xref: /openbmc/linux/mm/shmem.c (revision 90cb380f9ceb811059340d06ff5fd0c0e93ecbe1)
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/swap.h>
37  #include <linux/uio.h>
38  #include <linux/hugetlb.h>
39  #include <linux/fs_parser.h>
40  #include <linux/swapfile.h>
41  #include "swap.h"
42  
43  static struct vfsmount *shm_mnt;
44  
45  #ifdef CONFIG_SHMEM
46  /*
47   * This virtual memory filesystem is heavily based on the ramfs. It
48   * extends ramfs by the ability to use swap and honor resource limits
49   * which makes it a completely usable filesystem.
50   */
51  
52  #include <linux/xattr.h>
53  #include <linux/exportfs.h>
54  #include <linux/posix_acl.h>
55  #include <linux/posix_acl_xattr.h>
56  #include <linux/mman.h>
57  #include <linux/string.h>
58  #include <linux/slab.h>
59  #include <linux/backing-dev.h>
60  #include <linux/shmem_fs.h>
61  #include <linux/writeback.h>
62  #include <linux/pagevec.h>
63  #include <linux/percpu_counter.h>
64  #include <linux/falloc.h>
65  #include <linux/splice.h>
66  #include <linux/security.h>
67  #include <linux/swapops.h>
68  #include <linux/mempolicy.h>
69  #include <linux/namei.h>
70  #include <linux/ctype.h>
71  #include <linux/migrate.h>
72  #include <linux/highmem.h>
73  #include <linux/seq_file.h>
74  #include <linux/magic.h>
75  #include <linux/syscalls.h>
76  #include <linux/fcntl.h>
77  #include <uapi/linux/memfd.h>
78  #include <linux/userfaultfd_k.h>
79  #include <linux/rmap.h>
80  #include <linux/uuid.h>
81  
82  #include <linux/uaccess.h>
83  
84  #include "internal.h"
85  
86  #define BLOCKS_PER_PAGE  (PAGE_SIZE/512)
87  #define VM_ACCT(size)    (PAGE_ALIGN(size) >> PAGE_SHIFT)
88  
89  /* Pretend that each entry is of this size in directory's i_size */
90  #define BOGO_DIRENT_SIZE 20
91  
92  /* Symlink up to this size is kmalloc'ed instead of using a swappable page */
93  #define SHORT_SYMLINK_LEN 128
94  
95  /*
96   * shmem_fallocate communicates with shmem_fault or shmem_writepage via
97   * inode->i_private (with i_rwsem making sure that it has only one user at
98   * a time): we would prefer not to enlarge the shmem inode just for that.
99   */
100  struct shmem_falloc {
101  	wait_queue_head_t *waitq; /* faults into hole wait for punch to end */
102  	pgoff_t start;		/* start of range currently being fallocated */
103  	pgoff_t next;		/* the next page offset to be fallocated */
104  	pgoff_t nr_falloced;	/* how many new pages have been fallocated */
105  	pgoff_t nr_unswapped;	/* how often writepage refused to swap out */
106  };
107  
108  struct shmem_options {
109  	unsigned long long blocks;
110  	unsigned long long inodes;
111  	struct mempolicy *mpol;
112  	kuid_t uid;
113  	kgid_t gid;
114  	umode_t mode;
115  	bool full_inums;
116  	int huge;
117  	int seen;
118  #define SHMEM_SEEN_BLOCKS 1
119  #define SHMEM_SEEN_INODES 2
120  #define SHMEM_SEEN_HUGE 4
121  #define SHMEM_SEEN_INUMS 8
122  };
123  
124  #ifdef CONFIG_TMPFS
125  static unsigned long shmem_default_max_blocks(void)
126  {
127  	return totalram_pages() / 2;
128  }
129  
130  static unsigned long shmem_default_max_inodes(void)
131  {
132  	unsigned long nr_pages = totalram_pages();
133  
134  	return min(nr_pages - totalhigh_pages(), nr_pages / 2);
135  }
136  #endif
137  
138  static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
139  			     struct folio **foliop, enum sgp_type sgp,
140  			     gfp_t gfp, struct vm_area_struct *vma,
141  			     vm_fault_t *fault_type);
142  static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
143  		struct page **pagep, enum sgp_type sgp,
144  		gfp_t gfp, struct vm_area_struct *vma,
145  		struct vm_fault *vmf, vm_fault_t *fault_type);
146  
147  int shmem_getpage(struct inode *inode, pgoff_t index,
148  		struct page **pagep, enum sgp_type sgp)
149  {
150  	return shmem_getpage_gfp(inode, index, pagep, sgp,
151  		mapping_gfp_mask(inode->i_mapping), NULL, NULL, NULL);
152  }
153  
154  static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
155  {
156  	return sb->s_fs_info;
157  }
158  
159  /*
160   * shmem_file_setup pre-accounts the whole fixed size of a VM object,
161   * for shared memory and for shared anonymous (/dev/zero) mappings
162   * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
163   * consistent with the pre-accounting of private mappings ...
164   */
165  static inline int shmem_acct_size(unsigned long flags, loff_t size)
166  {
167  	return (flags & VM_NORESERVE) ?
168  		0 : security_vm_enough_memory_mm(current->mm, VM_ACCT(size));
169  }
170  
171  static inline void shmem_unacct_size(unsigned long flags, loff_t size)
172  {
173  	if (!(flags & VM_NORESERVE))
174  		vm_unacct_memory(VM_ACCT(size));
175  }
176  
177  static inline int shmem_reacct_size(unsigned long flags,
178  		loff_t oldsize, loff_t newsize)
179  {
180  	if (!(flags & VM_NORESERVE)) {
181  		if (VM_ACCT(newsize) > VM_ACCT(oldsize))
182  			return security_vm_enough_memory_mm(current->mm,
183  					VM_ACCT(newsize) - VM_ACCT(oldsize));
184  		else if (VM_ACCT(newsize) < VM_ACCT(oldsize))
185  			vm_unacct_memory(VM_ACCT(oldsize) - VM_ACCT(newsize));
186  	}
187  	return 0;
188  }
189  
190  /*
191   * ... whereas tmpfs objects are accounted incrementally as
192   * pages are allocated, in order to allow large sparse files.
193   * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
194   * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
195   */
196  static inline int shmem_acct_block(unsigned long flags, long pages)
197  {
198  	if (!(flags & VM_NORESERVE))
199  		return 0;
200  
201  	return security_vm_enough_memory_mm(current->mm,
202  			pages * VM_ACCT(PAGE_SIZE));
203  }
204  
205  static inline void shmem_unacct_blocks(unsigned long flags, long pages)
206  {
207  	if (flags & VM_NORESERVE)
208  		vm_unacct_memory(pages * VM_ACCT(PAGE_SIZE));
209  }
210  
211  static inline bool shmem_inode_acct_block(struct inode *inode, long pages)
212  {
213  	struct shmem_inode_info *info = SHMEM_I(inode);
214  	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
215  
216  	if (shmem_acct_block(info->flags, pages))
217  		return false;
218  
219  	if (sbinfo->max_blocks) {
220  		if (percpu_counter_compare(&sbinfo->used_blocks,
221  					   sbinfo->max_blocks - pages) > 0)
222  			goto unacct;
223  		percpu_counter_add(&sbinfo->used_blocks, pages);
224  	}
225  
226  	return true;
227  
228  unacct:
229  	shmem_unacct_blocks(info->flags, pages);
230  	return false;
231  }
232  
233  static inline void shmem_inode_unacct_blocks(struct inode *inode, long pages)
234  {
235  	struct shmem_inode_info *info = SHMEM_I(inode);
236  	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
237  
238  	if (sbinfo->max_blocks)
239  		percpu_counter_sub(&sbinfo->used_blocks, pages);
240  	shmem_unacct_blocks(info->flags, pages);
241  }
242  
243  static const struct super_operations shmem_ops;
244  const struct address_space_operations shmem_aops;
245  static const struct file_operations shmem_file_operations;
246  static const struct inode_operations shmem_inode_operations;
247  static const struct inode_operations shmem_dir_inode_operations;
248  static const struct inode_operations shmem_special_inode_operations;
249  static const struct vm_operations_struct shmem_vm_ops;
250  static struct file_system_type shmem_fs_type;
251  
252  bool vma_is_shmem(struct vm_area_struct *vma)
253  {
254  	return vma->vm_ops == &shmem_vm_ops;
255  }
256  
257  static LIST_HEAD(shmem_swaplist);
258  static DEFINE_MUTEX(shmem_swaplist_mutex);
259  
260  /*
261   * shmem_reserve_inode() performs bookkeeping to reserve a shmem inode, and
262   * produces a novel ino for the newly allocated inode.
263   *
264   * It may also be called when making a hard link to permit the space needed by
265   * each dentry. However, in that case, no new inode number is needed since that
266   * internally draws from another pool of inode numbers (currently global
267   * get_next_ino()). This case is indicated by passing NULL as inop.
268   */
269  #define SHMEM_INO_BATCH 1024
270  static int shmem_reserve_inode(struct super_block *sb, ino_t *inop)
271  {
272  	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
273  	ino_t ino;
274  
275  	if (!(sb->s_flags & SB_KERNMOUNT)) {
276  		raw_spin_lock(&sbinfo->stat_lock);
277  		if (sbinfo->max_inodes) {
278  			if (!sbinfo->free_inodes) {
279  				raw_spin_unlock(&sbinfo->stat_lock);
280  				return -ENOSPC;
281  			}
282  			sbinfo->free_inodes--;
283  		}
284  		if (inop) {
285  			ino = sbinfo->next_ino++;
286  			if (unlikely(is_zero_ino(ino)))
287  				ino = sbinfo->next_ino++;
288  			if (unlikely(!sbinfo->full_inums &&
289  				     ino > UINT_MAX)) {
290  				/*
291  				 * Emulate get_next_ino uint wraparound for
292  				 * compatibility
293  				 */
294  				if (IS_ENABLED(CONFIG_64BIT))
295  					pr_warn("%s: inode number overflow on device %d, consider using inode64 mount option\n",
296  						__func__, MINOR(sb->s_dev));
297  				sbinfo->next_ino = 1;
298  				ino = sbinfo->next_ino++;
299  			}
300  			*inop = ino;
301  		}
302  		raw_spin_unlock(&sbinfo->stat_lock);
303  	} else if (inop) {
304  		/*
305  		 * __shmem_file_setup, one of our callers, is lock-free: it
306  		 * doesn't hold stat_lock in shmem_reserve_inode since
307  		 * max_inodes is always 0, and is called from potentially
308  		 * unknown contexts. As such, use a per-cpu batched allocator
309  		 * which doesn't require the per-sb stat_lock unless we are at
310  		 * the batch boundary.
311  		 *
312  		 * We don't need to worry about inode{32,64} since SB_KERNMOUNT
313  		 * shmem mounts are not exposed to userspace, so we don't need
314  		 * to worry about things like glibc compatibility.
315  		 */
316  		ino_t *next_ino;
317  
318  		next_ino = per_cpu_ptr(sbinfo->ino_batch, get_cpu());
319  		ino = *next_ino;
320  		if (unlikely(ino % SHMEM_INO_BATCH == 0)) {
321  			raw_spin_lock(&sbinfo->stat_lock);
322  			ino = sbinfo->next_ino;
323  			sbinfo->next_ino += SHMEM_INO_BATCH;
324  			raw_spin_unlock(&sbinfo->stat_lock);
325  			if (unlikely(is_zero_ino(ino)))
326  				ino++;
327  		}
328  		*inop = ino;
329  		*next_ino = ++ino;
330  		put_cpu();
331  	}
332  
333  	return 0;
334  }
335  
336  static void shmem_free_inode(struct super_block *sb)
337  {
338  	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
339  	if (sbinfo->max_inodes) {
340  		raw_spin_lock(&sbinfo->stat_lock);
341  		sbinfo->free_inodes++;
342  		raw_spin_unlock(&sbinfo->stat_lock);
343  	}
344  }
345  
346  /**
347   * shmem_recalc_inode - recalculate the block usage of an inode
348   * @inode: inode to recalc
349   *
350   * We have to calculate the free blocks since the mm can drop
351   * undirtied hole pages behind our back.
352   *
353   * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
354   * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
355   *
356   * It has to be called with the spinlock held.
357   */
358  static void shmem_recalc_inode(struct inode *inode)
359  {
360  	struct shmem_inode_info *info = SHMEM_I(inode);
361  	long freed;
362  
363  	freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
364  	if (freed > 0) {
365  		info->alloced -= freed;
366  		inode->i_blocks -= freed * BLOCKS_PER_PAGE;
367  		shmem_inode_unacct_blocks(inode, freed);
368  	}
369  }
370  
371  bool shmem_charge(struct inode *inode, long pages)
372  {
373  	struct shmem_inode_info *info = SHMEM_I(inode);
374  	unsigned long flags;
375  
376  	if (!shmem_inode_acct_block(inode, pages))
377  		return false;
378  
379  	/* nrpages adjustment first, then shmem_recalc_inode() when balanced */
380  	inode->i_mapping->nrpages += pages;
381  
382  	spin_lock_irqsave(&info->lock, flags);
383  	info->alloced += pages;
384  	inode->i_blocks += pages * BLOCKS_PER_PAGE;
385  	shmem_recalc_inode(inode);
386  	spin_unlock_irqrestore(&info->lock, flags);
387  
388  	return true;
389  }
390  
391  void shmem_uncharge(struct inode *inode, long pages)
392  {
393  	struct shmem_inode_info *info = SHMEM_I(inode);
394  	unsigned long flags;
395  
396  	/* nrpages adjustment done by __filemap_remove_folio() or caller */
397  
398  	spin_lock_irqsave(&info->lock, flags);
399  	info->alloced -= pages;
400  	inode->i_blocks -= pages * BLOCKS_PER_PAGE;
401  	shmem_recalc_inode(inode);
402  	spin_unlock_irqrestore(&info->lock, flags);
403  
404  	shmem_inode_unacct_blocks(inode, pages);
405  }
406  
407  /*
408   * Replace item expected in xarray by a new item, while holding xa_lock.
409   */
410  static int shmem_replace_entry(struct address_space *mapping,
411  			pgoff_t index, void *expected, void *replacement)
412  {
413  	XA_STATE(xas, &mapping->i_pages, index);
414  	void *item;
415  
416  	VM_BUG_ON(!expected);
417  	VM_BUG_ON(!replacement);
418  	item = xas_load(&xas);
419  	if (item != expected)
420  		return -ENOENT;
421  	xas_store(&xas, replacement);
422  	return 0;
423  }
424  
425  /*
426   * Sometimes, before we decide whether to proceed or to fail, we must check
427   * that an entry was not already brought back from swap by a racing thread.
428   *
429   * Checking page is not enough: by the time a SwapCache page is locked, it
430   * might be reused, and again be SwapCache, using the same swap as before.
431   */
432  static bool shmem_confirm_swap(struct address_space *mapping,
433  			       pgoff_t index, swp_entry_t swap)
434  {
435  	return xa_load(&mapping->i_pages, index) == swp_to_radix_entry(swap);
436  }
437  
438  /*
439   * Definitions for "huge tmpfs": tmpfs mounted with the huge= option
440   *
441   * SHMEM_HUGE_NEVER:
442   *	disables huge pages for the mount;
443   * SHMEM_HUGE_ALWAYS:
444   *	enables huge pages for the mount;
445   * SHMEM_HUGE_WITHIN_SIZE:
446   *	only allocate huge pages if the page will be fully within i_size,
447   *	also respect fadvise()/madvise() hints;
448   * SHMEM_HUGE_ADVISE:
449   *	only allocate huge pages if requested with fadvise()/madvise();
450   */
451  
452  #define SHMEM_HUGE_NEVER	0
453  #define SHMEM_HUGE_ALWAYS	1
454  #define SHMEM_HUGE_WITHIN_SIZE	2
455  #define SHMEM_HUGE_ADVISE	3
456  
457  /*
458   * Special values.
459   * Only can be set via /sys/kernel/mm/transparent_hugepage/shmem_enabled:
460   *
461   * SHMEM_HUGE_DENY:
462   *	disables huge on shm_mnt and all mounts, for emergency use;
463   * SHMEM_HUGE_FORCE:
464   *	enables huge on shm_mnt and all mounts, w/o needing option, for testing;
465   *
466   */
467  #define SHMEM_HUGE_DENY		(-1)
468  #define SHMEM_HUGE_FORCE	(-2)
469  
470  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
471  /* ifdef here to avoid bloating shmem.o when not necessary */
472  
473  static int shmem_huge __read_mostly = SHMEM_HUGE_NEVER;
474  
475  bool shmem_is_huge(struct vm_area_struct *vma,
476  		   struct inode *inode, pgoff_t index)
477  {
478  	loff_t i_size;
479  
480  	if (!S_ISREG(inode->i_mode))
481  		return false;
482  	if (shmem_huge == SHMEM_HUGE_DENY)
483  		return false;
484  	if (vma && ((vma->vm_flags & VM_NOHUGEPAGE) ||
485  	    test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags)))
486  		return false;
487  	if (shmem_huge == SHMEM_HUGE_FORCE)
488  		return true;
489  
490  	switch (SHMEM_SB(inode->i_sb)->huge) {
491  	case SHMEM_HUGE_ALWAYS:
492  		return true;
493  	case SHMEM_HUGE_WITHIN_SIZE:
494  		index = round_up(index + 1, HPAGE_PMD_NR);
495  		i_size = round_up(i_size_read(inode), PAGE_SIZE);
496  		if (i_size >> PAGE_SHIFT >= index)
497  			return true;
498  		fallthrough;
499  	case SHMEM_HUGE_ADVISE:
500  		if (vma && (vma->vm_flags & VM_HUGEPAGE))
501  			return true;
502  		fallthrough;
503  	default:
504  		return false;
505  	}
506  }
507  
508  #if defined(CONFIG_SYSFS)
509  static int shmem_parse_huge(const char *str)
510  {
511  	if (!strcmp(str, "never"))
512  		return SHMEM_HUGE_NEVER;
513  	if (!strcmp(str, "always"))
514  		return SHMEM_HUGE_ALWAYS;
515  	if (!strcmp(str, "within_size"))
516  		return SHMEM_HUGE_WITHIN_SIZE;
517  	if (!strcmp(str, "advise"))
518  		return SHMEM_HUGE_ADVISE;
519  	if (!strcmp(str, "deny"))
520  		return SHMEM_HUGE_DENY;
521  	if (!strcmp(str, "force"))
522  		return SHMEM_HUGE_FORCE;
523  	return -EINVAL;
524  }
525  #endif
526  
527  #if defined(CONFIG_SYSFS) || defined(CONFIG_TMPFS)
528  static const char *shmem_format_huge(int huge)
529  {
530  	switch (huge) {
531  	case SHMEM_HUGE_NEVER:
532  		return "never";
533  	case SHMEM_HUGE_ALWAYS:
534  		return "always";
535  	case SHMEM_HUGE_WITHIN_SIZE:
536  		return "within_size";
537  	case SHMEM_HUGE_ADVISE:
538  		return "advise";
539  	case SHMEM_HUGE_DENY:
540  		return "deny";
541  	case SHMEM_HUGE_FORCE:
542  		return "force";
543  	default:
544  		VM_BUG_ON(1);
545  		return "bad_val";
546  	}
547  }
548  #endif
549  
550  static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
551  		struct shrink_control *sc, unsigned long nr_to_split)
552  {
553  	LIST_HEAD(list), *pos, *next;
554  	LIST_HEAD(to_remove);
555  	struct inode *inode;
556  	struct shmem_inode_info *info;
557  	struct folio *folio;
558  	unsigned long batch = sc ? sc->nr_to_scan : 128;
559  	int split = 0;
560  
561  	if (list_empty(&sbinfo->shrinklist))
562  		return SHRINK_STOP;
563  
564  	spin_lock(&sbinfo->shrinklist_lock);
565  	list_for_each_safe(pos, next, &sbinfo->shrinklist) {
566  		info = list_entry(pos, struct shmem_inode_info, shrinklist);
567  
568  		/* pin the inode */
569  		inode = igrab(&info->vfs_inode);
570  
571  		/* inode is about to be evicted */
572  		if (!inode) {
573  			list_del_init(&info->shrinklist);
574  			goto next;
575  		}
576  
577  		/* Check if there's anything to gain */
578  		if (round_up(inode->i_size, PAGE_SIZE) ==
579  				round_up(inode->i_size, HPAGE_PMD_SIZE)) {
580  			list_move(&info->shrinklist, &to_remove);
581  			goto next;
582  		}
583  
584  		list_move(&info->shrinklist, &list);
585  next:
586  		sbinfo->shrinklist_len--;
587  		if (!--batch)
588  			break;
589  	}
590  	spin_unlock(&sbinfo->shrinklist_lock);
591  
592  	list_for_each_safe(pos, next, &to_remove) {
593  		info = list_entry(pos, struct shmem_inode_info, shrinklist);
594  		inode = &info->vfs_inode;
595  		list_del_init(&info->shrinklist);
596  		iput(inode);
597  	}
598  
599  	list_for_each_safe(pos, next, &list) {
600  		int ret;
601  		pgoff_t index;
602  
603  		info = list_entry(pos, struct shmem_inode_info, shrinklist);
604  		inode = &info->vfs_inode;
605  
606  		if (nr_to_split && split >= nr_to_split)
607  			goto move_back;
608  
609  		index = (inode->i_size & HPAGE_PMD_MASK) >> PAGE_SHIFT;
610  		folio = filemap_get_folio(inode->i_mapping, index);
611  		if (!folio)
612  			goto drop;
613  
614  		/* No huge page at the end of the file: nothing to split */
615  		if (!folio_test_large(folio)) {
616  			folio_put(folio);
617  			goto drop;
618  		}
619  
620  		/*
621  		 * Move the inode on the list back to shrinklist if we failed
622  		 * to lock the page at this time.
