Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 4949 insertions, 0 deletions

diff --git a/mm/shmem.c b/mm/shmem.c
new file mode 100644
index 0000000000..e826be732b
--- /dev/null
+++ b/mm/shmem.c
@@ -0,0 +1,4949 @@
+/*
+ * 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/shmem_fs.h>
+#include <linux/swap.h>
+#include <linux/uio.h>
+#include <linux/hugetlb.h>
+#include <linux/fs_parser.h>
+#include <linux/swapfile.h>
+#include <linux/iversion.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/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/rmap.h>
+#include <linux/uuid.h>
+#include <linux/quotaops.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
+
+/* Pretend that one inode + its dentry occupy this much memory */
+#define BOGO_INODE_SIZE 1024
+
+/* 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;
+	bool noswap;
+	unsigned short quota_types;
+	struct shmem_quota_limits qlimits;
+#define SHMEM_SEEN_BLOCKS 1
+#define SHMEM_SEEN_INODES 2
+#define SHMEM_SEEN_HUGE 4
+#define SHMEM_SEEN_INUMS 8
+#define SHMEM_SEEN_NOSWAP 16
+#define SHMEM_SEEN_QUOTA 32
+};
+
+#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 min3(nr_pages - totalhigh_pages(), nr_pages / 2,
+			ULONG_MAX / BOGO_INODE_SIZE);
+}
+#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 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_get_folio 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 int 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);
+	int err = -ENOSPC;
+
+	if (shmem_acct_block(info->flags, pages))
+		return err;
+
+	might_sleep();	/* when quotas */
+	if (sbinfo->max_blocks) {
+		if (percpu_counter_compare(&sbinfo->used_blocks,
+					   sbinfo->max_blocks - pages) > 0)
+			goto unacct;
+
+		err = dquot_alloc_block_nodirty(inode, pages);
+		if (err)
+			goto unacct;
+
+		percpu_counter_add(&sbinfo->used_blocks, pages);
+	} else {
+		err = dquot_alloc_block_nodirty(inode, pages);
+		if (err)
+			goto unacct;
+	}
+
+	return 0;
+
+unacct:
+	shmem_unacct_blocks(info->flags, pages);
+	return err;
+}
+
+static 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);
+
+	might_sleep();	/* when quotas */
+	dquot_free_block_nodirty(inode, pages);
+
+	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 const struct vm_operations_struct shmem_anon_vm_ops;
+static struct file_system_type shmem_fs_type;
+
+bool vma_is_anon_shmem(struct vm_area_struct *vma)
+{
+	return vma->vm_ops == &shmem_anon_vm_ops;
+}
+
+bool vma_is_shmem(struct vm_area_struct *vma)
+{
+	return vma_is_anon_shmem(vma) || vma->vm_ops == &shmem_vm_ops;
+}
+
+static LIST_HEAD(shmem_swaplist);
+static DEFINE_MUTEX(shmem_swaplist_mutex);
+
+#ifdef CONFIG_TMPFS_QUOTA
+
+static int shmem_enable_quotas(struct super_block *sb,
+			       unsigned short quota_types)
+{
+	int type, err = 0;
+
+	sb_dqopt(sb)->flags |= DQUOT_QUOTA_SYS_FILE | DQUOT_NOLIST_DIRTY;
+	for (type = 0; type < SHMEM_MAXQUOTAS; type++) {
+		if (!(quota_types & (1 << type)))
+			continue;
+		err = dquot_load_quota_sb(sb, type, QFMT_SHMEM,
+					  DQUOT_USAGE_ENABLED |
+					  DQUOT_LIMITS_ENABLED);
+		if (err)
+			goto out_err;
+	}
+	return 0;
+
+out_err:
+	pr_warn("tmpfs: failed to enable quota tracking (type=%d, err=%d)\n",
+		type, err);
+	for (type--; type >= 0; type--)
+		dquot_quota_off(sb, type);
+	return err;
+}
+
+static void shmem_disable_quotas(struct super_block *sb)
+{
+	int type;
+
+	for (type = 0; type < SHMEM_MAXQUOTAS; type++)
+		dquot_quota_off(sb, type);
+}
+
+static struct dquot **shmem_get_dquots(struct inode *inode)
+{
+	return SHMEM_I(inode)->i_dquot;
+}
+#endif /* CONFIG_TMPFS_QUOTA */
+
+/*
+ * 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_ispace < BOGO_INODE_SIZE) {
+				raw_spin_unlock(&sbinfo->stat_lock);
+				return -ENOSPC;
+			}
+			sbinfo->free_ispace -= BOGO_INODE_SIZE;
+		}
+		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, size_t freed_ispace)
+{
+	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
+	if (sbinfo->max_inodes) {
+		raw_spin_lock(&sbinfo->stat_lock);
+		sbinfo->free_ispace += BOGO_INODE_SIZE + freed_ispace;
+		raw_spin_unlock(&sbinfo->stat_lock);
+	}
+}
+
+/**
+ * shmem_recalc_inode - recalculate the block usage of an inode
+ * @inode: inode to recalc
+ * @alloced: the change in number of pages allocated to inode
+ * @swapped: the change in number of pages swapped from inode
+ *
+ * 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)
+ */
+static void shmem_recalc_inode(struct inode *inode, long alloced, long swapped)
+{
+	struct shmem_inode_info *info = SHMEM_I(inode);
+	long freed;
+
+	spin_lock(&info->lock);
+	info->alloced += alloced;
+	info->swapped += swapped;
+	freed = info->alloced - info->swapped -
+		READ_ONCE(inode->i_mapping->nrpages);
+	/*
+	 * Special case: whereas normally shmem_recalc_inode() is called
+	 * after i_mapping->nrpages has already been adjusted (up or down),
+	 * shmem_writepage() has to raise swapped before nrpages is lowered -
+	 * to stop a racing shmem_recalc_inode() from thinking that a page has
+	 * been freed.  Compensate here, to avoid the need for a followup call.
+	 */
+	if (swapped > 0)
+		freed += swapped;
+	if (freed > 0)
+		info->alloced -= freed;
+	spin_unlock(&info->lock);
+
+	/* The quota case may block */
+	if (freed > 0)
+		shmem_inode_unacct_blocks(inode, freed);
+}
+
+bool shmem_charge(struct inode *inode, long pages)
+{
+	struct address_space *mapping = inode->i_mapping;
+
+	if (shmem_inode_acct_block(inode, pages))
+		return false;
+
+	/* nrpages adjustment first, then shmem_recalc_inode() when balanced */
+	xa_lock_irq(&mapping->i_pages);
+	mapping->nrpages += pages;
+	xa_unlock_irq(&mapping->i_pages);
+
+	shmem_recalc_inode(inode, pages, 0);
+	return true;
+}
+
+void shmem_uncharge(struct inode *inode, long pages)
+{
+	/* pages argument is currently unused: keep it to help debugging */
+	/* nrpages adjustment done by __filemap_remove_folio() or caller */
+
+	shmem_recalc_inode(inode, 0, 0);
+}
+
+/*
+ * 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 inode *inode, pgoff_t index, bool shmem_huge_force,
+		   struct mm_struct *mm, unsigned long vm_flags)
+{
+	loff_t i_size;
+
+	if (!S_ISREG(inode->i_mode))
+		return false;
+	if (mm && ((vm_flags & VM_NOHUGEPAGE) || test_bit(MMF_DISABLE_THP, &mm->flags)))
+		return false;
+	if (shmem_huge == SHMEM_HUGE_DENY)
+		return false;
+	if (shmem_huge_force || 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 (mm && (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 (IS_ERR(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_folio(folio);
+		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 inode *inode, pgoff_t index, bool shmem_huge_force,
+		   struct mm_struct *mm, unsigned long vm_flags)
+{
+	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 @folio.
