xref: /linux/mm/shmem.c (revision bd628c1bed7902ec1f24ba0fe70758949146abbe)
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/random.h>
33 #include <linux/sched/signal.h>
34 #include <linux/export.h>
35 #include <linux/swap.h>
36 #include <linux/uio.h>
37 #include <linux/khugepaged.h>
38 #include <linux/hugetlb.h>
39 
40 #include <asm/tlbflush.h> /* for arch/microblaze update_mmu_cache() */
41 
42 static struct vfsmount *shm_mnt;
43 
44 #ifdef CONFIG_SHMEM
45 /*
46  * This virtual memory filesystem is heavily based on the ramfs. It
47  * extends ramfs by the ability to use swap and honor resource limits
48  * which makes it a completely usable filesystem.
49  */
50 
51 #include <linux/xattr.h>
52 #include <linux/exportfs.h>
53 #include <linux/posix_acl.h>
54 #include <linux/posix_acl_xattr.h>
55 #include <linux/mman.h>
56 #include <linux/string.h>
57 #include <linux/slab.h>
58 #include <linux/backing-dev.h>
59 #include <linux/shmem_fs.h>
60 #include <linux/writeback.h>
61 #include <linux/blkdev.h>
62 #include <linux/pagevec.h>
63 #include <linux/percpu_counter.h>
64 #include <linux/falloc.h>
65 #include <linux/splice.h>
66 #include <linux/security.h>
67 #include <linux/swapops.h>
68 #include <linux/mempolicy.h>
69 #include <linux/namei.h>
70 #include <linux/ctype.h>
71 #include <linux/migrate.h>
72 #include <linux/highmem.h>
73 #include <linux/seq_file.h>
74 #include <linux/magic.h>
75 #include <linux/syscalls.h>
76 #include <linux/fcntl.h>
77 #include <uapi/linux/memfd.h>
78 #include <linux/userfaultfd_k.h>
79 #include <linux/rmap.h>
80 #include <linux/uuid.h>
81 
82 #include <linux/uaccess.h>
83 #include <asm/pgtable.h>
84 
85 #include "internal.h"
86 
87 #define BLOCKS_PER_PAGE  (PAGE_SIZE/512)
88 #define VM_ACCT(size)    (PAGE_ALIGN(size) >> PAGE_SHIFT)
89 
90 /* Pretend that each entry is of this size in directory's i_size */
91 #define BOGO_DIRENT_SIZE 20
92 
93 /* Symlink up to this size is kmalloc'ed instead of using a swappable page */
94 #define SHORT_SYMLINK_LEN 128
95 
96 /*
97  * shmem_fallocate communicates with shmem_fault or shmem_writepage via
98  * inode->i_private (with i_mutex making sure that it has only one user at
99  * a time): we would prefer not to enlarge the shmem inode just for that.
100  */
101 struct shmem_falloc {
102 	wait_queue_head_t *waitq; /* faults into hole wait for punch to end */
103 	pgoff_t start;		/* start of range currently being fallocated */
104 	pgoff_t next;		/* the next page offset to be fallocated */
105 	pgoff_t nr_falloced;	/* how many new pages have been fallocated */
106 	pgoff_t nr_unswapped;	/* how often writepage refused to swap out */
107 };
108 
109 #ifdef CONFIG_TMPFS
110 static unsigned long shmem_default_max_blocks(void)
111 {
112 	return totalram_pages() / 2;
113 }
114 
115 static unsigned long shmem_default_max_inodes(void)
116 {
117 	unsigned long nr_pages = totalram_pages();
118 
119 	return min(nr_pages - totalhigh_pages(), nr_pages / 2);
120 }
121 #endif
122 
123 static bool shmem_should_replace_page(struct page *page, gfp_t gfp);
124 static int shmem_replace_page(struct page **pagep, gfp_t gfp,
125 				struct shmem_inode_info *info, pgoff_t index);
126 static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
127 		struct page **pagep, enum sgp_type sgp,
128 		gfp_t gfp, struct vm_area_struct *vma,
129 		struct vm_fault *vmf, vm_fault_t *fault_type);
130 
131 int shmem_getpage(struct inode *inode, pgoff_t index,
132 		struct page **pagep, enum sgp_type sgp)
133 {
134 	return shmem_getpage_gfp(inode, index, pagep, sgp,
135 		mapping_gfp_mask(inode->i_mapping), NULL, NULL, NULL);
136 }
137 
138 static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
139 {
140 	return sb->s_fs_info;
141 }
142 
143 /*
144  * shmem_file_setup pre-accounts the whole fixed size of a VM object,
145  * for shared memory and for shared anonymous (/dev/zero) mappings
146  * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
147  * consistent with the pre-accounting of private mappings ...
148  */
149 static inline int shmem_acct_size(unsigned long flags, loff_t size)
150 {
151 	return (flags & VM_NORESERVE) ?
152 		0 : security_vm_enough_memory_mm(current->mm, VM_ACCT(size));
153 }
154 
155 static inline void shmem_unacct_size(unsigned long flags, loff_t size)
156 {
157 	if (!(flags & VM_NORESERVE))
158 		vm_unacct_memory(VM_ACCT(size));
159 }
160 
161 static inline int shmem_reacct_size(unsigned long flags,
162 		loff_t oldsize, loff_t newsize)
163 {
164 	if (!(flags & VM_NORESERVE)) {
165 		if (VM_ACCT(newsize) > VM_ACCT(oldsize))
166 			return security_vm_enough_memory_mm(current->mm,
167 					VM_ACCT(newsize) - VM_ACCT(oldsize));
168 		else if (VM_ACCT(newsize) < VM_ACCT(oldsize))
169 			vm_unacct_memory(VM_ACCT(oldsize) - VM_ACCT(newsize));
170 	}
171 	return 0;
172 }
173 
174 /*
175  * ... whereas tmpfs objects are accounted incrementally as
176  * pages are allocated, in order to allow large sparse files.
177  * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
178  * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
179  */
180 static inline int shmem_acct_block(unsigned long flags, long pages)
181 {
182 	if (!(flags & VM_NORESERVE))
183 		return 0;
184 
185 	return security_vm_enough_memory_mm(current->mm,
186 			pages * VM_ACCT(PAGE_SIZE));
187 }
188 
189 static inline void shmem_unacct_blocks(unsigned long flags, long pages)
190 {
191 	if (flags & VM_NORESERVE)
192 		vm_unacct_memory(pages * VM_ACCT(PAGE_SIZE));
193 }
194 
195 static inline bool shmem_inode_acct_block(struct inode *inode, long pages)
196 {
197 	struct shmem_inode_info *info = SHMEM_I(inode);
198 	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
199 
200 	if (shmem_acct_block(info->flags, pages))
201 		return false;
202 
203 	if (sbinfo->max_blocks) {
204 		if (percpu_counter_compare(&sbinfo->used_blocks,
205 					   sbinfo->max_blocks - pages) > 0)
206 			goto unacct;
207 		percpu_counter_add(&sbinfo->used_blocks, pages);
208 	}
209 
210 	return true;
211 
212 unacct:
213 	shmem_unacct_blocks(info->flags, pages);
214 	return false;
215 }
216 
217 static inline void shmem_inode_unacct_blocks(struct inode *inode, long pages)
218 {
219 	struct shmem_inode_info *info = SHMEM_I(inode);
220 	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
221 
222 	if (sbinfo->max_blocks)
223 		percpu_counter_sub(&sbinfo->used_blocks, pages);
224 	shmem_unacct_blocks(info->flags, pages);
225 }
226 
227 static const struct super_operations shmem_ops;
228 static const struct address_space_operations shmem_aops;
229 static const struct file_operations shmem_file_operations;
230 static const struct inode_operations shmem_inode_operations;
231 static const struct inode_operations shmem_dir_inode_operations;
232 static const struct inode_operations shmem_special_inode_operations;
233 static const struct vm_operations_struct shmem_vm_ops;
234 static struct file_system_type shmem_fs_type;
235 
236 bool vma_is_shmem(struct vm_area_struct *vma)
237 {
238 	return vma->vm_ops == &shmem_vm_ops;
239 }
240 
241 static LIST_HEAD(shmem_swaplist);
242 static DEFINE_MUTEX(shmem_swaplist_mutex);
243 
244 static int shmem_reserve_inode(struct super_block *sb)
245 {
246 	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
247 	if (sbinfo->max_inodes) {
248 		spin_lock(&sbinfo->stat_lock);
249 		if (!sbinfo->free_inodes) {
250 			spin_unlock(&sbinfo->stat_lock);
251 			return -ENOSPC;
252 		}
253 		sbinfo->free_inodes--;
254 		spin_unlock(&sbinfo->stat_lock);
255 	}
256 	return 0;
257 }
258 
259 static void shmem_free_inode(struct super_block *sb)
260 {
261 	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
262 	if (sbinfo->max_inodes) {
263 		spin_lock(&sbinfo->stat_lock);
264 		sbinfo->free_inodes++;
265 		spin_unlock(&sbinfo->stat_lock);
266 	}
267 }
268 
269 /**
270  * shmem_recalc_inode - recalculate the block usage of an inode
271  * @inode: inode to recalc
272  *
273  * We have to calculate the free blocks since the mm can drop
274  * undirtied hole pages behind our back.
275  *
276  * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
277  * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
278  *
279  * It has to be called with the spinlock held.
280  */
281 static void shmem_recalc_inode(struct inode *inode)
282 {
283 	struct shmem_inode_info *info = SHMEM_I(inode);
284 	long freed;
285 
286 	freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
287 	if (freed > 0) {
288 		info->alloced -= freed;
289 		inode->i_blocks -= freed * BLOCKS_PER_PAGE;
290 		shmem_inode_unacct_blocks(inode, freed);
291 	}
292 }
293 
294 bool shmem_charge(struct inode *inode, long pages)
295 {
296 	struct shmem_inode_info *info = SHMEM_I(inode);
297 	unsigned long flags;
298 
299 	if (!shmem_inode_acct_block(inode, pages))
300 		return false;
301 
302 	/* nrpages adjustment first, then shmem_recalc_inode() when balanced */
303 	inode->i_mapping->nrpages += pages;
304 
305 	spin_lock_irqsave(&info->lock, flags);
306 	info->alloced += pages;
307 	inode->i_blocks += pages * BLOCKS_PER_PAGE;
308 	shmem_recalc_inode(inode);
309 	spin_unlock_irqrestore(&info->lock, flags);
310 
311 	return true;
312 }
313 
314 void shmem_uncharge(struct inode *inode, long pages)
315 {
316 	struct shmem_inode_info *info = SHMEM_I(inode);
317 	unsigned long flags;
318 
319 	/* nrpages adjustment done by __delete_from_page_cache() or caller */
320 
321 	spin_lock_irqsave(&info->lock, flags);
322 	info->alloced -= pages;
323 	inode->i_blocks -= pages * BLOCKS_PER_PAGE;
324 	shmem_recalc_inode(inode);
325 	spin_unlock_irqrestore(&info->lock, flags);
326 
327 	shmem_inode_unacct_blocks(inode, pages);
328 }
329 
330 /*
331  * Replace item expected in xarray by a new item, while holding xa_lock.
332  */
333 static int shmem_replace_entry(struct address_space *mapping,
334 			pgoff_t index, void *expected, void *replacement)
335 {
336 	XA_STATE(xas, &mapping->i_pages, index);
337 	void *item;
338 
339 	VM_BUG_ON(!expected);
340 	VM_BUG_ON(!replacement);
341 	item = xas_load(&xas);
342 	if (item != expected)
343 		return -ENOENT;
344 	xas_store(&xas, replacement);
345 	return 0;
346 }
347 
348 /*
349  * Sometimes, before we decide whether to proceed or to fail, we must check
350  * that an entry was not already brought back from swap by a racing thread.
351  *
352  * Checking page is not enough: by the time a SwapCache page is locked, it
353  * might be reused, and again be SwapCache, using the same swap as before.
354  */
355 static bool shmem_confirm_swap(struct address_space *mapping,
356 			       pgoff_t index, swp_entry_t swap)
357 {
358 	return xa_load(&mapping->i_pages, index) == swp_to_radix_entry(swap);
359 }
360 
361 /*
362  * Definitions for "huge tmpfs": tmpfs mounted with the huge= option
363  *
364  * SHMEM_HUGE_NEVER:
365  *	disables huge pages for the mount;
366  * SHMEM_HUGE_ALWAYS:
367  *	enables huge pages for the mount;
368  * SHMEM_HUGE_WITHIN_SIZE:
369  *	only allocate huge pages if the page will be fully within i_size,
370  *	also respect fadvise()/madvise() hints;
371  * SHMEM_HUGE_ADVISE:
372  *	only allocate huge pages if requested with fadvise()/madvise();
373  */
374 
375 #define SHMEM_HUGE_NEVER	0
376 #define SHMEM_HUGE_ALWAYS	1
377 #define SHMEM_HUGE_WITHIN_SIZE	2
378 #define SHMEM_HUGE_ADVISE	3
379 
380 /*
381  * Special values.
382  * Only can be set via /sys/kernel/mm/transparent_hugepage/shmem_enabled:
383  *
384  * SHMEM_HUGE_DENY:
385  *	disables huge on shm_mnt and all mounts, for emergency use;
386  * SHMEM_HUGE_FORCE:
387  *	enables huge on shm_mnt and all mounts, w/o needing option, for testing;
388  *
389  */
390 #define SHMEM_HUGE_DENY		(-1)
391 #define SHMEM_HUGE_FORCE	(-2)
392 
393 #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
394 /* ifdef here to avoid bloating shmem.o when not necessary */
395 
396 static int shmem_huge __read_mostly;
397 
398 #if defined(CONFIG_SYSFS) || defined(CONFIG_TMPFS)
399 static int shmem_parse_huge(const char *str)
400 {
401 	if (!strcmp(str, "never"))
402 		return SHMEM_HUGE_NEVER;
403 	if (!strcmp(str, "always"))
404 		return SHMEM_HUGE_ALWAYS;
405 	if (!strcmp(str, "within_size"))
406 		return SHMEM_HUGE_WITHIN_SIZE;
407 	if (!strcmp(str, "advise"))
408 		return SHMEM_HUGE_ADVISE;
409 	if (!strcmp(str, "deny"))
410 		return SHMEM_HUGE_DENY;
411 	if (!strcmp(str, "force"))
412 		return SHMEM_HUGE_FORCE;
413 	return -EINVAL;
414 }
415 
416 static const char *shmem_format_huge(int huge)
417 {
418 	switch (huge) {
419 	case SHMEM_HUGE_NEVER:
420 		return "never";
421 	case SHMEM_HUGE_ALWAYS:
422 		return "always";
423 	case SHMEM_HUGE_WITHIN_SIZE:
424 		return "within_size";
425 	case SHMEM_HUGE_ADVISE:
426 		return "advise";
427 	case SHMEM_HUGE_DENY:
428 		return "deny";
429 	case SHMEM_HUGE_FORCE:
430 		return "force";
431 	default:
432 		VM_BUG_ON(1);
433 		return "bad_val";
434 	}
435 }
436 #endif
437 
438 static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
439 		struct shrink_control *sc, unsigned long nr_to_split)
440 {
441 	LIST_HEAD(list), *pos, *next;
442 	LIST_HEAD(to_remove);
443 	struct inode *inode;
444 	struct shmem_inode_info *info;
445 	struct page *page;
446 	unsigned long batch = sc ? sc->nr_to_scan : 128;
447 	int removed = 0, split = 0;
448 
449 	if (list_empty(&sbinfo->shrinklist))
450 		return SHRINK_STOP;
451 
452 	spin_lock(&sbinfo->shrinklist_lock);
453 	list_for_each_safe(pos, next, &sbinfo->shrinklist) {
454 		info = list_entry(pos, struct shmem_inode_info, shrinklist);
455 
456 		/* pin the inode */
457 		inode = igrab(&info->vfs_inode);
458 
459 		/* inode is about to be evicted */
460 		if (!inode) {
461 			list_del_init(&info->shrinklist);
462 			removed++;
463 			goto next;
464 		}
465 
466 		/* Check if there's anything to gain */
467 		if (round_up(inode->i_size, PAGE_SIZE) ==
468 				round_up(inode->i_size, HPAGE_PMD_SIZE)) {
469 			list_move(&info->shrinklist, &to_remove);
470 			removed++;
471 			goto next;
472 		}
473 
474 		list_move(&info->shrinklist, &list);
475 next:
476 		if (!--batch)
477 			break;
478 	}
479 	spin_unlock(&sbinfo->shrinklist_lock);
480 
481 	list_for_each_safe(pos, next, &to_remove) {
482 		info = list_entry(pos, struct shmem_inode_info, shrinklist);
483 		inode = &info->vfs_inode;
484 		list_del_init(&info->shrinklist);
485 		iput(inode);
486 	}
487 
488 	list_for_each_safe(pos, next, &list) {
489 		int ret;
490 
491 		info = list_entry(pos, struct shmem_inode_info, shrinklist);
492 		inode = &info->vfs_inode;
493 
494 		if (nr_to_split && split >= nr_to_split)
495 			goto leave;
496 
497 		page = find_get_page(inode->i_mapping,
498 				(inode->i_size & HPAGE_PMD_MASK) >> PAGE_SHIFT);
499 		if (!page)
500 			goto drop;
501 
502 		/* No huge page at the end of the file: nothing to split */
503 		if (!PageTransHuge(page)) {
504 			put_page(page);
505 			goto drop;
506 		}
507 
508 		/*
509 		 * Leave the inode on the list if we failed to lock
510 		 * the page at this time.
511 		 *
512 		 * Waiting for the lock may lead to deadlock in the
513 		 * reclaim path.
514 		 */
515 		if (!trylock_page(page)) {
516 			put_page(page);
517 			goto leave;
518 		}
519 
520 		ret = split_huge_page(page);
521 		unlock_page(page);
522 		put_page(page);
523 
524 		/* If split failed leave the inode on the list */
525 		if (ret)
526 			goto leave;
527 
528 		split++;
529 drop:
530 		list_del_init(&info->shrinklist);
531 		removed++;
532 leave:
533 		iput(inode);
534 	}
535 
536 	spin_lock(&sbinfo->shrinklist_lock);
537 	list_splice_tail(&list, &sbinfo->shrinklist);
538 	sbinfo->shrinklist_len -= removed;
539 	spin_unlock(&sbinfo->shrinklist_lock);
540 
541 	return split;
542 }
543 
544 static long shmem_unused_huge_scan(struct super_block *sb,
545 		struct shrink_control *sc)
546 {
547 	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
548 
549 	if (!READ_ONCE(sbinfo->shrinklist_len))
550 		return SHRINK_STOP;
551 
552 	return shmem_unused_huge_shrink(sbinfo, sc, 0);
553 }
554 
555 static long shmem_unused_huge_count(struct super_block *sb,
556 		struct shrink_control *sc)
557 {
558 	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
559 	return READ_ONCE(sbinfo->shrinklist_len);
560 }
561 #else /* !CONFIG_TRANSPARENT_HUGE_PAGECACHE */
562 
563 #define shmem_huge SHMEM_HUGE_DENY
564 
565 static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
566 		struct shrink_control *sc, unsigned long nr_to_split)
567 {
568 	return 0;
569 }
570 #endif /* CONFIG_TRANSPARENT_HUGE_PAGECACHE */
571 
572 static inline bool is_huge_enabled(struct shmem_sb_info *sbinfo)
573 {
574 	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE) &&
575 	    (shmem_huge == SHMEM_HUGE_FORCE || sbinfo->huge) &&
576 	    shmem_huge != SHMEM_HUGE_DENY)
577 		return true;
578 	return false;
579 }
580 
581 /*
582  * Like add_to_page_cache_locked, but error if expected item has gone.
