xref: /openbmc/linux/mm/shmem.c (revision 6ed7ffddcf61f668114edb676417e5fb33773b59)
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) 2002-2011 Hugh Dickins.
10  * Copyright (C) 2011 Google Inc.
11  * Copyright (C) 2002-2005 VERITAS Software Corporation.
12  * Copyright (C) 2004 Andi Kleen, SuSE Labs
13  *
14  * Extended attribute support for tmpfs:
15  * Copyright (c) 2004, Luke Kenneth Casson Leighton <lkcl@lkcl.net>
16  * Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
17  *
18  * tiny-shmem:
19  * Copyright (c) 2004, 2008 Matt Mackall <mpm@selenic.com>
20  *
21  * This file is released under the GPL.
22  */
23 
24 #include <linux/fs.h>
25 #include <linux/init.h>
26 #include <linux/vfs.h>
27 #include <linux/mount.h>
28 #include <linux/pagemap.h>
29 #include <linux/file.h>
30 #include <linux/mm.h>
31 #include <linux/export.h>
32 #include <linux/swap.h>
33 
34 static struct vfsmount *shm_mnt;
35 
36 #ifdef CONFIG_SHMEM
37 /*
38  * This virtual memory filesystem is heavily based on the ramfs. It
39  * extends ramfs by the ability to use swap and honor resource limits
40  * which makes it a completely usable filesystem.
41  */
42 
43 #include <linux/xattr.h>
44 #include <linux/exportfs.h>
45 #include <linux/posix_acl.h>
46 #include <linux/generic_acl.h>
47 #include <linux/mman.h>
48 #include <linux/string.h>
49 #include <linux/slab.h>
50 #include <linux/backing-dev.h>
51 #include <linux/shmem_fs.h>
52 #include <linux/writeback.h>
53 #include <linux/blkdev.h>
54 #include <linux/pagevec.h>
55 #include <linux/percpu_counter.h>
56 #include <linux/falloc.h>
57 #include <linux/splice.h>
58 #include <linux/security.h>
59 #include <linux/swapops.h>
60 #include <linux/mempolicy.h>
61 #include <linux/namei.h>
62 #include <linux/ctype.h>
63 #include <linux/migrate.h>
64 #include <linux/highmem.h>
65 #include <linux/seq_file.h>
66 #include <linux/magic.h>
67 
68 #include <asm/uaccess.h>
69 #include <asm/pgtable.h>
70 
71 #define BLOCKS_PER_PAGE  (PAGE_CACHE_SIZE/512)
72 #define VM_ACCT(size)    (PAGE_CACHE_ALIGN(size) >> PAGE_SHIFT)
73 
74 /* Pretend that each entry is of this size in directory's i_size */
75 #define BOGO_DIRENT_SIZE 20
76 
77 /* Symlink up to this size is kmalloc'ed instead of using a swappable page */
78 #define SHORT_SYMLINK_LEN 128
79 
80 /*
81  * shmem_fallocate and shmem_writepage communicate via inode->i_private
82  * (with i_mutex making sure that it has only one user at a time):
83  * we would prefer not to enlarge the shmem inode just for that.
84  */
85 struct shmem_falloc {
86 	pgoff_t start;		/* start of range currently being fallocated */
87 	pgoff_t next;		/* the next page offset to be fallocated */
88 	pgoff_t nr_falloced;	/* how many new pages have been fallocated */
89 	pgoff_t nr_unswapped;	/* how often writepage refused to swap out */
90 };
91 
92 /* Flag allocation requirements to shmem_getpage */
93 enum sgp_type {
94 	SGP_READ,	/* don't exceed i_size, don't allocate page */
95 	SGP_CACHE,	/* don't exceed i_size, may allocate page */
96 	SGP_DIRTY,	/* like SGP_CACHE, but set new page dirty */
97 	SGP_WRITE,	/* may exceed i_size, may allocate !Uptodate page */
98 	SGP_FALLOC,	/* like SGP_WRITE, but make existing page Uptodate */
99 };
100 
101 #ifdef CONFIG_TMPFS
102 static unsigned long shmem_default_max_blocks(void)
103 {
104 	return totalram_pages / 2;
105 }
106 
107 static unsigned long shmem_default_max_inodes(void)
108 {
109 	return min(totalram_pages - totalhigh_pages, totalram_pages / 2);
110 }
111 #endif
112 
113 static bool shmem_should_replace_page(struct page *page, gfp_t gfp);
114 static int shmem_replace_page(struct page **pagep, gfp_t gfp,
115 				struct shmem_inode_info *info, pgoff_t index);
116 static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
117 	struct page **pagep, enum sgp_type sgp, gfp_t gfp, int *fault_type);
118 
119 static inline int shmem_getpage(struct inode *inode, pgoff_t index,
120 	struct page **pagep, enum sgp_type sgp, int *fault_type)
121 {
122 	return shmem_getpage_gfp(inode, index, pagep, sgp,
123 			mapping_gfp_mask(inode->i_mapping), fault_type);
124 }
125 
126 static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
127 {
128 	return sb->s_fs_info;
129 }
130 
131 /*
132  * shmem_file_setup pre-accounts the whole fixed size of a VM object,
133  * for shared memory and for shared anonymous (/dev/zero) mappings
134  * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
135  * consistent with the pre-accounting of private mappings ...
136  */
137 static inline int shmem_acct_size(unsigned long flags, loff_t size)
138 {
139 	return (flags & VM_NORESERVE) ?
140 		0 : security_vm_enough_memory_mm(current->mm, VM_ACCT(size));
141 }
142 
143 static inline void shmem_unacct_size(unsigned long flags, loff_t size)
144 {
145 	if (!(flags & VM_NORESERVE))
146 		vm_unacct_memory(VM_ACCT(size));
147 }
148 
149 /*
150  * ... whereas tmpfs objects are accounted incrementally as
151  * pages are allocated, in order to allow huge sparse files.
152  * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
153  * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
154  */
155 static inline int shmem_acct_block(unsigned long flags)
156 {
157 	return (flags & VM_NORESERVE) ?
158 		security_vm_enough_memory_mm(current->mm, VM_ACCT(PAGE_CACHE_SIZE)) : 0;
159 }
160 
161 static inline void shmem_unacct_blocks(unsigned long flags, long pages)
162 {
163 	if (flags & VM_NORESERVE)
164 		vm_unacct_memory(pages * VM_ACCT(PAGE_CACHE_SIZE));
165 }
166 
167 static const struct super_operations shmem_ops;
168 static const struct address_space_operations shmem_aops;
169 static const struct file_operations shmem_file_operations;
170 static const struct inode_operations shmem_inode_operations;
171 static const struct inode_operations shmem_dir_inode_operations;
172 static const struct inode_operations shmem_special_inode_operations;
173 static const struct vm_operations_struct shmem_vm_ops;
174 
175 static struct backing_dev_info shmem_backing_dev_info  __read_mostly = {
176 	.ra_pages	= 0,	/* No readahead */
177 	.capabilities	= BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED,
178 };
179 
180 static LIST_HEAD(shmem_swaplist);
181 static DEFINE_MUTEX(shmem_swaplist_mutex);
182 
183 static int shmem_reserve_inode(struct super_block *sb)
184 {
185 	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
186 	if (sbinfo->max_inodes) {
187 		spin_lock(&sbinfo->stat_lock);
188 		if (!sbinfo->free_inodes) {
189 			spin_unlock(&sbinfo->stat_lock);
190 			return -ENOSPC;
191 		}
192 		sbinfo->free_inodes--;
193 		spin_unlock(&sbinfo->stat_lock);
194 	}
195 	return 0;
196 }
197 
198 static void shmem_free_inode(struct super_block *sb)
199 {
200 	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
201 	if (sbinfo->max_inodes) {
202 		spin_lock(&sbinfo->stat_lock);
203 		sbinfo->free_inodes++;
204 		spin_unlock(&sbinfo->stat_lock);
205 	}
206 }
207 
208 /**
209  * shmem_recalc_inode - recalculate the block usage of an inode
210  * @inode: inode to recalc
211  *
212  * We have to calculate the free blocks since the mm can drop
213  * undirtied hole pages behind our back.
214  *
215  * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
216  * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
217  *
218  * It has to be called with the spinlock held.
219  */
220 static void shmem_recalc_inode(struct inode *inode)
221 {
222 	struct shmem_inode_info *info = SHMEM_I(inode);
223 	long freed;
224 
225 	freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
226 	if (freed > 0) {
227 		struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
228 		if (sbinfo->max_blocks)
229 			percpu_counter_add(&sbinfo->used_blocks, -freed);
230 		info->alloced -= freed;
231 		inode->i_blocks -= freed * BLOCKS_PER_PAGE;
232 		shmem_unacct_blocks(info->flags, freed);
233 	}
234 }
235 
236 /*
237  * Replace item expected in radix tree by a new item, while holding tree lock.
238  */
239 static int shmem_radix_tree_replace(struct address_space *mapping,
240 			pgoff_t index, void *expected, void *replacement)
241 {
242 	void **pslot;
243 	void *item = NULL;
244 
245 	VM_BUG_ON(!expected);
246 	pslot = radix_tree_lookup_slot(&mapping->page_tree, index);
247 	if (pslot)
248 		item = radix_tree_deref_slot_protected(pslot,
249 							&mapping->tree_lock);
250 	if (item != expected)
251 		return -ENOENT;
252 	if (replacement)
253 		radix_tree_replace_slot(pslot, replacement);
254 	else
255 		radix_tree_delete(&mapping->page_tree, index);
256 	return 0;
257 }
258 
259 /*
260  * Sometimes, before we decide whether to proceed or to fail, we must check
261  * that an entry was not already brought back from swap by a racing thread.
262  *
263  * Checking page is not enough: by the time a SwapCache page is locked, it
264  * might be reused, and again be SwapCache, using the same swap as before.
265  */
266 static bool shmem_confirm_swap(struct address_space *mapping,
267 			       pgoff_t index, swp_entry_t swap)
268 {
269 	void *item;
270 
271 	rcu_read_lock();
272 	item = radix_tree_lookup(&mapping->page_tree, index);
273 	rcu_read_unlock();
274 	return item == swp_to_radix_entry(swap);
275 }
276 
277 /*
278  * Like add_to_page_cache_locked, but error if expected item has gone.
279  */
280 static int shmem_add_to_page_cache(struct page *page,
281 				   struct address_space *mapping,
282 				   pgoff_t index, gfp_t gfp, void *expected)
283 {
284 	int error;
285 
286 	VM_BUG_ON(!PageLocked(page));
287 	VM_BUG_ON(!PageSwapBacked(page));
288 
289 	page_cache_get(page);
290 	page->mapping = mapping;
291 	page->index = index;
292 
293 	spin_lock_irq(&mapping->tree_lock);
294 	if (!expected)
295 		error = radix_tree_insert(&mapping->page_tree, index, page);
296 	else
297 		error = shmem_radix_tree_replace(mapping, index, expected,
298 								 page);
299 	if (!error) {
300 		mapping->nrpages++;
301 		__inc_zone_page_state(page, NR_FILE_PAGES);
302 		__inc_zone_page_state(page, NR_SHMEM);
303 		spin_unlock_irq(&mapping->tree_lock);
304 	} else {
305 		page->mapping = NULL;
306 		spin_unlock_irq(&mapping->tree_lock);
307 		page_cache_release(page);
308 	}
309 	return error;
310 }
311 
312 /*
313  * Like delete_from_page_cache, but substitutes swap for page.
314  */
315 static void shmem_delete_from_page_cache(struct page *page, void *radswap)
316 {
317 	struct address_space *mapping = page->mapping;
318 	int error;
319 
320 	spin_lock_irq(&mapping->tree_lock);
321 	error = shmem_radix_tree_replace(mapping, page->index, page, radswap);
322 	page->mapping = NULL;
323 	mapping->nrpages--;
324 	__dec_zone_page_state(page, NR_FILE_PAGES);
325 	__dec_zone_page_state(page, NR_SHMEM);
326 	spin_unlock_irq(&mapping->tree_lock);
327 	page_cache_release(page);
328 	BUG_ON(error);
329 }
330 
331 /*
332  * Like find_get_pages, but collecting swap entries as well as pages.
333  */
334 static unsigned shmem_find_get_pages_and_swap(struct address_space *mapping,
335 					pgoff_t start, unsigned int nr_pages,
336 					struct page **pages, pgoff_t *indices)
337 {
338 	void **slot;
339 	unsigned int ret = 0;
340 	struct radix_tree_iter iter;
341 
342 	if (!nr_pages)
343 		return 0;
344 
345 	rcu_read_lock();
346 restart:
347 	radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
348 		struct page *page;
349 repeat:
350 		page = radix_tree_deref_slot(slot);
351 		if (unlikely(!page))
352 			continue;
353 		if (radix_tree_exception(page)) {
354 			if (radix_tree_deref_retry(page))
355 				goto restart;
356 			/*
357 			 * Otherwise, we must be storing a swap entry
358 			 * here as an exceptional entry: so return it
359 			 * without attempting to raise page count.
360 			 */
361 			goto export;
362 		}
363 		if (!page_cache_get_speculative(page))
364 			goto repeat;
365 
366 		/* Has the page moved? */
367 		if (unlikely(page != *slot)) {
368 			page_cache_release(page);
369 			goto repeat;
370 		}
371 export:
372 		indices[ret] = iter.index;
373 		pages[ret] = page;
374 		if (++ret == nr_pages)
375 			break;
376 	}
377 	rcu_read_unlock();
378 	return ret;
379 }
380 
381 /*
382  * Remove swap entry from radix tree, free the swap and its page cache.