+ */
+static void shmem_delete_from_page_cache(struct folio *folio, void *radswap)
+{
+	struct address_space *mapping = folio->mapping;
+	long nr = folio_nr_pages(folio);
+	int error;
+
+	xa_lock_irq(&mapping->i_pages);
+	error = shmem_replace_entry(mapping, folio->index, folio, radswap);
+	folio->mapping = NULL;
+	mapping->nrpages -= nr;
+	__lruvec_stat_mod_folio(folio, NR_FILE_PAGES, -nr);
+	__lruvec_stat_mod_folio(folio, NR_SHMEM, -nr);
+	xa_unlock_irq(&mapping->i_pages);
+	folio_put(folio);
+	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;
+	unsigned long max = end - 1;
+
+	rcu_read_lock();
+	xas_for_each(&xas, page, max) {
+		if (xas_retry(&xas, page))
+			continue;
+		if (xa_is_value(page))
+			swapped++;
+		if (xas.xa_index == max)
+			break;
+		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;
+
+	/*
+	 * At first avoid shmem_get_folio(,,,SGP_READ): that fails
+	 * beyond i_size, and reports fallocated folios as holes.
+	 */
+	folio = filemap_get_entry(inode->i_mapping, index);
+	if (!folio)
+		return folio;
+	if (!xa_is_value(folio)) {
+		folio_lock(folio);
+		if (folio->mapping == inode->i_mapping)
+			return folio;
+		/* The folio has been swapped out */
+		folio_unlock(folio);
+		folio_put(folio);
+	}
+	/*
+	 * But read a folio back from swap if any of it is within i_size
+	 * (although in some cases this is just a waste of time).
+	 */
+	folio = NULL;
+	shmem_get_folio(inode, index, &folio, SGP_READ);
+	return folio;
+}
+
+/*
+ * 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];
+
+			if (xa_is_value(folio)) {
+				if (unfalloc)
+					continue;
+				nr_swaps_freed += !shmem_free_swap(mapping,
+							indices[i], folio);
+				continue;
+			}
+
+			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();
+	}
+
+	/*
+	 * When undoing a failed fallocate, we want none of the partial folio
+	 * zeroing and splitting below, but shall want to truncate the whole
+	 * folio when !uptodate indicates that it was added by this fallocate,
+	 * even when [lstart, lend] covers only a part of the folio.
+	 */
+	if (unfalloc)
+		goto whole_folios;
+
+	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_next_index(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);
+	}
+
+whole_folios:
+
+	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];
+
+			if (xa_is_value(folio)) {
+				if (unfalloc)
+					continue;
+				if (shmem_free_swap(mapping, indices[i], folio)) {
+					/* Swap was replaced by page: retry */
+					index = indices[i];
+					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 = indices[i];
+					break;
+				}
+				VM_BUG_ON_FOLIO(folio_test_writeback(folio),
+						folio);
+
+				if (!folio_test_large(folio)) {
+					truncate_inode_folio(mapping, folio);
+				} else if (truncate_inode_partial_folio(folio, lstart, lend)) {
+					/*
+					 * If we split a page, reset the loop so
+					 * that we pick up the new sub pages.
+					 * Otherwise the THP was entirely
+					 * dropped or the target range was
+					 * zeroed, so just continue the loop as
+					 * is.
+					 */
+					if (!folio_test_large(folio)) {
+						folio_unlock(folio);
+						index = start;
+						break;
+					}
+				}
+			}
+			folio_unlock(folio);
+		}
+		folio_batch_remove_exceptionals(&fbatch);
+		folio_batch_release(&fbatch);
+	}
+
+	shmem_recalc_inode(inode, 0, -nr_swaps_freed);
+}
+
+void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
+{
+	shmem_undo_range(inode, lstart, lend, false);
+	inode->i_mtime = inode_set_ctime_current(inode);
+	inode_inc_iversion(inode);
+}
+EXPORT_SYMBOL_GPL(shmem_truncate_range);
+
+static int shmem_getattr(struct mnt_idmap *idmap,
+			 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)
+		shmem_recalc_inode(inode, 0, 0);
+
+	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(idmap, request_mask, inode, stat);
+
+	if (shmem_is_huge(inode, 0, false, NULL, 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 mnt_idmap *idmap,
+			 struct dentry *dentry, struct iattr *attr)
+{
+	struct inode *inode = d_inode(dentry);
+	struct shmem_inode_info *info = SHMEM_I(inode);
+	int error;
+	bool update_mtime = false;
+	bool update_ctime = true;
+
+	error = setattr_prepare(idmap, dentry, attr);
+	if (error)
+		return error;
+
+	if ((info->seals & F_SEAL_EXEC) && (attr->ia_valid & ATTR_MODE)) {
+		if ((inode->i_mode ^ attr->ia_mode) & 0111) {
+			return -EPERM;
+		}
+	}
+
+	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);
+			update_mtime = true;
+		} else {
+			update_ctime = false;
+		}
+		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);
+		}
+	}
+
+	if (is_quota_modification(idmap, inode, attr)) {
+		error = dquot_initialize(inode);
+		if (error)
+			return error;
+	}
+
+	/* Transfer quota accounting */
+	if (i_uid_needs_update(idmap, attr, inode) ||
+	    i_gid_needs_update(idmap, attr, inode)) {
+		error = dquot_transfer(idmap, inode, attr);
+
+		if (error)
+			return error;
+	}
+
+	setattr_copy(idmap, inode, attr);
+	if (attr->ia_valid & ATTR_MODE)
+		error = posix_acl_chmod(idmap, dentry, inode->i_mode);
+	if (!error && update_ctime) {
+		inode_set_ctime_current(inode);
+		if (update_mtime)
+			inode->i_mtime = inode_get_ctime(inode);
+		inode_inc_iversion(inode);
+	}
+	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);
+	size_t freed = 0;
+
+	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, sbinfo->max_inodes ? &freed : NULL);
+	shmem_free_inode(inode->i_sb, freed);
+	WARN_ON(inode->i_blocks);
+	clear_inode(inode);
+#ifdef CONFIG_TMPFS_QUOTA
+	dquot_free_inode(inode);
+	dquot_drop(inode);
+#endif
+}
+
+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 address_space *mapping = folio->mapping;
+	struct inode *inode = mapping->host;
+	struct shmem_inode_info *info = SHMEM_I(inode);
+	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
+	swp_entry_t swap;
+	pgoff_t index;
+
+	/*
+	 * 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 (WARN_ON_ONCE(!wbc->for_reclaim))
+		goto redirty;
+
+	if (WARN_ON_ONCE((info->flags & VM_LOCKED) || sbinfo->noswap))
+		goto redirty;
+
+	if (!total_swap_pages)
+		goto redirty;
+
+	/*
+	 * 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 (folio_test_large(folio)) {
+		/* Ensure the subpages are still dirty */
+		folio_test_set_dirty(folio);
+		if (split_huge_page(page) < 0)
+			goto redirty;
+		folio = page_folio(page);
+		folio_clear_dirty(folio);
+	}
+
+	index = folio->index;
+
+	/*
+	 * 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 folio arriving here is now to initialize it and write it.
+	 *
+	 * That's okay for a folio already fallocated earlier, but if we have
+	 * not yet completed the fallocation, then (a) we want to keep track
+	 * of this folio 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 folio, and let shmem_fallocate() quit when too many.