583  */
584 static int shmem_add_to_page_cache(struct page *page,
585 				   struct address_space *mapping,
586 				   pgoff_t index, void *expected, gfp_t gfp)
587 {
588 	XA_STATE_ORDER(xas, &mapping->i_pages, index, compound_order(page));
589 	unsigned long i = 0;
590 	unsigned long nr = 1UL << compound_order(page);
591 
592 	VM_BUG_ON_PAGE(PageTail(page), page);
593 	VM_BUG_ON_PAGE(index != round_down(index, nr), page);
594 	VM_BUG_ON_PAGE(!PageLocked(page), page);
595 	VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
596 	VM_BUG_ON(expected && PageTransHuge(page));
597 
598 	page_ref_add(page, nr);
599 	page->mapping = mapping;
600 	page->index = index;
601 
602 	do {
603 		void *entry;
604 		xas_lock_irq(&xas);
605 		entry = xas_find_conflict(&xas);
606 		if (entry != expected)
607 			xas_set_err(&xas, -EEXIST);
608 		xas_create_range(&xas);
609 		if (xas_error(&xas))
610 			goto unlock;
611 next:
612 		xas_store(&xas, page + i);
613 		if (++i < nr) {
614 			xas_next(&xas);
615 			goto next;
616 		}
617 		if (PageTransHuge(page)) {
618 			count_vm_event(THP_FILE_ALLOC);
619 			__inc_node_page_state(page, NR_SHMEM_THPS);
620 		}
621 		mapping->nrpages += nr;
622 		__mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, nr);
623 		__mod_node_page_state(page_pgdat(page), NR_SHMEM, nr);
624 unlock:
625 		xas_unlock_irq(&xas);
626 	} while (xas_nomem(&xas, gfp));
627 
628 	if (xas_error(&xas)) {
629 		page->mapping = NULL;
630 		page_ref_sub(page, nr);
631 		return xas_error(&xas);
632 	}
633 
634 	return 0;
635 }
636 
637 /*
638  * Like delete_from_page_cache, but substitutes swap for page.
639  */
640 static void shmem_delete_from_page_cache(struct page *page, void *radswap)
641 {
642 	struct address_space *mapping = page->mapping;
643 	int error;
644 
645 	VM_BUG_ON_PAGE(PageCompound(page), page);
646 
647 	xa_lock_irq(&mapping->i_pages);
648 	error = shmem_replace_entry(mapping, page->index, page, radswap);
649 	page->mapping = NULL;
650 	mapping->nrpages--;
651 	__dec_node_page_state(page, NR_FILE_PAGES);
652 	__dec_node_page_state(page, NR_SHMEM);
653 	xa_unlock_irq(&mapping->i_pages);
654 	put_page(page);
655 	BUG_ON(error);
656 }
657 
658 /*
659  * Remove swap entry from page cache, free the swap and its page cache.
660  */
661 static int shmem_free_swap(struct address_space *mapping,
662 			   pgoff_t index, void *radswap)
663 {
664 	void *old;
665 
666 	old = xa_cmpxchg_irq(&mapping->i_pages, index, radswap, NULL, 0);
667 	if (old != radswap)
668 		return -ENOENT;
669 	free_swap_and_cache(radix_to_swp_entry(radswap));
670 	return 0;
671 }
672 
673 /*
674  * Determine (in bytes) how many of the shmem object's pages mapped by the
675  * given offsets are swapped out.
676  *
677  * This is safe to call without i_mutex or the i_pages lock thanks to RCU,
678  * as long as the inode doesn't go away and racy results are not a problem.
679  */
680 unsigned long shmem_partial_swap_usage(struct address_space *mapping,
681 						pgoff_t start, pgoff_t end)
682 {
683 	XA_STATE(xas, &mapping->i_pages, start);
684 	struct page *page;
685 	unsigned long swapped = 0;
686 
687 	rcu_read_lock();
688 	xas_for_each(&xas, page, end - 1) {
689 		if (xas_retry(&xas, page))
690 			continue;
691 		if (xa_is_value(page))
692 			swapped++;
693 
694 		if (need_resched()) {
695 			xas_pause(&xas);
696 			cond_resched_rcu();
697 		}
698 	}
699 
700 	rcu_read_unlock();
701 
702 	return swapped << PAGE_SHIFT;
703 }
704 
705 /*
706  * Determine (in bytes) how many of the shmem object's pages mapped by the
707  * given vma is swapped out.
708  *
709  * This is safe to call without i_mutex or the i_pages lock thanks to RCU,
710  * as long as the inode doesn't go away and racy results are not a problem.
711  */
712 unsigned long shmem_swap_usage(struct vm_area_struct *vma)
713 {
714 	struct inode *inode = file_inode(vma->vm_file);
715 	struct shmem_inode_info *info = SHMEM_I(inode);
716 	struct address_space *mapping = inode->i_mapping;
717 	unsigned long swapped;
718 
719 	/* Be careful as we don't hold info->lock */
720 	swapped = READ_ONCE(info->swapped);
721 
722 	/*
723 	 * The easier cases are when the shmem object has nothing in swap, or
724 	 * the vma maps it whole. Then we can simply use the stats that we
725 	 * already track.
726 	 */
727 	if (!swapped)
728 		return 0;
729 
730 	if (!vma->vm_pgoff && vma->vm_end - vma->vm_start >= inode->i_size)
731 		return swapped << PAGE_SHIFT;
732 
733 	/* Here comes the more involved part */
734 	return shmem_partial_swap_usage(mapping,
735 			linear_page_index(vma, vma->vm_start),
736 			linear_page_index(vma, vma->vm_end));
737 }
738 
739 /*
740  * SysV IPC SHM_UNLOCK restore Unevictable pages to their evictable lists.
741  */
742 void shmem_unlock_mapping(struct address_space *mapping)
743 {
744 	struct pagevec pvec;
745 	pgoff_t indices[PAGEVEC_SIZE];
746 	pgoff_t index = 0;
747 
748 	pagevec_init(&pvec);
749 	/*
750 	 * Minor point, but we might as well stop if someone else SHM_LOCKs it.
751 	 */
752 	while (!mapping_unevictable(mapping)) {
753 		/*
754 		 * Avoid pagevec_lookup(): find_get_pages() returns 0 as if it
755 		 * has finished, if it hits a row of PAGEVEC_SIZE swap entries.
756 		 */
757 		pvec.nr = find_get_entries(mapping, index,
758 					   PAGEVEC_SIZE, pvec.pages, indices);
759 		if (!pvec.nr)
760 			break;
761 		index = indices[pvec.nr - 1] + 1;
762 		pagevec_remove_exceptionals(&pvec);
763 		check_move_unevictable_pages(&pvec);
764 		pagevec_release(&pvec);
765 		cond_resched();
766 	}
767 }
768 
769 /*
770  * Remove range of pages and swap entries from page cache, and free them.
771  * If !unfalloc, truncate or punch hole; if unfalloc, undo failed fallocate.
772  */
773 static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
774 								 bool unfalloc)
775 {
776 	struct address_space *mapping = inode->i_mapping;
777 	struct shmem_inode_info *info = SHMEM_I(inode);
778 	pgoff_t start = (lstart + PAGE_SIZE - 1) >> PAGE_SHIFT;
779 	pgoff_t end = (lend + 1) >> PAGE_SHIFT;
780 	unsigned int partial_start = lstart & (PAGE_SIZE - 1);
781 	unsigned int partial_end = (lend + 1) & (PAGE_SIZE - 1);
782 	struct pagevec pvec;
783 	pgoff_t indices[PAGEVEC_SIZE];
784 	long nr_swaps_freed = 0;
785 	pgoff_t index;
786 	int i;
787 
788 	if (lend == -1)
789 		end = -1;	/* unsigned, so actually very big */
790 
791 	pagevec_init(&pvec);
792 	index = start;
793 	while (index < end) {
794 		pvec.nr = find_get_entries(mapping, index,
795 			min(end - index, (pgoff_t)PAGEVEC_SIZE),
796 			pvec.pages, indices);
797 		if (!pvec.nr)
798 			break;
799 		for (i = 0; i < pagevec_count(&pvec); i++) {
800 			struct page *page = pvec.pages[i];
801 
802 			index = indices[i];
803 			if (index >= end)
804 				break;
805 
806 			if (xa_is_value(page)) {
807 				if (unfalloc)
808 					continue;
809 				nr_swaps_freed += !shmem_free_swap(mapping,
810 								index, page);
811 				continue;
812 			}
813 
814 			VM_BUG_ON_PAGE(page_to_pgoff(page) != index, page);
815 
816 			if (!trylock_page(page))
817 				continue;
818 
819 			if (PageTransTail(page)) {
820 				/* Middle of THP: zero out the page */
821 				clear_highpage(page);
822 				unlock_page(page);
823 				continue;
824 			} else if (PageTransHuge(page)) {
825 				if (index == round_down(end, HPAGE_PMD_NR)) {
826 					/*
827 					 * Range ends in the middle of THP:
828 					 * zero out the page
829 					 */
830 					clear_highpage(page);
831 					unlock_page(page);
832 					continue;
833 				}
834 				index += HPAGE_PMD_NR - 1;
835 				i += HPAGE_PMD_NR - 1;
836 			}
837 
838 			if (!unfalloc || !PageUptodate(page)) {
839 				VM_BUG_ON_PAGE(PageTail(page), page);
840 				if (page_mapping(page) == mapping) {
841 					VM_BUG_ON_PAGE(PageWriteback(page), page);
842 					truncate_inode_page(mapping, page);
843 				}
844 			}
845 			unlock_page(page);
846 		}
847 		pagevec_remove_exceptionals(&pvec);
848 		pagevec_release(&pvec);
849 		cond_resched();
850 		index++;
851 	}
852 
853 	if (partial_start) {
854 		struct page *page = NULL;
855 		shmem_getpage(inode, start - 1, &page, SGP_READ);
856 		if (page) {
857 			unsigned int top = PAGE_SIZE;
858 			if (start > end) {
859 				top = partial_end;
860 				partial_end = 0;
861 			}
862 			zero_user_segment(page, partial_start, top);
863 			set_page_dirty(page);
864 			unlock_page(page);
865 			put_page(page);
866 		}
867 	}
868 	if (partial_end) {
869 		struct page *page = NULL;
870 		shmem_getpage(inode, end, &page, SGP_READ);
871 		if (page) {
872 			zero_user_segment(page, 0, partial_end);
873 			set_page_dirty(page);
874 			unlock_page(page);
875 			put_page(page);
876 		}
877 	}
878 	if (start >= end)
879 		return;
880 
881 	index = start;
882 	while (index < end) {
883 		cond_resched();
884 
885 		pvec.nr = find_get_entries(mapping, index,
886 				min(end - index, (pgoff_t)PAGEVEC_SIZE),
887 				pvec.pages, indices);
888 		if (!pvec.nr) {
889 			/* If all gone or hole-punch or unfalloc, we're done */
890 			if (index == start || end != -1)
891 				break;
892 			/* But if truncating, restart to make sure all gone */
893 			index = start;
894 			continue;
895 		}
896 		for (i = 0; i < pagevec_count(&pvec); i++) {
897 			struct page *page = pvec.pages[i];
898 
899 			index = indices[i];
900 			if (index >= end)
901 				break;
902 
903 			if (xa_is_value(page)) {
904 				if (unfalloc)
905 					continue;
906 				if (shmem_free_swap(mapping, index, page)) {
907 					/* Swap was replaced by page: retry */
908 					index--;
909 					break;
910 				}
911 				nr_swaps_freed++;
912 				continue;
913 			}
914 
915 			lock_page(page);
916 
917 			if (PageTransTail(page)) {
918 				/* Middle of THP: zero out the page */
919 				clear_highpage(page);
920 				unlock_page(page);
921 				/*
922 				 * Partial thp truncate due 'start' in middle
923 				 * of THP: don't need to look on these pages
924 				 * again on !pvec.nr restart.
925 				 */
926 				if (index != round_down(end, HPAGE_PMD_NR))
927 					start++;
928 				continue;
929 			} else if (PageTransHuge(page)) {
930 				if (index == round_down(end, HPAGE_PMD_NR)) {
931 					/*
932 					 * Range ends in the middle of THP:
933 					 * zero out the page
934 					 */
935 					clear_highpage(page);
936 					unlock_page(page);
937 					continue;
938 				}
939 				index += HPAGE_PMD_NR - 1;
940 				i += HPAGE_PMD_NR - 1;
941 			}
942 
943 			if (!unfalloc || !PageUptodate(page)) {
944 				VM_BUG_ON_PAGE(PageTail(page), page);
945 				if (page_mapping(page) == mapping) {
946 					VM_BUG_ON_PAGE(PageWriteback(page), page);
947 					truncate_inode_page(mapping, page);
948 				} else {
949 					/* Page was replaced by swap: retry */
950 					unlock_page(page);
951 					index--;
952 					break;
953 				}
954 			}
955 			unlock_page(page);
956 		}
957 		pagevec_remove_exceptionals(&pvec);
958 		pagevec_release(&pvec);
959 		index++;
960 	}
961 
962 	spin_lock_irq(&info->lock);
963 	info->swapped -= nr_swaps_freed;
964 	shmem_recalc_inode(inode);
965 	spin_unlock_irq(&info->lock);
966 }
967 
968 void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
969 {
970 	shmem_undo_range(inode, lstart, lend, false);
971 	inode->i_ctime = inode->i_mtime = current_time(inode);
972 }
973 EXPORT_SYMBOL_GPL(shmem_truncate_range);
974 
975 static int shmem_getattr(const struct path *path, struct kstat *stat,
976 			 u32 request_mask, unsigned int query_flags)
977 {
978 	struct inode *inode = path->dentry->d_inode;
979 	struct shmem_inode_info *info = SHMEM_I(inode);
980 	struct shmem_sb_info *sb_info = SHMEM_SB(inode->i_sb);
981 
982 	if (info->alloced - info->swapped != inode->i_mapping->nrpages) {
983 		spin_lock_irq(&info->lock);
984 		shmem_recalc_inode(inode);
985 		spin_unlock_irq(&info->lock);
986 	}
987 	generic_fillattr(inode, stat);
988 
989 	if (is_huge_enabled(sb_info))
990 		stat->blksize = HPAGE_PMD_SIZE;
991 
992 	return 0;
993 }
994 
995 static int shmem_setattr(struct dentry *dentry, struct iattr *attr)
996 {
997 	struct inode *inode = d_inode(dentry);
998 	struct shmem_inode_info *info = SHMEM_I(inode);
999 	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
1000 	int error;
1001 
1002 	error = setattr_prepare(dentry, attr);
1003 	if (error)
1004 		return error;
1005 
1006 	if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
1007 		loff_t oldsize = inode->i_size;
1008 		loff_t newsize = attr->ia_size;
1009 
1010 		/* protected by i_mutex */
1011 		if ((newsize < oldsize && (info->seals & F_SEAL_SHRINK)) ||
1012 		    (newsize > oldsize && (info->seals & F_SEAL_GROW)))
1013 			return -EPERM;
1014 
1015 		if (newsize != oldsize) {
1016 			error = shmem_reacct_size(SHMEM_I(inode)->flags,
1017 					oldsize, newsize);
1018 			if (error)
1019 				return error;
1020 			i_size_write(inode, newsize);
1021 			inode->i_ctime = inode->i_mtime = current_time(inode);
1022 		}
1023 		if (newsize <= oldsize) {
1024 			loff_t holebegin = round_up(newsize, PAGE_SIZE);
1025 			if (oldsize > holebegin)
1026 				unmap_mapping_range(inode->i_mapping,
1027 							holebegin, 0, 1);
1028 			if (info->alloced)
1029 				shmem_truncate_range(inode,
1030 							newsize, (loff_t)-1);
1031 			/* unmap again to remove racily COWed private pages */
1032 			if (oldsize > holebegin)
1033 				unmap_mapping_range(inode->i_mapping,
1034 							holebegin, 0, 1);
1035 
1036 			/*
1037 			 * Part of the huge page can be beyond i_size: subject
1038 			 * to shrink under memory pressure.
1039 			 */
1040 			if (IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE)) {
1041 				spin_lock(&sbinfo->shrinklist_lock);
1042 				/*
1043 				 * _careful to defend against unlocked access to
1044 				 * ->shrink_list in shmem_unused_huge_shrink()
1045 				 */
1046 				if (list_empty_careful(&info->shrinklist)) {
1047 					list_add_tail(&info->shrinklist,
1048 							&sbinfo->shrinklist);
1049 					sbinfo->shrinklist_len++;
1050 				}
1051 				spin_unlock(&sbinfo->shrinklist_lock);
1052 			}
1053 		}
1054 	}
1055 
1056 	setattr_copy(inode, attr);
1057 	if (attr->ia_valid & ATTR_MODE)
1058 		error = posix_acl_chmod(inode, inode->i_mode);
1059 	return error;
1060 }
1061 
1062 static void shmem_evict_inode(struct inode *inode)
1063 {
1064 	struct shmem_inode_info *info = SHMEM_I(inode);
1065 	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
1066 
1067 	if (inode->i_mapping->a_ops == &shmem_aops) {
1068 		shmem_unacct_size(info->flags, inode->i_size);
1069 		inode->i_size = 0;
1070 		shmem_truncate_range(inode, 0, (loff_t)-1);
1071 		if (!list_empty(&info->shrinklist)) {
1072 			spin_lock(&sbinfo->shrinklist_lock);
1073 			if (!list_empty(&info->shrinklist)) {
1074 				list_del_init(&info->shrinklist);
1075 				sbinfo->shrinklist_len--;
1076 			}
1077 			spin_unlock(&sbinfo->shrinklist_lock);
1078 		}
1079 		if (!list_empty(&info->swaplist)) {
1080 			mutex_lock(&shmem_swaplist_mutex);
1081 			list_del_init(&info->swaplist);
1082 			mutex_unlock(&shmem_swaplist_mutex);
1083 		}
1084 	}
1085 
1086 	simple_xattrs_free(&info->xattrs);
1087 	WARN_ON(inode->i_blocks);
1088 	shmem_free_inode(inode->i_sb);
1089 	clear_inode(inode);
1090 }
1091 
1092 static unsigned long find_swap_entry(struct xarray *xa, void *item)
1093 {
1094 	XA_STATE(xas, xa, 0);
1095 	unsigned int checked = 0;
1096 	void *entry;
1097 
1098 	rcu_read_lock();
1099 	xas_for_each(&xas, entry, ULONG_MAX) {
1100 		if (xas_retry(&xas, entry))
1101 			continue;
1102 		if (entry == item)
1103 			break;
1104 		checked++;
1105 		if ((checked % XA_CHECK_SCHED) != 0)
1106 			continue;
1107 		xas_pause(&xas);
1108 		cond_resched_rcu();
1109 	}
1110 	rcu_read_unlock();
1111 
1112 	return entry ? xas.xa_index : -1;
1113 }
1114 
1115 /*
1116  * If swap found in inode, free it and move page from swapcache to filecache.