623  		 *
624  		 * Waiting for the lock may lead to deadlock in the
625  		 * reclaim path.
626  		 */
627  		if (!folio_trylock(folio)) {
628  			folio_put(folio);
629  			goto move_back;
630  		}
631  
632  		ret = split_huge_page(&folio->page);
633  		folio_unlock(folio);
634  		folio_put(folio);
635  
636  		/* If split failed move the inode on the list back to shrinklist */
637  		if (ret)
638  			goto move_back;
639  
640  		split++;
641  drop:
642  		list_del_init(&info->shrinklist);
643  		goto put;
644  move_back:
645  		/*
646  		 * Make sure the inode is either on the global list or deleted
647  		 * from any local list before iput() since it could be deleted
648  		 * in another thread once we put the inode (then the local list
649  		 * is corrupted).
650  		 */
651  		spin_lock(&sbinfo->shrinklist_lock);
652  		list_move(&info->shrinklist, &sbinfo->shrinklist);
653  		sbinfo->shrinklist_len++;
654  		spin_unlock(&sbinfo->shrinklist_lock);
655  put:
656  		iput(inode);
657  	}
658  
659  	return split;
660  }
661  
662  static long shmem_unused_huge_scan(struct super_block *sb,
663  		struct shrink_control *sc)
664  {
665  	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
666  
667  	if (!READ_ONCE(sbinfo->shrinklist_len))
668  		return SHRINK_STOP;
669  
670  	return shmem_unused_huge_shrink(sbinfo, sc, 0);
671  }
672  
673  static long shmem_unused_huge_count(struct super_block *sb,
674  		struct shrink_control *sc)
675  {
676  	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
677  	return READ_ONCE(sbinfo->shrinklist_len);
678  }
679  #else /* !CONFIG_TRANSPARENT_HUGEPAGE */
680  
681  #define shmem_huge SHMEM_HUGE_DENY
682  
683  bool shmem_is_huge(struct vm_area_struct *vma,
684  		   struct inode *inode, pgoff_t index)
685  {
686  	return false;
687  }
688  
689  static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
690  		struct shrink_control *sc, unsigned long nr_to_split)
691  {
692  	return 0;
693  }
694  #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
695  
696  /*
697   * Like filemap_add_folio, but error if expected item has gone.
698   */
699  static int shmem_add_to_page_cache(struct folio *folio,
700  				   struct address_space *mapping,
701  				   pgoff_t index, void *expected, gfp_t gfp,
702  				   struct mm_struct *charge_mm)
703  {
704  	XA_STATE_ORDER(xas, &mapping->i_pages, index, folio_order(folio));
705  	long nr = folio_nr_pages(folio);
706  	int error;
707  
708  	VM_BUG_ON_FOLIO(index != round_down(index, nr), folio);
709  	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
710  	VM_BUG_ON_FOLIO(!folio_test_swapbacked(folio), folio);
711  	VM_BUG_ON(expected && folio_test_large(folio));
712  
713  	folio_ref_add(folio, nr);
714  	folio->mapping = mapping;
715  	folio->index = index;
716  
717  	if (!folio_test_swapcache(folio)) {
718  		error = mem_cgroup_charge(folio, charge_mm, gfp);
719  		if (error) {
720  			if (folio_test_pmd_mappable(folio)) {
721  				count_vm_event(THP_FILE_FALLBACK);
722  				count_vm_event(THP_FILE_FALLBACK_CHARGE);
723  			}
724  			goto error;
725  		}
726  	}
727  	folio_throttle_swaprate(folio, gfp);
728  
729  	do {
730  		xas_lock_irq(&xas);
731  		if (expected != xas_find_conflict(&xas)) {
732  			xas_set_err(&xas, -EEXIST);
733  			goto unlock;
734  		}
735  		if (expected && xas_find_conflict(&xas)) {
736  			xas_set_err(&xas, -EEXIST);
737  			goto unlock;
738  		}
739  		xas_store(&xas, folio);
740  		if (xas_error(&xas))
741  			goto unlock;
742  		if (folio_test_pmd_mappable(folio)) {
743  			count_vm_event(THP_FILE_ALLOC);
744  			__lruvec_stat_mod_folio(folio, NR_SHMEM_THPS, nr);
745  		}
746  		mapping->nrpages += nr;
747  		__lruvec_stat_mod_folio(folio, NR_FILE_PAGES, nr);
748  		__lruvec_stat_mod_folio(folio, NR_SHMEM, nr);
749  unlock:
750  		xas_unlock_irq(&xas);
751  	} while (xas_nomem(&xas, gfp));
752  
753  	if (xas_error(&xas)) {
754  		error = xas_error(&xas);
755  		goto error;
756  	}
757  
758  	return 0;
759  error:
760  	folio->mapping = NULL;
761  	folio_ref_sub(folio, nr);
762  	return error;
763  }
764  
765  /*
766   * Like delete_from_page_cache, but substitutes swap for page.
767   */
768  static void shmem_delete_from_page_cache(struct page *page, void *radswap)
769  {
770  	struct address_space *mapping = page->mapping;
771  	int error;
772  
773  	VM_BUG_ON_PAGE(PageCompound(page), page);
774  
775  	xa_lock_irq(&mapping->i_pages);
776  	error = shmem_replace_entry(mapping, page->index, page, radswap);
777  	page->mapping = NULL;
778  	mapping->nrpages--;
779  	__dec_lruvec_page_state(page, NR_FILE_PAGES);
780  	__dec_lruvec_page_state(page, NR_SHMEM);
781  	xa_unlock_irq(&mapping->i_pages);
782  	put_page(page);
783  	BUG_ON(error);
784  }
785  
786  /*
787   * Remove swap entry from page cache, free the swap and its page cache.
788   */
789  static int shmem_free_swap(struct address_space *mapping,
790  			   pgoff_t index, void *radswap)
791  {
792  	void *old;
793  
794  	old = xa_cmpxchg_irq(&mapping->i_pages, index, radswap, NULL, 0);
795  	if (old != radswap)
796  		return -ENOENT;
797  	free_swap_and_cache(radix_to_swp_entry(radswap));
798  	return 0;
799  }
800  
801  /*
802   * Determine (in bytes) how many of the shmem object's pages mapped by the
803   * given offsets are swapped out.
804   *
805   * This is safe to call without i_rwsem or the i_pages lock thanks to RCU,
806   * as long as the inode doesn't go away and racy results are not a problem.
807   */
808  unsigned long shmem_partial_swap_usage(struct address_space *mapping,
809  						pgoff_t start, pgoff_t end)
810  {
811  	XA_STATE(xas, &mapping->i_pages, start);
812  	struct page *page;
813  	unsigned long swapped = 0;
814  
815  	rcu_read_lock();
816  	xas_for_each(&xas, page, end - 1) {
817  		if (xas_retry(&xas, page))
818  			continue;
819  		if (xa_is_value(page))
820  			swapped++;
821  
822  		if (need_resched()) {
823  			xas_pause(&xas);
824  			cond_resched_rcu();
825  		}
826  	}
827  
828  	rcu_read_unlock();
829  
830  	return swapped << PAGE_SHIFT;
831  }
832  
833  /*
834   * Determine (in bytes) how many of the shmem object's pages mapped by the
835   * given vma is swapped out.
836   *
837   * This is safe to call without i_rwsem or the i_pages lock thanks to RCU,
838   * as long as the inode doesn't go away and racy results are not a problem.
839   */
840  unsigned long shmem_swap_usage(struct vm_area_struct *vma)
841  {
842  	struct inode *inode = file_inode(vma->vm_file);
843  	struct shmem_inode_info *info = SHMEM_I(inode);
844  	struct address_space *mapping = inode->i_mapping;
845  	unsigned long swapped;
846  
847  	/* Be careful as we don't hold info->lock */
848  	swapped = READ_ONCE(info->swapped);
849  
850  	/*
851  	 * The easier cases are when the shmem object has nothing in swap, or
852  	 * the vma maps it whole. Then we can simply use the stats that we
853  	 * already track.
854  	 */
855  	if (!swapped)
856  		return 0;
857  
858  	if (!vma->vm_pgoff && vma->vm_end - vma->vm_start >= inode->i_size)
859  		return swapped << PAGE_SHIFT;
860  
861  	/* Here comes the more involved part */
862  	return shmem_partial_swap_usage(mapping, vma->vm_pgoff,
863  					vma->vm_pgoff + vma_pages(vma));
864  }
865  
866  /*
867   * SysV IPC SHM_UNLOCK restore Unevictable pages to their evictable lists.
868   */
869  void shmem_unlock_mapping(struct address_space *mapping)
870  {
871  	struct folio_batch fbatch;
872  	pgoff_t index = 0;
873  
874  	folio_batch_init(&fbatch);
875  	/*
876  	 * Minor point, but we might as well stop if someone else SHM_LOCKs it.
877  	 */
878  	while (!mapping_unevictable(mapping) &&
879  	       filemap_get_folios(mapping, &index, ~0UL, &fbatch)) {
880  		check_move_unevictable_folios(&fbatch);
881  		folio_batch_release(&fbatch);
882  		cond_resched();
883  	}
884  }
885  
886  static struct folio *shmem_get_partial_folio(struct inode *inode, pgoff_t index)
887  {
888  	struct folio *folio;
889  	struct page *page;
890  
891  	/*
892  	 * At first avoid shmem_getpage(,,,SGP_READ): that fails
893  	 * beyond i_size, and reports fallocated pages as holes.
894  	 */
895  	folio = __filemap_get_folio(inode->i_mapping, index,
896  					FGP_ENTRY | FGP_LOCK, 0);
897  	if (!xa_is_value(folio))
898  		return folio;
899  	/*
900  	 * But read a page back from swap if any of it is within i_size
901  	 * (although in some cases this is just a waste of time).
902  	 */
903  	page = NULL;
904  	shmem_getpage(inode, index, &page, SGP_READ);
905  	return page ? page_folio(page) : NULL;
906  }
907  
908  /*
909   * Remove range of pages and swap entries from page cache, and free them.
910   * If !unfalloc, truncate or punch hole; if unfalloc, undo failed fallocate.
911   */
912  static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
913  								 bool unfalloc)
914  {
915  	struct address_space *mapping = inode->i_mapping;
916  	struct shmem_inode_info *info = SHMEM_I(inode);
917  	pgoff_t start = (lstart + PAGE_SIZE - 1) >> PAGE_SHIFT;
918  	pgoff_t end = (lend + 1) >> PAGE_SHIFT;
919  	struct folio_batch fbatch;
920  	pgoff_t indices[PAGEVEC_SIZE];
921  	struct folio *folio;
922  	bool same_folio;
923  	long nr_swaps_freed = 0;
924  	pgoff_t index;
925  	int i;
926  
927  	if (lend == -1)
928  		end = -1;	/* unsigned, so actually very big */
929  
930  	if (info->fallocend > start && info->fallocend <= end && !unfalloc)
931  		info->fallocend = start;
932  
933  	folio_batch_init(&fbatch);
934  	index = start;
935  	while (index < end && find_lock_entries(mapping, index, end - 1,
936  			&fbatch, indices)) {
937  		for (i = 0; i < folio_batch_count(&fbatch); i++) {
938  			folio = fbatch.folios[i];
939  
940  			index = indices[i];
941  
942  			if (xa_is_value(folio)) {
943  				if (unfalloc)
944  					continue;
945  				nr_swaps_freed += !shmem_free_swap(mapping,
946  								index, folio);
947  				continue;
948  			}
949  			index += folio_nr_pages(folio) - 1;
950  
951  			if (!unfalloc || !folio_test_uptodate(folio))
952  				truncate_inode_folio(mapping, folio);
953  			folio_unlock(folio);
954  		}
955  		folio_batch_remove_exceptionals(&fbatch);
956  		folio_batch_release(&fbatch);
957  		cond_resched();
958  		index++;
959  	}
960  
961  	same_folio = (lstart >> PAGE_SHIFT) == (lend >> PAGE_SHIFT);
962  	folio = shmem_get_partial_folio(inode, lstart >> PAGE_SHIFT);
963  	if (folio) {
964  		same_folio = lend < folio_pos(folio) + folio_size(folio);
965  		folio_mark_dirty(folio);
966  		if (!truncate_inode_partial_folio(folio, lstart, lend)) {
967  			start = folio->index + folio_nr_pages(folio);
968  			if (same_folio)
969  				end = folio->index;
970  		}
971  		folio_unlock(folio);
972  		folio_put(folio);
973  		folio = NULL;
974  	}
975  
976  	if (!same_folio)
977  		folio = shmem_get_partial_folio(inode, lend >> PAGE_SHIFT);
978  	if (folio) {
979  		folio_mark_dirty(folio);
980  		if (!truncate_inode_partial_folio(folio, lstart, lend))
981  			end = folio->index;
982  		folio_unlock(folio);
983  		folio_put(folio);
984  	}
985  
986  	index = start;
987  	while (index < end) {
988  		cond_resched();
989  
990  		if (!find_get_entries(mapping, index, end - 1, &fbatch,
991  				indices)) {
992  			/* If all gone or hole-punch or unfalloc, we're done */
993  			if (index == start || end != -1)
994  				break;
995  			/* But if truncating, restart to make sure all gone */
996  			index = start;
997  			continue;
998  		}
999  		for (i = 0; i < folio_batch_count(&fbatch); i++) {
1000  			folio = fbatch.folios[i];
1001  
1002  			index = indices[i];
1003  			if (xa_is_value(folio)) {
1004  				if (unfalloc)
1005  					continue;
1006  				if (shmem_free_swap(mapping, index, folio)) {
1007  					/* Swap was replaced by page: retry */
1008  					index--;
1009  					break;
1010  				}
1011  				nr_swaps_freed++;
1012  				continue;
1013  			}
1014  
1015  			folio_lock(folio);
1016  
1017  			if (!unfalloc || !folio_test_uptodate(folio)) {
1018  				if (folio_mapping(folio) != mapping) {
1019  					/* Page was replaced by swap: retry */
1020  					folio_unlock(folio);
1021  					index--;
1022  					break;
1023  				}
1024  				VM_BUG_ON_FOLIO(folio_test_writeback(folio),
1025  						folio);
1026  				truncate_inode_folio(mapping, folio);
1027  			}
1028  			index = folio->index + folio_nr_pages(folio) - 1;
1029  			folio_unlock(folio);
1030  		}
1031  		folio_batch_remove_exceptionals(&fbatch);
1032  		folio_batch_release(&fbatch);
1033  		index++;
1034  	}
1035  
1036  	spin_lock_irq(&info->lock);
1037  	info->swapped -= nr_swaps_freed;
1038  	shmem_recalc_inode(inode);
1039  	spin_unlock_irq(&info->lock);
1040  }
1041  
1042  void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
1043  {
1044  	shmem_undo_range(inode, lstart, lend, false);
1045  	inode->i_ctime = inode->i_mtime = current_time(inode);
1046  }
1047  EXPORT_SYMBOL_GPL(shmem_truncate_range);
1048  
1049  static int shmem_getattr(struct user_namespace *mnt_userns,
1050  			 const struct path *path, struct kstat *stat,
1051  			 u32 request_mask, unsigned int query_flags)
1052  {
1053  	struct inode *inode = path->dentry->d_inode;
1054  	struct shmem_inode_info *info = SHMEM_I(inode);
1055  
1056  	if (info->alloced - info->swapped != inode->i_mapping->nrpages) {
1057  		spin_lock_irq(&info->lock);
1058  		shmem_recalc_inode(inode);
1059  		spin_unlock_irq(&info->lock);
1060  	}
1061  	if (info->fsflags & FS_APPEND_FL)
1062  		stat->attributes |= STATX_ATTR_APPEND;
1063  	if (info->fsflags & FS_IMMUTABLE_FL)
1064  		stat->attributes |= STATX_ATTR_IMMUTABLE;
1065  	if (info->fsflags & FS_NODUMP_FL)
1066  		stat->attributes |= STATX_ATTR_NODUMP;
1067  	stat->attributes_mask |= (STATX_ATTR_APPEND |
1068  			STATX_ATTR_IMMUTABLE |
1069  			STATX_ATTR_NODUMP);
1070  	generic_fillattr(&init_user_ns, inode, stat);
1071  
1072  	if (shmem_is_huge(NULL, inode, 0))
1073  		stat->blksize = HPAGE_PMD_SIZE;
1074  
1075  	if (request_mask & STATX_BTIME) {
1076  		stat->result_mask |= STATX_BTIME;
1077  		stat->btime.tv_sec = info->i_crtime.tv_sec;
1078  		stat->btime.tv_nsec = info->i_crtime.tv_nsec;
1079  	}
1080  
1081  	return 0;
1082  }
1083  
1084  static int shmem_setattr(struct user_namespace *mnt_userns,
1085  			 struct dentry *dentry, struct iattr *attr)
1086  {
1087  	struct inode *inode = d_inode(dentry);
1088  	struct shmem_inode_info *info = SHMEM_I(inode);
1089  	int error;
1090  
1091  	error = setattr_prepare(&init_user_ns, dentry, attr);
1092  	if (error)
1093  		return error;
1094  
1095  	if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
1096  		loff_t oldsize = inode->i_size;
1097  		loff_t newsize = attr->ia_size;
1098  
1099  		/* protected by i_rwsem */
1100  		if ((newsize < oldsize && (info->seals & F_SEAL_SHRINK)) ||
1101  		    (newsize > oldsize && (info->seals & F_SEAL_GROW)))
1102  			return -EPERM;
1103  
1104  		if (newsize != oldsize) {
1105  			error = shmem_reacct_size(SHMEM_I(inode)->flags,
1106  					oldsize, newsize);
1107  			if (error)
1108  				return error;
1109  			i_size_write(inode, newsize);
1110  			inode->i_ctime = inode->i_mtime = current_time(inode);
1111  		}
1112  		if (newsize <= oldsize) {
1113  			loff_t holebegin = round_up(newsize, PAGE_SIZE);
1114  			if (oldsize > holebegin)
1115  				unmap_mapping_range(inode->i_mapping,
1116  							holebegin, 0, 1);
1117  			if (info->alloced)
1118  				shmem_truncate_range(inode,
1119  							newsize, (loff_t)-1);
1120  			/* unmap again to remove racily COWed private pages */
1121  			if (oldsize > holebegin)
1122  				unmap_mapping_range(inode->i_mapping,
1123  							holebegin, 0, 1);
1124  		}
1125  	}
1126  
1127  	setattr_copy(&init_user_ns, inode, attr);
1128  	if (attr->ia_valid & ATTR_MODE)
1129  		error = posix_acl_chmod(&init_user_ns, inode, inode->i_mode);
1130  	return error;
1131  }
1132  
1133  static void shmem_evict_inode(struct inode *inode)
1134  {
1135  	struct shmem_inode_info *info = SHMEM_I(inode);
1136  	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
1137  
1138  	if (shmem_mapping(inode->i_mapping)) {
1139  		shmem_unacct_size(info->flags, inode->i_size);
1140  		inode->i_size = 0;
1141  		mapping_set_exiting(inode->i_mapping);
1142  		shmem_truncate_range(inode, 0, (loff_t)-1);
1143  		if (!list_empty(&info->shrinklist)) {
1144  			spin_lock(&sbinfo->shrinklist_lock);
1145  			if (!list_empty(&info->shrinklist)) {
1146  				list_del_init(&info->shrinklist);
1147  				sbinfo->shrinklist_len--;
1148  			}
1149  			spin_unlock(&sbinfo->shrinklist_lock);
1150  		}
1151  		while (!list_empty(&info->swaplist)) {
1152  			/* Wait while shmem_unuse() is scanning this inode... */
1153  			wait_var_event(&info->stop_eviction,
1154  				       !atomic_read(&info->stop_eviction));
1155  			mutex_lock(&shmem_swaplist_mutex);
1156  			/* ...but beware of the race if we peeked too early */
1157  			if (!atomic_read(&info->stop_eviction))
1158  				list_del_init(&info->swaplist);
1159  			mutex_unlock(&shmem_swaplist_mutex);
1160  		}
1161  	}
1162  
1163  	simple_xattrs_free(&info->xattrs);
1164  	WARN_ON(inode->i_blocks);
1165  	shmem_free_inode(inode->i_sb);
1166  	clear_inode(inode);
1167  }
1168  
1169  static int shmem_find_swap_entries(struct address_space *mapping,
1170  				   pgoff_t start, struct folio_batch *fbatch,
1171  				   pgoff_t *indices, unsigned int type)
1172  {
1173  	XA_STATE(xas, &mapping->i_pages, start);
1174  	struct folio *folio;
1175  	swp_entry_t entry;
1176  
1177  	rcu_read_lock();
1178  	xas_for_each(&xas, folio, ULONG_MAX) {
1179  		if (xas_retry(&xas, folio))
1180  			continue;
1181  
1182  		if (!xa_is_value(folio))
1183  			continue;
1184  
1185  		entry = radix_to_swp_entry(folio);
1186  		/*
1187  		 * swapin error entries can be found in the mapping. But they're
1188  		 * deliberately ignored here as we've done everything we can do.