+	 */
+	if (!folio_test_uptodate(folio)) {
+		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;
+		}
+		folio_zero_range(folio, 0, folio_size(folio));
+		flush_dcache_folio(folio);
+		folio_mark_uptodate(folio);
+	}
+
+	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 folio 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(folio, swap,
+			__GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN,
+			NULL) == 0) {
+		shmem_recalc_inode(inode, 0, 1);
+		swap_shmem_alloc(swap);
+		shmem_delete_from_page_cache(folio, swp_to_radix_entry(swap));
+
+		mutex_unlock(&shmem_swaplist_mutex);
+		BUG_ON(folio_mapped(folio));
+		swap_writepage(&folio->page, wbc);
+		return 0;
+	}
+
+	mutex_unlock(&shmem_swaplist_mutex);
+	put_swap_folio(folio, swap);
+redirty:
+	folio_mark_dirty(folio);
+	if (wbc->for_reclaim)
+		return AOP_WRITEPAGE_ACTIVATE;	/* Return with folio locked */
+	folio_unlock(folio);
+	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 folio *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);
+
+	if (!page)
+		return NULL;
+	return page_folio(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 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;
+
+	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
+		huge = false;
+	nr = huge ? HPAGE_PMD_NR : 1;
+
+	err = shmem_inode_acct_block(inode, nr);
+	if (err)
+		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_get_folio_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_folio(struct folio **foliop, gfp_t gfp,
+				struct shmem_inode_info *info, pgoff_t index)
+{
+	struct folio *old, *new;
+	struct address_space *swap_mapping;
+	swp_entry_t entry;
+	pgoff_t swap_index;
+	int error;
+
+	old = *foliop;
+	entry = old->swap;
+	swap_index = swp_offset(entry);
+	swap_mapping = swap_address_space(entry);
+
+	/*
+	 * 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;
+	VM_BUG_ON_FOLIO(folio_test_large(old), old);
+	new = shmem_alloc_folio(gfp, info, index);
+	if (!new)
+		return -ENOMEM;
+
+	folio_get(new);
+	folio_copy(new, old);
+	flush_dcache_folio(new);
+
+	__folio_set_locked(new);
+	__folio_set_swapbacked(new);
+	folio_mark_uptodate(new);
+	new->swap = entry;
+	folio_set_swapcache(new);
+
+	/*
+	 * 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, old, new);
+	if (!error) {
+		mem_cgroup_migrate(old, new);
+		__lruvec_stat_mod_folio(new, NR_FILE_PAGES, 1);
+		__lruvec_stat_mod_folio(new, NR_SHMEM, 1);
+		__lruvec_stat_mod_folio(old, NR_FILE_PAGES, -1);
+		__lruvec_stat_mod_folio(old, NR_SHMEM, -1);
+	}
+	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.
+		 */
+		old = new;
+	} else {
+		folio_add_lru(new);
+		*foliop = new;
+	}
+
+	folio_clear_swapcache(old);
+	old->private = NULL;
+
+	folio_unlock(old);
+	folio_put_refs(old, 2);
+	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;
+	swp_entry_t swapin_error;
+	void *old;
+
+	swapin_error = make_poisoned_swp_entry();
+	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);
+	/*
+	 * 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(i_blocks)
+	 * in shmem_evict_inode().
+	 */
+	shmem_recalc_inode(inode, -1, -1);
+	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 swap_info_struct *si;
+	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_poisoned_swp_entry(swap))
+		return -EIO;
+
+	si = get_swap_device(swap);
+	if (!si) {
+		if (!shmem_confirm_swap(mapping, index, swap))
+			return -EEXIST;
+		else
+			return -EINVAL;
+	}
+
+	/* Look it up and read it in.. */
+	folio = swap_cache_get_folio(swap, NULL, 0);
+	if (!folio) {
+		/* 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 */
+		folio = shmem_swapin(swap, gfp, info, index);
+		if (!folio) {
+			error = -ENOMEM;
+			goto failed;
+		}
+	}
+
+	/* We have to do this with folio locked to prevent races */
+	folio_lock(folio);
+	if (!folio_test_swapcache(folio) ||
+	    folio->swap.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_folio(&folio, gfp, info, index);
+		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;
+
+	shmem_recalc_inode(inode, 0, -1);
+
+	if (sgp == SGP_WRITE)
+		folio_mark_accessed(folio);
+
+	delete_from_swap_cache(folio);
+	folio_mark_dirty(folio);
+	swap_free(swap);
+	put_swap_device(si);
+
+	*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);
+	}
+	put_swap_device(si);
+
+	return error;
+}
+
+/*
+ * shmem_get_folio_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_get_folio_gfp(struct inode *inode, pgoff_t index,
+		struct folio **foliop, 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;
+	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_entry(mapping, index);
+	if (folio && vma && userfaultfd_minor(vma)) {
+		if (!xa_is_value(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;
+
+		*foliop = folio;
+		return error;
+	}
+
+	if (folio) {
+		folio_lock(folio);
+
+		/* Has the folio been truncated or swapped out? */
+		if (unlikely(folio->mapping != mapping)) {
+			folio_unlock(folio);
+			folio_put(folio);
+			goto repeat;
+		}
+		if (sgp == SGP_WRITE)
+			folio_mark_accessed(folio);
+		if (folio_test_uptodate(folio))
+			goto out;
+		/* fallocated folio */
+		if (sgp != SGP_READ)
+			goto clear;
+		folio_unlock(folio);
+		folio_put(folio);
+	}
+
+	/*
+	 * SGP_READ: succeed on hole, with NULL folio, letting caller zero.
+	 * SGP_NOALLOC: fail on hole, with NULL folio, letting caller fail.
+	 */
+	*foliop = 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(inode, index, false,
+			   vma ? vma->vm_mm : NULL, vma ? vma->vm_flags : 0))
+		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 large folio
+		 * 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);
+	shmem_recalc_inode(inode, folio_nr_pages(folio), 0);
+	alloced = true;
+
+	if (folio_test_pmd_mappable(folio) &&
+	    DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE) <
+					folio_next_index(folio) - 1) {
+		/*
+		 * Part of the large folio 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 folio.
