xref: /linux/mm/shmem.c (revision ac5399d48616644cb6ddfe39f8babe807d5f5cbd)
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/fileattr.h>
32 #include <linux/mm.h>
33 #include <linux/random.h>
34 #include <linux/sched/signal.h>
35 #include <linux/export.h>
36 #include <linux/shmem_fs.h>
37 #include <linux/swap.h>
38 #include <linux/uio.h>
39 #include <linux/hugetlb.h>
40 #include <linux/fs_parser.h>
41 #include <linux/swapfile.h>
42 #include <linux/iversion.h>
43 #include "swap.h"
44 
45 static struct vfsmount *shm_mnt __ro_after_init;
46 
47 #ifdef CONFIG_SHMEM
48 /*
49  * This virtual memory filesystem is heavily based on the ramfs. It
50  * extends ramfs by the ability to use swap and honor resource limits
51  * which makes it a completely usable filesystem.
52  */
53 
54 #include <linux/xattr.h>
55 #include <linux/exportfs.h>
56 #include <linux/posix_acl.h>
57 #include <linux/posix_acl_xattr.h>
58 #include <linux/mman.h>
59 #include <linux/string.h>
60 #include <linux/slab.h>
61 #include <linux/backing-dev.h>
62 #include <linux/writeback.h>
63 #include <linux/pagevec.h>
64 #include <linux/percpu_counter.h>
65 #include <linux/falloc.h>
66 #include <linux/splice.h>
67 #include <linux/security.h>
68 #include <linux/swapops.h>
69 #include <linux/mempolicy.h>
70 #include <linux/namei.h>
71 #include <linux/ctype.h>
72 #include <linux/migrate.h>
73 #include <linux/highmem.h>
74 #include <linux/seq_file.h>
75 #include <linux/magic.h>
76 #include <linux/syscalls.h>
77 #include <linux/fcntl.h>
78 #include <uapi/linux/memfd.h>
79 #include <linux/rmap.h>
80 #include <linux/uuid.h>
81 #include <linux/quotaops.h>
82 #include <linux/rcupdate_wait.h>
83 
84 #include <linux/uaccess.h>
85 
86 #include "internal.h"
87 
88 #define BLOCKS_PER_PAGE  (PAGE_SIZE/512)
89 #define VM_ACCT(size)    (PAGE_ALIGN(size) >> PAGE_SHIFT)
90 
91 /* Pretend that each entry is of this size in directory's i_size */
92 #define BOGO_DIRENT_SIZE 20
93 
94 /* Pretend that one inode + its dentry occupy this much memory */
95 #define BOGO_INODE_SIZE 1024
96 
97 /* Symlink up to this size is kmalloc'ed instead of using a swappable page */
98 #define SHORT_SYMLINK_LEN 128
99 
100 /*
101  * shmem_fallocate communicates with shmem_fault or shmem_writepage via
102  * inode->i_private (with i_rwsem making sure that it has only one user at
103  * a time): we would prefer not to enlarge the shmem inode just for that.
104  */
105 struct shmem_falloc {
106 	wait_queue_head_t *waitq; /* faults into hole wait for punch to end */
107 	pgoff_t start;		/* start of range currently being fallocated */
108 	pgoff_t next;		/* the next page offset to be fallocated */
109 	pgoff_t nr_falloced;	/* how many new pages have been fallocated */
110 	pgoff_t nr_unswapped;	/* how often writepage refused to swap out */
111 };
112 
113 struct shmem_options {
114 	unsigned long long blocks;
115 	unsigned long long inodes;
116 	struct mempolicy *mpol;
117 	kuid_t uid;
118 	kgid_t gid;
119 	umode_t mode;
120 	bool full_inums;
121 	int huge;
122 	int seen;
123 	bool noswap;
124 	unsigned short quota_types;
125 	struct shmem_quota_limits qlimits;
126 #define SHMEM_SEEN_BLOCKS 1
127 #define SHMEM_SEEN_INODES 2
128 #define SHMEM_SEEN_HUGE 4
129 #define SHMEM_SEEN_INUMS 8
130 #define SHMEM_SEEN_NOSWAP 16
131 #define SHMEM_SEEN_QUOTA 32
132 };
133 
134 #ifdef CONFIG_TMPFS
135 static unsigned long shmem_default_max_blocks(void)
136 {
137 	return totalram_pages() / 2;
138 }
139 
140 static unsigned long shmem_default_max_inodes(void)
141 {
142 	unsigned long nr_pages = totalram_pages();
143 
144 	return min3(nr_pages - totalhigh_pages(), nr_pages / 2,
145 			ULONG_MAX / BOGO_INODE_SIZE);
146 }
147 #endif
148 
149 static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
150 			struct folio **foliop, enum sgp_type sgp, gfp_t gfp,
151 			struct mm_struct *fault_mm, vm_fault_t *fault_type);
152 
153 static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
154 {
155 	return sb->s_fs_info;
156 }
157 
158 /*
159  * shmem_file_setup pre-accounts the whole fixed size of a VM object,
160  * for shared memory and for shared anonymous (/dev/zero) mappings
161  * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
162  * consistent with the pre-accounting of private mappings ...
163  */
164 static inline int shmem_acct_size(unsigned long flags, loff_t size)
165 {
166 	return (flags & VM_NORESERVE) ?
167 		0 : security_vm_enough_memory_mm(current->mm, VM_ACCT(size));
168 }
169 
170 static inline void shmem_unacct_size(unsigned long flags, loff_t size)
171 {
172 	if (!(flags & VM_NORESERVE))
173 		vm_unacct_memory(VM_ACCT(size));
174 }
175 
176 static inline int shmem_reacct_size(unsigned long flags,
177 		loff_t oldsize, loff_t newsize)
178 {
179 	if (!(flags & VM_NORESERVE)) {
180 		if (VM_ACCT(newsize) > VM_ACCT(oldsize))
181 			return security_vm_enough_memory_mm(current->mm,
182 					VM_ACCT(newsize) - VM_ACCT(oldsize));
183 		else if (VM_ACCT(newsize) < VM_ACCT(oldsize))
184 			vm_unacct_memory(VM_ACCT(oldsize) - VM_ACCT(newsize));
185 	}
186 	return 0;
187 }
188 
189 /*
190  * ... whereas tmpfs objects are accounted incrementally as
191  * pages are allocated, in order to allow large sparse files.
192  * shmem_get_folio reports shmem_acct_blocks failure as -ENOSPC not -ENOMEM,
193  * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
194  */
195 static inline int shmem_acct_blocks(unsigned long flags, long pages)
196 {
197 	if (!(flags & VM_NORESERVE))
198 		return 0;
199 
200 	return security_vm_enough_memory_mm(current->mm,
201 			pages * VM_ACCT(PAGE_SIZE));
202 }
203 
204 static inline void shmem_unacct_blocks(unsigned long flags, long pages)
205 {
206 	if (flags & VM_NORESERVE)
207 		vm_unacct_memory(pages * VM_ACCT(PAGE_SIZE));
208 }
209 
210 static int shmem_inode_acct_blocks(struct inode *inode, long pages)
211 {
212 	struct shmem_inode_info *info = SHMEM_I(inode);
213 	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
214 	int err = -ENOSPC;
215 
216 	if (shmem_acct_blocks(info->flags, pages))
217 		return err;
218 
219 	might_sleep();	/* when quotas */
220 	if (sbinfo->max_blocks) {
221 		if (!percpu_counter_limited_add(&sbinfo->used_blocks,
222 						sbinfo->max_blocks, pages))
223 			goto unacct;
224 
225 		err = dquot_alloc_block_nodirty(inode, pages);
226 		if (err) {
227 			percpu_counter_sub(&sbinfo->used_blocks, pages);
228 			goto unacct;
229 		}
230 	} else {
231 		err = dquot_alloc_block_nodirty(inode, pages);
232 		if (err)
233 			goto unacct;
234 	}
235 
236 	return 0;
237 
238 unacct:
239 	shmem_unacct_blocks(info->flags, pages);
240 	return err;
241 }
242 
243 static void shmem_inode_unacct_blocks(struct inode *inode, long pages)
244 {
245 	struct shmem_inode_info *info = SHMEM_I(inode);
246 	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
247 
248 	might_sleep();	/* when quotas */
249 	dquot_free_block_nodirty(inode, pages);
250 
251 	if (sbinfo->max_blocks)
252 		percpu_counter_sub(&sbinfo->used_blocks, pages);
253 	shmem_unacct_blocks(info->flags, pages);
254 }
255 
256 static const struct super_operations shmem_ops;
257 static const struct address_space_operations shmem_aops;
258 static const struct file_operations shmem_file_operations;
259 static const struct inode_operations shmem_inode_operations;
260 static const struct inode_operations shmem_dir_inode_operations;
261 static const struct inode_operations shmem_special_inode_operations;
262 static const struct vm_operations_struct shmem_vm_ops;
263 static const struct vm_operations_struct shmem_anon_vm_ops;
264 static struct file_system_type shmem_fs_type;
265 
266 bool shmem_mapping(struct address_space *mapping)
267 {
268 	return mapping->a_ops == &shmem_aops;
269 }
270 EXPORT_SYMBOL_GPL(shmem_mapping);
271 
272 bool vma_is_anon_shmem(struct vm_area_struct *vma)
273 {
274 	return vma->vm_ops == &shmem_anon_vm_ops;
275 }
276 
277 bool vma_is_shmem(struct vm_area_struct *vma)
278 {
279 	return vma_is_anon_shmem(vma) || vma->vm_ops == &shmem_vm_ops;
280 }
281 
282 static LIST_HEAD(shmem_swaplist);
283 static DEFINE_MUTEX(shmem_swaplist_mutex);
284 
285 #ifdef CONFIG_TMPFS_QUOTA
286 
287 static int shmem_enable_quotas(struct super_block *sb,
288 			       unsigned short quota_types)
289 {
290 	int type, err = 0;
291 
292 	sb_dqopt(sb)->flags |= DQUOT_QUOTA_SYS_FILE | DQUOT_NOLIST_DIRTY;
293 	for (type = 0; type < SHMEM_MAXQUOTAS; type++) {
294 		if (!(quota_types & (1 << type)))
295 			continue;
296 		err = dquot_load_quota_sb(sb, type, QFMT_SHMEM,
297 					  DQUOT_USAGE_ENABLED |
298 					  DQUOT_LIMITS_ENABLED);
299 		if (err)
300 			goto out_err;
301 	}
302 	return 0;
303 
304 out_err:
305 	pr_warn("tmpfs: failed to enable quota tracking (type=%d, err=%d)\n",
306 		type, err);
307 	for (type--; type >= 0; type--)
308 		dquot_quota_off(sb, type);
309 	return err;
310 }
311 
312 static void shmem_disable_quotas(struct super_block *sb)
313 {
314 	int type;
315 
316 	for (type = 0; type < SHMEM_MAXQUOTAS; type++)
317 		dquot_quota_off(sb, type);
318 }
319 
320 static struct dquot __rcu **shmem_get_dquots(struct inode *inode)
321 {
322 	return SHMEM_I(inode)->i_dquot;
323 }
324 #endif /* CONFIG_TMPFS_QUOTA */
325 
326 /*
327  * shmem_reserve_inode() performs bookkeeping to reserve a shmem inode, and
328  * produces a novel ino for the newly allocated inode.
329  *
330  * It may also be called when making a hard link to permit the space needed by
331  * each dentry. However, in that case, no new inode number is needed since that
332  * internally draws from another pool of inode numbers (currently global
333  * get_next_ino()). This case is indicated by passing NULL as inop.
334  */
335 #define SHMEM_INO_BATCH 1024
336 static int shmem_reserve_inode(struct super_block *sb, ino_t *inop)
337 {
338 	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
339 	ino_t ino;
340 
341 	if (!(sb->s_flags & SB_KERNMOUNT)) {
342 		raw_spin_lock(&sbinfo->stat_lock);
343 		if (sbinfo->max_inodes) {
344 			if (sbinfo->free_ispace < BOGO_INODE_SIZE) {
345 				raw_spin_unlock(&sbinfo->stat_lock);
346 				return -ENOSPC;
347 			}
348 			sbinfo->free_ispace -= BOGO_INODE_SIZE;
349 		}
350 		if (inop) {
351 			ino = sbinfo->next_ino++;
352 			if (unlikely(is_zero_ino(ino)))
353 				ino = sbinfo->next_ino++;
354 			if (unlikely(!sbinfo->full_inums &&
355 				     ino > UINT_MAX)) {
356 				/*
357 				 * Emulate get_next_ino uint wraparound for
358 				 * compatibility
359 				 */
360 				if (IS_ENABLED(CONFIG_64BIT))
361 					pr_warn("%s: inode number overflow on device %d, consider using inode64 mount option\n",
362 						__func__, MINOR(sb->s_dev));
363 				sbinfo->next_ino = 1;
364 				ino = sbinfo->next_ino++;
365 			}
366 			*inop = ino;
367 		}
368 		raw_spin_unlock(&sbinfo->stat_lock);
369 	} else if (inop) {
370 		/*
371 		 * __shmem_file_setup, one of our callers, is lock-free: it
372 		 * doesn't hold stat_lock in shmem_reserve_inode since
373 		 * max_inodes is always 0, and is called from potentially
374 		 * unknown contexts. As such, use a per-cpu batched allocator
375 		 * which doesn't require the per-sb stat_lock unless we are at
376 		 * the batch boundary.
377 		 *
378 		 * We don't need to worry about inode{32,64} since SB_KERNMOUNT
379 		 * shmem mounts are not exposed to userspace, so we don't need
380 		 * to worry about things like glibc compatibility.
381 		 */
382 		ino_t *next_ino;
383 
384 		next_ino = per_cpu_ptr(sbinfo->ino_batch, get_cpu());
385 		ino = *next_ino;
386 		if (unlikely(ino % SHMEM_INO_BATCH == 0)) {
387 			raw_spin_lock(&sbinfo->stat_lock);
388 			ino = sbinfo->next_ino;
389 			sbinfo->next_ino += SHMEM_INO_BATCH;
390 			raw_spin_unlock(&sbinfo->stat_lock);
391 			if (unlikely(is_zero_ino(ino)))
392 				ino++;
393 		}
394 		*inop = ino;
395 		*next_ino = ++ino;
396 		put_cpu();
397 	}
398 
399 	return 0;
400 }
401 
402 static void shmem_free_inode(struct super_block *sb, size_t freed_ispace)
403 {
404 	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
405 	if (sbinfo->max_inodes) {
406 		raw_spin_lock(&sbinfo->stat_lock);
407 		sbinfo->free_ispace += BOGO_INODE_SIZE + freed_ispace;
408 		raw_spin_unlock(&sbinfo->stat_lock);
409 	}
410 }
411 
412 /**
413  * shmem_recalc_inode - recalculate the block usage of an inode
414  * @inode: inode to recalc
415  * @alloced: the change in number of pages allocated to inode
416  * @swapped: the change in number of pages swapped from inode
417  *
418  * We have to calculate the free blocks since the mm can drop
419  * undirtied hole pages behind our back.
420  *
421  * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
422  * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
423  */
424 static void shmem_recalc_inode(struct inode *inode, long alloced, long swapped)
425 {
426 	struct shmem_inode_info *info = SHMEM_I(inode);
427 	long freed;
428 
429 	spin_lock(&info->lock);
430 	info->alloced += alloced;
431 	info->swapped += swapped;
432 	freed = info->alloced - info->swapped -
433 		READ_ONCE(inode->i_mapping->nrpages);
434 	/*
435 	 * Special case: whereas normally shmem_recalc_inode() is called
436 	 * after i_mapping->nrpages has already been adjusted (up or down),
437 	 * shmem_writepage() has to raise swapped before nrpages is lowered -
438 	 * to stop a racing shmem_recalc_inode() from thinking that a page has
439 	 * been freed.  Compensate here, to avoid the need for a followup call.
440 	 */
441 	if (swapped > 0)
442 		freed += swapped;
443 	if (freed > 0)
444 		info->alloced -= freed;
445 	spin_unlock(&info->lock);
446 
447 	/* The quota case may block */
448 	if (freed > 0)
449 		shmem_inode_unacct_blocks(inode, freed);
450 }
451 
452 bool shmem_charge(struct inode *inode, long pages)
453 {
454 	struct address_space *mapping = inode->i_mapping;
455 
456 	if (shmem_inode_acct_blocks(inode, pages))
457 		return false;
458 
459 	/* nrpages adjustment first, then shmem_recalc_inode() when balanced */
460 	xa_lock_irq(&mapping->i_pages);
461 	mapping->nrpages += pages;
462 	xa_unlock_irq(&mapping->i_pages);
463 
464 	shmem_recalc_inode(inode, pages, 0);
465 	return true;
466 }
467 
468 void shmem_uncharge(struct inode *inode, long pages)
469 {
470 	/* pages argument is currently unused: keep it to help debugging */
471 	/* nrpages adjustment done by __filemap_remove_folio() or caller */
472 
473 	shmem_recalc_inode(inode, 0, 0);
474 }
475 
476 /*
477  * Replace item expected in xarray by a new item, while holding xa_lock.
478  */
479 static int shmem_replace_entry(struct address_space *mapping,
480 			pgoff_t index, void *expected, void *replacement)
481 {
482 	XA_STATE(xas, &mapping->i_pages, index);
483 	void *item;
484 
485 	VM_BUG_ON(!expected);
486 	VM_BUG_ON(!replacement);
487 	item = xas_load(&xas);
488 	if (item != expected)
489 		return -ENOENT;
490 	xas_store(&xas, replacement);
491 	return 0;
492 }
493 
494 /*
495  * Sometimes, before we decide whether to proceed or to fail, we must check
496  * that an entry was not already brought back from swap by a racing thread.
497  *
498  * Checking page is not enough: by the time a SwapCache page is locked, it
499  * might be reused, and again be SwapCache, using the same swap as before.
500  */
501 static bool shmem_confirm_swap(struct address_space *mapping,
502 			       pgoff_t index, swp_entry_t swap)
503 {
504 	return xa_load(&mapping->i_pages, index) == swp_to_radix_entry(swap);
505 }
506 
507 /*
508  * Definitions for "huge tmpfs": tmpfs mounted with the huge= option
509  *
510  * SHMEM_HUGE_NEVER:
511  *	disables huge pages for the mount;
512  * SHMEM_HUGE_ALWAYS:
513  *	enables huge pages for the mount;
514  * SHMEM_HUGE_WITHIN_SIZE:
515  *	only allocate huge pages if the page will be fully within i_size,
516  *	also respect fadvise()/madvise() hints;
517  * SHMEM_HUGE_ADVISE:
518  *	only allocate huge pages if requested with fadvise()/madvise();
519  */
520 
521 #define SHMEM_HUGE_NEVER	0
522 #define SHMEM_HUGE_ALWAYS	1
523 #define SHMEM_HUGE_WITHIN_SIZE	2
524 #define SHMEM_HUGE_ADVISE	3
525 
526 /*
527  * Special values.
528  * Only can be set via /sys/kernel/mm/transparent_hugepage/shmem_enabled:
529  *
530  * SHMEM_HUGE_DENY:
531  *	disables huge on shm_mnt and all mounts, for emergency use;
532  * SHMEM_HUGE_FORCE:
533  *	enables huge on shm_mnt and all mounts, w/o needing option, for testing;
534  *
535  */
536 #define SHMEM_HUGE_DENY		(-1)
537 #define SHMEM_HUGE_FORCE	(-2)
538 
539 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
540 /* ifdef here to avoid bloating shmem.o when not necessary */
541 
542 static int shmem_huge __read_mostly = SHMEM_HUGE_NEVER;
543 
544 static bool __shmem_is_huge(struct inode *inode, pgoff_t index,
545 			    bool shmem_huge_force, struct mm_struct *mm,
546 			    unsigned long vm_flags)
547 {
548 	loff_t i_size;
549 
550 	if (!S_ISREG(inode->i_mode))
551 		return false;
552 	if (mm && ((vm_flags & VM_NOHUGEPAGE) || test_bit(MMF_DISABLE_THP, &mm->flags)))
553 		return false;
554 	if (shmem_huge == SHMEM_HUGE_DENY)
555 		return false;
556 	if (shmem_huge_force || shmem_huge == SHMEM_HUGE_FORCE)
557 		return true;
558 
559 	switch (SHMEM_SB(inode->i_sb)->huge) {
560 	case SHMEM_HUGE_ALWAYS:
561 		return true;
562 	case SHMEM_HUGE_WITHIN_SIZE:
563 		index = round_up(index + 1, HPAGE_PMD_NR);
564 		i_size = round_up(i_size_read(inode), PAGE_SIZE);
565 		if (i_size >> PAGE_SHIFT >= index)
566 			return true;
567 		fallthrough;
568 	case SHMEM_HUGE_ADVISE:
569 		if (mm && (vm_flags & VM_HUGEPAGE))
570 			return true;
571 		fallthrough;
572 	default:
573 		return false;
574 	}
575 }
576 
577 bool shmem_is_huge(struct inode *inode, pgoff_t index,
578 		   bool shmem_huge_force, struct mm_struct *mm,
579 		   unsigned long vm_flags)
580 {
581 	if (HPAGE_PMD_ORDER > MAX_PAGECACHE_ORDER)
582 		return false;
583 
584 	return __shmem_is_huge(inode, index, shmem_huge_force, mm, vm_flags);
585 }
586 
587 #if defined(CONFIG_SYSFS)
588 static int shmem_parse_huge(const char *str)
589 {
590 	if (!strcmp(str, "never"))
591 		return SHMEM_HUGE_NEVER;
592 	if (!strcmp(str, "always"))
593 		return SHMEM_HUGE_ALWAYS;
594 	if (!strcmp(str, "within_size"))
595 		return SHMEM_HUGE_WITHIN_SIZE;
596 	if (!strcmp(str, "advise"))
597 		return SHMEM_HUGE_ADVISE;
598 	if (!strcmp(str, "deny"))
599 		return SHMEM_HUGE_DENY;
600 	if (!strcmp(str, "force"))
601 		return SHMEM_HUGE_FORCE;
602 	return -EINVAL;
603 }
604 #endif
605 
606 #if defined(CONFIG_SYSFS) || defined(CONFIG_TMPFS)
607 static const char *shmem_format_huge(int huge)
608 {
609 	switch (huge) {
610 	case SHMEM_HUGE_NEVER:
611 		return "never";
612 	case SHMEM_HUGE_ALWAYS:
613 		return "always";
614 	case SHMEM_HUGE_WITHIN_SIZE:
615 		return "within_size";
616 	case SHMEM_HUGE_ADVISE:
617 		return "advise";
618 	case SHMEM_HUGE_DENY:
619 		return "deny";
620 	case SHMEM_HUGE_FORCE:
621 		return "force";
622 	default:
623 		VM_BUG_ON(1);
624 		return "bad_val";
625 	}
626 }
627 #endif
628 
629 static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
630 		struct shrink_control *sc, unsigned long nr_to_split)
631 {
632 	LIST_HEAD(list), *pos, *next;
633 	LIST_HEAD(to_remove);
634 	struct inode *inode;
635 	struct shmem_inode_info *info;
636 	struct folio *folio;
637 	unsigned long batch = sc ? sc->nr_to_scan : 128;
638 	int split = 0;
639 
640 	if (list_empty(&sbinfo->shrinklist))
641 		return SHRINK_STOP;
642 
643 	spin_lock(&sbinfo->shrinklist_lock);
644 	list_for_each_safe(pos, next, &sbinfo->shrinklist) {
645 		info = list_entry(pos, struct shmem_inode_info, shrinklist);
646 
647 		/* pin the inode */
648 		inode = igrab(&info->vfs_inode);
649 
650 		/* inode is about to be evicted */
651 		if (!inode) {
652 			list_del_init(&info->shrinklist);
653 			goto next;
654 		}
655 
656 		/* Check if there's anything to gain */
657 		if (round_up(inode->i_size, PAGE_SIZE) ==
658 				round_up(inode->i_size, HPAGE_PMD_SIZE)) {
659 			list_move(&info->shrinklist, &to_remove);
660 			goto next;
661 		}
662 
663 		list_move(&info->shrinklist, &list);
664 next:
665 		sbinfo->shrinklist_len--;
666 		if (!--batch)
667 			break;
668 	}
669 	spin_unlock(&sbinfo->shrinklist_lock);
670 
671 	list_for_each_safe(pos, next, &to_remove) {
672 		info = list_entry(pos, struct shmem_inode_info, shrinklist);
673 		inode = &info->vfs_inode;
674 		list_del_init(&info->shrinklist);
675 		iput(inode);
676 	}
677 
678 	list_for_each_safe(pos, next, &list) {
679 		int ret;
680 		pgoff_t index;
681 
682 		info = list_entry(pos, struct shmem_inode_info, shrinklist);
683 		inode = &info->vfs_inode;
684 
685 		if (nr_to_split && split >= nr_to_split)
686 			goto move_back;
687 
688 		index = (inode->i_size & HPAGE_PMD_MASK) >> PAGE_SHIFT;
689 		folio = filemap_get_folio(inode->i_mapping, index);
690 		if (IS_ERR(folio))
691 			goto drop;
692 
693 		/* No huge page at the end of the file: nothing to split */
694 		if (!folio_test_large(folio)) {
695 			folio_put(folio);
696 			goto drop;
697 		}
698 
699 		/*
700 		 * Move the inode on the list back to shrinklist if we failed
701 		 * to lock the page at this time.
