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0001 /*
0002  * Resizable virtual memory filesystem for Linux.
0003  *
0004  * Copyright (C) 2000 Linus Torvalds.
0005  *       2000 Transmeta Corp.
0006  *       2000-2001 Christoph Rohland
0007  *       2000-2001 SAP AG
0008  *       2002 Red Hat Inc.
0009  * Copyright (C) 2002-2011 Hugh Dickins.
0010  * Copyright (C) 2011 Google Inc.
0011  * Copyright (C) 2002-2005 VERITAS Software Corporation.
0012  * Copyright (C) 2004 Andi Kleen, SuSE Labs
0013  *
0014  * Extended attribute support for tmpfs:
0015  * Copyright (c) 2004, Luke Kenneth Casson Leighton <lkcl@lkcl.net>
0016  * Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
0017  *
0018  * tiny-shmem:
0019  * Copyright (c) 2004, 2008 Matt Mackall <mpm@selenic.com>
0020  *
0021  * This file is released under the GPL.
0022  */
0023 
0024 #include <linux/fs.h>
0025 #include <linux/init.h>
0026 #include <linux/vfs.h>
0027 #include <linux/mount.h>
0028 #include <linux/ramfs.h>
0029 #include <linux/pagemap.h>
0030 #include <linux/file.h>
0031 #include <linux/mm.h>
0032 #include <linux/export.h>
0033 #include <linux/swap.h>
0034 #include <linux/uio.h>
0035 #include <linux/khugepaged.h>
0036 
0037 static struct vfsmount *shm_mnt;
0038 
0039 #ifdef CONFIG_SHMEM
0040 /*
0041  * This virtual memory filesystem is heavily based on the ramfs. It
0042  * extends ramfs by the ability to use swap and honor resource limits
0043  * which makes it a completely usable filesystem.
0044  */
0045 
0046 #include <linux/xattr.h>
0047 #include <linux/exportfs.h>
0048 #include <linux/posix_acl.h>
0049 #include <linux/posix_acl_xattr.h>
0050 #include <linux/mman.h>
0051 #include <linux/string.h>
0052 #include <linux/slab.h>
0053 #include <linux/backing-dev.h>
0054 #include <linux/shmem_fs.h>
0055 #include <linux/writeback.h>
0056 #include <linux/blkdev.h>
0057 #include <linux/pagevec.h>
0058 #include <linux/percpu_counter.h>
0059 #include <linux/falloc.h>
0060 #include <linux/splice.h>
0061 #include <linux/security.h>
0062 #include <linux/swapops.h>
0063 #include <linux/mempolicy.h>
0064 #include <linux/namei.h>
0065 #include <linux/ctype.h>
0066 #include <linux/migrate.h>
0067 #include <linux/highmem.h>
0068 #include <linux/seq_file.h>
0069 #include <linux/magic.h>
0070 #include <linux/syscalls.h>
0071 #include <linux/fcntl.h>
0072 #include <uapi/linux/memfd.h>
0073 
0074 #include <linux/uaccess.h>
0075 #include <asm/pgtable.h>
0076 
0077 #include "internal.h"
0078 
0079 #define BLOCKS_PER_PAGE  (PAGE_SIZE/512)
0080 #define VM_ACCT(size)    (PAGE_ALIGN(size) >> PAGE_SHIFT)
0081 
0082 /* Pretend that each entry is of this size in directory's i_size */
0083 #define BOGO_DIRENT_SIZE 20
0084 
0085 /* Symlink up to this size is kmalloc'ed instead of using a swappable page */
0086 #define SHORT_SYMLINK_LEN 128
0087 
0088 /*
0089  * shmem_fallocate communicates with shmem_fault or shmem_writepage via
0090  * inode->i_private (with i_mutex making sure that it has only one user at
0091  * a time): we would prefer not to enlarge the shmem inode just for that.
0092  */
0093 struct shmem_falloc {
0094     wait_queue_head_t *waitq; /* faults into hole wait for punch to end */
0095     pgoff_t start;      /* start of range currently being fallocated */
0096     pgoff_t next;       /* the next page offset to be fallocated */
0097     pgoff_t nr_falloced;    /* how many new pages have been fallocated */
0098     pgoff_t nr_unswapped;   /* how often writepage refused to swap out */
0099 };
0100 
0101 #ifdef CONFIG_TMPFS
0102 static unsigned long shmem_default_max_blocks(void)
0103 {
0104     return totalram_pages / 2;
0105 }
0106 
0107 static unsigned long shmem_default_max_inodes(void)
0108 {
0109     return min(totalram_pages - totalhigh_pages, totalram_pages / 2);
0110 }
0111 #endif
0112 
0113 static bool shmem_should_replace_page(struct page *page, gfp_t gfp);
0114 static int shmem_replace_page(struct page **pagep, gfp_t gfp,
0115                 struct shmem_inode_info *info, pgoff_t index);
0116 static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
0117         struct page **pagep, enum sgp_type sgp,
0118         gfp_t gfp, struct mm_struct *fault_mm, int *fault_type);
0119 
0120 int shmem_getpage(struct inode *inode, pgoff_t index,
0121         struct page **pagep, enum sgp_type sgp)
0122 {
0123     return shmem_getpage_gfp(inode, index, pagep, sgp,
0124         mapping_gfp_mask(inode->i_mapping), NULL, NULL);
0125 }
0126 
0127 static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
0128 {
0129     return sb->s_fs_info;
0130 }
0131 
0132 /*
0133  * shmem_file_setup pre-accounts the whole fixed size of a VM object,
0134  * for shared memory and for shared anonymous (/dev/zero) mappings
0135  * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
0136  * consistent with the pre-accounting of private mappings ...
0137  */
0138 static inline int shmem_acct_size(unsigned long flags, loff_t size)
0139 {
0140     return (flags & VM_NORESERVE) ?
0141         0 : security_vm_enough_memory_mm(current->mm, VM_ACCT(size));
0142 }
0143 
0144 static inline void shmem_unacct_size(unsigned long flags, loff_t size)
0145 {
0146     if (!(flags & VM_NORESERVE))
0147         vm_unacct_memory(VM_ACCT(size));
0148 }
0149 
0150 static inline int shmem_reacct_size(unsigned long flags,
0151         loff_t oldsize, loff_t newsize)
0152 {
0153     if (!(flags & VM_NORESERVE)) {
0154         if (VM_ACCT(newsize) > VM_ACCT(oldsize))
0155             return security_vm_enough_memory_mm(current->mm,
0156                     VM_ACCT(newsize) - VM_ACCT(oldsize));
0157         else if (VM_ACCT(newsize) < VM_ACCT(oldsize))
0158             vm_unacct_memory(VM_ACCT(oldsize) - VM_ACCT(newsize));
0159     }
0160     return 0;
0161 }
0162 
0163 /*
0164  * ... whereas tmpfs objects are accounted incrementally as
0165  * pages are allocated, in order to allow large sparse files.
0166  * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
0167  * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
0168  */
0169 static inline int shmem_acct_block(unsigned long flags, long pages)
0170 {
0171     if (!(flags & VM_NORESERVE))
0172         return 0;
0173 
0174     return security_vm_enough_memory_mm(current->mm,
0175             pages * VM_ACCT(PAGE_SIZE));
0176 }
0177 
0178 static inline void shmem_unacct_blocks(unsigned long flags, long pages)
0179 {
0180     if (flags & VM_NORESERVE)
0181         vm_unacct_memory(pages * VM_ACCT(PAGE_SIZE));
0182 }
0183 
0184 static const struct super_operations shmem_ops;
0185 static const struct address_space_operations shmem_aops;
0186 static const struct file_operations shmem_file_operations;
0187 static const struct inode_operations shmem_inode_operations;
0188 static const struct inode_operations shmem_dir_inode_operations;
0189 static const struct inode_operations shmem_special_inode_operations;
0190 static const struct vm_operations_struct shmem_vm_ops;
0191 static struct file_system_type shmem_fs_type;
0192 
0193 static LIST_HEAD(shmem_swaplist);
0194 static DEFINE_MUTEX(shmem_swaplist_mutex);
0195 
0196 static int shmem_reserve_inode(struct super_block *sb)
0197 {
0198     struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
0199     if (sbinfo->max_inodes) {
0200         spin_lock(&sbinfo->stat_lock);
0201         if (!sbinfo->free_inodes) {
0202             spin_unlock(&sbinfo->stat_lock);
0203             return -ENOSPC;
0204         }
0205         sbinfo->free_inodes--;
0206         spin_unlock(&sbinfo->stat_lock);
0207     }
0208     return 0;
0209 }
0210 
0211 static void shmem_free_inode(struct super_block *sb)
0212 {
0213     struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
0214     if (sbinfo->max_inodes) {
0215         spin_lock(&sbinfo->stat_lock);
0216         sbinfo->free_inodes++;
0217         spin_unlock(&sbinfo->stat_lock);
0218     }
0219 }
0220 
0221 /**
0222  * shmem_recalc_inode - recalculate the block usage of an inode
0223  * @inode: inode to recalc
0224  *
0225  * We have to calculate the free blocks since the mm can drop
0226  * undirtied hole pages behind our back.
0227  *
0228  * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
0229  * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
0230  *
0231  * It has to be called with the spinlock held.
0232  */
0233 static void shmem_recalc_inode(struct inode *inode)
0234 {
0235     struct shmem_inode_info *info = SHMEM_I(inode);
0236     long freed;
0237 
0238     freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
0239     if (freed > 0) {
0240         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
0241         if (sbinfo->max_blocks)
0242             percpu_counter_add(&sbinfo->used_blocks, -freed);
0243         info->alloced -= freed;
0244         inode->i_blocks -= freed * BLOCKS_PER_PAGE;
0245         shmem_unacct_blocks(info->flags, freed);
0246     }
0247 }
0248 
0249 bool shmem_charge(struct inode *inode, long pages)
0250 {
0251     struct shmem_inode_info *info = SHMEM_I(inode);
0252     struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
0253     unsigned long flags;
0254 
0255     if (shmem_acct_block(info->flags, pages))
0256         return false;
0257     spin_lock_irqsave(&info->lock, flags);
0258     info->alloced += pages;
0259     inode->i_blocks += pages * BLOCKS_PER_PAGE;
0260     shmem_recalc_inode(inode);
0261     spin_unlock_irqrestore(&info->lock, flags);
0262     inode->i_mapping->nrpages += pages;
0263 
0264     if (!sbinfo->max_blocks)
0265         return true;
0266     if (percpu_counter_compare(&sbinfo->used_blocks,
0267                 sbinfo->max_blocks - pages) > 0) {
0268         inode->i_mapping->nrpages -= pages;
0269         spin_lock_irqsave(&info->lock, flags);
0270         info->alloced -= pages;
0271         shmem_recalc_inode(inode);
0272         spin_unlock_irqrestore(&info->lock, flags);
0273         shmem_unacct_blocks(info->flags, pages);
0274         return false;
0275     }
0276     percpu_counter_add(&sbinfo->used_blocks, pages);
0277     return true;
0278 }
0279 
0280 void shmem_uncharge(struct inode *inode, long pages)
0281 {
0282     struct shmem_inode_info *info = SHMEM_I(inode);
0283     struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
0284     unsigned long flags;
0285 
0286     spin_lock_irqsave(&info->lock, flags);
0287     info->alloced -= pages;
0288     inode->i_blocks -= pages * BLOCKS_PER_PAGE;
0289     shmem_recalc_inode(inode);
0290     spin_unlock_irqrestore(&info->lock, flags);
0291 
0292     if (sbinfo->max_blocks)
0293         percpu_counter_sub(&sbinfo->used_blocks, pages);
0294     shmem_unacct_blocks(info->flags, pages);
0295 }
0296 
0297 /*
0298  * Replace item expected in radix tree by a new item, while holding tree lock.
0299  */
0300 static int shmem_radix_tree_replace(struct address_space *mapping,
0301             pgoff_t index, void *expected, void *replacement)
0302 {
0303     struct radix_tree_node *node;
0304     void **pslot;
0305     void *item;
0306 
0307     VM_BUG_ON(!expected);
0308     VM_BUG_ON(!replacement);
0309     item = __radix_tree_lookup(&mapping->page_tree, index, &node, &pslot);
0310     if (!item)
0311         return -ENOENT;
0312     if (item != expected)
0313         return -ENOENT;
0314     __radix_tree_replace(&mapping->page_tree, node, pslot,
0315                  replacement, NULL, NULL);
0316     return 0;
0317 }
0318 
0319 /*
0320  * Sometimes, before we decide whether to proceed or to fail, we must check
0321  * that an entry was not already brought back from swap by a racing thread.
0322  *
0323  * Checking page is not enough: by the time a SwapCache page is locked, it
0324  * might be reused, and again be SwapCache, using the same swap as before.
0325  */
0326 static bool shmem_confirm_swap(struct address_space *mapping,
0327                    pgoff_t index, swp_entry_t swap)
0328 {
0329     void *item;
0330 
0331     rcu_read_lock();
0332     item = radix_tree_lookup(&mapping->page_tree, index);
0333     rcu_read_unlock();
0334     return item == swp_to_radix_entry(swap);
0335 }
0336 
0337 /*
0338  * Definitions for "huge tmpfs": tmpfs mounted with the huge= option
0339  *
0340  * SHMEM_HUGE_NEVER:
0341  *  disables huge pages for the mount;
0342  * SHMEM_HUGE_ALWAYS:
0343  *  enables huge pages for the mount;
0344  * SHMEM_HUGE_WITHIN_SIZE:
0345  *  only allocate huge pages if the page will be fully within i_size,
0346  *  also respect fadvise()/madvise() hints;
0347  * SHMEM_HUGE_ADVISE:
0348  *  only allocate huge pages if requested with fadvise()/madvise();
0349  */
0350 
0351 #define SHMEM_HUGE_NEVER    0
0352 #define SHMEM_HUGE_ALWAYS   1
0353 #define SHMEM_HUGE_WITHIN_SIZE  2
0354 #define SHMEM_HUGE_ADVISE   3
0355 
0356 /*
0357  * Special values.
0358  * Only can be set via /sys/kernel/mm/transparent_hugepage/shmem_enabled:
0359  *
0360  * SHMEM_HUGE_DENY:
0361  *  disables huge on shm_mnt and all mounts, for emergency use;
0362  * SHMEM_HUGE_FORCE:
0363  *  enables huge on shm_mnt and all mounts, w/o needing option, for testing;
0364  *
0365  */
0366 #define SHMEM_HUGE_DENY     (-1)
0367 #define SHMEM_HUGE_FORCE    (-2)
0368 
0369 #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
0370 /* ifdef here to avoid bloating shmem.o when not necessary */
0371 
0372 int shmem_huge __read_mostly;
0373 
0374 #if defined(CONFIG_SYSFS) || defined(CONFIG_TMPFS)
0375 static int shmem_parse_huge(const char *str)
0376 {
0377     if (!strcmp(str, "never"))
0378         return SHMEM_HUGE_NEVER;
0379     if (!strcmp(str, "always"))
0380         return SHMEM_HUGE_ALWAYS;
0381     if (!strcmp(str, "within_size"))
0382         return SHMEM_HUGE_WITHIN_SIZE;
0383     if (!strcmp(str, "advise"))
0384         return SHMEM_HUGE_ADVISE;
0385     if (!strcmp(str, "deny"))
0386         return SHMEM_HUGE_DENY;
0387     if (!strcmp(str, "force"))
0388         return SHMEM_HUGE_FORCE;
0389     return -EINVAL;
0390 }
0391 
0392 static const char *shmem_format_huge(int huge)
0393 {
0394     switch (huge) {
0395     case SHMEM_HUGE_NEVER:
0396         return "never";
0397     case SHMEM_HUGE_ALWAYS:
0398         return "always";
0399     case SHMEM_HUGE_WITHIN_SIZE:
0400         return "within_size";
0401     case SHMEM_HUGE_ADVISE:
0402         return "advise";
0403     case SHMEM_HUGE_DENY:
0404         return "deny";
0405     case SHMEM_HUGE_FORCE:
0406         return "force";
0407     default:
0408         VM_BUG_ON(1);
0409         return "bad_val";
0410     }
0411 }
0412 #endif
0413 
0414 static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
0415         struct shrink_control *sc, unsigned long nr_to_split)
0416 {
0417     LIST_HEAD(list), *pos, *next;
0418     LIST_HEAD(to_remove);
0419     struct inode *inode;
0420     struct shmem_inode_info *info;
0421     struct page *page;
0422     unsigned long batch = sc ? sc->nr_to_scan : 128;
0423     int removed = 0, split = 0;
0424 
0425     if (list_empty(&sbinfo->shrinklist))
0426         return SHRINK_STOP;
0427 
0428     spin_lock(&sbinfo->shrinklist_lock);
0429     list_for_each_safe(pos, next, &sbinfo->shrinklist) {
0430         info = list_entry(pos, struct shmem_inode_info, shrinklist);
0431 
0432         /* pin the inode */
0433         inode = igrab(&info->vfs_inode);
0434 
0435         /* inode is about to be evicted */
0436         if (!inode) {
0437             list_del_init(&info->shrinklist);
0438             removed++;
0439             goto next;
0440         }
0441 
0442         /* Check if there's anything to gain */
0443         if (round_up(inode->i_size, PAGE_SIZE) ==
0444                 round_up(inode->i_size, HPAGE_PMD_SIZE)) {
0445             list_move(&info->shrinklist, &to_remove);
0446             removed++;
0447             goto next;
0448         }
0449 
0450         list_move(&info->shrinklist, &list);
0451 next:
0452         if (!--batch)
0453             break;
0454     }
0455     spin_unlock(&sbinfo->shrinklist_lock);
0456 
0457     list_for_each_safe(pos, next, &to_remove) {
0458         info = list_entry(pos, struct shmem_inode_info, shrinklist);
0459         inode = &info->vfs_inode;
0460         list_del_init(&info->shrinklist);
0461         iput(inode);
0462     }
0463 
0464     list_for_each_safe(pos, next, &list) {
0465         int ret;
0466 
0467         info = list_entry(pos, struct shmem_inode_info, shrinklist);
0468         inode = &info->vfs_inode;
0469 
0470         if (nr_to_split && split >= nr_to_split) {
0471             iput(inode);
0472             continue;
0473         }
0474 
0475         page = find_lock_page(inode->i_mapping,
0476                 (inode->i_size & HPAGE_PMD_MASK) >> PAGE_SHIFT);
0477         if (!page)
0478             goto drop;
0479 
0480         if (!PageTransHuge(page)) {
0481             unlock_page(page);
0482             put_page(page);
0483             goto drop;
0484         }
0485 
0486         ret = split_huge_page(page);
0487         unlock_page(page);
0488         put_page(page);
0489 
0490         if (ret) {
0491             /* split failed: leave it on the list */
0492             iput(inode);
0493             continue;
0494         }
0495 
0496         split++;
0497 drop:
0498         list_del_init(&info->shrinklist);
0499         removed++;
0500         iput(inode);
0501     }
0502 
0503     spin_lock(&sbinfo->shrinklist_lock);
0504     list_splice_tail(&list, &sbinfo->shrinklist);
0505     sbinfo->shrinklist_len -= removed;
0506     spin_unlock(&sbinfo->shrinklist_lock);
0507 
0508     return split;
0509 }
0510 
0511 static long shmem_unused_huge_scan(struct super_block *sb,
0512         struct shrink_control *sc)
0513 {
0514     struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
0515 
0516     if (!READ_ONCE(sbinfo->shrinklist_len))
0517         return SHRINK_STOP;
0518 
0519     return shmem_unused_huge_shrink(sbinfo, sc, 0);
0520 }
0521 
0522 static long shmem_unused_huge_count(struct super_block *sb,
0523         struct shrink_control *sc)
0524 {
0525     struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
0526     return READ_ONCE(sbinfo->shrinklist_len);
0527 }
0528 #else /* !CONFIG_TRANSPARENT_HUGE_PAGECACHE */
0529 
0530 #define shmem_huge SHMEM_HUGE_DENY
0531 
0532 static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
0533         struct shrink_control *sc, unsigned long nr_to_split)
0534 {
0535     return 0;
0536 }
0537 #endif /* CONFIG_TRANSPARENT_HUGE_PAGECACHE */
0538 
0539 /*
0540  * Like add_to_page_cache_locked, but error if expected item has gone.