383  */
384 static int shmem_free_swap(struct address_space *mapping,
385 			   pgoff_t index, void *radswap)
386 {
387 	int error;
388 
389 	spin_lock_irq(&mapping->tree_lock);
390 	error = shmem_radix_tree_replace(mapping, index, radswap, NULL);
391 	spin_unlock_irq(&mapping->tree_lock);
392 	if (!error)
393 		free_swap_and_cache(radix_to_swp_entry(radswap));
394 	return error;
395 }
396 
397 /*
398  * Pagevec may contain swap entries, so shuffle up pages before releasing.
399  */
400 static void shmem_deswap_pagevec(struct pagevec *pvec)
401 {
402 	int i, j;
403 
404 	for (i = 0, j = 0; i < pagevec_count(pvec); i++) {
405 		struct page *page = pvec->pages[i];
406 		if (!radix_tree_exceptional_entry(page))
407 			pvec->pages[j++] = page;
408 	}
409 	pvec->nr = j;
410 }
411 
412 /*
413  * SysV IPC SHM_UNLOCK restore Unevictable pages to their evictable lists.
414  */
415 void shmem_unlock_mapping(struct address_space *mapping)
416 {
417 	struct pagevec pvec;
418 	pgoff_t indices[PAGEVEC_SIZE];
419 	pgoff_t index = 0;
420 
421 	pagevec_init(&pvec, 0);
422 	/*
423 	 * Minor point, but we might as well stop if someone else SHM_LOCKs it.
424 	 */
425 	while (!mapping_unevictable(mapping)) {
426 		/*
427 		 * Avoid pagevec_lookup(): find_get_pages() returns 0 as if it
428 		 * has finished, if it hits a row of PAGEVEC_SIZE swap entries.
429 		 */
430 		pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
431 					PAGEVEC_SIZE, pvec.pages, indices);
432 		if (!pvec.nr)
433 			break;
434 		index = indices[pvec.nr - 1] + 1;
435 		shmem_deswap_pagevec(&pvec);
436 		check_move_unevictable_pages(pvec.pages, pvec.nr);
437 		pagevec_release(&pvec);
438 		cond_resched();
439 	}
440 }
441 
442 /*
443  * Remove range of pages and swap entries from radix tree, and free them.
444  * If !unfalloc, truncate or punch hole; if unfalloc, undo failed fallocate.
445  */
446 static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
447 								 bool unfalloc)
448 {
449 	struct address_space *mapping = inode->i_mapping;
450 	struct shmem_inode_info *info = SHMEM_I(inode);
451 	pgoff_t start = (lstart + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
452 	pgoff_t end = (lend + 1) >> PAGE_CACHE_SHIFT;
453 	unsigned int partial_start = lstart & (PAGE_CACHE_SIZE - 1);
454 	unsigned int partial_end = (lend + 1) & (PAGE_CACHE_SIZE - 1);
455 	struct pagevec pvec;
456 	pgoff_t indices[PAGEVEC_SIZE];
457 	long nr_swaps_freed = 0;
458 	pgoff_t index;
459 	int i;
460 
461 	if (lend == -1)
462 		end = -1;	/* unsigned, so actually very big */
463 
464 	pagevec_init(&pvec, 0);
465 	index = start;
466 	while (index < end) {
467 		pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
468 				min(end - index, (pgoff_t)PAGEVEC_SIZE),
469 							pvec.pages, indices);
470 		if (!pvec.nr)
471 			break;
472 		mem_cgroup_uncharge_start();
473 		for (i = 0; i < pagevec_count(&pvec); i++) {
474 			struct page *page = pvec.pages[i];
475 
476 			index = indices[i];
477 			if (index >= end)
478 				break;
479 
480 			if (radix_tree_exceptional_entry(page)) {
481 				if (unfalloc)
482 					continue;
483 				nr_swaps_freed += !shmem_free_swap(mapping,
484 								index, page);
485 				continue;
486 			}
487 
488 			if (!trylock_page(page))
489 				continue;
490 			if (!unfalloc || !PageUptodate(page)) {
491 				if (page->mapping == mapping) {
492 					VM_BUG_ON(PageWriteback(page));
493 					truncate_inode_page(mapping, page);
494 				}
495 			}
496 			unlock_page(page);
497 		}
498 		shmem_deswap_pagevec(&pvec);
499 		pagevec_release(&pvec);
500 		mem_cgroup_uncharge_end();
501 		cond_resched();
502 		index++;
503 	}
504 
505 	if (partial_start) {
506 		struct page *page = NULL;
507 		shmem_getpage(inode, start - 1, &page, SGP_READ, NULL);
508 		if (page) {
509 			unsigned int top = PAGE_CACHE_SIZE;
510 			if (start > end) {
511 				top = partial_end;
512 				partial_end = 0;
513 			}
514 			zero_user_segment(page, partial_start, top);
515 			set_page_dirty(page);
516 			unlock_page(page);
517 			page_cache_release(page);
518 		}
519 	}
520 	if (partial_end) {
521 		struct page *page = NULL;
522 		shmem_getpage(inode, end, &page, SGP_READ, NULL);
523 		if (page) {
524 			zero_user_segment(page, 0, partial_end);
525 			set_page_dirty(page);
526 			unlock_page(page);
527 			page_cache_release(page);
528 		}
529 	}
530 	if (start >= end)
531 		return;
532 
533 	index = start;
534 	for ( ; ; ) {
535 		cond_resched();
536 		pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
537 				min(end - index, (pgoff_t)PAGEVEC_SIZE),
538 							pvec.pages, indices);
539 		if (!pvec.nr) {
540 			if (index == start || unfalloc)
541 				break;
542 			index = start;
543 			continue;
544 		}
545 		if ((index == start || unfalloc) && indices[0] >= end) {
546 			shmem_deswap_pagevec(&pvec);
547 			pagevec_release(&pvec);
548 			break;
549 		}
550 		mem_cgroup_uncharge_start();
551 		for (i = 0; i < pagevec_count(&pvec); i++) {
552 			struct page *page = pvec.pages[i];
553 
554 			index = indices[i];
555 			if (index >= end)
556 				break;
557 
558 			if (radix_tree_exceptional_entry(page)) {
559 				if (unfalloc)
560 					continue;
561 				nr_swaps_freed += !shmem_free_swap(mapping,
562 								index, page);
563 				continue;
564 			}
565 
566 			lock_page(page);
567 			if (!unfalloc || !PageUptodate(page)) {
568 				if (page->mapping == mapping) {
569 					VM_BUG_ON(PageWriteback(page));
570 					truncate_inode_page(mapping, page);
571 				}
572 			}
573 			unlock_page(page);
574 		}
575 		shmem_deswap_pagevec(&pvec);
576 		pagevec_release(&pvec);
577 		mem_cgroup_uncharge_end();
578 		index++;
579 	}
580 
581 	spin_lock(&info->lock);
582 	info->swapped -= nr_swaps_freed;
583 	shmem_recalc_inode(inode);
584 	spin_unlock(&info->lock);
585 }
586 
587 void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
588 {
589 	shmem_undo_range(inode, lstart, lend, false);
590 	inode->i_ctime = inode->i_mtime = CURRENT_TIME;
591 }
592 EXPORT_SYMBOL_GPL(shmem_truncate_range);
593 
594 static int shmem_setattr(struct dentry *dentry, struct iattr *attr)
595 {
596 	struct inode *inode = dentry->d_inode;
597 	int error;
598 
599 	error = inode_change_ok(inode, attr);
600 	if (error)
601 		return error;
602 
603 	if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
604 		loff_t oldsize = inode->i_size;
605 		loff_t newsize = attr->ia_size;
606 
607 		if (newsize != oldsize) {
608 			i_size_write(inode, newsize);
609 			inode->i_ctime = inode->i_mtime = CURRENT_TIME;
610 		}
611 		if (newsize < oldsize) {
612 			loff_t holebegin = round_up(newsize, PAGE_SIZE);
613 			unmap_mapping_range(inode->i_mapping, holebegin, 0, 1);
614 			shmem_truncate_range(inode, newsize, (loff_t)-1);
615 			/* unmap again to remove racily COWed private pages */
616 			unmap_mapping_range(inode->i_mapping, holebegin, 0, 1);
617 		}
618 	}
619 
620 	setattr_copy(inode, attr);
621 #ifdef CONFIG_TMPFS_POSIX_ACL
622 	if (attr->ia_valid & ATTR_MODE)
623 		error = generic_acl_chmod(inode);
624 #endif
625 	return error;
626 }
627 
628 static void shmem_evict_inode(struct inode *inode)
629 {
630 	struct shmem_inode_info *info = SHMEM_I(inode);
631 
632 	if (inode->i_mapping->a_ops == &shmem_aops) {
633 		shmem_unacct_size(info->flags, inode->i_size);
634 		inode->i_size = 0;
635 		shmem_truncate_range(inode, 0, (loff_t)-1);
636 		if (!list_empty(&info->swaplist)) {
637 			mutex_lock(&shmem_swaplist_mutex);
638 			list_del_init(&info->swaplist);
639 			mutex_unlock(&shmem_swaplist_mutex);
640 		}
641 	} else
642 		kfree(info->symlink);
643 
644 	simple_xattrs_free(&info->xattrs);
645 	WARN_ON(inode->i_blocks);
646 	shmem_free_inode(inode->i_sb);
647 	clear_inode(inode);
648 }
649 
650 /*
651  * If swap found in inode, free it and move page from swapcache to filecache.
652  */
653 static int shmem_unuse_inode(struct shmem_inode_info *info,
654 			     swp_entry_t swap, struct page **pagep)
655 {
656 	struct address_space *mapping = info->vfs_inode.i_mapping;
657 	void *radswap;
658 	pgoff_t index;
659 	gfp_t gfp;
660 	int error = 0;
661 
662 	radswap = swp_to_radix_entry(swap);
663 	index = radix_tree_locate_item(&mapping->page_tree, radswap);
664 	if (index == -1)
665 		return 0;
666 
667 	/*
668 	 * Move _head_ to start search for next from here.
669 	 * But be careful: shmem_evict_inode checks list_empty without taking
670 	 * mutex, and there's an instant in list_move_tail when info->swaplist
671 	 * would appear empty, if it were the only one on shmem_swaplist.
672 	 */
673 	if (shmem_swaplist.next != &info->swaplist)
674 		list_move_tail(&shmem_swaplist, &info->swaplist);
675 
676 	gfp = mapping_gfp_mask(mapping);
677 	if (shmem_should_replace_page(*pagep, gfp)) {
678 		mutex_unlock(&shmem_swaplist_mutex);
679 		error = shmem_replace_page(pagep, gfp, info, index);
680 		mutex_lock(&shmem_swaplist_mutex);
681 		/*
682 		 * We needed to drop mutex to make that restrictive page
683 		 * allocation, but the inode might have been freed while we
684 		 * dropped it: although a racing shmem_evict_inode() cannot
685 		 * complete without emptying the radix_tree, our page lock
686 		 * on this swapcache page is not enough to prevent that -
687 		 * free_swap_and_cache() of our swap entry will only
688 		 * trylock_page(), removing swap from radix_tree whatever.
689 		 *
690 		 * We must not proceed to shmem_add_to_page_cache() if the
691 		 * inode has been freed, but of course we cannot rely on
692 		 * inode or mapping or info to check that.  However, we can
693 		 * safely check if our swap entry is still in use (and here
694 		 * it can't have got reused for another page): if it's still
695 		 * in use, then the inode cannot have been freed yet, and we
696 		 * can safely proceed (if it's no longer in use, that tells
697 		 * nothing about the inode, but we don't need to unuse swap).
698 		 */
699 		if (!page_swapcount(*pagep))
700 			error = -ENOENT;
701 	}
702 
703 	/*
704 	 * We rely on shmem_swaplist_mutex, not only to protect the swaplist,
705 	 * but also to hold up shmem_evict_inode(): so inode cannot be freed
706 	 * beneath us (pagelock doesn't help until the page is in pagecache).
707 	 */
708 	if (!error)
709 		error = shmem_add_to_page_cache(*pagep, mapping, index,
710 						GFP_NOWAIT, radswap);
711 	if (error != -ENOMEM) {
712 		/*
713 		 * Truncation and eviction use free_swap_and_cache(), which
714 		 * only does trylock page: if we raced, best clean up here.
715 		 */
716 		delete_from_swap_cache(*pagep);
717 		set_page_dirty(*pagep);
718 		if (!error) {
719 			spin_lock(&info->lock);
720 			info->swapped--;
721 			spin_unlock(&info->lock);
722 			swap_free(swap);
723 		}
724 		error = 1;	/* not an error, but entry was found */
725 	}
726 	return error;
727 }
728 
729 /*
730  * Search through swapped inodes to find and replace swap by page.
731  */
732 int shmem_unuse(swp_entry_t swap, struct page *page)
733 {
734 	struct list_head *this, *next;
735 	struct shmem_inode_info *info;
736 	int found = 0;
737 	int error = 0;
738 
739 	/*
740 	 * There's a faint possibility that swap page was replaced before
741 	 * caller locked it: caller will come back later with the right page.
742 	 */
743 	if (unlikely(!PageSwapCache(page) || page_private(page) != swap.val))
744 		goto out;
745 
746 	/*
747 	 * Charge page using GFP_KERNEL while we can wait, before taking
748 	 * the shmem_swaplist_mutex which might hold up shmem_writepage().
749 	 * Charged back to the user (not to caller) when swap account is used.
750 	 */
751 	error = mem_cgroup_cache_charge(page, current->mm, GFP_KERNEL);
752 	if (error)
753 		goto out;
754 	/* No radix_tree_preload: swap entry keeps a place for page in tree */
755 
756 	mutex_lock(&shmem_swaplist_mutex);
757 	list_for_each_safe(this, next, &shmem_swaplist) {
758 		info = list_entry(this, struct shmem_inode_info, swaplist);
759 		if (info->swapped)
760 			found = shmem_unuse_inode(info, swap, &page);
761 		else
762 			list_del_init(&info->swaplist);
763 		cond_resched();
764 		if (found)
765 			break;
766 	}
767 	mutex_unlock(&shmem_swaplist_mutex);
768 
769 	if (found < 0)
770 		error = found;
771 out:
772 	unlock_page(page);
773 	page_cache_release(page);
774 	return error;
775 }
776 
777 /*
778  * Move the page from the page cache to the swap cache.
