xref: /openbmc/linux/mm/shmem.c (revision d5cb9783536a41df9f9cba5b0a1d78047ed787f7)
1 /*
2  * Resizable virtual memory filesystem for Linux.
3  *
4  * Copyright (C) 2000 Linus Torvalds.
5  *		 2000 Transmeta Corp.
6  *		 2000-2001 Christoph Rohland
7  *		 2000-2001 SAP AG
8  *		 2002 Red Hat Inc.
9  * Copyright (C) 2002-2005 Hugh Dickins.
10  * Copyright (C) 2002-2005 VERITAS Software Corporation.
11  * Copyright (C) 2004 Andi Kleen, SuSE Labs
12  *
13  * Extended attribute support for tmpfs:
14  * Copyright (c) 2004, Luke Kenneth Casson Leighton <lkcl@lkcl.net>
15  * Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
16  *
17  * This file is released under the GPL.
18  */
19 
20 /*
21  * This virtual memory filesystem is heavily based on the ramfs. It
22  * extends ramfs by the ability to use swap and honor resource limits
23  * which makes it a completely usable filesystem.
24  */
25 
26 #include <linux/config.h>
27 #include <linux/module.h>
28 #include <linux/init.h>
29 #include <linux/devfs_fs_kernel.h>
30 #include <linux/fs.h>
31 #include <linux/mm.h>
32 #include <linux/mman.h>
33 #include <linux/file.h>
34 #include <linux/swap.h>
35 #include <linux/pagemap.h>
36 #include <linux/string.h>
37 #include <linux/slab.h>
38 #include <linux/backing-dev.h>
39 #include <linux/shmem_fs.h>
40 #include <linux/mount.h>
41 #include <linux/writeback.h>
42 #include <linux/vfs.h>
43 #include <linux/blkdev.h>
44 #include <linux/security.h>
45 #include <linux/swapops.h>
46 #include <linux/mempolicy.h>
47 #include <linux/namei.h>
48 #include <asm/uaccess.h>
49 #include <asm/div64.h>
50 #include <asm/pgtable.h>
51 
52 /* This magic number is used in glibc for posix shared memory */
53 #define TMPFS_MAGIC	0x01021994
54 
55 #define ENTRIES_PER_PAGE (PAGE_CACHE_SIZE/sizeof(unsigned long))
56 #define ENTRIES_PER_PAGEPAGE (ENTRIES_PER_PAGE*ENTRIES_PER_PAGE)
57 #define BLOCKS_PER_PAGE  (PAGE_CACHE_SIZE/512)
58 
59 #define SHMEM_MAX_INDEX  (SHMEM_NR_DIRECT + (ENTRIES_PER_PAGEPAGE/2) * (ENTRIES_PER_PAGE+1))
60 #define SHMEM_MAX_BYTES  ((unsigned long long)SHMEM_MAX_INDEX << PAGE_CACHE_SHIFT)
61 
62 #define VM_ACCT(size)    (PAGE_CACHE_ALIGN(size) >> PAGE_SHIFT)
63 
64 /* info->flags needs VM_flags to handle pagein/truncate races efficiently */
65 #define SHMEM_PAGEIN	 VM_READ
66 #define SHMEM_TRUNCATE	 VM_WRITE
67 
68 /* Definition to limit shmem_truncate's steps between cond_rescheds */
69 #define LATENCY_LIMIT	 64
70 
71 /* Pretend that each entry is of this size in directory's i_size */
72 #define BOGO_DIRENT_SIZE 20
73 
74 /* Flag allocation requirements to shmem_getpage and shmem_swp_alloc */
75 enum sgp_type {
76 	SGP_QUICK,	/* don't try more than file page cache lookup */
77 	SGP_READ,	/* don't exceed i_size, don't allocate page */
78 	SGP_CACHE,	/* don't exceed i_size, may allocate page */
79 	SGP_WRITE,	/* may exceed i_size, may allocate page */
80 };
81 
82 static int shmem_getpage(struct inode *inode, unsigned long idx,
83 			 struct page **pagep, enum sgp_type sgp, int *type);
84 
85 static inline struct page *shmem_dir_alloc(gfp_t gfp_mask)
86 {
87 	/*
88 	 * The above definition of ENTRIES_PER_PAGE, and the use of
89 	 * BLOCKS_PER_PAGE on indirect pages, assume PAGE_CACHE_SIZE:
90 	 * might be reconsidered if it ever diverges from PAGE_SIZE.
91 	 */
92 	return alloc_pages(gfp_mask, PAGE_CACHE_SHIFT-PAGE_SHIFT);
93 }
94 
95 static inline void shmem_dir_free(struct page *page)
96 {
97 	__free_pages(page, PAGE_CACHE_SHIFT-PAGE_SHIFT);
98 }
99 
100 static struct page **shmem_dir_map(struct page *page)
101 {
102 	return (struct page **)kmap_atomic(page, KM_USER0);
103 }
104 
105 static inline void shmem_dir_unmap(struct page **dir)
106 {
107 	kunmap_atomic(dir, KM_USER0);
108 }
109 
110 static swp_entry_t *shmem_swp_map(struct page *page)
111 {
112 	return (swp_entry_t *)kmap_atomic(page, KM_USER1);
113 }
114 
115 static inline void shmem_swp_balance_unmap(void)
116 {
117 	/*
118 	 * When passing a pointer to an i_direct entry, to code which
119 	 * also handles indirect entries and so will shmem_swp_unmap,
120 	 * we must arrange for the preempt count to remain in balance.
121 	 * What kmap_atomic of a lowmem page does depends on config
122 	 * and architecture, so pretend to kmap_atomic some lowmem page.
123 	 */
124 	(void) kmap_atomic(ZERO_PAGE(0), KM_USER1);
125 }
126 
127 static inline void shmem_swp_unmap(swp_entry_t *entry)
128 {
129 	kunmap_atomic(entry, KM_USER1);
130 }
131 
132 static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
133 {
134 	return sb->s_fs_info;
135 }
136 
137 /*
138  * shmem_file_setup pre-accounts the whole fixed size of a VM object,
139  * for shared memory and for shared anonymous (/dev/zero) mappings
140  * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
141  * consistent with the pre-accounting of private mappings ...
142  */
143 static inline int shmem_acct_size(unsigned long flags, loff_t size)
144 {
145 	return (flags & VM_ACCOUNT)?
146 		security_vm_enough_memory(VM_ACCT(size)): 0;
147 }
148 
149 static inline void shmem_unacct_size(unsigned long flags, loff_t size)
150 {
151 	if (flags & VM_ACCOUNT)
152 		vm_unacct_memory(VM_ACCT(size));
153 }
154 
155 /*
156  * ... whereas tmpfs objects are accounted incrementally as
157  * pages are allocated, in order to allow huge sparse files.
158  * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
159  * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
160  */
161 static inline int shmem_acct_block(unsigned long flags)
162 {
163 	return (flags & VM_ACCOUNT)?
164 		0: security_vm_enough_memory(VM_ACCT(PAGE_CACHE_SIZE));
165 }
166 
167 static inline void shmem_unacct_blocks(unsigned long flags, long pages)
168 {
169 	if (!(flags & VM_ACCOUNT))
170 		vm_unacct_memory(pages * VM_ACCT(PAGE_CACHE_SIZE));
171 }
172 
173 static struct super_operations shmem_ops;
174 static struct address_space_operations shmem_aops;
175 static struct file_operations shmem_file_operations;
176 static struct inode_operations shmem_inode_operations;
177 static struct inode_operations shmem_dir_inode_operations;
178 static struct vm_operations_struct shmem_vm_ops;
179 
180 static struct backing_dev_info shmem_backing_dev_info  __read_mostly = {
181 	.ra_pages	= 0,	/* No readahead */
182 	.capabilities	= BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
183 	.unplug_io_fn	= default_unplug_io_fn,
184 };
185 
186 static LIST_HEAD(shmem_swaplist);
187 static DEFINE_SPINLOCK(shmem_swaplist_lock);
188 
189 static void shmem_free_blocks(struct inode *inode, long pages)
190 {
191 	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
192 	if (sbinfo->max_blocks) {
193 		spin_lock(&sbinfo->stat_lock);
194 		sbinfo->free_blocks += pages;
195 		inode->i_blocks -= pages*BLOCKS_PER_PAGE;
196 		spin_unlock(&sbinfo->stat_lock);
197 	}
198 }
199 
200 /*
201  * shmem_recalc_inode - recalculate the size of an inode
202  *
203  * @inode: inode to recalc
204  *
205  * We have to calculate the free blocks since the mm can drop
206  * undirtied hole pages behind our back.
207  *
208  * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
209  * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
210  *
211  * It has to be called with the spinlock held.
212  */
213 static void shmem_recalc_inode(struct inode *inode)
214 {
215 	struct shmem_inode_info *info = SHMEM_I(inode);
216 	long freed;
217 
218 	freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
219 	if (freed > 0) {
220 		info->alloced -= freed;
221 		shmem_unacct_blocks(info->flags, freed);
222 		shmem_free_blocks(inode, freed);
223 	}
224 }
225 
226 /*
227  * shmem_swp_entry - find the swap vector position in the info structure
228  *
229  * @info:  info structure for the inode
230  * @index: index of the page to find
231  * @page:  optional page to add to the structure. Has to be preset to
232  *         all zeros
233  *
234  * If there is no space allocated yet it will return NULL when
235  * page is NULL, else it will use the page for the needed block,
236  * setting it to NULL on return to indicate that it has been used.
237  *
238  * The swap vector is organized the following way:
239  *
240  * There are SHMEM_NR_DIRECT entries directly stored in the
241  * shmem_inode_info structure. So small files do not need an addional
242  * allocation.
