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Linux/mm/shmem.c

  1 /*
  2  * Resizable virtual memory filesystem for Linux.
  3  *
  4  * Copyright (C) 2000 Linus Torvalds.
  5  *               2000 Transmeta Corp.
  6  *               2000-2001 Christoph Rohland
  7  *               2000-2001 SAP AG
  8  *               2002 Red Hat Inc.
  9  * Copyright (C) 2002-2011 Hugh Dickins.
 10  * Copyright (C) 2011 Google Inc.
 11  * Copyright (C) 2002-2005 VERITAS Software Corporation.
 12  * Copyright (C) 2004 Andi Kleen, SuSE Labs
 13  *
 14  * Extended attribute support for tmpfs:
 15  * Copyright (c) 2004, Luke Kenneth Casson Leighton <lkcl@lkcl.net>
 16  * Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
 17  *
 18  * tiny-shmem:
 19  * Copyright (c) 2004, 2008 Matt Mackall <mpm@selenic.com>
 20  *
 21  * This file is released under the GPL.
 22  */
 23 
 24 #include <linux/fs.h>
 25 #include <linux/init.h>
 26 #include <linux/vfs.h>
 27 #include <linux/mount.h>
 28 #include <linux/ramfs.h>
 29 #include <linux/pagemap.h>
 30 #include <linux/file.h>
 31 #include <linux/mm.h>
 32 #include <linux/export.h>
 33 #include <linux/swap.h>
 34 #include <linux/uio.h>
 35 
 36 static struct vfsmount *shm_mnt;
 37 
 38 #ifdef CONFIG_SHMEM
 39 /*
 40  * This virtual memory filesystem is heavily based on the ramfs. It
 41  * extends ramfs by the ability to use swap and honor resource limits
 42  * which makes it a completely usable filesystem.
 43  */
 44 
 45 #include <linux/xattr.h>
 46 #include <linux/exportfs.h>
 47 #include <linux/posix_acl.h>
 48 #include <linux/posix_acl_xattr.h>
 49 #include <linux/mman.h>
 50 #include <linux/string.h>
 51 #include <linux/slab.h>
 52 #include <linux/backing-dev.h>
 53 #include <linux/shmem_fs.h>
 54 #include <linux/writeback.h>
 55 #include <linux/blkdev.h>
 56 #include <linux/pagevec.h>
 57 #include <linux/percpu_counter.h>
 58 #include <linux/falloc.h>
 59 #include <linux/splice.h>
 60 #include <linux/security.h>
 61 #include <linux/swapops.h>
 62 #include <linux/mempolicy.h>
 63 #include <linux/namei.h>
 64 #include <linux/ctype.h>
 65 #include <linux/migrate.h>
 66 #include <linux/highmem.h>
 67 #include <linux/seq_file.h>
 68 #include <linux/magic.h>
 69 #include <linux/syscalls.h>
 70 #include <linux/fcntl.h>
 71 #include <uapi/linux/memfd.h>
 72 
 73 #include <asm/uaccess.h>
 74 #include <asm/pgtable.h>
 75 
 76 #include "internal.h"
 77 
 78 #define BLOCKS_PER_PAGE  (PAGE_SIZE/512)
 79 #define VM_ACCT(size)    (PAGE_ALIGN(size) >> PAGE_SHIFT)
 80 
 81 /* Pretend that each entry is of this size in directory's i_size */
 82 #define BOGO_DIRENT_SIZE 20
 83 
 84 /* Symlink up to this size is kmalloc'ed instead of using a swappable page */
 85 #define SHORT_SYMLINK_LEN 128
 86 
 87 /*
 88  * shmem_fallocate communicates with shmem_fault or shmem_writepage via
 89  * inode->i_private (with i_mutex making sure that it has only one user at
 90  * a time): we would prefer not to enlarge the shmem inode just for that.
 91  */
 92 struct shmem_falloc {
 93         wait_queue_head_t *waitq; /* faults into hole wait for punch to end */
 94         pgoff_t start;          /* start of range currently being fallocated */
 95         pgoff_t next;           /* the next page offset to be fallocated */
 96         pgoff_t nr_falloced;    /* how many new pages have been fallocated */
 97         pgoff_t nr_unswapped;   /* how often writepage refused to swap out */
 98 };
 99 
100 /* Flag allocation requirements to shmem_getpage */
101 enum sgp_type {
102         SGP_READ,       /* don't exceed i_size, don't allocate page */
103         SGP_CACHE,      /* don't exceed i_size, may allocate page */
104         SGP_DIRTY,      /* like SGP_CACHE, but set new page dirty */
105         SGP_WRITE,      /* may exceed i_size, may allocate !Uptodate page */
106         SGP_FALLOC,     /* like SGP_WRITE, but make existing page Uptodate */
107 };
108 
109 #ifdef CONFIG_TMPFS
110 static unsigned long shmem_default_max_blocks(void)
111 {
112         return totalram_pages / 2;
113 }
114 
115 static unsigned long shmem_default_max_inodes(void)
116 {
117         return min(totalram_pages - totalhigh_pages, totalram_pages / 2);
118 }
119 #endif
120 
121 static bool shmem_should_replace_page(struct page *page, gfp_t gfp);
122 static int shmem_replace_page(struct page **pagep, gfp_t gfp,
123                                 struct shmem_inode_info *info, pgoff_t index);
124 static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
125         struct page **pagep, enum sgp_type sgp, gfp_t gfp, int *fault_type);
126 
127 static inline int shmem_getpage(struct inode *inode, pgoff_t index,
128         struct page **pagep, enum sgp_type sgp, int *fault_type)
129 {
130         return shmem_getpage_gfp(inode, index, pagep, sgp,
131                         mapping_gfp_mask(inode->i_mapping), fault_type);
132 }
133 
134 static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
135 {
136         return sb->s_fs_info;
137 }
138 
139 /*
140  * shmem_file_setup pre-accounts the whole fixed size of a VM object,
141  * for shared memory and for shared anonymous (/dev/zero) mappings
142  * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
143  * consistent with the pre-accounting of private mappings ...
144  */
145 static inline int shmem_acct_size(unsigned long flags, loff_t size)
146 {
147         return (flags & VM_NORESERVE) ?
148                 0 : security_vm_enough_memory_mm(current->mm, VM_ACCT(size));
149 }
150 
151 static inline void shmem_unacct_size(unsigned long flags, loff_t size)
152 {
153         if (!(flags & VM_NORESERVE))
154                 vm_unacct_memory(VM_ACCT(size));
155 }
156 
157 static inline int shmem_reacct_size(unsigned long flags,
158                 loff_t oldsize, loff_t newsize)
159 {
160         if (!(flags & VM_NORESERVE)) {
161                 if (VM_ACCT(newsize) > VM_ACCT(oldsize))
162                         return security_vm_enough_memory_mm(current->mm,
163                                         VM_ACCT(newsize) - VM_ACCT(oldsize));
164                 else if (VM_ACCT(newsize) < VM_ACCT(oldsize))
165                         vm_unacct_memory(VM_ACCT(oldsize) - VM_ACCT(newsize));
166         }
167         return 0;
168 }
169 
170 /*
171  * ... whereas tmpfs objects are accounted incrementally as
172  * pages are allocated, in order to allow huge sparse files.
173  * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
174  * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
175  */
176 static inline int shmem_acct_block(unsigned long flags)
177 {
178         return (flags & VM_NORESERVE) ?
179                 security_vm_enough_memory_mm(current->mm, VM_ACCT(PAGE_SIZE)) : 0;
180 }
181 
182 static inline void shmem_unacct_blocks(unsigned long flags, long pages)
183 {
184         if (flags & VM_NORESERVE)
185                 vm_unacct_memory(pages * VM_ACCT(PAGE_SIZE));
186 }
187 
188 static const struct super_operations shmem_ops;
189 static const struct address_space_operations shmem_aops;
190 static const struct file_operations shmem_file_operations;
191 static const struct inode_operations shmem_inode_operations;
192 static const struct inode_operations shmem_dir_inode_operations;
193 static const struct inode_operations shmem_special_inode_operations;
194 static const struct vm_operations_struct shmem_vm_ops;
195 
196 static LIST_HEAD(shmem_swaplist);
197 static DEFINE_MUTEX(shmem_swaplist_mutex);
198 
199 static int shmem_reserve_inode(struct super_block *sb)
200 {
201         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
202         if (sbinfo->max_inodes) {
203                 spin_lock(&sbinfo->stat_lock);
204                 if (!sbinfo->free_inodes) {
205                         spin_unlock(&sbinfo->stat_lock);
206                         return -ENOSPC;
207                 }
208                 sbinfo->free_inodes--;
209                 spin_unlock(&sbinfo->stat_lock);
210         }
211         return 0;
212 }
213 
214 static void shmem_free_inode(struct super_block *sb)
215 {
216         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
217         if (sbinfo->max_inodes) {
218                 spin_lock(&sbinfo->stat_lock);
219                 sbinfo->free_inodes++;
220                 spin_unlock(&sbinfo->stat_lock);
221         }
222 }
223 
224 /**
225  * shmem_recalc_inode - recalculate the block usage of an inode
226  * @inode: inode to recalc
227  *
228  * We have to calculate the free blocks since the mm can drop
229  * undirtied hole pages behind our back.
230  *
231  * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
232  * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
233  *
234  * It has to be called with the spinlock held.
235  */
236 static void shmem_recalc_inode(struct inode *inode)
237 {
238         struct shmem_inode_info *info = SHMEM_I(inode);
239         long freed;
240 
241         freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
242         if (freed > 0) {
243                 struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
244                 if (sbinfo->max_blocks)
245                         percpu_counter_add(&sbinfo->used_blocks, -freed);
246                 info->alloced -= freed;
247                 inode->i_blocks -= freed * BLOCKS_PER_PAGE;
248                 shmem_unacct_blocks(info->flags, freed);
249         }
250 }
251 
252 /*
253  * Replace item expected in radix tree by a new item, while holding tree lock.
254  */
255 static int shmem_radix_tree_replace(struct address_space *mapping,
256                         pgoff_t index, void *expected, void *replacement)
257 {
258         void **pslot;
259         void *item;
260 
261         VM_BUG_ON(!expected);
262         VM_BUG_ON(!replacement);
263         pslot = radix_tree_lookup_slot(&mapping->page_tree, index);
264         if (!pslot)
265                 return -ENOENT;
266         item = radix_tree_deref_slot_protected(pslot, &mapping->tree_lock);
267         if (item != expected)
268                 return -ENOENT;
269         radix_tree_replace_slot(pslot, replacement);
270         return 0;
271 }
272 
273 /*
274  * Sometimes, before we decide whether to proceed or to fail, we must check
275  * that an entry was not already brought back from swap by a racing thread.
276  *
277  * Checking page is not enough: by the time a SwapCache page is locked, it
278  * might be reused, and again be SwapCache, using the same swap as before.
279  */
280 static bool shmem_confirm_swap(struct address_space *mapping,
281                                pgoff_t index, swp_entry_t swap)
282 {
283         void *item;
284 
285         rcu_read_lock();
286         item = radix_tree_lookup(&mapping->page_tree, index);
287         rcu_read_unlock();
288         return item == swp_to_radix_entry(swap);
289 }
290 
291 /*
292  * Like add_to_page_cache_locked, but error if expected item has gone.
293  */
294 static int shmem_add_to_page_cache(struct page *page,
295                                    struct address_space *mapping,
296                                    pgoff_t index, void *expected)
297 {
298         int error;
299 
300         VM_BUG_ON_PAGE(!PageLocked(page), page);
301         VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
302 
303         get_page(page);
304         page->mapping = mapping;
305         page->index = index;
306 
307         spin_lock_irq(&mapping->tree_lock);
308         if (!expected)
309                 error = radix_tree_insert(&mapping->page_tree, index, page);
310         else
311                 error = shmem_radix_tree_replace(mapping, index, expected,
312                                                                  page);
313         if (!error) {
314                 mapping->nrpages++;
315                 __inc_zone_page_state(page, NR_FILE_PAGES);
316                 __inc_zone_page_state(page, NR_SHMEM);
317                 spin_unlock_irq(&mapping->tree_lock);
318         } else {
319                 page->mapping = NULL;
320                 spin_unlock_irq(&mapping->tree_lock);
321                 put_page(page);
322         }
323         return error;
324 }
325 
326 /*
327  * Like delete_from_page_cache, but substitutes swap for page.
328  */
329 static void shmem_delete_from_page_cache(struct page *page, void *radswap)
330 {
331         struct address_space *mapping = page->mapping;
332         int error;
333 
334         spin_lock_irq(&mapping->tree_lock);
335         error = shmem_radix_tree_replace(mapping, page->index, page, radswap);
336         page->mapping = NULL;
337         mapping->nrpages--;
338         __dec_zone_page_state(page, NR_FILE_PAGES);
339         __dec_zone_page_state(page, NR_SHMEM);
340         spin_unlock_irq(&mapping->tree_lock);
341         put_page(page);
342         BUG_ON(error);
343 }
344 
345 /*
346  * Remove swap entry from radix tree, free the swap and its page cache.
347  */
348 static int shmem_free_swap(struct address_space *mapping,
349                            pgoff_t index, void *radswap)
350 {
351         void *old;
352 
353         spin_lock_irq(&mapping->tree_lock);
354         old = radix_tree_delete_item(&mapping->page_tree, index, radswap);
355         spin_unlock_irq(&mapping->tree_lock);
356         if (old != radswap)
357                 return -ENOENT;
358         free_swap_and_cache(radix_to_swp_entry(radswap));
359         return 0;
360 }
361 
362 /*
363  * Determine (in bytes) how many of the shmem object's pages mapped by the
364  * given offsets are swapped out.
365  *
366  * This is safe to call without i_mutex or mapping->tree_lock thanks to RCU,
367  * as long as the inode doesn't go away and racy results are not a problem.
368  */
369 unsigned long shmem_partial_swap_usage(struct address_space *mapping,
370                                                 pgoff_t start, pgoff_t end)
371 {
372         struct radix_tree_iter iter;
373         void **slot;
374         struct page *page;
375         unsigned long swapped = 0;
376 
377         rcu_read_lock();
378 
379         radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
380                 if (iter.index >= end)
381                         break;
382 
383                 page = radix_tree_deref_slot(slot);
384 
385                 if (radix_tree_deref_retry(page)) {
386                         slot = radix_tree_iter_retry(&iter);
387                         continue;
388                 }
389 
390                 if (radix_tree_exceptional_entry(page))
391                         swapped++;
392 
393                 if (need_resched()) {
394                         cond_resched_rcu();
395                         slot = radix_tree_iter_next(&iter);
396                 }
397         }
398 
399         rcu_read_unlock();
400 
401         return swapped << PAGE_SHIFT;
402 }
403 
404 /*
405  * Determine (in bytes) how many of the shmem object's pages mapped by the
406  * given vma is swapped out.
407  *
408  * This is safe to call without i_mutex or mapping->tree_lock thanks to RCU,
409  * as long as the inode doesn't go away and racy results are not a problem.
410  */
411 unsigned long shmem_swap_usage(struct vm_area_struct *vma)
412 {
413         struct inode *inode = file_inode(vma->vm_file);
414         struct shmem_inode_info *info = SHMEM_I(inode);
415         struct address_space *mapping = inode->i_mapping;
416         unsigned long swapped;
417 
418         /* Be careful as we don't hold info->lock */
419         swapped = READ_ONCE(info->swapped);
420 
421         /*
422          * The easier cases are when the shmem object has nothing in swap, or
423          * the vma maps it whole. Then we can simply use the stats that we
424          * already track.
425          */
426         if (!swapped)
427                 return 0;
428 
429         if (!vma->vm_pgoff && vma->vm_end - vma->vm_start >= inode->i_size)
430                 return swapped << PAGE_SHIFT;
431 
432         /* Here comes the more involved part */
433         return shmem_partial_swap_usage(mapping,
434                         linear_page_index(vma, vma->vm_start),
435                         linear_page_index(vma, vma->vm_end));
436 }
437 
438 /*
439  * SysV IPC SHM_UNLOCK restore Unevictable pages to their evictable lists.