702 		 *
703 		 * Waiting for the lock may lead to deadlock in the
704 		 * reclaim path.
705 		 */
706 		if (!folio_trylock(folio)) {
707 			folio_put(folio);
708 			goto move_back;
709 		}
710 
711 		ret = split_folio(folio);
712 		folio_unlock(folio);
713 		folio_put(folio);
714 
715 		/* If split failed move the inode on the list back to shrinklist */
716 		if (ret)
717 			goto move_back;
718 
719 		split++;
720 drop:
721 		list_del_init(&info->shrinklist);
722 		goto put;
723 move_back:
724 		/*
725 		 * Make sure the inode is either on the global list or deleted
726 		 * from any local list before iput() since it could be deleted
727 		 * in another thread once we put the inode (then the local list
728 		 * is corrupted).
729 		 */
730 		spin_lock(&sbinfo->shrinklist_lock);
731 		list_move(&info->shrinklist, &sbinfo->shrinklist);
732 		sbinfo->shrinklist_len++;
733 		spin_unlock(&sbinfo->shrinklist_lock);
734 put:
735 		iput(inode);
736 	}
737 
738 	return split;
739 }
740 
741 static long shmem_unused_huge_scan(struct super_block *sb,
742 		struct shrink_control *sc)
743 {
744 	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
745 
746 	if (!READ_ONCE(sbinfo->shrinklist_len))
747 		return SHRINK_STOP;
748 
749 	return shmem_unused_huge_shrink(sbinfo, sc, 0);
750 }
751 
752 static long shmem_unused_huge_count(struct super_block *sb,
753 		struct shrink_control *sc)
754 {
755 	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
756 	return READ_ONCE(sbinfo->shrinklist_len);
757 }
758 #else /* !CONFIG_TRANSPARENT_HUGEPAGE */
759 
760 #define shmem_huge SHMEM_HUGE_DENY
761 
762 static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
763 		struct shrink_control *sc, unsigned long nr_to_split)
764 {
765 	return 0;
766 }
767 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
768 
769 /*
770  * Somewhat like filemap_add_folio, but error if expected item has gone.
771  */
772 static int shmem_add_to_page_cache(struct folio *folio,
773 				   struct address_space *mapping,
774 				   pgoff_t index, void *expected, gfp_t gfp)
775 {
776 	XA_STATE_ORDER(xas, &mapping->i_pages, index, folio_order(folio));
777 	long nr = folio_nr_pages(folio);
778 
779 	VM_BUG_ON_FOLIO(index != round_down(index, nr), folio);
780 	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
781 	VM_BUG_ON_FOLIO(!folio_test_swapbacked(folio), folio);
782 	VM_BUG_ON(expected && folio_test_large(folio));
783 
784 	folio_ref_add(folio, nr);
785 	folio->mapping = mapping;
786 	folio->index = index;
787 
788 	gfp &= GFP_RECLAIM_MASK;
789 	folio_throttle_swaprate(folio, gfp);
790 
791 	do {
792 		xas_lock_irq(&xas);
793 		if (expected != xas_find_conflict(&xas)) {
794 			xas_set_err(&xas, -EEXIST);
795 			goto unlock;
796 		}
797 		if (expected && xas_find_conflict(&xas)) {
798 			xas_set_err(&xas, -EEXIST);
799 			goto unlock;
800 		}
801 		xas_store(&xas, folio);
802 		if (xas_error(&xas))
803 			goto unlock;
804 		if (folio_test_pmd_mappable(folio))
805 			__lruvec_stat_mod_folio(folio, NR_SHMEM_THPS, nr);
806 		__lruvec_stat_mod_folio(folio, NR_FILE_PAGES, nr);
807 		__lruvec_stat_mod_folio(folio, NR_SHMEM, nr);
808 		mapping->nrpages += nr;
809 unlock:
810 		xas_unlock_irq(&xas);
811 	} while (xas_nomem(&xas, gfp));
812 
813 	if (xas_error(&xas)) {
814 		folio->mapping = NULL;
815 		folio_ref_sub(folio, nr);
816 		return xas_error(&xas);
817 	}
818 
819 	return 0;
820 }
821 
822 /*
823  * Somewhat like filemap_remove_folio, but substitutes swap for @folio.
824  */
825 static void shmem_delete_from_page_cache(struct folio *folio, void *radswap)
826 {
827 	struct address_space *mapping = folio->mapping;
828 	long nr = folio_nr_pages(folio);
829 	int error;
830 
831 	xa_lock_irq(&mapping->i_pages);
832 	error = shmem_replace_entry(mapping, folio->index, folio, radswap);
833 	folio->mapping = NULL;
834 	mapping->nrpages -= nr;
835 	__lruvec_stat_mod_folio(folio, NR_FILE_PAGES, -nr);
836 	__lruvec_stat_mod_folio(folio, NR_SHMEM, -nr);
837 	xa_unlock_irq(&mapping->i_pages);
838 	folio_put(folio);
839 	BUG_ON(error);
840 }
841 
842 /*
843  * Remove swap entry from page cache, free the swap and its page cache.
844  */
845 static int shmem_free_swap(struct address_space *mapping,
846 			   pgoff_t index, void *radswap)
847 {
848 	void *old;
849 
850 	old = xa_cmpxchg_irq(&mapping->i_pages, index, radswap, NULL, 0);
851 	if (old != radswap)
852 		return -ENOENT;
853 	free_swap_and_cache(radix_to_swp_entry(radswap));
854 	return 0;
855 }
856 
857 /*
858  * Determine (in bytes) how many of the shmem object's pages mapped by the
859  * given offsets are swapped out.
860  *
861  * This is safe to call without i_rwsem or the i_pages lock thanks to RCU,
862  * as long as the inode doesn't go away and racy results are not a problem.
863  */
864 unsigned long shmem_partial_swap_usage(struct address_space *mapping,
865 						pgoff_t start, pgoff_t end)
866 {
867 	XA_STATE(xas, &mapping->i_pages, start);
868 	struct page *page;
869 	unsigned long swapped = 0;
870 	unsigned long max = end - 1;
871 
872 	rcu_read_lock();
873 	xas_for_each(&xas, page, max) {
874 		if (xas_retry(&xas, page))
875 			continue;
876 		if (xa_is_value(page))
877 			swapped++;
878 		if (xas.xa_index == max)
879 			break;
880 		if (need_resched()) {
881 			xas_pause(&xas);
882 			cond_resched_rcu();
883 		}
884 	}
885 	rcu_read_unlock();
886 
887 	return swapped << PAGE_SHIFT;
888 }
889 
890 /*
891  * Determine (in bytes) how many of the shmem object's pages mapped by the
892  * given vma is swapped out.
893  *
894  * This is safe to call without i_rwsem or the i_pages lock thanks to RCU,
895  * as long as the inode doesn't go away and racy results are not a problem.
896  */
897 unsigned long shmem_swap_usage(struct vm_area_struct *vma)
898 {
899 	struct inode *inode = file_inode(vma->vm_file);
900 	struct shmem_inode_info *info = SHMEM_I(inode);
901 	struct address_space *mapping = inode->i_mapping;
902 	unsigned long swapped;
903 
904 	/* Be careful as we don't hold info->lock */
905 	swapped = READ_ONCE(info->swapped);
906 
907 	/*
908 	 * The easier cases are when the shmem object has nothing in swap, or
909 	 * the vma maps it whole. Then we can simply use the stats that we
910 	 * already track.
911 	 */
912 	if (!swapped)
913 		return 0;
914 
915 	if (!vma->vm_pgoff && vma->vm_end - vma->vm_start >= inode->i_size)
916 		return swapped << PAGE_SHIFT;
917 
918 	/* Here comes the more involved part */
919 	return shmem_partial_swap_usage(mapping, vma->vm_pgoff,
920 					vma->vm_pgoff + vma_pages(vma));
921 }
922 
923 /*
924  * SysV IPC SHM_UNLOCK restore Unevictable pages to their evictable lists.
925  */
926 void shmem_unlock_mapping(struct address_space *mapping)
927 {
928 	struct folio_batch fbatch;
929 	pgoff_t index = 0;
930 
931 	folio_batch_init(&fbatch);
932 	/*
933 	 * Minor point, but we might as well stop if someone else SHM_LOCKs it.
934 	 */
935 	while (!mapping_unevictable(mapping) &&
936 	       filemap_get_folios(mapping, &index, ~0UL, &fbatch)) {
937 		check_move_unevictable_folios(&fbatch);
938 		folio_batch_release(&fbatch);
939 		cond_resched();
940 	}
941 }
942 
943 static struct folio *shmem_get_partial_folio(struct inode *inode, pgoff_t index)
944 {
945 	struct folio *folio;
946 
947 	/*
948 	 * At first avoid shmem_get_folio(,,,SGP_READ): that fails
949 	 * beyond i_size, and reports fallocated folios as holes.
950 	 */
951 	folio = filemap_get_entry(inode->i_mapping, index);
952 	if (!folio)
953 		return folio;
954 	if (!xa_is_value(folio)) {
955 		folio_lock(folio);
956 		if (folio->mapping == inode->i_mapping)
957 			return folio;
958 		/* The folio has been swapped out */
959 		folio_unlock(folio);
960 		folio_put(folio);
961 	}
962 	/*
963 	 * But read a folio back from swap if any of it is within i_size
964 	 * (although in some cases this is just a waste of time).
965 	 */
966 	folio = NULL;
967 	shmem_get_folio(inode, index, &folio, SGP_READ);
968 	return folio;
969 }
970 
971 /*
972  * Remove range of pages and swap entries from page cache, and free them.
973  * If !unfalloc, truncate or punch hole; if unfalloc, undo failed fallocate.
974  */
975 static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
976 								 bool unfalloc)
977 {
978 	struct address_space *mapping = inode->i_mapping;
979 	struct shmem_inode_info *info = SHMEM_I(inode);
980 	pgoff_t start = (lstart + PAGE_SIZE - 1) >> PAGE_SHIFT;
981 	pgoff_t end = (lend + 1) >> PAGE_SHIFT;
982 	struct folio_batch fbatch;
983 	pgoff_t indices[PAGEVEC_SIZE];
984 	struct folio *folio;
985 	bool same_folio;
986 	long nr_swaps_freed = 0;
987 	pgoff_t index;
988 	int i;
989 
990 	if (lend == -1)
991 		end = -1;	/* unsigned, so actually very big */
992 
993 	if (info->fallocend > start && info->fallocend <= end && !unfalloc)
994 		info->fallocend = start;
995 
996 	folio_batch_init(&fbatch);
997 	index = start;
998 	while (index < end && find_lock_entries(mapping, &index, end - 1,
999 			&fbatch, indices)) {
1000 		for (i = 0; i < folio_batch_count(&fbatch); i++) {
1001 			folio = fbatch.folios[i];
1002 
1003 			if (xa_is_value(folio)) {
1004 				if (unfalloc)
1005 					continue;
1006 				nr_swaps_freed += !shmem_free_swap(mapping,
1007 							indices[i], folio);
1008 				continue;
1009 			}
1010 
1011 			if (!unfalloc || !folio_test_uptodate(folio))
1012 				truncate_inode_folio(mapping, folio);
1013 			folio_unlock(folio);
1014 		}
1015 		folio_batch_remove_exceptionals(&fbatch);
1016 		folio_batch_release(&fbatch);
1017 		cond_resched();
1018 	}
1019 
1020 	/*
1021 	 * When undoing a failed fallocate, we want none of the partial folio
1022 	 * zeroing and splitting below, but shall want to truncate the whole
1023 	 * folio when !uptodate indicates that it was added by this fallocate,
1024 	 * even when [lstart, lend] covers only a part of the folio.
1025 	 */
1026 	if (unfalloc)
1027 		goto whole_folios;
1028 
1029 	same_folio = (lstart >> PAGE_SHIFT) == (lend >> PAGE_SHIFT);
1030 	folio = shmem_get_partial_folio(inode, lstart >> PAGE_SHIFT);
1031 	if (folio) {
1032 		same_folio = lend < folio_pos(folio) + folio_size(folio);
1033 		folio_mark_dirty(folio);
1034 		if (!truncate_inode_partial_folio(folio, lstart, lend)) {
1035 			start = folio_next_index(folio);
1036 			if (same_folio)
1037 				end = folio->index;
1038 		}
1039 		folio_unlock(folio);
1040 		folio_put(folio);
1041 		folio = NULL;
1042 	}
1043 
1044 	if (!same_folio)
1045 		folio = shmem_get_partial_folio(inode, lend >> PAGE_SHIFT);
1046 	if (folio) {
1047 		folio_mark_dirty(folio);
1048 		if (!truncate_inode_partial_folio(folio, lstart, lend))
1049 			end = folio->index;
1050 		folio_unlock(folio);
1051 		folio_put(folio);
1052 	}
1053 
1054 whole_folios:
1055 
1056 	index = start;
1057 	while (index < end) {
1058 		cond_resched();
1059 
1060 		if (!find_get_entries(mapping, &index, end - 1, &fbatch,
1061 				indices)) {
1062 			/* If all gone or hole-punch or unfalloc, we're done */
1063 			if (index == start || end != -1)
1064 				break;
1065 			/* But if truncating, restart to make sure all gone */
1066 			index = start;
1067 			continue;
1068 		}
1069 		for (i = 0; i < folio_batch_count(&fbatch); i++) {
1070 			folio = fbatch.folios[i];
1071 
1072 			if (xa_is_value(folio)) {
1073 				if (unfalloc)
1074 					continue;
1075 				if (shmem_free_swap(mapping, indices[i], folio)) {
1076 					/* Swap was replaced by page: retry */
1077 					index = indices[i];
1078 					break;
1079 				}
1080 				nr_swaps_freed++;
1081 				continue;
1082 			}
1083 
1084 			folio_lock(folio);
1085 
1086 			if (!unfalloc || !folio_test_uptodate(folio)) {
1087 				if (folio_mapping(folio) != mapping) {
1088 					/* Page was replaced by swap: retry */
1089 					folio_unlock(folio);
1090 					index = indices[i];
1091 					break;
1092 				}
1093 				VM_BUG_ON_FOLIO(folio_test_writeback(folio),
1094 						folio);
1095 
1096 				if (!folio_test_large(folio)) {
1097 					truncate_inode_folio(mapping, folio);
1098 				} else if (truncate_inode_partial_folio(folio, lstart, lend)) {
1099 					/*
1100 					 * If we split a page, reset the loop so
1101 					 * that we pick up the new sub pages.
1102 					 * Otherwise the THP was entirely
1103 					 * dropped or the target range was
1104 					 * zeroed, so just continue the loop as
1105 					 * is.
1106 					 */
1107 					if (!folio_test_large(folio)) {
1108 						folio_unlock(folio);
1109 						index = start;
1110 						break;
1111 					}
1112 				}
1113 			}
1114 			folio_unlock(folio);
1115 		}
1116 		folio_batch_remove_exceptionals(&fbatch);
1117 		folio_batch_release(&fbatch);
1118 	}
1119 
1120 	shmem_recalc_inode(inode, 0, -nr_swaps_freed);
1121 }
1122 
1123 void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
1124 {
1125 	shmem_undo_range(inode, lstart, lend, false);
1126 	inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode));
1127 	inode_inc_iversion(inode);
1128 }
1129 EXPORT_SYMBOL_GPL(shmem_truncate_range);
1130 
1131 static int shmem_getattr(struct mnt_idmap *idmap,
1132 			 const struct path *path, struct kstat *stat,
1133 			 u32 request_mask, unsigned int query_flags)
1134 {
1135 	struct inode *inode = path->dentry->d_inode;
1136 	struct shmem_inode_info *info = SHMEM_I(inode);
1137 
1138 	if (info->alloced - info->swapped != inode->i_mapping->nrpages)
1139 		shmem_recalc_inode(inode, 0, 0);
1140 
1141 	if (info->fsflags & FS_APPEND_FL)
1142 		stat->attributes |= STATX_ATTR_APPEND;
1143 	if (info->fsflags & FS_IMMUTABLE_FL)
1144 		stat->attributes |= STATX_ATTR_IMMUTABLE;
1145 	if (info->fsflags & FS_NODUMP_FL)
1146 		stat->attributes |= STATX_ATTR_NODUMP;
1147 	stat->attributes_mask |= (STATX_ATTR_APPEND |
1148 			STATX_ATTR_IMMUTABLE |
1149 			STATX_ATTR_NODUMP);
1150 	generic_fillattr(idmap, request_mask, inode, stat);
1151 
1152 	if (shmem_is_huge(inode, 0, false, NULL, 0))
1153 		stat->blksize = HPAGE_PMD_SIZE;
1154 
1155 	if (request_mask & STATX_BTIME) {
1156 		stat->result_mask |= STATX_BTIME;
1157 		stat->btime.tv_sec = info->i_crtime.tv_sec;
1158 		stat->btime.tv_nsec = info->i_crtime.tv_nsec;
1159 	}
1160 
1161 	return 0;
1162 }
1163 
1164 static int shmem_setattr(struct mnt_idmap *idmap,
1165 			 struct dentry *dentry, struct iattr *attr)
1166 {
1167 	struct inode *inode = d_inode(dentry);
1168 	struct shmem_inode_info *info = SHMEM_I(inode);
1169 	int error;
1170 	bool update_mtime = false;
1171 	bool update_ctime = true;
1172 
1173 	error = setattr_prepare(idmap, dentry, attr);
1174 	if (error)
1175 		return error;
1176 
1177 	if ((info->seals & F_SEAL_EXEC) && (attr->ia_valid & ATTR_MODE)) {
1178 		if ((inode->i_mode ^ attr->ia_mode) & 0111) {
1179 			return -EPERM;
1180 		}
1181 	}
1182 
1183 	if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
1184 		loff_t oldsize = inode->i_size;
1185 		loff_t newsize = attr->ia_size;
1186 
1187 		/* protected by i_rwsem */
1188 		if ((newsize < oldsize && (info->seals & F_SEAL_SHRINK)) ||
1189 		    (newsize > oldsize && (info->seals & F_SEAL_GROW)))
1190 			return -EPERM;
1191 
1192 		if (newsize != oldsize) {
1193 			error = shmem_reacct_size(SHMEM_I(inode)->flags,
1194 					oldsize, newsize);
1195 			if (error)
1196 				return error;
1197 			i_size_write(inode, newsize);
1198 			update_mtime = true;
1199 		} else {
1200 			update_ctime = false;
1201 		}
1202 		if (newsize <= oldsize) {
1203 			loff_t holebegin = round_up(newsize, PAGE_SIZE);
1204 			if (oldsize > holebegin)
1205 				unmap_mapping_range(inode->i_mapping,
1206 							holebegin, 0, 1);
1207 			if (info->alloced)
1208 				shmem_truncate_range(inode,
1209 							newsize, (loff_t)-1);
1210 			/* unmap again to remove racily COWed private pages */
1211 			if (oldsize > holebegin)
1212 				unmap_mapping_range(inode->i_mapping,
1213 							holebegin, 0, 1);
1214 		}
1215 	}
1216 
1217 	if (is_quota_modification(idmap, inode, attr)) {
1218 		error = dquot_initialize(inode);
1219 		if (error)
1220 			return error;
1221 	}
1222 
1223 	/* Transfer quota accounting */
1224 	if (i_uid_needs_update(idmap, attr, inode) ||
1225 	    i_gid_needs_update(idmap, attr, inode)) {
1226 		error = dquot_transfer(idmap, inode, attr);
1227 		if (error)
1228 			return error;
1229 	}
1230 
1231 	setattr_copy(idmap, inode, attr);
1232 	if (attr->ia_valid & ATTR_MODE)
1233 		error = posix_acl_chmod(idmap, dentry, inode->i_mode);
1234 	if (!error && update_ctime) {
1235 		inode_set_ctime_current(inode);
1236 		if (update_mtime)
1237 			inode_set_mtime_to_ts(inode, inode_get_ctime(inode));
1238 		inode_inc_iversion(inode);
1239 	}
1240 	return error;
1241 }
1242 
1243 static void shmem_evict_inode(struct inode *inode)
1244 {
1245 	struct shmem_inode_info *info = SHMEM_I(inode);
1246 	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
1247 	size_t freed = 0;
1248 
1249 	if (shmem_mapping(inode->i_mapping)) {
1250 		shmem_unacct_size(info->flags, inode->i_size);
1251 		inode->i_size = 0;
1252 		mapping_set_exiting(inode->i_mapping);
1253 		shmem_truncate_range(inode, 0, (loff_t)-1);
1254 		if (!list_empty(&info->shrinklist)) {
1255 			spin_lock(&sbinfo->shrinklist_lock);
1256 			if (!list_empty(&info->shrinklist)) {
1257 				list_del_init(&info->shrinklist);
1258 				sbinfo->shrinklist_len--;
1259 			}
1260 			spin_unlock(&sbinfo->shrinklist_lock);
1261 		}
1262 		while (!list_empty(&info->swaplist)) {
1263 			/* Wait while shmem_unuse() is scanning this inode... */
1264 			wait_var_event(&info->stop_eviction,
1265 				       !atomic_read(&info->stop_eviction));
1266 			mutex_lock(&shmem_swaplist_mutex);
1267 			/* ...but beware of the race if we peeked too early */
1268 			if (!atomic_read(&info->stop_eviction))
1269 				list_del_init(&info->swaplist);
1270 			mutex_unlock(&shmem_swaplist_mutex);
1271 		}
1272 	}
1273 
1274 	simple_xattrs_free(&info->xattrs, sbinfo->max_inodes ? &freed : NULL);
1275 	shmem_free_inode(inode->i_sb, freed);
1276 	WARN_ON(inode->i_blocks);
1277 	clear_inode(inode);
1278 #ifdef CONFIG_TMPFS_QUOTA
1279 	dquot_free_inode(inode);
1280 	dquot_drop(inode);
1281 #endif
1282 }
1283 
1284 static int shmem_find_swap_entries(struct address_space *mapping,
1285 				   pgoff_t start, struct folio_batch *fbatch,
1286 				   pgoff_t *indices, unsigned int type)
1287 {
1288 	XA_STATE(xas, &mapping->i_pages, start);
1289 	struct folio *folio;
1290 	swp_entry_t entry;
1291 
1292 	rcu_read_lock();
1293 	xas_for_each(&xas, folio, ULONG_MAX) {
1294 		if (xas_retry(&xas, folio))
1295 			continue;
1296 
1297 		if (!xa_is_value(folio))
1298 			continue;
1299 
1300 		entry = radix_to_swp_entry(folio);
1301 		/*
1302 		 * swapin error entries can be found in the mapping. But they're
1303 		 * deliberately ignored here as we've done everything we can do.
1304 		 */
1305 		if (swp_type(entry) != type)
1306 			continue;
1307 
1308 		indices[folio_batch_count(fbatch)] = xas.xa_index;
1309 		if (!folio_batch_add(fbatch, folio))
1310 			break;
1311 
1312 		if (need_resched()) {
1313 			xas_pause(&xas);
1314 			cond_resched_rcu();
1315 		}
1316 	}
1317 	rcu_read_unlock();
1318 
1319 	return xas.xa_index;
1320 }
1321 
1322 /*
1323  * Move the swapped pages for an inode to page cache. Returns the count
1324  * of pages swapped in, or the error in case of failure.
