 * On a 32bit, non LFS stat() call, glibc will generate an EOVERFLOW
539 	 * error if st_ino won't fit in target struct field. Use 32bit counter
540 	 * here to attempt to avoid that.
541 	 */
542 	static unsigned int last_ino;
543 	struct inode * inode;
544 
545 	spin_lock_prefetch(&inode_lock);
546 
547 	inode = alloc_inode(sb);
548 	if (inode) {
549 		spin_lock(&inode_lock);
550 		inodes_stat.nr_inodes++;
551 		list_add(&inode->i_list, &inode_in_use);
552 		list_add(&inode->i_sb_list, &sb->s_inodes);
553 		inode->i_ino = ++last_ino;
554 		inode->i_state = 0;
555 		spin_unlock(&inode_lock);
556 	}
557 	return inode;
558 }
559 
560 EXPORT_SYMBOL(new_inode);
561 
562 void unlock_new_inode(struct inode *inode)
563 {
564 	/*
565 	 * This is special!  We do not need the spinlock
566 	 * when clearing I_LOCK, because we're guaranteed
567 	 * that nobody else tries to do anything about the
568 	 * state of the inode when it is locked, as we
569 	 * just created it (so there can be no old holders
570 	 * that haven't tested I_LOCK).
571 	 */
572 	inode->i_state &= ~(I_LOCK|I_NEW);
573 	wake_up_inode(inode);
574 }
575 
576 EXPORT_SYMBOL(unlock_new_inode);
577 
578 /*
579  * This is called without the inode lock held.. Be careful.
580  *
581  * We no longer cache the sb_flags in i_flags - see fs.h
582  *	-- rmk@arm.uk.linux.org
583  */
584 static struct inode * get_new_inode(struct super_block *sb, struct hlist_head *head, int (*test)(struct inode *, void *), int (*set)(struct inode *, void *), void *data)
585 {
586 	struct inode * inode;
587 
588 	inode = alloc_inode(sb);
589 	if (inode) {
590 		struct inode * old;
591 
592 		spin_lock(&inode_lock);
593 		/* We released the lock, so.. */
594 		old = find_inode(sb, head, test, data);
595 		if (!old) {
596 			if (set(inode, data))
597 				goto set_failed;
598 
599 			inodes_stat.nr_inodes++;
600 			list_add(&inode->i_list, &inode_in_use);
601 			list_add(&inode->i_sb_list, &sb->s_inodes);
602 			hlist_add_head(&inode->i_hash, head);
603 			inode->i_state = I_LOCK|I_NEW;
604 			spin_unlock(&inode_lock);
605 
606 			/* Return the locked inode with I_NEW set, the
607 			 * caller is responsible for filling in the contents
608 			 */
609 			return inode;
610 		}
611 
612 		/*
613 		 * Uhhuh, somebody else created the same inode under
614 		 * us. Use the old inode instead of the one we just
615 		 * allocated.
616 		 */
617 		__iget(old);
618 		spin_unlock(&inode_lock);
619 		destroy_inode(inode);
620 		inode = old;
621 		wait_on_inode(inode);
622 	}
623 	return inode;
624 
625 set_failed:
626 	spin_unlock(&inode_lock);
627 	destroy_inode(inode);
628 	return NULL;
629 }
630 
631 /*
632  * get_new_inode_fast is the fast path version of get_new_inode, see the
633  * comment at iget_locked for details.
634  */
635 static struct inode * get_new_inode_fast(struct super_block *sb, struct hlist_head *head, unsigned long ino)
636 {
637 	struct inode * inode;
638 
639 	inode = alloc_inode(sb);
640 	if (inode) {
641 		struct inode * old;
642 
643 		spin_lock(&inode_lock);
644 		/* We released the lock, so.. */
645 		old = find_inode_fast(sb, head, ino);
646 		if (!old) {
647 			inode->i_ino = ino;
648 			inodes_stat.nr_inodes++;
649 			list_add(&inode->i_list, &inode_in_use);
650 			list_add(&inode->i_sb_list, &sb->s_inodes);
651 			hlist_add_head(&inode->i_hash, head);
652 			inode->i_state = I_LOCK|I_NEW;
653 			spin_unlock(&inode_lock);
654 
655 			/* Return the locked inode with I_NEW set, the
656 			 * caller is responsible for filling in the contents
657 			 */
658 			return inode;
659 		}
660 
661 		/*
662 		 * Uhhuh, somebody else created the same inode under
663 		 * us. Use the old inode instead of the one we just
664 		 * allocated.