243  *
244  * For pages with index > SHMEM_NR_DIRECT there is the pointer
245  * i_indirect which points to a page which holds in the first half
246  * doubly indirect blocks, in the second half triple indirect blocks:
247  *
248  * For an artificial ENTRIES_PER_PAGE = 4 this would lead to the
249  * following layout (for SHMEM_NR_DIRECT == 16):
250  *
251  * i_indirect -> dir --> 16-19
252  * 	      |	     +-> 20-23
253  * 	      |
254  * 	      +-->dir2 --> 24-27
255  * 	      |	       +-> 28-31
256  * 	      |	       +-> 32-35
257  * 	      |	       +-> 36-39
258  * 	      |
259  * 	      +-->dir3 --> 40-43
260  * 	       	       +-> 44-47
261  * 	      	       +-> 48-51
262  * 	      	       +-> 52-55
263  */
264 static swp_entry_t *shmem_swp_entry(struct shmem_inode_info *info, unsigned long index, struct page **page)
265 {
266 	unsigned long offset;
267 	struct page **dir;
268 	struct page *subdir;
269 
270 	if (index < SHMEM_NR_DIRECT) {
271 		shmem_swp_balance_unmap();
272 		return info->i_direct+index;
273 	}
274 	if (!info->i_indirect) {
275 		if (page) {
276 			info->i_indirect = *page;
277 			*page = NULL;
278 		}
279 		return NULL;			/* need another page */
280 	}
281 
282 	index -= SHMEM_NR_DIRECT;
283 	offset = index % ENTRIES_PER_PAGE;
284 	index /= ENTRIES_PER_PAGE;
285 	dir = shmem_dir_map(info->i_indirect);
286 
287 	if (index >= ENTRIES_PER_PAGE/2) {
288 		index -= ENTRIES_PER_PAGE/2;
289 		dir += ENTRIES_PER_PAGE/2 + index/ENTRIES_PER_PAGE;
290 		index %= ENTRIES_PER_PAGE;
291 		subdir = *dir;
292 		if (!subdir) {
293 			if (page) {
294 				*dir = *page;
295 				*page = NULL;
296 			}
297 			shmem_dir_unmap(dir);
298 			return NULL;		/* need another page */
299 		}
300 		shmem_dir_unmap(dir);
301 		dir = shmem_dir_map(subdir);
302 	}
303 
304 	dir += index;
305 	subdir = *dir;
306 	if (!subdir) {
307 		if (!page || !(subdir = *page)) {
308 			shmem_dir_unmap(dir);
309 			return NULL;		/* need a page */
310 		}
311 		*dir = subdir;
312 		*page = NULL;
313 	}
314 	shmem_dir_unmap(dir);
315 	return shmem_swp_map(subdir) + offset;
316 }
317 
318 static void shmem_swp_set(struct shmem_inode_info *info, swp_entry_t *entry, unsigned long value)
319 {
320 	long incdec = value? 1: -1;
321 
322 	entry->val = value;
323 	info->swapped += incdec;
324 	if ((unsigned long)(entry - info->i_direct) >= SHMEM_NR_DIRECT) {
325 		struct page *page = kmap_atomic_to_page(entry);
326 		set_page_private(page, page_private(page) + incdec);
327 	}
328 }
329 
330 /*
331  * shmem_swp_alloc - get the position of the swap entry for the page.
332  *                   If it does not exist allocate the entry.
333  *
334  * @info:	info structure for the inode
335  * @index:	index of the page to find
336  * @sgp:	check and recheck i_size? skip allocation?
337  */
338 static swp_entry_t *shmem_swp_alloc(struct shmem_inode_info *info, unsigned long index, enum sgp_type sgp)
339 {
340 	struct inode *inode = &info->vfs_inode;
341 	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
342 	struct page *page = NULL;
343 	swp_entry_t *entry;
344 
345 	if (sgp != SGP_WRITE &&
346 	    ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode))
347 		return ERR_PTR(-EINVAL);
348 
349 	while (!(entry = shmem_swp_entry(info, index, &page))) {
350 		if (sgp == SGP_READ)
351 			return shmem_swp_map(ZERO_PAGE(0));
352 		/*
353 		 * Test free_blocks against 1 not 0, since we have 1 data
354 		 * page (and perhaps indirect index pages) yet to allocate:
355 		 * a waste to allocate index if we cannot allocate data.
356 		 */
357 		if (sbinfo->max_blocks) {
358 			spin_lock(&sbinfo->stat_lock);
359 			if (sbinfo->free_blocks <= 1) {
360 				spin_unlock(&sbinfo->stat_lock);
361 				return ERR_PTR(-ENOSPC);
362 			}
363 			sbinfo->free_blocks--;
364 			inode->i_blocks += BLOCKS_PER_PAGE;
365 			spin_unlock(&sbinfo->stat_lock);
366 		}
367 
368 		spin_unlock(&info->lock);
369 		page = shmem_dir_alloc(mapping_gfp_mask(inode->i_mapping) | __GFP_ZERO);
370 		if (page)
371 			set_page_private(page, 0);
372 		spin_lock(&info->lock);
373 
374 		if (!page) {
375 			shmem_free_blocks(inode, 1);
376 			return ERR_PTR(-ENOMEM);
377 		}
378 		if (sgp != SGP_WRITE &&
379 		    ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
380 			entry = ERR_PTR(-EINVAL);
381 			break;
382 		}
383 		if (info->next_index <= index)
384 			info->next_index = index + 1;
385 	}
386 	if (page) {
387 		/* another task gave its page, or truncated the file */
388 		shmem_free_blocks(inode, 1);
389 		shmem_dir_free(page);
390 	}
391 	if (info->next_index <= index && !IS_ERR(entry))
392 		info->next_index = index + 1;
393 	return entry;
394 }
395 
396 /*
397  * shmem_free_swp - free some swap entries in a directory
398  *
399  * @dir:   pointer to the directory
400  * @edir:  pointer after last entry of the directory
401  */
402 static int shmem_free_swp(swp_entry_t *dir, swp_entry_t *edir)
403 {
404 	swp_entry_t *ptr;
405 	int freed = 0;
406 
407 	for (ptr = dir; ptr < edir; ptr++) {
408 		if (ptr->val) {
409 			free_swap_and_cache(*ptr);
410 			*ptr = (swp_entry_t){0};
411 			freed++;
412 		}
413 	}
414 	return freed;
415 }
416 
417 static int shmem_map_and_free_swp(struct page *subdir,
418 		int offset, int limit, struct page ***dir)
419 {
420 	swp_entry_t *ptr;
421 	int freed = 0;
422 
423 	ptr = shmem_swp_map(subdir);
424 	for (; offset < limit; offset += LATENCY_LIMIT) {
425 		int size = limit - offset;
426 		if (size > LATENCY_LIMIT)
427 			size = LATENCY_LIMIT;
428 		freed += shmem_free_swp(ptr+offset, ptr+offset+size);
429 		if (need_resched()) {
430 			shmem_swp_unmap(ptr);
431 			if (*dir) {
432 				shmem_dir_unmap(*dir);
433 				*dir = NULL;
434 			}
435 			cond_resched();
436 			ptr = shmem_swp_map(subdir);
437 		}
438 	}
439 	shmem_swp_unmap(ptr);
440 	return freed;
441 }
442 
443 static void shmem_free_pages(struct list_head *next)
444 {
445 	struct page *page;
446 	int freed = 0;
447 
448 	do {
449 		page = container_of(next, struct page, lru);
450 		next = next->next;
451 		shmem_dir_free(page);
452 		freed++;
453 		if (freed >= LATENCY_LIMIT) {
454 			cond_resched();
455 			freed = 0;
456 		}
457 	} while (next);
458 }
459 
460 static void shmem_truncate(struct inode *inode)
461 {
462 	struct shmem_inode_info *info = SHMEM_I(inode);
463 	unsigned long idx;
464 	unsigned long size;
465 	unsigned long limit;
466 	unsigned long stage;
467 	unsigned long diroff;
468 	struct page **dir;
469 	struct page *topdir;
470 	struct page *middir;
471 	struct page *subdir;
472 	swp_entry_t *ptr;
473 	LIST_HEAD(pages_to_free);
474 	long nr_pages_to_free = 0;
475 	long nr_swaps_freed = 0;
476 	int offset;
477 	int freed;
478 
479 	inode->i_ctime = inode->i_mtime = CURRENT_TIME;
480 	idx = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
481 	if (idx >= info->next_index)
482 		return;
483 
484 	spin_lock(&info->lock);
485 	info->flags |= SHMEM_TRUNCATE;
486 	limit = info->next_index;
487 	info->next_index = idx;
488 	topdir = info->i_indirect;
489 	if (topdir && idx <= SHMEM_NR_DIRECT) {
490 		info->i_indirect = NULL;
491 		nr_pages_to_free++;
492 		list_add(&topdir->lru, &pages_to_free);
493 	}
494 	spin_unlock(&info->lock);
495 
496 	if (info->swapped && idx < SHMEM_NR_DIRECT) {
497 		ptr = info->i_direct;
498 		size = limit;
499 		if (size > SHMEM_NR_DIRECT)
500 			size = SHMEM_NR_DIRECT;
501 		nr_swaps_freed = shmem_free_swp(ptr+idx, ptr+size);
502 	}
503 	if (!topdir)
504 		goto done2;
505 
506 	BUG_ON(limit <= SHMEM_NR_DIRECT);
507 	limit -= SHMEM_NR_DIRECT;
508 	idx = (idx > SHMEM_NR_DIRECT)? (idx - SHMEM_NR_DIRECT): 0;
509 	offset = idx % ENTRIES_PER_PAGE;
510 	idx -= offset;
511 
512 	dir = shmem_dir_map(topdir);
513 	stage = ENTRIES_PER_PAGEPAGE/2;
514 	if (idx < ENTRIES_PER_PAGEPAGE/2) {
515 		middir = topdir;
516 		diroff = idx/ENTRIES_PER_PAGE;
517 	} else {
518 		dir += ENTRIES_PER_PAGE/2;
519 		dir += (idx - ENTRIES_PER_PAGEPAGE/2)/ENTRIES_PER_PAGEPAGE;
520 		while (stage <= idx)
521 			stage += ENTRIES_PER_PAGEPAGE;
522 		middir = *dir;
523 		if (*dir) {
524 			diroff = ((idx - ENTRIES_PER_PAGEPAGE/2) %
525 				ENTRIES_PER_PAGEPAGE) / ENTRIES_PER_PAGE;
526 			if (!diroff && !offset) {
527 				*dir = NULL;
528 				nr_pages_to_free++;
529 				list_add(&middir->lru, &pages_to_free);
530 			}
531 			shmem_dir_unmap(dir);
532 			dir = shmem_dir_map(middir);
533 		} else {
534 			diroff = 0;
535 			offset = 0;
536 			idx = stage;
537 		}
538 	}
539 
540 	for (; idx < limit; idx += ENTRIES_PER_PAGE, diroff++) {
541 		if (unlikely(idx == stage)) {
542 			shmem_dir_unmap(dir);
543 			dir = shmem_dir_map(topdir) +
544 			    ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
545 			while (!*dir) {
546 				dir++;
547 				idx += ENTRIES_PER_PAGEPAGE;
548 				if (idx >= limit)
549 					goto done1;
550 			}
551 			stage = idx + ENTRIES_PER_PAGEPAGE;
552 			middir = *dir;
553 			*dir = NULL;
554 			nr_pages_to_free++;
555 			list_add(&middir->lru, &pages_to_free);
556 			shmem_dir_unmap(dir);
557 			cond_resched();
558 			dir = shmem_dir_map(middir);
559 			diroff = 0;
560 		}
561 		subdir = dir[diroff];
562 		if (subdir && page_private(subdir)) {
563 			size = limit - idx;
564 			if (size > ENTRIES_PER_PAGE)
565 				size = ENTRIES_PER_PAGE;
566 			freed = shmem_map_and_free_swp(subdir,
567 						offset, size, &dir);
568 			if (!dir)
569 				dir = shmem_dir_map(middir);
570 			nr_swaps_freed += freed;
571 			if (offset)
572 				spin_lock(&info->lock);
573 			set_page_private(subdir, page_private(subdir) - freed);
574 			if (offset)
575 				spin_unlock(&info->lock);
576 			BUG_ON(page_private(subdir) > offset);
577 		}
578 		if (offset)
579 			offset = 0;
580 		else if (subdir) {
581 			dir[diroff] = NULL;
582 			nr_pages_to_free++;
583 			list_add(&subdir->lru, &pages_to_free);
584 		}
585 	}
586 done1:
587 	shmem_dir_unmap(dir);
588 done2:
589 	if (inode->i_mapping->nrpages && (info->flags & SHMEM_PAGEIN)) {
590 		/*
591 		 * Call truncate_inode_pages again: racing shmem_unuse_inode
592 		 * may have swizzled a page in from swap since vmtruncate or
593 		 * generic_delete_inode did it, before we lowered next_index.