779  */
780 static int shmem_writepage(struct page *page, struct writeback_control *wbc)
781 {
782 	struct shmem_inode_info *info;
783 	struct address_space *mapping;
784 	struct inode *inode;
785 	swp_entry_t swap;
786 	pgoff_t index;
787 
788 	BUG_ON(!PageLocked(page));
789 	mapping = page->mapping;
790 	index = page->index;
791 	inode = mapping->host;
792 	info = SHMEM_I(inode);
793 	if (info->flags & VM_LOCKED)
794 		goto redirty;
795 	if (!total_swap_pages)
796 		goto redirty;
797 
798 	/*
799 	 * shmem_backing_dev_info's capabilities prevent regular writeback or
800 	 * sync from ever calling shmem_writepage; but a stacking filesystem
801 	 * might use ->writepage of its underlying filesystem, in which case
802 	 * tmpfs should write out to swap only in response to memory pressure,
803 	 * and not for the writeback threads or sync.
804 	 */
805 	if (!wbc->for_reclaim) {
806 		WARN_ON_ONCE(1);	/* Still happens? Tell us about it! */
807 		goto redirty;
808 	}
809 
810 	/*
811 	 * This is somewhat ridiculous, but without plumbing a SWAP_MAP_FALLOC
812 	 * value into swapfile.c, the only way we can correctly account for a
813 	 * fallocated page arriving here is now to initialize it and write it.
814 	 *
815 	 * That's okay for a page already fallocated earlier, but if we have
816 	 * not yet completed the fallocation, then (a) we want to keep track
817 	 * of this page in case we have to undo it, and (b) it may not be a
818 	 * good idea to continue anyway, once we're pushing into swap.  So
819 	 * reactivate the page, and let shmem_fallocate() quit when too many.
820 	 */
821 	if (!PageUptodate(page)) {
822 		if (inode->i_private) {
823 			struct shmem_falloc *shmem_falloc;
824 			spin_lock(&inode->i_lock);
825 			shmem_falloc = inode->i_private;
826 			if (shmem_falloc &&
827 			    index >= shmem_falloc->start &&
828 			    index < shmem_falloc->next)
829 				shmem_falloc->nr_unswapped++;
830 			else
831 				shmem_falloc = NULL;
832 			spin_unlock(&inode->i_lock);
833 			if (shmem_falloc)
834 				goto redirty;
835 		}
836 		clear_highpage(page);
837 		flush_dcache_page(page);
838 		SetPageUptodate(page);
839 	}
840 
841 	swap = get_swap_page();
842 	if (!swap.val)
843 		goto redirty;
844 
845 	/*
846 	 * Add inode to shmem_unuse()'s list of swapped-out inodes,
847 	 * if it's not already there.  Do it now before the page is
848 	 * moved to swap cache, when its pagelock no longer protects
849 	 * the inode from eviction.  But don't unlock the mutex until
850 	 * we've incremented swapped, because shmem_unuse_inode() will
851 	 * prune a !swapped inode from the swaplist under this mutex.
852 	 */
853 	mutex_lock(&shmem_swaplist_mutex);
854 	if (list_empty(&info->swaplist))
855 		list_add_tail(&info->swaplist, &shmem_swaplist);
856 
857 	if (add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
858 		swap_shmem_alloc(swap);
859 		shmem_delete_from_page_cache(page, swp_to_radix_entry(swap));
860 
861 		spin_lock(&info->lock);
862 		info->swapped++;
863 		shmem_recalc_inode(inode);
864 		spin_unlock(&info->lock);
865 
866 		mutex_unlock(&shmem_swaplist_mutex);
867 		BUG_ON(page_mapped(page));
868 		swap_writepage(page, wbc);
869 		return 0;
870 	}
871 
872 	mutex_unlock(&shmem_swaplist_mutex);
873 	swapcache_free(swap, NULL);
874 redirty:
875 	set_page_dirty(page);
876 	if (wbc->for_reclaim)
877 		return AOP_WRITEPAGE_ACTIVATE;	/* Return with page locked */
878 	unlock_page(page);
879 	return 0;
880 }
881 
882 #ifdef CONFIG_NUMA
883 #ifdef CONFIG_TMPFS
884 static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
885 {
886 	char buffer[64];
887 
888 	if (!mpol || mpol->mode == MPOL_DEFAULT)
889 		return;		/* show nothing */
890 
891 	mpol_to_str(buffer, sizeof(buffer), mpol);
892 
893 	seq_printf(seq, ",mpol=%s", buffer);
894 }
895 
896 static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
897 {
898 	struct mempolicy *mpol = NULL;
899 	if (sbinfo->mpol) {
900 		spin_lock(&sbinfo->stat_lock);	/* prevent replace/use races */
901 		mpol = sbinfo->mpol;
902 		mpol_get(mpol);
903 		spin_unlock(&sbinfo->stat_lock);
904 	}
905 	return mpol;
906 }
907 #endif /* CONFIG_TMPFS */
908 
909 static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
910 			struct shmem_inode_info *info, pgoff_t index)
911 {
912 	struct vm_area_struct pvma;
913 	struct page *page;
914 
915 	/* Create a pseudo vma that just contains the policy */
916 	pvma.vm_start = 0;
917 	/* Bias interleave by inode number to distribute better across nodes */
918 	pvma.vm_pgoff = index + info->vfs_inode.i_ino;
919 	pvma.vm_ops = NULL;
920 	pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
921 
922 	page = swapin_readahead(swap, gfp, &pvma, 0);
923 
924 	/* Drop reference taken by mpol_shared_policy_lookup() */
925 	mpol_cond_put(pvma.vm_policy);
926 
927 	return page;
928 }
929 
930 static struct page *shmem_alloc_page(gfp_t gfp,
931 			struct shmem_inode_info *info, pgoff_t index)
932 {
933 	struct vm_area_struct pvma;
934 	struct page *page;
935 
936 	/* Create a pseudo vma that just contains the policy */
937 	pvma.vm_start = 0;
938 	/* Bias interleave by inode number to distribute better across nodes */
939 	pvma.vm_pgoff = index + info->vfs_inode.i_ino;
940 	pvma.vm_ops = NULL;
941 	pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
942 
943 	page = alloc_page_vma(gfp, &pvma, 0);
944 
945 	/* Drop reference taken by mpol_shared_policy_lookup() */
946 	mpol_cond_put(pvma.vm_policy);
947 
948 	return page;
949 }
950 #else /* !CONFIG_NUMA */
951 #ifdef CONFIG_TMPFS
952 static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
953 {
954 }
955 #endif /* CONFIG_TMPFS */
956 
957 static inline struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
958 			struct shmem_inode_info *info, pgoff_t index)
959 {
960 	return swapin_readahead(swap, gfp, NULL, 0);
961 }
962 
963 static inline struct page *shmem_alloc_page(gfp_t gfp,
964 			struct shmem_inode_info *info, pgoff_t index)
965 {
966 	return alloc_page(gfp);
967 }
968 #endif /* CONFIG_NUMA */
969 
970 #if !defined(CONFIG_NUMA) || !defined(CONFIG_TMPFS)
971 static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
972 {
973 	return NULL;
974 }
975 #endif
976 
977 /*
978  * When a page is moved from swapcache to shmem filecache (either by the
979  * usual swapin of shmem_getpage_gfp(), or by the less common swapoff of
980  * shmem_unuse_inode()), it may have been read in earlier from swap, in
981  * ignorance of the mapping it belongs to.  If that mapping has special
982  * constraints (like the gma500 GEM driver, which requires RAM below 4GB),
983  * we may need to copy to a suitable page before moving to filecache.
984  *
985  * In a future release, this may well be extended to respect cpuset and
986  * NUMA mempolicy, and applied also to anonymous pages in do_swap_page();
987  * but for now it is a simple matter of zone.
988  */
989 static bool shmem_should_replace_page(struct page *page, gfp_t gfp)
990 {
991 	return page_zonenum(page) > gfp_zone(gfp);
992 }
993 
994 static int shmem_replace_page(struct page **pagep, gfp_t gfp,
995 				struct shmem_inode_info *info, pgoff_t index)
996 {
997 	struct page *oldpage, *newpage;
998 	struct address_space *swap_mapping;
999 	pgoff_t swap_index;
1000 	int error;
1001 
1002 	oldpage = *pagep;
1003 	swap_index = page_private(oldpage);
1004 	swap_mapping = page_mapping(oldpage);
1005 
1006 	/*
1007 	 * We have arrived here because our zones are constrained, so don't
1008 	 * limit chance of success by further cpuset and node constraints.
1009 	 */
1010 	gfp &= ~GFP_CONSTRAINT_MASK;
1011 	newpage = shmem_alloc_page(gfp, info, index);
1012 	if (!newpage)
1013 		return -ENOMEM;
1014 
1015 	page_cache_get(newpage);
1016 	copy_highpage(newpage, oldpage);
1017 	flush_dcache_page(newpage);
1018 
1019 	__set_page_locked(newpage);
1020 	SetPageUptodate(newpage);
1021 	SetPageSwapBacked(newpage);
1022 	set_page_private(newpage, swap_index);
1023 	SetPageSwapCache(newpage);
1024 
1025 	/*
1026 	 * Our caller will very soon move newpage out of swapcache, but it's
1027 	 * a nice clean interface for us to replace oldpage by newpage there.
1028 	 */
1029 	spin_lock_irq(&swap_mapping->tree_lock);
1030 	error = shmem_radix_tree_replace(swap_mapping, swap_index, oldpage,
1031 								   newpage);
1032 	if (!error) {
1033 		__inc_zone_page_state(newpage, NR_FILE_PAGES);
1034 		__dec_zone_page_state(oldpage, NR_FILE_PAGES);
1035 	}
1036 	spin_unlock_irq(&swap_mapping->tree_lock);
1037 
1038 	if (unlikely(error)) {
1039 		/*
1040 		 * Is this possible?  I think not, now that our callers check
1041 		 * both PageSwapCache and page_private after getting page lock;
1042 		 * but be defensive.  Reverse old to newpage for clear and free.
1043 		 */
1044 		oldpage = newpage;
1045 	} else {
1046 		mem_cgroup_replace_page_cache(oldpage, newpage);
1047 		lru_cache_add_anon(newpage);
1048 		*pagep = newpage;
1049 	}
1050 
1051 	ClearPageSwapCache(oldpage);
1052 	set_page_private(oldpage, 0);
1053 
1054 	unlock_page(oldpage);
1055 	page_cache_release(oldpage);
1056 	page_cache_release(oldpage);
1057 	return error;
1058 }
1059 
1060 /*
1061  * shmem_getpage_gfp - find page in cache, or get from swap, or allocate
1062  *
1063  * If we allocate a new one we do not mark it dirty. That's up to the
1064  * vm. If we swap it in we mark it dirty since we also free the swap
1065  * entry since a page cannot live in both the swap and page cache
1066  */
1067 static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
1068 	struct page **pagep, enum sgp_type sgp, gfp_t gfp, int *fault_type)
1069 {
1070 	struct address_space *mapping = inode->i_mapping;
1071 	struct shmem_inode_info *info;
1072 	struct shmem_sb_info *sbinfo;
1073 	struct page *page;
1074 	swp_entry_t swap;
1075 	int error;
1076 	int once = 0;
1077 	int alloced = 0;
1078 
1079 	if (index > (MAX_LFS_FILESIZE >> PAGE_CACHE_SHIFT))
1080 		return -EFBIG;
1081 repeat:
1082 	swap.val = 0;
1083 	page = find_lock_page(mapping, index);
1084 	if (radix_tree_exceptional_entry(page)) {
1085 		swap = radix_to_swp_entry(page);
1086 		page = NULL;
1087 	}
1088 
1089 	if (sgp != SGP_WRITE && sgp != SGP_FALLOC &&
1090 	    ((loff_t)index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
1091 		error = -EINVAL;
1092 		goto failed;
1093 	}
1094 
1095 	/* fallocated page? */
1096 	if (page && !PageUptodate(page)) {
1097 		if (sgp != SGP_READ)
1098 			goto clear;
1099 		unlock_page(page);
1100 		page_cache_release(page);
1101 		page = NULL;
1102 	}
1103 	if (page || (sgp == SGP_READ && !swap.val)) {
1104 		*pagep = page;
1105 		return 0;
1106 	}
1107 
1108 	/*
1109 	 * Fast cache lookup did not find it:
1110 	 * bring it back from swap or allocate.
1111 	 */
1112 	info = SHMEM_I(inode);
1113 	sbinfo = SHMEM_SB(inode->i_sb);
1114 
1115 	if (swap.val) {
1116 		/* Look it up and read it in.. */
1117 		page = lookup_swap_cache(swap);
1118 		if (!page) {
1119 			/* here we actually do the io */
1120 			if (fault_type)
1121 				*fault_type |= VM_FAULT_MAJOR;
1122 			page = shmem_swapin(swap, gfp, info, index);
1123 			if (!page) {
1124 				error = -ENOMEM;
1125 				goto failed;
1126 			}
1127 		}
1128 
1129 		/* We have to do this with page locked to prevent races */
1130 		lock_page(page);
1131 		if (!PageSwapCache(page) || page_private(page) != swap.val ||
1132 		    !shmem_confirm_swap(mapping, index, swap)) {
1133 			error = -EEXIST;	/* try again */
1134 			goto unlock;
1135 		}
1136 		if (!PageUptodate(page)) {
1137 			error = -EIO;
1138 			goto failed;
1139 		}
1140 		wait_on_page_writeback(page);
1141 
1142 		if (shmem_should_replace_page(page, gfp)) {
1143 			error = shmem_replace_page(&page, gfp, info, index);
1144 			if (error)
1145 				goto failed;
1146 		}
1147 
1148 		error = mem_cgroup_cache_charge(page, current->mm,
1149 						gfp & GFP_RECLAIM_MASK);
1150 		if (!error) {
1151 			error = shmem_add_to_page_cache(page, mapping, index,
1152 						gfp, swp_to_radix_entry(swap));
1153 			/*
1154 			 * We already confirmed swap under page lock, and make
1155 			 * no memory allocation here, so usually no possibility
1156 			 * of error; but free_swap_and_cache() only trylocks a
1157 			 * page, so it is just possible that the entry has been
1158 			 * truncated or holepunched since swap was confirmed.