+	 */
+	if (sgp == SGP_FALLOC)
+		sgp = SGP_WRITE;
+clear:
+	/*
+	 * Let SGP_WRITE caller clear ends if write does not fill folio;
+	 * but SGP_FALLOC on a folio 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);
+			shmem_recalc_inode(inode, 0, 0);
+		}
+		error = -EINVAL;
+		goto unlock;
+	}
+out:
+	*foliop = folio;
+	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++) {
+		shmem_recalc_inode(inode, 0, 0);
+		goto repeat;
+	}
+	if (error == -EEXIST)
+		goto repeat;
+	return error;
+}
+
+int shmem_get_folio(struct inode *inode, pgoff_t index, struct folio **foliop,
+		enum sgp_type sgp)
+{
+	return shmem_get_folio_gfp(inode, index, foliop, sgp,
+			mapping_gfp_mask(inode->i_mapping), NULL, NULL, NULL);
+}
+
+/*
+ * 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);
+	struct folio *folio = NULL;
+	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_get_folio_gfp(inode, vmf->pgoff, &folio, SGP_CACHE,
+				  gfp, vma, vmf, &ret);
+	if (err)
+		return vmf_error(err);
+	if (folio)
+		vmf->page = folio_file_page(folio, vmf->pgoff);
+	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 inode *inode = file_inode(file);
+	struct shmem_inode_info *info = SHMEM_I(inode);
+	int ret;
+
+	ret = seal_check_future_write(info->seals, vma);
+	if (ret)
+		return ret;
+
+	/* arm64 - allow memory tagging on RAM-based files */
+	vm_flags_set(vma, VM_MTE_ALLOWED);
+
+	file_accessed(file);
+	/* This is anonymous shared memory if it is unlinked at the time of mmap */
+	if (inode->i_nlink)
+		vma->vm_ops = &shmem_vm_ops;
+	else
+		vma->vm_ops = &shmem_anon_vm_ops;
+	return 0;
+}
+
+static int shmem_file_open(struct inode *inode, struct file *file)
+{
+	file->f_mode |= FMODE_CAN_ODIRECT;
+	return generic_file_open(inode, file);
+}
+
+#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 offset_ctx *shmem_get_offset_ctx(struct inode *inode)
+{
+	return &SHMEM_I(inode)->dir_offsets;
+}
+
+static struct inode *__shmem_get_inode(struct mnt_idmap *idmap,
+					     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;
+	int err;
+
+	err = shmem_reserve_inode(sb, &ino);
+	if (err)
+		return ERR_PTR(err);
+
+
+	inode = new_inode(sb);
+	if (!inode) {
+		shmem_free_inode(sb, 0);
+		return ERR_PTR(-ENOSPC);
+	}
+
+	inode->i_ino = ino;
+	inode_init_owner(idmap, inode, dir, mode);
+	inode->i_blocks = 0;
+	inode->i_atime = inode->i_mtime = inode_set_ctime_current(inode);
+	inode->i_generation = get_random_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);
+	INIT_LIST_HEAD(&info->swaplist);
+	if (sbinfo->noswap)
+		mapping_set_unevictable(inode->i_mapping);
+	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_offset_dir_operations;
+		simple_offset_init(shmem_get_offset_ctx(inode));
+		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);
+	return inode;
+}
+
+#ifdef CONFIG_TMPFS_QUOTA
+static struct inode *shmem_get_inode(struct mnt_idmap *idmap,
+				     struct super_block *sb, struct inode *dir,
+				     umode_t mode, dev_t dev, unsigned long flags)
+{
+	int err;
+	struct inode *inode;
+
+	inode = __shmem_get_inode(idmap, sb, dir, mode, dev, flags);
+	if (IS_ERR(inode))
+		return inode;
+
+	err = dquot_initialize(inode);
+	if (err)
+		goto errout;
+
+	err = dquot_alloc_inode(inode);
+	if (err) {
+		dquot_drop(inode);
+		goto errout;
+	}
+	return inode;
+
+errout:
+	inode->i_flags |= S_NOQUOTA;
+	iput(inode);
+	return ERR_PTR(err);
+}
+#else
+static inline struct inode *shmem_get_inode(struct mnt_idmap *idmap,
+				     struct super_block *sb, struct inode *dir,
+				     umode_t mode, dev_t dev, unsigned long flags)
+{
+	return __shmem_get_inode(idmap, sb, dir, mode, dev, flags);
+}
+#endif /* CONFIG_TMPFS_QUOTA */
+
+#ifdef CONFIG_USERFAULTFD
+int shmem_mfill_atomic_pte(pmd_t *dst_pmd,
+			   struct vm_area_struct *dst_vma,
+			   unsigned long dst_addr,
+			   unsigned long src_addr,
+			   uffd_flags_t flags,
+			   struct folio **foliop)
+{
+	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;
+	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(*foliop)) {
+			folio_put(*foliop);
+			*foliop = NULL;
+		}
+		return -ENOMEM;
+	}
+
+	if (!*foliop) {
+		ret = -ENOMEM;
+		folio = shmem_alloc_folio(gfp, info, pgoff);
+		if (!folio)
+			goto out_unacct_blocks;
+
+		if (uffd_flags_mode_is(flags, MFILL_ATOMIC_COPY)) {
+			page_kaddr = kmap_local_folio(folio, 0);
+			/*
+			 * The read mmap_lock is held here.  Despite the
+			 * mmap_lock being read recursive a deadlock is still
+			 * possible if a writer has taken a lock.  For example:
+			 *
+			 * process A thread 1 takes read lock on own mmap_lock
+			 * process A thread 2 calls mmap, blocks taking write lock
+			 * process B thread 1 takes page fault, read lock on own mmap lock
+			 * process B thread 2 calls mmap, blocks taking write lock
+			 * process A thread 1 blocks taking read lock on process B
+			 * process B thread 1 blocks taking read lock on process A
+			 *
+			 * Disable page faults to prevent potential deadlock
+			 * and retry the copy outside the mmap_lock.
+			 */
+			pagefault_disable();
+			ret = copy_from_user(page_kaddr,
+					     (const void __user *)src_addr,
+					     PAGE_SIZE);
+			pagefault_enable();
+			kunmap_local(page_kaddr);
+
+			/* fallback to copy_from_user outside mmap_lock */
+			if (unlikely(ret)) {
+				*foliop = folio;
+				ret = -ENOENT;
+				/* don't free the page */
+				goto out_unacct_blocks;
+			}
+
+			flush_dcache_folio(folio);
+		} else {		/* ZEROPAGE */
+			clear_user_highpage(&folio->page, dst_addr);
+		}
+	} else {
+		folio = *foliop;
+		VM_BUG_ON_FOLIO(folio_test_large(folio), folio);
+		*foliop = NULL;
+	}
+
+	VM_BUG_ON(folio_test_locked(folio));
+	VM_BUG_ON(folio_test_swapbacked(folio));
+	__folio_set_locked(folio);
+	__folio_set_swapbacked(folio);
+	__folio_mark_uptodate(folio);
+
+	ret = -EFAULT;
+	max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
+	if (unlikely(pgoff >= max_off))
+		goto out_release;
+
+	ret = shmem_add_to_page_cache(folio, mapping, pgoff, NULL,
+				      gfp & GFP_RECLAIM_MASK, dst_vma->vm_mm);
+	if (ret)
+		goto out_release;
+
+	ret = mfill_atomic_install_pte(dst_pmd, dst_vma, dst_addr,
+				       &folio->page, true, flags);
+	if (ret)
+		goto out_delete_from_cache;
+
+	shmem_recalc_inode(inode, 1, 0);
+	folio_unlock(folio);
+	return 0;
+out_delete_from_cache:
+	filemap_remove_folio(folio);
+out_release:
+	folio_unlock(folio);
+	folio_put(folio);
+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;
