xref: /openbmc/linux/mm/shmem.c (revision 9e255e2b)
1  /*
2   * Resizable virtual memory filesystem for Linux.
3   *
4   * Copyright (C) 2000 Linus Torvalds.
5   *		 2000 Transmeta Corp.
6   *		 2000-2001 Christoph Rohland
7   *		 2000-2001 SAP AG
8   *		 2002 Red Hat Inc.
9   * Copyright (C) 2002-2011 Hugh Dickins.
10   * Copyright (C) 2011 Google Inc.
11   * Copyright (C) 2002-2005 VERITAS Software Corporation.
12   * Copyright (C) 2004 Andi Kleen, SuSE Labs
13   *
14   * Extended attribute support for tmpfs:
15   * Copyright (c) 2004, Luke Kenneth Casson Leighton <lkcl@lkcl.net>
16   * Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
17   *
18   * tiny-shmem:
19   * Copyright (c) 2004, 2008 Matt Mackall <mpm@selenic.com>
20   *
21   * This file is released under the GPL.
22   */
23  
24  #include <linux/fs.h>
25  #include <linux/init.h>
26  #include <linux/vfs.h>
27  #include <linux/mount.h>
28  #include <linux/ramfs.h>
29  #include <linux/pagemap.h>
30  #include <linux/file.h>
31  #include <linux/mm.h>
32  #include <linux/random.h>
33  #include <linux/sched/signal.h>
34  #include <linux/export.h>
35  #include <linux/swap.h>
36  #include <linux/uio.h>
37  #include <linux/khugepaged.h>
38  #include <linux/hugetlb.h>
39  #include <linux/frontswap.h>
40  #include <linux/fs_parser.h>
41  
42  #include <asm/tlbflush.h> /* for arch/microblaze update_mmu_cache() */
43  
44  static struct vfsmount *shm_mnt;
45  
46  #ifdef CONFIG_SHMEM
47  /*
48   * This virtual memory filesystem is heavily based on the ramfs. It
49   * extends ramfs by the ability to use swap and honor resource limits
50   * which makes it a completely usable filesystem.
51   */
52  
53  #include <linux/xattr.h>
54  #include <linux/exportfs.h>
55  #include <linux/posix_acl.h>
56  #include <linux/posix_acl_xattr.h>
57  #include <linux/mman.h>
58  #include <linux/string.h>
59  #include <linux/slab.h>
60  #include <linux/backing-dev.h>
61  #include <linux/shmem_fs.h>
62  #include <linux/writeback.h>
63  #include <linux/blkdev.h>
64  #include <linux/pagevec.h>
65  #include <linux/percpu_counter.h>
66  #include <linux/falloc.h>
67  #include <linux/splice.h>
68  #include <linux/security.h>
69  #include <linux/swapops.h>
70  #include <linux/mempolicy.h>
71  #include <linux/namei.h>
72  #include <linux/ctype.h>
73  #include <linux/migrate.h>
74  #include <linux/highmem.h>
75  #include <linux/seq_file.h>
76  #include <linux/magic.h>
77  #include <linux/syscalls.h>
78  #include <linux/fcntl.h>
79  #include <uapi/linux/memfd.h>
80  #include <linux/userfaultfd_k.h>
81  #include <linux/rmap.h>
82  #include <linux/uuid.h>
83  
84  #include <linux/uaccess.h>
85  
86  #include "internal.h"
87  
88  #define BLOCKS_PER_PAGE  (PAGE_SIZE/512)
89  #define VM_ACCT(size)    (PAGE_ALIGN(size) >> PAGE_SHIFT)
90  
91  /* Pretend that each entry is of this size in directory's i_size */
92  #define BOGO_DIRENT_SIZE 20
93  
94  /* Symlink up to this size is kmalloc'ed instead of using a swappable page */
95  #define SHORT_SYMLINK_LEN 128
96  
97  /*
98   * shmem_fallocate communicates with shmem_fault or shmem_writepage via
99   * inode->i_private (with i_mutex making sure that it has only one user at
100   * a time): we would prefer not to enlarge the shmem inode just for that.
101   */
102  struct shmem_falloc {
103  	wait_queue_head_t *waitq; /* faults into hole wait for punch to end */
104  	pgoff_t start;		/* start of range currently being fallocated */
105  	pgoff_t next;		/* the next page offset to be fallocated */
106  	pgoff_t nr_falloced;	/* how many new pages have been fallocated */
107  	pgoff_t nr_unswapped;	/* how often writepage refused to swap out */
108  };
109  
110  struct shmem_options {
111  	unsigned long long blocks;
112  	unsigned long long inodes;
113  	struct mempolicy *mpol;
114  	kuid_t uid;
115  	kgid_t gid;
116  	umode_t mode;
117  	bool full_inums;
118  	int huge;
119  	int seen;
120  #define SHMEM_SEEN_BLOCKS 1
121  #define SHMEM_SEEN_INODES 2
122  #define SHMEM_SEEN_HUGE 4
123  #define SHMEM_SEEN_INUMS 8
124  };
125  
126  #ifdef CONFIG_TMPFS
127  static unsigned long shmem_default_max_blocks(void)
128  {
129  	return totalram_pages() / 2;
130  }
131  
132  static unsigned long shmem_default_max_inodes(void)
133  {
134  	unsigned long nr_pages = totalram_pages();
135  
136  	return min(nr_pages - totalhigh_pages(), nr_pages / 2);
137  }
138  #endif
139  
140  static bool shmem_should_replace_page(struct page *page, gfp_t gfp);
141  static int shmem_replace_page(struct page **pagep, gfp_t gfp,
142  				struct shmem_inode_info *info, pgoff_t index);
143  static int shmem_swapin_page(struct inode *inode, pgoff_t index,
144  			     struct page **pagep, enum sgp_type sgp,
145  			     gfp_t gfp, struct vm_area_struct *vma,
146  			     vm_fault_t *fault_type);
147  static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
148  		struct page **pagep, enum sgp_type sgp,
149  		gfp_t gfp, struct vm_area_struct *vma,
150  		struct vm_fault *vmf, vm_fault_t *fault_type);
151  
152  int shmem_getpage(struct inode *inode, pgoff_t index,
153  		struct page **pagep, enum sgp_type sgp)
154  {
155  	return shmem_getpage_gfp(inode, index, pagep, sgp,
156  		mapping_gfp_mask(inode->i_mapping), NULL, NULL, NULL);
157  }
158  
159  static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
160  {
161  	return sb->s_fs_info;
162  }
163  
164  /*
165   * shmem_file_setup pre-accounts the whole fixed size of a VM object,
166   * for shared memory and for shared anonymous (/dev/zero) mappings
167   * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
168   * consistent with the pre-accounting of private mappings ...
169   */
170  static inline int shmem_acct_size(unsigned long flags, loff_t size)
171  {
172  	return (flags & VM_NORESERVE) ?
173  		0 : security_vm_enough_memory_mm(current->mm, VM_ACCT(size));
174  }
175  
176  static inline void shmem_unacct_size(unsigned long flags, loff_t size)
177  {
178  	if (!(flags & VM_NORESERVE))
179  		vm_unacct_memory(VM_ACCT(size));
180  }
181  
182  static inline int shmem_reacct_size(unsigned long flags,
183  		loff_t oldsize, loff_t newsize)
184  {
185  	if (!(flags & VM_NORESERVE)) {
186  		if (VM_ACCT(newsize) > VM_ACCT(oldsize))
187  			return security_vm_enough_memory_mm(current->mm,
188  					VM_ACCT(newsize) - VM_ACCT(oldsize));
189  		else if (VM_ACCT(newsize) < VM_ACCT(oldsize))
190  			vm_unacct_memory(VM_ACCT(oldsize) - VM_ACCT(newsize));
191  	}
192  	return 0;
193  }
194  
195  /*
196   * ... whereas tmpfs objects are accounted incrementally as
197   * pages are allocated, in order to allow large sparse files.
198   * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
199   * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
200   */
201  static inline int shmem_acct_block(unsigned long flags, long pages)
202  {
203  	if (!(flags & VM_NORESERVE))
204  		return 0;
205  
206  	return security_vm_enough_memory_mm(current->mm,
207  			pages * VM_ACCT(PAGE_SIZE));
208  }
209  
210  static inline void shmem_unacct_blocks(unsigned long flags, long pages)
211  {
212  	if (flags & VM_NORESERVE)
213  		vm_unacct_memory(pages * VM_ACCT(PAGE_SIZE));
214  }
215  
216  static inline bool shmem_inode_acct_block(struct inode *inode, long pages)
217  {
218  	struct shmem_inode_info *info = SHMEM_I(inode);
219  	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
220  
221  	if (shmem_acct_block(info->flags, pages))
222  		return false;
223  
224  	if (sbinfo->max_blocks) {
225  		if (percpu_counter_compare(&sbinfo->used_blocks,
226  					   sbinfo->max_blocks - pages) > 0)
227  			goto unacct;
228  		percpu_counter_add(&sbinfo->used_blocks, pages);
229  	}
230  
231  	return true;
232  
233  unacct:
234  	shmem_unacct_blocks(info->flags, pages);
235  	return false;
236  }
237  
238  static inline void shmem_inode_unacct_blocks(struct inode *inode, long pages)
239  {
240  	struct shmem_inode_info *info = SHMEM_I(inode);
241  	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
242  
243  	if (sbinfo->max_blocks)
244  		percpu_counter_sub(&sbinfo->used_blocks, pages);
245  	shmem_unacct_blocks(info->flags, pages);
246  }
247  
248  static const struct super_operations shmem_ops;
249  const struct address_space_operations shmem_aops;
250  static const struct file_operations shmem_file_operations;
251  static const struct inode_operations shmem_inode_operations;
252  static const struct inode_operations shmem_dir_inode_operations;
253  static const struct inode_operations shmem_special_inode_operations;
254  static const struct vm_operations_struct shmem_vm_ops;
255  static struct file_system_type shmem_fs_type;
256  
257  bool vma_is_shmem(struct vm_area_struct *vma)
258  {
259  	return vma->vm_ops == &shmem_vm_ops;
260  }
261  
262  static LIST_HEAD(shmem_swaplist);
263  static DEFINE_MUTEX(shmem_swaplist_mutex);
264  
265  /*
266   * shmem_reserve_inode() performs bookkeeping to reserve a shmem inode, and
267   * produces a novel ino for the newly allocated inode.
268   *
269   * It may also be called when making a hard link to permit the space needed by
270   * each dentry. However, in that case, no new inode number is needed since that
271   * internally draws from another pool of inode numbers (currently global
272   * get_next_ino()). This case is indicated by passing NULL as inop.
273   */
274  #define SHMEM_INO_BATCH 1024
275  static int shmem_reserve_inode(struct super_block *sb, ino_t *inop)
276  {
277  	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
278  	ino_t ino;
279  
280  	if (!(sb->s_flags & SB_KERNMOUNT)) {
281  		spin_lock(&sbinfo->stat_lock);
282  		if (sbinfo->max_inodes) {
283  			if (!sbinfo->free_inodes) {
284  				spin_unlock(&sbinfo->stat_lock);
285  				return -ENOSPC;
286  			}
287  			sbinfo->free_inodes--;
288  		}
289  		if (inop) {
290  			ino = sbinfo->next_ino++;
291  			if (unlikely(is_zero_ino(ino)))
292  				ino = sbinfo->next_ino++;
293  			if (unlikely(!sbinfo->full_inums &&
294  				     ino > UINT_MAX)) {
295  				/*
296  				 * Emulate get_next_ino uint wraparound for
297  				 * compatibility
298  				 */
299  				if (IS_ENABLED(CONFIG_64BIT))
300  					pr_warn("%s: inode number overflow on device %d, consider using inode64 mount option\n",
301  						__func__, MINOR(sb->s_dev));
302  				sbinfo->next_ino = 1;
303  				ino = sbinfo->next_ino++;
304  			}
305  			*inop = ino;
306  		}
307  		spin_unlock(&sbinfo->stat_lock);
308  	} else if (inop) {
309  		/*
310  		 * __shmem_file_setup, one of our callers, is lock-free: it
311  		 * doesn't hold stat_lock in shmem_reserve_inode since
312  		 * max_inodes is always 0, and is called from potentially
313  		 * unknown contexts. As such, use a per-cpu batched allocator
314  		 * which doesn't require the per-sb stat_lock unless we are at
315  		 * the batch boundary.
316  		 *
317  		 * We don't need to worry about inode{32,64} since SB_KERNMOUNT
318  		 * shmem mounts are not exposed to userspace, so we don't need
319  		 * to worry about things like glibc compatibility.
320  		 */
321  		ino_t *next_ino;
322  		next_ino = per_cpu_ptr(sbinfo->ino_batch, get_cpu());
323  		ino = *next_ino;
324  		if (unlikely(ino % SHMEM_INO_BATCH == 0)) {
325  			spin_lock(&sbinfo->stat_lock);
326  			ino = sbinfo->next_ino;
327  			sbinfo->next_ino += SHMEM_INO_BATCH;
328  			spin_unlock(&sbinfo->stat_lock);
329  			if (unlikely(is_zero_ino(ino)))
330  				ino++;
331  		}
332  		*inop = ino;
333  		*next_ino = ++ino;
334  		put_cpu();
335  	}
336  
337  	return 0;
338  }
339  
340  static void shmem_free_inode(struct super_block *sb)
341  {
342  	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
343  	if (sbinfo->max_inodes) {
344  		spin_lock(&sbinfo->stat_lock);
345  		sbinfo->free_inodes++;
346  		spin_unlock(&sbinfo->stat_lock);
347  	}
348  }
349  
350  /**
351   * shmem_recalc_inode - recalculate the block usage of an inode
352   * @inode: inode to recalc
353   *
354   * We have to calculate the free blocks since the mm can drop
355   * undirtied hole pages behind our back.
356   *
357   * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
358   * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
359   *
360   * It has to be called with the spinlock held.
361   */
362  static void shmem_recalc_inode(struct inode *inode)
363  {
364  	struct shmem_inode_info *info = SHMEM_I(inode);
365  	long freed;
366  
367  	freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
368  	if (freed > 0) {
369  		info->alloced -= freed;
370  		inode->i_blocks -= freed * BLOCKS_PER_PAGE;
371  		shmem_inode_unacct_blocks(inode, freed);
372  	}
373  }
374  
375  bool shmem_charge(struct inode *inode, long pages)
376  {
377  	struct shmem_inode_info *info = SHMEM_I(inode);
378  	unsigned long flags;
379  
380  	if (!shmem_inode_acct_block(inode, pages))
381  		return false;
382  
383  	/* nrpages adjustment first, then shmem_recalc_inode() when balanced */
384  	inode->i_mapping->nrpages += pages;
385  
386  	spin_lock_irqsave(&info->lock, flags);
387  	info->alloced += pages;
388  	inode->i_blocks += pages * BLOCKS_PER_PAGE;
389  	shmem_recalc_inode(inode);
390  	spin_unlock_irqrestore(&info->lock, flags);
391  
392  	return true;
393  }
394  
395  void shmem_uncharge(struct inode *inode, long pages)
396  {
397  	struct shmem_inode_info *info = SHMEM_I(inode);
398  	unsigned long flags;
399  
400  	/* nrpages adjustment done by __delete_from_page_cache() or caller */
401  
402  	spin_lock_irqsave(&info->lock, flags);
403  	info->alloced -= pages;
404  	inode->i_blocks -= pages * BLOCKS_PER_PAGE;
405  	shmem_recalc_inode(inode);
406  	spin_unlock_irqrestore(&info->lock, flags);
407  
408  	shmem_inode_unacct_blocks(inode, pages);
409  }
410  
411  /*
412   * Replace item expected in xarray by a new item, while holding xa_lock.
413   */
414  static int shmem_replace_entry(struct address_space *mapping,
415  			pgoff_t index, void *expected, void *replacement)
416  {
417  	XA_STATE(xas, &mapping->i_pages, index);
418  	void *item;
419  
420  	VM_BUG_ON(!expected);
421  	VM_BUG_ON(!replacement);
422  	item = xas_load(&xas);
423  	if (item != expected)
424  		return -ENOENT;
425  	xas_store(&xas, replacement);
426  	return 0;
427  }
428  
429  /*
430   * Sometimes, before we decide whether to proceed or to fail, we must check
431   * that an entry was not already brought back from swap by a racing thread.
432   *
433   * Checking page is not enough: by the time a SwapCache page is locked, it
434   * might be reused, and again be SwapCache, using the same swap as before.
435   */
436  static bool shmem_confirm_swap(struct address_space *mapping,
437  			       pgoff_t index, swp_entry_t swap)
438  {
439  	return xa_load(&mapping->i_pages, index) == swp_to_radix_entry(swap);
440  }
441  
442  /*
443   * Definitions for "huge tmpfs": tmpfs mounted with the huge= option
444   *
445   * SHMEM_HUGE_NEVER:
446   *	disables huge pages for the mount;
447   * SHMEM_HUGE_ALWAYS:
448   *	enables huge pages for the mount;
449   * SHMEM_HUGE_WITHIN_SIZE:
450   *	only allocate huge pages if the page will be fully within i_size,
451   *	also respect fadvise()/madvise() hints;
452   * SHMEM_HUGE_ADVISE:
453   *	only allocate huge pages if requested with fadvise()/madvise();
454   */
455  
456  #define SHMEM_HUGE_NEVER	0
457  #define SHMEM_HUGE_ALWAYS	1
458  #define SHMEM_HUGE_WITHIN_SIZE	2
459  #define SHMEM_HUGE_ADVISE	3
460  
461  /*
462   * Special values.
463   * Only can be set via /sys/kernel/mm/transparent_hugepage/shmem_enabled:
464   *
465   * SHMEM_HUGE_DENY:
466   *	disables huge on shm_mnt and all mounts, for emergency use;
467   * SHMEM_HUGE_FORCE:
468   *	enables huge on shm_mnt and all mounts, w/o needing option, for testing;
469   *
470   */
471  #define SHMEM_HUGE_DENY		(-1)
472  #define SHMEM_HUGE_FORCE	(-2)
473  
474  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
475  /* ifdef here to avoid bloating shmem.o when not necessary */
476  
477  static int shmem_huge __read_mostly;
478  
479  #if defined(CONFIG_SYSFS)
480  static int shmem_parse_huge(const char *str)
481  {
482  	if (!strcmp(str, "never"))
483  		return SHMEM_HUGE_NEVER;
484  	if (!strcmp(str, "always"))
485  		return SHMEM_HUGE_ALWAYS;
486  	if (!strcmp(str, "within_size"))
487  		return SHMEM_HUGE_WITHIN_SIZE;
488  	if (!strcmp(str, "advise"))
489  		return SHMEM_HUGE_ADVISE;
490  	if (!strcmp(str, "deny"))
491  		return SHMEM_HUGE_DENY;
492  	if (!strcmp(str, "force"))
493  		return SHMEM_HUGE_FORCE;
494  	return -EINVAL;
495  }
496  #endif
497  
498  #if defined(CONFIG_SYSFS) || defined(CONFIG_TMPFS)
499  static const char *shmem_format_huge(int huge)
500  {
501  	switch (huge) {
502  	case SHMEM_HUGE_NEVER:
503  		return "never";
504  	case SHMEM_HUGE_ALWAYS:
505  		return "always";
506  	case SHMEM_HUGE_WITHIN_SIZE:
507  		return "within_size";
508  	case SHMEM_HUGE_ADVISE:
509  		return "advise";
510  	case SHMEM_HUGE_DENY:
511  		return "deny";
512  	case SHMEM_HUGE_FORCE:
513  		return "force";
514  	default:
515  		VM_BUG_ON(1);
516  		return "bad_val";
517  	}
518  }
519  #endif
520  
521  static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
522  		struct shrink_control *sc, unsigned long nr_to_split)
523  {
524  	LIST_HEAD(list), *pos, *next;
525  	LIST_HEAD(to_remove);
526  	struct inode *inode;
527  	struct shmem_inode_info *info;
528  	struct page *page;
529  	unsigned long batch = sc ? sc->nr_to_scan : 128;
530  	int removed = 0, split = 0;
531  
532  	if (list_empty(&sbinfo->shrinklist))
533  		return SHRINK_STOP;
534  
535  	spin_lock(&sbinfo->shrinklist_lock);
536  	list_for_each_safe(pos, next, &sbinfo->shrinklist) {
537  		info = list_entry(pos, struct shmem_inode_info, shrinklist);
538  
539  		/* pin the inode */
540  		inode = igrab(&info->vfs_inode);
541  
542  		/* inode is about to be evicted */
543  		if (!inode) {
544  			list_del_init(&info->shrinklist);
545  			removed++;
546  			goto next;
547  		}
548  
549  		/* Check if there's anything to gain */
550  		if (round_up(inode->i_size, PAGE_SIZE) ==
551  				round_up(inode->i_size, HPAGE_PMD_SIZE)) {
552  			list_move(&info->shrinklist, &to_remove);
553  			removed++;
554  			goto next;
555  		}
556  
557  		list_move(&info->shrinklist, &list);
558  next:
559  		if (!--batch)
560  			break;
561  	}
562  	spin_unlock(&sbinfo->shrinklist_lock);
563  
564  	list_for_each_safe(pos, next, &to_remove) {
565  		info = list_entry(pos, struct shmem_inode_info, shrinklist);
566  		inode = &info->vfs_inode;
567  		list_del_init(&info->shrinklist);
568  		iput(inode);
569  	}
570  
571  	list_for_each_safe(pos, next, &list) {
572  		int ret;
573  
574  		info = list_entry(pos, struct shmem_inode_info, shrinklist);
575  		inode = &info->vfs_inode;
576  
577  		if (nr_to_split && split >= nr_to_split)
578  			goto leave;
579  
580  		page = find_get_page(inode->i_mapping,
581  				(inode->i_size & HPAGE_PMD_MASK) >> PAGE_SHIFT);
582  		if (!page)
583  			goto drop;
584  
585  		/* No huge page at the end of the file: nothing to split */
586  		if (!PageTransHuge(page)) {
587  			put_page(page);
588  			goto drop;
589  		}
590  
591  		/*
592  		 * Leave the inode on the list if we failed to lock
593  		 * the page at this time.