1159 			 * shmem_undo_range() will have done some of the
1160 			 * unaccounting, now delete_from_swap_cache() will do
1161 			 * the rest (including mem_cgroup_uncharge_swapcache).
1162 			 * Reset swap.val? No, leave it so "failed" goes back to
1163 			 * "repeat": reading a hole and writing should succeed.
1164 			 */
1165 			if (error)
1166 				delete_from_swap_cache(page);
1167 		}
1168 		if (error)
1169 			goto failed;
1170 
1171 		spin_lock(&info->lock);
1172 		info->swapped--;
1173 		shmem_recalc_inode(inode);
1174 		spin_unlock(&info->lock);
1175 
1176 		delete_from_swap_cache(page);
1177 		set_page_dirty(page);
1178 		swap_free(swap);
1179 
1180 	} else {
1181 		if (shmem_acct_block(info->flags)) {
1182 			error = -ENOSPC;
1183 			goto failed;
1184 		}
1185 		if (sbinfo->max_blocks) {
1186 			if (percpu_counter_compare(&sbinfo->used_blocks,
1187 						sbinfo->max_blocks) >= 0) {
1188 				error = -ENOSPC;
1189 				goto unacct;
1190 			}
1191 			percpu_counter_inc(&sbinfo->used_blocks);
1192 		}
1193 
1194 		page = shmem_alloc_page(gfp, info, index);
1195 		if (!page) {
1196 			error = -ENOMEM;
1197 			goto decused;
1198 		}
1199 
1200 		SetPageSwapBacked(page);
1201 		__set_page_locked(page);
1202 		error = mem_cgroup_cache_charge(page, current->mm,
1203 						gfp & GFP_RECLAIM_MASK);
1204 		if (error)
1205 			goto decused;
1206 		error = radix_tree_preload(gfp & GFP_RECLAIM_MASK);
1207 		if (!error) {
1208 			error = shmem_add_to_page_cache(page, mapping, index,
1209 							gfp, NULL);
1210 			radix_tree_preload_end();
1211 		}
1212 		if (error) {
1213 			mem_cgroup_uncharge_cache_page(page);
1214 			goto decused;
1215 		}
1216 		lru_cache_add_anon(page);
1217 
1218 		spin_lock(&info->lock);
1219 		info->alloced++;
1220 		inode->i_blocks += BLOCKS_PER_PAGE;
1221 		shmem_recalc_inode(inode);
1222 		spin_unlock(&info->lock);
1223 		alloced = true;
1224 
1225 		/*
1226 		 * Let SGP_FALLOC use the SGP_WRITE optimization on a new page.
1227 		 */
1228 		if (sgp == SGP_FALLOC)
1229 			sgp = SGP_WRITE;
1230 clear:
1231 		/*
1232 		 * Let SGP_WRITE caller clear ends if write does not fill page;
1233 		 * but SGP_FALLOC on a page fallocated earlier must initialize
1234 		 * it now, lest undo on failure cancel our earlier guarantee.
1235 		 */
1236 		if (sgp != SGP_WRITE) {
1237 			clear_highpage(page);
1238 			flush_dcache_page(page);
1239 			SetPageUptodate(page);
1240 		}
1241 		if (sgp == SGP_DIRTY)
1242 			set_page_dirty(page);
1243 	}
1244 
1245 	/* Perhaps the file has been truncated since we checked */
1246 	if (sgp != SGP_WRITE && sgp != SGP_FALLOC &&
1247 	    ((loff_t)index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
1248 		error = -EINVAL;
1249 		if (alloced)
1250 			goto trunc;
1251 		else
1252 			goto failed;
1253 	}
1254 	*pagep = page;
1255 	return 0;
1256 
1257 	/*
1258 	 * Error recovery.
1259 	 */
1260 trunc:
1261 	info = SHMEM_I(inode);
1262 	ClearPageDirty(page);
1263 	delete_from_page_cache(page);
1264 	spin_lock(&info->lock);
1265 	info->alloced--;
1266 	inode->i_blocks -= BLOCKS_PER_PAGE;
1267 	spin_unlock(&info->lock);
1268 decused:
1269 	sbinfo = SHMEM_SB(inode->i_sb);
1270 	if (sbinfo->max_blocks)
1271 		percpu_counter_add(&sbinfo->used_blocks, -1);
1272 unacct:
1273 	shmem_unacct_blocks(info->flags, 1);
1274 failed:
1275 	if (swap.val && error != -EINVAL &&
1276 	    !shmem_confirm_swap(mapping, index, swap))
1277 		error = -EEXIST;
1278 unlock:
1279 	if (page) {
1280 		unlock_page(page);
1281 		page_cache_release(page);
1282 	}
1283 	if (error == -ENOSPC && !once++) {
1284 		info = SHMEM_I(inode);
1285 		spin_lock(&info->lock);
1286 		shmem_recalc_inode(inode);
1287 		spin_unlock(&info->lock);
1288 		goto repeat;
1289 	}
1290 	if (error == -EEXIST)	/* from above or from radix_tree_insert */
1291 		goto repeat;
1292 	return error;
1293 }
1294 
1295 static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1296 {
1297 	struct inode *inode = file_inode(vma->vm_file);
1298 	int error;
1299 	int ret = VM_FAULT_LOCKED;
1300 
1301 	error = shmem_getpage(inode, vmf->pgoff, &vmf->page, SGP_CACHE, &ret);
1302 	if (error)
1303 		return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
1304 
1305 	if (ret & VM_FAULT_MAJOR) {
1306 		count_vm_event(PGMAJFAULT);
1307 		mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
1308 	}
1309 	return ret;
1310 }
1311 
1312 #ifdef CONFIG_NUMA
1313 static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *mpol)
1314 {
1315 	struct inode *inode = file_inode(vma->vm_file);
1316 	return mpol_set_shared_policy(&SHMEM_I(inode)->policy, vma, mpol);
1317 }
1318 
1319 static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
1320 					  unsigned long addr)
1321 {
1322 	struct inode *inode = file_inode(vma->vm_file);
1323 	pgoff_t index;
1324 
1325 	index = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
1326 	return mpol_shared_policy_lookup(&SHMEM_I(inode)->policy, index);
1327 }
1328 #endif
1329 
1330 int shmem_lock(struct file *file, int lock, struct user_struct *user)
1331 {
1332 	struct inode *inode = file_inode(file);
1333 	struct shmem_inode_info *info = SHMEM_I(inode);
1334 	int retval = -ENOMEM;
1335 
1336 	spin_lock(&info->lock);
1337 	if (lock && !(info->flags & VM_LOCKED)) {
1338 		if (!user_shm_lock(inode->i_size, user))
1339 			goto out_nomem;
1340 		info->flags |= VM_LOCKED;
1341 		mapping_set_unevictable(file->f_mapping);
1342 	}
1343 	if (!lock && (info->flags & VM_LOCKED) && user) {
1344 		user_shm_unlock(inode->i_size, user);
1345 		info->flags &= ~VM_LOCKED;
1346 		mapping_clear_unevictable(file->f_mapping);
1347 	}
1348 	retval = 0;
1349 
1350 out_nomem:
1351 	spin_unlock(&info->lock);
1352 	return retval;
1353 }
1354 
1355 static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
1356 {
1357 	file_accessed(file);
1358 	vma->vm_ops = &shmem_vm_ops;
1359 	return 0;
1360 }
1361 
1362 static struct inode *shmem_get_inode(struct super_block *sb, const struct inode *dir,
1363 				     umode_t mode, dev_t dev, unsigned long flags)
1364 {
1365 	struct inode *inode;
1366 	struct shmem_inode_info *info;
1367 	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
1368 
1369 	if (shmem_reserve_inode(sb))
1370 		return NULL;
1371 
1372 	inode = new_inode(sb);
1373 	if (inode) {
1374 		inode->i_ino = get_next_ino();
1375 		inode_init_owner(inode, dir, mode);
1376 		inode->i_blocks = 0;
1377 		inode->i_mapping->backing_dev_info = &shmem_backing_dev_info;
1378 		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1379 		inode->i_generation = get_seconds();
1380 		info = SHMEM_I(inode);
1381 		memset(info, 0, (char *)inode - (char *)info);
1382 		spin_lock_init(&info->lock);
1383 		info->flags = flags & VM_NORESERVE;
1384 		INIT_LIST_HEAD(&info->swaplist);
1385 		simple_xattrs_init(&info->xattrs);
1386 		cache_no_acl(inode);
1387 
1388 		switch (mode & S_IFMT) {
1389 		default:
1390 			inode->i_op = &shmem_special_inode_operations;
1391 			init_special_inode(inode, mode, dev);
1392 			break;
1393 		case S_IFREG:
1394 			inode->i_mapping->a_ops = &shmem_aops;
1395 			inode->i_op = &shmem_inode_operations;
1396 			inode->i_fop = &shmem_file_operations;
1397 			mpol_shared_policy_init(&info->policy,
1398 						 shmem_get_sbmpol(sbinfo));
1399 			break;
1400 		case S_IFDIR:
1401 			inc_nlink(inode);
1402 			/* Some things misbehave if size == 0 on a directory */
1403 			inode->i_size = 2 * BOGO_DIRENT_SIZE;
1404 			inode->i_op = &shmem_dir_inode_operations;
1405 			inode->i_fop = &simple_dir_operations;
1406 			break;
1407 		case S_IFLNK:
1408 			/*
1409 			 * Must not load anything in the rbtree,
1410 			 * mpol_free_shared_policy will not be called.
1411 			 */
1412 			mpol_shared_policy_init(&info->policy, NULL);
1413 			break;
1414 		}
1415 	} else
1416 		shmem_free_inode(sb);
1417 	return inode;
1418 }
1419 
1420 #ifdef CONFIG_TMPFS
1421 static const struct inode_operations shmem_symlink_inode_operations;
1422 static const struct inode_operations shmem_short_symlink_operations;
1423 
1424 #ifdef CONFIG_TMPFS_XATTR
1425 static int shmem_initxattrs(struct inode *, const struct xattr *, void *);
1426 #else
1427 #define shmem_initxattrs NULL
1428 #endif
1429 
1430 static int
1431 shmem_write_begin(struct file *file, struct address_space *mapping,
1432 			loff_t pos, unsigned len, unsigned flags,
1433 			struct page **pagep, void **fsdata)
1434 {
1435 	struct inode *inode = mapping->host;
1436 	pgoff_t index = pos >> PAGE_CACHE_SHIFT;
1437 	return shmem_getpage(inode, index, pagep, SGP_WRITE, NULL);
1438 }
1439 
1440 static int
1441 shmem_write_end(struct file *file, struct address_space *mapping,
1442 			loff_t pos, unsigned len, unsigned copied,
1443 			struct page *page, void *fsdata)
1444 {
1445 	struct inode *inode = mapping->host;
1446 
1447 	if (pos + copied > inode->i_size)
1448 		i_size_write(inode, pos + copied);
1449 
1450 	if (!PageUptodate(page)) {
1451 		if (copied < PAGE_CACHE_SIZE) {
1452 			unsigned from = pos & (PAGE_CACHE_SIZE - 1);
1453 			zero_user_segments(page, 0, from,
1454 					from + copied, PAGE_CACHE_SIZE);
1455 		}
1456 		SetPageUptodate(page);
1457 	}
1458 	set_page_dirty(page);
1459 	unlock_page(page);
1460 	page_cache_release(page);
1461 
1462 	return copied;
1463 }
1464 
1465 static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_t *desc, read_actor_t actor)
1466 {
1467 	struct inode *inode = file_inode(filp);
1468 	struct address_space *mapping = inode->i_mapping;
1469 	pgoff_t index;
1470 	unsigned long offset;
1471 	enum sgp_type sgp = SGP_READ;
1472 
1473 	/*
1474 	 * Might this read be for a stacking filesystem?  Then when reading
1475 	 * holes of a sparse file, we actually need to allocate those pages,
1476 	 * and even mark them dirty, so it cannot exceed the max_blocks limit.