0541  */
0542 static int shmem_add_to_page_cache(struct page *page,
0543                    struct address_space *mapping,
0544                    pgoff_t index, void *expected)
0545 {
0546     int error, nr = hpage_nr_pages(page);
0547 
0548     VM_BUG_ON_PAGE(PageTail(page), page);
0549     VM_BUG_ON_PAGE(index != round_down(index, nr), page);
0550     VM_BUG_ON_PAGE(!PageLocked(page), page);
0551     VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
0552     VM_BUG_ON(expected && PageTransHuge(page));
0553 
0554     page_ref_add(page, nr);
0555     page->mapping = mapping;
0556     page->index = index;
0557 
0558     spin_lock_irq(&mapping->tree_lock);
0559     if (PageTransHuge(page)) {
0560         void __rcu **results;
0561         pgoff_t idx;
0562         int i;
0563 
0564         error = 0;
0565         if (radix_tree_gang_lookup_slot(&mapping->page_tree,
0566                     &results, &idx, index, 1) &&
0567                 idx < index + HPAGE_PMD_NR) {
0568             error = -EEXIST;
0569         }
0570 
0571         if (!error) {
0572             for (i = 0; i < HPAGE_PMD_NR; i++) {
0573                 error = radix_tree_insert(&mapping->page_tree,
0574                         index + i, page + i);
0575                 VM_BUG_ON(error);
0576             }
0577             count_vm_event(THP_FILE_ALLOC);
0578         }
0579     } else if (!expected) {
0580         error = radix_tree_insert(&mapping->page_tree, index, page);
0581     } else {
0582         error = shmem_radix_tree_replace(mapping, index, expected,
0583                                  page);
0584     }
0585 
0586     if (!error) {
0587         mapping->nrpages += nr;
0588         if (PageTransHuge(page))
0589             __inc_node_page_state(page, NR_SHMEM_THPS);
0590         __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, nr);
0591         __mod_node_page_state(page_pgdat(page), NR_SHMEM, nr);
0592         spin_unlock_irq(&mapping->tree_lock);
0593     } else {
0594         page->mapping = NULL;
0595         spin_unlock_irq(&mapping->tree_lock);
0596         page_ref_sub(page, nr);
0597     }
0598     return error;
0599 }
0600 
0601 /*
0602  * Like delete_from_page_cache, but substitutes swap for page.
0603  */
0604 static void shmem_delete_from_page_cache(struct page *page, void *radswap)
0605 {
0606     struct address_space *mapping = page->mapping;
0607     int error;
0608 
0609     VM_BUG_ON_PAGE(PageCompound(page), page);
0610 
0611     spin_lock_irq(&mapping->tree_lock);
0612     error = shmem_radix_tree_replace(mapping, page->index, page, radswap);
0613     page->mapping = NULL;
0614     mapping->nrpages--;
0615     __dec_node_page_state(page, NR_FILE_PAGES);
0616     __dec_node_page_state(page, NR_SHMEM);
0617     spin_unlock_irq(&mapping->tree_lock);
0618     put_page(page);
0619     BUG_ON(error);
0620 }
0621 
0622 /*
0623  * Remove swap entry from radix tree, free the swap and its page cache.
0624  */
0625 static int shmem_free_swap(struct address_space *mapping,
0626                pgoff_t index, void *radswap)
0627 {
0628     void *old;
0629 
0630     spin_lock_irq(&mapping->tree_lock);
0631     old = radix_tree_delete_item(&mapping->page_tree, index, radswap);
0632     spin_unlock_irq(&mapping->tree_lock);
0633     if (old != radswap)
0634         return -ENOENT;
0635     free_swap_and_cache(radix_to_swp_entry(radswap));
0636     return 0;
0637 }
0638 
0639 /*
0640  * Determine (in bytes) how many of the shmem object's pages mapped by the
0641  * given offsets are swapped out.
0642  *
0643  * This is safe to call without i_mutex or mapping->tree_lock thanks to RCU,
0644  * as long as the inode doesn't go away and racy results are not a problem.
0645  */
0646 unsigned long shmem_partial_swap_usage(struct address_space *mapping,
0647                         pgoff_t start, pgoff_t end)
0648 {
0649     struct radix_tree_iter iter;
0650     void **slot;
0651     struct page *page;
0652     unsigned long swapped = 0;
0653 
0654     rcu_read_lock();
0655 
0656     radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
0657         if (iter.index >= end)
0658             break;
0659 
0660         page = radix_tree_deref_slot(slot);
0661 
0662         if (radix_tree_deref_retry(page)) {
0663             slot = radix_tree_iter_retry(&iter);
0664             continue;
0665         }
0666 
0667         if (radix_tree_exceptional_entry(page))
0668             swapped++;
0669 
0670         if (need_resched()) {
0671             slot = radix_tree_iter_resume(slot, &iter);
0672             cond_resched_rcu();
0673         }
0674     }
0675 
0676     rcu_read_unlock();
0677 
0678     return swapped << PAGE_SHIFT;
0679 }
0680 
0681 /*
0682  * Determine (in bytes) how many of the shmem object's pages mapped by the
0683  * given vma is swapped out.
0684  *
0685  * This is safe to call without i_mutex or mapping->tree_lock thanks to RCU,
0686  * as long as the inode doesn't go away and racy results are not a problem.
0687  */
0688 unsigned long shmem_swap_usage(struct vm_area_struct *vma)
0689 {
0690     struct inode *inode = file_inode(vma->vm_file);
0691     struct shmem_inode_info *info = SHMEM_I(inode);
0692     struct address_space *mapping = inode->i_mapping;
0693     unsigned long swapped;
0694 
0695     /* Be careful as we don't hold info->lock */
0696     swapped = READ_ONCE(info->swapped);
0697 
0698     /*
0699      * The easier cases are when the shmem object has nothing in swap, or
0700      * the vma maps it whole. Then we can simply use the stats that we
0701      * already track.
0702      */
0703     if (!swapped)
0704         return 0;
0705 
0706     if (!vma->vm_pgoff && vma->vm_end - vma->vm_start >= inode->i_size)
0707         return swapped << PAGE_SHIFT;
0708 
0709     /* Here comes the more involved part */
0710     return shmem_partial_swap_usage(mapping,
0711             linear_page_index(vma, vma->vm_start),
0712             linear_page_index(vma, vma->vm_end));
0713 }
0714 
0715 /*
0716  * SysV IPC SHM_UNLOCK restore Unevictable pages to their evictable lists.
0717  */
0718 void shmem_unlock_mapping(struct address_space *mapping)
0719 {
0720     struct pagevec pvec;
0721     pgoff_t indices[PAGEVEC_SIZE];
0722     pgoff_t index = 0;
0723 
0724     pagevec_init(&pvec, 0);
0725     /*
0726      * Minor point, but we might as well stop if someone else SHM_LOCKs it.
0727      */
0728     while (!mapping_unevictable(mapping)) {
0729         /*
0730          * Avoid pagevec_lookup(): find_get_pages() returns 0 as if it
0731          * has finished, if it hits a row of PAGEVEC_SIZE swap entries.
0732          */
0733         pvec.nr = find_get_entries(mapping, index,
0734                        PAGEVEC_SIZE, pvec.pages, indices);
0735         if (!pvec.nr)
0736             break;
0737         index = indices[pvec.nr - 1] + 1;
0738         pagevec_remove_exceptionals(&pvec);
0739         check_move_unevictable_pages(pvec.pages, pvec.nr);
0740         pagevec_release(&pvec);
0741         cond_resched();
0742     }
0743 }
0744 
0745 /*
0746  * Remove range of pages and swap entries from radix tree, and free them.
0747  * If !unfalloc, truncate or punch hole; if unfalloc, undo failed fallocate.
0748  */
0749 static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
0750                                  bool unfalloc)
0751 {
0752     struct address_space *mapping = inode->i_mapping;
0753     struct shmem_inode_info *info = SHMEM_I(inode);
0754     pgoff_t start = (lstart + PAGE_SIZE - 1) >> PAGE_SHIFT;
0755     pgoff_t end = (lend + 1) >> PAGE_SHIFT;
0756     unsigned int partial_start = lstart & (PAGE_SIZE - 1);
0757     unsigned int partial_end = (lend + 1) & (PAGE_SIZE - 1);
0758     struct pagevec pvec;
0759     pgoff_t indices[PAGEVEC_SIZE];
0760     long nr_swaps_freed = 0;
0761     pgoff_t index;
0762     int i;
0763 
0764     if (lend == -1)
0765         end = -1;   /* unsigned, so actually very big */
0766 
0767     pagevec_init(&pvec, 0);
0768     index = start;
0769     while (index < end) {
0770         pvec.nr = find_get_entries(mapping, index,
0771             min(end - index, (pgoff_t)PAGEVEC_SIZE),
0772             pvec.pages, indices);
0773         if (!pvec.nr)
0774             break;
0775         for (i = 0; i < pagevec_count(&pvec); i++) {
0776             struct page *page = pvec.pages[i];
0777 
0778             index = indices[i];
0779             if (index >= end)
0780                 break;
0781 
0782             if (radix_tree_exceptional_entry(page)) {
0783                 if (unfalloc)
0784                     continue;
0785                 nr_swaps_freed += !shmem_free_swap(mapping,
0786                                 index, page);
0787                 continue;
0788             }
0789 
0790             VM_BUG_ON_PAGE(page_to_pgoff(page) != index, page);
0791 
0792             if (!trylock_page(page))
0793                 continue;
0794 
0795             if (PageTransTail(page)) {
0796                 /* Middle of THP: zero out the page */
0797                 clear_highpage(page);
0798                 unlock_page(page);
0799                 continue;
0800             } else if (PageTransHuge(page)) {
0801                 if (index == round_down(end, HPAGE_PMD_NR)) {
0802                     /*
0803                      * Range ends in the middle of THP:
0804                      * zero out the page
0805                      */
0806                     clear_highpage(page);
0807                     unlock_page(page);
0808                     continue;
0809                 }
0810                 index += HPAGE_PMD_NR - 1;
0811                 i += HPAGE_PMD_NR - 1;
0812             }
0813 
0814             if (!unfalloc || !PageUptodate(page)) {
0815                 VM_BUG_ON_PAGE(PageTail(page), page);
0816                 if (page_mapping(page) == mapping) {
0817                     VM_BUG_ON_PAGE(PageWriteback(page), page);
0818                     truncate_inode_page(mapping, page);
0819                 }
0820             }
0821             unlock_page(page);
0822         }
0823         pagevec_remove_exceptionals(&pvec);
0824         pagevec_release(&pvec);
0825         cond_resched();
0826         index++;
0827     }
0828 
0829     if (partial_start) {
0830         struct page *page = NULL;
0831         shmem_getpage(inode, start - 1, &page, SGP_READ);
0832         if (page) {
0833             unsigned int top = PAGE_SIZE;
0834             if (start > end) {
0835                 top = partial_end;
0836                 partial_end = 0;
0837             }
0838             zero_user_segment(page, partial_start, top);
0839             set_page_dirty(page);
0840             unlock_page(page);
0841             put_page(page);
0842         }
0843     }
0844     if (partial_end) {
0845         struct page *page = NULL;
0846         shmem_getpage(inode, end, &page, SGP_READ);
0847         if (page) {
0848             zero_user_segment(page, 0, partial_end);
0849             set_page_dirty(page);
0850             unlock_page(page);
0851             put_page(page);
0852         }
0853     }
0854     if (start >= end)
0855         return;
0856 
0857     index = start;
0858     while (index < end) {
0859         cond_resched();
0860 
0861         pvec.nr = find_get_entries(mapping, index,
0862                 min(end - index, (pgoff_t)PAGEVEC_SIZE),
0863                 pvec.pages, indices);
0864         if (!pvec.nr) {
0865             /* If all gone or hole-punch or unfalloc, we're done */
0866             if (index == start || end != -1)
0867                 break;
0868             /* But if truncating, restart to make sure all gone */
0869             index = start;
0870             continue;
0871         }
0872         for (i = 0; i < pagevec_count(&pvec); i++) {
0873             struct page *page = pvec.pages[i];
0874 
0875             index = indices[i];
0876             if (index >= end)
0877                 break;
0878 
0879             if (radix_tree_exceptional_entry(page)) {
0880                 if (unfalloc)
0881                     continue;
0882                 if (shmem_free_swap(mapping, index, page)) {
0883                     /* Swap was replaced by page: retry */
0884                     index--;
0885                     break;
0886                 }
0887                 nr_swaps_freed++;
0888                 continue;
0889             }
0890 
0891             lock_page(page);
0892 
0893             if (PageTransTail(page)) {
0894                 /* Middle of THP: zero out the page */
0895                 clear_highpage(page);
0896                 unlock_page(page);
0897                 /*
0898                  * Partial thp truncate due 'start' in middle
0899                  * of THP: don't need to look on these pages
0900                  * again on !pvec.nr restart.
0901                  */
0902                 if (index != round_down(end, HPAGE_PMD_NR))
0903                     start++;
0904                 continue;
0905             } else if (PageTransHuge(page)) {
0906                 if (index == round_down(end, HPAGE_PMD_NR)) {
0907                     /*
0908                      * Range ends in the middle of THP:
0909                      * zero out the page
0910                      */
0911                     clear_highpage(page);
0912                     unlock_page(page);
0913                     continue;
0914                 }
0915                 index += HPAGE_PMD_NR - 1;
0916                 i += HPAGE_PMD_NR - 1;
0917             }
0918 
0919             if (!unfalloc || !PageUptodate(page)) {
0920                 VM_BUG_ON_PAGE(PageTail(page), page);
0921                 if (page_mapping(page) == mapping) {
0922                     VM_BUG_ON_PAGE(PageWriteback(page), page);
0923                     truncate_inode_page(mapping, page);
0924                 } else {
0925                     /* Page was replaced by swap: retry */
0926                     unlock_page(page);
0927                     index--;
0928                     break;
0929                 }
0930             }
0931             unlock_page(page);
0932         }
0933         pagevec_remove_exceptionals(&pvec);
0934         pagevec_release(&pvec);
0935         index++;
0936     }
0937 
0938     spin_lock_irq(&info->lock);
0939     info->swapped -= nr_swaps_freed;
0940     shmem_recalc_inode(inode);
0941     spin_unlock_irq(&info->lock);
0942 }
0943 
0944 void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
0945 {
0946     shmem_undo_range(inode, lstart, lend, false);
0947     inode->i_ctime = inode->i_mtime = current_time(inode);
0948 }
0949 EXPORT_SYMBOL_GPL(shmem_truncate_range);
0950 
0951 static int shmem_getattr(struct vfsmount *mnt, struct dentry *dentry,
0952              struct kstat *stat)
0953 {
0954     struct inode *inode = dentry->d_inode;
0955     struct shmem_inode_info *info = SHMEM_I(inode);
0956 
0957     if (info->alloced - info->swapped != inode->i_mapping->nrpages) {
0958         spin_lock_irq(&info->lock);
0959         shmem_recalc_inode(inode);
0960         spin_unlock_irq(&info->lock);
0961     }
0962     generic_fillattr(inode, stat);
0963     return 0;
0964 }
0965 
0966 static int shmem_setattr(struct dentry *dentry, struct iattr *attr)
0967 {
0968     struct inode *inode = d_inode(dentry);
0969     struct shmem_inode_info *info = SHMEM_I(inode);
0970     struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
0971     int error;
0972 
0973     error = setattr_prepare(dentry, attr);
0974     if (error)
0975         return error;
0976 
0977     if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
0978         loff_t oldsize = inode->i_size;
0979         loff_t newsize = attr->ia_size;
0980 
0981         /* protected by i_mutex */
0982         if ((newsize < oldsize && (info->seals & F_SEAL_SHRINK)) ||
0983             (newsize > oldsize && (info->seals & F_SEAL_GROW)))
0984             return -EPERM;
0985 
0986         if (newsize != oldsize) {
0987             error = shmem_reacct_size(SHMEM_I(inode)->flags,
0988                     oldsize, newsize);
0989             if (error)
0990                 return error;
0991             i_size_write(inode, newsize);
0992             inode->i_ctime = inode->i_mtime = current_time(inode);
0993         }
0994         if (newsize <= oldsize) {
0995             loff_t holebegin = round_up(newsize, PAGE_SIZE);
0996             if (oldsize > holebegin)
0997                 unmap_mapping_range(inode->i_mapping,
0998                             holebegin, 0, 1);
0999             if (info->alloced)
1000                 shmem_truncate_range(inode,
1001                             newsize, (loff_t)-1);
1002             /* unmap again to remove racily COWed private pages */
1003             if (oldsize > holebegin)
1004                 unmap_mapping_range(inode->i_mapping,
1005                             holebegin, 0, 1);
1006 
1007             /*
1008              * Part of the huge page can be beyond i_size: subject
1009              * to shrink under memory pressure.
