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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 /*
  * Resizable virtual memory filesystem for Linux.
  *
  * Copyright (C) 2000 Linus Torvalds.
  *       2000 Transmeta Corp.
  *       2000-2001 Christoph Rohland
  *       2000-2001 SAP AG
  *       2002 Red Hat Inc.
  * Copyright (C) 2002-2011 Hugh Dickins.
  * Copyright (C) 2011 Google Inc.
  * Copyright (C) 2002-2005 VERITAS Software Corporation.
  * Copyright (C) 2004 Andi Kleen, SuSE Labs
  *
  * Extended attribute support for tmpfs:
  * Copyright (c) 2004, Luke Kenneth Casson Leighton <lkcl@lkcl.net>
  * Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
  *
  * tiny-shmem:
  * Copyright (c) 2004, 2008 Matt Mackall <mpm@selenic.com>
  *
  * This file is released under the GPL.
  */
 
 #include <linux/fs.h>
 #include <linux/init.h>
 #include <linux/vfs.h>
 #include <linux/mount.h>
 #include <linux/ramfs.h>
 #include <linux/pagemap.h>
 #include <linux/file.h>
 #include <linux/fileattr.h>
 #include <linux/mm.h>
 #include <linux/random.h>
 #include <linux/sched/signal.h>
 #include <linux/export.h>
 #include <linux/swap.h>
 #include <linux/uio.h>
 #include <linux/hugetlb.h>
 #include <linux/fs_parser.h>
 #include <linux/swapfile.h>
 #include "swap.h"
 
 static struct vfsmount *shm_mnt;
 
 #ifdef CONFIG_SHMEM
 /*
  * This virtual memory filesystem is heavily based on the ramfs. It
  * extends ramfs by the ability to use swap and honor resource limits
  * which makes it a completely usable filesystem.
  */
 
 #include <linux/xattr.h>
 #include <linux/exportfs.h>
 #include <linux/posix_acl.h>
 #include <linux/posix_acl_xattr.h>
 #include <linux/mman.h>
 #include <linux/string.h>
 #include <linux/slab.h>
 #include <linux/backing-dev.h>
 #include <linux/shmem_fs.h>
 #include <linux/writeback.h>
 #include <linux/pagevec.h>
 #include <linux/percpu_counter.h>
 #include <linux/falloc.h>
 #include <linux/splice.h>
 #include <linux/security.h>
 #include <linux/swapops.h>
 #include <linux/mempolicy.h>
 #include <linux/namei.h>
 #include <linux/ctype.h>
 #include <linux/migrate.h>
 #include <linux/highmem.h>
 #include <linux/seq_file.h>
 #include <linux/magic.h>
 #include <linux/syscalls.h>
 #include <linux/fcntl.h>
 #include <uapi/linux/memfd.h>
 #include <linux/userfaultfd_k.h>
 #include <linux/rmap.h>
 #include <linux/uuid.h>
 
 #include <linux/uaccess.h>
 
 #include "internal.h"
 
 #define BLOCKS_PER_PAGE  (PAGE_SIZE/512)
 #define VM_ACCT(size)    (PAGE_ALIGN(size) >> PAGE_SHIFT)
 
 /* Pretend that each entry is of this size in directory's i_size */
 #define BOGO_DIRENT_SIZE 20
 
 /* Symlink up to this size is kmalloc'ed instead of using a swappable page */
 #define SHORT_SYMLINK_LEN 128
 
 /*
  * shmem_fallocate communicates with shmem_fault or shmem_writepage via
  * inode->i_private (with i_rwsem making sure that it has only one user at
  * a time): we would prefer not to enlarge the shmem inode just for that.
  */
 struct shmem_falloc {
     wait_queue_head_t *waitq; /* faults into hole wait for punch to end */
     pgoff_t start;      /* start of range currently being fallocated */
     pgoff_t next;       /* the next page offset to be fallocated */
     pgoff_t nr_falloced;    /* how many new pages have been fallocated */
     pgoff_t nr_unswapped;   /* how often writepage refused to swap out */
 };
 
 struct shmem_options {
     unsigned long long blocks;
     unsigned long long inodes;
     struct mempolicy *mpol;
     kuid_t uid;
     kgid_t gid;
     umode_t mode;
     bool full_inums;
     int huge;
     int seen;
 #define SHMEM_SEEN_BLOCKS 1
 #define SHMEM_SEEN_INODES 2
 #define SHMEM_SEEN_HUGE 4
 #define SHMEM_SEEN_INUMS 8
 };
 
 #ifdef CONFIG_TMPFS
 static unsigned long shmem_default_max_blocks(void)
 {
     return totalram_pages() / 2;
 }
 
 static unsigned long shmem_default_max_inodes(void)
 {
     unsigned long nr_pages = totalram_pages();
 
     return min(nr_pages - totalhigh_pages(), nr_pages / 2);
 }
 #endif
 
 static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
                  struct folio **foliop, enum sgp_type sgp,
                  gfp_t gfp, struct vm_area_struct *vma,
                  vm_fault_t *fault_type);
 static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
         struct page **pagep, enum sgp_type sgp,
         gfp_t gfp, struct vm_area_struct *vma,
         struct vm_fault *vmf, vm_fault_t *fault_type);
 
 int shmem_getpage(struct inode *inode, pgoff_t index,
         struct page **pagep, enum sgp_type sgp)
 {
     return shmem_getpage_gfp(inode, index, pagep, sgp,
         mapping_gfp_mask(inode->i_mapping), NULL, NULL, NULL);
 }
 
 static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
 {
     return sb->s_fs_info;
 }
 
 /*
  * shmem_file_setup pre-accounts the whole fixed size of a VM object,
  * for shared memory and for shared anonymous (/dev/zero) mappings
  * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
  * consistent with the pre-accounting of private mappings ...
  */
 static inline int shmem_acct_size(unsigned long flags, loff_t size)
 {
     return (flags & VM_NORESERVE) ?
         0 : security_vm_enough_memory_mm(current->mm, VM_ACCT(size));
 }
 
 static inline void shmem_unacct_size(unsigned long flags, loff_t size)
 {
     if (!(flags & VM_NORESERVE))
         vm_unacct_memory(VM_ACCT(size));
 }
 
 static inline int shmem_reacct_size(unsigned long flags,
         loff_t oldsize, loff_t newsize)
 {
     if (!(flags & VM_NORESERVE)) {
         if (VM_ACCT(newsize) > VM_ACCT(oldsize))
             return security_vm_enough_memory_mm(current->mm,
                     VM_ACCT(newsize) - VM_ACCT(oldsize));
         else if (VM_ACCT(newsize) < VM_ACCT(oldsize))
             vm_unacct_memory(VM_ACCT(oldsize) - VM_ACCT(newsize));
     }
     return 0;
 }
 
 /*
  * ... whereas tmpfs objects are accounted incrementally as
  * pages are allocated, in order to allow large sparse files.
  * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
  * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
  */
 static inline int shmem_acct_block(unsigned long flags, long pages)
 {
     if (!(flags & VM_NORESERVE))
         return 0;
 
     return security_vm_enough_memory_mm(current->mm,
             pages * VM_ACCT(PAGE_SIZE));
 }
 
 static inline void shmem_unacct_blocks(unsigned long flags, long pages)
 {
     if (flags & VM_NORESERVE)
         vm_unacct_memory(pages * VM_ACCT(PAGE_SIZE));
 }
 
 static inline bool shmem_inode_acct_block(struct inode *inode, long pages)
 {
     struct shmem_inode_info *info = SHMEM_I(inode);
     struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 
     if (shmem_acct_block(info->flags, pages))
         return false;
 
     if (sbinfo->max_blocks) {
         if (percpu_counter_compare(&sbinfo->used_blocks,
                        sbinfo->max_blocks - pages) > 0)
             goto unacct;
         percpu_counter_add(&sbinfo->used_blocks, pages);
     }
 
     return true;
 
 unacct:
     shmem_unacct_blocks(info->flags, pages);
     return false;
 }
 
 static inline void shmem_inode_unacct_blocks(struct inode *inode, long pages)
 {
     struct shmem_inode_info *info = SHMEM_I(inode);
     struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 
     if (sbinfo->max_blocks)
         percpu_counter_sub(&sbinfo->used_blocks, pages);
     shmem_unacct_blocks(info->flags, pages);
 }
 
 static const struct super_operations shmem_ops;
 const struct address_space_operations shmem_aops;
 static const struct file_operations shmem_file_operations;
 static const struct inode_operations shmem_inode_operations;
 static const struct inode_operations shmem_dir_inode_operations;
 static const struct inode_operations shmem_special_inode_operations;
 static const struct vm_operations_struct shmem_vm_ops;
 static struct file_system_type shmem_fs_type;
 
 bool vma_is_shmem(struct vm_area_struct *vma)
 {
     return vma->vm_ops == &shmem_vm_ops;
 }
 
 static LIST_HEAD(shmem_swaplist);
 static DEFINE_MUTEX(shmem_swaplist_mutex);
 
 /*
  * shmem_reserve_inode() performs bookkeeping to reserve a shmem inode, and
  * produces a novel ino for the newly allocated inode.
  *
  * It may also be called when making a hard link to permit the space needed by
  * each dentry. However, in that case, no new inode number is needed since that
  * internally draws from another pool of inode numbers (currently global
  * get_next_ino()). This case is indicated by passing NULL as inop.
  */
 #define SHMEM_INO_BATCH 1024
 static int shmem_reserve_inode(struct super_block *sb, ino_t *inop)
 {
     struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
     ino_t ino;
 
     if (!(sb->s_flags & SB_KERNMOUNT)) {
         raw_spin_lock(&sbinfo->stat_lock);
         if (sbinfo->max_inodes) {
             if (!sbinfo->free_inodes) {
                 raw_spin_unlock(&sbinfo->stat_lock);
                 return -ENOSPC;
             }
             sbinfo->free_inodes--;
         }
         if (inop) {
             ino = sbinfo->next_ino++;
             if (unlikely(is_zero_ino(ino)))
                 ino = sbinfo->next_ino++;
             if (unlikely(!sbinfo->full_inums &&
                      ino > UINT_MAX)) {
                 /*
                  * Emulate get_next_ino uint wraparound for
                  * compatibility
                  */
                 if (IS_ENABLED(CONFIG_64BIT))
                     pr_warn("%s: inode number overflow on device %d, consider using inode64 mount option\n",
                         __func__, MINOR(sb->s_dev));
                 sbinfo->next_ino = 1;
                 ino = sbinfo->next_ino++;
             }
             *inop = ino;
         }
         raw_spin_unlock(&sbinfo->stat_lock);
     } else if (inop) {
         /*
          * __shmem_file_setup, one of our callers, is lock-free: it
          * doesn't hold stat_lock in shmem_reserve_inode since
          * max_inodes is always 0, and is called from potentially
          * unknown contexts. As such, use a per-cpu batched allocator
          * which doesn't require the per-sb stat_lock unless we are at
          * the batch boundary.
          *
          * We don't need to worry about inode{32,64} since SB_KERNMOUNT
          * shmem mounts are not exposed to userspace, so we don't need
          * to worry about things like glibc compatibility.
          */
         ino_t *next_ino;
 
         next_ino = per_cpu_ptr(sbinfo->ino_batch, get_cpu());
         ino = *next_ino;
         if (unlikely(ino % SHMEM_INO_BATCH == 0)) {
             raw_spin_lock(&sbinfo->stat_lock);
             ino = sbinfo->next_ino;
             sbinfo->next_ino += SHMEM_INO_BATCH;
             raw_spin_unlock(&sbinfo->stat_lock);
             if (unlikely(is_zero_ino(ino)))
                 ino++;
         }
         *inop = ino;
         *next_ino = ++ino;
         put_cpu();
     }
 
     return 0;
 }
 
 static void shmem_free_inode(struct super_block *sb)
 {
     struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
     if (sbinfo->max_inodes) {
         raw_spin_lock(&sbinfo->stat_lock);
         sbinfo->free_inodes++;
         raw_spin_unlock(&sbinfo->stat_lock);
     }
 }
 
 /**
  * shmem_recalc_inode - recalculate the block usage of an inode
  * @inode: inode to recalc
  *
  * We have to calculate the free blocks since the mm can drop
  * undirtied hole pages behind our back.
  *
  * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
  * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
  *
  * It has to be called with the spinlock held.
  */
 static void shmem_recalc_inode(struct inode *inode)
 {
     struct shmem_inode_info *info = SHMEM_I(inode);
     long freed;
 
     freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
     if (freed > 0) {
         info->alloced -= freed;
         inode->i_blocks -= freed * BLOCKS_PER_PAGE;
         shmem_inode_unacct_blocks(inode, freed);
     }
 }
 
 bool shmem_charge(struct inode *inode, long pages)
 {
     struct shmem_inode_info *info = SHMEM_I(inode);
     unsigned long flags;
 
     if (!shmem_inode_acct_block(inode, pages))
         return false;
 
     /* nrpages adjustment first, then shmem_recalc_inode() when balanced */
     inode->i_mapping->nrpages += pages;
 
     spin_lock_irqsave(&info->lock, flags);
     info->alloced += pages;
     inode->i_blocks += pages * BLOCKS_PER_PAGE;
     shmem_recalc_inode(inode);
     spin_unlock_irqrestore(&info->lock, flags);
 
     return true;
 }
 
 void shmem_uncharge(struct inode *inode, long pages)
 {
     struct shmem_inode_info *info = SHMEM_I(inode);
     unsigned long flags;
 
     /* nrpages adjustment done by __filemap_remove_folio() or caller */
 
     spin_lock_irqsave(&info->lock, flags);
     info->alloced -= pages;
     inode->i_blocks -= pages * BLOCKS_PER_PAGE;
     shmem_recalc_inode(inode);
     spin_unlock_irqrestore(&info->lock, flags);
 
     shmem_inode_unacct_blocks(inode, pages);
 }
 
 /*
  * Replace item expected in xarray by a new item, while holding xa_lock.
  */
 static int shmem_replace_entry(struct address_space *mapping,
             pgoff_t index, void *expected, void *replacement)
 {
     XA_STATE(xas, &mapping->i_pages, index);
     void *item;
 
     VM_BUG_ON(!expected);
     VM_BUG_ON(!replacement);
     item = xas_load(&xas);
     if (item != expected)
         return -ENOENT;
     xas_store(&xas, replacement);
     return 0;
 }
 
 /*
  * Sometimes, before we decide whether to proceed or to fail, we must check
  * that an entry was not already brought back from swap by a racing thread.
  *
  * Checking page is not enough: by the time a SwapCache page is locked, it
  * might be reused, and again be SwapCache, using the same swap as before.
  */
 static bool shmem_confirm_swap(struct address_space *mapping,
                    pgoff_t index, swp_entry_t swap)
 {
     return xa_load(&mapping->i_pages, index) == swp_to_radix_entry(swap);
 }
 
 /*
  * Definitions for "huge tmpfs": tmpfs mounted with the huge= option
  *
  * SHMEM_HUGE_NEVER:
  *  disables huge pages for the mount;
  * SHMEM_HUGE_ALWAYS:
  *  enables huge pages for the mount;
  * SHMEM_HUGE_WITHIN_SIZE:
  *  only allocate huge pages if the page will be fully within i_size,
  *  also respect fadvise()/madvise() hints;
  * SHMEM_HUGE_ADVISE:
  *  only allocate huge pages if requested with fadvise()/madvise();
  */
 
 #define SHMEM_HUGE_NEVER    0
 #define SHMEM_HUGE_ALWAYS   1
 #define SHMEM_HUGE_WITHIN_SIZE  2
 #define SHMEM_HUGE_ADVISE   3
 
 /*
  * Special values.
  * Only can be set via /sys/kernel/mm/transparent_hugepage/shmem_enabled:
  *
  * SHMEM_HUGE_DENY:
  *  disables huge on shm_mnt and all mounts, for emergency use;
  * SHMEM_HUGE_FORCE:
  *  enables huge on shm_mnt and all mounts, w/o needing option, for testing;
  *
  */
 #define SHMEM_HUGE_DENY     (-1)
 #define SHMEM_HUGE_FORCE    (-2)
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 /* ifdef here to avoid bloating shmem.o when not necessary */
 
 static int shmem_huge __read_mostly = SHMEM_HUGE_NEVER;
 
 bool shmem_is_huge(struct vm_area_struct *vma,
            struct inode *inode, pgoff_t index)
 {
     loff_t i_size;
 
     if (!S_ISREG(inode->i_mode))
         return false;
     if (shmem_huge == SHMEM_HUGE_DENY)
         return false;
     if (vma && ((vma->vm_flags & VM_NOHUGEPAGE) ||
         test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags)))
         return false;
     if (shmem_huge == SHMEM_HUGE_FORCE)
         return true;
 
     switch (SHMEM_SB(inode->i_sb)->huge) {
     case SHMEM_HUGE_ALWAYS:
         return true;
     case SHMEM_HUGE_WITHIN_SIZE:
         index = round_up(index + 1, HPAGE_PMD_NR);
         i_size = round_up(i_size_read(inode), PAGE_SIZE);
         if (i_size >> PAGE_SHIFT >= index)
             return true;
         fallthrough;
     case SHMEM_HUGE_ADVISE:
         if (vma && (vma->vm_flags & VM_HUGEPAGE))
             return true;
         fallthrough;
     default:
         return false;
     }
 }
 