1325  */
1326 static int shmem_unuse_swap_entries(struct inode *inode,
1327 		struct folio_batch *fbatch, pgoff_t *indices)
1328 {
1329 	int i = 0;
1330 	int ret = 0;
1331 	int error = 0;
1332 	struct address_space *mapping = inode->i_mapping;
1333 
1334 	for (i = 0; i < folio_batch_count(fbatch); i++) {
1335 		struct folio *folio = fbatch->folios[i];
1336 
1337 		if (!xa_is_value(folio))
1338 			continue;
1339 		error = shmem_swapin_folio(inode, indices[i], &folio, SGP_CACHE,
1340 					mapping_gfp_mask(mapping), NULL, NULL);
1341 		if (error == 0) {
1342 			folio_unlock(folio);
1343 			folio_put(folio);
1344 			ret++;
1345 		}
1346 		if (error == -ENOMEM)
1347 			break;
1348 		error = 0;
1349 	}
1350 	return error ? error : ret;
1351 }
1352 
1353 /*
1354  * If swap found in inode, free it and move page from swapcache to filecache.
1355  */
1356 static int shmem_unuse_inode(struct inode *inode, unsigned int type)
1357 {
1358 	struct address_space *mapping = inode->i_mapping;
1359 	pgoff_t start = 0;
1360 	struct folio_batch fbatch;
1361 	pgoff_t indices[PAGEVEC_SIZE];
1362 	int ret = 0;
1363 
1364 	do {
1365 		folio_batch_init(&fbatch);
1366 		shmem_find_swap_entries(mapping, start, &fbatch, indices, type);
1367 		if (folio_batch_count(&fbatch) == 0) {
1368 			ret = 0;
1369 			break;
1370 		}
1371 
1372 		ret = shmem_unuse_swap_entries(inode, &fbatch, indices);
1373 		if (ret < 0)
1374 			break;
1375 
1376 		start = indices[folio_batch_count(&fbatch) - 1];
1377 	} while (true);
1378 
1379 	return ret;
1380 }
1381 
1382 /*
1383  * Read all the shared memory data that resides in the swap
1384  * device 'type' back into memory, so the swap device can be
1385  * unused.
1386  */
1387 int shmem_unuse(unsigned int type)
1388 {
1389 	struct shmem_inode_info *info, *next;
1390 	int error = 0;
1391 
1392 	if (list_empty(&shmem_swaplist))
1393 		return 0;
1394 
1395 	mutex_lock(&shmem_swaplist_mutex);
1396 	list_for_each_entry_safe(info, next, &shmem_swaplist, swaplist) {
1397 		if (!info->swapped) {
1398 			list_del_init(&info->swaplist);
1399 			continue;
1400 		}
1401 		/*
1402 		 * Drop the swaplist mutex while searching the inode for swap;
1403 		 * but before doing so, make sure shmem_evict_inode() will not
1404 		 * remove placeholder inode from swaplist, nor let it be freed
1405 		 * (igrab() would protect from unlink, but not from unmount).
1406 		 */
1407 		atomic_inc(&info->stop_eviction);
1408 		mutex_unlock(&shmem_swaplist_mutex);
1409 
1410 		error = shmem_unuse_inode(&info->vfs_inode, type);
1411 		cond_resched();
1412 
1413 		mutex_lock(&shmem_swaplist_mutex);
1414 		next = list_next_entry(info, swaplist);
1415 		if (!info->swapped)
1416 			list_del_init(&info->swaplist);
1417 		if (atomic_dec_and_test(&info->stop_eviction))
1418 			wake_up_var(&info->stop_eviction);
1419 		if (error)
1420 			break;
1421 	}
1422 	mutex_unlock(&shmem_swaplist_mutex);
1423 
1424 	return error;
1425 }
1426 
1427 /*
1428  * Move the page from the page cache to the swap cache.
1429  */
1430 static int shmem_writepage(struct page *page, struct writeback_control *wbc)
1431 {
1432 	struct folio *folio = page_folio(page);
1433 	struct address_space *mapping = folio->mapping;
1434 	struct inode *inode = mapping->host;
1435 	struct shmem_inode_info *info = SHMEM_I(inode);
1436 	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
1437 	swp_entry_t swap;
1438 	pgoff_t index;
1439 
1440 	/*
1441 	 * Our capabilities prevent regular writeback or sync from ever calling
1442 	 * shmem_writepage; but a stacking filesystem might use ->writepage of
1443 	 * its underlying filesystem, in which case tmpfs should write out to
1444 	 * swap only in response to memory pressure, and not for the writeback
1445 	 * threads or sync.
1446 	 */
1447 	if (WARN_ON_ONCE(!wbc->for_reclaim))
1448 		goto redirty;
1449 
1450 	if (WARN_ON_ONCE((info->flags & VM_LOCKED) || sbinfo->noswap))
1451 		goto redirty;
1452 
1453 	if (!total_swap_pages)
1454 		goto redirty;
1455 
1456 	/*
1457 	 * If /sys/kernel/mm/transparent_hugepage/shmem_enabled is "always" or
1458 	 * "force", drivers/gpu/drm/i915/gem/i915_gem_shmem.c gets huge pages,
1459 	 * and its shmem_writeback() needs them to be split when swapping.
1460 	 */
1461 	if (folio_test_large(folio)) {
1462 		/* Ensure the subpages are still dirty */
1463 		folio_test_set_dirty(folio);
1464 		if (split_huge_page(page) < 0)
1465 			goto redirty;
1466 		folio = page_folio(page);
1467 		folio_clear_dirty(folio);
1468 	}
1469 
1470 	index = folio->index;
1471 
1472 	/*
1473 	 * This is somewhat ridiculous, but without plumbing a SWAP_MAP_FALLOC
1474 	 * value into swapfile.c, the only way we can correctly account for a
1475 	 * fallocated folio arriving here is now to initialize it and write it.
1476 	 *
1477 	 * That's okay for a folio already fallocated earlier, but if we have
1478 	 * not yet completed the fallocation, then (a) we want to keep track
1479 	 * of this folio in case we have to undo it, and (b) it may not be a
1480 	 * good idea to continue anyway, once we're pushing into swap.  So
1481 	 * reactivate the folio, and let shmem_fallocate() quit when too many.
1482 	 */
1483 	if (!folio_test_uptodate(folio)) {
1484 		if (inode->i_private) {
1485 			struct shmem_falloc *shmem_falloc;
1486 			spin_lock(&inode->i_lock);
1487 			shmem_falloc = inode->i_private;
1488 			if (shmem_falloc &&
1489 			    !shmem_falloc->waitq &&
1490 			    index >= shmem_falloc->start &&
1491 			    index < shmem_falloc->next)
1492 				shmem_falloc->nr_unswapped++;
1493 			else
1494 				shmem_falloc = NULL;
1495 			spin_unlock(&inode->i_lock);
1496 			if (shmem_falloc)
1497 				goto redirty;
1498 		}
1499 		folio_zero_range(folio, 0, folio_size(folio));
1500 		flush_dcache_folio(folio);
1501 		folio_mark_uptodate(folio);
1502 	}
1503 
1504 	swap = folio_alloc_swap(folio);
1505 	if (!swap.val)
1506 		goto redirty;
1507 
1508 	/*
1509 	 * Add inode to shmem_unuse()'s list of swapped-out inodes,
1510 	 * if it's not already there.  Do it now before the folio is
1511 	 * moved to swap cache, when its pagelock no longer protects
1512 	 * the inode from eviction.  But don't unlock the mutex until
1513 	 * we've incremented swapped, because shmem_unuse_inode() will
1514 	 * prune a !swapped inode from the swaplist under this mutex.
1515 	 */
1516 	mutex_lock(&shmem_swaplist_mutex);
1517 	if (list_empty(&info->swaplist))
1518 		list_add(&info->swaplist, &shmem_swaplist);
1519 
1520 	if (add_to_swap_cache(folio, swap,
1521 			__GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN,
1522 			NULL) == 0) {
1523 		shmem_recalc_inode(inode, 0, 1);
1524 		swap_shmem_alloc(swap);
1525 		shmem_delete_from_page_cache(folio, swp_to_radix_entry(swap));
1526 
1527 		mutex_unlock(&shmem_swaplist_mutex);
1528 		BUG_ON(folio_mapped(folio));
1529 		return swap_writepage(&folio->page, wbc);
1530 	}
1531 
1532 	mutex_unlock(&shmem_swaplist_mutex);
1533 	put_swap_folio(folio, swap);
1534 redirty:
1535 	folio_mark_dirty(folio);
1536 	if (wbc->for_reclaim)
1537 		return AOP_WRITEPAGE_ACTIVATE;	/* Return with folio locked */
1538 	folio_unlock(folio);
1539 	return 0;
1540 }
1541 
1542 #if defined(CONFIG_NUMA) && defined(CONFIG_TMPFS)
1543 static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
1544 {
1545 	char buffer[64];
1546 
1547 	if (!mpol || mpol->mode == MPOL_DEFAULT)
1548 		return;		/* show nothing */
1549 
1550 	mpol_to_str(buffer, sizeof(buffer), mpol);
1551 
1552 	seq_printf(seq, ",mpol=%s", buffer);
1553 }
1554 
1555 static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
1556 {
1557 	struct mempolicy *mpol = NULL;
1558 	if (sbinfo->mpol) {
1559 		raw_spin_lock(&sbinfo->stat_lock);	/* prevent replace/use races */
1560 		mpol = sbinfo->mpol;
1561 		mpol_get(mpol);
1562 		raw_spin_unlock(&sbinfo->stat_lock);
1563 	}
1564 	return mpol;
1565 }
1566 #else /* !CONFIG_NUMA || !CONFIG_TMPFS */
1567 static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
1568 {
1569 }
1570 static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
1571 {
1572 	return NULL;
1573 }
1574 #endif /* CONFIG_NUMA && CONFIG_TMPFS */
1575 
1576 static struct mempolicy *shmem_get_pgoff_policy(struct shmem_inode_info *info,
1577 			pgoff_t index, unsigned int order, pgoff_t *ilx);
1578 
1579 static struct folio *shmem_swapin_cluster(swp_entry_t swap, gfp_t gfp,
1580 			struct shmem_inode_info *info, pgoff_t index)
1581 {
1582 	struct mempolicy *mpol;
1583 	pgoff_t ilx;
1584 	struct folio *folio;
1585 
1586 	mpol = shmem_get_pgoff_policy(info, index, 0, &ilx);
1587 	folio = swap_cluster_readahead(swap, gfp, mpol, ilx);
1588 	mpol_cond_put(mpol);
1589 
1590 	return folio;
1591 }
1592 
1593 /*
1594  * Make sure huge_gfp is always more limited than limit_gfp.
1595  * Some of the flags set permissions, while others set limitations.
1596  */
1597 static gfp_t limit_gfp_mask(gfp_t huge_gfp, gfp_t limit_gfp)
1598 {
1599 	gfp_t allowflags = __GFP_IO | __GFP_FS | __GFP_RECLAIM;
1600 	gfp_t denyflags = __GFP_NOWARN | __GFP_NORETRY;
1601 	gfp_t zoneflags = limit_gfp & GFP_ZONEMASK;
1602 	gfp_t result = huge_gfp & ~(allowflags | GFP_ZONEMASK);
1603 
1604 	/* Allow allocations only from the originally specified zones. */
1605 	result |= zoneflags;
1606 
1607 	/*
1608 	 * Minimize the result gfp by taking the union with the deny flags,
1609 	 * and the intersection of the allow flags.
1610 	 */
1611 	result |= (limit_gfp & denyflags);
1612 	result |= (huge_gfp & limit_gfp) & allowflags;
1613 
1614 	return result;
1615 }
1616 
1617 static struct folio *shmem_alloc_hugefolio(gfp_t gfp,
1618 		struct shmem_inode_info *info, pgoff_t index)
1619 {
1620 	struct mempolicy *mpol;
1621 	pgoff_t ilx;
1622 	struct page *page;
1623 
1624 	mpol = shmem_get_pgoff_policy(info, index, HPAGE_PMD_ORDER, &ilx);
1625 	page = alloc_pages_mpol(gfp, HPAGE_PMD_ORDER, mpol, ilx, numa_node_id());
1626 	mpol_cond_put(mpol);
1627 
1628 	return page_rmappable_folio(page);
1629 }
1630 
1631 static struct folio *shmem_alloc_folio(gfp_t gfp,
1632 		struct shmem_inode_info *info, pgoff_t index)
1633 {
1634 	struct mempolicy *mpol;
1635 	pgoff_t ilx;
1636 	struct page *page;
1637 
1638 	mpol = shmem_get_pgoff_policy(info, index, 0, &ilx);
1639 	page = alloc_pages_mpol(gfp, 0, mpol, ilx, numa_node_id());
1640 	mpol_cond_put(mpol);
1641 
1642 	return (struct folio *)page;
1643 }
1644 
1645 static struct folio *shmem_alloc_and_add_folio(gfp_t gfp,
1646 		struct inode *inode, pgoff_t index,
1647 		struct mm_struct *fault_mm, bool huge)
1648 {
1649 	struct address_space *mapping = inode->i_mapping;
1650 	struct shmem_inode_info *info = SHMEM_I(inode);
1651 	struct folio *folio;
1652 	long pages;
1653 	int error;
1654 
1655 	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
1656 		huge = false;
1657 
1658 	if (huge) {
1659 		pages = HPAGE_PMD_NR;
1660 		index = round_down(index, HPAGE_PMD_NR);
1661 
1662 		/*
1663 		 * Check for conflict before waiting on a huge allocation.
1664 		 * Conflict might be that a huge page has just been allocated
1665 		 * and added to page cache by a racing thread, or that there
1666 		 * is already at least one small page in the huge extent.
1667 		 * Be careful to retry when appropriate, but not forever!
1668 		 * Elsewhere -EEXIST would be the right code, but not here.
1669 		 */
1670 		if (xa_find(&mapping->i_pages, &index,
1671 				index + HPAGE_PMD_NR - 1, XA_PRESENT))
1672 			return ERR_PTR(-E2BIG);
1673 
1674 		folio = shmem_alloc_hugefolio(gfp, info, index);
1675 		if (!folio)
1676 			count_vm_event(THP_FILE_FALLBACK);
1677 	} else {
1678 		pages = 1;
1679 		folio = shmem_alloc_folio(gfp, info, index);
1680 	}
1681 	if (!folio)
1682 		return ERR_PTR(-ENOMEM);
1683 
1684 	__folio_set_locked(folio);
1685 	__folio_set_swapbacked(folio);
1686 
1687 	gfp &= GFP_RECLAIM_MASK;
1688 	error = mem_cgroup_charge(folio, fault_mm, gfp);
1689 	if (error) {
1690 		if (xa_find(&mapping->i_pages, &index,
1691 				index + pages - 1, XA_PRESENT)) {
1692 			error = -EEXIST;
1693 		} else if (huge) {
1694 			count_vm_event(THP_FILE_FALLBACK);
1695 			count_vm_event(THP_FILE_FALLBACK_CHARGE);
1696 		}
1697 		goto unlock;
1698 	}
1699 
1700 	error = shmem_add_to_page_cache(folio, mapping, index, NULL, gfp);
1701 	if (error)
1702 		goto unlock;
1703 
1704 	error = shmem_inode_acct_blocks(inode, pages);
1705 	if (error) {
1706 		struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
1707 		long freed;
1708 		/*
1709 		 * Try to reclaim some space by splitting a few
1710 		 * large folios beyond i_size on the filesystem.
1711 		 */
1712 		shmem_unused_huge_shrink(sbinfo, NULL, 2);
1713 		/*
1714 		 * And do a shmem_recalc_inode() to account for freed pages:
1715 		 * except our folio is there in cache, so not quite balanced.
1716 		 */
1717 		spin_lock(&info->lock);
1718 		freed = pages + info->alloced - info->swapped -
1719 			READ_ONCE(mapping->nrpages);
1720 		if (freed > 0)
1721 			info->alloced -= freed;
1722 		spin_unlock(&info->lock);
1723 		if (freed > 0)
1724 			shmem_inode_unacct_blocks(inode, freed);
1725 		error = shmem_inode_acct_blocks(inode, pages);
1726 		if (error) {
1727 			filemap_remove_folio(folio);
1728 			goto unlock;
1729 		}
1730 	}
1731 
1732 	shmem_recalc_inode(inode, pages, 0);
1733 	folio_add_lru(folio);
1734 	return folio;
1735 
1736 unlock:
1737 	folio_unlock(folio);
1738 	folio_put(folio);
1739 	return ERR_PTR(error);
1740 }
1741 
1742 /*
1743  * When a page is moved from swapcache to shmem filecache (either by the
1744  * usual swapin of shmem_get_folio_gfp(), or by the less common swapoff of
1745  * shmem_unuse_inode()), it may have been read in earlier from swap, in
1746  * ignorance of the mapping it belongs to.  If that mapping has special
1747  * constraints (like the gma500 GEM driver, which requires RAM below 4GB),
1748  * we may need to copy to a suitable page before moving to filecache.
1749  *
1750  * In a future release, this may well be extended to respect cpuset and
1751  * NUMA mempolicy, and applied also to anonymous pages in do_swap_page();
1752  * but for now it is a simple matter of zone.
1753  */
1754 static bool shmem_should_replace_folio(struct folio *folio, gfp_t gfp)
1755 {
1756 	return folio_zonenum(folio) > gfp_zone(gfp);
1757 }
1758 
1759 static int shmem_replace_folio(struct folio **foliop, gfp_t gfp,
1760 				struct shmem_inode_info *info, pgoff_t index)
1761 {
1762 	struct folio *old, *new;
1763 	struct address_space *swap_mapping;
1764 	swp_entry_t entry;
1765 	pgoff_t swap_index;
1766 	int error;
1767 
1768 	old = *foliop;
1769 	entry = old->swap;
1770 	swap_index = swp_offset(entry);
1771 	swap_mapping = swap_address_space(entry);
1772 
1773 	/*
1774 	 * We have arrived here because our zones are constrained, so don't
1775 	 * limit chance of success by further cpuset and node constraints.
1776 	 */
1777 	gfp &= ~GFP_CONSTRAINT_MASK;
1778 	VM_BUG_ON_FOLIO(folio_test_large(old), old);
1779 	new = shmem_alloc_folio(gfp, info, index);
1780 	if (!new)
1781 		return -ENOMEM;
1782 
1783 	folio_get(new);
1784 	folio_copy(new, old);
1785 	flush_dcache_folio(new);
1786 
1787 	__folio_set_locked(new);
1788 	__folio_set_swapbacked(new);
1789 	folio_mark_uptodate(new);
1790 	new->swap = entry;
1791 	folio_set_swapcache(new);
1792 
1793 	/*
1794 	 * Our caller will very soon move newpage out of swapcache, but it's
1795 	 * a nice clean interface for us to replace oldpage by newpage there.
1796 	 */
1797 	xa_lock_irq(&swap_mapping->i_pages);
1798 	error = shmem_replace_entry(swap_mapping, swap_index, old, new);
1799 	if (!error) {
1800 		mem_cgroup_replace_folio(old, new);
1801 		__lruvec_stat_mod_folio(new, NR_FILE_PAGES, 1);
1802 		__lruvec_stat_mod_folio(new, NR_SHMEM, 1);
1803 		__lruvec_stat_mod_folio(old, NR_FILE_PAGES, -1);
1804 		__lruvec_stat_mod_folio(old, NR_SHMEM, -1);
1805 	}
1806 	xa_unlock_irq(&swap_mapping->i_pages);
1807 
1808 	if (unlikely(error)) {
1809 		/*
1810 		 * Is this possible?  I think not, now that our callers check
1811 		 * both PageSwapCache and page_private after getting page lock;
1812 		 * but be defensive.  Reverse old to newpage for clear and free.
1813 		 */
1814 		old = new;
1815 	} else {
1816 		folio_add_lru(new);
1817 		*foliop = new;
1818 	}
1819 
1820 	folio_clear_swapcache(old);
1821 	old->private = NULL;
1822 
1823 	folio_unlock(old);
1824 	folio_put_refs(old, 2);
1825 	return error;
1826 }
1827 
1828 static void shmem_set_folio_swapin_error(struct inode *inode, pgoff_t index,
1829 					 struct folio *folio, swp_entry_t swap)
1830 {
1831 	struct address_space *mapping = inode->i_mapping;
1832 	swp_entry_t swapin_error;
1833 	void *old;
1834 
1835 	swapin_error = make_poisoned_swp_entry();
1836 	old = xa_cmpxchg_irq(&mapping->i_pages, index,
1837 			     swp_to_radix_entry(swap),
1838 			     swp_to_radix_entry(swapin_error), 0);
1839 	if (old != swp_to_radix_entry(swap))
1840 		return;
1841 
1842 	folio_wait_writeback(folio);
1843 	delete_from_swap_cache(folio);
1844 	/*
1845 	 * Don't treat swapin error folio as alloced. Otherwise inode->i_blocks
1846 	 * won't be 0 when inode is released and thus trigger WARN_ON(i_blocks)
1847 	 * in shmem_evict_inode().
1848 	 */
1849 	shmem_recalc_inode(inode, -1, -1);
1850 	swap_free(swap);
1851 }
1852 
1853 /*
1854  * Swap in the folio pointed to by *foliop.
1855  * Caller has to make sure that *foliop contains a valid swapped folio.
1856  * Returns 0 and the folio in foliop if success. On failure, returns the
1857  * error code and NULL in *foliop.
1858  */
1859 static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
1860 			     struct folio **foliop, enum sgp_type sgp,
1861 			     gfp_t gfp, struct mm_struct *fault_mm,
1862 			     vm_fault_t *fault_type)
1863 {
1864 	struct address_space *mapping = inode->i_mapping;
1865 	struct shmem_inode_info *info = SHMEM_I(inode);
1866 	struct swap_info_struct *si;
1867 	struct folio *folio = NULL;
1868 	swp_entry_t swap;
1869 	int error;
1870 
1871 	VM_BUG_ON(!*foliop || !xa_is_value(*foliop));
1872 	swap = radix_to_swp_entry(*foliop);
1873 	*foliop = NULL;
1874 
1875 	if (is_poisoned_swp_entry(swap))
1876 		return -EIO;
1877 
1878 	si = get_swap_device(swap);
1879 	if (!si) {
1880 		if (!shmem_confirm_swap(mapping, index, swap))
1881 			return -EEXIST;
1882 		else
1883 			return -EINVAL;
1884 	}
1885 
1886 	/* Look it up and read it in.. */
1887 	folio = swap_cache_get_folio(swap, NULL, 0);
1888 	if (!folio) {
1889 		/* Or update major stats only when swapin succeeds?? */
1890 		if (fault_type) {
1891 			*fault_type |= VM_FAULT_MAJOR;
1892 			count_vm_event(PGMAJFAULT);
1893 			count_memcg_event_mm(fault_mm, PGMAJFAULT);
1894 		}
1895 		/* Here we actually start the io */
1896 		folio = shmem_swapin_cluster(swap, gfp, info, index);
1897 		if (!folio) {
1898 			error = -ENOMEM;
1899 			goto failed;
1900 		}
1901 	}
1902 
1903 	/* We have to do this with folio locked to prevent races */
1904 	folio_lock(folio);
1905 	if (!folio_test_swapcache(folio) ||
1906 	    folio->swap.val != swap.val ||
1907 	    !shmem_confirm_swap(mapping, index, swap)) {
1908 		error = -EEXIST;
1909 		goto unlock;
1910 	}
1911 	if (!folio_test_uptodate(folio)) {
1912 		error = -EIO;
1913 		goto failed;
1914 	}
1915 	folio_wait_writeback(folio);
1916 
1917 	/*
1918 	 * Some architectures may have to restore extra metadata to the
1919 	 * folio after reading from swap.
1920 	 */
1921 	arch_swap_restore(folio_swap(swap, folio), folio);
1922 
1923 	if (shmem_should_replace_folio(folio, gfp)) {
1924 		error = shmem_replace_folio(&folio, gfp, info, index);
1925 		if (error)
1926 			goto failed;
1927 	}
1928 
1929 	error = shmem_add_to_page_cache(folio, mapping, index,
1930 					swp_to_radix_entry(swap), gfp);
1931 	if (error)
1932 		goto failed;
1933 
1934 	shmem_recalc_inode(inode, 0, -1);
1935 
1936 	if (sgp == SGP_WRITE)
1937 		folio_mark_accessed(folio);
1938 
1939 	delete_from_swap_cache(folio);
1940 	folio_mark_dirty(folio);
1941 	swap_free(swap);
1942 	put_swap_device(si);
1943 
1944 	*foliop = folio;
1945 	return 0;
1946 failed:
1947 	if (!shmem_confirm_swap(mapping, index, swap))
1948 		error = -EEXIST;
1949 	if (error == -EIO)
1950 		shmem_set_folio_swapin_error(inode, index, folio, swap);
1951 unlock:
1952 	if (folio) {
1953 		folio_unlock(folio);
1954 		folio_put(folio);
1955 	}
1956 	put_swap_device(si);
1957 
1958 	return error;
1959 }
1960 
1961 /*
1962  * shmem_get_folio_gfp - find page in cache, or get from swap, or allocate
1963  *
1964  * If we allocate a new one we do not mark it dirty. That's up to the
1965  * vm. If we swap it in we mark it dirty since we also free the swap
1966  * entry since a page cannot live in both the swap and page cache.