594  		 *
595  		 * Waiting for the lock may lead to deadlock in the
596  		 * reclaim path.
597  		 */
598  		if (!trylock_page(page)) {
599  			put_page(page);
600  			goto leave;
601  		}
602  
603  		ret = split_huge_page(page);
604  		unlock_page(page);
605  		put_page(page);
606  
607  		/* If split failed leave the inode on the list */
608  		if (ret)
609  			goto leave;
610  
611  		split++;
612  drop:
613  		list_del_init(&info->shrinklist);
614  		removed++;
615  leave:
616  		iput(inode);
617  	}
618  
619  	spin_lock(&sbinfo->shrinklist_lock);
620  	list_splice_tail(&list, &sbinfo->shrinklist);
621  	sbinfo->shrinklist_len -= removed;
622  	spin_unlock(&sbinfo->shrinklist_lock);
623  
624  	return split;
625  }
626  
627  static long shmem_unused_huge_scan(struct super_block *sb,
628  		struct shrink_control *sc)
629  {
630  	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
631  
632  	if (!READ_ONCE(sbinfo->shrinklist_len))
633  		return SHRINK_STOP;
634  
635  	return shmem_unused_huge_shrink(sbinfo, sc, 0);
636  }
637  
638  static long shmem_unused_huge_count(struct super_block *sb,
639  		struct shrink_control *sc)
640  {
641  	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
642  	return READ_ONCE(sbinfo->shrinklist_len);
643  }
644  #else /* !CONFIG_TRANSPARENT_HUGEPAGE */
645  
646  #define shmem_huge SHMEM_HUGE_DENY
647  
648  static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
649  		struct shrink_control *sc, unsigned long nr_to_split)
650  {
651  	return 0;
652  }
653  #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
654  
655  static inline bool is_huge_enabled(struct shmem_sb_info *sbinfo)
656  {
657  	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
658  	    (shmem_huge == SHMEM_HUGE_FORCE || sbinfo->huge) &&
659  	    shmem_huge != SHMEM_HUGE_DENY)
660  		return true;
661  	return false;
662  }
663  
664  /*
665   * Like add_to_page_cache_locked, but error if expected item has gone.
666   */
667  static int shmem_add_to_page_cache(struct page *page,
668  				   struct address_space *mapping,
669  				   pgoff_t index, void *expected, gfp_t gfp,
670  				   struct mm_struct *charge_mm)
671  {
672  	XA_STATE_ORDER(xas, &mapping->i_pages, index, compound_order(page));
673  	unsigned long i = 0;
674  	unsigned long nr = compound_nr(page);
675  	int error;
676  
677  	VM_BUG_ON_PAGE(PageTail(page), page);
678  	VM_BUG_ON_PAGE(index != round_down(index, nr), page);
679  	VM_BUG_ON_PAGE(!PageLocked(page), page);
680  	VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
681  	VM_BUG_ON(expected && PageTransHuge(page));
682  
683  	page_ref_add(page, nr);
684  	page->mapping = mapping;
685  	page->index = index;
686  
687  	if (!PageSwapCache(page)) {
688  		error = mem_cgroup_charge(page, charge_mm, gfp);
689  		if (error) {
690  			if (PageTransHuge(page)) {
691  				count_vm_event(THP_FILE_FALLBACK);
692  				count_vm_event(THP_FILE_FALLBACK_CHARGE);
693  			}
694  			goto error;
695  		}
696  	}
697  	cgroup_throttle_swaprate(page, gfp);
698  
699  	do {
700  		void *entry;
701  		xas_lock_irq(&xas);
702  		entry = xas_find_conflict(&xas);
703  		if (entry != expected)
704  			xas_set_err(&xas, -EEXIST);
705  		xas_create_range(&xas);
706  		if (xas_error(&xas))
707  			goto unlock;
708  next:
709  		xas_store(&xas, page);
710  		if (++i < nr) {
711  			xas_next(&xas);
712  			goto next;
713  		}
714  		if (PageTransHuge(page)) {
715  			count_vm_event(THP_FILE_ALLOC);
716  			__mod_lruvec_page_state(page, NR_SHMEM_THPS, nr);
717  		}
718  		mapping->nrpages += nr;
719  		__mod_lruvec_page_state(page, NR_FILE_PAGES, nr);
720  		__mod_lruvec_page_state(page, NR_SHMEM, nr);
721  unlock:
722  		xas_unlock_irq(&xas);
723  	} while (xas_nomem(&xas, gfp));
724  
725  	if (xas_error(&xas)) {
726  		error = xas_error(&xas);
727  		goto error;
728  	}
729  
730  	return 0;
731  error:
732  	page->mapping = NULL;
733  	page_ref_sub(page, nr);
734  	return error;
735  }
736  
737  /*
738   * Like delete_from_page_cache, but substitutes swap for page.
739   */
740  static void shmem_delete_from_page_cache(struct page *page, void *radswap)
741  {
742  	struct address_space *mapping = page->mapping;
743  	int error;
744  
745  	VM_BUG_ON_PAGE(PageCompound(page), page);
746  
747  	xa_lock_irq(&mapping->i_pages);
748  	error = shmem_replace_entry(mapping, page->index, page, radswap);
749  	page->mapping = NULL;
750  	mapping->nrpages--;
751  	__dec_lruvec_page_state(page, NR_FILE_PAGES);
752  	__dec_lruvec_page_state(page, NR_SHMEM);
753  	xa_unlock_irq(&mapping->i_pages);
754  	put_page(page);
755  	BUG_ON(error);
756  }
757  
758  /*
759   * Remove swap entry from page cache, free the swap and its page cache.
760   */
761  static int shmem_free_swap(struct address_space *mapping,
762  			   pgoff_t index, void *radswap)
763  {
764  	void *old;
765  
766  	old = xa_cmpxchg_irq(&mapping->i_pages, index, radswap, NULL, 0);
767  	if (old != radswap)
768  		return -ENOENT;
769  	free_swap_and_cache(radix_to_swp_entry(radswap));
770  	return 0;
771  }
772  
773  /*
774   * Determine (in bytes) how many of the shmem object's pages mapped by the
775   * given offsets are swapped out.
776   *
777   * This is safe to call without i_mutex or the i_pages lock thanks to RCU,
778   * as long as the inode doesn't go away and racy results are not a problem.
779   */
780  unsigned long shmem_partial_swap_usage(struct address_space *mapping,
781  						pgoff_t start, pgoff_t end)
782  {
783  	XA_STATE(xas, &mapping->i_pages, start);
784  	struct page *page;
785  	unsigned long swapped = 0;
786  
787  	rcu_read_lock();
788  	xas_for_each(&xas, page, end - 1) {
789  		if (xas_retry(&xas, page))
790  			continue;
791  		if (xa_is_value(page))
792  			swapped++;
793  
794  		if (need_resched()) {
795  			xas_pause(&xas);
796  			cond_resched_rcu();
797  		}
798  	}
799  
800  	rcu_read_unlock();
801  
802  	return swapped << PAGE_SHIFT;
803  }
804  
805  /*
806   * Determine (in bytes) how many of the shmem object's pages mapped by the
807   * given vma is swapped out.
808   *
809   * This is safe to call without i_mutex or the i_pages lock thanks to RCU,
810   * as long as the inode doesn't go away and racy results are not a problem.
811   */
812  unsigned long shmem_swap_usage(struct vm_area_struct *vma)
813  {
814  	struct inode *inode = file_inode(vma->vm_file);
815  	struct shmem_inode_info *info = SHMEM_I(inode);
816  	struct address_space *mapping = inode->i_mapping;
817  	unsigned long swapped;
818  
819  	/* Be careful as we don't hold info->lock */
820  	swapped = READ_ONCE(info->swapped);
821  
822  	/*
823  	 * The easier cases are when the shmem object has nothing in swap, or
824  	 * the vma maps it whole. Then we can simply use the stats that we
825  	 * already track.
826  	 */
827  	if (!swapped)
828  		return 0;
829  
830  	if (!vma->vm_pgoff && vma->vm_end - vma->vm_start >= inode->i_size)
831  		return swapped << PAGE_SHIFT;
832  
833  	/* Here comes the more involved part */
834  	return shmem_partial_swap_usage(mapping,
835  			linear_page_index(vma, vma->vm_start),
836  			linear_page_index(vma, vma->vm_end));
837  }
838  
839  /*
840   * SysV IPC SHM_UNLOCK restore Unevictable pages to their evictable lists.
841   */
842  void shmem_unlock_mapping(struct address_space *mapping)
843  {
844  	struct pagevec pvec;
845  	pgoff_t index = 0;
846  
847  	pagevec_init(&pvec);
848  	/*
849  	 * Minor point, but we might as well stop if someone else SHM_LOCKs it.
850  	 */
851  	while (!mapping_unevictable(mapping)) {
852  		if (!pagevec_lookup(&pvec, mapping, &index))
853  			break;
854  		check_move_unevictable_pages(&pvec);
855  		pagevec_release(&pvec);
856  		cond_resched();
857  	}
858  }
859  
860  /*
861   * Check whether a hole-punch or truncation needs to split a huge page,
862   * returning true if no split was required, or the split has been successful.
863   *
864   * Eviction (or truncation to 0 size) should never need to split a huge page;
865   * but in rare cases might do so, if shmem_undo_range() failed to trylock on
866   * head, and then succeeded to trylock on tail.
867   *
868   * A split can only succeed when there are no additional references on the
869   * huge page: so the split below relies upon find_get_entries() having stopped
870   * when it found a subpage of the huge page, without getting further references.
871   */
872  static bool shmem_punch_compound(struct page *page, pgoff_t start, pgoff_t end)
873  {
874  	if (!PageTransCompound(page))
875  		return true;
876  
877  	/* Just proceed to delete a huge page wholly within the range punched */
878  	if (PageHead(page) &&
879  	    page->index >= start && page->index + HPAGE_PMD_NR <= end)
880  		return true;
881  
882  	/* Try to split huge page, so we can truly punch the hole or truncate */
883  	return split_huge_page(page) >= 0;
884  }
885  
886  /*
887   * Remove range of pages and swap entries from page cache, and free them.
888   * If !unfalloc, truncate or punch hole; if unfalloc, undo failed fallocate.
889   */
890  static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
891  								 bool unfalloc)
892  {
893  	struct address_space *mapping = inode->i_mapping;
894  	struct shmem_inode_info *info = SHMEM_I(inode);
895  	pgoff_t start = (lstart + PAGE_SIZE - 1) >> PAGE_SHIFT;
896  	pgoff_t end = (lend + 1) >> PAGE_SHIFT;
897  	unsigned int partial_start = lstart & (PAGE_SIZE - 1);
898  	unsigned int partial_end = (lend + 1) & (PAGE_SIZE - 1);
899  	struct pagevec pvec;
900  	pgoff_t indices[PAGEVEC_SIZE];
901  	long nr_swaps_freed = 0;
902  	pgoff_t index;
903  	int i;
904  
905  	if (lend == -1)
906  		end = -1;	/* unsigned, so actually very big */
907  
908  	pagevec_init(&pvec);
909  	index = start;
910  	while (index < end && find_lock_entries(mapping, index, end - 1,
911  			&pvec, indices)) {
912  		for (i = 0; i < pagevec_count(&pvec); i++) {
913  			struct page *page = pvec.pages[i];
914  
915  			index = indices[i];
916  
917  			if (xa_is_value(page)) {
918  				if (unfalloc)
919  					continue;
920  				nr_swaps_freed += !shmem_free_swap(mapping,
921  								index, page);
922  				continue;
923  			}
924  			index += thp_nr_pages(page) - 1;
925  
926  			if (!unfalloc || !PageUptodate(page))
927  				truncate_inode_page(mapping, page);
928  			unlock_page(page);
929  		}
930  		pagevec_remove_exceptionals(&pvec);
931  		pagevec_release(&pvec);
932  		cond_resched();
933  		index++;
934  	}
935  
936  	if (partial_start) {
937  		struct page *page = NULL;
938  		shmem_getpage(inode, start - 1, &page, SGP_READ);
939  		if (page) {
940  			unsigned int top = PAGE_SIZE;
941  			if (start > end) {
942  				top = partial_end;
943  				partial_end = 0;
944  			}
945  			zero_user_segment(page, partial_start, top);
946  			set_page_dirty(page);
947  			unlock_page(page);
948  			put_page(page);
949  		}
950  	}
951  	if (partial_end) {
952  		struct page *page = NULL;
953  		shmem_getpage(inode, end, &page, SGP_READ);
954  		if (page) {
955  			zero_user_segment(page, 0, partial_end);
956  			set_page_dirty(page);
957  			unlock_page(page);
958  			put_page(page);
959  		}
960  	}
961  	if (start >= end)
962  		return;
963  
964  	index = start;
965  	while (index < end) {
966  		cond_resched();
967  
968  		if (!find_get_entries(mapping, index, end - 1, &pvec,
969  				indices)) {
970  			/* If all gone or hole-punch or unfalloc, we're done */
971  			if (index == start || end != -1)
972  				break;
973  			/* But if truncating, restart to make sure all gone */
974  			index = start;
975  			continue;
976  		}
977  		for (i = 0; i < pagevec_count(&pvec); i++) {
978  			struct page *page = pvec.pages[i];
979  
980  			index = indices[i];
981  			if (xa_is_value(page)) {
982  				if (unfalloc)
983  					continue;
984  				if (shmem_free_swap(mapping, index, page)) {
985  					/* Swap was replaced by page: retry */
986  					index--;
987  					break;
988  				}
989  				nr_swaps_freed++;
990  				continue;
991  			}
992  
993  			lock_page(page);
994  
995  			if (!unfalloc || !PageUptodate(page)) {
996  				if (page_mapping(page) != mapping) {
997  					/* Page was replaced by swap: retry */
998  					unlock_page(page);
999  					index--;
1000  					break;
1001  				}
1002  				VM_BUG_ON_PAGE(PageWriteback(page), page);
1003  				if (shmem_punch_compound(page, start, end))
1004  					truncate_inode_page(mapping, page);
1005  				else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
1006  					/* Wipe the page and don't get stuck */
1007  					clear_highpage(page);
1008  					flush_dcache_page(page);
1009  					set_page_dirty(page);
1010  					if (index <
1011  					    round_up(start, HPAGE_PMD_NR))
1012  						start = index + 1;
1013  				}
1014  			}
1015  			unlock_page(page);
1016  		}
1017  		pagevec_remove_exceptionals(&pvec);
1018  		pagevec_release(&pvec);
1019  		index++;
1020  	}
1021  
1022  	spin_lock_irq(&info->lock);
1023  	info->swapped -= nr_swaps_freed;
1024  	shmem_recalc_inode(inode);
1025  	spin_unlock_irq(&info->lock);
1026  }
1027  
1028  void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
1029  {
1030  	shmem_undo_range(inode, lstart, lend, false);
1031  	inode->i_ctime = inode->i_mtime = current_time(inode);
1032  }
1033  EXPORT_SYMBOL_GPL(shmem_truncate_range);
1034  
1035  static int shmem_getattr(struct user_namespace *mnt_userns,
1036  			 const struct path *path, struct kstat *stat,
1037  			 u32 request_mask, unsigned int query_flags)
1038  {
1039  	struct inode *inode = path->dentry->d_inode;
1040  	struct shmem_inode_info *info = SHMEM_I(inode);
1041  	struct shmem_sb_info *sb_info = SHMEM_SB(inode->i_sb);
1042  
1043  	if (info->alloced - info->swapped != inode->i_mapping->nrpages) {
1044  		spin_lock_irq(&info->lock);
1045  		shmem_recalc_inode(inode);
1046  		spin_unlock_irq(&info->lock);
1047  	}
1048  	generic_fillattr(&init_user_ns, inode, stat);
1049  
1050  	if (is_huge_enabled(sb_info))
1051  		stat->blksize = HPAGE_PMD_SIZE;
1052  
1053  	return 0;
1054  }
1055  
1056  static int shmem_setattr(struct user_namespace *mnt_userns,
1057  			 struct dentry *dentry, struct iattr *attr)
1058  {
1059  	struct inode *inode = d_inode(dentry);
1060  	struct shmem_inode_info *info = SHMEM_I(inode);
1061  	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
1062  	int error;
1063  
1064  	error = setattr_prepare(&init_user_ns, dentry, attr);
1065  	if (error)
1066  		return error;
1067  
1068  	if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
1069  		loff_t oldsize = inode->i_size;
1070  		loff_t newsize = attr->ia_size;
1071  
1072  		/* protected by i_mutex */
1073  		if ((newsize < oldsize && (info->seals & F_SEAL_SHRINK)) ||
1074  		    (newsize > oldsize && (info->seals & F_SEAL_GROW)))
1075  			return -EPERM;
1076  
1077  		if (newsize != oldsize) {
1078  			error = shmem_reacct_size(SHMEM_I(inode)->flags,
1079  					oldsize, newsize);
1080  			if (error)
1081  				return error;
1082  			i_size_write(inode, newsize);
1083  			inode->i_ctime = inode->i_mtime = current_time(inode);
1084  		}
1085  		if (newsize <= oldsize) {
1086  			loff_t holebegin = round_up(newsize, PAGE_SIZE);
1087  			if (oldsize > holebegin)
1088  				unmap_mapping_range(inode->i_mapping,
1089  							holebegin, 0, 1);
1090  			if (info->alloced)
1091  				shmem_truncate_range(inode,
1092  							newsize, (loff_t)-1);
1093  			/* unmap again to remove racily COWed private pages */
1094  			if (oldsize > holebegin)
1095  				unmap_mapping_range(inode->i_mapping,
1096  							holebegin, 0, 1);
1097  
1098  			/*
1099  			 * Part of the huge page can be beyond i_size: subject
1100  			 * to shrink under memory pressure.