1117  */
1118 static int shmem_unuse_inode(struct shmem_inode_info *info,
1119 			     swp_entry_t swap, struct page **pagep)
1120 {
1121 	struct address_space *mapping = info->vfs_inode.i_mapping;
1122 	void *radswap;
1123 	pgoff_t index;
1124 	gfp_t gfp;
1125 	int error = 0;
1126 
1127 	radswap = swp_to_radix_entry(swap);
1128 	index = find_swap_entry(&mapping->i_pages, radswap);
1129 	if (index == -1)
1130 		return -EAGAIN;	/* tell shmem_unuse we found nothing */
1131 
1132 	/*
1133 	 * Move _head_ to start search for next from here.
1134 	 * But be careful: shmem_evict_inode checks list_empty without taking
1135 	 * mutex, and there's an instant in list_move_tail when info->swaplist
1136 	 * would appear empty, if it were the only one on shmem_swaplist.
1137 	 */
1138 	if (shmem_swaplist.next != &info->swaplist)
1139 		list_move_tail(&shmem_swaplist, &info->swaplist);
1140 
1141 	gfp = mapping_gfp_mask(mapping);
1142 	if (shmem_should_replace_page(*pagep, gfp)) {
1143 		mutex_unlock(&shmem_swaplist_mutex);
1144 		error = shmem_replace_page(pagep, gfp, info, index);
1145 		mutex_lock(&shmem_swaplist_mutex);
1146 		/*
1147 		 * We needed to drop mutex to make that restrictive page
1148 		 * allocation, but the inode might have been freed while we
1149 		 * dropped it: although a racing shmem_evict_inode() cannot
1150 		 * complete without emptying the page cache, our page lock
1151 		 * on this swapcache page is not enough to prevent that -
1152 		 * free_swap_and_cache() of our swap entry will only
1153 		 * trylock_page(), removing swap from page cache whatever.
1154 		 *
1155 		 * We must not proceed to shmem_add_to_page_cache() if the
1156 		 * inode has been freed, but of course we cannot rely on
1157 		 * inode or mapping or info to check that.  However, we can
1158 		 * safely check if our swap entry is still in use (and here
1159 		 * it can't have got reused for another page): if it's still
1160 		 * in use, then the inode cannot have been freed yet, and we
1161 		 * can safely proceed (if it's no longer in use, that tells
1162 		 * nothing about the inode, but we don't need to unuse swap).
1163 		 */
1164 		if (!page_swapcount(*pagep))
1165 			error = -ENOENT;
1166 	}
1167 
1168 	/*
1169 	 * We rely on shmem_swaplist_mutex, not only to protect the swaplist,
1170 	 * but also to hold up shmem_evict_inode(): so inode cannot be freed
1171 	 * beneath us (pagelock doesn't help until the page is in pagecache).
1172 	 */
1173 	if (!error)
1174 		error = shmem_add_to_page_cache(*pagep, mapping, index,
1175 						radswap, gfp);
1176 	if (error != -ENOMEM) {
1177 		/*
1178 		 * Truncation and eviction use free_swap_and_cache(), which
1179 		 * only does trylock page: if we raced, best clean up here.
1180 		 */
1181 		delete_from_swap_cache(*pagep);
1182 		set_page_dirty(*pagep);
1183 		if (!error) {
1184 			spin_lock_irq(&info->lock);
1185 			info->swapped--;
1186 			spin_unlock_irq(&info->lock);
1187 			swap_free(swap);
1188 		}
1189 	}
1190 	return error;
1191 }
1192 
1193 /*
1194  * Search through swapped inodes to find and replace swap by page.
1195  */
1196 int shmem_unuse(swp_entry_t swap, struct page *page)
1197 {
1198 	struct list_head *this, *next;
1199 	struct shmem_inode_info *info;
1200 	struct mem_cgroup *memcg;
1201 	int error = 0;
1202 
1203 	/*
1204 	 * There's a faint possibility that swap page was replaced before
1205 	 * caller locked it: caller will come back later with the right page.
1206 	 */
1207 	if (unlikely(!PageSwapCache(page) || page_private(page) != swap.val))
1208 		goto out;
1209 
1210 	/*
1211 	 * Charge page using GFP_KERNEL while we can wait, before taking
1212 	 * the shmem_swaplist_mutex which might hold up shmem_writepage().
1213 	 * Charged back to the user (not to caller) when swap account is used.
1214 	 */
1215 	error = mem_cgroup_try_charge_delay(page, current->mm, GFP_KERNEL,
1216 					    &memcg, false);
1217 	if (error)
1218 		goto out;
1219 	/* No memory allocation: swap entry occupies the slot for the page */
1220 	error = -EAGAIN;
1221 
1222 	mutex_lock(&shmem_swaplist_mutex);
1223 	list_for_each_safe(this, next, &shmem_swaplist) {
1224 		info = list_entry(this, struct shmem_inode_info, swaplist);
1225 		if (info->swapped)
1226 			error = shmem_unuse_inode(info, swap, &page);
1227 		else
1228 			list_del_init(&info->swaplist);
1229 		cond_resched();
1230 		if (error != -EAGAIN)
1231 			break;
1232 		/* found nothing in this: move on to search the next */
1233 	}
1234 	mutex_unlock(&shmem_swaplist_mutex);
1235 
1236 	if (error) {
1237 		if (error != -ENOMEM)
1238 			error = 0;
1239 		mem_cgroup_cancel_charge(page, memcg, false);
1240 	} else
1241 		mem_cgroup_commit_charge(page, memcg, true, false);
1242 out:
1243 	unlock_page(page);
1244 	put_page(page);
1245 	return error;
1246 }
1247 
1248 /*
1249  * Move the page from the page cache to the swap cache.
1250  */
1251 static int shmem_writepage(struct page *page, struct writeback_control *wbc)
1252 {
1253 	struct shmem_inode_info *info;
1254 	struct address_space *mapping;
1255 	struct inode *inode;
1256 	swp_entry_t swap;
1257 	pgoff_t index;
1258 
1259 	VM_BUG_ON_PAGE(PageCompound(page), page);
1260 	BUG_ON(!PageLocked(page));
1261 	mapping = page->mapping;
1262 	index = page->index;
1263 	inode = mapping->host;
1264 	info = SHMEM_I(inode);
1265 	if (info->flags & VM_LOCKED)
1266 		goto redirty;
1267 	if (!total_swap_pages)
1268 		goto redirty;
1269 
1270 	/*
1271 	 * Our capabilities prevent regular writeback or sync from ever calling
1272 	 * shmem_writepage; but a stacking filesystem might use ->writepage of
1273 	 * its underlying filesystem, in which case tmpfs should write out to
1274 	 * swap only in response to memory pressure, and not for the writeback
1275 	 * threads or sync.
1276 	 */
1277 	if (!wbc->for_reclaim) {
1278 		WARN_ON_ONCE(1);	/* Still happens? Tell us about it! */
1279 		goto redirty;
1280 	}
1281 
1282 	/*
1283 	 * This is somewhat ridiculous, but without plumbing a SWAP_MAP_FALLOC
1284 	 * value into swapfile.c, the only way we can correctly account for a
1285 	 * fallocated page arriving here is now to initialize it and write it.
1286 	 *
1287 	 * That's okay for a page already fallocated earlier, but if we have
1288 	 * not yet completed the fallocation, then (a) we want to keep track
1289 	 * of this page in case we have to undo it, and (b) it may not be a
1290 	 * good idea to continue anyway, once we're pushing into swap.  So
1291 	 * reactivate the page, and let shmem_fallocate() quit when too many.
1292 	 */
1293 	if (!PageUptodate(page)) {
1294 		if (inode->i_private) {
1295 			struct shmem_falloc *shmem_falloc;
1296 			spin_lock(&inode->i_lock);
1297 			shmem_falloc = inode->i_private;
1298 			if (shmem_falloc &&
1299 			    !shmem_falloc->waitq &&
1300 			    index >= shmem_falloc->start &&
1301 			    index < shmem_falloc->next)
1302 				shmem_falloc->nr_unswapped++;
1303 			else
1304 				shmem_falloc = NULL;
1305 			spin_unlock(&inode->i_lock);
1306 			if (shmem_falloc)
1307 				goto redirty;
1308 		}
1309 		clear_highpage(page);
1310 		flush_dcache_page(page);
1311 		SetPageUptodate(page);
1312 	}
1313 
1314 	swap = get_swap_page(page);
1315 	if (!swap.val)
1316 		goto redirty;
1317 
1318 	/*
1319 	 * Add inode to shmem_unuse()'s list of swapped-out inodes,
1320 	 * if it's not already there.  Do it now before the page is
1321 	 * moved to swap cache, when its pagelock no longer protects
1322 	 * the inode from eviction.  But don't unlock the mutex until
1323 	 * we've incremented swapped, because shmem_unuse_inode() will
1324 	 * prune a !swapped inode from the swaplist under this mutex.
1325 	 */
1326 	mutex_lock(&shmem_swaplist_mutex);
1327 	if (list_empty(&info->swaplist))
1328 		list_add_tail(&info->swaplist, &shmem_swaplist);
1329 
1330 	if (add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
1331 		spin_lock_irq(&info->lock);
1332 		shmem_recalc_inode(inode);
1333 		info->swapped++;
1334 		spin_unlock_irq(&info->lock);
1335 
1336 		swap_shmem_alloc(swap);
1337 		shmem_delete_from_page_cache(page, swp_to_radix_entry(swap));
1338 
1339 		mutex_unlock(&shmem_swaplist_mutex);
1340 		BUG_ON(page_mapped(page));
1341 		swap_writepage(page, wbc);
1342 		return 0;
1343 	}
1344 
1345 	mutex_unlock(&shmem_swaplist_mutex);
1346 	put_swap_page(page, swap);
1347 redirty:
1348 	set_page_dirty(page);
1349 	if (wbc->for_reclaim)
1350 		return AOP_WRITEPAGE_ACTIVATE;	/* Return with page locked */
1351 	unlock_page(page);
1352 	return 0;
1353 }
1354 
1355 #if defined(CONFIG_NUMA) && defined(CONFIG_TMPFS)
1356 static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
1357 {
1358 	char buffer[64];
1359 
1360 	if (!mpol || mpol->mode == MPOL_DEFAULT)
1361 		return;		/* show nothing */
1362 
1363 	mpol_to_str(buffer, sizeof(buffer), mpol);
1364 
1365 	seq_printf(seq, ",mpol=%s", buffer);
1366 }
1367 
1368 static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
1369 {
1370 	struct mempolicy *mpol = NULL;
1371 	if (sbinfo->mpol) {
1372 		spin_lock(&sbinfo->stat_lock);	/* prevent replace/use races */
1373 		mpol = sbinfo->mpol;
1374 		mpol_get(mpol);
1375 		spin_unlock(&sbinfo->stat_lock);
1376 	}
1377 	return mpol;
1378 }
1379 #else /* !CONFIG_NUMA || !CONFIG_TMPFS */
1380 static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
1381 {
1382 }
1383 static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
1384 {
1385 	return NULL;
1386 }
1387 #endif /* CONFIG_NUMA && CONFIG_TMPFS */
1388 #ifndef CONFIG_NUMA
1389 #define vm_policy vm_private_data
1390 #endif
1391 
1392 static void shmem_pseudo_vma_init(struct vm_area_struct *vma,
1393 		struct shmem_inode_info *info, pgoff_t index)
1394 {
1395 	/* Create a pseudo vma that just contains the policy */
1396 	vma_init(vma, NULL);
1397 	/* Bias interleave by inode number to distribute better across nodes */
1398 	vma->vm_pgoff = index + info->vfs_inode.i_ino;
1399 	vma->vm_policy = mpol_shared_policy_lookup(&info->policy, index);
1400 }
1401 
1402 static void shmem_pseudo_vma_destroy(struct vm_area_struct *vma)
1403 {
1404 	/* Drop reference taken by mpol_shared_policy_lookup() */
1405 	mpol_cond_put(vma->vm_policy);
1406 }
1407 
1408 static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
1409 			struct shmem_inode_info *info, pgoff_t index)
1410 {
1411 	struct vm_area_struct pvma;
1412 	struct page *page;
1413 	struct vm_fault vmf;
1414 
1415 	shmem_pseudo_vma_init(&pvma, info, index);
1416 	vmf.vma = &pvma;
1417 	vmf.address = 0;
1418 	page = swap_cluster_readahead(swap, gfp, &vmf);
1419 	shmem_pseudo_vma_destroy(&pvma);
1420 
1421 	return page;
1422 }
1423 
1424 static struct page *shmem_alloc_hugepage(gfp_t gfp,
1425 		struct shmem_inode_info *info, pgoff_t index)
1426 {
1427 	struct vm_area_struct pvma;
1428 	struct address_space *mapping = info->vfs_inode.i_mapping;
1429 	pgoff_t hindex;
1430 	struct page *page;
1431 
1432 	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE))
1433 		return NULL;
1434 
1435 	hindex = round_down(index, HPAGE_PMD_NR);
1436 	if (xa_find(&mapping->i_pages, &hindex, hindex + HPAGE_PMD_NR - 1,
1437 								XA_PRESENT))
1438 		return NULL;
1439 
1440 	shmem_pseudo_vma_init(&pvma, info, hindex);
1441 	page = alloc_pages_vma(gfp | __GFP_COMP | __GFP_NORETRY | __GFP_NOWARN,
1442 			HPAGE_PMD_ORDER, &pvma, 0, numa_node_id(), true);
1443 	shmem_pseudo_vma_destroy(&pvma);
1444 	if (page)
1445 		prep_transhuge_page(page);
1446 	return page;
1447 }
1448 
1449 static struct page *shmem_alloc_page(gfp_t gfp,
1450 			struct shmem_inode_info *info, pgoff_t index)
1451 {
1452 	struct vm_area_struct pvma;
1453 	struct page *page;
1454 
1455 	shmem_pseudo_vma_init(&pvma, info, index);
1456 	page = alloc_page_vma(gfp, &pvma, 0);
1457 	shmem_pseudo_vma_destroy(&pvma);
1458 
1459 	return page;
1460 }
1461 
1462 static struct page *shmem_alloc_and_acct_page(gfp_t gfp,
1463 		struct inode *inode,
1464 		pgoff_t index, bool huge)
1465 {
1466 	struct shmem_inode_info *info = SHMEM_I(inode);
1467 	struct page *page;
1468 	int nr;
1469 	int err = -ENOSPC;
1470 
1471 	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE))
1472 		huge = false;
1473 	nr = huge ? HPAGE_PMD_NR : 1;
1474 
1475 	if (!shmem_inode_acct_block(inode, nr))
1476 		goto failed;
1477 
1478 	if (huge)
1479 		page = shmem_alloc_hugepage(gfp, info, index);
1480 	else
1481 		page = shmem_alloc_page(gfp, info, index);
1482 	if (page) {
1483 		__SetPageLocked(page);
1484 		__SetPageSwapBacked(page);
1485 		return page;
1486 	}
1487 
1488 	err = -ENOMEM;
1489 	shmem_inode_unacct_blocks(inode, nr);
1490 failed:
1491 	return ERR_PTR(err);
1492 }
1493 
1494 /*
1495  * When a page is moved from swapcache to shmem filecache (either by the
1496  * usual swapin of shmem_getpage_gfp(), or by the less common swapoff of
1497  * shmem_unuse_inode()), it may have been read in earlier from swap, in
1498  * ignorance of the mapping it belongs to.  If that mapping has special
1499  * constraints (like the gma500 GEM driver, which requires RAM below 4GB),
1500  * we may need to copy to a suitable page before moving to filecache.
1501  *
1502  * In a future release, this may well be extended to respect cpuset and
1503  * NUMA mempolicy, and applied also to anonymous pages in do_swap_page();
1504  * but for now it is a simple matter of zone.
1505  */
1506 static bool shmem_should_replace_page(struct page *page, gfp_t gfp)
1507 {
1508 	return page_zonenum(page) > gfp_zone(gfp);
1509 }
1510 
1511 static int shmem_replace_page(struct page **pagep, gfp_t gfp,
1512 				struct shmem_inode_info *info, pgoff_t index)
1513 {
1514 	struct page *oldpage, *newpage;
1515 	struct address_space *swap_mapping;
1516 	swp_entry_t entry;
1517 	pgoff_t swap_index;
1518 	int error;
1519 
1520 	oldpage = *pagep;
1521 	entry.val = page_private(oldpage);
1522 	swap_index = swp_offset(entry);
1523 	swap_mapping = page_mapping(oldpage);
1524 
1525 	/*
1526 	 * We have arrived here because our zones are constrained, so don't
1527 	 * limit chance of success by further cpuset and node constraints.
1528 	 */
1529 	gfp &= ~GFP_CONSTRAINT_MASK;
1530 	newpage = shmem_alloc_page(gfp, info, index);
1531 	if (!newpage)
1532 		return -ENOMEM;
1533 
1534 	get_page(newpage);
1535 	copy_highpage(newpage, oldpage);
1536 	flush_dcache_page(newpage);
1537 
1538 	__SetPageLocked(newpage);
1539 	__SetPageSwapBacked(newpage);
1540 	SetPageUptodate(newpage);
1541 	set_page_private(newpage, entry.val);
1542 	SetPageSwapCache(newpage);
1543 
1544 	/*
1545 	 * Our caller will very soon move newpage out of swapcache, but it's
1546 	 * a nice clean interface for us to replace oldpage by newpage there.
1547 	 */
1548 	xa_lock_irq(&swap_mapping->i_pages);
1549 	error = shmem_replace_entry(swap_mapping, swap_index, oldpage, newpage);
1550 	if (!error) {
1551 		__inc_node_page_state(newpage, NR_FILE_PAGES);
1552 		__dec_node_page_state(oldpage, NR_FILE_PAGES);
1553 	}
1554 	xa_unlock_irq(&swap_mapping->i_pages);
1555 
1556 	if (unlikely(error)) {
1557 		/*
1558 		 * Is this possible?  I think not, now that our callers check
1559 		 * both PageSwapCache and page_private after getting page lock;
1560 		 * but be defensive.  Reverse old to newpage for clear and free.