1189  		 */
1190  		if (swp_type(entry) != type)
1191  			continue;
1192  
1193  		indices[folio_batch_count(fbatch)] = xas.xa_index;
1194  		if (!folio_batch_add(fbatch, folio))
1195  			break;
1196  
1197  		if (need_resched()) {
1198  			xas_pause(&xas);
1199  			cond_resched_rcu();
1200  		}
1201  	}
1202  	rcu_read_unlock();
1203  
1204  	return xas.xa_index;
1205  }
1206  
1207  /*
1208   * Move the swapped pages for an inode to page cache. Returns the count
1209   * of pages swapped in, or the error in case of failure.
1210   */
1211  static int shmem_unuse_swap_entries(struct inode *inode,
1212  		struct folio_batch *fbatch, pgoff_t *indices)
1213  {
1214  	int i = 0;
1215  	int ret = 0;
1216  	int error = 0;
1217  	struct address_space *mapping = inode->i_mapping;
1218  
1219  	for (i = 0; i < folio_batch_count(fbatch); i++) {
1220  		struct folio *folio = fbatch->folios[i];
1221  
1222  		if (!xa_is_value(folio))
1223  			continue;
1224  		error = shmem_swapin_folio(inode, indices[i],
1225  					  &folio, SGP_CACHE,
1226  					  mapping_gfp_mask(mapping),
1227  					  NULL, NULL);
1228  		if (error == 0) {
1229  			folio_unlock(folio);
1230  			folio_put(folio);
1231  			ret++;
1232  		}
1233  		if (error == -ENOMEM)
1234  			break;
1235  		error = 0;
1236  	}
1237  	return error ? error : ret;
1238  }
1239  
1240  /*
1241   * If swap found in inode, free it and move page from swapcache to filecache.
1242   */
1243  static int shmem_unuse_inode(struct inode *inode, unsigned int type)
1244  {
1245  	struct address_space *mapping = inode->i_mapping;
1246  	pgoff_t start = 0;
1247  	struct folio_batch fbatch;
1248  	pgoff_t indices[PAGEVEC_SIZE];
1249  	int ret = 0;
1250  
1251  	do {
1252  		folio_batch_init(&fbatch);
1253  		shmem_find_swap_entries(mapping, start, &fbatch, indices, type);
1254  		if (folio_batch_count(&fbatch) == 0) {
1255  			ret = 0;
1256  			break;
1257  		}
1258  
1259  		ret = shmem_unuse_swap_entries(inode, &fbatch, indices);
1260  		if (ret < 0)
1261  			break;
1262  
1263  		start = indices[folio_batch_count(&fbatch) - 1];
1264  	} while (true);
1265  
1266  	return ret;
1267  }
1268  
1269  /*
1270   * Read all the shared memory data that resides in the swap
1271   * device 'type' back into memory, so the swap device can be
1272   * unused.
1273   */
1274  int shmem_unuse(unsigned int type)
1275  {
1276  	struct shmem_inode_info *info, *next;
1277  	int error = 0;
1278  
1279  	if (list_empty(&shmem_swaplist))
1280  		return 0;
1281  
1282  	mutex_lock(&shmem_swaplist_mutex);
1283  	list_for_each_entry_safe(info, next, &shmem_swaplist, swaplist) {
1284  		if (!info->swapped) {
1285  			list_del_init(&info->swaplist);
1286  			continue;
1287  		}
1288  		/*
1289  		 * Drop the swaplist mutex while searching the inode for swap;
1290  		 * but before doing so, make sure shmem_evict_inode() will not
1291  		 * remove placeholder inode from swaplist, nor let it be freed
1292  		 * (igrab() would protect from unlink, but not from unmount).
1293  		 */
1294  		atomic_inc(&info->stop_eviction);
1295  		mutex_unlock(&shmem_swaplist_mutex);
1296  
1297  		error = shmem_unuse_inode(&info->vfs_inode, type);
1298  		cond_resched();
1299  
1300  		mutex_lock(&shmem_swaplist_mutex);
1301  		next = list_next_entry(info, swaplist);
1302  		if (!info->swapped)
1303  			list_del_init(&info->swaplist);
1304  		if (atomic_dec_and_test(&info->stop_eviction))
1305  			wake_up_var(&info->stop_eviction);
1306  		if (error)
1307  			break;
1308  	}
1309  	mutex_unlock(&shmem_swaplist_mutex);
1310  
1311  	return error;
1312  }
1313  
1314  /*
1315   * Move the page from the page cache to the swap cache.
1316   */
1317  static int shmem_writepage(struct page *page, struct writeback_control *wbc)
1318  {
1319  	struct folio *folio = page_folio(page);
1320  	struct shmem_inode_info *info;
1321  	struct address_space *mapping;
1322  	struct inode *inode;
1323  	swp_entry_t swap;
1324  	pgoff_t index;
1325  
1326  	/*
1327  	 * If /sys/kernel/mm/transparent_hugepage/shmem_enabled is "always" or
1328  	 * "force", drivers/gpu/drm/i915/gem/i915_gem_shmem.c gets huge pages,
1329  	 * and its shmem_writeback() needs them to be split when swapping.
1330  	 */
1331  	if (PageTransCompound(page)) {
1332  		/* Ensure the subpages are still dirty */
1333  		SetPageDirty(page);
1334  		if (split_huge_page(page) < 0)
1335  			goto redirty;
1336  		ClearPageDirty(page);
1337  	}
1338  
1339  	BUG_ON(!PageLocked(page));
1340  	mapping = page->mapping;
1341  	index = page->index;
1342  	inode = mapping->host;
1343  	info = SHMEM_I(inode);
1344  	if (info->flags & VM_LOCKED)
1345  		goto redirty;
1346  	if (!total_swap_pages)
1347  		goto redirty;
1348  
1349  	/*
1350  	 * Our capabilities prevent regular writeback or sync from ever calling
1351  	 * shmem_writepage; but a stacking filesystem might use ->writepage of
1352  	 * its underlying filesystem, in which case tmpfs should write out to
1353  	 * swap only in response to memory pressure, and not for the writeback
1354  	 * threads or sync.
1355  	 */
1356  	if (!wbc->for_reclaim) {
1357  		WARN_ON_ONCE(1);	/* Still happens? Tell us about it! */
1358  		goto redirty;
1359  	}
1360  
1361  	/*
1362  	 * This is somewhat ridiculous, but without plumbing a SWAP_MAP_FALLOC
1363  	 * value into swapfile.c, the only way we can correctly account for a
1364  	 * fallocated page arriving here is now to initialize it and write it.
1365  	 *
1366  	 * That's okay for a page already fallocated earlier, but if we have
1367  	 * not yet completed the fallocation, then (a) we want to keep track
1368  	 * of this page in case we have to undo it, and (b) it may not be a
1369  	 * good idea to continue anyway, once we're pushing into swap.  So
1370  	 * reactivate the page, and let shmem_fallocate() quit when too many.
1371  	 */
1372  	if (!PageUptodate(page)) {
1373  		if (inode->i_private) {
1374  			struct shmem_falloc *shmem_falloc;
1375  			spin_lock(&inode->i_lock);
1376  			shmem_falloc = inode->i_private;
1377  			if (shmem_falloc &&
1378  			    !shmem_falloc->waitq &&
1379  			    index >= shmem_falloc->start &&
1380  			    index < shmem_falloc->next)
1381  				shmem_falloc->nr_unswapped++;
1382  			else
1383  				shmem_falloc = NULL;
1384  			spin_unlock(&inode->i_lock);
1385  			if (shmem_falloc)
1386  				goto redirty;
1387  		}
1388  		clear_highpage(page);
1389  		flush_dcache_page(page);
1390  		SetPageUptodate(page);
1391  	}
1392  
1393  	swap = folio_alloc_swap(folio);
1394  	if (!swap.val)
1395  		goto redirty;
1396  
1397  	/*
1398  	 * Add inode to shmem_unuse()'s list of swapped-out inodes,
1399  	 * if it's not already there.  Do it now before the page is
1400  	 * moved to swap cache, when its pagelock no longer protects
1401  	 * the inode from eviction.  But don't unlock the mutex until
1402  	 * we've incremented swapped, because shmem_unuse_inode() will
1403  	 * prune a !swapped inode from the swaplist under this mutex.
1404  	 */
1405  	mutex_lock(&shmem_swaplist_mutex);
1406  	if (list_empty(&info->swaplist))
1407  		list_add(&info->swaplist, &shmem_swaplist);
1408  
1409  	if (add_to_swap_cache(page, swap,
1410  			__GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN,
1411  			NULL) == 0) {
1412  		spin_lock_irq(&info->lock);
1413  		shmem_recalc_inode(inode);
1414  		info->swapped++;
1415  		spin_unlock_irq(&info->lock);
1416  
1417  		swap_shmem_alloc(swap);
1418  		shmem_delete_from_page_cache(page, swp_to_radix_entry(swap));
1419  
1420  		mutex_unlock(&shmem_swaplist_mutex);
1421  		BUG_ON(page_mapped(page));
1422  		swap_writepage(page, wbc);
1423  		return 0;
1424  	}
1425  
1426  	mutex_unlock(&shmem_swaplist_mutex);
1427  	put_swap_page(page, swap);
1428  redirty:
1429  	set_page_dirty(page);
1430  	if (wbc->for_reclaim)
1431  		return AOP_WRITEPAGE_ACTIVATE;	/* Return with page locked */
1432  	unlock_page(page);
1433  	return 0;
1434  }
1435  
1436  #if defined(CONFIG_NUMA) && defined(CONFIG_TMPFS)
1437  static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
1438  {
1439  	char buffer[64];
1440  
1441  	if (!mpol || mpol->mode == MPOL_DEFAULT)
1442  		return;		/* show nothing */
1443  
1444  	mpol_to_str(buffer, sizeof(buffer), mpol);
1445  
1446  	seq_printf(seq, ",mpol=%s", buffer);
1447  }
1448  
1449  static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
1450  {
1451  	struct mempolicy *mpol = NULL;
1452  	if (sbinfo->mpol) {
1453  		raw_spin_lock(&sbinfo->stat_lock);	/* prevent replace/use races */
1454  		mpol = sbinfo->mpol;
1455  		mpol_get(mpol);
1456  		raw_spin_unlock(&sbinfo->stat_lock);
1457  	}
1458  	return mpol;
1459  }
1460  #else /* !CONFIG_NUMA || !CONFIG_TMPFS */
1461  static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
1462  {
1463  }
1464  static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
1465  {
1466  	return NULL;
1467  }
1468  #endif /* CONFIG_NUMA && CONFIG_TMPFS */
1469  #ifndef CONFIG_NUMA
1470  #define vm_policy vm_private_data
1471  #endif
1472  
1473  static void shmem_pseudo_vma_init(struct vm_area_struct *vma,
1474  		struct shmem_inode_info *info, pgoff_t index)
1475  {
1476  	/* Create a pseudo vma that just contains the policy */
1477  	vma_init(vma, NULL);
1478  	/* Bias interleave by inode number to distribute better across nodes */
1479  	vma->vm_pgoff = index + info->vfs_inode.i_ino;
1480  	vma->vm_policy = mpol_shared_policy_lookup(&info->policy, index);
1481  }
1482  
1483  static void shmem_pseudo_vma_destroy(struct vm_area_struct *vma)
1484  {
1485  	/* Drop reference taken by mpol_shared_policy_lookup() */
1486  	mpol_cond_put(vma->vm_policy);
1487  }
1488  
1489  static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
1490  			struct shmem_inode_info *info, pgoff_t index)
1491  {
1492  	struct vm_area_struct pvma;
1493  	struct page *page;
1494  	struct vm_fault vmf = {
1495  		.vma = &pvma,
1496  	};
1497  
1498  	shmem_pseudo_vma_init(&pvma, info, index);
1499  	page = swap_cluster_readahead(swap, gfp, &vmf);
1500  	shmem_pseudo_vma_destroy(&pvma);
1501  
1502  	return page;
1503  }
1504  
1505  /*
1506   * Make sure huge_gfp is always more limited than limit_gfp.
1507   * Some of the flags set permissions, while others set limitations.
1508   */
1509  static gfp_t limit_gfp_mask(gfp_t huge_gfp, gfp_t limit_gfp)
1510  {
1511  	gfp_t allowflags = __GFP_IO | __GFP_FS | __GFP_RECLAIM;
1512  	gfp_t denyflags = __GFP_NOWARN | __GFP_NORETRY;
1513  	gfp_t zoneflags = limit_gfp & GFP_ZONEMASK;
1514  	gfp_t result = huge_gfp & ~(allowflags | GFP_ZONEMASK);
1515  
1516  	/* Allow allocations only from the originally specified zones. */
1517  	result |= zoneflags;
1518  
1519  	/*
1520  	 * Minimize the result gfp by taking the union with the deny flags,
1521  	 * and the intersection of the allow flags.
1522  	 */
1523  	result |= (limit_gfp & denyflags);
1524  	result |= (huge_gfp & limit_gfp) & allowflags;
1525  
1526  	return result;
1527  }
1528  
1529  static struct folio *shmem_alloc_hugefolio(gfp_t gfp,
1530  		struct shmem_inode_info *info, pgoff_t index)
1531  {
1532  	struct vm_area_struct pvma;
1533  	struct address_space *mapping = info->vfs_inode.i_mapping;
1534  	pgoff_t hindex;
1535  	struct folio *folio;
1536  
1537  	hindex = round_down(index, HPAGE_PMD_NR);
1538  	if (xa_find(&mapping->i_pages, &hindex, hindex + HPAGE_PMD_NR - 1,
1539  								XA_PRESENT))
1540  		return NULL;
1541  
1542  	shmem_pseudo_vma_init(&pvma, info, hindex);
1543  	folio = vma_alloc_folio(gfp, HPAGE_PMD_ORDER, &pvma, 0, true);
1544  	shmem_pseudo_vma_destroy(&pvma);
1545  	if (!folio)
1546  		count_vm_event(THP_FILE_FALLBACK);
1547  	return folio;
1548  }
1549  
1550  static struct folio *shmem_alloc_folio(gfp_t gfp,
1551  			struct shmem_inode_info *info, pgoff_t index)
1552  {
1553  	struct vm_area_struct pvma;
1554  	struct folio *folio;
1555  
1556  	shmem_pseudo_vma_init(&pvma, info, index);
1557  	folio = vma_alloc_folio(gfp, 0, &pvma, 0, false);
1558  	shmem_pseudo_vma_destroy(&pvma);
1559  
1560  	return folio;
1561  }
1562  
1563  static struct page *shmem_alloc_page(gfp_t gfp,
1564  			struct shmem_inode_info *info, pgoff_t index)
1565  {
1566  	return &shmem_alloc_folio(gfp, info, index)->page;
1567  }
1568  
1569  static struct folio *shmem_alloc_and_acct_folio(gfp_t gfp, struct inode *inode,
1570  		pgoff_t index, bool huge)
1571  {
1572  	struct shmem_inode_info *info = SHMEM_I(inode);
1573  	struct folio *folio;
1574  	int nr;
1575  	int err = -ENOSPC;
1576  
1577  	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
1578  		huge = false;
1579  	nr = huge ? HPAGE_PMD_NR : 1;
1580  
1581  	if (!shmem_inode_acct_block(inode, nr))
1582  		goto failed;
1583  
1584  	if (huge)
1585  		folio = shmem_alloc_hugefolio(gfp, info, index);
1586  	else
1587  		folio = shmem_alloc_folio(gfp, info, index);
1588  	if (folio) {
1589  		__folio_set_locked(folio);
1590  		__folio_set_swapbacked(folio);
1591  		return folio;
1592  	}
1593  
1594  	err = -ENOMEM;
1595  	shmem_inode_unacct_blocks(inode, nr);
1596  failed:
1597  	return ERR_PTR(err);
1598  }
1599  
1600  /*
1601   * When a page is moved from swapcache to shmem filecache (either by the
1602   * usual swapin of shmem_getpage_gfp(), or by the less common swapoff of
1603   * shmem_unuse_inode()), it may have been read in earlier from swap, in
1604   * ignorance of the mapping it belongs to.  If that mapping has special
1605   * constraints (like the gma500 GEM driver, which requires RAM below 4GB),
1606   * we may need to copy to a suitable page before moving to filecache.
1607   *
1608   * In a future release, this may well be extended to respect cpuset and
1609   * NUMA mempolicy, and applied also to anonymous pages in do_swap_page();
1610   * but for now it is a simple matter of zone.
1611   */
1612  static bool shmem_should_replace_folio(struct folio *folio, gfp_t gfp)
1613  {
1614  	return folio_zonenum(folio) > gfp_zone(gfp);
1615  }
1616  
1617  static int shmem_replace_page(struct page **pagep, gfp_t gfp,
1618  				struct shmem_inode_info *info, pgoff_t index)
1619  {
1620  	struct page *oldpage, *newpage;
1621  	struct folio *old, *new;
1622  	struct address_space *swap_mapping;
1623  	swp_entry_t entry;
1624  	pgoff_t swap_index;
1625  	int error;
1626  
1627  	oldpage = *pagep;
1628  	entry.val = page_private(oldpage);
1629  	swap_index = swp_offset(entry);
1630  	swap_mapping = page_mapping(oldpage);
1631  
1632  	/*
1633  	 * We have arrived here because our zones are constrained, so don't
1634  	 * limit chance of success by further cpuset and node constraints.
1635  	 */
1636  	gfp &= ~GFP_CONSTRAINT_MASK;
1637  	newpage = shmem_alloc_page(gfp, info, index);
1638  	if (!newpage)
1639  		return -ENOMEM;
1640  
1641  	get_page(newpage);
1642  	copy_highpage(newpage, oldpage);
1643  	flush_dcache_page(newpage);
1644  
1645  	__SetPageLocked(newpage);
1646  	__SetPageSwapBacked(newpage);
1647  	SetPageUptodate(newpage);
1648  	set_page_private(newpage, entry.val);
1649  	SetPageSwapCache(newpage);
1650  
1651  	/*
1652  	 * Our caller will very soon move newpage out of swapcache, but it's
1653  	 * a nice clean interface for us to replace oldpage by newpage there.
1654  	 */
1655  	xa_lock_irq(&swap_mapping->i_pages);
1656  	error = shmem_replace_entry(swap_mapping, swap_index, oldpage, newpage);
1657  	if (!error) {
1658  		old = page_folio(oldpage);
1659  		new = page_folio(newpage);
1660  		mem_cgroup_migrate(old, new);
1661  		__inc_lruvec_page_state(newpage, NR_FILE_PAGES);
1662  		__dec_lruvec_page_state(oldpage, NR_FILE_PAGES);
1663  	}
1664  	xa_unlock_irq(&swap_mapping->i_pages);
1665  
1666  	if (unlikely(error)) {
1667  		/*
1668  		 * Is this possible?  I think not, now that our callers check
1669  		 * both PageSwapCache and page_private after getting page lock;
1670  		 * but be defensive.  Reverse old to newpage for clear and free.