 #if defined(CONFIG_SYSFS)
 static int shmem_parse_huge(const char *str)
 {
     if (!strcmp(str, "never"))
         return SHMEM_HUGE_NEVER;
     if (!strcmp(str, "always"))
         return SHMEM_HUGE_ALWAYS;
     if (!strcmp(str, "within_size"))
         return SHMEM_HUGE_WITHIN_SIZE;
     if (!strcmp(str, "advise"))
         return SHMEM_HUGE_ADVISE;
     if (!strcmp(str, "deny"))
         return SHMEM_HUGE_DENY;
     if (!strcmp(str, "force"))
         return SHMEM_HUGE_FORCE;
     return -EINVAL;
 }
 #endif
 
 #if defined(CONFIG_SYSFS) || defined(CONFIG_TMPFS)
 static const char *shmem_format_huge(int huge)
 {
     switch (huge) {
     case SHMEM_HUGE_NEVER:
         return "never";
     case SHMEM_HUGE_ALWAYS:
         return "always";
     case SHMEM_HUGE_WITHIN_SIZE:
         return "within_size";
     case SHMEM_HUGE_ADVISE:
         return "advise";
     case SHMEM_HUGE_DENY:
         return "deny";
     case SHMEM_HUGE_FORCE:
         return "force";
     default:
         VM_BUG_ON(1);
         return "bad_val";
     }
 }
 #endif
 
 static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
         struct shrink_control *sc, unsigned long nr_to_split)
 {
     LIST_HEAD(list), *pos, *next;
     LIST_HEAD(to_remove);
     struct inode *inode;
     struct shmem_inode_info *info;
     struct folio *folio;
     unsigned long batch = sc ? sc->nr_to_scan : 128;
     int split = 0;
 
     if (list_empty(&sbinfo->shrinklist))
         return SHRINK_STOP;
 
     spin_lock(&sbinfo->shrinklist_lock);
     list_for_each_safe(pos, next, &sbinfo->shrinklist) {
         info = list_entry(pos, struct shmem_inode_info, shrinklist);
 
         /* pin the inode */
         inode = igrab(&info->vfs_inode);
 
         /* inode is about to be evicted */
         if (!inode) {
             list_del_init(&info->shrinklist);
             goto next;
         }
 
         /* Check if there's anything to gain */
         if (round_up(inode->i_size, PAGE_SIZE) ==
                 round_up(inode->i_size, HPAGE_PMD_SIZE)) {
             list_move(&info->shrinklist, &to_remove);
             goto next;
         }
 
         list_move(&info->shrinklist, &list);
 next:
         sbinfo->shrinklist_len--;
         if (!--batch)
             break;
     }
     spin_unlock(&sbinfo->shrinklist_lock);
 
     list_for_each_safe(pos, next, &to_remove) {
         info = list_entry(pos, struct shmem_inode_info, shrinklist);
         inode = &info->vfs_inode;
         list_del_init(&info->shrinklist);
         iput(inode);
     }
 
     list_for_each_safe(pos, next, &list) {
         int ret;
         pgoff_t index;
 
         info = list_entry(pos, struct shmem_inode_info, shrinklist);
         inode = &info->vfs_inode;
 
         if (nr_to_split && split >= nr_to_split)
             goto move_back;
 
         index = (inode->i_size & HPAGE_PMD_MASK) >> PAGE_SHIFT;
         folio = filemap_get_folio(inode->i_mapping, index);
         if (!folio)
             goto drop;
 
         /* No huge page at the end of the file: nothing to split */
         if (!folio_test_large(folio)) {
             folio_put(folio);
             goto drop;
         }
 
         /*
          * Move the inode on the list back to shrinklist if we failed
          * to lock the page at this time.
          *
          * Waiting for the lock may lead to deadlock in the
          * reclaim path.
          */
         if (!folio_trylock(folio)) {
             folio_put(folio);
             goto move_back;
         }
 
         ret = split_huge_page(&folio->page);
         folio_unlock(folio);
         folio_put(folio);
 
         /* If split failed move the inode on the list back to shrinklist */
         if (ret)
             goto move_back;
 
         split++;
 drop:
         list_del_init(&info->shrinklist);
         goto put;
 move_back:
         /*
          * Make sure the inode is either on the global list or deleted
          * from any local list before iput() since it could be deleted
          * in another thread once we put the inode (then the local list
          * is corrupted).
          */
         spin_lock(&sbinfo->shrinklist_lock);
         list_move(&info->shrinklist, &sbinfo->shrinklist);
         sbinfo->shrinklist_len++;
         spin_unlock(&sbinfo->shrinklist_lock);
 put:
         iput(inode);
     }
 
     return split;
 }
 
 static long shmem_unused_huge_scan(struct super_block *sb,
         struct shrink_control *sc)
 {
     struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
 
     if (!READ_ONCE(sbinfo->shrinklist_len))
         return SHRINK_STOP;
 
     return shmem_unused_huge_shrink(sbinfo, sc, 0);
 }
 
 static long shmem_unused_huge_count(struct super_block *sb,
         struct shrink_control *sc)
 {
     struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
     return READ_ONCE(sbinfo->shrinklist_len);
 }
 #else /* !CONFIG_TRANSPARENT_HUGEPAGE */
 
 #define shmem_huge SHMEM_HUGE_DENY
 
 bool shmem_is_huge(struct vm_area_struct *vma,
            struct inode *inode, pgoff_t index)
 {
     return false;
 }
 
 static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
         struct shrink_control *sc, unsigned long nr_to_split)
 {
     return 0;
 }
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 
 /*
  * Like filemap_add_folio, but error if expected item has gone.
  */
 static int shmem_add_to_page_cache(struct folio *folio,
                    struct address_space *mapping,
                    pgoff_t index, void *expected, gfp_t gfp,
                    struct mm_struct *charge_mm)
 {
     XA_STATE_ORDER(xas, &mapping->i_pages, index, folio_order(folio));
     long nr = folio_nr_pages(folio);
     int error;
 
     VM_BUG_ON_FOLIO(index != round_down(index, nr), folio);
     VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
     VM_BUG_ON_FOLIO(!folio_test_swapbacked(folio), folio);
     VM_BUG_ON(expected && folio_test_large(folio));
 
     folio_ref_add(folio, nr);
     folio->mapping = mapping;
     folio->index = index;
 
     if (!folio_test_swapcache(folio)) {
         error = mem_cgroup_charge(folio, charge_mm, gfp);
         if (error) {
             if (folio_test_pmd_mappable(folio)) {
                 count_vm_event(THP_FILE_FALLBACK);
                 count_vm_event(THP_FILE_FALLBACK_CHARGE);
             }
             goto error;
         }
     }
     folio_throttle_swaprate(folio, gfp);
 
     do {
         xas_lock_irq(&xas);
         if (expected != xas_find_conflict(&xas)) {
             xas_set_err(&xas, -EEXIST);
             goto unlock;
         }
         if (expected && xas_find_conflict(&xas)) {
             xas_set_err(&xas, -EEXIST);
             goto unlock;
         }
         xas_store(&xas, folio);
         if (xas_error(&xas))
             goto unlock;
         if (folio_test_pmd_mappable(folio)) {
             count_vm_event(THP_FILE_ALLOC);
             __lruvec_stat_mod_folio(folio, NR_SHMEM_THPS, nr);
         }
         mapping->nrpages += nr;
         __lruvec_stat_mod_folio(folio, NR_FILE_PAGES, nr);
         __lruvec_stat_mod_folio(folio, NR_SHMEM, nr);
 unlock:
         xas_unlock_irq(&xas);
     } while (xas_nomem(&xas, gfp));
 
     if (xas_error(&xas)) {
         error = xas_error(&xas);
         goto error;
     }
 
     return 0;
 error:
     folio->mapping = NULL;
     folio_ref_sub(folio, nr);
     return error;
 }
 
 /*
  * Like delete_from_page_cache, but substitutes swap for page.
  */
 static void shmem_delete_from_page_cache(struct page *page, void *radswap)
 {
     struct address_space *mapping = page->mapping;
     int error;
 
     VM_BUG_ON_PAGE(PageCompound(page), page);
 
     xa_lock_irq(&mapping->i_pages);
     error = shmem_replace_entry(mapping, page->index, page, radswap);
     page->mapping = NULL;
     mapping->nrpages--;
     __dec_lruvec_page_state(page, NR_FILE_PAGES);
     __dec_lruvec_page_state(page, NR_SHMEM);
     xa_unlock_irq(&mapping->i_pages);
     put_page(page);
     BUG_ON(error);
 }
 
 /*
  * Remove swap entry from page cache, free the swap and its page cache.
  */
 static int shmem_free_swap(struct address_space *mapping,
                pgoff_t index, void *radswap)
 {
     void *old;
 
     old = xa_cmpxchg_irq(&mapping->i_pages, index, radswap, NULL, 0);
     if (old != radswap)
         return -ENOENT;
     free_swap_and_cache(radix_to_swp_entry(radswap));
     return 0;
 }
 
 /*
  * Determine (in bytes) how many of the shmem object's pages mapped by the
  * given offsets are swapped out.
  *
  * This is safe to call without i_rwsem or the i_pages lock thanks to RCU,
  * as long as the inode doesn't go away and racy results are not a problem.
  */
 unsigned long shmem_partial_swap_usage(struct address_space *mapping,
                         pgoff_t start, pgoff_t end)
 {
     XA_STATE(xas, &mapping->i_pages, start);
     struct page *page;
     unsigned long swapped = 0;
 
     rcu_read_lock();
     xas_for_each(&xas, page, end - 1) {
         if (xas_retry(&xas, page))
             continue;
         if (xa_is_value(page))
             swapped++;
 
         if (need_resched()) {
             xas_pause(&xas);
             cond_resched_rcu();
         }
     }
 
     rcu_read_unlock();
 
     return swapped << PAGE_SHIFT;
 }
 
 /*
  * Determine (in bytes) how many of the shmem object's pages mapped by the
  * given vma is swapped out.
  *
  * This is safe to call without i_rwsem or the i_pages lock thanks to RCU,
  * as long as the inode doesn't go away and racy results are not a problem.
  */
 unsigned long shmem_swap_usage(struct vm_area_struct *vma)
 {
     struct inode *inode = file_inode(vma->vm_file);
     struct shmem_inode_info *info = SHMEM_I(inode);
     struct address_space *mapping = inode->i_mapping;
     unsigned long swapped;
 
     /* Be careful as we don't hold info->lock */
     swapped = READ_ONCE(info->swapped);
 
     /*
      * The easier cases are when the shmem object has nothing in swap, or
      * the vma maps it whole. Then we can simply use the stats that we
      * already track.
      */
     if (!swapped)
         return 0;
 
     if (!vma->vm_pgoff && vma->vm_end - vma->vm_start >= inode->i_size)
         return swapped << PAGE_SHIFT;
 
     /* Here comes the more involved part */
     return shmem_partial_swap_usage(mapping, vma->vm_pgoff,
                     vma->vm_pgoff + vma_pages(vma));
 }
 
 /*
  * SysV IPC SHM_UNLOCK restore Unevictable pages to their evictable lists.
  */
 void shmem_unlock_mapping(struct address_space *mapping)
 {
     struct folio_batch fbatch;
     pgoff_t index = 0;
 
     folio_batch_init(&fbatch);
     /*
      * Minor point, but we might as well stop if someone else SHM_LOCKs it.
      */
     while (!mapping_unevictable(mapping) &&
            filemap_get_folios(mapping, &index, ~0UL, &fbatch)) {
         check_move_unevictable_folios(&fbatch);
         folio_batch_release(&fbatch);
         cond_resched();
     }
 }
 
 static struct folio *shmem_get_partial_folio(struct inode *inode, pgoff_t index)
 {
     struct folio *folio;
     struct page *page;
 
     /*
      * At first avoid shmem_getpage(,,,SGP_READ): that fails
      * beyond i_size, and reports fallocated pages as holes.
      */
     folio = __filemap_get_folio(inode->i_mapping, index,
                     FGP_ENTRY | FGP_LOCK, 0);
     if (!xa_is_value(folio))
         return folio;
     /*
      * But read a page back from swap if any of it is within i_size
      * (although in some cases this is just a waste of time).
      */
     page = NULL;
     shmem_getpage(inode, index, &page, SGP_READ);
     return page ? page_folio(page) : NULL;
 }
 
 /*
  * Remove range of pages and swap entries from page cache, and free them.
  * If !unfalloc, truncate or punch hole; if unfalloc, undo failed fallocate.
  */
 static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
                                  bool unfalloc)
 {
     struct address_space *mapping = inode->i_mapping;
     struct shmem_inode_info *info = SHMEM_I(inode);
     pgoff_t start = (lstart + PAGE_SIZE - 1) >> PAGE_SHIFT;
     pgoff_t end = (lend + 1) >> PAGE_SHIFT;
     struct folio_batch fbatch;
     pgoff_t indices[PAGEVEC_SIZE];
     struct folio *folio;
     bool same_folio;
     long nr_swaps_freed = 0;
     pgoff_t index;
     int i;
 
     if (lend == -1)
         end = -1;   /* unsigned, so actually very big */
 
     if (info->fallocend > start && info->fallocend <= end && !unfalloc)
         info->fallocend = start;
 
     folio_batch_init(&fbatch);
     index = start;
     while (index < end && find_lock_entries(mapping, index, end - 1,
             &fbatch, indices)) {
         for (i = 0; i < folio_batch_count(&fbatch); i++) {
             folio = fbatch.folios[i];
 
             index = indices[i];
 
             if (xa_is_value(folio)) {
                 if (unfalloc)
                     continue;
                 nr_swaps_freed += !shmem_free_swap(mapping,
                                 index, folio);
                 continue;
             }
             index += folio_nr_pages(folio) - 1;
 
             if (!unfalloc || !folio_test_uptodate(folio))
                 truncate_inode_folio(mapping, folio);
             folio_unlock(folio);
         }
         folio_batch_remove_exceptionals(&fbatch);
         folio_batch_release(&fbatch);
         cond_resched();
         index++;
     }
 
     same_folio = (lstart >> PAGE_SHIFT) == (lend >> PAGE_SHIFT);
     folio = shmem_get_partial_folio(inode, lstart >> PAGE_SHIFT);
     if (folio) {
         same_folio = lend < folio_pos(folio) + folio_size(folio);
         folio_mark_dirty(folio);
         if (!truncate_inode_partial_folio(folio, lstart, lend)) {
             start = folio->index + folio_nr_pages(folio);
             if (same_folio)
                 end = folio->index;
         }
         folio_unlock(folio);
         folio_put(folio);
         folio = NULL;
     }
 
     if (!same_folio)
         folio = shmem_get_partial_folio(inode, lend >> PAGE_SHIFT);
     if (folio) {
         folio_mark_dirty(folio);
         if (!truncate_inode_partial_folio(folio, lstart, lend))
             end = folio->index;
         folio_unlock(folio);
         folio_put(folio);
     }
 
     index = start;
     while (index < end) {
         cond_resched();
 
         if (!find_get_entries(mapping, index, end - 1, &fbatch,
                 indices)) {
             /* If all gone or hole-punch or unfalloc, we're done */
             if (index == start || end != -1)
                 break;
             /* But if truncating, restart to make sure all gone */
             index = start;
             continue;
         }
         for (i = 0; i < folio_batch_count(&fbatch); i++) {
             folio = fbatch.folios[i];
 
             index = indices[i];
             if (xa_is_value(folio)) {
                 if (unfalloc)
                     continue;
                 if (shmem_free_swap(mapping, index, folio)) {
                     /* Swap was replaced by page: retry */
                     index--;
                     break;
                 }
                 nr_swaps_freed++;
                 continue;
             }
 
             folio_lock(folio);
 
             if (!unfalloc || !folio_test_uptodate(folio)) {
                 if (folio_mapping(folio) != mapping) {
                     /* Page was replaced by swap: retry */
                     folio_unlock(folio);
                     index--;
                     break;
                 }
                 VM_BUG_ON_FOLIO(folio_test_writeback(folio),
                         folio);
                 truncate_inode_folio(mapping, folio);
             }
             index = folio->index + folio_nr_pages(folio) - 1;
             folio_unlock(folio);
         }
         folio_batch_remove_exceptionals(&fbatch);
         folio_batch_release(&fbatch);
         index++;
     }
 
     spin_lock_irq(&info->lock);
     info->swapped -= nr_swaps_freed;
     shmem_recalc_inode(inode);
     spin_unlock_irq(&info->lock);
 }
 
 void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
 {
     shmem_undo_range(inode, lstart, lend, false);
     inode->i_ctime = inode->i_mtime = current_time(inode);
 }
 EXPORT_SYMBOL_GPL(shmem_truncate_range);
 
 static int shmem_getattr(struct user_namespace *mnt_userns,
              const struct path *path, struct kstat *stat,
              u32 request_mask, unsigned int query_flags)
 {
     struct inode *inode = path->dentry->d_inode;
     struct shmem_inode_info *info = SHMEM_I(inode);
 
     if (info->alloced - info->swapped != inode->i_mapping->nrpages) {
         spin_lock_irq(&info->lock);
         shmem_recalc_inode(inode);
         spin_unlock_irq(&info->lock);
     }
     if (info->fsflags & FS_APPEND_FL)
         stat->attributes |= STATX_ATTR_APPEND;
     if (info->fsflags & FS_IMMUTABLE_FL)
         stat->attributes |= STATX_ATTR_IMMUTABLE;
     if (info->fsflags & FS_NODUMP_FL)
         stat->attributes |= STATX_ATTR_NODUMP;
     stat->attributes_mask |= (STATX_ATTR_APPEND |
             STATX_ATTR_IMMUTABLE |
             STATX_ATTR_NODUMP);
     generic_fillattr(&init_user_ns, inode, stat);
 
     if (shmem_is_huge(NULL, inode, 0))
         stat->blksize = HPAGE_PMD_SIZE;
 
     if (request_mask & STATX_BTIME) {
         stat->result_mask |= STATX_BTIME;
         stat->btime.tv_sec = info->i_crtime.tv_sec;
         stat->btime.tv_nsec = info->i_crtime.tv_nsec;
     }
 
     return 0;
 }
 
 static int shmem_setattr(struct user_namespace *mnt_userns,
              struct dentry *dentry, struct iattr *attr)
 {
     struct inode *inode = d_inode(dentry);
     struct shmem_inode_info *info = SHMEM_I(inode);
     int error;
 
     error = setattr_prepare(&init_user_ns, dentry, attr);
     if (error)
         return error;
 
     if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
         loff_t oldsize = inode->i_size;
         loff_t newsize = attr->ia_size;
 
