Adding upstream version 4.19.249.upstream/4.19.249upstream

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

1 files changed, 4100 insertions, 0 deletions

diff --git a/mm/shmem.c b/mm/shmem.c
new file mode 100644
index 000000000..078861669
--- /dev/null
+++ b/mm/shmem.c
@@ -0,0 +1,4100 @@
+/*
+ * 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/mm.h>
+#include <linux/random.h>
+#include <linux/sched/signal.h>
+#include <linux/export.h>
+#include <linux/swap.h>
+#include <linux/uio.h>
+#include <linux/khugepaged.h>
+#include <linux/hugetlb.h>
+
+#include <asm/tlbflush.h> /* for arch/microblaze update_mmu_cache() */
+
+static struct vfsmount *shm_mnt;
+
+#ifdef CONFIG_SHMEM
+/*
+ * This virtual memory filesystem is heavily based on the ramfs. It
+ * extends ramfs by the ability to use swap and honor resource limits
+ * which makes it a completely usable filesystem.
+ */
+
+#include <linux/xattr.h>
+#include <linux/exportfs.h>
+#include <linux/posix_acl.h>
+#include <linux/posix_acl_xattr.h>
+#include <linux/mman.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/backing-dev.h>
+#include <linux/shmem_fs.h>
+#include <linux/writeback.h>
+#include <linux/blkdev.h>
+#include <linux/pagevec.h>
+#include <linux/percpu_counter.h>
+#include <linux/falloc.h>
+#include <linux/splice.h>
+#include <linux/security.h>
+#include <linux/swapops.h>
+#include <linux/mempolicy.h>
+#include <linux/namei.h>
+#include <linux/ctype.h>
+#include <linux/migrate.h>
+#include <linux/highmem.h>
+#include <linux/seq_file.h>
+#include <linux/magic.h>
+#include <linux/syscalls.h>
+#include <linux/fcntl.h>
+#include <uapi/linux/memfd.h>
+#include <linux/userfaultfd_k.h>
+#include <linux/rmap.h>
+#include <linux/uuid.h>
+
+#include <linux/uaccess.h>
+#include <asm/pgtable.h>
+
+#include "internal.h"
+
+#define BLOCKS_PER_PAGE  (PAGE_SIZE/512)
+#define VM_ACCT(size)    (PAGE_ALIGN(size) >> PAGE_SHIFT)
+
+/* Pretend that each entry is of this size in directory's i_size */
+#define BOGO_DIRENT_SIZE 20
+
+/* Symlink up to this size is kmalloc'ed instead of using a swappable page */
+#define SHORT_SYMLINK_LEN 128
+
+/*
+ * shmem_fallocate communicates with shmem_fault or shmem_writepage via
+ * inode->i_private (with i_mutex 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 */
+};
+
+#ifdef CONFIG_TMPFS
+static unsigned long shmem_default_max_blocks(void)
+{
+	return totalram_pages / 2;
+}
+
+static unsigned long shmem_default_max_inodes(void)
+{
+	return min(totalram_pages - totalhigh_pages, totalram_pages / 2);
+}
+#endif
+
+static bool shmem_should_replace_page(struct page *page, gfp_t gfp);
+static int shmem_replace_page(struct page **pagep, gfp_t gfp,
+				struct shmem_inode_info *info, pgoff_t index);
+static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
+		struct page **pagep, enum sgp_type sgp,
+		gfp_t gfp, struct vm_area_struct *vma,
+		struct vm_fault *vmf, vm_fault_t *fault_type);
+
+int shmem_getpage(struct inode *inode, pgoff_t index,
+		struct page **pagep, enum sgp_type sgp)
+{
+	return shmem_getpage_gfp(inode, index, pagep, sgp,
+		mapping_gfp_mask(inode->i_mapping), NULL, NULL, NULL);
+}
+
+static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
+{
+	return sb->s_fs_info;
+}
+
+/*
+ * shmem_file_setup pre-accounts the whole fixed size of a VM object,
+ * for shared memory and for shared anonymous (/dev/zero) mappings
+ * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
+ * consistent with the pre-accounting of private mappings ...
+ */
+static inline int shmem_acct_size(unsigned long flags, loff_t size)
+{
+	return (flags & VM_NORESERVE) ?
+		0 : security_vm_enough_memory_mm(current->mm, VM_ACCT(size));
+}
+
+static inline void shmem_unacct_size(unsigned long flags, loff_t size)
+{
+	if (!(flags & VM_NORESERVE))
+		vm_unacct_memory(VM_ACCT(size));
+}
+
+static inline int shmem_reacct_size(unsigned long flags,
+		loff_t oldsize, loff_t newsize)
+{
+	if (!(flags & VM_NORESERVE)) {
+		if (VM_ACCT(newsize) > VM_ACCT(oldsize))
+			return security_vm_enough_memory_mm(current->mm,
+					VM_ACCT(newsize) - VM_ACCT(oldsize));
+		else if (VM_ACCT(newsize) < VM_ACCT(oldsize))
+			vm_unacct_memory(VM_ACCT(oldsize) - VM_ACCT(newsize));
+	}
+	return 0;
+}
+
+/*
+ * ... whereas tmpfs objects are accounted incrementally as
+ * pages are allocated, in order to allow large sparse files.
+ * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
+ * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
+ */
+static inline int shmem_acct_block(unsigned long flags, long pages)
+{
+	if (!(flags & VM_NORESERVE))
+		return 0;
+
+	return security_vm_enough_memory_mm(current->mm,
+			pages * VM_ACCT(PAGE_SIZE));
+}
+
+static inline void shmem_unacct_blocks(unsigned long flags, long pages)
+{
+	if (flags & VM_NORESERVE)
+		vm_unacct_memory(pages * VM_ACCT(PAGE_SIZE));
+}
+
+static inline bool shmem_inode_acct_block(struct inode *inode, long pages)
+{
+	struct shmem_inode_info *info = SHMEM_I(inode);
+	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
+
+	if (shmem_acct_block(info->flags, pages))
+		return false;
+
+	if (sbinfo->max_blocks) {
+		if (percpu_counter_compare(&sbinfo->used_blocks,
+					   sbinfo->max_blocks - pages) > 0)
+			goto unacct;
+		percpu_counter_add(&sbinfo->used_blocks, pages);
+	}
+
+	return true;
+
+unacct:
+	shmem_unacct_blocks(info->flags, pages);
+	return false;
+}
+
+static inline void shmem_inode_unacct_blocks(struct inode *inode, long pages)
+{
+	struct shmem_inode_info *info = SHMEM_I(inode);
+	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
+
+	if (sbinfo->max_blocks)
+		percpu_counter_sub(&sbinfo->used_blocks, pages);
+	shmem_unacct_blocks(info->flags, pages);
+}
+
+static const struct super_operations shmem_ops;
+static const struct address_space_operations shmem_aops;
+static const struct file_operations shmem_file_operations;
+static const struct inode_operations shmem_inode_operations;
+static const struct inode_operations shmem_dir_inode_operations;
+static const struct inode_operations shmem_special_inode_operations;
+static const struct vm_operations_struct shmem_vm_ops;
+static struct file_system_type shmem_fs_type;
+
+bool vma_is_shmem(struct vm_area_struct *vma)
+{
+	return vma->vm_ops == &shmem_vm_ops;
+}
+
+static LIST_HEAD(shmem_swaplist);
+static DEFINE_MUTEX(shmem_swaplist_mutex);
+
+static int shmem_reserve_inode(struct super_block *sb)
+{
+	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
+	if (sbinfo->max_inodes) {
+		spin_lock(&sbinfo->stat_lock);
+		if (!sbinfo->free_inodes) {
+			spin_unlock(&sbinfo->stat_lock);
+			return -ENOSPC;
+		}
+		sbinfo->free_inodes--;
+		spin_unlock(&sbinfo->stat_lock);
+	}
+	return 0;
+}
+
+static void shmem_free_inode(struct super_block *sb)
+{
+	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
+	if (sbinfo->max_inodes) {
+		spin_lock(&sbinfo->stat_lock);
+		sbinfo->free_inodes++;
+		spin_unlock(&sbinfo->stat_lock);
+	}
+}
+
+/**
+ * shmem_recalc_inode - recalculate the block usage of an inode
+ * @inode: inode to recalc
+ *
+ * We have to calculate the free blocks since the mm can drop
+ * undirtied hole pages behind our back.
+ *
+ * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
+ * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
+ *
+ * It has to be called with the spinlock held.