1010              */
1011             if (IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE)) {
1012                 spin_lock(&sbinfo->shrinklist_lock);
1013                 if (list_empty(&info->shrinklist)) {
1014                     list_add_tail(&info->shrinklist,
1015                             &sbinfo->shrinklist);
1016                     sbinfo->shrinklist_len++;
1017                 }
1018                 spin_unlock(&sbinfo->shrinklist_lock);
1019             }
1020         }
1021     }
1022 
1023     setattr_copy(inode, attr);
1024     if (attr->ia_valid & ATTR_MODE)
1025         error = posix_acl_chmod(inode, inode->i_mode);
1026     return error;
1027 }
1028 
1029 static void shmem_evict_inode(struct inode *inode)
1030 {
1031     struct shmem_inode_info *info = SHMEM_I(inode);
1032     struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
1033 
1034     if (inode->i_mapping->a_ops == &shmem_aops) {
1035         shmem_unacct_size(info->flags, inode->i_size);
1036         inode->i_size = 0;
1037         shmem_truncate_range(inode, 0, (loff_t)-1);
1038         if (!list_empty(&info->shrinklist)) {
1039             spin_lock(&sbinfo->shrinklist_lock);
1040             if (!list_empty(&info->shrinklist)) {
1041                 list_del_init(&info->shrinklist);
1042                 sbinfo->shrinklist_len--;
1043             }
1044             spin_unlock(&sbinfo->shrinklist_lock);
1045         }
1046         if (!list_empty(&info->swaplist)) {
1047             mutex_lock(&shmem_swaplist_mutex);
1048             list_del_init(&info->swaplist);
1049             mutex_unlock(&shmem_swaplist_mutex);
1050         }
1051     }
1052 
1053     simple_xattrs_free(&info->xattrs);
1054     WARN_ON(inode->i_blocks);
1055     shmem_free_inode(inode->i_sb);
1056     clear_inode(inode);
1057 }
1058 
1059 static unsigned long find_swap_entry(struct radix_tree_root *root, void *item)
1060 {
1061     struct radix_tree_iter iter;
1062     void **slot;
1063     unsigned long found = -1;
1064     unsigned int checked = 0;
1065 
1066     rcu_read_lock();
1067     radix_tree_for_each_slot(slot, root, &iter, 0) {
1068         if (*slot == item) {
1069             found = iter.index;
1070             break;
1071         }
1072         checked++;
1073         if ((checked % 4096) != 0)
1074             continue;
1075         slot = radix_tree_iter_resume(slot, &iter);
1076         cond_resched_rcu();
1077     }
1078 
1079     rcu_read_unlock();
1080     return found;
1081 }
1082 
1083 /*
1084  * If swap found in inode, free it and move page from swapcache to filecache.
1085  */
1086 static int shmem_unuse_inode(struct shmem_inode_info *info,
1087                  swp_entry_t swap, struct page **pagep)
1088 {
1089     struct address_space *mapping = info->vfs_inode.i_mapping;
1090     void *radswap;
1091     pgoff_t index;
1092     gfp_t gfp;
1093     int error = 0;
1094 
1095     radswap = swp_to_radix_entry(swap);
1096     index = find_swap_entry(&mapping->page_tree, radswap);
1097     if (index == -1)
1098         return -EAGAIN; /* tell shmem_unuse we found nothing */
1099 
1100     /*
1101      * Move _head_ to start search for next from here.
1102      * But be careful: shmem_evict_inode checks list_empty without taking
1103      * mutex, and there's an instant in list_move_tail when info->swaplist
1104      * would appear empty, if it were the only one on shmem_swaplist.
1105      */
1106     if (shmem_swaplist.next != &info->swaplist)
1107         list_move_tail(&shmem_swaplist, &info->swaplist);
1108 
1109     gfp = mapping_gfp_mask(mapping);
1110     if (shmem_should_replace_page(*pagep, gfp)) {
1111         mutex_unlock(&shmem_swaplist_mutex);
1112         error = shmem_replace_page(pagep, gfp, info, index);
1113         mutex_lock(&shmem_swaplist_mutex);
1114         /*
1115          * We needed to drop mutex to make that restrictive page
1116          * allocation, but the inode might have been freed while we
1117          * dropped it: although a racing shmem_evict_inode() cannot
1118          * complete without emptying the radix_tree, our page lock
1119          * on this swapcache page is not enough to prevent that -
1120          * free_swap_and_cache() of our swap entry will only
1121          * trylock_page(), removing swap from radix_tree whatever.
1122          *
1123          * We must not proceed to shmem_add_to_page_cache() if the
1124          * inode has been freed, but of course we cannot rely on
1125          * inode or mapping or info to check that.  However, we can
1126          * safely check if our swap entry is still in use (and here
1127          * it can't have got reused for another page): if it's still
1128          * in use, then the inode cannot have been freed yet, and we
1129          * can safely proceed (if it's no longer in use, that tells
1130          * nothing about the inode, but we don't need to unuse swap).
1131          */
1132         if (!page_swapcount(*pagep))
1133             error = -ENOENT;
1134     }
1135 
1136     /*
1137      * We rely on shmem_swaplist_mutex, not only to protect the swaplist,
1138      * but also to hold up shmem_evict_inode(): so inode cannot be freed
1139      * beneath us (pagelock doesn't help until the page is in pagecache).
1140      */
1141     if (!error)
1142         error = shmem_add_to_page_cache(*pagep, mapping, index,
1143                         radswap);
1144     if (error != -ENOMEM) {
1145         /*
1146          * Truncation and eviction use free_swap_and_cache(), which
1147          * only does trylock page: if we raced, best clean up here.
1148          */
1149         delete_from_swap_cache(*pagep);
1150         set_page_dirty(*pagep);
1151         if (!error) {
1152             spin_lock_irq(&info->lock);
1153             info->swapped--;
1154             spin_unlock_irq(&info->lock);
1155             swap_free(swap);
1156         }
1157     }
1158     return error;
1159 }
1160 
1161 /*
1162  * Search through swapped inodes to find and replace swap by page.
1163  */
1164 int shmem_unuse(swp_entry_t swap, struct page *page)
1165 {
1166     struct list_head *this, *next;
1167     struct shmem_inode_info *info;
1168     struct mem_cgroup *memcg;
1169     int error = 0;
1170 
1171     /*
1172      * There's a faint possibility that swap page was replaced before
1173      * caller locked it: caller will come back later with the right page.
1174      */
1175     if (unlikely(!PageSwapCache(page) || page_private(page) != swap.val))
1176         goto out;
1177 
1178     /*
1179      * Charge page using GFP_KERNEL while we can wait, before taking
1180      * the shmem_swaplist_mutex which might hold up shmem_writepage().
1181      * Charged back to the user (not to caller) when swap account is used.
1182      */
1183     error = mem_cgroup_try_charge(page, current->mm, GFP_KERNEL, &memcg,
1184             false);
1185     if (error)
1186         goto out;
1187     /* No radix_tree_preload: swap entry keeps a place for page in tree */
1188     error = -EAGAIN;
1189 
1190     mutex_lock(&shmem_swaplist_mutex);
1191     list_for_each_safe(this, next, &shmem_swaplist) {
1192         info = list_entry(this, struct shmem_inode_info, swaplist);
1193         if (info->swapped)
1194             error = shmem_unuse_inode(info, swap, &page);
1195         else
1196             list_del_init(&info->swaplist);
1197         cond_resched();
1198         if (error != -EAGAIN)
1199             break;
1200         /* found nothing in this: move on to search the next */
1201     }
1202     mutex_unlock(&shmem_swaplist_mutex);
1203 
1204     if (error) {
1205         if (error != -ENOMEM)
1206             error = 0;
1207         mem_cgroup_cancel_charge(page, memcg, false);
1208     } else
1209         mem_cgroup_commit_charge(page, memcg, true, false);
1210 out:
1211     unlock_page(page);
1212     put_page(page);
1213     return error;
1214 }
1215 
1216 /*
1217  * Move the page from the page cache to the swap cache.
1218  */
1219 static int shmem_writepage(struct page *page, struct writeback_control *wbc)
1220 {
1221     struct shmem_inode_info *info;
1222     struct address_space *mapping;
1223     struct inode *inode;
1224     swp_entry_t swap;
1225     pgoff_t index;
1226 
1227     VM_BUG_ON_PAGE(PageCompound(page), page);
1228     BUG_ON(!PageLocked(page));
1229     mapping = page->mapping;
1230     index = page->index;
1231     inode = mapping->host;
1232     info = SHMEM_I(inode);
1233     if (info->flags & VM_LOCKED)
1234         goto redirty;
1235     if (!total_swap_pages)
1236         goto redirty;
1237 
1238     /*
1239      * Our capabilities prevent regular writeback or sync from ever calling
1240      * shmem_writepage; but a stacking filesystem might use ->writepage of
1241      * its underlying filesystem, in which case tmpfs should write out to
1242      * swap only in response to memory pressure, and not for the writeback
1243      * threads or sync.
1244      */
1245     if (!wbc->for_reclaim) {
1246         WARN_ON_ONCE(1);    /* Still happens? Tell us about it! */
1247         goto redirty;
1248     }
1249 
1250     /*
1251      * This is somewhat ridiculous, but without plumbing a SWAP_MAP_FALLOC
1252      * value into swapfile.c, the only way we can correctly account for a
1253      * fallocated page arriving here is now to initialize it and write it.
1254      *
1255      * That's okay for a page already fallocated earlier, but if we have
1256      * not yet completed the fallocation, then (a) we want to keep track
1257      * of this page in case we have to undo it, and (b) it may not be a
1258      * good idea to continue anyway, once we're pushing into swap.  So
1259      * reactivate the page, and let shmem_fallocate() quit when too many.
1260      */
1261     if (!PageUptodate(page)) {
1262         if (inode->i_private) {
1263             struct shmem_falloc *shmem_falloc;
1264             spin_lock(&inode->i_lock);
1265             shmem_falloc = inode->i_private;
1266             if (shmem_falloc &&
1267                 !shmem_falloc->waitq &&
1268                 index >= shmem_falloc->start &&
1269                 index < shmem_falloc->next)
1270                 shmem_falloc->nr_unswapped++;
1271             else
1272                 shmem_falloc = NULL;
1273             spin_unlock(&inode->i_lock);
1274             if (shmem_falloc)
1275                 goto redirty;
1276         }
1277         clear_highpage(page);
1278         flush_dcache_page(page);
1279         SetPageUptodate(page);
1280     }
1281 
1282     swap = get_swap_page();
1283     if (!swap.val)
1284         goto redirty;
1285 
1286     if (mem_cgroup_try_charge_swap(page, swap))
1287         goto free_swap;
1288 
1289     /*
1290      * Add inode to shmem_unuse()'s list of swapped-out inodes,
1291      * if it's not already there.  Do it now before the page is
1292      * moved to swap cache, when its pagelock no longer protects
1293      * the inode from eviction.  But don't unlock the mutex until
1294      * we've incremented swapped, because shmem_unuse_inode() will
1295      * prune a !swapped inode from the swaplist under this mutex.
1296      */
1297     mutex_lock(&shmem_swaplist_mutex);
1298     if (list_empty(&info->swaplist))
1299         list_add_tail(&info->swaplist, &shmem_swaplist);
1300 
1301     if (add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
1302         spin_lock_irq(&info->lock);
1303         shmem_recalc_inode(inode);
1304         info->swapped++;
1305         spin_unlock_irq(&info->lock);
1306 
1307         swap_shmem_alloc(swap);
1308         shmem_delete_from_page_cache(page, swp_to_radix_entry(swap));
1309 
1310         mutex_unlock(&shmem_swaplist_mutex);
1311         BUG_ON(page_mapped(page));
1312         swap_writepage(page, wbc);
1313         return 0;
1314     }
1315 
1316     mutex_unlock(&shmem_swaplist_mutex);
1317 free_swap:
1318     swapcache_free(swap);
1319 redirty:
1320     set_page_dirty(page);
1321     if (wbc->for_reclaim)
1322         return AOP_WRITEPAGE_ACTIVATE;  /* Return with page locked */
1323     unlock_page(page);
1324     return 0;
1325 }
1326 
1327 #if defined(CONFIG_NUMA) && defined(CONFIG_TMPFS)
1328 static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
1329 {
1330     char buffer[64];
1331 
1332     if (!mpol || mpol->mode == MPOL_DEFAULT)
1333         return;     /* show nothing */
1334 
1335     mpol_to_str(buffer, sizeof(buffer), mpol);
1336 
1337     seq_printf(seq, ",mpol=%s", buffer);
1338 }
1339 
1340 static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
1341 {
1342     struct mempolicy *mpol = NULL;
1343     if (sbinfo->mpol) {
1344         spin_lock(&sbinfo->stat_lock);  /* prevent replace/use races */
1345         mpol = sbinfo->mpol;
1346         mpol_get(mpol);
1347         spin_unlock(&sbinfo->stat_lock);
1348     }
1349     return mpol;
1350 }
1351 #else /* !CONFIG_NUMA || !CONFIG_TMPFS */
1352 static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
1353 {
1354 }
1355 static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
1356 {
1357     return NULL;
1358 }
1359 #endif /* CONFIG_NUMA && CONFIG_TMPFS */
1360 #ifndef CONFIG_NUMA
1361 #define vm_policy vm_private_data
1362 #endif
1363 
1364 static void shmem_pseudo_vma_init(struct vm_area_struct *vma,
1365         struct shmem_inode_info *info, pgoff_t index)
1366 {
1367     /* Create a pseudo vma that just contains the policy */
1368     vma->vm_start = 0;
1369     /* Bias interleave by inode number to distribute better across nodes */
1370     vma->vm_pgoff = index + info->vfs_inode.i_ino;
1371     vma->vm_ops = NULL;
1372     vma->vm_policy = mpol_shared_policy_lookup(&info->policy, index);
1373 }
1374 
1375 static void shmem_pseudo_vma_destroy(struct vm_area_struct *vma)
1376 {
1377     /* Drop reference taken by mpol_shared_policy_lookup() */
1378     mpol_cond_put(vma->vm_policy);
1379 }
1380 
1381 static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
1382             struct shmem_inode_info *info, pgoff_t index)
1383 {
1384     struct vm_area_struct pvma;
1385     struct page *page;
1386 
1387     shmem_pseudo_vma_init(&pvma, info, index);
1388     page = swapin_readahead(swap, gfp, &pvma, 0);
1389     shmem_pseudo_vma_destroy(&pvma);
1390 
1391     return page;
1392 }
1393 
1394 static struct page *shmem_alloc_hugepage(gfp_t gfp,
1395         struct shmem_inode_info *info, pgoff_t index)
1396 {
1397     struct vm_area_struct pvma;
1398     struct inode *inode = &info->vfs_inode;
1399     struct address_space *mapping = inode->i_mapping;
1400     pgoff_t idx, hindex;
1401     void __rcu **results;
1402     struct page *page;
1403 
1404     if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE))
1405         return NULL;
1406 
1407     hindex = round_down(index, HPAGE_PMD_NR);
1408     rcu_read_lock();
1409     if (radix_tree_gang_lookup_slot(&mapping->page_tree, &results, &idx,
1410                 hindex, 1) && idx < hindex + HPAGE_PMD_NR) {
1411         rcu_read_unlock();
1412         return NULL;
1413     }
1414     rcu_read_unlock();
1415 
1416     shmem_pseudo_vma_init(&pvma, info, hindex);
1417     page = alloc_pages_vma(gfp | __GFP_COMP | __GFP_NORETRY | __GFP_NOWARN,
1418             HPAGE_PMD_ORDER, &pvma, 0, numa_node_id(), true);
1419     shmem_pseudo_vma_destroy(&pvma);
1420     if (page)
1421         prep_transhuge_page(page);
1422     return page;
1423 }
1424 
1425 static struct page *shmem_alloc_page(gfp_t gfp,
1426             struct shmem_inode_info *info, pgoff_t index)
1427 {
1428     struct vm_area_struct pvma;
1429     struct page *page;
1430 
1431     shmem_pseudo_vma_init(&pvma, info, index);
1432     page = alloc_page_vma(gfp, &pvma, 0);
1433     shmem_pseudo_vma_destroy(&pvma);
1434 
1435     return page;
1436 }
1437 
1438 static struct page *shmem_alloc_and_acct_page(gfp_t gfp,
1439         struct shmem_inode_info *info, struct shmem_sb_info *sbinfo,
1440         pgoff_t index, bool huge)
1441 {
1442     struct page *page;
1443     int nr;
1444     int err = -ENOSPC;
1445 
1446     if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE))
1447         huge = false;
1448     nr = huge ? HPAGE_PMD_NR : 1;
1449 
1450     if (shmem_acct_block(info->flags, nr))
1451         goto failed;
1452     if (sbinfo->max_blocks) {
1453         if (percpu_counter_compare(&sbinfo->used_blocks,
1454                     sbinfo->max_blocks - nr) > 0)
1455             goto unacct;
1456         percpu_counter_add(&sbinfo->used_blocks, nr);
1457     }
1458 
1459     if (huge)
1460         page = shmem_alloc_hugepage(gfp, info, index);
1461     else
1462         page = shmem_alloc_page(gfp, info, index);
1463     if (page) {
1464         __SetPageLocked(page);
1465         __SetPageSwapBacked(page);
1466         return page;
1467     }
1468 
1469     err = -ENOMEM;
1470     if (sbinfo->max_blocks)
1471         percpu_counter_add(&sbinfo->used_blocks, -nr);
1472 unacct:
1473     shmem_unacct_blocks(info->flags, nr);
1474 failed:
1475     return ERR_PTR(err);
1476 }
1477 
1478 /*
1479  * When a page is moved from swapcache to shmem filecache (either by the
1480  * usual swapin of shmem_getpage_gfp(), or by the less common swapoff of
1481  * shmem_unuse_inode()), it may have been read in earlier from swap, in
1482  * ignorance of the mapping it belongs to.  If that mapping has special
1483  * constraints (like the gma500 GEM driver, which requires RAM below 4GB),
1484  * we may need to copy to a suitable page before moving to filecache.
1485  *
1486  * In a future release, this may well be extended to respect cpuset and
1487  * NUMA mempolicy, and applied also to anonymous pages in do_swap_page();
1488  * but for now it is a simple matter of zone.
1489  */
1490 static bool shmem_should_replace_page(struct page *page, gfp_t gfp)
1491 {
1492     return page_zonenum(page) > gfp_zone(gfp);
1493 }
1494 
1495 static int shmem_replace_page(struct page **pagep, gfp_t gfp,
1496                 struct shmem_inode_info *info, pgoff_t index)
1497 {
1498     struct page *oldpage, *newpage;
1499     struct address_space *swap_mapping;
1500     pgoff_t swap_index;
1501     int error;
1502 
1503     oldpage = *pagep;
1504     swap_index = page_private(oldpage);
1505     swap_mapping = page_mapping(oldpage);
1506 
1507     /*
1508      * We have arrived here because our zones are constrained, so don't
1509      * limit chance of success by further cpuset and node constraints.
1510      */
1511     gfp &= ~GFP_CONSTRAINT_MASK;
1512     newpage = shmem_alloc_page(gfp, info, index);
1513     if (!newpage)
1514         return -ENOMEM;
1515 
1516     get_page(newpage);
1517     copy_highpage(newpage, oldpage);
1518     flush_dcache_page(newpage);
1519 
1520     __SetPageLocked(newpage);
1521     __SetPageSwapBacked(newpage);
1522     SetPageUptodate(newpage);
1523     set_page_private(newpage, swap_index);
1524     SetPageSwapCache(newpage);
1525 
1526     /*
1527      * Our caller will very soon move newpage out of swapcache, but it's
1528      * a nice clean interface for us to replace oldpage by newpage there.