1671  		 */
1672  		oldpage = newpage;
1673  	} else {
1674  		lru_cache_add(newpage);
1675  		*pagep = newpage;
1676  	}
1677  
1678  	ClearPageSwapCache(oldpage);
1679  	set_page_private(oldpage, 0);
1680  
1681  	unlock_page(oldpage);
1682  	put_page(oldpage);
1683  	put_page(oldpage);
1684  	return error;
1685  }
1686  
1687  static void shmem_set_folio_swapin_error(struct inode *inode, pgoff_t index,
1688  					 struct folio *folio, swp_entry_t swap)
1689  {
1690  	struct address_space *mapping = inode->i_mapping;
1691  	struct shmem_inode_info *info = SHMEM_I(inode);
1692  	swp_entry_t swapin_error;
1693  	void *old;
1694  
1695  	swapin_error = make_swapin_error_entry(&folio->page);
1696  	old = xa_cmpxchg_irq(&mapping->i_pages, index,
1697  			     swp_to_radix_entry(swap),
1698  			     swp_to_radix_entry(swapin_error), 0);
1699  	if (old != swp_to_radix_entry(swap))
1700  		return;
1701  
1702  	folio_wait_writeback(folio);
1703  	delete_from_swap_cache(folio);
1704  	spin_lock_irq(&info->lock);
1705  	/*
1706  	 * Don't treat swapin error folio as alloced. Otherwise inode->i_blocks won't
1707  	 * be 0 when inode is released and thus trigger WARN_ON(inode->i_blocks) in
1708  	 * shmem_evict_inode.
1709  	 */
1710  	info->alloced--;
1711  	info->swapped--;
1712  	shmem_recalc_inode(inode);
1713  	spin_unlock_irq(&info->lock);
1714  	swap_free(swap);
1715  }
1716  
1717  /*
1718   * Swap in the folio pointed to by *foliop.
1719   * Caller has to make sure that *foliop contains a valid swapped folio.
1720   * Returns 0 and the folio in foliop if success. On failure, returns the
1721   * error code and NULL in *foliop.
1722   */
1723  static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
1724  			     struct folio **foliop, enum sgp_type sgp,
1725  			     gfp_t gfp, struct vm_area_struct *vma,
1726  			     vm_fault_t *fault_type)
1727  {
1728  	struct address_space *mapping = inode->i_mapping;
1729  	struct shmem_inode_info *info = SHMEM_I(inode);
1730  	struct mm_struct *charge_mm = vma ? vma->vm_mm : NULL;
1731  	struct page *page;
1732  	struct folio *folio = NULL;
1733  	swp_entry_t swap;
1734  	int error;
1735  
1736  	VM_BUG_ON(!*foliop || !xa_is_value(*foliop));
1737  	swap = radix_to_swp_entry(*foliop);
1738  	*foliop = NULL;
1739  
1740  	if (is_swapin_error_entry(swap))
1741  		return -EIO;
1742  
1743  	/* Look it up and read it in.. */
1744  	page = lookup_swap_cache(swap, NULL, 0);
1745  	if (!page) {
1746  		/* Or update major stats only when swapin succeeds?? */
1747  		if (fault_type) {
1748  			*fault_type |= VM_FAULT_MAJOR;
1749  			count_vm_event(PGMAJFAULT);
1750  			count_memcg_event_mm(charge_mm, PGMAJFAULT);
1751  		}
1752  		/* Here we actually start the io */
1753  		page = shmem_swapin(swap, gfp, info, index);
1754  		if (!page) {
1755  			error = -ENOMEM;
1756  			goto failed;
1757  		}
1758  	}
1759  	folio = page_folio(page);
1760  
1761  	/* We have to do this with folio locked to prevent races */
1762  	folio_lock(folio);
1763  	if (!folio_test_swapcache(folio) ||
1764  	    folio_swap_entry(folio).val != swap.val ||
1765  	    !shmem_confirm_swap(mapping, index, swap)) {
1766  		error = -EEXIST;
1767  		goto unlock;
1768  	}
1769  	if (!folio_test_uptodate(folio)) {
1770  		error = -EIO;
1771  		goto failed;
1772  	}
1773  	folio_wait_writeback(folio);
1774  
1775  	/*
1776  	 * Some architectures may have to restore extra metadata to the
1777  	 * folio after reading from swap.
1778  	 */
1779  	arch_swap_restore(swap, folio);
1780  
1781  	if (shmem_should_replace_folio(folio, gfp)) {
1782  		error = shmem_replace_page(&page, gfp, info, index);
1783  		if (error)
1784  			goto failed;
1785  	}
1786  
1787  	error = shmem_add_to_page_cache(folio, mapping, index,
1788  					swp_to_radix_entry(swap), gfp,
1789  					charge_mm);
1790  	if (error)
1791  		goto failed;
1792  
1793  	spin_lock_irq(&info->lock);
1794  	info->swapped--;
1795  	shmem_recalc_inode(inode);
1796  	spin_unlock_irq(&info->lock);
1797  
1798  	if (sgp == SGP_WRITE)
1799  		folio_mark_accessed(folio);
1800  
1801  	delete_from_swap_cache(folio);
1802  	folio_mark_dirty(folio);
1803  	swap_free(swap);
1804  
1805  	*foliop = folio;
1806  	return 0;
1807  failed:
1808  	if (!shmem_confirm_swap(mapping, index, swap))
1809  		error = -EEXIST;
1810  	if (error == -EIO)
1811  		shmem_set_folio_swapin_error(inode, index, folio, swap);
1812  unlock:
1813  	if (folio) {
1814  		folio_unlock(folio);
1815  		folio_put(folio);
1816  	}
1817  
1818  	return error;
1819  }
1820  
1821  /*
1822   * shmem_getpage_gfp - find page in cache, or get from swap, or allocate
1823   *
1824   * If we allocate a new one we do not mark it dirty. That's up to the
1825   * vm. If we swap it in we mark it dirty since we also free the swap
1826   * entry since a page cannot live in both the swap and page cache.
1827   *
1828   * vma, vmf, and fault_type are only supplied by shmem_fault:
1829   * otherwise they are NULL.
1830   */
1831  static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
1832  	struct page **pagep, enum sgp_type sgp, gfp_t gfp,
1833  	struct vm_area_struct *vma, struct vm_fault *vmf,
1834  			vm_fault_t *fault_type)
1835  {
1836  	struct address_space *mapping = inode->i_mapping;
1837  	struct shmem_inode_info *info = SHMEM_I(inode);
1838  	struct shmem_sb_info *sbinfo;
1839  	struct mm_struct *charge_mm;
1840  	struct folio *folio;
1841  	pgoff_t hindex = index;
1842  	gfp_t huge_gfp;
1843  	int error;
1844  	int once = 0;
1845  	int alloced = 0;
1846  
1847  	if (index > (MAX_LFS_FILESIZE >> PAGE_SHIFT))
1848  		return -EFBIG;
1849  repeat:
1850  	if (sgp <= SGP_CACHE &&
1851  	    ((loff_t)index << PAGE_SHIFT) >= i_size_read(inode)) {
1852  		return -EINVAL;
1853  	}
1854  
1855  	sbinfo = SHMEM_SB(inode->i_sb);
1856  	charge_mm = vma ? vma->vm_mm : NULL;
1857  
1858  	folio = __filemap_get_folio(mapping, index, FGP_ENTRY | FGP_LOCK, 0);
1859  	if (folio && vma && userfaultfd_minor(vma)) {
1860  		if (!xa_is_value(folio)) {
1861  			folio_unlock(folio);
1862  			folio_put(folio);
1863  		}
1864  		*fault_type = handle_userfault(vmf, VM_UFFD_MINOR);
1865  		return 0;
1866  	}
1867  
1868  	if (xa_is_value(folio)) {
1869  		error = shmem_swapin_folio(inode, index, &folio,
1870  					  sgp, gfp, vma, fault_type);
1871  		if (error == -EEXIST)
1872  			goto repeat;
1873  
1874  		*pagep = &folio->page;
1875  		return error;
1876  	}
1877  
1878  	if (folio) {
1879  		hindex = folio->index;
1880  		if (sgp == SGP_WRITE)
1881  			folio_mark_accessed(folio);
1882  		if (folio_test_uptodate(folio))
1883  			goto out;
1884  		/* fallocated page */
1885  		if (sgp != SGP_READ)
1886  			goto clear;
1887  		folio_unlock(folio);
1888  		folio_put(folio);
1889  	}
1890  
1891  	/*
1892  	 * SGP_READ: succeed on hole, with NULL page, letting caller zero.
1893  	 * SGP_NOALLOC: fail on hole, with NULL page, letting caller fail.
1894  	 */
1895  	*pagep = NULL;
1896  	if (sgp == SGP_READ)
1897  		return 0;
1898  	if (sgp == SGP_NOALLOC)
1899  		return -ENOENT;
1900  
1901  	/*
1902  	 * Fast cache lookup and swap lookup did not find it: allocate.
1903  	 */
1904  
1905  	if (vma && userfaultfd_missing(vma)) {
1906  		*fault_type = handle_userfault(vmf, VM_UFFD_MISSING);
1907  		return 0;
1908  	}
1909  
1910  	if (!shmem_is_huge(vma, inode, index))
1911  		goto alloc_nohuge;
1912  
1913  	huge_gfp = vma_thp_gfp_mask(vma);
1914  	huge_gfp = limit_gfp_mask(huge_gfp, gfp);
1915  	folio = shmem_alloc_and_acct_folio(huge_gfp, inode, index, true);
1916  	if (IS_ERR(folio)) {
1917  alloc_nohuge:
1918  		folio = shmem_alloc_and_acct_folio(gfp, inode, index, false);
1919  	}
1920  	if (IS_ERR(folio)) {
1921  		int retry = 5;
1922  
1923  		error = PTR_ERR(folio);
1924  		folio = NULL;
1925  		if (error != -ENOSPC)
1926  			goto unlock;
1927  		/*
1928  		 * Try to reclaim some space by splitting a huge page
1929  		 * beyond i_size on the filesystem.
1930  		 */
1931  		while (retry--) {
1932  			int ret;
1933  
1934  			ret = shmem_unused_huge_shrink(sbinfo, NULL, 1);
1935  			if (ret == SHRINK_STOP)
1936  				break;
1937  			if (ret)
1938  				goto alloc_nohuge;
1939  		}
1940  		goto unlock;
1941  	}
1942  
1943  	hindex = round_down(index, folio_nr_pages(folio));
1944  
1945  	if (sgp == SGP_WRITE)
1946  		__folio_set_referenced(folio);
1947  
1948  	error = shmem_add_to_page_cache(folio, mapping, hindex,
1949  					NULL, gfp & GFP_RECLAIM_MASK,
1950  					charge_mm);
1951  	if (error)
1952  		goto unacct;
1953  	folio_add_lru(folio);
1954  
1955  	spin_lock_irq(&info->lock);
1956  	info->alloced += folio_nr_pages(folio);
1957  	inode->i_blocks += (blkcnt_t)BLOCKS_PER_PAGE << folio_order(folio);
1958  	shmem_recalc_inode(inode);
1959  	spin_unlock_irq(&info->lock);
1960  	alloced = true;
1961  
1962  	if (folio_test_pmd_mappable(folio) &&
1963  	    DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE) <
1964  			hindex + HPAGE_PMD_NR - 1) {
1965  		/*
1966  		 * Part of the huge page is beyond i_size: subject
1967  		 * to shrink under memory pressure.
1968  		 */
1969  		spin_lock(&sbinfo->shrinklist_lock);
1970  		/*
1971  		 * _careful to defend against unlocked access to
1972  		 * ->shrink_list in shmem_unused_huge_shrink()
1973  		 */
1974  		if (list_empty_careful(&info->shrinklist)) {
1975  			list_add_tail(&info->shrinklist,
1976  				      &sbinfo->shrinklist);
1977  			sbinfo->shrinklist_len++;
1978  		}
1979  		spin_unlock(&sbinfo->shrinklist_lock);
1980  	}
1981  
1982  	/*
1983  	 * Let SGP_FALLOC use the SGP_WRITE optimization on a new page.
1984  	 */
1985  	if (sgp == SGP_FALLOC)
1986  		sgp = SGP_WRITE;
1987  clear:
1988  	/*
1989  	 * Let SGP_WRITE caller clear ends if write does not fill page;
1990  	 * but SGP_FALLOC on a page fallocated earlier must initialize
1991  	 * it now, lest undo on failure cancel our earlier guarantee.
1992  	 */
1993  	if (sgp != SGP_WRITE && !folio_test_uptodate(folio)) {
1994  		long i, n = folio_nr_pages(folio);
1995  
1996  		for (i = 0; i < n; i++)
1997  			clear_highpage(folio_page(folio, i));
1998  		flush_dcache_folio(folio);
1999  		folio_mark_uptodate(folio);
2000  	}
2001  
2002  	/* Perhaps the file has been truncated since we checked */
2003  	if (sgp <= SGP_CACHE &&
2004  	    ((loff_t)index << PAGE_SHIFT) >= i_size_read(inode)) {
2005  		if (alloced) {
2006  			folio_clear_dirty(folio);
2007  			filemap_remove_folio(folio);
2008  			spin_lock_irq(&info->lock);
2009  			shmem_recalc_inode(inode);
2010  			spin_unlock_irq(&info->lock);
2011  		}
2012  		error = -EINVAL;
2013  		goto unlock;
2014  	}
2015  out:
2016  	*pagep = folio_page(folio, index - hindex);
2017  	return 0;
2018  
2019  	/*
2020  	 * Error recovery.
2021  	 */
2022  unacct:
2023  	shmem_inode_unacct_blocks(inode, folio_nr_pages(folio));
2024  
2025  	if (folio_test_large(folio)) {
2026  		folio_unlock(folio);
2027  		folio_put(folio);
2028  		goto alloc_nohuge;
2029  	}
2030  unlock:
2031  	if (folio) {
2032  		folio_unlock(folio);
2033  		folio_put(folio);
2034  	}
2035  	if (error == -ENOSPC && !once++) {
2036  		spin_lock_irq(&info->lock);
2037  		shmem_recalc_inode(inode);
2038  		spin_unlock_irq(&info->lock);
2039  		goto repeat;
2040  	}
2041  	if (error == -EEXIST)
2042  		goto repeat;
2043  	return error;
2044  }
2045  
2046  /*
2047   * This is like autoremove_wake_function, but it removes the wait queue
2048   * entry unconditionally - even if something else had already woken the
2049   * target.
2050   */
2051  static int synchronous_wake_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
2052  {
2053  	int ret = default_wake_function(wait, mode, sync, key);
2054  	list_del_init(&wait->entry);
2055  	return ret;
2056  }
2057  
2058  static vm_fault_t shmem_fault(struct vm_fault *vmf)
2059  {
2060  	struct vm_area_struct *vma = vmf->vma;
2061  	struct inode *inode = file_inode(vma->vm_file);
2062  	gfp_t gfp = mapping_gfp_mask(inode->i_mapping);
2063  	int err;
2064  	vm_fault_t ret = VM_FAULT_LOCKED;
2065  
2066  	/*
2067  	 * Trinity finds that probing a hole which tmpfs is punching can
2068  	 * prevent the hole-punch from ever completing: which in turn
2069  	 * locks writers out with its hold on i_rwsem.  So refrain from
2070  	 * faulting pages into the hole while it's being punched.  Although
2071  	 * shmem_undo_range() does remove the additions, it may be unable to
2072  	 * keep up, as each new page needs its own unmap_mapping_range() call,
2073  	 * and the i_mmap tree grows ever slower to scan if new vmas are added.
2074  	 *
2075  	 * It does not matter if we sometimes reach this check just before the
2076  	 * hole-punch begins, so that one fault then races with the punch:
2077  	 * we just need to make racing faults a rare case.
2078  	 *
2079  	 * The implementation below would be much simpler if we just used a
2080  	 * standard mutex or completion: but we cannot take i_rwsem in fault,
2081  	 * and bloating every shmem inode for this unlikely case would be sad.
2082  	 */
2083  	if (unlikely(inode->i_private)) {
2084  		struct shmem_falloc *shmem_falloc;
2085  
2086  		spin_lock(&inode->i_lock);
2087  		shmem_falloc = inode->i_private;
2088  		if (shmem_falloc &&
2089  		    shmem_falloc->waitq &&
2090  		    vmf->pgoff >= shmem_falloc->start &&
2091  		    vmf->pgoff < shmem_falloc->next) {
2092  			struct file *fpin;
2093  			wait_queue_head_t *shmem_falloc_waitq;
2094  			DEFINE_WAIT_FUNC(shmem_fault_wait, synchronous_wake_function);
2095  
2096  			ret = VM_FAULT_NOPAGE;
2097  			fpin = maybe_unlock_mmap_for_io(vmf, NULL);
2098  			if (fpin)
2099  				ret = VM_FAULT_RETRY;
2100  
2101  			shmem_falloc_waitq = shmem_falloc->waitq;
2102  			prepare_to_wait(shmem_falloc_waitq, &shmem_fault_wait,
2103  					TASK_UNINTERRUPTIBLE);
2104  			spin_unlock(&inode->i_lock);
2105  			schedule();
2106  
2107  			/*
2108  			 * shmem_falloc_waitq points into the shmem_fallocate()
2109  			 * stack of the hole-punching task: shmem_falloc_waitq
2110  			 * is usually invalid by the time we reach here, but
2111  			 * finish_wait() does not dereference it in that case;
2112  			 * though i_lock needed lest racing with wake_up_all().
2113  			 */
2114  			spin_lock(&inode->i_lock);
2115  			finish_wait(shmem_falloc_waitq, &shmem_fault_wait);
2116  			spin_unlock(&inode->i_lock);
2117  
2118  			if (fpin)
2119  				fput(fpin);
2120  			return ret;
2121  		}
2122  		spin_unlock(&inode->i_lock);
2123  	}
2124  
2125  	err = shmem_getpage_gfp(inode, vmf->pgoff, &vmf->page, SGP_CACHE,
2126  				  gfp, vma, vmf, &ret);
2127  	if (err)
2128  		return vmf_error(err);
2129  	return ret;
2130  }
2131  
2132  unsigned long shmem_get_unmapped_area(struct file *file,
2133  				      unsigned long uaddr, unsigned long len,
2134  				      unsigned long pgoff, unsigned long flags)
2135  {
2136  	unsigned long (*get_area)(struct file *,
2137  		unsigned long, unsigned long, unsigned long, unsigned long);
2138  	unsigned long addr;
2139  	unsigned long offset;
2140  	unsigned long inflated_len;
2141  	unsigned long inflated_addr;
2142  	unsigned long inflated_offset;
2143  
2144  	if (len > TASK_SIZE)
2145  		return -ENOMEM;
2146  
2147  	get_area = current->mm->get_unmapped_area;
2148  	addr = get_area(file, uaddr, len, pgoff, flags);
2149  
2150  	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
2151  		return addr;
2152  	if (IS_ERR_VALUE(addr))
2153  		return addr;
2154  	if (addr & ~PAGE_MASK)
2155  		return addr;
2156  	if (addr > TASK_SIZE - len)
2157  		return addr;
2158  
2159  	if (shmem_huge == SHMEM_HUGE_DENY)
2160  		return addr;
2161  	if (len < HPAGE_PMD_SIZE)
2162  		return addr;
2163  	if (flags & MAP_FIXED)
2164  		return addr;
2165  	/*
2166  	 * Our priority is to support MAP_SHARED mapped hugely;
2167  	 * and support MAP_PRIVATE mapped hugely too, until it is COWed.
2168  	 * But if caller specified an address hint and we allocated area there
2169  	 * successfully, respect that as before.
2170  	 */
2171  	if (uaddr == addr)
2172  		return addr;
2173  
2174  	if (shmem_huge != SHMEM_HUGE_FORCE) {
2175  		struct super_block *sb;
2176  
2177  		if (file) {
2178  			VM_BUG_ON(file->f_op != &shmem_file_operations);
2179  			sb = file_inode(file)->i_sb;
2180  		} else {
2181  			/*
2182  			 * Called directly from mm/mmap.c, or drivers/char/mem.c
2183  			 * for "/dev/zero", to create a shared anonymous object.