+ */
+static void shmem_recalc_inode(struct inode *inode)
+{
+	struct shmem_inode_info *info = SHMEM_I(inode);
+	long freed;
+
+	freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
+	if (freed > 0) {
+		info->alloced -= freed;
+		inode->i_blocks -= freed * BLOCKS_PER_PAGE;
+		shmem_inode_unacct_blocks(inode, freed);
+	}
+}
+
+bool shmem_charge(struct inode *inode, long pages)
+{
+	struct shmem_inode_info *info = SHMEM_I(inode);
+	unsigned long flags;
+
+	if (!shmem_inode_acct_block(inode, pages))
+		return false;
+
+	/* nrpages adjustment first, then shmem_recalc_inode() when balanced */
+	inode->i_mapping->nrpages += pages;
+
+	spin_lock_irqsave(&info->lock, flags);
+	info->alloced += pages;
+	inode->i_blocks += pages * BLOCKS_PER_PAGE;
+	shmem_recalc_inode(inode);
+	spin_unlock_irqrestore(&info->lock, flags);
+
+	return true;
+}
+
+void shmem_uncharge(struct inode *inode, long pages)
+{
+	struct shmem_inode_info *info = SHMEM_I(inode);
+	unsigned long flags;
+
+	/* nrpages adjustment done by __delete_from_page_cache() or caller */
+
+	spin_lock_irqsave(&info->lock, flags);
+	info->alloced -= pages;
+	inode->i_blocks -= pages * BLOCKS_PER_PAGE;
+	shmem_recalc_inode(inode);
+	spin_unlock_irqrestore(&info->lock, flags);
+
+	shmem_inode_unacct_blocks(inode, pages);
+}
+
+/*
+ * Replace item expected in radix tree by a new item, while holding tree lock.
+ */
+static int shmem_radix_tree_replace(struct address_space *mapping,
+			pgoff_t index, void *expected, void *replacement)
+{
+	struct radix_tree_node *node;
+	void __rcu **pslot;
+	void *item;
+
+	VM_BUG_ON(!expected);
+	VM_BUG_ON(!replacement);
+	item = __radix_tree_lookup(&mapping->i_pages, index, &node, &pslot);
+	if (!item)
+		return -ENOENT;
+	if (item != expected)
+		return -ENOENT;
+	__radix_tree_replace(&mapping->i_pages, node, pslot,
+			     replacement, NULL);
+	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)
+{
+	void *item;
+
+	rcu_read_lock();
+	item = radix_tree_lookup(&mapping->i_pages, index);
+	rcu_read_unlock();
+	return item == 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_HUGE_PAGECACHE
+/* ifdef here to avoid bloating shmem.o when not necessary */
+
+static int shmem_huge __read_mostly;
+
+#if defined(CONFIG_SYSFS) || defined(CONFIG_TMPFS)
+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;
+}
+
+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 page *page;
+	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;
+
+		info = list_entry(pos, struct shmem_inode_info, shrinklist);
+		inode = &info->vfs_inode;
+
+		if (nr_to_split && split >= nr_to_split)
+			goto move_back;
+
+		page = find_get_page(inode->i_mapping,
+				(inode->i_size & HPAGE_PMD_MASK) >> PAGE_SHIFT);
+		if (!page)
+			goto drop;
+
+		/* No huge page at the end of the file: nothing to split */
+		if (!PageTransHuge(page)) {
+			put_page(page);
+			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 (!trylock_page(page)) {
+			put_page(page);
+			goto move_back;
+		}
+
+		ret = split_huge_page(page);
+		unlock_page(page);
+		put_page(page);
+
+		/* 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_HUGE_PAGECACHE */
+
+#define shmem_huge SHMEM_HUGE_DENY
+
+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_HUGE_PAGECACHE */
+
+static inline bool is_huge_enabled(struct shmem_sb_info *sbinfo)
+{
+	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE) &&
+	    (shmem_huge == SHMEM_HUGE_FORCE || sbinfo->huge) &&
+	    shmem_huge != SHMEM_HUGE_DENY)
+		return true;
+	return false;
+}
+
+/*
+ * Like add_to_page_cache_locked, but error if expected item has gone.
+ */
+static int shmem_add_to_page_cache(struct page *page,
+				   struct address_space *mapping,
+				   pgoff_t index, void *expected)
+{
+	int error, nr = hpage_nr_pages(page);
+
+	VM_BUG_ON_PAGE(PageTail(page), page);
+	VM_BUG_ON_PAGE(index != round_down(index, nr), page);
+	VM_BUG_ON_PAGE(!PageLocked(page), page);
+	VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
+	VM_BUG_ON(expected && PageTransHuge(page));
+
+	page_ref_add(page, nr);
+	page->mapping = mapping;
+	page->index = index;
+
+	xa_lock_irq(&mapping->i_pages);
+	if (PageTransHuge(page)) {
+		void __rcu **results;
+		pgoff_t idx;
+		int i;
+
+		error = 0;
+		if (radix_tree_gang_lookup_slot(&mapping->i_pages,
+					&results, &idx, index, 1) &&
+				idx < index + HPAGE_PMD_NR) {
+			error = -EEXIST;
+		}
+
+		if (!error) {
+			for (i = 0; i < HPAGE_PMD_NR; i++) {
+				error = radix_tree_insert(&mapping->i_pages,
+						index + i, page + i);
+				VM_BUG_ON(error);
+			}
+			count_vm_event(THP_FILE_ALLOC);
+		}
+	} else if (!expected) {
+		error = radix_tree_insert(&mapping->i_pages, index, page);
+	} else {
+		error = shmem_radix_tree_replace(mapping, index, expected,
+								 page);
+	}
+
+	if (!error) {
+		mapping->nrpages += nr;
+		if (PageTransHuge(page))
+			__inc_node_page_state(page, NR_SHMEM_THPS);
+		__mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, nr);
+		__mod_node_page_state(page_pgdat(page), NR_SHMEM, nr);
+		xa_unlock_irq(&mapping->i_pages);
+	} else {
+		page->mapping = NULL;
+		xa_unlock_irq(&mapping->i_pages);
+		page_ref_sub(page, nr);
+	}
+	return error;
+}
+
+/*
+ * Like delete_from_page_cache, but substitutes swap for page.
+ */
+static void shmem_delete_from_page_cache(struct page *page, void *radswap)
+{
+	struct address_space *mapping = page->mapping;
+	int error;
+
+	VM_BUG_ON_PAGE(PageCompound(page), page);
+
+	xa_lock_irq(&mapping->i_pages);
+	error = shmem_radix_tree_replace(mapping, page->index, page, radswap);
+	page->mapping = NULL;
+	mapping->nrpages--;
+	__dec_node_page_state(page, NR_FILE_PAGES);
+	__dec_node_page_state(page, NR_SHMEM);
+	xa_unlock_irq(&mapping->i_pages);
+	put_page(page);
+	BUG_ON(error);
+}
+
+/*
+ * Remove swap entry from radix tree, free the swap and its page cache.
+ */
+static int shmem_free_swap(struct address_space *mapping,
+			   pgoff_t index, void *radswap)
+{
+	void *old;
+
+	xa_lock_irq(&mapping->i_pages);
+	old = radix_tree_delete_item(&mapping->i_pages, index, radswap);
+	xa_unlock_irq(&mapping->i_pages);
+	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_mutex 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)
+{
+	struct radix_tree_iter iter;
+	void __rcu **slot;
+	struct page *page;
+	unsigned long swapped = 0;
+
+	rcu_read_lock();
+
+	radix_tree_for_each_slot(slot, &mapping->i_pages, &iter, start) {
+		if (iter.index >= end)
+			break;
+
+		page = radix_tree_deref_slot(slot);
+
+		if (radix_tree_deref_retry(page)) {
+			slot = radix_tree_iter_retry(&iter);
+			continue;
+		}
+
+		if (radix_tree_exceptional_entry(page))
+			swapped++;
+
+		if (need_resched()) {
+			slot = radix_tree_iter_resume(slot, &iter);
+			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_mutex 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,
+			linear_page_index(vma, vma->vm_start),
+			linear_page_index(vma, vma->vm_end));
+}
+
+/*
+ * SysV IPC SHM_UNLOCK restore Unevictable pages to their evictable lists.
+ */
+void shmem_unlock_mapping(struct address_space *mapping)
+{
+	struct pagevec pvec;
+	pgoff_t indices[PAGEVEC_SIZE];
+	pgoff_t index = 0;
+
+	pagevec_init(&pvec);
+	/*
+	 * Minor point, but we might as well stop if someone else SHM_LOCKs it.
+	 */
+	while (!mapping_unevictable(mapping)) {
+		/*
+		 * Avoid pagevec_lookup(): find_get_pages() returns 0 as if it
+		 * has finished, if it hits a row of PAGEVEC_SIZE swap entries.