1967  *
1968  * vmf and fault_type are only supplied by shmem_fault: otherwise they are NULL.
1969  */
1970 static int shmem_get_folio_gfp(struct inode *inode, pgoff_t index,
1971 		struct folio **foliop, enum sgp_type sgp, gfp_t gfp,
1972 		struct vm_fault *vmf, vm_fault_t *fault_type)
1973 {
1974 	struct vm_area_struct *vma = vmf ? vmf->vma : NULL;
1975 	struct mm_struct *fault_mm;
1976 	struct folio *folio;
1977 	int error;
1978 	bool alloced;
1979 
1980 	if (WARN_ON_ONCE(!shmem_mapping(inode->i_mapping)))
1981 		return -EINVAL;
1982 
1983 	if (index > (MAX_LFS_FILESIZE >> PAGE_SHIFT))
1984 		return -EFBIG;
1985 repeat:
1986 	if (sgp <= SGP_CACHE &&
1987 	    ((loff_t)index << PAGE_SHIFT) >= i_size_read(inode))
1988 		return -EINVAL;
1989 
1990 	alloced = false;
1991 	fault_mm = vma ? vma->vm_mm : NULL;
1992 
1993 	folio = filemap_get_entry(inode->i_mapping, index);
1994 	if (folio && vma && userfaultfd_minor(vma)) {
1995 		if (!xa_is_value(folio))
1996 			folio_put(folio);
1997 		*fault_type = handle_userfault(vmf, VM_UFFD_MINOR);
1998 		return 0;
1999 	}
2000 
2001 	if (xa_is_value(folio)) {
2002 		error = shmem_swapin_folio(inode, index, &folio,
2003 					   sgp, gfp, fault_mm, fault_type);
2004 		if (error == -EEXIST)
2005 			goto repeat;
2006 
2007 		*foliop = folio;
2008 		return error;
2009 	}
2010 
2011 	if (folio) {
2012 		folio_lock(folio);
2013 
2014 		/* Has the folio been truncated or swapped out? */
2015 		if (unlikely(folio->mapping != inode->i_mapping)) {
2016 			folio_unlock(folio);
2017 			folio_put(folio);
2018 			goto repeat;
2019 		}
2020 		if (sgp == SGP_WRITE)
2021 			folio_mark_accessed(folio);
2022 		if (folio_test_uptodate(folio))
2023 			goto out;
2024 		/* fallocated folio */
2025 		if (sgp != SGP_READ)
2026 			goto clear;
2027 		folio_unlock(folio);
2028 		folio_put(folio);
2029 	}
2030 
2031 	/*
2032 	 * SGP_READ: succeed on hole, with NULL folio, letting caller zero.
2033 	 * SGP_NOALLOC: fail on hole, with NULL folio, letting caller fail.
2034 	 */
2035 	*foliop = NULL;
2036 	if (sgp == SGP_READ)
2037 		return 0;
2038 	if (sgp == SGP_NOALLOC)
2039 		return -ENOENT;
2040 
2041 	/*
2042 	 * Fast cache lookup and swap lookup did not find it: allocate.
2043 	 */
2044 
2045 	if (vma && userfaultfd_missing(vma)) {
2046 		*fault_type = handle_userfault(vmf, VM_UFFD_MISSING);
2047 		return 0;
2048 	}
2049 
2050 	if (shmem_is_huge(inode, index, false, fault_mm,
2051 			  vma ? vma->vm_flags : 0)) {
2052 		gfp_t huge_gfp;
2053 
2054 		huge_gfp = vma_thp_gfp_mask(vma);
2055 		huge_gfp = limit_gfp_mask(huge_gfp, gfp);
2056 		folio = shmem_alloc_and_add_folio(huge_gfp,
2057 				inode, index, fault_mm, true);
2058 		if (!IS_ERR(folio)) {
2059 			count_vm_event(THP_FILE_ALLOC);
2060 			goto alloced;
2061 		}
2062 		if (PTR_ERR(folio) == -EEXIST)
2063 			goto repeat;
2064 	}
2065 
2066 	folio = shmem_alloc_and_add_folio(gfp, inode, index, fault_mm, false);
2067 	if (IS_ERR(folio)) {
2068 		error = PTR_ERR(folio);
2069 		if (error == -EEXIST)
2070 			goto repeat;
2071 		folio = NULL;
2072 		goto unlock;
2073 	}
2074 
2075 alloced:
2076 	alloced = true;
2077 	if (folio_test_pmd_mappable(folio) &&
2078 	    DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE) <
2079 					folio_next_index(folio) - 1) {
2080 		struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
2081 		struct shmem_inode_info *info = SHMEM_I(inode);
2082 		/*
2083 		 * Part of the large folio is beyond i_size: subject
2084 		 * to shrink under memory pressure.
2085 		 */
2086 		spin_lock(&sbinfo->shrinklist_lock);
2087 		/*
2088 		 * _careful to defend against unlocked access to
2089 		 * ->shrink_list in shmem_unused_huge_shrink()
2090 		 */
2091 		if (list_empty_careful(&info->shrinklist)) {
2092 			list_add_tail(&info->shrinklist,
2093 				      &sbinfo->shrinklist);
2094 			sbinfo->shrinklist_len++;
2095 		}
2096 		spin_unlock(&sbinfo->shrinklist_lock);
2097 	}
2098 
2099 	if (sgp == SGP_WRITE)
2100 		folio_set_referenced(folio);
2101 	/*
2102 	 * Let SGP_FALLOC use the SGP_WRITE optimization on a new folio.
2103 	 */
2104 	if (sgp == SGP_FALLOC)
2105 		sgp = SGP_WRITE;
2106 clear:
2107 	/*
2108 	 * Let SGP_WRITE caller clear ends if write does not fill folio;
2109 	 * but SGP_FALLOC on a folio fallocated earlier must initialize
2110 	 * it now, lest undo on failure cancel our earlier guarantee.
2111 	 */
2112 	if (sgp != SGP_WRITE && !folio_test_uptodate(folio)) {
2113 		long i, n = folio_nr_pages(folio);
2114 
2115 		for (i = 0; i < n; i++)
2116 			clear_highpage(folio_page(folio, i));
2117 		flush_dcache_folio(folio);
2118 		folio_mark_uptodate(folio);
2119 	}
2120 
2121 	/* Perhaps the file has been truncated since we checked */
2122 	if (sgp <= SGP_CACHE &&
2123 	    ((loff_t)index << PAGE_SHIFT) >= i_size_read(inode)) {
2124 		error = -EINVAL;
2125 		goto unlock;
2126 	}
2127 out:
2128 	*foliop = folio;
2129 	return 0;
2130 
2131 	/*
2132 	 * Error recovery.
2133 	 */
2134 unlock:
2135 	if (alloced)
2136 		filemap_remove_folio(folio);
2137 	shmem_recalc_inode(inode, 0, 0);
2138 	if (folio) {
2139 		folio_unlock(folio);
2140 		folio_put(folio);
2141 	}
2142 	return error;
2143 }
2144 
2145 /**
2146  * shmem_get_folio - find, and lock a shmem folio.
2147  * @inode:	inode to search
2148  * @index:	the page index.
2149  * @foliop:	pointer to the folio if found
2150  * @sgp:	SGP_* flags to control behavior
2151  *
2152  * Looks up the page cache entry at @inode & @index.  If a folio is
2153  * present, it is returned locked with an increased refcount.
2154  *
2155  * If the caller modifies data in the folio, it must call folio_mark_dirty()
2156  * before unlocking the folio to ensure that the folio is not reclaimed.
2157  * There is no need to reserve space before calling folio_mark_dirty().
2158  *
2159  * When no folio is found, the behavior depends on @sgp:
2160  *  - for SGP_READ, *@foliop is %NULL and 0 is returned
2161  *  - for SGP_NOALLOC, *@foliop is %NULL and -ENOENT is returned
2162  *  - for all other flags a new folio is allocated, inserted into the
2163  *    page cache and returned locked in @foliop.
2164  *
2165  * Context: May sleep.
2166  * Return: 0 if successful, else a negative error code.
2167  */
2168 int shmem_get_folio(struct inode *inode, pgoff_t index, struct folio **foliop,
2169 		enum sgp_type sgp)
2170 {
2171 	return shmem_get_folio_gfp(inode, index, foliop, sgp,
2172 			mapping_gfp_mask(inode->i_mapping), NULL, NULL);
2173 }
2174 EXPORT_SYMBOL_GPL(shmem_get_folio);
2175 
2176 /*
2177  * This is like autoremove_wake_function, but it removes the wait queue
2178  * entry unconditionally - even if something else had already woken the
2179  * target.
2180  */
2181 static int synchronous_wake_function(wait_queue_entry_t *wait,
2182 			unsigned int mode, int sync, void *key)
2183 {
2184 	int ret = default_wake_function(wait, mode, sync, key);
2185 	list_del_init(&wait->entry);
2186 	return ret;
2187 }
2188 
2189 /*
2190  * Trinity finds that probing a hole which tmpfs is punching can
2191  * prevent the hole-punch from ever completing: which in turn
2192  * locks writers out with its hold on i_rwsem.  So refrain from
2193  * faulting pages into the hole while it's being punched.  Although
2194  * shmem_undo_range() does remove the additions, it may be unable to
2195  * keep up, as each new page needs its own unmap_mapping_range() call,
2196  * and the i_mmap tree grows ever slower to scan if new vmas are added.
2197  *
2198  * It does not matter if we sometimes reach this check just before the
2199  * hole-punch begins, so that one fault then races with the punch:
2200  * we just need to make racing faults a rare case.
2201  *
2202  * The implementation below would be much simpler if we just used a
2203  * standard mutex or completion: but we cannot take i_rwsem in fault,
2204  * and bloating every shmem inode for this unlikely case would be sad.
2205  */
2206 static vm_fault_t shmem_falloc_wait(struct vm_fault *vmf, struct inode *inode)
2207 {
2208 	struct shmem_falloc *shmem_falloc;
2209 	struct file *fpin = NULL;
2210 	vm_fault_t ret = 0;
2211 
2212 	spin_lock(&inode->i_lock);
2213 	shmem_falloc = inode->i_private;
2214 	if (shmem_falloc &&
2215 	    shmem_falloc->waitq &&
2216 	    vmf->pgoff >= shmem_falloc->start &&
2217 	    vmf->pgoff < shmem_falloc->next) {
2218 		wait_queue_head_t *shmem_falloc_waitq;
2219 		DEFINE_WAIT_FUNC(shmem_fault_wait, synchronous_wake_function);
2220 
2221 		ret = VM_FAULT_NOPAGE;
2222 		fpin = maybe_unlock_mmap_for_io(vmf, NULL);
2223 		shmem_falloc_waitq = shmem_falloc->waitq;
2224 		prepare_to_wait(shmem_falloc_waitq, &shmem_fault_wait,
2225 				TASK_UNINTERRUPTIBLE);
2226 		spin_unlock(&inode->i_lock);
2227 		schedule();
2228 
2229 		/*
2230 		 * shmem_falloc_waitq points into the shmem_fallocate()
2231 		 * stack of the hole-punching task: shmem_falloc_waitq
2232 		 * is usually invalid by the time we reach here, but
2233 		 * finish_wait() does not dereference it in that case;
2234 		 * though i_lock needed lest racing with wake_up_all().
2235 		 */
2236 		spin_lock(&inode->i_lock);
2237 		finish_wait(shmem_falloc_waitq, &shmem_fault_wait);
2238 	}
2239 	spin_unlock(&inode->i_lock);
2240 	if (fpin) {
2241 		fput(fpin);
2242 		ret = VM_FAULT_RETRY;
2243 	}
2244 	return ret;
2245 }
2246 
2247 static vm_fault_t shmem_fault(struct vm_fault *vmf)
2248 {
2249 	struct inode *inode = file_inode(vmf->vma->vm_file);
2250 	gfp_t gfp = mapping_gfp_mask(inode->i_mapping);
2251 	struct folio *folio = NULL;
2252 	vm_fault_t ret = 0;
2253 	int err;
2254 
2255 	/*
2256 	 * Trinity finds that probing a hole which tmpfs is punching can
2257 	 * prevent the hole-punch from ever completing: noted in i_private.
2258 	 */
2259 	if (unlikely(inode->i_private)) {
2260 		ret = shmem_falloc_wait(vmf, inode);
2261 		if (ret)
2262 			return ret;
2263 	}
2264 
2265 	WARN_ON_ONCE(vmf->page != NULL);
2266 	err = shmem_get_folio_gfp(inode, vmf->pgoff, &folio, SGP_CACHE,
2267 				  gfp, vmf, &ret);
2268 	if (err)
2269 		return vmf_error(err);
2270 	if (folio) {
2271 		vmf->page = folio_file_page(folio, vmf->pgoff);
2272 		ret |= VM_FAULT_LOCKED;
2273 	}
2274 	return ret;
2275 }
2276 
2277 unsigned long shmem_get_unmapped_area(struct file *file,
2278 				      unsigned long uaddr, unsigned long len,
2279 				      unsigned long pgoff, unsigned long flags)
2280 {
2281 	unsigned long addr;
2282 	unsigned long offset;
2283 	unsigned long inflated_len;
2284 	unsigned long inflated_addr;
2285 	unsigned long inflated_offset;
2286 
2287 	if (len > TASK_SIZE)
2288 		return -ENOMEM;
2289 
2290 	addr = mm_get_unmapped_area(current->mm, file, uaddr, len, pgoff,
2291 				    flags);
2292 
2293 	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
2294 		return addr;
2295 	if (IS_ERR_VALUE(addr))
2296 		return addr;
2297 	if (addr & ~PAGE_MASK)
2298 		return addr;
2299 	if (addr > TASK_SIZE - len)
2300 		return addr;
2301 
2302 	if (shmem_huge == SHMEM_HUGE_DENY)
2303 		return addr;
2304 	if (len < HPAGE_PMD_SIZE)
2305 		return addr;
2306 	if (flags & MAP_FIXED)
2307 		return addr;
2308 	/*
2309 	 * Our priority is to support MAP_SHARED mapped hugely;
2310 	 * and support MAP_PRIVATE mapped hugely too, until it is COWed.
2311 	 * But if caller specified an address hint and we allocated area there
2312 	 * successfully, respect that as before.
2313 	 */
2314 	if (uaddr == addr)
2315 		return addr;
2316 
2317 	if (shmem_huge != SHMEM_HUGE_FORCE) {
2318 		struct super_block *sb;
2319 
2320 		if (file) {
2321 			VM_BUG_ON(file->f_op != &shmem_file_operations);
2322 			sb = file_inode(file)->i_sb;
2323 		} else {
2324 			/*
2325 			 * Called directly from mm/mmap.c, or drivers/char/mem.c
2326 			 * for "/dev/zero", to create a shared anonymous object.
2327 			 */
2328 			if (IS_ERR(shm_mnt))
2329 				return addr;
2330 			sb = shm_mnt->mnt_sb;
2331 		}
2332 		if (SHMEM_SB(sb)->huge == SHMEM_HUGE_NEVER)
2333 			return addr;
2334 	}
2335 
2336 	offset = (pgoff << PAGE_SHIFT) & (HPAGE_PMD_SIZE-1);
2337 	if (offset && offset + len < 2 * HPAGE_PMD_SIZE)
2338 		return addr;
2339 	if ((addr & (HPAGE_PMD_SIZE-1)) == offset)
2340 		return addr;
2341 
2342 	inflated_len = len + HPAGE_PMD_SIZE - PAGE_SIZE;
2343 	if (inflated_len > TASK_SIZE)
2344 		return addr;
2345 	if (inflated_len < len)
2346 		return addr;
2347 
2348 	inflated_addr = mm_get_unmapped_area(current->mm, NULL, uaddr,
2349 					     inflated_len, 0, flags);
2350 	if (IS_ERR_VALUE(inflated_addr))
2351 		return addr;
2352 	if (inflated_addr & ~PAGE_MASK)
2353 		return addr;
2354 
2355 	inflated_offset = inflated_addr & (HPAGE_PMD_SIZE-1);
2356 	inflated_addr += offset - inflated_offset;
2357 	if (inflated_offset > offset)
2358 		inflated_addr += HPAGE_PMD_SIZE;
2359 
2360 	if (inflated_addr > TASK_SIZE - len)
2361 		return addr;
2362 	return inflated_addr;
2363 }
2364 
2365 #ifdef CONFIG_NUMA
2366 static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *mpol)
2367 {
2368 	struct inode *inode = file_inode(vma->vm_file);
2369 	return mpol_set_shared_policy(&SHMEM_I(inode)->policy, vma, mpol);
2370 }
2371 
2372 static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
2373 					  unsigned long addr, pgoff_t *ilx)
2374 {
2375 	struct inode *inode = file_inode(vma->vm_file);
2376 	pgoff_t index;
2377 
2378 	/*
2379 	 * Bias interleave by inode number to distribute better across nodes;
2380 	 * but this interface is independent of which page order is used, so
2381 	 * supplies only that bias, letting caller apply the offset (adjusted
2382 	 * by page order, as in shmem_get_pgoff_policy() and get_vma_policy()).
2383 	 */
2384 	*ilx = inode->i_ino;
2385 	index = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
2386 	return mpol_shared_policy_lookup(&SHMEM_I(inode)->policy, index);
2387 }
2388 
2389 static struct mempolicy *shmem_get_pgoff_policy(struct shmem_inode_info *info,
2390 			pgoff_t index, unsigned int order, pgoff_t *ilx)
2391 {
2392 	struct mempolicy *mpol;
2393 
2394 	/* Bias interleave by inode number to distribute better across nodes */
2395 	*ilx = info->vfs_inode.i_ino + (index >> order);
2396 
2397 	mpol = mpol_shared_policy_lookup(&info->policy, index);
2398 	return mpol ? mpol : get_task_policy(current);
2399 }
2400 #else
2401 static struct mempolicy *shmem_get_pgoff_policy(struct shmem_inode_info *info,
2402 			pgoff_t index, unsigned int order, pgoff_t *ilx)
2403 {
2404 	*ilx = 0;
2405 	return NULL;
2406 }
2407 #endif /* CONFIG_NUMA */
2408 
2409 int shmem_lock(struct file *file, int lock, struct ucounts *ucounts)
2410 {
2411 	struct inode *inode = file_inode(file);
2412 	struct shmem_inode_info *info = SHMEM_I(inode);
2413 	int retval = -ENOMEM;
2414 
2415 	/*
2416 	 * What serializes the accesses to info->flags?
2417 	 * ipc_lock_object() when called from shmctl_do_lock(),
2418 	 * no serialization needed when called from shm_destroy().
2419 	 */
2420 	if (lock && !(info->flags & VM_LOCKED)) {
2421 		if (!user_shm_lock(inode->i_size, ucounts))
2422 			goto out_nomem;
2423 		info->flags |= VM_LOCKED;
2424 		mapping_set_unevictable(file->f_mapping);
2425 	}
2426 	if (!lock && (info->flags & VM_LOCKED) && ucounts) {
2427 		user_shm_unlock(inode->i_size, ucounts);
2428 		info->flags &= ~VM_LOCKED;
2429 		mapping_clear_unevictable(file->f_mapping);
2430 	}
2431 	retval = 0;
2432 
2433 out_nomem:
2434 	return retval;
2435 }
2436 
2437 static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
2438 {
2439 	struct inode *inode = file_inode(file);
2440 	struct shmem_inode_info *info = SHMEM_I(inode);
2441 	int ret;
2442 
2443 	ret = seal_check_write(info->seals, vma);
2444 	if (ret)
2445 		return ret;
2446 
2447 	/* arm64 - allow memory tagging on RAM-based files */
2448 	vm_flags_set(vma, VM_MTE_ALLOWED);
2449 
2450 	file_accessed(file);
2451 	/* This is anonymous shared memory if it is unlinked at the time of mmap */
2452 	if (inode->i_nlink)
2453 		vma->vm_ops = &shmem_vm_ops;
2454 	else
2455 		vma->vm_ops = &shmem_anon_vm_ops;
2456 	return 0;
2457 }
2458 
2459 static int shmem_file_open(struct inode *inode, struct file *file)
2460 {
2461 	file->f_mode |= FMODE_CAN_ODIRECT;
2462 	return generic_file_open(inode, file);
2463 }
2464 
2465 #ifdef CONFIG_TMPFS_XATTR
2466 static int shmem_initxattrs(struct inode *, const struct xattr *, void *);
2467 
2468 /*
2469  * chattr's fsflags are unrelated to extended attributes,
2470  * but tmpfs has chosen to enable them under the same config option.
2471  */
2472 static void shmem_set_inode_flags(struct inode *inode, unsigned int fsflags)
2473 {
2474 	unsigned int i_flags = 0;
2475 
2476 	if (fsflags & FS_NOATIME_FL)
2477 		i_flags |= S_NOATIME;
2478 	if (fsflags & FS_APPEND_FL)
2479 		i_flags |= S_APPEND;
2480 	if (fsflags & FS_IMMUTABLE_FL)
2481 		i_flags |= S_IMMUTABLE;
2482 	/*
2483 	 * But FS_NODUMP_FL does not require any action in i_flags.
2484 	 */
2485 	inode_set_flags(inode, i_flags, S_NOATIME | S_APPEND | S_IMMUTABLE);
2486 }
2487 #else
2488 static void shmem_set_inode_flags(struct inode *inode, unsigned int fsflags)
2489 {
2490 }
2491 #define shmem_initxattrs NULL
2492 #endif
2493 
2494 static struct offset_ctx *shmem_get_offset_ctx(struct inode *inode)
2495 {
2496 	return &SHMEM_I(inode)->dir_offsets;
2497 }
2498 
2499 static struct inode *__shmem_get_inode(struct mnt_idmap *idmap,
2500 					     struct super_block *sb,
2501 					     struct inode *dir, umode_t mode,
2502 					     dev_t dev, unsigned long flags)
2503 {
2504 	struct inode *inode;
2505 	struct shmem_inode_info *info;
2506 	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2507 	ino_t ino;
2508 	int err;
2509 
2510 	err = shmem_reserve_inode(sb, &ino);
2511 	if (err)
2512 		return ERR_PTR(err);
2513 
2514 	inode = new_inode(sb);
2515 	if (!inode) {
2516 		shmem_free_inode(sb, 0);
2517 		return ERR_PTR(-ENOSPC);
2518 	}
2519 
2520 	inode->i_ino = ino;
2521 	inode_init_owner(idmap, inode, dir, mode);
2522 	inode->i_blocks = 0;
2523 	simple_inode_init_ts(inode);
2524 	inode->i_generation = get_random_u32();
2525 	info = SHMEM_I(inode);
2526 	memset(info, 0, (char *)inode - (char *)info);
2527 	spin_lock_init(&info->lock);
2528 	atomic_set(&info->stop_eviction, 0);
2529 	info->seals = F_SEAL_SEAL;
2530 	info->flags = flags & VM_NORESERVE;
2531 	info->i_crtime = inode_get_mtime(inode);
2532 	info->fsflags = (dir == NULL) ? 0 :
2533 		SHMEM_I(dir)->fsflags & SHMEM_FL_INHERITED;
2534 	if (info->fsflags)
2535 		shmem_set_inode_flags(inode, info->fsflags);
2536 	INIT_LIST_HEAD(&info->shrinklist);
2537 	INIT_LIST_HEAD(&info->swaplist);
2538 	simple_xattrs_init(&info->xattrs);
2539 	cache_no_acl(inode);
2540 	if (sbinfo->noswap)
2541 		mapping_set_unevictable(inode->i_mapping);
2542 	mapping_set_large_folios(inode->i_mapping);
2543 
2544 	switch (mode & S_IFMT) {
2545 	default:
2546 		inode->i_op = &shmem_special_inode_operations;
2547 		init_special_inode(inode, mode, dev);
2548 		break;
2549 	case S_IFREG:
2550 		inode->i_mapping->a_ops = &shmem_aops;
2551 		inode->i_op = &shmem_inode_operations;
2552 		inode->i_fop = &shmem_file_operations;
2553 		mpol_shared_policy_init(&info->policy,
2554 					 shmem_get_sbmpol(sbinfo));
2555 		break;
2556 	case S_IFDIR:
2557 		inc_nlink(inode);
2558 		/* Some things misbehave if size == 0 on a directory */
2559 		inode->i_size = 2 * BOGO_DIRENT_SIZE;
2560 		inode->i_op = &shmem_dir_inode_operations;
2561 		inode->i_fop = &simple_offset_dir_operations;
2562 		simple_offset_init(shmem_get_offset_ctx(inode));
2563 		break;
2564 	case S_IFLNK:
2565 		/*
2566 		 * Must not load anything in the rbtree,
2567 		 * mpol_free_shared_policy will not be called.