1477 	 */
1478 	if (segment_eq(get_fs(), KERNEL_DS))
1479 		sgp = SGP_DIRTY;
1480 
1481 	index = *ppos >> PAGE_CACHE_SHIFT;
1482 	offset = *ppos & ~PAGE_CACHE_MASK;
1483 
1484 	for (;;) {
1485 		struct page *page = NULL;
1486 		pgoff_t end_index;
1487 		unsigned long nr, ret;
1488 		loff_t i_size = i_size_read(inode);
1489 
1490 		end_index = i_size >> PAGE_CACHE_SHIFT;
1491 		if (index > end_index)
1492 			break;
1493 		if (index == end_index) {
1494 			nr = i_size & ~PAGE_CACHE_MASK;
1495 			if (nr <= offset)
1496 				break;
1497 		}
1498 
1499 		desc->error = shmem_getpage(inode, index, &page, sgp, NULL);
1500 		if (desc->error) {
1501 			if (desc->error == -EINVAL)
1502 				desc->error = 0;
1503 			break;
1504 		}
1505 		if (page)
1506 			unlock_page(page);
1507 
1508 		/*
1509 		 * We must evaluate after, since reads (unlike writes)
1510 		 * are called without i_mutex protection against truncate
1511 		 */
1512 		nr = PAGE_CACHE_SIZE;
1513 		i_size = i_size_read(inode);
1514 		end_index = i_size >> PAGE_CACHE_SHIFT;
1515 		if (index == end_index) {
1516 			nr = i_size & ~PAGE_CACHE_MASK;
1517 			if (nr <= offset) {
1518 				if (page)
1519 					page_cache_release(page);
1520 				break;
1521 			}
1522 		}
1523 		nr -= offset;
1524 
1525 		if (page) {
1526 			/*
1527 			 * If users can be writing to this page using arbitrary
1528 			 * virtual addresses, take care about potential aliasing
1529 			 * before reading the page on the kernel side.
1530 			 */
1531 			if (mapping_writably_mapped(mapping))
1532 				flush_dcache_page(page);
1533 			/*
1534 			 * Mark the page accessed if we read the beginning.
1535 			 */
1536 			if (!offset)
1537 				mark_page_accessed(page);
1538 		} else {
1539 			page = ZERO_PAGE(0);
1540 			page_cache_get(page);
1541 		}
1542 
1543 		/*
1544 		 * Ok, we have the page, and it's up-to-date, so
1545 		 * now we can copy it to user space...
1546 		 *
1547 		 * The actor routine returns how many bytes were actually used..
1548 		 * NOTE! This may not be the same as how much of a user buffer
1549 		 * we filled up (we may be padding etc), so we can only update
1550 		 * "pos" here (the actor routine has to update the user buffer
1551 		 * pointers and the remaining count).
1552 		 */
1553 		ret = actor(desc, page, offset, nr);
1554 		offset += ret;
1555 		index += offset >> PAGE_CACHE_SHIFT;
1556 		offset &= ~PAGE_CACHE_MASK;
1557 
1558 		page_cache_release(page);
1559 		if (ret != nr || !desc->count)
1560 			break;
1561 
1562 		cond_resched();
1563 	}
1564 
1565 	*ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
1566 	file_accessed(filp);
1567 }
1568 
1569 static ssize_t shmem_file_aio_read(struct kiocb *iocb,
1570 		const struct iovec *iov, unsigned long nr_segs, loff_t pos)
1571 {
1572 	struct file *filp = iocb->ki_filp;
1573 	ssize_t retval;
1574 	unsigned long seg;
1575 	size_t count;
1576 	loff_t *ppos = &iocb->ki_pos;
1577 
1578 	retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1579 	if (retval)
1580 		return retval;
1581 
1582 	for (seg = 0; seg < nr_segs; seg++) {
1583 		read_descriptor_t desc;
1584 
1585 		desc.written = 0;
1586 		desc.arg.buf = iov[seg].iov_base;
1587 		desc.count = iov[seg].iov_len;
1588 		if (desc.count == 0)
1589 			continue;
1590 		desc.error = 0;
1591 		do_shmem_file_read(filp, ppos, &desc, file_read_actor);
1592 		retval += desc.written;
1593 		if (desc.error) {
1594 			retval = retval ?: desc.error;
1595 			break;
1596 		}
1597 		if (desc.count > 0)
1598 			break;
1599 	}
1600 	return retval;
1601 }
1602 
1603 static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos,
1604 				struct pipe_inode_info *pipe, size_t len,
1605 				unsigned int flags)
1606 {
1607 	struct address_space *mapping = in->f_mapping;
1608 	struct inode *inode = mapping->host;
1609 	unsigned int loff, nr_pages, req_pages;
1610 	struct page *pages[PIPE_DEF_BUFFERS];
1611 	struct partial_page partial[PIPE_DEF_BUFFERS];
1612 	struct page *page;
1613 	pgoff_t index, end_index;
1614 	loff_t isize, left;
1615 	int error, page_nr;
1616 	struct splice_pipe_desc spd = {
1617 		.pages = pages,
1618 		.partial = partial,
1619 		.nr_pages_max = PIPE_DEF_BUFFERS,
1620 		.flags = flags,
1621 		.ops = &page_cache_pipe_buf_ops,
1622 		.spd_release = spd_release_page,
1623 	};
1624 
1625 	isize = i_size_read(inode);
1626 	if (unlikely(*ppos >= isize))
1627 		return 0;
1628 
1629 	left = isize - *ppos;
1630 	if (unlikely(left < len))
1631 		len = left;
1632 
1633 	if (splice_grow_spd(pipe, &spd))
1634 		return -ENOMEM;
1635 
1636 	index = *ppos >> PAGE_CACHE_SHIFT;
1637 	loff = *ppos & ~PAGE_CACHE_MASK;
1638 	req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1639 	nr_pages = min(req_pages, pipe->buffers);
1640 
1641 	spd.nr_pages = find_get_pages_contig(mapping, index,
1642 						nr_pages, spd.pages);
1643 	index += spd.nr_pages;
1644 	error = 0;
1645 
1646 	while (spd.nr_pages < nr_pages) {
1647 		error = shmem_getpage(inode, index, &page, SGP_CACHE, NULL);
1648 		if (error)
1649 			break;
1650 		unlock_page(page);
1651 		spd.pages[spd.nr_pages++] = page;
1652 		index++;
1653 	}
1654 
1655 	index = *ppos >> PAGE_CACHE_SHIFT;
1656 	nr_pages = spd.nr_pages;
1657 	spd.nr_pages = 0;
1658 
1659 	for (page_nr = 0; page_nr < nr_pages; page_nr++) {
1660 		unsigned int this_len;
1661 
1662 		if (!len)
1663 			break;
1664 
1665 		this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
1666 		page = spd.pages[page_nr];
1667 
1668 		if (!PageUptodate(page) || page->mapping != mapping) {
1669 			error = shmem_getpage(inode, index, &page,
1670 							SGP_CACHE, NULL);
1671 			if (error)
1672 				break;
1673 			unlock_page(page);
1674 			page_cache_release(spd.pages[page_nr]);
1675 			spd.pages[page_nr] = page;
1676 		}
1677 
1678 		isize = i_size_read(inode);
1679 		end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
1680 		if (unlikely(!isize || index > end_index))
1681 			break;
1682 
1683 		if (end_index == index) {
1684 			unsigned int plen;
1685 
1686 			plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
1687 			if (plen <= loff)
1688 				break;
1689 
1690 			this_len = min(this_len, plen - loff);
1691 			len = this_len;
1692 		}
1693 
1694 		spd.partial[page_nr].offset = loff;
1695 		spd.partial[page_nr].len = this_len;
1696 		len -= this_len;
1697 		loff = 0;
1698 		spd.nr_pages++;
1699 		index++;
1700 	}
1701 
1702 	while (page_nr < nr_pages)
1703 		page_cache_release(spd.pages[page_nr++]);
1704 
1705 	if (spd.nr_pages)
1706 		error = splice_to_pipe(pipe, &spd);
1707 
1708 	splice_shrink_spd(&spd);
1709 
1710 	if (error > 0) {
1711 		*ppos += error;
1712 		file_accessed(in);
1713 	}
1714 	return error;
1715 }
1716 
1717 /*
1718  * llseek SEEK_DATA or SEEK_HOLE through the radix_tree.
1719  */
1720 static pgoff_t shmem_seek_hole_data(struct address_space *mapping,
1721 				    pgoff_t index, pgoff_t end, int whence)
1722 {
1723 	struct page *page;
1724 	struct pagevec pvec;
1725 	pgoff_t indices[PAGEVEC_SIZE];
1726 	bool done = false;
1727 	int i;
1728 
1729 	pagevec_init(&pvec, 0);
1730 	pvec.nr = 1;		/* start small: we may be there already */
1731 	while (!done) {
1732 		pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
1733 					pvec.nr, pvec.pages, indices);
1734 		if (!pvec.nr) {
1735 			if (whence == SEEK_DATA)
1736 				index = end;
1737 			break;
1738 		}
1739 		for (i = 0; i < pvec.nr; i++, index++) {
1740 			if (index < indices[i]) {
1741 				if (whence == SEEK_HOLE) {
1742 					done = true;
1743 					break;
1744 				}
1745 				index = indices[i];
1746 			}
1747 			page = pvec.pages[i];
1748 			if (page && !radix_tree_exceptional_entry(page)) {
1749 				if (!PageUptodate(page))
1750 					page = NULL;
1751 			}
1752 			if (index >= end ||
1753 			    (page && whence == SEEK_DATA) ||
1754 			    (!page && whence == SEEK_HOLE)) {
1755 				done = true;
1756 				break;
1757 			}
1758 		}
1759 		shmem_deswap_pagevec(&pvec);
1760 		pagevec_release(&pvec);
1761 		pvec.nr = PAGEVEC_SIZE;
1762 		cond_resched();
1763 	}
1764 	return index;
1765 }
1766 
1767 static loff_t shmem_file_llseek(struct file *file, loff_t offset, int whence)
1768 {
1769 	struct address_space *mapping = file->f_mapping;
1770 	struct inode *inode = mapping->host;
1771 	pgoff_t start, end;
1772 	loff_t new_offset;
1773 
1774 	if (whence != SEEK_DATA && whence != SEEK_HOLE)
1775 		return generic_file_llseek_size(file, offset, whence,
1776 					MAX_LFS_FILESIZE, i_size_read(inode));
1777 	mutex_lock(&inode->i_mutex);
1778 	/* We're holding i_mutex so we can access i_size directly */
1779 
1780 	if (offset < 0)
1781 		offset = -EINVAL;
1782 	else if (offset >= inode->i_size)
1783 		offset = -ENXIO;
1784 	else {
1785 		start = offset >> PAGE_CACHE_SHIFT;
1786 		end = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1787 		new_offset = shmem_seek_hole_data(mapping, start, end, whence);
1788 		new_offset <<= PAGE_CACHE_SHIFT;
1789 		if (new_offset > offset) {
1790 			if (new_offset < inode->i_size)
1791 				offset = new_offset;
1792 			else if (whence == SEEK_DATA)
1793 				offset = -ENXIO;
1794 			else
1795 				offset = inode->i_size;
1796 		}
1797 	}
1798 
1799 	if (offset >= 0 && offset != file->f_pos) {
1800 		file->f_pos = offset;
1801 		file->f_version = 0;
1802 	}
1803 	mutex_unlock(&inode->i_mutex);
1804 	return offset;
1805 }
1806 
1807 static long shmem_fallocate(struct file *file, int mode, loff_t offset,
1808 							 loff_t len)
1809 {
1810 	struct inode *inode = file_inode(file);
1811 	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
1812 	struct shmem_falloc shmem_falloc;
1813 	pgoff_t start, index, end;
1814 	int error;
1815 
1816 	mutex_lock(&inode->i_mutex);
1817 
1818 	if (mode & FALLOC_FL_PUNCH_HOLE) {
1819 		struct address_space *mapping = file->f_mapping;
1820 		loff_t unmap_start = round_up(offset, PAGE_SIZE);
1821 		loff_t unmap_end = round_down(offset + len, PAGE_SIZE) - 1;
1822 
1823 		if ((u64)unmap_end > (u64)unmap_start)
1824 			unmap_mapping_range(mapping, unmap_start,
1825 					    1 + unmap_end - unmap_start, 0);
1826 		shmem_truncate_range(inode, offset, offset + len - 1);
1827 		/* No need to unmap again: hole-punching leaves COWed pages */
1828 		error = 0;
1829 		goto out;
1830 	}
1831 
1832 	/* We need to check rlimit even when FALLOC_FL_KEEP_SIZE */
1833 	error = inode_newsize_ok(inode, offset + len);
1834 	if (error)
1835 		goto out;
1836 
1837 	start = offset >> PAGE_CACHE_SHIFT;
1838 	end = (offset + len + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1839 	/* Try to avoid a swapstorm if len is impossible to satisfy */
1840 	if (sbinfo->max_blocks && end - start > sbinfo->max_blocks) {
1841 		error = -ENOSPC;
1842 		goto out;
1843 	}
1844 
1845 	shmem_falloc.start = start;
1846 	shmem_falloc.next  = start;
1847 	shmem_falloc.nr_falloced = 0;
1848 	shmem_falloc.nr_unswapped = 0;
1849 	spin_lock(&inode->i_lock);
1850 	inode->i_private = &shmem_falloc;
1851 	spin_unlock(&inode->i_lock);
1852 
1853 	for (index = start; index < end; index++) {
1854 		struct page *page;
1855 
1856 		/*
1857 		 * Good, the fallocate(2) manpage permits EINTR: we may have
1858 		 * been interrupted because we are using up too much memory.
1859 		 */
1860 		if (signal_pending(current))
1861 			error = -EINTR;
1862 		else if (shmem_falloc.nr_unswapped > shmem_falloc.nr_falloced)
1863 			error = -ENOMEM;
1864 		else
1865 			error = shmem_getpage(inode, index, &page, SGP_FALLOC,
1866 									NULL);
1867 		if (error) {
1868 			/* Remove the !PageUptodate pages we added */
1869 			shmem_undo_range(inode,
1870 				(loff_t)start << PAGE_CACHE_SHIFT,
1871 				(loff_t)index << PAGE_CACHE_SHIFT, true);
1872 			goto undone;
1873 		}
1874 
1875 		/*
1876 		 * Inform shmem_writepage() how far we have reached.
1877 		 * No need for lock or barrier: we have the page lock.
1878 		 */
1879 		shmem_falloc.next++;
1880 		if (!PageUptodate(page))
1881 			shmem_falloc.nr_falloced++;
1882 
1883 		/*
1884 		 * If !PageUptodate, leave it that way so that freeable pages
1885 		 * can be recognized if we need to rollback on error later.
