xref: /openbmc/linux/mm/shmem.c (revision f3b827e0b1841f4cfc18436e09f4f269f3be908e)
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/ramfs.h>
29 #include <linux/pagemap.h>
30 #include <linux/file.h>
31 #include <linux/mm.h>
32 #include <linux/export.h>
33 #include <linux/swap.h>
34 #include <linux/uio.h>
35 #include <linux/khugepaged.h>
36 
37 static struct vfsmount *shm_mnt;
38 
39 #ifdef CONFIG_SHMEM
40 /*
41  * This virtual memory filesystem is heavily based on the ramfs. It
42  * extends ramfs by the ability to use swap and honor resource limits
43  * which makes it a completely usable filesystem.
44  */
45 
46 #include <linux/xattr.h>
47 #include <linux/exportfs.h>
48 #include <linux/posix_acl.h>
49 #include <linux/posix_acl_xattr.h>
50 #include <linux/mman.h>
51 #include <linux/string.h>
52 #include <linux/slab.h>
53 #include <linux/backing-dev.h>
54 #include <linux/shmem_fs.h>
55 #include <linux/writeback.h>
56 #include <linux/blkdev.h>
57 #include <linux/pagevec.h>
58 #include <linux/percpu_counter.h>
59 #include <linux/falloc.h>
60 #include <linux/splice.h>
61 #include <linux/security.h>
62 #include <linux/swapops.h>
63 #include <linux/mempolicy.h>
64 #include <linux/namei.h>
65 #include <linux/ctype.h>
66 #include <linux/migrate.h>
67 #include <linux/highmem.h>
68 #include <linux/seq_file.h>
69 #include <linux/magic.h>
70 #include <linux/syscalls.h>
71 #include <linux/fcntl.h>
72 #include <uapi/linux/memfd.h>
73 
74 #include <linux/uaccess.h>
75 #include <asm/pgtable.h>
76 
77 #include "internal.h"
78 
79 #define BLOCKS_PER_PAGE  (PAGE_SIZE/512)
80 #define VM_ACCT(size)    (PAGE_ALIGN(size) >> PAGE_SHIFT)
81 
82 /* Pretend that each entry is of this size in directory's i_size */
83 #define BOGO_DIRENT_SIZE 20
84 
85 /* Symlink up to this size is kmalloc'ed instead of using a swappable page */
86 #define SHORT_SYMLINK_LEN 128
87 
88 /*
89  * shmem_fallocate communicates with shmem_fault or shmem_writepage via
90  * inode->i_private (with i_mutex making sure that it has only one user at
91  * a time): we would prefer not to enlarge the shmem inode just for that.
92  */
93 struct shmem_falloc {
94 	wait_queue_head_t *waitq; /* faults into hole wait for punch to end */
95 	pgoff_t start;		/* start of range currently being fallocated */
96 	pgoff_t next;		/* the next page offset to be fallocated */
97 	pgoff_t nr_falloced;	/* how many new pages have been fallocated */
98 	pgoff_t nr_unswapped;	/* how often writepage refused to swap out */
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,
118 		gfp_t gfp, struct mm_struct *fault_mm, int *fault_type);
119 
120 int shmem_getpage(struct inode *inode, pgoff_t index,
121 		struct page **pagep, enum sgp_type sgp)
122 {
123 	return shmem_getpage_gfp(inode, index, pagep, sgp,
124 		mapping_gfp_mask(inode->i_mapping), NULL, NULL);
125 }
126 
127 static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
128 {
129 	return sb->s_fs_info;
130 }
131 
132 /*
133  * shmem_file_setup pre-accounts the whole fixed size of a VM object,
134  * for shared memory and for shared anonymous (/dev/zero) mappings
135  * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
136  * consistent with the pre-accounting of private mappings ...
137  */
138 static inline int shmem_acct_size(unsigned long flags, loff_t size)
139 {
140 	return (flags & VM_NORESERVE) ?
141 		0 : security_vm_enough_memory_mm(current->mm, VM_ACCT(size));
142 }
143 
144 static inline void shmem_unacct_size(unsigned long flags, loff_t size)
145 {
146 	if (!(flags & VM_NORESERVE))
147 		vm_unacct_memory(VM_ACCT(size));
148 }
149 
150 static inline int shmem_reacct_size(unsigned long flags,
151 		loff_t oldsize, loff_t newsize)
152 {
153 	if (!(flags & VM_NORESERVE)) {
154 		if (VM_ACCT(newsize) > VM_ACCT(oldsize))
155 			return security_vm_enough_memory_mm(current->mm,
156 					VM_ACCT(newsize) - VM_ACCT(oldsize));
157 		else if (VM_ACCT(newsize) < VM_ACCT(oldsize))
158 			vm_unacct_memory(VM_ACCT(oldsize) - VM_ACCT(newsize));
159 	}
160 	return 0;
161 }
162 
163 /*
164  * ... whereas tmpfs objects are accounted incrementally as
165  * pages are allocated, in order to allow large sparse files.
166  * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
167  * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
168  */
169 static inline int shmem_acct_block(unsigned long flags, long pages)
170 {
171 	if (!(flags & VM_NORESERVE))
172 		return 0;
173 
174 	return security_vm_enough_memory_mm(current->mm,
175 			pages * VM_ACCT(PAGE_SIZE));
176 }
177 
178 static inline void shmem_unacct_blocks(unsigned long flags, long pages)
179 {
180 	if (flags & VM_NORESERVE)
181 		vm_unacct_memory(pages * VM_ACCT(PAGE_SIZE));
182 }
183 
184 static const struct super_operations shmem_ops;
185 static const struct address_space_operations shmem_aops;
186 static const struct file_operations shmem_file_operations;
187 static const struct inode_operations shmem_inode_operations;
188 static const struct inode_operations shmem_dir_inode_operations;
189 static const struct inode_operations shmem_special_inode_operations;
190 static const struct vm_operations_struct shmem_vm_ops;
191 static struct file_system_type shmem_fs_type;
192 
193 static LIST_HEAD(shmem_swaplist);
194 static DEFINE_MUTEX(shmem_swaplist_mutex);
195 
196 static int shmem_reserve_inode(struct super_block *sb)
197 {
198 	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
199 	if (sbinfo->max_inodes) {
200 		spin_lock(&sbinfo->stat_lock);
201 		if (!sbinfo->free_inodes) {
202 			spin_unlock(&sbinfo->stat_lock);
203 			return -ENOSPC;
204 		}
205 		sbinfo->free_inodes--;
206 		spin_unlock(&sbinfo->stat_lock);
207 	}
208 	return 0;
209 }
210 
211 static void shmem_free_inode(struct super_block *sb)
212 {
213 	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
214 	if (sbinfo->max_inodes) {
215 		spin_lock(&sbinfo->stat_lock);
216 		sbinfo->free_inodes++;
217 		spin_unlock(&sbinfo->stat_lock);
218 	}
219 }
220 
221 /**
222  * shmem_recalc_inode - recalculate the block usage of an inode
223  * @inode: inode to recalc
224  *
225  * We have to calculate the free blocks since the mm can drop
226  * undirtied hole pages behind our back.
227  *
228  * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
229  * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
230  *
231  * It has to be called with the spinlock held.
232  */
233 static void shmem_recalc_inode(struct inode *inode)
234 {
235 	struct shmem_inode_info *info = SHMEM_I(inode);
236 	long freed;
237 
238 	freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
239 	if (freed > 0) {
240 		struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
241 		if (sbinfo->max_blocks)
242 			percpu_counter_add(&sbinfo->used_blocks, -freed);
243 		info->alloced -= freed;
244 		inode->i_blocks -= freed * BLOCKS_PER_PAGE;
245 		shmem_unacct_blocks(info->flags, freed);
246 	}
247 }
248 
249 bool shmem_charge(struct inode *inode, long pages)
250 {
251 	struct shmem_inode_info *info = SHMEM_I(inode);
252 	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
253 	unsigned long flags;
254 
255 	if (shmem_acct_block(info->flags, pages))
256 		return false;
257 	spin_lock_irqsave(&info->lock, flags);
258 	info->alloced += pages;
259 	inode->i_blocks += pages * BLOCKS_PER_PAGE;
260 	shmem_recalc_inode(inode);
261 	spin_unlock_irqrestore(&info->lock, flags);
262 	inode->i_mapping->nrpages += pages;
263 
264 	if (!sbinfo->max_blocks)
265 		return true;
266 	if (percpu_counter_compare(&sbinfo->used_blocks,
267 				sbinfo->max_blocks - pages) > 0) {
268 		inode->i_mapping->nrpages -= pages;
269 		spin_lock_irqsave(&info->lock, flags);
270 		info->alloced -= pages;
271 		shmem_recalc_inode(inode);
272 		spin_unlock_irqrestore(&info->lock, flags);
273 		shmem_unacct_blocks(info->flags, pages);
274 		return false;
275 	}
276 	percpu_counter_add(&sbinfo->used_blocks, pages);
277 	return true;
278 }
279 
280 void shmem_uncharge(struct inode *inode, long pages)
281 {
282 	struct shmem_inode_info *info = SHMEM_I(inode);
283 	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
284 	unsigned long flags;
285 
286 	spin_lock_irqsave(&info->lock, flags);
287 	info->alloced -= pages;
288 	inode->i_blocks -= pages * BLOCKS_PER_PAGE;
289 	shmem_recalc_inode(inode);
290 	spin_unlock_irqrestore(&info->lock, flags);
291 
292 	if (sbinfo->max_blocks)
293 		percpu_counter_sub(&sbinfo->used_blocks, pages);
294 	shmem_unacct_blocks(info->flags, pages);
295 }
296 
297 /*
298  * Replace item expected in radix tree by a new item, while holding tree lock.
299  */
300 static int shmem_radix_tree_replace(struct address_space *mapping,
301 			pgoff_t index, void *expected, void *replacement)
302 {
303 	struct radix_tree_node *node;
304 	void **pslot;
305 	void *item;
306 
307 	VM_BUG_ON(!expected);
308 	VM_BUG_ON(!replacement);
309 	item = __radix_tree_lookup(&mapping->page_tree, index, &node, &pslot);
310 	if (!item)
311 		return -ENOENT;
312 	if (item != expected)
313 		return -ENOENT;
314 	__radix_tree_replace(&mapping->page_tree, node, pslot,
315 			     replacement, NULL, NULL);
316 	return 0;
317 }
318 
319 /*
320  * Sometimes, before we decide whether to proceed or to fail, we must check
321  * that an entry was not already brought back from swap by a racing thread.
322  *
323  * Checking page is not enough: by the time a SwapCache page is locked, it
324  * might be reused, and again be SwapCache, using the same swap as before.
325  */
326 static bool shmem_confirm_swap(struct address_space *mapping,
327 			       pgoff_t index, swp_entry_t swap)
328 {
329 	void *item;
330 
331 	rcu_read_lock();
332 	item = radix_tree_lookup(&mapping->page_tree, index);
333 	rcu_read_unlock();
334 	return item == swp_to_radix_entry(swap);
335 }
336 
337 /*
338  * Definitions for "huge tmpfs": tmpfs mounted with the huge= option
339  *
340  * SHMEM_HUGE_NEVER:
341  *	disables huge pages for the mount;
342  * SHMEM_HUGE_ALWAYS:
343  *	enables huge pages for the mount;
344  * SHMEM_HUGE_WITHIN_SIZE:
345  *	only allocate huge pages if the page will be fully within i_size,
346  *	also respect fadvise()/madvise() hints;
347  * SHMEM_HUGE_ADVISE:
348  *	only allocate huge pages if requested with fadvise()/madvise();
349  */
350 
351 #define SHMEM_HUGE_NEVER	0
352 #define SHMEM_HUGE_ALWAYS	1
353 #define SHMEM_HUGE_WITHIN_SIZE	2
354 #define SHMEM_HUGE_ADVISE	3
355 
356 /*
357  * Special values.
358  * Only can be set via /sys/kernel/mm/transparent_hugepage/shmem_enabled:
359  *
360  * SHMEM_HUGE_DENY:
361  *	disables huge on shm_mnt and all mounts, for emergency use;
362  * SHMEM_HUGE_FORCE:
363  *	enables huge on shm_mnt and all mounts, w/o needing option, for testing;
364  *
365  */
366 #define SHMEM_HUGE_DENY		(-1)
367 #define SHMEM_HUGE_FORCE	(-2)
368 
369 #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
370 /* ifdef here to avoid bloating shmem.o when not necessary */
371 
372 int shmem_huge __read_mostly;
373 
374 #if defined(CONFIG_SYSFS) || defined(CONFIG_TMPFS)
375 static int shmem_parse_huge(const char *str)
376 {
377 	if (!strcmp(str, "never"))
378 		return SHMEM_HUGE_NEVER;
379 	if (!strcmp(str, "always"))
380 		return SHMEM_HUGE_ALWAYS;
381 	if (!strcmp(str, "within_size"))
382 		return SHMEM_HUGE_WITHIN_SIZE;
383 	if (!strcmp(str, "advise"))
384 		return SHMEM_HUGE_ADVISE;
385 	if (!strcmp(str, "deny"))
386 		return SHMEM_HUGE_DENY;
387 	if (!strcmp(str, "force"))
388 		return SHMEM_HUGE_FORCE;
389 	return -EINVAL;
390 }
391 
392 static const char *shmem_format_huge(int huge)
393 {
394 	switch (huge) {
395 	case SHMEM_HUGE_NEVER:
396 		return "never";
397 	case SHMEM_HUGE_ALWAYS:
398 		return "always";
399 	case SHMEM_HUGE_WITHIN_SIZE:
400 		return "within_size";
401 	case SHMEM_HUGE_ADVISE:
402 		return "advise";
403 	case SHMEM_HUGE_DENY:
404 		return "deny";
405 	case SHMEM_HUGE_FORCE:
406 		return "force";
407 	default:
408 		VM_BUG_ON(1);
409 		return "bad_val";
410 	}
411 }
412 #endif
413 
414 static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
415 		struct shrink_control *sc, unsigned long nr_to_split)
416 {
417 	LIST_HEAD(list), *pos, *next;
418 	LIST_HEAD(to_remove);
419 	struct inode *inode;
420 	struct shmem_inode_info *info;
421 	struct page *page;
422 	unsigned long batch = sc ? sc->nr_to_scan : 128;
423 	int removed = 0, split = 0;
424 
425 	if (list_empty(&sbinfo->shrinklist))
426 		return SHRINK_STOP;
427 
428 	spin_lock(&sbinfo->shrinklist_lock);
429 	list_for_each_safe(pos, next, &sbinfo->shrinklist) {
430 		info = list_entry(pos, struct shmem_inode_info, shrinklist);
431 
432 		/* pin the inode */
433 		inode = igrab(&info->vfs_inode);
434 
435 		/* inode is about to be evicted */
436 		if (!inode) {
437 			list_del_init(&info->shrinklist);
438 			removed++;
439 			goto next;
440 		}
441 
442 		/* Check if there's anything to gain */
443 		if (round_up(inode->i_size, PAGE_SIZE) ==
444 				round_up(inode->i_size, HPAGE_PMD_SIZE)) {
445 			list_move(&info->shrinklist, &to_remove);
446 			removed++;
447 			goto next;
448 		}
449 
450 		list_move(&info->shrinklist, &list);
451 next:
452 		if (!--batch)
453 			break;
454 	}
455 	spin_unlock(&sbinfo->shrinklist_lock);
456 
457 	list_for_each_safe(pos, next, &to_remove) {
458 		info = list_entry(pos, struct shmem_inode_info, shrinklist);
459 		inode = &info->vfs_inode;
460 		list_del_init(&info->shrinklist);
461 		iput(inode);
462 	}
463 
464 	list_for_each_safe(pos, next, &list) {
465 		int ret;
466 
467 		info = list_entry(pos, struct shmem_inode_info, shrinklist);
468 		inode = &info->vfs_inode;
469 
470 		if (nr_to_split && split >= nr_to_split) {
471 			iput(inode);
472 			continue;
473 		}
474 
475 		page = find_lock_page(inode->i_mapping,
476 				(inode->i_size & HPAGE_PMD_MASK) >> PAGE_SHIFT);
477 		if (!page)
478 			goto drop;
479 
480 		if (!PageTransHuge(page)) {
481 			unlock_page(page);
482 			put_page(page);
483 			goto drop;
484 		}
485 
486 		ret = split_huge_page(page);
487 		unlock_page(page);
488 		put_page(page);
489 
490 		if (ret) {
491 			/* split failed: leave it on the list */
492 			iput(inode);
493 			continue;
494 		}
495 
496 		split++;
497 drop:
498 		list_del_init(&info->shrinklist);
499 		removed++;
500 		iput(inode);
501 	}
502 
503 	spin_lock(&sbinfo->shrinklist_lock);
504 	list_splice_tail(&list, &sbinfo->shrinklist);
505 	sbinfo->shrinklist_len -= removed;
506 	spin_unlock(&sbinfo->shrinklist_lock);
507 
508 	return split;
509 }
510 
511 static long shmem_unused_huge_scan(struct super_block *sb,
512 		struct shrink_control *sc)
513 {
514 	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
515 
516 	if (!READ_ONCE(sbinfo->shrinklist_len))
517 		return SHRINK_STOP;
518 
519 	return shmem_unused_huge_shrink(sbinfo, sc, 0);
520 }
521 
522 static long shmem_unused_huge_count(struct super_block *sb,
523 		struct shrink_control *sc)
524 {
525 	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
526 	return READ_ONCE(sbinfo->shrinklist_len);
527 }
528 #else /* !CONFIG_TRANSPARENT_HUGE_PAGECACHE */
529 
530 #define shmem_huge SHMEM_HUGE_DENY
531 
532 static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
533 		struct shrink_control *sc, unsigned long nr_to_split)
534 {
535 	return 0;
536 }
537 #endif /* CONFIG_TRANSPARENT_HUGE_PAGECACHE */
538 
539 /*
540  * Like add_to_page_cache_locked, but error if expected item has gone.
541  */
542 static int shmem_add_to_page_cache(struct page *page,
543 				   struct address_space *mapping,
544 				   pgoff_t index, void *expected)
545 {
546 	int error, nr = hpage_nr_pages(page);
547 
548 	VM_BUG_ON_PAGE(PageTail(page), page);
549 	VM_BUG_ON_PAGE(index != round_down(index, nr), page);
550 	VM_BUG_ON_PAGE(!PageLocked(page), page);
551 	VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
552 	VM_BUG_ON(expected && PageTransHuge(page));
553 
554 	page_ref_add(page, nr);
555 	page->mapping = mapping;
556 	page->index = index;
557 
558 	spin_lock_irq(&mapping->tree_lock);
559 	if (PageTransHuge(page)) {
560 		void __rcu **results;
561 		pgoff_t idx;
562 		int i;
563 
564 		error = 0;
565 		if (radix_tree_gang_lookup_slot(&mapping->page_tree,
566 					&results, &idx, index, 1) &&
567 				idx < index + HPAGE_PMD_NR) {
568 			error = -EEXIST;
569 		}
570 
571 		if (!error) {
572 			for (i = 0; i < HPAGE_PMD_NR; i++) {
573 				error = radix_tree_insert(&mapping->page_tree,
574 						index + i, page + i);
575 				VM_BUG_ON(error);
576 			}
577 			count_vm_event(THP_FILE_ALLOC);
578 		}
579 	} else if (!expected) {
580 		error = radix_tree_insert(&mapping->page_tree, index, page);
581 	} else {
582 		error = shmem_radix_tree_replace(mapping, index, expected,
583 								 page);
584 	}
585 
586 	if (!error) {
587 		mapping->nrpages += nr;
588 		if (PageTransHuge(page))
589 			__inc_node_page_state(page, NR_SHMEM_THPS);
590 		__mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, nr);
591 		__mod_node_page_state(page_pgdat(page), NR_SHMEM, nr);
592 		spin_unlock_irq(&mapping->tree_lock);
593 	} else {
594 		page->mapping = NULL;
595 		spin_unlock_irq(&mapping->tree_lock);
596 		page_ref_sub(page, nr);
597 	}
598 	return error;
599 }
600 
601 /*
602  * Like delete_from_page_cache, but substitutes swap for page.