         /* protected by i_rwsem */
         if ((newsize < oldsize && (info->seals & F_SEAL_SHRINK)) ||
             (newsize > oldsize && (info->seals & F_SEAL_GROW)))
             return -EPERM;
 
         if (newsize != oldsize) {
             error = shmem_reacct_size(SHMEM_I(inode)->flags,
                     oldsize, newsize);
             if (error)
                 return error;
             i_size_write(inode, newsize);
             inode->i_ctime = inode->i_mtime = current_time(inode);
         }
         if (newsize <= oldsize) {
             loff_t holebegin = round_up(newsize, PAGE_SIZE);
             if (oldsize > holebegin)
                 unmap_mapping_range(inode->i_mapping,
                             holebegin, 0, 1);
             if (info->alloced)
                 shmem_truncate_range(inode,
                             newsize, (loff_t)-1);
             /* unmap again to remove racily COWed private pages */
             if (oldsize > holebegin)
                 unmap_mapping_range(inode->i_mapping,
                             holebegin, 0, 1);
         }
     }
 
     setattr_copy(&init_user_ns, inode, attr);
     if (attr->ia_valid & ATTR_MODE)
         error = posix_acl_chmod(&init_user_ns, inode, inode->i_mode);
     return error;
 }
 
 static void shmem_evict_inode(struct inode *inode)
 {
     struct shmem_inode_info *info = SHMEM_I(inode);
     struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 
     if (shmem_mapping(inode->i_mapping)) {
         shmem_unacct_size(info->flags, inode->i_size);
         inode->i_size = 0;
         mapping_set_exiting(inode->i_mapping);
         shmem_truncate_range(inode, 0, (loff_t)-1);
         if (!list_empty(&info->shrinklist)) {
             spin_lock(&sbinfo->shrinklist_lock);
             if (!list_empty(&info->shrinklist)) {
                 list_del_init(&info->shrinklist);
                 sbinfo->shrinklist_len--;
             }
             spin_unlock(&sbinfo->shrinklist_lock);
         }
         while (!list_empty(&info->swaplist)) {
             /* Wait while shmem_unuse() is scanning this inode... */
             wait_var_event(&info->stop_eviction,
                        !atomic_read(&info->stop_eviction));
             mutex_lock(&shmem_swaplist_mutex);
             /* ...but beware of the race if we peeked too early */
             if (!atomic_read(&info->stop_eviction))
                 list_del_init(&info->swaplist);
             mutex_unlock(&shmem_swaplist_mutex);
         }
     }
 
     simple_xattrs_free(&info->xattrs);
     WARN_ON(inode->i_blocks);
     shmem_free_inode(inode->i_sb);
     clear_inode(inode);
 }
 
 static int shmem_find_swap_entries(struct address_space *mapping,
                    pgoff_t start, struct folio_batch *fbatch,
                    pgoff_t *indices, unsigned int type)
 {
     XA_STATE(xas, &mapping->i_pages, start);
     struct folio *folio;
     swp_entry_t entry;
 
     rcu_read_lock();
     xas_for_each(&xas, folio, ULONG_MAX) {
         if (xas_retry(&xas, folio))
             continue;
 
         if (!xa_is_value(folio))
             continue;
 
         entry = radix_to_swp_entry(folio);
         /*
          * swapin error entries can be found in the mapping. But they're
          * deliberately ignored here as we've done everything we can do.
          */
         if (swp_type(entry) != type)
             continue;
 
         indices[folio_batch_count(fbatch)] = xas.xa_index;
         if (!folio_batch_add(fbatch, folio))
             break;
 
         if (need_resched()) {
             xas_pause(&xas);
             cond_resched_rcu();
         }
     }
     rcu_read_unlock();
 
     return xas.xa_index;
 }
 
 /*
  * Move the swapped pages for an inode to page cache. Returns the count
  * of pages swapped in, or the error in case of failure.
  */
 static int shmem_unuse_swap_entries(struct inode *inode,
         struct folio_batch *fbatch, pgoff_t *indices)
 {
     int i = 0;
     int ret = 0;
     int error = 0;
     struct address_space *mapping = inode->i_mapping;
 
     for (i = 0; i < folio_batch_count(fbatch); i++) {
         struct folio *folio = fbatch->folios[i];
 
         if (!xa_is_value(folio))
             continue;
         error = shmem_swapin_folio(inode, indices[i],
                       &folio, SGP_CACHE,
                       mapping_gfp_mask(mapping),
                       NULL, NULL);
         if (error == 0) {
             folio_unlock(folio);
             folio_put(folio);
             ret++;
         }
         if (error == -ENOMEM)
             break;
         error = 0;
     }
     return error ? error : ret;
 }
 
 /*
  * If swap found in inode, free it and move page from swapcache to filecache.
  */
 static int shmem_unuse_inode(struct inode *inode, unsigned int type)
 {
     struct address_space *mapping = inode->i_mapping;
     pgoff_t start = 0;
     struct folio_batch fbatch;
     pgoff_t indices[PAGEVEC_SIZE];
     int ret = 0;
 
     do {
         folio_batch_init(&fbatch);
         shmem_find_swap_entries(mapping, start, &fbatch, indices, type);
         if (folio_batch_count(&fbatch) == 0) {
             ret = 0;
             break;
         }
 
         ret = shmem_unuse_swap_entries(inode, &fbatch, indices);
         if (ret < 0)
             break;
 
         start = indices[folio_batch_count(&fbatch) - 1];
     } while (true);
 
     return ret;
 }
 
 /*
  * Read all the shared memory data that resides in the swap
  * device 'type' back into memory, so the swap device can be
  * unused.
  */
 int shmem_unuse(unsigned int type)
 {
     struct shmem_inode_info *info, *next;
     int error = 0;
 
     if (list_empty(&shmem_swaplist))
         return 0;
 
     mutex_lock(&shmem_swaplist_mutex);
     list_for_each_entry_safe(info, next, &shmem_swaplist, swaplist) {
         if (!info->swapped) {
             list_del_init(&info->swaplist);
             continue;
         }
         /*
          * Drop the swaplist mutex while searching the inode for swap;
          * but before doing so, make sure shmem_evict_inode() will not
          * remove placeholder inode from swaplist, nor let it be freed
          * (igrab() would protect from unlink, but not from unmount).
          */
         atomic_inc(&info->stop_eviction);
         mutex_unlock(&shmem_swaplist_mutex);
 
         error = shmem_unuse_inode(&info->vfs_inode, type);
         cond_resched();
 
         mutex_lock(&shmem_swaplist_mutex);
         next = list_next_entry(info, swaplist);
         if (!info->swapped)
             list_del_init(&info->swaplist);
         if (atomic_dec_and_test(&info->stop_eviction))
             wake_up_var(&info->stop_eviction);
         if (error)
             break;
     }
     mutex_unlock(&shmem_swaplist_mutex);
 
     return error;
 }
 
 /*
  * Move the page from the page cache to the swap cache.
  */
 static int shmem_writepage(struct page *page, struct writeback_control *wbc)
 {
     struct folio *folio = page_folio(page);
     struct shmem_inode_info *info;
     struct address_space *mapping;
     struct inode *inode;
     swp_entry_t swap;
     pgoff_t index;
 
     /*
      * If /sys/kernel/mm/transparent_hugepage/shmem_enabled is "always" or
      * "force", drivers/gpu/drm/i915/gem/i915_gem_shmem.c gets huge pages,
      * and its shmem_writeback() needs them to be split when swapping.
      */
     if (PageTransCompound(page)) {
         /* Ensure the subpages are still dirty */
         SetPageDirty(page);
         if (split_huge_page(page) < 0)
             goto redirty;
         ClearPageDirty(page);
     }
 
     BUG_ON(!PageLocked(page));
     mapping = page->mapping;
     index = page->index;
     inode = mapping->host;
     info = SHMEM_I(inode);
     if (info->flags & VM_LOCKED)
         goto redirty;
     if (!total_swap_pages)
         goto redirty;
 
     /*
      * Our capabilities prevent regular writeback or sync from ever calling
      * shmem_writepage; but a stacking filesystem might use ->writepage of
      * its underlying filesystem, in which case tmpfs should write out to
      * swap only in response to memory pressure, and not for the writeback
      * threads or sync.
      */
     if (!wbc->for_reclaim) {
         WARN_ON_ONCE(1);    /* Still happens? Tell us about it! */
         goto redirty;
     }
 
     /*
      * This is somewhat ridiculous, but without plumbing a SWAP_MAP_FALLOC
      * value into swapfile.c, the only way we can correctly account for a
      * fallocated page arriving here is now to initialize it and write it.
      *
      * That's okay for a page already fallocated earlier, but if we have
      * not yet completed the fallocation, then (a) we want to keep track
      * of this page in case we have to undo it, and (b) it may not be a
      * good idea to continue anyway, once we're pushing into swap.  So
      * reactivate the page, and let shmem_fallocate() quit when too many.
      */
     if (!PageUptodate(page)) {
         if (inode->i_private) {
             struct shmem_falloc *shmem_falloc;
             spin_lock(&inode->i_lock);
             shmem_falloc = inode->i_private;
             if (shmem_falloc &&
                 !shmem_falloc->waitq &&
                 index >= shmem_falloc->start &&
                 index < shmem_falloc->next)
                 shmem_falloc->nr_unswapped++;
             else
                 shmem_falloc = NULL;
             spin_unlock(&inode->i_lock);
             if (shmem_falloc)
                 goto redirty;
         }
         clear_highpage(page);
         flush_dcache_page(page);
         SetPageUptodate(page);
     }
 
     swap = folio_alloc_swap(folio);
     if (!swap.val)
         goto redirty;
 
     /*
      * Add inode to shmem_unuse()'s list of swapped-out inodes,
      * if it's not already there.  Do it now before the page is
      * moved to swap cache, when its pagelock no longer protects
      * the inode from eviction.  But don't unlock the mutex until
      * we've incremented swapped, because shmem_unuse_inode() will
      * prune a !swapped inode from the swaplist under this mutex.
      */
     mutex_lock(&shmem_swaplist_mutex);
     if (list_empty(&info->swaplist))
         list_add(&info->swaplist, &shmem_swaplist);
 
     if (add_to_swap_cache(page, swap,
             __GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN,
             NULL) == 0) {
         spin_lock_irq(&info->lock);
         shmem_recalc_inode(inode);
         info->swapped++;
         spin_unlock_irq(&info->lock);
 
         swap_shmem_alloc(swap);
         shmem_delete_from_page_cache(page, swp_to_radix_entry(swap));
 
         mutex_unlock(&shmem_swaplist_mutex);
         BUG_ON(page_mapped(page));
         swap_writepage(page, wbc);
         return 0;
     }
 
     mutex_unlock(&shmem_swaplist_mutex);
     put_swap_page(page, swap);
 redirty:
     set_page_dirty(page);
     if (wbc->for_reclaim)
         return AOP_WRITEPAGE_ACTIVATE;  /* Return with page locked */
     unlock_page(page);
     return 0;
 }
 
 #if defined(CONFIG_NUMA) && defined(CONFIG_TMPFS)
 static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
 {
     char buffer[64];
 
     if (!mpol || mpol->mode == MPOL_DEFAULT)
         return;     /* show nothing */
 
     mpol_to_str(buffer, sizeof(buffer), mpol);
 
     seq_printf(seq, ",mpol=%s", buffer);
 }
 
 static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
 {
     struct mempolicy *mpol = NULL;
     if (sbinfo->mpol) {
         raw_spin_lock(&sbinfo->stat_lock);  /* prevent replace/use races */
         mpol = sbinfo->mpol;
         mpol_get(mpol);
         raw_spin_unlock(&sbinfo->stat_lock);
     }
     return mpol;
 }
 #else /* !CONFIG_NUMA || !CONFIG_TMPFS */
 static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
 {
 }
 static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
 {
     return NULL;
 }
 #endif /* CONFIG_NUMA && CONFIG_TMPFS */
 #ifndef CONFIG_NUMA
 #define vm_policy vm_private_data
 #endif
 
 static void shmem_pseudo_vma_init(struct vm_area_struct *vma,
         struct shmem_inode_info *info, pgoff_t index)
 {
     /* Create a pseudo vma that just contains the policy */
     vma_init(vma, NULL);
     /* Bias interleave by inode number to distribute better across nodes */
     vma->vm_pgoff = index + info->vfs_inode.i_ino;
     vma->vm_policy = mpol_shared_policy_lookup(&info->policy, index);
 }
 
 static void shmem_pseudo_vma_destroy(struct vm_area_struct *vma)
 {
     /* Drop reference taken by mpol_shared_policy_lookup() */
     mpol_cond_put(vma->vm_policy);
 }
 
 static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
             struct shmem_inode_info *info, pgoff_t index)
 {
     struct vm_area_struct pvma;
     struct page *page;
     struct vm_fault vmf = {
         .vma = &pvma,
     };
 
     shmem_pseudo_vma_init(&pvma, info, index);
     page = swap_cluster_readahead(swap, gfp, &vmf);
     shmem_pseudo_vma_destroy(&pvma);
 
     return page;
 }
 
 /*
  * Make sure huge_gfp is always more limited than limit_gfp.
  * Some of the flags set permissions, while others set limitations.
  */
 static gfp_t limit_gfp_mask(gfp_t huge_gfp, gfp_t limit_gfp)
 {
     gfp_t allowflags = __GFP_IO | __GFP_FS | __GFP_RECLAIM;
     gfp_t denyflags = __GFP_NOWARN | __GFP_NORETRY;
     gfp_t zoneflags = limit_gfp & GFP_ZONEMASK;
     gfp_t result = huge_gfp & ~(allowflags | GFP_ZONEMASK);
 
     /* Allow allocations only from the originally specified zones. */
     result |= zoneflags;
 
     /*
      * Minimize the result gfp by taking the union with the deny flags,
      * and the intersection of the allow flags.
      */
     result |= (limit_gfp & denyflags);
     result |= (huge_gfp & limit_gfp) & allowflags;
 
     return result;
 }
 
 static struct folio *shmem_alloc_hugefolio(gfp_t gfp,
         struct shmem_inode_info *info, pgoff_t index)
 {
     struct vm_area_struct pvma;
     struct address_space *mapping = info->vfs_inode.i_mapping;
     pgoff_t hindex;
     struct folio *folio;
 
     hindex = round_down(index, HPAGE_PMD_NR);
     if (xa_find(&mapping->i_pages, &hindex, hindex + HPAGE_PMD_NR - 1,
                                 XA_PRESENT))
         return NULL;
 
     shmem_pseudo_vma_init(&pvma, info, hindex);
     folio = vma_alloc_folio(gfp, HPAGE_PMD_ORDER, &pvma, 0, true);
     shmem_pseudo_vma_destroy(&pvma);
     if (!folio)
         count_vm_event(THP_FILE_FALLBACK);
     return folio;
 }
 
 static struct folio *shmem_alloc_folio(gfp_t gfp,
             struct shmem_inode_info *info, pgoff_t index)
 {
     struct vm_area_struct pvma;
     struct folio *folio;
 
     shmem_pseudo_vma_init(&pvma, info, index);
     folio = vma_alloc_folio(gfp, 0, &pvma, 0, false);
     shmem_pseudo_vma_destroy(&pvma);
 
     return folio;
 }
 
 static struct page *shmem_alloc_page(gfp_t gfp,
             struct shmem_inode_info *info, pgoff_t index)
 {
     return &shmem_alloc_folio(gfp, info, index)->page;
 }
 
 static struct folio *shmem_alloc_and_acct_folio(gfp_t gfp, struct inode *inode,
         pgoff_t index, bool huge)
 {
     struct shmem_inode_info *info = SHMEM_I(inode);
     struct folio *folio;
     int nr;
     int err = -ENOSPC;
 
     if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
         huge = false;
     nr = huge ? HPAGE_PMD_NR : 1;
 
     if (!shmem_inode_acct_block(inode, nr))
         goto failed;
 
     if (huge)
         folio = shmem_alloc_hugefolio(gfp, info, index);
     else
         folio = shmem_alloc_folio(gfp, info, index);
     if (folio) {
         __folio_set_locked(folio);
         __folio_set_swapbacked(folio);
         return folio;
     }
 
     err = -ENOMEM;
     shmem_inode_unacct_blocks(inode, nr);
 failed:
     return ERR_PTR(err);
 }
 