1886 		 * But set_page_dirty so that memory pressure will swap rather
1887 		 * than free the pages we are allocating (and SGP_CACHE pages
1888 		 * might still be clean: we now need to mark those dirty too).
1889 		 */
1890 		set_page_dirty(page);
1891 		unlock_page(page);
1892 		page_cache_release(page);
1893 		cond_resched();
1894 	}
1895 
1896 	if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size)
1897 		i_size_write(inode, offset + len);
1898 	inode->i_ctime = CURRENT_TIME;
1899 undone:
1900 	spin_lock(&inode->i_lock);
1901 	inode->i_private = NULL;
1902 	spin_unlock(&inode->i_lock);
1903 out:
1904 	mutex_unlock(&inode->i_mutex);
1905 	return error;
1906 }
1907 
1908 static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
1909 {
1910 	struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
1911 
1912 	buf->f_type = TMPFS_MAGIC;
1913 	buf->f_bsize = PAGE_CACHE_SIZE;
1914 	buf->f_namelen = NAME_MAX;
1915 	if (sbinfo->max_blocks) {
1916 		buf->f_blocks = sbinfo->max_blocks;
1917 		buf->f_bavail =
1918 		buf->f_bfree  = sbinfo->max_blocks -
1919 				percpu_counter_sum(&sbinfo->used_blocks);
1920 	}
1921 	if (sbinfo->max_inodes) {
1922 		buf->f_files = sbinfo->max_inodes;
1923 		buf->f_ffree = sbinfo->free_inodes;
1924 	}
1925 	/* else leave those fields 0 like simple_statfs */
1926 	return 0;
1927 }
1928 
1929 /*
1930  * File creation. Allocate an inode, and we're done..
1931  */
1932 static int
1933 shmem_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
1934 {
1935 	struct inode *inode;
1936 	int error = -ENOSPC;
1937 
1938 	inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE);
1939 	if (inode) {
1940 		error = security_inode_init_security(inode, dir,
1941 						     &dentry->d_name,
1942 						     shmem_initxattrs, NULL);
1943 		if (error) {
1944 			if (error != -EOPNOTSUPP) {
1945 				iput(inode);
1946 				return error;
1947 			}
1948 		}
1949 #ifdef CONFIG_TMPFS_POSIX_ACL
1950 		error = generic_acl_init(inode, dir);
1951 		if (error) {
1952 			iput(inode);
1953 			return error;
1954 		}
1955 #else
1956 		error = 0;
1957 #endif
1958 		dir->i_size += BOGO_DIRENT_SIZE;
1959 		dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1960 		d_instantiate(dentry, inode);
1961 		dget(dentry); /* Extra count - pin the dentry in core */
1962 	}
1963 	return error;
1964 }
1965 
1966 static int shmem_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
1967 {
1968 	int error;
1969 
1970 	if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
1971 		return error;
1972 	inc_nlink(dir);
1973 	return 0;
1974 }
1975 
1976 static int shmem_create(struct inode *dir, struct dentry *dentry, umode_t mode,
1977 		bool excl)
1978 {
1979 	return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
1980 }
1981 
1982 /*
1983  * Link a file..
1984  */
1985 static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
1986 {
1987 	struct inode *inode = old_dentry->d_inode;
1988 	int ret;
1989 
1990 	/*
1991 	 * No ordinary (disk based) filesystem counts links as inodes;
1992 	 * but each new link needs a new dentry, pinning lowmem, and
1993 	 * tmpfs dentries cannot be pruned until they are unlinked.
1994 	 */
1995 	ret = shmem_reserve_inode(inode->i_sb);
1996 	if (ret)
1997 		goto out;
1998 
1999 	dir->i_size += BOGO_DIRENT_SIZE;
2000 	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2001 	inc_nlink(inode);
2002 	ihold(inode);	/* New dentry reference */
2003 	dget(dentry);		/* Extra pinning count for the created dentry */
2004 	d_instantiate(dentry, inode);
2005 out:
2006 	return ret;
2007 }
2008 
2009 static int shmem_unlink(struct inode *dir, struct dentry *dentry)
2010 {
2011 	struct inode *inode = dentry->d_inode;
2012 
2013 	if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
2014 		shmem_free_inode(inode->i_sb);
2015 
2016 	dir->i_size -= BOGO_DIRENT_SIZE;
2017 	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2018 	drop_nlink(inode);
2019 	dput(dentry);	/* Undo the count from "create" - this does all the work */
2020 	return 0;
2021 }
2022 
2023 static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
2024 {
2025 	if (!simple_empty(dentry))
2026 		return -ENOTEMPTY;
2027 
2028 	drop_nlink(dentry->d_inode);
2029 	drop_nlink(dir);
2030 	return shmem_unlink(dir, dentry);
2031 }
2032 
2033 /*
2034  * The VFS layer already does all the dentry stuff for rename,
2035  * we just have to decrement the usage count for the target if
2036  * it exists so that the VFS layer correctly free's it when it
2037  * gets overwritten.
2038  */
2039 static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
2040 {
2041 	struct inode *inode = old_dentry->d_inode;
2042 	int they_are_dirs = S_ISDIR(inode->i_mode);
2043 
2044 	if (!simple_empty(new_dentry))
2045 		return -ENOTEMPTY;
2046 
2047 	if (new_dentry->d_inode) {
2048 		(void) shmem_unlink(new_dir, new_dentry);
2049 		if (they_are_dirs)
2050 			drop_nlink(old_dir);
2051 	} else if (they_are_dirs) {
2052 		drop_nlink(old_dir);
2053 		inc_nlink(new_dir);
2054 	}
2055 
2056 	old_dir->i_size -= BOGO_DIRENT_SIZE;
2057 	new_dir->i_size += BOGO_DIRENT_SIZE;
2058 	old_dir->i_ctime = old_dir->i_mtime =
2059 	new_dir->i_ctime = new_dir->i_mtime =
2060 	inode->i_ctime = CURRENT_TIME;
2061 	return 0;
2062 }
2063 
2064 static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
2065 {
2066 	int error;
2067 	int len;
2068 	struct inode *inode;
2069 	struct page *page;
2070 	char *kaddr;
2071 	struct shmem_inode_info *info;
2072 
2073 	len = strlen(symname) + 1;
2074 	if (len > PAGE_CACHE_SIZE)
2075 		return -ENAMETOOLONG;
2076 
2077 	inode = shmem_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0, VM_NORESERVE);
2078 	if (!inode)
2079 		return -ENOSPC;
2080 
2081 	error = security_inode_init_security(inode, dir, &dentry->d_name,
2082 					     shmem_initxattrs, NULL);
2083 	if (error) {
2084 		if (error != -EOPNOTSUPP) {
2085 			iput(inode);
2086 			return error;
2087 		}
2088 		error = 0;
2089 	}
2090 
2091 	info = SHMEM_I(inode);
2092 	inode->i_size = len-1;
2093 	if (len <= SHORT_SYMLINK_LEN) {
2094 		info->symlink = kmemdup(symname, len, GFP_KERNEL);
2095 		if (!info->symlink) {
2096 			iput(inode);
2097 			return -ENOMEM;
2098 		}
2099 		inode->i_op = &shmem_short_symlink_operations;
2100 	} else {
2101 		error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
2102 		if (error) {
2103 			iput(inode);
2104 			return error;
2105 		}
2106 		inode->i_mapping->a_ops = &shmem_aops;
2107 		inode->i_op = &shmem_symlink_inode_operations;
2108 		kaddr = kmap_atomic(page);
2109 		memcpy(kaddr, symname, len);
2110 		kunmap_atomic(kaddr);
2111 		SetPageUptodate(page);
2112 		set_page_dirty(page);
2113 		unlock_page(page);
2114 		page_cache_release(page);
2115 	}
2116 	dir->i_size += BOGO_DIRENT_SIZE;
2117 	dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2118 	d_instantiate(dentry, inode);
2119 	dget(dentry);
2120 	return 0;
2121 }
2122 
2123 static void *shmem_follow_short_symlink(struct dentry *dentry, struct nameidata *nd)
2124 {
2125 	nd_set_link(nd, SHMEM_I(dentry->d_inode)->symlink);
2126 	return NULL;
2127 }
2128 
2129 static void *shmem_follow_link(struct dentry *dentry, struct nameidata *nd)
2130 {
2131 	struct page *page = NULL;
2132 	int error = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL);
2133 	nd_set_link(nd, error ? ERR_PTR(error) : kmap(page));
2134 	if (page)
2135 		unlock_page(page);
2136 	return page;
2137 }
2138 
2139 static void shmem_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
2140 {
2141 	if (!IS_ERR(nd_get_link(nd))) {
2142 		struct page *page = cookie;
2143 		kunmap(page);
2144 		mark_page_accessed(page);
2145 		page_cache_release(page);
2146 	}
2147 }
2148 
2149 #ifdef CONFIG_TMPFS_XATTR
2150 /*
2151  * Superblocks without xattr inode operations may get some security.* xattr
2152  * support from the LSM "for free". As soon as we have any other xattrs
2153  * like ACLs, we also need to implement the security.* handlers at
2154  * filesystem level, though.
2155  */
2156 
2157 /*
2158  * Callback for security_inode_init_security() for acquiring xattrs.
2159  */
2160 static int shmem_initxattrs(struct inode *inode,
2161 			    const struct xattr *xattr_array,
2162 			    void *fs_info)
2163 {
2164 	struct shmem_inode_info *info = SHMEM_I(inode);
2165 	const struct xattr *xattr;
2166 	struct simple_xattr *new_xattr;
2167 	size_t len;
2168 
2169 	for (xattr = xattr_array; xattr->name != NULL; xattr++) {
2170 		new_xattr = simple_xattr_alloc(xattr->value, xattr->value_len);
2171 		if (!new_xattr)
2172 			return -ENOMEM;
2173 
2174 		len = strlen(xattr->name) + 1;
2175 		new_xattr->name = kmalloc(XATTR_SECURITY_PREFIX_LEN + len,
2176 					  GFP_KERNEL);
2177 		if (!new_xattr->name) {
2178 			kfree(new_xattr);
2179 			return -ENOMEM;
2180 		}
2181 
2182 		memcpy(new_xattr->name, XATTR_SECURITY_PREFIX,
2183 		       XATTR_SECURITY_PREFIX_LEN);
2184 		memcpy(new_xattr->name + XATTR_SECURITY_PREFIX_LEN,
2185 		       xattr->name, len);
2186 
2187 		simple_xattr_list_add(&info->xattrs, new_xattr);
2188 	}
2189 
2190 	return 0;
2191 }
2192 
2193 static const struct xattr_handler *shmem_xattr_handlers[] = {
2194 #ifdef CONFIG_TMPFS_POSIX_ACL
2195 	&generic_acl_access_handler,
2196 	&generic_acl_default_handler,
2197 #endif
2198 	NULL
2199 };
2200 
2201 static int shmem_xattr_validate(const char *name)
2202 {
2203 	struct { const char *prefix; size_t len; } arr[] = {
2204 		{ XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN },
2205 		{ XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN }
2206 	};
2207 	int i;
2208 
2209 	for (i = 0; i < ARRAY_SIZE(arr); i++) {
2210 		size_t preflen = arr[i].len;
2211 		if (strncmp(name, arr[i].prefix, preflen) == 0) {
2212 			if (!name[preflen])
2213 				return -EINVAL;
2214 			return 0;
2215 		}
2216 	}
2217 	return -EOPNOTSUPP;
2218 }
2219 
2220 static ssize_t shmem_getxattr(struct dentry *dentry, const char *name,
2221 			      void *buffer, size_t size)
2222 {
2223 	struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
2224 	int err;
2225 
2226 	/*
2227 	 * If this is a request for a synthetic attribute in the system.*
2228 	 * namespace use the generic infrastructure to resolve a handler
2229 	 * for it via sb->s_xattr.
2230 	 */
2231 	if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
2232 		return generic_getxattr(dentry, name, buffer, size);
2233 
2234 	err = shmem_xattr_validate(name);
2235 	if (err)
2236 		return err;
2237 
2238 	return simple_xattr_get(&info->xattrs, name, buffer, size);
2239 }
2240 
2241 static int shmem_setxattr(struct dentry *dentry, const char *name,
2242 			  const void *value, size_t size, int flags)
2243 {
2244 	struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
2245 	int err;
2246 
2247 	/*
2248 	 * If this is a request for a synthetic attribute in the system.*
2249 	 * namespace use the generic infrastructure to resolve a handler
2250 	 * for it via sb->s_xattr.
2251 	 */
2252 	if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
2253 		return generic_setxattr(dentry, name, value, size, flags);
2254 
2255 	err = shmem_xattr_validate(name);
2256 	if (err)
2257 		return err;
2258 
2259 	return simple_xattr_set(&info->xattrs, name, value, size, flags);
2260 }
2261 
2262 static int shmem_removexattr(struct dentry *dentry, const char *name)
2263 {
2264 	struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
2265 	int err;
2266 
2267 	/*
2268 	 * If this is a request for a synthetic attribute in the system.*
2269 	 * namespace use the generic infrastructure to resolve a handler
2270 	 * for it via sb->s_xattr.