603  */
604 static void shmem_delete_from_page_cache(struct page *page, void *radswap)
605 {
606 	struct address_space *mapping = page->mapping;
607 	int error;
608 
609 	VM_BUG_ON_PAGE(PageCompound(page), page);
610 
611 	spin_lock_irq(&mapping->tree_lock);
612 	error = shmem_radix_tree_replace(mapping, page->index, page, radswap);
613 	page->mapping = NULL;
614 	mapping->nrpages--;
615 	__dec_node_page_state(page, NR_FILE_PAGES);
616 	__dec_node_page_state(page, NR_SHMEM);
617 	spin_unlock_irq(&mapping->tree_lock);
618 	put_page(page);
619 	BUG_ON(error);
620 }
621 
622 /*
623  * Remove swap entry from radix tree, free the swap and its page cache.
624  */
625 static int shmem_free_swap(struct address_space *mapping,
626 			   pgoff_t index, void *radswap)
627 {
628 	void *old;
629 
630 	spin_lock_irq(&mapping->tree_lock);
631 	old = radix_tree_delete_item(&mapping->page_tree, index, radswap);
632 	spin_unlock_irq(&mapping->tree_lock);
633 	if (old != radswap)
634 		return -ENOENT;
635 	free_swap_and_cache(radix_to_swp_entry(radswap));
636 	return 0;
637 }
638 
639 /*
640  * Determine (in bytes) how many of the shmem object's pages mapped by the
641  * given offsets are swapped out.
642  *
643  * This is safe to call without i_mutex or mapping->tree_lock thanks to RCU,
644  * as long as the inode doesn't go away and racy results are not a problem.
645  */
646 unsigned long shmem_partial_swap_usage(struct address_space *mapping,
647 						pgoff_t start, pgoff_t end)
648 {
649 	struct radix_tree_iter iter;
650 	void **slot;
651 	struct page *page;
652 	unsigned long swapped = 0;
653 
654 	rcu_read_lock();
655 
656 	radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
657 		if (iter.index >= end)
658 			break;
659 
660 		page = radix_tree_deref_slot(slot);
661 
662 		if (radix_tree_deref_retry(page)) {
663 			slot = radix_tree_iter_retry(&iter);
664 			continue;
665 		}
666 
667 		if (radix_tree_exceptional_entry(page))
668 			swapped++;
669 
670 		if (need_resched()) {
671 			slot = radix_tree_iter_resume(slot, &iter);
672 			cond_resched_rcu();
673 		}
674 	}
675 
676 	rcu_read_unlock();
677 
678 	return swapped << PAGE_SHIFT;
679 }
680 
681 /*
682  * Determine (in bytes) how many of the shmem object's pages mapped by the
683  * given vma is swapped out.
684  *
685  * This is safe to call without i_mutex or mapping->tree_lock thanks to RCU,
686  * as long as the inode doesn't go away and racy results are not a problem.
687  */
688 unsigned long shmem_swap_usage(struct vm_area_struct *vma)
689 {
690 	struct inode *inode = file_inode(vma->vm_file);
691 	struct shmem_inode_info *info = SHMEM_I(inode);
692 	struct address_space *mapping = inode->i_mapping;
693 	unsigned long swapped;
694 
695 	/* Be careful as we don't hold info->lock */
696 	swapped = READ_ONCE(info->swapped);
697 
698 	/*
699 	 * The easier cases are when the shmem object has nothing in swap, or
700 	 * the vma maps it whole. Then we can simply use the stats that we
701 	 * already track.
702 	 */
703 	if (!swapped)
704 		return 0;
705 
706 	if (!vma->vm_pgoff && vma->vm_end - vma->vm_start >= inode->i_size)
707 		return swapped << PAGE_SHIFT;
708 
709 	/* Here comes the more involved part */
710 	return shmem_partial_swap_usage(mapping,
711 			linear_page_index(vma, vma->vm_start),
712 			linear_page_index(vma, vma->vm_end));
713 }
714 
715 /*
716  * SysV IPC SHM_UNLOCK restore Unevictable pages to their evictable lists.
717  */
718 void shmem_unlock_mapping(struct address_space *mapping)
719 {
720 	struct pagevec pvec;
721 	pgoff_t indices[PAGEVEC_SIZE];
722 	pgoff_t index = 0;
723 
724 	pagevec_init(&pvec, 0);
725 	/*
726 	 * Minor point, but we might as well stop if someone else SHM_LOCKs it.
727 	 */
728 	while (!mapping_unevictable(mapping)) {
729 		/*
730 		 * Avoid pagevec_lookup(): find_get_pages() returns 0 as if it
731 		 * has finished, if it hits a row of PAGEVEC_SIZE swap entries.
732 		 */
733 		pvec.nr = find_get_entries(mapping, index,
734 					   PAGEVEC_SIZE, pvec.pages, indices);
735 		if (!pvec.nr)
736 			break;
737 		index = indices[pvec.nr - 1] + 1;
738 		pagevec_remove_exceptionals(&pvec);
739 		check_move_unevictable_pages(pvec.pages, pvec.nr);
740 		pagevec_release(&pvec);
741 		cond_resched();
742 	}
743 }
744 
745 /*
746  * Remove range of pages and swap entries from radix tree, and free them.
747  * If !unfalloc, truncate or punch hole; if unfalloc, undo failed fallocate.
748  */
749 static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
750 								 bool unfalloc)
751 {
752 	struct address_space *mapping = inode->i_mapping;
753 	struct shmem_inode_info *info = SHMEM_I(inode);
754 	pgoff_t start = (lstart + PAGE_SIZE - 1) >> PAGE_SHIFT;
755 	pgoff_t end = (lend + 1) >> PAGE_SHIFT;
756 	unsigned int partial_start = lstart & (PAGE_SIZE - 1);
757 	unsigned int partial_end = (lend + 1) & (PAGE_SIZE - 1);
758 	struct pagevec pvec;
759 	pgoff_t indices[PAGEVEC_SIZE];
760 	long nr_swaps_freed = 0;
761 	pgoff_t index;
762 	int i;
763 
764 	if (lend == -1)
765 		end = -1;	/* unsigned, so actually very big */
766 
767 	pagevec_init(&pvec, 0);
768 	index = start;
769 	while (index < end) {
770 		pvec.nr = find_get_entries(mapping, index,
771 			min(end - index, (pgoff_t)PAGEVEC_SIZE),
772 			pvec.pages, indices);
773 		if (!pvec.nr)
774 			break;
775 		for (i = 0; i < pagevec_count(&pvec); i++) {
776 			struct page *page = pvec.pages[i];
777 
778 			index = indices[i];
779 			if (index >= end)
780 				break;
781 
782 			if (radix_tree_exceptional_entry(page)) {
783 				if (unfalloc)
784 					continue;
785 				nr_swaps_freed += !shmem_free_swap(mapping,
786 								index, page);
787 				continue;
788 			}
789 
790 			VM_BUG_ON_PAGE(page_to_pgoff(page) != index, page);
791 
792 			if (!trylock_page(page))
793 				continue;
794 
795 			if (PageTransTail(page)) {
796 				/* Middle of THP: zero out the page */
797 				clear_highpage(page);
798 				unlock_page(page);
799 				continue;
800 			} else if (PageTransHuge(page)) {
801 				if (index == round_down(end, HPAGE_PMD_NR)) {
802 					/*
803 					 * Range ends in the middle of THP:
804 					 * zero out the page
805 					 */
806 					clear_highpage(page);
807 					unlock_page(page);
808 					continue;
809 				}
810 				index += HPAGE_PMD_NR - 1;
811 				i += HPAGE_PMD_NR - 1;
812 			}
813 
814 			if (!unfalloc || !PageUptodate(page)) {
815 				VM_BUG_ON_PAGE(PageTail(page), page);
816 				if (page_mapping(page) == mapping) {
817 					VM_BUG_ON_PAGE(PageWriteback(page), page);
818 					truncate_inode_page(mapping, page);
819 				}
820 			}
821 			unlock_page(page);
822 		}
823 		pagevec_remove_exceptionals(&pvec);
824 		pagevec_release(&pvec);
825 		cond_resched();
826 		index++;
827 	}
828 
829 	if (partial_start) {
830 		struct page *page = NULL;
831 		shmem_getpage(inode, start - 1, &page, SGP_READ);
832 		if (page) {
833 			unsigned int top = PAGE_SIZE;
834 			if (start > end) {
835 				top = partial_end;
836 				partial_end = 0;
837 			}
838 			zero_user_segment(page, partial_start, top);
839 			set_page_dirty(page);
840 			unlock_page(page);
841 			put_page(page);
842 		}
843 	}
844 	if (partial_end) {
845 		struct page *page = NULL;
846 		shmem_getpage(inode, end, &page, SGP_READ);
847 		if (page) {
848 			zero_user_segment(page, 0, partial_end);
849 			set_page_dirty(page);
850 			unlock_page(page);
851 			put_page(page);
852 		}
853 	}
854 	if (start >= end)
855 		return;
856 
857 	index = start;
858 	while (index < end) {
859 		cond_resched();
860 
861 		pvec.nr = find_get_entries(mapping, index,
862 				min(end - index, (pgoff_t)PAGEVEC_SIZE),
863 				pvec.pages, indices);
864 		if (!pvec.nr) {
865 			/* If all gone or hole-punch or unfalloc, we're done */
866 			if (index == start || end != -1)
867 				break;
868 			/* But if truncating, restart to make sure all gone */
869 			index = start;
870 			continue;
871 		}
872 		for (i = 0; i < pagevec_count(&pvec); i++) {
873 			struct page *page = pvec.pages[i];
874 
875 			index = indices[i];
876 			if (index >= end)
877 				break;
878 
879 			if (radix_tree_exceptional_entry(page)) {
880 				if (unfalloc)
881 					continue;
882 				if (shmem_free_swap(mapping, index, page)) {
883 					/* Swap was replaced by page: retry */
884 					index--;
885 					break;
886 				}
887 				nr_swaps_freed++;
888 				continue;
889 			}
890 
891 			lock_page(page);
892 
893 			if (PageTransTail(page)) {
894 				/* Middle of THP: zero out the page */
895 				clear_highpage(page);
896 				unlock_page(page);
897 				/*
898 				 * Partial thp truncate due 'start' in middle
899 				 * of THP: don't need to look on these pages
900 				 * again on !pvec.nr restart.
901 				 */
902 				if (index != round_down(end, HPAGE_PMD_NR))
903 					start++;
904 				continue;
905 			} else if (PageTransHuge(page)) {
906 				if (index == round_down(end, HPAGE_PMD_NR)) {
907 					/*
908 					 * Range ends in the middle of THP:
909 					 * zero out the page
910 					 */
911 					clear_highpage(page);
912 					unlock_page(page);
913 					continue;
914 				}
915 				index += HPAGE_PMD_NR - 1;
916 				i += HPAGE_PMD_NR - 1;
917 			}
918 
919 			if (!unfalloc || !PageUptodate(page)) {
920 				VM_BUG_ON_PAGE(PageTail(page), page);
921 				if (page_mapping(page) == mapping) {
922 					VM_BUG_ON_PAGE(PageWriteback(page), page);
923 					truncate_inode_page(mapping, page);
924 				} else {
925 					/* Page was replaced by swap: retry */
926 					unlock_page(page);
927 					index--;
928 					break;
929 				}
930 			}
931 			unlock_page(page);
932 		}
933 		pagevec_remove_exceptionals(&pvec);
934 		pagevec_release(&pvec);
935 		index++;
936 	}
937 
938 	spin_lock_irq(&info->lock);
939 	info->swapped -= nr_swaps_freed;
940 	shmem_recalc_inode(inode);
941 	spin_unlock_irq(&info->lock);
942 }
943 
944 void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
945 {
946 	shmem_undo_range(inode, lstart, lend, false);
947 	inode->i_ctime = inode->i_mtime = current_time(inode);
948 }
949 EXPORT_SYMBOL_GPL(shmem_truncate_range);
950 
951 static int shmem_getattr(struct vfsmount *mnt, struct dentry *dentry,
952 			 struct kstat *stat)
953 {
954 	struct inode *inode = dentry->d_inode;
955 	struct shmem_inode_info *info = SHMEM_I(inode);
956 
957 	if (info->alloced - info->swapped != inode->i_mapping->nrpages) {
958 		spin_lock_irq(&info->lock);
959 		shmem_recalc_inode(inode);
960 		spin_unlock_irq(&info->lock);
961 	}
962 	generic_fillattr(inode, stat);
963 	return 0;
964 }
965 
966 static int shmem_setattr(struct dentry *dentry, struct iattr *attr)
967 {
968 	struct inode *inode = d_inode(dentry);
969 	struct shmem_inode_info *info = SHMEM_I(inode);
970 	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
971 	int error;
972 
973 	error = setattr_prepare(dentry, attr);
974 	if (error)
975 		return error;
976 
977 	if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
978 		loff_t oldsize = inode->i_size;
979 		loff_t newsize = attr->ia_size;
980 
981 		/* protected by i_mutex */
982 		if ((newsize < oldsize && (info->seals & F_SEAL_SHRINK)) ||
983 		    (newsize > oldsize && (info->seals & F_SEAL_GROW)))
984 			return -EPERM;
985 
986 		if (newsize != oldsize) {
987 			error = shmem_reacct_size(SHMEM_I(inode)->flags,
988 					oldsize, newsize);
989 			if (error)
990 				return error;
991 			i_size_write(inode, newsize);
992 			inode->i_ctime = inode->i_mtime = current_time(inode);
993 		}
994 		if (newsize <= oldsize) {
995 			loff_t holebegin = round_up(newsize, PAGE_SIZE);
996 			if (oldsize > holebegin)
997 				unmap_mapping_range(inode->i_mapping,
998 							holebegin, 0, 1);
999 			if (info->alloced)
1000 				shmem_truncate_range(inode,
1001 							newsize, (loff_t)-1);
1002 			/* unmap again to remove racily COWed private pages */
1003 			if (oldsize > holebegin)
1004 				unmap_mapping_range(inode->i_mapping,
1005 							holebegin, 0, 1);
1006 
1007 			/*
1008 			 * Part of the huge page can be beyond i_size: subject
1009 			 * to shrink under memory pressure.
1010 			 */
1011 			if (IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE)) {
1012 				spin_lock(&sbinfo->shrinklist_lock);
1013 				if (list_empty(&info->shrinklist)) {
1014 					list_add_tail(&info->shrinklist,
1015 							&sbinfo->shrinklist);
1016 					sbinfo->shrinklist_len++;
1017 				}
1018 				spin_unlock(&sbinfo->shrinklist_lock);
1019 			}
1020 		}
1021 	}
1022 
1023 	setattr_copy(inode, attr);
1024 	if (attr->ia_valid & ATTR_MODE)
1025 		error = posix_acl_chmod(inode, inode->i_mode);
1026 	return error;
1027 }
1028 
1029 static void shmem_evict_inode(struct inode *inode)
1030 {
1031 	struct shmem_inode_info *info = SHMEM_I(inode);
1032 	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
1033 
1034 	if (inode->i_mapping->a_ops == &shmem_aops) {
1035 		shmem_unacct_size(info->flags, inode->i_size);
1036 		inode->i_size = 0;
1037 		shmem_truncate_range(inode, 0, (loff_t)-1);
1038 		if (!list_empty(&info->shrinklist)) {
1039 			spin_lock(&sbinfo->shrinklist_lock);
1040 			if (!list_empty(&info->shrinklist)) {
1041 				list_del_init(&info->shrinklist);
1042 				sbinfo->shrinklist_len--;
1043 			}
1044 			spin_unlock(&sbinfo->shrinklist_lock);
1045 		}
1046 		if (!list_empty(&info->swaplist)) {
1047 			mutex_lock(&shmem_swaplist_mutex);
1048 			list_del_init(&info->swaplist);
1049 			mutex_unlock(&shmem_swaplist_mutex);
1050 		}
1051 	}
1052 
1053 	simple_xattrs_free(&info->xattrs);
1054 	WARN_ON(inode->i_blocks);
1055 	shmem_free_inode(inode->i_sb);
1056 	clear_inode(inode);
1057 }
1058 
1059 static unsigned long find_swap_entry(struct radix_tree_root *root, void *item)
1060 {
1061 	struct radix_tree_iter iter;
1062 	void **slot;
1063 	unsigned long found = -1;
1064 	unsigned int checked = 0;
1065 
1066 	rcu_read_lock();
1067 	radix_tree_for_each_slot(slot, root, &iter, 0) {
1068 		if (*slot == item) {
1069 			found = iter.index;
1070 			break;
1071 		}
1072 		checked++;
1073 		if ((checked % 4096) != 0)
1074 			continue;
1075 		slot = radix_tree_iter_resume(slot, &iter);
1076 		cond_resched_rcu();
1077 	}
1078 
1079 	rcu_read_unlock();
1080 	return found;
1081 }
1082 
1083 /*
1084  * If swap found in inode, free it and move page from swapcache to filecache.
1085  */
1086 static int shmem_unuse_inode(struct shmem_inode_info *info,
1087 			     swp_entry_t swap, struct page **pagep)
1088 {
1089 	struct address_space *mapping = info->vfs_inode.i_mapping;
1090 	void *radswap;
1091 	pgoff_t index;
1092 	gfp_t gfp;
1093 	int error = 0;
1094 
1095 	radswap = swp_to_radix_entry(swap);
1096 	index = find_swap_entry(&mapping->page_tree, radswap);
1097 	if (index == -1)
1098 		return -EAGAIN;	/* tell shmem_unuse we found nothing */
1099 
1100 	/*
1101 	 * Move _head_ to start search for next from here.
1102 	 * But be careful: shmem_evict_inode checks list_empty without taking
1103 	 * mutex, and there's an instant in list_move_tail when info->swaplist
1104 	 * would appear empty, if it were the only one on shmem_swaplist.
1105 	 */
1106 	if (shmem_swaplist.next != &info->swaplist)
1107 		list_move_tail(&shmem_swaplist, &info->swaplist);
1108 
1109 	gfp = mapping_gfp_mask(mapping);
1110 	if (shmem_should_replace_page(*pagep, gfp)) {
1111 		mutex_unlock(&shmem_swaplist_mutex);
1112 		error = shmem_replace_page(pagep, gfp, info, index);
1113 		mutex_lock(&shmem_swaplist_mutex);
1114 		/*
1115 		 * We needed to drop mutex to make that restrictive page
1116 		 * allocation, but the inode might have been freed while we
1117 		 * dropped it: although a racing shmem_evict_inode() cannot
1118 		 * complete without emptying the radix_tree, our page lock
1119 		 * on this swapcache page is not enough to prevent that -
1120 		 * free_swap_and_cache() of our swap entry will only
1121 		 * trylock_page(), removing swap from radix_tree whatever.