 /*
  * When a page is moved from swapcache to shmem filecache (either by the
  * usual swapin of shmem_getpage_gfp(), or by the less common swapoff of
  * shmem_unuse_inode()), it may have been read in earlier from swap, in
  * ignorance of the mapping it belongs to.  If that mapping has special
  * constraints (like the gma500 GEM driver, which requires RAM below 4GB),
  * we may need to copy to a suitable page before moving to filecache.
  *
  * In a future release, this may well be extended to respect cpuset and
  * NUMA mempolicy, and applied also to anonymous pages in do_swap_page();
  * but for now it is a simple matter of zone.
  */
 static bool shmem_should_replace_folio(struct folio *folio, gfp_t gfp)
 {
     return folio_zonenum(folio) > gfp_zone(gfp);
 }
 
 static int shmem_replace_page(struct page **pagep, gfp_t gfp,
                 struct shmem_inode_info *info, pgoff_t index)
 {
     struct page *oldpage, *newpage;
     struct folio *old, *new;
     struct address_space *swap_mapping;
     swp_entry_t entry;
     pgoff_t swap_index;
     int error;
 
     oldpage = *pagep;
     entry.val = page_private(oldpage);
     swap_index = swp_offset(entry);
     swap_mapping = page_mapping(oldpage);
 
     /*
      * We have arrived here because our zones are constrained, so don't
      * limit chance of success by further cpuset and node constraints.
      */
     gfp &= ~GFP_CONSTRAINT_MASK;
     newpage = shmem_alloc_page(gfp, info, index);
     if (!newpage)
         return -ENOMEM;
 
     get_page(newpage);
     copy_highpage(newpage, oldpage);
     flush_dcache_page(newpage);
 
     __SetPageLocked(newpage);
     __SetPageSwapBacked(newpage);
     SetPageUptodate(newpage);
     set_page_private(newpage, entry.val);
     SetPageSwapCache(newpage);
 
     /*
      * Our caller will very soon move newpage out of swapcache, but it's
      * a nice clean interface for us to replace oldpage by newpage there.
      */
     xa_lock_irq(&swap_mapping->i_pages);
     error = shmem_replace_entry(swap_mapping, swap_index, oldpage, newpage);
     if (!error) {
         old = page_folio(oldpage);
         new = page_folio(newpage);
         mem_cgroup_migrate(old, new);
         __inc_lruvec_page_state(newpage, NR_FILE_PAGES);
         __inc_lruvec_page_state(newpage, NR_SHMEM);
         __dec_lruvec_page_state(oldpage, NR_FILE_PAGES);
         __dec_lruvec_page_state(oldpage, NR_SHMEM);
     }
     xa_unlock_irq(&swap_mapping->i_pages);
 
     if (unlikely(error)) {
         /*
          * Is this possible?  I think not, now that our callers check
          * both PageSwapCache and page_private after getting page lock;
          * but be defensive.  Reverse old to newpage for clear and free.
          */
         oldpage = newpage;
     } else {
         lru_cache_add(newpage);
         *pagep = newpage;
     }
 
     ClearPageSwapCache(oldpage);
     set_page_private(oldpage, 0);
 
     unlock_page(oldpage);
     put_page(oldpage);
     put_page(oldpage);
     return error;
 }
 
 static void shmem_set_folio_swapin_error(struct inode *inode, pgoff_t index,
                      struct folio *folio, swp_entry_t swap)
 {
     struct address_space *mapping = inode->i_mapping;
     struct shmem_inode_info *info = SHMEM_I(inode);
     swp_entry_t swapin_error;
     void *old;
 
     swapin_error = make_swapin_error_entry(&folio->page);
     old = xa_cmpxchg_irq(&mapping->i_pages, index,
                  swp_to_radix_entry(swap),
                  swp_to_radix_entry(swapin_error), 0);
     if (old != swp_to_radix_entry(swap))
         return;
 
     folio_wait_writeback(folio);
     delete_from_swap_cache(folio);
     spin_lock_irq(&info->lock);
     /*
      * Don't treat swapin error folio as alloced. Otherwise inode->i_blocks won't
      * be 0 when inode is released and thus trigger WARN_ON(inode->i_blocks) in
      * shmem_evict_inode.
      */
     info->alloced--;
     info->swapped--;
     shmem_recalc_inode(inode);
     spin_unlock_irq(&info->lock);
     swap_free(swap);
 }
 
 /*
  * Swap in the folio pointed to by *foliop.
  * Caller has to make sure that *foliop contains a valid swapped folio.
  * Returns 0 and the folio in foliop if success. On failure, returns the
  * error code and NULL in *foliop.
  */
 static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
                  struct folio **foliop, enum sgp_type sgp,
                  gfp_t gfp, struct vm_area_struct *vma,
                  vm_fault_t *fault_type)
 {
     struct address_space *mapping = inode->i_mapping;
     struct shmem_inode_info *info = SHMEM_I(inode);
     struct mm_struct *charge_mm = vma ? vma->vm_mm : NULL;
     struct page *page;
     struct folio *folio = NULL;
     swp_entry_t swap;
     int error;
 
     VM_BUG_ON(!*foliop || !xa_is_value(*foliop));
     swap = radix_to_swp_entry(*foliop);
     *foliop = NULL;
 
     if (is_swapin_error_entry(swap))
         return -EIO;
 
     /* Look it up and read it in.. */
     page = lookup_swap_cache(swap, NULL, 0);
     if (!page) {
         /* Or update major stats only when swapin succeeds?? */
         if (fault_type) {
             *fault_type |= VM_FAULT_MAJOR;
             count_vm_event(PGMAJFAULT);
             count_memcg_event_mm(charge_mm, PGMAJFAULT);
         }
         /* Here we actually start the io */
         page = shmem_swapin(swap, gfp, info, index);
         if (!page) {
             error = -ENOMEM;
             goto failed;
         }
     }
     folio = page_folio(page);
 
     /* We have to do this with folio locked to prevent races */
     folio_lock(folio);
     if (!folio_test_swapcache(folio) ||
         folio_swap_entry(folio).val != swap.val ||
         !shmem_confirm_swap(mapping, index, swap)) {
         error = -EEXIST;
         goto unlock;
     }
     if (!folio_test_uptodate(folio)) {
         error = -EIO;
         goto failed;
     }
     folio_wait_writeback(folio);
 
     /*
      * Some architectures may have to restore extra metadata to the
      * folio after reading from swap.
      */
     arch_swap_restore(swap, folio);
 
     if (shmem_should_replace_folio(folio, gfp)) {
         error = shmem_replace_page(&page, gfp, info, index);
         folio = page_folio(page);
         if (error)
             goto failed;
     }
 
     error = shmem_add_to_page_cache(folio, mapping, index,
                     swp_to_radix_entry(swap), gfp,
                     charge_mm);
     if (error)
         goto failed;
 
     spin_lock_irq(&info->lock);
     info->swapped--;
     shmem_recalc_inode(inode);
     spin_unlock_irq(&info->lock);
 
     if (sgp == SGP_WRITE)
         folio_mark_accessed(folio);
 
     delete_from_swap_cache(folio);
     folio_mark_dirty(folio);
     swap_free(swap);
 
     *foliop = folio;
     return 0;
 failed:
     if (!shmem_confirm_swap(mapping, index, swap))
         error = -EEXIST;
     if (error == -EIO)
         shmem_set_folio_swapin_error(inode, index, folio, swap);
 unlock:
     if (folio) {
         folio_unlock(folio);
         folio_put(folio);
     }
 
     return error;
 }
 
 /*
  * shmem_getpage_gfp - find page in cache, or get from swap, or allocate
  *
  * If we allocate a new one we do not mark it dirty. That's up to the
  * vm. If we swap it in we mark it dirty since we also free the swap
  * entry since a page cannot live in both the swap and page cache.
  *
  * vma, vmf, and fault_type are only supplied by shmem_fault:
  * otherwise they are NULL.
  */
 static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
     struct page **pagep, enum sgp_type sgp, gfp_t gfp,
     struct vm_area_struct *vma, struct vm_fault *vmf,
             vm_fault_t *fault_type)
 {
     struct address_space *mapping = inode->i_mapping;
     struct shmem_inode_info *info = SHMEM_I(inode);
     struct shmem_sb_info *sbinfo;
     struct mm_struct *charge_mm;
     struct folio *folio;
     pgoff_t hindex = index;
     gfp_t huge_gfp;
     int error;
     int once = 0;
     int alloced = 0;
 
     if (index > (MAX_LFS_FILESIZE >> PAGE_SHIFT))
         return -EFBIG;
 repeat:
     if (sgp <= SGP_CACHE &&
         ((loff_t)index << PAGE_SHIFT) >= i_size_read(inode)) {
         return -EINVAL;
     }
 
     sbinfo = SHMEM_SB(inode->i_sb);
     charge_mm = vma ? vma->vm_mm : NULL;
 
     folio = __filemap_get_folio(mapping, index, FGP_ENTRY | FGP_LOCK, 0);
     if (folio && vma && userfaultfd_minor(vma)) {
         if (!xa_is_value(folio)) {
             folio_unlock(folio);
             folio_put(folio);
         }
         *fault_type = handle_userfault(vmf, VM_UFFD_MINOR);
         return 0;
     }
 
     if (xa_is_value(folio)) {
         error = shmem_swapin_folio(inode, index, &folio,
                       sgp, gfp, vma, fault_type);
         if (error == -EEXIST)
             goto repeat;
 
         *pagep = &folio->page;
         return error;
     }
 
     if (folio) {
         hindex = folio->index;
         if (sgp == SGP_WRITE)
             folio_mark_accessed(folio);
         if (folio_test_uptodate(folio))
             goto out;
         /* fallocated page */
         if (sgp != SGP_READ)
             goto clear;
         folio_unlock(folio);
         folio_put(folio);
     }
 
     /*
      * SGP_READ: succeed on hole, with NULL page, letting caller zero.
      * SGP_NOALLOC: fail on hole, with NULL page, letting caller fail.
      */
     *pagep = NULL;
     if (sgp == SGP_READ)
         return 0;
     if (sgp == SGP_NOALLOC)
         return -ENOENT;
 
     /*
      * Fast cache lookup and swap lookup did not find it: allocate.
      */
 
     if (vma && userfaultfd_missing(vma)) {
         *fault_type = handle_userfault(vmf, VM_UFFD_MISSING);
         return 0;
     }
 
     if (!shmem_is_huge(vma, inode, index))
         goto alloc_nohuge;
 
     huge_gfp = vma_thp_gfp_mask(vma);
     huge_gfp = limit_gfp_mask(huge_gfp, gfp);
     folio = shmem_alloc_and_acct_folio(huge_gfp, inode, index, true);
     if (IS_ERR(folio)) {
 alloc_nohuge:
         folio = shmem_alloc_and_acct_folio(gfp, inode, index, false);
     }
     if (IS_ERR(folio)) {
         int retry = 5;
 
         error = PTR_ERR(folio);
         folio = NULL;
         if (error != -ENOSPC)
             goto unlock;
         /*
          * Try to reclaim some space by splitting a huge page
          * beyond i_size on the filesystem.
          */
         while (retry--) {
             int ret;
 
             ret = shmem_unused_huge_shrink(sbinfo, NULL, 1);
             if (ret == SHRINK_STOP)
                 break;
             if (ret)
                 goto alloc_nohuge;
         }
         goto unlock;
     }
 
     hindex = round_down(index, folio_nr_pages(folio));
 
     if (sgp == SGP_WRITE)
         __folio_set_referenced(folio);
 
     error = shmem_add_to_page_cache(folio, mapping, hindex,
                     NULL, gfp & GFP_RECLAIM_MASK,
                     charge_mm);
     if (error)
         goto unacct;
     folio_add_lru(folio);
 
     spin_lock_irq(&info->lock);
     info->alloced += folio_nr_pages(folio);
     inode->i_blocks += (blkcnt_t)BLOCKS_PER_PAGE << folio_order(folio);
     shmem_recalc_inode(inode);
     spin_unlock_irq(&info->lock);
     alloced = true;
 
     if (folio_test_pmd_mappable(folio) &&
         DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE) <
             hindex + HPAGE_PMD_NR - 1) {
         /*
          * Part of the huge page is beyond i_size: subject
          * to shrink under memory pressure.
          */
         spin_lock(&sbinfo->shrinklist_lock);
         /*
          * _careful to defend against unlocked access to
          * ->shrink_list in shmem_unused_huge_shrink()
          */
         if (list_empty_careful(&info->shrinklist)) {
             list_add_tail(&info->shrinklist,
                       &sbinfo->shrinklist);
             sbinfo->shrinklist_len++;
         }
         spin_unlock(&sbinfo->shrinklist_lock);
     }
 
     /*
      * Let SGP_FALLOC use the SGP_WRITE optimization on a new page.
      */
     if (sgp == SGP_FALLOC)
         sgp = SGP_WRITE;
 clear:
     /*
      * Let SGP_WRITE caller clear ends if write does not fill page;
      * but SGP_FALLOC on a page fallocated earlier must initialize
      * it now, lest undo on failure cancel our earlier guarantee.
      */
     if (sgp != SGP_WRITE && !folio_test_uptodate(folio)) {
         long i, n = folio_nr_pages(folio);
 
         for (i = 0; i < n; i++)
             clear_highpage(folio_page(folio, i));
         flush_dcache_folio(folio);
         folio_mark_uptodate(folio);
     }
 
     /* Perhaps the file has been truncated since we checked */
     if (sgp <= SGP_CACHE &&
         ((loff_t)index << PAGE_SHIFT) >= i_size_read(inode)) {
         if (alloced) {
             folio_clear_dirty(folio);
             filemap_remove_folio(folio);
             spin_lock_irq(&info->lock);
             shmem_recalc_inode(inode);
             spin_unlock_irq(&info->lock);
         }
         error = -EINVAL;
         goto unlock;
     }
 out:
     *pagep = folio_page(folio, index - hindex);
     return 0;
 
     /*
      * Error recovery.
      */
 unacct:
     shmem_inode_unacct_blocks(inode, folio_nr_pages(folio));
 
     if (folio_test_large(folio)) {
         folio_unlock(folio);
         folio_put(folio);
         goto alloc_nohuge;
     }
 unlock:
     if (folio) {
         folio_unlock(folio);
         folio_put(folio);
     }
     if (error == -ENOSPC && !once++) {
         spin_lock_irq(&info->lock);
         shmem_recalc_inode(inode);
         spin_unlock_irq(&info->lock);
         goto repeat;
     }
     if (error == -EEXIST)
         goto repeat;
     return error;
 }
 
 /*
  * This is like autoremove_wake_function, but it removes the wait queue
  * entry unconditionally - even if something else had already woken the
  * target.
  */
 static int synchronous_wake_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
 {
     int ret = default_wake_function(wait, mode, sync, key);
     list_del_init(&wait->entry);
     return ret;
 }
 
 static vm_fault_t shmem_fault(struct vm_fault *vmf)
 {
     struct vm_area_struct *vma = vmf->vma;
     struct inode *inode = file_inode(vma->vm_file);
     gfp_t gfp = mapping_gfp_mask(inode->i_mapping);
     int err;
     vm_fault_t ret = VM_FAULT_LOCKED;
 
     /*
      * Trinity finds that probing a hole which tmpfs is punching can
      * prevent the hole-punch from ever completing: which in turn
      * locks writers out with its hold on i_rwsem.  So refrain from
      * faulting pages into the hole while it's being punched.  Although
      * shmem_undo_range() does remove the additions, it may be unable to
      * keep up, as each new page needs its own unmap_mapping_range() call,
      * and the i_mmap tree grows ever slower to scan if new vmas are added.
      *
      * It does not matter if we sometimes reach this check just before the
      * hole-punch begins, so that one fault then races with the punch:
      * we just need to make racing faults a rare case.
      *
      * The implementation below would be much simpler if we just used a
      * standard mutex or completion: but we cannot take i_rwsem in fault,
      * and bloating every shmem inode for this unlikely case would be sad.
      */
     if (unlikely(inode->i_private)) {
         struct shmem_falloc *shmem_falloc;
 
         spin_lock(&inode->i_lock);
         shmem_falloc = inode->i_private;
         if (shmem_falloc &&
             shmem_falloc->waitq &&
             vmf->pgoff >= shmem_falloc->start &&
             vmf->pgoff < shmem_falloc->next) {
             struct file *fpin;
             wait_queue_head_t *shmem_falloc_waitq;
             DEFINE_WAIT_FUNC(shmem_fault_wait, synchronous_wake_function);
 
             ret = VM_FAULT_NOPAGE;
             fpin = maybe_unlock_mmap_for_io(vmf, NULL);
             if (fpin)
                 ret = VM_FAULT_RETRY;
 
             shmem_falloc_waitq = shmem_falloc->waitq;
             prepare_to_wait(shmem_falloc_waitq, &shmem_fault_wait,
                     TASK_UNINTERRUPTIBLE);
             spin_unlock(&inode->i_lock);
             schedule();
 