440  */
441 void shmem_unlock_mapping(struct address_space *mapping)
442 {
443         struct pagevec pvec;
444         pgoff_t indices[PAGEVEC_SIZE];
445         pgoff_t index = 0;
446 
447         pagevec_init(&pvec, 0);
448         /*
449          * Minor point, but we might as well stop if someone else SHM_LOCKs it.
450          */
451         while (!mapping_unevictable(mapping)) {
452                 /*
453                  * Avoid pagevec_lookup(): find_get_pages() returns 0 as if it
454                  * has finished, if it hits a row of PAGEVEC_SIZE swap entries.
455                  */
456                 pvec.nr = find_get_entries(mapping, index,
457                                            PAGEVEC_SIZE, pvec.pages, indices);
458                 if (!pvec.nr)
459                         break;
460                 index = indices[pvec.nr - 1] + 1;
461                 pagevec_remove_exceptionals(&pvec);
462                 check_move_unevictable_pages(pvec.pages, pvec.nr);
463                 pagevec_release(&pvec);
464                 cond_resched();
465         }
466 }
467 
468 /*
469  * Remove range of pages and swap entries from radix tree, and free them.
470  * If !unfalloc, truncate or punch hole; if unfalloc, undo failed fallocate.
471  */
472 static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
473                                                                  bool unfalloc)
474 {
475         struct address_space *mapping = inode->i_mapping;
476         struct shmem_inode_info *info = SHMEM_I(inode);
477         pgoff_t start = (lstart + PAGE_SIZE - 1) >> PAGE_SHIFT;
478         pgoff_t end = (lend + 1) >> PAGE_SHIFT;
479         unsigned int partial_start = lstart & (PAGE_SIZE - 1);
480         unsigned int partial_end = (lend + 1) & (PAGE_SIZE - 1);
481         struct pagevec pvec;
482         pgoff_t indices[PAGEVEC_SIZE];
483         long nr_swaps_freed = 0;
484         pgoff_t index;
485         int i;
486 
487         if (lend == -1)
488                 end = -1;       /* unsigned, so actually very big */
489 
490         pagevec_init(&pvec, 0);
491         index = start;
492         while (index < end) {
493                 pvec.nr = find_get_entries(mapping, index,
494                         min(end - index, (pgoff_t)PAGEVEC_SIZE),
495                         pvec.pages, indices);
496                 if (!pvec.nr)
497                         break;
498                 for (i = 0; i < pagevec_count(&pvec); i++) {
499                         struct page *page = pvec.pages[i];
500 
501                         index = indices[i];
502                         if (index >= end)
503                                 break;
504 
505                         if (radix_tree_exceptional_entry(page)) {
506                                 if (unfalloc)
507                                         continue;
508                                 nr_swaps_freed += !shmem_free_swap(mapping,
509                                                                 index, page);
510                                 continue;
511                         }
512 
513                         if (!trylock_page(page))
514                                 continue;
515                         if (!unfalloc || !PageUptodate(page)) {
516                                 if (page->mapping == mapping) {
517                                         VM_BUG_ON_PAGE(PageWriteback(page), page);
518                                         truncate_inode_page(mapping, page);
519                                 }
520                         }
521                         unlock_page(page);
522                 }
523                 pagevec_remove_exceptionals(&pvec);
524                 pagevec_release(&pvec);
525                 cond_resched();
526                 index++;
527         }
528 
529         if (partial_start) {
530                 struct page *page = NULL;
531                 shmem_getpage(inode, start - 1, &page, SGP_READ, NULL);
532                 if (page) {
533                         unsigned int top = PAGE_SIZE;
534                         if (start > end) {
535                                 top = partial_end;
536                                 partial_end = 0;
537                         }
538                         zero_user_segment(page, partial_start, top);
539                         set_page_dirty(page);
540                         unlock_page(page);
541                         put_page(page);
542                 }
543         }
544         if (partial_end) {
545                 struct page *page = NULL;
546                 shmem_getpage(inode, end, &page, SGP_READ, NULL);
547                 if (page) {
548                         zero_user_segment(page, 0, partial_end);
549                         set_page_dirty(page);
550                         unlock_page(page);
551                         put_page(page);
552                 }
553         }
554         if (start >= end)
555                 return;
556 
557         index = start;
558         while (index < end) {
559                 cond_resched();
560 
561                 pvec.nr = find_get_entries(mapping, index,
562                                 min(end - index, (pgoff_t)PAGEVEC_SIZE),
563                                 pvec.pages, indices);
564                 if (!pvec.nr) {
565                         /* If all gone or hole-punch or unfalloc, we're done */
566                         if (index == start || end != -1)
567                                 break;
568                         /* But if truncating, restart to make sure all gone */
569                         index = start;
570                         continue;
571                 }
572                 for (i = 0; i < pagevec_count(&pvec); i++) {
573                         struct page *page = pvec.pages[i];
574 
575                         index = indices[i];
576                         if (index >= end)
577                                 break;
578 
579                         if (radix_tree_exceptional_entry(page)) {
580                                 if (unfalloc)
581                                         continue;
582                                 if (shmem_free_swap(mapping, index, page)) {
583                                         /* Swap was replaced by page: retry */
584                                         index--;
585                                         break;
586                                 }
587                                 nr_swaps_freed++;
588                                 continue;
589                         }
590 
591                         lock_page(page);
592                         if (!unfalloc || !PageUptodate(page)) {
593                                 if (page->mapping == mapping) {
594                                         VM_BUG_ON_PAGE(PageWriteback(page), page);
595                                         truncate_inode_page(mapping, page);
596                                 } else {
597                                         /* Page was replaced by swap: retry */
598                                         unlock_page(page);
599                                         index--;
600                                         break;
601                                 }
602                         }
603                         unlock_page(page);
604                 }
605                 pagevec_remove_exceptionals(&pvec);
606                 pagevec_release(&pvec);
607                 index++;
608         }
609 
610         spin_lock(&info->lock);
611         info->swapped -= nr_swaps_freed;
612         shmem_recalc_inode(inode);
613         spin_unlock(&info->lock);
614 }
615 
616 void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
617 {
618         shmem_undo_range(inode, lstart, lend, false);
619         inode->i_ctime = inode->i_mtime = CURRENT_TIME;
620 }
621 EXPORT_SYMBOL_GPL(shmem_truncate_range);
622 
623 static int shmem_getattr(struct vfsmount *mnt, struct dentry *dentry,
624                          struct kstat *stat)
625 {
626         struct inode *inode = dentry->d_inode;
627         struct shmem_inode_info *info = SHMEM_I(inode);
628 
629         if (info->alloced - info->swapped != inode->i_mapping->nrpages) {
630                 spin_lock(&info->lock);
631                 shmem_recalc_inode(inode);
632                 spin_unlock(&info->lock);
633         }
634         generic_fillattr(inode, stat);
635         return 0;
636 }
637 
638 static int shmem_setattr(struct dentry *dentry, struct iattr *attr)
639 {
640         struct inode *inode = d_inode(dentry);
641         struct shmem_inode_info *info = SHMEM_I(inode);
642         int error;
643 
644         error = inode_change_ok(inode, attr);
645         if (error)
646                 return error;
647 
648         if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
649                 loff_t oldsize = inode->i_size;
650                 loff_t newsize = attr->ia_size;
651 
652                 /* protected by i_mutex */
653                 if ((newsize < oldsize && (info->seals & F_SEAL_SHRINK)) ||
654                     (newsize > oldsize && (info->seals & F_SEAL_GROW)))
655                         return -EPERM;
656 
657                 if (newsize != oldsize) {
658                         error = shmem_reacct_size(SHMEM_I(inode)->flags,
659                                         oldsize, newsize);
660                         if (error)
661                                 return error;
662                         i_size_write(inode, newsize);
663                         inode->i_ctime = inode->i_mtime = CURRENT_TIME;
664                 }
665                 if (newsize <= oldsize) {
666                         loff_t holebegin = round_up(newsize, PAGE_SIZE);
667                         if (oldsize > holebegin)
668                                 unmap_mapping_range(inode->i_mapping,
669                                                         holebegin, 0, 1);
670                         if (info->alloced)
671                                 shmem_truncate_range(inode,
672                                                         newsize, (loff_t)-1);
673                         /* unmap again to remove racily COWed private pages */
674                         if (oldsize > holebegin)
675                                 unmap_mapping_range(inode->i_mapping,
676                                                         holebegin, 0, 1);
677                 }
678         }
679 
680         setattr_copy(inode, attr);
681         if (attr->ia_valid & ATTR_MODE)
682                 error = posix_acl_chmod(inode, inode->i_mode);
683         return error;
684 }
685 
686 static void shmem_evict_inode(struct inode *inode)
687 {
688         struct shmem_inode_info *info = SHMEM_I(inode);
689 
690         if (inode->i_mapping->a_ops == &shmem_aops) {
691                 shmem_unacct_size(info->flags, inode->i_size);
692                 inode->i_size = 0;
693                 shmem_truncate_range(inode, 0, (loff_t)-1);
694                 if (!list_empty(&info->swaplist)) {
695                         mutex_lock(&shmem_swaplist_mutex);
696                         list_del_init(&info->swaplist);
697                         mutex_unlock(&shmem_swaplist_mutex);
698                 }
699         }
700 
701         simple_xattrs_free(&info->xattrs);
702         WARN_ON(inode->i_blocks);
703         shmem_free_inode(inode->i_sb);
704         clear_inode(inode);
705 }
706 
707 /*
708  * If swap found in inode, free it and move page from swapcache to filecache.
709  */
710 static int shmem_unuse_inode(struct shmem_inode_info *info,
711                              swp_entry_t swap, struct page **pagep)
712 {
713         struct address_space *mapping = info->vfs_inode.i_mapping;
714         void *radswap;
715         pgoff_t index;
716         gfp_t gfp;
717         int error = 0;
718 
719         radswap = swp_to_radix_entry(swap);
720         index = radix_tree_locate_item(&mapping->page_tree, radswap);
721         if (index == -1)
722                 return -EAGAIN; /* tell shmem_unuse we found nothing */
723 
724         /*
725          * Move _head_ to start search for next from here.
726          * But be careful: shmem_evict_inode checks list_empty without taking
727          * mutex, and there's an instant in list_move_tail when info->swaplist
728          * would appear empty, if it were the only one on shmem_swaplist.
729          */
730         if (shmem_swaplist.next != &info->swaplist)
731                 list_move_tail(&shmem_swaplist, &info->swaplist);
732 
733         gfp = mapping_gfp_mask(mapping);
734         if (shmem_should_replace_page(*pagep, gfp)) {
735                 mutex_unlock(&shmem_swaplist_mutex);
736                 error = shmem_replace_page(pagep, gfp, info, index);
737                 mutex_lock(&shmem_swaplist_mutex);
738                 /*
739                  * We needed to drop mutex to make that restrictive page
740                  * allocation, but the inode might have been freed while we
741                  * dropped it: although a racing shmem_evict_inode() cannot
742                  * complete without emptying the radix_tree, our page lock
743                  * on this swapcache page is not enough to prevent that -
744                  * free_swap_and_cache() of our swap entry will only
745                  * trylock_page(), removing swap from radix_tree whatever.
746                  *
747                  * We must not proceed to shmem_add_to_page_cache() if the
748                  * inode has been freed, but of course we cannot rely on
749                  * inode or mapping or info to check that.  However, we can
750                  * safely check if our swap entry is still in use (and here
751                  * it can't have got reused for another page): if it's still
752                  * in use, then the inode cannot have been freed yet, and we
753                  * can safely proceed (if it's no longer in use, that tells
754                  * nothing about the inode, but we don't need to unuse swap).
755                  */
756                 if (!page_swapcount(*pagep))
757                         error = -ENOENT;
758         }
759 
760         /*
761          * We rely on shmem_swaplist_mutex, not only to protect the swaplist,
762          * but also to hold up shmem_evict_inode(): so inode cannot be freed
763          * beneath us (pagelock doesn't help until the page is in pagecache).
764          */
765         if (!error)
766                 error = shmem_add_to_page_cache(*pagep, mapping, index,
767                                                 radswap);
768         if (error != -ENOMEM) {
769                 /*
770                  * Truncation and eviction use free_swap_and_cache(), which
771                  * only does trylock page: if we raced, best clean up here.
772                  */
773                 delete_from_swap_cache(*pagep);
774                 set_page_dirty(*pagep);
775                 if (!error) {
776                         spin_lock(&info->lock);
777                         info->swapped--;
778                         spin_unlock(&info->lock);
779                         swap_free(swap);
780                 }
781         }
782         return error;
783 }
784 
785 /*
786  * Search through swapped inodes to find and replace swap by page.
787  */
788 int shmem_unuse(swp_entry_t swap, struct page *page)
789 {
790         struct list_head *this, *next;
791         struct shmem_inode_info *info;
792         struct mem_cgroup *memcg;
793         int error = 0;
794 
795         /*
796          * There's a faint possibility that swap page was replaced before
797          * caller locked it: caller will come back later with the right page.
798          */
799         if (unlikely(!PageSwapCache(page) || page_private(page) != swap.val))
800                 goto out;
801 
802         /*
803          * Charge page using GFP_KERNEL while we can wait, before taking
804          * the shmem_swaplist_mutex which might hold up shmem_writepage().
805          * Charged back to the user (not to caller) when swap account is used.
806          */
807         error = mem_cgroup_try_charge(page, current->mm, GFP_KERNEL, &memcg,
808                         false);
809         if (error)
810                 goto out;
811         /* No radix_tree_preload: swap entry keeps a place for page in tree */
812         error = -EAGAIN;
813 
814         mutex_lock(&shmem_swaplist_mutex);
815         list_for_each_safe(this, next, &shmem_swaplist) {
816                 info = list_entry(this, struct shmem_inode_info, swaplist);
817                 if (info->swapped)
818                         error = shmem_unuse_inode(info, swap, &page);
819                 else
820                         list_del_init(&info->swaplist);
821                 cond_resched();
822                 if (error != -EAGAIN)
823                         break;
824                 /* found nothing in this: move on to search the next */
825         }
826         mutex_unlock(&shmem_swaplist_mutex);
827 
828         if (error) {
829                 if (error != -ENOMEM)
830                         error = 0;
831                 mem_cgroup_cancel_charge(page, memcg, false);
832         } else
833                 mem_cgroup_commit_charge(page, memcg, true, false);
834 out:
835         unlock_page(page);
836         put_page(page);
837         return error;
838 }
839 
840 /*
841  * Move the page from the page cache to the swap cache.
842  */
843 static int shmem_writepage(struct page *page, struct writeback_control *wbc)
844 {
845         struct shmem_inode_info *info;
846         struct address_space *mapping;
847         struct inode *inode;
848         swp_entry_t swap;
849         pgoff_t index;
850 
851         BUG_ON(!PageLocked(page));
852         mapping = page->mapping;
853         index = page->index;
854         inode = mapping->host;
855         info = SHMEM_I(inode);
856         if (info->flags & VM_LOCKED)
857                 goto redirty;
858         if (!total_swap_pages)
859                 goto redirty;
860 
861         /*
862          * Our capabilities prevent regular writeback or sync from ever calling
863          * shmem_writepage; but a stacking filesystem might use ->writepage of
864          * its underlying filesystem, in which case tmpfs should write out to
865          * swap only in response to memory pressure, and not for the writeback
866          * threads or sync.
867          */
868         if (!wbc->for_reclaim) {
869                 WARN_ON_ONCE(1);        /* Still happens? Tell us about it! */
870                 goto redirty;
871         }
872 
873         /*
874          * This is somewhat ridiculous, but without plumbing a SWAP_MAP_FALLOC
875          * value into swapfile.c, the only way we can correctly account for a
876          * fallocated page arriving here is now to initialize it and write it.
877          *
878          * That's okay for a page already fallocated earlier, but if we have
879          * not yet completed the fallocation, then (a) we want to keep track
880          * of this page in case we have to undo it, and (b) it may not be a
881          * good idea to continue anyway, once we're pushing into swap.  So
882          * reactivate the page, and let shmem_fallocate() quit when too many.