1122 		 *
1123 		 * We must not proceed to shmem_add_to_page_cache() if the
1124 		 * inode has been freed, but of course we cannot rely on
1125 		 * inode or mapping or info to check that.  However, we can
1126 		 * safely check if our swap entry is still in use (and here
1127 		 * it can't have got reused for another page): if it's still
1128 		 * in use, then the inode cannot have been freed yet, and we
1129 		 * can safely proceed (if it's no longer in use, that tells
1130 		 * nothing about the inode, but we don't need to unuse swap).
1131 		 */
1132 		if (!page_swapcount(*pagep))
1133 			error = -ENOENT;
1134 	}
1135 
1136 	/*
1137 	 * We rely on shmem_swaplist_mutex, not only to protect the swaplist,
1138 	 * but also to hold up shmem_evict_inode(): so inode cannot be freed
1139 	 * beneath us (pagelock doesn't help until the page is in pagecache).
1140 	 */
1141 	if (!error)
1142 		error = shmem_add_to_page_cache(*pagep, mapping, index,
1143 						radswap);
1144 	if (error != -ENOMEM) {
1145 		/*
1146 		 * Truncation and eviction use free_swap_and_cache(), which
1147 		 * only does trylock page: if we raced, best clean up here.
1148 		 */
1149 		delete_from_swap_cache(*pagep);
1150 		set_page_dirty(*pagep);
1151 		if (!error) {
1152 			spin_lock_irq(&info->lock);
1153 			info->swapped--;
1154 			spin_unlock_irq(&info->lock);
1155 			swap_free(swap);
1156 		}
1157 	}
1158 	return error;
1159 }
1160 
1161 /*
1162  * Search through swapped inodes to find and replace swap by page.
1163  */
1164 int shmem_unuse(swp_entry_t swap, struct page *page)
1165 {
1166 	struct list_head *this, *next;
1167 	struct shmem_inode_info *info;
1168 	struct mem_cgroup *memcg;
1169 	int error = 0;
1170 
1171 	/*
1172 	 * There's a faint possibility that swap page was replaced before
1173 	 * caller locked it: caller will come back later with the right page.
1174 	 */
1175 	if (unlikely(!PageSwapCache(page) || page_private(page) != swap.val))
1176 		goto out;
1177 
1178 	/*
1179 	 * Charge page using GFP_KERNEL while we can wait, before taking
1180 	 * the shmem_swaplist_mutex which might hold up shmem_writepage().
1181 	 * Charged back to the user (not to caller) when swap account is used.
1182 	 */
1183 	error = mem_cgroup_try_charge(page, current->mm, GFP_KERNEL, &memcg,
1184 			false);
1185 	if (error)
1186 		goto out;
1187 	/* No radix_tree_preload: swap entry keeps a place for page in tree */
1188 	error = -EAGAIN;
1189 
1190 	mutex_lock(&shmem_swaplist_mutex);
1191 	list_for_each_safe(this, next, &shmem_swaplist) {
1192 		info = list_entry(this, struct shmem_inode_info, swaplist);
1193 		if (info->swapped)
1194 			error = shmem_unuse_inode(info, swap, &page);
1195 		else
1196 			list_del_init(&info->swaplist);
1197 		cond_resched();
1198 		if (error != -EAGAIN)
1199 			break;
1200 		/* found nothing in this: move on to search the next */
1201 	}
1202 	mutex_unlock(&shmem_swaplist_mutex);
1203 
1204 	if (error) {
1205 		if (error != -ENOMEM)
1206 			error = 0;
1207 		mem_cgroup_cancel_charge(page, memcg, false);
1208 	} else
1209 		mem_cgroup_commit_charge(page, memcg, true, false);
1210 out:
1211 	unlock_page(page);
1212 	put_page(page);
1213 	return error;
1214 }
1215 
1216 /*
1217  * Move the page from the page cache to the swap cache.
1218  */
1219 static int shmem_writepage(struct page *page, struct writeback_control *wbc)
1220 {
1221 	struct shmem_inode_info *info;
1222 	struct address_space *mapping;
1223 	struct inode *inode;
1224 	swp_entry_t swap;
1225 	pgoff_t index;
1226 
1227 	VM_BUG_ON_PAGE(PageCompound(page), page);
1228 	BUG_ON(!PageLocked(page));
1229 	mapping = page->mapping;
1230 	index = page->index;
1231 	inode = mapping->host;
1232 	info = SHMEM_I(inode);
1233 	if (info->flags & VM_LOCKED)
1234 		goto redirty;
1235 	if (!total_swap_pages)
1236 		goto redirty;
1237 
1238 	/*
1239 	 * Our capabilities prevent regular writeback or sync from ever calling
1240 	 * shmem_writepage; but a stacking filesystem might use ->writepage of
1241 	 * its underlying filesystem, in which case tmpfs should write out to
1242 	 * swap only in response to memory pressure, and not for the writeback
1243 	 * threads or sync.
1244 	 */
1245 	if (!wbc->for_reclaim) {
1246 		WARN_ON_ONCE(1);	/* Still happens? Tell us about it! */
1247 		goto redirty;
1248 	}
1249 
1250 	/*
1251 	 * This is somewhat ridiculous, but without plumbing a SWAP_MAP_FALLOC
1252 	 * value into swapfile.c, the only way we can correctly account for a
1253 	 * fallocated page arriving here is now to initialize it and write it.
1254 	 *
1255 	 * That's okay for a page already fallocated earlier, but if we have
1256 	 * not yet completed the fallocation, then (a) we want to keep track
1257 	 * of this page in case we have to undo it, and (b) it may not be a
1258 	 * good idea to continue anyway, once we're pushing into swap.  So
1259 	 * reactivate the page, and let shmem_fallocate() quit when too many.
1260 	 */
1261 	if (!PageUptodate(page)) {
1262 		if (inode->i_private) {
1263 			struct shmem_falloc *shmem_falloc;
1264 			spin_lock(&inode->i_lock);
1265 			shmem_falloc = inode->i_private;
1266 			if (shmem_falloc &&
1267 			    !shmem_falloc->waitq &&
1268 			    index >= shmem_falloc->start &&
1269 			    index < shmem_falloc->next)
1270 				shmem_falloc->nr_unswapped++;
1271 			else
1272 				shmem_falloc = NULL;
1273 			spin_unlock(&inode->i_lock);
1274 			if (shmem_falloc)
1275 				goto redirty;
1276 		}
1277 		clear_highpage(page);
1278 		flush_dcache_page(page);
1279 		SetPageUptodate(page);
1280 	}
1281 
1282 	swap = get_swap_page();
1283 	if (!swap.val)
1284 		goto redirty;
1285 
1286 	if (mem_cgroup_try_charge_swap(page, swap))
1287 		goto free_swap;
1288 
1289 	/*
1290 	 * Add inode to shmem_unuse()'s list of swapped-out inodes,
1291 	 * if it's not already there.  Do it now before the page is
1292 	 * moved to swap cache, when its pagelock no longer protects
1293 	 * the inode from eviction.  But don't unlock the mutex until
1294 	 * we've incremented swapped, because shmem_unuse_inode() will
1295 	 * prune a !swapped inode from the swaplist under this mutex.
1296 	 */
1297 	mutex_lock(&shmem_swaplist_mutex);
1298 	if (list_empty(&info->swaplist))
1299 		list_add_tail(&info->swaplist, &shmem_swaplist);
1300 
1301 	if (add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
1302 		spin_lock_irq(&info->lock);
1303 		shmem_recalc_inode(inode);
1304 		info->swapped++;
1305 		spin_unlock_irq(&info->lock);
1306 
1307 		swap_shmem_alloc(swap);
1308 		shmem_delete_from_page_cache(page, swp_to_radix_entry(swap));
1309 
1310 		mutex_unlock(&shmem_swaplist_mutex);
1311 		BUG_ON(page_mapped(page));
1312 		swap_writepage(page, wbc);
1313 		return 0;
1314 	}
1315 
1316 	mutex_unlock(&shmem_swaplist_mutex);
1317 free_swap:
1318 	swapcache_free(swap);
1319 redirty:
1320 	set_page_dirty(page);
1321 	if (wbc->for_reclaim)
1322 		return AOP_WRITEPAGE_ACTIVATE;	/* Return with page locked */
1323 	unlock_page(page);
1324 	return 0;
1325 }
1326 
1327 #if defined(CONFIG_NUMA) && defined(CONFIG_TMPFS)
1328 static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
1329 {
1330 	char buffer[64];
1331 
1332 	if (!mpol || mpol->mode == MPOL_DEFAULT)
1333 		return;		/* show nothing */
1334 
1335 	mpol_to_str(buffer, sizeof(buffer), mpol);
1336 
1337 	seq_printf(seq, ",mpol=%s", buffer);
1338 }
1339 
1340 static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
1341 {
1342 	struct mempolicy *mpol = NULL;
1343 	if (sbinfo->mpol) {
1344 		spin_lock(&sbinfo->stat_lock);	/* prevent replace/use races */
1345 		mpol = sbinfo->mpol;
1346 		mpol_get(mpol);
1347 		spin_unlock(&sbinfo->stat_lock);
1348 	}
1349 	return mpol;
1350 }
1351 #else /* !CONFIG_NUMA || !CONFIG_TMPFS */
1352 static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
1353 {
1354 }
1355 static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
1356 {
1357 	return NULL;
1358 }
1359 #endif /* CONFIG_NUMA && CONFIG_TMPFS */
1360 #ifndef CONFIG_NUMA
1361 #define vm_policy vm_private_data
1362 #endif
1363 
1364 static void shmem_pseudo_vma_init(struct vm_area_struct *vma,
1365 		struct shmem_inode_info *info, pgoff_t index)
1366 {
1367 	/* Create a pseudo vma that just contains the policy */
1368 	vma->vm_start = 0;
1369 	/* Bias interleave by inode number to distribute better across nodes */
1370 	vma->vm_pgoff = index + info->vfs_inode.i_ino;
1371 	vma->vm_ops = NULL;
1372 	vma->vm_policy = mpol_shared_policy_lookup(&info->policy, index);
1373 }
1374 
1375 static void shmem_pseudo_vma_destroy(struct vm_area_struct *vma)
1376 {
1377 	/* Drop reference taken by mpol_shared_policy_lookup() */
1378 	mpol_cond_put(vma->vm_policy);
1379 }
1380 
1381 static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
1382 			struct shmem_inode_info *info, pgoff_t index)
1383 {
1384 	struct vm_area_struct pvma;
1385 	struct page *page;
1386 
1387 	shmem_pseudo_vma_init(&pvma, info, index);
1388 	page = swapin_readahead(swap, gfp, &pvma, 0);
1389 	shmem_pseudo_vma_destroy(&pvma);
1390 
1391 	return page;
1392 }
1393 
1394 static struct page *shmem_alloc_hugepage(gfp_t gfp,
1395 		struct shmem_inode_info *info, pgoff_t index)
1396 {
1397 	struct vm_area_struct pvma;
1398 	struct inode *inode = &info->vfs_inode;
1399 	struct address_space *mapping = inode->i_mapping;
1400 	pgoff_t idx, hindex;
1401 	void __rcu **results;
1402 	struct page *page;
1403 
1404 	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE))
1405 		return NULL;
1406 
1407 	hindex = round_down(index, HPAGE_PMD_NR);
1408 	rcu_read_lock();
1409 	if (radix_tree_gang_lookup_slot(&mapping->page_tree, &results, &idx,
1410 				hindex, 1) && idx < hindex + HPAGE_PMD_NR) {
1411 		rcu_read_unlock();
1412 		return NULL;
1413 	}
1414 	rcu_read_unlock();
1415 
1416 	shmem_pseudo_vma_init(&pvma, info, hindex);
1417 	page = alloc_pages_vma(gfp | __GFP_COMP | __GFP_NORETRY | __GFP_NOWARN,
1418 			HPAGE_PMD_ORDER, &pvma, 0, numa_node_id(), true);
1419 	shmem_pseudo_vma_destroy(&pvma);
1420 	if (page)
1421 		prep_transhuge_page(page);
1422 	return page;
1423 }
1424 
1425 static struct page *shmem_alloc_page(gfp_t gfp,
1426 			struct shmem_inode_info *info, pgoff_t index)
1427 {
1428 	struct vm_area_struct pvma;
1429 	struct page *page;
1430 
1431 	shmem_pseudo_vma_init(&pvma, info, index);
1432 	page = alloc_page_vma(gfp, &pvma, 0);
1433 	shmem_pseudo_vma_destroy(&pvma);
1434 
1435 	return page;
1436 }
1437 
1438 static struct page *shmem_alloc_and_acct_page(gfp_t gfp,
1439 		struct shmem_inode_info *info, struct shmem_sb_info *sbinfo,
1440 		pgoff_t index, bool huge)
1441 {
1442 	struct page *page;
1443 	int nr;
1444 	int err = -ENOSPC;
1445 
1446 	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE))
1447 		huge = false;
1448 	nr = huge ? HPAGE_PMD_NR : 1;
1449 
1450 	if (shmem_acct_block(info->flags, nr))
1451 		goto failed;
1452 	if (sbinfo->max_blocks) {
1453 		if (percpu_counter_compare(&sbinfo->used_blocks,
1454 					sbinfo->max_blocks - nr) > 0)
1455 			goto unacct;
1456 		percpu_counter_add(&sbinfo->used_blocks, nr);
1457 	}
1458 
1459 	if (huge)
1460 		page = shmem_alloc_hugepage(gfp, info, index);
1461 	else
1462 		page = shmem_alloc_page(gfp, info, index);
1463 	if (page) {
1464 		__SetPageLocked(page);
1465 		__SetPageSwapBacked(page);
1466 		return page;
1467 	}
1468 
1469 	err = -ENOMEM;
1470 	if (sbinfo->max_blocks)
1471 		percpu_counter_add(&sbinfo->used_blocks, -nr);
1472 unacct:
1473 	shmem_unacct_blocks(info->flags, nr);
1474 failed:
1475 	return ERR_PTR(err);
1476 }
1477 
1478 /*
1479  * When a page is moved from swapcache to shmem filecache (either by the
1480  * usual swapin of shmem_getpage_gfp(), or by the less common swapoff of
1481  * shmem_unuse_inode()), it may have been read in earlier from swap, in
1482  * ignorance of the mapping it belongs to.  If that mapping has special
1483  * constraints (like the gma500 GEM driver, which requires RAM below 4GB),
1484  * we may need to copy to a suitable page before moving to filecache.
1485  *
1486  * In a future release, this may well be extended to respect cpuset and
1487  * NUMA mempolicy, and applied also to anonymous pages in do_swap_page();
1488  * but for now it is a simple matter of zone.
1489  */
1490 static bool shmem_should_replace_page(struct page *page, gfp_t gfp)
1491 {
1492 	return page_zonenum(page) > gfp_zone(gfp);
1493 }
1494 
1495 static int shmem_replace_page(struct page **pagep, gfp_t gfp,
1496 				struct shmem_inode_info *info, pgoff_t index)
1497 {
1498 	struct page *oldpage, *newpage;
1499 	struct address_space *swap_mapping;
1500 	pgoff_t swap_index;
1501 	int error;
1502 
1503 	oldpage = *pagep;
1504 	swap_index = page_private(oldpage);
1505 	swap_mapping = page_mapping(oldpage);
1506 
1507 	/*
1508 	 * We have arrived here because our zones are constrained, so don't
1509 	 * limit chance of success by further cpuset and node constraints.
1510 	 */
1511 	gfp &= ~GFP_CONSTRAINT_MASK;
1512 	newpage = shmem_alloc_page(gfp, info, index);
1513 	if (!newpage)
1514 		return -ENOMEM;
1515 
1516 	get_page(newpage);
1517 	copy_highpage(newpage, oldpage);
1518 	flush_dcache_page(newpage);
1519 
1520 	__SetPageLocked(newpage);
1521 	__SetPageSwapBacked(newpage);
1522 	SetPageUptodate(newpage);
1523 	set_page_private(newpage, swap_index);
1524 	SetPageSwapCache(newpage);
1525 
1526 	/*
1527 	 * Our caller will very soon move newpage out of swapcache, but it's
1528 	 * a nice clean interface for us to replace oldpage by newpage there.
1529 	 */
1530 	spin_lock_irq(&swap_mapping->tree_lock);
1531 	error = shmem_radix_tree_replace(swap_mapping, swap_index, oldpage,
1532 								   newpage);
1533 	if (!error) {
1534 		__inc_node_page_state(newpage, NR_FILE_PAGES);
1535 		__dec_node_page_state(oldpage, NR_FILE_PAGES);
1536 	}
1537 	spin_unlock_irq(&swap_mapping->tree_lock);
1538 
1539 	if (unlikely(error)) {
1540 		/*
1541 		 * Is this possible?  I think not, now that our callers check
1542 		 * both PageSwapCache and page_private after getting page lock;
1543 		 * but be defensive.  Reverse old to newpage for clear and free.
1544 		 */
1545 		oldpage = newpage;
1546 	} else {
1547 		mem_cgroup_migrate(oldpage, newpage);
1548 		lru_cache_add_anon(newpage);
1549 		*pagep = newpage;
1550 	}
1551 
1552 	ClearPageSwapCache(oldpage);
1553 	set_page_private(oldpage, 0);
1554 
1555 	unlock_page(oldpage);
1556 	put_page(oldpage);
1557 	put_page(oldpage);
1558 	return error;
1559 }
1560 
1561 /*
1562  * shmem_getpage_gfp - find page in cache, or get from swap, or allocate
1563  *
1564  * If we allocate a new one we do not mark it dirty. That's up to the
1565  * vm. If we swap it in we mark it dirty since we also free the swap
1566  * entry since a page cannot live in both the swap and page cache.
1567  *
1568  * fault_mm and fault_type are only supplied by shmem_fault:
1569  * otherwise they are NULL.
1570  */
1571 static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
1572 	struct page **pagep, enum sgp_type sgp, gfp_t gfp,
1573 	struct mm_struct *fault_mm, int *fault_type)
1574 {
1575 	struct address_space *mapping = inode->i_mapping;
1576 	struct shmem_inode_info *info = SHMEM_I(inode);
1577 	struct shmem_sb_info *sbinfo;
1578 	struct mm_struct *charge_mm;
1579 	struct mem_cgroup *memcg;
1580 	struct page *page;
1581 	swp_entry_t swap;
1582 	enum sgp_type sgp_huge = sgp;
1583 	pgoff_t hindex = index;
1584 	int error;
1585 	int once = 0;
1586 	int alloced = 0;
1587 
1588 	if (index > (MAX_LFS_FILESIZE >> PAGE_SHIFT))
1589 		return -EFBIG;
1590 	if (sgp == SGP_NOHUGE || sgp == SGP_HUGE)
1591 		sgp = SGP_CACHE;
1592 repeat:
1593 	swap.val = 0;
1594 	page = find_lock_entry(mapping, index);
1595 	if (radix_tree_exceptional_entry(page)) {
1596 		swap = radix_to_swp_entry(page);
1597 		page = NULL;
1598 	}
1599 
1600 	if (sgp <= SGP_CACHE &&
1601 	    ((loff_t)index << PAGE_SHIFT) >= i_size_read(inode)) {
1602 		error = -EINVAL;
1603 		goto unlock;
1604 	}
1605 
1606 	if (page && sgp == SGP_WRITE)
1607 		mark_page_accessed(page);
1608 
1609 	/* fallocated page? */
1610 	if (page && !PageUptodate(page)) {
1611 		if (sgp != SGP_READ)
1612 			goto clear;
1613 		unlock_page(page);
1614 		put_page(page);
1615 		page = NULL;
1616 	}
1617 	if (page || (sgp == SGP_READ && !swap.val)) {
1618 		*pagep = page;
1619 		return 0;
1620 	}
1621 
1622 	/*
1623 	 * Fast cache lookup did not find it:
1624 	 * bring it back from swap or allocate.