665 		 */
666 		__iget(old);
667 		spin_unlock(&inode_lock);
668 		destroy_inode(inode);
669 		inode = old;
670 		wait_on_inode(inode);
671 	}
672 	return inode;
673 }
674 
675 static unsigned long hash(struct super_block *sb, unsigned long hashval)
676 {
677 	unsigned long tmp;
678 
679 	tmp = (hashval * (unsigned long)sb) ^ (GOLDEN_RATIO_PRIME + hashval) /
680 			L1_CACHE_BYTES;
681 	tmp = tmp ^ ((tmp ^ GOLDEN_RATIO_PRIME) >> I_HASHBITS);
682 	return tmp & I_HASHMASK;
683 }
684 
685 /**
686  *	iunique - get a unique inode number
687  *	@sb: superblock
688  *	@max_reserved: highest reserved inode number
689  *
690  *	Obtain an inode number that is unique on the system for a given
691  *	superblock. This is used by file systems that have no natural
692  *	permanent inode numbering system. An inode number is returned that
693  *	is higher than the reserved limit but unique.
694  *
695  *	BUGS:
696  *	With a large number of inodes live on the file system this function
697  *	currently becomes quite slow.
698  */
699 ino_t iunique(struct super_block *sb, ino_t max_reserved)
700 {
701 	/*
702 	 * On a 32bit, non LFS stat() call, glibc will generate an EOVERFLOW
703 	 * error if st_ino won't fit in target struct field. Use 32bit counter
704 	 * here to attempt to avoid that.
705 	 */
706 	static unsigned int counter;
707 	struct inode *inode;
708 	struct hlist_head *head;
709 	ino_t res;
710 
711 	spin_lock(&inode_lock);
712 	do {
713 		if (counter <= max_reserved)
714 			counter = max_reserved + 1;
715 		res = counter++;
716 		head = inode_hashtable + hash(sb, res);
717 		inode = find_inode_fast(sb, head, res);
718 	} while (inode != NULL);
719 	spin_unlock(&inode_lock);
720 
721 	return res;
722 }
723 EXPORT_SYMBOL(iunique);
724 
725 struct inode *igrab(struct inode *inode)
726 {
727 	spin_lock(&inode_lock);
728 	if (!(inode->i_state & (I_FREEING|I_CLEAR|I_WILL_FREE)))
729 		__iget(inode);
730 	else
731 		/*
732 		 * Handle the case where s_op->clear_inode is not been
733 		 * called yet, and somebody is calling igrab
734 		 * while the inode is getting freed.
735 		 */
736 		inode = NULL;
737 	spin_unlock(&inode_lock);
738 	return inode;
739 }
740 
741 EXPORT_SYMBOL(igrab);
742 
743 /**
744  * ifind - internal function, you want ilookup5() or iget5().
745  * @sb:		super block of file system to search
746  * @head:       the head of the list to search
747  * @test:	callback used for comparisons between inodes
748  * @data:	opaque data pointer to pass to @test
749  * @wait:	if true wait for the inode to be unlocked, if false do not
750  *
751  * ifind() searches for the inode specified by @data in the inode
752  * cache. This is a generalized version of ifind_fast() for file systems where
753  * the inode number is not sufficient for unique identification of an inode.
754  *
755  * If the inode is in the cache, the inode is returned with an incremented
756  * reference count.
757  *
758  * Otherwise NULL is returned.
759  *
760  * Note, @test is called with the inode_lock held, so can't sleep.