2184  			 */
2185  			if (IS_ERR(shm_mnt))
2186  				return addr;
2187  			sb = shm_mnt->mnt_sb;
2188  		}
2189  		if (SHMEM_SB(sb)->huge == SHMEM_HUGE_NEVER)
2190  			return addr;
2191  	}
2192  
2193  	offset = (pgoff << PAGE_SHIFT) & (HPAGE_PMD_SIZE-1);
2194  	if (offset && offset + len < 2 * HPAGE_PMD_SIZE)
2195  		return addr;
2196  	if ((addr & (HPAGE_PMD_SIZE-1)) == offset)
2197  		return addr;
2198  
2199  	inflated_len = len + HPAGE_PMD_SIZE - PAGE_SIZE;
2200  	if (inflated_len > TASK_SIZE)
2201  		return addr;
2202  	if (inflated_len < len)
2203  		return addr;
2204  
2205  	inflated_addr = get_area(NULL, uaddr, inflated_len, 0, flags);
2206  	if (IS_ERR_VALUE(inflated_addr))
2207  		return addr;
2208  	if (inflated_addr & ~PAGE_MASK)
2209  		return addr;
2210  
2211  	inflated_offset = inflated_addr & (HPAGE_PMD_SIZE-1);
2212  	inflated_addr += offset - inflated_offset;
2213  	if (inflated_offset > offset)
2214  		inflated_addr += HPAGE_PMD_SIZE;
2215  
2216  	if (inflated_addr > TASK_SIZE - len)
2217  		return addr;
2218  	return inflated_addr;
2219  }
2220  
2221  #ifdef CONFIG_NUMA
2222  static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *mpol)
2223  {
2224  	struct inode *inode = file_inode(vma->vm_file);
2225  	return mpol_set_shared_policy(&SHMEM_I(inode)->policy, vma, mpol);
2226  }
2227  
2228  static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
2229  					  unsigned long addr)
2230  {
2231  	struct inode *inode = file_inode(vma->vm_file);
2232  	pgoff_t index;
2233  
2234  	index = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
2235  	return mpol_shared_policy_lookup(&SHMEM_I(inode)->policy, index);
2236  }
2237  #endif
2238  
2239  int shmem_lock(struct file *file, int lock, struct ucounts *ucounts)
2240  {
2241  	struct inode *inode = file_inode(file);
2242  	struct shmem_inode_info *info = SHMEM_I(inode);
2243  	int retval = -ENOMEM;
2244  
2245  	/*
2246  	 * What serializes the accesses to info->flags?
2247  	 * ipc_lock_object() when called from shmctl_do_lock(),
2248  	 * no serialization needed when called from shm_destroy().
2249  	 */
2250  	if (lock && !(info->flags & VM_LOCKED)) {
2251  		if (!user_shm_lock(inode->i_size, ucounts))
2252  			goto out_nomem;
2253  		info->flags |= VM_LOCKED;
2254  		mapping_set_unevictable(file->f_mapping);
2255  	}
2256  	if (!lock && (info->flags & VM_LOCKED) && ucounts) {
2257  		user_shm_unlock(inode->i_size, ucounts);
2258  		info->flags &= ~VM_LOCKED;
2259  		mapping_clear_unevictable(file->f_mapping);
2260  	}
2261  	retval = 0;
2262  
2263  out_nomem:
2264  	return retval;
2265  }
2266  
2267  static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
2268  {
2269  	struct shmem_inode_info *info = SHMEM_I(file_inode(file));
2270  	int ret;
2271  
2272  	ret = seal_check_future_write(info->seals, vma);
2273  	if (ret)
2274  		return ret;
2275  
2276  	/* arm64 - allow memory tagging on RAM-based files */
2277  	vma->vm_flags |= VM_MTE_ALLOWED;
2278  
2279  	file_accessed(file);
2280  	vma->vm_ops = &shmem_vm_ops;
2281  	return 0;
2282  }
2283  
2284  /* Mask out flags that are inappropriate for the given type of inode. */
2285  static unsigned shmem_mask_flags(umode_t mode, __u32 flags)
2286  {
2287  	if (S_ISDIR(mode))
2288  		return flags;
2289  	else if (S_ISREG(mode))
2290  		return flags & SHMEM_REG_FLMASK;
2291  	else
2292  		return flags & SHMEM_OTHER_FLMASK;
2293  }
2294  
2295  static struct inode *shmem_get_inode(struct super_block *sb, struct inode *dir,
2296  				     umode_t mode, dev_t dev, unsigned long flags)
2297  {
2298  	struct inode *inode;
2299  	struct shmem_inode_info *info;
2300  	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2301  	ino_t ino;
2302  
2303  	if (shmem_reserve_inode(sb, &ino))
2304  		return NULL;
2305  
2306  	inode = new_inode(sb);
2307  	if (inode) {
2308  		inode->i_ino = ino;
2309  		inode_init_owner(&init_user_ns, inode, dir, mode);
2310  		inode->i_blocks = 0;
2311  		inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
2312  		inode->i_generation = prandom_u32();
2313  		info = SHMEM_I(inode);
2314  		memset(info, 0, (char *)inode - (char *)info);
2315  		spin_lock_init(&info->lock);
2316  		atomic_set(&info->stop_eviction, 0);
2317  		info->seals = F_SEAL_SEAL;
2318  		info->flags = flags & VM_NORESERVE;
2319  		info->i_crtime = inode->i_mtime;
2320  		info->fsflags = (dir == NULL) ? 0 :
2321  			SHMEM_I(dir)->fsflags & SHMEM_FL_INHERITED;
2322  		info->fsflags = shmem_mask_flags(mode, info->fsflags);
2323  		INIT_LIST_HEAD(&info->shrinklist);
2324  		INIT_LIST_HEAD(&info->swaplist);
2325  		simple_xattrs_init(&info->xattrs);
2326  		cache_no_acl(inode);
2327  		mapping_set_large_folios(inode->i_mapping);
2328  
2329  		switch (mode & S_IFMT) {
2330  		default:
2331  			inode->i_op = &shmem_special_inode_operations;
2332  			init_special_inode(inode, mode, dev);
2333  			break;
2334  		case S_IFREG:
2335  			inode->i_mapping->a_ops = &shmem_aops;
2336  			inode->i_op = &shmem_inode_operations;
2337  			inode->i_fop = &shmem_file_operations;
2338  			mpol_shared_policy_init(&info->policy,
2339  						 shmem_get_sbmpol(sbinfo));
2340  			break;
2341  		case S_IFDIR:
2342  			inc_nlink(inode);
2343  			/* Some things misbehave if size == 0 on a directory */
2344  			inode->i_size = 2 * BOGO_DIRENT_SIZE;
2345  			inode->i_op = &shmem_dir_inode_operations;
2346  			inode->i_fop = &simple_dir_operations;
2347  			break;
2348  		case S_IFLNK:
2349  			/*
2350  			 * Must not load anything in the rbtree,
2351  			 * mpol_free_shared_policy will not be called.
2352  			 */
2353  			mpol_shared_policy_init(&info->policy, NULL);
2354  			break;
2355  		}
2356  
2357  		lockdep_annotate_inode_mutex_key(inode);
2358  	} else
2359  		shmem_free_inode(sb);
2360  	return inode;
2361  }
2362  
2363  #ifdef CONFIG_USERFAULTFD
2364  int shmem_mfill_atomic_pte(struct mm_struct *dst_mm,
2365  			   pmd_t *dst_pmd,
2366  			   struct vm_area_struct *dst_vma,
2367  			   unsigned long dst_addr,
2368  			   unsigned long src_addr,
2369  			   bool zeropage, bool wp_copy,
2370  			   struct page **pagep)
2371  {
2372  	struct inode *inode = file_inode(dst_vma->vm_file);
2373  	struct shmem_inode_info *info = SHMEM_I(inode);
2374  	struct address_space *mapping = inode->i_mapping;
2375  	gfp_t gfp = mapping_gfp_mask(mapping);
2376  	pgoff_t pgoff = linear_page_index(dst_vma, dst_addr);
2377  	void *page_kaddr;
2378  	struct folio *folio;
2379  	struct page *page;
2380  	int ret;
2381  	pgoff_t max_off;
2382  
2383  	if (!shmem_inode_acct_block(inode, 1)) {
2384  		/*
2385  		 * We may have got a page, returned -ENOENT triggering a retry,
2386  		 * and now we find ourselves with -ENOMEM. Release the page, to
2387  		 * avoid a BUG_ON in our caller.
2388  		 */
2389  		if (unlikely(*pagep)) {
2390  			put_page(*pagep);
2391  			*pagep = NULL;
2392  		}
2393  		return -ENOMEM;
2394  	}
2395  
2396  	if (!*pagep) {
2397  		ret = -ENOMEM;
2398  		page = shmem_alloc_page(gfp, info, pgoff);
2399  		if (!page)
2400  			goto out_unacct_blocks;
2401  
2402  		if (!zeropage) {	/* COPY */
2403  			page_kaddr = kmap_atomic(page);
2404  			ret = copy_from_user(page_kaddr,
2405  					     (const void __user *)src_addr,
2406  					     PAGE_SIZE);
2407  			kunmap_atomic(page_kaddr);
2408  
2409  			/* fallback to copy_from_user outside mmap_lock */
2410  			if (unlikely(ret)) {
2411  				*pagep = page;
2412  				ret = -ENOENT;
2413  				/* don't free the page */
2414  				goto out_unacct_blocks;
2415  			}
2416  
2417  			flush_dcache_page(page);
2418  		} else {		/* ZEROPAGE */
2419  			clear_user_highpage(page, dst_addr);
2420  		}
2421  	} else {
2422  		page = *pagep;
2423  		*pagep = NULL;
2424  	}
2425  
2426  	VM_BUG_ON(PageLocked(page));
2427  	VM_BUG_ON(PageSwapBacked(page));
2428  	__SetPageLocked(page);
2429  	__SetPageSwapBacked(page);
2430  	__SetPageUptodate(page);
2431  
2432  	ret = -EFAULT;
2433  	max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
2434  	if (unlikely(pgoff >= max_off))
2435  		goto out_release;
2436  
2437  	folio = page_folio(page);
2438  	ret = shmem_add_to_page_cache(folio, mapping, pgoff, NULL,
2439  				      gfp & GFP_RECLAIM_MASK, dst_mm);
2440  	if (ret)
2441  		goto out_release;
2442  
2443  	ret = mfill_atomic_install_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
2444  				       page, true, wp_copy);
2445  	if (ret)
2446  		goto out_delete_from_cache;
2447  
2448  	spin_lock_irq(&info->lock);
2449  	info->alloced++;
2450  	inode->i_blocks += BLOCKS_PER_PAGE;
2451  	shmem_recalc_inode(inode);
2452  	spin_unlock_irq(&info->lock);
2453  
2454  	unlock_page(page);
2455  	return 0;
2456  out_delete_from_cache:
2457  	delete_from_page_cache(page);
2458  out_release:
2459  	unlock_page(page);
2460  	put_page(page);
2461  out_unacct_blocks:
2462  	shmem_inode_unacct_blocks(inode, 1);
2463  	return ret;
2464  }
2465  #endif /* CONFIG_USERFAULTFD */
2466  
2467  #ifdef CONFIG_TMPFS
2468  static const struct inode_operations shmem_symlink_inode_operations;
2469  static const struct inode_operations shmem_short_symlink_operations;
2470  
2471  #ifdef CONFIG_TMPFS_XATTR
2472  static int shmem_initxattrs(struct inode *, const struct xattr *, void *);
2473  #else
2474  #define shmem_initxattrs NULL
2475  #endif
2476  
2477  static int
2478  shmem_write_begin(struct file *file, struct address_space *mapping,
2479  			loff_t pos, unsigned len,
2480  			struct page **pagep, void **fsdata)
2481  {
2482  	struct inode *inode = mapping->host;
2483  	struct shmem_inode_info *info = SHMEM_I(inode);
2484  	pgoff_t index = pos >> PAGE_SHIFT;
2485  	int ret = 0;
2486  
2487  	/* i_rwsem is held by caller */
2488  	if (unlikely(info->seals & (F_SEAL_GROW |
2489  				   F_SEAL_WRITE | F_SEAL_FUTURE_WRITE))) {
2490  		if (info->seals & (F_SEAL_WRITE | F_SEAL_FUTURE_WRITE))
2491  			return -EPERM;
2492  		if ((info->seals & F_SEAL_GROW) && pos + len > inode->i_size)
2493  			return -EPERM;
2494  	}
2495  
2496  	ret = shmem_getpage(inode, index, pagep, SGP_WRITE);
2497  
2498  	if (ret)
2499  		return ret;
2500  
2501  	if (PageHWPoison(*pagep)) {
2502  		unlock_page(*pagep);
2503  		put_page(*pagep);
2504  		*pagep = NULL;
2505  		return -EIO;
2506  	}
2507  
2508  	return 0;
2509  }
2510  
2511  static int
2512  shmem_write_end(struct file *file, struct address_space *mapping,
2513  			loff_t pos, unsigned len, unsigned copied,
2514  			struct page *page, void *fsdata)
2515  {
2516  	struct inode *inode = mapping->host;
2517  
2518  	if (pos + copied > inode->i_size)
2519  		i_size_write(inode, pos + copied);
2520  
2521  	if (!PageUptodate(page)) {
2522  		struct page *head = compound_head(page);
2523  		if (PageTransCompound(page)) {
2524  			int i;
2525  
2526  			for (i = 0; i < HPAGE_PMD_NR; i++) {
2527  				if (head + i == page)
2528  					continue;
2529  				clear_highpage(head + i);
2530  				flush_dcache_page(head + i);
2531  			}
2532  		}
2533  		if (copied < PAGE_SIZE) {
2534  			unsigned from = pos & (PAGE_SIZE - 1);
2535  			zero_user_segments(page, 0, from,
2536  					from + copied, PAGE_SIZE);
2537  		}
2538  		SetPageUptodate(head);
2539  	}
2540  	set_page_dirty(page);
2541  	unlock_page(page);
2542  	put_page(page);
2543  
2544  	return copied;
2545  }
2546  
2547  static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
2548  {
2549  	struct file *file = iocb->ki_filp;
2550  	struct inode *inode = file_inode(file);
2551  	struct address_space *mapping = inode->i_mapping;
2552  	pgoff_t index;
2553  	unsigned long offset;
2554  	int error = 0;
2555  	ssize_t retval = 0;
2556  	loff_t *ppos = &iocb->ki_pos;
2557  
2558  	index = *ppos >> PAGE_SHIFT;
2559  	offset = *ppos & ~PAGE_MASK;
2560  
2561  	for (;;) {
2562  		struct page *page = NULL;
2563  		pgoff_t end_index;
2564  		unsigned long nr, ret;
2565  		loff_t i_size = i_size_read(inode);
2566  
2567  		end_index = i_size >> PAGE_SHIFT;
2568  		if (index > end_index)
2569  			break;
2570  		if (index == end_index) {
2571  			nr = i_size & ~PAGE_MASK;
2572  			if (nr <= offset)
2573  				break;
2574  		}
2575  
2576  		error = shmem_getpage(inode, index, &page, SGP_READ);
2577  		if (error) {
2578  			if (error == -EINVAL)
2579  				error = 0;
2580  			break;
2581  		}
2582  		if (page) {
2583  			unlock_page(page);
2584  
2585  			if (PageHWPoison(page)) {
2586  				put_page(page);
2587  				error = -EIO;
2588  				break;
2589  			}
2590  		}
2591  
2592  		/*
2593  		 * We must evaluate after, since reads (unlike writes)
2594  		 * are called without i_rwsem protection against truncate
2595  		 */
2596  		nr = PAGE_SIZE;
2597  		i_size = i_size_read(inode);
2598  		end_index = i_size >> PAGE_SHIFT;
2599  		if (index == end_index) {
2600  			nr = i_size & ~PAGE_MASK;
2601  			if (nr <= offset) {
2602  				if (page)
2603  					put_page(page);
2604  				break;
2605  			}
2606  		}
2607  		nr -= offset;
2608  
2609  		if (page) {
2610  			/*
2611  			 * If users can be writing to this page using arbitrary
2612  			 * virtual addresses, take care about potential aliasing
2613  			 * before reading the page on the kernel side.
2614  			 */
2615  			if (mapping_writably_mapped(mapping))
2616  				flush_dcache_page(page);
2617  			/*
2618  			 * Mark the page accessed if we read the beginning.
2619  			 */
2620  			if (!offset)
2621  				mark_page_accessed(page);
2622  			/*
2623  			 * Ok, we have the page, and it's up-to-date, so
2624  			 * now we can copy it to user space...
2625  			 */
2626  			ret = copy_page_to_iter(page, offset, nr, to);
2627  			put_page(page);
2628  
2629  		} else if (user_backed_iter(to)) {
2630  			/*
2631  			 * Copy to user tends to be so well optimized, but
2632  			 * clear_user() not so much, that it is noticeably
2633  			 * faster to copy the zero page instead of clearing.
2634  			 */
2635  			ret = copy_page_to_iter(ZERO_PAGE(0), offset, nr, to);
2636  		} else {
2637  			/*
2638  			 * But submitting the same page twice in a row to
2639  			 * splice() - or others? - can result in confusion:
2640  			 * so don't attempt that optimization on pipes etc.
2641  			 */
2642  			ret = iov_iter_zero(nr, to);
2643  		}
2644  
2645  		retval += ret;
2646  		offset += ret;
2647  		index += offset >> PAGE_SHIFT;
2648  		offset &= ~PAGE_MASK;
2649  
2650  		if (!iov_iter_count(to))
2651  			break;
2652  		if (ret < nr) {
2653  			error = -EFAULT;
2654  			break;
2655  		}
2656  		cond_resched();
2657  	}
2658  
2659  	*ppos = ((loff_t) index << PAGE_SHIFT) + offset;
2660  	file_accessed(file);
2661  	return retval ? retval : error;
2662  }
2663  
2664  static loff_t shmem_file_llseek(struct file *file, loff_t offset, int whence)
2665  {
2666  	struct address_space *mapping = file->f_mapping;
2667  	struct inode *inode = mapping->host;
2668  
2669  	if (whence != SEEK_DATA && whence != SEEK_HOLE)
2670  		return generic_file_llseek_size(file, offset, whence,
2671  					MAX_LFS_FILESIZE, i_size_read(inode));
2672  	if (offset < 0)
2673  		return -ENXIO;
2674  
2675  	inode_lock(inode);
2676  	/* We're holding i_rwsem so we can access i_size directly */
2677  	offset = mapping_seek_hole_data(mapping, offset, inode->i_size, whence);
2678  	if (offset >= 0)
2679  		offset = vfs_setpos(file, offset, MAX_LFS_FILESIZE);
2680  	inode_unlock(inode);
2681  	return offset;
2682  }
2683  
2684  static long shmem_fallocate(struct file *file, int mode, loff_t offset,
2685  							 loff_t len)
2686  {
2687  	struct inode *inode = file_inode(file);
2688  	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
2689  	struct shmem_inode_info *info = SHMEM_I(inode);
2690  	struct shmem_falloc shmem_falloc;
2691  	pgoff_t start, index, end, undo_fallocend;
2692  	int error;
2693  
2694  	if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
2695  		return -EOPNOTSUPP;
2696  
2697  	inode_lock(inode);
2698  
2699  	if (mode & FALLOC_FL_PUNCH_HOLE) {
2700  		struct address_space *mapping = file->f_mapping;
2701  		loff_t unmap_start = round_up(offset, PAGE_SIZE);
2702  		loff_t unmap_end = round_down(offset + len, PAGE_SIZE) - 1;
2703  		DECLARE_WAIT_QUEUE_HEAD_ONSTACK(shmem_falloc_waitq);
2704  
2705  		/* protected by i_rwsem */
2706  		if (info->seals & (F_SEAL_WRITE | F_SEAL_FUTURE_WRITE)) {
2707  			error = -EPERM;
2708  			goto out;
2709  		}
2710  
2711  		shmem_falloc.waitq = &shmem_falloc_waitq;
2712  		shmem_falloc.start = (u64)unmap_start >> PAGE_SHIFT;
2713  		shmem_falloc.next = (unmap_end + 1) >> PAGE_SHIFT;
2714  		spin_lock(&inode->i_lock);
2715  		inode->i_private = &shmem_falloc;
2716  		spin_unlock(&inode->i_lock);
2717  
2718  		if ((u64)unmap_end > (u64)unmap_start)
2719  			unmap_mapping_range(mapping, unmap_start,
2720  					    1 + unmap_end - unmap_start, 0);
2721  		shmem_truncate_range(inode, offset, offset + len - 1);
2722  		/* No need to unmap again: hole-punching leaves COWed pages */
2723  
2724  		spin_lock(&inode->i_lock);
2725  		inode->i_private = NULL;
2726  		wake_up_all(&shmem_falloc_waitq);
2727  		WARN_ON_ONCE(!list_empty(&shmem_falloc_waitq.head));
2728  		spin_unlock(&inode->i_lock);
2729  		error = 0;
2730  		goto out;
2731  	}
2732  
2733  	/* We need to check rlimit even when FALLOC_FL_KEEP_SIZE */
2734  	error = inode_newsize_ok(inode, offset + len);
2735  	if (error)
2736  		goto out;
2737  
2738  	if ((info->seals & F_SEAL_GROW) && offset + len > inode->i_size) {
2739  		error = -EPERM;
2740  		goto out;
2741  	}
2742  
2743  	start = offset >> PAGE_SHIFT;
2744  	end = (offset + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
2745  	/* Try to avoid a swapstorm if len is impossible to satisfy */
2746  	if (sbinfo->max_blocks && end - start > sbinfo->max_blocks) {
2747  		error = -ENOSPC;
2748  		goto out;
2749  	}
2750  
2751  	shmem_falloc.waitq = NULL;
2752  	shmem_falloc.start = start;
2753  	shmem_falloc.next  = start;
2754  	shmem_falloc.nr_falloced = 0;
2755  	shmem_falloc.nr_unswapped = 0;
2756  	spin_lock(&inode->i_lock);
2757  	inode->i_private = &shmem_falloc;
2758  	spin_unlock(&inode->i_lock);
2759  
2760  	/*
2761  	 * info->fallocend is only relevant when huge pages might be
2762  	 * involved: to prevent split_huge_page() freeing fallocated
2763  	 * pages when FALLOC_FL_KEEP_SIZE committed beyond i_size.