1625 	 */
1626 	sbinfo = SHMEM_SB(inode->i_sb);
1627 	charge_mm = fault_mm ? : current->mm;
1628 
1629 	if (swap.val) {
1630 		/* Look it up and read it in.. */
1631 		page = lookup_swap_cache(swap);
1632 		if (!page) {
1633 			/* Or update major stats only when swapin succeeds?? */
1634 			if (fault_type) {
1635 				*fault_type |= VM_FAULT_MAJOR;
1636 				count_vm_event(PGMAJFAULT);
1637 				mem_cgroup_count_vm_event(fault_mm, PGMAJFAULT);
1638 			}
1639 			/* Here we actually start the io */
1640 			page = shmem_swapin(swap, gfp, info, index);
1641 			if (!page) {
1642 				error = -ENOMEM;
1643 				goto failed;
1644 			}
1645 		}
1646 
1647 		/* We have to do this with page locked to prevent races */
1648 		lock_page(page);
1649 		if (!PageSwapCache(page) || page_private(page) != swap.val ||
1650 		    !shmem_confirm_swap(mapping, index, swap)) {
1651 			error = -EEXIST;	/* try again */
1652 			goto unlock;
1653 		}
1654 		if (!PageUptodate(page)) {
1655 			error = -EIO;
1656 			goto failed;
1657 		}
1658 		wait_on_page_writeback(page);
1659 
1660 		if (shmem_should_replace_page(page, gfp)) {
1661 			error = shmem_replace_page(&page, gfp, info, index);
1662 			if (error)
1663 				goto failed;
1664 		}
1665 
1666 		error = mem_cgroup_try_charge(page, charge_mm, gfp, &memcg,
1667 				false);
1668 		if (!error) {
1669 			error = shmem_add_to_page_cache(page, mapping, index,
1670 						swp_to_radix_entry(swap));
1671 			/*
1672 			 * We already confirmed swap under page lock, and make
1673 			 * no memory allocation here, so usually no possibility
1674 			 * of error; but free_swap_and_cache() only trylocks a
1675 			 * page, so it is just possible that the entry has been
1676 			 * truncated or holepunched since swap was confirmed.
1677 			 * shmem_undo_range() will have done some of the
1678 			 * unaccounting, now delete_from_swap_cache() will do
1679 			 * the rest.
1680 			 * Reset swap.val? No, leave it so "failed" goes back to
1681 			 * "repeat": reading a hole and writing should succeed.
1682 			 */
1683 			if (error) {
1684 				mem_cgroup_cancel_charge(page, memcg, false);
1685 				delete_from_swap_cache(page);
1686 			}
1687 		}
1688 		if (error)
1689 			goto failed;
1690 
1691 		mem_cgroup_commit_charge(page, memcg, true, false);
1692 
1693 		spin_lock_irq(&info->lock);
1694 		info->swapped--;
1695 		shmem_recalc_inode(inode);
1696 		spin_unlock_irq(&info->lock);
1697 
1698 		if (sgp == SGP_WRITE)
1699 			mark_page_accessed(page);
1700 
1701 		delete_from_swap_cache(page);
1702 		set_page_dirty(page);
1703 		swap_free(swap);
1704 
1705 	} else {
1706 		/* shmem_symlink() */
1707 		if (mapping->a_ops != &shmem_aops)
1708 			goto alloc_nohuge;
1709 		if (shmem_huge == SHMEM_HUGE_DENY || sgp_huge == SGP_NOHUGE)
1710 			goto alloc_nohuge;
1711 		if (shmem_huge == SHMEM_HUGE_FORCE)
1712 			goto alloc_huge;
1713 		switch (sbinfo->huge) {
1714 			loff_t i_size;
1715 			pgoff_t off;
1716 		case SHMEM_HUGE_NEVER:
1717 			goto alloc_nohuge;
1718 		case SHMEM_HUGE_WITHIN_SIZE:
1719 			off = round_up(index, HPAGE_PMD_NR);
1720 			i_size = round_up(i_size_read(inode), PAGE_SIZE);
1721 			if (i_size >= HPAGE_PMD_SIZE &&
1722 					i_size >> PAGE_SHIFT >= off)
1723 				goto alloc_huge;
1724 			/* fallthrough */
1725 		case SHMEM_HUGE_ADVISE:
1726 			if (sgp_huge == SGP_HUGE)
1727 				goto alloc_huge;
1728 			/* TODO: implement fadvise() hints */
1729 			goto alloc_nohuge;
1730 		}
1731 
1732 alloc_huge:
1733 		page = shmem_alloc_and_acct_page(gfp, info, sbinfo,
1734 				index, true);
1735 		if (IS_ERR(page)) {
1736 alloc_nohuge:		page = shmem_alloc_and_acct_page(gfp, info, sbinfo,
1737 					index, false);
1738 		}
1739 		if (IS_ERR(page)) {
1740 			int retry = 5;
1741 			error = PTR_ERR(page);
1742 			page = NULL;
1743 			if (error != -ENOSPC)
1744 				goto failed;
1745 			/*
1746 			 * Try to reclaim some spece by splitting a huge page
1747 			 * beyond i_size on the filesystem.
1748 			 */
1749 			while (retry--) {
1750 				int ret;
1751 				ret = shmem_unused_huge_shrink(sbinfo, NULL, 1);
1752 				if (ret == SHRINK_STOP)
1753 					break;
1754 				if (ret)
1755 					goto alloc_nohuge;
1756 			}
1757 			goto failed;
1758 		}
1759 
1760 		if (PageTransHuge(page))
1761 			hindex = round_down(index, HPAGE_PMD_NR);
1762 		else
1763 			hindex = index;
1764 
1765 		if (sgp == SGP_WRITE)
1766 			__SetPageReferenced(page);
1767 
1768 		error = mem_cgroup_try_charge(page, charge_mm, gfp, &memcg,
1769 				PageTransHuge(page));
1770 		if (error)
1771 			goto unacct;
1772 		error = radix_tree_maybe_preload_order(gfp & GFP_RECLAIM_MASK,
1773 				compound_order(page));
1774 		if (!error) {
1775 			error = shmem_add_to_page_cache(page, mapping, hindex,
1776 							NULL);
1777 			radix_tree_preload_end();
1778 		}
1779 		if (error) {
1780 			mem_cgroup_cancel_charge(page, memcg,
1781 					PageTransHuge(page));
1782 			goto unacct;
1783 		}
1784 		mem_cgroup_commit_charge(page, memcg, false,
1785 				PageTransHuge(page));
1786 		lru_cache_add_anon(page);
1787 
1788 		spin_lock_irq(&info->lock);
1789 		info->alloced += 1 << compound_order(page);
1790 		inode->i_blocks += BLOCKS_PER_PAGE << compound_order(page);
1791 		shmem_recalc_inode(inode);
1792 		spin_unlock_irq(&info->lock);
1793 		alloced = true;
1794 
1795 		if (PageTransHuge(page) &&
1796 				DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE) <
1797 				hindex + HPAGE_PMD_NR - 1) {
1798 			/*
1799 			 * Part of the huge page is beyond i_size: subject
1800 			 * to shrink under memory pressure.
1801 			 */
1802 			spin_lock(&sbinfo->shrinklist_lock);
1803 			if (list_empty(&info->shrinklist)) {
1804 				list_add_tail(&info->shrinklist,
1805 						&sbinfo->shrinklist);
1806 				sbinfo->shrinklist_len++;
1807 			}
1808 			spin_unlock(&sbinfo->shrinklist_lock);
1809 		}
1810 
1811 		/*
1812 		 * Let SGP_FALLOC use the SGP_WRITE optimization on a new page.
1813 		 */
1814 		if (sgp == SGP_FALLOC)
1815 			sgp = SGP_WRITE;
1816 clear:
1817 		/*
1818 		 * Let SGP_WRITE caller clear ends if write does not fill page;
1819 		 * but SGP_FALLOC on a page fallocated earlier must initialize
1820 		 * it now, lest undo on failure cancel our earlier guarantee.
1821 		 */
1822 		if (sgp != SGP_WRITE && !PageUptodate(page)) {
1823 			struct page *head = compound_head(page);
1824 			int i;
1825 
1826 			for (i = 0; i < (1 << compound_order(head)); i++) {
1827 				clear_highpage(head + i);
1828 				flush_dcache_page(head + i);
1829 			}
1830 			SetPageUptodate(head);
1831 		}
1832 	}
1833 
1834 	/* Perhaps the file has been truncated since we checked */
1835 	if (sgp <= SGP_CACHE &&
1836 	    ((loff_t)index << PAGE_SHIFT) >= i_size_read(inode)) {
1837 		if (alloced) {
1838 			ClearPageDirty(page);
1839 			delete_from_page_cache(page);
1840 			spin_lock_irq(&info->lock);
1841 			shmem_recalc_inode(inode);
1842 			spin_unlock_irq(&info->lock);
1843 		}
1844 		error = -EINVAL;
1845 		goto unlock;
1846 	}
1847 	*pagep = page + index - hindex;
1848 	return 0;
1849 
1850 	/*
1851 	 * Error recovery.
1852 	 */
1853 unacct:
1854 	if (sbinfo->max_blocks)
1855 		percpu_counter_sub(&sbinfo->used_blocks,
1856 				1 << compound_order(page));
1857 	shmem_unacct_blocks(info->flags, 1 << compound_order(page));
1858 
1859 	if (PageTransHuge(page)) {
1860 		unlock_page(page);
1861 		put_page(page);
1862 		goto alloc_nohuge;
1863 	}
1864 failed:
1865 	if (swap.val && !shmem_confirm_swap(mapping, index, swap))
1866 		error = -EEXIST;
1867 unlock:
1868 	if (page) {
1869 		unlock_page(page);
1870 		put_page(page);
1871 	}
1872 	if (error == -ENOSPC && !once++) {
1873 		spin_lock_irq(&info->lock);
1874 		shmem_recalc_inode(inode);
1875 		spin_unlock_irq(&info->lock);
1876 		goto repeat;
1877 	}
1878 	if (error == -EEXIST)	/* from above or from radix_tree_insert */
1879 		goto repeat;
1880 	return error;
1881 }
1882 
1883 /*
1884  * This is like autoremove_wake_function, but it removes the wait queue
1885  * entry unconditionally - even if something else had already woken the
1886  * target.
1887  */
1888 static int synchronous_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key)
1889 {
1890 	int ret = default_wake_function(wait, mode, sync, key);
1891 	list_del_init(&wait->task_list);
1892 	return ret;
1893 }
1894 
1895 static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1896 {
1897 	struct inode *inode = file_inode(vma->vm_file);
1898 	gfp_t gfp = mapping_gfp_mask(inode->i_mapping);
1899 	enum sgp_type sgp;
1900 	int error;
1901 	int ret = VM_FAULT_LOCKED;
1902 
1903 	/*
1904 	 * Trinity finds that probing a hole which tmpfs is punching can
1905 	 * prevent the hole-punch from ever completing: which in turn
1906 	 * locks writers out with its hold on i_mutex.  So refrain from
1907 	 * faulting pages into the hole while it's being punched.  Although
1908 	 * shmem_undo_range() does remove the additions, it may be unable to
1909 	 * keep up, as each new page needs its own unmap_mapping_range() call,
1910 	 * and the i_mmap tree grows ever slower to scan if new vmas are added.
1911 	 *
1912 	 * It does not matter if we sometimes reach this check just before the
1913 	 * hole-punch begins, so that one fault then races with the punch:
1914 	 * we just need to make racing faults a rare case.
1915 	 *
1916 	 * The implementation below would be much simpler if we just used a
1917 	 * standard mutex or completion: but we cannot take i_mutex in fault,
1918 	 * and bloating every shmem inode for this unlikely case would be sad.
1919 	 */
1920 	if (unlikely(inode->i_private)) {
1921 		struct shmem_falloc *shmem_falloc;
1922 
1923 		spin_lock(&inode->i_lock);
1924 		shmem_falloc = inode->i_private;
1925 		if (shmem_falloc &&
1926 		    shmem_falloc->waitq &&
1927 		    vmf->pgoff >= shmem_falloc->start &&
1928 		    vmf->pgoff < shmem_falloc->next) {
1929 			wait_queue_head_t *shmem_falloc_waitq;
1930 			DEFINE_WAIT_FUNC(shmem_fault_wait, synchronous_wake_function);
1931 
1932 			ret = VM_FAULT_NOPAGE;
1933 			if ((vmf->flags & FAULT_FLAG_ALLOW_RETRY) &&
1934 			   !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT)) {
1935 				/* It's polite to up mmap_sem if we can */
1936 				up_read(&vma->vm_mm->mmap_sem);
1937 				ret = VM_FAULT_RETRY;
1938 			}
1939 
1940 			shmem_falloc_waitq = shmem_falloc->waitq;
1941 			prepare_to_wait(shmem_falloc_waitq, &shmem_fault_wait,
1942 					TASK_UNINTERRUPTIBLE);
1943 			spin_unlock(&inode->i_lock);
1944 			schedule();
1945 
1946 			/*
1947 			 * shmem_falloc_waitq points into the shmem_fallocate()
1948 			 * stack of the hole-punching task: shmem_falloc_waitq
1949 			 * is usually invalid by the time we reach here, but
1950 			 * finish_wait() does not dereference it in that case;
1951 			 * though i_lock needed lest racing with wake_up_all().
1952 			 */
1953 			spin_lock(&inode->i_lock);
1954 			finish_wait(shmem_falloc_waitq, &shmem_fault_wait);
1955 			spin_unlock(&inode->i_lock);
1956 			return ret;
1957 		}
1958 		spin_unlock(&inode->i_lock);
1959 	}
1960 
1961 	sgp = SGP_CACHE;
1962 	if (vma->vm_flags & VM_HUGEPAGE)
1963 		sgp = SGP_HUGE;
1964 	else if (vma->vm_flags & VM_NOHUGEPAGE)
1965 		sgp = SGP_NOHUGE;
1966 
1967 	error = shmem_getpage_gfp(inode, vmf->pgoff, &vmf->page, sgp,
1968 				  gfp, vma->vm_mm, &ret);
1969 	if (error)
1970 		return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
1971 	return ret;
1972 }
1973 
1974 unsigned long shmem_get_unmapped_area(struct file *file,
1975 				      unsigned long uaddr, unsigned long len,
1976 				      unsigned long pgoff, unsigned long flags)
1977 {
1978 	unsigned long (*get_area)(struct file *,
1979 		unsigned long, unsigned long, unsigned long, unsigned long);
1980 	unsigned long addr;
1981 	unsigned long offset;
1982 	unsigned long inflated_len;
1983 	unsigned long inflated_addr;
1984 	unsigned long inflated_offset;
1985 
1986 	if (len > TASK_SIZE)
1987 		return -ENOMEM;
1988 
1989 	get_area = current->mm->get_unmapped_area;
1990 	addr = get_area(file, uaddr, len, pgoff, flags);
1991 
1992 	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE))
1993 		return addr;
1994 	if (IS_ERR_VALUE(addr))
1995 		return addr;
1996 	if (addr & ~PAGE_MASK)
1997 		return addr;
1998 	if (addr > TASK_SIZE - len)
1999 		return addr;
2000 
2001 	if (shmem_huge == SHMEM_HUGE_DENY)
2002 		return addr;
2003 	if (len < HPAGE_PMD_SIZE)
2004 		return addr;
2005 	if (flags & MAP_FIXED)
2006 		return addr;
2007 	/*
2008 	 * Our priority is to support MAP_SHARED mapped hugely;
2009 	 * and support MAP_PRIVATE mapped hugely too, until it is COWed.
2010 	 * But if caller specified an address hint, respect that as before.
2011 	 */
2012 	if (uaddr)
2013 		return addr;
2014 
2015 	if (shmem_huge != SHMEM_HUGE_FORCE) {
2016 		struct super_block *sb;
2017 
2018 		if (file) {
2019 			VM_BUG_ON(file->f_op != &shmem_file_operations);
2020 			sb = file_inode(file)->i_sb;
2021 		} else {
2022 			/*
2023 			 * Called directly from mm/mmap.c, or drivers/char/mem.c
2024 			 * for "/dev/zero", to create a shared anonymous object.