761  */
762 static struct inode *ifind(struct super_block *sb,
763 		struct hlist_head *head, int (*test)(struct inode *, void *),
764 		void *data, const int wait)
765 {
766 	struct inode *inode;
767 
768 	spin_lock(&inode_lock);
769 	inode = find_inode(sb, head, test, data);
770 	if (inode) {
771 		__iget(inode);
772 		spin_unlock(&inode_lock);
773 		if (likely(wait))
774 			wait_on_inode(inode);
775 		return inode;
776 	}
777 	spin_unlock(&inode_lock);
778 	return NULL;
779 }
780 
781 /**
782  * ifind_fast - internal function, you want ilookup() or iget().
783  * @sb:		super block of file system to search
784  * @head:       head of the list to search
785  * @ino:	inode number to search for
786  *
787  * ifind_fast() searches for the inode @ino in the inode cache. This is for
788  * file systems where the inode number is sufficient for unique identification
789  * of an inode.
790  *
791  * If the inode is in the cache, the inode is returned with an incremented
792  * reference count.
793  *
794  * Otherwise NULL is returned.
795  */
796 static struct inode *ifind_fast(struct super_block *sb,
797 		struct hlist_head *head, unsigned long ino)
798 {
799 	struct inode *inode;
800 
801 	spin_lock(&inode_lock);
802 	inode = find_inode_fast(sb, head, ino);
803 	if (inode) {
804 		__iget(inode);
805 		spin_unlock(&inode_lock);
806 		wait_on_inode(inode);
807 		return inode;
808 	}
809 	spin_unlock(&inode_lock);
810 	return NULL;
811 }
812 
813 /**
814  * ilookup5_nowait - search for an inode in the inode cache
815  * @sb:		super block of file system to search
816  * @hashval:	hash value (usually inode number) to search for
817  * @test:	callback used for comparisons between inodes
818  * @data:	opaque data pointer to pass to @test
819  *
820  * ilookup5() uses ifind() to search for the inode specified by @hashval and
821  * @data in the inode cache. This is a generalized version of ilookup() for
822  * file systems where the inode number is not sufficient for unique
823  * identification of an inode.
824  *
825  * If the inode is in the cache, the inode is returned with an incremented
826  * reference count.  Note, the inode lock is not waited upon so you have to be
827  * very careful what you do with the returned inode.  You probably should be
828  * using ilookup5() instead.
829  *
830  * Otherwise NULL is returned.
831  *
832  * Note, @test is called with the inode_lock held, so can't sleep.
833  */
834 struct inode *ilookup5_nowait(struct super_block *sb, unsigned long hashval,
835 		int (*test)(struct inode *, void *), void *data)
836 {
837 	struct hlist_head *head = inode_hashtable + hash(sb, hashval);
838 
839 	return ifind(sb, head, test, data, 0);
840 }
841 
842 EXPORT_SYMBOL(ilookup5_nowait);
843 
844 /**
845  * ilookup5 - search for an inode in the inode cache
846  * @sb:		super block of file system to search
847  * @hashval:	hash value (usually inode number) to search for
848  * @test:	callback used for comparisons between inodes
849  * @data:	opaque data pointer to pass to @test
850  *
851  * ilookup5() uses ifind() to search for the inode specified by @hashval and
852  * @data in the inode cache. This is a generalized version of ilookup() for
853  * file systems where the inode number is not sufficient for unique
854  * identification of an inode.
855  *
856  * If the inode is in the cache, the inode lock is waited upon and the inode is
857  * returned with an incremented reference count.
858  *
859  * Otherwise NULL is returned.
860  *
861  * Note, @test is called with the inode_lock held, so can't sleep.
862  */
863 struct inode *ilookup5(struct super_block *sb, unsigned long hashval,
864 		int (*test)(struct inode *, void *), void *data)
865 {
866 	struct hlist_head *head = inode_hashtable + hash(sb, hashval);
867 
868 	return ifind(sb, head, test, data, 1);
869 }
870 
871 EXPORT_SYMBOL(ilookup5);
872 
873 /**
874  * ilookup - search for an inode in the inode cache
875  * @sb:		super block of file system to search
876  * @ino:	inode number to search for
877  *
878  * ilookup() uses ifind_fast() to search for the inode @ino in the inode cache.
879  * This is for file systems where the inode number is sufficient for unique
880  * identification of an inode.
881  *
882  * If the inode is in the cache, the inode is returned with an incremented
883  * reference count.