1529      */
1530     spin_lock_irq(&swap_mapping->tree_lock);
1531     error = shmem_radix_tree_replace(swap_mapping, swap_index, oldpage,
1532                                    newpage);
1533     if (!error) {
1534         __inc_node_page_state(newpage, NR_FILE_PAGES);
1535         __dec_node_page_state(oldpage, NR_FILE_PAGES);
1536     }
1537     spin_unlock_irq(&swap_mapping->tree_lock);
1538 
1539     if (unlikely(error)) {
1540         /*
1541          * Is this possible?  I think not, now that our callers check
1542          * both PageSwapCache and page_private after getting page lock;
1543          * but be defensive.  Reverse old to newpage for clear and free.
1544          */
1545         oldpage = newpage;
1546     } else {
1547         mem_cgroup_migrate(oldpage, newpage);
1548         lru_cache_add_anon(newpage);
1549         *pagep = newpage;
1550     }
1551 
1552     ClearPageSwapCache(oldpage);
1553     set_page_private(oldpage, 0);
1554 
1555     unlock_page(oldpage);
1556     put_page(oldpage);
1557     put_page(oldpage);
1558     return error;
1559 }
1560 
1561 /*
1562  * shmem_getpage_gfp - find page in cache, or get from swap, or allocate
1563  *
1564  * If we allocate a new one we do not mark it dirty. That's up to the
1565  * vm. If we swap it in we mark it dirty since we also free the swap
1566  * entry since a page cannot live in both the swap and page cache.
1567  *
1568  * fault_mm and fault_type are only supplied by shmem_fault:
1569  * otherwise they are NULL.
1570  */
1571 static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
1572     struct page **pagep, enum sgp_type sgp, gfp_t gfp,
1573     struct mm_struct *fault_mm, int *fault_type)
1574 {
1575     struct address_space *mapping = inode->i_mapping;
1576     struct shmem_inode_info *info = SHMEM_I(inode);
1577     struct shmem_sb_info *sbinfo;
1578     struct mm_struct *charge_mm;
1579     struct mem_cgroup *memcg;
1580     struct page *page;
1581     swp_entry_t swap;
1582     enum sgp_type sgp_huge = sgp;
1583     pgoff_t hindex = index;
1584     int error;
1585     int once = 0;
1586     int alloced = 0;
1587 
1588     if (index > (MAX_LFS_FILESIZE >> PAGE_SHIFT))
1589         return -EFBIG;
1590     if (sgp == SGP_NOHUGE || sgp == SGP_HUGE)
1591         sgp = SGP_CACHE;
1592 repeat:
1593     swap.val = 0;
1594     page = find_lock_entry(mapping, index);
1595     if (radix_tree_exceptional_entry(page)) {
1596         swap = radix_to_swp_entry(page);
1597         page = NULL;
1598     }
1599 
1600     if (sgp <= SGP_CACHE &&
1601         ((loff_t)index << PAGE_SHIFT) >= i_size_read(inode)) {
1602         error = -EINVAL;
1603         goto unlock;
1604     }
1605 
1606     if (page && sgp == SGP_WRITE)
1607         mark_page_accessed(page);
1608 
1609     /* fallocated page? */
1610     if (page && !PageUptodate(page)) {
1611         if (sgp != SGP_READ)
1612             goto clear;
1613         unlock_page(page);
1614         put_page(page);
1615         page = NULL;
1616     }
1617     if (page || (sgp == SGP_READ && !swap.val)) {
1618         *pagep = page;
1619         return 0;
1620     }
1621 
1622     /*
1623      * Fast cache lookup did not find it:
1624      * bring it back from swap or allocate.
1625      */
1626     sbinfo = SHMEM_SB(inode->i_sb);
1627     charge_mm = fault_mm ? : current->mm;
1628 
1629     if (swap.val) {
1630         /* Look it up and read it in.. */
1631         page = lookup_swap_cache(swap);
1632         if (!page) {
1633             /* Or update major stats only when swapin succeeds?? */
1634             if (fault_type) {
1635                 *fault_type |= VM_FAULT_MAJOR;
1636                 count_vm_event(PGMAJFAULT);
1637                 mem_cgroup_count_vm_event(fault_mm, PGMAJFAULT);
1638             }
1639             /* Here we actually start the io */
1640             page = shmem_swapin(swap, gfp, info, index);
1641             if (!page) {
1642                 error = -ENOMEM;
1643                 goto failed;
1644             }
1645         }
1646 
1647         /* We have to do this with page locked to prevent races */
1648         lock_page(page);
1649         if (!PageSwapCache(page) || page_private(page) != swap.val ||
1650             !shmem_confirm_swap(mapping, index, swap)) {
1651             error = -EEXIST;    /* try again */
1652             goto unlock;
1653         }
1654         if (!PageUptodate(page)) {
1655             error = -EIO;
1656             goto failed;
1657         }
1658         wait_on_page_writeback(page);
1659 
1660         if (shmem_should_replace_page(page, gfp)) {
1661             error = shmem_replace_page(&page, gfp, info, index);
1662             if (error)
1663                 goto failed;
1664         }
1665 
1666         error = mem_cgroup_try_charge(page, charge_mm, gfp, &memcg,
1667                 false);
1668         if (!error) {
1669             error = shmem_add_to_page_cache(page, mapping, index,
1670                         swp_to_radix_entry(swap));
1671             /*
1672              * We already confirmed swap under page lock, and make
1673              * no memory allocation here, so usually no possibility
1674              * of error; but free_swap_and_cache() only trylocks a
1675              * page, so it is just possible that the entry has been
1676              * truncated or holepunched since swap was confirmed.
1677              * shmem_undo_range() will have done some of the
1678              * unaccounting, now delete_from_swap_cache() will do
1679              * the rest.
1680              * Reset swap.val? No, leave it so "failed" goes back to
1681              * "repeat": reading a hole and writing should succeed.
1682              */
1683             if (error) {
1684                 mem_cgroup_cancel_charge(page, memcg, false);
1685                 delete_from_swap_cache(page);
1686             }
1687         }
1688         if (error)
1689             goto failed;
1690 
1691         mem_cgroup_commit_charge(page, memcg, true, false);
1692 
1693         spin_lock_irq(&info->lock);
1694         info->swapped--;
1695         shmem_recalc_inode(inode);
1696         spin_unlock_irq(&info->lock);
1697 
1698         if (sgp == SGP_WRITE)
1699             mark_page_accessed(page);
1700 
1701         delete_from_swap_cache(page);
1702         set_page_dirty(page);
1703         swap_free(swap);
1704 
1705     } else {
1706         /* shmem_symlink() */
1707         if (mapping->a_ops != &shmem_aops)
1708             goto alloc_nohuge;
1709         if (shmem_huge == SHMEM_HUGE_DENY || sgp_huge == SGP_NOHUGE)
1710             goto alloc_nohuge;
1711         if (shmem_huge == SHMEM_HUGE_FORCE)
1712             goto alloc_huge;
1713         switch (sbinfo->huge) {
1714             loff_t i_size;
1715             pgoff_t off;
1716         case SHMEM_HUGE_NEVER:
1717             goto alloc_nohuge;
1718         case SHMEM_HUGE_WITHIN_SIZE:
1719             off = round_up(index, HPAGE_PMD_NR);
1720             i_size = round_up(i_size_read(inode), PAGE_SIZE);
1721             if (i_size >= HPAGE_PMD_SIZE &&
1722                     i_size >> PAGE_SHIFT >= off)
1723                 goto alloc_huge;
1724             /* fallthrough */
1725         case SHMEM_HUGE_ADVISE:
1726             if (sgp_huge == SGP_HUGE)
1727                 goto alloc_huge;
1728             /* TODO: implement fadvise() hints */
1729             goto alloc_nohuge;
1730         }
1731 
1732 alloc_huge:
1733         page = shmem_alloc_and_acct_page(gfp, info, sbinfo,
1734                 index, true);
1735         if (IS_ERR(page)) {
1736 alloc_nohuge:       page = shmem_alloc_and_acct_page(gfp, info, sbinfo,
1737                     index, false);
1738         }
1739         if (IS_ERR(page)) {
1740             int retry = 5;
1741             error = PTR_ERR(page);
1742             page = NULL;
1743             if (error != -ENOSPC)
1744                 goto failed;
1745             /*
1746              * Try to reclaim some spece by splitting a huge page
1747              * beyond i_size on the filesystem.
1748              */
1749             while (retry--) {
1750                 int ret;
1751                 ret = shmem_unused_huge_shrink(sbinfo, NULL, 1);
1752                 if (ret == SHRINK_STOP)
1753                     break;
1754                 if (ret)
1755                     goto alloc_nohuge;
1756             }
1757             goto failed;
1758         }
1759 
1760         if (PageTransHuge(page))
1761             hindex = round_down(index, HPAGE_PMD_NR);
1762         else
1763             hindex = index;
1764 
1765         if (sgp == SGP_WRITE)
1766             __SetPageReferenced(page);
1767 
1768         error = mem_cgroup_try_charge(page, charge_mm, gfp, &memcg,
1769                 PageTransHuge(page));
1770         if (error)
1771             goto unacct;
1772         error = radix_tree_maybe_preload_order(gfp & GFP_RECLAIM_MASK,
1773                 compound_order(page));
1774         if (!error) {
1775             error = shmem_add_to_page_cache(page, mapping, hindex,
1776                             NULL);
1777             radix_tree_preload_end();
1778         }
1779         if (error) {
1780             mem_cgroup_cancel_charge(page, memcg,
1781                     PageTransHuge(page));
1782             goto unacct;
1783         }
1784         mem_cgroup_commit_charge(page, memcg, false,
1785                 PageTransHuge(page));
1786         lru_cache_add_anon(page);
1787 
1788         spin_lock_irq(&info->lock);
1789         info->alloced += 1 << compound_order(page);
1790         inode->i_blocks += BLOCKS_PER_PAGE << compound_order(page);
1791         shmem_recalc_inode(inode);
1792         spin_unlock_irq(&info->lock);
1793         alloced = true;
1794 
1795         if (PageTransHuge(page) &&
1796                 DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE) <
1797                 hindex + HPAGE_PMD_NR - 1) {
1798             /*
1799              * Part of the huge page is beyond i_size: subject
1800              * to shrink under memory pressure.
1801              */
1802             spin_lock(&sbinfo->shrinklist_lock);
1803             if (list_empty(&info->shrinklist)) {
1804                 list_add_tail(&info->shrinklist,
1805                         &sbinfo->shrinklist);
1806                 sbinfo->shrinklist_len++;
1807             }
1808             spin_unlock(&sbinfo->shrinklist_lock);
1809         }
1810 
1811         /*
1812          * Let SGP_FALLOC use the SGP_WRITE optimization on a new page.
1813          */
1814         if (sgp == SGP_FALLOC)
1815             sgp = SGP_WRITE;
1816 clear:
1817         /*
1818          * Let SGP_WRITE caller clear ends if write does not fill page;
1819          * but SGP_FALLOC on a page fallocated earlier must initialize
1820          * it now, lest undo on failure cancel our earlier guarantee.
1821          */
1822         if (sgp != SGP_WRITE && !PageUptodate(page)) {
1823             struct page *head = compound_head(page);
1824             int i;
1825 
1826             for (i = 0; i < (1 << compound_order(head)); i++) {
1827                 clear_highpage(head + i);
1828                 flush_dcache_page(head + i);
1829             }
1830             SetPageUptodate(head);
1831         }
1832     }
1833 
1834     /* Perhaps the file has been truncated since we checked */
1835     if (sgp <= SGP_CACHE &&
1836         ((loff_t)index << PAGE_SHIFT) >= i_size_read(inode)) {
1837         if (alloced) {
1838             ClearPageDirty(page);
1839             delete_from_page_cache(page);
1840             spin_lock_irq(&info->lock);
1841             shmem_recalc_inode(inode);
1842             spin_unlock_irq(&info->lock);
1843         }
1844         error = -EINVAL;
1845         goto unlock;
1846     }
1847     *pagep = page + index - hindex;
1848     return 0;
1849 
1850     /*
1851      * Error recovery.
1852      */
1853 unacct:
1854     if (sbinfo->max_blocks)
1855         percpu_counter_sub(&sbinfo->used_blocks,
1856                 1 << compound_order(page));
1857     shmem_unacct_blocks(info->flags, 1 << compound_order(page));
1858 
1859     if (PageTransHuge(page)) {
1860         unlock_page(page);
1861         put_page(page);
1862         goto alloc_nohuge;
1863     }
1864 failed:
1865     if (swap.val && !shmem_confirm_swap(mapping, index, swap))
1866         error = -EEXIST;
1867 unlock:
1868     if (page) {
1869         unlock_page(page);
1870         put_page(page);
1871     }
1872     if (error == -ENOSPC && !once++) {
1873         spin_lock_irq(&info->lock);
1874         shmem_recalc_inode(inode);
1875         spin_unlock_irq(&info->lock);
1876         goto repeat;
1877     }
1878     if (error == -EEXIST)   /* from above or from radix_tree_insert */
1879         goto repeat;
1880     return error;
1881 }
1882 
1883 /*
1884  * This is like autoremove_wake_function, but it removes the wait queue
1885  * entry unconditionally - even if something else had already woken the
1886  * target.
1887  */
1888 static int synchronous_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key)
1889 {
1890     int ret = default_wake_function(wait, mode, sync, key);
1891     list_del_init(&wait->task_list);
1892     return ret;
1893 }
1894 
1895 static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1896 {
1897     struct inode *inode = file_inode(vma->vm_file);
1898     gfp_t gfp = mapping_gfp_mask(inode->i_mapping);
1899     enum sgp_type sgp;
1900     int error;
1901     int ret = VM_FAULT_LOCKED;
1902 
1903     /*
1904      * Trinity finds that probing a hole which tmpfs is punching can
1905      * prevent the hole-punch from ever completing: which in turn
1906      * locks writers out with its hold on i_mutex.  So refrain from
1907      * faulting pages into the hole while it's being punched.  Although
1908      * shmem_undo_range() does remove the additions, it may be unable to
1909      * keep up, as each new page needs its own unmap_mapping_range() call,
1910      * and the i_mmap tree grows ever slower to scan if new vmas are added.
1911      *
1912      * It does not matter if we sometimes reach this check just before the
1913      * hole-punch begins, so that one fault then races with the punch:
1914      * we just need to make racing faults a rare case.
1915      *
1916      * The implementation below would be much simpler if we just used a
1917      * standard mutex or completion: but we cannot take i_mutex in fault,
1918      * and bloating every shmem inode for this unlikely case would be sad.
1919      */
1920     if (unlikely(inode->i_private)) {
1921         struct shmem_falloc *shmem_falloc;
1922 
1923         spin_lock(&inode->i_lock);
1924         shmem_falloc = inode->i_private;
1925         if (shmem_falloc &&
1926             shmem_falloc->waitq &&
1927             vmf->pgoff >= shmem_falloc->start &&
1928             vmf->pgoff < shmem_falloc->next) {
1929             wait_queue_head_t *shmem_falloc_waitq;
1930             DEFINE_WAIT_FUNC(shmem_fault_wait, synchronous_wake_function);
1931 
1932             ret = VM_FAULT_NOPAGE;
1933             if ((vmf->flags & FAULT_FLAG_ALLOW_RETRY) &&
1934                !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT)) {
1935                 /* It's polite to up mmap_sem if we can */
1936                 up_read(&vma->vm_mm->mmap_sem);
1937                 ret = VM_FAULT_RETRY;
1938             }
1939 
1940             shmem_falloc_waitq = shmem_falloc->waitq;
1941             prepare_to_wait(shmem_falloc_waitq, &shmem_fault_wait,
1942                     TASK_UNINTERRUPTIBLE);
1943             spin_unlock(&inode->i_lock);
1944             schedule();
1945 
1946             /*
1947              * shmem_falloc_waitq points into the shmem_fallocate()
1948              * stack of the hole-punching task: shmem_falloc_waitq
1949              * is usually invalid by the time we reach here, but
1950              * finish_wait() does not dereference it in that case;
1951              * though i_lock needed lest racing with wake_up_all().
1952              */
1953             spin_lock(&inode->i_lock);
1954             finish_wait(shmem_falloc_waitq, &shmem_fault_wait);
1955             spin_unlock(&inode->i_lock);
1956             return ret;
1957         }
1958         spin_unlock(&inode->i_lock);
1959     }
1960 
1961     sgp = SGP_CACHE;
1962     if (vma->vm_flags & VM_HUGEPAGE)
1963         sgp = SGP_HUGE;
1964     else if (vma->vm_flags & VM_NOHUGEPAGE)
1965         sgp = SGP_NOHUGE;
1966 
1967     error = shmem_getpage_gfp(inode, vmf->pgoff, &vmf->page, sgp,
1968                   gfp, vma->vm_mm, &ret);
1969     if (error)
1970         return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
1971     return ret;
1972 }
1973 
1974 unsigned long shmem_get_unmapped_area(struct file *file,
1975                       unsigned long uaddr, unsigned long len,
1976                       unsigned long pgoff, unsigned long flags)
1977 {
1978     unsigned long (*get_area)(struct file *,
1979         unsigned long, unsigned long, unsigned long, unsigned long);
1980     unsigned long addr;
1981     unsigned long offset;
1982     unsigned long inflated_len;
1983     unsigned long inflated_addr;
1984     unsigned long inflated_offset;
1985 
1986     if (len > TASK_SIZE)
1987         return -ENOMEM;
1988 
1989     get_area = current->mm->get_unmapped_area;
1990     addr = get_area(file, uaddr, len, pgoff, flags);
1991 
1992     if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE))
1993         return addr;
1994     if (IS_ERR_VALUE(addr))
1995         return addr;
1996     if (addr & ~PAGE_MASK)
1997         return addr;
1998     if (addr > TASK_SIZE - len)
1999         return addr;
2000 
2001     if (shmem_huge == SHMEM_HUGE_DENY)
2002         return addr;
2003     if (len < HPAGE_PMD_SIZE)
2004         return addr;
2005     if (flags & MAP_FIXED)
2006         return addr;
2007     /*
2008      * Our priority is to support MAP_SHARED mapped hugely;
2009      * and support MAP_PRIVATE mapped hugely too, until it is COWed.
2010      * But if caller specified an address hint, respect that as before.
2011      */
2012     if (uaddr)
2013         return addr;
2014 
2015     if (shmem_huge != SHMEM_HUGE_FORCE) {
2016         struct super_block *sb;
2017 
2018         if (file) {
2019             VM_BUG_ON(file->f_op != &shmem_file_operations);
2020             sb = file_inode(file)->i_sb;
2021         } else {
2022             /*
2023              * Called directly from mm/mmap.c, or drivers/char/mem.c
2024              * for "/dev/zero", to create a shared anonymous object.