883          */
884         if (!PageUptodate(page)) {
885                 if (inode->i_private) {
886                         struct shmem_falloc *shmem_falloc;
887                         spin_lock(&inode->i_lock);
888                         shmem_falloc = inode->i_private;
889                         if (shmem_falloc &&
890                             !shmem_falloc->waitq &&
891                             index >= shmem_falloc->start &&
892                             index < shmem_falloc->next)
893                                 shmem_falloc->nr_unswapped++;
894                         else
895                                 shmem_falloc = NULL;
896                         spin_unlock(&inode->i_lock);
897                         if (shmem_falloc)
898                                 goto redirty;
899                 }
900                 clear_highpage(page);
901                 flush_dcache_page(page);
902                 SetPageUptodate(page);
903         }
904 
905         swap = get_swap_page();
906         if (!swap.val)
907                 goto redirty;
908 
909         if (mem_cgroup_try_charge_swap(page, swap))
910                 goto free_swap;
911 
912         /*
913          * Add inode to shmem_unuse()'s list of swapped-out inodes,
914          * if it's not already there.  Do it now before the page is
915          * moved to swap cache, when its pagelock no longer protects
916          * the inode from eviction.  But don't unlock the mutex until
917          * we've incremented swapped, because shmem_unuse_inode() will
918          * prune a !swapped inode from the swaplist under this mutex.
919          */
920         mutex_lock(&shmem_swaplist_mutex);
921         if (list_empty(&info->swaplist))
922                 list_add_tail(&info->swaplist, &shmem_swaplist);
923 
924         if (add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
925                 spin_lock(&info->lock);
926                 shmem_recalc_inode(inode);
927                 info->swapped++;
928                 spin_unlock(&info->lock);
929 
930                 swap_shmem_alloc(swap);
931                 shmem_delete_from_page_cache(page, swp_to_radix_entry(swap));
932 
933                 mutex_unlock(&shmem_swaplist_mutex);
934                 BUG_ON(page_mapped(page));
935                 swap_writepage(page, wbc);
936                 return 0;
937         }
938 
939         mutex_unlock(&shmem_swaplist_mutex);
940 free_swap:
941         swapcache_free(swap);
942 redirty:
943         set_page_dirty(page);
944         if (wbc->for_reclaim)
945                 return AOP_WRITEPAGE_ACTIVATE;  /* Return with page locked */
946         unlock_page(page);
947         return 0;
948 }
949 
950 #ifdef CONFIG_NUMA
951 #ifdef CONFIG_TMPFS
952 static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
953 {
954         char buffer[64];
955 
956         if (!mpol || mpol->mode == MPOL_DEFAULT)
957                 return;         /* show nothing */
958 
959         mpol_to_str(buffer, sizeof(buffer), mpol);
960 
961         seq_printf(seq, ",mpol=%s", buffer);
962 }
963 
964 static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
965 {
966         struct mempolicy *mpol = NULL;
967         if (sbinfo->mpol) {
968                 spin_lock(&sbinfo->stat_lock);  /* prevent replace/use races */
969                 mpol = sbinfo->mpol;
970                 mpol_get(mpol);
971                 spin_unlock(&sbinfo->stat_lock);
972         }
973         return mpol;
974 }
975 #endif /* CONFIG_TMPFS */
976 
977 static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
978                         struct shmem_inode_info *info, pgoff_t index)
979 {
980         struct vm_area_struct pvma;
981         struct page *page;
982 
983         /* Create a pseudo vma that just contains the policy */
984         pvma.vm_start = 0;
985         /* Bias interleave by inode number to distribute better across nodes */
986         pvma.vm_pgoff = index + info->vfs_inode.i_ino;
987         pvma.vm_ops = NULL;
988         pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
989 
990         page = swapin_readahead(swap, gfp, &pvma, 0);
991 
992         /* Drop reference taken by mpol_shared_policy_lookup() */
993         mpol_cond_put(pvma.vm_policy);
994 
995         return page;
996 }
997 
998 static struct page *shmem_alloc_page(gfp_t gfp,
999                         struct shmem_inode_info *info, pgoff_t index)
1000 {
1001         struct vm_area_struct pvma;
1002         struct page *page;
1003 
1004         /* Create a pseudo vma that just contains the policy */
1005         pvma.vm_start = 0;
1006         /* Bias interleave by inode number to distribute better across nodes */
1007         pvma.vm_pgoff = index + info->vfs_inode.i_ino;
1008         pvma.vm_ops = NULL;
1009         pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
1010 
1011         page = alloc_page_vma(gfp, &pvma, 0);
1012 
1013         /* Drop reference taken by mpol_shared_policy_lookup() */
1014         mpol_cond_put(pvma.vm_policy);
1015 
1016         return page;
1017 }
1018 #else /* !CONFIG_NUMA */
1019 #ifdef CONFIG_TMPFS
1020 static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
1021 {
1022 }
1023 #endif /* CONFIG_TMPFS */
1024 
1025 static inline struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
1026                         struct shmem_inode_info *info, pgoff_t index)
1027 {
1028         return swapin_readahead(swap, gfp, NULL, 0);
1029 }
1030 
1031 static inline struct page *shmem_alloc_page(gfp_t gfp,
1032                         struct shmem_inode_info *info, pgoff_t index)
1033 {
1034         return alloc_page(gfp);
1035 }
1036 #endif /* CONFIG_NUMA */
1037 
1038 #if !defined(CONFIG_NUMA) || !defined(CONFIG_TMPFS)
1039 static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
1040 {
1041         return NULL;
1042 }
1043 #endif
1044 
1045 /*
1046  * When a page is moved from swapcache to shmem filecache (either by the
1047  * usual swapin of shmem_getpage_gfp(), or by the less common swapoff of
1048  * shmem_unuse_inode()), it may have been read in earlier from swap, in
1049  * ignorance of the mapping it belongs to.  If that mapping has special
1050  * constraints (like the gma500 GEM driver, which requires RAM below 4GB),
1051  * we may need to copy to a suitable page before moving to filecache.
1052  *
1053  * In a future release, this may well be extended to respect cpuset and
1054  * NUMA mempolicy, and applied also to anonymous pages in do_swap_page();
1055  * but for now it is a simple matter of zone.
1056  */
1057 static bool shmem_should_replace_page(struct page *page, gfp_t gfp)
1058 {
1059         return page_zonenum(page) > gfp_zone(gfp);
1060 }
1061 
1062 static int shmem_replace_page(struct page **pagep, gfp_t gfp,
1063                                 struct shmem_inode_info *info, pgoff_t index)
1064 {
1065         struct page *oldpage, *newpage;
1066         struct address_space *swap_mapping;
1067         pgoff_t swap_index;
1068         int error;
1069 
1070         oldpage = *pagep;
1071         swap_index = page_private(oldpage);
1072         swap_mapping = page_mapping(oldpage);
1073 
1074         /*
1075          * We have arrived here because our zones are constrained, so don't
1076          * limit chance of success by further cpuset and node constraints.
1077          */
1078         gfp &= ~GFP_CONSTRAINT_MASK;
1079         newpage = shmem_alloc_page(gfp, info, index);
1080         if (!newpage)
1081                 return -ENOMEM;
1082 
1083         get_page(newpage);
1084         copy_highpage(newpage, oldpage);
1085         flush_dcache_page(newpage);
1086 
1087         __SetPageLocked(newpage);
1088         SetPageUptodate(newpage);
1089         SetPageSwapBacked(newpage);
1090         set_page_private(newpage, swap_index);
1091         SetPageSwapCache(newpage);
1092 
1093         /*
1094          * Our caller will very soon move newpage out of swapcache, but it's
1095          * a nice clean interface for us to replace oldpage by newpage there.
1096          */
1097         spin_lock_irq(&swap_mapping->tree_lock);
1098         error = shmem_radix_tree_replace(swap_mapping, swap_index, oldpage,
1099                                                                    newpage);
1100         if (!error) {
1101                 __inc_zone_page_state(newpage, NR_FILE_PAGES);
1102                 __dec_zone_page_state(oldpage, NR_FILE_PAGES);
1103         }
1104         spin_unlock_irq(&swap_mapping->tree_lock);
1105 
1106         if (unlikely(error)) {
1107                 /*
1108                  * Is this possible?  I think not, now that our callers check
1109                  * both PageSwapCache and page_private after getting page lock;
1110                  * but be defensive.  Reverse old to newpage for clear and free.
1111                  */
1112                 oldpage = newpage;
1113         } else {
1114                 mem_cgroup_migrate(oldpage, newpage);
1115                 lru_cache_add_anon(newpage);
1116                 *pagep = newpage;
1117         }
1118 
1119         ClearPageSwapCache(oldpage);
1120         set_page_private(oldpage, 0);
1121 
1122         unlock_page(oldpage);
1123         put_page(oldpage);
1124         put_page(oldpage);
1125         return error;
1126 }
1127 
1128 /*
1129  * shmem_getpage_gfp - find page in cache, or get from swap, or allocate
1130  *
1131  * If we allocate a new one we do not mark it dirty. That's up to the
1132  * vm. If we swap it in we mark it dirty since we also free the swap
1133  * entry since a page cannot live in both the swap and page cache
1134  */
1135 static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
1136         struct page **pagep, enum sgp_type sgp, gfp_t gfp, int *fault_type)
1137 {
1138         struct address_space *mapping = inode->i_mapping;
1139         struct shmem_inode_info *info;
1140         struct shmem_sb_info *sbinfo;
1141         struct mem_cgroup *memcg;
1142         struct page *page;
1143         swp_entry_t swap;
1144         int error;
1145         int once = 0;
1146         int alloced = 0;
1147 
1148         if (index > (MAX_LFS_FILESIZE >> PAGE_SHIFT))
1149                 return -EFBIG;
1150 repeat:
1151         swap.val = 0;
1152         page = find_lock_entry(mapping, index);
1153         if (radix_tree_exceptional_entry(page)) {
1154                 swap = radix_to_swp_entry(page);
1155                 page = NULL;
1156         }
1157 
1158         if (sgp != SGP_WRITE && sgp != SGP_FALLOC &&
1159             ((loff_t)index << PAGE_SHIFT) >= i_size_read(inode)) {
1160                 error = -EINVAL;
1161                 goto unlock;
1162         }
1163 
1164         if (page && sgp == SGP_WRITE)
1165                 mark_page_accessed(page);
1166 
1167         /* fallocated page? */
1168         if (page && !PageUptodate(page)) {
1169                 if (sgp != SGP_READ)
1170                         goto clear;
1171                 unlock_page(page);
1172                 put_page(page);
1173                 page = NULL;
1174         }
1175         if (page || (sgp == SGP_READ && !swap.val)) {
1176                 *pagep = page;
1177                 return 0;
1178         }
1179 
1180         /*
1181          * Fast cache lookup did not find it:
1182          * bring it back from swap or allocate.
1183          */
1184         info = SHMEM_I(inode);
1185         sbinfo = SHMEM_SB(inode->i_sb);
1186 
1187         if (swap.val) {
1188                 /* Look it up and read it in.. */
1189                 page = lookup_swap_cache(swap);
1190                 if (!page) {
1191                         /* here we actually do the io */
1192                         if (fault_type)
1193                                 *fault_type |= VM_FAULT_MAJOR;
1194                         page = shmem_swapin(swap, gfp, info, index);
1195                         if (!page) {
1196                                 error = -ENOMEM;
1197                                 goto failed;
1198                         }
1199                 }
1200 
1201                 /* We have to do this with page locked to prevent races */
1202                 lock_page(page);
1203                 if (!PageSwapCache(page) || page_private(page) != swap.val ||
1204                     !shmem_confirm_swap(mapping, index, swap)) {
1205                         error = -EEXIST;        /* try again */
1206                         goto unlock;
1207                 }
1208                 if (!PageUptodate(page)) {
1209                         error = -EIO;
1210                         goto failed;
1211                 }
1212                 wait_on_page_writeback(page);
1213 
1214                 if (shmem_should_replace_page(page, gfp)) {
1215                         error = shmem_replace_page(&page, gfp, info, index);
1216                         if (error)
1217                                 goto failed;
1218                 }
1219 
1220                 error = mem_cgroup_try_charge(page, current->mm, gfp, &memcg,
1221                                 false);
1222                 if (!error) {
1223                         error = shmem_add_to_page_cache(page, mapping, index,
1224                                                 swp_to_radix_entry(swap));
1225                         /*
1226                          * We already confirmed swap under page lock, and make
1227                          * no memory allocation here, so usually no possibility
1228                          * of error; but free_swap_and_cache() only trylocks a
1229                          * page, so it is just possible that the entry has been
1230                          * truncated or holepunched since swap was confirmed.
1231                          * shmem_undo_range() will have done some of the
1232                          * unaccounting, now delete_from_swap_cache() will do
1233                          * the rest.
1234                          * Reset swap.val? No, leave it so "failed" goes back to
1235                          * "repeat": reading a hole and writing should succeed.
1236                          */
1237                         if (error) {
1238                                 mem_cgroup_cancel_charge(page, memcg, false);
1239                                 delete_from_swap_cache(page);
1240                         }
1241                 }
1242                 if (error)
1243                         goto failed;
1244 
1245                 mem_cgroup_commit_charge(page, memcg, true, false);
1246 
1247                 spin_lock(&info->lock);
1248                 info->swapped--;
1249                 shmem_recalc_inode(inode);
1250                 spin_unlock(&info->lock);
1251 
1252                 if (sgp == SGP_WRITE)
1253                         mark_page_accessed(page);
1254 
1255                 delete_from_swap_cache(page);
1256                 set_page_dirty(page);
1257                 swap_free(swap);
1258 
1259         } else {
1260                 if (shmem_acct_block(info->flags)) {
1261                         error = -ENOSPC;
1262                         goto failed;
1263                 }
1264                 if (sbinfo->max_blocks) {
1265                         if (percpu_counter_compare(&sbinfo->used_blocks,
1266                                                 sbinfo->max_blocks) >= 0) {
1267                                 error = -ENOSPC;
1268                                 goto unacct;
1269                         }
1270                         percpu_counter_inc(&sbinfo->used_blocks);
1271                 }
1272 
1273                 page = shmem_alloc_page(gfp, info, index);
1274                 if (!page) {
1275                         error = -ENOMEM;
1276                         goto decused;
1277                 }
1278 
1279                 __SetPageSwapBacked(page);
1280                 __SetPageLocked(page);
1281                 if (sgp == SGP_WRITE)
1282                         __SetPageReferenced(page);
1283 
1284                 error = mem_cgroup_try_charge(page, current->mm, gfp, &memcg,
1285                                 false);
1286                 if (error)
1287                         goto decused;
1288                 error = radix_tree_maybe_preload(gfp & GFP_RECLAIM_MASK);
1289                 if (!error) {
1290                         error = shmem_add_to_page_cache(page, mapping, index,
1291                                                         NULL);
1292                         radix_tree_preload_end();
1293                 }
1294                 if (error) {
1295                         mem_cgroup_cancel_charge(page, memcg, false);
1296                         goto decused;
1297                 }
1298                 mem_cgroup_commit_charge(page, memcg, false, false);
1299                 lru_cache_add_anon(page);
1300 
1301                 spin_lock(&info->lock);
1302                 info->alloced++;
1303                 inode->i_blocks += BLOCKS_PER_PAGE;
1304                 shmem_recalc_inode(inode);
1305                 spin_unlock(&info->lock);
1306                 alloced = true;
1307 
1308                 /*
1309                  * Let SGP_FALLOC use the SGP_WRITE optimization on a new page.
1310                  */
1311                 if (sgp == SGP_FALLOC)
1312                         sgp = SGP_WRITE;
1313 clear:
1314                 /*
1315                  * Let SGP_WRITE caller clear ends if write does not fill page;
1316                  * but SGP_FALLOC on a page fallocated earlier must initialize
1317                  * it now, lest undo on failure cancel our earlier guarantee.