             /*
              * shmem_falloc_waitq points into the shmem_fallocate()
              * stack of the hole-punching task: shmem_falloc_waitq
              * is usually invalid by the time we reach here, but
              * finish_wait() does not dereference it in that case;
              * though i_lock needed lest racing with wake_up_all().
              */
             spin_lock(&inode->i_lock);
             finish_wait(shmem_falloc_waitq, &shmem_fault_wait);
             spin_unlock(&inode->i_lock);
 
             if (fpin)
                 fput(fpin);
             return ret;
         }
         spin_unlock(&inode->i_lock);
     }
 
     err = shmem_getpage_gfp(inode, vmf->pgoff, &vmf->page, SGP_CACHE,
                   gfp, vma, vmf, &ret);
     if (err)
         return vmf_error(err);
     return ret;
 }
 
 unsigned long shmem_get_unmapped_area(struct file *file,
                       unsigned long uaddr, unsigned long len,
                       unsigned long pgoff, unsigned long flags)
 {
     unsigned long (*get_area)(struct file *,
         unsigned long, unsigned long, unsigned long, unsigned long);
     unsigned long addr;
     unsigned long offset;
     unsigned long inflated_len;
     unsigned long inflated_addr;
     unsigned long inflated_offset;
 
     if (len > TASK_SIZE)
         return -ENOMEM;
 
     get_area = current->mm->get_unmapped_area;
     addr = get_area(file, uaddr, len, pgoff, flags);
 
     if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
         return addr;
     if (IS_ERR_VALUE(addr))
         return addr;
     if (addr & ~PAGE_MASK)
         return addr;
     if (addr > TASK_SIZE - len)
         return addr;
 
     if (shmem_huge == SHMEM_HUGE_DENY)
         return addr;
     if (len < HPAGE_PMD_SIZE)
         return addr;
     if (flags & MAP_FIXED)
         return addr;
     /*
      * Our priority is to support MAP_SHARED mapped hugely;
      * and support MAP_PRIVATE mapped hugely too, until it is COWed.
      * But if caller specified an address hint and we allocated area there
      * successfully, respect that as before.
      */
     if (uaddr == addr)
         return addr;
 
     if (shmem_huge != SHMEM_HUGE_FORCE) {
         struct super_block *sb;
 
         if (file) {
             VM_BUG_ON(file->f_op != &shmem_file_operations);
             sb = file_inode(file)->i_sb;
         } else {
             /*
              * Called directly from mm/mmap.c, or drivers/char/mem.c
              * for "/dev/zero", to create a shared anonymous object.
              */
             if (IS_ERR(shm_mnt))
                 return addr;
             sb = shm_mnt->mnt_sb;
         }
         if (SHMEM_SB(sb)->huge == SHMEM_HUGE_NEVER)
             return addr;
     }
 
     offset = (pgoff << PAGE_SHIFT) & (HPAGE_PMD_SIZE-1);
     if (offset && offset + len < 2 * HPAGE_PMD_SIZE)
         return addr;
     if ((addr & (HPAGE_PMD_SIZE-1)) == offset)
         return addr;
 
     inflated_len = len + HPAGE_PMD_SIZE - PAGE_SIZE;
     if (inflated_len > TASK_SIZE)
         return addr;
     if (inflated_len < len)
         return addr;
 
     inflated_addr = get_area(NULL, uaddr, inflated_len, 0, flags);
     if (IS_ERR_VALUE(inflated_addr))
         return addr;
     if (inflated_addr & ~PAGE_MASK)
         return addr;
 
     inflated_offset = inflated_addr & (HPAGE_PMD_SIZE-1);
     inflated_addr += offset - inflated_offset;
     if (inflated_offset > offset)
         inflated_addr += HPAGE_PMD_SIZE;
 
     if (inflated_addr > TASK_SIZE - len)
         return addr;
     return inflated_addr;
 }
 
 #ifdef CONFIG_NUMA
 static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *mpol)
 {
     struct inode *inode = file_inode(vma->vm_file);
     return mpol_set_shared_policy(&SHMEM_I(inode)->policy, vma, mpol);
 }
 
 static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
                       unsigned long addr)
 {
     struct inode *inode = file_inode(vma->vm_file);
     pgoff_t index;
 
     index = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
     return mpol_shared_policy_lookup(&SHMEM_I(inode)->policy, index);
 }
 #endif
 
 int shmem_lock(struct file *file, int lock, struct ucounts *ucounts)
 {
     struct inode *inode = file_inode(file);
     struct shmem_inode_info *info = SHMEM_I(inode);
     int retval = -ENOMEM;
 
     /*
      * What serializes the accesses to info->flags?
      * ipc_lock_object() when called from shmctl_do_lock(),
      * no serialization needed when called from shm_destroy().
      */
     if (lock && !(info->flags & VM_LOCKED)) {
         if (!user_shm_lock(inode->i_size, ucounts))
             goto out_nomem;
         info->flags |= VM_LOCKED;
         mapping_set_unevictable(file->f_mapping);
     }
     if (!lock && (info->flags & VM_LOCKED) && ucounts) {
         user_shm_unlock(inode->i_size, ucounts);
         info->flags &= ~VM_LOCKED;
         mapping_clear_unevictable(file->f_mapping);
     }
     retval = 0;
 
 out_nomem:
     return retval;
 }
 
 static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
 {
     struct shmem_inode_info *info = SHMEM_I(file_inode(file));
     int ret;
 
     ret = seal_check_future_write(info->seals, vma);
     if (ret)
         return ret;
 
     /* arm64 - allow memory tagging on RAM-based files */
     vma->vm_flags |= VM_MTE_ALLOWED;
 
     file_accessed(file);
     vma->vm_ops = &shmem_vm_ops;
     return 0;
 }
 
 #ifdef CONFIG_TMPFS_XATTR
 static int shmem_initxattrs(struct inode *, const struct xattr *, void *);
 
 /*
  * chattr's fsflags are unrelated to extended attributes,
  * but tmpfs has chosen to enable them under the same config option.
  */
 static void shmem_set_inode_flags(struct inode *inode, unsigned int fsflags)
 {
     unsigned int i_flags = 0;
 
     if (fsflags & FS_NOATIME_FL)
         i_flags |= S_NOATIME;
     if (fsflags & FS_APPEND_FL)
         i_flags |= S_APPEND;
     if (fsflags & FS_IMMUTABLE_FL)
         i_flags |= S_IMMUTABLE;
     /*
      * But FS_NODUMP_FL does not require any action in i_flags.
      */
     inode_set_flags(inode, i_flags, S_NOATIME | S_APPEND | S_IMMUTABLE);
 }
 #else
 static void shmem_set_inode_flags(struct inode *inode, unsigned int fsflags)
 {
 }
 #define shmem_initxattrs NULL
 #endif
 
 static struct inode *shmem_get_inode(struct super_block *sb, struct inode *dir,
                      umode_t mode, dev_t dev, unsigned long flags)
 {
     struct inode *inode;
     struct shmem_inode_info *info;
     struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
     ino_t ino;
 
     if (shmem_reserve_inode(sb, &ino))
         return NULL;
 
     inode = new_inode(sb);
     if (inode) {
         inode->i_ino = ino;
         inode_init_owner(&init_user_ns, inode, dir, mode);
         inode->i_blocks = 0;
         inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
         inode->i_generation = prandom_u32();
         info = SHMEM_I(inode);
         memset(info, 0, (char *)inode - (char *)info);
         spin_lock_init(&info->lock);
         atomic_set(&info->stop_eviction, 0);
         info->seals = F_SEAL_SEAL;
         info->flags = flags & VM_NORESERVE;
         info->i_crtime = inode->i_mtime;
         info->fsflags = (dir == NULL) ? 0 :
             SHMEM_I(dir)->fsflags & SHMEM_FL_INHERITED;
         if (info->fsflags)
             shmem_set_inode_flags(inode, info->fsflags);
         INIT_LIST_HEAD(&info->shrinklist);
         INIT_LIST_HEAD(&info->swaplist);
         simple_xattrs_init(&info->xattrs);
         cache_no_acl(inode);
         mapping_set_large_folios(inode->i_mapping);
 
         switch (mode & S_IFMT) {
         default:
             inode->i_op = &shmem_special_inode_operations;
             init_special_inode(inode, mode, dev);
             break;
         case S_IFREG:
             inode->i_mapping->a_ops = &shmem_aops;
             inode->i_op = &shmem_inode_operations;
             inode->i_fop = &shmem_file_operations;
             mpol_shared_policy_init(&info->policy,
                          shmem_get_sbmpol(sbinfo));
             break;
         case S_IFDIR:
             inc_nlink(inode);
             /* Some things misbehave if size == 0 on a directory */
             inode->i_size = 2 * BOGO_DIRENT_SIZE;
             inode->i_op = &shmem_dir_inode_operations;
             inode->i_fop = &simple_dir_operations;
             break;
         case S_IFLNK:
             /*
              * Must not load anything in the rbtree,
              * mpol_free_shared_policy will not be called.
              */
             mpol_shared_policy_init(&info->policy, NULL);
             break;
         }
 
         lockdep_annotate_inode_mutex_key(inode);
     } else
         shmem_free_inode(sb);
     return inode;
 }
 
 #ifdef CONFIG_USERFAULTFD
 int shmem_mfill_atomic_pte(struct mm_struct *dst_mm,
                pmd_t *dst_pmd,
                struct vm_area_struct *dst_vma,
                unsigned long dst_addr,
                unsigned long src_addr,
                bool zeropage, bool wp_copy,
                struct page **pagep)
 {
     struct inode *inode = file_inode(dst_vma->vm_file);
     struct shmem_inode_info *info = SHMEM_I(inode);
     struct address_space *mapping = inode->i_mapping;
     gfp_t gfp = mapping_gfp_mask(mapping);
     pgoff_t pgoff = linear_page_index(dst_vma, dst_addr);
     void *page_kaddr;
     struct folio *folio;
     struct page *page;
     int ret;
     pgoff_t max_off;
 
     if (!shmem_inode_acct_block(inode, 1)) {
         /*
          * We may have got a page, returned -ENOENT triggering a retry,
          * and now we find ourselves with -ENOMEM. Release the page, to
          * avoid a BUG_ON in our caller.
          */
         if (unlikely(*pagep)) {
             put_page(*pagep);
             *pagep = NULL;
         }
         return -ENOMEM;
     }
 
     if (!*pagep) {
         ret = -ENOMEM;
         page = shmem_alloc_page(gfp, info, pgoff);
         if (!page)
             goto out_unacct_blocks;
 
         if (!zeropage) {    /* COPY */
             page_kaddr = kmap_atomic(page);
             ret = copy_from_user(page_kaddr,
                          (const void __user *)src_addr,
                          PAGE_SIZE);
             kunmap_atomic(page_kaddr);
 
             /* fallback to copy_from_user outside mmap_lock */
             if (unlikely(ret)) {
                 *pagep = page;
                 ret = -ENOENT;
                 /* don't free the page */
                 goto out_unacct_blocks;
             }
 
             flush_dcache_page(page);
         } else {        /* ZEROPAGE */
             clear_user_highpage(page, dst_addr);
         }
     } else {
         page = *pagep;
         *pagep = NULL;
     }
 
     VM_BUG_ON(PageLocked(page));
     VM_BUG_ON(PageSwapBacked(page));
     __SetPageLocked(page);
     __SetPageSwapBacked(page);
     __SetPageUptodate(page);
 
     ret = -EFAULT;
     max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
     if (unlikely(pgoff >= max_off))
         goto out_release;
 
     folio = page_folio(page);
     ret = shmem_add_to_page_cache(folio, mapping, pgoff, NULL,
                       gfp & GFP_RECLAIM_MASK, dst_mm);
     if (ret)
         goto out_release;
 
     ret = mfill_atomic_install_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
                        page, true, wp_copy);
     if (ret)
         goto out_delete_from_cache;
 
     spin_lock_irq(&info->lock);
     info->alloced++;
     inode->i_blocks += BLOCKS_PER_PAGE;
     shmem_recalc_inode(inode);
     spin_unlock_irq(&info->lock);
 
     unlock_page(page);
     return 0;
 out_delete_from_cache:
     delete_from_page_cache(page);
 out_release:
     unlock_page(page);
     put_page(page);
 out_unacct_blocks:
     shmem_inode_unacct_blocks(inode, 1);
     return ret;
 }
 #endif /* CONFIG_USERFAULTFD */
 
 #ifdef CONFIG_TMPFS
 static const struct inode_operations shmem_symlink_inode_operations;
 static const struct inode_operations shmem_short_symlink_operations;
 
 static int
 shmem_write_begin(struct file *file, struct address_space *mapping,
             loff_t pos, unsigned len,
             struct page **pagep, void **fsdata)
 {
     struct inode *inode = mapping->host;
     struct shmem_inode_info *info = SHMEM_I(inode);
     pgoff_t index = pos >> PAGE_SHIFT;
     int ret = 0;
 
     /* i_rwsem is held by caller */
     if (unlikely(info->seals & (F_SEAL_GROW |
                    F_SEAL_WRITE | F_SEAL_FUTURE_WRITE))) {
         if (info->seals & (F_SEAL_WRITE | F_SEAL_FUTURE_WRITE))
             return -EPERM;
         if ((info->seals & F_SEAL_GROW) && pos + len > inode->i_size)
             return -EPERM;
     }
 
     ret = shmem_getpage(inode, index, pagep, SGP_WRITE);
 
     if (ret)
         return ret;
 
     if (PageHWPoison(*pagep)) {
         unlock_page(*pagep);
         put_page(*pagep);
         *pagep = NULL;
         return -EIO;
     }
 
     return 0;
 }
 
 static int
 shmem_write_end(struct file *file, struct address_space *mapping,
             loff_t pos, unsigned len, unsigned copied,
             struct page *page, void *fsdata)
 {
     struct inode *inode = mapping->host;
 
     if (pos + copied > inode->i_size)
         i_size_write(inode, pos + copied);
 
     if (!PageUptodate(page)) {
         struct page *head = compound_head(page);
         if (PageTransCompound(page)) {
             int i;
 
             for (i = 0; i < HPAGE_PMD_NR; i++) {
                 if (head + i == page)
                     continue;
                 clear_highpage(head + i);
                 flush_dcache_page(head + i);
             }
         }
         if (copied < PAGE_SIZE) {
             unsigned from = pos & (PAGE_SIZE - 1);
             zero_user_segments(page, 0, from,
                     from + copied, PAGE_SIZE);
         }
         SetPageUptodate(head);
     }
     set_page_dirty(page);
     unlock_page(page);
     put_page(page);
 
     return copied;
 }
 
 static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
 {
     struct file *file = iocb->ki_filp;
     struct inode *inode = file_inode(file);
     struct address_space *mapping = inode->i_mapping;
     pgoff_t index;
     unsigned long offset;
     int error = 0;
     ssize_t retval = 0;
     loff_t *ppos = &iocb->ki_pos;
 
     index = *ppos >> PAGE_SHIFT;
     offset = *ppos & ~PAGE_MASK;
 
     for (;;) {
         struct page *page = NULL;
         pgoff_t end_index;
         unsigned long nr, ret;
         loff_t i_size = i_size_read(inode);
 
         end_index = i_size >> PAGE_SHIFT;
         if (index > end_index)
             break;
         if (index == end_index) {
             nr = i_size & ~PAGE_MASK;
             if (nr <= offset)
                 break;
         }
 
         error = shmem_getpage(inode, index, &page, SGP_READ);
         if (error) {
             if (error == -EINVAL)
                 error = 0;
             break;
         }
         if (page) {
             unlock_page(page);
 
             if (PageHWPoison(page)) {
                 put_page(page);
                 error = -EIO;
                 break;
             }
         }
 
         /*
          * We must evaluate after, since reads (unlike writes)
          * are called without i_rwsem protection against truncate
          */
         nr = PAGE_SIZE;
         i_size = i_size_read(inode);
         end_index = i_size >> PAGE_SHIFT;
         if (index == end_index) {
             nr = i_size & ~PAGE_MASK;
             if (nr <= offset) {
                 if (page)
                     put_page(page);
                 break;
             }
         }
         nr -= offset;
 
         if (page) {
             /*
              * If users can be writing to this page using arbitrary
              * virtual addresses, take care about potential aliasing
              * before reading the page on the kernel side.
              */
             if (mapping_writably_mapped(mapping))
                 flush_dcache_page(page);
             /*
              * Mark the page accessed if we read the beginning.
              */
             if (!offset)
                 mark_page_accessed(page);
             /*
              * Ok, we have the page, and it's up-to-date, so
              * now we can copy it to user space...
              */
             ret = copy_page_to_iter(page, offset, nr, to);
             put_page(page);
 
         } else if (user_backed_iter(to)) {
             /*
              * Copy to user tends to be so well optimized, but
              * clear_user() not so much, that it is noticeably
              * faster to copy the zero page instead of clearing.
              */
             ret = copy_page_to_iter(ZERO_PAGE(0), offset, nr, to);
         } else {
             /*
              * But submitting the same page twice in a row to
              * splice() - or others? - can result in confusion:
              * so don't attempt that optimization on pipes etc.
              */
             ret = iov_iter_zero(nr, to);
         }
 
         retval += ret;
         offset += ret;
         index += offset >> PAGE_SHIFT;
         offset &= ~PAGE_MASK;
 
         if (!iov_iter_count(to))
             break;
         if (ret < nr) {
             error = -EFAULT;
             break;
         }
         cond_resched();
     }
 
     *ppos = ((loff_t) index << PAGE_SHIFT) + offset;
     file_accessed(file);
     return retval ? retval : error;
 }
 
 static loff_t shmem_file_llseek(struct file *file, loff_t offset, int whence)
 {
     struct address_space *mapping = file->f_mapping;
     struct inode *inode = mapping->host;
 
     if (whence != SEEK_DATA && whence != SEEK_HOLE)
         return generic_file_llseek_size(file, offset, whence,
                     MAX_LFS_FILESIZE, i_size_read(inode));
     if (offset < 0)
         return -ENXIO;
 
     inode_lock(inode);
     /* We're holding i_rwsem so we can access i_size directly */
     offset = mapping_seek_hole_data(mapping, offset, inode->i_size, whence);
     if (offset >= 0)
         offset = vfs_setpos(file, offset, MAX_LFS_FILESIZE);
     inode_unlock(inode);
     return offset;
 }
 
 static long shmem_fallocate(struct file *file, int mode, loff_t offset,
                              loff_t len)
 {
     struct inode *inode = file_inode(file);
     struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
     struct shmem_inode_info *info = SHMEM_I(inode);
     struct shmem_falloc shmem_falloc;
     pgoff_t start, index, end, undo_fallocend;
     int error;
 
     if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
         return -EOPNOTSUPP;
 
     inode_lock(inode);
 
     if (mode & FALLOC_FL_PUNCH_HOLE) {
         struct address_space *mapping = file->f_mapping;
         loff_t unmap_start = round_up(offset, PAGE_SIZE);
         loff_t unmap_end = round_down(offset + len, PAGE_SIZE) - 1;
         DECLARE_WAIT_QUEUE_HEAD_ONSTACK(shmem_falloc_waitq);
 