+	struct folio *folio;
+	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_get_folio(inode, index, &folio, SGP_WRITE);
+
+	if (ret)
+		return ret;
+
+	*pagep = folio_file_page(folio, index);
+	if (PageHWPoison(*pagep)) {
+		folio_unlock(folio);
+		folio_put(folio);
+		*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 folio *folio = page_folio(page);
+	struct inode *inode = mapping->host;
+
+	if (pos + copied > inode->i_size)
+		i_size_write(inode, pos + copied);
+
+	if (!folio_test_uptodate(folio)) {
+		if (copied < folio_size(folio)) {
+			size_t from = offset_in_folio(folio, pos);
+			folio_zero_segments(folio, 0, from,
+					from + copied, folio_size(folio));
+		}
+		folio_mark_uptodate(folio);
+	}
+	folio_mark_dirty(folio);
+	folio_unlock(folio);
+	folio_put(folio);
+
+	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 folio *folio = NULL;
+		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_get_folio(inode, index, &folio, SGP_READ);
+		if (error) {
+			if (error == -EINVAL)
+				error = 0;
+			break;
+		}
+		if (folio) {
+			folio_unlock(folio);
+
+			page = folio_file_page(folio, index);
+			if (PageHWPoison(page)) {
+				folio_put(folio);
+				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 (folio)
+					folio_put(folio);
+				break;
+			}
+		}
+		nr -= offset;
+
+		if (folio) {
+			/*
+			 * 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)
+				folio_mark_accessed(folio);
+			/*
+			 * 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);
+			folio_put(folio);
+
+		} 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 ssize_t shmem_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+	struct file *file = iocb->ki_filp;
+	struct inode *inode = file->f_mapping->host;
+	ssize_t ret;
+
+	inode_lock(inode);
+	ret = generic_write_checks(iocb, from);
+	if (ret <= 0)
+		goto unlock;
+	ret = file_remove_privs(file);
+	if (ret)
+		goto unlock;
+	ret = file_update_time(file);
+	if (ret)
+		goto unlock;
+	ret = generic_perform_write(iocb, from);
+unlock:
+	inode_unlock(inode);
+	return ret;
+}
+
+static bool zero_pipe_buf_get(struct pipe_inode_info *pipe,
+			      struct pipe_buffer *buf)
+{
+	return true;
+}
+
+static void zero_pipe_buf_release(struct pipe_inode_info *pipe,
+				  struct pipe_buffer *buf)
+{
+}
+
+static bool zero_pipe_buf_try_steal(struct pipe_inode_info *pipe,
+				    struct pipe_buffer *buf)
+{
+	return false;
+}
+
+static const struct pipe_buf_operations zero_pipe_buf_ops = {
+	.release	= zero_pipe_buf_release,
+	.try_steal	= zero_pipe_buf_try_steal,
+	.get		= zero_pipe_buf_get,
+};
+
+static size_t splice_zeropage_into_pipe(struct pipe_inode_info *pipe,
+					loff_t fpos, size_t size)
+{
+	size_t offset = fpos & ~PAGE_MASK;
+
+	size = min_t(size_t, size, PAGE_SIZE - offset);
+
+	if (!pipe_full(pipe->head, pipe->tail, pipe->max_usage)) {
+		struct pipe_buffer *buf = pipe_head_buf(pipe);
+
+		*buf = (struct pipe_buffer) {
+			.ops	= &zero_pipe_buf_ops,
+			.page	= ZERO_PAGE(0),
+			.offset	= offset,
+			.len	= size,
+		};
+		pipe->head++;
+	}
+
+	return size;
+}
+
+static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos,
+				      struct pipe_inode_info *pipe,
+				      size_t len, unsigned int flags)
+{
+	struct inode *inode = file_inode(in);
+	struct address_space *mapping = inode->i_mapping;
+	struct folio *folio = NULL;
+	size_t total_spliced = 0, used, npages, n, part;
+	loff_t isize;
+	int error = 0;
+
+	/* Work out how much data we can actually add into the pipe */
+	used = pipe_occupancy(pipe->head, pipe->tail);
+	npages = max_t(ssize_t, pipe->max_usage - used, 0);
+	len = min_t(size_t, len, npages * PAGE_SIZE);
+
+	do {
+		if (*ppos >= i_size_read(inode))
+			break;
+
+		error = shmem_get_folio(inode, *ppos / PAGE_SIZE, &folio,
+					SGP_READ);
+		if (error) {
+			if (error == -EINVAL)
+				error = 0;
+			break;
+		}
+		if (folio) {
+			folio_unlock(folio);
+
+			if (folio_test_hwpoison(folio) ||
+			    (folio_test_large(folio) &&
+			     folio_test_has_hwpoisoned(folio))) {
+				error = -EIO;
+				break;
+			}
+		}
+
+		/*
+		 * i_size must be checked after we know the pages are Uptodate.
+		 *
+		 * Checking i_size after the check allows us to calculate
+		 * the correct value for "nr", which means the zero-filled
+		 * part of the page is not copied back to userspace (unless
+		 * another truncate extends the file - this is desired though).
+		 */
+		isize = i_size_read(inode);
+		if (unlikely(*ppos >= isize))
+			break;
+		part = min_t(loff_t, isize - *ppos, len);
+
+		if (folio) {
+			/*
+			 * 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_folio(folio);
+			folio_mark_accessed(folio);
+			/*
+			 * Ok, we have the page, and it's up-to-date, so we can
+			 * now splice it into the pipe.
+			 */
+			n = splice_folio_into_pipe(pipe, folio, *ppos, part);
+			folio_put(folio);
+			folio = NULL;
+		} else {
+			n = splice_zeropage_into_pipe(pipe, *ppos, part);
+		}
+
+		if (!n)
+			break;
+		len -= n;
+		total_spliced += n;
+		*ppos += n;
+		in->f_ra.prev_pos = *ppos;
+		if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
+			break;
+
+		cond_resched();
+	} while (len);
+
+	if (folio)
+		folio_put(folio);
+
+	file_accessed(in);
+	return total_spliced ? total_spliced : 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 folio *folio;
+
+		/*
+		 * 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_get_folio(inode, index, &folio,
+						SGP_FALLOC);
+		if (error) {
+			info->fallocend = undo_fallocend;
+			/* Remove the !uptodate folios we added */
+			if (index > start) {
+				shmem_undo_range(inode,
+				    (loff_t)start << PAGE_SHIFT,
+				    ((loff_t)index << PAGE_SHIFT) - 1, true);
+			}
+			goto undone;
+		}
+
+		/*
+		 * Here is a more important optimization than it appears:
+		 * a second SGP_FALLOC on the same large folio will clear it,
+		 * making it uptodate and un-undoable if we fail later.
+		 */
+		index = folio_next_index(folio);
+		/* 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 (!folio_test_uptodate(folio))
+			shmem_falloc.nr_falloced += index - shmem_falloc.next;
+		shmem_falloc.next = index;
+
+		/*
+		 * If !uptodate, leave it that way so that freeable folios
+		 * can be recognized if we need to rollback on error later.
+		 * But mark it dirty so that memory pressure will swap rather
+		 * than free the folios we are allocating (and SGP_CACHE folios
+		 * might still be clean: we now need to mark those dirty too).