594 		 * Also, though shmem_getpage checks i_size before adding to
595 		 * cache, no recheck after: so fix the narrow window there too.
596 		 */
597 		truncate_inode_pages(inode->i_mapping, inode->i_size);
598 	}
599 
600 	spin_lock(&info->lock);
601 	info->flags &= ~SHMEM_TRUNCATE;
602 	info->swapped -= nr_swaps_freed;
603 	if (nr_pages_to_free)
604 		shmem_free_blocks(inode, nr_pages_to_free);
605 	shmem_recalc_inode(inode);
606 	spin_unlock(&info->lock);
607 
608 	/*
609 	 * Empty swap vector directory pages to be freed?
610 	 */
611 	if (!list_empty(&pages_to_free)) {
612 		pages_to_free.prev->next = NULL;
613 		shmem_free_pages(pages_to_free.next);
614 	}
615 }
616 
617 static int shmem_notify_change(struct dentry *dentry, struct iattr *attr)
618 {
619 	struct inode *inode = dentry->d_inode;
620 	struct page *page = NULL;
621 	int error;
622 
623 	if (attr->ia_valid & ATTR_SIZE) {
624 		if (attr->ia_size < inode->i_size) {
625 			/*
626 			 * If truncating down to a partial page, then
627 			 * if that page is already allocated, hold it
628 			 * in memory until the truncation is over, so
629 			 * truncate_partial_page cannnot miss it were
630 			 * it assigned to swap.
631 			 */
632 			if (attr->ia_size & (PAGE_CACHE_SIZE-1)) {
633 				(void) shmem_getpage(inode,
634 					attr->ia_size>>PAGE_CACHE_SHIFT,
635 						&page, SGP_READ, NULL);
636 			}
637 			/*
638 			 * Reset SHMEM_PAGEIN flag so that shmem_truncate can
639 			 * detect if any pages might have been added to cache
640 			 * after truncate_inode_pages.  But we needn't bother
641 			 * if it's being fully truncated to zero-length: the
642 			 * nrpages check is efficient enough in that case.
643 			 */
644 			if (attr->ia_size) {
645 				struct shmem_inode_info *info = SHMEM_I(inode);
646 				spin_lock(&info->lock);
647 				info->flags &= ~SHMEM_PAGEIN;
648 				spin_unlock(&info->lock);
649 			}
650 		}
651 	}
652 
653 	error = inode_change_ok(inode, attr);
654 	if (!error)
655 		error = inode_setattr(inode, attr);
656 	if (page)
657 		page_cache_release(page);
658 	return error;
659 }
660 
661 static void shmem_delete_inode(struct inode *inode)
662 {
663 	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
664 	struct shmem_inode_info *info = SHMEM_I(inode);
665 
666 	if (inode->i_op->truncate == shmem_truncate) {
667 		truncate_inode_pages(inode->i_mapping, 0);
668 		shmem_unacct_size(info->flags, inode->i_size);
669 		inode->i_size = 0;
670 		shmem_truncate(inode);
671 		if (!list_empty(&info->swaplist)) {
672 			spin_lock(&shmem_swaplist_lock);
673 			list_del_init(&info->swaplist);
674 			spin_unlock(&shmem_swaplist_lock);
675 		}
676 	}
677 	BUG_ON(inode->i_blocks);
678 	if (sbinfo->max_inodes) {
679 		spin_lock(&sbinfo->stat_lock);
680 		sbinfo->free_inodes++;
681 		spin_unlock(&sbinfo->stat_lock);
682 	}
683 	clear_inode(inode);
684 }
685 
686 static inline int shmem_find_swp(swp_entry_t entry, swp_entry_t *dir, swp_entry_t *edir)
687 {
688 	swp_entry_t *ptr;
689 
690 	for (ptr = dir; ptr < edir; ptr++) {
691 		if (ptr->val == entry.val)
692 			return ptr - dir;
693 	}
694 	return -1;
695 }
696 
697 static int shmem_unuse_inode(struct shmem_inode_info *info, swp_entry_t entry, struct page *page)
698 {
699 	struct inode *inode;
700 	unsigned long idx;
701 	unsigned long size;
702 	unsigned long limit;
703 	unsigned long stage;
704 	struct page **dir;
705 	struct page *subdir;
706 	swp_entry_t *ptr;
707 	int offset;
708 
709 	idx = 0;
710 	ptr = info->i_direct;
711 	spin_lock(&info->lock);
712 	limit = info->next_index;
713 	size = limit;
714 	if (size > SHMEM_NR_DIRECT)
715 		size = SHMEM_NR_DIRECT;
716 	offset = shmem_find_swp(entry, ptr, ptr+size);
717 	if (offset >= 0) {
718 		shmem_swp_balance_unmap();
719 		goto found;
720 	}
721 	if (!info->i_indirect)
722 		goto lost2;
723 
724 	dir = shmem_dir_map(info->i_indirect);
725 	stage = SHMEM_NR_DIRECT + ENTRIES_PER_PAGEPAGE/2;
726 
727 	for (idx = SHMEM_NR_DIRECT; idx < limit; idx += ENTRIES_PER_PAGE, dir++) {
728 		if (unlikely(idx == stage)) {
729 			shmem_dir_unmap(dir-1);
730 			dir = shmem_dir_map(info->i_indirect) +
731 			    ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
732 			while (!*dir) {
733 				dir++;
734 				idx += ENTRIES_PER_PAGEPAGE;
735 				if (idx >= limit)
736 					goto lost1;
737 			}
738 			stage = idx + ENTRIES_PER_PAGEPAGE;
739 			subdir = *dir;
740 			shmem_dir_unmap(dir);
741 			dir = shmem_dir_map(subdir);
742 		}
743 		subdir = *dir;
744 		if (subdir && page_private(subdir)) {
745 			ptr = shmem_swp_map(subdir);
746 			size = limit - idx;
747 			if (size > ENTRIES_PER_PAGE)
748 				size = ENTRIES_PER_PAGE;
749 			offset = shmem_find_swp(entry, ptr, ptr+size);
750 			if (offset >= 0) {
751 				shmem_dir_unmap(dir);
752 				goto found;
753 			}
754 			shmem_swp_unmap(ptr);
755 		}
756 	}
757 lost1:
758 	shmem_dir_unmap(dir-1);
759 lost2:
760 	spin_unlock(&info->lock);
761 	return 0;
762 found:
763 	idx += offset;
764 	inode = &info->vfs_inode;
765 	if (move_from_swap_cache(page, idx, inode->i_mapping) == 0) {
766 		info->flags |= SHMEM_PAGEIN;
767 		shmem_swp_set(info, ptr + offset, 0);
768 	}
769 	shmem_swp_unmap(ptr);
770 	spin_unlock(&info->lock);
771 	/*
772 	 * Decrement swap count even when the entry is left behind:
773 	 * try_to_unuse will skip over mms, then reincrement count.
774 	 */
775 	swap_free(entry);
776 	return 1;
777 }
778 
779 /*
780  * shmem_unuse() search for an eventually swapped out shmem page.
781  */
782 int shmem_unuse(swp_entry_t entry, struct page *page)
783 {
784 	struct list_head *p, *next;
785 	struct shmem_inode_info *info;
786 	int found = 0;
787 
788 	spin_lock(&shmem_swaplist_lock);
789 	list_for_each_safe(p, next, &shmem_swaplist) {
790 		info = list_entry(p, struct shmem_inode_info, swaplist);
791 		if (!info->swapped)
792 			list_del_init(&info->swaplist);
793 		else if (shmem_unuse_inode(info, entry, page)) {
794 			/* move head to start search for next from here */
795 			list_move_tail(&shmem_swaplist, &info->swaplist);
796 			found = 1;
797 			break;
798 		}
799 	}
800 	spin_unlock(&shmem_swaplist_lock);
801 	return found;
802 }
803 
804 /*
805  * Move the page from the page cache to the swap cache.