1561 		 */
1562 		oldpage = newpage;
1563 	} else {
1564 		mem_cgroup_migrate(oldpage, newpage);
1565 		lru_cache_add_anon(newpage);
1566 		*pagep = newpage;
1567 	}
1568 
1569 	ClearPageSwapCache(oldpage);
1570 	set_page_private(oldpage, 0);
1571 
1572 	unlock_page(oldpage);
1573 	put_page(oldpage);
1574 	put_page(oldpage);
1575 	return error;
1576 }
1577 
1578 /*
1579  * shmem_getpage_gfp - find page in cache, or get from swap, or allocate
1580  *
1581  * If we allocate a new one we do not mark it dirty. That's up to the
1582  * vm. If we swap it in we mark it dirty since we also free the swap
1583  * entry since a page cannot live in both the swap and page cache.
1584  *
1585  * fault_mm and fault_type are only supplied by shmem_fault:
1586  * otherwise they are NULL.
1587  */
1588 static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
1589 	struct page **pagep, enum sgp_type sgp, gfp_t gfp,
1590 	struct vm_area_struct *vma, struct vm_fault *vmf,
1591 			vm_fault_t *fault_type)
1592 {
1593 	struct address_space *mapping = inode->i_mapping;
1594 	struct shmem_inode_info *info = SHMEM_I(inode);
1595 	struct shmem_sb_info *sbinfo;
1596 	struct mm_struct *charge_mm;
1597 	struct mem_cgroup *memcg;
1598 	struct page *page;
1599 	swp_entry_t swap;
1600 	enum sgp_type sgp_huge = sgp;
1601 	pgoff_t hindex = index;
1602 	int error;
1603 	int once = 0;
1604 	int alloced = 0;
1605 
1606 	if (index > (MAX_LFS_FILESIZE >> PAGE_SHIFT))
1607 		return -EFBIG;
1608 	if (sgp == SGP_NOHUGE || sgp == SGP_HUGE)
1609 		sgp = SGP_CACHE;
1610 repeat:
1611 	swap.val = 0;
1612 	page = find_lock_entry(mapping, index);
1613 	if (xa_is_value(page)) {
1614 		swap = radix_to_swp_entry(page);
1615 		page = NULL;
1616 	}
1617 
1618 	if (sgp <= SGP_CACHE &&
1619 	    ((loff_t)index << PAGE_SHIFT) >= i_size_read(inode)) {
1620 		error = -EINVAL;
1621 		goto unlock;
1622 	}
1623 
1624 	if (page && sgp == SGP_WRITE)
1625 		mark_page_accessed(page);
1626 
1627 	/* fallocated page? */
1628 	if (page && !PageUptodate(page)) {
1629 		if (sgp != SGP_READ)
1630 			goto clear;
1631 		unlock_page(page);
1632 		put_page(page);
1633 		page = NULL;
1634 	}
1635 	if (page || (sgp == SGP_READ && !swap.val)) {
1636 		*pagep = page;
1637 		return 0;
1638 	}
1639 
1640 	/*
1641 	 * Fast cache lookup did not find it:
1642 	 * bring it back from swap or allocate.
1643 	 */
1644 	sbinfo = SHMEM_SB(inode->i_sb);
1645 	charge_mm = vma ? vma->vm_mm : current->mm;
1646 
1647 	if (swap.val) {
1648 		/* Look it up and read it in.. */
1649 		page = lookup_swap_cache(swap, NULL, 0);
1650 		if (!page) {
1651 			/* Or update major stats only when swapin succeeds?? */
1652 			if (fault_type) {
1653 				*fault_type |= VM_FAULT_MAJOR;
1654 				count_vm_event(PGMAJFAULT);
1655 				count_memcg_event_mm(charge_mm, PGMAJFAULT);
1656 			}
1657 			/* Here we actually start the io */
1658 			page = shmem_swapin(swap, gfp, info, index);
1659 			if (!page) {
1660 				error = -ENOMEM;
1661 				goto failed;
1662 			}
1663 		}
1664 
1665 		/* We have to do this with page locked to prevent races */
1666 		lock_page(page);
1667 		if (!PageSwapCache(page) || page_private(page) != swap.val ||
1668 		    !shmem_confirm_swap(mapping, index, swap)) {
1669 			error = -EEXIST;	/* try again */
1670 			goto unlock;
1671 		}
1672 		if (!PageUptodate(page)) {
1673 			error = -EIO;
1674 			goto failed;
1675 		}
1676 		wait_on_page_writeback(page);
1677 
1678 		if (shmem_should_replace_page(page, gfp)) {
1679 			error = shmem_replace_page(&page, gfp, info, index);
1680 			if (error)
1681 				goto failed;
1682 		}
1683 
1684 		error = mem_cgroup_try_charge_delay(page, charge_mm, gfp, &memcg,
1685 				false);
1686 		if (!error) {
1687 			error = shmem_add_to_page_cache(page, mapping, index,
1688 						swp_to_radix_entry(swap), gfp);
1689 			/*
1690 			 * We already confirmed swap under page lock, and make
1691 			 * no memory allocation here, so usually no possibility
1692 			 * of error; but free_swap_and_cache() only trylocks a
1693 			 * page, so it is just possible that the entry has been
1694 			 * truncated or holepunched since swap was confirmed.
1695 			 * shmem_undo_range() will have done some of the
1696 			 * unaccounting, now delete_from_swap_cache() will do
1697 			 * the rest.
1698 			 * Reset swap.val? No, leave it so "failed" goes back to
1699 			 * "repeat": reading a hole and writing should succeed.
1700 			 */
1701 			if (error) {
1702 				mem_cgroup_cancel_charge(page, memcg, false);
1703 				delete_from_swap_cache(page);
1704 			}
1705 		}
1706 		if (error)
1707 			goto failed;
1708 
1709 		mem_cgroup_commit_charge(page, memcg, true, false);
1710 
1711 		spin_lock_irq(&info->lock);
1712 		info->swapped--;
1713 		shmem_recalc_inode(inode);
1714 		spin_unlock_irq(&info->lock);
1715 
1716 		if (sgp == SGP_WRITE)
1717 			mark_page_accessed(page);
1718 
1719 		delete_from_swap_cache(page);
1720 		set_page_dirty(page);
1721 		swap_free(swap);
1722 
1723 	} else {
1724 		if (vma && userfaultfd_missing(vma)) {
1725 			*fault_type = handle_userfault(vmf, VM_UFFD_MISSING);
1726 			return 0;
1727 		}
1728 
1729 		/* shmem_symlink() */
1730 		if (mapping->a_ops != &shmem_aops)
1731 			goto alloc_nohuge;
1732 		if (shmem_huge == SHMEM_HUGE_DENY || sgp_huge == SGP_NOHUGE)
1733 			goto alloc_nohuge;
1734 		if (shmem_huge == SHMEM_HUGE_FORCE)
1735 			goto alloc_huge;
1736 		switch (sbinfo->huge) {
1737 			loff_t i_size;
1738 			pgoff_t off;
1739 		case SHMEM_HUGE_NEVER:
1740 			goto alloc_nohuge;
1741 		case SHMEM_HUGE_WITHIN_SIZE:
1742 			off = round_up(index, HPAGE_PMD_NR);
1743 			i_size = round_up(i_size_read(inode), PAGE_SIZE);
1744 			if (i_size >= HPAGE_PMD_SIZE &&
1745 					i_size >> PAGE_SHIFT >= off)
1746 				goto alloc_huge;
1747 			/* fallthrough */
1748 		case SHMEM_HUGE_ADVISE:
1749 			if (sgp_huge == SGP_HUGE)
1750 				goto alloc_huge;
1751 			/* TODO: implement fadvise() hints */
1752 			goto alloc_nohuge;
1753 		}
1754 
1755 alloc_huge:
1756 		page = shmem_alloc_and_acct_page(gfp, inode, index, true);
1757 		if (IS_ERR(page)) {
1758 alloc_nohuge:		page = shmem_alloc_and_acct_page(gfp, inode,
1759 					index, false);
1760 		}
1761 		if (IS_ERR(page)) {
1762 			int retry = 5;
1763 			error = PTR_ERR(page);
1764 			page = NULL;
1765 			if (error != -ENOSPC)
1766 				goto failed;
1767 			/*
1768 			 * Try to reclaim some spece by splitting a huge page
1769 			 * beyond i_size on the filesystem.
1770 			 */
1771 			while (retry--) {
1772 				int ret;
1773 				ret = shmem_unused_huge_shrink(sbinfo, NULL, 1);
1774 				if (ret == SHRINK_STOP)
1775 					break;
1776 				if (ret)
1777 					goto alloc_nohuge;
1778 			}
1779 			goto failed;
1780 		}
1781 
1782 		if (PageTransHuge(page))
1783 			hindex = round_down(index, HPAGE_PMD_NR);
1784 		else
1785 			hindex = index;
1786 
1787 		if (sgp == SGP_WRITE)
1788 			__SetPageReferenced(page);
1789 
1790 		error = mem_cgroup_try_charge_delay(page, charge_mm, gfp, &memcg,
1791 				PageTransHuge(page));
1792 		if (error)
1793 			goto unacct;
1794 		error = shmem_add_to_page_cache(page, mapping, hindex,
1795 						NULL, gfp & GFP_RECLAIM_MASK);
1796 		if (error) {
1797 			mem_cgroup_cancel_charge(page, memcg,
1798 					PageTransHuge(page));
1799 			goto unacct;
1800 		}
1801 		mem_cgroup_commit_charge(page, memcg, false,
1802 				PageTransHuge(page));
1803 		lru_cache_add_anon(page);
1804 
1805 		spin_lock_irq(&info->lock);
1806 		info->alloced += 1 << compound_order(page);
1807 		inode->i_blocks += BLOCKS_PER_PAGE << compound_order(page);
1808 		shmem_recalc_inode(inode);
1809 		spin_unlock_irq(&info->lock);
1810 		alloced = true;
1811 
1812 		if (PageTransHuge(page) &&
1813 				DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE) <
1814 				hindex + HPAGE_PMD_NR - 1) {
1815 			/*
1816 			 * Part of the huge page is beyond i_size: subject
1817 			 * to shrink under memory pressure.
1818 			 */
1819 			spin_lock(&sbinfo->shrinklist_lock);
1820 			/*
1821 			 * _careful to defend against unlocked access to
1822 			 * ->shrink_list in shmem_unused_huge_shrink()
1823 			 */
1824 			if (list_empty_careful(&info->shrinklist)) {
1825 				list_add_tail(&info->shrinklist,
1826 						&sbinfo->shrinklist);
1827 				sbinfo->shrinklist_len++;
1828 			}
1829 			spin_unlock(&sbinfo->shrinklist_lock);
1830 		}
1831 
1832 		/*
1833 		 * Let SGP_FALLOC use the SGP_WRITE optimization on a new page.
1834 		 */
1835 		if (sgp == SGP_FALLOC)
1836 			sgp = SGP_WRITE;
1837 clear:
1838 		/*
1839 		 * Let SGP_WRITE caller clear ends if write does not fill page;
1840 		 * but SGP_FALLOC on a page fallocated earlier must initialize
1841 		 * it now, lest undo on failure cancel our earlier guarantee.
1842 		 */
1843 		if (sgp != SGP_WRITE && !PageUptodate(page)) {
1844 			struct page *head = compound_head(page);
1845 			int i;
1846 
1847 			for (i = 0; i < (1 << compound_order(head)); i++) {
1848 				clear_highpage(head + i);
1849 				flush_dcache_page(head + i);
1850 			}
1851 			SetPageUptodate(head);
1852 		}
1853 	}
1854 
1855 	/* Perhaps the file has been truncated since we checked */
1856 	if (sgp <= SGP_CACHE &&
1857 	    ((loff_t)index << PAGE_SHIFT) >= i_size_read(inode)) {
1858 		if (alloced) {
1859 			ClearPageDirty(page);
1860 			delete_from_page_cache(page);
1861 			spin_lock_irq(&info->lock);
1862 			shmem_recalc_inode(inode);
1863 			spin_unlock_irq(&info->lock);
1864 		}
1865 		error = -EINVAL;
1866 		goto unlock;
1867 	}
1868 	*pagep = page + index - hindex;
1869 	return 0;
1870 
1871 	/*
1872 	 * Error recovery.
1873 	 */
1874 unacct:
1875 	shmem_inode_unacct_blocks(inode, 1 << compound_order(page));
1876 
1877 	if (PageTransHuge(page)) {
1878 		unlock_page(page);
1879 		put_page(page);
1880 		goto alloc_nohuge;
1881 	}
1882 failed:
1883 	if (swap.val && !shmem_confirm_swap(mapping, index, swap))
1884 		error = -EEXIST;
1885 unlock:
1886 	if (page) {
1887 		unlock_page(page);
1888 		put_page(page);
1889 	}
1890 	if (error == -ENOSPC && !once++) {
1891 		spin_lock_irq(&info->lock);
1892 		shmem_recalc_inode(inode);
1893 		spin_unlock_irq(&info->lock);
1894 		goto repeat;
1895 	}
1896 	if (error == -EEXIST)
1897 		goto repeat;
1898 	return error;
1899 }
1900 
1901 /*
1902  * This is like autoremove_wake_function, but it removes the wait queue
1903  * entry unconditionally - even if something else had already woken the
1904  * target.
1905  */
1906 static int synchronous_wake_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
1907 {
1908 	int ret = default_wake_function(wait, mode, sync, key);
1909 	list_del_init(&wait->entry);
1910 	return ret;
1911 }
1912 
1913 static vm_fault_t shmem_fault(struct vm_fault *vmf)
1914 {
1915 	struct vm_area_struct *vma = vmf->vma;
1916 	struct inode *inode = file_inode(vma->vm_file);
1917 	gfp_t gfp = mapping_gfp_mask(inode->i_mapping);
1918 	enum sgp_type sgp;
1919 	int err;
1920 	vm_fault_t ret = VM_FAULT_LOCKED;
1921 
1922 	/*
1923 	 * Trinity finds that probing a hole which tmpfs is punching can
1924 	 * prevent the hole-punch from ever completing: which in turn
1925 	 * locks writers out with its hold on i_mutex.  So refrain from
1926 	 * faulting pages into the hole while it's being punched.  Although
1927 	 * shmem_undo_range() does remove the additions, it may be unable to
1928 	 * keep up, as each new page needs its own unmap_mapping_range() call,
1929 	 * and the i_mmap tree grows ever slower to scan if new vmas are added.
1930 	 *
1931 	 * It does not matter if we sometimes reach this check just before the
1932 	 * hole-punch begins, so that one fault then races with the punch:
1933 	 * we just need to make racing faults a rare case.
1934 	 *
1935 	 * The implementation below would be much simpler if we just used a
1936 	 * standard mutex or completion: but we cannot take i_mutex in fault,
1937 	 * and bloating every shmem inode for this unlikely case would be sad.
1938 	 */
1939 	if (unlikely(inode->i_private)) {
1940 		struct shmem_falloc *shmem_falloc;
1941 
1942 		spin_lock(&inode->i_lock);
1943 		shmem_falloc = inode->i_private;
1944 		if (shmem_falloc &&
1945 		    shmem_falloc->waitq &&
1946 		    vmf->pgoff >= shmem_falloc->start &&
1947 		    vmf->pgoff < shmem_falloc->next) {
1948 			wait_queue_head_t *shmem_falloc_waitq;
1949 			DEFINE_WAIT_FUNC(shmem_fault_wait, synchronous_wake_function);
1950 
1951 			ret = VM_FAULT_NOPAGE;
1952 			if ((vmf->flags & FAULT_FLAG_ALLOW_RETRY) &&
1953 			   !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT)) {
1954 				/* It's polite to up mmap_sem if we can */
1955 				up_read(&vma->vm_mm->mmap_sem);
1956 				ret = VM_FAULT_RETRY;
1957 			}
1958 
1959 			shmem_falloc_waitq = shmem_falloc->waitq;
1960 			prepare_to_wait(shmem_falloc_waitq, &shmem_fault_wait,
1961 					TASK_UNINTERRUPTIBLE);
1962 			spin_unlock(&inode->i_lock);
1963 			schedule();
1964 
1965 			/*
1966 			 * shmem_falloc_waitq points into the shmem_fallocate()
1967 			 * stack of the hole-punching task: shmem_falloc_waitq
1968 			 * is usually invalid by the time we reach here, but
1969 			 * finish_wait() does not dereference it in that case;
1970 			 * though i_lock needed lest racing with wake_up_all().
1971 			 */
1972 			spin_lock(&inode->i_lock);
1973 			finish_wait(shmem_falloc_waitq, &shmem_fault_wait);
1974 			spin_unlock(&inode->i_lock);
1975 			return ret;
1976 		}
1977 		spin_unlock(&inode->i_lock);
1978 	}
1979 
1980 	sgp = SGP_CACHE;
1981 
1982 	if ((vma->vm_flags & VM_NOHUGEPAGE) ||
1983 	    test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))
1984 		sgp = SGP_NOHUGE;
1985 	else if (vma->vm_flags & VM_HUGEPAGE)
1986 		sgp = SGP_HUGE;
1987 
1988 	err = shmem_getpage_gfp(inode, vmf->pgoff, &vmf->page, sgp,
1989 				  gfp, vma, vmf, &ret);
1990 	if (err)
1991 		return vmf_error(err);
1992 	return ret;
1993 }
1994 
1995 unsigned long shmem_get_unmapped_area(struct file *file,
1996 				      unsigned long uaddr, unsigned long len,
1997 				      unsigned long pgoff, unsigned long flags)
1998 {
1999 	unsigned long (*get_area)(struct file *,
2000 		unsigned long, unsigned long, unsigned long, unsigned long);
2001 	unsigned long addr;
2002 	unsigned long offset;
2003 	unsigned long inflated_len;
2004 	unsigned long inflated_addr;
2005 	unsigned long inflated_offset;
2006 
2007 	if (len > TASK_SIZE)
2008 		return -ENOMEM;
2009 
2010 	get_area = current->mm->get_unmapped_area;
2011 	addr = get_area(file, uaddr, len, pgoff, flags);
2012 
2013 	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE))
2014 		return addr;
2015 	if (IS_ERR_VALUE(addr))
2016 		return addr;
2017 	if (addr & ~PAGE_MASK)
2018 		return addr;
2019 	if (addr > TASK_SIZE - len)
2020 		return addr;
2021 
2022 	if (shmem_huge == SHMEM_HUGE_DENY)
2023 		return addr;
2024 	if (len < HPAGE_PMD_SIZE)
2025 		return addr;
2026 	if (flags & MAP_FIXED)
2027 		return addr;
2028 	/*
2029 	 * Our priority is to support MAP_SHARED mapped hugely;
2030 	 * and support MAP_PRIVATE mapped hugely too, until it is COWed.
2031 	 * But if caller specified an address hint, respect that as before.
2032 	 */
2033 	if (uaddr)
2034 		return addr;
2035 
2036 	if (shmem_huge != SHMEM_HUGE_FORCE) {
2037 		struct super_block *sb;
2038 
2039 		if (file) {
2040 			VM_BUG_ON(file->f_op != &shmem_file_operations);
2041 			sb = file_inode(file)->i_sb;
2042 		} else {
2043 			/*
2044 			 * Called directly from mm/mmap.c, or drivers/char/mem.c
2045 			 * for "/dev/zero", to create a shared anonymous object.