+		 */
+		folio_mark_dirty(folio);
+		folio_unlock(folio);
+		folio_put(folio);
+		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_ispace / BOGO_INODE_SIZE;
+	}
+	/* 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 mnt_idmap *idmap, struct inode *dir,
+	    struct dentry *dentry, umode_t mode, dev_t dev)
+{
+	struct inode *inode;
+	int error;
+
+	inode = shmem_get_inode(idmap, dir->i_sb, dir, mode, dev, VM_NORESERVE);
+	if (IS_ERR(inode))
+		return PTR_ERR(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 = simple_offset_add(shmem_get_offset_ctx(dir), dentry);
+	if (error)
+		goto out_iput;
+
+	dir->i_size += BOGO_DIRENT_SIZE;
+	dir->i_mtime = inode_set_ctime_current(dir);
+	inode_inc_iversion(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 mnt_idmap *idmap, struct inode *dir,
+	      struct file *file, umode_t mode)
+{
+	struct inode *inode;
+	int error;
+
+	inode = shmem_get_inode(idmap, dir->i_sb, dir, mode, 0, VM_NORESERVE);
+
+	if (IS_ERR(inode)) {
+		error = PTR_ERR(inode);
+		goto err_out;
+	}
+
+	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(file, inode);
+
+err_out:
+	return finish_open_simple(file, error);
+out_iput:
+	iput(inode);
+	return error;
+}
+
+static int shmem_mkdir(struct mnt_idmap *idmap, struct inode *dir,
+		       struct dentry *dentry, umode_t mode)
+{
+	int error;
+
+	error = shmem_mknod(idmap, dir, dentry, mode | S_IFDIR, 0);
+	if (error)
+		return error;
+	inc_nlink(dir);
+	return 0;
+}
+
+static int shmem_create(struct mnt_idmap *idmap, struct inode *dir,
+			struct dentry *dentry, umode_t mode, bool excl)
+{
+	return shmem_mknod(idmap, 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;
+	}
+
+	ret = simple_offset_add(shmem_get_offset_ctx(dir), dentry);
+	if (ret) {
+		if (inode->i_nlink)
+			shmem_free_inode(inode->i_sb, 0);
+		goto out;
+	}
+
+	dir->i_size += BOGO_DIRENT_SIZE;
+	dir->i_mtime = inode_set_ctime_to_ts(dir,
+					     inode_set_ctime_current(inode));
+	inode_inc_iversion(dir);
+	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, 0);
+
+	simple_offset_remove(shmem_get_offset_ctx(dir), dentry);
+
+	dir->i_size -= BOGO_DIRENT_SIZE;
+	dir->i_mtime = inode_set_ctime_to_ts(dir,
+					     inode_set_ctime_current(inode));
+	inode_inc_iversion(dir);
+	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 mnt_idmap *idmap,
+			  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(idmap, 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 mnt_idmap *idmap,
+			 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);
+	int error;
+
+	if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
+		return -EINVAL;
+
+	if (flags & RENAME_EXCHANGE)
+		return simple_offset_rename_exchange(old_dir, old_dentry,
+						     new_dir, new_dentry);
+
+	if (!simple_empty(new_dentry))
+		return -ENOTEMPTY;
+
+	if (flags & RENAME_WHITEOUT) {
+		error = shmem_whiteout(idmap, old_dir, old_dentry);
+		if (error)
+			return error;
+	}
+
+	simple_offset_remove(shmem_get_offset_ctx(old_dir), old_dentry);
+	error = simple_offset_add(shmem_get_offset_ctx(new_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;
+	simple_rename_timestamp(old_dir, old_dentry, new_dir, new_dentry);
+	inode_inc_iversion(old_dir);
+	inode_inc_iversion(new_dir);
+	return 0;
+}
+
+static int shmem_symlink(struct mnt_idmap *idmap, struct inode *dir,
+			 struct dentry *dentry, const char *symname)
+{
+	int error;
+	int len;
+	struct inode *inode;
+	struct folio *folio;
+
+	len = strlen(symname) + 1;
+	if (len > PAGE_SIZE)
+		return -ENAMETOOLONG;
+
+	inode = shmem_get_inode(idmap, dir->i_sb, dir, S_IFLNK | 0777, 0,
+				VM_NORESERVE);
+
+	if (IS_ERR(inode))
+		return PTR_ERR(inode);
+
+	error = security_inode_init_security(inode, dir, &dentry->d_name,
+					     shmem_initxattrs, NULL);
+	if (error && error != -EOPNOTSUPP)
+		goto out_iput;
+
+	error = simple_offset_add(shmem_get_offset_ctx(dir), dentry);
+	if (error)
+		goto out_iput;
+
+	inode->i_size = len-1;
+	if (len <= SHORT_SYMLINK_LEN) {
+		inode->i_link = kmemdup(symname, len, GFP_KERNEL);
+		if (!inode->i_link) {
+			error = -ENOMEM;
+			goto out_remove_offset;
+		}
+		inode->i_op = &shmem_short_symlink_operations;
+	} else {
+		inode_nohighmem(inode);
+		error = shmem_get_folio(inode, 0, &folio, SGP_WRITE);
+		if (error)
+			goto out_remove_offset;
+		inode->i_mapping->a_ops = &shmem_aops;
+		inode->i_op = &shmem_symlink_inode_operations;
+		memcpy(folio_address(folio), symname, len);
+		folio_mark_uptodate(folio);
+		folio_mark_dirty(folio);
+		folio_unlock(folio);
+		folio_put(folio);
+	}
+	dir->i_size += BOGO_DIRENT_SIZE;
+	dir->i_mtime = inode_set_ctime_current(dir);
+	inode_inc_iversion(dir);
+	d_instantiate(dentry, inode);
+	dget(dentry);
+	return 0;
+
+out_remove_offset:
+	simple_offset_remove(shmem_get_offset_ctx(dir), dentry);
+out_iput:
+	iput(inode);
+	return error;
+}
+
+static void shmem_put_link(void *arg)
+{
+	folio_mark_accessed(arg);
+	folio_put(arg);
+}
+
+static const char *shmem_get_link(struct dentry *dentry,
+				  struct inode *inode,
+				  struct delayed_call *done)
+{
+	struct folio *folio = NULL;
+	int error;
+
+	if (!dentry) {
+		folio = filemap_get_folio(inode->i_mapping, 0);
+		if (IS_ERR(folio))
+			return ERR_PTR(-ECHILD);
+		if (PageHWPoison(folio_page(folio, 0)) ||
+		    !folio_test_uptodate(folio)) {
+			folio_put(folio);
+			return ERR_PTR(-ECHILD);
+		}
+	} else {
+		error = shmem_get_folio(inode, 0, &folio, SGP_READ);
+		if (error)
+			return ERR_PTR(error);
+		if (!folio)
+			return ERR_PTR(-ECHILD);
+		if (PageHWPoison(folio_page(folio, 0))) {
+			folio_unlock(folio);
+			folio_put(folio);
+			return ERR_PTR(-ECHILD);
+		}
+		folio_unlock(folio);
+	}
+	set_delayed_call(done, shmem_put_link, folio);
+	return folio_address(folio);
+}
+
+#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 mnt_idmap *idmap,
+			      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_set_ctime_current(inode);
+	inode_inc_iversion(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);
+	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
+	const struct xattr *xattr;
+	struct simple_xattr *new_xattr;
+	size_t ispace = 0;
+	size_t len;
+
+	if (sbinfo->max_inodes) {
+		for (xattr = xattr_array; xattr->name != NULL; xattr++) {
+			ispace += simple_xattr_space(xattr->name,
+				xattr->value_len + XATTR_SECURITY_PREFIX_LEN);
+		}
+		if (ispace) {
+			raw_spin_lock(&sbinfo->stat_lock);
+			if (sbinfo->free_ispace < ispace)
+				ispace = 0;
+			else
+				sbinfo->free_ispace -= ispace;
+			raw_spin_unlock(&sbinfo->stat_lock);
+			if (!ispace)