806  */
807 static int shmem_writepage(struct page *page, struct writeback_control *wbc)
808 {
809 	struct shmem_inode_info *info;
810 	swp_entry_t *entry, swap;
811 	struct address_space *mapping;
812 	unsigned long index;
813 	struct inode *inode;
814 
815 	BUG_ON(!PageLocked(page));
816 	BUG_ON(page_mapped(page));
817 
818 	mapping = page->mapping;
819 	index = page->index;
820 	inode = mapping->host;
821 	info = SHMEM_I(inode);
822 	if (info->flags & VM_LOCKED)
823 		goto redirty;
824 	swap = get_swap_page();
825 	if (!swap.val)
826 		goto redirty;
827 
828 	spin_lock(&info->lock);
829 	shmem_recalc_inode(inode);
830 	if (index >= info->next_index) {
831 		BUG_ON(!(info->flags & SHMEM_TRUNCATE));
832 		goto unlock;
833 	}
834 	entry = shmem_swp_entry(info, index, NULL);
835 	BUG_ON(!entry);
836 	BUG_ON(entry->val);
837 
838 	if (move_to_swap_cache(page, swap) == 0) {
839 		shmem_swp_set(info, entry, swap.val);
840 		shmem_swp_unmap(entry);
841 		spin_unlock(&info->lock);
842 		if (list_empty(&info->swaplist)) {
843 			spin_lock(&shmem_swaplist_lock);
844 			/* move instead of add in case we're racing */
845 			list_move_tail(&info->swaplist, &shmem_swaplist);
846 			spin_unlock(&shmem_swaplist_lock);
847 		}
848 		unlock_page(page);
849 		return 0;
850 	}
851 
852 	shmem_swp_unmap(entry);
853 unlock:
854 	spin_unlock(&info->lock);
855 	swap_free(swap);
856 redirty:
857 	set_page_dirty(page);
858 	return WRITEPAGE_ACTIVATE;	/* Return with the page locked */
859 }
860 
861 #ifdef CONFIG_NUMA
862 static struct page *shmem_swapin_async(struct shared_policy *p,
863 				       swp_entry_t entry, unsigned long idx)
864 {
865 	struct page *page;
866 	struct vm_area_struct pvma;
867 
868 	/* Create a pseudo vma that just contains the policy */
869 	memset(&pvma, 0, sizeof(struct vm_area_struct));
870 	pvma.vm_end = PAGE_SIZE;
871 	pvma.vm_pgoff = idx;
872 	pvma.vm_policy = mpol_shared_policy_lookup(p, idx);
873 	page = read_swap_cache_async(entry, &pvma, 0);
874 	mpol_free(pvma.vm_policy);
875 	return page;
876 }
877 
878 struct page *shmem_swapin(struct shmem_inode_info *info, swp_entry_t entry,
879 			  unsigned long idx)
880 {
881 	struct shared_policy *p = &info->policy;
882 	int i, num;
883 	struct page *page;
884 	unsigned long offset;
885 
886 	num = valid_swaphandles(entry, &offset);
887 	for (i = 0; i < num; offset++, i++) {
888 		page = shmem_swapin_async(p,
889 				swp_entry(swp_type(entry), offset), idx);
890 		if (!page)
891 			break;
892 		page_cache_release(page);
893 	}
894 	lru_add_drain();	/* Push any new pages onto the LRU now */
895 	return shmem_swapin_async(p, entry, idx);
896 }
897 
898 static struct page *
899 shmem_alloc_page(gfp_t gfp, struct shmem_inode_info *info,
900 		 unsigned long idx)
901 {
902 	struct vm_area_struct pvma;
903 	struct page *page;
904 
905 	memset(&pvma, 0, sizeof(struct vm_area_struct));
906 	pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, idx);
907 	pvma.vm_pgoff = idx;
908 	pvma.vm_end = PAGE_SIZE;
909 	page = alloc_page_vma(gfp | __GFP_ZERO, &pvma, 0);
910 	mpol_free(pvma.vm_policy);
911 	return page;
912 }
913 #else
914 static inline struct page *
915 shmem_swapin(struct shmem_inode_info *info,swp_entry_t entry,unsigned long idx)
916 {
917 	swapin_readahead(entry, 0, NULL);
918 	return read_swap_cache_async(entry, NULL, 0);
919 }
920 
921 static inline struct page *
922 shmem_alloc_page(gfp_t gfp,struct shmem_inode_info *info, unsigned long idx)
923 {
924 	return alloc_page(gfp | __GFP_ZERO);
925 }
926 #endif
927 
928 /*
929  * shmem_getpage - either get the page from swap or allocate a new one
930  *
931  * If we allocate a new one we do not mark it dirty. That's up to the
932  * vm. If we swap it in we mark it dirty since we also free the swap
933  * entry since a page cannot live in both the swap and page cache
934  */
935 static int shmem_getpage(struct inode *inode, unsigned long idx,
936 			struct page **pagep, enum sgp_type sgp, int *type)
937 {
938 	struct address_space *mapping = inode->i_mapping;
939 	struct shmem_inode_info *info = SHMEM_I(inode);
940 	struct shmem_sb_info *sbinfo;
941 	struct page *filepage = *pagep;
942 	struct page *swappage;
943 	swp_entry_t *entry;
944 	swp_entry_t swap;
945 	int error;
946 
947 	if (idx >= SHMEM_MAX_INDEX)
948 		return -EFBIG;
949 	/*
950 	 * Normally, filepage is NULL on entry, and either found
951 	 * uptodate immediately, or allocated and zeroed, or read
952 	 * in under swappage, which is then assigned to filepage.
953 	 * But shmem_prepare_write passes in a locked filepage,
954 	 * which may be found not uptodate by other callers too,
955 	 * and may need to be copied from the swappage read in.
956 	 */
957 repeat:
958 	if (!filepage)
959 		filepage = find_lock_page(mapping, idx);
960 	if (filepage && PageUptodate(filepage))
961 		goto done;
962 	error = 0;
963 	if (sgp == SGP_QUICK)
964 		goto failed;
965 
966 	spin_lock(&info->lock);
967 	shmem_recalc_inode(inode);
968 	entry = shmem_swp_alloc(info, idx, sgp);
969 	if (IS_ERR(entry)) {
970 		spin_unlock(&info->lock);
971 		error = PTR_ERR(entry);
972 		goto failed;
973 	}
974 	swap = *entry;
975 
976 	if (swap.val) {
977 		/* Look it up and read it in.. */
978 		swappage = lookup_swap_cache(swap);
979 		if (!swappage) {
980 			shmem_swp_unmap(entry);
981 			spin_unlock(&info->lock);
982 			/* here we actually do the io */
983 			if (type && *type == VM_FAULT_MINOR) {
984 				inc_page_state(pgmajfault);
985 				*type = VM_FAULT_MAJOR;
986 			}
987 			swappage = shmem_swapin(info, swap, idx);
988 			if (!swappage) {
989 				spin_lock(&info->lock);
990 				entry = shmem_swp_alloc(info, idx, sgp);
991 				if (IS_ERR(entry))
992 					error = PTR_ERR(entry);
993 				else {
994 					if (entry->val == swap.val)
995 						error = -ENOMEM;
996 					shmem_swp_unmap(entry);
997 				}
998 				spin_unlock(&info->lock);
999 				if (error)
1000 					goto failed;
1001 				goto repeat;
1002 			}
1003 			wait_on_page_locked(swappage);
1004 			page_cache_release(swappage);
1005 			goto repeat;
1006 		}
1007 
1008 		/* We have to do this with page locked to prevent races */
1009 		if (TestSetPageLocked(swappage)) {
1010 			shmem_swp_unmap(entry);
1011 			spin_unlock(&info->lock);
1012 			wait_on_page_locked(swappage);
1013 			page_cache_release(swappage);
1014 			goto repeat;
1015 		}
1016 		if (PageWriteback(swappage)) {
1017 			shmem_swp_unmap(entry);
1018 			spin_unlock(&info->lock);
1019 			wait_on_page_writeback(swappage);
1020 			unlock_page(swappage);
1021 			page_cache_release(swappage);
1022 			goto repeat;
1023 		}
1024 		if (!PageUptodate(swappage)) {
1025 			shmem_swp_unmap(entry);
1026 			spin_unlock(&info->lock);
1027 			unlock_page(swappage);
1028 			page_cache_release(swappage);
1029 			error = -EIO;
1030 			goto failed;
1031 		}
1032 
1033 		if (filepage) {
1034 			shmem_swp_set(info, entry, 0);
1035 			shmem_swp_unmap(entry);
1036 			delete_from_swap_cache(swappage);
1037 			spin_unlock(&info->lock);
1038 			copy_highpage(filepage, swappage);
1039 			unlock_page(swappage);
1040 			page_cache_release(swappage);
1041 			flush_dcache_page(filepage);
1042 			SetPageUptodate(filepage);
1043 			set_page_dirty(filepage);
1044 			swap_free(swap);
1045 		} else if (!(error = move_from_swap_cache(
1046 				swappage, idx, mapping))) {
1047 			info->flags |= SHMEM_PAGEIN;
1048 			shmem_swp_set(info, entry, 0);
1049 			shmem_swp_unmap(entry);
1050 			spin_unlock(&info->lock);
1051 			filepage = swappage;
1052 			swap_free(swap);
1053 		} else {
1054 			shmem_swp_unmap(entry);
1055 			spin_unlock(&info->lock);
1056 			unlock_page(swappage);
1057 			page_cache_release(swappage);
1058 			if (error == -ENOMEM) {
1059 				/* let kswapd refresh zone for GFP_ATOMICs */
1060 				blk_congestion_wait(WRITE, HZ/50);
1061 			}
1062 			goto repeat;
1063 		}
1064 	} else if (sgp == SGP_READ && !filepage) {
1065 		shmem_swp_unmap(entry);
1066 		filepage = find_get_page(mapping, idx);
1067 		if (filepage &&
1068 		    (!PageUptodate(filepage) || TestSetPageLocked(filepage))) {
1069 			spin_unlock(&info->lock);
1070 			wait_on_page_locked(filepage);
1071 			page_cache_release(filepage);
1072 			filepage = NULL;
1073 			goto repeat;
1074 		}
1075 		spin_unlock(&info->lock);
1076 	} else {
1077 		shmem_swp_unmap(entry);
1078 		sbinfo = SHMEM_SB(inode->i_sb);
1079 		if (sbinfo->max_blocks) {
1080 			spin_lock(&sbinfo->stat_lock);
1081 			if (sbinfo->free_blocks == 0 ||
1082 			    shmem_acct_block(info->flags)) {
1083 				spin_unlock(&sbinfo->stat_lock);
1084 				spin_unlock(&info->lock);
1085 				error = -ENOSPC;
1086 				goto failed;
1087 			}
1088 			sbinfo->free_blocks--;
1089 			inode->i_blocks += BLOCKS_PER_PAGE;
1090 			spin_unlock(&sbinfo->stat_lock);
1091 		} else if (shmem_acct_block(info->flags)) {