+		 */
+		pvec.nr = find_get_entries(mapping, index,
+					   PAGEVEC_SIZE, pvec.pages, indices);
+		if (!pvec.nr)
+			break;
+		index = indices[pvec.nr - 1] + 1;
+		pagevec_remove_exceptionals(&pvec);
+		check_move_unevictable_pages(pvec.pages, pvec.nr);
+		pagevec_release(&pvec);
+		cond_resched();
+	}
+}
+
+/*
+ * Remove range of pages and swap entries from radix tree, 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;
+	unsigned int partial_start = lstart & (PAGE_SIZE - 1);
+	unsigned int partial_end = (lend + 1) & (PAGE_SIZE - 1);
+	struct pagevec pvec;
+	pgoff_t indices[PAGEVEC_SIZE];
+	long nr_swaps_freed = 0;
+	pgoff_t index;
+	int i;
+
+	if (lend == -1)
+		end = -1;	/* unsigned, so actually very big */
+
+	pagevec_init(&pvec);
+	index = start;
+	while (index < end) {
+		pvec.nr = find_get_entries(mapping, index,
+			min(end - index, (pgoff_t)PAGEVEC_SIZE),
+			pvec.pages, indices);
+		if (!pvec.nr)
+			break;
+		for (i = 0; i < pagevec_count(&pvec); i++) {
+			struct page *page = pvec.pages[i];
+
+			index = indices[i];
+			if (index >= end)
+				break;
+
+			if (radix_tree_exceptional_entry(page)) {
+				if (unfalloc)
+					continue;
+				nr_swaps_freed += !shmem_free_swap(mapping,
+								index, page);
+				continue;
+			}
+
+			VM_BUG_ON_PAGE(page_to_pgoff(page) != index, page);
+
+			if (!trylock_page(page))
+				continue;
+
+			if (PageTransTail(page)) {
+				/* Middle of THP: zero out the page */
+				clear_highpage(page);
+				unlock_page(page);
+				continue;
+			} else if (PageTransHuge(page)) {
+				if (index == round_down(end, HPAGE_PMD_NR)) {
+					/*
+					 * Range ends in the middle of THP:
+					 * zero out the page
+					 */
+					clear_highpage(page);
+					unlock_page(page);
+					continue;
+				}
+				index += HPAGE_PMD_NR - 1;
+				i += HPAGE_PMD_NR - 1;
+			}
+
+			if (!unfalloc || !PageUptodate(page)) {
+				VM_BUG_ON_PAGE(PageTail(page), page);
+				if (page_mapping(page) == mapping) {
+					VM_BUG_ON_PAGE(PageWriteback(page), page);
+					truncate_inode_page(mapping, page);
+				}
+			}
+			unlock_page(page);
+		}
+		pagevec_remove_exceptionals(&pvec);
+		pagevec_release(&pvec);
+		cond_resched();
+		index++;
+	}
+
+	if (partial_start) {
+		struct page *page = NULL;
+		shmem_getpage(inode, start - 1, &page, SGP_READ);
+		if (page) {
+			unsigned int top = PAGE_SIZE;
+			if (start > end) {
+				top = partial_end;
+				partial_end = 0;
+			}
+			zero_user_segment(page, partial_start, top);
+			set_page_dirty(page);
+			unlock_page(page);
+			put_page(page);
+		}
+	}
+	if (partial_end) {
+		struct page *page = NULL;
+		shmem_getpage(inode, end, &page, SGP_READ);
+		if (page) {
+			zero_user_segment(page, 0, partial_end);
+			set_page_dirty(page);
+			unlock_page(page);
+			put_page(page);
+		}
+	}
+	if (start >= end)
+		return;
+
+	index = start;
+	while (index < end) {
+		cond_resched();
+
+		pvec.nr = find_get_entries(mapping, index,
+				min(end - index, (pgoff_t)PAGEVEC_SIZE),
+				pvec.pages, indices);
+		if (!pvec.nr) {
+			/* 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 < pagevec_count(&pvec); i++) {
+			struct page *page = pvec.pages[i];
+
+			index = indices[i];
+			if (index >= end)
+				break;
+
+			if (radix_tree_exceptional_entry(page)) {
+				if (unfalloc)
+					continue;
+				if (shmem_free_swap(mapping, index, page)) {
+					/* Swap was replaced by page: retry */
+					index--;
+					break;
+				}
+				nr_swaps_freed++;
+				continue;
+			}
+
+			lock_page(page);
+
+			if (PageTransTail(page)) {
+				/* Middle of THP: zero out the page */
+				clear_highpage(page);
+				unlock_page(page);
+				/*
+				 * Partial thp truncate due 'start' in middle
+				 * of THP: don't need to look on these pages
+				 * again on !pvec.nr restart.
+				 */
+				if (index != round_down(end, HPAGE_PMD_NR))
+					start++;
+				continue;
+			} else if (PageTransHuge(page)) {
+				if (index == round_down(end, HPAGE_PMD_NR)) {
+					/*
+					 * Range ends in the middle of THP:
+					 * zero out the page
+					 */
+					clear_highpage(page);
+					unlock_page(page);
+					continue;
+				}
+				index += HPAGE_PMD_NR - 1;
+				i += HPAGE_PMD_NR - 1;
+			}
+
+			if (!unfalloc || !PageUptodate(page)) {
+				VM_BUG_ON_PAGE(PageTail(page), page);
+				if (page_mapping(page) == mapping) {
+					VM_BUG_ON_PAGE(PageWriteback(page), page);
+					truncate_inode_page(mapping, page);
+				} else {
+					/* Page was replaced by swap: retry */
+					unlock_page(page);
+					index--;
+					break;
+				}
+			}
+			unlock_page(page);
+		}
+		pagevec_remove_exceptionals(&pvec);
+		pagevec_release(&pvec);
+		index++;
+	}
+
+	spin_lock_irq(&info->lock);
+	info->swapped -= nr_swaps_freed;
+	shmem_recalc_inode(inode);
+	spin_unlock_irq(&info->lock);
+}
+
+void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
+{
+	shmem_undo_range(inode, lstart, lend, false);
+	inode->i_ctime = inode->i_mtime = current_time(inode);
+}
+EXPORT_SYMBOL_GPL(shmem_truncate_range);
+
+static int shmem_getattr(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);
+	struct shmem_sb_info *sb_info = SHMEM_SB(inode->i_sb);
+
+	if (info->alloced - info->swapped != inode->i_mapping->nrpages) {
+		spin_lock_irq(&info->lock);
+		shmem_recalc_inode(inode);
+		spin_unlock_irq(&info->lock);
+	}
+	generic_fillattr(inode, stat);
+
+	if (is_huge_enabled(sb_info))
+		stat->blksize = HPAGE_PMD_SIZE;
+
+	return 0;
+}
+
+static int shmem_setattr(struct dentry *dentry, struct iattr *attr)
+{
+	struct inode *inode = d_inode(dentry);
+	struct shmem_inode_info *info = SHMEM_I(inode);
+	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
+	int error;
+
+	error = setattr_prepare(dentry, attr);
+	if (error)
+		return error;
+
+	if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
+		loff_t oldsize = inode->i_size;
+		loff_t newsize = attr->ia_size;
+
+		/* protected by i_mutex */
+		if ((newsize < oldsize && (info->seals & F_SEAL_SHRINK)) ||
+		    (newsize > oldsize && (info->seals & F_SEAL_GROW)))
+			return -EPERM;
+
+		if (newsize != oldsize) {
+			error = shmem_reacct_size(SHMEM_I(inode)->flags,
+					oldsize, newsize);
+			if (error)
+				return error;
+			i_size_write(inode, newsize);
+			inode->i_ctime = inode->i_mtime = current_time(inode);
+		}
+		if (newsize <= oldsize) {
+			loff_t holebegin = round_up(newsize, PAGE_SIZE);
+			if (oldsize > holebegin)
+				unmap_mapping_range(inode->i_mapping,
+							holebegin, 0, 1);
+			if (info->alloced)
+				shmem_truncate_range(inode,
+							newsize, (loff_t)-1);
+			/* unmap again to remove racily COWed private pages */
+			if (oldsize > holebegin)
+				unmap_mapping_range(inode->i_mapping,
+							holebegin, 0, 1);
+
+			/*
+			 * Part of the huge page can be beyond i_size: subject
+			 * to shrink under memory pressure.
+			 */
+			if (IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE)) {
+				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);
+			}
+		}
+	}
+
+	setattr_copy(inode, attr);
+	if (attr->ia_valid & ATTR_MODE)
+		error = posix_acl_chmod(inode, inode->i_mode);
+	return error;
+}
+
+static void shmem_evict_inode(struct inode *inode)
+{
+	struct shmem_inode_info *info = SHMEM_I(inode);
+	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
+
+	if (inode->i_mapping->a_ops == &shmem_aops) {
+		shmem_unacct_size(info->flags, inode->i_size);
+		inode->i_size = 0;
+		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);
+		}
+		if (!list_empty(&info->swaplist)) {
+			mutex_lock(&shmem_swaplist_mutex);
+			list_del_init(&info->swaplist);
+			mutex_unlock(&shmem_swaplist_mutex);
+		}
+	}
+
+	simple_xattrs_free(&info->xattrs);
+	WARN_ON(inode->i_blocks);
+	shmem_free_inode(inode->i_sb);
+	clear_inode(inode);
+}
+
+static unsigned long find_swap_entry(struct radix_tree_root *root, void *item)
+{
+	struct radix_tree_iter iter;
+	void __rcu **slot;
+	unsigned long found = -1;
+	unsigned int checked = 0;
+
+	rcu_read_lock();
+	radix_tree_for_each_slot(slot, root, &iter, 0) {
+		void *entry = radix_tree_deref_slot(slot);
+
+		if (radix_tree_deref_retry(entry)) {
+			slot = radix_tree_iter_retry(&iter);
+			continue;
+		}
+		if (entry == item) {
+			found = iter.index;
+			break;
+		}
+		checked++;
+		if ((checked % 4096) != 0)
+			continue;
+		slot = radix_tree_iter_resume(slot, &iter);
+		cond_resched_rcu();
+	}
+
+	rcu_read_unlock();
+	return found;
+}
+
+/*
+ * If swap found in inode, free it and move page from swapcache to filecache.