884  *
885  * Otherwise NULL is returned.
886  */
887 struct inode *ilookup(struct super_block *sb, unsigned long ino)
888 {
889 	struct hlist_head *head = inode_hashtable + hash(sb, ino);
890 
891 	return ifind_fast(sb, head, ino);
892 }
893 
894 EXPORT_SYMBOL(ilookup);
895 
896 /**
897  * iget5_locked - obtain an inode from a mounted file system
898  * @sb:		super block of file system
899  * @hashval:	hash value (usually inode number) to get
900  * @test:	callback used for comparisons between inodes
901  * @set:	callback used to initialize a new struct inode
902  * @data:	opaque data pointer to pass to @test and @set
903  *
904  * This is iget() without the read_inode() portion of get_new_inode().
905  *
906  * iget5_locked() uses ifind() to search for the inode specified by @hashval
907  * and @data in the inode cache and if present it is returned with an increased
908  * reference count. This is a generalized version of iget_locked() for file
909  * systems where the inode number is not sufficient for unique identification
910  * of an inode.
911  *
912  * If the inode is not in cache, get_new_inode() is called to allocate a new
913  * inode and this is returned locked, hashed, and with the I_NEW flag set. The
914  * file system gets to fill it in before unlocking it via unlock_new_inode().
915  *
916  * Note both @test and @set are called with the inode_lock held, so can't sleep.
917  */
918 struct inode *iget5_locked(struct super_block *sb, unsigned long hashval,
919 		int (*test)(struct inode *, void *),
920 		int (*set)(struct inode *, void *), void *data)
921 {
922 	struct hlist_head *head = inode_hashtable + hash(sb, hashval);
923 	struct inode *inode;
924 
925 	inode = ifind(sb, head, test, data, 1);
926 	if (inode)
927 		return inode;
928 	/*
929 	 * get_new_inode() will do the right thing, re-trying the search
930 	 * in case it had to block at any point.
931 	 */
932 	return get_new_inode(sb, head, test, set, data);
933 }
934 
935 EXPORT_SYMBOL(iget5_locked);
936 
937 /**
938  * iget_locked - obtain an inode from a mounted file system
939  * @sb:		super block of file system
940  * @ino:	inode number to get
941  *
942  * This is iget() without the read_inode() portion of get_new_inode_fast().
943  *
944  * iget_locked() uses ifind_fast() to search for the inode specified by @ino in
945  * the inode cache and if present it is returned with an increased reference
946  * count. This is for file systems where the inode number is sufficient for
947  * unique identification of an inode.
948  *
949  * If the inode is not in cache, get_new_inode_fast() is called to allocate a
950  * new inode and this is returned locked, hashed, and with the I_NEW flag set.
951  * The file system gets to fill it in before unlocking it via
952  * unlock_new_inode().
953  */
954 struct inode *iget_locked(struct super_block *sb, unsigned long ino)
955 {
956 	struct hlist_head *head = inode_hashtable + hash(sb, ino);
957 	struct inode *inode;
958 
959 	inode = ifind_fast(sb, head, ino);
960 	if (inode)
961 		return inode;
962 	/*
963 	 * get_new_inode_fast() will do the right thing, re-trying the search
964 	 * in case it had to block at any point.
965 	 */
966 	return get_new_inode_fast(sb, head, ino);
967 }
968 
969 EXPORT_SYMBOL(iget_locked);
970 
971 /**
972  *	__insert_inode_hash - hash an inode
973  *	@inode: unhashed inode
974  *	@hashval: unsigned long value used to locate this object in the
975  *		inode_hashtable.
976  *
977  *	Add an inode to the inode hash for this superblock.
978  */
979 void __insert_inode_hash(struct inode *inode, unsigned long hashval)
980 {
981 	struct hlist_head *head = inode_hashtable + hash(inode->i_sb, hashval);
982 	spin_lock(&inode_lock);
983 	hlist_add_head(&inode->i_hash, head);
984 	spin_unlock(&inode_lock);
985 }
986 
987 EXPORT_SYMBOL(__insert_inode_hash);
988 
989 /**
990  *	remove_inode_hash - remove an inode from the hash
991  *	@inode: inode to unhash
992  *
993  *	Remove an inode from the superblock.