2025              */
2026             if (IS_ERR(shm_mnt))
2027                 return addr;
2028             sb = shm_mnt->mnt_sb;
2029         }
2030         if (SHMEM_SB(sb)->huge == SHMEM_HUGE_NEVER)
2031             return addr;
2032     }
2033 
2034     offset = (pgoff << PAGE_SHIFT) & (HPAGE_PMD_SIZE-1);
2035     if (offset && offset + len < 2 * HPAGE_PMD_SIZE)
2036         return addr;
2037     if ((addr & (HPAGE_PMD_SIZE-1)) == offset)
2038         return addr;
2039 
2040     inflated_len = len + HPAGE_PMD_SIZE - PAGE_SIZE;
2041     if (inflated_len > TASK_SIZE)
2042         return addr;
2043     if (inflated_len < len)
2044         return addr;
2045 
2046     inflated_addr = get_area(NULL, 0, inflated_len, 0, flags);
2047     if (IS_ERR_VALUE(inflated_addr))
2048         return addr;
2049     if (inflated_addr & ~PAGE_MASK)
2050         return addr;
2051 
2052     inflated_offset = inflated_addr & (HPAGE_PMD_SIZE-1);
2053     inflated_addr += offset - inflated_offset;
2054     if (inflated_offset > offset)
2055         inflated_addr += HPAGE_PMD_SIZE;
2056 
2057     if (inflated_addr > TASK_SIZE - len)
2058         return addr;
2059     return inflated_addr;
2060 }
2061 
2062 #ifdef CONFIG_NUMA
2063 static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *mpol)
2064 {
2065     struct inode *inode = file_inode(vma->vm_file);
2066     return mpol_set_shared_policy(&SHMEM_I(inode)->policy, vma, mpol);
2067 }
2068 
2069 static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
2070                       unsigned long addr)
2071 {
2072     struct inode *inode = file_inode(vma->vm_file);
2073     pgoff_t index;
2074 
2075     index = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
2076     return mpol_shared_policy_lookup(&SHMEM_I(inode)->policy, index);
2077 }
2078 #endif
2079 
2080 int shmem_lock(struct file *file, int lock, struct user_struct *user)
2081 {
2082     struct inode *inode = file_inode(file);
2083     struct shmem_inode_info *info = SHMEM_I(inode);
2084     int retval = -ENOMEM;
2085 
2086     spin_lock_irq(&info->lock);
2087     if (lock && !(info->flags & VM_LOCKED)) {
2088         if (!user_shm_lock(inode->i_size, user))
2089             goto out_nomem;
2090         info->flags |= VM_LOCKED;
2091         mapping_set_unevictable(file->f_mapping);
2092     }
2093     if (!lock && (info->flags & VM_LOCKED) && user) {
2094         user_shm_unlock(inode->i_size, user);
2095         info->flags &= ~VM_LOCKED;
2096         mapping_clear_unevictable(file->f_mapping);
2097     }
2098     retval = 0;
2099 
2100 out_nomem:
2101     spin_unlock_irq(&info->lock);
2102     return retval;
2103 }
2104 
2105 static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
2106 {
2107     file_accessed(file);
2108     vma->vm_ops = &shmem_vm_ops;
2109     if (IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE) &&
2110             ((vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK) <
2111             (vma->vm_end & HPAGE_PMD_MASK)) {
2112         khugepaged_enter(vma, vma->vm_flags);
2113     }
2114     return 0;
2115 }
2116 
2117 static struct inode *shmem_get_inode(struct super_block *sb, const struct inode *dir,
2118                      umode_t mode, dev_t dev, unsigned long flags)
2119 {
2120     struct inode *inode;
2121     struct shmem_inode_info *info;
2122     struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2123 
2124     if (shmem_reserve_inode(sb))
2125         return NULL;
2126 
2127     inode = new_inode(sb);
2128     if (inode) {
2129         inode->i_ino = get_next_ino();
2130         inode_init_owner(inode, dir, mode);
2131         inode->i_blocks = 0;
2132         inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
2133         inode->i_generation = get_seconds();
2134         info = SHMEM_I(inode);
2135         memset(info, 0, (char *)inode - (char *)info);
2136         spin_lock_init(&info->lock);
2137         info->seals = F_SEAL_SEAL;
2138         info->flags = flags & VM_NORESERVE;
2139         INIT_LIST_HEAD(&info->shrinklist);
2140         INIT_LIST_HEAD(&info->swaplist);
2141         simple_xattrs_init(&info->xattrs);
2142         cache_no_acl(inode);
2143 
2144         switch (mode & S_IFMT) {
2145         default:
2146             inode->i_op = &shmem_special_inode_operations;
2147             init_special_inode(inode, mode, dev);
2148             break;
2149         case S_IFREG:
2150             inode->i_mapping->a_ops = &shmem_aops;
2151             inode->i_op = &shmem_inode_operations;
2152             inode->i_fop = &shmem_file_operations;
2153             mpol_shared_policy_init(&info->policy,
2154                          shmem_get_sbmpol(sbinfo));
2155             break;
2156         case S_IFDIR:
2157             inc_nlink(inode);
2158             /* Some things misbehave if size == 0 on a directory */
2159             inode->i_size = 2 * BOGO_DIRENT_SIZE;
2160             inode->i_op = &shmem_dir_inode_operations;
2161             inode->i_fop = &simple_dir_operations;
2162             break;
2163         case S_IFLNK:
2164             /*
2165              * Must not load anything in the rbtree,
2166              * mpol_free_shared_policy will not be called.
2167              */
2168             mpol_shared_policy_init(&info->policy, NULL);
2169             break;
2170         }
2171     } else
2172         shmem_free_inode(sb);
2173     return inode;
2174 }
2175 
2176 bool shmem_mapping(struct address_space *mapping)
2177 {
2178     if (!mapping->host)
2179         return false;
2180 
2181     return mapping->host->i_sb->s_op == &shmem_ops;
2182 }
2183 
2184 #ifdef CONFIG_TMPFS
2185 static const struct inode_operations shmem_symlink_inode_operations;
2186 static const struct inode_operations shmem_short_symlink_operations;
2187 
2188 #ifdef CONFIG_TMPFS_XATTR
2189 static int shmem_initxattrs(struct inode *, const struct xattr *, void *);
2190 #else
2191 #define shmem_initxattrs NULL
2192 #endif
2193 
2194 static int
2195 shmem_write_begin(struct file *file, struct address_space *mapping,
2196             loff_t pos, unsigned len, unsigned flags,
2197             struct page **pagep, void **fsdata)
2198 {
2199     struct inode *inode = mapping->host;
2200     struct shmem_inode_info *info = SHMEM_I(inode);
2201     pgoff_t index = pos >> PAGE_SHIFT;
2202 
2203     /* i_mutex is held by caller */
2204     if (unlikely(info->seals)) {
2205         if (info->seals & F_SEAL_WRITE)
2206             return -EPERM;
2207         if ((info->seals & F_SEAL_GROW) && pos + len > inode->i_size)
2208             return -EPERM;
2209     }
2210 
2211     return shmem_getpage(inode, index, pagep, SGP_WRITE);
2212 }
2213 
2214 static int
2215 shmem_write_end(struct file *file, struct address_space *mapping,
2216             loff_t pos, unsigned len, unsigned copied,
2217             struct page *page, void *fsdata)
2218 {
2219     struct inode *inode = mapping->host;
2220 
2221     if (pos + copied > inode->i_size)
2222         i_size_write(inode, pos + copied);
2223 
2224     if (!PageUptodate(page)) {
2225         struct page *head = compound_head(page);
2226         if (PageTransCompound(page)) {
2227             int i;
2228 
2229             for (i = 0; i < HPAGE_PMD_NR; i++) {
2230                 if (head + i == page)
2231                     continue;
2232                 clear_highpage(head + i);
2233                 flush_dcache_page(head + i);
2234             }
2235         }
2236         if (copied < PAGE_SIZE) {
2237             unsigned from = pos & (PAGE_SIZE - 1);
2238             zero_user_segments(page, 0, from,
2239                     from + copied, PAGE_SIZE);
2240         }
2241         SetPageUptodate(head);
2242     }
2243     set_page_dirty(page);
2244     unlock_page(page);
2245     put_page(page);
2246 
2247     return copied;
2248 }
2249 
2250 static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
2251 {
2252     struct file *file = iocb->ki_filp;
2253     struct inode *inode = file_inode(file);
2254     struct address_space *mapping = inode->i_mapping;
2255     pgoff_t index;
2256     unsigned long offset;
2257     enum sgp_type sgp = SGP_READ;
2258     int error = 0;
2259     ssize_t retval = 0;
2260     loff_t *ppos = &iocb->ki_pos;
2261 
2262     /*
2263      * Might this read be for a stacking filesystem?  Then when reading
2264      * holes of a sparse file, we actually need to allocate those pages,
2265      * and even mark them dirty, so it cannot exceed the max_blocks limit.
2266      */
2267     if (!iter_is_iovec(to))
2268         sgp = SGP_CACHE;
2269 
2270     index = *ppos >> PAGE_SHIFT;
2271     offset = *ppos & ~PAGE_MASK;
2272 
2273     for (;;) {
2274         struct page *page = NULL;
2275         pgoff_t end_index;
2276         unsigned long nr, ret;
2277         loff_t i_size = i_size_read(inode);
2278 
2279         end_index = i_size >> PAGE_SHIFT;
2280         if (index > end_index)
2281             break;
2282         if (index == end_index) {
2283             nr = i_size & ~PAGE_MASK;
2284             if (nr <= offset)
2285                 break;
2286         }
2287 
2288         error = shmem_getpage(inode, index, &page, sgp);
2289         if (error) {
2290             if (error == -EINVAL)
2291                 error = 0;
2292             break;
2293         }
2294         if (page) {
2295             if (sgp == SGP_CACHE)
2296                 set_page_dirty(page);
2297             unlock_page(page);
2298         }
2299 
2300         /*
2301          * We must evaluate after, since reads (unlike writes)
2302          * are called without i_mutex protection against truncate
2303          */
2304         nr = PAGE_SIZE;
2305         i_size = i_size_read(inode);
2306         end_index = i_size >> PAGE_SHIFT;
2307         if (index == end_index) {
2308             nr = i_size & ~PAGE_MASK;
2309             if (nr <= offset) {
2310                 if (page)
2311                     put_page(page);
2312                 break;
2313             }
2314         }
2315         nr -= offset;
2316 
2317         if (page) {
2318             /*
2319              * If users can be writing to this page using arbitrary
2320              * virtual addresses, take care about potential aliasing
2321              * before reading the page on the kernel side.
2322              */
2323             if (mapping_writably_mapped(mapping))
2324                 flush_dcache_page(page);
2325             /*
2326              * Mark the page accessed if we read the beginning.
2327              */
2328             if (!offset)
2329                 mark_page_accessed(page);
2330         } else {
2331             page = ZERO_PAGE(0);
2332             get_page(page);
2333         }
2334 
2335         /*
2336          * Ok, we have the page, and it's up-to-date, so
2337          * now we can copy it to user space...
2338          */
2339         ret = copy_page_to_iter(page, offset, nr, to);
2340         retval += ret;
2341         offset += ret;
2342         index += offset >> PAGE_SHIFT;
2343         offset &= ~PAGE_MASK;
2344 
2345         put_page(page);
2346         if (!iov_iter_count(to))
2347             break;
2348         if (ret < nr) {
2349             error = -EFAULT;
2350             break;
2351         }
2352         cond_resched();
2353     }
2354 
2355     *ppos = ((loff_t) index << PAGE_SHIFT) + offset;
2356     file_accessed(file);
2357     return retval ? retval : error;
2358 }
2359 
2360 /*
2361  * llseek SEEK_DATA or SEEK_HOLE through the radix_tree.
2362  */
2363 static pgoff_t shmem_seek_hole_data(struct address_space *mapping,
2364                     pgoff_t index, pgoff_t end, int whence)
2365 {
2366     struct page *page;
2367     struct pagevec pvec;
2368     pgoff_t indices[PAGEVEC_SIZE];
2369     bool done = false;
2370     int i;
2371 
2372     pagevec_init(&pvec, 0);
2373     pvec.nr = 1;        /* start small: we may be there already */
2374     while (!done) {
2375         pvec.nr = find_get_entries(mapping, index,
2376                     pvec.nr, pvec.pages, indices);
2377         if (!pvec.nr) {
2378             if (whence == SEEK_DATA)
2379                 index = end;
2380             break;
2381         }
2382         for (i = 0; i < pvec.nr; i++, index++) {
2383             if (index < indices[i]) {
2384                 if (whence == SEEK_HOLE) {
2385                     done = true;
2386                     break;
2387                 }
2388                 index = indices[i];
2389             }
2390             page = pvec.pages[i];
2391             if (page && !radix_tree_exceptional_entry(page)) {
2392                 if (!PageUptodate(page))
2393                     page = NULL;
2394             }
2395             if (index >= end ||
2396                 (page && whence == SEEK_DATA) ||
2397                 (!page && whence == SEEK_HOLE)) {
2398                 done = true;
2399                 break;
2400             }
2401         }
2402         pagevec_remove_exceptionals(&pvec);
2403         pagevec_release(&pvec);
2404         pvec.nr = PAGEVEC_SIZE;
2405         cond_resched();
2406     }
2407     return index;
2408 }
2409 
2410 static loff_t shmem_file_llseek(struct file *file, loff_t offset, int whence)
2411 {
2412     struct address_space *mapping = file->f_mapping;
2413     struct inode *inode = mapping->host;
2414     pgoff_t start, end;
2415     loff_t new_offset;
2416 
2417     if (whence != SEEK_DATA && whence != SEEK_HOLE)
2418         return generic_file_llseek_size(file, offset, whence,
2419                     MAX_LFS_FILESIZE, i_size_read(inode));
2420     inode_lock(inode);
2421     /* We're holding i_mutex so we can access i_size directly */
2422 
2423     if (offset < 0)
2424         offset = -EINVAL;
2425     else if (offset >= inode->i_size)
2426         offset = -ENXIO;
2427     else {
2428         start = offset >> PAGE_SHIFT;
2429         end = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
2430         new_offset = shmem_seek_hole_data(mapping, start, end, whence);
2431         new_offset <<= PAGE_SHIFT;
2432         if (new_offset > offset) {
2433             if (new_offset < inode->i_size)
2434                 offset = new_offset;
2435             else if (whence == SEEK_DATA)
2436                 offset = -ENXIO;
2437             else
2438                 offset = inode->i_size;
2439         }
2440     }
2441 
2442     if (offset >= 0)
2443         offset = vfs_setpos(file, offset, MAX_LFS_FILESIZE);
2444     inode_unlock(inode);
2445     return offset;
2446 }
2447 
2448 /*
2449  * We need a tag: a new tag would expand every radix_tree_node by 8 bytes,
2450  * so reuse a tag which we firmly believe is never set or cleared on shmem.
2451  */
2452 #define SHMEM_TAG_PINNED        PAGECACHE_TAG_TOWRITE
2453 #define LAST_SCAN               4       /* about 150ms max */
2454 
2455 static void shmem_tag_pins(struct address_space *mapping)
2456 {
2457     struct radix_tree_iter iter;
2458     void **slot;
2459     pgoff_t start;
2460     struct page *page;
2461 
2462     lru_add_drain();
2463     start = 0;
2464     rcu_read_lock();
2465 
2466     radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
2467         page = radix_tree_deref_slot(slot);
2468         if (!page || radix_tree_exception(page)) {
2469             if (radix_tree_deref_retry(page)) {
2470                 slot = radix_tree_iter_retry(&iter);
2471                 continue;
2472             }
2473         } else if (page_count(page) - page_mapcount(page) > 1) {
2474             spin_lock_irq(&mapping->tree_lock);
2475             radix_tree_tag_set(&mapping->page_tree, iter.index,
2476                        SHMEM_TAG_PINNED);
2477             spin_unlock_irq(&mapping->tree_lock);
2478         }
2479 
2480         if (need_resched()) {
2481             slot = radix_tree_iter_resume(slot, &iter);
2482             cond_resched_rcu();
2483         }
2484     }
2485     rcu_read_unlock();
2486 }
2487 
2488 /*
2489  * Setting SEAL_WRITE requires us to verify there's no pending writer. However,
2490  * via get_user_pages(), drivers might have some pending I/O without any active
2491  * user-space mappings (eg., direct-IO, AIO). Therefore, we look at all pages
2492  * and see whether it has an elevated ref-count. If so, we tag them and wait for
2493  * them to be dropped.
2494  * The caller must guarantee that no new user will acquire writable references
2495  * to those pages to avoid races.
2496  */
2497 static int shmem_wait_for_pins(struct address_space *mapping)
2498 {
2499     struct radix_tree_iter iter;
2500     void **slot;
2501     pgoff_t start;
2502     struct page *page;
2503     int error, scan;
2504 
2505     shmem_tag_pins(mapping);
2506 
2507     error = 0;
2508     for (scan = 0; scan <= LAST_SCAN; scan++) {
2509         if (!radix_tree_tagged(&mapping->page_tree, SHMEM_TAG_PINNED))
2510             break;
2511 
2512         if (!scan)
2513             lru_add_drain_all();
2514         else if (schedule_timeout_killable((HZ << scan) / 200))
2515             scan = LAST_SCAN;
2516 
2517         start = 0;
2518         rcu_read_lock();
2519         radix_tree_for_each_tagged(slot, &mapping->page_tree, &iter,
2520                        start, SHMEM_TAG_PINNED) {
2521 
2522             page = radix_tree_deref_slot(slot);
2523             if (radix_tree_exception(page)) {
2524                 if (radix_tree_deref_retry(page)) {
2525                     slot = radix_tree_iter_retry(&iter);
2526                     continue;
2527                 }
2528 
2529                 page = NULL;
2530             }
2531 
2532             if (page &&
2533                 page_count(page) - page_mapcount(page) != 1) {
2534                 if (scan < LAST_SCAN)
2535                     goto continue_resched;
2536 
2537                 /*
2538                  * On the last scan, we clean up all those tags
2539                  * we inserted; but make a note that we still
2540                  * found pages pinned.
2541                  */
2542                 error = -EBUSY;
2543             }
2544 
2545             spin_lock_irq(&mapping->tree_lock);
2546             radix_tree_tag_clear(&mapping->page_tree,
2547                          iter.index, SHMEM_TAG_PINNED);
2548             spin_unlock_irq(&mapping->tree_lock);
2549 continue_resched:
2550             if (need_resched()) {
2551                 slot = radix_tree_iter_resume(slot, &iter);
2552                 cond_resched_rcu();
2553             }
2554         }
2555         rcu_read_unlock();
2556     }
2557 
2558     return error;
2559 }
2560 
2561 #define F_ALL_SEALS (F_SEAL_SEAL | \
2562              F_SEAL_SHRINK | \
2563              F_SEAL_GROW | \
2564              F_SEAL_WRITE)
2565 
2566 int shmem_add_seals(struct file *file, unsigned int seals)
2567 {
2568     struct inode *inode = file_inode(file);
2569     struct shmem_inode_info *info = SHMEM_I(inode);
2570     int error;
2571 
2572     /*
2573      * SEALING
2574      * Sealing allows multiple parties to share a shmem-file but restrict
2575      * access to a specific subset of file operations. Seals can only be
2576      * added, but never removed. This way, mutually untrusted parties can
2577      * share common memory regions with a well-defined policy. A malicious
2578      * peer can thus never perform unwanted operations on a shared object.