1318                  */
1319                 if (sgp != SGP_WRITE) {
1320                         clear_highpage(page);
1321                         flush_dcache_page(page);
1322                         SetPageUptodate(page);
1323                 }
1324                 if (sgp == SGP_DIRTY)
1325                         set_page_dirty(page);
1326         }
1327 
1328         /* Perhaps the file has been truncated since we checked */
1329         if (sgp != SGP_WRITE && sgp != SGP_FALLOC &&
1330             ((loff_t)index << PAGE_SHIFT) >= i_size_read(inode)) {
1331                 if (alloced) {
1332                         ClearPageDirty(page);
1333                         delete_from_page_cache(page);
1334                         spin_lock(&info->lock);
1335                         shmem_recalc_inode(inode);
1336                         spin_unlock(&info->lock);
1337                 }
1338                 error = -EINVAL;
1339                 goto unlock;
1340         }
1341         *pagep = page;
1342         return 0;
1343 
1344         /*
1345          * Error recovery.
1346          */
1347 decused:
1348         if (sbinfo->max_blocks)
1349                 percpu_counter_add(&sbinfo->used_blocks, -1);
1350 unacct:
1351         shmem_unacct_blocks(info->flags, 1);
1352 failed:
1353         if (swap.val && !shmem_confirm_swap(mapping, index, swap))
1354                 error = -EEXIST;
1355 unlock:
1356         if (page) {
1357                 unlock_page(page);
1358                 put_page(page);
1359         }
1360         if (error == -ENOSPC && !once++) {
1361                 info = SHMEM_I(inode);
1362                 spin_lock(&info->lock);
1363                 shmem_recalc_inode(inode);
1364                 spin_unlock(&info->lock);
1365                 goto repeat;
1366         }
1367         if (error == -EEXIST)   /* from above or from radix_tree_insert */
1368                 goto repeat;
1369         return error;
1370 }
1371 
1372 static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1373 {
1374         struct inode *inode = file_inode(vma->vm_file);
1375         int error;
1376         int ret = VM_FAULT_LOCKED;
1377 
1378         /*
1379          * Trinity finds that probing a hole which tmpfs is punching can
1380          * prevent the hole-punch from ever completing: which in turn
1381          * locks writers out with its hold on i_mutex.  So refrain from
1382          * faulting pages into the hole while it's being punched.  Although
1383          * shmem_undo_range() does remove the additions, it may be unable to
1384          * keep up, as each new page needs its own unmap_mapping_range() call,
1385          * and the i_mmap tree grows ever slower to scan if new vmas are added.
1386          *
1387          * It does not matter if we sometimes reach this check just before the
1388          * hole-punch begins, so that one fault then races with the punch:
1389          * we just need to make racing faults a rare case.
1390          *
1391          * The implementation below would be much simpler if we just used a
1392          * standard mutex or completion: but we cannot take i_mutex in fault,
1393          * and bloating every shmem inode for this unlikely case would be sad.
1394          */
1395         if (unlikely(inode->i_private)) {
1396                 struct shmem_falloc *shmem_falloc;
1397 
1398                 spin_lock(&inode->i_lock);
1399                 shmem_falloc = inode->i_private;
1400                 if (shmem_falloc &&
1401                     shmem_falloc->waitq &&
1402                     vmf->pgoff >= shmem_falloc->start &&
1403                     vmf->pgoff < shmem_falloc->next) {
1404                         wait_queue_head_t *shmem_falloc_waitq;
1405                         DEFINE_WAIT(shmem_fault_wait);
1406 
1407                         ret = VM_FAULT_NOPAGE;
1408                         if ((vmf->flags & FAULT_FLAG_ALLOW_RETRY) &&
1409                            !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT)) {
1410                                 /* It's polite to up mmap_sem if we can */
1411                                 up_read(&vma->vm_mm->mmap_sem);
1412                                 ret = VM_FAULT_RETRY;
1413                         }
1414 
1415                         shmem_falloc_waitq = shmem_falloc->waitq;
1416                         prepare_to_wait(shmem_falloc_waitq, &shmem_fault_wait,
1417                                         TASK_UNINTERRUPTIBLE);
1418                         spin_unlock(&inode->i_lock);
1419                         schedule();
1420 
1421                         /*
1422                          * shmem_falloc_waitq points into the shmem_fallocate()
1423                          * stack of the hole-punching task: shmem_falloc_waitq
1424                          * is usually invalid by the time we reach here, but
1425                          * finish_wait() does not dereference it in that case;
1426                          * though i_lock needed lest racing with wake_up_all().
1427                          */
1428                         spin_lock(&inode->i_lock);
1429                         finish_wait(shmem_falloc_waitq, &shmem_fault_wait);
1430                         spin_unlock(&inode->i_lock);
1431                         return ret;
1432                 }
1433                 spin_unlock(&inode->i_lock);
1434         }
1435 
1436         error = shmem_getpage(inode, vmf->pgoff, &vmf->page, SGP_CACHE, &ret);
1437         if (error)
1438                 return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
1439 
1440         if (ret & VM_FAULT_MAJOR) {
1441                 count_vm_event(PGMAJFAULT);
1442                 mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
1443         }
1444         return ret;
1445 }
1446 
1447 #ifdef CONFIG_NUMA
1448 static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *mpol)
1449 {
1450         struct inode *inode = file_inode(vma->vm_file);
1451         return mpol_set_shared_policy(&SHMEM_I(inode)->policy, vma, mpol);
1452 }
1453 
1454 static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
1455                                           unsigned long addr)
1456 {
1457         struct inode *inode = file_inode(vma->vm_file);
1458         pgoff_t index;
1459 
1460         index = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
1461         return mpol_shared_policy_lookup(&SHMEM_I(inode)->policy, index);
1462 }
1463 #endif
1464 
1465 int shmem_lock(struct file *file, int lock, struct user_struct *user)
1466 {
1467         struct inode *inode = file_inode(file);
1468         struct shmem_inode_info *info = SHMEM_I(inode);
1469         int retval = -ENOMEM;
1470 
1471         spin_lock(&info->lock);
1472         if (lock && !(info->flags & VM_LOCKED)) {
1473                 if (!user_shm_lock(inode->i_size, user))
1474                         goto out_nomem;
1475                 info->flags |= VM_LOCKED;
1476                 mapping_set_unevictable(file->f_mapping);
1477         }
1478         if (!lock && (info->flags & VM_LOCKED) && user) {
1479                 user_shm_unlock(inode->i_size, user);
1480                 info->flags &= ~VM_LOCKED;
1481                 mapping_clear_unevictable(file->f_mapping);
1482         }
1483         retval = 0;
1484 
1485 out_nomem:
1486         spin_unlock(&info->lock);
1487         return retval;
1488 }
1489 
1490 static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
1491 {
1492         file_accessed(file);
1493         vma->vm_ops = &shmem_vm_ops;
1494         return 0;
1495 }
1496 
1497 static struct inode *shmem_get_inode(struct super_block *sb, const struct inode *dir,
1498                                      umode_t mode, dev_t dev, unsigned long flags)
1499 {
1500         struct inode *inode;
1501         struct shmem_inode_info *info;
1502         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
1503 
1504         if (shmem_reserve_inode(sb))
1505                 return NULL;
1506 
1507         inode = new_inode(sb);
1508         if (inode) {
1509                 inode->i_ino = get_next_ino();
1510                 inode_init_owner(inode, dir, mode);
1511                 inode->i_blocks = 0;
1512                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1513                 inode->i_generation = get_seconds();
1514                 info = SHMEM_I(inode);
1515                 memset(info, 0, (char *)inode - (char *)info);
1516                 spin_lock_init(&info->lock);
1517                 info->seals = F_SEAL_SEAL;
1518                 info->flags = flags & VM_NORESERVE;
1519                 INIT_LIST_HEAD(&info->swaplist);
1520                 simple_xattrs_init(&info->xattrs);
1521                 cache_no_acl(inode);
1522 
1523                 switch (mode & S_IFMT) {
1524                 default:
1525                         inode->i_op = &shmem_special_inode_operations;
1526                         init_special_inode(inode, mode, dev);
1527                         break;
1528                 case S_IFREG:
1529                         inode->i_mapping->a_ops = &shmem_aops;
1530                         inode->i_op = &shmem_inode_operations;
1531                         inode->i_fop = &shmem_file_operations;
1532                         mpol_shared_policy_init(&info->policy,
1533                                                  shmem_get_sbmpol(sbinfo));
1534                         break;
1535                 case S_IFDIR:
1536                         inc_nlink(inode);
1537                         /* Some things misbehave if size == 0 on a directory */
1538                         inode->i_size = 2 * BOGO_DIRENT_SIZE;
1539                         inode->i_op = &shmem_dir_inode_operations;
1540                         inode->i_fop = &simple_dir_operations;
1541                         break;
1542                 case S_IFLNK:
1543                         /*
1544                          * Must not load anything in the rbtree,
1545                          * mpol_free_shared_policy will not be called.
1546                          */
1547                         mpol_shared_policy_init(&info->policy, NULL);
1548                         break;
1549                 }
1550         } else
1551                 shmem_free_inode(sb);
1552         return inode;
1553 }
1554 
1555 bool shmem_mapping(struct address_space *mapping)
1556 {
1557         if (!mapping->host)
1558                 return false;
1559 
1560         return mapping->host->i_sb->s_op == &shmem_ops;
1561 }
1562 
1563 #ifdef CONFIG_TMPFS
1564 static const struct inode_operations shmem_symlink_inode_operations;
1565 static const struct inode_operations shmem_short_symlink_operations;
1566 
1567 #ifdef CONFIG_TMPFS_XATTR
1568 static int shmem_initxattrs(struct inode *, const struct xattr *, void *);
1569 #else
1570 #define shmem_initxattrs NULL
1571 #endif
1572 
1573 static int
1574 shmem_write_begin(struct file *file, struct address_space *mapping,
1575                         loff_t pos, unsigned len, unsigned flags,
1576                         struct page **pagep, void **fsdata)
1577 {
1578         struct inode *inode = mapping->host;
1579         struct shmem_inode_info *info = SHMEM_I(inode);
1580         pgoff_t index = pos >> PAGE_SHIFT;
1581 
1582         /* i_mutex is held by caller */
1583         if (unlikely(info->seals)) {
1584                 if (info->seals & F_SEAL_WRITE)
1585                         return -EPERM;
1586                 if ((info->seals & F_SEAL_GROW) && pos + len > inode->i_size)
1587                         return -EPERM;
1588         }
1589 
1590         return shmem_getpage(inode, index, pagep, SGP_WRITE, NULL);
1591 }
1592 
1593 static int
1594 shmem_write_end(struct file *file, struct address_space *mapping,
1595                         loff_t pos, unsigned len, unsigned copied,
1596                         struct page *page, void *fsdata)
1597 {
1598         struct inode *inode = mapping->host;
1599 
1600         if (pos + copied > inode->i_size)
1601                 i_size_write(inode, pos + copied);
1602 
1603         if (!PageUptodate(page)) {
1604                 if (copied < PAGE_SIZE) {
1605                         unsigned from = pos & (PAGE_SIZE - 1);
1606                         zero_user_segments(page, 0, from,
1607                                         from + copied, PAGE_SIZE);
1608                 }
1609                 SetPageUptodate(page);
1610         }
1611         set_page_dirty(page);
1612         unlock_page(page);
1613         put_page(page);
1614 
1615         return copied;
1616 }
1617 
1618 static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
1619 {
1620         struct file *file = iocb->ki_filp;
1621         struct inode *inode = file_inode(file);
1622         struct address_space *mapping = inode->i_mapping;
1623         pgoff_t index;
1624         unsigned long offset;
1625         enum sgp_type sgp = SGP_READ;
1626         int error = 0;
1627         ssize_t retval = 0;
1628         loff_t *ppos = &iocb->ki_pos;
1629 
1630         /*
1631          * Might this read be for a stacking filesystem?  Then when reading
1632          * holes of a sparse file, we actually need to allocate those pages,
1633          * and even mark them dirty, so it cannot exceed the max_blocks limit.
1634          */
1635         if (!iter_is_iovec(to))
1636                 sgp = SGP_DIRTY;
1637 
1638         index = *ppos >> PAGE_SHIFT;
1639         offset = *ppos & ~PAGE_MASK;
1640 
1641         for (;;) {
1642                 struct page *page = NULL;
1643                 pgoff_t end_index;
1644                 unsigned long nr, ret;
1645                 loff_t i_size = i_size_read(inode);
1646 
1647                 end_index = i_size >> PAGE_SHIFT;
1648                 if (index > end_index)
1649                         break;
1650                 if (index == end_index) {
1651                         nr = i_size & ~PAGE_MASK;
1652                         if (nr <= offset)
1653                                 break;
1654                 }
1655 
1656                 error = shmem_getpage(inode, index, &page, sgp, NULL);
1657                 if (error) {
1658                         if (error == -EINVAL)
1659                                 error = 0;
1660                         break;
1661                 }
1662                 if (page)
1663                         unlock_page(page);
1664 
1665                 /*
1666                  * We must evaluate after, since reads (unlike writes)
1667                  * are called without i_mutex protection against truncate
1668                  */
1669                 nr = PAGE_SIZE;
1670                 i_size = i_size_read(inode);
1671                 end_index = i_size >> PAGE_SHIFT;
1672                 if (index == end_index) {
1673                         nr = i_size & ~PAGE_MASK;
1674                         if (nr <= offset) {
1675                                 if (page)
1676                                         put_page(page);
1677                                 break;
1678                         }
1679                 }
1680                 nr -= offset;
1681 
1682                 if (page) {
1683                         /*
1684                          * If users can be writing to this page using arbitrary
1685                          * virtual addresses, take care about potential aliasing
1686                          * before reading the page on the kernel side.
1687                          */
1688                         if (mapping_writably_mapped(mapping))
1689                                 flush_dcache_page(page);
1690                         /*
1691                          * Mark the page accessed if we read the beginning.
1692                          */
1693                         if (!offset)
1694                                 mark_page_accessed(page);
1695                 } else {
1696                         page = ZERO_PAGE(0);
1697                         get_page(page);
1698                 }
1699 
1700                 /*
1701                  * Ok, we have the page, and it's up-to-date, so
1702                  * now we can copy it to user space...