1092 			spin_unlock(&info->lock);
1093 			error = -ENOSPC;
1094 			goto failed;
1095 		}
1096 
1097 		if (!filepage) {
1098 			spin_unlock(&info->lock);
1099 			filepage = shmem_alloc_page(mapping_gfp_mask(mapping),
1100 						    info,
1101 						    idx);
1102 			if (!filepage) {
1103 				shmem_unacct_blocks(info->flags, 1);
1104 				shmem_free_blocks(inode, 1);
1105 				error = -ENOMEM;
1106 				goto failed;
1107 			}
1108 
1109 			spin_lock(&info->lock);
1110 			entry = shmem_swp_alloc(info, idx, sgp);
1111 			if (IS_ERR(entry))
1112 				error = PTR_ERR(entry);
1113 			else {
1114 				swap = *entry;
1115 				shmem_swp_unmap(entry);
1116 			}
1117 			if (error || swap.val || 0 != add_to_page_cache_lru(
1118 					filepage, mapping, idx, GFP_ATOMIC)) {
1119 				spin_unlock(&info->lock);
1120 				page_cache_release(filepage);
1121 				shmem_unacct_blocks(info->flags, 1);
1122 				shmem_free_blocks(inode, 1);
1123 				filepage = NULL;
1124 				if (error)
1125 					goto failed;
1126 				goto repeat;
1127 			}
1128 			info->flags |= SHMEM_PAGEIN;
1129 		}
1130 
1131 		info->alloced++;
1132 		spin_unlock(&info->lock);
1133 		flush_dcache_page(filepage);
1134 		SetPageUptodate(filepage);
1135 	}
1136 done:
1137 	if (*pagep != filepage) {
1138 		unlock_page(filepage);
1139 		*pagep = filepage;
1140 	}
1141 	return 0;
1142 
1143 failed:
1144 	if (*pagep != filepage) {
1145 		unlock_page(filepage);
1146 		page_cache_release(filepage);
1147 	}
1148 	return error;
1149 }
1150 
1151 struct page *shmem_nopage(struct vm_area_struct *vma, unsigned long address, int *type)
1152 {
1153 	struct inode *inode = vma->vm_file->f_dentry->d_inode;
1154 	struct page *page = NULL;
1155 	unsigned long idx;
1156 	int error;
1157 
1158 	idx = (address - vma->vm_start) >> PAGE_SHIFT;
1159 	idx += vma->vm_pgoff;
1160 	idx >>= PAGE_CACHE_SHIFT - PAGE_SHIFT;
1161 	if (((loff_t) idx << PAGE_CACHE_SHIFT) >= i_size_read(inode))
1162 		return NOPAGE_SIGBUS;
1163 
1164 	error = shmem_getpage(inode, idx, &page, SGP_CACHE, type);
1165 	if (error)
1166 		return (error == -ENOMEM)? NOPAGE_OOM: NOPAGE_SIGBUS;
1167 
1168 	mark_page_accessed(page);
1169 	return page;
1170 }
1171 
1172 static int shmem_populate(struct vm_area_struct *vma,
1173 	unsigned long addr, unsigned long len,
1174 	pgprot_t prot, unsigned long pgoff, int nonblock)
1175 {
1176 	struct inode *inode = vma->vm_file->f_dentry->d_inode;
1177 	struct mm_struct *mm = vma->vm_mm;
1178 	enum sgp_type sgp = nonblock? SGP_QUICK: SGP_CACHE;
1179 	unsigned long size;
1180 
1181 	size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
1182 	if (pgoff >= size || pgoff + (len >> PAGE_SHIFT) > size)
1183 		return -EINVAL;
1184 
1185 	while ((long) len > 0) {
1186 		struct page *page = NULL;
1187 		int err;
1188 		/*
1189 		 * Will need changing if PAGE_CACHE_SIZE != PAGE_SIZE
1190 		 */
1191 		err = shmem_getpage(inode, pgoff, &page, sgp, NULL);
1192 		if (err)
1193 			return err;
1194 		/* Page may still be null, but only if nonblock was set. */
1195 		if (page) {
1196 			mark_page_accessed(page);
1197 			err = install_page(mm, vma, addr, page, prot);
1198 			if (err) {
1199 				page_cache_release(page);
1200 				return err;
1201 			}
1202 		} else if (vma->vm_flags & VM_NONLINEAR) {
1203 			/* No page was found just because we can't read it in
1204 			 * now (being here implies nonblock != 0), but the page
1205 			 * may exist, so set the PTE to fault it in later. */
1206     			err = install_file_pte(mm, vma, addr, pgoff, prot);
1207 			if (err)
1208 	    			return err;
1209 		}
1210 
1211 		len -= PAGE_SIZE;
1212 		addr += PAGE_SIZE;
1213 		pgoff++;
1214 	}
1215 	return 0;
1216 }
1217 
1218 #ifdef CONFIG_NUMA
1219 int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *new)
1220 {
1221 	struct inode *i = vma->vm_file->f_dentry->d_inode;
1222 	return mpol_set_shared_policy(&SHMEM_I(i)->policy, vma, new);
1223 }
1224 
1225 struct mempolicy *
1226 shmem_get_policy(struct vm_area_struct *vma, unsigned long addr)
1227 {
1228 	struct inode *i = vma->vm_file->f_dentry->d_inode;
1229 	unsigned long idx;
1230 
1231 	idx = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
1232 	return mpol_shared_policy_lookup(&SHMEM_I(i)->policy, idx);
1233 }
1234 #endif
1235 
1236 int shmem_lock(struct file *file, int lock, struct user_struct *user)
1237 {
1238 	struct inode *inode = file->f_dentry->d_inode;
1239 	struct shmem_inode_info *info = SHMEM_I(inode);
1240 	int retval = -ENOMEM;
1241 
1242 	spin_lock(&info->lock);
1243 	if (lock && !(info->flags & VM_LOCKED)) {
1244 		if (!user_shm_lock(inode->i_size, user))
1245 			goto out_nomem;
1246 		info->flags |= VM_LOCKED;
1247 	}
1248 	if (!lock && (info->flags & VM_LOCKED) && user) {
1249 		user_shm_unlock(inode->i_size, user);
1250 		info->flags &= ~VM_LOCKED;
1251 	}
1252 	retval = 0;
1253 out_nomem:
1254 	spin_unlock(&info->lock);
1255 	return retval;
1256 }
1257 
1258 static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
1259 {
1260 	file_accessed(file);
1261 	vma->vm_ops = &shmem_vm_ops;
1262 	return 0;
1263 }
1264 
1265 static struct inode *
1266 shmem_get_inode(struct super_block *sb, int mode, dev_t dev)
1267 {
1268 	struct inode *inode;
1269 	struct shmem_inode_info *info;
1270 	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
1271 
1272 	if (sbinfo->max_inodes) {
1273 		spin_lock(&sbinfo->stat_lock);
1274 		if (!sbinfo->free_inodes) {
1275 			spin_unlock(&sbinfo->stat_lock);
1276 			return NULL;
1277 		}
1278 		sbinfo->free_inodes--;
1279 		spin_unlock(&sbinfo->stat_lock);
1280 	}
1281 
1282 	inode = new_inode(sb);
1283 	if (inode) {
1284 		inode->i_mode = mode;
1285 		inode->i_uid = current->fsuid;
1286 		inode->i_gid = current->fsgid;
1287 		inode->i_blksize = PAGE_CACHE_SIZE;
1288 		inode->i_blocks = 0;
1289 		inode->i_mapping->a_ops = &shmem_aops;
1290 		inode->i_mapping->backing_dev_info = &shmem_backing_dev_info;
1291 		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1292 		info = SHMEM_I(inode);
1293 		memset(info, 0, (char *)inode - (char *)info);
1294 		spin_lock_init(&info->lock);
1295 		INIT_LIST_HEAD(&info->swaplist);
1296 
1297 		switch (mode & S_IFMT) {
1298 		default:
1299 			init_special_inode(inode, mode, dev);
1300 			break;
1301 		case S_IFREG:
1302 			inode->i_op = &shmem_inode_operations;
1303 			inode->i_fop = &shmem_file_operations;
1304 			mpol_shared_policy_init(&info->policy);
1305 			break;
1306 		case S_IFDIR:
1307 			inode->i_nlink++;
1308 			/* Some things misbehave if size == 0 on a directory */
1309 			inode->i_size = 2 * BOGO_DIRENT_SIZE;
1310 			inode->i_op = &shmem_dir_inode_operations;
1311 			inode->i_fop = &simple_dir_operations;
1312 			break;
1313 		case S_IFLNK:
1314 			/*
1315 			 * Must not load anything in the rbtree,
1316 			 * mpol_free_shared_policy will not be called.
1317 			 */
1318 			mpol_shared_policy_init(&info->policy);
1319 			break;
1320 		}
1321 	} else if (sbinfo->max_inodes) {
1322 		spin_lock(&sbinfo->stat_lock);
1323 		sbinfo->free_inodes++;
1324 		spin_unlock(&sbinfo->stat_lock);
1325 	}
1326 	return inode;
1327 }
1328 
1329 #ifdef CONFIG_TMPFS
1330 static struct inode_operations shmem_symlink_inode_operations;
1331 static struct inode_operations shmem_symlink_inline_operations;
1332 
1333 /*
1334  * Normally tmpfs makes no use of shmem_prepare_write, but it
1335  * lets a tmpfs file be used read-write below the loop driver.
1336  */
1337 static int
1338 shmem_prepare_write(struct file *file, struct page *page, unsigned offset, unsigned to)
1339 {
1340 	struct inode *inode = page->mapping->host;
1341 	return shmem_getpage(inode, page->index, &page, SGP_WRITE, NULL);
1342 }
1343 
1344 static ssize_t
1345 shmem_file_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
1346 {
1347 	struct inode	*inode = file->f_dentry->d_inode;
1348 	loff_t		pos;
1349 	unsigned long	written;
1350 	ssize_t		err;
1351 
1352 	if ((ssize_t) count < 0)
1353 		return -EINVAL;
1354 
1355 	if (!access_ok(VERIFY_READ, buf, count))
1356 		return -EFAULT;
1357 
1358 	down(&inode->i_sem);
1359 
1360 	pos = *ppos;
1361 	written = 0;
1362 
1363 	err = generic_write_checks(file, &pos, &count, 0);
1364 	if (err || !count)
1365 		goto out;
1366 
1367 	err = remove_suid(file->f_dentry);
1368 	if (err)
1369 		goto out;
1370 
1371 	inode->i_ctime = inode->i_mtime = CURRENT_TIME;
1372 
1373 	do {
1374 		struct page *page = NULL;
1375 		unsigned long bytes, index, offset;
1376 		char *kaddr;
1377 		int left;
1378 
1379 		offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */
1380 		index = pos >> PAGE_CACHE_SHIFT;
1381 		bytes = PAGE_CACHE_SIZE - offset;
1382 		if (bytes > count)
1383 			bytes = count;
1384 
1385 		/*
1386 		 * We don't hold page lock across copy from user -
1387 		 * what would it guard against? - so no deadlock here.