+				return -ENOSPC;
+		}
+	}
+
+	for (xattr = xattr_array; xattr->name != NULL; xattr++) {
+		new_xattr = simple_xattr_alloc(xattr->value, xattr->value_len);
+		if (!new_xattr)
+			break;
+
+		len = strlen(xattr->name) + 1;
+		new_xattr->name = kmalloc(XATTR_SECURITY_PREFIX_LEN + len,
+					  GFP_KERNEL_ACCOUNT);
+		if (!new_xattr->name) {
+			kvfree(new_xattr);
+			break;
+		}
+
+		memcpy(new_xattr->name, XATTR_SECURITY_PREFIX,
+		       XATTR_SECURITY_PREFIX_LEN);
+		memcpy(new_xattr->name + XATTR_SECURITY_PREFIX_LEN,
+		       xattr->name, len);
+
+		simple_xattr_add(&info->xattrs, new_xattr);
+	}
+
+	if (xattr->name != NULL) {
+		if (ispace) {
+			raw_spin_lock(&sbinfo->stat_lock);
+			sbinfo->free_ispace += ispace;
+			raw_spin_unlock(&sbinfo->stat_lock);
+		}
+		simple_xattrs_free(&info->xattrs, NULL);
+		return -ENOMEM;
+	}
+
+	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 mnt_idmap *idmap,
+				   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);
+	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
+	struct simple_xattr *old_xattr;
+	size_t ispace = 0;
+
+	name = xattr_full_name(handler, name);
+	if (value && sbinfo->max_inodes) {
+		ispace = simple_xattr_space(name, size);
+		raw_spin_lock(&sbinfo->stat_lock);
+		if (sbinfo->free_ispace < ispace)
+			ispace = 0;
+		else
+			sbinfo->free_ispace -= ispace;
+		raw_spin_unlock(&sbinfo->stat_lock);
+		if (!ispace)
+			return -ENOSPC;
+	}
+
+	old_xattr = simple_xattr_set(&info->xattrs, name, value, size, flags);
+	if (!IS_ERR(old_xattr)) {
+		ispace = 0;
+		if (old_xattr && sbinfo->max_inodes)
+			ispace = simple_xattr_space(old_xattr->name,
+						    old_xattr->size);
+		simple_xattr_free(old_xattr);
+		old_xattr = NULL;
+		inode_set_ctime_current(inode);
+		inode_inc_iversion(inode);
+	}
+	if (ispace) {
+		raw_spin_lock(&sbinfo->stat_lock);
+		sbinfo->free_ispace += ispace;
+		raw_spin_unlock(&sbinfo->stat_lock);
+	}
+	return PTR_ERR(old_xattr);
+}
+
+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_user_xattr_handler = {
+	.prefix = XATTR_USER_PREFIX,
+	.get = shmem_xattr_handler_get,
+	.set = shmem_xattr_handler_set,
+};
+
+static const struct xattr_handler *shmem_xattr_handlers[] = {
+	&shmem_security_xattr_handler,
+	&shmem_trusted_xattr_handler,
+	&shmem_user_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,
+	.setattr	= shmem_setattr,
+	.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,
+	.setattr	= shmem_setattr,
+	.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,
+	Opt_noswap,
+	Opt_quota,
+	Opt_usrquota,
+	Opt_grpquota,
+	Opt_usrquota_block_hardlimit,
+	Opt_usrquota_inode_hardlimit,
+	Opt_grpquota_block_hardlimit,
+	Opt_grpquota_inode_hardlimit,
+};
+
+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),
+	fsparam_flag  ("noswap",	Opt_noswap),
+#ifdef CONFIG_TMPFS_QUOTA
+	fsparam_flag  ("quota",		Opt_quota),
+	fsparam_flag  ("usrquota",	Opt_usrquota),
+	fsparam_flag  ("grpquota",	Opt_grpquota),
+	fsparam_string("usrquota_block_hardlimit", Opt_usrquota_block_hardlimit),
+	fsparam_string("usrquota_inode_hardlimit", Opt_usrquota_inode_hardlimit),
+	fsparam_string("grpquota_block_hardlimit", Opt_grpquota_block_hardlimit),
+	fsparam_string("grpquota_inode_hardlimit", Opt_grpquota_inode_hardlimit),
+#endif
+	{}
+};
+
+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;
+	kuid_t kuid;
+	kgid_t kgid;
+
+	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 > LONG_MAX)
+			goto bad_value;
+		ctx->seen |= SHMEM_SEEN_BLOCKS;
+		break;
+	case Opt_nr_inodes:
+		ctx->inodes = memparse(param->string, &rest);
+		if (*rest || ctx->inodes > ULONG_MAX / BOGO_INODE_SIZE)
+			goto bad_value;
+		ctx->seen |= SHMEM_SEEN_INODES;
+		break;
+	case Opt_mode:
+		ctx->mode = result.uint_32 & 07777;
+		break;
+	case Opt_uid:
+		kuid = make_kuid(current_user_ns(), result.uint_32);
+		if (!uid_valid(kuid))
+			goto bad_value;
+
+		/*
+		 * The requested uid must be representable in the
+		 * filesystem's idmapping.
+		 */
+		if (!kuid_has_mapping(fc->user_ns, kuid))
+			goto bad_value;
+
+		ctx->uid = kuid;
+		break;
+	case Opt_gid:
+		kgid = make_kgid(current_user_ns(), result.uint_32);
+		if (!gid_valid(kgid))
+			goto bad_value;
+
+		/*
+		 * The requested gid must be representable in the
+		 * filesystem's idmapping.
+		 */
+		if (!kgid_has_mapping(fc->user_ns, kgid))
+			goto bad_value;
+
+		ctx->gid = kgid;
+		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;
+	case Opt_noswap:
+		if ((fc->user_ns != &init_user_ns) || !capable(CAP_SYS_ADMIN)) {
+			return invalfc(fc,
+				       "Turning off swap in unprivileged tmpfs mounts unsupported");
+		}
+		ctx->noswap = true;
+		ctx->seen |= SHMEM_SEEN_NOSWAP;
+		break;
+	case Opt_quota:
+		if (fc->user_ns != &init_user_ns)
+			return invalfc(fc, "Quotas in unprivileged tmpfs mounts are unsupported");
+		ctx->seen |= SHMEM_SEEN_QUOTA;
+		ctx->quota_types |= (QTYPE_MASK_USR | QTYPE_MASK_GRP);
+		break;
+	case Opt_usrquota:
+		if (fc->user_ns != &init_user_ns)
+			return invalfc(fc, "Quotas in unprivileged tmpfs mounts are unsupported");
+		ctx->seen |= SHMEM_SEEN_QUOTA;
+		ctx->quota_types |= QTYPE_MASK_USR;
+		break;
+	case Opt_grpquota:
+		if (fc->user_ns != &init_user_ns)
+			return invalfc(fc, "Quotas in unprivileged tmpfs mounts are unsupported");
+		ctx->seen |= SHMEM_SEEN_QUOTA;
+		ctx->quota_types |= QTYPE_MASK_GRP;
+		break;
+	case Opt_usrquota_block_hardlimit:
+		size = memparse(param->string, &rest);
+		if (*rest || !size)
+			goto bad_value;
+		if (size > SHMEM_QUOTA_MAX_SPC_LIMIT)
+			return invalfc(fc,
+				       "User quota block hardlimit too large.");
+		ctx->qlimits.usrquota_bhardlimit = size;
+		break;
+	case Opt_grpquota_block_hardlimit:
+		size = memparse(param->string, &rest);
+		if (*rest || !size)
+			goto bad_value;
+		if (size > SHMEM_QUOTA_MAX_SPC_LIMIT)
+			return invalfc(fc,
+				       "Group quota block hardlimit too large.");
+		ctx->qlimits.grpquota_bhardlimit = size;
+		break;
+	case Opt_usrquota_inode_hardlimit:
+		size = memparse(param->string, &rest);
+		if (*rest || !size)
+			goto bad_value;
+		if (size > SHMEM_QUOTA_MAX_INO_LIMIT)
+			return invalfc(fc,
+				       "User quota inode hardlimit too large.");
+		ctx->qlimits.usrquota_ihardlimit = size;
+		break;
+	case Opt_grpquota_inode_hardlimit:
+		size = memparse(param->string, &rest);
+		if (*rest || !size)
+			goto bad_value;
+		if (size > SHMEM_QUOTA_MAX_INO_LIMIT)
+			return invalfc(fc,
+				       "Group quota inode hardlimit too large.");
+		ctx->qlimits.grpquota_ihardlimit = size;
+		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.