2046 			 */
2047 			if (IS_ERR(shm_mnt))
2048 				return addr;
2049 			sb = shm_mnt->mnt_sb;
2050 		}
2051 		if (SHMEM_SB(sb)->huge == SHMEM_HUGE_NEVER)
2052 			return addr;
2053 	}
2054 
2055 	offset = (pgoff << PAGE_SHIFT) & (HPAGE_PMD_SIZE-1);
2056 	if (offset && offset + len < 2 * HPAGE_PMD_SIZE)
2057 		return addr;
2058 	if ((addr & (HPAGE_PMD_SIZE-1)) == offset)
2059 		return addr;
2060 
2061 	inflated_len = len + HPAGE_PMD_SIZE - PAGE_SIZE;
2062 	if (inflated_len > TASK_SIZE)
2063 		return addr;
2064 	if (inflated_len < len)
2065 		return addr;
2066 
2067 	inflated_addr = get_area(NULL, 0, inflated_len, 0, flags);
2068 	if (IS_ERR_VALUE(inflated_addr))
2069 		return addr;
2070 	if (inflated_addr & ~PAGE_MASK)
2071 		return addr;
2072 
2073 	inflated_offset = inflated_addr & (HPAGE_PMD_SIZE-1);
2074 	inflated_addr += offset - inflated_offset;
2075 	if (inflated_offset > offset)
2076 		inflated_addr += HPAGE_PMD_SIZE;
2077 
2078 	if (inflated_addr > TASK_SIZE - len)
2079 		return addr;
2080 	return inflated_addr;
2081 }
2082 
2083 #ifdef CONFIG_NUMA
2084 static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *mpol)
2085 {
2086 	struct inode *inode = file_inode(vma->vm_file);
2087 	return mpol_set_shared_policy(&SHMEM_I(inode)->policy, vma, mpol);
2088 }
2089 
2090 static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
2091 					  unsigned long addr)
2092 {
2093 	struct inode *inode = file_inode(vma->vm_file);
2094 	pgoff_t index;
2095 
2096 	index = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
2097 	return mpol_shared_policy_lookup(&SHMEM_I(inode)->policy, index);
2098 }
2099 #endif
2100 
2101 int shmem_lock(struct file *file, int lock, struct user_struct *user)
2102 {
2103 	struct inode *inode = file_inode(file);
2104 	struct shmem_inode_info *info = SHMEM_I(inode);
2105 	int retval = -ENOMEM;
2106 
2107 	spin_lock_irq(&info->lock);
2108 	if (lock && !(info->flags & VM_LOCKED)) {
2109 		if (!user_shm_lock(inode->i_size, user))
2110 			goto out_nomem;
2111 		info->flags |= VM_LOCKED;
2112 		mapping_set_unevictable(file->f_mapping);
2113 	}
2114 	if (!lock && (info->flags & VM_LOCKED) && user) {
2115 		user_shm_unlock(inode->i_size, user);
2116 		info->flags &= ~VM_LOCKED;
2117 		mapping_clear_unevictable(file->f_mapping);
2118 	}
2119 	retval = 0;
2120 
2121 out_nomem:
2122 	spin_unlock_irq(&info->lock);
2123 	return retval;
2124 }
2125 
2126 static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
2127 {
2128 	file_accessed(file);
2129 	vma->vm_ops = &shmem_vm_ops;
2130 	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE) &&
2131 			((vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK) <
2132 			(vma->vm_end & HPAGE_PMD_MASK)) {
2133 		khugepaged_enter(vma, vma->vm_flags);
2134 	}
2135 	return 0;
2136 }
2137 
2138 static struct inode *shmem_get_inode(struct super_block *sb, const struct inode *dir,
2139 				     umode_t mode, dev_t dev, unsigned long flags)
2140 {
2141 	struct inode *inode;
2142 	struct shmem_inode_info *info;
2143 	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2144 
2145 	if (shmem_reserve_inode(sb))
2146 		return NULL;
2147 
2148 	inode = new_inode(sb);
2149 	if (inode) {
2150 		inode->i_ino = get_next_ino();
2151 		inode_init_owner(inode, dir, mode);
2152 		inode->i_blocks = 0;
2153 		inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
2154 		inode->i_generation = prandom_u32();
2155 		info = SHMEM_I(inode);
2156 		memset(info, 0, (char *)inode - (char *)info);
2157 		spin_lock_init(&info->lock);
2158 		info->seals = F_SEAL_SEAL;
2159 		info->flags = flags & VM_NORESERVE;
2160 		INIT_LIST_HEAD(&info->shrinklist);
2161 		INIT_LIST_HEAD(&info->swaplist);
2162 		simple_xattrs_init(&info->xattrs);
2163 		cache_no_acl(inode);
2164 
2165 		switch (mode & S_IFMT) {
2166 		default:
2167 			inode->i_op = &shmem_special_inode_operations;
2168 			init_special_inode(inode, mode, dev);
2169 			break;
2170 		case S_IFREG:
2171 			inode->i_mapping->a_ops = &shmem_aops;
2172 			inode->i_op = &shmem_inode_operations;
2173 			inode->i_fop = &shmem_file_operations;
2174 			mpol_shared_policy_init(&info->policy,
2175 						 shmem_get_sbmpol(sbinfo));
2176 			break;
2177 		case S_IFDIR:
2178 			inc_nlink(inode);
2179 			/* Some things misbehave if size == 0 on a directory */
2180 			inode->i_size = 2 * BOGO_DIRENT_SIZE;
2181 			inode->i_op = &shmem_dir_inode_operations;
2182 			inode->i_fop = &simple_dir_operations;
2183 			break;
2184 		case S_IFLNK:
2185 			/*
2186 			 * Must not load anything in the rbtree,
2187 			 * mpol_free_shared_policy will not be called.
2188 			 */
2189 			mpol_shared_policy_init(&info->policy, NULL);
2190 			break;
2191 		}
2192 
2193 		lockdep_annotate_inode_mutex_key(inode);
2194 	} else
2195 		shmem_free_inode(sb);
2196 	return inode;
2197 }
2198 
2199 bool shmem_mapping(struct address_space *mapping)
2200 {
2201 	return mapping->a_ops == &shmem_aops;
2202 }
2203 
2204 static int shmem_mfill_atomic_pte(struct mm_struct *dst_mm,
2205 				  pmd_t *dst_pmd,
2206 				  struct vm_area_struct *dst_vma,
2207 				  unsigned long dst_addr,
2208 				  unsigned long src_addr,
2209 				  bool zeropage,
2210 				  struct page **pagep)
2211 {
2212 	struct inode *inode = file_inode(dst_vma->vm_file);
2213 	struct shmem_inode_info *info = SHMEM_I(inode);
2214 	struct address_space *mapping = inode->i_mapping;
2215 	gfp_t gfp = mapping_gfp_mask(mapping);
2216 	pgoff_t pgoff = linear_page_index(dst_vma, dst_addr);
2217 	struct mem_cgroup *memcg;
2218 	spinlock_t *ptl;
2219 	void *page_kaddr;
2220 	struct page *page;
2221 	pte_t _dst_pte, *dst_pte;
2222 	int ret;
2223 	pgoff_t offset, max_off;
2224 
2225 	ret = -ENOMEM;
2226 	if (!shmem_inode_acct_block(inode, 1))
2227 		goto out;
2228 
2229 	if (!*pagep) {
2230 		page = shmem_alloc_page(gfp, info, pgoff);
2231 		if (!page)
2232 			goto out_unacct_blocks;
2233 
2234 		if (!zeropage) {	/* mcopy_atomic */
2235 			page_kaddr = kmap_atomic(page);
2236 			ret = copy_from_user(page_kaddr,
2237 					     (const void __user *)src_addr,
2238 					     PAGE_SIZE);
2239 			kunmap_atomic(page_kaddr);
2240 
2241 			/* fallback to copy_from_user outside mmap_sem */
2242 			if (unlikely(ret)) {
2243 				*pagep = page;
2244 				shmem_inode_unacct_blocks(inode, 1);
2245 				/* don't free the page */
2246 				return -ENOENT;
2247 			}
2248 		} else {		/* mfill_zeropage_atomic */
2249 			clear_highpage(page);
2250 		}
2251 	} else {
2252 		page = *pagep;
2253 		*pagep = NULL;
2254 	}
2255 
2256 	VM_BUG_ON(PageLocked(page) || PageSwapBacked(page));
2257 	__SetPageLocked(page);
2258 	__SetPageSwapBacked(page);
2259 	__SetPageUptodate(page);
2260 
2261 	ret = -EFAULT;
2262 	offset = linear_page_index(dst_vma, dst_addr);
2263 	max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
2264 	if (unlikely(offset >= max_off))
2265 		goto out_release;
2266 
2267 	ret = mem_cgroup_try_charge_delay(page, dst_mm, gfp, &memcg, false);
2268 	if (ret)
2269 		goto out_release;
2270 
2271 	ret = shmem_add_to_page_cache(page, mapping, pgoff, NULL,
2272 						gfp & GFP_RECLAIM_MASK);
2273 	if (ret)
2274 		goto out_release_uncharge;
2275 
2276 	mem_cgroup_commit_charge(page, memcg, false, false);
2277 
2278 	_dst_pte = mk_pte(page, dst_vma->vm_page_prot);
2279 	if (dst_vma->vm_flags & VM_WRITE)
2280 		_dst_pte = pte_mkwrite(pte_mkdirty(_dst_pte));
2281 	else {
2282 		/*
2283 		 * We don't set the pte dirty if the vma has no
2284 		 * VM_WRITE permission, so mark the page dirty or it
2285 		 * could be freed from under us. We could do it
2286 		 * unconditionally before unlock_page(), but doing it
2287 		 * only if VM_WRITE is not set is faster.
2288 		 */
2289 		set_page_dirty(page);
2290 	}
2291 
2292 	dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
2293 
2294 	ret = -EFAULT;
2295 	max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
2296 	if (unlikely(offset >= max_off))
2297 		goto out_release_uncharge_unlock;
2298 
2299 	ret = -EEXIST;
2300 	if (!pte_none(*dst_pte))
2301 		goto out_release_uncharge_unlock;
2302 
2303 	lru_cache_add_anon(page);
2304 
2305 	spin_lock(&info->lock);
2306 	info->alloced++;
2307 	inode->i_blocks += BLOCKS_PER_PAGE;
2308 	shmem_recalc_inode(inode);
2309 	spin_unlock(&info->lock);
2310 
2311 	inc_mm_counter(dst_mm, mm_counter_file(page));
2312 	page_add_file_rmap(page, false);
2313 	set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
2314 
2315 	/* No need to invalidate - it was non-present before */
2316 	update_mmu_cache(dst_vma, dst_addr, dst_pte);
2317 	pte_unmap_unlock(dst_pte, ptl);
2318 	unlock_page(page);
2319 	ret = 0;
2320 out:
2321 	return ret;
2322 out_release_uncharge_unlock:
2323 	pte_unmap_unlock(dst_pte, ptl);
2324 	ClearPageDirty(page);
2325 	delete_from_page_cache(page);
2326 out_release_uncharge:
2327 	mem_cgroup_cancel_charge(page, memcg, false);
2328 out_release:
2329 	unlock_page(page);
2330 	put_page(page);
2331 out_unacct_blocks:
2332 	shmem_inode_unacct_blocks(inode, 1);
2333 	goto out;
2334 }
2335 
2336 int shmem_mcopy_atomic_pte(struct mm_struct *dst_mm,
2337 			   pmd_t *dst_pmd,
2338 			   struct vm_area_struct *dst_vma,
2339 			   unsigned long dst_addr,
2340 			   unsigned long src_addr,
2341 			   struct page **pagep)
2342 {
2343 	return shmem_mfill_atomic_pte(dst_mm, dst_pmd, dst_vma,
2344 				      dst_addr, src_addr, false, pagep);
2345 }
2346 
2347 int shmem_mfill_zeropage_pte(struct mm_struct *dst_mm,
2348 			     pmd_t *dst_pmd,
2349 			     struct vm_area_struct *dst_vma,
2350 			     unsigned long dst_addr)
2351 {
2352 	struct page *page = NULL;
2353 
2354 	return shmem_mfill_atomic_pte(dst_mm, dst_pmd, dst_vma,
2355 				      dst_addr, 0, true, &page);
2356 }
2357 
2358 #ifdef CONFIG_TMPFS
2359 static const struct inode_operations shmem_symlink_inode_operations;
2360 static const struct inode_operations shmem_short_symlink_operations;
2361 
2362 #ifdef CONFIG_TMPFS_XATTR
2363 static int shmem_initxattrs(struct inode *, const struct xattr *, void *);
2364 #else
2365 #define shmem_initxattrs NULL
2366 #endif
2367 
2368 static int
2369 shmem_write_begin(struct file *file, struct address_space *mapping,
2370 			loff_t pos, unsigned len, unsigned flags,
2371 			struct page **pagep, void **fsdata)
2372 {
2373 	struct inode *inode = mapping->host;
2374 	struct shmem_inode_info *info = SHMEM_I(inode);
2375 	pgoff_t index = pos >> PAGE_SHIFT;
2376 
2377 	/* i_mutex is held by caller */
2378 	if (unlikely(info->seals & (F_SEAL_WRITE | F_SEAL_GROW))) {
2379 		if (info->seals & F_SEAL_WRITE)
2380 			return -EPERM;
2381 		if ((info->seals & F_SEAL_GROW) && pos + len > inode->i_size)
2382 			return -EPERM;
2383 	}
2384 
2385 	return shmem_getpage(inode, index, pagep, SGP_WRITE);
2386 }
2387 
2388 static int
2389 shmem_write_end(struct file *file, struct address_space *mapping,
2390 			loff_t pos, unsigned len, unsigned copied,
2391 			struct page *page, void *fsdata)
2392 {
2393 	struct inode *inode = mapping->host;
2394 
2395 	if (pos + copied > inode->i_size)
2396 		i_size_write(inode, pos + copied);
2397 
2398 	if (!PageUptodate(page)) {
2399 		struct page *head = compound_head(page);
2400 		if (PageTransCompound(page)) {
2401 			int i;
2402 
2403 			for (i = 0; i < HPAGE_PMD_NR; i++) {
2404 				if (head + i == page)
2405 					continue;
2406 				clear_highpage(head + i);
2407 				flush_dcache_page(head + i);
2408 			}
2409 		}
2410 		if (copied < PAGE_SIZE) {
2411 			unsigned from = pos & (PAGE_SIZE - 1);
2412 			zero_user_segments(page, 0, from,
2413 					from + copied, PAGE_SIZE);
2414 		}
2415 		SetPageUptodate(head);
2416 	}
2417 	set_page_dirty(page);
2418 	unlock_page(page);
2419 	put_page(page);
2420 
2421 	return copied;
2422 }
2423 
2424 static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
2425 {
2426 	struct file *file = iocb->ki_filp;
2427 	struct inode *inode = file_inode(file);
2428 	struct address_space *mapping = inode->i_mapping;
2429 	pgoff_t index;
2430 	unsigned long offset;
2431 	enum sgp_type sgp = SGP_READ;
2432 	int error = 0;
2433 	ssize_t retval = 0;
2434 	loff_t *ppos = &iocb->ki_pos;
2435 
2436 	/*
2437 	 * Might this read be for a stacking filesystem?  Then when reading
2438 	 * holes of a sparse file, we actually need to allocate those pages,
2439 	 * and even mark them dirty, so it cannot exceed the max_blocks limit.
2440 	 */
2441 	if (!iter_is_iovec(to))
2442 		sgp = SGP_CACHE;
2443 
2444 	index = *ppos >> PAGE_SHIFT;
2445 	offset = *ppos & ~PAGE_MASK;
2446 
2447 	for (;;) {
2448 		struct page *page = NULL;
2449 		pgoff_t end_index;
2450 		unsigned long nr, ret;
2451 		loff_t i_size = i_size_read(inode);
2452 
2453 		end_index = i_size >> PAGE_SHIFT;
2454 		if (index > end_index)
2455 			break;
2456 		if (index == end_index) {
2457 			nr = i_size & ~PAGE_MASK;
2458 			if (nr <= offset)
2459 				break;
2460 		}
2461 
2462 		error = shmem_getpage(inode, index, &page, sgp);
2463 		if (error) {
2464 			if (error == -EINVAL)
2465 				error = 0;
2466 			break;
2467 		}
2468 		if (page) {
2469 			if (sgp == SGP_CACHE)
2470 				set_page_dirty(page);
2471 			unlock_page(page);
2472 		}
2473 
2474 		/*
2475 		 * We must evaluate after, since reads (unlike writes)
2476 		 * are called without i_mutex protection against truncate
2477 		 */
2478 		nr = PAGE_SIZE;
2479 		i_size = i_size_read(inode);
2480 		end_index = i_size >> PAGE_SHIFT;
2481 		if (index == end_index) {
2482 			nr = i_size & ~PAGE_MASK;
2483 			if (nr <= offset) {
2484 				if (page)
2485 					put_page(page);
2486 				break;
2487 			}
2488 		}
2489 		nr -= offset;
2490 
2491 		if (page) {
2492 			/*
2493 			 * If users can be writing to this page using arbitrary
2494 			 * virtual addresses, take care about potential aliasing
2495 			 * before reading the page on the kernel side.
2496 			 */
2497 			if (mapping_writably_mapped(mapping))
2498 				flush_dcache_page(page);
2499 			/*
2500 			 * Mark the page accessed if we read the beginning.
2501 			 */
2502 			if (!offset)
2503 				mark_page_accessed(page);
2504 		} else {
2505 			page = ZERO_PAGE(0);
2506 			get_page(page);
2507 		}
2508 
2509 		/*
2510 		 * Ok, we have the page, and it's up-to-date, so
2511 		 * now we can copy it to user space...
2512 		 */
2513 		ret = copy_page_to_iter(page, offset, nr, to);
2514 		retval += ret;
2515 		offset += ret;
2516 		index += offset >> PAGE_SHIFT;
2517 		offset &= ~PAGE_MASK;
2518 
2519 		put_page(page);
2520 		if (!iov_iter_count(to))
2521 			break;
2522 		if (ret < nr) {
2523 			error = -EFAULT;
2524 			break;
2525 		}
2526 		cond_resched();
2527 	}
2528 
2529 	*ppos = ((loff_t) index << PAGE_SHIFT) + offset;
2530 	file_accessed(file);
2531 	return retval ? retval : error;
2532 }
2533 
2534 /*
2535  * llseek SEEK_DATA or SEEK_HOLE through the page cache.