2568 		 */
2569 		mpol_shared_policy_init(&info->policy, NULL);
2570 		break;
2571 	}
2572 
2573 	lockdep_annotate_inode_mutex_key(inode);
2574 	return inode;
2575 }
2576 
2577 #ifdef CONFIG_TMPFS_QUOTA
2578 static struct inode *shmem_get_inode(struct mnt_idmap *idmap,
2579 				     struct super_block *sb, struct inode *dir,
2580 				     umode_t mode, dev_t dev, unsigned long flags)
2581 {
2582 	int err;
2583 	struct inode *inode;
2584 
2585 	inode = __shmem_get_inode(idmap, sb, dir, mode, dev, flags);
2586 	if (IS_ERR(inode))
2587 		return inode;
2588 
2589 	err = dquot_initialize(inode);
2590 	if (err)
2591 		goto errout;
2592 
2593 	err = dquot_alloc_inode(inode);
2594 	if (err) {
2595 		dquot_drop(inode);
2596 		goto errout;
2597 	}
2598 	return inode;
2599 
2600 errout:
2601 	inode->i_flags |= S_NOQUOTA;
2602 	iput(inode);
2603 	return ERR_PTR(err);
2604 }
2605 #else
2606 static inline struct inode *shmem_get_inode(struct mnt_idmap *idmap,
2607 				     struct super_block *sb, struct inode *dir,
2608 				     umode_t mode, dev_t dev, unsigned long flags)
2609 {
2610 	return __shmem_get_inode(idmap, sb, dir, mode, dev, flags);
2611 }
2612 #endif /* CONFIG_TMPFS_QUOTA */
2613 
2614 #ifdef CONFIG_USERFAULTFD
2615 int shmem_mfill_atomic_pte(pmd_t *dst_pmd,
2616 			   struct vm_area_struct *dst_vma,
2617 			   unsigned long dst_addr,
2618 			   unsigned long src_addr,
2619 			   uffd_flags_t flags,
2620 			   struct folio **foliop)
2621 {
2622 	struct inode *inode = file_inode(dst_vma->vm_file);
2623 	struct shmem_inode_info *info = SHMEM_I(inode);
2624 	struct address_space *mapping = inode->i_mapping;
2625 	gfp_t gfp = mapping_gfp_mask(mapping);
2626 	pgoff_t pgoff = linear_page_index(dst_vma, dst_addr);
2627 	void *page_kaddr;
2628 	struct folio *folio;
2629 	int ret;
2630 	pgoff_t max_off;
2631 
2632 	if (shmem_inode_acct_blocks(inode, 1)) {
2633 		/*
2634 		 * We may have got a page, returned -ENOENT triggering a retry,
2635 		 * and now we find ourselves with -ENOMEM. Release the page, to
2636 		 * avoid a BUG_ON in our caller.
2637 		 */
2638 		if (unlikely(*foliop)) {
2639 			folio_put(*foliop);
2640 			*foliop = NULL;
2641 		}
2642 		return -ENOMEM;
2643 	}
2644 
2645 	if (!*foliop) {
2646 		ret = -ENOMEM;
2647 		folio = shmem_alloc_folio(gfp, info, pgoff);
2648 		if (!folio)
2649 			goto out_unacct_blocks;
2650 
2651 		if (uffd_flags_mode_is(flags, MFILL_ATOMIC_COPY)) {
2652 			page_kaddr = kmap_local_folio(folio, 0);
2653 			/*
2654 			 * The read mmap_lock is held here.  Despite the
2655 			 * mmap_lock being read recursive a deadlock is still
2656 			 * possible if a writer has taken a lock.  For example:
2657 			 *
2658 			 * process A thread 1 takes read lock on own mmap_lock
2659 			 * process A thread 2 calls mmap, blocks taking write lock
2660 			 * process B thread 1 takes page fault, read lock on own mmap lock
2661 			 * process B thread 2 calls mmap, blocks taking write lock
2662 			 * process A thread 1 blocks taking read lock on process B
2663 			 * process B thread 1 blocks taking read lock on process A
2664 			 *
2665 			 * Disable page faults to prevent potential deadlock
2666 			 * and retry the copy outside the mmap_lock.
2667 			 */
2668 			pagefault_disable();
2669 			ret = copy_from_user(page_kaddr,
2670 					     (const void __user *)src_addr,
2671 					     PAGE_SIZE);
2672 			pagefault_enable();
2673 			kunmap_local(page_kaddr);
2674 
2675 			/* fallback to copy_from_user outside mmap_lock */
2676 			if (unlikely(ret)) {
2677 				*foliop = folio;
2678 				ret = -ENOENT;
2679 				/* don't free the page */
2680 				goto out_unacct_blocks;
2681 			}
2682 
2683 			flush_dcache_folio(folio);
2684 		} else {		/* ZEROPAGE */
2685 			clear_user_highpage(&folio->page, dst_addr);
2686 		}
2687 	} else {
2688 		folio = *foliop;
2689 		VM_BUG_ON_FOLIO(folio_test_large(folio), folio);
2690 		*foliop = NULL;
2691 	}
2692 
2693 	VM_BUG_ON(folio_test_locked(folio));
2694 	VM_BUG_ON(folio_test_swapbacked(folio));
2695 	__folio_set_locked(folio);
2696 	__folio_set_swapbacked(folio);
2697 	__folio_mark_uptodate(folio);
2698 
2699 	ret = -EFAULT;
2700 	max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
2701 	if (unlikely(pgoff >= max_off))
2702 		goto out_release;
2703 
2704 	ret = mem_cgroup_charge(folio, dst_vma->vm_mm, gfp);
2705 	if (ret)
2706 		goto out_release;
2707 	ret = shmem_add_to_page_cache(folio, mapping, pgoff, NULL, gfp);
2708 	if (ret)
2709 		goto out_release;
2710 
2711 	ret = mfill_atomic_install_pte(dst_pmd, dst_vma, dst_addr,
2712 				       &folio->page, true, flags);
2713 	if (ret)
2714 		goto out_delete_from_cache;
2715 
2716 	shmem_recalc_inode(inode, 1, 0);
2717 	folio_unlock(folio);
2718 	return 0;
2719 out_delete_from_cache:
2720 	filemap_remove_folio(folio);
2721 out_release:
2722 	folio_unlock(folio);
2723 	folio_put(folio);
2724 out_unacct_blocks:
2725 	shmem_inode_unacct_blocks(inode, 1);
2726 	return ret;
2727 }
2728 #endif /* CONFIG_USERFAULTFD */
2729 
2730 #ifdef CONFIG_TMPFS
2731 static const struct inode_operations shmem_symlink_inode_operations;
2732 static const struct inode_operations shmem_short_symlink_operations;
2733 
2734 static int
2735 shmem_write_begin(struct file *file, struct address_space *mapping,
2736 			loff_t pos, unsigned len,
2737 			struct page **pagep, void **fsdata)
2738 {
2739 	struct inode *inode = mapping->host;
2740 	struct shmem_inode_info *info = SHMEM_I(inode);
2741 	pgoff_t index = pos >> PAGE_SHIFT;
2742 	struct folio *folio;
2743 	int ret = 0;
2744 
2745 	/* i_rwsem is held by caller */
2746 	if (unlikely(info->seals & (F_SEAL_GROW |
2747 				   F_SEAL_WRITE | F_SEAL_FUTURE_WRITE))) {
2748 		if (info->seals & (F_SEAL_WRITE | F_SEAL_FUTURE_WRITE))
2749 			return -EPERM;
2750 		if ((info->seals & F_SEAL_GROW) && pos + len > inode->i_size)
2751 			return -EPERM;
2752 	}
2753 
2754 	ret = shmem_get_folio(inode, index, &folio, SGP_WRITE);
2755 	if (ret)
2756 		return ret;
2757 
2758 	*pagep = folio_file_page(folio, index);
2759 	if (PageHWPoison(*pagep)) {
2760 		folio_unlock(folio);
2761 		folio_put(folio);
2762 		*pagep = NULL;
2763 		return -EIO;
2764 	}
2765 
2766 	return 0;
2767 }
2768 
2769 static int
2770 shmem_write_end(struct file *file, struct address_space *mapping,
2771 			loff_t pos, unsigned len, unsigned copied,
2772 			struct page *page, void *fsdata)
2773 {
2774 	struct folio *folio = page_folio(page);
2775 	struct inode *inode = mapping->host;
2776 
2777 	if (pos + copied > inode->i_size)
2778 		i_size_write(inode, pos + copied);
2779 
2780 	if (!folio_test_uptodate(folio)) {
2781 		if (copied < folio_size(folio)) {
2782 			size_t from = offset_in_folio(folio, pos);
2783 			folio_zero_segments(folio, 0, from,
2784 					from + copied, folio_size(folio));
2785 		}
2786 		folio_mark_uptodate(folio);
2787 	}
2788 	folio_mark_dirty(folio);
2789 	folio_unlock(folio);
2790 	folio_put(folio);
2791 
2792 	return copied;
2793 }
2794 
2795 static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
2796 {
2797 	struct file *file = iocb->ki_filp;
2798 	struct inode *inode = file_inode(file);
2799 	struct address_space *mapping = inode->i_mapping;
2800 	pgoff_t index;
2801 	unsigned long offset;
2802 	int error = 0;
2803 	ssize_t retval = 0;
2804 	loff_t *ppos = &iocb->ki_pos;
2805 
2806 	index = *ppos >> PAGE_SHIFT;
2807 	offset = *ppos & ~PAGE_MASK;
2808 
2809 	for (;;) {
2810 		struct folio *folio = NULL;
2811 		struct page *page = NULL;
2812 		pgoff_t end_index;
2813 		unsigned long nr, ret;
2814 		loff_t i_size = i_size_read(inode);
2815 
2816 		end_index = i_size >> PAGE_SHIFT;
2817 		if (index > end_index)
2818 			break;
2819 		if (index == end_index) {
2820 			nr = i_size & ~PAGE_MASK;
2821 			if (nr <= offset)
2822 				break;
2823 		}
2824 
2825 		error = shmem_get_folio(inode, index, &folio, SGP_READ);
2826 		if (error) {
2827 			if (error == -EINVAL)
2828 				error = 0;
2829 			break;
2830 		}
2831 		if (folio) {
2832 			folio_unlock(folio);
2833 
2834 			page = folio_file_page(folio, index);
2835 			if (PageHWPoison(page)) {
2836 				folio_put(folio);
2837 				error = -EIO;
2838 				break;
2839 			}
2840 		}
2841 
2842 		/*
2843 		 * We must evaluate after, since reads (unlike writes)
2844 		 * are called without i_rwsem protection against truncate
2845 		 */
2846 		nr = PAGE_SIZE;
2847 		i_size = i_size_read(inode);
2848 		end_index = i_size >> PAGE_SHIFT;
2849 		if (index == end_index) {
2850 			nr = i_size & ~PAGE_MASK;
2851 			if (nr <= offset) {
2852 				if (folio)
2853 					folio_put(folio);
2854 				break;
2855 			}
2856 		}
2857 		nr -= offset;
2858 
2859 		if (folio) {
2860 			/*
2861 			 * If users can be writing to this page using arbitrary
2862 			 * virtual addresses, take care about potential aliasing
2863 			 * before reading the page on the kernel side.
2864 			 */
2865 			if (mapping_writably_mapped(mapping))
2866 				flush_dcache_page(page);
2867 			/*
2868 			 * Mark the page accessed if we read the beginning.
2869 			 */
2870 			if (!offset)
2871 				folio_mark_accessed(folio);
2872 			/*
2873 			 * Ok, we have the page, and it's up-to-date, so
2874 			 * now we can copy it to user space...
2875 			 */
2876 			ret = copy_page_to_iter(page, offset, nr, to);
2877 			folio_put(folio);
2878 
2879 		} else if (user_backed_iter(to)) {
2880 			/*
2881 			 * Copy to user tends to be so well optimized, but
2882 			 * clear_user() not so much, that it is noticeably
2883 			 * faster to copy the zero page instead of clearing.
2884 			 */
2885 			ret = copy_page_to_iter(ZERO_PAGE(0), offset, nr, to);
2886 		} else {
2887 			/*
2888 			 * But submitting the same page twice in a row to
2889 			 * splice() - or others? - can result in confusion:
2890 			 * so don't attempt that optimization on pipes etc.
2891 			 */
2892 			ret = iov_iter_zero(nr, to);
2893 		}
2894 
2895 		retval += ret;
2896 		offset += ret;
2897 		index += offset >> PAGE_SHIFT;
2898 		offset &= ~PAGE_MASK;
2899 
2900 		if (!iov_iter_count(to))
2901 			break;
2902 		if (ret < nr) {
2903 			error = -EFAULT;
2904 			break;
2905 		}
2906 		cond_resched();
2907 	}
2908 
2909 	*ppos = ((loff_t) index << PAGE_SHIFT) + offset;
2910 	file_accessed(file);
2911 	return retval ? retval : error;
2912 }
2913 
2914 static ssize_t shmem_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
2915 {
2916 	struct file *file = iocb->ki_filp;
2917 	struct inode *inode = file->f_mapping->host;
2918 	ssize_t ret;
2919 
2920 	inode_lock(inode);
2921 	ret = generic_write_checks(iocb, from);
2922 	if (ret <= 0)
2923 		goto unlock;
2924 	ret = file_remove_privs(file);
2925 	if (ret)
2926 		goto unlock;
2927 	ret = file_update_time(file);
2928 	if (ret)
2929 		goto unlock;
2930 	ret = generic_perform_write(iocb, from);
2931 unlock:
2932 	inode_unlock(inode);
2933 	return ret;
2934 }
2935 
2936 static bool zero_pipe_buf_get(struct pipe_inode_info *pipe,
2937 			      struct pipe_buffer *buf)
2938 {
2939 	return true;
2940 }
2941 
2942 static void zero_pipe_buf_release(struct pipe_inode_info *pipe,
2943 				  struct pipe_buffer *buf)
2944 {
2945 }
2946 
2947 static bool zero_pipe_buf_try_steal(struct pipe_inode_info *pipe,
2948 				    struct pipe_buffer *buf)
2949 {
2950 	return false;
2951 }
2952 
2953 static const struct pipe_buf_operations zero_pipe_buf_ops = {
2954 	.release	= zero_pipe_buf_release,
2955 	.try_steal	= zero_pipe_buf_try_steal,
2956 	.get		= zero_pipe_buf_get,
2957 };
2958 
2959 static size_t splice_zeropage_into_pipe(struct pipe_inode_info *pipe,
2960 					loff_t fpos, size_t size)
2961 {
2962 	size_t offset = fpos & ~PAGE_MASK;
2963 
2964 	size = min_t(size_t, size, PAGE_SIZE - offset);
2965 
2966 	if (!pipe_full(pipe->head, pipe->tail, pipe->max_usage)) {
2967 		struct pipe_buffer *buf = pipe_head_buf(pipe);
2968 
2969 		*buf = (struct pipe_buffer) {
2970 			.ops	= &zero_pipe_buf_ops,
2971 			.page	= ZERO_PAGE(0),
2972 			.offset	= offset,
2973 			.len	= size,
2974 		};
2975 		pipe->head++;
2976 	}
2977 
2978 	return size;
2979 }
2980 
2981 static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos,
2982 				      struct pipe_inode_info *pipe,
2983 				      size_t len, unsigned int flags)
2984 {
2985 	struct inode *inode = file_inode(in);
2986 	struct address_space *mapping = inode->i_mapping;
2987 	struct folio *folio = NULL;
2988 	size_t total_spliced = 0, used, npages, n, part;
2989 	loff_t isize;
2990 	int error = 0;
2991 
2992 	/* Work out how much data we can actually add into the pipe */
2993 	used = pipe_occupancy(pipe->head, pipe->tail);
2994 	npages = max_t(ssize_t, pipe->max_usage - used, 0);
2995 	len = min_t(size_t, len, npages * PAGE_SIZE);
2996 
2997 	do {
2998 		if (*ppos >= i_size_read(inode))
2999 			break;
3000 
3001 		error = shmem_get_folio(inode, *ppos / PAGE_SIZE, &folio,
3002 					SGP_READ);
3003 		if (error) {
3004 			if (error == -EINVAL)
3005 				error = 0;
3006 			break;
3007 		}
3008 		if (folio) {
3009 			folio_unlock(folio);
3010 
3011 			if (folio_test_hwpoison(folio) ||
3012 			    (folio_test_large(folio) &&
3013 			     folio_test_has_hwpoisoned(folio))) {
3014 				error = -EIO;
3015 				break;
3016 			}
3017 		}
3018 
3019 		/*
3020 		 * i_size must be checked after we know the pages are Uptodate.
3021 		 *
3022 		 * Checking i_size after the check allows us to calculate
3023 		 * the correct value for "nr", which means the zero-filled
3024 		 * part of the page is not copied back to userspace (unless
3025 		 * another truncate extends the file - this is desired though).
3026 		 */
3027 		isize = i_size_read(inode);
3028 		if (unlikely(*ppos >= isize))
3029 			break;
3030 		part = min_t(loff_t, isize - *ppos, len);
3031 
3032 		if (folio) {
3033 			/*
3034 			 * If users can be writing to this page using arbitrary
3035 			 * virtual addresses, take care about potential aliasing
3036 			 * before reading the page on the kernel side.
3037 			 */
3038 			if (mapping_writably_mapped(mapping))
3039 				flush_dcache_folio(folio);
3040 			folio_mark_accessed(folio);
3041 			/*
3042 			 * Ok, we have the page, and it's up-to-date, so we can
3043 			 * now splice it into the pipe.
3044 			 */
3045 			n = splice_folio_into_pipe(pipe, folio, *ppos, part);
3046 			folio_put(folio);
3047 			folio = NULL;
3048 		} else {
3049 			n = splice_zeropage_into_pipe(pipe, *ppos, part);
3050 		}
3051 
3052 		if (!n)
3053 			break;
3054 		len -= n;
3055 		total_spliced += n;
3056 		*ppos += n;
3057 		in->f_ra.prev_pos = *ppos;
3058 		if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
3059 			break;
3060 
3061 		cond_resched();
3062 	} while (len);
3063 
3064 	if (folio)
3065 		folio_put(folio);
3066 
3067 	file_accessed(in);
3068 	return total_spliced ? total_spliced : error;
3069 }
3070 
3071 static loff_t shmem_file_llseek(struct file *file, loff_t offset, int whence)
3072 {
3073 	struct address_space *mapping = file->f_mapping;
3074 	struct inode *inode = mapping->host;
3075 
3076 	if (whence != SEEK_DATA && whence != SEEK_HOLE)
3077 		return generic_file_llseek_size(file, offset, whence,
3078 					MAX_LFS_FILESIZE, i_size_read(inode));
3079 	if (offset < 0)
3080 		return -ENXIO;
3081 
3082 	inode_lock(inode);
3083 	/* We're holding i_rwsem so we can access i_size directly */
3084 	offset = mapping_seek_hole_data(mapping, offset, inode->i_size, whence);
3085 	if (offset >= 0)
3086 		offset = vfs_setpos(file, offset, MAX_LFS_FILESIZE);
3087 	inode_unlock(inode);
3088 	return offset;
3089 }
3090 
3091 static long shmem_fallocate(struct file *file, int mode, loff_t offset,
3092 							 loff_t len)
3093 {
3094 	struct inode *inode = file_inode(file);
3095 	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
3096 	struct shmem_inode_info *info = SHMEM_I(inode);
3097 	struct shmem_falloc shmem_falloc;
3098 	pgoff_t start, index, end, undo_fallocend;
3099 	int error;
3100 
3101 	if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
3102 		return -EOPNOTSUPP;
3103 
3104 	inode_lock(inode);
3105 
3106 	if (mode & FALLOC_FL_PUNCH_HOLE) {
3107 		struct address_space *mapping = file->f_mapping;
3108 		loff_t unmap_start = round_up(offset, PAGE_SIZE);
3109 		loff_t unmap_end = round_down(offset + len, PAGE_SIZE) - 1;
3110 		DECLARE_WAIT_QUEUE_HEAD_ONSTACK(shmem_falloc_waitq);
3111 
3112 		/* protected by i_rwsem */
3113 		if (info->seals & (F_SEAL_WRITE | F_SEAL_FUTURE_WRITE)) {
3114 			error = -EPERM;
3115 			goto out;
3116 		}
3117 
3118 		shmem_falloc.waitq = &shmem_falloc_waitq;
3119 		shmem_falloc.start = (u64)unmap_start >> PAGE_SHIFT;
3120 		shmem_falloc.next = (unmap_end + 1) >> PAGE_SHIFT;
3121 		spin_lock(&inode->i_lock);
3122 		inode->i_private = &shmem_falloc;
3123 		spin_unlock(&inode->i_lock);
3124 
3125 		if ((u64)unmap_end > (u64)unmap_start)
3126 			unmap_mapping_range(mapping, unmap_start,
3127 					    1 + unmap_end - unmap_start, 0);
3128 		shmem_truncate_range(inode, offset, offset + len - 1);
3129 		/* No need to unmap again: hole-punching leaves COWed pages */
3130 
3131 		spin_lock(&inode->i_lock);
3132 		inode->i_private = NULL;
3133 		wake_up_all(&shmem_falloc_waitq);
3134 		WARN_ON_ONCE(!list_empty(&shmem_falloc_waitq.head));
3135 		spin_unlock(&inode->i_lock);
3136 		error = 0;
3137 		goto out;
3138 	}
3139 
3140 	/* We need to check rlimit even when FALLOC_FL_KEEP_SIZE */
3141 	error = inode_newsize_ok(inode, offset + len);
3142 	if (error)
3143 		goto out;
3144 
3145 	if ((info->seals & F_SEAL_GROW) && offset + len > inode->i_size) {
3146 		error = -EPERM;
3147 		goto out;
3148 	}
3149 
3150 	start = offset >> PAGE_SHIFT;
3151 	end = (offset + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
3152 	/* Try to avoid a swapstorm if len is impossible to satisfy */
3153 	if (sbinfo->max_blocks && end - start > sbinfo->max_blocks) {
3154 		error = -ENOSPC;
3155 		goto out;
3156 	}
3157 
3158 	shmem_falloc.waitq = NULL;
3159 	shmem_falloc.start = start;
3160 	shmem_falloc.next  = start;
3161 	shmem_falloc.nr_falloced = 0;
3162 	shmem_falloc.nr_unswapped = 0;
3163 	spin_lock(&inode->i_lock);
3164 	inode->i_private = &shmem_falloc;
3165 	spin_unlock(&inode->i_lock);
3166 
3167 	/*
3168 	 * info->fallocend is only relevant when huge pages might be
3169 	 * involved: to prevent split_huge_page() freeing fallocated
3170 	 * pages when FALLOC_FL_KEEP_SIZE committed beyond i_size.
3171 	 */
3172 	undo_fallocend = info->fallocend;
3173 	if (info->fallocend < end)
3174 		info->fallocend = end;
3175 
3176 	for (index = start; index < end; ) {
3177 		struct folio *folio;
3178 
3179 		/*
3180 		 * Good, the fallocate(2) manpage permits EINTR: we may have
3181 		 * been interrupted because we are using up too much memory.
3182 		 */
3183 		if (signal_pending(current))
3184 			error = -EINTR;
3185 		else if (shmem_falloc.nr_unswapped > shmem_falloc.nr_falloced)
3186 			error = -ENOMEM;
3187 		else
3188 			error = shmem_get_folio(inode, index, &folio,
3189 						SGP_FALLOC);
3190 		if (error) {
3191 			info->fallocend = undo_fallocend;
3192 			/* Remove the !uptodate folios we added */
3193 			if (index > start) {
3194 				shmem_undo_range(inode,
3195 				    (loff_t)start << PAGE_SHIFT,
3196 				    ((loff_t)index << PAGE_SHIFT) - 1, true);
3197 			}
3198 			goto undone;
3199 		}
3200 
3201 		/*
3202 		 * Here is a more important optimization than it appears:
3203 		 * a second SGP_FALLOC on the same large folio will clear it,
3204 		 * making it uptodate and un-undoable if we fail later.