1388 		 * But it still may be a good idea to prefault below.
1389 		 */
1390 
1391 		err = shmem_getpage(inode, index, &page, SGP_WRITE, NULL);
1392 		if (err)
1393 			break;
1394 
1395 		left = bytes;
1396 		if (PageHighMem(page)) {
1397 			volatile unsigned char dummy;
1398 			__get_user(dummy, buf);
1399 			__get_user(dummy, buf + bytes - 1);
1400 
1401 			kaddr = kmap_atomic(page, KM_USER0);
1402 			left = __copy_from_user_inatomic(kaddr + offset,
1403 							buf, bytes);
1404 			kunmap_atomic(kaddr, KM_USER0);
1405 		}
1406 		if (left) {
1407 			kaddr = kmap(page);
1408 			left = __copy_from_user(kaddr + offset, buf, bytes);
1409 			kunmap(page);
1410 		}
1411 
1412 		written += bytes;
1413 		count -= bytes;
1414 		pos += bytes;
1415 		buf += bytes;
1416 		if (pos > inode->i_size)
1417 			i_size_write(inode, pos);
1418 
1419 		flush_dcache_page(page);
1420 		set_page_dirty(page);
1421 		mark_page_accessed(page);
1422 		page_cache_release(page);
1423 
1424 		if (left) {
1425 			pos -= left;
1426 			written -= left;
1427 			err = -EFAULT;
1428 			break;
1429 		}
1430 
1431 		/*
1432 		 * Our dirty pages are not counted in nr_dirty,
1433 		 * and we do not attempt to balance dirty pages.
1434 		 */
1435 
1436 		cond_resched();
1437 	} while (count);
1438 
1439 	*ppos = pos;
1440 	if (written)
1441 		err = written;
1442 out:
1443 	up(&inode->i_sem);
1444 	return err;
1445 }
1446 
1447 static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_t *desc, read_actor_t actor)
1448 {
1449 	struct inode *inode = filp->f_dentry->d_inode;
1450 	struct address_space *mapping = inode->i_mapping;
1451 	unsigned long index, offset;
1452 
1453 	index = *ppos >> PAGE_CACHE_SHIFT;
1454 	offset = *ppos & ~PAGE_CACHE_MASK;
1455 
1456 	for (;;) {
1457 		struct page *page = NULL;
1458 		unsigned long end_index, nr, ret;
1459 		loff_t i_size = i_size_read(inode);
1460 
1461 		end_index = i_size >> PAGE_CACHE_SHIFT;
1462 		if (index > end_index)
1463 			break;
1464 		if (index == end_index) {
1465 			nr = i_size & ~PAGE_CACHE_MASK;
1466 			if (nr <= offset)
1467 				break;
1468 		}
1469 
1470 		desc->error = shmem_getpage(inode, index, &page, SGP_READ, NULL);
1471 		if (desc->error) {
1472 			if (desc->error == -EINVAL)
1473 				desc->error = 0;
1474 			break;
1475 		}
1476 
1477 		/*
1478 		 * We must evaluate after, since reads (unlike writes)
1479 		 * are called without i_sem protection against truncate
1480 		 */
1481 		nr = PAGE_CACHE_SIZE;
1482 		i_size = i_size_read(inode);
1483 		end_index = i_size >> PAGE_CACHE_SHIFT;
1484 		if (index == end_index) {
1485 			nr = i_size & ~PAGE_CACHE_MASK;
1486 			if (nr <= offset) {
1487 				if (page)
1488 					page_cache_release(page);
1489 				break;
1490 			}
1491 		}
1492 		nr -= offset;
1493 
1494 		if (page) {
1495 			/*
1496 			 * If users can be writing to this page using arbitrary
1497 			 * virtual addresses, take care about potential aliasing
1498 			 * before reading the page on the kernel side.
1499 			 */
1500 			if (mapping_writably_mapped(mapping))
1501 				flush_dcache_page(page);
1502 			/*
1503 			 * Mark the page accessed if we read the beginning.
1504 			 */
1505 			if (!offset)
1506 				mark_page_accessed(page);
1507 		} else {
1508 			page = ZERO_PAGE(0);
1509 			page_cache_get(page);
1510 		}
1511 
1512 		/*
1513 		 * Ok, we have the page, and it's up-to-date, so
1514 		 * now we can copy it to user space...
1515 		 *
1516 		 * The actor routine returns how many bytes were actually used..
1517 		 * NOTE! This may not be the same as how much of a user buffer
1518 		 * we filled up (we may be padding etc), so we can only update
1519 		 * "pos" here (the actor routine has to update the user buffer
1520 		 * pointers and the remaining count).
1521 		 */
1522 		ret = actor(desc, page, offset, nr);
1523 		offset += ret;
1524 		index += offset >> PAGE_CACHE_SHIFT;
1525 		offset &= ~PAGE_CACHE_MASK;
1526 
1527 		page_cache_release(page);
1528 		if (ret != nr || !desc->count)
1529 			break;
1530 
1531 		cond_resched();
1532 	}
1533 
1534 	*ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
1535 	file_accessed(filp);
1536 }
1537 
1538 static ssize_t shmem_file_read(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
1539 {
1540 	read_descriptor_t desc;
1541 
1542 	if ((ssize_t) count < 0)
1543 		return -EINVAL;
1544 	if (!access_ok(VERIFY_WRITE, buf, count))
1545 		return -EFAULT;
1546 	if (!count)
1547 		return 0;
1548 
1549 	desc.written = 0;
1550 	desc.count = count;
1551 	desc.arg.buf = buf;
1552 	desc.error = 0;
1553 
1554 	do_shmem_file_read(filp, ppos, &desc, file_read_actor);
1555 	if (desc.written)
1556 		return desc.written;
1557 	return desc.error;
1558 }
1559 
1560 static ssize_t shmem_file_sendfile(struct file *in_file, loff_t *ppos,
1561 			 size_t count, read_actor_t actor, void *target)
1562 {
1563 	read_descriptor_t desc;
1564 
1565 	if (!count)
1566 		return 0;
1567 
1568 	desc.written = 0;
1569 	desc.count = count;
1570 	desc.arg.data = target;
1571 	desc.error = 0;
1572 
1573 	do_shmem_file_read(in_file, ppos, &desc, actor);
1574 	if (desc.written)
1575 		return desc.written;
1576 	return desc.error;
1577 }
1578 
1579 static int shmem_statfs(struct super_block *sb, struct kstatfs *buf)
1580 {
1581 	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
1582 
1583 	buf->f_type = TMPFS_MAGIC;
1584 	buf->f_bsize = PAGE_CACHE_SIZE;
1585 	buf->f_namelen = NAME_MAX;
1586 	spin_lock(&sbinfo->stat_lock);
1587 	if (sbinfo->max_blocks) {
1588 		buf->f_blocks = sbinfo->max_blocks;
1589 		buf->f_bavail = buf->f_bfree = sbinfo->free_blocks;
1590 	}
1591 	if (sbinfo->max_inodes) {
1592 		buf->f_files = sbinfo->max_inodes;
1593 		buf->f_ffree = sbinfo->free_inodes;
1594 	}
1595 	/* else leave those fields 0 like simple_statfs */
1596 	spin_unlock(&sbinfo->stat_lock);
1597 	return 0;
1598 }
1599 
1600 /*
1601  * File creation. Allocate an inode, and we're done..
1602  */
1603 static int
1604 shmem_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
1605 {
1606 	struct inode *inode = shmem_get_inode(dir->i_sb, mode, dev);
1607 	int error = -ENOSPC;
1608 
1609 	if (inode) {
1610 		error = security_inode_init_security(inode, dir, NULL, NULL,
1611 						     NULL);
1612 		if (error) {
1613 			if (error != -EOPNOTSUPP) {
1614 				iput(inode);
1615 				return error;
1616 			}
1617 			error = 0;
1618 		}
1619 		if (dir->i_mode & S_ISGID) {
1620 			inode->i_gid = dir->i_gid;
1621 			if (S_ISDIR(mode))
1622 				inode->i_mode |= S_ISGID;
1623 		}
1624 		dir->i_size += BOGO_DIRENT_SIZE;
1625 		dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1626 		d_instantiate(dentry, inode);
1627 		dget(dentry); /* Extra count - pin the dentry in core */
1628 	}
1629 	return error;
1630 }
1631 
1632 static int shmem_mkdir(struct inode *dir, struct dentry *dentry, int mode)
1633 {
1634 	int error;
1635 
1636 	if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
1637 		return error;
1638 	dir->i_nlink++;
1639 	return 0;
1640 }
1641 
1642 static int shmem_create(struct inode *dir, struct dentry *dentry, int mode,
1643 		struct nameidata *nd)
1644 {
1645 	return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
1646 }
1647 
1648 /*
1649  * Link a file..
1650  */
1651 static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
1652 {
1653 	struct inode *inode = old_dentry->d_inode;
1654 	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
1655 
1656 	/*
1657 	 * No ordinary (disk based) filesystem counts links as inodes;
1658 	 * but each new link needs a new dentry, pinning lowmem, and
1659 	 * tmpfs dentries cannot be pruned until they are unlinked.
1660 	 */
1661 	if (sbinfo->max_inodes) {
1662 		spin_lock(&sbinfo->stat_lock);
1663 		if (!sbinfo->free_inodes) {
1664 			spin_unlock(&sbinfo->stat_lock);
1665 			return -ENOSPC;
1666 		}
1667 		sbinfo->free_inodes--;
1668 		spin_unlock(&sbinfo->stat_lock);
1669 	}
1670 
1671 	dir->i_size += BOGO_DIRENT_SIZE;
1672 	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1673 	inode->i_nlink++;
1674 	atomic_inc(&inode->i_count);	/* New dentry reference */
1675 	dget(dentry);		/* Extra pinning count for the created dentry */
1676 	d_instantiate(dentry, inode);
1677 	return 0;
1678 }
1679 
1680 static int shmem_unlink(struct inode *dir, struct dentry *dentry)
1681 {
1682 	struct inode *inode = dentry->d_inode;
1683 
1684 	if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode)) {
1685 		struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
1686 		if (sbinfo->max_inodes) {
1687 			spin_lock(&sbinfo->stat_lock);
1688 			sbinfo->free_inodes++;
1689 			spin_unlock(&sbinfo->stat_lock);
1690 		}
1691 	}
1692 
1693 	dir->i_size -= BOGO_DIRENT_SIZE;
1694 	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1695 	inode->i_nlink--;
1696 	dput(dentry);	/* Undo the count from "create" - this does all the work */
1697 	return 0;
1698 }
1699 
1700 static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
1701 {
1702 	if (!simple_empty(dentry))
1703 		return -ENOTEMPTY;
1704 
1705 	dir->i_nlink--;
1706 	return shmem_unlink(dir, dentry);
1707 }
1708 
1709 /*
1710  * The VFS layer already does all the dentry stuff for rename,
1711  * we just have to decrement the usage count for the target if
1712  * it exists so that the VFS layer correctly free's it when it
1713  * gets overwritten.