2025 			 */
2026 			if (IS_ERR(shm_mnt))
2027 				return addr;
2028 			sb = shm_mnt->mnt_sb;
2029 		}
2030 		if (SHMEM_SB(sb)->huge == SHMEM_HUGE_NEVER)
2031 			return addr;
2032 	}
2033 
2034 	offset = (pgoff << PAGE_SHIFT) & (HPAGE_PMD_SIZE-1);
2035 	if (offset && offset + len < 2 * HPAGE_PMD_SIZE)
2036 		return addr;
2037 	if ((addr & (HPAGE_PMD_SIZE-1)) == offset)
2038 		return addr;
2039 
2040 	inflated_len = len + HPAGE_PMD_SIZE - PAGE_SIZE;
2041 	if (inflated_len > TASK_SIZE)
2042 		return addr;
2043 	if (inflated_len < len)
2044 		return addr;
2045 
2046 	inflated_addr = get_area(NULL, 0, inflated_len, 0, flags);
2047 	if (IS_ERR_VALUE(inflated_addr))
2048 		return addr;
2049 	if (inflated_addr & ~PAGE_MASK)
2050 		return addr;
2051 
2052 	inflated_offset = inflated_addr & (HPAGE_PMD_SIZE-1);
2053 	inflated_addr += offset - inflated_offset;
2054 	if (inflated_offset > offset)
2055 		inflated_addr += HPAGE_PMD_SIZE;
2056 
2057 	if (inflated_addr > TASK_SIZE - len)
2058 		return addr;
2059 	return inflated_addr;
2060 }
2061 
2062 #ifdef CONFIG_NUMA
2063 static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *mpol)
2064 {
2065 	struct inode *inode = file_inode(vma->vm_file);
2066 	return mpol_set_shared_policy(&SHMEM_I(inode)->policy, vma, mpol);
2067 }
2068 
2069 static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
2070 					  unsigned long addr)
2071 {
2072 	struct inode *inode = file_inode(vma->vm_file);
2073 	pgoff_t index;
2074 
2075 	index = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
2076 	return mpol_shared_policy_lookup(&SHMEM_I(inode)->policy, index);
2077 }
2078 #endif
2079 
2080 int shmem_lock(struct file *file, int lock, struct user_struct *user)
2081 {
2082 	struct inode *inode = file_inode(file);
2083 	struct shmem_inode_info *info = SHMEM_I(inode);
2084 	int retval = -ENOMEM;
2085 
2086 	spin_lock_irq(&info->lock);
2087 	if (lock && !(info->flags & VM_LOCKED)) {
2088 		if (!user_shm_lock(inode->i_size, user))
2089 			goto out_nomem;
2090 		info->flags |= VM_LOCKED;
2091 		mapping_set_unevictable(file->f_mapping);
2092 	}
2093 	if (!lock && (info->flags & VM_LOCKED) && user) {
2094 		user_shm_unlock(inode->i_size, user);
2095 		info->flags &= ~VM_LOCKED;
2096 		mapping_clear_unevictable(file->f_mapping);
2097 	}
2098 	retval = 0;
2099 
2100 out_nomem:
2101 	spin_unlock_irq(&info->lock);
2102 	return retval;
2103 }
2104 
2105 static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
2106 {
2107 	file_accessed(file);
2108 	vma->vm_ops = &shmem_vm_ops;
2109 	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE) &&
2110 			((vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK) <
2111 			(vma->vm_end & HPAGE_PMD_MASK)) {
2112 		khugepaged_enter(vma, vma->vm_flags);
2113 	}
2114 	return 0;
2115 }
2116 
2117 static struct inode *shmem_get_inode(struct super_block *sb, const struct inode *dir,
2118 				     umode_t mode, dev_t dev, unsigned long flags)
2119 {
2120 	struct inode *inode;
2121 	struct shmem_inode_info *info;
2122 	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2123 
2124 	if (shmem_reserve_inode(sb))
2125 		return NULL;
2126 
2127 	inode = new_inode(sb);
2128 	if (inode) {
2129 		inode->i_ino = get_next_ino();
2130 		inode_init_owner(inode, dir, mode);
2131 		inode->i_blocks = 0;
2132 		inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
2133 		inode->i_generation = get_seconds();
2134 		info = SHMEM_I(inode);
2135 		memset(info, 0, (char *)inode - (char *)info);
2136 		spin_lock_init(&info->lock);
2137 		info->seals = F_SEAL_SEAL;
2138 		info->flags = flags & VM_NORESERVE;
2139 		INIT_LIST_HEAD(&info->shrinklist);
2140 		INIT_LIST_HEAD(&info->swaplist);
2141 		simple_xattrs_init(&info->xattrs);
2142 		cache_no_acl(inode);
2143 
2144 		switch (mode & S_IFMT) {
2145 		default:
2146 			inode->i_op = &shmem_special_inode_operations;
2147 			init_special_inode(inode, mode, dev);
2148 			break;
2149 		case S_IFREG:
2150 			inode->i_mapping->a_ops = &shmem_aops;
2151 			inode->i_op = &shmem_inode_operations;
2152 			inode->i_fop = &shmem_file_operations;
2153 			mpol_shared_policy_init(&info->policy,
2154 						 shmem_get_sbmpol(sbinfo));
2155 			break;
2156 		case S_IFDIR:
2157 			inc_nlink(inode);
2158 			/* Some things misbehave if size == 0 on a directory */
2159 			inode->i_size = 2 * BOGO_DIRENT_SIZE;
2160 			inode->i_op = &shmem_dir_inode_operations;
2161 			inode->i_fop = &simple_dir_operations;
2162 			break;
2163 		case S_IFLNK:
2164 			/*
2165 			 * Must not load anything in the rbtree,
2166 			 * mpol_free_shared_policy will not be called.
2167 			 */
2168 			mpol_shared_policy_init(&info->policy, NULL);
2169 			break;
2170 		}
2171 	} else
2172 		shmem_free_inode(sb);
2173 	return inode;
2174 }
2175 
2176 bool shmem_mapping(struct address_space *mapping)
2177 {
2178 	if (!mapping->host)
2179 		return false;
2180 
2181 	return mapping->host->i_sb->s_op == &shmem_ops;
2182 }
2183 
2184 #ifdef CONFIG_TMPFS
2185 static const struct inode_operations shmem_symlink_inode_operations;
2186 static const struct inode_operations shmem_short_symlink_operations;
2187 
2188 #ifdef CONFIG_TMPFS_XATTR
2189 static int shmem_initxattrs(struct inode *, const struct xattr *, void *);
2190 #else
2191 #define shmem_initxattrs NULL
2192 #endif
2193 
2194 static int
2195 shmem_write_begin(struct file *file, struct address_space *mapping,
2196 			loff_t pos, unsigned len, unsigned flags,
2197 			struct page **pagep, void **fsdata)
2198 {
2199 	struct inode *inode = mapping->host;
2200 	struct shmem_inode_info *info = SHMEM_I(inode);
2201 	pgoff_t index = pos >> PAGE_SHIFT;
2202 
2203 	/* i_mutex is held by caller */
2204 	if (unlikely(info->seals)) {
2205 		if (info->seals & F_SEAL_WRITE)
2206 			return -EPERM;
2207 		if ((info->seals & F_SEAL_GROW) && pos + len > inode->i_size)
2208 			return -EPERM;
2209 	}
2210 
2211 	return shmem_getpage(inode, index, pagep, SGP_WRITE);
2212 }
2213 
2214 static int
2215 shmem_write_end(struct file *file, struct address_space *mapping,
2216 			loff_t pos, unsigned len, unsigned copied,
2217 			struct page *page, void *fsdata)
2218 {
2219 	struct inode *inode = mapping->host;
2220 
2221 	if (pos + copied > inode->i_size)
2222 		i_size_write(inode, pos + copied);
2223 
2224 	if (!PageUptodate(page)) {
2225 		struct page *head = compound_head(page);
2226 		if (PageTransCompound(page)) {
2227 			int i;
2228 
2229 			for (i = 0; i < HPAGE_PMD_NR; i++) {
2230 				if (head + i == page)
2231 					continue;
2232 				clear_highpage(head + i);
2233 				flush_dcache_page(head + i);
2234 			}
2235 		}
2236 		if (copied < PAGE_SIZE) {
2237 			unsigned from = pos & (PAGE_SIZE - 1);
2238 			zero_user_segments(page, 0, from,
2239 					from + copied, PAGE_SIZE);
2240 		}
2241 		SetPageUptodate(head);
2242 	}
2243 	set_page_dirty(page);
2244 	unlock_page(page);
2245 	put_page(page);
2246 
2247 	return copied;
2248 }
2249 
2250 static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
2251 {
2252 	struct file *file = iocb->ki_filp;
2253 	struct inode *inode = file_inode(file);
2254 	struct address_space *mapping = inode->i_mapping;
2255 	pgoff_t index;
2256 	unsigned long offset;
2257 	enum sgp_type sgp = SGP_READ;
2258 	int error = 0;
2259 	ssize_t retval = 0;
2260 	loff_t *ppos = &iocb->ki_pos;
2261 
2262 	/*
2263 	 * Might this read be for a stacking filesystem?  Then when reading
2264 	 * holes of a sparse file, we actually need to allocate those pages,
2265 	 * and even mark them dirty, so it cannot exceed the max_blocks limit.
2266 	 */
2267 	if (!iter_is_iovec(to))
2268 		sgp = SGP_CACHE;
2269 
2270 	index = *ppos >> PAGE_SHIFT;
2271 	offset = *ppos & ~PAGE_MASK;
2272 
2273 	for (;;) {
2274 		struct page *page = NULL;
2275 		pgoff_t end_index;
2276 		unsigned long nr, ret;
2277 		loff_t i_size = i_size_read(inode);
2278 
2279 		end_index = i_size >> PAGE_SHIFT;
2280 		if (index > end_index)
2281 			break;
2282 		if (index == end_index) {
2283 			nr = i_size & ~PAGE_MASK;
2284 			if (nr <= offset)
2285 				break;
2286 		}
2287 
2288 		error = shmem_getpage(inode, index, &page, sgp);
2289 		if (error) {
2290 			if (error == -EINVAL)
2291 				error = 0;
2292 			break;
2293 		}
2294 		if (page) {
2295 			if (sgp == SGP_CACHE)
2296 				set_page_dirty(page);
2297 			unlock_page(page);
2298 		}
2299 
2300 		/*
2301 		 * We must evaluate after, since reads (unlike writes)
2302 		 * are called without i_mutex protection against truncate
2303 		 */
2304 		nr = PAGE_SIZE;
2305 		i_size = i_size_read(inode);
2306 		end_index = i_size >> PAGE_SHIFT;
2307 		if (index == end_index) {
2308 			nr = i_size & ~PAGE_MASK;
2309 			if (nr <= offset) {
2310 				if (page)
2311 					put_page(page);
2312 				break;
2313 			}
2314 		}
2315 		nr -= offset;
2316 
2317 		if (page) {
2318 			/*
2319 			 * If users can be writing to this page using arbitrary
2320 			 * virtual addresses, take care about potential aliasing
2321 			 * before reading the page on the kernel side.
2322 			 */
2323 			if (mapping_writably_mapped(mapping))
2324 				flush_dcache_page(page);
2325 			/*
2326 			 * Mark the page accessed if we read the beginning.
2327 			 */
2328 			if (!offset)
2329 				mark_page_accessed(page);
2330 		} else {
2331 			page = ZERO_PAGE(0);
2332 			get_page(page);
2333 		}
2334 
2335 		/*
2336 		 * Ok, we have the page, and it's up-to-date, so
2337 		 * now we can copy it to user space...
2338 		 */
2339 		ret = copy_page_to_iter(page, offset, nr, to);
2340 		retval += ret;
2341 		offset += ret;
2342 		index += offset >> PAGE_SHIFT;
2343 		offset &= ~PAGE_MASK;
2344 
2345 		put_page(page);
2346 		if (!iov_iter_count(to))
2347 			break;
2348 		if (ret < nr) {
2349 			error = -EFAULT;
2350 			break;
2351 		}
2352 		cond_resched();
2353 	}
2354 
2355 	*ppos = ((loff_t) index << PAGE_SHIFT) + offset;
2356 	file_accessed(file);
2357 	return retval ? retval : error;
2358 }
2359 
2360 /*
2361  * llseek SEEK_DATA or SEEK_HOLE through the radix_tree.
2362  */
2363 static pgoff_t shmem_seek_hole_data(struct address_space *mapping,
2364 				    pgoff_t index, pgoff_t end, int whence)
2365 {
2366 	struct page *page;
2367 	struct pagevec pvec;
2368 	pgoff_t indices[PAGEVEC_SIZE];
2369 	bool done = false;
2370 	int i;
2371 
2372 	pagevec_init(&pvec, 0);
2373 	pvec.nr = 1;		/* start small: we may be there already */
2374 	while (!done) {
2375 		pvec.nr = find_get_entries(mapping, index,
2376 					pvec.nr, pvec.pages, indices);
2377 		if (!pvec.nr) {
2378 			if (whence == SEEK_DATA)
2379 				index = end;
2380 			break;
2381 		}
2382 		for (i = 0; i < pvec.nr; i++, index++) {
2383 			if (index < indices[i]) {
2384 				if (whence == SEEK_HOLE) {
2385 					done = true;
2386 					break;
2387 				}
2388 				index = indices[i];
2389 			}
2390 			page = pvec.pages[i];
2391 			if (page && !radix_tree_exceptional_entry(page)) {
2392 				if (!PageUptodate(page))
2393 					page = NULL;
2394 			}
2395 			if (index >= end ||
2396 			    (page && whence == SEEK_DATA) ||
2397 			    (!page && whence == SEEK_HOLE)) {
2398 				done = true;
2399 				break;
2400 			}
2401 		}
2402 		pagevec_remove_exceptionals(&pvec);
2403 		pagevec_release(&pvec);
2404 		pvec.nr = PAGEVEC_SIZE;
2405 		cond_resched();
2406 	}
2407 	return index;
2408 }
2409 
2410 static loff_t shmem_file_llseek(struct file *file, loff_t offset, int whence)
2411 {
2412 	struct address_space *mapping = file->f_mapping;
2413 	struct inode *inode = mapping->host;
2414 	pgoff_t start, end;
2415 	loff_t new_offset;
2416 
2417 	if (whence != SEEK_DATA && whence != SEEK_HOLE)
2418 		return generic_file_llseek_size(file, offset, whence,
2419 					MAX_LFS_FILESIZE, i_size_read(inode));
2420 	inode_lock(inode);
2421 	/* We're holding i_mutex so we can access i_size directly */
2422 
2423 	if (offset < 0)
2424 		offset = -EINVAL;
2425 	else if (offset >= inode->i_size)
2426 		offset = -ENXIO;
2427 	else {
2428 		start = offset >> PAGE_SHIFT;
2429 		end = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
2430 		new_offset = shmem_seek_hole_data(mapping, start, end, whence);
2431 		new_offset <<= PAGE_SHIFT;
2432 		if (new_offset > offset) {
2433 			if (new_offset < inode->i_size)
2434 				offset = new_offset;
2435 			else if (whence == SEEK_DATA)
2436 				offset = -ENXIO;
2437 			else
2438 				offset = inode->i_size;
2439 		}
2440 	}
2441 
2442 	if (offset >= 0)
2443 		offset = vfs_setpos(file, offset, MAX_LFS_FILESIZE);
2444 	inode_unlock(inode);
2445 	return offset;
2446 }
2447 
2448 /*
2449  * We need a tag: a new tag would expand every radix_tree_node by 8 bytes,
2450  * so reuse a tag which we firmly believe is never set or cleared on shmem.
2451  */
2452 #define SHMEM_TAG_PINNED        PAGECACHE_TAG_TOWRITE
2453 #define LAST_SCAN               4       /* about 150ms max */
2454 
2455 static void shmem_tag_pins(struct address_space *mapping)
2456 {
2457 	struct radix_tree_iter iter;
2458 	void **slot;
2459 	pgoff_t start;
2460 	struct page *page;
2461 
2462 	lru_add_drain();
2463 	start = 0;
2464 	rcu_read_lock();
2465 
2466 	radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
2467 		page = radix_tree_deref_slot(slot);
2468 		if (!page || radix_tree_exception(page)) {
2469 			if (radix_tree_deref_retry(page)) {
2470 				slot = radix_tree_iter_retry(&iter);
2471 				continue;
2472 			}
2473 		} else if (page_count(page) - page_mapcount(page) > 1) {
2474 			spin_lock_irq(&mapping->tree_lock);
2475 			radix_tree_tag_set(&mapping->page_tree, iter.index,
2476 					   SHMEM_TAG_PINNED);
2477 			spin_unlock_irq(&mapping->tree_lock);
2478 		}
2479 
2480 		if (need_resched()) {
2481 			slot = radix_tree_iter_resume(slot, &iter);
2482 			cond_resched_rcu();
2483 		}
2484 	}
2485 	rcu_read_unlock();
2486 }
2487 
2488 /*
2489  * Setting SEAL_WRITE requires us to verify there's no pending writer. However,
2490  * via get_user_pages(), drivers might have some pending I/O without any active
2491  * user-space mappings (eg., direct-IO, AIO). Therefore, we look at all pages
2492  * and see whether it has an elevated ref-count. If so, we tag them and wait for
2493  * them to be dropped.
2494  * The caller must guarantee that no new user will acquire writable references
2495  * to those pages to avoid races.
2496  */
2497 static int shmem_wait_for_pins(struct address_space *mapping)
2498 {
2499 	struct radix_tree_iter iter;
2500 	void **slot;
2501 	pgoff_t start;
2502 	struct page *page;
2503 	int error, scan;
2504 
2505 	shmem_tag_pins(mapping);
2506 
2507 	error = 0;
2508 	for (scan = 0; scan <= LAST_SCAN; scan++) {
2509 		if (!radix_tree_tagged(&mapping->page_tree, SHMEM_TAG_PINNED))
2510 			break;
2511 
2512 		if (!scan)
2513 			lru_add_drain_all();
2514 		else if (schedule_timeout_killable((HZ << scan) / 200))
2515 			scan = LAST_SCAN;
2516 
2517 		start = 0;
2518 		rcu_read_lock();
2519 		radix_tree_for_each_tagged(slot, &mapping->page_tree, &iter,
2520 					   start, SHMEM_TAG_PINNED) {
2521 
2522 			page = radix_tree_deref_slot(slot);
2523 			if (radix_tree_exception(page)) {
2524 				if (radix_tree_deref_retry(page)) {
2525 					slot = radix_tree_iter_retry(&iter);
2526 					continue;
2527 				}
2528 
2529 				page = NULL;
2530 			}
2531 
2532 			if (page &&
2533 			    page_count(page) - page_mapcount(page) != 1) {
2534 				if (scan < LAST_SCAN)
2535 					goto continue_resched;
2536 
2537 				/*
2538 				 * On the last scan, we clean up all those tags
2539 				 * we inserted; but make a note that we still
2540 				 * found pages pinned.
2541 				 */
2542 				error = -EBUSY;
2543 			}
2544 
2545 			spin_lock_irq(&mapping->tree_lock);
2546 			radix_tree_tag_clear(&mapping->page_tree,
2547 					     iter.index, SHMEM_TAG_PINNED);
2548 			spin_unlock_irq(&mapping->tree_lock);
2549 continue_resched:
2550 			if (need_resched()) {
2551 				slot = radix_tree_iter_resume(slot, &iter);
2552 				cond_resched_rcu();
2553 			}
2554 		}
2555 		rcu_read_unlock();
2556 	}
2557 
2558 	return error;
2559 }
2560 
2561 #define F_ALL_SEALS (F_SEAL_SEAL | \
2562 		     F_SEAL_SHRINK | \
2563 		     F_SEAL_GROW | \
2564 		     F_SEAL_WRITE)
2565 
2566 int shmem_add_seals(struct file *file, unsigned int seals)
2567 {
2568 	struct inode *inode = file_inode(file);
2569 	struct shmem_inode_info *info = SHMEM_I(inode);
2570 	int error;
2571 
2572 	/*
2573 	 * SEALING
2574 	 * Sealing allows multiple parties to share a shmem-file but restrict
2575 	 * access to a specific subset of file operations. Seals can only be
2576 	 * added, but never removed. This way, mutually untrusted parties can
2577 	 * share common memory regions with a well-defined policy. A malicious
2578 	 * peer can thus never perform unwanted operations on a shared object.
2579 	 *
2580 	 * Seals are only supported on special shmem-files and always affect
2581 	 * the whole underlying inode. Once a seal is set, it may prevent some
2582 	 * kinds of access to the file. Currently, the following seals are
2583 	 * defined:
2584 	 *   SEAL_SEAL: Prevent further seals from being set on this file
2585 	 *   SEAL_SHRINK: Prevent the file from shrinking
2586 	 *   SEAL_GROW: Prevent the file from growing
2587 	 *   SEAL_WRITE: Prevent write access to the file
2588 	 *
2589 	 * As we don't require any trust relationship between two parties, we
2590 	 * must prevent seals from being removed. Therefore, sealing a file
2591 	 * only adds a given set of seals to the file, it never touches
2592 	 * existing seals. Furthermore, the "setting seals"-operation can be
2593 	 * sealed itself, which basically prevents any further seal from being
2594 	 * added.
2595 	 *
2596 	 * Semantics of sealing are only defined on volatile files. Only
2597 	 * anonymous shmem files support sealing. More importantly, seals are
2598 	 * never written to disk. Therefore, there's no plan to support it on
2599 	 * other file types.