2271 	 */
2272 	if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
2273 		return generic_removexattr(dentry, name);
2274 
2275 	err = shmem_xattr_validate(name);
2276 	if (err)
2277 		return err;
2278 
2279 	return simple_xattr_remove(&info->xattrs, name);
2280 }
2281 
2282 static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t size)
2283 {
2284 	struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
2285 	return simple_xattr_list(&info->xattrs, buffer, size);
2286 }
2287 #endif /* CONFIG_TMPFS_XATTR */
2288 
2289 static const struct inode_operations shmem_short_symlink_operations = {
2290 	.readlink	= generic_readlink,
2291 	.follow_link	= shmem_follow_short_symlink,
2292 #ifdef CONFIG_TMPFS_XATTR
2293 	.setxattr	= shmem_setxattr,
2294 	.getxattr	= shmem_getxattr,
2295 	.listxattr	= shmem_listxattr,
2296 	.removexattr	= shmem_removexattr,
2297 #endif
2298 };
2299 
2300 static const struct inode_operations shmem_symlink_inode_operations = {
2301 	.readlink	= generic_readlink,
2302 	.follow_link	= shmem_follow_link,
2303 	.put_link	= shmem_put_link,
2304 #ifdef CONFIG_TMPFS_XATTR
2305 	.setxattr	= shmem_setxattr,
2306 	.getxattr	= shmem_getxattr,
2307 	.listxattr	= shmem_listxattr,
2308 	.removexattr	= shmem_removexattr,
2309 #endif
2310 };
2311 
2312 static struct dentry *shmem_get_parent(struct dentry *child)
2313 {
2314 	return ERR_PTR(-ESTALE);
2315 }
2316 
2317 static int shmem_match(struct inode *ino, void *vfh)
2318 {
2319 	__u32 *fh = vfh;
2320 	__u64 inum = fh[2];
2321 	inum = (inum << 32) | fh[1];
2322 	return ino->i_ino == inum && fh[0] == ino->i_generation;
2323 }
2324 
2325 static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
2326 		struct fid *fid, int fh_len, int fh_type)
2327 {
2328 	struct inode *inode;
2329 	struct dentry *dentry = NULL;
2330 	u64 inum;
2331 
2332 	if (fh_len < 3)
2333 		return NULL;
2334 
2335 	inum = fid->raw[2];
2336 	inum = (inum << 32) | fid->raw[1];
2337 
2338 	inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
2339 			shmem_match, fid->raw);
2340 	if (inode) {
2341 		dentry = d_find_alias(inode);
2342 		iput(inode);
2343 	}
2344 
2345 	return dentry;
2346 }
2347 
2348 static int shmem_encode_fh(struct inode *inode, __u32 *fh, int *len,
2349 				struct inode *parent)
2350 {
2351 	if (*len < 3) {
2352 		*len = 3;
2353 		return FILEID_INVALID;
2354 	}
2355 
2356 	if (inode_unhashed(inode)) {
2357 		/* Unfortunately insert_inode_hash is not idempotent,
2358 		 * so as we hash inodes here rather than at creation
2359 		 * time, we need a lock to ensure we only try
2360 		 * to do it once
2361 		 */
2362 		static DEFINE_SPINLOCK(lock);
2363 		spin_lock(&lock);
2364 		if (inode_unhashed(inode))
2365 			__insert_inode_hash(inode,
2366 					    inode->i_ino + inode->i_generation);
2367 		spin_unlock(&lock);
2368 	}
2369 
2370 	fh[0] = inode->i_generation;
2371 	fh[1] = inode->i_ino;
2372 	fh[2] = ((__u64)inode->i_ino) >> 32;
2373 
2374 	*len = 3;
2375 	return 1;
2376 }
2377 
2378 static const struct export_operations shmem_export_ops = {
2379 	.get_parent     = shmem_get_parent,
2380 	.encode_fh      = shmem_encode_fh,
2381 	.fh_to_dentry	= shmem_fh_to_dentry,
2382 };
2383 
2384 static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
2385 			       bool remount)
2386 {
2387 	char *this_char, *value, *rest;
2388 	struct mempolicy *mpol = NULL;
2389 	uid_t uid;
2390 	gid_t gid;
2391 
2392 	while (options != NULL) {
2393 		this_char = options;
2394 		for (;;) {
2395 			/*
2396 			 * NUL-terminate this option: unfortunately,
2397 			 * mount options form a comma-separated list,
2398 			 * but mpol's nodelist may also contain commas.
2399 			 */
2400 			options = strchr(options, ',');
2401 			if (options == NULL)
2402 				break;
2403 			options++;
2404 			if (!isdigit(*options)) {
2405 				options[-1] = '\0';
2406 				break;
2407 			}
2408 		}
2409 		if (!*this_char)
2410 			continue;
2411 		if ((value = strchr(this_char,'=')) != NULL) {
2412 			*value++ = 0;
2413 		} else {
2414 			printk(KERN_ERR
2415 			    "tmpfs: No value for mount option '%s'\n",
2416 			    this_char);
2417 			goto error;
2418 		}
2419 
2420 		if (!strcmp(this_char,"size")) {
2421 			unsigned long long size;
2422 			size = memparse(value,&rest);
2423 			if (*rest == '%') {
2424 				size <<= PAGE_SHIFT;
2425 				size *= totalram_pages;
2426 				do_div(size, 100);
2427 				rest++;
2428 			}
2429 			if (*rest)
2430 				goto bad_val;
2431 			sbinfo->max_blocks =
2432 				DIV_ROUND_UP(size, PAGE_CACHE_SIZE);
2433 		} else if (!strcmp(this_char,"nr_blocks")) {
2434 			sbinfo->max_blocks = memparse(value, &rest);
2435 			if (*rest)
2436 				goto bad_val;
2437 		} else if (!strcmp(this_char,"nr_inodes")) {
2438 			sbinfo->max_inodes = memparse(value, &rest);
2439 			if (*rest)
2440 				goto bad_val;
2441 		} else if (!strcmp(this_char,"mode")) {
2442 			if (remount)
2443 				continue;
2444 			sbinfo->mode = simple_strtoul(value, &rest, 8) & 07777;
2445 			if (*rest)
2446 				goto bad_val;
2447 		} else if (!strcmp(this_char,"uid")) {
2448 			if (remount)
2449 				continue;
2450 			uid = simple_strtoul(value, &rest, 0);
2451 			if (*rest)
2452 				goto bad_val;
2453 			sbinfo->uid = make_kuid(current_user_ns(), uid);
2454 			if (!uid_valid(sbinfo->uid))
2455 				goto bad_val;
2456 		} else if (!strcmp(this_char,"gid")) {
2457 			if (remount)
2458 				continue;
2459 			gid = simple_strtoul(value, &rest, 0);
2460 			if (*rest)
2461 				goto bad_val;
2462 			sbinfo->gid = make_kgid(current_user_ns(), gid);
2463 			if (!gid_valid(sbinfo->gid))
2464 				goto bad_val;
2465 		} else if (!strcmp(this_char,"mpol")) {
2466 			mpol_put(mpol);
2467 			mpol = NULL;
2468 			if (mpol_parse_str(value, &mpol))
2469 				goto bad_val;
2470 		} else {
2471 			printk(KERN_ERR "tmpfs: Bad mount option %s\n",
2472 			       this_char);
2473 			goto error;
2474 		}
2475 	}
2476 	sbinfo->mpol = mpol;
2477 	return 0;
2478 
2479 bad_val:
2480 	printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n",
2481 	       value, this_char);
2482 error:
2483 	mpol_put(mpol);
2484 	return 1;
2485 
2486 }
2487 
2488 static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
2489 {
2490 	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2491 	struct shmem_sb_info config = *sbinfo;
2492 	unsigned long inodes;
2493 	int error = -EINVAL;
2494 
2495 	config.mpol = NULL;
2496 	if (shmem_parse_options(data, &config, true))
2497 		return error;
2498 
2499 	spin_lock(&sbinfo->stat_lock);
2500 	inodes = sbinfo->max_inodes - sbinfo->free_inodes;
2501 	if (percpu_counter_compare(&sbinfo->used_blocks, config.max_blocks) > 0)
2502 		goto out;
2503 	if (config.max_inodes < inodes)
2504 		goto out;
2505 	/*
2506 	 * Those tests disallow limited->unlimited while any are in use;
2507 	 * but we must separately disallow unlimited->limited, because
2508 	 * in that case we have no record of how much is already in use.
2509 	 */
2510 	if (config.max_blocks && !sbinfo->max_blocks)
2511 		goto out;
2512 	if (config.max_inodes && !sbinfo->max_inodes)
2513 		goto out;
2514 
2515 	error = 0;
2516 	sbinfo->max_blocks  = config.max_blocks;
2517 	sbinfo->max_inodes  = config.max_inodes;
2518 	sbinfo->free_inodes = config.max_inodes - inodes;
2519 
2520 	/*
2521 	 * Preserve previous mempolicy unless mpol remount option was specified.
2522 	 */
2523 	if (config.mpol) {
2524 		mpol_put(sbinfo->mpol);
2525 		sbinfo->mpol = config.mpol;	/* transfers initial ref */
2526 	}
2527 out:
2528 	spin_unlock(&sbinfo->stat_lock);
2529 	return error;
2530 }
2531 
2532 static int shmem_show_options(struct seq_file *seq, struct dentry *root)
2533 {
2534 	struct shmem_sb_info *sbinfo = SHMEM_SB(root->d_sb);
2535 
2536 	if (sbinfo->max_blocks != shmem_default_max_blocks())
2537 		seq_printf(seq, ",size=%luk",
2538 			sbinfo->max_blocks << (PAGE_CACHE_SHIFT - 10));
2539 	if (sbinfo->max_inodes != shmem_default_max_inodes())
2540 		seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
2541 	if (sbinfo->mode != (S_IRWXUGO | S_ISVTX))
2542 		seq_printf(seq, ",mode=%03ho", sbinfo->mode);
2543 	if (!uid_eq(sbinfo->uid, GLOBAL_ROOT_UID))
2544 		seq_printf(seq, ",uid=%u",
2545 				from_kuid_munged(&init_user_ns, sbinfo->uid));
2546 	if (!gid_eq(sbinfo->gid, GLOBAL_ROOT_GID))
2547 		seq_printf(seq, ",gid=%u",
2548 				from_kgid_munged(&init_user_ns, sbinfo->gid));
2549 	shmem_show_mpol(seq, sbinfo->mpol);
2550 	return 0;
2551 }
2552 #endif /* CONFIG_TMPFS */
2553 
2554 static void shmem_put_super(struct super_block *sb)
2555 {
2556 	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2557 
2558 	percpu_counter_destroy(&sbinfo->used_blocks);
2559 	mpol_put(sbinfo->mpol);
2560 	kfree(sbinfo);
2561 	sb->s_fs_info = NULL;
2562 }
2563 
2564 int shmem_fill_super(struct super_block *sb, void *data, int silent)
2565 {
2566 	struct inode *inode;
2567 	struct shmem_sb_info *sbinfo;
2568 	int err = -ENOMEM;
2569 
2570 	/* Round up to L1_CACHE_BYTES to resist false sharing */
2571 	sbinfo = kzalloc(max((int)sizeof(struct shmem_sb_info),
2572 				L1_CACHE_BYTES), GFP_KERNEL);
2573 	if (!sbinfo)
2574 		return -ENOMEM;
2575 
2576 	sbinfo->mode = S_IRWXUGO | S_ISVTX;
2577 	sbinfo->uid = current_fsuid();
2578 	sbinfo->gid = current_fsgid();
2579 	sb->s_fs_info = sbinfo;
2580 
2581 #ifdef CONFIG_TMPFS
2582 	/*
2583 	 * Per default we only allow half of the physical ram per
2584 	 * tmpfs instance, limiting inodes to one per page of lowmem;
2585 	 * but the internal instance is left unlimited.