+ */
+static int shmem_unuse_inode(struct shmem_inode_info *info,
+			     swp_entry_t swap, struct page **pagep)
+{
+	struct address_space *mapping = info->vfs_inode.i_mapping;
+	void *radswap;
+	pgoff_t index;
+	gfp_t gfp;
+	int error = 0;
+
+	radswap = swp_to_radix_entry(swap);
+	index = find_swap_entry(&mapping->i_pages, radswap);
+	if (index == -1)
+		return -EAGAIN;	/* tell shmem_unuse we found nothing */
+
+	/*
+	 * Move _head_ to start search for next from here.
+	 * But be careful: shmem_evict_inode checks list_empty without taking
+	 * mutex, and there's an instant in list_move_tail when info->swaplist
+	 * would appear empty, if it were the only one on shmem_swaplist.
+	 */
+	if (shmem_swaplist.next != &info->swaplist)
+		list_move_tail(&shmem_swaplist, &info->swaplist);
+
+	gfp = mapping_gfp_mask(mapping);
+	if (shmem_should_replace_page(*pagep, gfp)) {
+		mutex_unlock(&shmem_swaplist_mutex);
+		error = shmem_replace_page(pagep, gfp, info, index);
+		mutex_lock(&shmem_swaplist_mutex);
+		/*
+		 * We needed to drop mutex to make that restrictive page
+		 * allocation, but the inode might have been freed while we
+		 * dropped it: although a racing shmem_evict_inode() cannot
+		 * complete without emptying the radix_tree, our page lock
+		 * on this swapcache page is not enough to prevent that -
+		 * free_swap_and_cache() of our swap entry will only
+		 * trylock_page(), removing swap from radix_tree whatever.
+		 *
+		 * We must not proceed to shmem_add_to_page_cache() if the
+		 * inode has been freed, but of course we cannot rely on
+		 * inode or mapping or info to check that.  However, we can
+		 * safely check if our swap entry is still in use (and here
+		 * it can't have got reused for another page): if it's still
+		 * in use, then the inode cannot have been freed yet, and we
+		 * can safely proceed (if it's no longer in use, that tells
+		 * nothing about the inode, but we don't need to unuse swap).
+		 */
+		if (!page_swapcount(*pagep))
+			error = -ENOENT;
+	}
+
+	/*
+	 * We rely on shmem_swaplist_mutex, not only to protect the swaplist,
+	 * but also to hold up shmem_evict_inode(): so inode cannot be freed
+	 * beneath us (pagelock doesn't help until the page is in pagecache).
+	 */
+	if (!error)
+		error = shmem_add_to_page_cache(*pagep, mapping, index,
+						radswap);
+	if (error != -ENOMEM) {
+		/*
+		 * Truncation and eviction use free_swap_and_cache(), which
+		 * only does trylock page: if we raced, best clean up here.
+		 */
+		delete_from_swap_cache(*pagep);
+		set_page_dirty(*pagep);
+		if (!error) {
+			spin_lock_irq(&info->lock);
+			info->swapped--;
+			spin_unlock_irq(&info->lock);
+			swap_free(swap);
+		}
+	}
+	return error;
+}
+
+/*
+ * Search through swapped inodes to find and replace swap by page.
+ */
+int shmem_unuse(swp_entry_t swap, struct page *page)
+{
+	struct list_head *this, *next;
+	struct shmem_inode_info *info;
+	struct mem_cgroup *memcg;
+	int error = 0;
+
+	/*
+	 * There's a faint possibility that swap page was replaced before
+	 * caller locked it: caller will come back later with the right page.
+	 */
+	if (unlikely(!PageSwapCache(page) || page_private(page) != swap.val))
+		goto out;
+
+	/*
+	 * Charge page using GFP_KERNEL while we can wait, before taking
+	 * the shmem_swaplist_mutex which might hold up shmem_writepage().
+	 * Charged back to the user (not to caller) when swap account is used.
+	 */
+	error = mem_cgroup_try_charge_delay(page, current->mm, GFP_KERNEL,
+					    &memcg, false);
+	if (error)
+		goto out;
+	/* No radix_tree_preload: swap entry keeps a place for page in tree */
+	error = -EAGAIN;
+
+	mutex_lock(&shmem_swaplist_mutex);
+	list_for_each_safe(this, next, &shmem_swaplist) {
+		info = list_entry(this, struct shmem_inode_info, swaplist);
+		if (info->swapped)
+			error = shmem_unuse_inode(info, swap, &page);
+		else
+			list_del_init(&info->swaplist);
+		cond_resched();
+		if (error != -EAGAIN)
+			break;
+		/* found nothing in this: move on to search the next */
+	}
+	mutex_unlock(&shmem_swaplist_mutex);
+
+	if (error) {
+		if (error != -ENOMEM)
+			error = 0;
+		mem_cgroup_cancel_charge(page, memcg, false);
+	} else
+		mem_cgroup_commit_charge(page, memcg, true, false);
+out:
+	unlock_page(page);
+	put_page(page);
+	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 shmem_inode_info *info;
+	struct address_space *mapping;
+	struct inode *inode;
+	swp_entry_t swap;
+	pgoff_t index;
+
+	VM_BUG_ON_PAGE(PageCompound(page), page);
+	BUG_ON(!PageLocked(page));
+	mapping = page->mapping;
+	index = page->index;
+	inode = mapping->host;
+	info = SHMEM_I(inode);
+	if (info->flags & VM_LOCKED)
+		goto redirty;
+	if (!total_swap_pages)
+		goto redirty;
+
+	/*
+	 * Our capabilities prevent regular writeback or sync from ever calling
+	 * shmem_writepage; but a stacking filesystem might use ->writepage of
+	 * its underlying filesystem, in which case tmpfs should write out to
+	 * swap only in response to memory pressure, and not for the writeback
+	 * threads or sync.
+	 */
+	if (!wbc->for_reclaim) {
+		WARN_ON_ONCE(1);	/* Still happens? Tell us about it! */
+		goto redirty;
+	}
+
+	/*
+	 * This is somewhat ridiculous, but without plumbing a SWAP_MAP_FALLOC
+	 * value into swapfile.c, the only way we can correctly account for a
+	 * fallocated page arriving here is now to initialize it and write it.
+	 *
+	 * That's okay for a page already fallocated earlier, but if we have
+	 * not yet completed the fallocation, then (a) we want to keep track
+	 * of this page in case we have to undo it, and (b) it may not be a
+	 * good idea to continue anyway, once we're pushing into swap.  So
+	 * reactivate the page, and let shmem_fallocate() quit when too many.
+	 */
+	if (!PageUptodate(page)) {
+		if (inode->i_private) {
+			struct shmem_falloc *shmem_falloc;
+			spin_lock(&inode->i_lock);
+			shmem_falloc = inode->i_private;
+			if (shmem_falloc &&
+			    !shmem_falloc->waitq &&
+			    index >= shmem_falloc->start &&
+			    index < shmem_falloc->next)
+				shmem_falloc->nr_unswapped++;
+			else
+				shmem_falloc = NULL;
+			spin_unlock(&inode->i_lock);
+			if (shmem_falloc)
+				goto redirty;
+		}
+		clear_highpage(page);
+		flush_dcache_page(page);
+		SetPageUptodate(page);
+	}
+
+	swap = get_swap_page(page);
+	if (!swap.val)
+		goto redirty;
+
+	/*
+	 * Add inode to shmem_unuse()'s list of swapped-out inodes,
+	 * if it's not already there.  Do it now before the page is
+	 * moved to swap cache, when its pagelock no longer protects
+	 * the inode from eviction.  But don't unlock the mutex until
+	 * we've incremented swapped, because shmem_unuse_inode() will
+	 * prune a !swapped inode from the swaplist under this mutex.