2600 	 */
2601 
2602 	if (file->f_op != &shmem_file_operations)
2603 		return -EINVAL;
2604 	if (!(file->f_mode & FMODE_WRITE))
2605 		return -EPERM;
2606 	if (seals & ~(unsigned int)F_ALL_SEALS)
2607 		return -EINVAL;
2608 
2609 	inode_lock(inode);
2610 
2611 	if (info->seals & F_SEAL_SEAL) {
2612 		error = -EPERM;
2613 		goto unlock;
2614 	}
2615 
2616 	if ((seals & F_SEAL_WRITE) && !(info->seals & F_SEAL_WRITE)) {
2617 		error = mapping_deny_writable(file->f_mapping);
2618 		if (error)
2619 			goto unlock;
2620 
2621 		error = shmem_wait_for_pins(file->f_mapping);
2622 		if (error) {
2623 			mapping_allow_writable(file->f_mapping);
2624 			goto unlock;
2625 		}
2626 	}
2627 
2628 	info->seals |= seals;
2629 	error = 0;
2630 
2631 unlock:
2632 	inode_unlock(inode);
2633 	return error;
2634 }
2635 EXPORT_SYMBOL_GPL(shmem_add_seals);
2636 
2637 int shmem_get_seals(struct file *file)
2638 {
2639 	if (file->f_op != &shmem_file_operations)
2640 		return -EINVAL;
2641 
2642 	return SHMEM_I(file_inode(file))->seals;
2643 }
2644 EXPORT_SYMBOL_GPL(shmem_get_seals);
2645 
2646 long shmem_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
2647 {
2648 	long error;
2649 
2650 	switch (cmd) {
2651 	case F_ADD_SEALS:
2652 		/* disallow upper 32bit */
2653 		if (arg > UINT_MAX)
2654 			return -EINVAL;
2655 
2656 		error = shmem_add_seals(file, arg);
2657 		break;
2658 	case F_GET_SEALS:
2659 		error = shmem_get_seals(file);
2660 		break;
2661 	default:
2662 		error = -EINVAL;
2663 		break;
2664 	}
2665 
2666 	return error;
2667 }
2668 
2669 static long shmem_fallocate(struct file *file, int mode, loff_t offset,
2670 							 loff_t len)
2671 {
2672 	struct inode *inode = file_inode(file);
2673 	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
2674 	struct shmem_inode_info *info = SHMEM_I(inode);
2675 	struct shmem_falloc shmem_falloc;
2676 	pgoff_t start, index, end;
2677 	int error;
2678 
2679 	if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
2680 		return -EOPNOTSUPP;
2681 
2682 	inode_lock(inode);
2683 
2684 	if (mode & FALLOC_FL_PUNCH_HOLE) {
2685 		struct address_space *mapping = file->f_mapping;
2686 		loff_t unmap_start = round_up(offset, PAGE_SIZE);
2687 		loff_t unmap_end = round_down(offset + len, PAGE_SIZE) - 1;
2688 		DECLARE_WAIT_QUEUE_HEAD_ONSTACK(shmem_falloc_waitq);
2689 
2690 		/* protected by i_mutex */
2691 		if (info->seals & F_SEAL_WRITE) {
2692 			error = -EPERM;
2693 			goto out;
2694 		}
2695 
2696 		shmem_falloc.waitq = &shmem_falloc_waitq;
2697 		shmem_falloc.start = unmap_start >> PAGE_SHIFT;
2698 		shmem_falloc.next = (unmap_end + 1) >> PAGE_SHIFT;
2699 		spin_lock(&inode->i_lock);
2700 		inode->i_private = &shmem_falloc;
2701 		spin_unlock(&inode->i_lock);
2702 
2703 		if ((u64)unmap_end > (u64)unmap_start)
2704 			unmap_mapping_range(mapping, unmap_start,
2705 					    1 + unmap_end - unmap_start, 0);
2706 		shmem_truncate_range(inode, offset, offset + len - 1);
2707 		/* No need to unmap again: hole-punching leaves COWed pages */
2708 
2709 		spin_lock(&inode->i_lock);
2710 		inode->i_private = NULL;
2711 		wake_up_all(&shmem_falloc_waitq);
2712 		WARN_ON_ONCE(!list_empty(&shmem_falloc_waitq.task_list));
2713 		spin_unlock(&inode->i_lock);
2714 		error = 0;
2715 		goto out;
2716 	}
2717 
2718 	/* We need to check rlimit even when FALLOC_FL_KEEP_SIZE */
2719 	error = inode_newsize_ok(inode, offset + len);
2720 	if (error)
2721 		goto out;
2722 
2723 	if ((info->seals & F_SEAL_GROW) && offset + len > inode->i_size) {
2724 		error = -EPERM;
2725 		goto out;
2726 	}
2727 
2728 	start = offset >> PAGE_SHIFT;
2729 	end = (offset + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
2730 	/* Try to avoid a swapstorm if len is impossible to satisfy */
2731 	if (sbinfo->max_blocks && end - start > sbinfo->max_blocks) {
2732 		error = -ENOSPC;
2733 		goto out;
2734 	}
2735 
2736 	shmem_falloc.waitq = NULL;
2737 	shmem_falloc.start = start;
2738 	shmem_falloc.next  = start;
2739 	shmem_falloc.nr_falloced = 0;
2740 	shmem_falloc.nr_unswapped = 0;
2741 	spin_lock(&inode->i_lock);
2742 	inode->i_private = &shmem_falloc;
2743 	spin_unlock(&inode->i_lock);
2744 
2745 	for (index = start; index < end; index++) {
2746 		struct page *page;
2747 
2748 		/*
2749 		 * Good, the fallocate(2) manpage permits EINTR: we may have
2750 		 * been interrupted because we are using up too much memory.
2751 		 */
2752 		if (signal_pending(current))
2753 			error = -EINTR;
2754 		else if (shmem_falloc.nr_unswapped > shmem_falloc.nr_falloced)
2755 			error = -ENOMEM;
2756 		else
2757 			error = shmem_getpage(inode, index, &page, SGP_FALLOC);
2758 		if (error) {
2759 			/* Remove the !PageUptodate pages we added */
2760 			if (index > start) {
2761 				shmem_undo_range(inode,
2762 				    (loff_t)start << PAGE_SHIFT,
2763 				    ((loff_t)index << PAGE_SHIFT) - 1, true);
2764 			}
2765 			goto undone;
2766 		}
2767 
2768 		/*
2769 		 * Inform shmem_writepage() how far we have reached.
2770 		 * No need for lock or barrier: we have the page lock.
2771 		 */
2772 		shmem_falloc.next++;
2773 		if (!PageUptodate(page))
2774 			shmem_falloc.nr_falloced++;
2775 
2776 		/*
2777 		 * If !PageUptodate, leave it that way so that freeable pages
2778 		 * can be recognized if we need to rollback on error later.
2779 		 * But set_page_dirty so that memory pressure will swap rather
2780 		 * than free the pages we are allocating (and SGP_CACHE pages
2781 		 * might still be clean: we now need to mark those dirty too).
2782 		 */
2783 		set_page_dirty(page);
2784 		unlock_page(page);
2785 		put_page(page);
2786 		cond_resched();
2787 	}
2788 
2789 	if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size)
2790 		i_size_write(inode, offset + len);
2791 	inode->i_ctime = current_time(inode);
2792 undone:
2793 	spin_lock(&inode->i_lock);
2794 	inode->i_private = NULL;
2795 	spin_unlock(&inode->i_lock);
2796 out:
2797 	inode_unlock(inode);
2798 	return error;
2799 }
2800 
2801 static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
2802 {
2803 	struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
2804 
2805 	buf->f_type = TMPFS_MAGIC;
2806 	buf->f_bsize = PAGE_SIZE;
2807 	buf->f_namelen = NAME_MAX;
2808 	if (sbinfo->max_blocks) {
2809 		buf->f_blocks = sbinfo->max_blocks;
2810 		buf->f_bavail =
2811 		buf->f_bfree  = sbinfo->max_blocks -
2812 				percpu_counter_sum(&sbinfo->used_blocks);
2813 	}
2814 	if (sbinfo->max_inodes) {
2815 		buf->f_files = sbinfo->max_inodes;
2816 		buf->f_ffree = sbinfo->free_inodes;
2817 	}
2818 	/* else leave those fields 0 like simple_statfs */
2819 	return 0;
2820 }
2821 
2822 /*
2823  * File creation. Allocate an inode, and we're done..
2824  */
2825 static int
2826 shmem_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
2827 {
2828 	struct inode *inode;
2829 	int error = -ENOSPC;
2830 
2831 	inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE);
2832 	if (inode) {
2833 		error = simple_acl_create(dir, inode);
2834 		if (error)
2835 			goto out_iput;
2836 		error = security_inode_init_security(inode, dir,
2837 						     &dentry->d_name,
2838 						     shmem_initxattrs, NULL);
2839 		if (error && error != -EOPNOTSUPP)
2840 			goto out_iput;
2841 
2842 		error = 0;
2843 		dir->i_size += BOGO_DIRENT_SIZE;
2844 		dir->i_ctime = dir->i_mtime = current_time(dir);
2845 		d_instantiate(dentry, inode);
2846 		dget(dentry); /* Extra count - pin the dentry in core */
2847 	}
2848 	return error;
2849 out_iput:
2850 	iput(inode);
2851 	return error;
2852 }
2853 
2854 static int
2855 shmem_tmpfile(struct inode *dir, struct dentry *dentry, umode_t mode)
2856 {
2857 	struct inode *inode;
2858 	int error = -ENOSPC;
2859 
2860 	inode = shmem_get_inode(dir->i_sb, dir, mode, 0, VM_NORESERVE);
2861 	if (inode) {
2862 		error = security_inode_init_security(inode, dir,
2863 						     NULL,
2864 						     shmem_initxattrs, NULL);
2865 		if (error && error != -EOPNOTSUPP)
2866 			goto out_iput;
2867 		error = simple_acl_create(dir, inode);
2868 		if (error)
2869 			goto out_iput;
2870 		d_tmpfile(dentry, inode);
2871 	}
2872 	return error;
2873 out_iput:
2874 	iput(inode);
2875 	return error;
2876 }
2877 
2878 static int shmem_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
2879 {
2880 	int error;
2881 
2882 	if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
2883 		return error;
2884 	inc_nlink(dir);
2885 	return 0;
2886 }
2887 
2888 static int shmem_create(struct inode *dir, struct dentry *dentry, umode_t mode,
2889 		bool excl)
2890 {
2891 	return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
2892 }
2893 
2894 /*
2895  * Link a file..
2896  */
2897 static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
2898 {
2899 	struct inode *inode = d_inode(old_dentry);
2900 	int ret;
2901 
2902 	/*
2903 	 * No ordinary (disk based) filesystem counts links as inodes;
2904 	 * but each new link needs a new dentry, pinning lowmem, and
2905 	 * tmpfs dentries cannot be pruned until they are unlinked.
2906 	 */
2907 	ret = shmem_reserve_inode(inode->i_sb);
2908 	if (ret)
2909 		goto out;
2910 
2911 	dir->i_size += BOGO_DIRENT_SIZE;
2912 	inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
2913 	inc_nlink(inode);
2914 	ihold(inode);	/* New dentry reference */
2915 	dget(dentry);		/* Extra pinning count for the created dentry */
2916 	d_instantiate(dentry, inode);
2917 out:
2918 	return ret;
2919 }
2920 
2921 static int shmem_unlink(struct inode *dir, struct dentry *dentry)
2922 {
2923 	struct inode *inode = d_inode(dentry);
2924 
2925 	if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
2926 		shmem_free_inode(inode->i_sb);
2927 
2928 	dir->i_size -= BOGO_DIRENT_SIZE;
2929 	inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
2930 	drop_nlink(inode);
2931 	dput(dentry);	/* Undo the count from "create" - this does all the work */
2932 	return 0;
2933 }
2934 
2935 static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
2936 {
2937 	if (!simple_empty(dentry))
2938 		return -ENOTEMPTY;
2939 
2940 	drop_nlink(d_inode(dentry));
2941 	drop_nlink(dir);
2942 	return shmem_unlink(dir, dentry);
2943 }
2944 
2945 static int shmem_exchange(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
2946 {
2947 	bool old_is_dir = d_is_dir(old_dentry);
2948 	bool new_is_dir = d_is_dir(new_dentry);
2949 
2950 	if (old_dir != new_dir && old_is_dir != new_is_dir) {
2951 		if (old_is_dir) {
2952 			drop_nlink(old_dir);
2953 			inc_nlink(new_dir);
2954 		} else {
2955 			drop_nlink(new_dir);
2956 			inc_nlink(old_dir);
2957 		}
2958 	}
2959 	old_dir->i_ctime = old_dir->i_mtime =
2960 	new_dir->i_ctime = new_dir->i_mtime =
2961 	d_inode(old_dentry)->i_ctime =
2962 	d_inode(new_dentry)->i_ctime = current_time(old_dir);
2963 
2964 	return 0;
2965 }
2966 
2967 static int shmem_whiteout(struct inode *old_dir, struct dentry *old_dentry)
2968 {
2969 	struct dentry *whiteout;
2970 	int error;
2971 
2972 	whiteout = d_alloc(old_dentry->d_parent, &old_dentry->d_name);
2973 	if (!whiteout)
2974 		return -ENOMEM;
2975 
2976 	error = shmem_mknod(old_dir, whiteout,
2977 			    S_IFCHR | WHITEOUT_MODE, WHITEOUT_DEV);
2978 	dput(whiteout);
2979 	if (error)
2980 		return error;
2981 
2982 	/*
2983 	 * Cheat and hash the whiteout while the old dentry is still in
2984 	 * place, instead of playing games with FS_RENAME_DOES_D_MOVE.
2985 	 *
2986 	 * d_lookup() will consistently find one of them at this point,
2987 	 * not sure which one, but that isn't even important.
2988 	 */
2989 	d_rehash(whiteout);
2990 	return 0;
2991 }
2992 
2993 /*
2994  * The VFS layer already does all the dentry stuff for rename,
2995  * we just have to decrement the usage count for the target if
2996  * it exists so that the VFS layer correctly free's it when it
2997  * gets overwritten.
2998  */
2999 static int shmem_rename2(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry, unsigned int flags)
3000 {
3001 	struct inode *inode = d_inode(old_dentry);
3002 	int they_are_dirs = S_ISDIR(inode->i_mode);
3003 
3004 	if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
3005 		return -EINVAL;
3006 
3007 	if (flags & RENAME_EXCHANGE)
3008 		return shmem_exchange(old_dir, old_dentry, new_dir, new_dentry);
3009 
3010 	if (!simple_empty(new_dentry))
3011 		return -ENOTEMPTY;
3012 
3013 	if (flags & RENAME_WHITEOUT) {
3014 		int error;
3015 
3016 		error = shmem_whiteout(old_dir, old_dentry);
3017 		if (error)
3018 			return error;
3019 	}
3020 
3021 	if (d_really_is_positive(new_dentry)) {
3022 		(void) shmem_unlink(new_dir, new_dentry);
3023 		if (they_are_dirs) {
3024 			drop_nlink(d_inode(new_dentry));
3025 			drop_nlink(old_dir);
3026 		}
3027 	} else if (they_are_dirs) {
3028 		drop_nlink(old_dir);
3029 		inc_nlink(new_dir);
3030 	}
3031 
3032 	old_dir->i_size -= BOGO_DIRENT_SIZE;
3033 	new_dir->i_size += BOGO_DIRENT_SIZE;
3034 	old_dir->i_ctime = old_dir->i_mtime =
3035 	new_dir->i_ctime = new_dir->i_mtime =
3036 	inode->i_ctime = current_time(old_dir);
3037 	return 0;
3038 }
3039 
3040 static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
3041 {
3042 	int error;
3043 	int len;
3044 	struct inode *inode;
3045 	struct page *page;
3046 	struct shmem_inode_info *info;
3047 
3048 	len = strlen(symname) + 1;
3049 	if (len > PAGE_SIZE)
3050 		return -ENAMETOOLONG;
3051 
3052 	inode = shmem_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0, VM_NORESERVE);
3053 	if (!inode)
3054 		return -ENOSPC;
3055 
3056 	error = security_inode_init_security(inode, dir, &dentry->d_name,
3057 					     shmem_initxattrs, NULL);
3058 	if (error) {
3059 		if (error != -EOPNOTSUPP) {
3060 			iput(inode);
3061 			return error;
3062 		}
3063 		error = 0;
3064 	}
3065 
3066 	info = SHMEM_I(inode);
3067 	inode->i_size = len-1;
3068 	if (len <= SHORT_SYMLINK_LEN) {
3069 		inode->i_link = kmemdup(symname, len, GFP_KERNEL);
3070 		if (!inode->i_link) {
3071 			iput(inode);
3072 			return -ENOMEM;
3073 		}
3074 		inode->i_op = &shmem_short_symlink_operations;
3075 	} else {
3076 		inode_nohighmem(inode);
3077 		error = shmem_getpage(inode, 0, &page, SGP_WRITE);
3078 		if (error) {
3079 			iput(inode);
3080 			return error;
3081 		}
3082 		inode->i_mapping->a_ops = &shmem_aops;
3083 		inode->i_op = &shmem_symlink_inode_operations;
3084 		memcpy(page_address(page), symname, len);
3085 		SetPageUptodate(page);
3086 		set_page_dirty(page);
3087 		unlock_page(page);
3088 		put_page(page);
3089 	}
3090 	dir->i_size += BOGO_DIRENT_SIZE;
3091 	dir->i_ctime = dir->i_mtime = current_time(dir);
3092 	d_instantiate(dentry, inode);
3093 	dget(dentry);
3094 	return 0;
3095 }
3096 
3097 static void shmem_put_link(void *arg)
3098 {
3099 	mark_page_accessed(arg);
3100 	put_page(arg);
3101 }
3102 
3103 static const char *shmem_get_link(struct dentry *dentry,
3104 				  struct inode *inode,
3105 				  struct delayed_call *done)
3106 {
3107 	struct page *page = NULL;
3108 	int error;
3109 	if (!dentry) {
3110 		page = find_get_page(inode->i_mapping, 0);
3111 		if (!page)
3112 			return ERR_PTR(-ECHILD);
3113 		if (!PageUptodate(page)) {
3114 			put_page(page);
3115 			return ERR_PTR(-ECHILD);
3116 		}
3117 	} else {
3118 		error = shmem_getpage(inode, 0, &page, SGP_READ);
3119 		if (error)
3120 			return ERR_PTR(error);
3121 		unlock_page(page);
3122 	}
3123 	set_delayed_call(done, shmem_put_link, page);
3124 	return page_address(page);
3125 }
3126 
3127 #ifdef CONFIG_TMPFS_XATTR
3128 /*
3129  * Superblocks without xattr inode operations may get some security.* xattr
3130  * support from the LSM "for free". As soon as we have any other xattrs
3131  * like ACLs, we also need to implement the security.* handlers at
3132  * filesystem level, though.
3133  */
3134 
3135 /*
3136  * Callback for security_inode_init_security() for acquiring xattrs.