994  */
995 void remove_inode_hash(struct inode *inode)
996 {
997 	spin_lock(&inode_lock);
998 	hlist_del_init(&inode->i_hash);
999 	spin_unlock(&inode_lock);
1000 }
1001 
1002 EXPORT_SYMBOL(remove_inode_hash);
1003 
1004 /*
1005  * Tell the filesystem that this inode is no longer of any interest and should
1006  * be completely destroyed.
1007  *
1008  * We leave the inode in the inode hash table until *after* the filesystem's
1009  * ->delete_inode completes.  This ensures that an iget (such as nfsd might
1010  * instigate) will always find up-to-date information either in the hash or on
1011  * disk.
1012  *
1013  * I_FREEING is set so that no-one will take a new reference to the inode while
1014  * it is being deleted.
1015  */
1016 void generic_delete_inode(struct inode *inode)
1017 {
1018 	const struct super_operations *op = inode->i_sb->s_op;
1019 
1020 	list_del_init(&inode->i_list);
1021 	list_del_init(&inode->i_sb_list);
1022 	inode->i_state |= I_FREEING;
1023 	inodes_stat.nr_inodes--;
1024 	spin_unlock(&inode_lock);
1025 
1026 	security_inode_delete(inode);
1027 
1028 	if (op->delete_inode) {
1029 		void (*delete)(struct inode *) = op->delete_inode;
1030 		if (!is_bad_inode(inode))
1031 			DQUOT_INIT(inode);
1032 		/* Filesystems implementing their own
1033 		 * s_op->delete_inode are required to call
1034 		 * truncate_inode_pages and clear_inode()
1035 		 * internally */
1036 		delete(inode);
1037 	} else {
1038 		truncate_inode_pages(&inode->i_data, 0);
1039 		clear_inode(inode);
1040 	}
1041 	spin_lock(&inode_lock);
1042 	hlist_del_init(&inode->i_hash);
1043 	spin_unlock(&inode_lock);
1044 	wake_up_inode(inode);
1045 	BUG_ON(inode->i_state != I_CLEAR);
1046 	destroy_inode(inode);
1047 }
1048 
1049 EXPORT_SYMBOL(generic_delete_inode);
1050 
1051 static void generic_forget_inode(struct inode *inode)
1052 {
1053 	struct super_block *sb = inode->i_sb;
1054 
1055 	if (!hlist_unhashed(&inode->i_hash)) {
1056 		if (!(inode->i_state & (I_DIRTY|I_LOCK)))
1057 			list_move(&inode->i_list, &inode_unused);
1058 		inodes_stat.nr_unused++;
1059 		if (sb->s_flags & MS_ACTIVE) {
1060 			spin_unlock(&inode_lock);
1061 			return;
1062 		}
1063 		inode->i_state |= I_WILL_FREE;
1064 		spin_unlock(&inode_lock);
1065 		write_inode_now(inode, 1);
1066 		spin_lock(&inode_lock);
1067 		inode->i_state &= ~I_WILL_FREE;
1068 		inodes_stat.nr_unused--;
1069 		hlist_del_init(&inode->i_hash);
1070 	}
1071 	list_del_init(&inode->i_list);
1072 	list_del_init(&inode->i_sb_list);
1073 	inode->i_state |= I_FREEING;
1074 	inodes_stat.nr_inodes--;
1075 	spin_unlock(&inode_lock);
1076 	if (inode->i_data.nrpages)
1077 		truncate_inode_pages(&inode->i_data, 0);
1078 	clear_inode(inode);
1079 	wake_up_inode(inode);
1080 	destroy_inode(inode);
1081 }
1082 
1083 /*
1084  * Normal UNIX filesystem behaviour: delete the
1085  * inode when the usage count drops to zero, and
1086  * i_nlink is zero.
1087  */
1088 void generic_drop_inode(struct inode *inode)
1089 {
1090 	if (!inode->i_nlink)
1091 		generic_delete_inode(inode);
1092 	else
1093 		generic_forget_inode(inode);
1094 }
1095 
1096 EXPORT_SYMBOL_GPL(generic_drop_inode);
1097 
1098 /*
1099  * Called when we're dropping the last reference
1100  * to an inode.