+	 */
+	mutex_lock(&shmem_swaplist_mutex);
+	if (list_empty(&info->swaplist))
+		list_add_tail(&info->swaplist, &shmem_swaplist);
+
+	if (add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
+		spin_lock_irq(&info->lock);
+		shmem_recalc_inode(inode);
+		info->swapped++;
+		spin_unlock_irq(&info->lock);
+
+		swap_shmem_alloc(swap);
+		shmem_delete_from_page_cache(page, swp_to_radix_entry(swap));
+
+		mutex_unlock(&shmem_swaplist_mutex);
+		BUG_ON(page_mapped(page));
+		swap_writepage(page, wbc);
+		return 0;
+	}
+
+	mutex_unlock(&shmem_swaplist_mutex);
+	put_swap_page(page, swap);
+redirty:
+	set_page_dirty(page);
+	if (wbc->for_reclaim)
+		return AOP_WRITEPAGE_ACTIVATE;	/* Return with page locked */
+	unlock_page(page);
+	return 0;
+}
+
+#if defined(CONFIG_NUMA) && defined(CONFIG_TMPFS)
+static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
+{
+	char buffer[64];
+
+	if (!mpol || mpol->mode == MPOL_DEFAULT)
+		return;		/* show nothing */
+
+	mpol_to_str(buffer, sizeof(buffer), mpol);
+
+	seq_printf(seq, ",mpol=%s", buffer);
+}
+
+static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
+{
+	struct mempolicy *mpol = NULL;
+	if (sbinfo->mpol) {
+		spin_lock(&sbinfo->stat_lock);	/* prevent replace/use races */
+		mpol = sbinfo->mpol;
+		mpol_get(mpol);
+		spin_unlock(&sbinfo->stat_lock);
+	}
+	return mpol;
+}
+#else /* !CONFIG_NUMA || !CONFIG_TMPFS */
+static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
+{
+}
+static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
+{
+	return NULL;
+}
+#endif /* CONFIG_NUMA && CONFIG_TMPFS */
+#ifndef CONFIG_NUMA
+#define vm_policy vm_private_data
+#endif
+
+static void shmem_pseudo_vma_init(struct vm_area_struct *vma,
+		struct shmem_inode_info *info, pgoff_t index)
+{
+	/* Create a pseudo vma that just contains the policy */
+	vma_init(vma, NULL);
+	/* Bias interleave by inode number to distribute better across nodes */
+	vma->vm_pgoff = index + info->vfs_inode.i_ino;
+	vma->vm_policy = mpol_shared_policy_lookup(&info->policy, index);
+}
+
+static void shmem_pseudo_vma_destroy(struct vm_area_struct *vma)
+{
+	/* Drop reference taken by mpol_shared_policy_lookup() */
+	mpol_cond_put(vma->vm_policy);
+}
+
+static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
+			struct shmem_inode_info *info, pgoff_t index)
+{
+	struct vm_area_struct pvma;
+	struct page *page;
+	struct vm_fault vmf;
+
+	shmem_pseudo_vma_init(&pvma, info, index);
+	vmf.vma = &pvma;
+	vmf.address = 0;
+	page = swap_cluster_readahead(swap, gfp, &vmf);
+	shmem_pseudo_vma_destroy(&pvma);
+
+	return page;
+}
+
+static struct page *shmem_alloc_hugepage(gfp_t gfp,
+		struct shmem_inode_info *info, pgoff_t index)
+{
+	struct vm_area_struct pvma;
+	struct inode *inode = &info->vfs_inode;
+	struct address_space *mapping = inode->i_mapping;
+	pgoff_t idx, hindex;
+	void __rcu **results;
+	struct page *page;
+
+	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE))
+		return NULL;
+
+	hindex = round_down(index, HPAGE_PMD_NR);
+	rcu_read_lock();
+	if (radix_tree_gang_lookup_slot(&mapping->i_pages, &results, &idx,
+				hindex, 1) && idx < hindex + HPAGE_PMD_NR) {
+		rcu_read_unlock();
+		return NULL;
+	}
+	rcu_read_unlock();
+
+	shmem_pseudo_vma_init(&pvma, info, hindex);
+	page = alloc_pages_vma(gfp | __GFP_COMP | __GFP_NORETRY | __GFP_NOWARN,
+			HPAGE_PMD_ORDER, &pvma, 0, numa_node_id(), true);
+	shmem_pseudo_vma_destroy(&pvma);
+	if (page)
+		prep_transhuge_page(page);
+	return page;
+}
+
+static struct page *shmem_alloc_page(gfp_t gfp,
+			struct shmem_inode_info *info, pgoff_t index)
+{
+	struct vm_area_struct pvma;
+	struct page *page;
+
+	shmem_pseudo_vma_init(&pvma, info, index);
+	page = alloc_page_vma(gfp, &pvma, 0);
+	shmem_pseudo_vma_destroy(&pvma);
+
+	return page;
+}
+
+static struct page *shmem_alloc_and_acct_page(gfp_t gfp,
+		struct inode *inode,
+		pgoff_t index, bool huge)
+{
+	struct shmem_inode_info *info = SHMEM_I(inode);
+	struct page *page;
+	int nr;
+	int err = -ENOSPC;
+
+	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE))
+		huge = false;
+	nr = huge ? HPAGE_PMD_NR : 1;
+
+	if (!shmem_inode_acct_block(inode, nr))
+		goto failed;
+
+	if (huge)
+		page = shmem_alloc_hugepage(gfp, info, index);
+	else
+		page = shmem_alloc_page(gfp, info, index);
+	if (page) {
+		__SetPageLocked(page);
+		__SetPageSwapBacked(page);
+		return page;
+	}
+
+	err = -ENOMEM;
+	shmem_inode_unacct_blocks(inode, nr);
+failed:
+	return ERR_PTR(err);
+}
+
+/*
+ * When a page is moved from swapcache to shmem filecache (either by the
+ * usual swapin of shmem_getpage_gfp(), or by the less common swapoff of
+ * shmem_unuse_inode()), it may have been read in earlier from swap, in
+ * ignorance of the mapping it belongs to.  If that mapping has special
+ * constraints (like the gma500 GEM driver, which requires RAM below 4GB),
+ * we may need to copy to a suitable page before moving to filecache.
+ *
+ * In a future release, this may well be extended to respect cpuset and
+ * NUMA mempolicy, and applied also to anonymous pages in do_swap_page();
+ * but for now it is a simple matter of zone.
+ */
+static bool shmem_should_replace_page(struct page *page, gfp_t gfp)
+{
+	return page_zonenum(page) > gfp_zone(gfp);
+}
+
+static int shmem_replace_page(struct page **pagep, gfp_t gfp,
+				struct shmem_inode_info *info, pgoff_t index)
+{
+	struct page *oldpage, *newpage;
+	struct address_space *swap_mapping;
+	swp_entry_t entry;
+	pgoff_t swap_index;
+	int error;
+
+	oldpage = *pagep;
+	entry.val = page_private(oldpage);
+	swap_index = swp_offset(entry);
+	swap_mapping = page_mapping(oldpage);
+
+	/*
+	 * We have arrived here because our zones are constrained, so don't
+	 * limit chance of success by further cpuset and node constraints.
+	 */
+	gfp &= ~GFP_CONSTRAINT_MASK;
+	newpage = shmem_alloc_page(gfp, info, index);
+	if (!newpage)
+		return -ENOMEM;
+
+	get_page(newpage);
+	copy_highpage(newpage, oldpage);
+	flush_dcache_page(newpage);
+
+	__SetPageLocked(newpage);
+	__SetPageSwapBacked(newpage);
+	SetPageUptodate(newpage);
+	set_page_private(newpage, entry.val);
+	SetPageSwapCache(newpage);
+
+	/*
+	 * Our caller will very soon move newpage out of swapcache, but it's
+	 * a nice clean interface for us to replace oldpage by newpage there.
+	 */
+	xa_lock_irq(&swap_mapping->i_pages);
+	error = shmem_radix_tree_replace(swap_mapping, swap_index, oldpage,
+								   newpage);
+	if (!error) {
+		__inc_node_page_state(newpage, NR_FILE_PAGES);
+		__dec_node_page_state(oldpage, NR_FILE_PAGES);
+	}
+	xa_unlock_irq(&swap_mapping->i_pages);
+
+	if (unlikely(error)) {
+		/*
+		 * Is this possible?  I think not, now that our callers check
+		 * both PageSwapCache and page_private after getting page lock;
+		 * but be defensive.  Reverse old to newpage for clear and free.
+		 */
+		oldpage = newpage;
+	} else {
+		mem_cgroup_migrate(oldpage, newpage);
+		lru_cache_add_anon(newpage);
+		*pagep = newpage;
+	}
+
+	ClearPageSwapCache(oldpage);
+	set_page_private(oldpage, 0);
+
+	unlock_page(oldpage);
+	put_page(oldpage);
+	put_page(oldpage);
+	return error;
+}
+
+/*
+ * shmem_getpage_gfp - find page in cache, or get from swap, or allocate
+ *
+ * If we allocate a new one we do not mark it dirty. That's up to the
+ * vm. If we swap it in we mark it dirty since we also free the swap
+ * entry since a page cannot live in both the swap and page cache.
+ *
+ * fault_mm and fault_type are only supplied by shmem_fault:
+ * otherwise they are NULL.