2764  	 */
2765  	undo_fallocend = info->fallocend;
2766  	if (info->fallocend < end)
2767  		info->fallocend = end;
2768  
2769  	for (index = start; index < end; ) {
2770  		struct page *page;
2771  
2772  		/*
2773  		 * Good, the fallocate(2) manpage permits EINTR: we may have
2774  		 * been interrupted because we are using up too much memory.
2775  		 */
2776  		if (signal_pending(current))
2777  			error = -EINTR;
2778  		else if (shmem_falloc.nr_unswapped > shmem_falloc.nr_falloced)
2779  			error = -ENOMEM;
2780  		else
2781  			error = shmem_getpage(inode, index, &page, SGP_FALLOC);
2782  		if (error) {
2783  			info->fallocend = undo_fallocend;
2784  			/* Remove the !PageUptodate pages we added */
2785  			if (index > start) {
2786  				shmem_undo_range(inode,
2787  				    (loff_t)start << PAGE_SHIFT,
2788  				    ((loff_t)index << PAGE_SHIFT) - 1, true);
2789  			}
2790  			goto undone;
2791  		}
2792  
2793  		index++;
2794  		/*
2795  		 * Here is a more important optimization than it appears:
2796  		 * a second SGP_FALLOC on the same huge page will clear it,
2797  		 * making it PageUptodate and un-undoable if we fail later.
2798  		 */
2799  		if (PageTransCompound(page)) {
2800  			index = round_up(index, HPAGE_PMD_NR);
2801  			/* Beware 32-bit wraparound */
2802  			if (!index)
2803  				index--;
2804  		}
2805  
2806  		/*
2807  		 * Inform shmem_writepage() how far we have reached.
2808  		 * No need for lock or barrier: we have the page lock.
2809  		 */
2810  		if (!PageUptodate(page))
2811  			shmem_falloc.nr_falloced += index - shmem_falloc.next;
2812  		shmem_falloc.next = index;
2813  
2814  		/*
2815  		 * If !PageUptodate, leave it that way so that freeable pages
2816  		 * can be recognized if we need to rollback on error later.
2817  		 * But set_page_dirty so that memory pressure will swap rather
2818  		 * than free the pages we are allocating (and SGP_CACHE pages
2819  		 * might still be clean: we now need to mark those dirty too).
2820  		 */
2821  		set_page_dirty(page);
2822  		unlock_page(page);
2823  		put_page(page);
2824  		cond_resched();
2825  	}
2826  
2827  	if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size)
2828  		i_size_write(inode, offset + len);
2829  	inode->i_ctime = current_time(inode);
2830  undone:
2831  	spin_lock(&inode->i_lock);
2832  	inode->i_private = NULL;
2833  	spin_unlock(&inode->i_lock);
2834  out:
2835  	inode_unlock(inode);
2836  	return error;
2837  }
2838  
2839  static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
2840  {
2841  	struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
2842  
2843  	buf->f_type = TMPFS_MAGIC;
2844  	buf->f_bsize = PAGE_SIZE;
2845  	buf->f_namelen = NAME_MAX;
2846  	if (sbinfo->max_blocks) {
2847  		buf->f_blocks = sbinfo->max_blocks;
2848  		buf->f_bavail =
2849  		buf->f_bfree  = sbinfo->max_blocks -
2850  				percpu_counter_sum(&sbinfo->used_blocks);
2851  	}
2852  	if (sbinfo->max_inodes) {
2853  		buf->f_files = sbinfo->max_inodes;
2854  		buf->f_ffree = sbinfo->free_inodes;
2855  	}
2856  	/* else leave those fields 0 like simple_statfs */
2857  
2858  	buf->f_fsid = uuid_to_fsid(dentry->d_sb->s_uuid.b);
2859  
2860  	return 0;
2861  }
2862  
2863  /*
2864   * File creation. Allocate an inode, and we're done..
2865   */
2866  static int
2867  shmem_mknod(struct user_namespace *mnt_userns, struct inode *dir,
2868  	    struct dentry *dentry, umode_t mode, dev_t dev)
2869  {
2870  	struct inode *inode;
2871  	int error = -ENOSPC;
2872  
2873  	inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE);
2874  	if (inode) {
2875  		error = simple_acl_create(dir, inode);
2876  		if (error)
2877  			goto out_iput;
2878  		error = security_inode_init_security(inode, dir,
2879  						     &dentry->d_name,
2880  						     shmem_initxattrs, NULL);
2881  		if (error && error != -EOPNOTSUPP)
2882  			goto out_iput;
2883  
2884  		error = 0;
2885  		dir->i_size += BOGO_DIRENT_SIZE;
2886  		dir->i_ctime = dir->i_mtime = current_time(dir);
2887  		d_instantiate(dentry, inode);
2888  		dget(dentry); /* Extra count - pin the dentry in core */
2889  	}
2890  	return error;
2891  out_iput:
2892  	iput(inode);
2893  	return error;
2894  }
2895  
2896  static int
2897  shmem_tmpfile(struct user_namespace *mnt_userns, struct inode *dir,
2898  	      struct dentry *dentry, umode_t mode)
2899  {
2900  	struct inode *inode;
2901  	int error = -ENOSPC;
2902  
2903  	inode = shmem_get_inode(dir->i_sb, dir, mode, 0, VM_NORESERVE);
2904  	if (inode) {
2905  		error = security_inode_init_security(inode, dir,
2906  						     NULL,
2907  						     shmem_initxattrs, NULL);
2908  		if (error && error != -EOPNOTSUPP)
2909  			goto out_iput;
2910  		error = simple_acl_create(dir, inode);
2911  		if (error)
2912  			goto out_iput;
2913  		d_tmpfile(dentry, inode);
2914  	}
2915  	return error;
2916  out_iput:
2917  	iput(inode);
2918  	return error;
2919  }
2920  
2921  static int shmem_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
2922  		       struct dentry *dentry, umode_t mode)
2923  {
2924  	int error;
2925  
2926  	if ((error = shmem_mknod(&init_user_ns, dir, dentry,
2927  				 mode | S_IFDIR, 0)))
2928  		return error;
2929  	inc_nlink(dir);
2930  	return 0;
2931  }
2932  
2933  static int shmem_create(struct user_namespace *mnt_userns, struct inode *dir,
2934  			struct dentry *dentry, umode_t mode, bool excl)
2935  {
2936  	return shmem_mknod(&init_user_ns, dir, dentry, mode | S_IFREG, 0);
2937  }
2938  
2939  /*
2940   * Link a file..
2941   */
2942  static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
2943  {
2944  	struct inode *inode = d_inode(old_dentry);
2945  	int ret = 0;
2946  
2947  	/*
2948  	 * No ordinary (disk based) filesystem counts links as inodes;
2949  	 * but each new link needs a new dentry, pinning lowmem, and
2950  	 * tmpfs dentries cannot be pruned until they are unlinked.
2951  	 * But if an O_TMPFILE file is linked into the tmpfs, the
2952  	 * first link must skip that, to get the accounting right.
2953  	 */
2954  	if (inode->i_nlink) {
2955  		ret = shmem_reserve_inode(inode->i_sb, NULL);
2956  		if (ret)
2957  			goto out;
2958  	}
2959  
2960  	dir->i_size += BOGO_DIRENT_SIZE;
2961  	inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
2962  	inc_nlink(inode);
2963  	ihold(inode);	/* New dentry reference */
2964  	dget(dentry);		/* Extra pinning count for the created dentry */
2965  	d_instantiate(dentry, inode);
2966  out:
2967  	return ret;
2968  }
2969  
2970  static int shmem_unlink(struct inode *dir, struct dentry *dentry)
2971  {
2972  	struct inode *inode = d_inode(dentry);
2973  
2974  	if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
2975  		shmem_free_inode(inode->i_sb);
2976  
2977  	dir->i_size -= BOGO_DIRENT_SIZE;
2978  	inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
2979  	drop_nlink(inode);
2980  	dput(dentry);	/* Undo the count from "create" - this does all the work */
2981  	return 0;
2982  }
2983  
2984  static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
2985  {
2986  	if (!simple_empty(dentry))
2987  		return -ENOTEMPTY;
2988  
2989  	drop_nlink(d_inode(dentry));
2990  	drop_nlink(dir);
2991  	return shmem_unlink(dir, dentry);
2992  }
2993  
2994  static int shmem_whiteout(struct user_namespace *mnt_userns,
2995  			  struct inode *old_dir, struct dentry *old_dentry)
2996  {
2997  	struct dentry *whiteout;
2998  	int error;
2999  
3000  	whiteout = d_alloc(old_dentry->d_parent, &old_dentry->d_name);
3001  	if (!whiteout)
3002  		return -ENOMEM;
3003  
3004  	error = shmem_mknod(&init_user_ns, old_dir, whiteout,
3005  			    S_IFCHR | WHITEOUT_MODE, WHITEOUT_DEV);
3006  	dput(whiteout);
3007  	if (error)
3008  		return error;
3009  
3010  	/*
3011  	 * Cheat and hash the whiteout while the old dentry is still in
3012  	 * place, instead of playing games with FS_RENAME_DOES_D_MOVE.
3013  	 *
3014  	 * d_lookup() will consistently find one of them at this point,
3015  	 * not sure which one, but that isn't even important.
3016  	 */
3017  	d_rehash(whiteout);
3018  	return 0;
3019  }
3020  
3021  /*
3022   * The VFS layer already does all the dentry stuff for rename,
3023   * we just have to decrement the usage count for the target if
3024   * it exists so that the VFS layer correctly free's it when it
3025   * gets overwritten.
3026   */
3027  static int shmem_rename2(struct user_namespace *mnt_userns,
3028  			 struct inode *old_dir, struct dentry *old_dentry,
3029  			 struct inode *new_dir, struct dentry *new_dentry,
3030  			 unsigned int flags)
3031  {
3032  	struct inode *inode = d_inode(old_dentry);
3033  	int they_are_dirs = S_ISDIR(inode->i_mode);
3034  
3035  	if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
3036  		return -EINVAL;
3037  
3038  	if (flags & RENAME_EXCHANGE)
3039  		return simple_rename_exchange(old_dir, old_dentry, new_dir, new_dentry);
3040  
3041  	if (!simple_empty(new_dentry))
3042  		return -ENOTEMPTY;
3043  
3044  	if (flags & RENAME_WHITEOUT) {
3045  		int error;
3046  
3047  		error = shmem_whiteout(&init_user_ns, old_dir, old_dentry);
3048  		if (error)
3049  			return error;
3050  	}
3051  
3052  	if (d_really_is_positive(new_dentry)) {
3053  		(void) shmem_unlink(new_dir, new_dentry);
3054  		if (they_are_dirs) {
3055  			drop_nlink(d_inode(new_dentry));
3056  			drop_nlink(old_dir);
3057  		}
3058  	} else if (they_are_dirs) {
3059  		drop_nlink(old_dir);
3060  		inc_nlink(new_dir);
3061  	}
3062  
3063  	old_dir->i_size -= BOGO_DIRENT_SIZE;
3064  	new_dir->i_size += BOGO_DIRENT_SIZE;
3065  	old_dir->i_ctime = old_dir->i_mtime =
3066  	new_dir->i_ctime = new_dir->i_mtime =
3067  	inode->i_ctime = current_time(old_dir);
3068  	return 0;
3069  }
3070  
3071  static int shmem_symlink(struct user_namespace *mnt_userns, struct inode *dir,
3072  			 struct dentry *dentry, const char *symname)
3073  {
3074  	int error;
3075  	int len;
3076  	struct inode *inode;
3077  	struct page *page;
3078  
3079  	len = strlen(symname) + 1;
3080  	if (len > PAGE_SIZE)
3081  		return -ENAMETOOLONG;
3082  
3083  	inode = shmem_get_inode(dir->i_sb, dir, S_IFLNK | 0777, 0,
3084  				VM_NORESERVE);
3085  	if (!inode)
3086  		return -ENOSPC;
3087  
3088  	error = security_inode_init_security(inode, dir, &dentry->d_name,
3089  					     shmem_initxattrs, NULL);
3090  	if (error && error != -EOPNOTSUPP) {
3091  		iput(inode);
3092  		return error;
3093  	}
3094  
3095  	inode->i_size = len-1;
3096  	if (len <= SHORT_SYMLINK_LEN) {
3097  		inode->i_link = kmemdup(symname, len, GFP_KERNEL);
3098  		if (!inode->i_link) {
3099  			iput(inode);
3100  			return -ENOMEM;
3101  		}
3102  		inode->i_op = &shmem_short_symlink_operations;
3103  	} else {
3104  		inode_nohighmem(inode);
3105  		error = shmem_getpage(inode, 0, &page, SGP_WRITE);
3106  		if (error) {
3107  			iput(inode);
3108  			return error;
3109  		}
3110  		inode->i_mapping->a_ops = &shmem_aops;
3111  		inode->i_op = &shmem_symlink_inode_operations;
3112  		memcpy(page_address(page), symname, len);
3113  		SetPageUptodate(page);
3114  		set_page_dirty(page);
3115  		unlock_page(page);
3116  		put_page(page);
3117  	}
3118  	dir->i_size += BOGO_DIRENT_SIZE;
3119  	dir->i_ctime = dir->i_mtime = current_time(dir);
3120  	d_instantiate(dentry, inode);
3121  	dget(dentry);
3122  	return 0;
3123  }
3124  
3125  static void shmem_put_link(void *arg)
3126  {
3127  	mark_page_accessed(arg);
3128  	put_page(arg);
3129  }
3130  
3131  static const char *shmem_get_link(struct dentry *dentry,
3132  				  struct inode *inode,
3133  				  struct delayed_call *done)
3134  {
3135  	struct page *page = NULL;
3136  	int error;
3137  	if (!dentry) {
3138  		page = find_get_page(inode->i_mapping, 0);
3139  		if (!page)
3140  			return ERR_PTR(-ECHILD);
3141  		if (PageHWPoison(page) ||
3142  		    !PageUptodate(page)) {
3143  			put_page(page);
3144  			return ERR_PTR(-ECHILD);
3145  		}
3146  	} else {
3147  		error = shmem_getpage(inode, 0, &page, SGP_READ);
3148  		if (error)
3149  			return ERR_PTR(error);
3150  		if (!page)
3151  			return ERR_PTR(-ECHILD);
3152  		if (PageHWPoison(page)) {
3153  			unlock_page(page);
3154  			put_page(page);
3155  			return ERR_PTR(-ECHILD);
3156  		}
3157  		unlock_page(page);
3158  	}
3159  	set_delayed_call(done, shmem_put_link, page);
3160  	return page_address(page);
3161  }
3162  
3163  #ifdef CONFIG_TMPFS_XATTR
3164  
3165  static int shmem_fileattr_get(struct dentry *dentry, struct fileattr *fa)
3166  {
3167  	struct shmem_inode_info *info = SHMEM_I(d_inode(dentry));
3168  
3169  	fileattr_fill_flags(fa, info->fsflags & SHMEM_FL_USER_VISIBLE);
3170  
3171  	return 0;
3172  }
3173  
3174  static int shmem_fileattr_set(struct user_namespace *mnt_userns,
3175  			      struct dentry *dentry, struct fileattr *fa)
3176  {
3177  	struct inode *inode = d_inode(dentry);
3178  	struct shmem_inode_info *info = SHMEM_I(inode);
3179  
3180  	if (fileattr_has_fsx(fa))
3181  		return -EOPNOTSUPP;
3182  
3183  	info->fsflags = (info->fsflags & ~SHMEM_FL_USER_MODIFIABLE) |
3184  		(fa->flags & SHMEM_FL_USER_MODIFIABLE);
3185  
3186  	inode->i_flags &= ~(S_APPEND | S_IMMUTABLE | S_NOATIME);
3187  	if (info->fsflags & FS_APPEND_FL)
3188  		inode->i_flags |= S_APPEND;
3189  	if (info->fsflags & FS_IMMUTABLE_FL)
3190  		inode->i_flags |= S_IMMUTABLE;
3191  	if (info->fsflags & FS_NOATIME_FL)
3192  		inode->i_flags |= S_NOATIME;
3193  
3194  	inode->i_ctime = current_time(inode);
3195  	return 0;
3196  }
3197  
3198  /*
3199   * Superblocks without xattr inode operations may get some security.* xattr
3200   * support from the LSM "for free". As soon as we have any other xattrs
3201   * like ACLs, we also need to implement the security.* handlers at
3202   * filesystem level, though.
3203   */
3204  
3205  /*
3206   * Callback for security_inode_init_security() for acquiring xattrs.