2536  */
2537 static pgoff_t shmem_seek_hole_data(struct address_space *mapping,
2538 				    pgoff_t index, pgoff_t end, int whence)
2539 {
2540 	struct page *page;
2541 	struct pagevec pvec;
2542 	pgoff_t indices[PAGEVEC_SIZE];
2543 	bool done = false;
2544 	int i;
2545 
2546 	pagevec_init(&pvec);
2547 	pvec.nr = 1;		/* start small: we may be there already */
2548 	while (!done) {
2549 		pvec.nr = find_get_entries(mapping, index,
2550 					pvec.nr, pvec.pages, indices);
2551 		if (!pvec.nr) {
2552 			if (whence == SEEK_DATA)
2553 				index = end;
2554 			break;
2555 		}
2556 		for (i = 0; i < pvec.nr; i++, index++) {
2557 			if (index < indices[i]) {
2558 				if (whence == SEEK_HOLE) {
2559 					done = true;
2560 					break;
2561 				}
2562 				index = indices[i];
2563 			}
2564 			page = pvec.pages[i];
2565 			if (page && !xa_is_value(page)) {
2566 				if (!PageUptodate(page))
2567 					page = NULL;
2568 			}
2569 			if (index >= end ||
2570 			    (page && whence == SEEK_DATA) ||
2571 			    (!page && whence == SEEK_HOLE)) {
2572 				done = true;
2573 				break;
2574 			}
2575 		}
2576 		pagevec_remove_exceptionals(&pvec);
2577 		pagevec_release(&pvec);
2578 		pvec.nr = PAGEVEC_SIZE;
2579 		cond_resched();
2580 	}
2581 	return index;
2582 }
2583 
2584 static loff_t shmem_file_llseek(struct file *file, loff_t offset, int whence)
2585 {
2586 	struct address_space *mapping = file->f_mapping;
2587 	struct inode *inode = mapping->host;
2588 	pgoff_t start, end;
2589 	loff_t new_offset;
2590 
2591 	if (whence != SEEK_DATA && whence != SEEK_HOLE)
2592 		return generic_file_llseek_size(file, offset, whence,
2593 					MAX_LFS_FILESIZE, i_size_read(inode));
2594 	inode_lock(inode);
2595 	/* We're holding i_mutex so we can access i_size directly */
2596 
2597 	if (offset < 0 || offset >= inode->i_size)
2598 		offset = -ENXIO;
2599 	else {
2600 		start = offset >> PAGE_SHIFT;
2601 		end = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
2602 		new_offset = shmem_seek_hole_data(mapping, start, end, whence);
2603 		new_offset <<= PAGE_SHIFT;
2604 		if (new_offset > offset) {
2605 			if (new_offset < inode->i_size)
2606 				offset = new_offset;
2607 			else if (whence == SEEK_DATA)
2608 				offset = -ENXIO;
2609 			else
2610 				offset = inode->i_size;
2611 		}
2612 	}
2613 
2614 	if (offset >= 0)
2615 		offset = vfs_setpos(file, offset, MAX_LFS_FILESIZE);
2616 	inode_unlock(inode);
2617 	return offset;
2618 }
2619 
2620 static long shmem_fallocate(struct file *file, int mode, loff_t offset,
2621 							 loff_t len)
2622 {
2623 	struct inode *inode = file_inode(file);
2624 	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
2625 	struct shmem_inode_info *info = SHMEM_I(inode);
2626 	struct shmem_falloc shmem_falloc;
2627 	pgoff_t start, index, end;
2628 	int error;
2629 
2630 	if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
2631 		return -EOPNOTSUPP;
2632 
2633 	inode_lock(inode);
2634 
2635 	if (mode & FALLOC_FL_PUNCH_HOLE) {
2636 		struct address_space *mapping = file->f_mapping;
2637 		loff_t unmap_start = round_up(offset, PAGE_SIZE);
2638 		loff_t unmap_end = round_down(offset + len, PAGE_SIZE) - 1;
2639 		DECLARE_WAIT_QUEUE_HEAD_ONSTACK(shmem_falloc_waitq);
2640 
2641 		/* protected by i_mutex */
2642 		if (info->seals & F_SEAL_WRITE) {
2643 			error = -EPERM;
2644 			goto out;
2645 		}
2646 
2647 		shmem_falloc.waitq = &shmem_falloc_waitq;
2648 		shmem_falloc.start = unmap_start >> PAGE_SHIFT;
2649 		shmem_falloc.next = (unmap_end + 1) >> PAGE_SHIFT;
2650 		spin_lock(&inode->i_lock);
2651 		inode->i_private = &shmem_falloc;
2652 		spin_unlock(&inode->i_lock);
2653 
2654 		if ((u64)unmap_end > (u64)unmap_start)
2655 			unmap_mapping_range(mapping, unmap_start,
2656 					    1 + unmap_end - unmap_start, 0);
2657 		shmem_truncate_range(inode, offset, offset + len - 1);
2658 		/* No need to unmap again: hole-punching leaves COWed pages */
2659 
2660 		spin_lock(&inode->i_lock);
2661 		inode->i_private = NULL;
2662 		wake_up_all(&shmem_falloc_waitq);
2663 		WARN_ON_ONCE(!list_empty(&shmem_falloc_waitq.head));
2664 		spin_unlock(&inode->i_lock);
2665 		error = 0;
2666 		goto out;
2667 	}
2668 
2669 	/* We need to check rlimit even when FALLOC_FL_KEEP_SIZE */
2670 	error = inode_newsize_ok(inode, offset + len);
2671 	if (error)
2672 		goto out;
2673 
2674 	if ((info->seals & F_SEAL_GROW) && offset + len > inode->i_size) {
2675 		error = -EPERM;
2676 		goto out;
2677 	}
2678 
2679 	start = offset >> PAGE_SHIFT;
2680 	end = (offset + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
2681 	/* Try to avoid a swapstorm if len is impossible to satisfy */
2682 	if (sbinfo->max_blocks && end - start > sbinfo->max_blocks) {
2683 		error = -ENOSPC;
2684 		goto out;
2685 	}
2686 
2687 	shmem_falloc.waitq = NULL;
2688 	shmem_falloc.start = start;
2689 	shmem_falloc.next  = start;
2690 	shmem_falloc.nr_falloced = 0;
2691 	shmem_falloc.nr_unswapped = 0;
2692 	spin_lock(&inode->i_lock);
2693 	inode->i_private = &shmem_falloc;
2694 	spin_unlock(&inode->i_lock);
2695 
2696 	for (index = start; index < end; index++) {
2697 		struct page *page;
2698 
2699 		/*
2700 		 * Good, the fallocate(2) manpage permits EINTR: we may have
2701 		 * been interrupted because we are using up too much memory.
2702 		 */
2703 		if (signal_pending(current))
2704 			error = -EINTR;
2705 		else if (shmem_falloc.nr_unswapped > shmem_falloc.nr_falloced)
2706 			error = -ENOMEM;
2707 		else
2708 			error = shmem_getpage(inode, index, &page, SGP_FALLOC);
2709 		if (error) {
2710 			/* Remove the !PageUptodate pages we added */
2711 			if (index > start) {
2712 				shmem_undo_range(inode,
2713 				    (loff_t)start << PAGE_SHIFT,
2714 				    ((loff_t)index << PAGE_SHIFT) - 1, true);
2715 			}
2716 			goto undone;
2717 		}
2718 
2719 		/*
2720 		 * Inform shmem_writepage() how far we have reached.
2721 		 * No need for lock or barrier: we have the page lock.
2722 		 */
2723 		shmem_falloc.next++;
2724 		if (!PageUptodate(page))
2725 			shmem_falloc.nr_falloced++;
2726 
2727 		/*
2728 		 * If !PageUptodate, leave it that way so that freeable pages
2729 		 * can be recognized if we need to rollback on error later.
2730 		 * But set_page_dirty so that memory pressure will swap rather
2731 		 * than free the pages we are allocating (and SGP_CACHE pages
2732 		 * might still be clean: we now need to mark those dirty too).
2733 		 */
2734 		set_page_dirty(page);
2735 		unlock_page(page);
2736 		put_page(page);
2737 		cond_resched();
2738 	}
2739 
2740 	if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size)
2741 		i_size_write(inode, offset + len);
2742 	inode->i_ctime = current_time(inode);
2743 undone:
2744 	spin_lock(&inode->i_lock);
2745 	inode->i_private = NULL;
2746 	spin_unlock(&inode->i_lock);
2747 out:
2748 	inode_unlock(inode);
2749 	return error;
2750 }
2751 
2752 static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
2753 {
2754 	struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
2755 
2756 	buf->f_type = TMPFS_MAGIC;
2757 	buf->f_bsize = PAGE_SIZE;
2758 	buf->f_namelen = NAME_MAX;
2759 	if (sbinfo->max_blocks) {
2760 		buf->f_blocks = sbinfo->max_blocks;
2761 		buf->f_bavail =
2762 		buf->f_bfree  = sbinfo->max_blocks -
2763 				percpu_counter_sum(&sbinfo->used_blocks);
2764 	}
2765 	if (sbinfo->max_inodes) {
2766 		buf->f_files = sbinfo->max_inodes;
2767 		buf->f_ffree = sbinfo->free_inodes;
2768 	}
2769 	/* else leave those fields 0 like simple_statfs */
2770 	return 0;
2771 }
2772 
2773 /*
2774  * File creation. Allocate an inode, and we're done..
2775  */
2776 static int
2777 shmem_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
2778 {
2779 	struct inode *inode;
2780 	int error = -ENOSPC;
2781 
2782 	inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE);
2783 	if (inode) {
2784 		error = simple_acl_create(dir, inode);
2785 		if (error)
2786 			goto out_iput;
2787 		error = security_inode_init_security(inode, dir,
2788 						     &dentry->d_name,
2789 						     shmem_initxattrs, NULL);
2790 		if (error && error != -EOPNOTSUPP)
2791 			goto out_iput;
2792 
2793 		error = 0;
2794 		dir->i_size += BOGO_DIRENT_SIZE;
2795 		dir->i_ctime = dir->i_mtime = current_time(dir);
2796 		d_instantiate(dentry, inode);
2797 		dget(dentry); /* Extra count - pin the dentry in core */
2798 	}
2799 	return error;
2800 out_iput:
2801 	iput(inode);
2802 	return error;
2803 }
2804 
2805 static int
2806 shmem_tmpfile(struct inode *dir, struct dentry *dentry, umode_t mode)
2807 {
2808 	struct inode *inode;
2809 	int error = -ENOSPC;
2810 
2811 	inode = shmem_get_inode(dir->i_sb, dir, mode, 0, VM_NORESERVE);
2812 	if (inode) {
2813 		error = security_inode_init_security(inode, dir,
2814 						     NULL,
2815 						     shmem_initxattrs, NULL);
2816 		if (error && error != -EOPNOTSUPP)
2817 			goto out_iput;
2818 		error = simple_acl_create(dir, inode);
2819 		if (error)
2820 			goto out_iput;
2821 		d_tmpfile(dentry, inode);
2822 	}
2823 	return error;
2824 out_iput:
2825 	iput(inode);
2826 	return error;
2827 }
2828 
2829 static int shmem_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
2830 {
2831 	int error;
2832 
2833 	if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
2834 		return error;
2835 	inc_nlink(dir);
2836 	return 0;
2837 }
2838 
2839 static int shmem_create(struct inode *dir, struct dentry *dentry, umode_t mode,
2840 		bool excl)
2841 {
2842 	return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
2843 }
2844 
2845 /*
2846  * Link a file..
2847  */
2848 static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
2849 {
2850 	struct inode *inode = d_inode(old_dentry);
2851 	int ret;
2852 
2853 	/*
2854 	 * No ordinary (disk based) filesystem counts links as inodes;
2855 	 * but each new link needs a new dentry, pinning lowmem, and
2856 	 * tmpfs dentries cannot be pruned until they are unlinked.
2857 	 */
2858 	ret = shmem_reserve_inode(inode->i_sb);
2859 	if (ret)
2860 		goto out;
2861 
2862 	dir->i_size += BOGO_DIRENT_SIZE;
2863 	inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
2864 	inc_nlink(inode);
2865 	ihold(inode);	/* New dentry reference */
2866 	dget(dentry);		/* Extra pinning count for the created dentry */
2867 	d_instantiate(dentry, inode);
2868 out:
2869 	return ret;
2870 }
2871 
2872 static int shmem_unlink(struct inode *dir, struct dentry *dentry)
2873 {
2874 	struct inode *inode = d_inode(dentry);
2875 
2876 	if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
2877 		shmem_free_inode(inode->i_sb);
2878 
2879 	dir->i_size -= BOGO_DIRENT_SIZE;
2880 	inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
2881 	drop_nlink(inode);
2882 	dput(dentry);	/* Undo the count from "create" - this does all the work */
2883 	return 0;
2884 }
2885 
2886 static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
2887 {
2888 	if (!simple_empty(dentry))
2889 		return -ENOTEMPTY;
2890 
2891 	drop_nlink(d_inode(dentry));
2892 	drop_nlink(dir);
2893 	return shmem_unlink(dir, dentry);
2894 }
2895 
2896 static int shmem_exchange(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
2897 {
2898 	bool old_is_dir = d_is_dir(old_dentry);
2899 	bool new_is_dir = d_is_dir(new_dentry);
2900 
2901 	if (old_dir != new_dir && old_is_dir != new_is_dir) {
2902 		if (old_is_dir) {
2903 			drop_nlink(old_dir);
2904 			inc_nlink(new_dir);
2905 		} else {
2906 			drop_nlink(new_dir);
2907 			inc_nlink(old_dir);
2908 		}
2909 	}
2910 	old_dir->i_ctime = old_dir->i_mtime =
2911 	new_dir->i_ctime = new_dir->i_mtime =
2912 	d_inode(old_dentry)->i_ctime =
2913 	d_inode(new_dentry)->i_ctime = current_time(old_dir);
2914 
2915 	return 0;
2916 }
2917 
2918 static int shmem_whiteout(struct inode *old_dir, struct dentry *old_dentry)
2919 {
2920 	struct dentry *whiteout;
2921 	int error;
2922 
2923 	whiteout = d_alloc(old_dentry->d_parent, &old_dentry->d_name);
2924 	if (!whiteout)
2925 		return -ENOMEM;
2926 
2927 	error = shmem_mknod(old_dir, whiteout,
2928 			    S_IFCHR | WHITEOUT_MODE, WHITEOUT_DEV);
2929 	dput(whiteout);
2930 	if (error)
2931 		return error;
2932 
2933 	/*
2934 	 * Cheat and hash the whiteout while the old dentry is still in
2935 	 * place, instead of playing games with FS_RENAME_DOES_D_MOVE.
2936 	 *
2937 	 * d_lookup() will consistently find one of them at this point,
2938 	 * not sure which one, but that isn't even important.
2939 	 */
2940 	d_rehash(whiteout);
2941 	return 0;
2942 }
2943 
2944 /*
2945  * The VFS layer already does all the dentry stuff for rename,
2946  * we just have to decrement the usage count for the target if
2947  * it exists so that the VFS layer correctly free's it when it
2948  * gets overwritten.
2949  */
2950 static int shmem_rename2(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry, unsigned int flags)
2951 {
2952 	struct inode *inode = d_inode(old_dentry);
2953 	int they_are_dirs = S_ISDIR(inode->i_mode);
2954 
2955 	if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
2956 		return -EINVAL;
2957 
2958 	if (flags & RENAME_EXCHANGE)
2959 		return shmem_exchange(old_dir, old_dentry, new_dir, new_dentry);
2960 
2961 	if (!simple_empty(new_dentry))
2962 		return -ENOTEMPTY;
2963 
2964 	if (flags & RENAME_WHITEOUT) {
2965 		int error;
2966 
2967 		error = shmem_whiteout(old_dir, old_dentry);
2968 		if (error)
2969 			return error;
2970 	}
2971 
2972 	if (d_really_is_positive(new_dentry)) {
2973 		(void) shmem_unlink(new_dir, new_dentry);
2974 		if (they_are_dirs) {
2975 			drop_nlink(d_inode(new_dentry));
2976 			drop_nlink(old_dir);
2977 		}
2978 	} else if (they_are_dirs) {
2979 		drop_nlink(old_dir);
2980 		inc_nlink(new_dir);
2981 	}
2982 
2983 	old_dir->i_size -= BOGO_DIRENT_SIZE;
2984 	new_dir->i_size += BOGO_DIRENT_SIZE;
2985 	old_dir->i_ctime = old_dir->i_mtime =
2986 	new_dir->i_ctime = new_dir->i_mtime =
2987 	inode->i_ctime = current_time(old_dir);
2988 	return 0;
2989 }
2990 
2991 static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
2992 {
2993 	int error;
2994 	int len;
2995 	struct inode *inode;
2996 	struct page *page;
2997 
2998 	len = strlen(symname) + 1;
2999 	if (len > PAGE_SIZE)
3000 		return -ENAMETOOLONG;
3001 
3002 	inode = shmem_get_inode(dir->i_sb, dir, S_IFLNK | 0777, 0,
3003 				VM_NORESERVE);
3004 	if (!inode)
3005 		return -ENOSPC;
3006 
3007 	error = security_inode_init_security(inode, dir, &dentry->d_name,
3008 					     shmem_initxattrs, NULL);
3009 	if (error) {
3010 		if (error != -EOPNOTSUPP) {
3011 			iput(inode);
3012 			return error;
3013 		}
3014 		error = 0;
3015 	}
3016 
3017 	inode->i_size = len-1;
3018 	if (len <= SHORT_SYMLINK_LEN) {
3019 		inode->i_link = kmemdup(symname, len, GFP_KERNEL);
3020 		if (!inode->i_link) {
3021 			iput(inode);
3022 			return -ENOMEM;
3023 		}
3024 		inode->i_op = &shmem_short_symlink_operations;
3025 	} else {
3026 		inode_nohighmem(inode);
3027 		error = shmem_getpage(inode, 0, &page, SGP_WRITE);
3028 		if (error) {
3029 			iput(inode);
3030 			return error;
3031 		}
3032 		inode->i_mapping->a_ops = &shmem_aops;
3033 		inode->i_op = &shmem_symlink_inode_operations;
3034 		memcpy(page_address(page), symname, len);
3035 		SetPageUptodate(page);
3036 		set_page_dirty(page);
3037 		unlock_page(page);
3038 		put_page(page);
3039 	}
3040 	dir->i_size += BOGO_DIRENT_SIZE;
3041 	dir->i_ctime = dir->i_mtime = current_time(dir);
3042 	d_instantiate(dentry, inode);
3043 	dget(dentry);
3044 	return 0;
3045 }
3046 
3047 static void shmem_put_link(void *arg)
3048 {
3049 	mark_page_accessed(arg);
3050 	put_page(arg);
3051 }
3052 
3053 static const char *shmem_get_link(struct dentry *dentry,
3054 				  struct inode *inode,
3055 				  struct delayed_call *done)
3056 {
3057 	struct page *page = NULL;
3058 	int error;
3059 	if (!dentry) {
3060 		page = find_get_page(inode->i_mapping, 0);
3061 		if (!page)
3062 			return ERR_PTR(-ECHILD);
3063 		if (!PageUptodate(page)) {
3064 			put_page(page);
3065 			return ERR_PTR(-ECHILD);
3066 		}
3067 	} else {
3068 		error = shmem_getpage(inode, 0, &page, SGP_READ);
3069 		if (error)
3070 			return ERR_PTR(error);
3071 		unlock_page(page);
3072 	}
3073 	set_delayed_call(done, shmem_put_link, page);
3074 	return page_address(page);
3075 }
3076 
3077 #ifdef CONFIG_TMPFS_XATTR
3078 /*
3079  * Superblocks without xattr inode operations may get some security.* xattr
3080  * support from the LSM "for free". As soon as we have any other xattrs
3081  * like ACLs, we also need to implement the security.* handlers at
3082  * filesystem level, though.