         /* protected by i_rwsem */
         if (info->seals & (F_SEAL_WRITE | F_SEAL_FUTURE_WRITE)) {
             error = -EPERM;
             goto out;
         }
 
         shmem_falloc.waitq = &shmem_falloc_waitq;
         shmem_falloc.start = (u64)unmap_start >> PAGE_SHIFT;
         shmem_falloc.next = (unmap_end + 1) >> PAGE_SHIFT;
         spin_lock(&inode->i_lock);
         inode->i_private = &shmem_falloc;
         spin_unlock(&inode->i_lock);
 
         if ((u64)unmap_end > (u64)unmap_start)
             unmap_mapping_range(mapping, unmap_start,
                         1 + unmap_end - unmap_start, 0);
         shmem_truncate_range(inode, offset, offset + len - 1);
         /* No need to unmap again: hole-punching leaves COWed pages */
 
         spin_lock(&inode->i_lock);
         inode->i_private = NULL;
         wake_up_all(&shmem_falloc_waitq);
         WARN_ON_ONCE(!list_empty(&shmem_falloc_waitq.head));
         spin_unlock(&inode->i_lock);
         error = 0;
         goto out;
     }
 
     /* We need to check rlimit even when FALLOC_FL_KEEP_SIZE */
     error = inode_newsize_ok(inode, offset + len);
     if (error)
         goto out;
 
     if ((info->seals & F_SEAL_GROW) && offset + len > inode->i_size) {
         error = -EPERM;
         goto out;
     }
 
     start = offset >> PAGE_SHIFT;
     end = (offset + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
     /* Try to avoid a swapstorm if len is impossible to satisfy */
     if (sbinfo->max_blocks && end - start > sbinfo->max_blocks) {
         error = -ENOSPC;
         goto out;
     }
 
     shmem_falloc.waitq = NULL;
     shmem_falloc.start = start;
     shmem_falloc.next  = start;
     shmem_falloc.nr_falloced = 0;
     shmem_falloc.nr_unswapped = 0;
     spin_lock(&inode->i_lock);
     inode->i_private = &shmem_falloc;
     spin_unlock(&inode->i_lock);
 
     /*
      * info->fallocend is only relevant when huge pages might be
      * involved: to prevent split_huge_page() freeing fallocated
      * pages when FALLOC_FL_KEEP_SIZE committed beyond i_size.
      */
     undo_fallocend = info->fallocend;
     if (info->fallocend < end)
         info->fallocend = end;
 
     for (index = start; index < end; ) {
         struct page *page;
 
         /*
          * Good, the fallocate(2) manpage permits EINTR: we may have
          * been interrupted because we are using up too much memory.
          */
         if (signal_pending(current))
             error = -EINTR;
         else if (shmem_falloc.nr_unswapped > shmem_falloc.nr_falloced)
             error = -ENOMEM;
         else
             error = shmem_getpage(inode, index, &page, SGP_FALLOC);
         if (error) {
             info->fallocend = undo_fallocend;
             /* Remove the !PageUptodate pages we added */
             if (index > start) {
                 shmem_undo_range(inode,
                     (loff_t)start << PAGE_SHIFT,
                     ((loff_t)index << PAGE_SHIFT) - 1, true);
             }
             goto undone;
         }
 
         index++;
         /*
          * Here is a more important optimization than it appears:
          * a second SGP_FALLOC on the same huge page will clear it,
          * making it PageUptodate and un-undoable if we fail later.
          */
         if (PageTransCompound(page)) {
             index = round_up(index, HPAGE_PMD_NR);
             /* Beware 32-bit wraparound */
             if (!index)
                 index--;
         }
 
         /*
          * Inform shmem_writepage() how far we have reached.
          * No need for lock or barrier: we have the page lock.
          */
         if (!PageUptodate(page))
             shmem_falloc.nr_falloced += index - shmem_falloc.next;
         shmem_falloc.next = index;
 
         /*
          * If !PageUptodate, leave it that way so that freeable pages
          * can be recognized if we need to rollback on error later.
          * But set_page_dirty so that memory pressure will swap rather
          * than free the pages we are allocating (and SGP_CACHE pages
          * might still be clean: we now need to mark those dirty too).
          */
         set_page_dirty(page);
         unlock_page(page);
         put_page(page);
         cond_resched();
     }
 
     if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size)
         i_size_write(inode, offset + len);
 undone:
     spin_lock(&inode->i_lock);
     inode->i_private = NULL;
     spin_unlock(&inode->i_lock);
 out:
     if (!error)
         file_modified(file);
     inode_unlock(inode);
     return error;
 }
 
 static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
     struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
 
     buf->f_type = TMPFS_MAGIC;
     buf->f_bsize = PAGE_SIZE;
     buf->f_namelen = NAME_MAX;
     if (sbinfo->max_blocks) {
         buf->f_blocks = sbinfo->max_blocks;
         buf->f_bavail =
         buf->f_bfree  = sbinfo->max_blocks -
                 percpu_counter_sum(&sbinfo->used_blocks);
     }
     if (sbinfo->max_inodes) {
         buf->f_files = sbinfo->max_inodes;
         buf->f_ffree = sbinfo->free_inodes;
     }
     /* else leave those fields 0 like simple_statfs */
 
     buf->f_fsid = uuid_to_fsid(dentry->d_sb->s_uuid.b);
 
     return 0;
 }
 
 /*
  * File creation. Allocate an inode, and we're done..
  */
 static int
 shmem_mknod(struct user_namespace *mnt_userns, struct inode *dir,
         struct dentry *dentry, umode_t mode, dev_t dev)
 {
     struct inode *inode;
     int error = -ENOSPC;
 
     inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE);
     if (inode) {
         error = simple_acl_create(dir, inode);
         if (error)
             goto out_iput;
         error = security_inode_init_security(inode, dir,
                              &dentry->d_name,
                              shmem_initxattrs, NULL);
         if (error && error != -EOPNOTSUPP)
             goto out_iput;
 
         error = 0;
         dir->i_size += BOGO_DIRENT_SIZE;
         dir->i_ctime = dir->i_mtime = current_time(dir);
         d_instantiate(dentry, inode);
         dget(dentry); /* Extra count - pin the dentry in core */
     }
     return error;
 out_iput:
     iput(inode);
     return error;
 }
 
 static int
 shmem_tmpfile(struct user_namespace *mnt_userns, struct inode *dir,
           struct dentry *dentry, umode_t mode)
 {
     struct inode *inode;
     int error = -ENOSPC;
 
     inode = shmem_get_inode(dir->i_sb, dir, mode, 0, VM_NORESERVE);
     if (inode) {
         error = security_inode_init_security(inode, dir,
                              NULL,
                              shmem_initxattrs, NULL);
         if (error && error != -EOPNOTSUPP)
             goto out_iput;
         error = simple_acl_create(dir, inode);
         if (error)
             goto out_iput;
         d_tmpfile(dentry, inode);
     }
     return error;
 out_iput:
     iput(inode);
     return error;
 }
 
 static int shmem_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
                struct dentry *dentry, umode_t mode)
 {
     int error;
 
     if ((error = shmem_mknod(&init_user_ns, dir, dentry,
                  mode | S_IFDIR, 0)))
         return error;
     inc_nlink(dir);
     return 0;
 }
 
 static int shmem_create(struct user_namespace *mnt_userns, struct inode *dir,
             struct dentry *dentry, umode_t mode, bool excl)
 {
     return shmem_mknod(&init_user_ns, dir, dentry, mode | S_IFREG, 0);
 }
 
 /*
  * Link a file..
  */
 static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
 {
     struct inode *inode = d_inode(old_dentry);
     int ret = 0;
 
     /*
      * No ordinary (disk based) filesystem counts links as inodes;
      * but each new link needs a new dentry, pinning lowmem, and
      * tmpfs dentries cannot be pruned until they are unlinked.
      * But if an O_TMPFILE file is linked into the tmpfs, the
      * first link must skip that, to get the accounting right.
      */
     if (inode->i_nlink) {
         ret = shmem_reserve_inode(inode->i_sb, NULL);
         if (ret)
             goto out;
     }
 
     dir->i_size += BOGO_DIRENT_SIZE;
     inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
     inc_nlink(inode);
     ihold(inode);   /* New dentry reference */
     dget(dentry);       /* Extra pinning count for the created dentry */
     d_instantiate(dentry, inode);
 out:
     return ret;
 }
 
 static int shmem_unlink(struct inode *dir, struct dentry *dentry)
 {
     struct inode *inode = d_inode(dentry);
 
     if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
         shmem_free_inode(inode->i_sb);
 
     dir->i_size -= BOGO_DIRENT_SIZE;
     inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
     drop_nlink(inode);
     dput(dentry);   /* Undo the count from "create" - this does all the work */
     return 0;
 }
 
 static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
 {
     if (!simple_empty(dentry))
         return -ENOTEMPTY;
 
     drop_nlink(d_inode(dentry));
     drop_nlink(dir);
     return shmem_unlink(dir, dentry);
 }
 
 static int shmem_whiteout(struct user_namespace *mnt_userns,
               struct inode *old_dir, struct dentry *old_dentry)
 {
     struct dentry *whiteout;
     int error;
 
     whiteout = d_alloc(old_dentry->d_parent, &old_dentry->d_name);
     if (!whiteout)
         return -ENOMEM;
 
     error = shmem_mknod(&init_user_ns, old_dir, whiteout,
                 S_IFCHR | WHITEOUT_MODE, WHITEOUT_DEV);
     dput(whiteout);
     if (error)
         return error;
 
     /*
      * Cheat and hash the whiteout while the old dentry is still in
      * place, instead of playing games with FS_RENAME_DOES_D_MOVE.
      *
      * d_lookup() will consistently find one of them at this point,
      * not sure which one, but that isn't even important.
      */
     d_rehash(whiteout);
     return 0;
 }
 
 /*
  * The VFS layer already does all the dentry stuff for rename,
  * we just have to decrement the usage count for the target if
  * it exists so that the VFS layer correctly free's it when it
  * gets overwritten.
  */
 static int shmem_rename2(struct user_namespace *mnt_userns,
              struct inode *old_dir, struct dentry *old_dentry,
              struct inode *new_dir, struct dentry *new_dentry,
              unsigned int flags)
 {
     struct inode *inode = d_inode(old_dentry);
     int they_are_dirs = S_ISDIR(inode->i_mode);
 
     if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
         return -EINVAL;
 
     if (flags & RENAME_EXCHANGE)
         return simple_rename_exchange(old_dir, old_dentry, new_dir, new_dentry);
 
     if (!simple_empty(new_dentry))
         return -ENOTEMPTY;
 
     if (flags & RENAME_WHITEOUT) {
         int error;
 
         error = shmem_whiteout(&init_user_ns, old_dir, old_dentry);
         if (error)
             return error;
     }
 
     if (d_really_is_positive(new_dentry)) {
         (void) shmem_unlink(new_dir, new_dentry);
         if (they_are_dirs) {
             drop_nlink(d_inode(new_dentry));
             drop_nlink(old_dir);
         }
     } else if (they_are_dirs) {
         drop_nlink(old_dir);
         inc_nlink(new_dir);
     }
 
     old_dir->i_size -= BOGO_DIRENT_SIZE;
     new_dir->i_size += BOGO_DIRENT_SIZE;
     old_dir->i_ctime = old_dir->i_mtime =
     new_dir->i_ctime = new_dir->i_mtime =
     inode->i_ctime = current_time(old_dir);
     return 0;
 }
 
 static int shmem_symlink(struct user_namespace *mnt_userns, struct inode *dir,
              struct dentry *dentry, const char *symname)
 {
     int error;
     int len;
     struct inode *inode;
     struct page *page;
 
     len = strlen(symname) + 1;
     if (len > PAGE_SIZE)
         return -ENAMETOOLONG;
 
     inode = shmem_get_inode(dir->i_sb, dir, S_IFLNK | 0777, 0,
                 VM_NORESERVE);
     if (!inode)
         return -ENOSPC;
 
     error = security_inode_init_security(inode, dir, &dentry->d_name,
                          shmem_initxattrs, NULL);
     if (error && error != -EOPNOTSUPP) {
         iput(inode);
         return error;
     }
 
     inode->i_size = len-1;
     if (len <= SHORT_SYMLINK_LEN) {
         inode->i_link = kmemdup(symname, len, GFP_KERNEL);
         if (!inode->i_link) {
             iput(inode);
             return -ENOMEM;
         }
         inode->i_op = &shmem_short_symlink_operations;
     } else {
         inode_nohighmem(inode);
         error = shmem_getpage(inode, 0, &page, SGP_WRITE);
         if (error) {
             iput(inode);
             return error;
         }
         inode->i_mapping->a_ops = &shmem_aops;
         inode->i_op = &shmem_symlink_inode_operations;
         memcpy(page_address(page), symname, len);
         SetPageUptodate(page);
         set_page_dirty(page);
         unlock_page(page);
         put_page(page);
     }
     dir->i_size += BOGO_DIRENT_SIZE;
     dir->i_ctime = dir->i_mtime = current_time(dir);
     d_instantiate(dentry, inode);
     dget(dentry);
     return 0;
 }
 
 static void shmem_put_link(void *arg)
 {
     mark_page_accessed(arg);
     put_page(arg);
 }
 
 static const char *shmem_get_link(struct dentry *dentry,
                   struct inode *inode,
                   struct delayed_call *done)
 {
     struct page *page = NULL;
     int error;
     if (!dentry) {
         page = find_get_page(inode->i_mapping, 0);
         if (!page)
             return ERR_PTR(-ECHILD);
         if (PageHWPoison(page) ||
             !PageUptodate(page)) {
             put_page(page);
             return ERR_PTR(-ECHILD);
         }
     } else {
         error = shmem_getpage(inode, 0, &page, SGP_READ);
         if (error)
             return ERR_PTR(error);
         if (!page)
             return ERR_PTR(-ECHILD);
         if (PageHWPoison(page)) {
             unlock_page(page);
             put_page(page);
             return ERR_PTR(-ECHILD);
         }
         unlock_page(page);
     }
     set_delayed_call(done, shmem_put_link, page);
     return page_address(page);
 }
 
 #ifdef CONFIG_TMPFS_XATTR
 
 static int shmem_fileattr_get(struct dentry *dentry, struct fileattr *fa)
 {
     struct shmem_inode_info *info = SHMEM_I(d_inode(dentry));
 
     fileattr_fill_flags(fa, info->fsflags & SHMEM_FL_USER_VISIBLE);
 
     return 0;
 }
 
 static int shmem_fileattr_set(struct user_namespace *mnt_userns,
                   struct dentry *dentry, struct fileattr *fa)
 {
     struct inode *inode = d_inode(dentry);
     struct shmem_inode_info *info = SHMEM_I(inode);
 
     if (fileattr_has_fsx(fa))
         return -EOPNOTSUPP;
     if (fa->flags & ~SHMEM_FL_USER_MODIFIABLE)
         return -EOPNOTSUPP;
 
     info->fsflags = (info->fsflags & ~SHMEM_FL_USER_MODIFIABLE) |
         (fa->flags & SHMEM_FL_USER_MODIFIABLE);
 
     shmem_set_inode_flags(inode, info->fsflags);
     inode->i_ctime = current_time(inode);
     return 0;
 }
 
 /*
  * Superblocks without xattr inode operations may get some security.* xattr
  * support from the LSM "for free". As soon as we have any other xattrs
  * like ACLs, we also need to implement the security.* handlers at
  * filesystem level, though.
  */
 