1714  */
1715 static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
1716 {
1717 	struct inode *inode = old_dentry->d_inode;
1718 	int they_are_dirs = S_ISDIR(inode->i_mode);
1719 
1720 	if (!simple_empty(new_dentry))
1721 		return -ENOTEMPTY;
1722 
1723 	if (new_dentry->d_inode) {
1724 		(void) shmem_unlink(new_dir, new_dentry);
1725 		if (they_are_dirs)
1726 			old_dir->i_nlink--;
1727 	} else if (they_are_dirs) {
1728 		old_dir->i_nlink--;
1729 		new_dir->i_nlink++;
1730 	}
1731 
1732 	old_dir->i_size -= BOGO_DIRENT_SIZE;
1733 	new_dir->i_size += BOGO_DIRENT_SIZE;
1734 	old_dir->i_ctime = old_dir->i_mtime =
1735 	new_dir->i_ctime = new_dir->i_mtime =
1736 	inode->i_ctime = CURRENT_TIME;
1737 	return 0;
1738 }
1739 
1740 static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
1741 {
1742 	int error;
1743 	int len;
1744 	struct inode *inode;
1745 	struct page *page = NULL;
1746 	char *kaddr;
1747 	struct shmem_inode_info *info;
1748 
1749 	len = strlen(symname) + 1;
1750 	if (len > PAGE_CACHE_SIZE)
1751 		return -ENAMETOOLONG;
1752 
1753 	inode = shmem_get_inode(dir->i_sb, S_IFLNK|S_IRWXUGO, 0);
1754 	if (!inode)
1755 		return -ENOSPC;
1756 
1757 	error = security_inode_init_security(inode, dir, NULL, NULL,
1758 					     NULL);
1759 	if (error) {
1760 		if (error != -EOPNOTSUPP) {
1761 			iput(inode);
1762 			return error;
1763 		}
1764 		error = 0;
1765 	}
1766 
1767 	info = SHMEM_I(inode);
1768 	inode->i_size = len-1;
1769 	if (len <= (char *)inode - (char *)info) {
1770 		/* do it inline */
1771 		memcpy(info, symname, len);
1772 		inode->i_op = &shmem_symlink_inline_operations;
1773 	} else {
1774 		error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
1775 		if (error) {
1776 			iput(inode);
1777 			return error;
1778 		}
1779 		inode->i_op = &shmem_symlink_inode_operations;
1780 		kaddr = kmap_atomic(page, KM_USER0);
1781 		memcpy(kaddr, symname, len);
1782 		kunmap_atomic(kaddr, KM_USER0);
1783 		set_page_dirty(page);
1784 		page_cache_release(page);
1785 	}
1786 	if (dir->i_mode & S_ISGID)
1787 		inode->i_gid = dir->i_gid;
1788 	dir->i_size += BOGO_DIRENT_SIZE;
1789 	dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1790 	d_instantiate(dentry, inode);
1791 	dget(dentry);
1792 	return 0;
1793 }
1794 
1795 static void *shmem_follow_link_inline(struct dentry *dentry, struct nameidata *nd)
1796 {
1797 	nd_set_link(nd, (char *)SHMEM_I(dentry->d_inode));
1798 	return NULL;
1799 }
1800 
1801 static void *shmem_follow_link(struct dentry *dentry, struct nameidata *nd)
1802 {
1803 	struct page *page = NULL;
1804 	int res = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL);
1805 	nd_set_link(nd, res ? ERR_PTR(res) : kmap(page));
1806 	return page;
1807 }
1808 
1809 static void shmem_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
1810 {
1811 	if (!IS_ERR(nd_get_link(nd))) {
1812 		struct page *page = cookie;
1813 		kunmap(page);
1814 		mark_page_accessed(page);
1815 		page_cache_release(page);
1816 	}
1817 }
1818 
1819 static struct inode_operations shmem_symlink_inline_operations = {
1820 	.readlink	= generic_readlink,
1821 	.follow_link	= shmem_follow_link_inline,
1822 };
1823 
1824 static struct inode_operations shmem_symlink_inode_operations = {
1825 	.truncate	= shmem_truncate,
1826 	.readlink	= generic_readlink,
1827 	.follow_link	= shmem_follow_link,
1828 	.put_link	= shmem_put_link,
1829 };
1830 
1831 static int shmem_parse_options(char *options, int *mode, uid_t *uid, gid_t *gid, unsigned long *blocks, unsigned long *inodes)
1832 {
1833 	char *this_char, *value, *rest;
1834 
1835 	while ((this_char = strsep(&options, ",")) != NULL) {
1836 		if (!*this_char)
1837 			continue;
1838 		if ((value = strchr(this_char,'=')) != NULL) {
1839 			*value++ = 0;
1840 		} else {
1841 			printk(KERN_ERR
1842 			    "tmpfs: No value for mount option '%s'\n",
1843 			    this_char);
1844 			return 1;
1845 		}
1846 
1847 		if (!strcmp(this_char,"size")) {
1848 			unsigned long long size;
1849 			size = memparse(value,&rest);
1850 			if (*rest == '%') {
1851 				size <<= PAGE_SHIFT;
1852 				size *= totalram_pages;
1853 				do_div(size, 100);
1854 				rest++;
1855 			}
1856 			if (*rest)
1857 				goto bad_val;
1858 			*blocks = size >> PAGE_CACHE_SHIFT;
1859 		} else if (!strcmp(this_char,"nr_blocks")) {
1860 			*blocks = memparse(value,&rest);
1861 			if (*rest)
1862 				goto bad_val;
1863 		} else if (!strcmp(this_char,"nr_inodes")) {
1864 			*inodes = memparse(value,&rest);
1865 			if (*rest)
1866 				goto bad_val;
1867 		} else if (!strcmp(this_char,"mode")) {
1868 			if (!mode)
1869 				continue;
1870 			*mode = simple_strtoul(value,&rest,8);
1871 			if (*rest)
1872 				goto bad_val;
1873 		} else if (!strcmp(this_char,"uid")) {
1874 			if (!uid)
1875 				continue;
1876 			*uid = simple_strtoul(value,&rest,0);
1877 			if (*rest)
1878 				goto bad_val;
1879 		} else if (!strcmp(this_char,"gid")) {
1880 			if (!gid)
1881 				continue;
1882 			*gid = simple_strtoul(value,&rest,0);
1883 			if (*rest)
1884 				goto bad_val;
1885 		} else {
1886 			printk(KERN_ERR "tmpfs: Bad mount option %s\n",
1887 			       this_char);
1888 			return 1;
1889 		}
1890 	}
1891 	return 0;
1892 
1893 bad_val:
1894 	printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n",
1895 	       value, this_char);
1896 	return 1;
1897 
1898 }
1899 
1900 static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
1901 {
1902 	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
1903 	unsigned long max_blocks = sbinfo->max_blocks;
1904 	unsigned long max_inodes = sbinfo->max_inodes;
1905 	unsigned long blocks;
1906 	unsigned long inodes;
1907 	int error = -EINVAL;
1908 
1909 	if (shmem_parse_options(data, NULL, NULL, NULL,
1910 				&max_blocks, &max_inodes))
1911 		return error;
1912 
1913 	spin_lock(&sbinfo->stat_lock);
1914 	blocks = sbinfo->max_blocks - sbinfo->free_blocks;
1915 	inodes = sbinfo->max_inodes - sbinfo->free_inodes;
1916 	if (max_blocks < blocks)
1917 		goto out;
1918 	if (max_inodes < inodes)
1919 		goto out;
1920 	/*
1921 	 * Those tests also disallow limited->unlimited while any are in
1922 	 * use, so i_blocks will always be zero when max_blocks is zero;
1923 	 * but we must separately disallow unlimited->limited, because
1924 	 * in that case we have no record of how much is already in use.
1925 	 */
1926 	if (max_blocks && !sbinfo->max_blocks)
1927 		goto out;
1928 	if (max_inodes && !sbinfo->max_inodes)
1929 		goto out;
1930 
1931 	error = 0;
1932 	sbinfo->max_blocks  = max_blocks;
1933 	sbinfo->free_blocks = max_blocks - blocks;
1934 	sbinfo->max_inodes  = max_inodes;
1935 	sbinfo->free_inodes = max_inodes - inodes;
1936 out:
1937 	spin_unlock(&sbinfo->stat_lock);
1938 	return error;
1939 }
1940 #endif
1941 
1942 static void shmem_put_super(struct super_block *sb)
1943 {
1944 	kfree(sb->s_fs_info);
1945 	sb->s_fs_info = NULL;
1946 }
1947 
1948 static int shmem_fill_super(struct super_block *sb,
1949 			    void *data, int silent)
1950 {
1951 	struct inode *inode;
1952 	struct dentry *root;
1953 	int mode   = S_IRWXUGO | S_ISVTX;
1954 	uid_t uid = current->fsuid;
1955 	gid_t gid = current->fsgid;
1956 	int err = -ENOMEM;
1957 	struct shmem_sb_info *sbinfo;
1958 	unsigned long blocks = 0;
1959 	unsigned long inodes = 0;
1960 
1961 #ifdef CONFIG_TMPFS
1962 	/*
1963 	 * Per default we only allow half of the physical ram per
1964 	 * tmpfs instance, limiting inodes to one per page of lowmem;
1965 	 * but the internal instance is left unlimited.