3083  */
3084 
3085 /*
3086  * Callback for security_inode_init_security() for acquiring xattrs.
3087  */
3088 static int shmem_initxattrs(struct inode *inode,
3089 			    const struct xattr *xattr_array,
3090 			    void *fs_info)
3091 {
3092 	struct shmem_inode_info *info = SHMEM_I(inode);
3093 	const struct xattr *xattr;
3094 	struct simple_xattr *new_xattr;
3095 	size_t len;
3096 
3097 	for (xattr = xattr_array; xattr->name != NULL; xattr++) {
3098 		new_xattr = simple_xattr_alloc(xattr->value, xattr->value_len);
3099 		if (!new_xattr)
3100 			return -ENOMEM;
3101 
3102 		len = strlen(xattr->name) + 1;
3103 		new_xattr->name = kmalloc(XATTR_SECURITY_PREFIX_LEN + len,
3104 					  GFP_KERNEL);
3105 		if (!new_xattr->name) {
3106 			kfree(new_xattr);
3107 			return -ENOMEM;
3108 		}
3109 
3110 		memcpy(new_xattr->name, XATTR_SECURITY_PREFIX,
3111 		       XATTR_SECURITY_PREFIX_LEN);
3112 		memcpy(new_xattr->name + XATTR_SECURITY_PREFIX_LEN,
3113 		       xattr->name, len);
3114 
3115 		simple_xattr_list_add(&info->xattrs, new_xattr);
3116 	}
3117 
3118 	return 0;
3119 }
3120 
3121 static int shmem_xattr_handler_get(const struct xattr_handler *handler,
3122 				   struct dentry *unused, struct inode *inode,
3123 				   const char *name, void *buffer, size_t size)
3124 {
3125 	struct shmem_inode_info *info = SHMEM_I(inode);
3126 
3127 	name = xattr_full_name(handler, name);
3128 	return simple_xattr_get(&info->xattrs, name, buffer, size);
3129 }
3130 
3131 static int shmem_xattr_handler_set(const struct xattr_handler *handler,
3132 				   struct dentry *unused, struct inode *inode,
3133 				   const char *name, const void *value,
3134 				   size_t size, int flags)
3135 {
3136 	struct shmem_inode_info *info = SHMEM_I(inode);
3137 
3138 	name = xattr_full_name(handler, name);
3139 	return simple_xattr_set(&info->xattrs, name, value, size, flags);
3140 }
3141 
3142 static const struct xattr_handler shmem_security_xattr_handler = {
3143 	.prefix = XATTR_SECURITY_PREFIX,
3144 	.get = shmem_xattr_handler_get,
3145 	.set = shmem_xattr_handler_set,
3146 };
3147 
3148 static const struct xattr_handler shmem_trusted_xattr_handler = {
3149 	.prefix = XATTR_TRUSTED_PREFIX,
3150 	.get = shmem_xattr_handler_get,
3151 	.set = shmem_xattr_handler_set,
3152 };
3153 
3154 static const struct xattr_handler *shmem_xattr_handlers[] = {
3155 #ifdef CONFIG_TMPFS_POSIX_ACL
3156 	&posix_acl_access_xattr_handler,
3157 	&posix_acl_default_xattr_handler,
3158 #endif
3159 	&shmem_security_xattr_handler,
3160 	&shmem_trusted_xattr_handler,
3161 	NULL
3162 };
3163 
3164 static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t size)
3165 {
3166 	struct shmem_inode_info *info = SHMEM_I(d_inode(dentry));
3167 	return simple_xattr_list(d_inode(dentry), &info->xattrs, buffer, size);
3168 }
3169 #endif /* CONFIG_TMPFS_XATTR */
3170 
3171 static const struct inode_operations shmem_short_symlink_operations = {
3172 	.get_link	= simple_get_link,
3173 #ifdef CONFIG_TMPFS_XATTR
3174 	.listxattr	= shmem_listxattr,
3175 #endif
3176 };
3177 
3178 static const struct inode_operations shmem_symlink_inode_operations = {
3179 	.get_link	= shmem_get_link,
3180 #ifdef CONFIG_TMPFS_XATTR
3181 	.listxattr	= shmem_listxattr,
3182 #endif
3183 };
3184 
3185 static struct dentry *shmem_get_parent(struct dentry *child)
3186 {
3187 	return ERR_PTR(-ESTALE);
3188 }
3189 
3190 static int shmem_match(struct inode *ino, void *vfh)
3191 {
3192 	__u32 *fh = vfh;
3193 	__u64 inum = fh[2];
3194 	inum = (inum << 32) | fh[1];
3195 	return ino->i_ino == inum && fh[0] == ino->i_generation;
3196 }
3197 
3198 /* Find any alias of inode, but prefer a hashed alias */
3199 static struct dentry *shmem_find_alias(struct inode *inode)
3200 {
3201 	struct dentry *alias = d_find_alias(inode);
3202 
3203 	return alias ?: d_find_any_alias(inode);
3204 }
3205 
3206 
3207 static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
3208 		struct fid *fid, int fh_len, int fh_type)
3209 {
3210 	struct inode *inode;
3211 	struct dentry *dentry = NULL;
3212 	u64 inum;
3213 
3214 	if (fh_len < 3)
3215 		return NULL;
3216 
3217 	inum = fid->raw[2];
3218 	inum = (inum << 32) | fid->raw[1];
3219 
3220 	inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
3221 			shmem_match, fid->raw);
3222 	if (inode) {
3223 		dentry = shmem_find_alias(inode);
3224 		iput(inode);
3225 	}
3226 
3227 	return dentry;
3228 }
3229 
3230 static int shmem_encode_fh(struct inode *inode, __u32 *fh, int *len,
3231 				struct inode *parent)
3232 {
3233 	if (*len < 3) {
3234 		*len = 3;
3235 		return FILEID_INVALID;
3236 	}
3237 
3238 	if (inode_unhashed(inode)) {
3239 		/* Unfortunately insert_inode_hash is not idempotent,
3240 		 * so as we hash inodes here rather than at creation
3241 		 * time, we need a lock to ensure we only try
3242 		 * to do it once
3243 		 */
3244 		static DEFINE_SPINLOCK(lock);
3245 		spin_lock(&lock);
3246 		if (inode_unhashed(inode))
3247 			__insert_inode_hash(inode,
3248 					    inode->i_ino + inode->i_generation);
3249 		spin_unlock(&lock);
3250 	}
3251 
3252 	fh[0] = inode->i_generation;
3253 	fh[1] = inode->i_ino;
3254 	fh[2] = ((__u64)inode->i_ino) >> 32;
3255 
3256 	*len = 3;
3257 	return 1;
3258 }
3259 
3260 static const struct export_operations shmem_export_ops = {
3261 	.get_parent     = shmem_get_parent,
3262 	.encode_fh      = shmem_encode_fh,
3263 	.fh_to_dentry	= shmem_fh_to_dentry,
3264 };
3265 
3266 static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
3267 			       bool remount)
3268 {
3269 	char *this_char, *value, *rest;
3270 	struct mempolicy *mpol = NULL;
3271 	uid_t uid;
3272 	gid_t gid;
3273 
3274 	while (options != NULL) {
3275 		this_char = options;
3276 		for (;;) {
3277 			/*
3278 			 * NUL-terminate this option: unfortunately,
3279 			 * mount options form a comma-separated list,
3280 			 * but mpol's nodelist may also contain commas.
3281 			 */
3282 			options = strchr(options, ',');
3283 			if (options == NULL)
3284 				break;
3285 			options++;
3286 			if (!isdigit(*options)) {
3287 				options[-1] = '\0';
3288 				break;
3289 			}
3290 		}
3291 		if (!*this_char)
3292 			continue;
3293 		if ((value = strchr(this_char,'=')) != NULL) {
3294 			*value++ = 0;
3295 		} else {
3296 			pr_err("tmpfs: No value for mount option '%s'\n",
3297 			       this_char);
3298 			goto error;
3299 		}
3300 
3301 		if (!strcmp(this_char,"size")) {
3302 			unsigned long long size;
3303 			size = memparse(value,&rest);
3304 			if (*rest == '%') {
3305 				size <<= PAGE_SHIFT;
3306 				size *= totalram_pages();
3307 				do_div(size, 100);
3308 				rest++;
3309 			}
3310 			if (*rest)
3311 				goto bad_val;
3312 			sbinfo->max_blocks =
3313 				DIV_ROUND_UP(size, PAGE_SIZE);
3314 		} else if (!strcmp(this_char,"nr_blocks")) {
3315 			sbinfo->max_blocks = memparse(value, &rest);
3316 			if (*rest)
3317 				goto bad_val;
3318 		} else if (!strcmp(this_char,"nr_inodes")) {
3319 			sbinfo->max_inodes = memparse(value, &rest);
3320 			if (*rest)
3321 				goto bad_val;
3322 		} else if (!strcmp(this_char,"mode")) {
3323 			if (remount)
3324 				continue;
3325 			sbinfo->mode = simple_strtoul(value, &rest, 8) & 07777;
3326 			if (*rest)
3327 				goto bad_val;
3328 		} else if (!strcmp(this_char,"uid")) {
3329 			if (remount)
3330 				continue;
3331 			uid = simple_strtoul(value, &rest, 0);
3332 			if (*rest)
3333 				goto bad_val;
3334 			sbinfo->uid = make_kuid(current_user_ns(), uid);
3335 			if (!uid_valid(sbinfo->uid))
3336 				goto bad_val;
3337 		} else if (!strcmp(this_char,"gid")) {
3338 			if (remount)
3339 				continue;
3340 			gid = simple_strtoul(value, &rest, 0);
3341 			if (*rest)
3342 				goto bad_val;
3343 			sbinfo->gid = make_kgid(current_user_ns(), gid);
3344 			if (!gid_valid(sbinfo->gid))
3345 				goto bad_val;
3346 #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
3347 		} else if (!strcmp(this_char, "huge")) {
3348 			int huge;
3349 			huge = shmem_parse_huge(value);
3350 			if (huge < 0)
3351 				goto bad_val;
3352 			if (!has_transparent_hugepage() &&
3353 					huge != SHMEM_HUGE_NEVER)
3354 				goto bad_val;
3355 			sbinfo->huge = huge;
3356 #endif
3357 #ifdef CONFIG_NUMA
3358 		} else if (!strcmp(this_char,"mpol")) {
3359 			mpol_put(mpol);
3360 			mpol = NULL;
3361 			if (mpol_parse_str(value, &mpol))
3362 				goto bad_val;
3363 #endif
3364 		} else {
3365 			pr_err("tmpfs: Bad mount option %s\n", this_char);
3366 			goto error;
3367 		}
3368 	}
3369 	sbinfo->mpol = mpol;
3370 	return 0;
3371 
3372 bad_val:
3373 	pr_err("tmpfs: Bad value '%s' for mount option '%s'\n",
3374 	       value, this_char);
3375 error:
3376 	mpol_put(mpol);
3377 	return 1;
3378 
3379 }
3380 
3381 static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
3382 {
3383 	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
3384 	struct shmem_sb_info config = *sbinfo;
3385 	unsigned long inodes;
3386 	int error = -EINVAL;
3387 
3388 	config.mpol = NULL;
3389 	if (shmem_parse_options(data, &config, true))
3390 		return error;
3391 
3392 	spin_lock(&sbinfo->stat_lock);
3393 	inodes = sbinfo->max_inodes - sbinfo->free_inodes;
3394 	if (percpu_counter_compare(&sbinfo->used_blocks, config.max_blocks) > 0)
3395 		goto out;
3396 	if (config.max_inodes < inodes)
3397 		goto out;
3398 	/*
3399 	 * Those tests disallow limited->unlimited while any are in use;
3400 	 * but we must separately disallow unlimited->limited, because
3401 	 * in that case we have no record of how much is already in use.
3402 	 */
3403 	if (config.max_blocks && !sbinfo->max_blocks)
3404 		goto out;
3405 	if (config.max_inodes && !sbinfo->max_inodes)
3406 		goto out;
3407 
3408 	error = 0;
3409 	sbinfo->huge = config.huge;
3410 	sbinfo->max_blocks  = config.max_blocks;
3411 	sbinfo->max_inodes  = config.max_inodes;
3412 	sbinfo->free_inodes = config.max_inodes - inodes;
3413 
3414 	/*
3415 	 * Preserve previous mempolicy unless mpol remount option was specified.
3416 	 */
3417 	if (config.mpol) {
3418 		mpol_put(sbinfo->mpol);
3419 		sbinfo->mpol = config.mpol;	/* transfers initial ref */
3420 	}
3421 out:
3422 	spin_unlock(&sbinfo->stat_lock);
3423 	return error;
3424 }
3425 
3426 static int shmem_show_options(struct seq_file *seq, struct dentry *root)
3427 {
3428 	struct shmem_sb_info *sbinfo = SHMEM_SB(root->d_sb);
3429 
3430 	if (sbinfo->max_blocks != shmem_default_max_blocks())
3431 		seq_printf(seq, ",size=%luk",
3432 			sbinfo->max_blocks << (PAGE_SHIFT - 10));
3433 	if (sbinfo->max_inodes != shmem_default_max_inodes())
3434 		seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
3435 	if (sbinfo->mode != (0777 | S_ISVTX))
3436 		seq_printf(seq, ",mode=%03ho", sbinfo->mode);
3437 	if (!uid_eq(sbinfo->uid, GLOBAL_ROOT_UID))
3438 		seq_printf(seq, ",uid=%u",
3439 				from_kuid_munged(&init_user_ns, sbinfo->uid));
3440 	if (!gid_eq(sbinfo->gid, GLOBAL_ROOT_GID))
3441 		seq_printf(seq, ",gid=%u",
3442 				from_kgid_munged(&init_user_ns, sbinfo->gid));
3443 #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
3444 	/* Rightly or wrongly, show huge mount option unmasked by shmem_huge */
3445 	if (sbinfo->huge)
3446 		seq_printf(seq, ",huge=%s", shmem_format_huge(sbinfo->huge));
3447 #endif
3448 	shmem_show_mpol(seq, sbinfo->mpol);
3449 	return 0;
3450 }
3451 
3452 #endif /* CONFIG_TMPFS */
3453 
3454 static void shmem_put_super(struct super_block *sb)
3455 {
3456 	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
3457 
3458 	percpu_counter_destroy(&sbinfo->used_blocks);
3459 	mpol_put(sbinfo->mpol);
3460 	kfree(sbinfo);
3461 	sb->s_fs_info = NULL;
3462 }
3463 
3464 int shmem_fill_super(struct super_block *sb, void *data, int silent)
3465 {
3466 	struct inode *inode;
3467 	struct shmem_sb_info *sbinfo;
3468 	int err = -ENOMEM;
3469 
3470 	/* Round up to L1_CACHE_BYTES to resist false sharing */
3471 	sbinfo = kzalloc(max((int)sizeof(struct shmem_sb_info),
3472 				L1_CACHE_BYTES), GFP_KERNEL);
3473 	if (!sbinfo)
3474 		return -ENOMEM;
3475 
3476 	sbinfo->mode = 0777 | S_ISVTX;
3477 	sbinfo->uid = current_fsuid();
3478 	sbinfo->gid = current_fsgid();
3479 	sb->s_fs_info = sbinfo;
3480 
3481 #ifdef CONFIG_TMPFS
3482 	/*
3483 	 * Per default we only allow half of the physical ram per
3484 	 * tmpfs instance, limiting inodes to one per page of lowmem;
3485 	 * but the internal instance is left unlimited.