1101  			 */
1102  			if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
1103  				spin_lock(&sbinfo->shrinklist_lock);
1104  				/*
1105  				 * _careful to defend against unlocked access to
1106  				 * ->shrink_list in shmem_unused_huge_shrink()
1107  				 */
1108  				if (list_empty_careful(&info->shrinklist)) {
1109  					list_add_tail(&info->shrinklist,
1110  							&sbinfo->shrinklist);
1111  					sbinfo->shrinklist_len++;
1112  				}
1113  				spin_unlock(&sbinfo->shrinklist_lock);
1114  			}
1115  		}
1116  	}
1117  
1118  	setattr_copy(&init_user_ns, inode, attr);
1119  	if (attr->ia_valid & ATTR_MODE)
1120  		error = posix_acl_chmod(&init_user_ns, inode, inode->i_mode);
1121  	return error;
1122  }
1123  
1124  static void shmem_evict_inode(struct inode *inode)
1125  {
1126  	struct shmem_inode_info *info = SHMEM_I(inode);
1127  	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
1128  
1129  	if (shmem_mapping(inode->i_mapping)) {
1130  		shmem_unacct_size(info->flags, inode->i_size);
1131  		inode->i_size = 0;
1132  		shmem_truncate_range(inode, 0, (loff_t)-1);
1133  		if (!list_empty(&info->shrinklist)) {
1134  			spin_lock(&sbinfo->shrinklist_lock);
1135  			if (!list_empty(&info->shrinklist)) {
1136  				list_del_init(&info->shrinklist);
1137  				sbinfo->shrinklist_len--;
1138  			}
1139  			spin_unlock(&sbinfo->shrinklist_lock);
1140  		}
1141  		while (!list_empty(&info->swaplist)) {
1142  			/* Wait while shmem_unuse() is scanning this inode... */
1143  			wait_var_event(&info->stop_eviction,
1144  				       !atomic_read(&info->stop_eviction));
1145  			mutex_lock(&shmem_swaplist_mutex);
1146  			/* ...but beware of the race if we peeked too early */
1147  			if (!atomic_read(&info->stop_eviction))
1148  				list_del_init(&info->swaplist);
1149  			mutex_unlock(&shmem_swaplist_mutex);
1150  		}
1151  	}
1152  
1153  	simple_xattrs_free(&info->xattrs);
1154  	WARN_ON(inode->i_blocks);
1155  	shmem_free_inode(inode->i_sb);
1156  	clear_inode(inode);
1157  }
1158  
1159  extern struct swap_info_struct *swap_info[];
1160  
1161  static int shmem_find_swap_entries(struct address_space *mapping,
1162  				   pgoff_t start, unsigned int nr_entries,
1163  				   struct page **entries, pgoff_t *indices,
1164  				   unsigned int type, bool frontswap)
1165  {
1166  	XA_STATE(xas, &mapping->i_pages, start);
1167  	struct page *page;
1168  	swp_entry_t entry;
1169  	unsigned int ret = 0;
1170  
1171  	if (!nr_entries)
1172  		return 0;
1173  
1174  	rcu_read_lock();
1175  	xas_for_each(&xas, page, ULONG_MAX) {
1176  		if (xas_retry(&xas, page))
1177  			continue;
1178  
1179  		if (!xa_is_value(page))
1180  			continue;
1181  
1182  		entry = radix_to_swp_entry(page);
1183  		if (swp_type(entry) != type)
1184  			continue;
1185  		if (frontswap &&
1186  		    !frontswap_test(swap_info[type], swp_offset(entry)))
1187  			continue;
1188  
1189  		indices[ret] = xas.xa_index;
1190  		entries[ret] = page;
1191  
1192  		if (need_resched()) {
1193  			xas_pause(&xas);
1194  			cond_resched_rcu();
1195  		}
1196  		if (++ret == nr_entries)
1197  			break;
1198  	}
1199  	rcu_read_unlock();
1200  
1201  	return ret;
1202  }
1203  
1204  /*
1205   * Move the swapped pages for an inode to page cache. Returns the count
1206   * of pages swapped in, or the error in case of failure.
1207   */
1208  static int shmem_unuse_swap_entries(struct inode *inode, struct pagevec pvec,
1209  				    pgoff_t *indices)
1210  {
1211  	int i = 0;
1212  	int ret = 0;
1213  	int error = 0;
1214  	struct address_space *mapping = inode->i_mapping;
1215  
1216  	for (i = 0; i < pvec.nr; i++) {
1217  		struct page *page = pvec.pages[i];
1218  
1219  		if (!xa_is_value(page))
1220  			continue;
1221  		error = shmem_swapin_page(inode, indices[i],
1222  					  &page, SGP_CACHE,
1223  					  mapping_gfp_mask(mapping),
1224  					  NULL, NULL);
1225  		if (error == 0) {
1226  			unlock_page(page);
1227  			put_page(page);
1228  			ret++;
1229  		}
1230  		if (error == -ENOMEM)
1231  			break;
1232  		error = 0;
1233  	}
1234  	return error ? error : ret;
1235  }
1236  
1237  /*
1238   * If swap found in inode, free it and move page from swapcache to filecache.
1239   */
1240  static int shmem_unuse_inode(struct inode *inode, unsigned int type,
1241  			     bool frontswap, unsigned long *fs_pages_to_unuse)
1242  {
1243  	struct address_space *mapping = inode->i_mapping;
1244  	pgoff_t start = 0;
1245  	struct pagevec pvec;
1246  	pgoff_t indices[PAGEVEC_SIZE];
1247  	bool frontswap_partial = (frontswap && *fs_pages_to_unuse > 0);
1248  	int ret = 0;
1249  
1250  	pagevec_init(&pvec);
1251  	do {
1252  		unsigned int nr_entries = PAGEVEC_SIZE;
1253  
1254  		if (frontswap_partial && *fs_pages_to_unuse < PAGEVEC_SIZE)
1255  			nr_entries = *fs_pages_to_unuse;
1256  
1257  		pvec.nr = shmem_find_swap_entries(mapping, start, nr_entries,
1258  						  pvec.pages, indices,
1259  						  type, frontswap);
1260  		if (pvec.nr == 0) {
1261  			ret = 0;
1262  			break;
1263  		}
1264  
1265  		ret = shmem_unuse_swap_entries(inode, pvec, indices);
1266  		if (ret < 0)
1267  			break;
1268  
1269  		if (frontswap_partial) {
1270  			*fs_pages_to_unuse -= ret;
1271  			if (*fs_pages_to_unuse == 0) {
1272  				ret = FRONTSWAP_PAGES_UNUSED;
1273  				break;
1274  			}
1275  		}
1276  
1277  		start = indices[pvec.nr - 1];
1278  	} while (true);
1279  
1280  	return ret;
1281  }
1282  
1283  /*
1284   * Read all the shared memory data that resides in the swap
1285   * device 'type' back into memory, so the swap device can be
1286   * unused.
1287   */
1288  int shmem_unuse(unsigned int type, bool frontswap,
1289  		unsigned long *fs_pages_to_unuse)
1290  {
1291  	struct shmem_inode_info *info, *next;
1292  	int error = 0;
1293  
1294  	if (list_empty(&shmem_swaplist))
1295  		return 0;
1296  
1297  	mutex_lock(&shmem_swaplist_mutex);
1298  	list_for_each_entry_safe(info, next, &shmem_swaplist, swaplist) {
1299  		if (!info->swapped) {
1300  			list_del_init(&info->swaplist);
1301  			continue;
1302  		}
1303  		/*
1304  		 * Drop the swaplist mutex while searching the inode for swap;
1305  		 * but before doing so, make sure shmem_evict_inode() will not
1306  		 * remove placeholder inode from swaplist, nor let it be freed
1307  		 * (igrab() would protect from unlink, but not from unmount).
1308  		 */
1309  		atomic_inc(&info->stop_eviction);
1310  		mutex_unlock(&shmem_swaplist_mutex);
1311  
1312  		error = shmem_unuse_inode(&info->vfs_inode, type, frontswap,
1313  					  fs_pages_to_unuse);
1314  		cond_resched();
1315  
1316  		mutex_lock(&shmem_swaplist_mutex);
1317  		next = list_next_entry(info, swaplist);
1318  		if (!info->swapped)
1319  			list_del_init(&info->swaplist);
1320  		if (atomic_dec_and_test(&info->stop_eviction))
1321  			wake_up_var(&info->stop_eviction);
1322  		if (error)
1323  			break;
1324  	}
1325  	mutex_unlock(&shmem_swaplist_mutex);
1326  
1327  	return error;
1328  }
1329  
1330  /*
1331   * Move the page from the page cache to the swap cache.
1332   */
1333  static int shmem_writepage(struct page *page, struct writeback_control *wbc)
1334  {
1335  	struct shmem_inode_info *info;
1336  	struct address_space *mapping;
1337  	struct inode *inode;
1338  	swp_entry_t swap;
1339  	pgoff_t index;
1340  
1341  	VM_BUG_ON_PAGE(PageCompound(page), page);
1342  	BUG_ON(!PageLocked(page));
1343  	mapping = page->mapping;
1344  	index = page->index;
1345  	inode = mapping->host;
1346  	info = SHMEM_I(inode);
1347  	if (info->flags & VM_LOCKED)
1348  		goto redirty;
1349  	if (!total_swap_pages)
1350  		goto redirty;
1351  
1352  	/*
1353  	 * Our capabilities prevent regular writeback or sync from ever calling
1354  	 * shmem_writepage; but a stacking filesystem might use ->writepage of
1355  	 * its underlying filesystem, in which case tmpfs should write out to
1356  	 * swap only in response to memory pressure, and not for the writeback
1357  	 * threads or sync.
1358  	 */
1359  	if (!wbc->for_reclaim) {
1360  		WARN_ON_ONCE(1);	/* Still happens? Tell us about it! */
1361  		goto redirty;
1362  	}
1363  
1364  	/*
1365  	 * This is somewhat ridiculous, but without plumbing a SWAP_MAP_FALLOC
1366  	 * value into swapfile.c, the only way we can correctly account for a
1367  	 * fallocated page arriving here is now to initialize it and write it.
1368  	 *
1369  	 * That's okay for a page already fallocated earlier, but if we have
1370  	 * not yet completed the fallocation, then (a) we want to keep track
1371  	 * of this page in case we have to undo it, and (b) it may not be a
1372  	 * good idea to continue anyway, once we're pushing into swap.  So
1373  	 * reactivate the page, and let shmem_fallocate() quit when too many.
1374  	 */
1375  	if (!PageUptodate(page)) {
1376  		if (inode->i_private) {
1377  			struct shmem_falloc *shmem_falloc;
1378  			spin_lock(&inode->i_lock);
1379  			shmem_falloc = inode->i_private;
1380  			if (shmem_falloc &&
1381  			    !shmem_falloc->waitq &&
1382  			    index >= shmem_falloc->start &&
1383  			    index < shmem_falloc->next)
1384  				shmem_falloc->nr_unswapped++;
1385  			else
1386  				shmem_falloc = NULL;
1387  			spin_unlock(&inode->i_lock);
1388  			if (shmem_falloc)
1389  				goto redirty;
1390  		}
1391  		clear_highpage(page);
1392  		flush_dcache_page(page);
1393  		SetPageUptodate(page);
1394  	}
1395  
1396  	swap = get_swap_page(page);
1397  	if (!swap.val)
1398  		goto redirty;
1399  
1400  	/*
1401  	 * Add inode to shmem_unuse()'s list of swapped-out inodes,
1402  	 * if it's not already there.  Do it now before the page is
1403  	 * moved to swap cache, when its pagelock no longer protects
1404  	 * the inode from eviction.  But don't unlock the mutex until
1405  	 * we've incremented swapped, because shmem_unuse_inode() will
1406  	 * prune a !swapped inode from the swaplist under this mutex.
1407  	 */
1408  	mutex_lock(&shmem_swaplist_mutex);
1409  	if (list_empty(&info->swaplist))
1410  		list_add(&info->swaplist, &shmem_swaplist);
1411  
1412  	if (add_to_swap_cache(page, swap,
1413  			__GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN,
1414  			NULL) == 0) {
1415  		spin_lock_irq(&info->lock);
1416  		shmem_recalc_inode(inode);
1417  		info->swapped++;
1418  		spin_unlock_irq(&info->lock);
1419  
1420  		swap_shmem_alloc(swap);
1421  		shmem_delete_from_page_cache(page, swp_to_radix_entry(swap));
1422  
1423  		mutex_unlock(&shmem_swaplist_mutex);
1424  		BUG_ON(page_mapped(page));
1425  		swap_writepage(page, wbc);
1426  		return 0;
1427  	}
1428  
1429  	mutex_unlock(&shmem_swaplist_mutex);
1430  	put_swap_page(page, swap);
1431  redirty:
1432  	set_page_dirty(page);
1433  	if (wbc->for_reclaim)
1434  		return AOP_WRITEPAGE_ACTIVATE;	/* Return with page locked */
1435  	unlock_page(page);
1436  	return 0;
1437  }
1438  
1439  #if defined(CONFIG_NUMA) && defined(CONFIG_TMPFS)
1440  static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
1441  {
1442  	char buffer[64];
1443  
1444  	if (!mpol || mpol->mode == MPOL_DEFAULT)
1445  		return;		/* show nothing */
1446  
1447  	mpol_to_str(buffer, sizeof(buffer), mpol);
1448  
1449  	seq_printf(seq, ",mpol=%s", buffer);
1450  }
1451  
1452  static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
1453  {
1454  	struct mempolicy *mpol = NULL;
1455  	if (sbinfo->mpol) {
1456  		spin_lock(&sbinfo->stat_lock);	/* prevent replace/use races */
1457  		mpol = sbinfo->mpol;
1458  		mpol_get(mpol);
1459  		spin_unlock(&sbinfo->stat_lock);
1460  	}
1461  	return mpol;
1462  }
1463  #else /* !CONFIG_NUMA || !CONFIG_TMPFS */
1464  static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
1465  {
1466  }
1467  static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
1468  {
1469  	return NULL;
1470  }
1471  #endif /* CONFIG_NUMA && CONFIG_TMPFS */
1472  #ifndef CONFIG_NUMA
1473  #define vm_policy vm_private_data
1474  #endif
1475  
1476  static void shmem_pseudo_vma_init(struct vm_area_struct *vma,
1477  		struct shmem_inode_info *info, pgoff_t index)
1478  {
1479  	/* Create a pseudo vma that just contains the policy */
1480  	vma_init(vma, NULL);
1481  	/* Bias interleave by inode number to distribute better across nodes */
1482  	vma->vm_pgoff = index + info->vfs_inode.i_ino;
1483  	vma->vm_policy = mpol_shared_policy_lookup(&info->policy, index);
1484  }
1485  
1486  static void shmem_pseudo_vma_destroy(struct vm_area_struct *vma)
1487  {
1488  	/* Drop reference taken by mpol_shared_policy_lookup() */
1489  	mpol_cond_put(vma->vm_policy);
1490  }
1491  
1492  static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
1493  			struct shmem_inode_info *info, pgoff_t index)
1494  {
1495  	struct vm_area_struct pvma;
1496  	struct page *page;
1497  	struct vm_fault vmf = {
1498  		.vma = &pvma,
1499  	};
1500  
1501  	shmem_pseudo_vma_init(&pvma, info, index);
1502  	page = swap_cluster_readahead(swap, gfp, &vmf);
1503  	shmem_pseudo_vma_destroy(&pvma);
1504  
1505  	return page;
1506  }
1507  
1508  /*
1509   * Make sure huge_gfp is always more limited than limit_gfp.
1510   * Some of the flags set permissions, while others set limitations.
1511   */
1512  static gfp_t limit_gfp_mask(gfp_t huge_gfp, gfp_t limit_gfp)
1513  {
1514  	gfp_t allowflags = __GFP_IO | __GFP_FS | __GFP_RECLAIM;
1515  	gfp_t denyflags = __GFP_NOWARN | __GFP_NORETRY;
1516  	gfp_t zoneflags = limit_gfp & GFP_ZONEMASK;
1517  	gfp_t result = huge_gfp & ~(allowflags | GFP_ZONEMASK);
1518  
1519  	/* Allow allocations only from the originally specified zones. */
1520  	result |= zoneflags;
1521  
1522  	/*
1523  	 * Minimize the result gfp by taking the union with the deny flags,
1524  	 * and the intersection of the allow flags.
1525  	 */
1526  	result |= (limit_gfp & denyflags);
1527  	result |= (huge_gfp & limit_gfp) & allowflags;
1528  
1529  	return result;
1530  }
1531  
1532  static struct page *shmem_alloc_hugepage(gfp_t gfp,
1533  		struct shmem_inode_info *info, pgoff_t index)
1534  {
1535  	struct vm_area_struct pvma;
1536  	struct address_space *mapping = info->vfs_inode.i_mapping;
1537  	pgoff_t hindex;
1538  	struct page *page;
1539  
1540  	hindex = round_down(index, HPAGE_PMD_NR);
1541  	if (xa_find(&mapping->i_pages, &hindex, hindex + HPAGE_PMD_NR - 1,
1542  								XA_PRESENT))
1543  		return NULL;
1544  
1545  	shmem_pseudo_vma_init(&pvma, info, hindex);
1546  	page = alloc_pages_vma(gfp, HPAGE_PMD_ORDER, &pvma, 0, numa_node_id(),
1547  			       true);
1548  	shmem_pseudo_vma_destroy(&pvma);
1549  	if (page)
1550  		prep_transhuge_page(page);
1551  	else
1552  		count_vm_event(THP_FILE_FALLBACK);
1553  	return page;
1554  }
1555  
1556  static struct page *shmem_alloc_page(gfp_t gfp,
1557  			struct shmem_inode_info *info, pgoff_t index)
1558  {
1559  	struct vm_area_struct pvma;
1560  	struct page *page;
1561  
1562  	shmem_pseudo_vma_init(&pvma, info, index);
1563  	page = alloc_page_vma(gfp, &pvma, 0);
1564  	shmem_pseudo_vma_destroy(&pvma);
1565  
1566  	return page;
1567  }
1568  
1569  static struct page *shmem_alloc_and_acct_page(gfp_t gfp,
1570  		struct inode *inode,
1571  		pgoff_t index, bool huge)
1572  {
1573  	struct shmem_inode_info *info = SHMEM_I(inode);
1574  	struct page *page;
1575  	int nr;
1576  	int err = -ENOSPC;
1577  
1578  	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
1579  		huge = false;
1580  	nr = huge ? HPAGE_PMD_NR : 1;
1581  
1582  	if (!shmem_inode_acct_block(inode, nr))
1583  		goto failed;
1584  
1585  	if (huge)
1586  		page = shmem_alloc_hugepage(gfp, info, index);
1587  	else
1588  		page = shmem_alloc_page(gfp, info, index);
1589  	if (page) {
1590  		__SetPageLocked(page);
1591  		__SetPageSwapBacked(page);
1592  		return page;
1593  	}
1594  
1595  	err = -ENOMEM;
1596  	shmem_inode_unacct_blocks(inode, nr);
1597  failed:
1598  	return ERR_PTR(err);
1599  }
1600  
1601  /*
1602   * When a page is moved from swapcache to shmem filecache (either by the
1603   * usual swapin of shmem_getpage_gfp(), or by the less common swapoff of
1604   * shmem_unuse_inode()), it may have been read in earlier from swap, in
1605   * ignorance of the mapping it belongs to.  If that mapping has special
1606   * constraints (like the gma500 GEM driver, which requires RAM below 4GB),
1607   * we may need to copy to a suitable page before moving to filecache.
1608   *
1609   * In a future release, this may well be extended to respect cpuset and
1610   * NUMA mempolicy, and applied also to anonymous pages in do_swap_page();
1611   * but for now it is a simple matter of zone.
1612   */
1613  static bool shmem_should_replace_page(struct page *page, gfp_t gfp)
1614  {
1615  	return page_zonenum(page) > gfp_zone(gfp);
1616  }
1617  
1618  static int shmem_replace_page(struct page **pagep, gfp_t gfp,
1619  				struct shmem_inode_info *info, pgoff_t index)
1620  {
1621  	struct page *oldpage, *newpage;
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  		mem_cgroup_migrate(oldpage, newpage);
1659  		__inc_lruvec_page_state(newpage, NR_FILE_PAGES);
1660  		__dec_lruvec_page_state(oldpage, NR_FILE_PAGES);
1661  	}
1662  	xa_unlock_irq(&swap_mapping->i_pages);
1663  
1664  	if (unlikely(error)) {
1665  		/*
1666  		 * Is this possible?  I think not, now that our callers check
1667  		 * both PageSwapCache and page_private after getting page lock;
1668  		 * but be defensive.  Reverse old to newpage for clear and free.
1669  		 */
1670  		oldpage = newpage;
1671  	} else {
1672  		lru_cache_add(newpage);
1673  		*pagep = newpage;
1674  	}
1675  
1676  	ClearPageSwapCache(oldpage);
1677  	set_page_private(oldpage, 0);
1678  
1679  	unlock_page(oldpage);
1680  	put_page(oldpage);
1681  	put_page(oldpage);
1682  	return error;
1683  }
1684  
1685  /*
1686   * Swap in the page pointed to by *pagep.