3205 		 */
3206 		index = folio_next_index(folio);
3207 		/* Beware 32-bit wraparound */
3208 		if (!index)
3209 			index--;
3210 
3211 		/*
3212 		 * Inform shmem_writepage() how far we have reached.
3213 		 * No need for lock or barrier: we have the page lock.
3214 		 */
3215 		if (!folio_test_uptodate(folio))
3216 			shmem_falloc.nr_falloced += index - shmem_falloc.next;
3217 		shmem_falloc.next = index;
3218 
3219 		/*
3220 		 * If !uptodate, leave it that way so that freeable folios
3221 		 * can be recognized if we need to rollback on error later.
3222 		 * But mark it dirty so that memory pressure will swap rather
3223 		 * than free the folios we are allocating (and SGP_CACHE folios
3224 		 * might still be clean: we now need to mark those dirty too).
3225 		 */
3226 		folio_mark_dirty(folio);
3227 		folio_unlock(folio);
3228 		folio_put(folio);
3229 		cond_resched();
3230 	}
3231 
3232 	if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size)
3233 		i_size_write(inode, offset + len);
3234 undone:
3235 	spin_lock(&inode->i_lock);
3236 	inode->i_private = NULL;
3237 	spin_unlock(&inode->i_lock);
3238 out:
3239 	if (!error)
3240 		file_modified(file);
3241 	inode_unlock(inode);
3242 	return error;
3243 }
3244 
3245 static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
3246 {
3247 	struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
3248 
3249 	buf->f_type = TMPFS_MAGIC;
3250 	buf->f_bsize = PAGE_SIZE;
3251 	buf->f_namelen = NAME_MAX;
3252 	if (sbinfo->max_blocks) {
3253 		buf->f_blocks = sbinfo->max_blocks;
3254 		buf->f_bavail =
3255 		buf->f_bfree  = sbinfo->max_blocks -
3256 				percpu_counter_sum(&sbinfo->used_blocks);
3257 	}
3258 	if (sbinfo->max_inodes) {
3259 		buf->f_files = sbinfo->max_inodes;
3260 		buf->f_ffree = sbinfo->free_ispace / BOGO_INODE_SIZE;
3261 	}
3262 	/* else leave those fields 0 like simple_statfs */
3263 
3264 	buf->f_fsid = uuid_to_fsid(dentry->d_sb->s_uuid.b);
3265 
3266 	return 0;
3267 }
3268 
3269 /*
3270  * File creation. Allocate an inode, and we're done..
3271  */
3272 static int
3273 shmem_mknod(struct mnt_idmap *idmap, struct inode *dir,
3274 	    struct dentry *dentry, umode_t mode, dev_t dev)
3275 {
3276 	struct inode *inode;
3277 	int error;
3278 
3279 	inode = shmem_get_inode(idmap, dir->i_sb, dir, mode, dev, VM_NORESERVE);
3280 	if (IS_ERR(inode))
3281 		return PTR_ERR(inode);
3282 
3283 	error = simple_acl_create(dir, inode);
3284 	if (error)
3285 		goto out_iput;
3286 	error = security_inode_init_security(inode, dir, &dentry->d_name,
3287 					     shmem_initxattrs, NULL);
3288 	if (error && error != -EOPNOTSUPP)
3289 		goto out_iput;
3290 
3291 	error = simple_offset_add(shmem_get_offset_ctx(dir), dentry);
3292 	if (error)
3293 		goto out_iput;
3294 
3295 	dir->i_size += BOGO_DIRENT_SIZE;
3296 	inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
3297 	inode_inc_iversion(dir);
3298 	d_instantiate(dentry, inode);
3299 	dget(dentry); /* Extra count - pin the dentry in core */
3300 	return error;
3301 
3302 out_iput:
3303 	iput(inode);
3304 	return error;
3305 }
3306 
3307 static int
3308 shmem_tmpfile(struct mnt_idmap *idmap, struct inode *dir,
3309 	      struct file *file, umode_t mode)
3310 {
3311 	struct inode *inode;
3312 	int error;
3313 
3314 	inode = shmem_get_inode(idmap, dir->i_sb, dir, mode, 0, VM_NORESERVE);
3315 	if (IS_ERR(inode)) {
3316 		error = PTR_ERR(inode);
3317 		goto err_out;
3318 	}
3319 	error = security_inode_init_security(inode, dir, NULL,
3320 					     shmem_initxattrs, NULL);
3321 	if (error && error != -EOPNOTSUPP)
3322 		goto out_iput;
3323 	error = simple_acl_create(dir, inode);
3324 	if (error)
3325 		goto out_iput;
3326 	d_tmpfile(file, inode);
3327 
3328 err_out:
3329 	return finish_open_simple(file, error);
3330 out_iput:
3331 	iput(inode);
3332 	return error;
3333 }
3334 
3335 static int shmem_mkdir(struct mnt_idmap *idmap, struct inode *dir,
3336 		       struct dentry *dentry, umode_t mode)
3337 {
3338 	int error;
3339 
3340 	error = shmem_mknod(idmap, dir, dentry, mode | S_IFDIR, 0);
3341 	if (error)
3342 		return error;
3343 	inc_nlink(dir);
3344 	return 0;
3345 }
3346 
3347 static int shmem_create(struct mnt_idmap *idmap, struct inode *dir,
3348 			struct dentry *dentry, umode_t mode, bool excl)
3349 {
3350 	return shmem_mknod(idmap, dir, dentry, mode | S_IFREG, 0);
3351 }
3352 
3353 /*
3354  * Link a file..
3355  */
3356 static int shmem_link(struct dentry *old_dentry, struct inode *dir,
3357 		      struct dentry *dentry)
3358 {
3359 	struct inode *inode = d_inode(old_dentry);
3360 	int ret = 0;
3361 
3362 	/*
3363 	 * No ordinary (disk based) filesystem counts links as inodes;
3364 	 * but each new link needs a new dentry, pinning lowmem, and
3365 	 * tmpfs dentries cannot be pruned until they are unlinked.
3366 	 * But if an O_TMPFILE file is linked into the tmpfs, the
3367 	 * first link must skip that, to get the accounting right.
3368 	 */
3369 	if (inode->i_nlink) {
3370 		ret = shmem_reserve_inode(inode->i_sb, NULL);
3371 		if (ret)
3372 			goto out;
3373 	}
3374 
3375 	ret = simple_offset_add(shmem_get_offset_ctx(dir), dentry);
3376 	if (ret) {
3377 		if (inode->i_nlink)
3378 			shmem_free_inode(inode->i_sb, 0);
3379 		goto out;
3380 	}
3381 
3382 	dir->i_size += BOGO_DIRENT_SIZE;
3383 	inode_set_mtime_to_ts(dir,
3384 			      inode_set_ctime_to_ts(dir, inode_set_ctime_current(inode)));
3385 	inode_inc_iversion(dir);
3386 	inc_nlink(inode);
3387 	ihold(inode);	/* New dentry reference */
3388 	dget(dentry);	/* Extra pinning count for the created dentry */
3389 	d_instantiate(dentry, inode);
3390 out:
3391 	return ret;
3392 }
3393 
3394 static int shmem_unlink(struct inode *dir, struct dentry *dentry)
3395 {
3396 	struct inode *inode = d_inode(dentry);
3397 
3398 	if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
3399 		shmem_free_inode(inode->i_sb, 0);
3400 
3401 	simple_offset_remove(shmem_get_offset_ctx(dir), dentry);
3402 
3403 	dir->i_size -= BOGO_DIRENT_SIZE;
3404 	inode_set_mtime_to_ts(dir,
3405 			      inode_set_ctime_to_ts(dir, inode_set_ctime_current(inode)));
3406 	inode_inc_iversion(dir);
3407 	drop_nlink(inode);
3408 	dput(dentry);	/* Undo the count from "create" - does all the work */
3409 	return 0;
3410 }
3411 
3412 static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
3413 {
3414 	if (!simple_offset_empty(dentry))
3415 		return -ENOTEMPTY;
3416 
3417 	drop_nlink(d_inode(dentry));
3418 	drop_nlink(dir);
3419 	return shmem_unlink(dir, dentry);
3420 }
3421 
3422 static int shmem_whiteout(struct mnt_idmap *idmap,
3423 			  struct inode *old_dir, struct dentry *old_dentry)
3424 {
3425 	struct dentry *whiteout;
3426 	int error;
3427 
3428 	whiteout = d_alloc(old_dentry->d_parent, &old_dentry->d_name);
3429 	if (!whiteout)
3430 		return -ENOMEM;
3431 
3432 	error = shmem_mknod(idmap, old_dir, whiteout,
3433 			    S_IFCHR | WHITEOUT_MODE, WHITEOUT_DEV);
3434 	dput(whiteout);
3435 	if (error)
3436 		return error;
3437 
3438 	/*
3439 	 * Cheat and hash the whiteout while the old dentry is still in
3440 	 * place, instead of playing games with FS_RENAME_DOES_D_MOVE.
3441 	 *
3442 	 * d_lookup() will consistently find one of them at this point,
3443 	 * not sure which one, but that isn't even important.
3444 	 */
3445 	d_rehash(whiteout);
3446 	return 0;
3447 }
3448 
3449 /*
3450  * The VFS layer already does all the dentry stuff for rename,
3451  * we just have to decrement the usage count for the target if
3452  * it exists so that the VFS layer correctly free's it when it
3453  * gets overwritten.
3454  */
3455 static int shmem_rename2(struct mnt_idmap *idmap,
3456 			 struct inode *old_dir, struct dentry *old_dentry,
3457 			 struct inode *new_dir, struct dentry *new_dentry,
3458 			 unsigned int flags)
3459 {
3460 	struct inode *inode = d_inode(old_dentry);
3461 	int they_are_dirs = S_ISDIR(inode->i_mode);
3462 	int error;
3463 
3464 	if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
3465 		return -EINVAL;
3466 
3467 	if (flags & RENAME_EXCHANGE)
3468 		return simple_offset_rename_exchange(old_dir, old_dentry,
3469 						     new_dir, new_dentry);
3470 
3471 	if (!simple_offset_empty(new_dentry))
3472 		return -ENOTEMPTY;
3473 
3474 	if (flags & RENAME_WHITEOUT) {
3475 		error = shmem_whiteout(idmap, old_dir, old_dentry);
3476 		if (error)
3477 			return error;
3478 	}
3479 
3480 	error = simple_offset_rename(old_dir, old_dentry, new_dir, new_dentry);
3481 	if (error)
3482 		return error;
3483 
3484 	if (d_really_is_positive(new_dentry)) {
3485 		(void) shmem_unlink(new_dir, new_dentry);
3486 		if (they_are_dirs) {
3487 			drop_nlink(d_inode(new_dentry));
3488 			drop_nlink(old_dir);
3489 		}
3490 	} else if (they_are_dirs) {
3491 		drop_nlink(old_dir);
3492 		inc_nlink(new_dir);
3493 	}
3494 
3495 	old_dir->i_size -= BOGO_DIRENT_SIZE;
3496 	new_dir->i_size += BOGO_DIRENT_SIZE;
3497 	simple_rename_timestamp(old_dir, old_dentry, new_dir, new_dentry);
3498 	inode_inc_iversion(old_dir);
3499 	inode_inc_iversion(new_dir);
3500 	return 0;
3501 }
3502 
3503 static int shmem_symlink(struct mnt_idmap *idmap, struct inode *dir,
3504 			 struct dentry *dentry, const char *symname)
3505 {
3506 	int error;
3507 	int len;
3508 	struct inode *inode;
3509 	struct folio *folio;
3510 
3511 	len = strlen(symname) + 1;
3512 	if (len > PAGE_SIZE)
3513 		return -ENAMETOOLONG;
3514 
3515 	inode = shmem_get_inode(idmap, dir->i_sb, dir, S_IFLNK | 0777, 0,
3516 				VM_NORESERVE);
3517 	if (IS_ERR(inode))
3518 		return PTR_ERR(inode);
3519 
3520 	error = security_inode_init_security(inode, dir, &dentry->d_name,
3521 					     shmem_initxattrs, NULL);
3522 	if (error && error != -EOPNOTSUPP)
3523 		goto out_iput;
3524 
3525 	error = simple_offset_add(shmem_get_offset_ctx(dir), dentry);
3526 	if (error)
3527 		goto out_iput;
3528 
3529 	inode->i_size = len-1;
3530 	if (len <= SHORT_SYMLINK_LEN) {
3531 		inode->i_link = kmemdup(symname, len, GFP_KERNEL);
3532 		if (!inode->i_link) {
3533 			error = -ENOMEM;
3534 			goto out_remove_offset;
3535 		}
3536 		inode->i_op = &shmem_short_symlink_operations;
3537 	} else {
3538 		inode_nohighmem(inode);
3539 		inode->i_mapping->a_ops = &shmem_aops;
3540 		error = shmem_get_folio(inode, 0, &folio, SGP_WRITE);
3541 		if (error)
3542 			goto out_remove_offset;
3543 		inode->i_op = &shmem_symlink_inode_operations;
3544 		memcpy(folio_address(folio), symname, len);
3545 		folio_mark_uptodate(folio);
3546 		folio_mark_dirty(folio);
3547 		folio_unlock(folio);
3548 		folio_put(folio);
3549 	}
3550 	dir->i_size += BOGO_DIRENT_SIZE;
3551 	inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
3552 	inode_inc_iversion(dir);
3553 	d_instantiate(dentry, inode);
3554 	dget(dentry);
3555 	return 0;
3556 
3557 out_remove_offset:
3558 	simple_offset_remove(shmem_get_offset_ctx(dir), dentry);
3559 out_iput:
3560 	iput(inode);
3561 	return error;
3562 }
3563 
3564 static void shmem_put_link(void *arg)
3565 {
3566 	folio_mark_accessed(arg);
3567 	folio_put(arg);
3568 }
3569 
3570 static const char *shmem_get_link(struct dentry *dentry, struct inode *inode,
3571 				  struct delayed_call *done)
3572 {
3573 	struct folio *folio = NULL;
3574 	int error;
3575 
3576 	if (!dentry) {
3577 		folio = filemap_get_folio(inode->i_mapping, 0);
3578 		if (IS_ERR(folio))
3579 			return ERR_PTR(-ECHILD);
3580 		if (PageHWPoison(folio_page(folio, 0)) ||
3581 		    !folio_test_uptodate(folio)) {
3582 			folio_put(folio);
3583 			return ERR_PTR(-ECHILD);
3584 		}
3585 	} else {
3586 		error = shmem_get_folio(inode, 0, &folio, SGP_READ);
3587 		if (error)
3588 			return ERR_PTR(error);
3589 		if (!folio)
3590 			return ERR_PTR(-ECHILD);
3591 		if (PageHWPoison(folio_page(folio, 0))) {
3592 			folio_unlock(folio);
3593 			folio_put(folio);
3594 			return ERR_PTR(-ECHILD);
3595 		}
3596 		folio_unlock(folio);
3597 	}
3598 	set_delayed_call(done, shmem_put_link, folio);
3599 	return folio_address(folio);
3600 }
3601 
3602 #ifdef CONFIG_TMPFS_XATTR
3603 
3604 static int shmem_fileattr_get(struct dentry *dentry, struct fileattr *fa)
3605 {
3606 	struct shmem_inode_info *info = SHMEM_I(d_inode(dentry));
3607 
3608 	fileattr_fill_flags(fa, info->fsflags & SHMEM_FL_USER_VISIBLE);
3609 
3610 	return 0;
3611 }
3612 
3613 static int shmem_fileattr_set(struct mnt_idmap *idmap,
3614 			      struct dentry *dentry, struct fileattr *fa)
3615 {
3616 	struct inode *inode = d_inode(dentry);
3617 	struct shmem_inode_info *info = SHMEM_I(inode);
3618 
3619 	if (fileattr_has_fsx(fa))
3620 		return -EOPNOTSUPP;
3621 	if (fa->flags & ~SHMEM_FL_USER_MODIFIABLE)
3622 		return -EOPNOTSUPP;
3623 
3624 	info->fsflags = (info->fsflags & ~SHMEM_FL_USER_MODIFIABLE) |
3625 		(fa->flags & SHMEM_FL_USER_MODIFIABLE);
3626 
3627 	shmem_set_inode_flags(inode, info->fsflags);
3628 	inode_set_ctime_current(inode);
3629 	inode_inc_iversion(inode);
3630 	return 0;
3631 }
3632 
3633 /*
3634  * Superblocks without xattr inode operations may get some security.* xattr
3635  * support from the LSM "for free". As soon as we have any other xattrs
3636  * like ACLs, we also need to implement the security.* handlers at
3637  * filesystem level, though.
3638  */
3639 
3640 /*
3641  * Callback for security_inode_init_security() for acquiring xattrs.
3642  */
3643 static int shmem_initxattrs(struct inode *inode,
3644 			    const struct xattr *xattr_array, void *fs_info)
3645 {
3646 	struct shmem_inode_info *info = SHMEM_I(inode);
3647 	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
3648 	const struct xattr *xattr;
3649 	struct simple_xattr *new_xattr;
3650 	size_t ispace = 0;
3651 	size_t len;
3652 
3653 	if (sbinfo->max_inodes) {
3654 		for (xattr = xattr_array; xattr->name != NULL; xattr++) {
3655 			ispace += simple_xattr_space(xattr->name,
3656 				xattr->value_len + XATTR_SECURITY_PREFIX_LEN);
3657 		}
3658 		if (ispace) {
3659 			raw_spin_lock(&sbinfo->stat_lock);
3660 			if (sbinfo->free_ispace < ispace)
3661 				ispace = 0;
3662 			else
3663 				sbinfo->free_ispace -= ispace;
3664 			raw_spin_unlock(&sbinfo->stat_lock);
3665 			if (!ispace)
3666 				return -ENOSPC;
3667 		}
3668 	}
3669 
3670 	for (xattr = xattr_array; xattr->name != NULL; xattr++) {
3671 		new_xattr = simple_xattr_alloc(xattr->value, xattr->value_len);
3672 		if (!new_xattr)
3673 			break;
3674 
3675 		len = strlen(xattr->name) + 1;
3676 		new_xattr->name = kmalloc(XATTR_SECURITY_PREFIX_LEN + len,
3677 					  GFP_KERNEL_ACCOUNT);
3678 		if (!new_xattr->name) {
3679 			kvfree(new_xattr);
3680 			break;
3681 		}
3682 
3683 		memcpy(new_xattr->name, XATTR_SECURITY_PREFIX,
3684 		       XATTR_SECURITY_PREFIX_LEN);
3685 		memcpy(new_xattr->name + XATTR_SECURITY_PREFIX_LEN,
3686 		       xattr->name, len);
3687 
3688 		simple_xattr_add(&info->xattrs, new_xattr);
3689 	}
3690 
3691 	if (xattr->name != NULL) {
3692 		if (ispace) {
3693 			raw_spin_lock(&sbinfo->stat_lock);
3694 			sbinfo->free_ispace += ispace;
3695 			raw_spin_unlock(&sbinfo->stat_lock);
3696 		}
3697 		simple_xattrs_free(&info->xattrs, NULL);
3698 		return -ENOMEM;
3699 	}
3700 
3701 	return 0;
3702 }
3703 
3704 static int shmem_xattr_handler_get(const struct xattr_handler *handler,
3705 				   struct dentry *unused, struct inode *inode,
3706 				   const char *name, void *buffer, size_t size)
3707 {
3708 	struct shmem_inode_info *info = SHMEM_I(inode);
3709 
3710 	name = xattr_full_name(handler, name);
3711 	return simple_xattr_get(&info->xattrs, name, buffer, size);
3712 }
3713 
3714 static int shmem_xattr_handler_set(const struct xattr_handler *handler,
3715 				   struct mnt_idmap *idmap,
3716 				   struct dentry *unused, struct inode *inode,
3717 				   const char *name, const void *value,
3718 				   size_t size, int flags)
3719 {
3720 	struct shmem_inode_info *info = SHMEM_I(inode);
3721 	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
3722 	struct simple_xattr *old_xattr;
3723 	size_t ispace = 0;
3724 
3725 	name = xattr_full_name(handler, name);
3726 	if (value && sbinfo->max_inodes) {
3727 		ispace = simple_xattr_space(name, size);
3728 		raw_spin_lock(&sbinfo->stat_lock);
3729 		if (sbinfo->free_ispace < ispace)
3730 			ispace = 0;
3731 		else
3732 			sbinfo->free_ispace -= ispace;
3733 		raw_spin_unlock(&sbinfo->stat_lock);
3734 		if (!ispace)
3735 			return -ENOSPC;
3736 	}
3737 
3738 	old_xattr = simple_xattr_set(&info->xattrs, name, value, size, flags);
3739 	if (!IS_ERR(old_xattr)) {
3740 		ispace = 0;
3741 		if (old_xattr && sbinfo->max_inodes)
3742 			ispace = simple_xattr_space(old_xattr->name,
3743 						    old_xattr->size);
3744 		simple_xattr_free(old_xattr);
3745 		old_xattr = NULL;
3746 		inode_set_ctime_current(inode);
3747 		inode_inc_iversion(inode);
3748 	}
3749 	if (ispace) {
3750 		raw_spin_lock(&sbinfo->stat_lock);
3751 		sbinfo->free_ispace += ispace;
3752 		raw_spin_unlock(&sbinfo->stat_lock);
3753 	}
3754 	return PTR_ERR(old_xattr);
3755 }
3756 
3757 static const struct xattr_handler shmem_security_xattr_handler = {
3758 	.prefix = XATTR_SECURITY_PREFIX,
3759 	.get = shmem_xattr_handler_get,
3760 	.set = shmem_xattr_handler_set,
3761 };
3762 
3763 static const struct xattr_handler shmem_trusted_xattr_handler = {
3764 	.prefix = XATTR_TRUSTED_PREFIX,
3765 	.get = shmem_xattr_handler_get,
3766 	.set = shmem_xattr_handler_set,
3767 };
3768 
3769 static const struct xattr_handler shmem_user_xattr_handler = {
3770 	.prefix = XATTR_USER_PREFIX,
3771 	.get = shmem_xattr_handler_get,
3772 	.set = shmem_xattr_handler_set,
3773 };
3774 
3775 static const struct xattr_handler * const shmem_xattr_handlers[] = {
3776 	&shmem_security_xattr_handler,
3777 	&shmem_trusted_xattr_handler,
3778 	&shmem_user_xattr_handler,
3779 	NULL
3780 };
3781 
3782 static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t size)
3783 {
3784 	struct shmem_inode_info *info = SHMEM_I(d_inode(dentry));
3785 	return simple_xattr_list(d_inode(dentry), &info->xattrs, buffer, size);
3786 }
3787 #endif /* CONFIG_TMPFS_XATTR */
3788 
3789 static const struct inode_operations shmem_short_symlink_operations = {
3790 	.getattr	= shmem_getattr,
3791 	.setattr	= shmem_setattr,
3792 	.get_link	= simple_get_link,
3793 #ifdef CONFIG_TMPFS_XATTR
3794 	.listxattr	= shmem_listxattr,
3795 #endif
3796 };
3797 
3798 static const struct inode_operations shmem_symlink_inode_operations = {
3799 	.getattr	= shmem_getattr,
3800 	.setattr	= shmem_setattr,
3801 	.get_link	= shmem_get_link,
3802 #ifdef CONFIG_TMPFS_XATTR
3803 	.listxattr	= shmem_listxattr,
3804 #endif
3805 };
3806 
3807 static struct dentry *shmem_get_parent(struct dentry *child)
3808 {
3809 	return ERR_PTR(-ESTALE);
3810 }
3811 
3812 static int shmem_match(struct inode *ino, void *vfh)
3813 {
3814 	__u32 *fh = vfh;
3815 	__u64 inum = fh[2];
3816 	inum = (inum << 32) | fh[1];
3817 	return ino->i_ino == inum && fh[0] == ino->i_generation;
3818 }
3819 
3820 /* Find any alias of inode, but prefer a hashed alias */
3821 static struct dentry *shmem_find_alias(struct inode *inode)
3822 {
3823 	struct dentry *alias = d_find_alias(inode);
3824 
3825 	return alias ?: d_find_any_alias(inode);
3826 }
3827 
3828 static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
3829 		struct fid *fid, int fh_len, int fh_type)
3830 {
3831 	struct inode *inode;
3832 	struct dentry *dentry = NULL;
3833 	u64 inum;
3834 
3835 	if (fh_len < 3)
3836 		return NULL;
3837 
3838 	inum = fid->raw[2];
3839 	inum = (inum << 32) | fid->raw[1];
3840 
3841 	inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
3842 			shmem_match, fid->raw);
3843 	if (inode) {
3844 		dentry = shmem_find_alias(inode);
3845 		iput(inode);
3846 	}
3847 
3848 	return dentry;
3849 }
3850 
3851 static int shmem_encode_fh(struct inode *inode, __u32 *fh, int *len,
3852 				struct inode *parent)
3853 {
3854 	if (*len < 3) {
3855 		*len = 3;
3856 		return FILEID_INVALID;
3857 	}
3858 
3859 	if (inode_unhashed(inode)) {
3860 		/* Unfortunately insert_inode_hash is not idempotent,
3861 		 * so as we hash inodes here rather than at creation
3862 		 * time, we need a lock to ensure we only try
3863 		 * to do it once
3864 		 */
3865 		static DEFINE_SPINLOCK(lock);
3866 		spin_lock(&lock);
3867 		if (inode_unhashed(inode))
3868 			__insert_inode_hash(inode,
3869 					    inode->i_ino + inode->i_generation);
3870 		spin_unlock(&lock);
3871 	}
3872 
3873 	fh[0] = inode->i_generation;
3874 	fh[1] = inode->i_ino;
3875 	fh[2] = ((__u64)inode->i_ino) >> 32;
3876 
3877 	*len = 3;
3878 	return 1;
3879 }
3880 
3881 static const struct export_operations shmem_export_ops = {
3882 	.get_parent     = shmem_get_parent,
3883 	.encode_fh      = shmem_encode_fh,
3884 	.fh_to_dentry	= shmem_fh_to_dentry,
3885 };
3886 
3887 enum shmem_param {
3888 	Opt_gid,
3889 	Opt_huge,
3890 	Opt_mode,
3891 	Opt_mpol,
3892 	Opt_nr_blocks,
3893 	Opt_nr_inodes,
3894 	Opt_size,
3895 	Opt_uid,
3896 	Opt_inode32,
3897 	Opt_inode64,
3898 	Opt_noswap,
3899 	Opt_quota,
3900 	Opt_usrquota,
3901 	Opt_grpquota,
3902 	Opt_usrquota_block_hardlimit,
3903 	Opt_usrquota_inode_hardlimit,
3904 	Opt_grpquota_block_hardlimit,
3905 	Opt_grpquota_inode_hardlimit,
3906 };
3907 
3908 static const struct constant_table shmem_param_enums_huge[] = {
3909 	{"never",	SHMEM_HUGE_NEVER },
3910 	{"always",	SHMEM_HUGE_ALWAYS },
3911 	{"within_size",	SHMEM_HUGE_WITHIN_SIZE },
3912 	{"advise",	SHMEM_HUGE_ADVISE },
3913 	{}
3914 };
3915 
3916 const struct fs_parameter_spec shmem_fs_parameters[] = {
3917 	fsparam_u32   ("gid",		Opt_gid),
3918 	fsparam_enum  ("huge",		Opt_huge,  shmem_param_enums_huge),
3919 	fsparam_u32oct("mode",		Opt_mode),
3920 	fsparam_string("mpol",		Opt_mpol),
3921 	fsparam_string("nr_blocks",	Opt_nr_blocks),
3922 	fsparam_string("nr_inodes",	Opt_nr_inodes),
3923 	fsparam_string("size",		Opt_size),
3924 	fsparam_u32   ("uid",		Opt_uid),
3925 	fsparam_flag  ("inode32",	Opt_inode32),
3926 	fsparam_flag  ("inode64",	Opt_inode64),
3927 	fsparam_flag  ("noswap",	Opt_noswap),
3928 #ifdef CONFIG_TMPFS_QUOTA
3929 	fsparam_flag  ("quota",		Opt_quota),
3930 	fsparam_flag  ("usrquota",	Opt_usrquota),
3931 	fsparam_flag  ("grpquota",	Opt_grpquota),
3932 	fsparam_string("usrquota_block_hardlimit", Opt_usrquota_block_hardlimit),
3933 	fsparam_string("usrquota_inode_hardlimit", Opt_usrquota_inode_hardlimit),
3934 	fsparam_string("grpquota_block_hardlimit", Opt_grpquota_block_hardlimit),
3935 	fsparam_string("grpquota_inode_hardlimit", Opt_grpquota_inode_hardlimit),
3936 #endif
3937 	{}
3938 };
3939 
3940 static int shmem_parse_one(struct fs_context *fc, struct fs_parameter *param)
3941 {
3942 	struct shmem_options *ctx = fc->fs_private;
3943 	struct fs_parse_result result;
3944 	unsigned long long size;
3945 	char *rest;
3946 	int opt;
3947 	kuid_t kuid;
3948 	kgid_t kgid;
3949 
3950 	opt = fs_parse(fc, shmem_fs_parameters, param, &result);
3951 	if (opt < 0)
3952 		return opt;
3953 
3954 	switch (opt) {
3955 	case Opt_size:
3956 		size = memparse(param->string, &rest);
3957 		if (*rest == '%') {
3958 			size <<= PAGE_SHIFT;
3959 			size *= totalram_pages();
3960 			do_div(size, 100);
3961 			rest++;
3962 		}
3963 		if (*rest)
3964 			goto bad_value;
3965 		ctx->blocks = DIV_ROUND_UP(size, PAGE_SIZE);
3966 		ctx->seen |= SHMEM_SEEN_BLOCKS;
3967 		break;
3968 	case Opt_nr_blocks:
3969 		ctx->blocks = memparse(param->string, &rest);
3970 		if (*rest || ctx->blocks > LONG_MAX)
3971 			goto bad_value;
3972 		ctx->seen |= SHMEM_SEEN_BLOCKS;
3973 		break;
3974 	case Opt_nr_inodes:
3975 		ctx->inodes = memparse(param->string, &rest);
3976 		if (*rest || ctx->inodes > ULONG_MAX / BOGO_INODE_SIZE)
3977 			goto bad_value;
3978 		ctx->seen |= SHMEM_SEEN_INODES;
3979 		break;
3980 	case Opt_mode:
3981 		ctx->mode = result.uint_32 & 07777;
3982 		break;
3983 	case Opt_uid:
3984 		kuid = make_kuid(current_user_ns(), result.uint_32);
3985 		if (!uid_valid(kuid))
3986 			goto bad_value;
3987 
3988 		/*
3989 		 * The requested uid must be representable in the
3990 		 * filesystem's idmapping.