1101  *
1102  * Call the FS "drop()" function, defaulting to
1103  * the legacy UNIX filesystem behaviour..
1104  *
1105  * NOTE! NOTE! NOTE! We're called with the inode lock
1106  * held, and the drop function is supposed to release
1107  * the lock!
1108  */
1109 static inline void iput_final(struct inode *inode)
1110 {
1111 	const struct super_operations *op = inode->i_sb->s_op;
1112 	void (*drop)(struct inode *) = generic_drop_inode;
1113 
1114 	if (op && op->drop_inode)
1115 		drop = op->drop_inode;
1116 	drop(inode);
1117 }
1118 
1119 /**
1120  *	iput	- put an inode
1121  *	@inode: inode to put
1122  *
1123  *	Puts an inode, dropping its usage count. If the inode use count hits
1124  *	zero, the inode is then freed and may also be destroyed.
1125  *
1126  *	Consequently, iput() can sleep.
1127  */
1128 void iput(struct inode *inode)
1129 {
1130 	if (inode) {
1131 		const struct super_operations *op = inode->i_sb->s_op;
1132 
1133 		BUG_ON(inode->i_state == I_CLEAR);
1134 
1135 		if (op && op->put_inode)
1136 			op->put_inode(inode);
1137 
1138 		if (atomic_dec_and_lock(&inode->i_count, &inode_lock))
1139 			iput_final(inode);
1140 	}
1141 }
1142 
1143 EXPORT_SYMBOL(iput);
1144 
1145 /**
1146  *	bmap	- find a block number in a file
1147  *	@inode: inode of file
1148  *	@block: block to find
1149  *
1150  *	Returns the block number on the device holding the inode that
1151  *	is the disk block number for the block of the file requested.
1152  *	That is, asked for block 4 of inode 1 the function will return the
1153  *	disk block relative to the disk start that holds that block of the
1154  *	file.
1155  */
1156 sector_t bmap(struct inode * inode, sector_t block)
1157 {
1158 	sector_t res = 0;
1159 	if (inode->i_mapping->a_ops->bmap)
1160 		res = inode->i_mapping->a_ops->bmap(inode->i_mapping, block);
1161 	return res;
1162 }
1163 EXPORT_SYMBOL(bmap);
1164 
1165 /**
1166  *	touch_atime	-	update the access time
1167  *	@mnt: mount the inode is accessed on
1168  *	@dentry: dentry accessed
1169  *
1170  *	Update the accessed time on an inode and mark it for writeback.
1171  *	This function automatically handles read only file systems and media,
1172  *	as well as the "noatime" flag and inode specific "noatime" markers.
1173  */
1174 void touch_atime(struct vfsmount *mnt, struct dentry *dentry)
1175 {
1176 	struct inode *inode = dentry->d_inode;
1177 	struct timespec now;
1178 
1179 	if (inode->i_flags & S_NOATIME)
1180 		return;
1181 	if (IS_NOATIME(inode))
1182 		return;
1183 	if ((inode->i_sb->s_flags & MS_NODIRATIME) && S_ISDIR(inode->i_mode))
1184 		return;
1185 
1186 	/*
1187 	 * We may have a NULL vfsmount when coming from NFSD
1188 	 */
1189 	if (mnt) {
1190 		if (mnt->mnt_flags & MNT_NOATIME)
1191 			return;
1192 		if ((mnt->mnt_flags & MNT_NODIRATIME) && S_ISDIR(inode->i_mode))
1193 			return;
1194 
1195 		if (mnt->mnt_flags & MNT_RELATIME) {
1196 			/*
1197 			 * With relative atime, only update atime if the
1198 			 * previous atime is earlier than either the ctime or
1199 			 * mtime.