2586 	 */
2587 	if (!(sb->s_flags & MS_NOUSER)) {
2588 		sbinfo->max_blocks = shmem_default_max_blocks();
2589 		sbinfo->max_inodes = shmem_default_max_inodes();
2590 		if (shmem_parse_options(data, sbinfo, false)) {
2591 			err = -EINVAL;
2592 			goto failed;
2593 		}
2594 	}
2595 	sb->s_export_op = &shmem_export_ops;
2596 	sb->s_flags |= MS_NOSEC;
2597 #else
2598 	sb->s_flags |= MS_NOUSER;
2599 #endif
2600 
2601 	spin_lock_init(&sbinfo->stat_lock);
2602 	if (percpu_counter_init(&sbinfo->used_blocks, 0))
2603 		goto failed;
2604 	sbinfo->free_inodes = sbinfo->max_inodes;
2605 
2606 	sb->s_maxbytes = MAX_LFS_FILESIZE;
2607 	sb->s_blocksize = PAGE_CACHE_SIZE;
2608 	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
2609 	sb->s_magic = TMPFS_MAGIC;
2610 	sb->s_op = &shmem_ops;
2611 	sb->s_time_gran = 1;
2612 #ifdef CONFIG_TMPFS_XATTR
2613 	sb->s_xattr = shmem_xattr_handlers;
2614 #endif
2615 #ifdef CONFIG_TMPFS_POSIX_ACL
2616 	sb->s_flags |= MS_POSIXACL;
2617 #endif
2618 
2619 	inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
2620 	if (!inode)
2621 		goto failed;
2622 	inode->i_uid = sbinfo->uid;
2623 	inode->i_gid = sbinfo->gid;
2624 	sb->s_root = d_make_root(inode);
2625 	if (!sb->s_root)
2626 		goto failed;
2627 	return 0;
2628 
2629 failed:
2630 	shmem_put_super(sb);
2631 	return err;
2632 }
2633 
2634 static struct kmem_cache *shmem_inode_cachep;
2635 
2636 static struct inode *shmem_alloc_inode(struct super_block *sb)
2637 {
2638 	struct shmem_inode_info *info;
2639 	info = kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
2640 	if (!info)
2641 		return NULL;
2642 	return &info->vfs_inode;
2643 }
2644 
2645 static void shmem_destroy_callback(struct rcu_head *head)
2646 {
2647 	struct inode *inode = container_of(head, struct inode, i_rcu);
2648 	kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
2649 }
2650 
2651 static void shmem_destroy_inode(struct inode *inode)
2652 {
2653 	if (S_ISREG(inode->i_mode))
2654 		mpol_free_shared_policy(&SHMEM_I(inode)->policy);
2655 	call_rcu(&inode->i_rcu, shmem_destroy_callback);
2656 }
2657 
2658 static void shmem_init_inode(void *foo)
2659 {
2660 	struct shmem_inode_info *info = foo;
2661 	inode_init_once(&info->vfs_inode);
2662 }
2663 
2664 static int shmem_init_inodecache(void)
2665 {
2666 	shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
2667 				sizeof(struct shmem_inode_info),
2668 				0, SLAB_PANIC, shmem_init_inode);
2669 	return 0;
2670 }
2671 
2672 static void shmem_destroy_inodecache(void)
2673 {
2674 	kmem_cache_destroy(shmem_inode_cachep);
2675 }
2676 
2677 static const struct address_space_operations shmem_aops = {
2678 	.writepage	= shmem_writepage,
2679 	.set_page_dirty	= __set_page_dirty_no_writeback,
2680 #ifdef CONFIG_TMPFS
2681 	.write_begin	= shmem_write_begin,
2682 	.write_end	= shmem_write_end,
2683 #endif
2684 	.migratepage	= migrate_page,
2685 	.error_remove_page = generic_error_remove_page,
2686 };
2687 
2688 static const struct file_operations shmem_file_operations = {
2689 	.mmap		= shmem_mmap,
2690 #ifdef CONFIG_TMPFS
2691 	.llseek		= shmem_file_llseek,
2692 	.read		= do_sync_read,
2693 	.write		= do_sync_write,
2694 	.aio_read	= shmem_file_aio_read,
2695 	.aio_write	= generic_file_aio_write,
2696 	.fsync		= noop_fsync,
2697 	.splice_read	= shmem_file_splice_read,
2698 	.splice_write	= generic_file_splice_write,
2699 	.fallocate	= shmem_fallocate,
2700 #endif
2701 };
2702 
2703 static const struct inode_operations shmem_inode_operations = {
2704 	.setattr	= shmem_setattr,
2705 #ifdef CONFIG_TMPFS_XATTR
2706 	.setxattr	= shmem_setxattr,
2707 	.getxattr	= shmem_getxattr,
2708 	.listxattr	= shmem_listxattr,
2709 	.removexattr	= shmem_removexattr,
2710 #endif
2711 };
2712 
2713 static const struct inode_operations shmem_dir_inode_operations = {
2714 #ifdef CONFIG_TMPFS
2715 	.create		= shmem_create,
2716 	.lookup		= simple_lookup,
2717 	.link		= shmem_link,
2718 	.unlink		= shmem_unlink,
2719 	.symlink	= shmem_symlink,
2720 	.mkdir		= shmem_mkdir,
2721 	.rmdir		= shmem_rmdir,
2722 	.mknod		= shmem_mknod,
2723 	.rename		= shmem_rename,
2724 #endif
2725 #ifdef CONFIG_TMPFS_XATTR
2726 	.setxattr	= shmem_setxattr,
2727 	.getxattr	= shmem_getxattr,
2728 	.listxattr	= shmem_listxattr,
2729 	.removexattr	= shmem_removexattr,
2730 #endif
2731 #ifdef CONFIG_TMPFS_POSIX_ACL
2732 	.setattr	= shmem_setattr,
2733 #endif
2734 };
2735 
2736 static const struct inode_operations shmem_special_inode_operations = {
2737 #ifdef CONFIG_TMPFS_XATTR
2738 	.setxattr	= shmem_setxattr,
2739 	.getxattr	= shmem_getxattr,
2740 	.listxattr	= shmem_listxattr,
2741 	.removexattr	= shmem_removexattr,
2742 #endif
2743 #ifdef CONFIG_TMPFS_POSIX_ACL
2744 	.setattr	= shmem_setattr,
2745 #endif
2746 };
2747 
2748 static const struct super_operations shmem_ops = {
2749 	.alloc_inode	= shmem_alloc_inode,
2750 	.destroy_inode	= shmem_destroy_inode,
2751 #ifdef CONFIG_TMPFS
2752 	.statfs		= shmem_statfs,
2753 	.remount_fs	= shmem_remount_fs,
2754 	.show_options	= shmem_show_options,
2755 #endif
2756 	.evict_inode	= shmem_evict_inode,
2757 	.drop_inode	= generic_delete_inode,
2758 	.put_super	= shmem_put_super,
2759 };
2760 
2761 static const struct vm_operations_struct shmem_vm_ops = {
2762 	.fault		= shmem_fault,
2763 #ifdef CONFIG_NUMA
2764 	.set_policy     = shmem_set_policy,
2765 	.get_policy     = shmem_get_policy,
2766 #endif
2767 	.remap_pages	= generic_file_remap_pages,
2768 };
2769 
2770 static struct dentry *shmem_mount(struct file_system_type *fs_type,
2771 	int flags, const char *dev_name, void *data)
2772 {
2773 	return mount_nodev(fs_type, flags, data, shmem_fill_super);
2774 }
2775 
2776 static struct file_system_type shmem_fs_type = {
2777 	.owner		= THIS_MODULE,
2778 	.name		= "tmpfs",
2779 	.mount		= shmem_mount,
2780 	.kill_sb	= kill_litter_super,
2781 	.fs_flags	= FS_USERNS_MOUNT,
2782 };
2783 
2784 int __init shmem_init(void)
2785 {
2786 	int error;
2787 
2788 	error = bdi_init(&shmem_backing_dev_info);
2789 	if (error)
2790 		goto out4;
2791 
2792 	error = shmem_init_inodecache();
2793 	if (error)
2794 		goto out3;
2795 
2796 	error = register_filesystem(&shmem_fs_type);
2797 	if (error) {
2798 		printk(KERN_ERR "Could not register tmpfs\n");
2799 		goto out2;
2800 	}
2801 
2802 	shm_mnt = vfs_kern_mount(&shmem_fs_type, MS_NOUSER,
2803 				 shmem_fs_type.name, NULL);
2804 	if (IS_ERR(shm_mnt)) {
2805 		error = PTR_ERR(shm_mnt);
2806 		printk(KERN_ERR "Could not kern_mount tmpfs\n");
2807 		goto out1;
2808 	}
2809 	return 0;
2810 
2811 out1:
2812 	unregister_filesystem(&shmem_fs_type);
2813 out2:
2814 	shmem_destroy_inodecache();
2815 out3:
2816 	bdi_destroy(&shmem_backing_dev_info);
2817 out4:
2818 	shm_mnt = ERR_PTR(error);
2819 	return error;
2820 }
2821 
2822 #else /* !CONFIG_SHMEM */
2823 
2824 /*
2825  * tiny-shmem: simple shmemfs and tmpfs using ramfs code
2826  *
2827  * This is intended for small system where the benefits of the full
2828  * shmem code (swap-backed and resource-limited) are outweighed by
2829  * their complexity. On systems without swap this code should be
2830  * effectively equivalent, but much lighter weight.
2831  */
2832 
2833 #include <linux/ramfs.h>
2834 
2835 static struct file_system_type shmem_fs_type = {
2836 	.name		= "tmpfs",
2837 	.mount		= ramfs_mount,
2838 	.kill_sb	= kill_litter_super,
2839 	.fs_flags	= FS_USERNS_MOUNT,
2840 };
2841 
2842 int __init shmem_init(void)
2843 {
2844 	BUG_ON(register_filesystem(&shmem_fs_type) != 0);
2845 
2846 	shm_mnt = kern_mount(&shmem_fs_type);
2847 	BUG_ON(IS_ERR(shm_mnt));
2848 
2849 	return 0;
2850 }
2851 
2852 int shmem_unuse(swp_entry_t swap, struct page *page)
2853 {
2854 	return 0;
2855 }
2856 
2857 int shmem_lock(struct file *file, int lock, struct user_struct *user)
2858 {
2859 	return 0;
2860 }
2861 
2862 void shmem_unlock_mapping(struct address_space *mapping)
2863 {
2864 }
2865 
2866 void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
2867 {
2868 	truncate_inode_pages_range(inode->i_mapping, lstart, lend);
2869 }
2870 EXPORT_SYMBOL_GPL(shmem_truncate_range);
2871 
2872 #define shmem_vm_ops				generic_file_vm_ops
2873 #define shmem_file_operations			ramfs_file_operations
2874 #define shmem_get_inode(sb, dir, mode, dev, flags)	ramfs_get_inode(sb, dir, mode, dev)
2875 #define shmem_acct_size(flags, size)		0
2876 #define shmem_unacct_size(flags, size)		do {} while (0)
2877 
2878 #endif /* CONFIG_SHMEM */
2879 
2880 /* common code */
2881 
2882 static char *shmem_dname(struct dentry *dentry, char *buffer, int buflen)
2883 {
2884 	return dynamic_dname(dentry, buffer, buflen, "/%s (deleted)",
2885 				dentry->d_name.name);
2886 }
2887 
2888 static struct dentry_operations anon_ops = {
2889 	.d_dname = shmem_dname
2890 };
2891 
2892 /**
2893  * shmem_file_setup - get an unlinked file living in tmpfs
2894  * @name: name for dentry (to be seen in /proc/<pid>/maps
2895  * @size: size to be set for the file
2896  * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
2897  */
2898 struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags)
2899 {
2900 	struct file *res;
2901 	struct inode *inode;
2902 	struct path path;
2903 	struct super_block *sb;
2904 	struct qstr this;
2905 
2906 	if (IS_ERR(shm_mnt))
2907 		return ERR_CAST(shm_mnt);
2908 
2909 	if (size < 0 || size > MAX_LFS_FILESIZE)
2910 		return ERR_PTR(-EINVAL);
2911 
2912 	if (shmem_acct_size(flags, size))
2913 		return ERR_PTR(-ENOMEM);
2914 
2915 	res = ERR_PTR(-ENOMEM);
2916 	this.name = name;
2917 	this.len = strlen(name);
2918 	this.hash = 0; /* will go */
2919 	sb = shm_mnt->mnt_sb;
2920 	path.dentry = d_alloc_pseudo(sb, &this);
2921 	if (!path.dentry)
2922 		goto put_memory;
2923 	d_set_d_op(path.dentry, &anon_ops);
2924 	path.mnt = mntget(shm_mnt);
2925 
2926 	res = ERR_PTR(-ENOSPC);
2927 	inode = shmem_get_inode(sb, NULL, S_IFREG | S_IRWXUGO, 0, flags);
2928 	if (!inode)
2929 		goto put_dentry;
2930 
2931 	d_instantiate(path.dentry, inode);
2932 	inode->i_size = size;
2933 	clear_nlink(inode);	/* It is unlinked */
2934 #ifndef CONFIG_MMU
2935 	res = ERR_PTR(ramfs_nommu_expand_for_mapping(inode, size));
2936 	if (IS_ERR(res))
2937 		goto put_dentry;
2938 #endif
2939 
2940 	res = alloc_file(&path, FMODE_WRITE | FMODE_READ,
2941 		  &shmem_file_operations);
2942 	if (IS_ERR(res))
2943 		goto put_dentry;
2944 
2945 	return res;
2946 
2947 put_dentry:
2948 	path_put(&path);
2949 put_memory:
2950 	shmem_unacct_size(flags, size);
2951 	return res;
2952 }
2953 EXPORT_SYMBOL_GPL(shmem_file_setup);
2954 
2955 /**
2956  * shmem_zero_setup - setup a shared anonymous mapping
2957  * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
2958  */
2959 int shmem_zero_setup(struct vm_area_struct *vma)
2960 {
2961 	struct file *file;
2962 	loff_t size = vma->vm_end - vma->vm_start;
2963 
2964 	file = shmem_file_setup("dev/zero", size, vma->vm_flags);
2965 	if (IS_ERR(file))
2966 		return PTR_ERR(file);
2967 
2968 	if (vma->vm_file)
2969 		fput(vma->vm_file);
2970 	vma->vm_file = file;
2971 	vma->vm_ops = &shmem_vm_ops;
2972 	return 0;
2973 }
2974 
2975 /**
2976  * shmem_read_mapping_page_gfp - read into page cache, using specified page allocation flags.
2977  * @mapping:	the page's address_space
2978  * @index:	the page index
2979  * @gfp:	the page allocator flags to use if allocating
2980  *
2981  * This behaves as a tmpfs "read_cache_page_gfp(mapping, index, gfp)",
2982  * with any new page allocations done using the specified allocation flags.
2983  * But read_cache_page_gfp() uses the ->readpage() method: which does not
2984  * suit tmpfs, since it may have pages in swapcache, and needs to find those
2985  * for itself; although drivers/gpu/drm i915 and ttm rely upon this support.
2986  *
2987  * i915_gem_object_get_pages_gtt() mixes __GFP_NORETRY | __GFP_NOWARN in
2988  * with the mapping_gfp_mask(), to avoid OOMing the machine unnecessarily.
2989  */
2990 struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
2991 					 pgoff_t index, gfp_t gfp)
2992 {
2993 #ifdef CONFIG_SHMEM
2994 	struct inode *inode = mapping->host;
2995 	struct page *page;
2996 	int error;
2997 
2998 	BUG_ON(mapping->a_ops != &shmem_aops);
2999 	error = shmem_getpage_gfp(inode, index, &page, SGP_CACHE, gfp, NULL);
3000 	if (error)
3001 		page = ERR_PTR(error);
3002 	else
3003 		unlock_page(page);
3004 	return page;
3005 #else
3006 	/*
3007 	 * The tiny !SHMEM case uses ramfs without swap
3008 	 */
3009 	return read_cache_page_gfp(mapping, index, gfp);
3010 #endif
3011 }
3012 EXPORT_SYMBOL_GPL(shmem_read_mapping_page_gfp);
3013