1703                  */
1704                 ret = copy_page_to_iter(page, offset, nr, to);
1705                 retval += ret;
1706                 offset += ret;
1707                 index += offset >> PAGE_SHIFT;
1708                 offset &= ~PAGE_MASK;
1709 
1710                 put_page(page);
1711                 if (!iov_iter_count(to))
1712                         break;
1713                 if (ret < nr) {
1714                         error = -EFAULT;
1715                         break;
1716                 }
1717                 cond_resched();
1718         }
1719 
1720         *ppos = ((loff_t) index << PAGE_SHIFT) + offset;
1721         file_accessed(file);
1722         return retval ? retval : error;
1723 }
1724 
1725 static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos,
1726                                 struct pipe_inode_info *pipe, size_t len,
1727                                 unsigned int flags)
1728 {
1729         struct address_space *mapping = in->f_mapping;
1730         struct inode *inode = mapping->host;
1731         unsigned int loff, nr_pages, req_pages;
1732         struct page *pages[PIPE_DEF_BUFFERS];
1733         struct partial_page partial[PIPE_DEF_BUFFERS];
1734         struct page *page;
1735         pgoff_t index, end_index;
1736         loff_t isize, left;
1737         int error, page_nr;
1738         struct splice_pipe_desc spd = {
1739                 .pages = pages,
1740                 .partial = partial,
1741                 .nr_pages_max = PIPE_DEF_BUFFERS,
1742                 .flags = flags,
1743                 .ops = &page_cache_pipe_buf_ops,
1744                 .spd_release = spd_release_page,
1745         };
1746 
1747         isize = i_size_read(inode);
1748         if (unlikely(*ppos >= isize))
1749                 return 0;
1750 
1751         left = isize - *ppos;
1752         if (unlikely(left < len))
1753                 len = left;
1754 
1755         if (splice_grow_spd(pipe, &spd))
1756                 return -ENOMEM;
1757 
1758         index = *ppos >> PAGE_SHIFT;
1759         loff = *ppos & ~PAGE_MASK;
1760         req_pages = (len + loff + PAGE_SIZE - 1) >> PAGE_SHIFT;
1761         nr_pages = min(req_pages, spd.nr_pages_max);
1762 
1763         spd.nr_pages = find_get_pages_contig(mapping, index,
1764                                                 nr_pages, spd.pages);
1765         index += spd.nr_pages;
1766         error = 0;
1767 
1768         while (spd.nr_pages < nr_pages) {
1769                 error = shmem_getpage(inode, index, &page, SGP_CACHE, NULL);
1770                 if (error)
1771                         break;
1772                 unlock_page(page);
1773                 spd.pages[spd.nr_pages++] = page;
1774                 index++;
1775         }
1776 
1777         index = *ppos >> PAGE_SHIFT;
1778         nr_pages = spd.nr_pages;
1779         spd.nr_pages = 0;
1780 
1781         for (page_nr = 0; page_nr < nr_pages; page_nr++) {
1782                 unsigned int this_len;
1783 
1784                 if (!len)
1785                         break;
1786 
1787                 this_len = min_t(unsigned long, len, PAGE_SIZE - loff);
1788                 page = spd.pages[page_nr];
1789 
1790                 if (!PageUptodate(page) || page->mapping != mapping) {
1791                         error = shmem_getpage(inode, index, &page,
1792                                                         SGP_CACHE, NULL);
1793                         if (error)
1794                                 break;
1795                         unlock_page(page);
1796                         put_page(spd.pages[page_nr]);
1797                         spd.pages[page_nr] = page;
1798                 }
1799 
1800                 isize = i_size_read(inode);
1801                 end_index = (isize - 1) >> PAGE_SHIFT;
1802                 if (unlikely(!isize || index > end_index))
1803                         break;
1804 
1805                 if (end_index == index) {
1806                         unsigned int plen;
1807 
1808                         plen = ((isize - 1) & ~PAGE_MASK) + 1;
1809                         if (plen <= loff)
1810                                 break;
1811 
1812                         this_len = min(this_len, plen - loff);
1813                         len = this_len;
1814                 }
1815 
1816                 spd.partial[page_nr].offset = loff;
1817                 spd.partial[page_nr].len = this_len;
1818                 len -= this_len;
1819                 loff = 0;
1820                 spd.nr_pages++;
1821                 index++;
1822         }
1823 
1824         while (page_nr < nr_pages)
1825                 put_page(spd.pages[page_nr++]);
1826 
1827         if (spd.nr_pages)
1828                 error = splice_to_pipe(pipe, &spd);
1829 
1830         splice_shrink_spd(&spd);
1831 
1832         if (error > 0) {
1833                 *ppos += error;
1834                 file_accessed(in);
1835         }
1836         return error;
1837 }
1838 
1839 /*
1840  * llseek SEEK_DATA or SEEK_HOLE through the radix_tree.
1841  */
1842 static pgoff_t shmem_seek_hole_data(struct address_space *mapping,
1843                                     pgoff_t index, pgoff_t end, int whence)
1844 {
1845         struct page *page;
1846         struct pagevec pvec;
1847         pgoff_t indices[PAGEVEC_SIZE];
1848         bool done = false;
1849         int i;
1850 
1851         pagevec_init(&pvec, 0);
1852         pvec.nr = 1;            /* start small: we may be there already */
1853         while (!done) {
1854                 pvec.nr = find_get_entries(mapping, index,
1855                                         pvec.nr, pvec.pages, indices);
1856                 if (!pvec.nr) {
1857                         if (whence == SEEK_DATA)
1858                                 index = end;
1859                         break;
1860                 }
1861                 for (i = 0; i < pvec.nr; i++, index++) {
1862                         if (index < indices[i]) {
1863                                 if (whence == SEEK_HOLE) {
1864                                         done = true;
1865                                         break;
1866                                 }
1867                                 index = indices[i];
1868                         }
1869                         page = pvec.pages[i];
1870                         if (page && !radix_tree_exceptional_entry(page)) {
1871                                 if (!PageUptodate(page))
1872                                         page = NULL;
1873                         }
1874                         if (index >= end ||
1875                             (page && whence == SEEK_DATA) ||
1876                             (!page && whence == SEEK_HOLE)) {
1877                                 done = true;
1878                                 break;
1879                         }
1880                 }
1881                 pagevec_remove_exceptionals(&pvec);
1882                 pagevec_release(&pvec);
1883                 pvec.nr = PAGEVEC_SIZE;
1884                 cond_resched();
1885         }
1886         return index;
1887 }
1888 
1889 static loff_t shmem_file_llseek(struct file *file, loff_t offset, int whence)
1890 {
1891         struct address_space *mapping = file->f_mapping;
1892         struct inode *inode = mapping->host;
1893         pgoff_t start, end;
1894         loff_t new_offset;
1895 
1896         if (whence != SEEK_DATA && whence != SEEK_HOLE)
1897                 return generic_file_llseek_size(file, offset, whence,
1898                                         MAX_LFS_FILESIZE, i_size_read(inode));
1899         inode_lock(inode);
1900         /* We're holding i_mutex so we can access i_size directly */
1901 
1902         if (offset < 0)
1903                 offset = -EINVAL;
1904         else if (offset >= inode->i_size)
1905                 offset = -ENXIO;
1906         else {
1907                 start = offset >> PAGE_SHIFT;
1908                 end = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
1909                 new_offset = shmem_seek_hole_data(mapping, start, end, whence);
1910                 new_offset <<= PAGE_SHIFT;
1911                 if (new_offset > offset) {
1912                         if (new_offset < inode->i_size)
1913                                 offset = new_offset;
1914                         else if (whence == SEEK_DATA)
1915                                 offset = -ENXIO;
1916                         else
1917                                 offset = inode->i_size;
1918                 }
1919         }
1920 
1921         if (offset >= 0)
1922                 offset = vfs_setpos(file, offset, MAX_LFS_FILESIZE);
1923         inode_unlock(inode);
1924         return offset;
1925 }
1926 
1927 /*
1928  * We need a tag: a new tag would expand every radix_tree_node by 8 bytes,
1929  * so reuse a tag which we firmly believe is never set or cleared on shmem.
1930  */
1931 #define SHMEM_TAG_PINNED        PAGECACHE_TAG_TOWRITE
1932 #define LAST_SCAN               4       /* about 150ms max */
1933 
1934 static void shmem_tag_pins(struct address_space *mapping)
1935 {
1936         struct radix_tree_iter iter;
1937         void **slot;
1938         pgoff_t start;
1939         struct page *page;
1940 
1941         lru_add_drain();
1942         start = 0;
1943         rcu_read_lock();
1944 
1945         radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
1946                 page = radix_tree_deref_slot(slot);
1947                 if (!page || radix_tree_exception(page)) {
1948                         if (radix_tree_deref_retry(page)) {
1949                                 slot = radix_tree_iter_retry(&iter);
1950                                 continue;
1951                         }
1952                 } else if (page_count(page) - page_mapcount(page) > 1) {
1953                         spin_lock_irq(&mapping->tree_lock);
1954                         radix_tree_tag_set(&mapping->page_tree, iter.index,
1955                                            SHMEM_TAG_PINNED);
1956                         spin_unlock_irq(&mapping->tree_lock);
1957                 }
1958 
1959                 if (need_resched()) {
1960                         cond_resched_rcu();
1961                         slot = radix_tree_iter_next(&iter);
1962                 }
1963         }
1964         rcu_read_unlock();
1965 }
1966 
1967 /*
1968  * Setting SEAL_WRITE requires us to verify there's no pending writer. However,
1969  * via get_user_pages(), drivers might have some pending I/O without any active
1970  * user-space mappings (eg., direct-IO, AIO). Therefore, we look at all pages
1971  * and see whether it has an elevated ref-count. If so, we tag them and wait for
1972  * them to be dropped.
1973  * The caller must guarantee that no new user will acquire writable references
1974  * to those pages to avoid races.
1975  */
1976 static int shmem_wait_for_pins(struct address_space *mapping)
1977 {
1978         struct radix_tree_iter iter;
1979         void **slot;
1980         pgoff_t start;
1981         struct page *page;
1982         int error, scan;
1983 
1984         shmem_tag_pins(mapping);
1985 
1986         error = 0;
1987         for (scan = 0; scan <= LAST_SCAN; scan++) {
1988                 if (!radix_tree_tagged(&mapping->page_tree, SHMEM_TAG_PINNED))
1989                         break;
1990 
1991                 if (!scan)
1992                         lru_add_drain_all();
1993                 else if (schedule_timeout_killable((HZ << scan) / 200))
1994                         scan = LAST_SCAN;
1995 
1996                 start = 0;
1997                 rcu_read_lock();
1998                 radix_tree_for_each_tagged(slot, &mapping->page_tree, &iter,
1999                                            start, SHMEM_TAG_PINNED) {
2000 
2001                         page = radix_tree_deref_slot(slot);
2002                         if (radix_tree_exception(page)) {
2003                                 if (radix_tree_deref_retry(page)) {
2004                                         slot = radix_tree_iter_retry(&iter);
2005                                         continue;
2006                                 }
2007 
2008                                 page = NULL;
2009                         }
2010 
2011                         if (page &&
2012                             page_count(page) - page_mapcount(page) != 1) {
2013                                 if (scan < LAST_SCAN)
2014                                         goto continue_resched;
2015 
2016                                 /*
2017                                  * On the last scan, we clean up all those tags
2018                                  * we inserted; but make a note that we still
2019                                  * found pages pinned.
2020                                  */
2021                                 error = -EBUSY;
2022                         }
2023 
2024                         spin_lock_irq(&mapping->tree_lock);
2025                         radix_tree_tag_clear(&mapping->page_tree,
2026                                              iter.index, SHMEM_TAG_PINNED);
2027                         spin_unlock_irq(&mapping->tree_lock);
2028 continue_resched:
2029                         if (need_resched()) {
2030                                 cond_resched_rcu();
2031                                 slot = radix_tree_iter_next(&iter);
2032                         }
2033                 }
2034                 rcu_read_unlock();
2035         }
2036 
2037         return error;
2038 }
2039 
2040 #define F_ALL_SEALS (F_SEAL_SEAL | \
2041                      F_SEAL_SHRINK | \
2042                      F_SEAL_GROW | \
2043                      F_SEAL_WRITE)
2044 
2045 int shmem_add_seals(struct file *file, unsigned int seals)
2046 {
2047         struct inode *inode = file_inode(file);
2048         struct shmem_inode_info *info = SHMEM_I(inode);
2049         int error;
2050 
2051         /*
2052          * SEALING
2053          * Sealing allows multiple parties to share a shmem-file but restrict
2054          * access to a specific subset of file operations. Seals can only be
2055          * added, but never removed. This way, mutually untrusted parties can
2056          * share common memory regions with a well-defined policy. A malicious
2057          * peer can thus never perform unwanted operations on a shared object.
2058          *
2059          * Seals are only supported on special shmem-files and always affect
2060          * the whole underlying inode. Once a seal is set, it may prevent some
2061          * kinds of access to the file. Currently, the following seals are
2062          * defined:
2063          *   SEAL_SEAL: Prevent further seals from being set on this file
2064          *   SEAL_SHRINK: Prevent the file from shrinking
2065          *   SEAL_GROW: Prevent the file from growing
2066          *   SEAL_WRITE: Prevent write access to the file
2067          *
2068          * As we don't require any trust relationship between two parties, we
2069          * must prevent seals from being removed. Therefore, sealing a file
2070          * only adds a given set of seals to the file, it never touches
2071          * existing seals. Furthermore, the "setting seals"-operation can be
2072          * sealed itself, which basically prevents any further seal from being
2073          * added.
2074          *
2075          * Semantics of sealing are only defined on volatile files. Only
2076          * anonymous shmem files support sealing. More importantly, seals are
2077          * never written to disk. Therefore, there's no plan to support it on
2078          * other file types.
2079          */
2080 
2081         if (file->f_op != &shmem_file_operations)
2082                 return -EINVAL;
2083         if (!(file->f_mode & FMODE_WRITE))
2084                 return -EPERM;
2085         if (seals & ~(unsigned int)F_ALL_SEALS)
2086                 return -EINVAL;
2087 
2088         inode_lock(inode);
2089 
2090         if (info->seals & F_SEAL_SEAL) {
2091                 error = -EPERM;
2092                 goto unlock;
2093         }
2094 
2095         if ((seals & F_SEAL_WRITE) && !(info->seals & F_SEAL_WRITE)) {
2096                 error = mapping_deny_writable(file->f_mapping);
2097                 if (error)
2098                         goto unlock;
2099 
2100                 error = shmem_wait_for_pins(file->f_mapping);
2101                 if (error) {
2102                         mapping_allow_writable(file->f_mapping);
2103                         goto unlock;
2104                 }
2105         }
2106 
2107         info->seals |= seals;
2108         error = 0;
2109 
2110 unlock:
2111         inode_unlock(inode);
2112         return error;
2113 }
2114 EXPORT_SYMBOL_GPL(shmem_add_seals);
2115 
2116 int shmem_get_seals(struct file *file)
2117 {
2118         if (file->f_op != &shmem_file_operations)
2119                 return -EINVAL;
2120 
2121         return SHMEM_I(file_inode(file))->seals;
2122 }
2123 EXPORT_SYMBOL_GPL(shmem_get_seals);
2124 
2125 long shmem_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
2126 {
2127         long error;
2128 
2129         switch (cmd) {
2130         case F_ADD_SEALS:
2131                 /* disallow upper 32bit */
2132                 if (arg > UINT_MAX)
2133                         return -EINVAL;
2134 
2135                 error = shmem_add_seals(file, arg);
2136                 break;
2137         case F_GET_SEALS:
2138                 error = shmem_get_seals(file);
2139                 break;
2140         default:
2141                 error = -EINVAL;
2142                 break;
2143         }
2144 
2145         return error;
2146 }
2147 
2148 static long shmem_fallocate(struct file *file, int mode, loff_t offset,
2149                                                          loff_t len)
2150 {
2151         struct inode *inode = file_inode(file);
2152         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
2153         struct shmem_inode_info *info = SHMEM_I(inode);
2154         struct shmem_falloc shmem_falloc;
2155         pgoff_t start, index, end;
2156         int error;
2157 
2158         if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
2159                 return -EOPNOTSUPP;
2160 
2161         inode_lock(inode);
2162 
2163         if (mode & FALLOC_FL_PUNCH_HOLE) {
2164                 struct address_space *mapping = file->f_mapping;
2165                 loff_t unmap_start = round_up(offset, PAGE_SIZE);
2166                 loff_t unmap_end = round_down(offset + len, PAGE_SIZE) - 1;
2167                 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(shmem_falloc_waitq);
2168 
2169                 /* protected by i_mutex */
2170                 if (info->seals & F_SEAL_WRITE) {
2171                         error = -EPERM;
2172                         goto out;
2173                 }
2174 
2175                 shmem_falloc.waitq = &shmem_falloc_waitq;
2176                 shmem_falloc.start = unmap_start >> PAGE_SHIFT;
2177                 shmem_falloc.next = (unmap_end + 1) >> PAGE_SHIFT;
2178                 spin_lock(&inode->i_lock);
2179                 inode->i_private = &shmem_falloc;
2180                 spin_unlock(&inode->i_lock);
2181 
2182                 if ((u64)unmap_end > (u64)unmap_start)
2183                         unmap_mapping_range(mapping, unmap_start,
2184                                             1 + unmap_end - unmap_start, 0);
2185                 shmem_truncate_range(inode, offset, offset + len - 1);
2186                 /* No need to unmap again: hole-punching leaves COWed pages */
2187 
2188                 spin_lock(&inode->i_lock);
2189                 inode->i_private = NULL;
2190                 wake_up_all(&shmem_falloc_waitq);
2191                 spin_unlock(&inode->i_lock);
2192                 error = 0;
2193                 goto out;
2194         }
2195 
2196         /* We need to check rlimit even when FALLOC_FL_KEEP_SIZE */
2197         error = inode_newsize_ok(inode, offset + len);
2198         if (error)
2199                 goto out;
2200 
2201         if ((info->seals & F_SEAL_GROW) && offset + len > inode->i_size) {
2202                 error = -EPERM;
2203                 goto out;
2204         }
2205 
2206         start = offset >> PAGE_SHIFT;
2207         end = (offset + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
2208         /* Try to avoid a swapstorm if len is impossible to satisfy */
2209         if (sbinfo->max_blocks && end - start > sbinfo->max_blocks) {
2210                 error = -ENOSPC;
2211                 goto out;
2212         }
2213 
2214         shmem_falloc.waitq = NULL;
2215         shmem_falloc.start = start;
2216         shmem_falloc.next  = start;
2217         shmem_falloc.nr_falloced = 0;
2218         shmem_falloc.nr_unswapped = 0;
2219         spin_lock(&inode->i_lock);
2220         inode->i_private = &shmem_falloc;
2221         spin_unlock(&inode->i_lock);
2222 
2223         for (index = start; index < end; index++) {
2224                 struct page *page;
2225 
2226                 /*
2227                  * Good, the fallocate(2) manpage permits EINTR: we may have
2228                  * been interrupted because we are using up too much memory.