2579      *
2580      * Seals are only supported on special shmem-files and always affect
2581      * the whole underlying inode. Once a seal is set, it may prevent some
2582      * kinds of access to the file. Currently, the following seals are
2583      * defined:
2584      *   SEAL_SEAL: Prevent further seals from being set on this file
2585      *   SEAL_SHRINK: Prevent the file from shrinking
2586      *   SEAL_GROW: Prevent the file from growing
2587      *   SEAL_WRITE: Prevent write access to the file
2588      *
2589      * As we don't require any trust relationship between two parties, we
2590      * must prevent seals from being removed. Therefore, sealing a file
2591      * only adds a given set of seals to the file, it never touches
2592      * existing seals. Furthermore, the "setting seals"-operation can be
2593      * sealed itself, which basically prevents any further seal from being
2594      * added.
2595      *
2596      * Semantics of sealing are only defined on volatile files. Only
2597      * anonymous shmem files support sealing. More importantly, seals are
2598      * never written to disk. Therefore, there's no plan to support it on
2599      * other file types.
2600      */
2601 
2602     if (file->f_op != &shmem_file_operations)
2603         return -EINVAL;
2604     if (!(file->f_mode & FMODE_WRITE))
2605         return -EPERM;
2606     if (seals & ~(unsigned int)F_ALL_SEALS)
2607         return -EINVAL;
2608 
2609     inode_lock(inode);
2610 
2611     if (info->seals & F_SEAL_SEAL) {
2612         error = -EPERM;
2613         goto unlock;
2614     }
2615 
2616     if ((seals & F_SEAL_WRITE) && !(info->seals & F_SEAL_WRITE)) {
2617         error = mapping_deny_writable(file->f_mapping);
2618         if (error)
2619             goto unlock;
2620 
2621         error = shmem_wait_for_pins(file->f_mapping);
2622         if (error) {
2623             mapping_allow_writable(file->f_mapping);
2624             goto unlock;
2625         }
2626     }
2627 
2628     info->seals |= seals;
2629     error = 0;
2630 
2631 unlock:
2632     inode_unlock(inode);
2633     return error;
2634 }
2635 EXPORT_SYMBOL_GPL(shmem_add_seals);
2636 
2637 int shmem_get_seals(struct file *file)
2638 {
2639     if (file->f_op != &shmem_file_operations)
2640         return -EINVAL;
2641 
2642     return SHMEM_I(file_inode(file))->seals;
2643 }
2644 EXPORT_SYMBOL_GPL(shmem_get_seals);
2645 
2646 long shmem_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
2647 {
2648     long error;
2649 
2650     switch (cmd) {
2651     case F_ADD_SEALS:
2652         /* disallow upper 32bit */
2653         if (arg > UINT_MAX)
2654             return -EINVAL;
2655 
2656         error = shmem_add_seals(file, arg);
2657         break;
2658     case F_GET_SEALS:
2659         error = shmem_get_seals(file);
2660         break;
2661     default:
2662         error = -EINVAL;
2663         break;
2664     }
2665 
2666     return error;
2667 }
2668 
2669 static long shmem_fallocate(struct file *file, int mode, loff_t offset,
2670                              loff_t len)
2671 {
2672     struct inode *inode = file_inode(file);
2673     struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
2674     struct shmem_inode_info *info = SHMEM_I(inode);
2675     struct shmem_falloc shmem_falloc;
2676     pgoff_t start, index, end;
2677     int error;
2678 
2679     if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
2680         return -EOPNOTSUPP;
2681 
2682     inode_lock(inode);
2683 
2684     if (mode & FALLOC_FL_PUNCH_HOLE) {
2685         struct address_space *mapping = file->f_mapping;
2686         loff_t unmap_start = round_up(offset, PAGE_SIZE);
2687         loff_t unmap_end = round_down(offset + len, PAGE_SIZE) - 1;
2688         DECLARE_WAIT_QUEUE_HEAD_ONSTACK(shmem_falloc_waitq);
2689 
2690         /* protected by i_mutex */
2691         if (info->seals & F_SEAL_WRITE) {
2692             error = -EPERM;
2693             goto out;
2694         }
2695 
2696         shmem_falloc.waitq = &shmem_falloc_waitq;
2697         shmem_falloc.start = unmap_start >> PAGE_SHIFT;
2698         shmem_falloc.next = (unmap_end + 1) >> PAGE_SHIFT;
2699         spin_lock(&inode->i_lock);
2700         inode->i_private = &shmem_falloc;
2701         spin_unlock(&inode->i_lock);
2702 
2703         if ((u64)unmap_end > (u64)unmap_start)
2704             unmap_mapping_range(mapping, unmap_start,
2705                         1 + unmap_end - unmap_start, 0);
2706         shmem_truncate_range(inode, offset, offset + len - 1);
2707         /* No need to unmap again: hole-punching leaves COWed pages */
2708 
2709         spin_lock(&inode->i_lock);
2710         inode->i_private = NULL;
2711         wake_up_all(&shmem_falloc_waitq);
2712         WARN_ON_ONCE(!list_empty(&shmem_falloc_waitq.task_list));
2713         spin_unlock(&inode->i_lock);
2714         error = 0;
2715         goto out;
2716     }
2717 
2718     /* We need to check rlimit even when FALLOC_FL_KEEP_SIZE */
2719     error = inode_newsize_ok(inode, offset + len);
2720     if (error)
2721         goto out;
2722 
2723     if ((info->seals & F_SEAL_GROW) && offset + len > inode->i_size) {
2724         error = -EPERM;
2725         goto out;
2726     }
2727 
2728     start = offset >> PAGE_SHIFT;
2729     end = (offset + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
2730     /* Try to avoid a swapstorm if len is impossible to satisfy */
2731     if (sbinfo->max_blocks && end - start > sbinfo->max_blocks) {
2732         error = -ENOSPC;
2733         goto out;
2734     }
2735 
2736     shmem_falloc.waitq = NULL;
2737     shmem_falloc.start = start;
2738     shmem_falloc.next  = start;
2739     shmem_falloc.nr_falloced = 0;
2740     shmem_falloc.nr_unswapped = 0;
2741     spin_lock(&inode->i_lock);
2742     inode->i_private = &shmem_falloc;
2743     spin_unlock(&inode->i_lock);
2744 
2745     for (index = start; index < end; index++) {
2746         struct page *page;
2747 
2748         /*
2749          * Good, the fallocate(2) manpage permits EINTR: we may have
2750          * been interrupted because we are using up too much memory.
2751          */
2752         if (signal_pending(current))
2753             error = -EINTR;
2754         else if (shmem_falloc.nr_unswapped > shmem_falloc.nr_falloced)
2755             error = -ENOMEM;
2756         else
2757             error = shmem_getpage(inode, index, &page, SGP_FALLOC);
2758         if (error) {
2759             /* Remove the !PageUptodate pages we added */
2760             if (index > start) {
2761                 shmem_undo_range(inode,
2762                     (loff_t)start << PAGE_SHIFT,
2763                     ((loff_t)index << PAGE_SHIFT) - 1, true);
2764             }
2765             goto undone;
2766         }
2767 
2768         /*
2769          * Inform shmem_writepage() how far we have reached.
2770          * No need for lock or barrier: we have the page lock.
2771          */
2772         shmem_falloc.next++;
2773         if (!PageUptodate(page))
2774             shmem_falloc.nr_falloced++;
2775 
2776         /*
2777          * If !PageUptodate, leave it that way so that freeable pages
2778          * can be recognized if we need to rollback on error later.
2779          * But set_page_dirty so that memory pressure will swap rather
2780          * than free the pages we are allocating (and SGP_CACHE pages
2781          * might still be clean: we now need to mark those dirty too).
2782          */
2783         set_page_dirty(page);
2784         unlock_page(page);
2785         put_page(page);
2786         cond_resched();
2787     }
2788 
2789     if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size)
2790         i_size_write(inode, offset + len);
2791     inode->i_ctime = current_time(inode);
2792 undone:
2793     spin_lock(&inode->i_lock);
2794     inode->i_private = NULL;
2795     spin_unlock(&inode->i_lock);
2796 out:
2797     inode_unlock(inode);
2798     return error;
2799 }
2800 
2801 static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
2802 {
2803     struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
2804 
2805     buf->f_type = TMPFS_MAGIC;
2806     buf->f_bsize = PAGE_SIZE;
2807     buf->f_namelen = NAME_MAX;
2808     if (sbinfo->max_blocks) {
2809         buf->f_blocks = sbinfo->max_blocks;
2810         buf->f_bavail =
2811         buf->f_bfree  = sbinfo->max_blocks -
2812                 percpu_counter_sum(&sbinfo->used_blocks);
2813     }
2814     if (sbinfo->max_inodes) {
2815         buf->f_files = sbinfo->max_inodes;
2816         buf->f_ffree = sbinfo->free_inodes;
2817     }
2818     /* else leave those fields 0 like simple_statfs */
2819     return 0;
2820 }
2821 
2822 /*
2823  * File creation. Allocate an inode, and we're done..
2824  */
2825 static int
2826 shmem_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
2827 {
2828     struct inode *inode;
2829     int error = -ENOSPC;
2830 
2831     inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE);
2832     if (inode) {
2833         error = simple_acl_create(dir, inode);
2834         if (error)
2835             goto out_iput;
2836         error = security_inode_init_security(inode, dir,
2837                              &dentry->d_name,
2838                              shmem_initxattrs, NULL);
2839         if (error && error != -EOPNOTSUPP)
2840             goto out_iput;
2841 
2842         error = 0;
2843         dir->i_size += BOGO_DIRENT_SIZE;
2844         dir->i_ctime = dir->i_mtime = current_time(dir);
2845         d_instantiate(dentry, inode);
2846         dget(dentry); /* Extra count - pin the dentry in core */
2847     }
2848     return error;
2849 out_iput:
2850     iput(inode);
2851     return error;
2852 }
2853 
2854 static int
2855 shmem_tmpfile(struct inode *dir, struct dentry *dentry, umode_t mode)
2856 {
2857     struct inode *inode;
2858     int error = -ENOSPC;
2859 
2860     inode = shmem_get_inode(dir->i_sb, dir, mode, 0, VM_NORESERVE);
2861     if (inode) {
2862         error = security_inode_init_security(inode, dir,
2863                              NULL,
2864                              shmem_initxattrs, NULL);
2865         if (error && error != -EOPNOTSUPP)
2866             goto out_iput;
2867         error = simple_acl_create(dir, inode);
2868         if (error)
2869             goto out_iput;
2870         d_tmpfile(dentry, inode);
2871     }
2872     return error;
2873 out_iput:
2874     iput(inode);
2875     return error;
2876 }
2877 
2878 static int shmem_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
2879 {
2880     int error;
2881 
2882     if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
2883         return error;
2884     inc_nlink(dir);
2885     return 0;
2886 }
2887 
2888 static int shmem_create(struct inode *dir, struct dentry *dentry, umode_t mode,
2889         bool excl)
2890 {
2891     return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
2892 }
2893 
2894 /*
2895  * Link a file..
2896  */
2897 static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
2898 {
2899     struct inode *inode = d_inode(old_dentry);
2900     int ret;
2901 
2902     /*
2903      * No ordinary (disk based) filesystem counts links as inodes;
2904      * but each new link needs a new dentry, pinning lowmem, and
2905      * tmpfs dentries cannot be pruned until they are unlinked.
2906      */
2907     ret = shmem_reserve_inode(inode->i_sb);
2908     if (ret)
2909         goto out;
2910 
2911     dir->i_size += BOGO_DIRENT_SIZE;
2912     inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
2913     inc_nlink(inode);
2914     ihold(inode);   /* New dentry reference */
2915     dget(dentry);       /* Extra pinning count for the created dentry */
2916     d_instantiate(dentry, inode);
2917 out:
2918     return ret;
2919 }
2920 
2921 static int shmem_unlink(struct inode *dir, struct dentry *dentry)
2922 {
2923     struct inode *inode = d_inode(dentry);
2924 
2925     if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
2926         shmem_free_inode(inode->i_sb);
2927 
2928     dir->i_size -= BOGO_DIRENT_SIZE;
2929     inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
2930     drop_nlink(inode);
2931     dput(dentry);   /* Undo the count from "create" - this does all the work */
2932     return 0;
2933 }
2934 
2935 static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
2936 {
2937     if (!simple_empty(dentry))
2938         return -ENOTEMPTY;
2939 
2940     drop_nlink(d_inode(dentry));
2941     drop_nlink(dir);
2942     return shmem_unlink(dir, dentry);
2943 }
2944 
2945 static int shmem_exchange(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
2946 {
2947     bool old_is_dir = d_is_dir(old_dentry);
2948     bool new_is_dir = d_is_dir(new_dentry);
2949 
2950     if (old_dir != new_dir && old_is_dir != new_is_dir) {
2951         if (old_is_dir) {
2952             drop_nlink(old_dir);
2953             inc_nlink(new_dir);
2954         } else {
2955             drop_nlink(new_dir);
2956             inc_nlink(old_dir);
2957         }
2958     }
2959     old_dir->i_ctime = old_dir->i_mtime =
2960     new_dir->i_ctime = new_dir->i_mtime =
2961     d_inode(old_dentry)->i_ctime =
2962     d_inode(new_dentry)->i_ctime = current_time(old_dir);
2963 
2964     return 0;
2965 }
2966 
2967 static int shmem_whiteout(struct inode *old_dir, struct dentry *old_dentry)
2968 {
2969     struct dentry *whiteout;
2970     int error;
2971 
2972     whiteout = d_alloc(old_dentry->d_parent, &old_dentry->d_name);
2973     if (!whiteout)
2974         return -ENOMEM;
2975 
2976     error = shmem_mknod(old_dir, whiteout,
2977                 S_IFCHR | WHITEOUT_MODE, WHITEOUT_DEV);
2978     dput(whiteout);
2979     if (error)
2980         return error;
2981 
2982     /*
2983      * Cheat and hash the whiteout while the old dentry is still in
2984      * place, instead of playing games with FS_RENAME_DOES_D_MOVE.
2985      *
2986      * d_lookup() will consistently find one of them at this point,
2987      * not sure which one, but that isn't even important.
2988      */
2989     d_rehash(whiteout);
2990     return 0;
2991 }
2992 
2993 /*
2994  * The VFS layer already does all the dentry stuff for rename,
2995  * we just have to decrement the usage count for the target if
2996  * it exists so that the VFS layer correctly free's it when it
2997  * gets overwritten.
2998  */
2999 static int shmem_rename2(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry, unsigned int flags)
3000 {
3001     struct inode *inode = d_inode(old_dentry);
3002     int they_are_dirs = S_ISDIR(inode->i_mode);
3003 
3004     if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
3005         return -EINVAL;
3006 
3007     if (flags & RENAME_EXCHANGE)
3008         return shmem_exchange(old_dir, old_dentry, new_dir, new_dentry);
3009 
3010     if (!simple_empty(new_dentry))
3011         return -ENOTEMPTY;
3012 
3013     if (flags & RENAME_WHITEOUT) {
3014         int error;
3015 
3016         error = shmem_whiteout(old_dir, old_dentry);
3017         if (error)
3018             return error;
3019     }
3020 
3021     if (d_really_is_positive(new_dentry)) {
3022         (void) shmem_unlink(new_dir, new_dentry);
3023         if (they_are_dirs) {
3024             drop_nlink(d_inode(new_dentry));
3025             drop_nlink(old_dir);
3026         }
3027     } else if (they_are_dirs) {
3028         drop_nlink(old_dir);
3029         inc_nlink(new_dir);
3030     }
3031 
3032     old_dir->i_size -= BOGO_DIRENT_SIZE;
3033     new_dir->i_size += BOGO_DIRENT_SIZE;
3034     old_dir->i_ctime = old_dir->i_mtime =
3035     new_dir->i_ctime = new_dir->i_mtime =
3036     inode->i_ctime = current_time(old_dir);
3037     return 0;
3038 }
3039 
3040 static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
3041 {
3042     int error;
3043     int len;
3044     struct inode *inode;
3045     struct page *page;
3046     struct shmem_inode_info *info;
3047 
3048     len = strlen(symname) + 1;
3049     if (len > PAGE_SIZE)
3050         return -ENAMETOOLONG;
3051 
3052     inode = shmem_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0, VM_NORESERVE);
3053     if (!inode)
3054         return -ENOSPC;
3055 
3056     error = security_inode_init_security(inode, dir, &dentry->d_name,
3057                          shmem_initxattrs, NULL);
3058     if (error) {
3059         if (error != -EOPNOTSUPP) {
3060             iput(inode);
3061             return error;
3062         }
3063         error = 0;
3064     }
3065 
3066     info = SHMEM_I(inode);
3067     inode->i_size = len-1;
3068     if (len <= SHORT_SYMLINK_LEN) {
3069         inode->i_link = kmemdup(symname, len, GFP_KERNEL);
3070         if (!inode->i_link) {
3071             iput(inode);
3072             return -ENOMEM;
3073         }
3074         inode->i_op = &shmem_short_symlink_operations;
3075     } else {
3076         inode_nohighmem(inode);
3077         error = shmem_getpage(inode, 0, &page, SGP_WRITE);
3078         if (error) {
3079             iput(inode);
3080             return error;
3081         }
3082         inode->i_mapping->a_ops = &shmem_aops;
3083         inode->i_op = &shmem_symlink_inode_operations;
3084         memcpy(page_address(page), symname, len);
3085         SetPageUptodate(page);
3086         set_page_dirty(page);
3087         unlock_page(page);
3088         put_page(page);
3089     }
3090     dir->i_size += BOGO_DIRENT_SIZE;
3091     dir->i_ctime = dir->i_mtime = current_time(dir);
3092     d_instantiate(dentry, inode);
3093     dget(dentry);
3094     return 0;
3095 }
3096 
3097 static void shmem_put_link(void *arg)
3098 {
3099     mark_page_accessed(arg);
3100     put_page(arg);
3101 }
3102 
3103 static const char *shmem_get_link(struct dentry *dentry,
3104                   struct inode *inode,
3105                   struct delayed_call *done)
3106 {
3107     struct page *page = NULL;
3108     int error;
3109     if (!dentry) {
3110         page = find_get_page(inode->i_mapping, 0);
3111         if (!page)
3112             return ERR_PTR(-ECHILD);
3113         if (!PageUptodate(page)) {
3114             put_page(page);
3115             return ERR_PTR(-ECHILD);
3116         }
3117     } else {
3118         error = shmem_getpage(inode, 0, &page, SGP_READ);
3119         if (error)
3120             return ERR_PTR(error);
3121         unlock_page(page);
3122     }
3123     set_delayed_call(done, shmem_put_link, page);
3124     return page_address(page);
3125 }
3126 
3127 #ifdef CONFIG_TMPFS_XATTR
3128 /*
3129  * Superblocks without xattr inode operations may get some security.* xattr
3130  * support from the LSM "for free". As soon as we have any other xattrs
3131  * like ACLs, we also need to implement the security.* handlers at
3132  * filesystem level, though.
3133  */
3134 
3135 /*
3136  * Callback for security_inode_init_security() for acquiring xattrs.