3137  */
3138 static int shmem_initxattrs(struct inode *inode,
3139 			    const struct xattr *xattr_array,
3140 			    void *fs_info)
3141 {
3142 	struct shmem_inode_info *info = SHMEM_I(inode);
3143 	const struct xattr *xattr;
3144 	struct simple_xattr *new_xattr;
3145 	size_t len;
3146 
3147 	for (xattr = xattr_array; xattr->name != NULL; xattr++) {
3148 		new_xattr = simple_xattr_alloc(xattr->value, xattr->value_len);
3149 		if (!new_xattr)
3150 			return -ENOMEM;
3151 
3152 		len = strlen(xattr->name) + 1;
3153 		new_xattr->name = kmalloc(XATTR_SECURITY_PREFIX_LEN + len,
3154 					  GFP_KERNEL);
3155 		if (!new_xattr->name) {
3156 			kfree(new_xattr);
3157 			return -ENOMEM;
3158 		}
3159 
3160 		memcpy(new_xattr->name, XATTR_SECURITY_PREFIX,
3161 		       XATTR_SECURITY_PREFIX_LEN);
3162 		memcpy(new_xattr->name + XATTR_SECURITY_PREFIX_LEN,
3163 		       xattr->name, len);
3164 
3165 		simple_xattr_list_add(&info->xattrs, new_xattr);
3166 	}
3167 
3168 	return 0;
3169 }
3170 
3171 static int shmem_xattr_handler_get(const struct xattr_handler *handler,
3172 				   struct dentry *unused, struct inode *inode,
3173 				   const char *name, void *buffer, size_t size)
3174 {
3175 	struct shmem_inode_info *info = SHMEM_I(inode);
3176 
3177 	name = xattr_full_name(handler, name);
3178 	return simple_xattr_get(&info->xattrs, name, buffer, size);
3179 }
3180 
3181 static int shmem_xattr_handler_set(const struct xattr_handler *handler,
3182 				   struct dentry *unused, struct inode *inode,
3183 				   const char *name, const void *value,
3184 				   size_t size, int flags)
3185 {
3186 	struct shmem_inode_info *info = SHMEM_I(inode);
3187 
3188 	name = xattr_full_name(handler, name);
3189 	return simple_xattr_set(&info->xattrs, name, value, size, flags);
3190 }
3191 
3192 static const struct xattr_handler shmem_security_xattr_handler = {
3193 	.prefix = XATTR_SECURITY_PREFIX,
3194 	.get = shmem_xattr_handler_get,
3195 	.set = shmem_xattr_handler_set,
3196 };
3197 
3198 static const struct xattr_handler shmem_trusted_xattr_handler = {
3199 	.prefix = XATTR_TRUSTED_PREFIX,
3200 	.get = shmem_xattr_handler_get,
3201 	.set = shmem_xattr_handler_set,
3202 };
3203 
3204 static const struct xattr_handler *shmem_xattr_handlers[] = {
3205 #ifdef CONFIG_TMPFS_POSIX_ACL
3206 	&posix_acl_access_xattr_handler,
3207 	&posix_acl_default_xattr_handler,
3208 #endif
3209 	&shmem_security_xattr_handler,
3210 	&shmem_trusted_xattr_handler,
3211 	NULL
3212 };
3213 
3214 static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t size)
3215 {
3216 	struct shmem_inode_info *info = SHMEM_I(d_inode(dentry));
3217 	return simple_xattr_list(d_inode(dentry), &info->xattrs, buffer, size);
3218 }
3219 #endif /* CONFIG_TMPFS_XATTR */
3220 
3221 static const struct inode_operations shmem_short_symlink_operations = {
3222 	.get_link	= simple_get_link,
3223 #ifdef CONFIG_TMPFS_XATTR
3224 	.listxattr	= shmem_listxattr,
3225 #endif
3226 };
3227 
3228 static const struct inode_operations shmem_symlink_inode_operations = {
3229 	.get_link	= shmem_get_link,
3230 #ifdef CONFIG_TMPFS_XATTR
3231 	.listxattr	= shmem_listxattr,
3232 #endif
3233 };
3234 
3235 static struct dentry *shmem_get_parent(struct dentry *child)
3236 {
3237 	return ERR_PTR(-ESTALE);
3238 }
3239 
3240 static int shmem_match(struct inode *ino, void *vfh)
3241 {
3242 	__u32 *fh = vfh;
3243 	__u64 inum = fh[2];
3244 	inum = (inum << 32) | fh[1];
3245 	return ino->i_ino == inum && fh[0] == ino->i_generation;
3246 }
3247 
3248 static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
3249 		struct fid *fid, int fh_len, int fh_type)
3250 {
3251 	struct inode *inode;
3252 	struct dentry *dentry = NULL;
3253 	u64 inum;
3254 
3255 	if (fh_len < 3)
3256 		return NULL;
3257 
3258 	inum = fid->raw[2];
3259 	inum = (inum << 32) | fid->raw[1];
3260 
3261 	inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
3262 			shmem_match, fid->raw);
3263 	if (inode) {
3264 		dentry = d_find_alias(inode);
3265 		iput(inode);
3266 	}
3267 
3268 	return dentry;
3269 }
3270 
3271 static int shmem_encode_fh(struct inode *inode, __u32 *fh, int *len,
3272 				struct inode *parent)
3273 {
3274 	if (*len < 3) {
3275 		*len = 3;
3276 		return FILEID_INVALID;
3277 	}
3278 
3279 	if (inode_unhashed(inode)) {
3280 		/* Unfortunately insert_inode_hash is not idempotent,
3281 		 * so as we hash inodes here rather than at creation
3282 		 * time, we need a lock to ensure we only try
3283 		 * to do it once
3284 		 */
3285 		static DEFINE_SPINLOCK(lock);
3286 		spin_lock(&lock);
3287 		if (inode_unhashed(inode))
3288 			__insert_inode_hash(inode,
3289 					    inode->i_ino + inode->i_generation);
3290 		spin_unlock(&lock);
3291 	}
3292 
3293 	fh[0] = inode->i_generation;
3294 	fh[1] = inode->i_ino;
3295 	fh[2] = ((__u64)inode->i_ino) >> 32;
3296 
3297 	*len = 3;
3298 	return 1;
3299 }
3300 
3301 static const struct export_operations shmem_export_ops = {
3302 	.get_parent     = shmem_get_parent,
3303 	.encode_fh      = shmem_encode_fh,
3304 	.fh_to_dentry	= shmem_fh_to_dentry,
3305 };
3306 
3307 static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
3308 			       bool remount)
3309 {
3310 	char *this_char, *value, *rest;
3311 	struct mempolicy *mpol = NULL;
3312 	uid_t uid;
3313 	gid_t gid;
3314 
3315 	while (options != NULL) {
3316 		this_char = options;
3317 		for (;;) {
3318 			/*
3319 			 * NUL-terminate this option: unfortunately,
3320 			 * mount options form a comma-separated list,
3321 			 * but mpol's nodelist may also contain commas.
3322 			 */
3323 			options = strchr(options, ',');
3324 			if (options == NULL)
3325 				break;
3326 			options++;
3327 			if (!isdigit(*options)) {
3328 				options[-1] = '\0';
3329 				break;
3330 			}
3331 		}
3332 		if (!*this_char)
3333 			continue;
3334 		if ((value = strchr(this_char,'=')) != NULL) {
3335 			*value++ = 0;
3336 		} else {
3337 			pr_err("tmpfs: No value for mount option '%s'\n",
3338 			       this_char);
3339 			goto error;
3340 		}
3341 
3342 		if (!strcmp(this_char,"size")) {
3343 			unsigned long long size;
3344 			size = memparse(value,&rest);
3345 			if (*rest == '%') {
3346 				size <<= PAGE_SHIFT;
3347 				size *= totalram_pages;
3348 				do_div(size, 100);
3349 				rest++;
3350 			}
3351 			if (*rest)
3352 				goto bad_val;
3353 			sbinfo->max_blocks =
3354 				DIV_ROUND_UP(size, PAGE_SIZE);
3355 		} else if (!strcmp(this_char,"nr_blocks")) {
3356 			sbinfo->max_blocks = memparse(value, &rest);
3357 			if (*rest)
3358 				goto bad_val;
3359 		} else if (!strcmp(this_char,"nr_inodes")) {
3360 			sbinfo->max_inodes = memparse(value, &rest);
3361 			if (*rest)
3362 				goto bad_val;
3363 		} else if (!strcmp(this_char,"mode")) {
3364 			if (remount)
3365 				continue;
3366 			sbinfo->mode = simple_strtoul(value, &rest, 8) & 07777;
3367 			if (*rest)
3368 				goto bad_val;
3369 		} else if (!strcmp(this_char,"uid")) {
3370 			if (remount)
3371 				continue;
3372 			uid = simple_strtoul(value, &rest, 0);
3373 			if (*rest)
3374 				goto bad_val;
3375 			sbinfo->uid = make_kuid(current_user_ns(), uid);
3376 			if (!uid_valid(sbinfo->uid))
3377 				goto bad_val;
3378 		} else if (!strcmp(this_char,"gid")) {
3379 			if (remount)
3380 				continue;
3381 			gid = simple_strtoul(value, &rest, 0);
3382 			if (*rest)
3383 				goto bad_val;
3384 			sbinfo->gid = make_kgid(current_user_ns(), gid);
3385 			if (!gid_valid(sbinfo->gid))
3386 				goto bad_val;
3387 #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
3388 		} else if (!strcmp(this_char, "huge")) {
3389 			int huge;
3390 			huge = shmem_parse_huge(value);
3391 			if (huge < 0)
3392 				goto bad_val;
3393 			if (!has_transparent_hugepage() &&
3394 					huge != SHMEM_HUGE_NEVER)
3395 				goto bad_val;
3396 			sbinfo->huge = huge;
3397 #endif
3398 #ifdef CONFIG_NUMA
3399 		} else if (!strcmp(this_char,"mpol")) {
3400 			mpol_put(mpol);
3401 			mpol = NULL;
3402 			if (mpol_parse_str(value, &mpol))
3403 				goto bad_val;
3404 #endif
3405 		} else {
3406 			pr_err("tmpfs: Bad mount option %s\n", this_char);
3407 			goto error;
3408 		}
3409 	}
3410 	sbinfo->mpol = mpol;
3411 	return 0;
3412 
3413 bad_val:
3414 	pr_err("tmpfs: Bad value '%s' for mount option '%s'\n",
3415 	       value, this_char);
3416 error:
3417 	mpol_put(mpol);
3418 	return 1;
3419 
3420 }
3421 
3422 static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
3423 {
3424 	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
3425 	struct shmem_sb_info config = *sbinfo;
3426 	unsigned long inodes;
3427 	int error = -EINVAL;
3428 
3429 	config.mpol = NULL;
3430 	if (shmem_parse_options(data, &config, true))
3431 		return error;
3432 
3433 	spin_lock(&sbinfo->stat_lock);
3434 	inodes = sbinfo->max_inodes - sbinfo->free_inodes;
3435 	if (percpu_counter_compare(&sbinfo->used_blocks, config.max_blocks) > 0)
3436 		goto out;
3437 	if (config.max_inodes < inodes)
3438 		goto out;
3439 	/*
3440 	 * Those tests disallow limited->unlimited while any are in use;
3441 	 * but we must separately disallow unlimited->limited, because
3442 	 * in that case we have no record of how much is already in use.
3443 	 */
3444 	if (config.max_blocks && !sbinfo->max_blocks)
3445 		goto out;
3446 	if (config.max_inodes && !sbinfo->max_inodes)
3447 		goto out;
3448 
3449 	error = 0;
3450 	sbinfo->huge = config.huge;
3451 	sbinfo->max_blocks  = config.max_blocks;
3452 	sbinfo->max_inodes  = config.max_inodes;
3453 	sbinfo->free_inodes = config.max_inodes - inodes;
3454 
3455 	/*
3456 	 * Preserve previous mempolicy unless mpol remount option was specified.
3457 	 */
3458 	if (config.mpol) {
3459 		mpol_put(sbinfo->mpol);
3460 		sbinfo->mpol = config.mpol;	/* transfers initial ref */
3461 	}
3462 out:
3463 	spin_unlock(&sbinfo->stat_lock);
3464 	return error;
3465 }
3466 
3467 static int shmem_show_options(struct seq_file *seq, struct dentry *root)
3468 {
3469 	struct shmem_sb_info *sbinfo = SHMEM_SB(root->d_sb);
3470 
3471 	if (sbinfo->max_blocks != shmem_default_max_blocks())
3472 		seq_printf(seq, ",size=%luk",
3473 			sbinfo->max_blocks << (PAGE_SHIFT - 10));
3474 	if (sbinfo->max_inodes != shmem_default_max_inodes())
3475 		seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
3476 	if (sbinfo->mode != (S_IRWXUGO | S_ISVTX))
3477 		seq_printf(seq, ",mode=%03ho", sbinfo->mode);
3478 	if (!uid_eq(sbinfo->uid, GLOBAL_ROOT_UID))
3479 		seq_printf(seq, ",uid=%u",
3480 				from_kuid_munged(&init_user_ns, sbinfo->uid));
3481 	if (!gid_eq(sbinfo->gid, GLOBAL_ROOT_GID))
3482 		seq_printf(seq, ",gid=%u",
3483 				from_kgid_munged(&init_user_ns, sbinfo->gid));
3484 #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
3485 	/* Rightly or wrongly, show huge mount option unmasked by shmem_huge */
3486 	if (sbinfo->huge)
3487 		seq_printf(seq, ",huge=%s", shmem_format_huge(sbinfo->huge));
3488 #endif
3489 	shmem_show_mpol(seq, sbinfo->mpol);
3490 	return 0;
3491 }
3492 
3493 #define MFD_NAME_PREFIX "memfd:"
3494 #define MFD_NAME_PREFIX_LEN (sizeof(MFD_NAME_PREFIX) - 1)
3495 #define MFD_NAME_MAX_LEN (NAME_MAX - MFD_NAME_PREFIX_LEN)
3496 
3497 #define MFD_ALL_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING)
3498 
3499 SYSCALL_DEFINE2(memfd_create,
3500 		const char __user *, uname,
3501 		unsigned int, flags)
3502 {
3503 	struct shmem_inode_info *info;
3504 	struct file *file;
3505 	int fd, error;
3506 	char *name;
3507 	long len;
3508 
3509 	if (flags & ~(unsigned int)MFD_ALL_FLAGS)
3510 		return -EINVAL;
3511 
3512 	/* length includes terminating zero */
3513 	len = strnlen_user(uname, MFD_NAME_MAX_LEN + 1);
3514 	if (len <= 0)
3515 		return -EFAULT;
3516 	if (len > MFD_NAME_MAX_LEN + 1)
3517 		return -EINVAL;
3518 
3519 	name = kmalloc(len + MFD_NAME_PREFIX_LEN, GFP_TEMPORARY);
3520 	if (!name)
3521 		return -ENOMEM;
3522 
3523 	strcpy(name, MFD_NAME_PREFIX);
3524 	if (copy_from_user(&name[MFD_NAME_PREFIX_LEN], uname, len)) {
3525 		error = -EFAULT;
3526 		goto err_name;
3527 	}
3528 
3529 	/* terminating-zero may have changed after strnlen_user() returned */
3530 	if (name[len + MFD_NAME_PREFIX_LEN - 1]) {
3531 		error = -EFAULT;
3532 		goto err_name;
3533 	}
3534 
3535 	fd = get_unused_fd_flags((flags & MFD_CLOEXEC) ? O_CLOEXEC : 0);
3536 	if (fd < 0) {
3537 		error = fd;
3538 		goto err_name;
3539 	}
3540 
3541 	file = shmem_file_setup(name, 0, VM_NORESERVE);
3542 	if (IS_ERR(file)) {
3543 		error = PTR_ERR(file);
3544 		goto err_fd;
3545 	}
3546 	info = SHMEM_I(file_inode(file));
3547 	file->f_mode |= FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE;
3548 	file->f_flags |= O_RDWR | O_LARGEFILE;
3549 	if (flags & MFD_ALLOW_SEALING)
3550 		info->seals &= ~F_SEAL_SEAL;
3551 
3552 	fd_install(fd, file);
3553 	kfree(name);
3554 	return fd;
3555 
3556 err_fd:
3557 	put_unused_fd(fd);
3558 err_name:
3559 	kfree(name);
3560 	return error;
3561 }
3562 
3563 #endif /* CONFIG_TMPFS */
3564 
3565 static void shmem_put_super(struct super_block *sb)
3566 {
3567 	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
3568 
3569 	percpu_counter_destroy(&sbinfo->used_blocks);
3570 	mpol_put(sbinfo->mpol);
3571 	kfree(sbinfo);
3572 	sb->s_fs_info = NULL;
3573 }
3574 
3575 int shmem_fill_super(struct super_block *sb, void *data, int silent)
3576 {
3577 	struct inode *inode;
3578 	struct shmem_sb_info *sbinfo;
3579 	int err = -ENOMEM;
3580 
3581 	/* Round up to L1_CACHE_BYTES to resist false sharing */
3582 	sbinfo = kzalloc(max((int)sizeof(struct shmem_sb_info),
3583 				L1_CACHE_BYTES), GFP_KERNEL);
3584 	if (!sbinfo)
3585 		return -ENOMEM;
3586 
3587 	sbinfo->mode = S_IRWXUGO | S_ISVTX;
3588 	sbinfo->uid = current_fsuid();
3589 	sbinfo->gid = current_fsgid();
3590 	sb->s_fs_info = sbinfo;
3591 
3592 #ifdef CONFIG_TMPFS
3593 	/*
3594 	 * Per default we only allow half of the physical ram per
3595 	 * tmpfs instance, limiting inodes to one per page of lowmem;
3596 	 * but the internal instance is left unlimited.