1687   * Caller has to make sure that *pagep contains a valid swapped page.
1688   * Returns 0 and the page in pagep if success. On failure, returns the
1689   * error code and NULL in *pagep.
1690   */
1691  static int shmem_swapin_page(struct inode *inode, pgoff_t index,
1692  			     struct page **pagep, enum sgp_type sgp,
1693  			     gfp_t gfp, struct vm_area_struct *vma,
1694  			     vm_fault_t *fault_type)
1695  {
1696  	struct address_space *mapping = inode->i_mapping;
1697  	struct shmem_inode_info *info = SHMEM_I(inode);
1698  	struct mm_struct *charge_mm = vma ? vma->vm_mm : current->mm;
1699  	struct page *page;
1700  	swp_entry_t swap;
1701  	int error;
1702  
1703  	VM_BUG_ON(!*pagep || !xa_is_value(*pagep));
1704  	swap = radix_to_swp_entry(*pagep);
1705  	*pagep = NULL;
1706  
1707  	/* Look it up and read it in.. */
1708  	page = lookup_swap_cache(swap, NULL, 0);
1709  	if (!page) {
1710  		/* Or update major stats only when swapin succeeds?? */
1711  		if (fault_type) {
1712  			*fault_type |= VM_FAULT_MAJOR;
1713  			count_vm_event(PGMAJFAULT);
1714  			count_memcg_event_mm(charge_mm, PGMAJFAULT);
1715  		}
1716  		/* Here we actually start the io */
1717  		page = shmem_swapin(swap, gfp, info, index);
1718  		if (!page) {
1719  			error = -ENOMEM;
1720  			goto failed;
1721  		}
1722  	}
1723  
1724  	/* We have to do this with page locked to prevent races */
1725  	lock_page(page);
1726  	if (!PageSwapCache(page) || page_private(page) != swap.val ||
1727  	    !shmem_confirm_swap(mapping, index, swap)) {
1728  		error = -EEXIST;
1729  		goto unlock;
1730  	}
1731  	if (!PageUptodate(page)) {
1732  		error = -EIO;
1733  		goto failed;
1734  	}
1735  	wait_on_page_writeback(page);
1736  
1737  	/*
1738  	 * Some architectures may have to restore extra metadata to the
1739  	 * physical page after reading from swap.
1740  	 */
1741  	arch_swap_restore(swap, page);
1742  
1743  	if (shmem_should_replace_page(page, gfp)) {
1744  		error = shmem_replace_page(&page, gfp, info, index);
1745  		if (error)
1746  			goto failed;
1747  	}
1748  
1749  	error = shmem_add_to_page_cache(page, mapping, index,
1750  					swp_to_radix_entry(swap), gfp,
1751  					charge_mm);
1752  	if (error)
1753  		goto failed;
1754  
1755  	spin_lock_irq(&info->lock);
1756  	info->swapped--;
1757  	shmem_recalc_inode(inode);
1758  	spin_unlock_irq(&info->lock);
1759  
1760  	if (sgp == SGP_WRITE)
1761  		mark_page_accessed(page);
1762  
1763  	delete_from_swap_cache(page);
1764  	set_page_dirty(page);
1765  	swap_free(swap);
1766  
1767  	*pagep = page;
1768  	return 0;
1769  failed:
1770  	if (!shmem_confirm_swap(mapping, index, swap))
1771  		error = -EEXIST;
1772  unlock:
1773  	if (page) {
1774  		unlock_page(page);
1775  		put_page(page);
1776  	}
1777  
1778  	return error;
1779  }
1780  
1781  /*
1782   * shmem_getpage_gfp - find page in cache, or get from swap, or allocate
1783   *
1784   * If we allocate a new one we do not mark it dirty. That's up to the
1785   * vm. If we swap it in we mark it dirty since we also free the swap
1786   * entry since a page cannot live in both the swap and page cache.
1787   *
1788   * vmf and fault_type are only supplied by shmem_fault:
1789   * otherwise they are NULL.
1790   */
1791  static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
1792  	struct page **pagep, enum sgp_type sgp, gfp_t gfp,
1793  	struct vm_area_struct *vma, struct vm_fault *vmf,
1794  			vm_fault_t *fault_type)
1795  {
1796  	struct address_space *mapping = inode->i_mapping;
1797  	struct shmem_inode_info *info = SHMEM_I(inode);
1798  	struct shmem_sb_info *sbinfo;
1799  	struct mm_struct *charge_mm;
1800  	struct page *page;
1801  	enum sgp_type sgp_huge = sgp;
1802  	pgoff_t hindex = index;
1803  	gfp_t huge_gfp;
1804  	int error;
1805  	int once = 0;
1806  	int alloced = 0;
1807  
1808  	if (index > (MAX_LFS_FILESIZE >> PAGE_SHIFT))
1809  		return -EFBIG;
1810  	if (sgp == SGP_NOHUGE || sgp == SGP_HUGE)
1811  		sgp = SGP_CACHE;
1812  repeat:
1813  	if (sgp <= SGP_CACHE &&
1814  	    ((loff_t)index << PAGE_SHIFT) >= i_size_read(inode)) {
1815  		return -EINVAL;
1816  	}
1817  
1818  	sbinfo = SHMEM_SB(inode->i_sb);
1819  	charge_mm = vma ? vma->vm_mm : current->mm;
1820  
1821  	page = pagecache_get_page(mapping, index,
1822  					FGP_ENTRY | FGP_HEAD | FGP_LOCK, 0);
1823  	if (xa_is_value(page)) {
1824  		error = shmem_swapin_page(inode, index, &page,
1825  					  sgp, gfp, vma, fault_type);
1826  		if (error == -EEXIST)
1827  			goto repeat;
1828  
1829  		*pagep = page;
1830  		return error;
1831  	}
1832  
1833  	if (page)
1834  		hindex = page->index;
1835  	if (page && sgp == SGP_WRITE)
1836  		mark_page_accessed(page);
1837  
1838  	/* fallocated page? */
1839  	if (page && !PageUptodate(page)) {
1840  		if (sgp != SGP_READ)
1841  			goto clear;
1842  		unlock_page(page);
1843  		put_page(page);
1844  		page = NULL;
1845  		hindex = index;
1846  	}
1847  	if (page || sgp == SGP_READ)
1848  		goto out;
1849  
1850  	/*
1851  	 * Fast cache lookup did not find it:
1852  	 * bring it back from swap or allocate.
1853  	 */
1854  
1855  	if (vma && userfaultfd_missing(vma)) {
1856  		*fault_type = handle_userfault(vmf, VM_UFFD_MISSING);
1857  		return 0;
1858  	}
1859  
1860  	/* shmem_symlink() */
1861  	if (!shmem_mapping(mapping))
1862  		goto alloc_nohuge;
1863  	if (shmem_huge == SHMEM_HUGE_DENY || sgp_huge == SGP_NOHUGE)
1864  		goto alloc_nohuge;
1865  	if (shmem_huge == SHMEM_HUGE_FORCE)
1866  		goto alloc_huge;
1867  	switch (sbinfo->huge) {
1868  	case SHMEM_HUGE_NEVER:
1869  		goto alloc_nohuge;
1870  	case SHMEM_HUGE_WITHIN_SIZE: {
1871  		loff_t i_size;
1872  		pgoff_t off;
1873  
1874  		off = round_up(index, HPAGE_PMD_NR);
1875  		i_size = round_up(i_size_read(inode), PAGE_SIZE);
1876  		if (i_size >= HPAGE_PMD_SIZE &&
1877  		    i_size >> PAGE_SHIFT >= off)
1878  			goto alloc_huge;
1879  
1880  		fallthrough;
1881  	}
1882  	case SHMEM_HUGE_ADVISE:
1883  		if (sgp_huge == SGP_HUGE)
1884  			goto alloc_huge;
1885  		/* TODO: implement fadvise() hints */
1886  		goto alloc_nohuge;
1887  	}
1888  
1889  alloc_huge:
1890  	huge_gfp = vma_thp_gfp_mask(vma);
1891  	huge_gfp = limit_gfp_mask(huge_gfp, gfp);
1892  	page = shmem_alloc_and_acct_page(huge_gfp, inode, index, true);
1893  	if (IS_ERR(page)) {
1894  alloc_nohuge:
1895  		page = shmem_alloc_and_acct_page(gfp, inode,
1896  						 index, false);
1897  	}
1898  	if (IS_ERR(page)) {
1899  		int retry = 5;
1900  
1901  		error = PTR_ERR(page);
1902  		page = NULL;
1903  		if (error != -ENOSPC)
1904  			goto unlock;
1905  		/*
1906  		 * Try to reclaim some space by splitting a huge page
1907  		 * beyond i_size on the filesystem.
1908  		 */
1909  		while (retry--) {
1910  			int ret;
1911  
1912  			ret = shmem_unused_huge_shrink(sbinfo, NULL, 1);
1913  			if (ret == SHRINK_STOP)
1914  				break;
1915  			if (ret)
1916  				goto alloc_nohuge;
1917  		}
1918  		goto unlock;
1919  	}
1920  
1921  	if (PageTransHuge(page))
1922  		hindex = round_down(index, HPAGE_PMD_NR);
1923  	else
1924  		hindex = index;
1925  
1926  	if (sgp == SGP_WRITE)
1927  		__SetPageReferenced(page);
1928  
1929  	error = shmem_add_to_page_cache(page, mapping, hindex,
1930  					NULL, gfp & GFP_RECLAIM_MASK,
1931  					charge_mm);
1932  	if (error)
1933  		goto unacct;
1934  	lru_cache_add(page);
1935  
1936  	spin_lock_irq(&info->lock);
1937  	info->alloced += compound_nr(page);
1938  	inode->i_blocks += BLOCKS_PER_PAGE << compound_order(page);
1939  	shmem_recalc_inode(inode);
1940  	spin_unlock_irq(&info->lock);
1941  	alloced = true;
1942  
1943  	if (PageTransHuge(page) &&
1944  	    DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE) <
1945  			hindex + HPAGE_PMD_NR - 1) {
1946  		/*
1947  		 * Part of the huge page is beyond i_size: subject
1948  		 * to shrink under memory pressure.
1949  		 */
1950  		spin_lock(&sbinfo->shrinklist_lock);
1951  		/*
1952  		 * _careful to defend against unlocked access to
1953  		 * ->shrink_list in shmem_unused_huge_shrink()
1954  		 */
1955  		if (list_empty_careful(&info->shrinklist)) {
1956  			list_add_tail(&info->shrinklist,
1957  				      &sbinfo->shrinklist);
1958  			sbinfo->shrinklist_len++;
1959  		}
1960  		spin_unlock(&sbinfo->shrinklist_lock);
1961  	}
1962  
1963  	/*
1964  	 * Let SGP_FALLOC use the SGP_WRITE optimization on a new page.
1965  	 */
1966  	if (sgp == SGP_FALLOC)
1967  		sgp = SGP_WRITE;
1968  clear:
1969  	/*
1970  	 * Let SGP_WRITE caller clear ends if write does not fill page;
1971  	 * but SGP_FALLOC on a page fallocated earlier must initialize
1972  	 * it now, lest undo on failure cancel our earlier guarantee.
1973  	 */
1974  	if (sgp != SGP_WRITE && !PageUptodate(page)) {
1975  		int i;
1976  
1977  		for (i = 0; i < compound_nr(page); i++) {
1978  			clear_highpage(page + i);
1979  			flush_dcache_page(page + i);
1980  		}
1981  		SetPageUptodate(page);
1982  	}
1983  
1984  	/* Perhaps the file has been truncated since we checked */
1985  	if (sgp <= SGP_CACHE &&
1986  	    ((loff_t)index << PAGE_SHIFT) >= i_size_read(inode)) {
1987  		if (alloced) {
1988  			ClearPageDirty(page);
1989  			delete_from_page_cache(page);
1990  			spin_lock_irq(&info->lock);
1991  			shmem_recalc_inode(inode);
1992  			spin_unlock_irq(&info->lock);
1993  		}
1994  		error = -EINVAL;
1995  		goto unlock;
1996  	}
1997  out:
1998  	*pagep = page + index - hindex;
1999  	return 0;
2000  
2001  	/*
2002  	 * Error recovery.
2003  	 */
2004  unacct:
2005  	shmem_inode_unacct_blocks(inode, compound_nr(page));
2006  
2007  	if (PageTransHuge(page)) {
2008  		unlock_page(page);
2009  		put_page(page);
2010  		goto alloc_nohuge;
2011  	}
2012  unlock:
2013  	if (page) {
2014  		unlock_page(page);
2015  		put_page(page);
2016  	}
2017  	if (error == -ENOSPC && !once++) {
2018  		spin_lock_irq(&info->lock);
2019  		shmem_recalc_inode(inode);
2020  		spin_unlock_irq(&info->lock);
2021  		goto repeat;
2022  	}
2023  	if (error == -EEXIST)
2024  		goto repeat;
2025  	return error;
2026  }
2027  
2028  /*
2029   * This is like autoremove_wake_function, but it removes the wait queue
2030   * entry unconditionally - even if something else had already woken the
2031   * target.
2032   */
2033  static int synchronous_wake_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
2034  {
2035  	int ret = default_wake_function(wait, mode, sync, key);
2036  	list_del_init(&wait->entry);
2037  	return ret;
2038  }
2039  
2040  static vm_fault_t shmem_fault(struct vm_fault *vmf)
2041  {
2042  	struct vm_area_struct *vma = vmf->vma;
2043  	struct inode *inode = file_inode(vma->vm_file);
2044  	gfp_t gfp = mapping_gfp_mask(inode->i_mapping);
2045  	enum sgp_type sgp;
2046  	int err;
2047  	vm_fault_t ret = VM_FAULT_LOCKED;
2048  
2049  	/*
2050  	 * Trinity finds that probing a hole which tmpfs is punching can
2051  	 * prevent the hole-punch from ever completing: which in turn
2052  	 * locks writers out with its hold on i_mutex.  So refrain from
2053  	 * faulting pages into the hole while it's being punched.  Although
2054  	 * shmem_undo_range() does remove the additions, it may be unable to
2055  	 * keep up, as each new page needs its own unmap_mapping_range() call,
2056  	 * and the i_mmap tree grows ever slower to scan if new vmas are added.
2057  	 *
2058  	 * It does not matter if we sometimes reach this check just before the
2059  	 * hole-punch begins, so that one fault then races with the punch:
2060  	 * we just need to make racing faults a rare case.
2061  	 *
2062  	 * The implementation below would be much simpler if we just used a
2063  	 * standard mutex or completion: but we cannot take i_mutex in fault,
2064  	 * and bloating every shmem inode for this unlikely case would be sad.
2065  	 */
2066  	if (unlikely(inode->i_private)) {
2067  		struct shmem_falloc *shmem_falloc;
2068  
2069  		spin_lock(&inode->i_lock);
2070  		shmem_falloc = inode->i_private;
2071  		if (shmem_falloc &&
2072  		    shmem_falloc->waitq &&
2073  		    vmf->pgoff >= shmem_falloc->start &&
2074  		    vmf->pgoff < shmem_falloc->next) {
2075  			struct file *fpin;
2076  			wait_queue_head_t *shmem_falloc_waitq;
2077  			DEFINE_WAIT_FUNC(shmem_fault_wait, synchronous_wake_function);
2078  
2079  			ret = VM_FAULT_NOPAGE;
2080  			fpin = maybe_unlock_mmap_for_io(vmf, NULL);
2081  			if (fpin)
2082  				ret = VM_FAULT_RETRY;
2083  
2084  			shmem_falloc_waitq = shmem_falloc->waitq;
2085  			prepare_to_wait(shmem_falloc_waitq, &shmem_fault_wait,
2086  					TASK_UNINTERRUPTIBLE);
2087  			spin_unlock(&inode->i_lock);
2088  			schedule();
2089  
2090  			/*
2091  			 * shmem_falloc_waitq points into the shmem_fallocate()
2092  			 * stack of the hole-punching task: shmem_falloc_waitq
2093  			 * is usually invalid by the time we reach here, but
2094  			 * finish_wait() does not dereference it in that case;
2095  			 * though i_lock needed lest racing with wake_up_all().
2096  			 */
2097  			spin_lock(&inode->i_lock);
2098  			finish_wait(shmem_falloc_waitq, &shmem_fault_wait);
2099  			spin_unlock(&inode->i_lock);
2100  
2101  			if (fpin)
2102  				fput(fpin);
2103  			return ret;
2104  		}
2105  		spin_unlock(&inode->i_lock);
2106  	}
2107  
2108  	sgp = SGP_CACHE;
2109  
2110  	if ((vma->vm_flags & VM_NOHUGEPAGE) ||
2111  	    test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))
2112  		sgp = SGP_NOHUGE;
2113  	else if (vma->vm_flags & VM_HUGEPAGE)
2114  		sgp = SGP_HUGE;
2115  
2116  	err = shmem_getpage_gfp(inode, vmf->pgoff, &vmf->page, sgp,
2117  				  gfp, vma, vmf, &ret);
2118  	if (err)
2119  		return vmf_error(err);
2120  	return ret;
2121  }
2122  
2123  unsigned long shmem_get_unmapped_area(struct file *file,
2124  				      unsigned long uaddr, unsigned long len,
2125  				      unsigned long pgoff, unsigned long flags)
2126  {
2127  	unsigned long (*get_area)(struct file *,
2128  		unsigned long, unsigned long, unsigned long, unsigned long);
2129  	unsigned long addr;
2130  	unsigned long offset;
2131  	unsigned long inflated_len;
2132  	unsigned long inflated_addr;
2133  	unsigned long inflated_offset;
2134  
2135  	if (len > TASK_SIZE)
2136  		return -ENOMEM;
2137  
2138  	get_area = current->mm->get_unmapped_area;
2139  	addr = get_area(file, uaddr, len, pgoff, flags);
2140  
2141  	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
2142  		return addr;
2143  	if (IS_ERR_VALUE(addr))
2144  		return addr;
2145  	if (addr & ~PAGE_MASK)
2146  		return addr;
2147  	if (addr > TASK_SIZE - len)
2148  		return addr;
2149  
2150  	if (shmem_huge == SHMEM_HUGE_DENY)
2151  		return addr;
2152  	if (len < HPAGE_PMD_SIZE)
2153  		return addr;
2154  	if (flags & MAP_FIXED)
2155  		return addr;
2156  	/*
2157  	 * Our priority is to support MAP_SHARED mapped hugely;
2158  	 * and support MAP_PRIVATE mapped hugely too, until it is COWed.
2159  	 * But if caller specified an address hint and we allocated area there
2160  	 * successfully, respect that as before.
2161  	 */
2162  	if (uaddr == addr)
2163  		return addr;
2164  
2165  	if (shmem_huge != SHMEM_HUGE_FORCE) {
2166  		struct super_block *sb;
2167  
2168  		if (file) {
2169  			VM_BUG_ON(file->f_op != &shmem_file_operations);
2170  			sb = file_inode(file)->i_sb;
2171  		} else {
2172  			/*
2173  			 * Called directly from mm/mmap.c, or drivers/char/mem.c
2174  			 * for "/dev/zero", to create a shared anonymous object.