1200 			 */
1201 			if (timespec_compare(&inode->i_mtime,
1202 						&inode->i_atime) < 0 &&
1203 			    timespec_compare(&inode->i_ctime,
1204 						&inode->i_atime) < 0)
1205 				return;
1206 		}
1207 	}
1208 
1209 	now = current_fs_time(inode->i_sb);
1210 	if (timespec_equal(&inode->i_atime, &now))
1211 		return;
1212 
1213 	inode->i_atime = now;
1214 	mark_inode_dirty_sync(inode);
1215 }
1216 EXPORT_SYMBOL(touch_atime);
1217 
1218 /**
1219  *	file_update_time	-	update mtime and ctime time
1220  *	@file: file accessed
1221  *
1222  *	Update the mtime and ctime members of an inode and mark the inode
1223  *	for writeback.  Note that this function is meant exclusively for
1224  *	usage in the file write path of filesystems, and filesystems may
1225  *	choose to explicitly ignore update via this function with the
1226  *	S_NOCTIME inode flag, e.g. for network filesystem where these
1227  *	timestamps are handled by the server.
1228  */
1229 
1230 void file_update_time(struct file *file)
1231 {
1232 	struct inode *inode = file->f_path.dentry->d_inode;
1233 	struct timespec now;
1234 	int sync_it = 0;
1235 
1236 	if (IS_NOCMTIME(inode))
1237 		return;
1238 	if (IS_RDONLY(inode))
1239 		return;
1240 
1241 	now = current_fs_time(inode->i_sb);
1242 	if (!timespec_equal(&inode->i_mtime, &now)) {
1243 		inode->i_mtime = now;
1244 		sync_it = 1;
1245 	}
1246 
1247 	if (!timespec_equal(&inode->i_ctime, &now)) {
1248 		inode->i_ctime = now;
1249 		sync_it = 1;
1250 	}
1251 
1252 	if (sync_it)
1253 		mark_inode_dirty_sync(inode);
1254 }
1255 
1256 EXPORT_SYMBOL(file_update_time);
1257 
1258 int inode_needs_sync(struct inode *inode)
1259 {
1260 	if (IS_SYNC(inode))
1261 		return 1;
1262 	if (S_ISDIR(inode->i_mode) && IS_DIRSYNC(inode))
1263 		return 1;
1264 	return 0;
1265 }
1266 
1267 EXPORT_SYMBOL(inode_needs_sync);
1268 
1269 int inode_wait(void *word)
1270 {
1271 	schedule();
1272 	return 0;
1273 }
1274 
1275 /*
1276  * If we try to find an inode in the inode hash while it is being
1277  * deleted, we have to wait until the filesystem completes its
1278  * deletion before reporting that it isn't found.  This function waits
1279  * until the deletion _might_ have completed.  Callers are responsible
1280  * to recheck inode state.
1281  *
1282  * It doesn't matter if I_LOCK is not set initially, a call to
1283  * wake_up_inode() after removing from the hash list will DTRT.
1284  *
1285  * This is called with inode_lock held.
1286  */
1287 static void __wait_on_freeing_inode(struct inode *inode)
1288 {
1289 	wait_queue_head_t *wq;
1290 	DEFINE_WAIT_BIT(wait, &inode->i_state, __I_LOCK);
1291 	wq = bit_waitqueue(&inode->i_state, __I_LOCK);
1292 	prepare_to_wait(wq, &wait.wait, TASK_UNINTERRUPTIBLE);
1293 	spin_unlock(&inode_lock);
1294 	schedule();
1295 	finish_wait(wq, &wait.wait);
1296 	spin_lock(&inode_lock);
1297 }
1298 
1299 void wake_up_inode(struct inode *inode)
1300 {
1301 	/*
1302 	 * Prevent speculative execution through spin_unlock(&inode_lock);
1303 	 */
1304 	smp_mb();
1305 	wake_up_bit(&inode->i_state, __I_LOCK);
1306 }
1307 
1308 /*
1309  * We rarely want to lock two inodes that do not have a parent/child
1310  * relationship (such as directory, child inode) simultaneously. The
1311  * vast majority of file systems should be able to get along fine
1312  * without this. Do not use these functions except as a last resort.