3137  */
3138 static int shmem_initxattrs(struct inode *inode,
3139                 const struct xattr *xattr_array,
3140                 void *fs_info)
3141 {
3142     struct shmem_inode_info *info = SHMEM_I(inode);
3143     const struct xattr *xattr;
3144     struct simple_xattr *new_xattr;
3145     size_t len;
3146 
3147     for (xattr = xattr_array; xattr->name != NULL; xattr++) {
3148         new_xattr = simple_xattr_alloc(xattr->value, xattr->value_len);
3149         if (!new_xattr)
3150             return -ENOMEM;
3151 
3152         len = strlen(xattr->name) + 1;
3153         new_xattr->name = kmalloc(XATTR_SECURITY_PREFIX_LEN + len,
3154                       GFP_KERNEL);
3155         if (!new_xattr->name) {
3156             kfree(new_xattr);
3157             return -ENOMEM;
3158         }
3159 
3160         memcpy(new_xattr->name, XATTR_SECURITY_PREFIX,
3161                XATTR_SECURITY_PREFIX_LEN);
3162         memcpy(new_xattr->name + XATTR_SECURITY_PREFIX_LEN,
3163                xattr->name, len);
3164 
3165         simple_xattr_list_add(&info->xattrs, new_xattr);
3166     }
3167 
3168     return 0;
3169 }
3170 
3171 static int shmem_xattr_handler_get(const struct xattr_handler *handler,
3172                    struct dentry *unused, struct inode *inode,
3173                    const char *name, void *buffer, size_t size)
3174 {
3175     struct shmem_inode_info *info = SHMEM_I(inode);
3176 
3177     name = xattr_full_name(handler, name);
3178     return simple_xattr_get(&info->xattrs, name, buffer, size);
3179 }
3180 
3181 static int shmem_xattr_handler_set(const struct xattr_handler *handler,
3182                    struct dentry *unused, struct inode *inode,
3183                    const char *name, const void *value,
3184                    size_t size, int flags)
3185 {
3186     struct shmem_inode_info *info = SHMEM_I(inode);
3187 
3188     name = xattr_full_name(handler, name);
3189     return simple_xattr_set(&info->xattrs, name, value, size, flags);
3190 }
3191 
3192 static const struct xattr_handler shmem_security_xattr_handler = {
3193     .prefix = XATTR_SECURITY_PREFIX,
3194     .get = shmem_xattr_handler_get,
3195     .set = shmem_xattr_handler_set,
3196 };
3197 
3198 static const struct xattr_handler shmem_trusted_xattr_handler = {
3199     .prefix = XATTR_TRUSTED_PREFIX,
3200     .get = shmem_xattr_handler_get,
3201     .set = shmem_xattr_handler_set,
3202 };
3203 
3204 static const struct xattr_handler *shmem_xattr_handlers[] = {
3205 #ifdef CONFIG_TMPFS_POSIX_ACL
3206     &posix_acl_access_xattr_handler,
3207     &posix_acl_default_xattr_handler,
3208 #endif
3209     &shmem_security_xattr_handler,
3210     &shmem_trusted_xattr_handler,
3211     NULL
3212 };
3213 
3214 static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t size)
3215 {
3216     struct shmem_inode_info *info = SHMEM_I(d_inode(dentry));
3217     return simple_xattr_list(d_inode(dentry), &info->xattrs, buffer, size);
3218 }
3219 #endif /* CONFIG_TMPFS_XATTR */
3220 
3221 static const struct inode_operations shmem_short_symlink_operations = {
3222     .get_link   = simple_get_link,
3223 #ifdef CONFIG_TMPFS_XATTR
3224     .listxattr  = shmem_listxattr,
3225 #endif
3226 };
3227 
3228 static const struct inode_operations shmem_symlink_inode_operations = {
3229     .get_link   = shmem_get_link,
3230 #ifdef CONFIG_TMPFS_XATTR
3231     .listxattr  = shmem_listxattr,
3232 #endif
3233 };
3234 
3235 static struct dentry *shmem_get_parent(struct dentry *child)
3236 {
3237     return ERR_PTR(-ESTALE);
3238 }
3239 
3240 static int shmem_match(struct inode *ino, void *vfh)
3241 {
3242     __u32 *fh = vfh;
3243     __u64 inum = fh[2];
3244     inum = (inum << 32) | fh[1];
3245     return ino->i_ino == inum && fh[0] == ino->i_generation;
3246 }
3247 
3248 static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
3249         struct fid *fid, int fh_len, int fh_type)
3250 {
3251     struct inode *inode;
3252     struct dentry *dentry = NULL;
3253     u64 inum;
3254 
3255     if (fh_len < 3)
3256         return NULL;
3257 
3258     inum = fid->raw[2];
3259     inum = (inum << 32) | fid->raw[1];
3260 
3261     inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
3262             shmem_match, fid->raw);
3263     if (inode) {
3264         dentry = d_find_alias(inode);
3265         iput(inode);
3266     }
3267 
3268     return dentry;
3269 }
3270 
3271 static int shmem_encode_fh(struct inode *inode, __u32 *fh, int *len,
3272                 struct inode *parent)
3273 {
3274     if (*len < 3) {
3275         *len = 3;
3276         return FILEID_INVALID;
3277     }
3278 
3279     if (inode_unhashed(inode)) {
3280         /* Unfortunately insert_inode_hash is not idempotent,
3281          * so as we hash inodes here rather than at creation
3282          * time, we need a lock to ensure we only try
3283          * to do it once
3284          */
3285         static DEFINE_SPINLOCK(lock);
3286         spin_lock(&lock);
3287         if (inode_unhashed(inode))
3288             __insert_inode_hash(inode,
3289                         inode->i_ino + inode->i_generation);
3290         spin_unlock(&lock);
3291     }
3292 
3293     fh[0] = inode->i_generation;
3294     fh[1] = inode->i_ino;
3295     fh[2] = ((__u64)inode->i_ino) >> 32;
3296 
3297     *len = 3;
3298     return 1;
3299 }
3300 
3301 static const struct export_operations shmem_export_ops = {
3302     .get_parent     = shmem_get_parent,
3303     .encode_fh      = shmem_encode_fh,
3304     .fh_to_dentry   = shmem_fh_to_dentry,
3305 };
3306 
3307 static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
3308                    bool remount)
3309 {
3310     char *this_char, *value, *rest;
3311     struct mempolicy *mpol = NULL;
3312     uid_t uid;
3313     gid_t gid;
3314 
3315     while (options != NULL) {
3316         this_char = options;
3317         for (;;) {
3318             /*
3319              * NUL-terminate this option: unfortunately,
3320              * mount options form a comma-separated list,
3321              * but mpol's nodelist may also contain commas.
3322              */
3323             options = strchr(options, ',');
3324             if (options == NULL)
3325                 break;
3326             options++;
3327             if (!isdigit(*options)) {
3328                 options[-1] = '\0';
3329                 break;
3330             }
3331         }
3332         if (!*this_char)
3333             continue;
3334         if ((value = strchr(this_char,'=')) != NULL) {
3335             *value++ = 0;
3336         } else {
3337             pr_err("tmpfs: No value for mount option '%s'\n",
3338                    this_char);
3339             goto error;
3340         }
3341 
3342         if (!strcmp(this_char,"size")) {
3343             unsigned long long size;
3344             size = memparse(value,&rest);
3345             if (*rest == '%') {
3346                 size <<= PAGE_SHIFT;
3347                 size *= totalram_pages;
3348                 do_div(size, 100);
3349                 rest++;
3350             }
3351             if (*rest)
3352                 goto bad_val;
3353             sbinfo->max_blocks =
3354                 DIV_ROUND_UP(size, PAGE_SIZE);
3355         } else if (!strcmp(this_char,"nr_blocks")) {
3356             sbinfo->max_blocks = memparse(value, &rest);
3357             if (*rest)
3358                 goto bad_val;
3359         } else if (!strcmp(this_char,"nr_inodes")) {
3360             sbinfo->max_inodes = memparse(value, &rest);
3361             if (*rest)
3362                 goto bad_val;
3363         } else if (!strcmp(this_char,"mode")) {
3364             if (remount)
3365                 continue;
3366             sbinfo->mode = simple_strtoul(value, &rest, 8) & 07777;
3367             if (*rest)
3368                 goto bad_val;
3369         } else if (!strcmp(this_char,"uid")) {
3370             if (remount)
3371                 continue;
3372             uid = simple_strtoul(value, &rest, 0);
3373             if (*rest)
3374                 goto bad_val;
3375             sbinfo->uid = make_kuid(current_user_ns(), uid);
3376             if (!uid_valid(sbinfo->uid))
3377                 goto bad_val;
3378         } else if (!strcmp(this_char,"gid")) {
3379             if (remount)
3380                 continue;
3381             gid = simple_strtoul(value, &rest, 0);
3382             if (*rest)
3383                 goto bad_val;
3384             sbinfo->gid = make_kgid(current_user_ns(), gid);
3385             if (!gid_valid(sbinfo->gid))
3386                 goto bad_val;
3387 #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
3388         } else if (!strcmp(this_char, "huge")) {
3389             int huge;
3390             huge = shmem_parse_huge(value);
3391             if (huge < 0)
3392                 goto bad_val;
3393             if (!has_transparent_hugepage() &&
3394                     huge != SHMEM_HUGE_NEVER)
3395                 goto bad_val;
3396             sbinfo->huge = huge;
3397 #endif
3398 #ifdef CONFIG_NUMA
3399         } else if (!strcmp(this_char,"mpol")) {
3400             mpol_put(mpol);
3401             mpol = NULL;
3402             if (mpol_parse_str(value, &mpol))
3403                 goto bad_val;
3404 #endif
3405         } else {
3406             pr_err("tmpfs: Bad mount option %s\n", this_char);
3407             goto error;
3408         }
3409     }
3410     sbinfo->mpol = mpol;
3411     return 0;
3412 
3413 bad_val:
3414     pr_err("tmpfs: Bad value '%s' for mount option '%s'\n",
3415            value, this_char);
3416 error:
3417     mpol_put(mpol);
3418     return 1;
3419 
3420 }
3421 
3422 static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
3423 {
3424     struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
3425     struct shmem_sb_info config = *sbinfo;
3426     unsigned long inodes;
3427     int error = -EINVAL;
3428 
3429     config.mpol = NULL;
3430     if (shmem_parse_options(data, &config, true))
3431         return error;
3432 
3433     spin_lock(&sbinfo->stat_lock);
3434     inodes = sbinfo->max_inodes - sbinfo->free_inodes;
3435     if (percpu_counter_compare(&sbinfo->used_blocks, config.max_blocks) > 0)
3436         goto out;
3437     if (config.max_inodes < inodes)
3438         goto out;
3439     /*
3440      * Those tests disallow limited->unlimited while any are in use;
3441      * but we must separately disallow unlimited->limited, because
3442      * in that case we have no record of how much is already in use.
3443      */
3444     if (config.max_blocks && !sbinfo->max_blocks)
3445         goto out;
3446     if (config.max_inodes && !sbinfo->max_inodes)
3447         goto out;
3448 
3449     error = 0;
3450     sbinfo->huge = config.huge;
3451     sbinfo->max_blocks  = config.max_blocks;
3452     sbinfo->max_inodes  = config.max_inodes;
3453     sbinfo->free_inodes = config.max_inodes - inodes;
3454 
3455     /*
3456      * Preserve previous mempolicy unless mpol remount option was specified.
3457      */
3458     if (config.mpol) {
3459         mpol_put(sbinfo->mpol);
3460         sbinfo->mpol = config.mpol; /* transfers initial ref */
3461     }
3462 out:
3463     spin_unlock(&sbinfo->stat_lock);
3464     return error;
3465 }
3466 
3467 static int shmem_show_options(struct seq_file *seq, struct dentry *root)
3468 {
3469     struct shmem_sb_info *sbinfo = SHMEM_SB(root->d_sb);
3470 
3471     if (sbinfo->max_blocks != shmem_default_max_blocks())
3472         seq_printf(seq, ",size=%luk",
3473             sbinfo->max_blocks << (PAGE_SHIFT - 10));
3474     if (sbinfo->max_inodes != shmem_default_max_inodes())
3475         seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
3476     if (sbinfo->mode != (S_IRWXUGO | S_ISVTX))
3477         seq_printf(seq, ",mode=%03ho", sbinfo->mode);
3478     if (!uid_eq(sbinfo->uid, GLOBAL_ROOT_UID))
3479         seq_printf(seq, ",uid=%u",
3480                 from_kuid_munged(&init_user_ns, sbinfo->uid));
3481     if (!gid_eq(sbinfo->gid, GLOBAL_ROOT_GID))
3482         seq_printf(seq, ",gid=%u",
3483                 from_kgid_munged(&init_user_ns, sbinfo->gid));
3484 #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
3485     /* Rightly or wrongly, show huge mount option unmasked by shmem_huge */
3486     if (sbinfo->huge)
3487         seq_printf(seq, ",huge=%s", shmem_format_huge(sbinfo->huge));
3488 #endif
3489     shmem_show_mpol(seq, sbinfo->mpol);
3490     return 0;
3491 }
3492 
3493 #define MFD_NAME_PREFIX "memfd:"
3494 #define MFD_NAME_PREFIX_LEN (sizeof(MFD_NAME_PREFIX) - 1)
3495 #define MFD_NAME_MAX_LEN (NAME_MAX - MFD_NAME_PREFIX_LEN)
3496 
3497 #define MFD_ALL_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING)
3498 
3499 SYSCALL_DEFINE2(memfd_create,
3500         const char __user *, uname,
3501         unsigned int, flags)
3502 {
3503     struct shmem_inode_info *info;
3504     struct file *file;
3505     int fd, error;
3506     char *name;
3507     long len;
3508 
3509     if (flags & ~(unsigned int)MFD_ALL_FLAGS)
3510         return -EINVAL;
3511 
3512     /* length includes terminating zero */
3513     len = strnlen_user(uname, MFD_NAME_MAX_LEN + 1);
3514     if (len <= 0)
3515         return -EFAULT;
3516     if (len > MFD_NAME_MAX_LEN + 1)
3517         return -EINVAL;
3518 
3519     name = kmalloc(len + MFD_NAME_PREFIX_LEN, GFP_TEMPORARY);
3520     if (!name)
3521         return -ENOMEM;
3522 
3523     strcpy(name, MFD_NAME_PREFIX);
3524     if (copy_from_user(&name[MFD_NAME_PREFIX_LEN], uname, len)) {
3525         error = -EFAULT;
3526         goto err_name;
3527     }
3528 
3529     /* terminating-zero may have changed after strnlen_user() returned */
3530     if (name[len + MFD_NAME_PREFIX_LEN - 1]) {
3531         error = -EFAULT;
3532         goto err_name;
3533     }
3534 
3535     fd = get_unused_fd_flags((flags & MFD_CLOEXEC) ? O_CLOEXEC : 0);
3536     if (fd < 0) {
3537         error = fd;
3538         goto err_name;
3539     }
3540 
3541     file = shmem_file_setup(name, 0, VM_NORESERVE);
3542     if (IS_ERR(file)) {
3543         error = PTR_ERR(file);
3544         goto err_fd;
3545     }
3546     info = SHMEM_I(file_inode(file));
3547     file->f_mode |= FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE;
3548     file->f_flags |= O_RDWR | O_LARGEFILE;
3549     if (flags & MFD_ALLOW_SEALING)
3550         info->seals &= ~F_SEAL_SEAL;
3551 
3552     fd_install(fd, file);
3553     kfree(name);
3554     return fd;
3555 
3556 err_fd:
3557     put_unused_fd(fd);
3558 err_name:
3559     kfree(name);
3560     return error;
3561 }
3562 
3563 #endif /* CONFIG_TMPFS */
3564 
3565 static void shmem_put_super(struct super_block *sb)
3566 {
3567     struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
3568 
3569     percpu_counter_destroy(&sbinfo->used_blocks);
3570     mpol_put(sbinfo->mpol);
3571     kfree(sbinfo);
3572     sb->s_fs_info = NULL;
3573 }
3574 
3575 int shmem_fill_super(struct super_block *sb, void *data, int silent)
3576 {
3577     struct inode *inode;
3578     struct shmem_sb_info *sbinfo;
3579     int err = -ENOMEM;
3580 
3581     /* Round up to L1_CACHE_BYTES to resist false sharing */
3582     sbinfo = kzalloc(max((int)sizeof(struct shmem_sb_info),
3583                 L1_CACHE_BYTES), GFP_KERNEL);
3584     if (!sbinfo)
3585         return -ENOMEM;
3586 
3587     sbinfo->mode = S_IRWXUGO | S_ISVTX;
3588     sbinfo->uid = current_fsuid();
3589     sbinfo->gid = current_fsgid();
3590     sb->s_fs_info = sbinfo;
3591 
3592 #ifdef CONFIG_TMPFS
3593     /*
3594      * Per default we only allow half of the physical ram per
3595      * tmpfs instance, limiting inodes to one per page of lowmem;
3596      * but the internal instance is left unlimited.