3207   */
3208  static int shmem_initxattrs(struct inode *inode,
3209  			    const struct xattr *xattr_array,
3210  			    void *fs_info)
3211  {
3212  	struct shmem_inode_info *info = SHMEM_I(inode);
3213  	const struct xattr *xattr;
3214  	struct simple_xattr *new_xattr;
3215  	size_t len;
3216  
3217  	for (xattr = xattr_array; xattr->name != NULL; xattr++) {
3218  		new_xattr = simple_xattr_alloc(xattr->value, xattr->value_len);
3219  		if (!new_xattr)
3220  			return -ENOMEM;
3221  
3222  		len = strlen(xattr->name) + 1;
3223  		new_xattr->name = kmalloc(XATTR_SECURITY_PREFIX_LEN + len,
3224  					  GFP_KERNEL);
3225  		if (!new_xattr->name) {
3226  			kvfree(new_xattr);
3227  			return -ENOMEM;
3228  		}
3229  
3230  		memcpy(new_xattr->name, XATTR_SECURITY_PREFIX,
3231  		       XATTR_SECURITY_PREFIX_LEN);
3232  		memcpy(new_xattr->name + XATTR_SECURITY_PREFIX_LEN,
3233  		       xattr->name, len);
3234  
3235  		simple_xattr_list_add(&info->xattrs, new_xattr);
3236  	}
3237  
3238  	return 0;
3239  }
3240  
3241  static int shmem_xattr_handler_get(const struct xattr_handler *handler,
3242  				   struct dentry *unused, struct inode *inode,
3243  				   const char *name, void *buffer, size_t size)
3244  {
3245  	struct shmem_inode_info *info = SHMEM_I(inode);
3246  
3247  	name = xattr_full_name(handler, name);
3248  	return simple_xattr_get(&info->xattrs, name, buffer, size);
3249  }
3250  
3251  static int shmem_xattr_handler_set(const struct xattr_handler *handler,
3252  				   struct user_namespace *mnt_userns,
3253  				   struct dentry *unused, struct inode *inode,
3254  				   const char *name, const void *value,
3255  				   size_t size, int flags)
3256  {
3257  	struct shmem_inode_info *info = SHMEM_I(inode);
3258  
3259  	name = xattr_full_name(handler, name);
3260  	return simple_xattr_set(&info->xattrs, name, value, size, flags, NULL);
3261  }
3262  
3263  static const struct xattr_handler shmem_security_xattr_handler = {
3264  	.prefix = XATTR_SECURITY_PREFIX,
3265  	.get = shmem_xattr_handler_get,
3266  	.set = shmem_xattr_handler_set,
3267  };
3268  
3269  static const struct xattr_handler shmem_trusted_xattr_handler = {
3270  	.prefix = XATTR_TRUSTED_PREFIX,
3271  	.get = shmem_xattr_handler_get,
3272  	.set = shmem_xattr_handler_set,
3273  };
3274  
3275  static const struct xattr_handler *shmem_xattr_handlers[] = {
3276  #ifdef CONFIG_TMPFS_POSIX_ACL
3277  	&posix_acl_access_xattr_handler,
3278  	&posix_acl_default_xattr_handler,
3279  #endif
3280  	&shmem_security_xattr_handler,
3281  	&shmem_trusted_xattr_handler,
3282  	NULL
3283  };
3284  
3285  static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t size)
3286  {
3287  	struct shmem_inode_info *info = SHMEM_I(d_inode(dentry));
3288  	return simple_xattr_list(d_inode(dentry), &info->xattrs, buffer, size);
3289  }
3290  #endif /* CONFIG_TMPFS_XATTR */
3291  
3292  static const struct inode_operations shmem_short_symlink_operations = {
3293  	.getattr	= shmem_getattr,
3294  	.get_link	= simple_get_link,
3295  #ifdef CONFIG_TMPFS_XATTR
3296  	.listxattr	= shmem_listxattr,
3297  #endif
3298  };
3299  
3300  static const struct inode_operations shmem_symlink_inode_operations = {
3301  	.getattr	= shmem_getattr,
3302  	.get_link	= shmem_get_link,
3303  #ifdef CONFIG_TMPFS_XATTR
3304  	.listxattr	= shmem_listxattr,
3305  #endif
3306  };
3307  
3308  static struct dentry *shmem_get_parent(struct dentry *child)
3309  {
3310  	return ERR_PTR(-ESTALE);
3311  }
3312  
3313  static int shmem_match(struct inode *ino, void *vfh)
3314  {
3315  	__u32 *fh = vfh;
3316  	__u64 inum = fh[2];
3317  	inum = (inum << 32) | fh[1];
3318  	return ino->i_ino == inum && fh[0] == ino->i_generation;
3319  }
3320  
3321  /* Find any alias of inode, but prefer a hashed alias */
3322  static struct dentry *shmem_find_alias(struct inode *inode)
3323  {
3324  	struct dentry *alias = d_find_alias(inode);
3325  
3326  	return alias ?: d_find_any_alias(inode);
3327  }
3328  
3329  
3330  static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
3331  		struct fid *fid, int fh_len, int fh_type)
3332  {
3333  	struct inode *inode;
3334  	struct dentry *dentry = NULL;
3335  	u64 inum;
3336  
3337  	if (fh_len < 3)
3338  		return NULL;
3339  
3340  	inum = fid->raw[2];
3341  	inum = (inum << 32) | fid->raw[1];
3342  
3343  	inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
3344  			shmem_match, fid->raw);
3345  	if (inode) {
3346  		dentry = shmem_find_alias(inode);
3347  		iput(inode);
3348  	}
3349  
3350  	return dentry;
3351  }
3352  
3353  static int shmem_encode_fh(struct inode *inode, __u32 *fh, int *len,
3354  				struct inode *parent)
3355  {
3356  	if (*len < 3) {
3357  		*len = 3;
3358  		return FILEID_INVALID;
3359  	}
3360  
3361  	if (inode_unhashed(inode)) {
3362  		/* Unfortunately insert_inode_hash is not idempotent,
3363  		 * so as we hash inodes here rather than at creation
3364  		 * time, we need a lock to ensure we only try
3365  		 * to do it once
3366  		 */
3367  		static DEFINE_SPINLOCK(lock);
3368  		spin_lock(&lock);
3369  		if (inode_unhashed(inode))
3370  			__insert_inode_hash(inode,
3371  					    inode->i_ino + inode->i_generation);
3372  		spin_unlock(&lock);
3373  	}
3374  
3375  	fh[0] = inode->i_generation;
3376  	fh[1] = inode->i_ino;
3377  	fh[2] = ((__u64)inode->i_ino) >> 32;
3378  
3379  	*len = 3;
3380  	return 1;
3381  }
3382  
3383  static const struct export_operations shmem_export_ops = {
3384  	.get_parent     = shmem_get_parent,
3385  	.encode_fh      = shmem_encode_fh,
3386  	.fh_to_dentry	= shmem_fh_to_dentry,
3387  };
3388  
3389  enum shmem_param {
3390  	Opt_gid,
3391  	Opt_huge,
3392  	Opt_mode,
3393  	Opt_mpol,
3394  	Opt_nr_blocks,
3395  	Opt_nr_inodes,
3396  	Opt_size,
3397  	Opt_uid,
3398  	Opt_inode32,
3399  	Opt_inode64,
3400  };
3401  
3402  static const struct constant_table shmem_param_enums_huge[] = {
3403  	{"never",	SHMEM_HUGE_NEVER },
3404  	{"always",	SHMEM_HUGE_ALWAYS },
3405  	{"within_size",	SHMEM_HUGE_WITHIN_SIZE },
3406  	{"advise",	SHMEM_HUGE_ADVISE },
3407  	{}
3408  };
3409  
3410  const struct fs_parameter_spec shmem_fs_parameters[] = {
3411  	fsparam_u32   ("gid",		Opt_gid),
3412  	fsparam_enum  ("huge",		Opt_huge,  shmem_param_enums_huge),
3413  	fsparam_u32oct("mode",		Opt_mode),
3414  	fsparam_string("mpol",		Opt_mpol),
3415  	fsparam_string("nr_blocks",	Opt_nr_blocks),
3416  	fsparam_string("nr_inodes",	Opt_nr_inodes),
3417  	fsparam_string("size",		Opt_size),
3418  	fsparam_u32   ("uid",		Opt_uid),
3419  	fsparam_flag  ("inode32",	Opt_inode32),
3420  	fsparam_flag  ("inode64",	Opt_inode64),
3421  	{}
3422  };
3423  
3424  static int shmem_parse_one(struct fs_context *fc, struct fs_parameter *param)
3425  {
3426  	struct shmem_options *ctx = fc->fs_private;
3427  	struct fs_parse_result result;
3428  	unsigned long long size;
3429  	char *rest;
3430  	int opt;
3431  
3432  	opt = fs_parse(fc, shmem_fs_parameters, param, &result);
3433  	if (opt < 0)
3434  		return opt;
3435  
3436  	switch (opt) {
3437  	case Opt_size:
3438  		size = memparse(param->string, &rest);
3439  		if (*rest == '%') {
3440  			size <<= PAGE_SHIFT;
3441  			size *= totalram_pages();
3442  			do_div(size, 100);
3443  			rest++;
3444  		}
3445  		if (*rest)
3446  			goto bad_value;
3447  		ctx->blocks = DIV_ROUND_UP(size, PAGE_SIZE);
3448  		ctx->seen |= SHMEM_SEEN_BLOCKS;
3449  		break;
3450  	case Opt_nr_blocks:
3451  		ctx->blocks = memparse(param->string, &rest);
3452  		if (*rest || ctx->blocks > S64_MAX)
3453  			goto bad_value;
3454  		ctx->seen |= SHMEM_SEEN_BLOCKS;
3455  		break;
3456  	case Opt_nr_inodes:
3457  		ctx->inodes = memparse(param->string, &rest);
3458  		if (*rest)
3459  			goto bad_value;
3460  		ctx->seen |= SHMEM_SEEN_INODES;
3461  		break;
3462  	case Opt_mode:
3463  		ctx->mode = result.uint_32 & 07777;
3464  		break;
3465  	case Opt_uid:
3466  		ctx->uid = make_kuid(current_user_ns(), result.uint_32);
3467  		if (!uid_valid(ctx->uid))
3468  			goto bad_value;
3469  		break;
3470  	case Opt_gid:
3471  		ctx->gid = make_kgid(current_user_ns(), result.uint_32);
3472  		if (!gid_valid(ctx->gid))
3473  			goto bad_value;
3474  		break;
3475  	case Opt_huge:
3476  		ctx->huge = result.uint_32;
3477  		if (ctx->huge != SHMEM_HUGE_NEVER &&
3478  		    !(IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
3479  		      has_transparent_hugepage()))
3480  			goto unsupported_parameter;
3481  		ctx->seen |= SHMEM_SEEN_HUGE;
3482  		break;
3483  	case Opt_mpol:
3484  		if (IS_ENABLED(CONFIG_NUMA)) {
3485  			mpol_put(ctx->mpol);
3486  			ctx->mpol = NULL;
3487  			if (mpol_parse_str(param->string, &ctx->mpol))
3488  				goto bad_value;
3489  			break;
3490  		}
3491  		goto unsupported_parameter;
3492  	case Opt_inode32:
3493  		ctx->full_inums = false;
3494  		ctx->seen |= SHMEM_SEEN_INUMS;
3495  		break;
3496  	case Opt_inode64:
3497  		if (sizeof(ino_t) < 8) {
3498  			return invalfc(fc,
3499  				       "Cannot use inode64 with <64bit inums in kernel\n");
3500  		}
3501  		ctx->full_inums = true;
3502  		ctx->seen |= SHMEM_SEEN_INUMS;
3503  		break;
3504  	}
3505  	return 0;
3506  
3507  unsupported_parameter:
3508  	return invalfc(fc, "Unsupported parameter '%s'", param->key);
3509  bad_value:
3510  	return invalfc(fc, "Bad value for '%s'", param->key);
3511  }
3512  
3513  static int shmem_parse_options(struct fs_context *fc, void *data)
3514  {
3515  	char *options = data;
3516  
3517  	if (options) {
3518  		int err = security_sb_eat_lsm_opts(options, &fc->security);
3519  		if (err)
3520  			return err;
3521  	}
3522  
3523  	while (options != NULL) {
3524  		char *this_char = options;
3525  		for (;;) {
3526  			/*
3527  			 * NUL-terminate this option: unfortunately,
3528  			 * mount options form a comma-separated list,
3529  			 * but mpol's nodelist may also contain commas.
3530  			 */
3531  			options = strchr(options, ',');
3532  			if (options == NULL)
3533  				break;
3534  			options++;
3535  			if (!isdigit(*options)) {
3536  				options[-1] = '\0';
3537  				break;
3538  			}
3539  		}
3540  		if (*this_char) {
3541  			char *value = strchr(this_char, '=');
3542  			size_t len = 0;
3543  			int err;
3544  
3545  			if (value) {
3546  				*value++ = '\0';
3547  				len = strlen(value);
3548  			}
3549  			err = vfs_parse_fs_string(fc, this_char, value, len);
3550  			if (err < 0)
3551  				return err;
3552  		}
3553  	}
3554  	return 0;
3555  }
3556  
3557  /*
3558   * Reconfigure a shmem filesystem.
3559   *
3560   * Note that we disallow change from limited->unlimited blocks/inodes while any
3561   * are in use; but we must separately disallow unlimited->limited, because in
3562   * that case we have no record of how much is already in use.
3563   */
3564  static int shmem_reconfigure(struct fs_context *fc)
3565  {
3566  	struct shmem_options *ctx = fc->fs_private;
3567  	struct shmem_sb_info *sbinfo = SHMEM_SB(fc->root->d_sb);
3568  	unsigned long inodes;
3569  	struct mempolicy *mpol = NULL;
3570  	const char *err;
3571  
3572  	raw_spin_lock(&sbinfo->stat_lock);
3573  	inodes = sbinfo->max_inodes - sbinfo->free_inodes;
3574  
3575  	if ((ctx->seen & SHMEM_SEEN_BLOCKS) && ctx->blocks) {
3576  		if (!sbinfo->max_blocks) {
3577  			err = "Cannot retroactively limit size";
3578  			goto out;
3579  		}
3580  		if (percpu_counter_compare(&sbinfo->used_blocks,
3581  					   ctx->blocks) > 0) {
3582  			err = "Too small a size for current use";
3583  			goto out;
3584  		}
3585  	}
3586  	if ((ctx->seen & SHMEM_SEEN_INODES) && ctx->inodes) {
3587  		if (!sbinfo->max_inodes) {
3588  			err = "Cannot retroactively limit inodes";
3589  			goto out;
3590  		}
3591  		if (ctx->inodes < inodes) {
3592  			err = "Too few inodes for current use";
3593  			goto out;
3594  		}
3595  	}
3596  
3597  	if ((ctx->seen & SHMEM_SEEN_INUMS) && !ctx->full_inums &&
3598  	    sbinfo->next_ino > UINT_MAX) {
3599  		err = "Current inum too high to switch to 32-bit inums";
3600  		goto out;
3601  	}
3602  
3603  	if (ctx->seen & SHMEM_SEEN_HUGE)
3604  		sbinfo->huge = ctx->huge;
3605  	if (ctx->seen & SHMEM_SEEN_INUMS)
3606  		sbinfo->full_inums = ctx->full_inums;
3607  	if (ctx->seen & SHMEM_SEEN_BLOCKS)
3608  		sbinfo->max_blocks  = ctx->blocks;
3609  	if (ctx->seen & SHMEM_SEEN_INODES) {
3610  		sbinfo->max_inodes  = ctx->inodes;
3611  		sbinfo->free_inodes = ctx->inodes - inodes;
3612  	}
3613  
3614  	/*
3615  	 * Preserve previous mempolicy unless mpol remount option was specified.
3616  	 */
3617  	if (ctx->mpol) {
3618  		mpol = sbinfo->mpol;
3619  		sbinfo->mpol = ctx->mpol;	/* transfers initial ref */
3620  		ctx->mpol = NULL;
3621  	}
3622  	raw_spin_unlock(&sbinfo->stat_lock);
3623  	mpol_put(mpol);
3624  	return 0;
3625  out:
3626  	raw_spin_unlock(&sbinfo->stat_lock);
3627  	return invalfc(fc, "%s", err);
3628  }
3629  
3630  static int shmem_show_options(struct seq_file *seq, struct dentry *root)
3631  {
3632  	struct shmem_sb_info *sbinfo = SHMEM_SB(root->d_sb);
3633  
3634  	if (sbinfo->max_blocks != shmem_default_max_blocks())
3635  		seq_printf(seq, ",size=%luk",
3636  			sbinfo->max_blocks << (PAGE_SHIFT - 10));
3637  	if (sbinfo->max_inodes != shmem_default_max_inodes())
3638  		seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
3639  	if (sbinfo->mode != (0777 | S_ISVTX))
3640  		seq_printf(seq, ",mode=%03ho", sbinfo->mode);
3641  	if (!uid_eq(sbinfo->uid, GLOBAL_ROOT_UID))
3642  		seq_printf(seq, ",uid=%u",
3643  				from_kuid_munged(&init_user_ns, sbinfo->uid));
3644  	if (!gid_eq(sbinfo->gid, GLOBAL_ROOT_GID))
3645  		seq_printf(seq, ",gid=%u",
3646  				from_kgid_munged(&init_user_ns, sbinfo->gid));
3647  
3648  	/*
3649  	 * Showing inode{64,32} might be useful even if it's the system default,
3650  	 * since then people don't have to resort to checking both here and
3651  	 * /proc/config.gz to confirm 64-bit inums were successfully applied
3652  	 * (which may not even exist if IKCONFIG_PROC isn't enabled).
3653  	 *
3654  	 * We hide it when inode64 isn't the default and we are using 32-bit
3655  	 * inodes, since that probably just means the feature isn't even under
3656  	 * consideration.
3657  	 *
3658  	 * As such:
3659  	 *
3660  	 *                     +-----------------+-----------------+
3661  	 *                     | TMPFS_INODE64=y | TMPFS_INODE64=n |
3662  	 *  +------------------+-----------------+-----------------+
3663  	 *  | full_inums=true  | show            | show            |
3664  	 *  | full_inums=false | show            | hide            |
3665  	 *  +------------------+-----------------+-----------------+
3666  	 *
3667  	 */
3668  	if (IS_ENABLED(CONFIG_TMPFS_INODE64) || sbinfo->full_inums)
3669  		seq_printf(seq, ",inode%d", (sbinfo->full_inums ? 64 : 32));
3670  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
3671  	/* Rightly or wrongly, show huge mount option unmasked by shmem_huge */
3672  	if (sbinfo->huge)
3673  		seq_printf(seq, ",huge=%s", shmem_format_huge(sbinfo->huge));
3674  #endif
3675  	shmem_show_mpol(seq, sbinfo->mpol);
3676  	return 0;
3677  }
3678  
3679  #endif /* CONFIG_TMPFS */
3680  
3681  static void shmem_put_super(struct super_block *sb)
3682  {
3683  	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
3684  
3685  	free_percpu(sbinfo->ino_batch);
3686  	percpu_counter_destroy(&sbinfo->used_blocks);
3687  	mpol_put(sbinfo->mpol);
3688  	kfree(sbinfo);
3689  	sb->s_fs_info = NULL;
3690  }
3691  
3692  static int shmem_fill_super(struct super_block *sb, struct fs_context *fc)
3693  {
3694  	struct shmem_options *ctx = fc->fs_private;
3695  	struct inode *inode;
3696  	struct shmem_sb_info *sbinfo;
3697  
3698  	/* Round up to L1_CACHE_BYTES to resist false sharing */
3699  	sbinfo = kzalloc(max((int)sizeof(struct shmem_sb_info),
3700  				L1_CACHE_BYTES), GFP_KERNEL);
3701  	if (!sbinfo)
3702  		return -ENOMEM;
3703  
3704  	sb->s_fs_info = sbinfo;
3705  
3706  #ifdef CONFIG_TMPFS
3707  	/*
3708  	 * Per default we only allow half of the physical ram per
3709  	 * tmpfs instance, limiting inodes to one per page of lowmem;
3710  	 * but the internal instance is left unlimited.