+ */
+static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
+	struct page **pagep, enum sgp_type sgp, gfp_t gfp,
+	struct vm_area_struct *vma, struct vm_fault *vmf,
+			vm_fault_t *fault_type)
+{
+	struct address_space *mapping = inode->i_mapping;
+	struct shmem_inode_info *info = SHMEM_I(inode);
+	struct shmem_sb_info *sbinfo;
+	struct mm_struct *charge_mm;
+	struct mem_cgroup *memcg;
+	struct page *page;
+	swp_entry_t swap;
+	enum sgp_type sgp_huge = sgp;
+	pgoff_t hindex = index;
+	int error;
+	int once = 0;
+	int alloced = 0;
+
+	if (index > (MAX_LFS_FILESIZE >> PAGE_SHIFT))
+		return -EFBIG;
+	if (sgp == SGP_NOHUGE || sgp == SGP_HUGE)
+		sgp = SGP_CACHE;
+repeat:
+	swap.val = 0;
+	page = find_lock_entry(mapping, index);
+	if (radix_tree_exceptional_entry(page)) {
+		swap = radix_to_swp_entry(page);
+		page = NULL;
+	}
+
+	if (sgp <= SGP_CACHE &&
+	    ((loff_t)index << PAGE_SHIFT) >= i_size_read(inode)) {
+		error = -EINVAL;
+		goto unlock;
+	}
+
+	if (page && sgp == SGP_WRITE)
+		mark_page_accessed(page);
+
+	/* fallocated page? */
+	if (page && !PageUptodate(page)) {
+		if (sgp != SGP_READ)
+			goto clear;
+		unlock_page(page);
+		put_page(page);
+		page = NULL;
+	}
+	if (page || (sgp == SGP_READ && !swap.val)) {
+		*pagep = page;
+		return 0;
+	}
+
+	/*
+	 * Fast cache lookup did not find it:
+	 * bring it back from swap or allocate.
+	 */
+	sbinfo = SHMEM_SB(inode->i_sb);
+	charge_mm = vma ? vma->vm_mm : current->mm;
+
+	if (swap.val) {
+		/* Look it up and read it in.. */
+		page = lookup_swap_cache(swap, NULL, 0);
+		if (!page) {
+			/* Or update major stats only when swapin succeeds?? */
+			if (fault_type) {
+				*fault_type |= VM_FAULT_MAJOR;
+				count_vm_event(PGMAJFAULT);
+				count_memcg_event_mm(charge_mm, PGMAJFAULT);
+			}
+			/* Here we actually start the io */
+			page = shmem_swapin(swap, gfp, info, index);
+			if (!page) {
+				error = -ENOMEM;
+				goto failed;
+			}
+		}
+
+		/* We have to do this with page locked to prevent races */
+		lock_page(page);
+		if (!PageSwapCache(page) || page_private(page) != swap.val ||
+		    !shmem_confirm_swap(mapping, index, swap)) {
+			error = -EEXIST;	/* try again */
+			goto unlock;
+		}
+		if (!PageUptodate(page)) {
+			error = -EIO;
+			goto failed;
+		}
+		wait_on_page_writeback(page);
+
+		if (shmem_should_replace_page(page, gfp)) {
+			error = shmem_replace_page(&page, gfp, info, index);
+			if (error)
+				goto failed;
+		}
+
+		error = mem_cgroup_try_charge_delay(page, charge_mm, gfp, &memcg,
+				false);
+		if (!error) {
+			error = shmem_add_to_page_cache(page, mapping, index,
+						swp_to_radix_entry(swap));
+			/*
+			 * We already confirmed swap under page lock, and make
+			 * no memory allocation here, so usually no possibility
+			 * of error; but free_swap_and_cache() only trylocks a
+			 * page, so it is just possible that the entry has been
+			 * truncated or holepunched since swap was confirmed.
+			 * shmem_undo_range() will have done some of the
+			 * unaccounting, now delete_from_swap_cache() will do
+			 * the rest.
+			 * Reset swap.val? No, leave it so "failed" goes back to
+			 * "repeat": reading a hole and writing should succeed.
+			 */
+			if (error) {
+				mem_cgroup_cancel_charge(page, memcg, false);
+				delete_from_swap_cache(page);
+			}
+		}
+		if (error)
+			goto failed;
+
+		mem_cgroup_commit_charge(page, memcg, true, false);
+
+		spin_lock_irq(&info->lock);
+		info->swapped--;
+		shmem_recalc_inode(inode);
+		spin_unlock_irq(&info->lock);
+
+		if (sgp == SGP_WRITE)
+			mark_page_accessed(page);
+
+		delete_from_swap_cache(page);
+		set_page_dirty(page);
+		swap_free(swap);
+
+	} else {
+		if (vma && userfaultfd_missing(vma)) {
+			*fault_type = handle_userfault(vmf, VM_UFFD_MISSING);
+			return 0;
+		}
+
+		/* shmem_symlink() */
+		if (mapping->a_ops != &shmem_aops)
+			goto alloc_nohuge;
+		if (shmem_huge == SHMEM_HUGE_DENY || sgp_huge == SGP_NOHUGE)
+			goto alloc_nohuge;
+		if (shmem_huge == SHMEM_HUGE_FORCE)
+			goto alloc_huge;
+		switch (sbinfo->huge) {
+			loff_t i_size;
+			pgoff_t off;
+		case SHMEM_HUGE_NEVER:
+			goto alloc_nohuge;
+		case SHMEM_HUGE_WITHIN_SIZE:
+			off = round_up(index, HPAGE_PMD_NR);
+			i_size = round_up(i_size_read(inode), PAGE_SIZE);
+			if (i_size >= HPAGE_PMD_SIZE &&
+					i_size >> PAGE_SHIFT >= off)
+				goto alloc_huge;
+			/* fallthrough */
+		case SHMEM_HUGE_ADVISE:
+			if (sgp_huge == SGP_HUGE)
+				goto alloc_huge;
+			/* TODO: implement fadvise() hints */
+			goto alloc_nohuge;
+		}
+
+alloc_huge:
+		page = shmem_alloc_and_acct_page(gfp, inode, index, true);
+		if (IS_ERR(page)) {
+alloc_nohuge:		page = shmem_alloc_and_acct_page(gfp, inode,
+					index, false);
+		}
+		if (IS_ERR(page)) {
+			int retry = 5;
+			error = PTR_ERR(page);
+			page = NULL;
+			if (error != -ENOSPC)
+				goto failed;
+			/*
+			 * Try to reclaim some spece by splitting a huge page
+			 * beyond i_size on the filesystem.
+			 */
+			while (retry--) {
+				int ret;
+				ret = shmem_unused_huge_shrink(sbinfo, NULL, 1);
+				if (ret == SHRINK_STOP)
+					break;
+				if (ret)
+					goto alloc_nohuge;
+			}
+			goto failed;
+		}
+
+		if (PageTransHuge(page))
+			hindex = round_down(index, HPAGE_PMD_NR);
+		else
+			hindex = index;
+
+		if (sgp == SGP_WRITE)
+			__SetPageReferenced(page);
+
+		error = mem_cgroup_try_charge_delay(page, charge_mm, gfp, &memcg,
+				PageTransHuge(page));
+		if (error)
+			goto unacct;
+		error = radix_tree_maybe_preload_order(gfp & GFP_RECLAIM_MASK,
+				compound_order(page));
+		if (!error) {
+			error = shmem_add_to_page_cache(page, mapping, hindex,
+							NULL);
+			radix_tree_preload_end();
+		}
+		if (error) {
+			mem_cgroup_cancel_charge(page, memcg,
+					PageTransHuge(page));
+			goto unacct;
+		}
+		mem_cgroup_commit_charge(page, memcg, false,
+				PageTransHuge(page));
+		lru_cache_add_anon(page);
+
+		spin_lock_irq(&info->lock);
+		info->alloced += 1 << compound_order(page);
+		inode->i_blocks += BLOCKS_PER_PAGE << compound_order(page);
+		shmem_recalc_inode(inode);
+		spin_unlock_irq(&info->lock);
+		alloced = true;
+
+		if (PageTransHuge(page) &&
+				DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE) <
+				hindex + HPAGE_PMD_NR - 1) {
+			/*
+			 * Part of the huge page is beyond i_size: subject
+			 * to shrink under memory pressure.
+			 */
+			spin_lock(&sbinfo->shrinklist_lock);
+			/*
+			 * _careful to defend against unlocked access to
+			 * ->shrink_list in shmem_unused_huge_shrink()
+			 */
+			if (list_empty_careful(&info->shrinklist)) {
+				list_add_tail(&info->shrinklist,
+						&sbinfo->shrinklist);
+				sbinfo->shrinklist_len++;
+			}
+			spin_unlock(&sbinfo->shrinklist_lock);
+		}
+
+		/*
+		 * Let SGP_FALLOC use the SGP_WRITE optimization on a new page.
+		 */
+		if (sgp == SGP_FALLOC)
+			sgp = SGP_WRITE;
+clear:
+		/*
+		 * Let SGP_WRITE caller clear ends if write does not fill page;
+		 * but SGP_FALLOC on a page fallocated earlier must initialize
+		 * it now, lest undo on failure cancel our earlier guarantee.