1966 	 */
1967 	if (!(sb->s_flags & MS_NOUSER)) {
1968 		blocks = totalram_pages / 2;
1969 		inodes = totalram_pages - totalhigh_pages;
1970 		if (inodes > blocks)
1971 			inodes = blocks;
1972 		if (shmem_parse_options(data, &mode, &uid, &gid,
1973 					&blocks, &inodes))
1974 			return -EINVAL;
1975 	}
1976 #else
1977 	sb->s_flags |= MS_NOUSER;
1978 #endif
1979 
1980 	/* Round up to L1_CACHE_BYTES to resist false sharing */
1981 	sbinfo = kmalloc(max((int)sizeof(struct shmem_sb_info),
1982 				L1_CACHE_BYTES), GFP_KERNEL);
1983 	if (!sbinfo)
1984 		return -ENOMEM;
1985 
1986 	spin_lock_init(&sbinfo->stat_lock);
1987 	sbinfo->max_blocks = blocks;
1988 	sbinfo->free_blocks = blocks;
1989 	sbinfo->max_inodes = inodes;
1990 	sbinfo->free_inodes = inodes;
1991 
1992 	sb->s_fs_info = sbinfo;
1993 	sb->s_maxbytes = SHMEM_MAX_BYTES;
1994 	sb->s_blocksize = PAGE_CACHE_SIZE;
1995 	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
1996 	sb->s_magic = TMPFS_MAGIC;
1997 	sb->s_op = &shmem_ops;
1998 
1999 	inode = shmem_get_inode(sb, S_IFDIR | mode, 0);
2000 	if (!inode)
2001 		goto failed;
2002 	inode->i_uid = uid;
2003 	inode->i_gid = gid;
2004 	root = d_alloc_root(inode);
2005 	if (!root)
2006 		goto failed_iput;
2007 	sb->s_root = root;
2008 	return 0;
2009 
2010 failed_iput:
2011 	iput(inode);
2012 failed:
2013 	shmem_put_super(sb);
2014 	return err;
2015 }
2016 
2017 static kmem_cache_t *shmem_inode_cachep;
2018 
2019 static struct inode *shmem_alloc_inode(struct super_block *sb)
2020 {
2021 	struct shmem_inode_info *p;
2022 	p = (struct shmem_inode_info *)kmem_cache_alloc(shmem_inode_cachep, SLAB_KERNEL);
2023 	if (!p)
2024 		return NULL;
2025 	return &p->vfs_inode;
2026 }
2027 
2028 static void shmem_destroy_inode(struct inode *inode)
2029 {
2030 	if ((inode->i_mode & S_IFMT) == S_IFREG) {
2031 		/* only struct inode is valid if it's an inline symlink */
2032 		mpol_free_shared_policy(&SHMEM_I(inode)->policy);
2033 	}
2034 	kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
2035 }
2036 
2037 static void init_once(void *foo, kmem_cache_t *cachep, unsigned long flags)
2038 {
2039 	struct shmem_inode_info *p = (struct shmem_inode_info *) foo;
2040 
2041 	if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
2042 	    SLAB_CTOR_CONSTRUCTOR) {
2043 		inode_init_once(&p->vfs_inode);
2044 	}
2045 }
2046 
2047 static int init_inodecache(void)
2048 {
2049 	shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
2050 				sizeof(struct shmem_inode_info),
2051 				0, 0, init_once, NULL);
2052 	if (shmem_inode_cachep == NULL)
2053 		return -ENOMEM;
2054 	return 0;
2055 }
2056 
2057 static void destroy_inodecache(void)
2058 {
2059 	if (kmem_cache_destroy(shmem_inode_cachep))
2060 		printk(KERN_INFO "shmem_inode_cache: not all structures were freed\n");
2061 }
2062 
2063 static struct address_space_operations shmem_aops = {
2064 	.writepage	= shmem_writepage,
2065 	.set_page_dirty	= __set_page_dirty_nobuffers,
2066 #ifdef CONFIG_TMPFS
2067 	.prepare_write	= shmem_prepare_write,
2068 	.commit_write	= simple_commit_write,
2069 #endif
2070 };
2071 
2072 static struct file_operations shmem_file_operations = {
2073 	.mmap		= shmem_mmap,
2074 #ifdef CONFIG_TMPFS
2075 	.llseek		= generic_file_llseek,
2076 	.read		= shmem_file_read,
2077 	.write		= shmem_file_write,
2078 	.fsync		= simple_sync_file,
2079 	.sendfile	= shmem_file_sendfile,
2080 #endif
2081 };
2082 
2083 static struct inode_operations shmem_inode_operations = {
2084 	.truncate	= shmem_truncate,
2085 	.setattr	= shmem_notify_change,
2086 };
2087 
2088 static struct inode_operations shmem_dir_inode_operations = {
2089 #ifdef CONFIG_TMPFS
2090 	.create		= shmem_create,
2091 	.lookup		= simple_lookup,
2092 	.link		= shmem_link,
2093 	.unlink		= shmem_unlink,
2094 	.symlink	= shmem_symlink,
2095 	.mkdir		= shmem_mkdir,
2096 	.rmdir		= shmem_rmdir,
2097 	.mknod		= shmem_mknod,
2098 	.rename		= shmem_rename,
2099 #endif
2100 };
2101 
2102 static struct super_operations shmem_ops = {
2103 	.alloc_inode	= shmem_alloc_inode,
2104 	.destroy_inode	= shmem_destroy_inode,
2105 #ifdef CONFIG_TMPFS
2106 	.statfs		= shmem_statfs,
2107 	.remount_fs	= shmem_remount_fs,
2108 #endif
2109 	.delete_inode	= shmem_delete_inode,
2110 	.drop_inode	= generic_delete_inode,
2111 	.put_super	= shmem_put_super,
2112 };
2113 
2114 static struct vm_operations_struct shmem_vm_ops = {
2115 	.nopage		= shmem_nopage,
2116 	.populate	= shmem_populate,
2117 #ifdef CONFIG_NUMA
2118 	.set_policy     = shmem_set_policy,
2119 	.get_policy     = shmem_get_policy,
2120 #endif
2121 };
2122 
2123 
2124 static struct super_block *shmem_get_sb(struct file_system_type *fs_type,
2125 	int flags, const char *dev_name, void *data)
2126 {
2127 	return get_sb_nodev(fs_type, flags, data, shmem_fill_super);
2128 }
2129 
2130 static struct file_system_type tmpfs_fs_type = {
2131 	.owner		= THIS_MODULE,
2132 	.name		= "tmpfs",
2133 	.get_sb		= shmem_get_sb,
2134 	.kill_sb	= kill_litter_super,
2135 };
2136 static struct vfsmount *shm_mnt;
2137 
2138 static int __init init_tmpfs(void)
2139 {
2140 	int error;
2141 
2142 	error = init_inodecache();
2143 	if (error)
2144 		goto out3;
2145 
2146 	error = register_filesystem(&tmpfs_fs_type);
2147 	if (error) {
2148 		printk(KERN_ERR "Could not register tmpfs\n");
2149 		goto out2;
2150 	}
2151 #ifdef CONFIG_TMPFS
2152 	devfs_mk_dir("shm");
2153 #endif
2154 	shm_mnt = do_kern_mount(tmpfs_fs_type.name, MS_NOUSER,
2155 				tmpfs_fs_type.name, NULL);
2156 	if (IS_ERR(shm_mnt)) {
2157 		error = PTR_ERR(shm_mnt);
2158 		printk(KERN_ERR "Could not kern_mount tmpfs\n");
2159 		goto out1;
2160 	}
2161 	return 0;
2162 
2163 out1:
2164 	unregister_filesystem(&tmpfs_fs_type);
2165 out2:
2166 	destroy_inodecache();
2167 out3:
2168 	shm_mnt = ERR_PTR(error);
2169 	return error;
2170 }
2171 module_init(init_tmpfs)
2172 
2173 /*
2174  * shmem_file_setup - get an unlinked file living in tmpfs
2175  *
2176  * @name: name for dentry (to be seen in /proc/<pid>/maps
2177  * @size: size to be set for the file
2178  *
2179  */
2180 struct file *shmem_file_setup(char *name, loff_t size, unsigned long flags)
2181 {
2182 	int error;
2183 	struct file *file;
2184 	struct inode *inode;
2185 	struct dentry *dentry, *root;
2186 	struct qstr this;
2187 
2188 	if (IS_ERR(shm_mnt))
2189 		return (void *)shm_mnt;
2190 
2191 	if (size < 0 || size > SHMEM_MAX_BYTES)
2192 		return ERR_PTR(-EINVAL);
2193 
2194 	if (shmem_acct_size(flags, size))
2195 		return ERR_PTR(-ENOMEM);
2196 
2197 	error = -ENOMEM;
2198 	this.name = name;
2199 	this.len = strlen(name);
2200 	this.hash = 0; /* will go */
2201 	root = shm_mnt->mnt_root;
2202 	dentry = d_alloc(root, &this);
2203 	if (!dentry)
2204 		goto put_memory;
2205 
2206 	error = -ENFILE;
2207 	file = get_empty_filp();
2208 	if (!file)
2209 		goto put_dentry;
2210 
2211 	error = -ENOSPC;
2212 	inode = shmem_get_inode(root->d_sb, S_IFREG | S_IRWXUGO, 0);
2213 	if (!inode)
2214 		goto close_file;
2215 
2216 	SHMEM_I(inode)->flags = flags & VM_ACCOUNT;
2217 	d_instantiate(dentry, inode);
2218 	inode->i_size = size;
2219 	inode->i_nlink = 0;	/* It is unlinked */
2220 	file->f_vfsmnt = mntget(shm_mnt);
2221 	file->f_dentry = dentry;
2222 	file->f_mapping = inode->i_mapping;
2223 	file->f_op = &shmem_file_operations;
2224 	file->f_mode = FMODE_WRITE | FMODE_READ;
2225 	return file;
2226 
2227 close_file:
2228 	put_filp(file);
2229 put_dentry:
2230 	dput(dentry);
2231 put_memory:
2232 	shmem_unacct_size(flags, size);
2233 	return ERR_PTR(error);
2234 }
2235 
2236 /*
2237  * shmem_zero_setup - setup a shared anonymous mapping
2238  *
2239  * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
2240  */
2241 int shmem_zero_setup(struct vm_area_struct *vma)
2242 {
2243 	struct file *file;
2244 	loff_t size = vma->vm_end - vma->vm_start;
2245 
2246 	file = shmem_file_setup("dev/zero", size, vma->vm_flags);
2247 	if (IS_ERR(file))
2248 		return PTR_ERR(file);
2249 
2250 	if (vma->vm_file)
2251 		fput(vma->vm_file);
2252 	vma->vm_file = file;
2253 	vma->vm_ops = &shmem_vm_ops;
2254 	return 0;
2255 }
2256