1313  */
1314 void inode_double_lock(struct inode *inode1, struct inode *inode2)
1315 {
1316 	if (inode1 == NULL || inode2 == NULL || inode1 == inode2) {
1317 		if (inode1)
1318 			mutex_lock(&inode1->i_mutex);
1319 		else if (inode2)
1320 			mutex_lock(&inode2->i_mutex);
1321 		return;
1322 	}
1323 
1324 	if (inode1 < inode2) {
1325 		mutex_lock_nested(&inode1->i_mutex, I_MUTEX_PARENT);
1326 		mutex_lock_nested(&inode2->i_mutex, I_MUTEX_CHILD);
1327 	} else {
1328 		mutex_lock_nested(&inode2->i_mutex, I_MUTEX_PARENT);
1329 		mutex_lock_nested(&inode1->i_mutex, I_MUTEX_CHILD);
1330 	}
1331 }
1332 EXPORT_SYMBOL(inode_double_lock);
1333 
1334 void inode_double_unlock(struct inode *inode1, struct inode *inode2)
1335 {
1336 	if (inode1)
1337 		mutex_unlock(&inode1->i_mutex);
1338 
1339 	if (inode2 && inode2 != inode1)
1340 		mutex_unlock(&inode2->i_mutex);
1341 }
1342 EXPORT_SYMBOL(inode_double_unlock);
1343 
1344 static __initdata unsigned long ihash_entries;
1345 static int __init set_ihash_entries(char *str)
1346 {
1347 	if (!str)
1348 		return 0;
1349 	ihash_entries = simple_strtoul(str, &str, 0);
1350 	return 1;
1351 }
1352 __setup("ihash_entries=", set_ihash_entries);
1353 
1354 /*
1355  * Initialize the waitqueues and inode hash table.
1356  */
1357 void __init inode_init_early(void)
1358 {
1359 	int loop;
1360 
1361 	/* If hashes are distributed across NUMA nodes, defer
1362 	 * hash allocation until vmalloc space is available.
1363 	 */
1364 	if (hashdist)
1365 		return;
1366 
1367 	inode_hashtable =
1368 		alloc_large_system_hash("Inode-cache",
1369 					sizeof(struct hlist_head),
1370 					ihash_entries,
1371 					14,
1372 					HASH_EARLY,
1373 					&i_hash_shift,
1374 					&i_hash_mask,
1375 					0);
1376 
1377 	for (loop = 0; loop < (1 << i_hash_shift); loop++)
1378 		INIT_HLIST_HEAD(&inode_hashtable[loop]);
1379 }
1380 
1381 void __init inode_init(unsigned long mempages)
1382 {
1383 	int loop;
1384 
1385 	/* inode slab cache */
1386 	inode_cachep = kmem_cache_create("inode_cache",
1387 					 sizeof(struct inode),
1388 					 0,
1389 					 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
1390 					 SLAB_MEM_SPREAD),
1391 					 init_once);
1392 	register_shrinker(&icache_shrinker);
1393 
1394 	/* Hash may have been set up in inode_init_early */
1395 	if (!hashdist)
1396 		return;
1397 
1398 	inode_hashtable =
1399 		alloc_large_system_hash("Inode-cache",
1400 					sizeof(struct hlist_head),
1401 					ihash_entries,
1402 					14,
1403 					0,
1404 					&i_hash_shift,
1405 					&i_hash_mask,
1406 					0);
1407 
1408 	for (loop = 0; loop < (1 << i_hash_shift); loop++)
1409 		INIT_HLIST_HEAD(&inode_hashtable[loop]);
1410 }
1411 
1412 void init_special_inode(struct inode *inode, umode_t mode, dev_t rdev)
1413 {
1414 	inode->i_mode = mode;
1415 	if (S_ISCHR(mode)) {
1416 		inode->i_fop = &def_chr_fops;
1417 		inode->i_rdev = rdev;
1418 	} else if (S_ISBLK(mode)) {
1419 		inode->i_fop = &def_blk_fops;
1420 		inode->i_rdev = rdev;
1421 	} else if (S_ISFIFO(mode))
1422 		inode->i_fop = &def_fifo_fops;
1423 	else if (S_ISSOCK(mode))
1424 		inode->i_fop = &bad_sock_fops;
1425 	else
1426 		printk(KERN_DEBUG "init_special_inode: bogus i_mode (%o)\n",
1427 		       mode);
1428 }
1429 EXPORT_SYMBOL(init_special_inode);
1430