 /*
  * Callback for security_inode_init_security() for acquiring xattrs.
  */
 static int shmem_initxattrs(struct inode *inode,
                 const struct xattr *xattr_array,
                 void *fs_info)
 {
     struct shmem_inode_info *info = SHMEM_I(inode);
     const struct xattr *xattr;
     struct simple_xattr *new_xattr;
     size_t len;
 
     for (xattr = xattr_array; xattr->name != NULL; xattr++) {
         new_xattr = simple_xattr_alloc(xattr->value, xattr->value_len);
         if (!new_xattr)
             return -ENOMEM;
 
         len = strlen(xattr->name) + 1;
         new_xattr->name = kmalloc(XATTR_SECURITY_PREFIX_LEN + len,
                       GFP_KERNEL);
         if (!new_xattr->name) {
             kvfree(new_xattr);
             return -ENOMEM;
         }
 
         memcpy(new_xattr->name, XATTR_SECURITY_PREFIX,
                XATTR_SECURITY_PREFIX_LEN);
         memcpy(new_xattr->name + XATTR_SECURITY_PREFIX_LEN,
                xattr->name, len);
 
         simple_xattr_list_add(&info->xattrs, new_xattr);
     }
 
     return 0;
 }
 
 static int shmem_xattr_handler_get(const struct xattr_handler *handler,
                    struct dentry *unused, struct inode *inode,
                    const char *name, void *buffer, size_t size)
 {
     struct shmem_inode_info *info = SHMEM_I(inode);
 
     name = xattr_full_name(handler, name);
     return simple_xattr_get(&info->xattrs, name, buffer, size);
 }
 
 static int shmem_xattr_handler_set(const struct xattr_handler *handler,
                    struct user_namespace *mnt_userns,
                    struct dentry *unused, struct inode *inode,
                    const char *name, const void *value,
                    size_t size, int flags)
 {
     struct shmem_inode_info *info = SHMEM_I(inode);
 
     name = xattr_full_name(handler, name);
     return simple_xattr_set(&info->xattrs, name, value, size, flags, NULL);
 }
 
 static const struct xattr_handler shmem_security_xattr_handler = {
     .prefix = XATTR_SECURITY_PREFIX,
     .get = shmem_xattr_handler_get,
     .set = shmem_xattr_handler_set,
 };
 
 static const struct xattr_handler shmem_trusted_xattr_handler = {
     .prefix = XATTR_TRUSTED_PREFIX,
     .get = shmem_xattr_handler_get,
     .set = shmem_xattr_handler_set,
 };
 
 static const struct xattr_handler *shmem_xattr_handlers[] = {
 #ifdef CONFIG_TMPFS_POSIX_ACL
     &posix_acl_access_xattr_handler,
     &posix_acl_default_xattr_handler,
 #endif
     &shmem_security_xattr_handler,
     &shmem_trusted_xattr_handler,
     NULL
 };
 
 static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t size)
 {
     struct shmem_inode_info *info = SHMEM_I(d_inode(dentry));
     return simple_xattr_list(d_inode(dentry), &info->xattrs, buffer, size);
 }
 #endif /* CONFIG_TMPFS_XATTR */
 
 static const struct inode_operations shmem_short_symlink_operations = {
     .getattr    = shmem_getattr,
     .get_link   = simple_get_link,
 #ifdef CONFIG_TMPFS_XATTR
     .listxattr  = shmem_listxattr,
 #endif
 };
 
 static const struct inode_operations shmem_symlink_inode_operations = {
     .getattr    = shmem_getattr,
     .get_link   = shmem_get_link,
 #ifdef CONFIG_TMPFS_XATTR
     .listxattr  = shmem_listxattr,
 #endif
 };
 
 static struct dentry *shmem_get_parent(struct dentry *child)
 {
     return ERR_PTR(-ESTALE);
 }
 
 static int shmem_match(struct inode *ino, void *vfh)
 {
     __u32 *fh = vfh;
     __u64 inum = fh[2];
     inum = (inum << 32) | fh[1];
     return ino->i_ino == inum && fh[0] == ino->i_generation;
 }
 
 /* Find any alias of inode, but prefer a hashed alias */
 static struct dentry *shmem_find_alias(struct inode *inode)
 {
     struct dentry *alias = d_find_alias(inode);
 
     return alias ?: d_find_any_alias(inode);
 }
 
 
 static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
         struct fid *fid, int fh_len, int fh_type)
 {
     struct inode *inode;
     struct dentry *dentry = NULL;
     u64 inum;
 
     if (fh_len < 3)
         return NULL;
 
     inum = fid->raw[2];
     inum = (inum << 32) | fid->raw[1];
 
     inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
             shmem_match, fid->raw);
     if (inode) {
         dentry = shmem_find_alias(inode);
         iput(inode);
     }
 
     return dentry;
 }
 
 static int shmem_encode_fh(struct inode *inode, __u32 *fh, int *len,
                 struct inode *parent)
 {
     if (*len < 3) {
         *len = 3;
         return FILEID_INVALID;
     }
 
     if (inode_unhashed(inode)) {
         /* Unfortunately insert_inode_hash is not idempotent,
          * so as we hash inodes here rather than at creation
          * time, we need a lock to ensure we only try
          * to do it once
          */
         static DEFINE_SPINLOCK(lock);
         spin_lock(&lock);
         if (inode_unhashed(inode))
             __insert_inode_hash(inode,
                         inode->i_ino + inode->i_generation);
         spin_unlock(&lock);
     }
 
     fh[0] = inode->i_generation;
     fh[1] = inode->i_ino;
     fh[2] = ((__u64)inode->i_ino) >> 32;
 
     *len = 3;
     return 1;
 }
 
 static const struct export_operations shmem_export_ops = {
     .get_parent     = shmem_get_parent,
     .encode_fh      = shmem_encode_fh,
     .fh_to_dentry   = shmem_fh_to_dentry,
 };
 
 enum shmem_param {
     Opt_gid,
     Opt_huge,
     Opt_mode,
     Opt_mpol,
     Opt_nr_blocks,
     Opt_nr_inodes,
     Opt_size,
     Opt_uid,
     Opt_inode32,
     Opt_inode64,
 };
 
 static const struct constant_table shmem_param_enums_huge[] = {
     {"never",   SHMEM_HUGE_NEVER },
     {"always",  SHMEM_HUGE_ALWAYS },
     {"within_size", SHMEM_HUGE_WITHIN_SIZE },
     {"advise",  SHMEM_HUGE_ADVISE },
     {}
 };
 
 const struct fs_parameter_spec shmem_fs_parameters[] = {
     fsparam_u32   ("gid",       Opt_gid),
     fsparam_enum  ("huge",      Opt_huge,  shmem_param_enums_huge),
     fsparam_u32oct("mode",      Opt_mode),
     fsparam_string("mpol",      Opt_mpol),
     fsparam_string("nr_blocks", Opt_nr_blocks),
     fsparam_string("nr_inodes", Opt_nr_inodes),
     fsparam_string("size",      Opt_size),
     fsparam_u32   ("uid",       Opt_uid),
     fsparam_flag  ("inode32",   Opt_inode32),
     fsparam_flag  ("inode64",   Opt_inode64),
     {}
 };
 
 static int shmem_parse_one(struct fs_context *fc, struct fs_parameter *param)
 {
     struct shmem_options *ctx = fc->fs_private;
     struct fs_parse_result result;
     unsigned long long size;
     char *rest;
     int opt;
 
     opt = fs_parse(fc, shmem_fs_parameters, param, &result);
     if (opt < 0)
         return opt;
 
     switch (opt) {
     case Opt_size:
         size = memparse(param->string, &rest);
         if (*rest == '%') {
             size <<= PAGE_SHIFT;
             size *= totalram_pages();
             do_div(size, 100);
             rest++;
         }
         if (*rest)
             goto bad_value;
         ctx->blocks = DIV_ROUND_UP(size, PAGE_SIZE);
         ctx->seen |= SHMEM_SEEN_BLOCKS;
         break;
     case Opt_nr_blocks:
         ctx->blocks = memparse(param->string, &rest);
         if (*rest || ctx->blocks > S64_MAX)
             goto bad_value;
         ctx->seen |= SHMEM_SEEN_BLOCKS;
         break;
     case Opt_nr_inodes:
         ctx->inodes = memparse(param->string, &rest);
         if (*rest)
             goto bad_value;
         ctx->seen |= SHMEM_SEEN_INODES;
         break;
     case Opt_mode:
         ctx->mode = result.uint_32 & 07777;
         break;
     case Opt_uid:
         ctx->uid = make_kuid(current_user_ns(), result.uint_32);
         if (!uid_valid(ctx->uid))
             goto bad_value;
         break;
     case Opt_gid:
         ctx->gid = make_kgid(current_user_ns(), result.uint_32);
         if (!gid_valid(ctx->gid))
             goto bad_value;
         break;
     case Opt_huge:
         ctx->huge = result.uint_32;
         if (ctx->huge != SHMEM_HUGE_NEVER &&
             !(IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
               has_transparent_hugepage()))
             goto unsupported_parameter;
         ctx->seen |= SHMEM_SEEN_HUGE;
         break;
     case Opt_mpol:
         if (IS_ENABLED(CONFIG_NUMA)) {
             mpol_put(ctx->mpol);
             ctx->mpol = NULL;
             if (mpol_parse_str(param->string, &ctx->mpol))
                 goto bad_value;
             break;
         }
         goto unsupported_parameter;
     case Opt_inode32:
         ctx->full_inums = false;
         ctx->seen |= SHMEM_SEEN_INUMS;
         break;
     case Opt_inode64:
         if (sizeof(ino_t) < 8) {
             return invalfc(fc,
                        "Cannot use inode64 with <64bit inums in kernel\n");
         }
         ctx->full_inums = true;
         ctx->seen |= SHMEM_SEEN_INUMS;
         break;
     }
     return 0;
 
 unsupported_parameter:
     return invalfc(fc, "Unsupported parameter '%s'", param->key);
 bad_value:
     return invalfc(fc, "Bad value for '%s'", param->key);
 }
 
 static int shmem_parse_options(struct fs_context *fc, void *data)
 {
     char *options = data;
 
     if (options) {
         int err = security_sb_eat_lsm_opts(options, &fc->security);
         if (err)
             return err;
     }
 
     while (options != NULL) {
         char *this_char = options;
         for (;;) {
             /*
              * NUL-terminate this option: unfortunately,
              * mount options form a comma-separated list,
              * but mpol's nodelist may also contain commas.
              */
             options = strchr(options, ',');
             if (options == NULL)
                 break;
             options++;
             if (!isdigit(*options)) {
                 options[-1] = '\0';
                 break;
             }
         }
         if (*this_char) {
             char *value = strchr(this_char, '=');
             size_t len = 0;
             int err;
 
             if (value) {
                 *value++ = '\0';
                 len = strlen(value);
             }
             err = vfs_parse_fs_string(fc, this_char, value, len);
             if (err < 0)
                 return err;
         }
     }
     return 0;
 }
 
 /*
  * Reconfigure a shmem filesystem.
  *
  * Note that we disallow change from limited->unlimited blocks/inodes while any
  * are in use; but we must separately disallow unlimited->limited, because in
  * that case we have no record of how much is already in use.
  */
 static int shmem_reconfigure(struct fs_context *fc)
 {
     struct shmem_options *ctx = fc->fs_private;
     struct shmem_sb_info *sbinfo = SHMEM_SB(fc->root->d_sb);
     unsigned long inodes;
     struct mempolicy *mpol = NULL;
     const char *err;
 
     raw_spin_lock(&sbinfo->stat_lock);
     inodes = sbinfo->max_inodes - sbinfo->free_inodes;
 
     if ((ctx->seen & SHMEM_SEEN_BLOCKS) && ctx->blocks) {
         if (!sbinfo->max_blocks) {
             err = "Cannot retroactively limit size";
             goto out;
         }
         if (percpu_counter_compare(&sbinfo->used_blocks,
                        ctx->blocks) > 0) {
             err = "Too small a size for current use";
             goto out;
         }
     }
     if ((ctx->seen & SHMEM_SEEN_INODES) && ctx->inodes) {
         if (!sbinfo->max_inodes) {
             err = "Cannot retroactively limit inodes";
             goto out;
         }
         if (ctx->inodes < inodes) {
             err = "Too few inodes for current use";
             goto out;
         }
     }
 
     if ((ctx->seen & SHMEM_SEEN_INUMS) && !ctx->full_inums &&
         sbinfo->next_ino > UINT_MAX) {
         err = "Current inum too high to switch to 32-bit inums";
         goto out;
     }
 
     if (ctx->seen & SHMEM_SEEN_HUGE)
         sbinfo->huge = ctx->huge;
     if (ctx->seen & SHMEM_SEEN_INUMS)
         sbinfo->full_inums = ctx->full_inums;
     if (ctx->seen & SHMEM_SEEN_BLOCKS)
         sbinfo->max_blocks  = ctx->blocks;
     if (ctx->seen & SHMEM_SEEN_INODES) {
         sbinfo->max_inodes  = ctx->inodes;
         sbinfo->free_inodes = ctx->inodes - inodes;
     }
 
     /*
      * Preserve previous mempolicy unless mpol remount option was specified.
      */
     if (ctx->mpol) {
         mpol = sbinfo->mpol;
         sbinfo->mpol = ctx->mpol;   /* transfers initial ref */
         ctx->mpol = NULL;
     }
     raw_spin_unlock(&sbinfo->stat_lock);
     mpol_put(mpol);
     return 0;
 out:
     raw_spin_unlock(&sbinfo->stat_lock);
     return invalfc(fc, "%s", err);
 }
 
 static int shmem_show_options(struct seq_file *seq, struct dentry *root)
 {
     struct shmem_sb_info *sbinfo = SHMEM_SB(root->d_sb);
 
     if (sbinfo->max_blocks != shmem_default_max_blocks())
         seq_printf(seq, ",size=%luk",
             sbinfo->max_blocks << (PAGE_SHIFT - 10));
     if (sbinfo->max_inodes != shmem_default_max_inodes())
         seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
     if (sbinfo->mode != (0777 | S_ISVTX))
         seq_printf(seq, ",mode=%03ho", sbinfo->mode);
     if (!uid_eq(sbinfo->uid, GLOBAL_ROOT_UID))
         seq_printf(seq, ",uid=%u",
                 from_kuid_munged(&init_user_ns, sbinfo->uid));
     if (!gid_eq(sbinfo->gid, GLOBAL_ROOT_GID))
         seq_printf(seq, ",gid=%u",
                 from_kgid_munged(&init_user_ns, sbinfo->gid));
 
     /*
      * Showing inode{64,32} might be useful even if it's the system default,
      * since then people don't have to resort to checking both here and
      * /proc/config.gz to confirm 64-bit inums were successfully applied
      * (which may not even exist if IKCONFIG_PROC isn't enabled).
      *
      * We hide it when inode64 isn't the default and we are using 32-bit
      * inodes, since that probably just means the feature isn't even under
      * consideration.
      *
      * As such:
      *
      *                     +-----------------+-----------------+
      *                     | TMPFS_INODE64=y | TMPFS_INODE64=n |
      *  +------------------+-----------------+-----------------+
      *  | full_inums=true  | show            | show            |
      *  | full_inums=false | show            | hide            |
      *  +------------------+-----------------+-----------------+
      *
      */
     if (IS_ENABLED(CONFIG_TMPFS_INODE64) || sbinfo->full_inums)
         seq_printf(seq, ",inode%d", (sbinfo->full_inums ? 64 : 32));
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
     /* Rightly or wrongly, show huge mount option unmasked by shmem_huge */
     if (sbinfo->huge)
         seq_printf(seq, ",huge=%s", shmem_format_huge(sbinfo->huge));
 #endif
     shmem_show_mpol(seq, sbinfo->mpol);
     return 0;
 }
 
 #endif /* CONFIG_TMPFS */
 
 static void shmem_put_super(struct super_block *sb)
 {
     struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
 
     free_percpu(sbinfo->ino_batch);
     percpu_counter_destroy(&sbinfo->used_blocks);
     mpol_put(sbinfo->mpol);
     kfree(sbinfo);
     sb->s_fs_info = NULL;
 }
 
 static int shmem_fill_super(struct super_block *sb, struct fs_context *fc)
 {
     struct shmem_options *ctx = fc->fs_private;
     struct inode *inode;
     struct shmem_sb_info *sbinfo;
 
     /* Round up to L1_CACHE_BYTES to resist false sharing */
     sbinfo = kzalloc(max((int)sizeof(struct shmem_sb_info),
                 L1_CACHE_BYTES), GFP_KERNEL);
     if (!sbinfo)
         return -ENOMEM;
 
     sb->s_fs_info = sbinfo;
 