3711  	 */
3712  	if (!(sb->s_flags & SB_KERNMOUNT)) {
3713  		if (!(ctx->seen & SHMEM_SEEN_BLOCKS))
3714  			ctx->blocks = shmem_default_max_blocks();
3715  		if (!(ctx->seen & SHMEM_SEEN_INODES))
3716  			ctx->inodes = shmem_default_max_inodes();
3717  		if (!(ctx->seen & SHMEM_SEEN_INUMS))
3718  			ctx->full_inums = IS_ENABLED(CONFIG_TMPFS_INODE64);
3719  	} else {
3720  		sb->s_flags |= SB_NOUSER;
3721  	}
3722  	sb->s_export_op = &shmem_export_ops;
3723  	sb->s_flags |= SB_NOSEC;
3724  #else
3725  	sb->s_flags |= SB_NOUSER;
3726  #endif
3727  	sbinfo->max_blocks = ctx->blocks;
3728  	sbinfo->free_inodes = sbinfo->max_inodes = ctx->inodes;
3729  	if (sb->s_flags & SB_KERNMOUNT) {
3730  		sbinfo->ino_batch = alloc_percpu(ino_t);
3731  		if (!sbinfo->ino_batch)
3732  			goto failed;
3733  	}
3734  	sbinfo->uid = ctx->uid;
3735  	sbinfo->gid = ctx->gid;
3736  	sbinfo->full_inums = ctx->full_inums;
3737  	sbinfo->mode = ctx->mode;
3738  	sbinfo->huge = ctx->huge;
3739  	sbinfo->mpol = ctx->mpol;
3740  	ctx->mpol = NULL;
3741  
3742  	raw_spin_lock_init(&sbinfo->stat_lock);
3743  	if (percpu_counter_init(&sbinfo->used_blocks, 0, GFP_KERNEL))
3744  		goto failed;
3745  	spin_lock_init(&sbinfo->shrinklist_lock);
3746  	INIT_LIST_HEAD(&sbinfo->shrinklist);
3747  
3748  	sb->s_maxbytes = MAX_LFS_FILESIZE;
3749  	sb->s_blocksize = PAGE_SIZE;
3750  	sb->s_blocksize_bits = PAGE_SHIFT;
3751  	sb->s_magic = TMPFS_MAGIC;
3752  	sb->s_op = &shmem_ops;
3753  	sb->s_time_gran = 1;
3754  #ifdef CONFIG_TMPFS_XATTR
3755  	sb->s_xattr = shmem_xattr_handlers;
3756  #endif
3757  #ifdef CONFIG_TMPFS_POSIX_ACL
3758  	sb->s_flags |= SB_POSIXACL;
3759  #endif
3760  	uuid_gen(&sb->s_uuid);
3761  
3762  	inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
3763  	if (!inode)
3764  		goto failed;
3765  	inode->i_uid = sbinfo->uid;
3766  	inode->i_gid = sbinfo->gid;
3767  	sb->s_root = d_make_root(inode);
3768  	if (!sb->s_root)
3769  		goto failed;
3770  	return 0;
3771  
3772  failed:
3773  	shmem_put_super(sb);
3774  	return -ENOMEM;
3775  }
3776  
3777  static int shmem_get_tree(struct fs_context *fc)
3778  {
3779  	return get_tree_nodev(fc, shmem_fill_super);
3780  }
3781  
3782  static void shmem_free_fc(struct fs_context *fc)
3783  {
3784  	struct shmem_options *ctx = fc->fs_private;
3785  
3786  	if (ctx) {
3787  		mpol_put(ctx->mpol);
3788  		kfree(ctx);
3789  	}
3790  }
3791  
3792  static const struct fs_context_operations shmem_fs_context_ops = {
3793  	.free			= shmem_free_fc,
3794  	.get_tree		= shmem_get_tree,
3795  #ifdef CONFIG_TMPFS
3796  	.parse_monolithic	= shmem_parse_options,
3797  	.parse_param		= shmem_parse_one,
3798  	.reconfigure		= shmem_reconfigure,
3799  #endif
3800  };
3801  
3802  static struct kmem_cache *shmem_inode_cachep;
3803  
3804  static struct inode *shmem_alloc_inode(struct super_block *sb)
3805  {
3806  	struct shmem_inode_info *info;
3807  	info = alloc_inode_sb(sb, shmem_inode_cachep, GFP_KERNEL);
3808  	if (!info)
3809  		return NULL;
3810  	return &info->vfs_inode;
3811  }
3812  
3813  static void shmem_free_in_core_inode(struct inode *inode)
3814  {
3815  	if (S_ISLNK(inode->i_mode))
3816  		kfree(inode->i_link);
3817  	kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
3818  }
3819  
3820  static void shmem_destroy_inode(struct inode *inode)
3821  {
3822  	if (S_ISREG(inode->i_mode))
3823  		mpol_free_shared_policy(&SHMEM_I(inode)->policy);
3824  }
3825  
3826  static void shmem_init_inode(void *foo)
3827  {
3828  	struct shmem_inode_info *info = foo;
3829  	inode_init_once(&info->vfs_inode);
3830  }
3831  
3832  static void shmem_init_inodecache(void)
3833  {
3834  	shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
3835  				sizeof(struct shmem_inode_info),
3836  				0, SLAB_PANIC|SLAB_ACCOUNT, shmem_init_inode);
3837  }
3838  
3839  static void shmem_destroy_inodecache(void)
3840  {
3841  	kmem_cache_destroy(shmem_inode_cachep);
3842  }
3843  
3844  /* Keep the page in page cache instead of truncating it */
3845  static int shmem_error_remove_page(struct address_space *mapping,
3846  				   struct page *page)
3847  {
3848  	return 0;
3849  }
3850  
3851  const struct address_space_operations shmem_aops = {
3852  	.writepage	= shmem_writepage,
3853  	.dirty_folio	= noop_dirty_folio,
3854  #ifdef CONFIG_TMPFS
3855  	.write_begin	= shmem_write_begin,
3856  	.write_end	= shmem_write_end,
3857  #endif
3858  #ifdef CONFIG_MIGRATION
3859  	.migrate_folio	= migrate_folio,
3860  #endif
3861  	.error_remove_page = shmem_error_remove_page,
3862  };
3863  EXPORT_SYMBOL(shmem_aops);
3864  
3865  static const struct file_operations shmem_file_operations = {
3866  	.mmap		= shmem_mmap,
3867  	.get_unmapped_area = shmem_get_unmapped_area,
3868  #ifdef CONFIG_TMPFS
3869  	.llseek		= shmem_file_llseek,
3870  	.read_iter	= shmem_file_read_iter,
3871  	.write_iter	= generic_file_write_iter,
3872  	.fsync		= noop_fsync,
3873  	.splice_read	= generic_file_splice_read,
3874  	.splice_write	= iter_file_splice_write,
3875  	.fallocate	= shmem_fallocate,
3876  #endif
3877  };
3878  
3879  static const struct inode_operations shmem_inode_operations = {
3880  	.getattr	= shmem_getattr,
3881  	.setattr	= shmem_setattr,
3882  #ifdef CONFIG_TMPFS_XATTR
3883  	.listxattr	= shmem_listxattr,
3884  	.set_acl	= simple_set_acl,
3885  	.fileattr_get	= shmem_fileattr_get,
3886  	.fileattr_set	= shmem_fileattr_set,
3887  #endif
3888  };
3889  
3890  static const struct inode_operations shmem_dir_inode_operations = {
3891  #ifdef CONFIG_TMPFS
3892  	.getattr	= shmem_getattr,
3893  	.create		= shmem_create,
3894  	.lookup		= simple_lookup,
3895  	.link		= shmem_link,
3896  	.unlink		= shmem_unlink,
3897  	.symlink	= shmem_symlink,
3898  	.mkdir		= shmem_mkdir,
3899  	.rmdir		= shmem_rmdir,
3900  	.mknod		= shmem_mknod,
3901  	.rename		= shmem_rename2,
3902  	.tmpfile	= shmem_tmpfile,
3903  #endif
3904  #ifdef CONFIG_TMPFS_XATTR
3905  	.listxattr	= shmem_listxattr,
3906  	.fileattr_get	= shmem_fileattr_get,
3907  	.fileattr_set	= shmem_fileattr_set,
3908  #endif
3909  #ifdef CONFIG_TMPFS_POSIX_ACL
3910  	.setattr	= shmem_setattr,
3911  	.set_acl	= simple_set_acl,
3912  #endif
3913  };
3914  
3915  static const struct inode_operations shmem_special_inode_operations = {
3916  	.getattr	= shmem_getattr,
3917  #ifdef CONFIG_TMPFS_XATTR
3918  	.listxattr	= shmem_listxattr,
3919  #endif
3920  #ifdef CONFIG_TMPFS_POSIX_ACL
3921  	.setattr	= shmem_setattr,
3922  	.set_acl	= simple_set_acl,
3923  #endif
3924  };
3925  
3926  static const struct super_operations shmem_ops = {
3927  	.alloc_inode	= shmem_alloc_inode,
3928  	.free_inode	= shmem_free_in_core_inode,
3929  	.destroy_inode	= shmem_destroy_inode,
3930  #ifdef CONFIG_TMPFS
3931  	.statfs		= shmem_statfs,
3932  	.show_options	= shmem_show_options,
3933  #endif
3934  	.evict_inode	= shmem_evict_inode,
3935  	.drop_inode	= generic_delete_inode,
3936  	.put_super	= shmem_put_super,
3937  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
3938  	.nr_cached_objects	= shmem_unused_huge_count,
3939  	.free_cached_objects	= shmem_unused_huge_scan,
3940  #endif
3941  };
3942  
3943  static const struct vm_operations_struct shmem_vm_ops = {
3944  	.fault		= shmem_fault,
3945  	.map_pages	= filemap_map_pages,
3946  #ifdef CONFIG_NUMA
3947  	.set_policy     = shmem_set_policy,
3948  	.get_policy     = shmem_get_policy,
3949  #endif
3950  };
3951  
3952  int shmem_init_fs_context(struct fs_context *fc)
3953  {
3954  	struct shmem_options *ctx;
3955  
3956  	ctx = kzalloc(sizeof(struct shmem_options), GFP_KERNEL);
3957  	if (!ctx)
3958  		return -ENOMEM;
3959  
3960  	ctx->mode = 0777 | S_ISVTX;
3961  	ctx->uid = current_fsuid();
3962  	ctx->gid = current_fsgid();
3963  
3964  	fc->fs_private = ctx;
3965  	fc->ops = &shmem_fs_context_ops;
3966  	return 0;
3967  }
3968  
3969  static struct file_system_type shmem_fs_type = {
3970  	.owner		= THIS_MODULE,
3971  	.name		= "tmpfs",
3972  	.init_fs_context = shmem_init_fs_context,
3973  #ifdef CONFIG_TMPFS
3974  	.parameters	= shmem_fs_parameters,
3975  #endif
3976  	.kill_sb	= kill_litter_super,
3977  	.fs_flags	= FS_USERNS_MOUNT,
3978  };
3979  
3980  void __init shmem_init(void)
3981  {
3982  	int error;
3983  
3984  	shmem_init_inodecache();
3985  
3986  	error = register_filesystem(&shmem_fs_type);
3987  	if (error) {
3988  		pr_err("Could not register tmpfs\n");
3989  		goto out2;
3990  	}
3991  
3992  	shm_mnt = kern_mount(&shmem_fs_type);
3993  	if (IS_ERR(shm_mnt)) {
3994  		error = PTR_ERR(shm_mnt);
3995  		pr_err("Could not kern_mount tmpfs\n");
3996  		goto out1;
3997  	}
3998  
3999  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
4000  	if (has_transparent_hugepage() && shmem_huge > SHMEM_HUGE_DENY)
4001  		SHMEM_SB(shm_mnt->mnt_sb)->huge = shmem_huge;
4002  	else
4003  		shmem_huge = SHMEM_HUGE_NEVER; /* just in case it was patched */
4004  #endif
4005  	return;
4006  
4007  out1:
4008  	unregister_filesystem(&shmem_fs_type);
4009  out2:
4010  	shmem_destroy_inodecache();
4011  	shm_mnt = ERR_PTR(error);
4012  }
4013  
4014  #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && defined(CONFIG_SYSFS)
4015  static ssize_t shmem_enabled_show(struct kobject *kobj,
4016  				  struct kobj_attribute *attr, char *buf)
4017  {
4018  	static const int values[] = {
4019  		SHMEM_HUGE_ALWAYS,
4020  		SHMEM_HUGE_WITHIN_SIZE,
4021  		SHMEM_HUGE_ADVISE,
4022  		SHMEM_HUGE_NEVER,
4023  		SHMEM_HUGE_DENY,
4024  		SHMEM_HUGE_FORCE,
4025  	};
4026  	int len = 0;
4027  	int i;
4028  
4029  	for (i = 0; i < ARRAY_SIZE(values); i++) {
4030  		len += sysfs_emit_at(buf, len,
4031  				     shmem_huge == values[i] ? "%s[%s]" : "%s%s",
4032  				     i ? " " : "",
4033  				     shmem_format_huge(values[i]));
4034  	}
4035  
4036  	len += sysfs_emit_at(buf, len, "\n");
4037  
4038  	return len;
4039  }
4040  
4041  static ssize_t shmem_enabled_store(struct kobject *kobj,
4042  		struct kobj_attribute *attr, const char *buf, size_t count)
4043  {
4044  	char tmp[16];
4045  	int huge;
4046  
4047  	if (count + 1 > sizeof(tmp))
4048  		return -EINVAL;
4049  	memcpy(tmp, buf, count);
4050  	tmp[count] = '\0';
4051  	if (count && tmp[count - 1] == '\n')
4052  		tmp[count - 1] = '\0';
4053  
4054  	huge = shmem_parse_huge(tmp);
4055  	if (huge == -EINVAL)
4056  		return -EINVAL;
4057  	if (!has_transparent_hugepage() &&
4058  			huge != SHMEM_HUGE_NEVER && huge != SHMEM_HUGE_DENY)
4059  		return -EINVAL;
4060  
4061  	shmem_huge = huge;
4062  	if (shmem_huge > SHMEM_HUGE_DENY)
4063  		SHMEM_SB(shm_mnt->mnt_sb)->huge = shmem_huge;
4064  	return count;
4065  }
4066  
4067  struct kobj_attribute shmem_enabled_attr = __ATTR_RW(shmem_enabled);
4068  #endif /* CONFIG_TRANSPARENT_HUGEPAGE && CONFIG_SYSFS */
4069  
4070  #else /* !CONFIG_SHMEM */
4071  
4072  /*
4073   * tiny-shmem: simple shmemfs and tmpfs using ramfs code
4074   *
4075   * This is intended for small system where the benefits of the full
4076   * shmem code (swap-backed and resource-limited) are outweighed by
4077   * their complexity. On systems without swap this code should be
4078   * effectively equivalent, but much lighter weight.
4079   */
4080  
4081  static struct file_system_type shmem_fs_type = {
4082  	.name		= "tmpfs",
4083  	.init_fs_context = ramfs_init_fs_context,
4084  	.parameters	= ramfs_fs_parameters,
4085  	.kill_sb	= kill_litter_super,
4086  	.fs_flags	= FS_USERNS_MOUNT,
4087  };
4088  
4089  void __init shmem_init(void)
4090  {
4091  	BUG_ON(register_filesystem(&shmem_fs_type) != 0);
4092  
4093  	shm_mnt = kern_mount(&shmem_fs_type);
4094  	BUG_ON(IS_ERR(shm_mnt));
4095  }
4096  
4097  int shmem_unuse(unsigned int type)
4098  {
4099  	return 0;
4100  }
4101  
4102  int shmem_lock(struct file *file, int lock, struct ucounts *ucounts)
4103  {
4104  	return 0;
4105  }
4106  
4107  void shmem_unlock_mapping(struct address_space *mapping)
4108  {
4109  }
4110  
4111  #ifdef CONFIG_MMU
4112  unsigned long shmem_get_unmapped_area(struct file *file,
4113  				      unsigned long addr, unsigned long len,
4114  				      unsigned long pgoff, unsigned long flags)
4115  {
4116  	return current->mm->get_unmapped_area(file, addr, len, pgoff, flags);
4117  }
4118  #endif
4119  
4120  void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
4121  {
4122  	truncate_inode_pages_range(inode->i_mapping, lstart, lend);
4123  }
4124  EXPORT_SYMBOL_GPL(shmem_truncate_range);
4125  
4126  #define shmem_vm_ops				generic_file_vm_ops
4127  #define shmem_file_operations			ramfs_file_operations
4128  #define shmem_get_inode(sb, dir, mode, dev, flags)	ramfs_get_inode(sb, dir, mode, dev)
4129  #define shmem_acct_size(flags, size)		0
4130  #define shmem_unacct_size(flags, size)		do {} while (0)
4131  
4132  #endif /* CONFIG_SHMEM */
4133  
4134  /* common code */
4135  
4136  static struct file *__shmem_file_setup(struct vfsmount *mnt, const char *name, loff_t size,
4137  				       unsigned long flags, unsigned int i_flags)
4138  {
4139  	struct inode *inode;
4140  	struct file *res;
4141  
4142  	if (IS_ERR(mnt))
4143  		return ERR_CAST(mnt);
4144  
4145  	if (size < 0 || size > MAX_LFS_FILESIZE)
4146  		return ERR_PTR(-EINVAL);
4147  
4148  	if (shmem_acct_size(flags, size))
4149  		return ERR_PTR(-ENOMEM);
4150  
4151  	inode = shmem_get_inode(mnt->mnt_sb, NULL, S_IFREG | S_IRWXUGO, 0,
4152  				flags);
4153  	if (unlikely(!inode)) {
4154  		shmem_unacct_size(flags, size);
4155  		return ERR_PTR(-ENOSPC);
4156  	}
4157  	inode->i_flags |= i_flags;
4158  	inode->i_size = size;
4159  	clear_nlink(inode);	/* It is unlinked */
4160  	res = ERR_PTR(ramfs_nommu_expand_for_mapping(inode, size));
4161  	if (!IS_ERR(res))
4162  		res = alloc_file_pseudo(inode, mnt, name, O_RDWR,
4163  				&shmem_file_operations);
4164  	if (IS_ERR(res))
4165  		iput(inode);
4166  	return res;
4167  }
4168  
4169  /**
4170   * shmem_kernel_file_setup - get an unlinked file living in tmpfs which must be
4171   * 	kernel internal.  There will be NO LSM permission checks against the
4172   * 	underlying inode.  So users of this interface must do LSM checks at a
4173   *	higher layer.  The users are the big_key and shm implementations.  LSM
4174   *	checks are provided at the key or shm level rather than the inode.
4175   * @name: name for dentry (to be seen in /proc/<pid>/maps
4176   * @size: size to be set for the file
4177   * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
4178   */
4179  struct file *shmem_kernel_file_setup(const char *name, loff_t size, unsigned long flags)
4180  {
4181  	return __shmem_file_setup(shm_mnt, name, size, flags, S_PRIVATE);
4182  }
4183  
4184  /**
4185   * shmem_file_setup - get an unlinked file living in tmpfs
4186   * @name: name for dentry (to be seen in /proc/<pid>/maps
4187   * @size: size to be set for the file
4188   * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
4189   */
4190  struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags)
4191  {
4192  	return __shmem_file_setup(shm_mnt, name, size, flags, 0);
4193  }
4194  EXPORT_SYMBOL_GPL(shmem_file_setup);
4195  
4196  /**
4197   * shmem_file_setup_with_mnt - get an unlinked file living in tmpfs
4198   * @mnt: the tmpfs mount where the file will be created
4199   * @name: name for dentry (to be seen in /proc/<pid>/maps
4200   * @size: size to be set for the file
4201   * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
4202   */
4203  struct file *shmem_file_setup_with_mnt(struct vfsmount *mnt, const char *name,
4204  				       loff_t size, unsigned long flags)
4205  {
4206  	return __shmem_file_setup(mnt, name, size, flags, 0);
4207  }
4208  EXPORT_SYMBOL_GPL(shmem_file_setup_with_mnt);
4209  
4210  /**
4211   * shmem_zero_setup - setup a shared anonymous mapping
4212   * @vma: the vma to be mmapped is prepared by do_mmap
4213   */
4214  int shmem_zero_setup(struct vm_area_struct *vma)
4215  {
4216  	struct file *file;
4217  	loff_t size = vma->vm_end - vma->vm_start;
4218  
4219  	/*
4220  	 * Cloning a new file under mmap_lock leads to a lock ordering conflict
4221  	 * between XFS directory reading and selinux: since this file is only
4222  	 * accessible to the user through its mapping, use S_PRIVATE flag to
4223  	 * bypass file security, in the same way as shmem_kernel_file_setup().
4224  	 */
4225  	file = shmem_kernel_file_setup("dev/zero", size, vma->vm_flags);
4226  	if (IS_ERR(file))
4227  		return PTR_ERR(file);
4228  
4229  	if (vma->vm_file)
4230  		fput(vma->vm_file);
4231  	vma->vm_file = file;
4232  	vma->vm_ops = &shmem_vm_ops;
4233  
4234  	return 0;
4235  }
4236  
4237  /**
4238   * shmem_read_mapping_page_gfp - read into page cache, using specified page allocation flags.
4239   * @mapping:	the page's address_space
4240   * @index:	the page index
4241   * @gfp:	the page allocator flags to use if allocating
4242   *
4243   * This behaves as a tmpfs "read_cache_page_gfp(mapping, index, gfp)",
4244   * with any new page allocations done using the specified allocation flags.
4245   * But read_cache_page_gfp() uses the ->read_folio() method: which does not
4246   * suit tmpfs, since it may have pages in swapcache, and needs to find those
4247   * for itself; although drivers/gpu/drm i915 and ttm rely upon this support.
4248   *
4249   * i915_gem_object_get_pages_gtt() mixes __GFP_NORETRY | __GFP_NOWARN in
4250   * with the mapping_gfp_mask(), to avoid OOMing the machine unnecessarily.
4251   */
4252  struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
4253  					 pgoff_t index, gfp_t gfp)
4254  {
4255  #ifdef CONFIG_SHMEM
4256  	struct inode *inode = mapping->host;
4257  	struct page *page;
4258  	int error;
4259  
4260  	BUG_ON(!shmem_mapping(mapping));
4261  	error = shmem_getpage_gfp(inode, index, &page, SGP_CACHE,
4262  				  gfp, NULL, NULL, NULL);
4263  	if (error)
4264  		return ERR_PTR(error);
4265  
4266  	unlock_page(page);
4267  	if (PageHWPoison(page)) {
4268  		put_page(page);
4269  		return ERR_PTR(-EIO);
4270  	}
4271  
4272  	return page;
4273  #else
4274  	/*
4275  	 * The tiny !SHMEM case uses ramfs without swap
4276  	 */
4277  	return read_cache_page_gfp(mapping, index, gfp);
4278  #endif
4279  }
4280  EXPORT_SYMBOL_GPL(shmem_read_mapping_page_gfp);
4281