2229                  */
2230                 if (signal_pending(current))
2231                         error = -EINTR;
2232                 else if (shmem_falloc.nr_unswapped > shmem_falloc.nr_falloced)
2233                         error = -ENOMEM;
2234                 else
2235                         error = shmem_getpage(inode, index, &page, SGP_FALLOC,
2236                                                                         NULL);
2237                 if (error) {
2238                         /* Remove the !PageUptodate pages we added */
2239                         shmem_undo_range(inode,
2240                                 (loff_t)start << PAGE_SHIFT,
2241                                 (loff_t)index << PAGE_SHIFT, true);
2242                         goto undone;
2243                 }
2244 
2245                 /*
2246                  * Inform shmem_writepage() how far we have reached.
2247                  * No need for lock or barrier: we have the page lock.
2248                  */
2249                 shmem_falloc.next++;
2250                 if (!PageUptodate(page))
2251                         shmem_falloc.nr_falloced++;
2252 
2253                 /*
2254                  * If !PageUptodate, leave it that way so that freeable pages
2255                  * can be recognized if we need to rollback on error later.
2256                  * But set_page_dirty so that memory pressure will swap rather
2257                  * than free the pages we are allocating (and SGP_CACHE pages
2258                  * might still be clean: we now need to mark those dirty too).
2259                  */
2260                 set_page_dirty(page);
2261                 unlock_page(page);
2262                 put_page(page);
2263                 cond_resched();
2264         }
2265 
2266         if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size)
2267                 i_size_write(inode, offset + len);
2268         inode->i_ctime = CURRENT_TIME;
2269 undone:
2270         spin_lock(&inode->i_lock);
2271         inode->i_private = NULL;
2272         spin_unlock(&inode->i_lock);
2273 out:
2274         inode_unlock(inode);
2275         return error;
2276 }
2277 
2278 static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
2279 {
2280         struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
2281 
2282         buf->f_type = TMPFS_MAGIC;
2283         buf->f_bsize = PAGE_SIZE;
2284         buf->f_namelen = NAME_MAX;
2285         if (sbinfo->max_blocks) {
2286                 buf->f_blocks = sbinfo->max_blocks;
2287                 buf->f_bavail =
2288                 buf->f_bfree  = sbinfo->max_blocks -
2289                                 percpu_counter_sum(&sbinfo->used_blocks);
2290         }
2291         if (sbinfo->max_inodes) {
2292                 buf->f_files = sbinfo->max_inodes;
2293                 buf->f_ffree = sbinfo->free_inodes;
2294         }
2295         /* else leave those fields 0 like simple_statfs */
2296         return 0;
2297 }
2298 
2299 /*
2300  * File creation. Allocate an inode, and we're done..
2301  */
2302 static int
2303 shmem_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
2304 {
2305         struct inode *inode;
2306         int error = -ENOSPC;
2307 
2308         inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE);
2309         if (inode) {
2310                 error = simple_acl_create(dir, inode);
2311                 if (error)
2312                         goto out_iput;
2313                 error = security_inode_init_security(inode, dir,
2314                                                      &dentry->d_name,
2315                                                      shmem_initxattrs, NULL);
2316                 if (error && error != -EOPNOTSUPP)
2317                         goto out_iput;
2318 
2319                 error = 0;
2320                 dir->i_size += BOGO_DIRENT_SIZE;
2321                 dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2322                 d_instantiate(dentry, inode);
2323                 dget(dentry); /* Extra count - pin the dentry in core */
2324         }
2325         return error;
2326 out_iput:
2327         iput(inode);
2328         return error;
2329 }
2330 
2331 static int
2332 shmem_tmpfile(struct inode *dir, struct dentry *dentry, umode_t mode)
2333 {
2334         struct inode *inode;
2335         int error = -ENOSPC;
2336 
2337         inode = shmem_get_inode(dir->i_sb, dir, mode, 0, VM_NORESERVE);
2338         if (inode) {
2339                 error = security_inode_init_security(inode, dir,
2340                                                      NULL,
2341                                                      shmem_initxattrs, NULL);
2342                 if (error && error != -EOPNOTSUPP)
2343                         goto out_iput;
2344                 error = simple_acl_create(dir, inode);
2345                 if (error)
2346                         goto out_iput;
2347                 d_tmpfile(dentry, inode);
2348         }
2349         return error;
2350 out_iput:
2351         iput(inode);
2352         return error;
2353 }
2354 
2355 static int shmem_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
2356 {
2357         int error;
2358 
2359         if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
2360                 return error;
2361         inc_nlink(dir);
2362         return 0;
2363 }
2364 
2365 static int shmem_create(struct inode *dir, struct dentry *dentry, umode_t mode,
2366                 bool excl)
2367 {
2368         return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
2369 }
2370 
2371 /*
2372  * Link a file..
2373  */
2374 static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
2375 {
2376         struct inode *inode = d_inode(old_dentry);
2377         int ret;
2378 
2379         /*
2380          * No ordinary (disk based) filesystem counts links as inodes;
2381          * but each new link needs a new dentry, pinning lowmem, and
2382          * tmpfs dentries cannot be pruned until they are unlinked.
2383          */
2384         ret = shmem_reserve_inode(inode->i_sb);
2385         if (ret)
2386                 goto out;
2387 
2388         dir->i_size += BOGO_DIRENT_SIZE;
2389         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2390         inc_nlink(inode);
2391         ihold(inode);   /* New dentry reference */
2392         dget(dentry);           /* Extra pinning count for the created dentry */
2393         d_instantiate(dentry, inode);
2394 out:
2395         return ret;
2396 }
2397 
2398 static int shmem_unlink(struct inode *dir, struct dentry *dentry)
2399 {
2400         struct inode *inode = d_inode(dentry);
2401 
2402         if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
2403                 shmem_free_inode(inode->i_sb);
2404 
2405         dir->i_size -= BOGO_DIRENT_SIZE;
2406         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2407         drop_nlink(inode);
2408         dput(dentry);   /* Undo the count from "create" - this does all the work */
2409         return 0;
2410 }
2411 
2412 static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
2413 {
2414         if (!simple_empty(dentry))
2415                 return -ENOTEMPTY;
2416 
2417         drop_nlink(d_inode(dentry));
2418         drop_nlink(dir);
2419         return shmem_unlink(dir, dentry);
2420 }
2421 
2422 static int shmem_exchange(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
2423 {
2424         bool old_is_dir = d_is_dir(old_dentry);
2425         bool new_is_dir = d_is_dir(new_dentry);
2426 
2427         if (old_dir != new_dir && old_is_dir != new_is_dir) {
2428                 if (old_is_dir) {
2429                         drop_nlink(old_dir);
2430                         inc_nlink(new_dir);
2431                 } else {
2432                         drop_nlink(new_dir);
2433                         inc_nlink(old_dir);
2434                 }
2435         }
2436         old_dir->i_ctime = old_dir->i_mtime =
2437         new_dir->i_ctime = new_dir->i_mtime =
2438         d_inode(old_dentry)->i_ctime =
2439         d_inode(new_dentry)->i_ctime = CURRENT_TIME;
2440 
2441         return 0;
2442 }
2443 
2444 static int shmem_whiteout(struct inode *old_dir, struct dentry *old_dentry)
2445 {
2446         struct dentry *whiteout;
2447         int error;
2448 
2449         whiteout = d_alloc(old_dentry->d_parent, &old_dentry->d_name);
2450         if (!whiteout)
2451                 return -ENOMEM;
2452 
2453         error = shmem_mknod(old_dir, whiteout,
2454                             S_IFCHR | WHITEOUT_MODE, WHITEOUT_DEV);
2455         dput(whiteout);
2456         if (error)
2457                 return error;
2458 
2459         /*
2460          * Cheat and hash the whiteout while the old dentry is still in
2461          * place, instead of playing games with FS_RENAME_DOES_D_MOVE.
2462          *
2463          * d_lookup() will consistently find one of them at this point,
2464          * not sure which one, but that isn't even important.
2465          */
2466         d_rehash(whiteout);
2467         return 0;
2468 }
2469 
2470 /*
2471  * The VFS layer already does all the dentry stuff for rename,
2472  * we just have to decrement the usage count for the target if
2473  * it exists so that the VFS layer correctly free's it when it
2474  * gets overwritten.
2475  */
2476 static int shmem_rename2(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry, unsigned int flags)
2477 {
2478         struct inode *inode = d_inode(old_dentry);
2479         int they_are_dirs = S_ISDIR(inode->i_mode);
2480 
2481         if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
2482                 return -EINVAL;
2483 
2484         if (flags & RENAME_EXCHANGE)
2485                 return shmem_exchange(old_dir, old_dentry, new_dir, new_dentry);
2486 
2487         if (!simple_empty(new_dentry))
2488                 return -ENOTEMPTY;
2489 
2490         if (flags & RENAME_WHITEOUT) {
2491                 int error;
2492 
2493                 error = shmem_whiteout(old_dir, old_dentry);
2494                 if (error)
2495                         return error;
2496         }
2497 
2498         if (d_really_is_positive(new_dentry)) {
2499                 (void) shmem_unlink(new_dir, new_dentry);
2500                 if (they_are_dirs) {
2501                         drop_nlink(d_inode(new_dentry));
2502                         drop_nlink(old_dir);
2503                 }
2504         } else if (they_are_dirs) {
2505                 drop_nlink(old_dir);
2506                 inc_nlink(new_dir);
2507         }
2508 
2509         old_dir->i_size -= BOGO_DIRENT_SIZE;
2510         new_dir->i_size += BOGO_DIRENT_SIZE;
2511         old_dir->i_ctime = old_dir->i_mtime =
2512         new_dir->i_ctime = new_dir->i_mtime =
2513         inode->i_ctime = CURRENT_TIME;
2514         return 0;
2515 }
2516 
2517 static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
2518 {
2519         int error;
2520         int len;
2521         struct inode *inode;
2522         struct page *page;
2523         struct shmem_inode_info *info;
2524 
2525         len = strlen(symname) + 1;
2526         if (len > PAGE_SIZE)
2527                 return -ENAMETOOLONG;
2528 
2529         inode = shmem_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0, VM_NORESERVE);
2530         if (!inode)
2531                 return -ENOSPC;
2532 
2533         error = security_inode_init_security(inode, dir, &dentry->d_name,
2534                                              shmem_initxattrs, NULL);
2535         if (error) {
2536                 if (error != -EOPNOTSUPP) {
2537                         iput(inode);
2538                         return error;
2539                 }
2540                 error = 0;
2541         }
2542 
2543         info = SHMEM_I(inode);
2544         inode->i_size = len-1;
2545         if (len <= SHORT_SYMLINK_LEN) {
2546                 inode->i_link = kmemdup(symname, len, GFP_KERNEL);
2547                 if (!inode->i_link) {
2548                         iput(inode);
2549                         return -ENOMEM;
2550                 }
2551                 inode->i_op = &shmem_short_symlink_operations;
2552         } else {
2553                 inode_nohighmem(inode);
2554                 error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
2555                 if (error) {
2556                         iput(inode);
2557                         return error;
2558                 }
2559                 inode->i_mapping->a_ops = &shmem_aops;
2560                 inode->i_op = &shmem_symlink_inode_operations;
2561                 memcpy(page_address(page), symname, len);
2562                 SetPageUptodate(page);
2563                 set_page_dirty(page);
2564                 unlock_page(page);
2565                 put_page(page);
2566         }
2567         dir->i_size += BOGO_DIRENT_SIZE;
2568         dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2569         d_instantiate(dentry, inode);
2570         dget(dentry);
2571         return 0;
2572 }
2573 
2574 static void shmem_put_link(void *arg)
2575 {
2576         mark_page_accessed(arg);
2577         put_page(arg);
2578 }
2579 
2580 static const char *shmem_get_link(struct dentry *dentry,
2581                                   struct inode *inode,
2582                                   struct delayed_call *done)
2583 {
2584         struct page *page = NULL;
2585         int error;
2586         if (!dentry) {
2587                 page = find_get_page(inode->i_mapping, 0);
2588                 if (!page)
2589                         return ERR_PTR(-ECHILD);
2590                 if (!PageUptodate(page)) {
2591                         put_page(page);
2592                         return ERR_PTR(-ECHILD);
2593                 }
2594         } else {
2595                 error = shmem_getpage(inode, 0, &page, SGP_READ, NULL);
2596                 if (error)
2597                         return ERR_PTR(error);
2598                 unlock_page(page);
2599         }
2600         set_delayed_call(done, shmem_put_link, page);
2601         return page_address(page);
2602 }
2603 
2604 #ifdef CONFIG_TMPFS_XATTR
2605 /*
2606  * Superblocks without xattr inode operations may get some security.* xattr
2607  * support from the LSM "for free". As soon as we have any other xattrs
2608  * like ACLs, we also need to implement the security.* handlers at
2609  * filesystem level, though.
2610  */
2611 
2612 /*
2613  * Callback for security_inode_init_security() for acquiring xattrs.