3597      */
3598     if (!(sb->s_flags & MS_KERNMOUNT)) {
3599         sbinfo->max_blocks = shmem_default_max_blocks();
3600         sbinfo->max_inodes = shmem_default_max_inodes();
3601         if (shmem_parse_options(data, sbinfo, false)) {
3602             err = -EINVAL;
3603             goto failed;
3604         }
3605     } else {
3606         sb->s_flags |= MS_NOUSER;
3607     }
3608     sb->s_export_op = &shmem_export_ops;
3609     sb->s_flags |= MS_NOSEC;
3610 #else
3611     sb->s_flags |= MS_NOUSER;
3612 #endif
3613 
3614     spin_lock_init(&sbinfo->stat_lock);
3615     if (percpu_counter_init(&sbinfo->used_blocks, 0, GFP_KERNEL))
3616         goto failed;
3617     sbinfo->free_inodes = sbinfo->max_inodes;
3618     spin_lock_init(&sbinfo->shrinklist_lock);
3619     INIT_LIST_HEAD(&sbinfo->shrinklist);
3620 
3621     sb->s_maxbytes = MAX_LFS_FILESIZE;
3622     sb->s_blocksize = PAGE_SIZE;
3623     sb->s_blocksize_bits = PAGE_SHIFT;
3624     sb->s_magic = TMPFS_MAGIC;
3625     sb->s_op = &shmem_ops;
3626     sb->s_time_gran = 1;
3627 #ifdef CONFIG_TMPFS_XATTR
3628     sb->s_xattr = shmem_xattr_handlers;
3629 #endif
3630 #ifdef CONFIG_TMPFS_POSIX_ACL
3631     sb->s_flags |= MS_POSIXACL;
3632 #endif
3633 
3634     inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
3635     if (!inode)
3636         goto failed;
3637     inode->i_uid = sbinfo->uid;
3638     inode->i_gid = sbinfo->gid;
3639     sb->s_root = d_make_root(inode);
3640     if (!sb->s_root)
3641         goto failed;
3642     return 0;
3643 
3644 failed:
3645     shmem_put_super(sb);
3646     return err;
3647 }
3648 
3649 static struct kmem_cache *shmem_inode_cachep;
3650 
3651 static struct inode *shmem_alloc_inode(struct super_block *sb)
3652 {
3653     struct shmem_inode_info *info;
3654     info = kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
3655     if (!info)
3656         return NULL;
3657     return &info->vfs_inode;
3658 }
3659 
3660 static void shmem_destroy_callback(struct rcu_head *head)
3661 {
3662     struct inode *inode = container_of(head, struct inode, i_rcu);
3663     if (S_ISLNK(inode->i_mode))
3664         kfree(inode->i_link);
3665     kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
3666 }
3667 
3668 static void shmem_destroy_inode(struct inode *inode)
3669 {
3670     if (S_ISREG(inode->i_mode))
3671         mpol_free_shared_policy(&SHMEM_I(inode)->policy);
3672     call_rcu(&inode->i_rcu, shmem_destroy_callback);
3673 }
3674 
3675 static void shmem_init_inode(void *foo)
3676 {
3677     struct shmem_inode_info *info = foo;
3678     inode_init_once(&info->vfs_inode);
3679 }
3680 
3681 static int shmem_init_inodecache(void)
3682 {
3683     shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
3684                 sizeof(struct shmem_inode_info),
3685                 0, SLAB_PANIC|SLAB_ACCOUNT, shmem_init_inode);
3686     return 0;
3687 }
3688 
3689 static void shmem_destroy_inodecache(void)
3690 {
3691     kmem_cache_destroy(shmem_inode_cachep);
3692 }
3693 
3694 static const struct address_space_operations shmem_aops = {
3695     .writepage  = shmem_writepage,
3696     .set_page_dirty = __set_page_dirty_no_writeback,
3697 #ifdef CONFIG_TMPFS
3698     .write_begin    = shmem_write_begin,
3699     .write_end  = shmem_write_end,
3700 #endif
3701 #ifdef CONFIG_MIGRATION
3702     .migratepage    = migrate_page,
3703 #endif
3704     .error_remove_page = generic_error_remove_page,
3705 };
3706 
3707 static const struct file_operations shmem_file_operations = {
3708     .mmap       = shmem_mmap,
3709     .get_unmapped_area = shmem_get_unmapped_area,
3710 #ifdef CONFIG_TMPFS
3711     .llseek     = shmem_file_llseek,
3712     .read_iter  = shmem_file_read_iter,
3713     .write_iter = generic_file_write_iter,
3714     .fsync      = noop_fsync,
3715     .splice_read    = generic_file_splice_read,
3716     .splice_write   = iter_file_splice_write,
3717     .fallocate  = shmem_fallocate,
3718 #endif
3719 };
3720 
3721 static const struct inode_operations shmem_inode_operations = {
3722     .getattr    = shmem_getattr,
3723     .setattr    = shmem_setattr,
3724 #ifdef CONFIG_TMPFS_XATTR
3725     .listxattr  = shmem_listxattr,
3726     .set_acl    = simple_set_acl,
3727 #endif
3728 };
3729 
3730 static const struct inode_operations shmem_dir_inode_operations = {
3731 #ifdef CONFIG_TMPFS
3732     .create     = shmem_create,
3733     .lookup     = simple_lookup,
3734     .link       = shmem_link,
3735     .unlink     = shmem_unlink,
3736     .symlink    = shmem_symlink,
3737     .mkdir      = shmem_mkdir,
3738     .rmdir      = shmem_rmdir,
3739     .mknod      = shmem_mknod,
3740     .rename     = shmem_rename2,
3741     .tmpfile    = shmem_tmpfile,
3742 #endif
3743 #ifdef CONFIG_TMPFS_XATTR
3744     .listxattr  = shmem_listxattr,
3745 #endif
3746 #ifdef CONFIG_TMPFS_POSIX_ACL
3747     .setattr    = shmem_setattr,
3748     .set_acl    = simple_set_acl,
3749 #endif
3750 };
3751 
3752 static const struct inode_operations shmem_special_inode_operations = {
3753 #ifdef CONFIG_TMPFS_XATTR
3754     .listxattr  = shmem_listxattr,
3755 #endif
3756 #ifdef CONFIG_TMPFS_POSIX_ACL
3757     .setattr    = shmem_setattr,
3758     .set_acl    = simple_set_acl,
3759 #endif
3760 };
3761 
3762 static const struct super_operations shmem_ops = {
3763     .alloc_inode    = shmem_alloc_inode,
3764     .destroy_inode  = shmem_destroy_inode,
3765 #ifdef CONFIG_TMPFS
3766     .statfs     = shmem_statfs,
3767     .remount_fs = shmem_remount_fs,
3768     .show_options   = shmem_show_options,
3769 #endif
3770     .evict_inode    = shmem_evict_inode,
3771     .drop_inode = generic_delete_inode,
3772     .put_super  = shmem_put_super,
3773 #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
3774     .nr_cached_objects  = shmem_unused_huge_count,
3775     .free_cached_objects    = shmem_unused_huge_scan,
3776 #endif
3777 };
3778 
3779 static const struct vm_operations_struct shmem_vm_ops = {
3780     .fault      = shmem_fault,
3781     .map_pages  = filemap_map_pages,
3782 #ifdef CONFIG_NUMA
3783     .set_policy     = shmem_set_policy,
3784     .get_policy     = shmem_get_policy,
3785 #endif
3786 };
3787 
3788 static struct dentry *shmem_mount(struct file_system_type *fs_type,
3789     int flags, const char *dev_name, void *data)
3790 {
3791     return mount_nodev(fs_type, flags, data, shmem_fill_super);
3792 }
3793 
3794 static struct file_system_type shmem_fs_type = {
3795     .owner      = THIS_MODULE,
3796     .name       = "tmpfs",
3797     .mount      = shmem_mount,
3798     .kill_sb    = kill_litter_super,
3799     .fs_flags   = FS_USERNS_MOUNT,
3800 };
3801 
3802 int __init shmem_init(void)
3803 {
3804     int error;
3805 
3806     /* If rootfs called this, don't re-init */
3807     if (shmem_inode_cachep)
3808         return 0;
3809 
3810     error = shmem_init_inodecache();
3811     if (error)
3812         goto out3;
3813 
3814     error = register_filesystem(&shmem_fs_type);
3815     if (error) {
3816         pr_err("Could not register tmpfs\n");
3817         goto out2;
3818     }
3819 
3820     shm_mnt = kern_mount(&shmem_fs_type);
3821     if (IS_ERR(shm_mnt)) {
3822         error = PTR_ERR(shm_mnt);
3823         pr_err("Could not kern_mount tmpfs\n");
3824         goto out1;
3825     }
3826 
3827 #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
3828     if (has_transparent_hugepage() && shmem_huge < SHMEM_HUGE_DENY)
3829         SHMEM_SB(shm_mnt->mnt_sb)->huge = shmem_huge;
3830     else
3831         shmem_huge = 0; /* just in case it was patched */
3832 #endif
3833     return 0;
3834 
3835 out1:
3836     unregister_filesystem(&shmem_fs_type);
3837 out2:
3838     shmem_destroy_inodecache();
3839 out3:
3840     shm_mnt = ERR_PTR(error);
3841     return error;
3842 }
3843 
3844 #if defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE) && defined(CONFIG_SYSFS)
3845 static ssize_t shmem_enabled_show(struct kobject *kobj,
3846         struct kobj_attribute *attr, char *buf)
3847 {
3848     int values[] = {
3849         SHMEM_HUGE_ALWAYS,
3850         SHMEM_HUGE_WITHIN_SIZE,
3851         SHMEM_HUGE_ADVISE,
3852         SHMEM_HUGE_NEVER,
3853         SHMEM_HUGE_DENY,
3854         SHMEM_HUGE_FORCE,
3855     };
3856     int i, count;
3857 
3858     for (i = 0, count = 0; i < ARRAY_SIZE(values); i++) {
3859         const char *fmt = shmem_huge == values[i] ? "[%s] " : "%s ";
3860 
3861         count += sprintf(buf + count, fmt,
3862                 shmem_format_huge(values[i]));
3863     }
3864     buf[count - 1] = '\n';
3865     return count;
3866 }
3867 
3868 static ssize_t shmem_enabled_store(struct kobject *kobj,
3869         struct kobj_attribute *attr, const char *buf, size_t count)
3870 {
3871     char tmp[16];
3872     int huge;
3873 
3874     if (count + 1 > sizeof(tmp))
3875         return -EINVAL;
3876     memcpy(tmp, buf, count);
3877     tmp[count] = '\0';
3878     if (count && tmp[count - 1] == '\n')
3879         tmp[count - 1] = '\0';
3880 
3881     huge = shmem_parse_huge(tmp);
3882     if (huge == -EINVAL)
3883         return -EINVAL;
3884     if (!has_transparent_hugepage() &&
3885             huge != SHMEM_HUGE_NEVER && huge != SHMEM_HUGE_DENY)
3886         return -EINVAL;
3887 
3888     shmem_huge = huge;
3889     if (shmem_huge < SHMEM_HUGE_DENY)
3890         SHMEM_SB(shm_mnt->mnt_sb)->huge = shmem_huge;
3891     return count;
3892 }
3893 
3894 struct kobj_attribute shmem_enabled_attr =
3895     __ATTR(shmem_enabled, 0644, shmem_enabled_show, shmem_enabled_store);
3896 #endif /* CONFIG_TRANSPARENT_HUGE_PAGECACHE && CONFIG_SYSFS */
3897 
3898 #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
3899 bool shmem_huge_enabled(struct vm_area_struct *vma)
3900 {
3901     struct inode *inode = file_inode(vma->vm_file);
3902     struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
3903     loff_t i_size;
3904     pgoff_t off;
3905 
3906     if (shmem_huge == SHMEM_HUGE_FORCE)
3907         return true;
3908     if (shmem_huge == SHMEM_HUGE_DENY)
3909         return false;
3910     switch (sbinfo->huge) {
3911         case SHMEM_HUGE_NEVER:
3912             return false;
3913         case SHMEM_HUGE_ALWAYS:
3914             return true;
3915         case SHMEM_HUGE_WITHIN_SIZE:
3916             off = round_up(vma->vm_pgoff, HPAGE_PMD_NR);
3917             i_size = round_up(i_size_read(inode), PAGE_SIZE);
3918             if (i_size >= HPAGE_PMD_SIZE &&
3919                     i_size >> PAGE_SHIFT >= off)
3920                 return true;
3921         case SHMEM_HUGE_ADVISE:
3922             /* TODO: implement fadvise() hints */
3923             return (vma->vm_flags & VM_HUGEPAGE);
3924         default:
3925             VM_BUG_ON(1);
3926             return false;
3927     }
3928 }
3929 #endif /* CONFIG_TRANSPARENT_HUGE_PAGECACHE */
3930 
3931 #else /* !CONFIG_SHMEM */
3932 
3933 /*
3934  * tiny-shmem: simple shmemfs and tmpfs using ramfs code
3935  *
3936  * This is intended for small system where the benefits of the full
3937  * shmem code (swap-backed and resource-limited) are outweighed by
3938  * their complexity. On systems without swap this code should be
3939  * effectively equivalent, but much lighter weight.
3940  */
3941 
3942 static struct file_system_type shmem_fs_type = {
3943     .name       = "tmpfs",
3944     .mount      = ramfs_mount,
3945     .kill_sb    = kill_litter_super,
3946     .fs_flags   = FS_USERNS_MOUNT,
3947 };
3948 
3949 int __init shmem_init(void)
3950 {
3951     BUG_ON(register_filesystem(&shmem_fs_type) != 0);
3952 
3953     shm_mnt = kern_mount(&shmem_fs_type);
3954     BUG_ON(IS_ERR(shm_mnt));
3955 
3956     return 0;
3957 }
3958 
3959 int shmem_unuse(swp_entry_t swap, struct page *page)
3960 {
3961     return 0;
3962 }
3963 
3964 int shmem_lock(struct file *file, int lock, struct user_struct *user)
3965 {
3966     return 0;
3967 }
3968 
3969 void shmem_unlock_mapping(struct address_space *mapping)
3970 {
3971 }
3972 
3973 #ifdef CONFIG_MMU
3974 unsigned long shmem_get_unmapped_area(struct file *file,
3975                       unsigned long addr, unsigned long len,
3976                       unsigned long pgoff, unsigned long flags)
3977 {
3978     return current->mm->get_unmapped_area(file, addr, len, pgoff, flags);
3979 }
3980 #endif
3981 
3982 void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
3983 {
3984     truncate_inode_pages_range(inode->i_mapping, lstart, lend);
3985 }
3986 EXPORT_SYMBOL_GPL(shmem_truncate_range);
3987 
3988 #define shmem_vm_ops                generic_file_vm_ops
3989 #define shmem_file_operations           ramfs_file_operations
3990 #define shmem_get_inode(sb, dir, mode, dev, flags)  ramfs_get_inode(sb, dir, mode, dev)
3991 #define shmem_acct_size(flags, size)        0
3992 #define shmem_unacct_size(flags, size)      do {} while (0)
3993 
3994 #endif /* CONFIG_SHMEM */
3995 
3996 /* common code */
3997 
3998 static const struct dentry_operations anon_ops = {
3999     .d_dname = simple_dname
4000 };
4001 
4002 static struct file *__shmem_file_setup(const char *name, loff_t size,
4003                        unsigned long flags, unsigned int i_flags)
4004 {
4005     struct file *res;
4006     struct inode *inode;
4007     struct path path;
4008     struct super_block *sb;
4009     struct qstr this;
4010 
4011     if (IS_ERR(shm_mnt))
4012         return ERR_CAST(shm_mnt);
4013 
4014     if (size < 0 || size > MAX_LFS_FILESIZE)
4015         return ERR_PTR(-EINVAL);
4016 
4017     if (shmem_acct_size(flags, size))
4018         return ERR_PTR(-ENOMEM);
4019 
4020     res = ERR_PTR(-ENOMEM);
4021     this.name = name;
4022     this.len = strlen(name);
4023     this.hash = 0; /* will go */
4024     sb = shm_mnt->mnt_sb;
4025     path.mnt = mntget(shm_mnt);
4026     path.dentry = d_alloc_pseudo(sb, &this);
4027     if (!path.dentry)
4028         goto put_memory;
4029     d_set_d_op(path.dentry, &anon_ops);
4030 
4031     res = ERR_PTR(-ENOSPC);
4032     inode = shmem_get_inode(sb, NULL, S_IFREG | S_IRWXUGO, 0, flags);
4033     if (!inode)
4034         goto put_memory;
4035 
4036     inode->i_flags |= i_flags;
4037     d_instantiate(path.dentry, inode);
4038     inode->i_size = size;
4039     clear_nlink(inode); /* It is unlinked */
4040     res = ERR_PTR(ramfs_nommu_expand_for_mapping(inode, size));
4041     if (IS_ERR(res))
4042         goto put_path;
4043 
4044     res = alloc_file(&path, FMODE_WRITE | FMODE_READ,
4045           &shmem_file_operations);
4046     if (IS_ERR(res))
4047         goto put_path;
4048 
4049     return res;
4050 
4051 put_memory:
4052     shmem_unacct_size(flags, size);
4053 put_path:
4054     path_put(&path);
4055     return res;
4056 }
4057 
4058 /**
4059  * shmem_kernel_file_setup - get an unlinked file living in tmpfs which must be
4060  *  kernel internal.  There will be NO LSM permission checks against the
4061  *  underlying inode.  So users of this interface must do LSM checks at a
4062  *  higher layer.  The users are the big_key and shm implementations.  LSM
4063  *  checks are provided at the key or shm level rather than the inode.
4064  * @name: name for dentry (to be seen in /proc/<pid>/maps
4065  * @size: size to be set for the file
4066  * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
4067  */
4068 struct file *shmem_kernel_file_setup(const char *name, loff_t size, unsigned long flags)
4069 {
4070     return __shmem_file_setup(name, size, flags, S_PRIVATE);
4071 }
4072 
4073 /**
4074  * shmem_file_setup - get an unlinked file living in tmpfs
4075  * @name: name for dentry (to be seen in /proc/<pid>/maps
4076  * @size: size to be set for the file
4077  * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
4078  */
4079 struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags)
4080 {
4081     return __shmem_file_setup(name, size, flags, 0);
4082 }
4083 EXPORT_SYMBOL_GPL(shmem_file_setup);
4084 
4085 /**
4086  * shmem_zero_setup - setup a shared anonymous mapping
4087  * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
4088  */
4089 int shmem_zero_setup(struct vm_area_struct *vma)
4090 {
4091     struct file *file;
4092     loff_t size = vma->vm_end - vma->vm_start;
4093 
4094     /*
4095      * Cloning a new file under mmap_sem leads to a lock ordering conflict
4096      * between XFS directory reading and selinux: since this file is only
4097      * accessible to the user through its mapping, use S_PRIVATE flag to
4098      * bypass file security, in the same way as shmem_kernel_file_setup().
4099      */
4100     file = __shmem_file_setup("dev/zero", size, vma->vm_flags, S_PRIVATE);
4101     if (IS_ERR(file))
4102         return PTR_ERR(file);
4103 
4104     if (vma->vm_file)
4105         fput(vma->vm_file);
4106     vma->vm_file = file;
4107     vma->vm_ops = &shmem_vm_ops;
4108 
4109     if (IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE) &&
4110             ((vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK) <
4111             (vma->vm_end & HPAGE_PMD_MASK)) {
4112         khugepaged_enter(vma, vma->vm_flags);
4113     }
4114 
4115     return 0;
4116 }
4117 
4118 /**
4119  * shmem_read_mapping_page_gfp - read into page cache, using specified page allocation flags.
4120  * @mapping:    the page's address_space
4121  * @index:  the page index
4122  * @gfp:    the page allocator flags to use if allocating
4123  *
4124  * This behaves as a tmpfs "read_cache_page_gfp(mapping, index, gfp)",
4125  * with any new page allocations done using the specified allocation flags.
4126  * But read_cache_page_gfp() uses the ->readpage() method: which does not
4127  * suit tmpfs, since it may have pages in swapcache, and needs to find those
4128  * for itself; although drivers/gpu/drm i915 and ttm rely upon this support.
4129  *
4130  * i915_gem_object_get_pages_gtt() mixes __GFP_NORETRY | __GFP_NOWARN in
4131  * with the mapping_gfp_mask(), to avoid OOMing the machine unnecessarily.
4132  */
4133 struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
4134                      pgoff_t index, gfp_t gfp)
4135 {
4136 #ifdef CONFIG_SHMEM
4137     struct inode *inode = mapping->host;
4138     struct page *page;
4139     int error;
4140 
4141     BUG_ON(mapping->a_ops != &shmem_aops);
4142     error = shmem_getpage_gfp(inode, index, &page, SGP_CACHE,
4143                   gfp, NULL, NULL);
4144     if (error)
4145         page = ERR_PTR(error);
4146     else
4147         unlock_page(page);
4148     return page;
4149 #else
4150     /*
4151      * The tiny !SHMEM case uses ramfs without swap
4152      */
4153     return read_cache_page_gfp(mapping, index, gfp);
4154 #endif
4155 }
4156 EXPORT_SYMBOL_GPL(shmem_read_mapping_page_gfp);