3991 		 */
3992 		if (!kuid_has_mapping(fc->user_ns, kuid))
3993 			goto bad_value;
3994 
3995 		ctx->uid = kuid;
3996 		break;
3997 	case Opt_gid:
3998 		kgid = make_kgid(current_user_ns(), result.uint_32);
3999 		if (!gid_valid(kgid))
4000 			goto bad_value;
4001 
4002 		/*
4003 		 * The requested gid must be representable in the
4004 		 * filesystem's idmapping.
4005 		 */
4006 		if (!kgid_has_mapping(fc->user_ns, kgid))
4007 			goto bad_value;
4008 
4009 		ctx->gid = kgid;
4010 		break;
4011 	case Opt_huge:
4012 		ctx->huge = result.uint_32;
4013 		if (ctx->huge != SHMEM_HUGE_NEVER &&
4014 		    !(IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
4015 		      has_transparent_hugepage()))
4016 			goto unsupported_parameter;
4017 		ctx->seen |= SHMEM_SEEN_HUGE;
4018 		break;
4019 	case Opt_mpol:
4020 		if (IS_ENABLED(CONFIG_NUMA)) {
4021 			mpol_put(ctx->mpol);
4022 			ctx->mpol = NULL;
4023 			if (mpol_parse_str(param->string, &ctx->mpol))
4024 				goto bad_value;
4025 			break;
4026 		}
4027 		goto unsupported_parameter;
4028 	case Opt_inode32:
4029 		ctx->full_inums = false;
4030 		ctx->seen |= SHMEM_SEEN_INUMS;
4031 		break;
4032 	case Opt_inode64:
4033 		if (sizeof(ino_t) < 8) {
4034 			return invalfc(fc,
4035 				       "Cannot use inode64 with <64bit inums in kernel\n");
4036 		}
4037 		ctx->full_inums = true;
4038 		ctx->seen |= SHMEM_SEEN_INUMS;
4039 		break;
4040 	case Opt_noswap:
4041 		if ((fc->user_ns != &init_user_ns) || !capable(CAP_SYS_ADMIN)) {
4042 			return invalfc(fc,
4043 				       "Turning off swap in unprivileged tmpfs mounts unsupported");
4044 		}
4045 		ctx->noswap = true;
4046 		ctx->seen |= SHMEM_SEEN_NOSWAP;
4047 		break;
4048 	case Opt_quota:
4049 		if (fc->user_ns != &init_user_ns)
4050 			return invalfc(fc, "Quotas in unprivileged tmpfs mounts are unsupported");
4051 		ctx->seen |= SHMEM_SEEN_QUOTA;
4052 		ctx->quota_types |= (QTYPE_MASK_USR | QTYPE_MASK_GRP);
4053 		break;
4054 	case Opt_usrquota:
4055 		if (fc->user_ns != &init_user_ns)
4056 			return invalfc(fc, "Quotas in unprivileged tmpfs mounts are unsupported");
4057 		ctx->seen |= SHMEM_SEEN_QUOTA;
4058 		ctx->quota_types |= QTYPE_MASK_USR;
4059 		break;
4060 	case Opt_grpquota:
4061 		if (fc->user_ns != &init_user_ns)
4062 			return invalfc(fc, "Quotas in unprivileged tmpfs mounts are unsupported");
4063 		ctx->seen |= SHMEM_SEEN_QUOTA;
4064 		ctx->quota_types |= QTYPE_MASK_GRP;
4065 		break;
4066 	case Opt_usrquota_block_hardlimit:
4067 		size = memparse(param->string, &rest);
4068 		if (*rest || !size)
4069 			goto bad_value;
4070 		if (size > SHMEM_QUOTA_MAX_SPC_LIMIT)
4071 			return invalfc(fc,
4072 				       "User quota block hardlimit too large.");
4073 		ctx->qlimits.usrquota_bhardlimit = size;
4074 		break;
4075 	case Opt_grpquota_block_hardlimit:
4076 		size = memparse(param->string, &rest);
4077 		if (*rest || !size)
4078 			goto bad_value;
4079 		if (size > SHMEM_QUOTA_MAX_SPC_LIMIT)
4080 			return invalfc(fc,
4081 				       "Group quota block hardlimit too large.");
4082 		ctx->qlimits.grpquota_bhardlimit = size;
4083 		break;
4084 	case Opt_usrquota_inode_hardlimit:
4085 		size = memparse(param->string, &rest);
4086 		if (*rest || !size)
4087 			goto bad_value;
4088 		if (size > SHMEM_QUOTA_MAX_INO_LIMIT)
4089 			return invalfc(fc,
4090 				       "User quota inode hardlimit too large.");
4091 		ctx->qlimits.usrquota_ihardlimit = size;
4092 		break;
4093 	case Opt_grpquota_inode_hardlimit:
4094 		size = memparse(param->string, &rest);
4095 		if (*rest || !size)
4096 			goto bad_value;
4097 		if (size > SHMEM_QUOTA_MAX_INO_LIMIT)
4098 			return invalfc(fc,
4099 				       "Group quota inode hardlimit too large.");
4100 		ctx->qlimits.grpquota_ihardlimit = size;
4101 		break;
4102 	}
4103 	return 0;
4104 
4105 unsupported_parameter:
4106 	return invalfc(fc, "Unsupported parameter '%s'", param->key);
4107 bad_value:
4108 	return invalfc(fc, "Bad value for '%s'", param->key);
4109 }
4110 
4111 static int shmem_parse_options(struct fs_context *fc, void *data)
4112 {
4113 	char *options = data;
4114 
4115 	if (options) {
4116 		int err = security_sb_eat_lsm_opts(options, &fc->security);
4117 		if (err)
4118 			return err;
4119 	}
4120 
4121 	while (options != NULL) {
4122 		char *this_char = options;
4123 		for (;;) {
4124 			/*
4125 			 * NUL-terminate this option: unfortunately,
4126 			 * mount options form a comma-separated list,
4127 			 * but mpol's nodelist may also contain commas.
4128 			 */
4129 			options = strchr(options, ',');
4130 			if (options == NULL)
4131 				break;
4132 			options++;
4133 			if (!isdigit(*options)) {
4134 				options[-1] = '\0';
4135 				break;
4136 			}
4137 		}
4138 		if (*this_char) {
4139 			char *value = strchr(this_char, '=');
4140 			size_t len = 0;
4141 			int err;
4142 
4143 			if (value) {
4144 				*value++ = '\0';
4145 				len = strlen(value);
4146 			}
4147 			err = vfs_parse_fs_string(fc, this_char, value, len);
4148 			if (err < 0)
4149 				return err;
4150 		}
4151 	}
4152 	return 0;
4153 }
4154 
4155 /*
4156  * Reconfigure a shmem filesystem.
4157  */
4158 static int shmem_reconfigure(struct fs_context *fc)
4159 {
4160 	struct shmem_options *ctx = fc->fs_private;
4161 	struct shmem_sb_info *sbinfo = SHMEM_SB(fc->root->d_sb);
4162 	unsigned long used_isp;
4163 	struct mempolicy *mpol = NULL;
4164 	const char *err;
4165 
4166 	raw_spin_lock(&sbinfo->stat_lock);
4167 	used_isp = sbinfo->max_inodes * BOGO_INODE_SIZE - sbinfo->free_ispace;
4168 
4169 	if ((ctx->seen & SHMEM_SEEN_BLOCKS) && ctx->blocks) {
4170 		if (!sbinfo->max_blocks) {
4171 			err = "Cannot retroactively limit size";
4172 			goto out;
4173 		}
4174 		if (percpu_counter_compare(&sbinfo->used_blocks,
4175 					   ctx->blocks) > 0) {
4176 			err = "Too small a size for current use";
4177 			goto out;
4178 		}
4179 	}
4180 	if ((ctx->seen & SHMEM_SEEN_INODES) && ctx->inodes) {
4181 		if (!sbinfo->max_inodes) {
4182 			err = "Cannot retroactively limit inodes";
4183 			goto out;
4184 		}
4185 		if (ctx->inodes * BOGO_INODE_SIZE < used_isp) {
4186 			err = "Too few inodes for current use";
4187 			goto out;
4188 		}
4189 	}
4190 
4191 	if ((ctx->seen & SHMEM_SEEN_INUMS) && !ctx->full_inums &&
4192 	    sbinfo->next_ino > UINT_MAX) {
4193 		err = "Current inum too high to switch to 32-bit inums";
4194 		goto out;
4195 	}
4196 	if ((ctx->seen & SHMEM_SEEN_NOSWAP) && ctx->noswap && !sbinfo->noswap) {
4197 		err = "Cannot disable swap on remount";
4198 		goto out;
4199 	}
4200 	if (!(ctx->seen & SHMEM_SEEN_NOSWAP) && !ctx->noswap && sbinfo->noswap) {
4201 		err = "Cannot enable swap on remount if it was disabled on first mount";
4202 		goto out;
4203 	}
4204 
4205 	if (ctx->seen & SHMEM_SEEN_QUOTA &&
4206 	    !sb_any_quota_loaded(fc->root->d_sb)) {
4207 		err = "Cannot enable quota on remount";
4208 		goto out;
4209 	}
4210 
4211 #ifdef CONFIG_TMPFS_QUOTA
4212 #define CHANGED_LIMIT(name)						\
4213 	(ctx->qlimits.name## hardlimit &&				\
4214 	(ctx->qlimits.name## hardlimit != sbinfo->qlimits.name## hardlimit))
4215 
4216 	if (CHANGED_LIMIT(usrquota_b) || CHANGED_LIMIT(usrquota_i) ||
4217 	    CHANGED_LIMIT(grpquota_b) || CHANGED_LIMIT(grpquota_i)) {
4218 		err = "Cannot change global quota limit on remount";
4219 		goto out;
4220 	}
4221 #endif /* CONFIG_TMPFS_QUOTA */
4222 
4223 	if (ctx->seen & SHMEM_SEEN_HUGE)
4224 		sbinfo->huge = ctx->huge;
4225 	if (ctx->seen & SHMEM_SEEN_INUMS)
4226 		sbinfo->full_inums = ctx->full_inums;
4227 	if (ctx->seen & SHMEM_SEEN_BLOCKS)
4228 		sbinfo->max_blocks  = ctx->blocks;
4229 	if (ctx->seen & SHMEM_SEEN_INODES) {
4230 		sbinfo->max_inodes  = ctx->inodes;
4231 		sbinfo->free_ispace = ctx->inodes * BOGO_INODE_SIZE - used_isp;
4232 	}
4233 
4234 	/*
4235 	 * Preserve previous mempolicy unless mpol remount option was specified.
4236 	 */
4237 	if (ctx->mpol) {
4238 		mpol = sbinfo->mpol;
4239 		sbinfo->mpol = ctx->mpol;	/* transfers initial ref */
4240 		ctx->mpol = NULL;
4241 	}
4242 
4243 	if (ctx->noswap)
4244 		sbinfo->noswap = true;
4245 
4246 	raw_spin_unlock(&sbinfo->stat_lock);
4247 	mpol_put(mpol);
4248 	return 0;
4249 out:
4250 	raw_spin_unlock(&sbinfo->stat_lock);
4251 	return invalfc(fc, "%s", err);
4252 }
4253 
4254 static int shmem_show_options(struct seq_file *seq, struct dentry *root)
4255 {
4256 	struct shmem_sb_info *sbinfo = SHMEM_SB(root->d_sb);
4257 	struct mempolicy *mpol;
4258 
4259 	if (sbinfo->max_blocks != shmem_default_max_blocks())
4260 		seq_printf(seq, ",size=%luk", K(sbinfo->max_blocks));
4261 	if (sbinfo->max_inodes != shmem_default_max_inodes())
4262 		seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
4263 	if (sbinfo->mode != (0777 | S_ISVTX))
4264 		seq_printf(seq, ",mode=%03ho", sbinfo->mode);
4265 	if (!uid_eq(sbinfo->uid, GLOBAL_ROOT_UID))
4266 		seq_printf(seq, ",uid=%u",
4267 				from_kuid_munged(&init_user_ns, sbinfo->uid));
4268 	if (!gid_eq(sbinfo->gid, GLOBAL_ROOT_GID))
4269 		seq_printf(seq, ",gid=%u",
4270 				from_kgid_munged(&init_user_ns, sbinfo->gid));
4271 
4272 	/*
4273 	 * Showing inode{64,32} might be useful even if it's the system default,
4274 	 * since then people don't have to resort to checking both here and
4275 	 * /proc/config.gz to confirm 64-bit inums were successfully applied
4276 	 * (which may not even exist if IKCONFIG_PROC isn't enabled).
4277 	 *
4278 	 * We hide it when inode64 isn't the default and we are using 32-bit
4279 	 * inodes, since that probably just means the feature isn't even under
4280 	 * consideration.
4281 	 *
4282 	 * As such:
4283 	 *
4284 	 *                     +-----------------+-----------------+
4285 	 *                     | TMPFS_INODE64=y | TMPFS_INODE64=n |
4286 	 *  +------------------+-----------------+-----------------+
4287 	 *  | full_inums=true  | show            | show            |
4288 	 *  | full_inums=false | show            | hide            |
4289 	 *  +------------------+-----------------+-----------------+
4290 	 *
4291 	 */
4292 	if (IS_ENABLED(CONFIG_TMPFS_INODE64) || sbinfo->full_inums)
4293 		seq_printf(seq, ",inode%d", (sbinfo->full_inums ? 64 : 32));
4294 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
4295 	/* Rightly or wrongly, show huge mount option unmasked by shmem_huge */
4296 	if (sbinfo->huge)
4297 		seq_printf(seq, ",huge=%s", shmem_format_huge(sbinfo->huge));
4298 #endif
4299 	mpol = shmem_get_sbmpol(sbinfo);
4300 	shmem_show_mpol(seq, mpol);
4301 	mpol_put(mpol);
4302 	if (sbinfo->noswap)
4303 		seq_printf(seq, ",noswap");
4304 #ifdef CONFIG_TMPFS_QUOTA
4305 	if (sb_has_quota_active(root->d_sb, USRQUOTA))
4306 		seq_printf(seq, ",usrquota");
4307 	if (sb_has_quota_active(root->d_sb, GRPQUOTA))
4308 		seq_printf(seq, ",grpquota");
4309 	if (sbinfo->qlimits.usrquota_bhardlimit)
4310 		seq_printf(seq, ",usrquota_block_hardlimit=%lld",
4311 			   sbinfo->qlimits.usrquota_bhardlimit);
4312 	if (sbinfo->qlimits.grpquota_bhardlimit)
4313 		seq_printf(seq, ",grpquota_block_hardlimit=%lld",
4314 			   sbinfo->qlimits.grpquota_bhardlimit);
4315 	if (sbinfo->qlimits.usrquota_ihardlimit)
4316 		seq_printf(seq, ",usrquota_inode_hardlimit=%lld",
4317 			   sbinfo->qlimits.usrquota_ihardlimit);
4318 	if (sbinfo->qlimits.grpquota_ihardlimit)
4319 		seq_printf(seq, ",grpquota_inode_hardlimit=%lld",
4320 			   sbinfo->qlimits.grpquota_ihardlimit);
4321 #endif
4322 	return 0;
4323 }
4324 
4325 #endif /* CONFIG_TMPFS */
4326 
4327 static void shmem_put_super(struct super_block *sb)
4328 {
4329 	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
4330 
4331 #ifdef CONFIG_TMPFS_QUOTA
4332 	shmem_disable_quotas(sb);
4333 #endif
4334 	free_percpu(sbinfo->ino_batch);
4335 	percpu_counter_destroy(&sbinfo->used_blocks);
4336 	mpol_put(sbinfo->mpol);
4337 	kfree(sbinfo);
4338 	sb->s_fs_info = NULL;
4339 }
4340 
4341 static int shmem_fill_super(struct super_block *sb, struct fs_context *fc)
4342 {
4343 	struct shmem_options *ctx = fc->fs_private;
4344 	struct inode *inode;
4345 	struct shmem_sb_info *sbinfo;
4346 	int error = -ENOMEM;
4347 
4348 	/* Round up to L1_CACHE_BYTES to resist false sharing */
4349 	sbinfo = kzalloc(max((int)sizeof(struct shmem_sb_info),
4350 				L1_CACHE_BYTES), GFP_KERNEL);
4351 	if (!sbinfo)
4352 		return error;
4353 
4354 	sb->s_fs_info = sbinfo;
4355 
4356 #ifdef CONFIG_TMPFS
4357 	/*
4358 	 * Per default we only allow half of the physical ram per
4359 	 * tmpfs instance, limiting inodes to one per page of lowmem;
4360 	 * but the internal instance is left unlimited.