+ */
+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 used_isp;
+	struct mempolicy *mpol = NULL;
+	const char *err;
+
+	raw_spin_lock(&sbinfo->stat_lock);
+	used_isp = sbinfo->max_inodes * BOGO_INODE_SIZE - sbinfo->free_ispace;
+
+	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 * BOGO_INODE_SIZE < used_isp) {
+			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_NOSWAP) && ctx->noswap && !sbinfo->noswap) {
+		err = "Cannot disable swap on remount";
+		goto out;
+	}
+	if (!(ctx->seen & SHMEM_SEEN_NOSWAP) && !ctx->noswap && sbinfo->noswap) {
+		err = "Cannot enable swap on remount if it was disabled on first mount";
+		goto out;
+	}
+
+	if (ctx->seen & SHMEM_SEEN_QUOTA &&
+	    !sb_any_quota_loaded(fc->root->d_sb)) {
+		err = "Cannot enable quota on remount";
+		goto out;
+	}
+
+#ifdef CONFIG_TMPFS_QUOTA
+#define CHANGED_LIMIT(name)						\
+	(ctx->qlimits.name## hardlimit &&				\
+	(ctx->qlimits.name## hardlimit != sbinfo->qlimits.name## hardlimit))
+
+	if (CHANGED_LIMIT(usrquota_b) || CHANGED_LIMIT(usrquota_i) ||
+	    CHANGED_LIMIT(grpquota_b) || CHANGED_LIMIT(grpquota_i)) {
+		err = "Cannot change global quota limit on remount";
+		goto out;
+	}
+#endif /* CONFIG_TMPFS_QUOTA */
+
+	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_ispace = ctx->inodes * BOGO_INODE_SIZE - used_isp;
+	}
+
+	/*
+	 * 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;
+	}
+
+	if (ctx->noswap)
+		sbinfo->noswap = true;
+
+	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);
+	struct mempolicy *mpol;
+
+	if (sbinfo->max_blocks != shmem_default_max_blocks())
+		seq_printf(seq, ",size=%luk", K(sbinfo->max_blocks));
+	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
+	mpol = shmem_get_sbmpol(sbinfo);
+	shmem_show_mpol(seq, mpol);
+	mpol_put(mpol);
+	if (sbinfo->noswap)
+		seq_printf(seq, ",noswap");
+	return 0;
+}
+
+#endif /* CONFIG_TMPFS */
+
+static void shmem_put_super(struct super_block *sb)
+{
+	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
+
+#ifdef CONFIG_TMPFS_QUOTA
+	shmem_disable_quotas(sb);
+#endif
+	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;
+	int error = -ENOMEM;
+
+	/* 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 error;
+
+	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);
+		sbinfo->noswap = ctx->noswap;
+	} else {
+		sb->s_flags |= SB_NOUSER;
+	}
+	sb->s_export_op = &shmem_export_ops;
+	sb->s_flags |= SB_NOSEC | SB_I_VERSION;
+#else
+	sb->s_flags |= SB_NOUSER;
+#endif
+	sbinfo->max_blocks = ctx->blocks;
+	sbinfo->max_inodes = ctx->inodes;
+	sbinfo->free_ispace = sbinfo->max_inodes * BOGO_INODE_SIZE;
+	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);
+
+#ifdef CONFIG_TMPFS_QUOTA
+	if (ctx->seen & SHMEM_SEEN_QUOTA) {
+		sb->dq_op = &shmem_quota_operations;
+		sb->s_qcop = &dquot_quotactl_sysfile_ops;
+		sb->s_quota_types = QTYPE_MASK_USR | QTYPE_MASK_GRP;
+
+		/* Copy the default limits from ctx into sbinfo */
+		memcpy(&sbinfo->qlimits, &ctx->qlimits,
+		       sizeof(struct shmem_quota_limits));
+
+		if (shmem_enable_quotas(sb, ctx->quota_types))
+			goto failed;
+	}
+#endif /* CONFIG_TMPFS_QUOTA */
+
+	inode = shmem_get_inode(&nop_mnt_idmap, sb, NULL, S_IFDIR | sbinfo->mode, 0,
+				VM_NORESERVE);
+	if (IS_ERR(inode)) {
+		error = PTR_ERR(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 error;
+}
+
+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);
+	if (S_ISDIR(inode->i_mode))
+		simple_offset_destroy(shmem_get_offset_ctx(inode));
+}
+
+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,
+	.open		= shmem_file_open,
+	.get_unmapped_area = shmem_get_unmapped_area,
+#ifdef CONFIG_TMPFS
+	.llseek		= shmem_file_llseek,
+	.read_iter	= shmem_file_read_iter,
+	.write_iter	= shmem_file_write_iter,
+	.fsync		= noop_fsync,
+	.splice_read	= shmem_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,
+	.get_offset_ctx	= shmem_get_offset_ctx,
+#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
+#ifdef CONFIG_TMPFS_QUOTA
+	.get_dquots	= shmem_get_dquots,
+#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
+};
+
+static const struct vm_operations_struct shmem_anon_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,
+#ifdef CONFIG_SHMEM
+	.fs_flags	= FS_USERNS_MOUNT | FS_ALLOW_IDMAP,
+#else
+	.fs_flags	= FS_USERNS_MOUNT,
+#endif
+};
+
+void __init shmem_init(void)
+{
+	int error;
+
+	shmem_init_inodecache();
+
+#ifdef CONFIG_TMPFS_QUOTA
+	error = register_quota_format(&shmem_quota_format);
+	if (error < 0) {
+		pr_err("Could not register quota format\n");
+		goto out3;
+	}
+#endif
+
+	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:
+#ifdef CONFIG_TMPFS_QUOTA
+	unregister_quota_format(&shmem_quota_format);
+out3:
+#endif
+	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	= ramfs_kill_sb,
+	.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_anon_vm_ops			generic_file_vm_ops
+#define shmem_file_operations			ramfs_file_operations
+#define shmem_acct_size(flags, size)		0
+#define shmem_unacct_size(flags, size)		do {} while (0)
+
+static inline struct inode *shmem_get_inode(struct mnt_idmap *idmap, struct super_block *sb, struct inode *dir,
+					    umode_t mode, dev_t dev, unsigned long flags)
+{
+	struct inode *inode = ramfs_get_inode(sb, dir, mode, dev);
+	return inode ? inode : ERR_PTR(-ENOSPC);
+}
+
+#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);
+
+	if (is_idmapped_mnt(mnt))
+		return ERR_PTR(-EINVAL);
+
+	inode = shmem_get_inode(&nop_mnt_idmap, mnt->mnt_sb, NULL,
+				S_IFREG | S_IRWXUGO, 0, flags);
+
+	if (IS_ERR(inode)) {
+		shmem_unacct_size(flags, size);
+		return ERR_CAST(inode);
+	}
+	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_anon_vm_ops;
+
+	return 0;
+}
+
+/**
+ * shmem_read_folio_gfp - read into page cache, using specified page allocation flags.
+ * @mapping:	the folio's address_space
+ * @index:	the folio 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 folio *shmem_read_folio_gfp(struct address_space *mapping,
+		pgoff_t index, gfp_t gfp)
+{
+#ifdef CONFIG_SHMEM
+	struct inode *inode = mapping->host;
+	struct folio *folio;
+	int error;
+
+	BUG_ON(!shmem_mapping(mapping));
+	error = shmem_get_folio_gfp(inode, index, &folio, SGP_CACHE,
+				  gfp, NULL, NULL, NULL);
+	if (error)
+		return ERR_PTR(error);
+
+	folio_unlock(folio);
+	return folio;
+#else
+	/*
+	 * The tiny !SHMEM case uses ramfs without swap
+	 */
+	return mapping_read_folio_gfp(mapping, index, gfp);
+#endif
+}
+EXPORT_SYMBOL_GPL(shmem_read_folio_gfp);
+
+struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
+					 pgoff_t index, gfp_t gfp)
+{
+	struct folio *folio = shmem_read_folio_gfp(mapping, index, gfp);
+	struct page *page;
+
+	if (IS_ERR(folio))
+		return &folio->page;
+
+	page = folio_file_page(folio, index);
+	if (PageHWPoison(page)) {
+		folio_put(folio);
+		return ERR_PTR(-EIO);
+	}
+
+	return page;
+}
+EXPORT_SYMBOL_GPL(shmem_read_mapping_page_gfp);