 #ifdef CONFIG_TMPFS
     /*
      * Per default we only allow half of the physical ram per
      * tmpfs instance, limiting inodes to one per page of lowmem;
      * but the internal instance is left unlimited.
      */
     if (!(sb->s_flags & SB_KERNMOUNT)) {
         if (!(ctx->seen & SHMEM_SEEN_BLOCKS))
             ctx->blocks = shmem_default_max_blocks();
         if (!(ctx->seen & SHMEM_SEEN_INODES))
             ctx->inodes = shmem_default_max_inodes();
         if (!(ctx->seen & SHMEM_SEEN_INUMS))
             ctx->full_inums = IS_ENABLED(CONFIG_TMPFS_INODE64);
     } else {
         sb->s_flags |= SB_NOUSER;
     }
     sb->s_export_op = &shmem_export_ops;
     sb->s_flags |= SB_NOSEC;
 #else
     sb->s_flags |= SB_NOUSER;
 #endif
     sbinfo->max_blocks = ctx->blocks;
     sbinfo->free_inodes = sbinfo->max_inodes = ctx->inodes;
     if (sb->s_flags & SB_KERNMOUNT) {
         sbinfo->ino_batch = alloc_percpu(ino_t);
         if (!sbinfo->ino_batch)
             goto failed;
     }
     sbinfo->uid = ctx->uid;
     sbinfo->gid = ctx->gid;
     sbinfo->full_inums = ctx->full_inums;
     sbinfo->mode = ctx->mode;
     sbinfo->huge = ctx->huge;
     sbinfo->mpol = ctx->mpol;
     ctx->mpol = NULL;
 
     raw_spin_lock_init(&sbinfo->stat_lock);
     if (percpu_counter_init(&sbinfo->used_blocks, 0, GFP_KERNEL))
         goto failed;
     spin_lock_init(&sbinfo->shrinklist_lock);
     INIT_LIST_HEAD(&sbinfo->shrinklist);
 
     sb->s_maxbytes = MAX_LFS_FILESIZE;
     sb->s_blocksize = PAGE_SIZE;
     sb->s_blocksize_bits = PAGE_SHIFT;
     sb->s_magic = TMPFS_MAGIC;
     sb->s_op = &shmem_ops;
     sb->s_time_gran = 1;
 #ifdef CONFIG_TMPFS_XATTR
     sb->s_xattr = shmem_xattr_handlers;
 #endif
 #ifdef CONFIG_TMPFS_POSIX_ACL
     sb->s_flags |= SB_POSIXACL;
 #endif
     uuid_gen(&sb->s_uuid);
 
     inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
     if (!inode)
         goto failed;
     inode->i_uid = sbinfo->uid;
     inode->i_gid = sbinfo->gid;
     sb->s_root = d_make_root(inode);
     if (!sb->s_root)
         goto failed;
     return 0;
 
 failed:
     shmem_put_super(sb);
     return -ENOMEM;
 }
 
 static int shmem_get_tree(struct fs_context *fc)
 {
     return get_tree_nodev(fc, shmem_fill_super);
 }
 
 static void shmem_free_fc(struct fs_context *fc)
 {
     struct shmem_options *ctx = fc->fs_private;
 
     if (ctx) {
         mpol_put(ctx->mpol);
         kfree(ctx);
     }
 }
 
 static const struct fs_context_operations shmem_fs_context_ops = {
     .free           = shmem_free_fc,
     .get_tree       = shmem_get_tree,
 #ifdef CONFIG_TMPFS
     .parse_monolithic   = shmem_parse_options,
     .parse_param        = shmem_parse_one,
     .reconfigure        = shmem_reconfigure,
 #endif
 };
 
 static struct kmem_cache *shmem_inode_cachep;
 
 static struct inode *shmem_alloc_inode(struct super_block *sb)
 {
     struct shmem_inode_info *info;
     info = alloc_inode_sb(sb, shmem_inode_cachep, GFP_KERNEL);
     if (!info)
         return NULL;
     return &info->vfs_inode;
 }
 
 static void shmem_free_in_core_inode(struct inode *inode)
 {
     if (S_ISLNK(inode->i_mode))
         kfree(inode->i_link);
     kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
 }
 
 static void shmem_destroy_inode(struct inode *inode)
 {
     if (S_ISREG(inode->i_mode))
         mpol_free_shared_policy(&SHMEM_I(inode)->policy);
 }
 
 static void shmem_init_inode(void *foo)
 {
     struct shmem_inode_info *info = foo;
     inode_init_once(&info->vfs_inode);
 }
 
 static void shmem_init_inodecache(void)
 {
     shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
                 sizeof(struct shmem_inode_info),
                 0, SLAB_PANIC|SLAB_ACCOUNT, shmem_init_inode);
 }
 
 static void shmem_destroy_inodecache(void)
 {
     kmem_cache_destroy(shmem_inode_cachep);
 }
 
 /* Keep the page in page cache instead of truncating it */
 static int shmem_error_remove_page(struct address_space *mapping,
                    struct page *page)
 {
     return 0;
 }
 
 const struct address_space_operations shmem_aops = {
     .writepage  = shmem_writepage,
     .dirty_folio    = noop_dirty_folio,
 #ifdef CONFIG_TMPFS
     .write_begin    = shmem_write_begin,
     .write_end  = shmem_write_end,
 #endif
 #ifdef CONFIG_MIGRATION
     .migrate_folio  = migrate_folio,
 #endif
     .error_remove_page = shmem_error_remove_page,
 };
 EXPORT_SYMBOL(shmem_aops);
 
 static const struct file_operations shmem_file_operations = {
     .mmap       = shmem_mmap,
     .get_unmapped_area = shmem_get_unmapped_area,
 #ifdef CONFIG_TMPFS
     .llseek     = shmem_file_llseek,
     .read_iter  = shmem_file_read_iter,
     .write_iter = generic_file_write_iter,
     .fsync      = noop_fsync,
     .splice_read    = generic_file_splice_read,
     .splice_write   = iter_file_splice_write,
     .fallocate  = shmem_fallocate,
 #endif
 };
 
 static const struct inode_operations shmem_inode_operations = {
     .getattr    = shmem_getattr,
     .setattr    = shmem_setattr,
 #ifdef CONFIG_TMPFS_XATTR
     .listxattr  = shmem_listxattr,
     .set_acl    = simple_set_acl,
     .fileattr_get   = shmem_fileattr_get,
     .fileattr_set   = shmem_fileattr_set,
 #endif
 };
 
 static const struct inode_operations shmem_dir_inode_operations = {
 #ifdef CONFIG_TMPFS
     .getattr    = shmem_getattr,
     .create     = shmem_create,
     .lookup     = simple_lookup,
     .link       = shmem_link,
     .unlink     = shmem_unlink,
     .symlink    = shmem_symlink,
     .mkdir      = shmem_mkdir,
     .rmdir      = shmem_rmdir,
     .mknod      = shmem_mknod,
     .rename     = shmem_rename2,
     .tmpfile    = shmem_tmpfile,
 #endif
 #ifdef CONFIG_TMPFS_XATTR
     .listxattr  = shmem_listxattr,
     .fileattr_get   = shmem_fileattr_get,
     .fileattr_set   = shmem_fileattr_set,
 #endif
 #ifdef CONFIG_TMPFS_POSIX_ACL
     .setattr    = shmem_setattr,
     .set_acl    = simple_set_acl,
 #endif
 };
 
 static const struct inode_operations shmem_special_inode_operations = {
     .getattr    = shmem_getattr,
 #ifdef CONFIG_TMPFS_XATTR
     .listxattr  = shmem_listxattr,
 #endif
 #ifdef CONFIG_TMPFS_POSIX_ACL
     .setattr    = shmem_setattr,
     .set_acl    = simple_set_acl,
 #endif
 };
 
 static const struct super_operations shmem_ops = {
     .alloc_inode    = shmem_alloc_inode,
     .free_inode = shmem_free_in_core_inode,
     .destroy_inode  = shmem_destroy_inode,
 #ifdef CONFIG_TMPFS
     .statfs     = shmem_statfs,
     .show_options   = shmem_show_options,
 #endif
     .evict_inode    = shmem_evict_inode,
     .drop_inode = generic_delete_inode,
     .put_super  = shmem_put_super,
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
     .nr_cached_objects  = shmem_unused_huge_count,
     .free_cached_objects    = shmem_unused_huge_scan,
 #endif
 };
 
 static const struct vm_operations_struct shmem_vm_ops = {
     .fault      = shmem_fault,
     .map_pages  = filemap_map_pages,
 #ifdef CONFIG_NUMA
     .set_policy     = shmem_set_policy,
     .get_policy     = shmem_get_policy,
 #endif
 };
 
 int shmem_init_fs_context(struct fs_context *fc)
 {
     struct shmem_options *ctx;
 
     ctx = kzalloc(sizeof(struct shmem_options), GFP_KERNEL);
     if (!ctx)
         return -ENOMEM;
 
     ctx->mode = 0777 | S_ISVTX;
     ctx->uid = current_fsuid();
     ctx->gid = current_fsgid();
 
     fc->fs_private = ctx;
     fc->ops = &shmem_fs_context_ops;
     return 0;
 }
 
 static struct file_system_type shmem_fs_type = {
     .owner      = THIS_MODULE,
     .name       = "tmpfs",
     .init_fs_context = shmem_init_fs_context,
 #ifdef CONFIG_TMPFS
     .parameters = shmem_fs_parameters,
 #endif
     .kill_sb    = kill_litter_super,
     .fs_flags   = FS_USERNS_MOUNT,
 };
 
 void __init shmem_init(void)
 {
     int error;
 
     shmem_init_inodecache();
 
     error = register_filesystem(&shmem_fs_type);
     if (error) {
         pr_err("Could not register tmpfs\n");
         goto out2;
     }
 
     shm_mnt = kern_mount(&shmem_fs_type);
     if (IS_ERR(shm_mnt)) {
         error = PTR_ERR(shm_mnt);
         pr_err("Could not kern_mount tmpfs\n");
         goto out1;
     }
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
     if (has_transparent_hugepage() && shmem_huge > SHMEM_HUGE_DENY)
         SHMEM_SB(shm_mnt->mnt_sb)->huge = shmem_huge;
     else
         shmem_huge = SHMEM_HUGE_NEVER; /* just in case it was patched */
 #endif
     return;
 
 out1:
     unregister_filesystem(&shmem_fs_type);
 out2:
     shmem_destroy_inodecache();
     shm_mnt = ERR_PTR(error);
 }
 
 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && defined(CONFIG_SYSFS)
 static ssize_t shmem_enabled_show(struct kobject *kobj,
                   struct kobj_attribute *attr, char *buf)
 {
     static const int values[] = {
         SHMEM_HUGE_ALWAYS,
         SHMEM_HUGE_WITHIN_SIZE,
         SHMEM_HUGE_ADVISE,
         SHMEM_HUGE_NEVER,
         SHMEM_HUGE_DENY,
         SHMEM_HUGE_FORCE,
     };
     int len = 0;
     int i;
 
     for (i = 0; i < ARRAY_SIZE(values); i++) {
         len += sysfs_emit_at(buf, len,
                      shmem_huge == values[i] ? "%s[%s]" : "%s%s",
                      i ? " " : "",
                      shmem_format_huge(values[i]));
     }
 
     len += sysfs_emit_at(buf, len, "\n");
 
     return len;
 }
 
 static ssize_t shmem_enabled_store(struct kobject *kobj,
         struct kobj_attribute *attr, const char *buf, size_t count)
 {
     char tmp[16];
     int huge;
 
     if (count + 1 > sizeof(tmp))
         return -EINVAL;
     memcpy(tmp, buf, count);
     tmp[count] = '\0';
     if (count && tmp[count - 1] == '\n')
         tmp[count - 1] = '\0';
 
     huge = shmem_parse_huge(tmp);
     if (huge == -EINVAL)
         return -EINVAL;
     if (!has_transparent_hugepage() &&
             huge != SHMEM_HUGE_NEVER && huge != SHMEM_HUGE_DENY)
         return -EINVAL;
 
     shmem_huge = huge;
     if (shmem_huge > SHMEM_HUGE_DENY)
         SHMEM_SB(shm_mnt->mnt_sb)->huge = shmem_huge;
     return count;
 }
 
 struct kobj_attribute shmem_enabled_attr = __ATTR_RW(shmem_enabled);
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE && CONFIG_SYSFS */
 
 #else /* !CONFIG_SHMEM */
 
 /*
  * tiny-shmem: simple shmemfs and tmpfs using ramfs code
  *
  * This is intended for small system where the benefits of the full
  * shmem code (swap-backed and resource-limited) are outweighed by
  * their complexity. On systems without swap this code should be
  * effectively equivalent, but much lighter weight.
  */
 
 static struct file_system_type shmem_fs_type = {
     .name       = "tmpfs",
     .init_fs_context = ramfs_init_fs_context,
     .parameters = ramfs_fs_parameters,
     .kill_sb    = kill_litter_super,
     .fs_flags   = FS_USERNS_MOUNT,
 };
 
 void __init shmem_init(void)
 {
     BUG_ON(register_filesystem(&shmem_fs_type) != 0);
 
     shm_mnt = kern_mount(&shmem_fs_type);
     BUG_ON(IS_ERR(shm_mnt));
 }
 
 int shmem_unuse(unsigned int type)
 {
     return 0;
 }
 
 int shmem_lock(struct file *file, int lock, struct ucounts *ucounts)
 {
     return 0;
 }
 
 void shmem_unlock_mapping(struct address_space *mapping)
 {
 }
 
 #ifdef CONFIG_MMU
 unsigned long shmem_get_unmapped_area(struct file *file,
                       unsigned long addr, unsigned long len,
                       unsigned long pgoff, unsigned long flags)
 {
     return current->mm->get_unmapped_area(file, addr, len, pgoff, flags);
 }
 #endif
 
 void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
 {
     truncate_inode_pages_range(inode->i_mapping, lstart, lend);
 }
 EXPORT_SYMBOL_GPL(shmem_truncate_range);
 
 #define shmem_vm_ops                generic_file_vm_ops
 #define shmem_file_operations           ramfs_file_operations
 #define shmem_get_inode(sb, dir, mode, dev, flags)  ramfs_get_inode(sb, dir, mode, dev)
 #define shmem_acct_size(flags, size)        0
 #define shmem_unacct_size(flags, size)      do {} while (0)
 
 #endif /* CONFIG_SHMEM */
 
 /* common code */
 
 static struct file *__shmem_file_setup(struct vfsmount *mnt, const char *name, loff_t size,
                        unsigned long flags, unsigned int i_flags)
 {
     struct inode *inode;
     struct file *res;
 
     if (IS_ERR(mnt))
         return ERR_CAST(mnt);
 
     if (size < 0 || size > MAX_LFS_FILESIZE)
         return ERR_PTR(-EINVAL);
 
     if (shmem_acct_size(flags, size))
         return ERR_PTR(-ENOMEM);
 
     inode = shmem_get_inode(mnt->mnt_sb, NULL, S_IFREG | S_IRWXUGO, 0,
                 flags);
     if (unlikely(!inode)) {
         shmem_unacct_size(flags, size);
         return ERR_PTR(-ENOSPC);
     }
     inode->i_flags |= i_flags;
     inode->i_size = size;
     clear_nlink(inode); /* It is unlinked */
     res = ERR_PTR(ramfs_nommu_expand_for_mapping(inode, size));
     if (!IS_ERR(res))
         res = alloc_file_pseudo(inode, mnt, name, O_RDWR,
                 &shmem_file_operations);
     if (IS_ERR(res))
         iput(inode);
     return res;
 }
 
 /**
  * shmem_kernel_file_setup - get an unlinked file living in tmpfs which must be
  *  kernel internal.  There will be NO LSM permission checks against the
  *  underlying inode.  So users of this interface must do LSM checks at a
  *  higher layer.  The users are the big_key and shm implementations.  LSM
  *  checks are provided at the key or shm level rather than the inode.
  * @name: name for dentry (to be seen in /proc/<pid>/maps
  * @size: size to be set for the file
  * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
  */
 struct file *shmem_kernel_file_setup(const char *name, loff_t size, unsigned long flags)
 {
     return __shmem_file_setup(shm_mnt, name, size, flags, S_PRIVATE);
 }
 
 /**
  * shmem_file_setup - get an unlinked file living in tmpfs
  * @name: name for dentry (to be seen in /proc/<pid>/maps
  * @size: size to be set for the file
  * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
  */
 struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags)
 {
     return __shmem_file_setup(shm_mnt, name, size, flags, 0);
 }
 EXPORT_SYMBOL_GPL(shmem_file_setup);
 
 /**
  * shmem_file_setup_with_mnt - get an unlinked file living in tmpfs
  * @mnt: the tmpfs mount where the file will be created
  * @name: name for dentry (to be seen in /proc/<pid>/maps
  * @size: size to be set for the file
  * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
  */
 struct file *shmem_file_setup_with_mnt(struct vfsmount *mnt, const char *name,
                        loff_t size, unsigned long flags)
 {
     return __shmem_file_setup(mnt, name, size, flags, 0);
 }
 EXPORT_SYMBOL_GPL(shmem_file_setup_with_mnt);
 
 /**
  * shmem_zero_setup - setup a shared anonymous mapping
  * @vma: the vma to be mmapped is prepared by do_mmap
  */
 int shmem_zero_setup(struct vm_area_struct *vma)
 {
     struct file *file;
     loff_t size = vma->vm_end - vma->vm_start;
 
     /*
      * Cloning a new file under mmap_lock leads to a lock ordering conflict
      * between XFS directory reading and selinux: since this file is only
      * accessible to the user through its mapping, use S_PRIVATE flag to
      * bypass file security, in the same way as shmem_kernel_file_setup().
      */
     file = shmem_kernel_file_setup("dev/zero", size, vma->vm_flags);
     if (IS_ERR(file))
         return PTR_ERR(file);
 
     if (vma->vm_file)
         fput(vma->vm_file);
     vma->vm_file = file;
     vma->vm_ops = &shmem_vm_ops;
 
     return 0;
 }
 
 /**
  * shmem_read_mapping_page_gfp - read into page cache, using specified page allocation flags.
  * @mapping:    the page's address_space
  * @index:  the page index
  * @gfp:    the page allocator flags to use if allocating
  *
  * This behaves as a tmpfs "read_cache_page_gfp(mapping, index, gfp)",
  * with any new page allocations done using the specified allocation flags.
  * But read_cache_page_gfp() uses the ->read_folio() method: which does not
  * suit tmpfs, since it may have pages in swapcache, and needs to find those
  * for itself; although drivers/gpu/drm i915 and ttm rely upon this support.
  *
  * i915_gem_object_get_pages_gtt() mixes __GFP_NORETRY | __GFP_NOWARN in
  * with the mapping_gfp_mask(), to avoid OOMing the machine unnecessarily.
  */
 struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
                      pgoff_t index, gfp_t gfp)
 {
 #ifdef CONFIG_SHMEM
     struct inode *inode = mapping->host;
     struct page *page;
     int error;
 
     BUG_ON(!shmem_mapping(mapping));
     error = shmem_getpage_gfp(inode, index, &page, SGP_CACHE,
                   gfp, NULL, NULL, NULL);
     if (error)
         return ERR_PTR(error);
 
     unlock_page(page);
     if (PageHWPoison(page)) {
         put_page(page);
         return ERR_PTR(-EIO);
     }
 
     return page;
 #else
     /*
      * The tiny !SHMEM case uses ramfs without swap
      */
     return read_cache_page_gfp(mapping, index, gfp);
 #endif
 }
 EXPORT_SYMBOL_GPL(shmem_read_mapping_page_gfp);