2614  */
2615 static int shmem_initxattrs(struct inode *inode,
2616                             const struct xattr *xattr_array,
2617                             void *fs_info)
2618 {
2619         struct shmem_inode_info *info = SHMEM_I(inode);
2620         const struct xattr *xattr;
2621         struct simple_xattr *new_xattr;
2622         size_t len;
2623 
2624         for (xattr = xattr_array; xattr->name != NULL; xattr++) {
2625                 new_xattr = simple_xattr_alloc(xattr->value, xattr->value_len);
2626                 if (!new_xattr)
2627                         return -ENOMEM;
2628 
2629                 len = strlen(xattr->name) + 1;
2630                 new_xattr->name = kmalloc(XATTR_SECURITY_PREFIX_LEN + len,
2631                                           GFP_KERNEL);
2632                 if (!new_xattr->name) {
2633                         kfree(new_xattr);
2634                         return -ENOMEM;
2635                 }
2636 
2637                 memcpy(new_xattr->name, XATTR_SECURITY_PREFIX,
2638                        XATTR_SECURITY_PREFIX_LEN);
2639                 memcpy(new_xattr->name + XATTR_SECURITY_PREFIX_LEN,
2640                        xattr->name, len);
2641 
2642                 simple_xattr_list_add(&info->xattrs, new_xattr);
2643         }
2644 
2645         return 0;
2646 }
2647 
2648 static int shmem_xattr_handler_get(const struct xattr_handler *handler,
2649                                    struct dentry *dentry, const char *name,
2650                                    void *buffer, size_t size)
2651 {
2652         struct shmem_inode_info *info = SHMEM_I(d_inode(dentry));
2653 
2654         name = xattr_full_name(handler, name);
2655         return simple_xattr_get(&info->xattrs, name, buffer, size);
2656 }
2657 
2658 static int shmem_xattr_handler_set(const struct xattr_handler *handler,
2659                                    struct dentry *dentry, const char *name,
2660                                    const void *value, size_t size, int flags)
2661 {
2662         struct shmem_inode_info *info = SHMEM_I(d_inode(dentry));
2663 
2664         name = xattr_full_name(handler, name);
2665         return simple_xattr_set(&info->xattrs, name, value, size, flags);
2666 }
2667 
2668 static const struct xattr_handler shmem_security_xattr_handler = {
2669         .prefix = XATTR_SECURITY_PREFIX,
2670         .get = shmem_xattr_handler_get,
2671         .set = shmem_xattr_handler_set,
2672 };
2673 
2674 static const struct xattr_handler shmem_trusted_xattr_handler = {
2675         .prefix = XATTR_TRUSTED_PREFIX,
2676         .get = shmem_xattr_handler_get,
2677         .set = shmem_xattr_handler_set,
2678 };
2679 
2680 static const struct xattr_handler *shmem_xattr_handlers[] = {
2681 #ifdef CONFIG_TMPFS_POSIX_ACL
2682         &posix_acl_access_xattr_handler,
2683         &posix_acl_default_xattr_handler,
2684 #endif
2685         &shmem_security_xattr_handler,
2686         &shmem_trusted_xattr_handler,
2687         NULL
2688 };
2689 
2690 static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t size)
2691 {
2692         struct shmem_inode_info *info = SHMEM_I(d_inode(dentry));
2693         return simple_xattr_list(d_inode(dentry), &info->xattrs, buffer, size);
2694 }
2695 #endif /* CONFIG_TMPFS_XATTR */
2696 
2697 static const struct inode_operations shmem_short_symlink_operations = {
2698         .readlink       = generic_readlink,
2699         .get_link       = simple_get_link,
2700 #ifdef CONFIG_TMPFS_XATTR
2701         .setxattr       = generic_setxattr,
2702         .getxattr       = generic_getxattr,
2703         .listxattr      = shmem_listxattr,
2704         .removexattr    = generic_removexattr,
2705 #endif
2706 };
2707 
2708 static const struct inode_operations shmem_symlink_inode_operations = {
2709         .readlink       = generic_readlink,
2710         .get_link       = shmem_get_link,
2711 #ifdef CONFIG_TMPFS_XATTR
2712         .setxattr       = generic_setxattr,
2713         .getxattr       = generic_getxattr,
2714         .listxattr      = shmem_listxattr,
2715         .removexattr    = generic_removexattr,
2716 #endif
2717 };
2718 
2719 static struct dentry *shmem_get_parent(struct dentry *child)
2720 {
2721         return ERR_PTR(-ESTALE);
2722 }
2723 
2724 static int shmem_match(struct inode *ino, void *vfh)
2725 {
2726         __u32 *fh = vfh;
2727         __u64 inum = fh[2];
2728         inum = (inum << 32) | fh[1];
2729         return ino->i_ino == inum && fh[0] == ino->i_generation;
2730 }
2731 
2732 static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
2733                 struct fid *fid, int fh_len, int fh_type)
2734 {
2735         struct inode *inode;
2736         struct dentry *dentry = NULL;
2737         u64 inum;
2738 
2739         if (fh_len < 3)
2740                 return NULL;
2741 
2742         inum = fid->raw[2];
2743         inum = (inum << 32) | fid->raw[1];
2744 
2745         inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
2746                         shmem_match, fid->raw);
2747         if (inode) {
2748                 dentry = d_find_alias(inode);
2749                 iput(inode);
2750         }
2751 
2752         return dentry;
2753 }
2754 
2755 static int shmem_encode_fh(struct inode *inode, __u32 *fh, int *len,
2756                                 struct inode *parent)
2757 {
2758         if (*len < 3) {
2759                 *len = 3;
2760                 return FILEID_INVALID;
2761         }
2762 
2763         if (inode_unhashed(inode)) {
2764                 /* Unfortunately insert_inode_hash is not idempotent,
2765                  * so as we hash inodes here rather than at creation
2766                  * time, we need a lock to ensure we only try
2767                  * to do it once
2768                  */
2769                 static DEFINE_SPINLOCK(lock);
2770                 spin_lock(&lock);
2771                 if (inode_unhashed(inode))
2772                         __insert_inode_hash(inode,
2773                                             inode->i_ino + inode->i_generation);
2774                 spin_unlock(&lock);
2775         }
2776 
2777         fh[0] = inode->i_generation;
2778         fh[1] = inode->i_ino;
2779         fh[2] = ((__u64)inode->i_ino) >> 32;
2780 
2781         *len = 3;
2782         return 1;
2783 }
2784 
2785 static const struct export_operations shmem_export_ops = {
2786         .get_parent     = shmem_get_parent,
2787         .encode_fh      = shmem_encode_fh,
2788         .fh_to_dentry   = shmem_fh_to_dentry,
2789 };
2790 
2791 static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
2792                                bool remount)
2793 {
2794         char *this_char, *value, *rest;
2795         struct mempolicy *mpol = NULL;
2796         uid_t uid;
2797         gid_t gid;
2798 
2799         while (options != NULL) {
2800                 this_char = options;
2801                 for (;;) {
2802                         /*
2803                          * NUL-terminate this option: unfortunately,
2804                          * mount options form a comma-separated list,
2805                          * but mpol's nodelist may also contain commas.
2806                          */
2807                         options = strchr(options, ',');
2808                         if (options == NULL)
2809                                 break;
2810                         options++;
2811                         if (!isdigit(*options)) {
2812                                 options[-1] = '\0';
2813                                 break;
2814                         }
2815                 }
2816                 if (!*this_char)
2817                         continue;
2818                 if ((value = strchr(this_char,'=')) != NULL) {
2819                         *value++ = 0;
2820                 } else {
2821                         pr_err("tmpfs: No value for mount option '%s'\n",
2822                                this_char);
2823                         goto error;
2824                 }
2825 
2826                 if (!strcmp(this_char,"size")) {
2827                         unsigned long long size;
2828                         size = memparse(value,&rest);
2829                         if (*rest == '%') {
2830                                 size <<= PAGE_SHIFT;
2831                                 size *= totalram_pages;
2832                                 do_div(size, 100);
2833                                 rest++;
2834                         }
2835                         if (*rest)
2836                                 goto bad_val;
2837                         sbinfo->max_blocks =
2838                                 DIV_ROUND_UP(size, PAGE_SIZE);
2839                 } else if (!strcmp(this_char,"nr_blocks")) {
2840                         sbinfo->max_blocks = memparse(value, &rest);
2841                         if (*rest)
2842                                 goto bad_val;
2843                 } else if (!strcmp(this_char,"nr_inodes")) {
2844                         sbinfo->max_inodes = memparse(value, &rest);
2845                         if (*rest)
2846                                 goto bad_val;
2847                 } else if (!strcmp(this_char,"mode")) {
2848                         if (remount)
2849                                 continue;
2850                         sbinfo->mode = simple_strtoul(value, &rest, 8) & 07777;
2851                         if (*rest)
2852                                 goto bad_val;
2853                 } else if (!strcmp(this_char,"uid")) {
2854                         if (remount)
2855                                 continue;
2856                         uid = simple_strtoul(value, &rest, 0);
2857                         if (*rest)
2858                                 goto bad_val;
2859                         sbinfo->uid = make_kuid(current_user_ns(), uid);
2860                         if (!uid_valid(sbinfo->uid))
2861                                 goto bad_val;
2862                 } else if (!strcmp(this_char,"gid")) {
2863                         if (remount)
2864                                 continue;
2865                         gid = simple_strtoul(value, &rest, 0);
2866                         if (*rest)
2867                                 goto bad_val;
2868                         sbinfo->gid = make_kgid(current_user_ns(), gid);
2869                         if (!gid_valid(sbinfo->gid))
2870                                 goto bad_val;
2871                 } else if (!strcmp(this_char,"mpol")) {
2872                         mpol_put(mpol);
2873                         mpol = NULL;
2874                         if (mpol_parse_str(value, &mpol))
2875                                 goto bad_val;
2876                 } else {
2877                         pr_err("tmpfs: Bad mount option %s\n", this_char);
2878                         goto error;
2879                 }
2880         }
2881         sbinfo->mpol = mpol;
2882         return 0;
2883 
2884 bad_val:
2885         pr_err("tmpfs: Bad value '%s' for mount option '%s'\n",
2886                value, this_char);
2887 error:
2888         mpol_put(mpol);
2889         return 1;
2890 
2891 }
2892 
2893 static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
2894 {
2895         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2896         struct shmem_sb_info config = *sbinfo;
2897         unsigned long inodes;
2898         int error = -EINVAL;
2899 
2900         config.mpol = NULL;
2901         if (shmem_parse_options(data, &config, true))
2902                 return error;
2903 
2904         spin_lock(&sbinfo->stat_lock);
2905         inodes = sbinfo->max_inodes - sbinfo->free_inodes;
2906         if (percpu_counter_compare(&sbinfo->used_blocks, config.max_blocks) > 0)
2907                 goto out;
2908         if (config.max_inodes < inodes)
2909                 goto out;
2910         /*
2911          * Those tests disallow limited->unlimited while any are in use;
2912          * but we must separately disallow unlimited->limited, because
2913          * in that case we have no record of how much is already in use.
2914          */
2915         if (config.max_blocks && !sbinfo->max_blocks)
2916                 goto out;
2917         if (config.max_inodes && !sbinfo->max_inodes)
2918                 goto out;
2919 
2920         error = 0;
2921         sbinfo->max_blocks  = config.max_blocks;
2922         sbinfo->max_inodes  = config.max_inodes;
2923         sbinfo->free_inodes = config.max_inodes - inodes;
2924 
2925         /*
2926          * Preserve previous mempolicy unless mpol remount option was specified.
2927          */
2928         if (config.mpol) {
2929                 mpol_put(sbinfo->mpol);
2930                 sbinfo->mpol = config.mpol;     /* transfers initial ref */
2931         }
2932 out:
2933         spin_unlock(&sbinfo->stat_lock);
2934         return error;
2935 }
2936 
2937 static int shmem_show_options(struct seq_file *seq, struct dentry *root)
2938 {
2939         struct shmem_sb_info *sbinfo = SHMEM_SB(root->d_sb);
2940 
2941         if (sbinfo->max_blocks != shmem_default_max_blocks())
2942                 seq_printf(seq, ",size=%luk",
2943                         sbinfo->max_blocks << (PAGE_SHIFT - 10));
2944         if (sbinfo->max_inodes != shmem_default_max_inodes())
2945                 seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
2946         if (sbinfo->mode != (S_IRWXUGO | S_ISVTX))
2947                 seq_printf(seq, ",mode=%03ho", sbinfo->mode);
2948         if (!uid_eq(sbinfo->uid, GLOBAL_ROOT_UID))
2949                 seq_printf(seq, ",uid=%u",
2950                                 from_kuid_munged(&init_user_ns, sbinfo->uid));
2951         if (!gid_eq(sbinfo->gid, GLOBAL_ROOT_GID))
2952                 seq_printf(seq, ",gid=%u",
2953                                 from_kgid_munged(&init_user_ns, sbinfo->gid));
2954         shmem_show_mpol(seq, sbinfo->mpol);
2955         return 0;
2956 }
2957 
2958 #define MFD_NAME_PREFIX "memfd:"
2959 #define MFD_NAME_PREFIX_LEN (sizeof(MFD_NAME_PREFIX) - 1)
2960 #define MFD_NAME_MAX_LEN (NAME_MAX - MFD_NAME_PREFIX_LEN)
2961 
2962 #define MFD_ALL_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING)
2963 
2964 SYSCALL_DEFINE2(memfd_create,
2965                 const char __user *, uname,
2966                 unsigned int, flags)
2967 {
2968         struct shmem_inode_info *info;
2969         struct file *file;
2970         int fd, error;
2971         char *name;
2972         long len;
2973 
2974         if (flags & ~(unsigned int)MFD_ALL_FLAGS)
2975                 return -EINVAL;
2976 
2977         /* length includes terminating zero */
2978         len = strnlen_user(uname, MFD_NAME_MAX_LEN + 1);
2979         if (len <= 0)
2980                 return -EFAULT;
2981         if (len > MFD_NAME_MAX_LEN + 1)
2982                 return -EINVAL;
2983 
2984         name = kmalloc(len + MFD_NAME_PREFIX_LEN, GFP_TEMPORARY);
2985         if (!name)
2986                 return -ENOMEM;
2987 
2988         strcpy(name, MFD_NAME_PREFIX);
2989         if (copy_from_user(&name[MFD_NAME_PREFIX_LEN], uname, len)) {
2990                 error = -EFAULT;
2991                 goto err_name;
2992         }
2993 
2994         /* terminating-zero may have changed after strnlen_user() returned */
2995         if (name[len + MFD_NAME_PREFIX_LEN - 1]) {
2996                 error = -EFAULT;
2997                 goto err_name;
2998         }
2999 
3000         fd = get_unused_fd_flags((flags & MFD_CLOEXEC) ? O_CLOEXEC : 0);
3001         if (fd < 0) {
3002                 error = fd;
3003                 goto err_name;
3004         }
3005 
3006         file = shmem_file_setup(name, 0, VM_NORESERVE);
3007         if (IS_ERR(file)) {
3008                 error = PTR_ERR(file);
3009                 goto err_fd;
3010         }
3011         info = SHMEM_I(file_inode(file));
3012         file->f_mode |= FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE;
3013         file->f_flags |= O_RDWR | O_LARGEFILE;
3014         if (flags & MFD_ALLOW_SEALING)
3015                 info->seals &= ~F_SEAL_SEAL;
3016 
3017         fd_install(fd, file);
3018         kfree(name);
3019         return fd;
3020 
3021 err_fd:
3022         put_unused_fd(fd);
3023 err_name:
3024         kfree(name);
3025         return error;
3026 }
3027 
3028 #endif /* CONFIG_TMPFS */
3029 
3030 static void shmem_put_super(struct super_block *sb)
3031 {
3032         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
3033 
3034         percpu_counter_destroy(&sbinfo->used_blocks);
3035         mpol_put(sbinfo->mpol);
3036         kfree(sbinfo);
3037         sb->s_fs_info = NULL;
3038 }
3039 
3040 int shmem_fill_super(struct super_block *sb, void *data, int silent)
3041 {
3042         struct inode *inode;
3043         struct shmem_sb_info *sbinfo;
3044         int err = -ENOMEM;
3045 
3046         /* Round up to L1_CACHE_BYTES to resist false sharing */
3047         sbinfo = kzalloc(max((int)sizeof(struct shmem_sb_info),
3048                                 L1_CACHE_BYTES), GFP_KERNEL);
3049         if (!sbinfo)
3050                 return -ENOMEM;
3051 
3052         sbinfo->mode = S_IRWXUGO | S_ISVTX;
3053         sbinfo->uid = current_fsuid();
3054         sbinfo->gid = current_fsgid();
3055         sb->s_fs_info = sbinfo;
3056 
3057 #ifdef CONFIG_TMPFS
3058         /*
3059          * Per default we only allow half of the physical ram per
3060          * tmpfs instance, limiting inodes to one per page of lowmem;
3061          * but the internal instance is left unlimited.