2175  			 */
2176  			if (IS_ERR(shm_mnt))
2177  				return addr;
2178  			sb = shm_mnt->mnt_sb;
2179  		}
2180  		if (SHMEM_SB(sb)->huge == SHMEM_HUGE_NEVER)
2181  			return addr;
2182  	}
2183  
2184  	offset = (pgoff << PAGE_SHIFT) & (HPAGE_PMD_SIZE-1);
2185  	if (offset && offset + len < 2 * HPAGE_PMD_SIZE)
2186  		return addr;
2187  	if ((addr & (HPAGE_PMD_SIZE-1)) == offset)
2188  		return addr;
2189  
2190  	inflated_len = len + HPAGE_PMD_SIZE - PAGE_SIZE;
2191  	if (inflated_len > TASK_SIZE)
2192  		return addr;
2193  	if (inflated_len < len)
2194  		return addr;
2195  
2196  	inflated_addr = get_area(NULL, uaddr, inflated_len, 0, flags);
2197  	if (IS_ERR_VALUE(inflated_addr))
2198  		return addr;
2199  	if (inflated_addr & ~PAGE_MASK)
2200  		return addr;
2201  
2202  	inflated_offset = inflated_addr & (HPAGE_PMD_SIZE-1);
2203  	inflated_addr += offset - inflated_offset;
2204  	if (inflated_offset > offset)
2205  		inflated_addr += HPAGE_PMD_SIZE;
2206  
2207  	if (inflated_addr > TASK_SIZE - len)
2208  		return addr;
2209  	return inflated_addr;
2210  }
2211  
2212  #ifdef CONFIG_NUMA
2213  static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *mpol)
2214  {
2215  	struct inode *inode = file_inode(vma->vm_file);
2216  	return mpol_set_shared_policy(&SHMEM_I(inode)->policy, vma, mpol);
2217  }
2218  
2219  static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
2220  					  unsigned long addr)
2221  {
2222  	struct inode *inode = file_inode(vma->vm_file);
2223  	pgoff_t index;
2224  
2225  	index = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
2226  	return mpol_shared_policy_lookup(&SHMEM_I(inode)->policy, index);
2227  }
2228  #endif
2229  
2230  int shmem_lock(struct file *file, int lock, struct user_struct *user)
2231  {
2232  	struct inode *inode = file_inode(file);
2233  	struct shmem_inode_info *info = SHMEM_I(inode);
2234  	int retval = -ENOMEM;
2235  
2236  	/*
2237  	 * What serializes the accesses to info->flags?
2238  	 * ipc_lock_object() when called from shmctl_do_lock(),
2239  	 * no serialization needed when called from shm_destroy().
2240  	 */
2241  	if (lock && !(info->flags & VM_LOCKED)) {
2242  		if (!user_shm_lock(inode->i_size, user))
2243  			goto out_nomem;
2244  		info->flags |= VM_LOCKED;
2245  		mapping_set_unevictable(file->f_mapping);
2246  	}
2247  	if (!lock && (info->flags & VM_LOCKED) && user) {
2248  		user_shm_unlock(inode->i_size, user);
2249  		info->flags &= ~VM_LOCKED;
2250  		mapping_clear_unevictable(file->f_mapping);
2251  	}
2252  	retval = 0;
2253  
2254  out_nomem:
2255  	return retval;
2256  }
2257  
2258  static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
2259  {
2260  	struct shmem_inode_info *info = SHMEM_I(file_inode(file));
2261  
2262  	if (info->seals & F_SEAL_FUTURE_WRITE) {
2263  		/*
2264  		 * New PROT_WRITE and MAP_SHARED mmaps are not allowed when
2265  		 * "future write" seal active.
2266  		 */
2267  		if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_WRITE))
2268  			return -EPERM;
2269  
2270  		/*
2271  		 * Since an F_SEAL_FUTURE_WRITE sealed memfd can be mapped as
2272  		 * MAP_SHARED and read-only, take care to not allow mprotect to
2273  		 * revert protections on such mappings. Do this only for shared
2274  		 * mappings. For private mappings, don't need to mask
2275  		 * VM_MAYWRITE as we still want them to be COW-writable.
2276  		 */
2277  		if (vma->vm_flags & VM_SHARED)
2278  			vma->vm_flags &= ~(VM_MAYWRITE);
2279  	}
2280  
2281  	/* arm64 - allow memory tagging on RAM-based files */
2282  	vma->vm_flags |= VM_MTE_ALLOWED;
2283  
2284  	file_accessed(file);
2285  	vma->vm_ops = &shmem_vm_ops;
2286  	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
2287  			((vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK) <
2288  			(vma->vm_end & HPAGE_PMD_MASK)) {
2289  		khugepaged_enter(vma, vma->vm_flags);
2290  	}
2291  	return 0;
2292  }
2293  
2294  static struct inode *shmem_get_inode(struct super_block *sb, const struct inode *dir,
2295  				     umode_t mode, dev_t dev, unsigned long flags)
2296  {
2297  	struct inode *inode;
2298  	struct shmem_inode_info *info;
2299  	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2300  	ino_t ino;
2301  
2302  	if (shmem_reserve_inode(sb, &ino))
2303  		return NULL;
2304  
2305  	inode = new_inode(sb);
2306  	if (inode) {
2307  		inode->i_ino = ino;
2308  		inode_init_owner(&init_user_ns, inode, dir, mode);
2309  		inode->i_blocks = 0;
2310  		inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
2311  		inode->i_generation = prandom_u32();
2312  		info = SHMEM_I(inode);
2313  		memset(info, 0, (char *)inode - (char *)info);
2314  		spin_lock_init(&info->lock);
2315  		atomic_set(&info->stop_eviction, 0);
2316  		info->seals = F_SEAL_SEAL;
2317  		info->flags = flags & VM_NORESERVE;
2318  		INIT_LIST_HEAD(&info->shrinklist);
2319  		INIT_LIST_HEAD(&info->swaplist);
2320  		simple_xattrs_init(&info->xattrs);
2321  		cache_no_acl(inode);
2322  
2323  		switch (mode & S_IFMT) {
2324  		default:
2325  			inode->i_op = &shmem_special_inode_operations;
2326  			init_special_inode(inode, mode, dev);
2327  			break;
2328  		case S_IFREG:
2329  			inode->i_mapping->a_ops = &shmem_aops;
2330  			inode->i_op = &shmem_inode_operations;
2331  			inode->i_fop = &shmem_file_operations;
2332  			mpol_shared_policy_init(&info->policy,
2333  						 shmem_get_sbmpol(sbinfo));
2334  			break;
2335  		case S_IFDIR:
2336  			inc_nlink(inode);
2337  			/* Some things misbehave if size == 0 on a directory */
2338  			inode->i_size = 2 * BOGO_DIRENT_SIZE;
2339  			inode->i_op = &shmem_dir_inode_operations;
2340  			inode->i_fop = &simple_dir_operations;
2341  			break;
2342  		case S_IFLNK:
2343  			/*
2344  			 * Must not load anything in the rbtree,
2345  			 * mpol_free_shared_policy will not be called.
2346  			 */
2347  			mpol_shared_policy_init(&info->policy, NULL);
2348  			break;
2349  		}
2350  
2351  		lockdep_annotate_inode_mutex_key(inode);
2352  	} else
2353  		shmem_free_inode(sb);
2354  	return inode;
2355  }
2356  
2357  static int shmem_mfill_atomic_pte(struct mm_struct *dst_mm,
2358  				  pmd_t *dst_pmd,
2359  				  struct vm_area_struct *dst_vma,
2360  				  unsigned long dst_addr,
2361  				  unsigned long src_addr,
2362  				  bool zeropage,
2363  				  struct page **pagep)
2364  {
2365  	struct inode *inode = file_inode(dst_vma->vm_file);
2366  	struct shmem_inode_info *info = SHMEM_I(inode);
2367  	struct address_space *mapping = inode->i_mapping;
2368  	gfp_t gfp = mapping_gfp_mask(mapping);
2369  	pgoff_t pgoff = linear_page_index(dst_vma, dst_addr);
2370  	spinlock_t *ptl;
2371  	void *page_kaddr;
2372  	struct page *page;
2373  	pte_t _dst_pte, *dst_pte;
2374  	int ret;
2375  	pgoff_t offset, max_off;
2376  
2377  	ret = -ENOMEM;
2378  	if (!shmem_inode_acct_block(inode, 1))
2379  		goto out;
2380  
2381  	if (!*pagep) {
2382  		page = shmem_alloc_page(gfp, info, pgoff);
2383  		if (!page)
2384  			goto out_unacct_blocks;
2385  
2386  		if (!zeropage) {	/* mcopy_atomic */
2387  			page_kaddr = kmap_atomic(page);
2388  			ret = copy_from_user(page_kaddr,
2389  					     (const void __user *)src_addr,
2390  					     PAGE_SIZE);
2391  			kunmap_atomic(page_kaddr);
2392  
2393  			/* fallback to copy_from_user outside mmap_lock */
2394  			if (unlikely(ret)) {
2395  				*pagep = page;
2396  				shmem_inode_unacct_blocks(inode, 1);
2397  				/* don't free the page */
2398  				return -ENOENT;
2399  			}
2400  		} else {		/* mfill_zeropage_atomic */
2401  			clear_highpage(page);
2402  		}
2403  	} else {
2404  		page = *pagep;
2405  		*pagep = NULL;
2406  	}
2407  
2408  	VM_BUG_ON(PageLocked(page) || PageSwapBacked(page));
2409  	__SetPageLocked(page);
2410  	__SetPageSwapBacked(page);
2411  	__SetPageUptodate(page);
2412  
2413  	ret = -EFAULT;
2414  	offset = linear_page_index(dst_vma, dst_addr);
2415  	max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
2416  	if (unlikely(offset >= max_off))
2417  		goto out_release;
2418  
2419  	ret = shmem_add_to_page_cache(page, mapping, pgoff, NULL,
2420  				      gfp & GFP_RECLAIM_MASK, dst_mm);
2421  	if (ret)
2422  		goto out_release;
2423  
2424  	_dst_pte = mk_pte(page, dst_vma->vm_page_prot);
2425  	if (dst_vma->vm_flags & VM_WRITE)
2426  		_dst_pte = pte_mkwrite(pte_mkdirty(_dst_pte));
2427  	else {
2428  		/*
2429  		 * We don't set the pte dirty if the vma has no
2430  		 * VM_WRITE permission, so mark the page dirty or it
2431  		 * could be freed from under us. We could do it
2432  		 * unconditionally before unlock_page(), but doing it
2433  		 * only if VM_WRITE is not set is faster.
2434  		 */
2435  		set_page_dirty(page);
2436  	}
2437  
2438  	dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
2439  
2440  	ret = -EFAULT;
2441  	max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
2442  	if (unlikely(offset >= max_off))
2443  		goto out_release_unlock;
2444  
2445  	ret = -EEXIST;
2446  	if (!pte_none(*dst_pte))
2447  		goto out_release_unlock;
2448  
2449  	lru_cache_add(page);
2450  
2451  	spin_lock_irq(&info->lock);
2452  	info->alloced++;
2453  	inode->i_blocks += BLOCKS_PER_PAGE;
2454  	shmem_recalc_inode(inode);
2455  	spin_unlock_irq(&info->lock);
2456  
2457  	inc_mm_counter(dst_mm, mm_counter_file(page));
2458  	page_add_file_rmap(page, false);
2459  	set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
2460  
2461  	/* No need to invalidate - it was non-present before */
2462  	update_mmu_cache(dst_vma, dst_addr, dst_pte);
2463  	pte_unmap_unlock(dst_pte, ptl);
2464  	unlock_page(page);
2465  	ret = 0;
2466  out:
2467  	return ret;
2468  out_release_unlock:
2469  	pte_unmap_unlock(dst_pte, ptl);
2470  	ClearPageDirty(page);
2471  	delete_from_page_cache(page);
2472  out_release:
2473  	unlock_page(page);
2474  	put_page(page);
2475  out_unacct_blocks:
2476  	shmem_inode_unacct_blocks(inode, 1);
2477  	goto out;
2478  }
2479  
2480  int shmem_mcopy_atomic_pte(struct mm_struct *dst_mm,
2481  			   pmd_t *dst_pmd,
2482  			   struct vm_area_struct *dst_vma,
2483  			   unsigned long dst_addr,
2484  			   unsigned long src_addr,
2485  			   struct page **pagep)
2486  {
2487  	return shmem_mfill_atomic_pte(dst_mm, dst_pmd, dst_vma,
2488  				      dst_addr, src_addr, false, pagep);
2489  }
2490  
2491  int shmem_mfill_zeropage_pte(struct mm_struct *dst_mm,
2492  			     pmd_t *dst_pmd,
2493  			     struct vm_area_struct *dst_vma,
2494  			     unsigned long dst_addr)
2495  {
2496  	struct page *page = NULL;
2497  
2498  	return shmem_mfill_atomic_pte(dst_mm, dst_pmd, dst_vma,
2499  				      dst_addr, 0, true, &page);
2500  }
2501  
2502  #ifdef CONFIG_TMPFS
2503  static const struct inode_operations shmem_symlink_inode_operations;
2504  static const struct inode_operations shmem_short_symlink_operations;
2505  
2506  #ifdef CONFIG_TMPFS_XATTR
2507  static int shmem_initxattrs(struct inode *, const struct xattr *, void *);
2508  #else
2509  #define shmem_initxattrs NULL
2510  #endif
2511  
2512  static int
2513  shmem_write_begin(struct file *file, struct address_space *mapping,
2514  			loff_t pos, unsigned len, unsigned flags,
2515  			struct page **pagep, void **fsdata)
2516  {
2517  	struct inode *inode = mapping->host;
2518  	struct shmem_inode_info *info = SHMEM_I(inode);
2519  	pgoff_t index = pos >> PAGE_SHIFT;
2520  
2521  	/* i_mutex is held by caller */
2522  	if (unlikely(info->seals & (F_SEAL_GROW |
2523  				   F_SEAL_WRITE | F_SEAL_FUTURE_WRITE))) {
2524  		if (info->seals & (F_SEAL_WRITE | F_SEAL_FUTURE_WRITE))
2525  			return -EPERM;
2526  		if ((info->seals & F_SEAL_GROW) && pos + len > inode->i_size)
2527  			return -EPERM;
2528  	}
2529  
2530  	return shmem_getpage(inode, index, pagep, SGP_WRITE);
2531  }
2532  
2533  static int
2534  shmem_write_end(struct file *file, struct address_space *mapping,
2535  			loff_t pos, unsigned len, unsigned copied,
2536  			struct page *page, void *fsdata)
2537  {
2538  	struct inode *inode = mapping->host;
2539  
2540  	if (pos + copied > inode->i_size)
2541  		i_size_write(inode, pos + copied);
2542  
2543  	if (!PageUptodate(page)) {
2544  		struct page *head = compound_head(page);
2545  		if (PageTransCompound(page)) {
2546  			int i;
2547  
2548  			for (i = 0; i < HPAGE_PMD_NR; i++) {
2549  				if (head + i == page)
2550  					continue;
2551  				clear_highpage(head + i);
2552  				flush_dcache_page(head + i);
2553  			}
2554  		}
2555  		if (copied < PAGE_SIZE) {
2556  			unsigned from = pos & (PAGE_SIZE - 1);
2557  			zero_user_segments(page, 0, from,
2558  					from + copied, PAGE_SIZE);
2559  		}
2560  		SetPageUptodate(head);
2561  	}
2562  	set_page_dirty(page);
2563  	unlock_page(page);
2564  	put_page(page);
2565  
2566  	return copied;
2567  }
2568  
2569  static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
2570  {
2571  	struct file *file = iocb->ki_filp;
2572  	struct inode *inode = file_inode(file);
2573  	struct address_space *mapping = inode->i_mapping;
2574  	pgoff_t index;
2575  	unsigned long offset;
2576  	enum sgp_type sgp = SGP_READ;
2577  	int error = 0;
2578  	ssize_t retval = 0;
2579  	loff_t *ppos = &iocb->ki_pos;
2580  
2581  	/*
2582  	 * Might this read be for a stacking filesystem?  Then when reading
2583  	 * holes of a sparse file, we actually need to allocate those pages,
2584  	 * and even mark them dirty, so it cannot exceed the max_blocks limit.
2585  	 */
2586  	if (!iter_is_iovec(to))
2587  		sgp = SGP_CACHE;
2588  
2589  	index = *ppos >> PAGE_SHIFT;
2590  	offset = *ppos & ~PAGE_MASK;
2591  
2592  	for (;;) {
2593  		struct page *page = NULL;
2594  		pgoff_t end_index;
2595  		unsigned long nr, ret;
2596  		loff_t i_size = i_size_read(inode);
2597  
2598  		end_index = i_size >> PAGE_SHIFT;
2599  		if (index > end_index)
2600  			break;
2601  		if (index == end_index) {
2602  			nr = i_size & ~PAGE_MASK;
2603  			if (nr <= offset)
2604  				break;
2605  		}
2606  
2607  		error = shmem_getpage(inode, index, &page, sgp);
2608  		if (error) {
2609  			if (error == -EINVAL)
2610  				error = 0;
2611  			break;
2612  		}
2613  		if (page) {
2614  			if (sgp == SGP_CACHE)
2615  				set_page_dirty(page);
2616  			unlock_page(page);
2617  		}
2618  
2619  		/*
2620  		 * We must evaluate after, since reads (unlike writes)
2621  		 * are called without i_mutex protection against truncate
2622  		 */
2623  		nr = PAGE_SIZE;
2624  		i_size = i_size_read(inode);
2625  		end_index = i_size >> PAGE_SHIFT;
2626  		if (index == end_index) {
2627  			nr = i_size & ~PAGE_MASK;
2628  			if (nr <= offset) {
2629  				if (page)
2630  					put_page(page);
2631  				break;
2632  			}
2633  		}
2634  		nr -= offset;
2635  
2636  		if (page) {
2637  			/*
2638  			 * If users can be writing to this page using arbitrary
2639  			 * virtual addresses, take care about potential aliasing
2640  			 * before reading the page on the kernel side.
2641  			 */
2642  			if (mapping_writably_mapped(mapping))
2643  				flush_dcache_page(page);
2644  			/*
2645  			 * Mark the page accessed if we read the beginning.
2646  			 */
2647  			if (!offset)
2648  				mark_page_accessed(page);
2649  		} else {
2650  			page = ZERO_PAGE(0);
2651  			get_page(page);
2652  		}
2653  
2654  		/*
2655  		 * Ok, we have the page, and it's up-to-date, so
2656  		 * now we can copy it to user space...
2657  		 */
2658  		ret = copy_page_to_iter(page, offset, nr, to);
2659  		retval += ret;
2660  		offset += ret;
2661  		index += offset >> PAGE_SHIFT;
2662  		offset &= ~PAGE_MASK;
2663  
2664  		put_page(page);
2665  		if (!iov_iter_count(to))
2666  			break;
2667  		if (ret < nr) {
2668  			error = -EFAULT;
2669  			break;
2670  		}
2671  		cond_resched();
2672  	}
2673  
2674  	*ppos = ((loff_t) index << PAGE_SHIFT) + offset;
2675  	file_accessed(file);
2676  	return retval ? retval : error;
2677  }
2678  
2679  static loff_t shmem_file_llseek(struct file *file, loff_t offset, int whence)
2680  {
2681  	struct address_space *mapping = file->f_mapping;
2682  	struct inode *inode = mapping->host;
2683  
2684  	if (whence != SEEK_DATA && whence != SEEK_HOLE)
2685  		return generic_file_llseek_size(file, offset, whence,
2686  					MAX_LFS_FILESIZE, i_size_read(inode));
2687  	if (offset < 0)
2688  		return -ENXIO;
2689  
2690  	inode_lock(inode);
2691  	/* We're holding i_mutex so we can access i_size directly */
2692  	offset = mapping_seek_hole_data(mapping, offset, inode->i_size, whence);
2693  	if (offset >= 0)
2694  		offset = vfs_setpos(file, offset, MAX_LFS_FILESIZE);
2695  	inode_unlock(inode);
2696  	return offset;
2697  }
2698  
2699  static long shmem_fallocate(struct file *file, int mode, loff_t offset,
2700  							 loff_t len)
2701  {
2702  	struct inode *inode = file_inode(file);
2703  	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
2704  	struct shmem_inode_info *info = SHMEM_I(inode);
2705  	struct shmem_falloc shmem_falloc;
2706  	pgoff_t start, index, end;
2707  	int error;
2708  
2709  	if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
2710  		return -EOPNOTSUPP;
2711  
2712  	inode_lock(inode);
2713  
2714  	if (mode & FALLOC_FL_PUNCH_HOLE) {
2715  		struct address_space *mapping = file->f_mapping;
2716  		loff_t unmap_start = round_up(offset, PAGE_SIZE);
2717  		loff_t unmap_end = round_down(offset + len, PAGE_SIZE) - 1;
2718  		DECLARE_WAIT_QUEUE_HEAD_ONSTACK(shmem_falloc_waitq);
2719  
2720  		/* protected by i_mutex */
2721  		if (info->seals & (F_SEAL_WRITE | F_SEAL_FUTURE_WRITE)) {
2722  			error = -EPERM;
2723  			goto out;
2724  		}
2725  
2726  		shmem_falloc.waitq = &shmem_falloc_waitq;
2727  		shmem_falloc.start = (u64)unmap_start >> PAGE_SHIFT;
2728  		shmem_falloc.next = (unmap_end + 1) >> PAGE_SHIFT;
2729  		spin_lock(&inode->i_lock);
2730  		inode->i_private = &shmem_falloc;
2731  		spin_unlock(&inode->i_lock);
2732  
2733  		if ((u64)unmap_end > (u64)unmap_start)
2734  			unmap_mapping_range(mapping, unmap_start,
2735  					    1 + unmap_end - unmap_start, 0);
2736  		shmem_truncate_range(inode, offset, offset + len - 1);
2737  		/* No need to unmap again: hole-punching leaves COWed pages */
2738  
2739  		spin_lock(&inode->i_lock);
2740  		inode->i_private = NULL;
2741  		wake_up_all(&shmem_falloc_waitq);
2742  		WARN_ON_ONCE(!list_empty(&shmem_falloc_waitq.head));
2743  		spin_unlock(&inode->i_lock);
2744  		error = 0;
2745  		goto out;
2746  	}
2747  
2748  	/* We need to check rlimit even when FALLOC_FL_KEEP_SIZE */
2749  	error = inode_newsize_ok(inode, offset + len);
2750  	if (error)
2751  		goto out;
2752  
2753  	if ((info->seals & F_SEAL_GROW) && offset + len > inode->i_size) {
2754  		error = -EPERM;
2755  		goto out;
2756  	}
2757  
2758  	start = offset >> PAGE_SHIFT;
2759  	end = (offset + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
2760  	/* Try to avoid a swapstorm if len is impossible to satisfy */
2761  	if (sbinfo->max_blocks && end - start > sbinfo->max_blocks) {
2762  		error = -ENOSPC;
2763  		goto out;
2764  	}
2765  
2766  	shmem_falloc.waitq = NULL;
2767  	shmem_falloc.start = start;
2768  	shmem_falloc.next  = start;
2769  	shmem_falloc.nr_falloced = 0;
2770  	shmem_falloc.nr_unswapped = 0;
2771  	spin_lock(&inode->i_lock);
2772  	inode->i_private = &shmem_falloc;
2773  	spin_unlock(&inode->i_lock);
2774  
2775  	for (index = start; index < end; index++) {
2776  		struct page *page;
2777  
2778  		/*
2779  		 * Good, the fallocate(2) manpage permits EINTR: we may have
2780  		 * been interrupted because we are using up too much memory.