3597 	 */
3598 	if (!(sb->s_flags & MS_KERNMOUNT)) {
3599 		sbinfo->max_blocks = shmem_default_max_blocks();
3600 		sbinfo->max_inodes = shmem_default_max_inodes();
3601 		if (shmem_parse_options(data, sbinfo, false)) {
3602 			err = -EINVAL;
3603 			goto failed;
3604 		}
3605 	} else {
3606 		sb->s_flags |= MS_NOUSER;
3607 	}
3608 	sb->s_export_op = &shmem_export_ops;
3609 	sb->s_flags |= MS_NOSEC;
3610 #else
3611 	sb->s_flags |= MS_NOUSER;
3612 #endif
3613 
3614 	spin_lock_init(&sbinfo->stat_lock);
3615 	if (percpu_counter_init(&sbinfo->used_blocks, 0, GFP_KERNEL))
3616 		goto failed;
3617 	sbinfo->free_inodes = sbinfo->max_inodes;
3618 	spin_lock_init(&sbinfo->shrinklist_lock);
3619 	INIT_LIST_HEAD(&sbinfo->shrinklist);
3620 
3621 	sb->s_maxbytes = MAX_LFS_FILESIZE;
3622 	sb->s_blocksize = PAGE_SIZE;
3623 	sb->s_blocksize_bits = PAGE_SHIFT;
3624 	sb->s_magic = TMPFS_MAGIC;
3625 	sb->s_op = &shmem_ops;
3626 	sb->s_time_gran = 1;
3627 #ifdef CONFIG_TMPFS_XATTR
3628 	sb->s_xattr = shmem_xattr_handlers;
3629 #endif
3630 #ifdef CONFIG_TMPFS_POSIX_ACL
3631 	sb->s_flags |= MS_POSIXACL;
3632 #endif
3633 
3634 	inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
3635 	if (!inode)
3636 		goto failed;
3637 	inode->i_uid = sbinfo->uid;
3638 	inode->i_gid = sbinfo->gid;
3639 	sb->s_root = d_make_root(inode);
3640 	if (!sb->s_root)
3641 		goto failed;
3642 	return 0;
3643 
3644 failed:
3645 	shmem_put_super(sb);
3646 	return err;
3647 }
3648 
3649 static struct kmem_cache *shmem_inode_cachep;
3650 
3651 static struct inode *shmem_alloc_inode(struct super_block *sb)
3652 {
3653 	struct shmem_inode_info *info;
3654 	info = kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
3655 	if (!info)
3656 		return NULL;
3657 	return &info->vfs_inode;
3658 }
3659 
3660 static void shmem_destroy_callback(struct rcu_head *head)
3661 {
3662 	struct inode *inode = container_of(head, struct inode, i_rcu);
3663 	if (S_ISLNK(inode->i_mode))
3664 		kfree(inode->i_link);
3665 	kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
3666 }
3667 
3668 static void shmem_destroy_inode(struct inode *inode)
3669 {
3670 	if (S_ISREG(inode->i_mode))
3671 		mpol_free_shared_policy(&SHMEM_I(inode)->policy);
3672 	call_rcu(&inode->i_rcu, shmem_destroy_callback);
3673 }
3674 
3675 static void shmem_init_inode(void *foo)
3676 {
3677 	struct shmem_inode_info *info = foo;
3678 	inode_init_once(&info->vfs_inode);
3679 }
3680 
3681 static int shmem_init_inodecache(void)
3682 {
3683 	shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
3684 				sizeof(struct shmem_inode_info),
3685 				0, SLAB_PANIC|SLAB_ACCOUNT, shmem_init_inode);
3686 	return 0;
3687 }
3688 
3689 static void shmem_destroy_inodecache(void)
3690 {
3691 	kmem_cache_destroy(shmem_inode_cachep);
3692 }
3693 
3694 static const struct address_space_operations shmem_aops = {
3695 	.writepage	= shmem_writepage,
3696 	.set_page_dirty	= __set_page_dirty_no_writeback,
3697 #ifdef CONFIG_TMPFS
3698 	.write_begin	= shmem_write_begin,
3699 	.write_end	= shmem_write_end,
3700 #endif
3701 #ifdef CONFIG_MIGRATION
3702 	.migratepage	= migrate_page,
3703 #endif
3704 	.error_remove_page = generic_error_remove_page,
3705 };
3706 
3707 static const struct file_operations shmem_file_operations = {
3708 	.mmap		= shmem_mmap,
3709 	.get_unmapped_area = shmem_get_unmapped_area,
3710 #ifdef CONFIG_TMPFS
3711 	.llseek		= shmem_file_llseek,
3712 	.read_iter	= shmem_file_read_iter,
3713 	.write_iter	= generic_file_write_iter,
3714 	.fsync		= noop_fsync,
3715 	.splice_read	= generic_file_splice_read,
3716 	.splice_write	= iter_file_splice_write,
3717 	.fallocate	= shmem_fallocate,
3718 #endif
3719 };
3720 
3721 static const struct inode_operations shmem_inode_operations = {
3722 	.getattr	= shmem_getattr,
3723 	.setattr	= shmem_setattr,
3724 #ifdef CONFIG_TMPFS_XATTR
3725 	.listxattr	= shmem_listxattr,
3726 	.set_acl	= simple_set_acl,
3727 #endif
3728 };
3729 
3730 static const struct inode_operations shmem_dir_inode_operations = {
3731 #ifdef CONFIG_TMPFS
3732 	.create		= shmem_create,
3733 	.lookup		= simple_lookup,
3734 	.link		= shmem_link,
3735 	.unlink		= shmem_unlink,
3736 	.symlink	= shmem_symlink,
3737 	.mkdir		= shmem_mkdir,
3738 	.rmdir		= shmem_rmdir,
3739 	.mknod		= shmem_mknod,
3740 	.rename		= shmem_rename2,
3741 	.tmpfile	= shmem_tmpfile,
3742 #endif
3743 #ifdef CONFIG_TMPFS_XATTR
3744 	.listxattr	= shmem_listxattr,
3745 #endif
3746 #ifdef CONFIG_TMPFS_POSIX_ACL
3747 	.setattr	= shmem_setattr,
3748 	.set_acl	= simple_set_acl,
3749 #endif
3750 };
3751 
3752 static const struct inode_operations shmem_special_inode_operations = {
3753 #ifdef CONFIG_TMPFS_XATTR
3754 	.listxattr	= shmem_listxattr,
3755 #endif
3756 #ifdef CONFIG_TMPFS_POSIX_ACL
3757 	.setattr	= shmem_setattr,
3758 	.set_acl	= simple_set_acl,
3759 #endif
3760 };
3761 
3762 static const struct super_operations shmem_ops = {
3763 	.alloc_inode	= shmem_alloc_inode,
3764 	.destroy_inode	= shmem_destroy_inode,
3765 #ifdef CONFIG_TMPFS
3766 	.statfs		= shmem_statfs,
3767 	.remount_fs	= shmem_remount_fs,
3768 	.show_options	= shmem_show_options,
3769 #endif
3770 	.evict_inode	= shmem_evict_inode,
3771 	.drop_inode	= generic_delete_inode,
3772 	.put_super	= shmem_put_super,
3773 #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
3774 	.nr_cached_objects	= shmem_unused_huge_count,
3775 	.free_cached_objects	= shmem_unused_huge_scan,
3776 #endif
3777 };
3778 
3779 static const struct vm_operations_struct shmem_vm_ops = {
3780 	.fault		= shmem_fault,
3781 	.map_pages	= filemap_map_pages,
3782 #ifdef CONFIG_NUMA
3783 	.set_policy     = shmem_set_policy,
3784 	.get_policy     = shmem_get_policy,
3785 #endif
3786 };
3787 
3788 static struct dentry *shmem_mount(struct file_system_type *fs_type,
3789 	int flags, const char *dev_name, void *data)
3790 {
3791 	return mount_nodev(fs_type, flags, data, shmem_fill_super);
3792 }
3793 
3794 static struct file_system_type shmem_fs_type = {
3795 	.owner		= THIS_MODULE,
3796 	.name		= "tmpfs",
3797 	.mount		= shmem_mount,
3798 	.kill_sb	= kill_litter_super,
3799 	.fs_flags	= FS_USERNS_MOUNT,
3800 };
3801 
3802 int __init shmem_init(void)
3803 {
3804 	int error;
3805 
3806 	/* If rootfs called this, don't re-init */
3807 	if (shmem_inode_cachep)
3808 		return 0;
3809 
3810 	error = shmem_init_inodecache();
3811 	if (error)
3812 		goto out3;
3813 
3814 	error = register_filesystem(&shmem_fs_type);
3815 	if (error) {
3816 		pr_err("Could not register tmpfs\n");
3817 		goto out2;
3818 	}
3819 
3820 	shm_mnt = kern_mount(&shmem_fs_type);
3821 	if (IS_ERR(shm_mnt)) {
3822 		error = PTR_ERR(shm_mnt);
3823 		pr_err("Could not kern_mount tmpfs\n");
3824 		goto out1;
3825 	}
3826 
3827 #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
3828 	if (has_transparent_hugepage() && shmem_huge < SHMEM_HUGE_DENY)
3829 		SHMEM_SB(shm_mnt->mnt_sb)->huge = shmem_huge;
3830 	else
3831 		shmem_huge = 0; /* just in case it was patched */
3832 #endif
3833 	return 0;
3834 
3835 out1:
3836 	unregister_filesystem(&shmem_fs_type);
3837 out2:
3838 	shmem_destroy_inodecache();
3839 out3:
3840 	shm_mnt = ERR_PTR(error);
3841 	return error;
3842 }
3843 
3844 #if defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE) && defined(CONFIG_SYSFS)
3845 static ssize_t shmem_enabled_show(struct kobject *kobj,
3846 		struct kobj_attribute *attr, char *buf)
3847 {
3848 	int values[] = {
3849 		SHMEM_HUGE_ALWAYS,
3850 		SHMEM_HUGE_WITHIN_SIZE,
3851 		SHMEM_HUGE_ADVISE,
3852 		SHMEM_HUGE_NEVER,
3853 		SHMEM_HUGE_DENY,
3854 		SHMEM_HUGE_FORCE,
3855 	};
3856 	int i, count;
3857 
3858 	for (i = 0, count = 0; i < ARRAY_SIZE(values); i++) {
3859 		const char *fmt = shmem_huge == values[i] ? "[%s] " : "%s ";
3860 
3861 		count += sprintf(buf + count, fmt,
3862 				shmem_format_huge(values[i]));
3863 	}
3864 	buf[count - 1] = '\n';
3865 	return count;
3866 }
3867 
3868 static ssize_t shmem_enabled_store(struct kobject *kobj,
3869 		struct kobj_attribute *attr, const char *buf, size_t count)
3870 {
3871 	char tmp[16];
3872 	int huge;
3873 
3874 	if (count + 1 > sizeof(tmp))
3875 		return -EINVAL;
3876 	memcpy(tmp, buf, count);
3877 	tmp[count] = '\0';
3878 	if (count && tmp[count - 1] == '\n')
3879 		tmp[count - 1] = '\0';
3880 
3881 	huge = shmem_parse_huge(tmp);
3882 	if (huge == -EINVAL)
3883 		return -EINVAL;
3884 	if (!has_transparent_hugepage() &&
3885 			huge != SHMEM_HUGE_NEVER && huge != SHMEM_HUGE_DENY)
3886 		return -EINVAL;
3887 
3888 	shmem_huge = huge;
3889 	if (shmem_huge < SHMEM_HUGE_DENY)
3890 		SHMEM_SB(shm_mnt->mnt_sb)->huge = shmem_huge;
3891 	return count;
3892 }
3893 
3894 struct kobj_attribute shmem_enabled_attr =
3895 	__ATTR(shmem_enabled, 0644, shmem_enabled_show, shmem_enabled_store);
3896 #endif /* CONFIG_TRANSPARENT_HUGE_PAGECACHE && CONFIG_SYSFS */
3897 
3898 #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
3899 bool shmem_huge_enabled(struct vm_area_struct *vma)
3900 {
3901 	struct inode *inode = file_inode(vma->vm_file);
3902 	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
3903 	loff_t i_size;
3904 	pgoff_t off;
3905 
3906 	if (shmem_huge == SHMEM_HUGE_FORCE)
3907 		return true;
3908 	if (shmem_huge == SHMEM_HUGE_DENY)
3909 		return false;
3910 	switch (sbinfo->huge) {
3911 		case SHMEM_HUGE_NEVER:
3912 			return false;
3913 		case SHMEM_HUGE_ALWAYS:
3914 			return true;
3915 		case SHMEM_HUGE_WITHIN_SIZE:
3916 			off = round_up(vma->vm_pgoff, HPAGE_PMD_NR);
3917 			i_size = round_up(i_size_read(inode), PAGE_SIZE);
3918 			if (i_size >= HPAGE_PMD_SIZE &&
3919 					i_size >> PAGE_SHIFT >= off)
3920 				return true;
3921 		case SHMEM_HUGE_ADVISE:
3922 			/* TODO: implement fadvise() hints */
3923 			return (vma->vm_flags & VM_HUGEPAGE);
3924 		default:
3925 			VM_BUG_ON(1);
3926 			return false;
3927 	}
3928 }
3929 #endif /* CONFIG_TRANSPARENT_HUGE_PAGECACHE */
3930 
3931 #else /* !CONFIG_SHMEM */
3932 
3933 /*
3934  * tiny-shmem: simple shmemfs and tmpfs using ramfs code
3935  *
3936  * This is intended for small system where the benefits of the full
3937  * shmem code (swap-backed and resource-limited) are outweighed by
3938  * their complexity. On systems without swap this code should be
3939  * effectively equivalent, but much lighter weight.
3940  */
3941 
3942 static struct file_system_type shmem_fs_type = {
3943 	.name		= "tmpfs",
3944 	.mount		= ramfs_mount,
3945 	.kill_sb	= kill_litter_super,
3946 	.fs_flags	= FS_USERNS_MOUNT,
3947 };
3948 
3949 int __init shmem_init(void)
3950 {
3951 	BUG_ON(register_filesystem(&shmem_fs_type) != 0);
3952 
3953 	shm_mnt = kern_mount(&shmem_fs_type);
3954 	BUG_ON(IS_ERR(shm_mnt));
3955 
3956 	return 0;
3957 }
3958 
3959 int shmem_unuse(swp_entry_t swap, struct page *page)
3960 {
3961 	return 0;
3962 }
3963 
3964 int shmem_lock(struct file *file, int lock, struct user_struct *user)
3965 {
3966 	return 0;
3967 }
3968 
3969 void shmem_unlock_mapping(struct address_space *mapping)
3970 {
3971 }
3972 
3973 #ifdef CONFIG_MMU
3974 unsigned long shmem_get_unmapped_area(struct file *file,
3975 				      unsigned long addr, unsigned long len,
3976 				      unsigned long pgoff, unsigned long flags)
3977 {
3978 	return current->mm->get_unmapped_area(file, addr, len, pgoff, flags);
3979 }
3980 #endif
3981 
3982 void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
3983 {
3984 	truncate_inode_pages_range(inode->i_mapping, lstart, lend);
3985 }
3986 EXPORT_SYMBOL_GPL(shmem_truncate_range);
3987 
3988 #define shmem_vm_ops				generic_file_vm_ops
3989 #define shmem_file_operations			ramfs_file_operations
3990 #define shmem_get_inode(sb, dir, mode, dev, flags)	ramfs_get_inode(sb, dir, mode, dev)
3991 #define shmem_acct_size(flags, size)		0
3992 #define shmem_unacct_size(flags, size)		do {} while (0)
3993 
3994 #endif /* CONFIG_SHMEM */
3995 
3996 /* common code */
3997 
3998 static const struct dentry_operations anon_ops = {
3999 	.d_dname = simple_dname
4000 };
4001 
4002 static struct file *__shmem_file_setup(const char *name, loff_t size,
4003 				       unsigned long flags, unsigned int i_flags)
4004 {
4005 	struct file *res;
4006 	struct inode *inode;
4007 	struct path path;
4008 	struct super_block *sb;
4009 	struct qstr this;
4010 
4011 	if (IS_ERR(shm_mnt))
4012 		return ERR_CAST(shm_mnt);
4013 
4014 	if (size < 0 || size > MAX_LFS_FILESIZE)
4015 		return ERR_PTR(-EINVAL);
4016 
4017 	if (shmem_acct_size(flags, size))
4018 		return ERR_PTR(-ENOMEM);
4019 
4020 	res = ERR_PTR(-ENOMEM);
4021 	this.name = name;
4022 	this.len = strlen(name);
4023 	this.hash = 0; /* will go */
4024 	sb = shm_mnt->mnt_sb;
4025 	path.mnt = mntget(shm_mnt);
4026 	path.dentry = d_alloc_pseudo(sb, &this);
4027 	if (!path.dentry)
4028 		goto put_memory;
4029 	d_set_d_op(path.dentry, &anon_ops);
4030 
4031 	res = ERR_PTR(-ENOSPC);
4032 	inode = shmem_get_inode(sb, NULL, S_IFREG | S_IRWXUGO, 0, flags);
4033 	if (!inode)
4034 		goto put_memory;
4035 
4036 	inode->i_flags |= i_flags;
4037 	d_instantiate(path.dentry, inode);
4038 	inode->i_size = size;
4039 	clear_nlink(inode);	/* It is unlinked */
4040 	res = ERR_PTR(ramfs_nommu_expand_for_mapping(inode, size));
4041 	if (IS_ERR(res))
4042 		goto put_path;
4043 
4044 	res = alloc_file(&path, FMODE_WRITE | FMODE_READ,
4045 		  &shmem_file_operations);
4046 	if (IS_ERR(res))
4047 		goto put_path;
4048 
4049 	return res;
4050 
4051 put_memory:
4052 	shmem_unacct_size(flags, size);
4053 put_path:
4054 	path_put(&path);
4055 	return res;
4056 }
4057 
4058 /**
4059  * shmem_kernel_file_setup - get an unlinked file living in tmpfs which must be
4060  * 	kernel internal.  There will be NO LSM permission checks against the
4061  * 	underlying inode.  So users of this interface must do LSM checks at a
4062  *	higher layer.  The users are the big_key and shm implementations.  LSM
4063  *	checks are provided at the key or shm level rather than the inode.
4064  * @name: name for dentry (to be seen in /proc/<pid>/maps
4065  * @size: size to be set for the file
4066  * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
4067  */
4068 struct file *shmem_kernel_file_setup(const char *name, loff_t size, unsigned long flags)
4069 {
4070 	return __shmem_file_setup(name, size, flags, S_PRIVATE);
4071 }
4072 
4073 /**
4074  * shmem_file_setup - get an unlinked file living in tmpfs
4075  * @name: name for dentry (to be seen in /proc/<pid>/maps
4076  * @size: size to be set for the file
4077  * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
4078  */
4079 struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags)
4080 {
4081 	return __shmem_file_setup(name, size, flags, 0);
4082 }
4083 EXPORT_SYMBOL_GPL(shmem_file_setup);
4084 
4085 /**
4086  * shmem_zero_setup - setup a shared anonymous mapping
4087  * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
4088  */
4089 int shmem_zero_setup(struct vm_area_struct *vma)
4090 {
4091 	struct file *file;
4092 	loff_t size = vma->vm_end - vma->vm_start;
4093 
4094 	/*
4095 	 * Cloning a new file under mmap_sem leads to a lock ordering conflict
4096 	 * between XFS directory reading and selinux: since this file is only
4097 	 * accessible to the user through its mapping, use S_PRIVATE flag to
4098 	 * bypass file security, in the same way as shmem_kernel_file_setup().
4099 	 */
4100 	file = __shmem_file_setup("dev/zero", size, vma->vm_flags, S_PRIVATE);
4101 	if (IS_ERR(file))
4102 		return PTR_ERR(file);
4103 
4104 	if (vma->vm_file)
4105 		fput(vma->vm_file);
4106 	vma->vm_file = file;
4107 	vma->vm_ops = &shmem_vm_ops;
4108 
4109 	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE) &&
4110 			((vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK) <
4111 			(vma->vm_end & HPAGE_PMD_MASK)) {
4112 		khugepaged_enter(vma, vma->vm_flags);
4113 	}
4114 
4115 	return 0;
4116 }
4117 
4118 /**
4119  * shmem_read_mapping_page_gfp - read into page cache, using specified page allocation flags.
4120  * @mapping:	the page's address_space
4121  * @index:	the page index
4122  * @gfp:	the page allocator flags to use if allocating
4123  *
4124  * This behaves as a tmpfs "read_cache_page_gfp(mapping, index, gfp)",
4125  * with any new page allocations done using the specified allocation flags.
4126  * But read_cache_page_gfp() uses the ->readpage() method: which does not
4127  * suit tmpfs, since it may have pages in swapcache, and needs to find those
4128  * for itself; although drivers/gpu/drm i915 and ttm rely upon this support.
4129  *
4130  * i915_gem_object_get_pages_gtt() mixes __GFP_NORETRY | __GFP_NOWARN in
4131  * with the mapping_gfp_mask(), to avoid OOMing the machine unnecessarily.
4132  */
4133 struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
4134 					 pgoff_t index, gfp_t gfp)
4135 {
4136 #ifdef CONFIG_SHMEM
4137 	struct inode *inode = mapping->host;
4138 	struct page *page;
4139 	int error;
4140 
4141 	BUG_ON(mapping->a_ops != &shmem_aops);
4142 	error = shmem_getpage_gfp(inode, index, &page, SGP_CACHE,
4143 				  gfp, NULL, NULL);
4144 	if (error)
4145 		page = ERR_PTR(error);
4146 	else
4147 		unlock_page(page);
4148 	return page;
4149 #else
4150 	/*
4151 	 * The tiny !SHMEM case uses ramfs without swap
4152 	 */
4153 	return read_cache_page_gfp(mapping, index, gfp);
4154 #endif
4155 }
4156 EXPORT_SYMBOL_GPL(shmem_read_mapping_page_gfp);
4157