3062          */
3063         if (!(sb->s_flags & MS_KERNMOUNT)) {
3064                 sbinfo->max_blocks = shmem_default_max_blocks();
3065                 sbinfo->max_inodes = shmem_default_max_inodes();
3066                 if (shmem_parse_options(data, sbinfo, false)) {
3067                         err = -EINVAL;
3068                         goto failed;
3069                 }
3070         } else {
3071                 sb->s_flags |= MS_NOUSER;
3072         }
3073         sb->s_export_op = &shmem_export_ops;
3074         sb->s_flags |= MS_NOSEC;
3075 #else
3076         sb->s_flags |= MS_NOUSER;
3077 #endif
3078 
3079         spin_lock_init(&sbinfo->stat_lock);
3080         if (percpu_counter_init(&sbinfo->used_blocks, 0, GFP_KERNEL))
3081                 goto failed;
3082         sbinfo->free_inodes = sbinfo->max_inodes;
3083 
3084         sb->s_maxbytes = MAX_LFS_FILESIZE;
3085         sb->s_blocksize = PAGE_SIZE;
3086         sb->s_blocksize_bits = PAGE_SHIFT;
3087         sb->s_magic = TMPFS_MAGIC;
3088         sb->s_op = &shmem_ops;
3089         sb->s_time_gran = 1;
3090 #ifdef CONFIG_TMPFS_XATTR
3091         sb->s_xattr = shmem_xattr_handlers;
3092 #endif
3093 #ifdef CONFIG_TMPFS_POSIX_ACL
3094         sb->s_flags |= MS_POSIXACL;
3095 #endif
3096 
3097         inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
3098         if (!inode)
3099                 goto failed;
3100         inode->i_uid = sbinfo->uid;
3101         inode->i_gid = sbinfo->gid;
3102         sb->s_root = d_make_root(inode);
3103         if (!sb->s_root)
3104                 goto failed;
3105         return 0;
3106 
3107 failed:
3108         shmem_put_super(sb);
3109         return err;
3110 }
3111 
3112 static struct kmem_cache *shmem_inode_cachep;
3113 
3114 static struct inode *shmem_alloc_inode(struct super_block *sb)
3115 {
3116         struct shmem_inode_info *info;
3117         info = kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
3118         if (!info)
3119                 return NULL;
3120         return &info->vfs_inode;
3121 }
3122 
3123 static void shmem_destroy_callback(struct rcu_head *head)
3124 {
3125         struct inode *inode = container_of(head, struct inode, i_rcu);
3126         kfree(inode->i_link);
3127         kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
3128 }
3129 
3130 static void shmem_destroy_inode(struct inode *inode)
3131 {
3132         if (S_ISREG(inode->i_mode))
3133                 mpol_free_shared_policy(&SHMEM_I(inode)->policy);
3134         call_rcu(&inode->i_rcu, shmem_destroy_callback);
3135 }
3136 
3137 static void shmem_init_inode(void *foo)
3138 {
3139         struct shmem_inode_info *info = foo;
3140         inode_init_once(&info->vfs_inode);
3141 }
3142 
3143 static int shmem_init_inodecache(void)
3144 {
3145         shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
3146                                 sizeof(struct shmem_inode_info),
3147                                 0, SLAB_PANIC|SLAB_ACCOUNT, shmem_init_inode);
3148         return 0;
3149 }
3150 
3151 static void shmem_destroy_inodecache(void)
3152 {
3153         kmem_cache_destroy(shmem_inode_cachep);
3154 }
3155 
3156 static const struct address_space_operations shmem_aops = {
3157         .writepage      = shmem_writepage,
3158         .set_page_dirty = __set_page_dirty_no_writeback,
3159 #ifdef CONFIG_TMPFS
3160         .write_begin    = shmem_write_begin,
3161         .write_end      = shmem_write_end,
3162 #endif
3163 #ifdef CONFIG_MIGRATION
3164         .migratepage    = migrate_page,
3165 #endif
3166         .error_remove_page = generic_error_remove_page,
3167 };
3168 
3169 static const struct file_operations shmem_file_operations = {
3170         .mmap           = shmem_mmap,
3171 #ifdef CONFIG_TMPFS
3172         .llseek         = shmem_file_llseek,
3173         .read_iter      = shmem_file_read_iter,
3174         .write_iter     = generic_file_write_iter,
3175         .fsync          = noop_fsync,
3176         .splice_read    = shmem_file_splice_read,
3177         .splice_write   = iter_file_splice_write,
3178         .fallocate      = shmem_fallocate,
3179 #endif
3180 };
3181 
3182 static const struct inode_operations shmem_inode_operations = {
3183         .getattr        = shmem_getattr,
3184         .setattr        = shmem_setattr,
3185 #ifdef CONFIG_TMPFS_XATTR
3186         .setxattr       = generic_setxattr,
3187         .getxattr       = generic_getxattr,
3188         .listxattr      = shmem_listxattr,
3189         .removexattr    = generic_removexattr,
3190         .set_acl        = simple_set_acl,
3191 #endif
3192 };
3193 
3194 static const struct inode_operations shmem_dir_inode_operations = {
3195 #ifdef CONFIG_TMPFS
3196         .create         = shmem_create,
3197         .lookup         = simple_lookup,
3198         .link           = shmem_link,
3199         .unlink         = shmem_unlink,
3200         .symlink        = shmem_symlink,
3201         .mkdir          = shmem_mkdir,
3202         .rmdir          = shmem_rmdir,
3203         .mknod          = shmem_mknod,
3204         .rename2        = shmem_rename2,
3205         .tmpfile        = shmem_tmpfile,
3206 #endif
3207 #ifdef CONFIG_TMPFS_XATTR
3208         .setxattr       = generic_setxattr,
3209         .getxattr       = generic_getxattr,
3210         .listxattr      = shmem_listxattr,
3211         .removexattr    = generic_removexattr,
3212 #endif
3213 #ifdef CONFIG_TMPFS_POSIX_ACL
3214         .setattr        = shmem_setattr,
3215         .set_acl        = simple_set_acl,
3216 #endif
3217 };
3218 
3219 static const struct inode_operations shmem_special_inode_operations = {
3220 #ifdef CONFIG_TMPFS_XATTR
3221         .setxattr       = generic_setxattr,
3222         .getxattr       = generic_getxattr,
3223         .listxattr      = shmem_listxattr,
3224         .removexattr    = generic_removexattr,
3225 #endif
3226 #ifdef CONFIG_TMPFS_POSIX_ACL
3227         .setattr        = shmem_setattr,
3228         .set_acl        = simple_set_acl,
3229 #endif
3230 };
3231 
3232 static const struct super_operations shmem_ops = {
3233         .alloc_inode    = shmem_alloc_inode,
3234         .destroy_inode  = shmem_destroy_inode,
3235 #ifdef CONFIG_TMPFS
3236         .statfs         = shmem_statfs,
3237         .remount_fs     = shmem_remount_fs,
3238         .show_options   = shmem_show_options,
3239 #endif
3240         .evict_inode    = shmem_evict_inode,
3241         .drop_inode     = generic_delete_inode,
3242         .put_super      = shmem_put_super,
3243 };
3244 
3245 static const struct vm_operations_struct shmem_vm_ops = {
3246         .fault          = shmem_fault,
3247         .map_pages      = filemap_map_pages,
3248 #ifdef CONFIG_NUMA
3249         .set_policy     = shmem_set_policy,
3250         .get_policy     = shmem_get_policy,
3251 #endif
3252 };
3253 
3254 static struct dentry *shmem_mount(struct file_system_type *fs_type,
3255         int flags, const char *dev_name, void *data)
3256 {
3257         return mount_nodev(fs_type, flags, data, shmem_fill_super);
3258 }
3259 
3260 static struct file_system_type shmem_fs_type = {
3261         .owner          = THIS_MODULE,
3262         .name           = "tmpfs",
3263         .mount          = shmem_mount,
3264         .kill_sb        = kill_litter_super,
3265         .fs_flags       = FS_USERNS_MOUNT,
3266 };
3267 
3268 int __init shmem_init(void)
3269 {
3270         int error;
3271 
3272         /* If rootfs called this, don't re-init */
3273         if (shmem_inode_cachep)
3274                 return 0;
3275 
3276         error = shmem_init_inodecache();
3277         if (error)
3278                 goto out3;
3279 
3280         error = register_filesystem(&shmem_fs_type);
3281         if (error) {
3282                 pr_err("Could not register tmpfs\n");
3283                 goto out2;
3284         }
3285 
3286         shm_mnt = kern_mount(&shmem_fs_type);
3287         if (IS_ERR(shm_mnt)) {
3288                 error = PTR_ERR(shm_mnt);
3289                 pr_err("Could not kern_mount tmpfs\n");
3290                 goto out1;
3291         }
3292         return 0;
3293 
3294 out1:
3295         unregister_filesystem(&shmem_fs_type);
3296 out2:
3297         shmem_destroy_inodecache();
3298 out3:
3299         shm_mnt = ERR_PTR(error);
3300         return error;
3301 }
3302 
3303 #else /* !CONFIG_SHMEM */
3304 
3305 /*
3306  * tiny-shmem: simple shmemfs and tmpfs using ramfs code
3307  *
3308  * This is intended for small system where the benefits of the full
3309  * shmem code (swap-backed and resource-limited) are outweighed by
3310  * their complexity. On systems without swap this code should be
3311  * effectively equivalent, but much lighter weight.
3312  */
3313 
3314 static struct file_system_type shmem_fs_type = {
3315         .name           = "tmpfs",
3316         .mount          = ramfs_mount,
3317         .kill_sb        = kill_litter_super,
3318         .fs_flags       = FS_USERNS_MOUNT,
3319 };
3320 
3321 int __init shmem_init(void)
3322 {
3323         BUG_ON(register_filesystem(&shmem_fs_type) != 0);
3324 
3325         shm_mnt = kern_mount(&shmem_fs_type);
3326         BUG_ON(IS_ERR(shm_mnt));
3327 
3328         return 0;
3329 }
3330 
3331 int shmem_unuse(swp_entry_t swap, struct page *page)
3332 {
3333         return 0;
3334 }
3335 
3336 int shmem_lock(struct file *file, int lock, struct user_struct *user)
3337 {
3338         return 0;
3339 }
3340 
3341 void shmem_unlock_mapping(struct address_space *mapping)
3342 {
3343 }
3344 
3345 void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
3346 {
3347         truncate_inode_pages_range(inode->i_mapping, lstart, lend);
3348 }
3349 EXPORT_SYMBOL_GPL(shmem_truncate_range);
3350 
3351 #define shmem_vm_ops                            generic_file_vm_ops
3352 #define shmem_file_operations                   ramfs_file_operations
3353 #define shmem_get_inode(sb, dir, mode, dev, flags)      ramfs_get_inode(sb, dir, mode, dev)
3354 #define shmem_acct_size(flags, size)            0
3355 #define shmem_unacct_size(flags, size)          do {} while (0)
3356 
3357 #endif /* CONFIG_SHMEM */
3358 
3359 /* common code */
3360 
3361 static struct dentry_operations anon_ops = {
3362         .d_dname = simple_dname
3363 };
3364 
3365 static struct file *__shmem_file_setup(const char *name, loff_t size,
3366                                        unsigned long flags, unsigned int i_flags)
3367 {
3368         struct file *res;
3369         struct inode *inode;
3370         struct path path;
3371         struct super_block *sb;
3372         struct qstr this;
3373 
3374         if (IS_ERR(shm_mnt))
3375                 return ERR_CAST(shm_mnt);
3376 
3377         if (size < 0 || size > MAX_LFS_FILESIZE)
3378                 return ERR_PTR(-EINVAL);
3379 
3380         if (shmem_acct_size(flags, size))
3381                 return ERR_PTR(-ENOMEM);
3382 
3383         res = ERR_PTR(-ENOMEM);
3384         this.name = name;
3385         this.len = strlen(name);
3386         this.hash = 0; /* will go */
3387         sb = shm_mnt->mnt_sb;
3388         path.mnt = mntget(shm_mnt);
3389         path.dentry = d_alloc_pseudo(sb, &this);
3390         if (!path.dentry)
3391                 goto put_memory;
3392         d_set_d_op(path.dentry, &anon_ops);
3393 
3394         res = ERR_PTR(-ENOSPC);
3395         inode = shmem_get_inode(sb, NULL, S_IFREG | S_IRWXUGO, 0, flags);
3396         if (!inode)
3397                 goto put_memory;
3398 
3399         inode->i_flags |= i_flags;
3400         d_instantiate(path.dentry, inode);
3401         inode->i_size = size;
3402         clear_nlink(inode);     /* It is unlinked */
3403         res = ERR_PTR(ramfs_nommu_expand_for_mapping(inode, size));
3404         if (IS_ERR(res))
3405                 goto put_path;
3406 
3407         res = alloc_file(&path, FMODE_WRITE | FMODE_READ,
3408                   &shmem_file_operations);
3409         if (IS_ERR(res))
3410                 goto put_path;
3411 
3412         return res;
3413 
3414 put_memory:
3415         shmem_unacct_size(flags, size);
3416 put_path:
3417         path_put(&path);
3418         return res;
3419 }
3420 
3421 /**
3422  * shmem_kernel_file_setup - get an unlinked file living in tmpfs which must be
3423  *      kernel internal.  There will be NO LSM permission checks against the
3424  *      underlying inode.  So users of this interface must do LSM checks at a
3425  *      higher layer.  The users are the big_key and shm implementations.  LSM
3426  *      checks are provided at the key or shm level rather than the inode.
3427  * @name: name for dentry (to be seen in /proc/<pid>/maps
3428  * @size: size to be set for the file
3429  * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
3430  */
3431 struct file *shmem_kernel_file_setup(const char *name, loff_t size, unsigned long flags)
3432 {
3433         return __shmem_file_setup(name, size, flags, S_PRIVATE);
3434 }
3435 
3436 /**
3437  * shmem_file_setup - get an unlinked file living in tmpfs
3438  * @name: name for dentry (to be seen in /proc/<pid>/maps
3439  * @size: size to be set for the file
3440  * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
3441  */
3442 struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags)
3443 {
3444         return __shmem_file_setup(name, size, flags, 0);
3445 }
3446 EXPORT_SYMBOL_GPL(shmem_file_setup);
3447 
3448 /**
3449  * shmem_zero_setup - setup a shared anonymous mapping
3450  * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
3451  */
3452 int shmem_zero_setup(struct vm_area_struct *vma)
3453 {
3454         struct file *file;
3455         loff_t size = vma->vm_end - vma->vm_start;
3456 
3457         /*
3458          * Cloning a new file under mmap_sem leads to a lock ordering conflict
3459          * between XFS directory reading and selinux: since this file is only
3460          * accessible to the user through its mapping, use S_PRIVATE flag to
3461          * bypass file security, in the same way as shmem_kernel_file_setup().
3462          */
3463         file = __shmem_file_setup("dev/zero", size, vma->vm_flags, S_PRIVATE);
3464         if (IS_ERR(file))
3465                 return PTR_ERR(file);
3466 
3467         if (vma->vm_file)
3468                 fput(vma->vm_file);
3469         vma->vm_file = file;
3470         vma->vm_ops = &shmem_vm_ops;
3471         return 0;
3472 }
3473 
3474 /**
3475  * shmem_read_mapping_page_gfp - read into page cache, using specified page allocation flags.
3476  * @mapping:    the page's address_space
3477  * @index:      the page index
3478  * @gfp:        the page allocator flags to use if allocating
3479  *
3480  * This behaves as a tmpfs "read_cache_page_gfp(mapping, index, gfp)",
3481  * with any new page allocations done using the specified allocation flags.
3482  * But read_cache_page_gfp() uses the ->readpage() method: which does not
3483  * suit tmpfs, since it may have pages in swapcache, and needs to find those
3484  * for itself; although drivers/gpu/drm i915 and ttm rely upon this support.
3485  *
3486  * i915_gem_object_get_pages_gtt() mixes __GFP_NORETRY | __GFP_NOWARN in
3487  * with the mapping_gfp_mask(), to avoid OOMing the machine unnecessarily.
3488  */
3489 struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
3490                                          pgoff_t index, gfp_t gfp)
3491 {
3492 #ifdef CONFIG_SHMEM
3493         struct inode *inode = mapping->host;
3494         struct page *page;
3495         int error;
3496 
3497         BUG_ON(mapping->a_ops != &shmem_aops);
3498         error = shmem_getpage_gfp(inode, index, &page, SGP_CACHE, gfp, NULL);
3499         if (error)
3500                 page = ERR_PTR(error);
3501         else
3502                 unlock_page(page);
3503         return page;
3504 #else
3505         /*
3506          * The tiny !SHMEM case uses ramfs without swap
3507          */
3508         return read_cache_page_gfp(mapping, index, gfp);
3509 #endif
3510 }
3511 EXPORT_SYMBOL_GPL(shmem_read_mapping_page_gfp);
3512 

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