+		 */
+		if (sgp != SGP_WRITE && !PageUptodate(page)) {
+			struct page *head = compound_head(page);
+			int i;
+
+			for (i = 0; i < (1 << compound_order(head)); i++) {
+				clear_highpage(head + i);
+				flush_dcache_page(head + i);
+			}
+			SetPageUptodate(head);
+		}
+	}
+
+	/* Perhaps the file has been truncated since we checked */
+	if (sgp <= SGP_CACHE &&
+	    ((loff_t)index << PAGE_SHIFT) >= i_size_read(inode)) {
+		if (alloced) {
+			ClearPageDirty(page);
+			delete_from_page_cache(page);
+			spin_lock_irq(&info->lock);
+			shmem_recalc_inode(inode);
+			spin_unlock_irq(&info->lock);
+		}
+		error = -EINVAL;
+		goto unlock;
+	}
+	*pagep = page + index - hindex;
+	return 0;
+
+	/*
+	 * Error recovery.
+	 */
+unacct:
+	shmem_inode_unacct_blocks(inode, 1 << compound_order(page));
+
+	if (PageTransHuge(page)) {
+		unlock_page(page);
+		put_page(page);
+		goto alloc_nohuge;
+	}
+failed:
+	if (swap.val && !shmem_confirm_swap(mapping, index, swap))
+		error = -EEXIST;
+unlock:
+	if (page) {
+		unlock_page(page);
+		put_page(page);
+	}
+	if (error == -ENOSPC && !once++) {
+		spin_lock_irq(&info->lock);
+		shmem_recalc_inode(inode);
+		spin_unlock_irq(&info->lock);
+		goto repeat;
+	}
+	if (error == -EEXIST)	/* from above or from radix_tree_insert */
+		goto repeat;
+	return error;
+}
+
+/*
+ * This is like autoremove_wake_function, but it removes the wait queue
+ * entry unconditionally - even if something else had already woken the
+ * target.
+ */
+static int synchronous_wake_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
+{
+	int ret = default_wake_function(wait, mode, sync, key);
+	list_del_init(&wait->entry);
+	return ret;
+}
+
+static vm_fault_t shmem_fault(struct vm_fault *vmf)
+{
+	struct vm_area_struct *vma = vmf->vma;
+	struct inode *inode = file_inode(vma->vm_file);
+	gfp_t gfp = mapping_gfp_mask(inode->i_mapping);
+	enum sgp_type sgp;
+	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_mutex.  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_mutex 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) {
+			wait_queue_head_t *shmem_falloc_waitq;
+			DEFINE_WAIT_FUNC(shmem_fault_wait, synchronous_wake_function);
+
+			ret = VM_FAULT_NOPAGE;
+			if ((vmf->flags & FAULT_FLAG_ALLOW_RETRY) &&
+			   !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT)) {
+				/* It's polite to up mmap_sem if we can */
+				up_read(&vma->vm_mm->mmap_sem);
+				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);
+			return ret;
+		}
+		spin_unlock(&inode->i_lock);
+	}
+
+	sgp = SGP_CACHE;
+
+	if ((vma->vm_flags & VM_NOHUGEPAGE) ||
+	    test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))
+		sgp = SGP_NOHUGE;
+	else if (vma->vm_flags & VM_HUGEPAGE)
+		sgp = SGP_HUGE;
+
+	err = shmem_getpage_gfp(inode, vmf->pgoff, &vmf->page, sgp,
+				  gfp, vma, vmf, &ret);
+	if (err)
+		return vmf_error(err);
+	return ret;
+}
+
+unsigned long shmem_get_unmapped_area(struct file *file,
+				      unsigned long uaddr, unsigned long len,
+				      unsigned long pgoff, unsigned long flags)
+{
+	unsigned long (*get_area)(struct file *,
+		unsigned long, unsigned long, unsigned long, unsigned long);
+	unsigned long addr;
+	unsigned long offset;
+	unsigned long inflated_len;
+	unsigned long inflated_addr;
+	unsigned long inflated_offset;
+
+	if (len > TASK_SIZE)
+		return -ENOMEM;
+
+	get_area = current->mm->get_unmapped_area;
+	addr = get_area(file, uaddr, len, pgoff, flags);
+
+	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE))
+		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 user_struct *user)
+{
+	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, user))
+			goto out_nomem;
+		info->flags |= VM_LOCKED;
+		mapping_set_unevictable(file->f_mapping);
+	}
+	if (!lock && (info->flags & VM_LOCKED) && user) {
+		user_shm_unlock(inode->i_size, user);
+		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)
+{
+	file_accessed(file);
+	vma->vm_ops = &shmem_vm_ops;
+	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE) &&
+			((vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK) <
+			(vma->vm_end & HPAGE_PMD_MASK)) {
+		khugepaged_enter(vma, vma->vm_flags);
+	}
+	return 0;
+}
+
+static struct inode *shmem_get_inode(struct super_block *sb, const 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);
+
+	if (shmem_reserve_inode(sb))
+		return NULL;
+
+	inode = new_inode(sb);
+	if (inode) {
+		inode->i_ino = get_next_ino();
+		inode_init_owner(inode, dir, mode);
+		inode->i_blocks = 0;
+		inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
+		inode->i_generation = prandom_u32();
+		info = SHMEM_I(inode);
+		memset(info, 0, (char *)inode - (char *)info);
+		spin_lock_init(&info->lock);
+		info->seals = F_SEAL_SEAL;
+		info->flags = flags & VM_NORESERVE;
+		INIT_LIST_HEAD(&info->shrinklist);
+		INIT_LIST_HEAD(&info->swaplist);
+		simple_xattrs_init(&info->xattrs);
+		cache_no_acl(inode);
+
+		switch (mode & S_IFMT) {
+		default:
+			inode->i_op = &shmem_special_inode_operations;
+			init_special_inode(inode, mode, dev);
+			break;
+		case S_IFREG:
+			inode->i_mapping->a_ops = &shmem_aops;
+			inode->i_op = &shmem_inode_operations;
+			inode->i_fop = &shmem_file_operations;
+			mpol_shared_policy_init(&info->policy,
+						 shmem_get_sbmpol(sbinfo));
+			break;
+		case S_IFDIR:
+			inc_nlink(inode);
+			/* Some things misbehave if size == 0 on a directory */
+			inode->i_size = 2 * BOGO_DIRENT_SIZE;
+			inode->i_op = &shmem_dir_inode_operations;
+			inode->i_fop = &simple_dir_operations;
+			break;
+		case S_IFLNK:
+			/*
+			 * Must not load anything in the rbtree,
+			 * mpol_free_shared_policy will not be called.
+			 */
+			mpol_shared_policy_init(&info->policy, NULL);
+			break;
+		}
+
+		lockdep_annotate_inode_mutex_key(inode);
+	} else
+		shmem_free_inode(sb);
+	return inode;
+}
+
+bool shmem_mapping(struct address_space *mapping)
+{
+	return mapping->a_ops == &shmem_aops;
+}
+
+static int shmem_mfill_atomic_pte(struct mm_struct *dst_mm,
+				  pmd_t *dst_pmd,
+				  struct vm_area_struct *dst_vma,
+				  unsigned long dst_addr,
+				  unsigned long src_addr,
+				  bool zeropage,
+				  struct page **pagep)
+{
+	struct inode *inode = file_inode(dst_vma->vm_file);
+	struct shmem_inode_info *info = SHMEM_I(inode);
+	struct address_space *mapping = inode->i_mapping;
+	gfp_t gfp = mapping_gfp_mask(mapping);
+	pgoff_t pgoff = linear_page_index(dst_vma, dst_addr);
+	struct mem_cgroup *memcg;
+	spinlock_t *ptl;
+	void *page_kaddr;
+	struct page *page;
+	pte_t _dst_pte, *dst_pte;
+	int ret;
+	pgoff_t offset, max_off;
+
+	ret = -ENOMEM;
+	if (!shmem_inode_acct_block(inode, 1)) {
+		/*
+		 * We may have got a page, returned -ENOENT triggering a retry,
+		 * and now we find ourselves with -ENOMEM. Release the page, to
+		 * avoid a BUG_ON in our caller.