2781  		 */
2782  		if (signal_pending(current))
2783  			error = -EINTR;
2784  		else if (shmem_falloc.nr_unswapped > shmem_falloc.nr_falloced)
2785  			error = -ENOMEM;
2786  		else
2787  			error = shmem_getpage(inode, index, &page, SGP_FALLOC);
2788  		if (error) {
2789  			/* Remove the !PageUptodate pages we added */
2790  			if (index > start) {
2791  				shmem_undo_range(inode,
2792  				    (loff_t)start << PAGE_SHIFT,
2793  				    ((loff_t)index << PAGE_SHIFT) - 1, true);
2794  			}
2795  			goto undone;
2796  		}
2797  
2798  		/*
2799  		 * Inform shmem_writepage() how far we have reached.
2800  		 * No need for lock or barrier: we have the page lock.
2801  		 */
2802  		shmem_falloc.next++;
2803  		if (!PageUptodate(page))
2804  			shmem_falloc.nr_falloced++;
2805  
2806  		/*
2807  		 * If !PageUptodate, leave it that way so that freeable pages
2808  		 * can be recognized if we need to rollback on error later.
2809  		 * But set_page_dirty so that memory pressure will swap rather
2810  		 * than free the pages we are allocating (and SGP_CACHE pages
2811  		 * might still be clean: we now need to mark those dirty too).
2812  		 */
2813  		set_page_dirty(page);
2814  		unlock_page(page);
2815  		put_page(page);
2816  		cond_resched();
2817  	}
2818  
2819  	if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size)
2820  		i_size_write(inode, offset + len);
2821  	inode->i_ctime = current_time(inode);
2822  undone:
2823  	spin_lock(&inode->i_lock);
2824  	inode->i_private = NULL;
2825  	spin_unlock(&inode->i_lock);
2826  out:
2827  	inode_unlock(inode);
2828  	return error;
2829  }
2830  
2831  static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
2832  {
2833  	struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
2834  
2835  	buf->f_type = TMPFS_MAGIC;
2836  	buf->f_bsize = PAGE_SIZE;
2837  	buf->f_namelen = NAME_MAX;
2838  	if (sbinfo->max_blocks) {
2839  		buf->f_blocks = sbinfo->max_blocks;
2840  		buf->f_bavail =
2841  		buf->f_bfree  = sbinfo->max_blocks -
2842  				percpu_counter_sum(&sbinfo->used_blocks);
2843  	}
2844  	if (sbinfo->max_inodes) {
2845  		buf->f_files = sbinfo->max_inodes;
2846  		buf->f_ffree = sbinfo->free_inodes;
2847  	}
2848  	/* else leave those fields 0 like simple_statfs */
2849  
2850  	buf->f_fsid = uuid_to_fsid(dentry->d_sb->s_uuid.b);
2851  
2852  	return 0;
2853  }
2854  
2855  /*
2856   * File creation. Allocate an inode, and we're done..
2857   */
2858  static int
2859  shmem_mknod(struct user_namespace *mnt_userns, struct inode *dir,
2860  	    struct dentry *dentry, umode_t mode, dev_t dev)
2861  {
2862  	struct inode *inode;
2863  	int error = -ENOSPC;
2864  
2865  	inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE);
2866  	if (inode) {
2867  		error = simple_acl_create(dir, inode);
2868  		if (error)
2869  			goto out_iput;
2870  		error = security_inode_init_security(inode, dir,
2871  						     &dentry->d_name,
2872  						     shmem_initxattrs, NULL);
2873  		if (error && error != -EOPNOTSUPP)
2874  			goto out_iput;
2875  
2876  		error = 0;
2877  		dir->i_size += BOGO_DIRENT_SIZE;
2878  		dir->i_ctime = dir->i_mtime = current_time(dir);
2879  		d_instantiate(dentry, inode);
2880  		dget(dentry); /* Extra count - pin the dentry in core */
2881  	}
2882  	return error;
2883  out_iput:
2884  	iput(inode);
2885  	return error;
2886  }
2887  
2888  static int
2889  shmem_tmpfile(struct user_namespace *mnt_userns, struct inode *dir,
2890  	      struct dentry *dentry, umode_t mode)
2891  {
2892  	struct inode *inode;
2893  	int error = -ENOSPC;
2894  
2895  	inode = shmem_get_inode(dir->i_sb, dir, mode, 0, VM_NORESERVE);
2896  	if (inode) {
2897  		error = security_inode_init_security(inode, dir,
2898  						     NULL,
2899  						     shmem_initxattrs, NULL);
2900  		if (error && error != -EOPNOTSUPP)
2901  			goto out_iput;
2902  		error = simple_acl_create(dir, inode);
2903  		if (error)
2904  			goto out_iput;
2905  		d_tmpfile(dentry, inode);
2906  	}
2907  	return error;
2908  out_iput:
2909  	iput(inode);
2910  	return error;
2911  }
2912  
2913  static int shmem_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
2914  		       struct dentry *dentry, umode_t mode)
2915  {
2916  	int error;
2917  
2918  	if ((error = shmem_mknod(&init_user_ns, dir, dentry,
2919  				 mode | S_IFDIR, 0)))
2920  		return error;
2921  	inc_nlink(dir);
2922  	return 0;
2923  }
2924  
2925  static int shmem_create(struct user_namespace *mnt_userns, struct inode *dir,
2926  			struct dentry *dentry, umode_t mode, bool excl)
2927  {
2928  	return shmem_mknod(&init_user_ns, dir, dentry, mode | S_IFREG, 0);
2929  }
2930  
2931  /*
2932   * Link a file..
2933   */
2934  static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
2935  {
2936  	struct inode *inode = d_inode(old_dentry);
2937  	int ret = 0;
2938  
2939  	/*
2940  	 * No ordinary (disk based) filesystem counts links as inodes;
2941  	 * but each new link needs a new dentry, pinning lowmem, and
2942  	 * tmpfs dentries cannot be pruned until they are unlinked.
2943  	 * But if an O_TMPFILE file is linked into the tmpfs, the
2944  	 * first link must skip that, to get the accounting right.
2945  	 */
2946  	if (inode->i_nlink) {
2947  		ret = shmem_reserve_inode(inode->i_sb, NULL);
2948  		if (ret)
2949  			goto out;
2950  	}
2951  
2952  	dir->i_size += BOGO_DIRENT_SIZE;
2953  	inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
2954  	inc_nlink(inode);
2955  	ihold(inode);	/* New dentry reference */
2956  	dget(dentry);		/* Extra pinning count for the created dentry */
2957  	d_instantiate(dentry, inode);
2958  out:
2959  	return ret;
2960  }
2961  
2962  static int shmem_unlink(struct inode *dir, struct dentry *dentry)
2963  {
2964  	struct inode *inode = d_inode(dentry);
2965  
2966  	if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
2967  		shmem_free_inode(inode->i_sb);
2968  
2969  	dir->i_size -= BOGO_DIRENT_SIZE;
2970  	inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
2971  	drop_nlink(inode);
2972  	dput(dentry);	/* Undo the count from "create" - this does all the work */
2973  	return 0;
2974  }
2975  
2976  static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
2977  {
2978  	if (!simple_empty(dentry))
2979  		return -ENOTEMPTY;
2980  
2981  	drop_nlink(d_inode(dentry));
2982  	drop_nlink(dir);
2983  	return shmem_unlink(dir, dentry);
2984  }
2985  
2986  static int shmem_exchange(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
2987  {
2988  	bool old_is_dir = d_is_dir(old_dentry);
2989  	bool new_is_dir = d_is_dir(new_dentry);
2990  
2991  	if (old_dir != new_dir && old_is_dir != new_is_dir) {
2992  		if (old_is_dir) {
2993  			drop_nlink(old_dir);
2994  			inc_nlink(new_dir);
2995  		} else {
2996  			drop_nlink(new_dir);
2997  			inc_nlink(old_dir);
2998  		}
2999  	}
3000  	old_dir->i_ctime = old_dir->i_mtime =
3001  	new_dir->i_ctime = new_dir->i_mtime =
3002  	d_inode(old_dentry)->i_ctime =
3003  	d_inode(new_dentry)->i_ctime = current_time(old_dir);
3004  
3005  	return 0;
3006  }
3007  
3008  static int shmem_whiteout(struct user_namespace *mnt_userns,
3009  			  struct inode *old_dir, struct dentry *old_dentry)
3010  {
3011  	struct dentry *whiteout;
3012  	int error;
3013  
3014  	whiteout = d_alloc(old_dentry->d_parent, &old_dentry->d_name);
3015  	if (!whiteout)
3016  		return -ENOMEM;
3017  
3018  	error = shmem_mknod(&init_user_ns, old_dir, whiteout,
3019  			    S_IFCHR | WHITEOUT_MODE, WHITEOUT_DEV);
3020  	dput(whiteout);
3021  	if (error)
3022  		return error;
3023  
3024  	/*
3025  	 * Cheat and hash the whiteout while the old dentry is still in
3026  	 * place, instead of playing games with FS_RENAME_DOES_D_MOVE.
3027  	 *
3028  	 * d_lookup() will consistently find one of them at this point,
3029  	 * not sure which one, but that isn't even important.
3030  	 */
3031  	d_rehash(whiteout);
3032  	return 0;
3033  }
3034  
3035  /*
3036   * The VFS layer already does all the dentry stuff for rename,
3037   * we just have to decrement the usage count for the target if
3038   * it exists so that the VFS layer correctly free's it when it
3039   * gets overwritten.
3040   */
3041  static int shmem_rename2(struct user_namespace *mnt_userns,
3042  			 struct inode *old_dir, struct dentry *old_dentry,
3043  			 struct inode *new_dir, struct dentry *new_dentry,
3044  			 unsigned int flags)
3045  {
3046  	struct inode *inode = d_inode(old_dentry);
3047  	int they_are_dirs = S_ISDIR(inode->i_mode);
3048  
3049  	if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
3050  		return -EINVAL;
3051  
3052  	if (flags & RENAME_EXCHANGE)
3053  		return shmem_exchange(old_dir, old_dentry, new_dir, new_dentry);
3054  
3055  	if (!simple_empty(new_dentry))
3056  		return -ENOTEMPTY;
3057  
3058  	if (flags & RENAME_WHITEOUT) {
3059  		int error;
3060  
3061  		error = shmem_whiteout(&init_user_ns, old_dir, old_dentry);
3062  		if (error)
3063  			return error;
3064  	}
3065  
3066  	if (d_really_is_positive(new_dentry)) {
3067  		(void) shmem_unlink(new_dir, new_dentry);
3068  		if (they_are_dirs) {
3069  			drop_nlink(d_inode(new_dentry));
3070  			drop_nlink(old_dir);
3071  		}
3072  	} else if (they_are_dirs) {
3073  		drop_nlink(old_dir);
3074  		inc_nlink(new_dir);
3075  	}
3076  
3077  	old_dir->i_size -= BOGO_DIRENT_SIZE;
3078  	new_dir->i_size += BOGO_DIRENT_SIZE;
3079  	old_dir->i_ctime = old_dir->i_mtime =
3080  	new_dir->i_ctime = new_dir->i_mtime =
3081  	inode->i_ctime = current_time(old_dir);
3082  	return 0;
3083  }
3084  
3085  static int shmem_symlink(struct user_namespace *mnt_userns, struct inode *dir,
3086  			 struct dentry *dentry, const char *symname)
3087  {
3088  	int error;
3089  	int len;
3090  	struct inode *inode;
3091  	struct page *page;
3092  
3093  	len = strlen(symname) + 1;
3094  	if (len > PAGE_SIZE)
3095  		return -ENAMETOOLONG;
3096  
3097  	inode = shmem_get_inode(dir->i_sb, dir, S_IFLNK | 0777, 0,
3098  				VM_NORESERVE);
3099  	if (!inode)
3100  		return -ENOSPC;
3101  
3102  	error = security_inode_init_security(inode, dir, &dentry->d_name,
3103  					     shmem_initxattrs, NULL);
3104  	if (error && error != -EOPNOTSUPP) {
3105  		iput(inode);
3106  		return error;
3107  	}
3108  
3109  	inode->i_size = len-1;
3110  	if (len <= SHORT_SYMLINK_LEN) {
3111  		inode->i_link = kmemdup(symname, len, GFP_KERNEL);
3112  		if (!inode->i_link) {
3113  			iput(inode);
3114  			return -ENOMEM;
3115  		}
3116  		inode->i_op = &shmem_short_symlink_operations;
3117  	} else {
3118  		inode_nohighmem(inode);
3119  		error = shmem_getpage(inode, 0, &page, SGP_WRITE);
3120  		if (error) {
3121  			iput(inode);
3122  			return error;
3123  		}
3124  		inode->i_mapping->a_ops = &shmem_aops;
3125  		inode->i_op = &shmem_symlink_inode_operations;
3126  		memcpy(page_address(page), symname, len);
3127  		SetPageUptodate(page);
3128  		set_page_dirty(page);
3129  		unlock_page(page);
3130  		put_page(page);
3131  	}
3132  	dir->i_size += BOGO_DIRENT_SIZE;
3133  	dir->i_ctime = dir->i_mtime = current_time(dir);
3134  	d_instantiate(dentry, inode);
3135  	dget(dentry);
3136  	return 0;
3137  }
3138  
3139  static void shmem_put_link(void *arg)
3140  {
3141  	mark_page_accessed(arg);
3142  	put_page(arg);
3143  }
3144  
3145  static const char *shmem_get_link(struct dentry *dentry,
3146  				  struct inode *inode,
3147  				  struct delayed_call *done)
3148  {
3149  	struct page *page = NULL;
3150  	int error;
3151  	if (!dentry) {
3152  		page = find_get_page(inode->i_mapping, 0);
3153  		if (!page)
3154  			return ERR_PTR(-ECHILD);
3155  		if (!PageUptodate(page)) {
3156  			put_page(page);
3157  			return ERR_PTR(-ECHILD);
3158  		}
3159  	} else {
3160  		error = shmem_getpage(inode, 0, &page, SGP_READ);
3161  		if (error)
3162  			return ERR_PTR(error);
3163  		unlock_page(page);
3164  	}
3165  	set_delayed_call(done, shmem_put_link, page);
3166  	return page_address(page);
3167  }
3168  
3169  #ifdef CONFIG_TMPFS_XATTR
3170  /*
3171   * Superblocks without xattr inode operations may get some security.* xattr
3172   * support from the LSM "for free". As soon as we have any other xattrs
3173   * like ACLs, we also need to implement the security.* handlers at
3174   * filesystem level, though.
3175   */
3176  
3177  /*
3178   * Callback for security_inode_init_security() for acquiring xattrs.