3486 	 */
3487 	if (!(sb->s_flags & SB_KERNMOUNT)) {
3488 		sbinfo->max_blocks = shmem_default_max_blocks();
3489 		sbinfo->max_inodes = shmem_default_max_inodes();
3490 		if (shmem_parse_options(data, sbinfo, false)) {
3491 			err = -EINVAL;
3492 			goto failed;
3493 		}
3494 	} else {
3495 		sb->s_flags |= SB_NOUSER;
3496 	}
3497 	sb->s_export_op = &shmem_export_ops;
3498 	sb->s_flags |= SB_NOSEC;
3499 #else
3500 	sb->s_flags |= SB_NOUSER;
3501 #endif
3502 
3503 	spin_lock_init(&sbinfo->stat_lock);
3504 	if (percpu_counter_init(&sbinfo->used_blocks, 0, GFP_KERNEL))
3505 		goto failed;
3506 	sbinfo->free_inodes = sbinfo->max_inodes;
3507 	spin_lock_init(&sbinfo->shrinklist_lock);
3508 	INIT_LIST_HEAD(&sbinfo->shrinklist);
3509 
3510 	sb->s_maxbytes = MAX_LFS_FILESIZE;
3511 	sb->s_blocksize = PAGE_SIZE;
3512 	sb->s_blocksize_bits = PAGE_SHIFT;
3513 	sb->s_magic = TMPFS_MAGIC;
3514 	sb->s_op = &shmem_ops;
3515 	sb->s_time_gran = 1;
3516 #ifdef CONFIG_TMPFS_XATTR
3517 	sb->s_xattr = shmem_xattr_handlers;
3518 #endif
3519 #ifdef CONFIG_TMPFS_POSIX_ACL
3520 	sb->s_flags |= SB_POSIXACL;
3521 #endif
3522 	uuid_gen(&sb->s_uuid);
3523 
3524 	inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
3525 	if (!inode)
3526 		goto failed;
3527 	inode->i_uid = sbinfo->uid;
3528 	inode->i_gid = sbinfo->gid;
3529 	sb->s_root = d_make_root(inode);
3530 	if (!sb->s_root)
3531 		goto failed;
3532 	return 0;
3533 
3534 failed:
3535 	shmem_put_super(sb);
3536 	return err;
3537 }
3538 
3539 static struct kmem_cache *shmem_inode_cachep;
3540 
3541 static struct inode *shmem_alloc_inode(struct super_block *sb)
3542 {
3543 	struct shmem_inode_info *info;
3544 	info = kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
3545 	if (!info)
3546 		return NULL;
3547 	return &info->vfs_inode;
3548 }
3549 
3550 static void shmem_destroy_callback(struct rcu_head *head)
3551 {
3552 	struct inode *inode = container_of(head, struct inode, i_rcu);
3553 	if (S_ISLNK(inode->i_mode))
3554 		kfree(inode->i_link);
3555 	kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
3556 }
3557 
3558 static void shmem_destroy_inode(struct inode *inode)
3559 {
3560 	if (S_ISREG(inode->i_mode))
3561 		mpol_free_shared_policy(&SHMEM_I(inode)->policy);
3562 	call_rcu(&inode->i_rcu, shmem_destroy_callback);
3563 }
3564 
3565 static void shmem_init_inode(void *foo)
3566 {
3567 	struct shmem_inode_info *info = foo;
3568 	inode_init_once(&info->vfs_inode);
3569 }
3570 
3571 static void shmem_init_inodecache(void)
3572 {
3573 	shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
3574 				sizeof(struct shmem_inode_info),
3575 				0, SLAB_PANIC|SLAB_ACCOUNT, shmem_init_inode);
3576 }
3577 
3578 static void shmem_destroy_inodecache(void)
3579 {
3580 	kmem_cache_destroy(shmem_inode_cachep);
3581 }
3582 
3583 static const struct address_space_operations shmem_aops = {
3584 	.writepage	= shmem_writepage,
3585 	.set_page_dirty	= __set_page_dirty_no_writeback,
3586 #ifdef CONFIG_TMPFS
3587 	.write_begin	= shmem_write_begin,
3588 	.write_end	= shmem_write_end,
3589 #endif
3590 #ifdef CONFIG_MIGRATION
3591 	.migratepage	= migrate_page,
3592 #endif
3593 	.error_remove_page = generic_error_remove_page,
3594 };
3595 
3596 static const struct file_operations shmem_file_operations = {
3597 	.mmap		= shmem_mmap,
3598 	.get_unmapped_area = shmem_get_unmapped_area,
3599 #ifdef CONFIG_TMPFS
3600 	.llseek		= shmem_file_llseek,
3601 	.read_iter	= shmem_file_read_iter,
3602 	.write_iter	= generic_file_write_iter,
3603 	.fsync		= noop_fsync,
3604 	.splice_read	= generic_file_splice_read,
3605 	.splice_write	= iter_file_splice_write,
3606 	.fallocate	= shmem_fallocate,
3607 #endif
3608 };
3609 
3610 static const struct inode_operations shmem_inode_operations = {
3611 	.getattr	= shmem_getattr,
3612 	.setattr	= shmem_setattr,
3613 #ifdef CONFIG_TMPFS_XATTR
3614 	.listxattr	= shmem_listxattr,
3615 	.set_acl	= simple_set_acl,
3616 #endif
3617 };
3618 
3619 static const struct inode_operations shmem_dir_inode_operations = {
3620 #ifdef CONFIG_TMPFS
3621 	.create		= shmem_create,
3622 	.lookup		= simple_lookup,
3623 	.link		= shmem_link,
3624 	.unlink		= shmem_unlink,
3625 	.symlink	= shmem_symlink,
3626 	.mkdir		= shmem_mkdir,
3627 	.rmdir		= shmem_rmdir,
3628 	.mknod		= shmem_mknod,
3629 	.rename		= shmem_rename2,
3630 	.tmpfile	= shmem_tmpfile,
3631 #endif
3632 #ifdef CONFIG_TMPFS_XATTR
3633 	.listxattr	= shmem_listxattr,
3634 #endif
3635 #ifdef CONFIG_TMPFS_POSIX_ACL
3636 	.setattr	= shmem_setattr,
3637 	.set_acl	= simple_set_acl,
3638 #endif
3639 };
3640 
3641 static const struct inode_operations shmem_special_inode_operations = {
3642 #ifdef CONFIG_TMPFS_XATTR
3643 	.listxattr	= shmem_listxattr,
3644 #endif
3645 #ifdef CONFIG_TMPFS_POSIX_ACL
3646 	.setattr	= shmem_setattr,
3647 	.set_acl	= simple_set_acl,
3648 #endif
3649 };
3650 
3651 static const struct super_operations shmem_ops = {
3652 	.alloc_inode	= shmem_alloc_inode,
3653 	.destroy_inode	= shmem_destroy_inode,
3654 #ifdef CONFIG_TMPFS
3655 	.statfs		= shmem_statfs,
3656 	.remount_fs	= shmem_remount_fs,
3657 	.show_options	= shmem_show_options,
3658 #endif
3659 	.evict_inode	= shmem_evict_inode,
3660 	.drop_inode	= generic_delete_inode,
3661 	.put_super	= shmem_put_super,
3662 #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
3663 	.nr_cached_objects	= shmem_unused_huge_count,
3664 	.free_cached_objects	= shmem_unused_huge_scan,
3665 #endif
3666 };
3667 
3668 static const struct vm_operations_struct shmem_vm_ops = {
3669 	.fault		= shmem_fault,
3670 	.map_pages	= filemap_map_pages,
3671 #ifdef CONFIG_NUMA
3672 	.set_policy     = shmem_set_policy,
3673 	.get_policy     = shmem_get_policy,
3674 #endif
3675 };
3676 
3677 static struct dentry *shmem_mount(struct file_system_type *fs_type,
3678 	int flags, const char *dev_name, void *data)
3679 {
3680 	return mount_nodev(fs_type, flags, data, shmem_fill_super);
3681 }
3682 
3683 static struct file_system_type shmem_fs_type = {
3684 	.owner		= THIS_MODULE,
3685 	.name		= "tmpfs",
3686 	.mount		= shmem_mount,
3687 	.kill_sb	= kill_litter_super,
3688 	.fs_flags	= FS_USERNS_MOUNT,
3689 };
3690 
3691 int __init shmem_init(void)
3692 {
3693 	int error;
3694 
3695 	/* If rootfs called this, don't re-init */
3696 	if (shmem_inode_cachep)
3697 		return 0;
3698 
3699 	shmem_init_inodecache();
3700 
3701 	error = register_filesystem(&shmem_fs_type);
3702 	if (error) {
3703 		pr_err("Could not register tmpfs\n");
3704 		goto out2;
3705 	}
3706 
3707 	shm_mnt = kern_mount(&shmem_fs_type);
3708 	if (IS_ERR(shm_mnt)) {
3709 		error = PTR_ERR(shm_mnt);
3710 		pr_err("Could not kern_mount tmpfs\n");
3711 		goto out1;
3712 	}
3713 
3714 #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
3715 	if (has_transparent_hugepage() && shmem_huge > SHMEM_HUGE_DENY)
3716 		SHMEM_SB(shm_mnt->mnt_sb)->huge = shmem_huge;
3717 	else
3718 		shmem_huge = 0; /* just in case it was patched */
3719 #endif
3720 	return 0;
3721 
3722 out1:
3723 	unregister_filesystem(&shmem_fs_type);
3724 out2:
3725 	shmem_destroy_inodecache();
3726 	shm_mnt = ERR_PTR(error);
3727 	return error;
3728 }
3729 
3730 #if defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE) && defined(CONFIG_SYSFS)
3731 static ssize_t shmem_enabled_show(struct kobject *kobj,
3732 		struct kobj_attribute *attr, char *buf)
3733 {
3734 	int values[] = {
3735 		SHMEM_HUGE_ALWAYS,
3736 		SHMEM_HUGE_WITHIN_SIZE,
3737 		SHMEM_HUGE_ADVISE,
3738 		SHMEM_HUGE_NEVER,
3739 		SHMEM_HUGE_DENY,
3740 		SHMEM_HUGE_FORCE,
3741 	};
3742 	int i, count;
3743 
3744 	for (i = 0, count = 0; i < ARRAY_SIZE(values); i++) {
3745 		const char *fmt = shmem_huge == values[i] ? "[%s] " : "%s ";
3746 
3747 		count += sprintf(buf + count, fmt,
3748 				shmem_format_huge(values[i]));
3749 	}
3750 	buf[count - 1] = '\n';
3751 	return count;
3752 }
3753 
3754 static ssize_t shmem_enabled_store(struct kobject *kobj,
3755 		struct kobj_attribute *attr, const char *buf, size_t count)
3756 {
3757 	char tmp[16];
3758 	int huge;
3759 
3760 	if (count + 1 > sizeof(tmp))
3761 		return -EINVAL;
3762 	memcpy(tmp, buf, count);
3763 	tmp[count] = '\0';
3764 	if (count && tmp[count - 1] == '\n')
3765 		tmp[count - 1] = '\0';
3766 
3767 	huge = shmem_parse_huge(tmp);
3768 	if (huge == -EINVAL)
3769 		return -EINVAL;
3770 	if (!has_transparent_hugepage() &&
3771 			huge != SHMEM_HUGE_NEVER && huge != SHMEM_HUGE_DENY)
3772 		return -EINVAL;
3773 
3774 	shmem_huge = huge;
3775 	if (shmem_huge > SHMEM_HUGE_DENY)
3776 		SHMEM_SB(shm_mnt->mnt_sb)->huge = shmem_huge;
3777 	return count;
3778 }
3779 
3780 struct kobj_attribute shmem_enabled_attr =
3781 	__ATTR(shmem_enabled, 0644, shmem_enabled_show, shmem_enabled_store);
3782 #endif /* CONFIG_TRANSPARENT_HUGE_PAGECACHE && CONFIG_SYSFS */
3783 
3784 #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
3785 bool shmem_huge_enabled(struct vm_area_struct *vma)
3786 {
3787 	struct inode *inode = file_inode(vma->vm_file);
3788 	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
3789 	loff_t i_size;
3790 	pgoff_t off;
3791 
3792 	if (shmem_huge == SHMEM_HUGE_FORCE)
3793 		return true;
3794 	if (shmem_huge == SHMEM_HUGE_DENY)
3795 		return false;
3796 	switch (sbinfo->huge) {
3797 		case SHMEM_HUGE_NEVER:
3798 			return false;
3799 		case SHMEM_HUGE_ALWAYS:
3800 			return true;
3801 		case SHMEM_HUGE_WITHIN_SIZE:
3802 			off = round_up(vma->vm_pgoff, HPAGE_PMD_NR);
3803 			i_size = round_up(i_size_read(inode), PAGE_SIZE);
3804 			if (i_size >= HPAGE_PMD_SIZE &&
3805 					i_size >> PAGE_SHIFT >= off)
3806 				return true;
3807 			/* fall through */
3808 		case SHMEM_HUGE_ADVISE:
3809 			/* TODO: implement fadvise() hints */
3810 			return (vma->vm_flags & VM_HUGEPAGE);
3811 		default:
3812 			VM_BUG_ON(1);
3813 			return false;
3814 	}
3815 }
3816 #endif /* CONFIG_TRANSPARENT_HUGE_PAGECACHE */
3817 
3818 #else /* !CONFIG_SHMEM */
3819 
3820 /*
3821  * tiny-shmem: simple shmemfs and tmpfs using ramfs code
3822  *
3823  * This is intended for small system where the benefits of the full
3824  * shmem code (swap-backed and resource-limited) are outweighed by
3825  * their complexity. On systems without swap this code should be
3826  * effectively equivalent, but much lighter weight.
3827  */
3828 
3829 static struct file_system_type shmem_fs_type = {
3830 	.name		= "tmpfs",
3831 	.mount		= ramfs_mount,
3832 	.kill_sb	= kill_litter_super,
3833 	.fs_flags	= FS_USERNS_MOUNT,
3834 };
3835 
3836 int __init shmem_init(void)
3837 {
3838 	BUG_ON(register_filesystem(&shmem_fs_type) != 0);
3839 
3840 	shm_mnt = kern_mount(&shmem_fs_type);
3841 	BUG_ON(IS_ERR(shm_mnt));
3842 
3843 	return 0;
3844 }
3845 
3846 int shmem_unuse(swp_entry_t swap, struct page *page)
3847 {
3848 	return 0;
3849 }
3850 
3851 int shmem_lock(struct file *file, int lock, struct user_struct *user)
3852 {
3853 	return 0;
3854 }
3855 
3856 void shmem_unlock_mapping(struct address_space *mapping)
3857 {
3858 }
3859 
3860 #ifdef CONFIG_MMU
3861 unsigned long shmem_get_unmapped_area(struct file *file,
3862 				      unsigned long addr, unsigned long len,
3863 				      unsigned long pgoff, unsigned long flags)
3864 {
3865 	return current->mm->get_unmapped_area(file, addr, len, pgoff, flags);
3866 }
3867 #endif
3868 
3869 void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
3870 {
3871 	truncate_inode_pages_range(inode->i_mapping, lstart, lend);
3872 }
3873 EXPORT_SYMBOL_GPL(shmem_truncate_range);
3874 
3875 #define shmem_vm_ops				generic_file_vm_ops
3876 #define shmem_file_operations			ramfs_file_operations
3877 #define shmem_get_inode(sb, dir, mode, dev, flags)	ramfs_get_inode(sb, dir, mode, dev)
3878 #define shmem_acct_size(flags, size)		0
3879 #define shmem_unacct_size(flags, size)		do {} while (0)
3880 
3881 #endif /* CONFIG_SHMEM */
3882 
3883 /* common code */
3884 
3885 static struct file *__shmem_file_setup(struct vfsmount *mnt, const char *name, loff_t size,
3886 				       unsigned long flags, unsigned int i_flags)
3887 {
3888 	struct inode *inode;
3889 	struct file *res;
3890 
3891 	if (IS_ERR(mnt))
3892 		return ERR_CAST(mnt);
3893 
3894 	if (size < 0 || size > MAX_LFS_FILESIZE)
3895 		return ERR_PTR(-EINVAL);
3896 
3897 	if (shmem_acct_size(flags, size))
3898 		return ERR_PTR(-ENOMEM);
3899 
3900 	inode = shmem_get_inode(mnt->mnt_sb, NULL, S_IFREG | S_IRWXUGO, 0,
3901 				flags);
3902 	if (unlikely(!inode)) {
3903 		shmem_unacct_size(flags, size);
3904 		return ERR_PTR(-ENOSPC);
3905 	}
3906 	inode->i_flags |= i_flags;
3907 	inode->i_size = size;
3908 	clear_nlink(inode);	/* It is unlinked */
3909 	res = ERR_PTR(ramfs_nommu_expand_for_mapping(inode, size));
3910 	if (!IS_ERR(res))
3911 		res = alloc_file_pseudo(inode, mnt, name, O_RDWR,
3912 				&shmem_file_operations);
3913 	if (IS_ERR(res))
3914 		iput(inode);
3915 	return res;
3916 }
3917 
3918 /**
3919  * shmem_kernel_file_setup - get an unlinked file living in tmpfs which must be
3920  * 	kernel internal.  There will be NO LSM permission checks against the
3921  * 	underlying inode.  So users of this interface must do LSM checks at a
3922  *	higher layer.  The users are the big_key and shm implementations.  LSM
3923  *	checks are provided at the key or shm level rather than the inode.
3924  * @name: name for dentry (to be seen in /proc/<pid>/maps
3925  * @size: size to be set for the file
3926  * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
3927  */
3928 struct file *shmem_kernel_file_setup(const char *name, loff_t size, unsigned long flags)
3929 {
3930 	return __shmem_file_setup(shm_mnt, name, size, flags, S_PRIVATE);
3931 }
3932 
3933 /**
3934  * shmem_file_setup - get an unlinked file living in tmpfs
3935  * @name: name for dentry (to be seen in /proc/<pid>/maps
3936  * @size: size to be set for the file
3937  * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
3938  */
3939 struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags)
3940 {
3941 	return __shmem_file_setup(shm_mnt, name, size, flags, 0);
3942 }
3943 EXPORT_SYMBOL_GPL(shmem_file_setup);
3944 
3945 /**
3946  * shmem_file_setup_with_mnt - get an unlinked file living in tmpfs
3947  * @mnt: the tmpfs mount where the file will be created
3948  * @name: name for dentry (to be seen in /proc/<pid>/maps
3949  * @size: size to be set for the file
3950  * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
3951  */
3952 struct file *shmem_file_setup_with_mnt(struct vfsmount *mnt, const char *name,
3953 				       loff_t size, unsigned long flags)
3954 {
3955 	return __shmem_file_setup(mnt, name, size, flags, 0);
3956 }
3957 EXPORT_SYMBOL_GPL(shmem_file_setup_with_mnt);
3958 
3959 /**
3960  * shmem_zero_setup - setup a shared anonymous mapping
3961  * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
3962  */
3963 int shmem_zero_setup(struct vm_area_struct *vma)
3964 {
3965 	struct file *file;
3966 	loff_t size = vma->vm_end - vma->vm_start;
3967 
3968 	/*
3969 	 * Cloning a new file under mmap_sem leads to a lock ordering conflict
3970 	 * between XFS directory reading and selinux: since this file is only
3971 	 * accessible to the user through its mapping, use S_PRIVATE flag to
3972 	 * bypass file security, in the same way as shmem_kernel_file_setup().
3973 	 */
3974 	file = shmem_kernel_file_setup("dev/zero", size, vma->vm_flags);
3975 	if (IS_ERR(file))
3976 		return PTR_ERR(file);
3977 
3978 	if (vma->vm_file)
3979 		fput(vma->vm_file);
3980 	vma->vm_file = file;
3981 	vma->vm_ops = &shmem_vm_ops;
3982 
3983 	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE) &&
3984 			((vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK) <
3985 			(vma->vm_end & HPAGE_PMD_MASK)) {
3986 		khugepaged_enter(vma, vma->vm_flags);
3987 	}
3988 
3989 	return 0;
3990 }
3991 
3992 /**
3993  * shmem_read_mapping_page_gfp - read into page cache, using specified page allocation flags.
3994  * @mapping:	the page's address_space
3995  * @index:	the page index
3996  * @gfp:	the page allocator flags to use if allocating
3997  *
3998  * This behaves as a tmpfs "read_cache_page_gfp(mapping, index, gfp)",
3999  * with any new page allocations done using the specified allocation flags.
4000  * But read_cache_page_gfp() uses the ->readpage() method: which does not
4001  * suit tmpfs, since it may have pages in swapcache, and needs to find those
4002  * for itself; although drivers/gpu/drm i915 and ttm rely upon this support.
4003  *
4004  * i915_gem_object_get_pages_gtt() mixes __GFP_NORETRY | __GFP_NOWARN in
4005  * with the mapping_gfp_mask(), to avoid OOMing the machine unnecessarily.
4006  */
4007 struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
4008 					 pgoff_t index, gfp_t gfp)
4009 {
4010 #ifdef CONFIG_SHMEM
4011 	struct inode *inode = mapping->host;
4012 	struct page *page;
4013 	int error;
4014 
4015 	BUG_ON(mapping->a_ops != &shmem_aops);
4016 	error = shmem_getpage_gfp(inode, index, &page, SGP_CACHE,
4017 				  gfp, NULL, NULL, NULL);
4018 	if (error)
4019 		page = ERR_PTR(error);
4020 	else
4021 		unlock_page(page);
4022 	return page;
4023 #else
4024 	/*
4025 	 * The tiny !SHMEM case uses ramfs without swap
4026 	 */
4027 	return read_cache_page_gfp(mapping, index, gfp);
4028 #endif
4029 }
4030 EXPORT_SYMBOL_GPL(shmem_read_mapping_page_gfp);
4031