4361 	 */
4362 	if (!(sb->s_flags & SB_KERNMOUNT)) {
4363 		if (!(ctx->seen & SHMEM_SEEN_BLOCKS))
4364 			ctx->blocks = shmem_default_max_blocks();
4365 		if (!(ctx->seen & SHMEM_SEEN_INODES))
4366 			ctx->inodes = shmem_default_max_inodes();
4367 		if (!(ctx->seen & SHMEM_SEEN_INUMS))
4368 			ctx->full_inums = IS_ENABLED(CONFIG_TMPFS_INODE64);
4369 		sbinfo->noswap = ctx->noswap;
4370 	} else {
4371 		sb->s_flags |= SB_NOUSER;
4372 	}
4373 	sb->s_export_op = &shmem_export_ops;
4374 	sb->s_flags |= SB_NOSEC | SB_I_VERSION;
4375 #else
4376 	sb->s_flags |= SB_NOUSER;
4377 #endif
4378 	sbinfo->max_blocks = ctx->blocks;
4379 	sbinfo->max_inodes = ctx->inodes;
4380 	sbinfo->free_ispace = sbinfo->max_inodes * BOGO_INODE_SIZE;
4381 	if (sb->s_flags & SB_KERNMOUNT) {
4382 		sbinfo->ino_batch = alloc_percpu(ino_t);
4383 		if (!sbinfo->ino_batch)
4384 			goto failed;
4385 	}
4386 	sbinfo->uid = ctx->uid;
4387 	sbinfo->gid = ctx->gid;
4388 	sbinfo->full_inums = ctx->full_inums;
4389 	sbinfo->mode = ctx->mode;
4390 	sbinfo->huge = ctx->huge;
4391 	sbinfo->mpol = ctx->mpol;
4392 	ctx->mpol = NULL;
4393 
4394 	raw_spin_lock_init(&sbinfo->stat_lock);
4395 	if (percpu_counter_init(&sbinfo->used_blocks, 0, GFP_KERNEL))
4396 		goto failed;
4397 	spin_lock_init(&sbinfo->shrinklist_lock);
4398 	INIT_LIST_HEAD(&sbinfo->shrinklist);
4399 
4400 	sb->s_maxbytes = MAX_LFS_FILESIZE;
4401 	sb->s_blocksize = PAGE_SIZE;
4402 	sb->s_blocksize_bits = PAGE_SHIFT;
4403 	sb->s_magic = TMPFS_MAGIC;
4404 	sb->s_op = &shmem_ops;
4405 	sb->s_time_gran = 1;
4406 #ifdef CONFIG_TMPFS_XATTR
4407 	sb->s_xattr = shmem_xattr_handlers;
4408 #endif
4409 #ifdef CONFIG_TMPFS_POSIX_ACL
4410 	sb->s_flags |= SB_POSIXACL;
4411 #endif
4412 	uuid_t uuid;
4413 	uuid_gen(&uuid);
4414 	super_set_uuid(sb, uuid.b, sizeof(uuid));
4415 
4416 #ifdef CONFIG_TMPFS_QUOTA
4417 	if (ctx->seen & SHMEM_SEEN_QUOTA) {
4418 		sb->dq_op = &shmem_quota_operations;
4419 		sb->s_qcop = &dquot_quotactl_sysfile_ops;
4420 		sb->s_quota_types = QTYPE_MASK_USR | QTYPE_MASK_GRP;
4421 
4422 		/* Copy the default limits from ctx into sbinfo */
4423 		memcpy(&sbinfo->qlimits, &ctx->qlimits,
4424 		       sizeof(struct shmem_quota_limits));
4425 
4426 		if (shmem_enable_quotas(sb, ctx->quota_types))
4427 			goto failed;
4428 	}
4429 #endif /* CONFIG_TMPFS_QUOTA */
4430 
4431 	inode = shmem_get_inode(&nop_mnt_idmap, sb, NULL,
4432 				S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
4433 	if (IS_ERR(inode)) {
4434 		error = PTR_ERR(inode);
4435 		goto failed;
4436 	}
4437 	inode->i_uid = sbinfo->uid;
4438 	inode->i_gid = sbinfo->gid;
4439 	sb->s_root = d_make_root(inode);
4440 	if (!sb->s_root)
4441 		goto failed;
4442 	return 0;
4443 
4444 failed:
4445 	shmem_put_super(sb);
4446 	return error;
4447 }
4448 
4449 static int shmem_get_tree(struct fs_context *fc)
4450 {
4451 	return get_tree_nodev(fc, shmem_fill_super);
4452 }
4453 
4454 static void shmem_free_fc(struct fs_context *fc)
4455 {
4456 	struct shmem_options *ctx = fc->fs_private;
4457 
4458 	if (ctx) {
4459 		mpol_put(ctx->mpol);
4460 		kfree(ctx);
4461 	}
4462 }
4463 
4464 static const struct fs_context_operations shmem_fs_context_ops = {
4465 	.free			= shmem_free_fc,
4466 	.get_tree		= shmem_get_tree,
4467 #ifdef CONFIG_TMPFS
4468 	.parse_monolithic	= shmem_parse_options,
4469 	.parse_param		= shmem_parse_one,
4470 	.reconfigure		= shmem_reconfigure,
4471 #endif
4472 };
4473 
4474 static struct kmem_cache *shmem_inode_cachep __ro_after_init;
4475 
4476 static struct inode *shmem_alloc_inode(struct super_block *sb)
4477 {
4478 	struct shmem_inode_info *info;
4479 	info = alloc_inode_sb(sb, shmem_inode_cachep, GFP_KERNEL);
4480 	if (!info)
4481 		return NULL;
4482 	return &info->vfs_inode;
4483 }
4484 
4485 static void shmem_free_in_core_inode(struct inode *inode)
4486 {
4487 	if (S_ISLNK(inode->i_mode))
4488 		kfree(inode->i_link);
4489 	kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
4490 }
4491 
4492 static void shmem_destroy_inode(struct inode *inode)
4493 {
4494 	if (S_ISREG(inode->i_mode))
4495 		mpol_free_shared_policy(&SHMEM_I(inode)->policy);
4496 	if (S_ISDIR(inode->i_mode))
4497 		simple_offset_destroy(shmem_get_offset_ctx(inode));
4498 }
4499 
4500 static void shmem_init_inode(void *foo)
4501 {
4502 	struct shmem_inode_info *info = foo;
4503 	inode_init_once(&info->vfs_inode);
4504 }
4505 
4506 static void __init shmem_init_inodecache(void)
4507 {
4508 	shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
4509 				sizeof(struct shmem_inode_info),
4510 				0, SLAB_PANIC|SLAB_ACCOUNT, shmem_init_inode);
4511 }
4512 
4513 static void __init shmem_destroy_inodecache(void)
4514 {
4515 	kmem_cache_destroy(shmem_inode_cachep);
4516 }
4517 
4518 /* Keep the page in page cache instead of truncating it */
4519 static int shmem_error_remove_folio(struct address_space *mapping,
4520 				   struct folio *folio)
4521 {
4522 	return 0;
4523 }
4524 
4525 static const struct address_space_operations shmem_aops = {
4526 	.writepage	= shmem_writepage,
4527 	.dirty_folio	= noop_dirty_folio,
4528 #ifdef CONFIG_TMPFS
4529 	.write_begin	= shmem_write_begin,
4530 	.write_end	= shmem_write_end,
4531 #endif
4532 #ifdef CONFIG_MIGRATION
4533 	.migrate_folio	= migrate_folio,
4534 #endif
4535 	.error_remove_folio = shmem_error_remove_folio,
4536 };
4537 
4538 static const struct file_operations shmem_file_operations = {
4539 	.mmap		= shmem_mmap,
4540 	.open		= shmem_file_open,
4541 	.get_unmapped_area = shmem_get_unmapped_area,
4542 #ifdef CONFIG_TMPFS
4543 	.llseek		= shmem_file_llseek,
4544 	.read_iter	= shmem_file_read_iter,
4545 	.write_iter	= shmem_file_write_iter,
4546 	.fsync		= noop_fsync,
4547 	.splice_read	= shmem_file_splice_read,
4548 	.splice_write	= iter_file_splice_write,
4549 	.fallocate	= shmem_fallocate,
4550 #endif
4551 };
4552 
4553 static const struct inode_operations shmem_inode_operations = {
4554 	.getattr	= shmem_getattr,
4555 	.setattr	= shmem_setattr,
4556 #ifdef CONFIG_TMPFS_XATTR
4557 	.listxattr	= shmem_listxattr,
4558 	.set_acl	= simple_set_acl,
4559 	.fileattr_get	= shmem_fileattr_get,
4560 	.fileattr_set	= shmem_fileattr_set,
4561 #endif
4562 };
4563 
4564 static const struct inode_operations shmem_dir_inode_operations = {
4565 #ifdef CONFIG_TMPFS
4566 	.getattr	= shmem_getattr,
4567 	.create		= shmem_create,
4568 	.lookup		= simple_lookup,
4569 	.link		= shmem_link,
4570 	.unlink		= shmem_unlink,
4571 	.symlink	= shmem_symlink,
4572 	.mkdir		= shmem_mkdir,
4573 	.rmdir		= shmem_rmdir,
4574 	.mknod		= shmem_mknod,
4575 	.rename		= shmem_rename2,
4576 	.tmpfile	= shmem_tmpfile,
4577 	.get_offset_ctx	= shmem_get_offset_ctx,
4578 #endif
4579 #ifdef CONFIG_TMPFS_XATTR
4580 	.listxattr	= shmem_listxattr,
4581 	.fileattr_get	= shmem_fileattr_get,
4582 	.fileattr_set	= shmem_fileattr_set,
4583 #endif
4584 #ifdef CONFIG_TMPFS_POSIX_ACL
4585 	.setattr	= shmem_setattr,
4586 	.set_acl	= simple_set_acl,
4587 #endif
4588 };
4589 
4590 static const struct inode_operations shmem_special_inode_operations = {
4591 	.getattr	= shmem_getattr,
4592 #ifdef CONFIG_TMPFS_XATTR
4593 	.listxattr	= shmem_listxattr,
4594 #endif
4595 #ifdef CONFIG_TMPFS_POSIX_ACL
4596 	.setattr	= shmem_setattr,
4597 	.set_acl	= simple_set_acl,
4598 #endif
4599 };
4600 
4601 static const struct super_operations shmem_ops = {
4602 	.alloc_inode	= shmem_alloc_inode,
4603 	.free_inode	= shmem_free_in_core_inode,
4604 	.destroy_inode	= shmem_destroy_inode,
4605 #ifdef CONFIG_TMPFS
4606 	.statfs		= shmem_statfs,
4607 	.show_options	= shmem_show_options,
4608 #endif
4609 #ifdef CONFIG_TMPFS_QUOTA
4610 	.get_dquots	= shmem_get_dquots,
4611 #endif
4612 	.evict_inode	= shmem_evict_inode,
4613 	.drop_inode	= generic_delete_inode,
4614 	.put_super	= shmem_put_super,
4615 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
4616 	.nr_cached_objects	= shmem_unused_huge_count,
4617 	.free_cached_objects	= shmem_unused_huge_scan,
4618 #endif
4619 };
4620 
4621 static const struct vm_operations_struct shmem_vm_ops = {
4622 	.fault		= shmem_fault,
4623 	.map_pages	= filemap_map_pages,
4624 #ifdef CONFIG_NUMA
4625 	.set_policy     = shmem_set_policy,
4626 	.get_policy     = shmem_get_policy,
4627 #endif
4628 };
4629 
4630 static const struct vm_operations_struct shmem_anon_vm_ops = {
4631 	.fault		= shmem_fault,
4632 	.map_pages	= filemap_map_pages,
4633 #ifdef CONFIG_NUMA
4634 	.set_policy     = shmem_set_policy,
4635 	.get_policy     = shmem_get_policy,
4636 #endif
4637 };
4638 
4639 int shmem_init_fs_context(struct fs_context *fc)
4640 {
4641 	struct shmem_options *ctx;
4642 
4643 	ctx = kzalloc(sizeof(struct shmem_options), GFP_KERNEL);
4644 	if (!ctx)
4645 		return -ENOMEM;
4646 
4647 	ctx->mode = 0777 | S_ISVTX;
4648 	ctx->uid = current_fsuid();
4649 	ctx->gid = current_fsgid();
4650 
4651 	fc->fs_private = ctx;
4652 	fc->ops = &shmem_fs_context_ops;
4653 	return 0;
4654 }
4655 
4656 static struct file_system_type shmem_fs_type = {
4657 	.owner		= THIS_MODULE,
4658 	.name		= "tmpfs",
4659 	.init_fs_context = shmem_init_fs_context,
4660 #ifdef CONFIG_TMPFS
4661 	.parameters	= shmem_fs_parameters,
4662 #endif
4663 	.kill_sb	= kill_litter_super,
4664 	.fs_flags	= FS_USERNS_MOUNT | FS_ALLOW_IDMAP,
4665 };
4666 
4667 void __init shmem_init(void)
4668 {
4669 	int error;
4670 
4671 	shmem_init_inodecache();
4672 
4673 #ifdef CONFIG_TMPFS_QUOTA
4674 	error = register_quota_format(&shmem_quota_format);
4675 	if (error < 0) {
4676 		pr_err("Could not register quota format\n");
4677 		goto out3;
4678 	}
4679 #endif
4680 
4681 	error = register_filesystem(&shmem_fs_type);
4682 	if (error) {
4683 		pr_err("Could not register tmpfs\n");
4684 		goto out2;
4685 	}
4686 
4687 	shm_mnt = kern_mount(&shmem_fs_type);
4688 	if (IS_ERR(shm_mnt)) {
4689 		error = PTR_ERR(shm_mnt);
4690 		pr_err("Could not kern_mount tmpfs\n");
4691 		goto out1;
4692 	}
4693 
4694 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
4695 	if (has_transparent_hugepage() && shmem_huge > SHMEM_HUGE_DENY)
4696 		SHMEM_SB(shm_mnt->mnt_sb)->huge = shmem_huge;
4697 	else
4698 		shmem_huge = SHMEM_HUGE_NEVER; /* just in case it was patched */
4699 #endif
4700 	return;
4701 
4702 out1:
4703 	unregister_filesystem(&shmem_fs_type);
4704 out2:
4705 #ifdef CONFIG_TMPFS_QUOTA
4706 	unregister_quota_format(&shmem_quota_format);
4707 out3:
4708 #endif
4709 	shmem_destroy_inodecache();
4710 	shm_mnt = ERR_PTR(error);
4711 }
4712 
4713 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && defined(CONFIG_SYSFS)
4714 static ssize_t shmem_enabled_show(struct kobject *kobj,
4715 				  struct kobj_attribute *attr, char *buf)
4716 {
4717 	static const int values[] = {
4718 		SHMEM_HUGE_ALWAYS,
4719 		SHMEM_HUGE_WITHIN_SIZE,
4720 		SHMEM_HUGE_ADVISE,
4721 		SHMEM_HUGE_NEVER,
4722 		SHMEM_HUGE_DENY,
4723 		SHMEM_HUGE_FORCE,
4724 	};
4725 	int len = 0;
4726 	int i;
4727 
4728 	for (i = 0; i < ARRAY_SIZE(values); i++) {
4729 		len += sysfs_emit_at(buf, len,
4730 				shmem_huge == values[i] ? "%s[%s]" : "%s%s",
4731 				i ? " " : "", shmem_format_huge(values[i]));
4732 	}
4733 	len += sysfs_emit_at(buf, len, "\n");
4734 
4735 	return len;
4736 }
4737 
4738 static ssize_t shmem_enabled_store(struct kobject *kobj,
4739 		struct kobj_attribute *attr, const char *buf, size_t count)
4740 {
4741 	char tmp[16];
4742 	int huge;
4743 
4744 	if (count + 1 > sizeof(tmp))
4745 		return -EINVAL;
4746 	memcpy(tmp, buf, count);
4747 	tmp[count] = '\0';
4748 	if (count && tmp[count - 1] == '\n')
4749 		tmp[count - 1] = '\0';
4750 
4751 	huge = shmem_parse_huge(tmp);
4752 	if (huge == -EINVAL)
4753 		return -EINVAL;
4754 	if (!has_transparent_hugepage() &&
4755 			huge != SHMEM_HUGE_NEVER && huge != SHMEM_HUGE_DENY)
4756 		return -EINVAL;
4757 
4758 	shmem_huge = huge;
4759 	if (shmem_huge > SHMEM_HUGE_DENY)
4760 		SHMEM_SB(shm_mnt->mnt_sb)->huge = shmem_huge;
4761 	return count;
4762 }
4763 
4764 struct kobj_attribute shmem_enabled_attr = __ATTR_RW(shmem_enabled);
4765 #endif /* CONFIG_TRANSPARENT_HUGEPAGE && CONFIG_SYSFS */
4766 
4767 #else /* !CONFIG_SHMEM */
4768 
4769 /*
4770  * tiny-shmem: simple shmemfs and tmpfs using ramfs code
4771  *
4772  * This is intended for small system where the benefits of the full
4773  * shmem code (swap-backed and resource-limited) are outweighed by
4774  * their complexity. On systems without swap this code should be
4775  * effectively equivalent, but much lighter weight.
4776  */
4777 
4778 static struct file_system_type shmem_fs_type = {
4779 	.name		= "tmpfs",
4780 	.init_fs_context = ramfs_init_fs_context,
4781 	.parameters	= ramfs_fs_parameters,
4782 	.kill_sb	= ramfs_kill_sb,
4783 	.fs_flags	= FS_USERNS_MOUNT,
4784 };
4785 
4786 void __init shmem_init(void)
4787 {
4788 	BUG_ON(register_filesystem(&shmem_fs_type) != 0);
4789 
4790 	shm_mnt = kern_mount(&shmem_fs_type);
4791 	BUG_ON(IS_ERR(shm_mnt));
4792 }
4793 
4794 int shmem_unuse(unsigned int type)
4795 {
4796 	return 0;
4797 }
4798 
4799 int shmem_lock(struct file *file, int lock, struct ucounts *ucounts)
4800 {
4801 	return 0;
4802 }
4803 
4804 void shmem_unlock_mapping(struct address_space *mapping)
4805 {
4806 }
4807 
4808 #ifdef CONFIG_MMU
4809 unsigned long shmem_get_unmapped_area(struct file *file,
4810 				      unsigned long addr, unsigned long len,
4811 				      unsigned long pgoff, unsigned long flags)
4812 {
4813 	return mm_get_unmapped_area(current->mm, file, addr, len, pgoff, flags);
4814 }
4815 #endif
4816 
4817 void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
4818 {
4819 	truncate_inode_pages_range(inode->i_mapping, lstart, lend);
4820 }
4821 EXPORT_SYMBOL_GPL(shmem_truncate_range);
4822 
4823 #define shmem_vm_ops				generic_file_vm_ops
4824 #define shmem_anon_vm_ops			generic_file_vm_ops
4825 #define shmem_file_operations			ramfs_file_operations
4826 #define shmem_acct_size(flags, size)		0
4827 #define shmem_unacct_size(flags, size)		do {} while (0)
4828 
4829 static inline struct inode *shmem_get_inode(struct mnt_idmap *idmap,
4830 				struct super_block *sb, struct inode *dir,
4831 				umode_t mode, dev_t dev, unsigned long flags)
4832 {
4833 	struct inode *inode = ramfs_get_inode(sb, dir, mode, dev);
4834 	return inode ? inode : ERR_PTR(-ENOSPC);
4835 }
4836 
4837 #endif /* CONFIG_SHMEM */
4838 
4839 /* common code */
4840 
4841 static struct file *__shmem_file_setup(struct vfsmount *mnt, const char *name,
4842 			loff_t size, unsigned long flags, unsigned int i_flags)
4843 {
4844 	struct inode *inode;
4845 	struct file *res;
4846 
4847 	if (IS_ERR(mnt))
4848 		return ERR_CAST(mnt);
4849 
4850 	if (size < 0 || size > MAX_LFS_FILESIZE)
4851 		return ERR_PTR(-EINVAL);
4852 
4853 	if (shmem_acct_size(flags, size))
4854 		return ERR_PTR(-ENOMEM);
4855 
4856 	if (is_idmapped_mnt(mnt))
4857 		return ERR_PTR(-EINVAL);
4858 
4859 	inode = shmem_get_inode(&nop_mnt_idmap, mnt->mnt_sb, NULL,
4860 				S_IFREG | S_IRWXUGO, 0, flags);
4861 	if (IS_ERR(inode)) {
4862 		shmem_unacct_size(flags, size);
4863 		return ERR_CAST(inode);
4864 	}
4865 	inode->i_flags |= i_flags;
4866 	inode->i_size = size;
4867 	clear_nlink(inode);	/* It is unlinked */
4868 	res = ERR_PTR(ramfs_nommu_expand_for_mapping(inode, size));
4869 	if (!IS_ERR(res))
4870 		res = alloc_file_pseudo(inode, mnt, name, O_RDWR,
4871 				&shmem_file_operations);
4872 	if (IS_ERR(res))
4873 		iput(inode);
4874 	return res;
4875 }
4876 
4877 /**
4878  * shmem_kernel_file_setup - get an unlinked file living in tmpfs which must be
4879  * 	kernel internal.  There will be NO LSM permission checks against the
4880  * 	underlying inode.  So users of this interface must do LSM checks at a
4881  *	higher layer.  The users are the big_key and shm implementations.  LSM
4882  *	checks are provided at the key or shm level rather than the inode.
4883  * @name: name for dentry (to be seen in /proc/<pid>/maps
4884  * @size: size to be set for the file
4885  * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
4886  */
4887 struct file *shmem_kernel_file_setup(const char *name, loff_t size, unsigned long flags)
4888 {
4889 	return __shmem_file_setup(shm_mnt, name, size, flags, S_PRIVATE);
4890 }
4891 EXPORT_SYMBOL_GPL(shmem_kernel_file_setup);
4892 
4893 /**
4894  * shmem_file_setup - get an unlinked file living in tmpfs
4895  * @name: name for dentry (to be seen in /proc/<pid>/maps
4896  * @size: size to be set for the file
4897  * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
4898  */
4899 struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags)
4900 {
4901 	return __shmem_file_setup(shm_mnt, name, size, flags, 0);
4902 }
4903 EXPORT_SYMBOL_GPL(shmem_file_setup);
4904 
4905 /**
4906  * shmem_file_setup_with_mnt - get an unlinked file living in tmpfs
4907  * @mnt: the tmpfs mount where the file will be created
4908  * @name: name for dentry (to be seen in /proc/<pid>/maps
4909  * @size: size to be set for the file
4910  * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
4911  */
4912 struct file *shmem_file_setup_with_mnt(struct vfsmount *mnt, const char *name,
4913 				       loff_t size, unsigned long flags)
4914 {
4915 	return __shmem_file_setup(mnt, name, size, flags, 0);
4916 }
4917 EXPORT_SYMBOL_GPL(shmem_file_setup_with_mnt);
4918 
4919 /**
4920  * shmem_zero_setup - setup a shared anonymous mapping
4921  * @vma: the vma to be mmapped is prepared by do_mmap
4922  */
4923 int shmem_zero_setup(struct vm_area_struct *vma)
4924 {
4925 	struct file *file;
4926 	loff_t size = vma->vm_end - vma->vm_start;
4927 
4928 	/*
4929 	 * Cloning a new file under mmap_lock leads to a lock ordering conflict
4930 	 * between XFS directory reading and selinux: since this file is only
4931 	 * accessible to the user through its mapping, use S_PRIVATE flag to
4932 	 * bypass file security, in the same way as shmem_kernel_file_setup().
4933 	 */
4934 	file = shmem_kernel_file_setup("dev/zero", size, vma->vm_flags);
4935 	if (IS_ERR(file))
4936 		return PTR_ERR(file);
4937 
4938 	if (vma->vm_file)
4939 		fput(vma->vm_file);
4940 	vma->vm_file = file;
4941 	vma->vm_ops = &shmem_anon_vm_ops;
4942 
4943 	return 0;
4944 }
4945 
4946 /**
4947  * shmem_read_folio_gfp - read into page cache, using specified page allocation flags.
4948  * @mapping:	the folio's address_space
4949  * @index:	the folio index
4950  * @gfp:	the page allocator flags to use if allocating
4951  *
4952  * This behaves as a tmpfs "read_cache_page_gfp(mapping, index, gfp)",
4953  * with any new page allocations done using the specified allocation flags.
4954  * But read_cache_page_gfp() uses the ->read_folio() method: which does not
4955  * suit tmpfs, since it may have pages in swapcache, and needs to find those
4956  * for itself; although drivers/gpu/drm i915 and ttm rely upon this support.
4957  *
4958  * i915_gem_object_get_pages_gtt() mixes __GFP_NORETRY | __GFP_NOWARN in
4959  * with the mapping_gfp_mask(), to avoid OOMing the machine unnecessarily.
4960  */
4961 struct folio *shmem_read_folio_gfp(struct address_space *mapping,
4962 		pgoff_t index, gfp_t gfp)
4963 {
4964 #ifdef CONFIG_SHMEM
4965 	struct inode *inode = mapping->host;
4966 	struct folio *folio;
4967 	int error;
4968 
4969 	error = shmem_get_folio_gfp(inode, index, &folio, SGP_CACHE,
4970 				    gfp, NULL, NULL);
4971 	if (error)
4972 		return ERR_PTR(error);
4973 
4974 	folio_unlock(folio);
4975 	return folio;
4976 #else
4977 	/*
4978 	 * The tiny !SHMEM case uses ramfs without swap
4979 	 */
4980 	return mapping_read_folio_gfp(mapping, index, gfp);
4981 #endif
4982 }
4983 EXPORT_SYMBOL_GPL(shmem_read_folio_gfp);
4984 
4985 struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
4986 					 pgoff_t index, gfp_t gfp)
4987 {
4988 	struct folio *folio = shmem_read_folio_gfp(mapping, index, gfp);
4989 	struct page *page;
4990 
4991 	if (IS_ERR(folio))
4992 		return &folio->page;
4993 
4994 	page = folio_file_page(folio, index);
4995 	if (PageHWPoison(page)) {
4996 		folio_put(folio);
4997 		return ERR_PTR(-EIO);
4998 	}
4999 
5000 	return page;
5001 }
5002 EXPORT_SYMBOL_GPL(shmem_read_mapping_page_gfp);
5003