3179   */
3180  static int shmem_initxattrs(struct inode *inode,
3181  			    const struct xattr *xattr_array,
3182  			    void *fs_info)
3183  {
3184  	struct shmem_inode_info *info = SHMEM_I(inode);
3185  	const struct xattr *xattr;
3186  	struct simple_xattr *new_xattr;
3187  	size_t len;
3188  
3189  	for (xattr = xattr_array; xattr->name != NULL; xattr++) {
3190  		new_xattr = simple_xattr_alloc(xattr->value, xattr->value_len);
3191  		if (!new_xattr)
3192  			return -ENOMEM;
3193  
3194  		len = strlen(xattr->name) + 1;
3195  		new_xattr->name = kmalloc(XATTR_SECURITY_PREFIX_LEN + len,
3196  					  GFP_KERNEL);
3197  		if (!new_xattr->name) {
3198  			kvfree(new_xattr);
3199  			return -ENOMEM;
3200  		}
3201  
3202  		memcpy(new_xattr->name, XATTR_SECURITY_PREFIX,
3203  		       XATTR_SECURITY_PREFIX_LEN);
3204  		memcpy(new_xattr->name + XATTR_SECURITY_PREFIX_LEN,
3205  		       xattr->name, len);
3206  
3207  		simple_xattr_list_add(&info->xattrs, new_xattr);
3208  	}
3209  
3210  	return 0;
3211  }
3212  
3213  static int shmem_xattr_handler_get(const struct xattr_handler *handler,
3214  				   struct dentry *unused, struct inode *inode,
3215  				   const char *name, void *buffer, size_t size)
3216  {
3217  	struct shmem_inode_info *info = SHMEM_I(inode);
3218  
3219  	name = xattr_full_name(handler, name);
3220  	return simple_xattr_get(&info->xattrs, name, buffer, size);
3221  }
3222  
3223  static int shmem_xattr_handler_set(const struct xattr_handler *handler,
3224  				   struct user_namespace *mnt_userns,
3225  				   struct dentry *unused, struct inode *inode,
3226  				   const char *name, const void *value,
3227  				   size_t size, int flags)
3228  {
3229  	struct shmem_inode_info *info = SHMEM_I(inode);
3230  
3231  	name = xattr_full_name(handler, name);
3232  	return simple_xattr_set(&info->xattrs, name, value, size, flags, NULL);
3233  }
3234  
3235  static const struct xattr_handler shmem_security_xattr_handler = {
3236  	.prefix = XATTR_SECURITY_PREFIX,
3237  	.get = shmem_xattr_handler_get,
3238  	.set = shmem_xattr_handler_set,
3239  };
3240  
3241  static const struct xattr_handler shmem_trusted_xattr_handler = {
3242  	.prefix = XATTR_TRUSTED_PREFIX,
3243  	.get = shmem_xattr_handler_get,
3244  	.set = shmem_xattr_handler_set,
3245  };
3246  
3247  static const struct xattr_handler *shmem_xattr_handlers[] = {
3248  #ifdef CONFIG_TMPFS_POSIX_ACL
3249  	&posix_acl_access_xattr_handler,
3250  	&posix_acl_default_xattr_handler,
3251  #endif
3252  	&shmem_security_xattr_handler,
3253  	&shmem_trusted_xattr_handler,
3254  	NULL
3255  };
3256  
3257  static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t size)
3258  {
3259  	struct shmem_inode_info *info = SHMEM_I(d_inode(dentry));
3260  	return simple_xattr_list(d_inode(dentry), &info->xattrs, buffer, size);
3261  }
3262  #endif /* CONFIG_TMPFS_XATTR */
3263  
3264  static const struct inode_operations shmem_short_symlink_operations = {
3265  	.get_link	= simple_get_link,
3266  #ifdef CONFIG_TMPFS_XATTR
3267  	.listxattr	= shmem_listxattr,
3268  #endif
3269  };
3270  
3271  static const struct inode_operations shmem_symlink_inode_operations = {
3272  	.get_link	= shmem_get_link,
3273  #ifdef CONFIG_TMPFS_XATTR
3274  	.listxattr	= shmem_listxattr,
3275  #endif
3276  };
3277  
3278  static struct dentry *shmem_get_parent(struct dentry *child)
3279  {
3280  	return ERR_PTR(-ESTALE);
3281  }
3282  
3283  static int shmem_match(struct inode *ino, void *vfh)
3284  {
3285  	__u32 *fh = vfh;
3286  	__u64 inum = fh[2];
3287  	inum = (inum << 32) | fh[1];
3288  	return ino->i_ino == inum && fh[0] == ino->i_generation;
3289  }
3290  
3291  /* Find any alias of inode, but prefer a hashed alias */
3292  static struct dentry *shmem_find_alias(struct inode *inode)
3293  {
3294  	struct dentry *alias = d_find_alias(inode);
3295  
3296  	return alias ?: d_find_any_alias(inode);
3297  }
3298  
3299  
3300  static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
3301  		struct fid *fid, int fh_len, int fh_type)
3302  {
3303  	struct inode *inode;
3304  	struct dentry *dentry = NULL;
3305  	u64 inum;
3306  
3307  	if (fh_len < 3)
3308  		return NULL;
3309  
3310  	inum = fid->raw[2];
3311  	inum = (inum << 32) | fid->raw[1];
3312  
3313  	inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
3314  			shmem_match, fid->raw);
3315  	if (inode) {
3316  		dentry = shmem_find_alias(inode);
3317  		iput(inode);
3318  	}
3319  
3320  	return dentry;
3321  }
3322  
3323  static int shmem_encode_fh(struct inode *inode, __u32 *fh, int *len,
3324  				struct inode *parent)
3325  {
3326  	if (*len < 3) {
3327  		*len = 3;
3328  		return FILEID_INVALID;
3329  	}
3330  
3331  	if (inode_unhashed(inode)) {
3332  		/* Unfortunately insert_inode_hash is not idempotent,
3333  		 * so as we hash inodes here rather than at creation
3334  		 * time, we need a lock to ensure we only try
3335  		 * to do it once
3336  		 */
3337  		static DEFINE_SPINLOCK(lock);
3338  		spin_lock(&lock);
3339  		if (inode_unhashed(inode))
3340  			__insert_inode_hash(inode,
3341  					    inode->i_ino + inode->i_generation);
3342  		spin_unlock(&lock);
3343  	}
3344  
3345  	fh[0] = inode->i_generation;
3346  	fh[1] = inode->i_ino;
3347  	fh[2] = ((__u64)inode->i_ino) >> 32;
3348  
3349  	*len = 3;
3350  	return 1;
3351  }
3352  
3353  static const struct export_operations shmem_export_ops = {
3354  	.get_parent     = shmem_get_parent,
3355  	.encode_fh      = shmem_encode_fh,
3356  	.fh_to_dentry	= shmem_fh_to_dentry,
3357  };
3358  
3359  enum shmem_param {
3360  	Opt_gid,
3361  	Opt_huge,
3362  	Opt_mode,
3363  	Opt_mpol,
3364  	Opt_nr_blocks,
3365  	Opt_nr_inodes,
3366  	Opt_size,
3367  	Opt_uid,
3368  	Opt_inode32,
3369  	Opt_inode64,
3370  };
3371  
3372  static const struct constant_table shmem_param_enums_huge[] = {
3373  	{"never",	SHMEM_HUGE_NEVER },
3374  	{"always",	SHMEM_HUGE_ALWAYS },
3375  	{"within_size",	SHMEM_HUGE_WITHIN_SIZE },
3376  	{"advise",	SHMEM_HUGE_ADVISE },
3377  	{}
3378  };
3379  
3380  const struct fs_parameter_spec shmem_fs_parameters[] = {
3381  	fsparam_u32   ("gid",		Opt_gid),
3382  	fsparam_enum  ("huge",		Opt_huge,  shmem_param_enums_huge),
3383  	fsparam_u32oct("mode",		Opt_mode),
3384  	fsparam_string("mpol",		Opt_mpol),
3385  	fsparam_string("nr_blocks",	Opt_nr_blocks),
3386  	fsparam_string("nr_inodes",	Opt_nr_inodes),
3387  	fsparam_string("size",		Opt_size),
3388  	fsparam_u32   ("uid",		Opt_uid),
3389  	fsparam_flag  ("inode32",	Opt_inode32),
3390  	fsparam_flag  ("inode64",	Opt_inode64),
3391  	{}
3392  };
3393  
3394  static int shmem_parse_one(struct fs_context *fc, struct fs_parameter *param)
3395  {
3396  	struct shmem_options *ctx = fc->fs_private;
3397  	struct fs_parse_result result;
3398  	unsigned long long size;
3399  	char *rest;
3400  	int opt;
3401  
3402  	opt = fs_parse(fc, shmem_fs_parameters, param, &result);
3403  	if (opt < 0)
3404  		return opt;
3405  
3406  	switch (opt) {
3407  	case Opt_size:
3408  		size = memparse(param->string, &rest);
3409  		if (*rest == '%') {
3410  			size <<= PAGE_SHIFT;
3411  			size *= totalram_pages();
3412  			do_div(size, 100);
3413  			rest++;
3414  		}
3415  		if (*rest)
3416  			goto bad_value;
3417  		ctx->blocks = DIV_ROUND_UP(size, PAGE_SIZE);
3418  		ctx->seen |= SHMEM_SEEN_BLOCKS;
3419  		break;
3420  	case Opt_nr_blocks:
3421  		ctx->blocks = memparse(param->string, &rest);
3422  		if (*rest)
3423  			goto bad_value;
3424  		ctx->seen |= SHMEM_SEEN_BLOCKS;
3425  		break;
3426  	case Opt_nr_inodes:
3427  		ctx->inodes = memparse(param->string, &rest);
3428  		if (*rest)
3429  			goto bad_value;
3430  		ctx->seen |= SHMEM_SEEN_INODES;
3431  		break;
3432  	case Opt_mode:
3433  		ctx->mode = result.uint_32 & 07777;
3434  		break;
3435  	case Opt_uid:
3436  		ctx->uid = make_kuid(current_user_ns(), result.uint_32);
3437  		if (!uid_valid(ctx->uid))
3438  			goto bad_value;
3439  		break;
3440  	case Opt_gid:
3441  		ctx->gid = make_kgid(current_user_ns(), result.uint_32);
3442  		if (!gid_valid(ctx->gid))
3443  			goto bad_value;
3444  		break;
3445  	case Opt_huge:
3446  		ctx->huge = result.uint_32;
3447  		if (ctx->huge != SHMEM_HUGE_NEVER &&
3448  		    !(IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
3449  		      has_transparent_hugepage()))
3450  			goto unsupported_parameter;
3451  		ctx->seen |= SHMEM_SEEN_HUGE;
3452  		break;
3453  	case Opt_mpol:
3454  		if (IS_ENABLED(CONFIG_NUMA)) {
3455  			mpol_put(ctx->mpol);
3456  			ctx->mpol = NULL;
3457  			if (mpol_parse_str(param->string, &ctx->mpol))
3458  				goto bad_value;
3459  			break;
3460  		}
3461  		goto unsupported_parameter;
3462  	case Opt_inode32:
3463  		ctx->full_inums = false;
3464  		ctx->seen |= SHMEM_SEEN_INUMS;
3465  		break;
3466  	case Opt_inode64:
3467  		if (sizeof(ino_t) < 8) {
3468  			return invalfc(fc,
3469  				       "Cannot use inode64 with <64bit inums in kernel\n");
3470  		}
3471  		ctx->full_inums = true;
3472  		ctx->seen |= SHMEM_SEEN_INUMS;
3473  		break;
3474  	}
3475  	return 0;
3476  
3477  unsupported_parameter:
3478  	return invalfc(fc, "Unsupported parameter '%s'", param->key);
3479  bad_value:
3480  	return invalfc(fc, "Bad value for '%s'", param->key);
3481  }
3482  
3483  static int shmem_parse_options(struct fs_context *fc, void *data)
3484  {
3485  	char *options = data;
3486  
3487  	if (options) {
3488  		int err = security_sb_eat_lsm_opts(options, &fc->security);
3489  		if (err)
3490  			return err;
3491  	}
3492  
3493  	while (options != NULL) {
3494  		char *this_char = options;
3495  		for (;;) {
3496  			/*
3497  			 * NUL-terminate this option: unfortunately,
3498  			 * mount options form a comma-separated list,
3499  			 * but mpol's nodelist may also contain commas.
3500  			 */
3501  			options = strchr(options, ',');
3502  			if (options == NULL)
3503  				break;
3504  			options++;
3505  			if (!isdigit(*options)) {
3506  				options[-1] = '\0';
3507  				break;
3508  			}
3509  		}
3510  		if (*this_char) {
3511  			char *value = strchr(this_char, '=');
3512  			size_t len = 0;
3513  			int err;
3514  
3515  			if (value) {
3516  				*value++ = '\0';
3517  				len = strlen(value);
3518  			}
3519  			err = vfs_parse_fs_string(fc, this_char, value, len);
3520  			if (err < 0)
3521  				return err;
3522  		}
3523  	}
3524  	return 0;
3525  }
3526  
3527  /*
3528   * Reconfigure a shmem filesystem.
3529   *
3530   * Note that we disallow change from limited->unlimited blocks/inodes while any
3531   * are in use; but we must separately disallow unlimited->limited, because in
3532   * that case we have no record of how much is already in use.
3533   */
3534  static int shmem_reconfigure(struct fs_context *fc)
3535  {
3536  	struct shmem_options *ctx = fc->fs_private;
3537  	struct shmem_sb_info *sbinfo = SHMEM_SB(fc->root->d_sb);
3538  	unsigned long inodes;
3539  	const char *err;
3540  
3541  	spin_lock(&sbinfo->stat_lock);
3542  	inodes = sbinfo->max_inodes - sbinfo->free_inodes;
3543  	if ((ctx->seen & SHMEM_SEEN_BLOCKS) && ctx->blocks) {
3544  		if (!sbinfo->max_blocks) {
3545  			err = "Cannot retroactively limit size";
3546  			goto out;
3547  		}
3548  		if (percpu_counter_compare(&sbinfo->used_blocks,
3549  					   ctx->blocks) > 0) {
3550  			err = "Too small a size for current use";
3551  			goto out;
3552  		}
3553  	}
3554  	if ((ctx->seen & SHMEM_SEEN_INODES) && ctx->inodes) {
3555  		if (!sbinfo->max_inodes) {
3556  			err = "Cannot retroactively limit inodes";
3557  			goto out;
3558  		}
3559  		if (ctx->inodes < inodes) {
3560  			err = "Too few inodes for current use";
3561  			goto out;
3562  		}
3563  	}
3564  
3565  	if ((ctx->seen & SHMEM_SEEN_INUMS) && !ctx->full_inums &&
3566  	    sbinfo->next_ino > UINT_MAX) {
3567  		err = "Current inum too high to switch to 32-bit inums";
3568  		goto out;
3569  	}
3570  
3571  	if (ctx->seen & SHMEM_SEEN_HUGE)
3572  		sbinfo->huge = ctx->huge;
3573  	if (ctx->seen & SHMEM_SEEN_INUMS)
3574  		sbinfo->full_inums = ctx->full_inums;
3575  	if (ctx->seen & SHMEM_SEEN_BLOCKS)
3576  		sbinfo->max_blocks  = ctx->blocks;
3577  	if (ctx->seen & SHMEM_SEEN_INODES) {
3578  		sbinfo->max_inodes  = ctx->inodes;
3579  		sbinfo->free_inodes = ctx->inodes - inodes;
3580  	}
3581  
3582  	/*
3583  	 * Preserve previous mempolicy unless mpol remount option was specified.
3584  	 */
3585  	if (ctx->mpol) {
3586  		mpol_put(sbinfo->mpol);
3587  		sbinfo->mpol = ctx->mpol;	/* transfers initial ref */
3588  		ctx->mpol = NULL;
3589  	}
3590  	spin_unlock(&sbinfo->stat_lock);
3591  	return 0;
3592  out:
3593  	spin_unlock(&sbinfo->stat_lock);
3594  	return invalfc(fc, "%s", err);
3595  }
3596  
3597  static int shmem_show_options(struct seq_file *seq, struct dentry *root)
3598  {
3599  	struct shmem_sb_info *sbinfo = SHMEM_SB(root->d_sb);
3600  
3601  	if (sbinfo->max_blocks != shmem_default_max_blocks())
3602  		seq_printf(seq, ",size=%luk",
3603  			sbinfo->max_blocks << (PAGE_SHIFT - 10));
3604  	if (sbinfo->max_inodes != shmem_default_max_inodes())
3605  		seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
3606  	if (sbinfo->mode != (0777 | S_ISVTX))
3607  		seq_printf(seq, ",mode=%03ho", sbinfo->mode);
3608  	if (!uid_eq(sbinfo->uid, GLOBAL_ROOT_UID))
3609  		seq_printf(seq, ",uid=%u",
3610  				from_kuid_munged(&init_user_ns, sbinfo->uid));
3611  	if (!gid_eq(sbinfo->gid, GLOBAL_ROOT_GID))
3612  		seq_printf(seq, ",gid=%u",
3613  				from_kgid_munged(&init_user_ns, sbinfo->gid));
3614  
3615  	/*
3616  	 * Showing inode{64,32} might be useful even if it's the system default,
3617  	 * since then people don't have to resort to checking both here and
3618  	 * /proc/config.gz to confirm 64-bit inums were successfully applied
3619  	 * (which may not even exist if IKCONFIG_PROC isn't enabled).
3620  	 *
3621  	 * We hide it when inode64 isn't the default and we are using 32-bit
3622  	 * inodes, since that probably just means the feature isn't even under
3623  	 * consideration.
3624  	 *
3625  	 * As such:
3626  	 *
3627  	 *                     +-----------------+-----------------+
3628  	 *                     | TMPFS_INODE64=y | TMPFS_INODE64=n |
3629  	 *  +------------------+-----------------+-----------------+
3630  	 *  | full_inums=true  | show            | show            |
3631  	 *  | full_inums=false | show            | hide            |
3632  	 *  +------------------+-----------------+-----------------+
3633  	 *
3634  	 */
3635  	if (IS_ENABLED(CONFIG_TMPFS_INODE64) || sbinfo->full_inums)
3636  		seq_printf(seq, ",inode%d", (sbinfo->full_inums ? 64 : 32));
3637  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
3638  	/* Rightly or wrongly, show huge mount option unmasked by shmem_huge */
3639  	if (sbinfo->huge)
3640  		seq_printf(seq, ",huge=%s", shmem_format_huge(sbinfo->huge));
3641  #endif
3642  	shmem_show_mpol(seq, sbinfo->mpol);
3643  	return 0;
3644  }
3645  
3646  #endif /* CONFIG_TMPFS */
3647  
3648  static void shmem_put_super(struct super_block *sb)
3649  {
3650  	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
3651  
3652  	free_percpu(sbinfo->ino_batch);
3653  	percpu_counter_destroy(&sbinfo->used_blocks);
3654  	mpol_put(sbinfo->mpol);
3655  	kfree(sbinfo);
3656  	sb->s_fs_info = NULL;
3657  }
3658  
3659  static int shmem_fill_super(struct super_block *sb, struct fs_context *fc)
3660  {
3661  	struct shmem_options *ctx = fc->fs_private;
3662  	struct inode *inode;
3663  	struct shmem_sb_info *sbinfo;
3664  	int err = -ENOMEM;
3665  
3666  	/* Round up to L1_CACHE_BYTES to resist false sharing */
3667  	sbinfo = kzalloc(max((int)sizeof(struct shmem_sb_info),
3668  				L1_CACHE_BYTES), GFP_KERNEL);
3669  	if (!sbinfo)
3670  		return -ENOMEM;
3671  
3672  	sb->s_fs_info = sbinfo;
3673  
3674  #ifdef CONFIG_TMPFS
3675  	/*
3676  	 * Per default we only allow half of the physical ram per
3677  	 * tmpfs instance, limiting inodes to one per page of lowmem;
3678  	 * but the internal instance is left unlimited.
3679  	 */
3680  	if (!(sb->s_flags & SB_KERNMOUNT)) {
3681  		if (!(ctx->seen & SHMEM_SEEN_BLOCKS))
3682  			ctx->blocks = shmem_default_max_blocks();
3683  		if (!(ctx->seen & SHMEM_SEEN_INODES))
3684  			ctx->inodes = shmem_default_max_inodes();
3685  		if (!(ctx->seen & SHMEM_SEEN_INUMS))
3686  			ctx->full_inums = IS_ENABLED(CONFIG_TMPFS_INODE64);
3687  	} else {
3688  		sb->s_flags |= SB_NOUSER;
3689  	}
3690  	sb->s_export_op = &shmem_export_ops;
3691  	sb->s_flags |= SB_NOSEC;
3692  #else
3693  	sb->s_flags |= SB_NOUSER;
3694  #endif
3695  	sbinfo->max_blocks = ctx->blocks;
3696  	sbinfo->free_inodes = sbinfo->max_inodes = ctx->inodes;
3697  	if (sb->s_flags & SB_KERNMOUNT) {
3698  		sbinfo->ino_batch = alloc_percpu(ino_t);
3699  		if (!sbinfo->ino_batch)
3700  			goto failed;
3701  	}
3702  	sbinfo->uid = ctx->uid;
3703  	sbinfo->gid = ctx->gid;
3704  	sbinfo->full_inums = ctx->full_inums;
3705  	sbinfo->mode = ctx->mode;
3706  	sbinfo->huge = ctx->huge;
3707  	sbinfo->mpol = ctx->mpol;
3708  	ctx->mpol = NULL;
3709  
3710  	spin_lock_init(&sbinfo->stat_lock);
3711  	if (percpu_counter_init(&sbinfo->used_blocks, 0, GFP_KERNEL))
3712  		goto failed;
3713  	spin_lock_init(&sbinfo->shrinklist_lock);
3714  	INIT_LIST_HEAD(&sbinfo->shrinklist);
3715  
3716  	sb->s_maxbytes = MAX_LFS_FILESIZE;
3717  	sb->s_blocksize = PAGE_SIZE;
3718  	sb->s_blocksize_bits = PAGE_SHIFT;
3719  	sb->s_magic = TMPFS_MAGIC;
3720  	sb->s_op = &shmem_ops;
3721  	sb->s_time_gran = 1;
3722  #ifdef CONFIG_TMPFS_XATTR
3723  	sb->s_xattr = shmem_xattr_handlers;
3724  #endif
3725  #ifdef CONFIG_TMPFS_POSIX_ACL
3726  	sb->s_flags |= SB_POSIXACL;
3727  #endif
3728  	uuid_gen(&sb->s_uuid);
3729  
3730  	inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
3731  	if (!inode)
3732  		goto failed;
3733  	inode->i_uid = sbinfo->uid;
3734  	inode->i_gid = sbinfo->gid;
3735  	sb->s_root = d_make_root(inode);
3736  	if (!sb->s_root)
3737  		goto failed;
3738  	return 0;
3739  
3740  failed:
3741  	shmem_put_super(sb);
3742  	return err;
3743  }
3744  
3745  static int shmem_get_tree(struct fs_context *fc)
3746  {
3747  	return get_tree_nodev(fc, shmem_fill_super);
3748  }
3749  
3750  static void shmem_free_fc(struct fs_context *fc)
3751  {
3752  	struct shmem_options *ctx = fc->fs_private;
3753  
3754  	if (ctx) {
3755  		mpol_put(ctx->mpol);
3756  		kfree(ctx);
3757  	}
3758  }
3759  
3760  static const struct fs_context_operations shmem_fs_context_ops = {
3761  	.free			= shmem_free_fc,
3762  	.get_tree		= shmem_get_tree,
3763  #ifdef CONFIG_TMPFS
3764  	.parse_monolithic	= shmem_parse_options,
3765  	.parse_param		= shmem_parse_one,
3766  	.reconfigure		= shmem_reconfigure,
3767  #endif
3768  };
3769  
3770  static struct kmem_cache *shmem_inode_cachep;
3771  
3772  static struct inode *shmem_alloc_inode(struct super_block *sb)
3773  {
3774  	struct shmem_inode_info *info;
3775  	info = kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
3776  	if (!info)
3777  		return NULL;
3778  	return &info->vfs_inode;
3779  }
3780  
3781  static void shmem_free_in_core_inode(struct inode *inode)
3782  {
3783  	if (S_ISLNK(inode->i_mode))
3784  		kfree(inode->i_link);
3785  	kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
3786  }
3787  
3788  static void shmem_destroy_inode(struct inode *inode)
3789  {
3790  	if (S_ISREG(inode->i_mode))
3791  		mpol_free_shared_policy(&SHMEM_I(inode)->policy);
3792  }
3793  
3794  static void shmem_init_inode(void *foo)
3795  {
3796  	struct shmem_inode_info *info = foo;
3797  	inode_init_once(&info->vfs_inode);
3798  }
3799  
3800  static void shmem_init_inodecache(void)
3801  {
3802  	shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
3803  				sizeof(struct shmem_inode_info),
3804  				0, SLAB_PANIC|SLAB_ACCOUNT, shmem_init_inode);
3805  }
3806  
3807  static void shmem_destroy_inodecache(void)
3808  {
3809  	kmem_cache_destroy(shmem_inode_cachep);
3810  }
3811  
3812  const struct address_space_operations shmem_aops = {
3813  	.writepage	= shmem_writepage,
3814  	.set_page_dirty	= __set_page_dirty_no_writeback,
3815  #ifdef CONFIG_TMPFS
3816  	.write_begin	= shmem_write_begin,
3817  	.write_end	= shmem_write_end,
3818  #endif
3819  #ifdef CONFIG_MIGRATION
3820  	.migratepage	= migrate_page,
3821  #endif
3822  	.error_remove_page = generic_error_remove_page,
3823  };
3824  EXPORT_SYMBOL(shmem_aops);
3825  
3826  static const struct file_operations shmem_file_operations = {
3827  	.mmap		= shmem_mmap,
3828  	.get_unmapped_area = shmem_get_unmapped_area,
3829  #ifdef CONFIG_TMPFS
3830  	.llseek		= shmem_file_llseek,
3831  	.read_iter	= shmem_file_read_iter,
3832  	.write_iter	= generic_file_write_iter,
3833  	.fsync		= noop_fsync,
3834  	.splice_read	= generic_file_splice_read,
3835  	.splice_write	= iter_file_splice_write,
3836  	.fallocate	= shmem_fallocate,
3837  #endif
3838  };
3839  
3840  static const struct inode_operations shmem_inode_operations = {
3841  	.getattr	= shmem_getattr,
3842  	.setattr	= shmem_setattr,
3843  #ifdef CONFIG_TMPFS_XATTR
3844  	.listxattr	= shmem_listxattr,
3845  	.set_acl	= simple_set_acl,
3846  #endif
3847  };
3848  
3849  static const struct inode_operations shmem_dir_inode_operations = {
3850  #ifdef CONFIG_TMPFS
3851  	.create		= shmem_create,
3852  	.lookup		= simple_lookup,
3853  	.link		= shmem_link,
3854  	.unlink		= shmem_unlink,
3855  	.symlink	= shmem_symlink,
3856  	.mkdir		= shmem_mkdir,
3857  	.rmdir		= shmem_rmdir,
3858  	.mknod		= shmem_mknod,
3859  	.rename		= shmem_rename2,
3860  	.tmpfile	= shmem_tmpfile,
3861  #endif
3862  #ifdef CONFIG_TMPFS_XATTR
3863  	.listxattr	= shmem_listxattr,
3864  #endif
3865  #ifdef CONFIG_TMPFS_POSIX_ACL
3866  	.setattr	= shmem_setattr,
3867  	.set_acl	= simple_set_acl,
3868  #endif
3869  };
3870  
3871  static const struct inode_operations shmem_special_inode_operations = {
3872  #ifdef CONFIG_TMPFS_XATTR
3873  	.listxattr	= shmem_listxattr,
3874  #endif
3875  #ifdef CONFIG_TMPFS_POSIX_ACL
3876  	.setattr	= shmem_setattr,
3877  	.set_acl	= simple_set_acl,
3878  #endif
3879  };
3880  
3881  static const struct super_operations shmem_ops = {
3882  	.alloc_inode	= shmem_alloc_inode,
3883  	.free_inode	= shmem_free_in_core_inode,
3884  	.destroy_inode	= shmem_destroy_inode,
3885  #ifdef CONFIG_TMPFS
3886  	.statfs		= shmem_statfs,
3887  	.show_options	= shmem_show_options,
3888  #endif
3889  	.evict_inode	= shmem_evict_inode,
3890  	.drop_inode	= generic_delete_inode,
3891  	.put_super	= shmem_put_super,
3892  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
3893  	.nr_cached_objects	= shmem_unused_huge_count,
3894  	.free_cached_objects	= shmem_unused_huge_scan,
3895  #endif
3896  };
3897  
3898  static const struct vm_operations_struct shmem_vm_ops = {
3899  	.fault		= shmem_fault,
3900  	.map_pages	= filemap_map_pages,
3901  #ifdef CONFIG_NUMA
3902  	.set_policy     = shmem_set_policy,
3903  	.get_policy     = shmem_get_policy,
3904  #endif
3905  };
3906  
3907  int shmem_init_fs_context(struct fs_context *fc)
3908  {
3909  	struct shmem_options *ctx;
3910  
3911  	ctx = kzalloc(sizeof(struct shmem_options), GFP_KERNEL);
3912  	if (!ctx)
3913  		return -ENOMEM;
3914  
3915  	ctx->mode = 0777 | S_ISVTX;
3916  	ctx->uid = current_fsuid();
3917  	ctx->gid = current_fsgid();
3918  
3919  	fc->fs_private = ctx;
3920  	fc->ops = &shmem_fs_context_ops;
3921  	return 0;
3922  }
3923  
3924  static struct file_system_type shmem_fs_type = {
3925  	.owner		= THIS_MODULE,
3926  	.name		= "tmpfs",
3927  	.init_fs_context = shmem_init_fs_context,
3928  #ifdef CONFIG_TMPFS
3929  	.parameters	= shmem_fs_parameters,
3930  #endif
3931  	.kill_sb	= kill_litter_super,
3932  	.fs_flags	= FS_USERNS_MOUNT | FS_THP_SUPPORT,
3933  };
3934  
3935  int __init shmem_init(void)
3936  {
3937  	int error;
3938  
3939  	shmem_init_inodecache();
3940  
3941  	error = register_filesystem(&shmem_fs_type);
3942  	if (error) {
3943  		pr_err("Could not register tmpfs\n");
3944  		goto out2;
3945  	}
3946  
3947  	shm_mnt = kern_mount(&shmem_fs_type);
3948  	if (IS_ERR(shm_mnt)) {
3949  		error = PTR_ERR(shm_mnt);
3950  		pr_err("Could not kern_mount tmpfs\n");
3951  		goto out1;
3952  	}
3953  
3954  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
3955  	if (has_transparent_hugepage() && shmem_huge > SHMEM_HUGE_DENY)
3956  		SHMEM_SB(shm_mnt->mnt_sb)->huge = shmem_huge;
3957  	else
3958  		shmem_huge = 0; /* just in case it was patched */
3959  #endif
3960  	return 0;
3961  
3962  out1:
3963  	unregister_filesystem(&shmem_fs_type);
3964  out2:
3965  	shmem_destroy_inodecache();
3966  	shm_mnt = ERR_PTR(error);
3967  	return error;
3968  }
3969  
3970  #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && defined(CONFIG_SYSFS)
3971  static ssize_t shmem_enabled_show(struct kobject *kobj,
3972  				  struct kobj_attribute *attr, char *buf)
3973  {
3974  	static const int values[] = {
3975  		SHMEM_HUGE_ALWAYS,
3976  		SHMEM_HUGE_WITHIN_SIZE,
3977  		SHMEM_HUGE_ADVISE,
3978  		SHMEM_HUGE_NEVER,
3979  		SHMEM_HUGE_DENY,
3980  		SHMEM_HUGE_FORCE,
3981  	};
3982  	int len = 0;
3983  	int i;
3984  
3985  	for (i = 0; i < ARRAY_SIZE(values); i++) {
3986  		len += sysfs_emit_at(buf, len,
3987  				     shmem_huge == values[i] ? "%s[%s]" : "%s%s",
3988  				     i ? " " : "",
3989  				     shmem_format_huge(values[i]));
3990  	}
3991  
3992  	len += sysfs_emit_at(buf, len, "\n");
3993  
3994  	return len;
3995  }
3996  
3997  static ssize_t shmem_enabled_store(struct kobject *kobj,
3998  		struct kobj_attribute *attr, const char *buf, size_t count)
3999  {
4000  	char tmp[16];
4001  	int huge;
4002  
4003  	if (count + 1 > sizeof(tmp))
4004  		return -EINVAL;
4005  	memcpy(tmp, buf, count);
4006  	tmp[count] = '\0';
4007  	if (count && tmp[count - 1] == '\n')
4008  		tmp[count - 1] = '\0';
4009  
4010  	huge = shmem_parse_huge(tmp);
4011  	if (huge == -EINVAL)
4012  		return -EINVAL;
4013  	if (!has_transparent_hugepage() &&
4014  			huge != SHMEM_HUGE_NEVER && huge != SHMEM_HUGE_DENY)
4015  		return -EINVAL;
4016  
4017  	shmem_huge = huge;
4018  	if (shmem_huge > SHMEM_HUGE_DENY)
4019  		SHMEM_SB(shm_mnt->mnt_sb)->huge = shmem_huge;
4020  	return count;
4021  }
4022  
4023  struct kobj_attribute shmem_enabled_attr =
4024  	__ATTR(shmem_enabled, 0644, shmem_enabled_show, shmem_enabled_store);
4025  #endif /* CONFIG_TRANSPARENT_HUGEPAGE && CONFIG_SYSFS */
4026  
4027  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
4028  bool shmem_huge_enabled(struct vm_area_struct *vma)
4029  {
4030  	struct inode *inode = file_inode(vma->vm_file);
4031  	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
4032  	loff_t i_size;
4033  	pgoff_t off;
4034  
4035  	if ((vma->vm_flags & VM_NOHUGEPAGE) ||
4036  	    test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))
4037  		return false;
4038  	if (shmem_huge == SHMEM_HUGE_FORCE)
4039  		return true;
4040  	if (shmem_huge == SHMEM_HUGE_DENY)
4041  		return false;
4042  	switch (sbinfo->huge) {
4043  		case SHMEM_HUGE_NEVER:
4044  			return false;
4045  		case SHMEM_HUGE_ALWAYS:
4046  			return true;
4047  		case SHMEM_HUGE_WITHIN_SIZE:
4048  			off = round_up(vma->vm_pgoff, HPAGE_PMD_NR);
4049  			i_size = round_up(i_size_read(inode), PAGE_SIZE);
4050  			if (i_size >= HPAGE_PMD_SIZE &&
4051  					i_size >> PAGE_SHIFT >= off)
4052  				return true;
4053  			fallthrough;
4054  		case SHMEM_HUGE_ADVISE:
4055  			/* TODO: implement fadvise() hints */
4056  			return (vma->vm_flags & VM_HUGEPAGE);
4057  		default:
4058  			VM_BUG_ON(1);
4059  			return false;
4060  	}
4061  }
4062  #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
4063  
4064  #else /* !CONFIG_SHMEM */
4065  
4066  /*
4067   * tiny-shmem: simple shmemfs and tmpfs using ramfs code
4068   *
4069   * This is intended for small system where the benefits of the full
4070   * shmem code (swap-backed and resource-limited) are outweighed by
4071   * their complexity. On systems without swap this code should be
4072   * effectively equivalent, but much lighter weight.
4073   */
4074  
4075  static struct file_system_type shmem_fs_type = {
4076  	.name		= "tmpfs",
4077  	.init_fs_context = ramfs_init_fs_context,
4078  	.parameters	= ramfs_fs_parameters,
4079  	.kill_sb	= kill_litter_super,
4080  	.fs_flags	= FS_USERNS_MOUNT,
4081  };
4082  
4083  int __init shmem_init(void)
4084  {
4085  	BUG_ON(register_filesystem(&shmem_fs_type) != 0);
4086  
4087  	shm_mnt = kern_mount(&shmem_fs_type);
4088  	BUG_ON(IS_ERR(shm_mnt));
4089  
4090  	return 0;
4091  }
4092  
4093  int shmem_unuse(unsigned int type, bool frontswap,
4094  		unsigned long *fs_pages_to_unuse)
4095  {
4096  	return 0;
4097  }
4098  
4099  int shmem_lock(struct file *file, int lock, struct user_struct *user)
4100  {
4101  	return 0;
4102  }
4103  
4104  void shmem_unlock_mapping(struct address_space *mapping)
4105  {
4106  }
4107  
4108  #ifdef CONFIG_MMU
4109  unsigned long shmem_get_unmapped_area(struct file *file,
4110  				      unsigned long addr, unsigned long len,
4111  				      unsigned long pgoff, unsigned long flags)
4112  {
4113  	return current->mm->get_unmapped_area(file, addr, len, pgoff, flags);
4114  }
4115  #endif
4116  
4117  void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
4118  {
4119  	truncate_inode_pages_range(inode->i_mapping, lstart, lend);
4120  }
4121  EXPORT_SYMBOL_GPL(shmem_truncate_range);
4122  
4123  #define shmem_vm_ops				generic_file_vm_ops
4124  #define shmem_file_operations			ramfs_file_operations
4125  #define shmem_get_inode(sb, dir, mode, dev, flags)	ramfs_get_inode(sb, dir, mode, dev)
4126  #define shmem_acct_size(flags, size)		0
4127  #define shmem_unacct_size(flags, size)		do {} while (0)
4128  
4129  #endif /* CONFIG_SHMEM */
4130  
4131  /* common code */
4132  
4133  static struct file *__shmem_file_setup(struct vfsmount *mnt, const char *name, loff_t size,
4134  				       unsigned long flags, unsigned int i_flags)
4135  {
4136  	struct inode *inode;
4137  	struct file *res;
4138  
4139  	if (IS_ERR(mnt))
4140  		return ERR_CAST(mnt);
4141  
4142  	if (size < 0 || size > MAX_LFS_FILESIZE)
4143  		return ERR_PTR(-EINVAL);
4144  
4145  	if (shmem_acct_size(flags, size))
4146  		return ERR_PTR(-ENOMEM);
4147  
4148  	inode = shmem_get_inode(mnt->mnt_sb, NULL, S_IFREG | S_IRWXUGO, 0,
4149  				flags);
4150  	if (unlikely(!inode)) {
4151  		shmem_unacct_size(flags, size);
4152  		return ERR_PTR(-ENOSPC);
4153  	}
4154  	inode->i_flags |= i_flags;
4155  	inode->i_size = size;
4156  	clear_nlink(inode);	/* It is unlinked */
4157  	res = ERR_PTR(ramfs_nommu_expand_for_mapping(inode, size));
4158  	if (!IS_ERR(res))
4159  		res = alloc_file_pseudo(inode, mnt, name, O_RDWR,
4160  				&shmem_file_operations);
4161  	if (IS_ERR(res))
4162  		iput(inode);
4163  	return res;
4164  }
4165  
4166  /**
4167   * shmem_kernel_file_setup - get an unlinked file living in tmpfs which must be
4168   * 	kernel internal.  There will be NO LSM permission checks against the
4169   * 	underlying inode.  So users of this interface must do LSM checks at a
4170   *	higher layer.  The users are the big_key and shm implementations.  LSM
4171   *	checks are provided at the key or shm level rather than the inode.
4172   * @name: name for dentry (to be seen in /proc/<pid>/maps
4173   * @size: size to be set for the file
4174   * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
4175   */
4176  struct file *shmem_kernel_file_setup(const char *name, loff_t size, unsigned long flags)
4177  {
4178  	return __shmem_file_setup(shm_mnt, name, size, flags, S_PRIVATE);
4179  }
4180  
4181  /**
4182   * shmem_file_setup - get an unlinked file living in tmpfs
4183   * @name: name for dentry (to be seen in /proc/<pid>/maps
4184   * @size: size to be set for the file
4185   * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
4186   */
4187  struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags)
4188  {
4189  	return __shmem_file_setup(shm_mnt, name, size, flags, 0);
4190  }
4191  EXPORT_SYMBOL_GPL(shmem_file_setup);
4192  
4193  /**
4194   * shmem_file_setup_with_mnt - get an unlinked file living in tmpfs
4195   * @mnt: the tmpfs mount where the file will be created
4196   * @name: name for dentry (to be seen in /proc/<pid>/maps
4197   * @size: size to be set for the file
4198   * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
4199   */
4200  struct file *shmem_file_setup_with_mnt(struct vfsmount *mnt, const char *name,
4201  				       loff_t size, unsigned long flags)
4202  {
4203  	return __shmem_file_setup(mnt, name, size, flags, 0);
4204  }
4205  EXPORT_SYMBOL_GPL(shmem_file_setup_with_mnt);
4206  
4207  /**
4208   * shmem_zero_setup - setup a shared anonymous mapping
4209   * @vma: the vma to be mmapped is prepared by do_mmap
4210   */
4211  int shmem_zero_setup(struct vm_area_struct *vma)
4212  {
4213  	struct file *file;
4214  	loff_t size = vma->vm_end - vma->vm_start;
4215  
4216  	/*
4217  	 * Cloning a new file under mmap_lock leads to a lock ordering conflict
4218  	 * between XFS directory reading and selinux: since this file is only
4219  	 * accessible to the user through its mapping, use S_PRIVATE flag to
4220  	 * bypass file security, in the same way as shmem_kernel_file_setup().
4221  	 */
4222  	file = shmem_kernel_file_setup("dev/zero", size, vma->vm_flags);
4223  	if (IS_ERR(file))
4224  		return PTR_ERR(file);
4225  
4226  	if (vma->vm_file)
4227  		fput(vma->vm_file);
4228  	vma->vm_file = file;
4229  	vma->vm_ops = &shmem_vm_ops;
4230  
4231  	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
4232  			((vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK) <
4233  			(vma->vm_end & HPAGE_PMD_MASK)) {
4234  		khugepaged_enter(vma, vma->vm_flags);
4235  	}
4236  
4237  	return 0;
4238  }
4239  
4240  /**
4241   * shmem_read_mapping_page_gfp - read into page cache, using specified page allocation flags.
4242   * @mapping:	the page's address_space
4243   * @index:	the page index
4244   * @gfp:	the page allocator flags to use if allocating
4245   *
4246   * This behaves as a tmpfs "read_cache_page_gfp(mapping, index, gfp)",
4247   * with any new page allocations done using the specified allocation flags.
4248   * But read_cache_page_gfp() uses the ->readpage() method: which does not
4249   * suit tmpfs, since it may have pages in swapcache, and needs to find those
4250   * for itself; although drivers/gpu/drm i915 and ttm rely upon this support.
4251   *
4252   * i915_gem_object_get_pages_gtt() mixes __GFP_NORETRY | __GFP_NOWARN in
4253   * with the mapping_gfp_mask(), to avoid OOMing the machine unnecessarily.
4254   */
4255  struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
4256  					 pgoff_t index, gfp_t gfp)
4257  {
4258  #ifdef CONFIG_SHMEM
4259  	struct inode *inode = mapping->host;
4260  	struct page *page;
4261  	int error;
4262  
4263  	BUG_ON(!shmem_mapping(mapping));
4264  	error = shmem_getpage_gfp(inode, index, &page, SGP_CACHE,
4265  				  gfp, NULL, NULL, NULL);
4266  	if (error)
4267  		page = ERR_PTR(error);
4268  	else
4269  		unlock_page(page);
4270  	return page;
4271  #else
4272  	/*
4273  	 * The tiny !SHMEM case uses ramfs without swap
4274  	 */
4275  	return read_cache_page_gfp(mapping, index, gfp);
4276  #endif
4277  }
4278  EXPORT_SYMBOL_GPL(shmem_read_mapping_page_gfp);
4279