+		 */
+		if (unlikely(*pagep)) {
+			put_page(*pagep);
+			*pagep = NULL;
+		}
+		goto out;
+	}
+
+	if (!*pagep) {
+		page = shmem_alloc_page(gfp, info, pgoff);
+		if (!page)
+			goto out_unacct_blocks;
+
+		if (!zeropage) {	/* mcopy_atomic */
+			page_kaddr = kmap_atomic(page);
+			ret = copy_from_user(page_kaddr,
+					     (const void __user *)src_addr,
+					     PAGE_SIZE);
+			kunmap_atomic(page_kaddr);
+
+			/* fallback to copy_from_user outside mmap_sem */
+			if (unlikely(ret)) {
+				*pagep = page;
+				shmem_inode_unacct_blocks(inode, 1);
+				/* don't free the page */
+				return -ENOENT;
+			}
+		} else {		/* mfill_zeropage_atomic */
+			clear_highpage(page);
+		}
+	} else {
+		page = *pagep;
+		*pagep = NULL;
+	}
+
+	VM_BUG_ON(PageLocked(page) || PageSwapBacked(page));
+	__SetPageLocked(page);
+	__SetPageSwapBacked(page);
+	__SetPageUptodate(page);
+
+	ret = -EFAULT;
+	offset = linear_page_index(dst_vma, dst_addr);
+	max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
+	if (unlikely(offset >= max_off))
+		goto out_release;
+
+	ret = mem_cgroup_try_charge_delay(page, dst_mm, gfp, &memcg, false);
+	if (ret)
+		goto out_release;
+
+	ret = radix_tree_maybe_preload(gfp & GFP_RECLAIM_MASK);
+	if (!ret) {
+		ret = shmem_add_to_page_cache(page, mapping, pgoff, NULL);
+		radix_tree_preload_end();
+	}
+	if (ret)
+		goto out_release_uncharge;
+
+	mem_cgroup_commit_charge(page, memcg, false, false);
+
+	_dst_pte = mk_pte(page, dst_vma->vm_page_prot);
+	if (dst_vma->vm_flags & VM_WRITE)
+		_dst_pte = pte_mkwrite(pte_mkdirty(_dst_pte));
+	else {
+		/*
+		 * We don't set the pte dirty if the vma has no
+		 * VM_WRITE permission, so mark the page dirty or it
+		 * could be freed from under us. We could do it
+		 * unconditionally before unlock_page(), but doing it
+		 * only if VM_WRITE is not set is faster.
+		 */
+		set_page_dirty(page);
+	}
+
+	dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
+
+	ret = -EFAULT;
+	max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
+	if (unlikely(offset >= max_off))
+		goto out_release_uncharge_unlock;
+
+	ret = -EEXIST;
+	if (!pte_none(*dst_pte))
+		goto out_release_uncharge_unlock;
+
+	lru_cache_add_anon(page);
+
+	spin_lock_irq(&info->lock);
+	info->alloced++;
+	inode->i_blocks += BLOCKS_PER_PAGE;
+	shmem_recalc_inode(inode);
+	spin_unlock_irq(&info->lock);
+
+	inc_mm_counter(dst_mm, mm_counter_file(page));
+	page_add_file_rmap(page, false);
+	set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
+
+	/* No need to invalidate - it was non-present before */
+	update_mmu_cache(dst_vma, dst_addr, dst_pte);
+	pte_unmap_unlock(dst_pte, ptl);
+	unlock_page(page);
+	ret = 0;
+out:
+	return ret;
+out_release_uncharge_unlock:
+	pte_unmap_unlock(dst_pte, ptl);
+	ClearPageDirty(page);
+	delete_from_page_cache(page);
+out_release_uncharge:
+	mem_cgroup_cancel_charge(page, memcg, false);
+out_release:
+	unlock_page(page);
+	put_page(page);
+out_unacct_blocks:
+	shmem_inode_unacct_blocks(inode, 1);
+	goto out;
+}
+
+int shmem_mcopy_atomic_pte(struct mm_struct *dst_mm,
+			   pmd_t *dst_pmd,
+			   struct vm_area_struct *dst_vma,
+			   unsigned long dst_addr,
+			   unsigned long src_addr,
+			   struct page **pagep)
+{
+	return shmem_mfill_atomic_pte(dst_mm, dst_pmd, dst_vma,
+				      dst_addr, src_addr, false, pagep);
+}
+
+int shmem_mfill_zeropage_pte(struct mm_struct *dst_mm,
+			     pmd_t *dst_pmd,
+			     struct vm_area_struct *dst_vma,
+			     unsigned long dst_addr)
+{
+	struct page *page = NULL;
+
+	return shmem_mfill_atomic_pte(dst_mm, dst_pmd, dst_vma,
+				      dst_addr, 0, true, &page);
+}
+
+#ifdef CONFIG_TMPFS
+static const struct inode_operations shmem_symlink_inode_operations;
+static const struct inode_operations shmem_short_symlink_operations;
+
+#ifdef CONFIG_TMPFS_XATTR
+static int shmem_initxattrs(struct inode *, const struct xattr *, void *);
+#else
+#define shmem_initxattrs NULL
+#endif
+
+static int
+shmem_write_begin(struct file *file, struct address_space *mapping,
+			loff_t pos, unsigned len, unsigned flags,
+			struct page **pagep, void **fsdata)
+{
+	struct inode *inode = mapping->host;
+	struct shmem_inode_info *info = SHMEM_I(inode);
+	pgoff_t index = pos >> PAGE_SHIFT;
+
+	/* i_mutex is held by caller */
+	if (unlikely(info->seals & (F_SEAL_WRITE | F_SEAL_GROW))) {
+		if (info->seals & F_SEAL_WRITE)
+			return -EPERM;
+		if ((info->seals & F_SEAL_GROW) && pos + len > inode->i_size)
+			return -EPERM;
+	}
+
+	return shmem_getpage(inode, index, pagep, SGP_WRITE);
+}
+
+static int
+shmem_write_end(struct file *file, struct address_space *mapping,
+			loff_t pos, unsigned len, unsigned copied,
+			struct page *page, void *fsdata)
+{
+	struct inode *inode = mapping->host;
+
+	if (pos + copied > inode->i_size)
+		i_size_write(inode, pos + copied);
+
+	if (!PageUptodate(page)) {
+		struct page *head = compound_head(page);
+		if (PageTransCompound(page)) {
+			int i;
+
+			for (i = 0; i < HPAGE_PMD_NR; i++) {
+				if (head + i == page)
+					continue;
+				clear_highpage(head + i);
+				flush_dcache_page(head + i);
+			}
+		}
+		if (copied < PAGE_SIZE) {
+			unsigned from = pos & (PAGE_SIZE - 1);
+			zero_user_segments(page, 0, from,
+					from + copied, PAGE_SIZE);
+		}
+		SetPageUptodate(head);
+	}
+	set_page_dirty(page);
+	unlock_page(page);
+	put_page(page);
+
+	return copied;
+}
+
+static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
+{
+	struct file *file = iocb->ki_filp;
+	struct inode *inode = file_inode(file);
+	struct address_space *mapping = inode->i_mapping;
+	pgoff_t index;
+	unsigned long offset;
+	enum sgp_type sgp = SGP_READ;
+	int error = 0;
+	ssize_t retval = 0;
+	loff_t *ppos = &iocb->ki_pos;
+
+	/*
+	 * Might this read be for a stacking filesystem?  Then when reading
+	 * holes of a sparse file, we actually need to allocate those pages,
+	 * and even mark them dirty, so it cannot exceed the max_blocks limit.
+	 */
+	if (!iter_is_iovec(to))
+		sgp = SGP_CACHE;
+
+	index = *ppos >> PAGE_SHIFT;
+	offset = *ppos & ~PAGE_MASK;
+
+	for (;;) {
+		struct page *page = NULL;
+		pgoff_t end_index;
+		unsigned long nr, ret;
+		loff_t i_size = i_size_read(inode);
+
+		end_index = i_size >> PAGE_SHIFT;
+		if (index > end_index)
+			break;
+		if (index == end_index) {
+			nr = i_size & ~PAGE_MASK;
+			if (nr <= offset)
+				break;
+		}
+
+		error = shmem_getpage(inode, index, &page, sgp);
+		if (error) {
+			if (error == -EINVAL)
+				error = 0;
+			break;
+		}
+		if (page) {
+			if (sgp == SGP_CACHE)
+				set_page_dirty(page);
+			unlock_page(page);
+		}
+
+		/*
+		 * We must evaluate after, since reads (unlike writes)
+		 * are called without i_mutex protection against truncate
+		 */
+		nr = PAGE_SIZE;
+		i_size = i_size_read(inode);
+		end_index = i_size >> PAGE_SHIFT;
+		if (index == end_index) {
+			nr = i_size & ~PAGE_MASK;
+			if (nr <= offset) {
+				if (page)
+					put_page(page);
+				break;
+			}
+		}
+		nr -= offset;
+
+		if (page) {
+			/*
+			 * If users can be writing to this page using arbitrary
+			 * virtual addresses, take care about potential aliasing
+			 * before reading the page on the kernel side.
+			 */
+			if (mapping_writably_mapped(mapping))
+				flush_dcache_page(page);
+			/*
+			 * Mark the page accessed if we read the beginning.
+			 */
+			if (!offset)
+				mark_page_accessed(page);
+		} else {
+			page = ZERO_PAGE(0);
+			get_page(page);
+		}
+
+		/*
+		 * Ok, we have the page, and it's up-to-date, so
+		 * now we can copy it to user space...
+		 */
+		ret = copy_page_to_iter(page, offset, nr, to);
+		retval += ret;
+		offset += ret;
+		index += offset >> PAGE_SHIFT;
+		offset &= ~PAGE_MASK;
+
+		put_page(page);
+		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;
+}
+
+/*
+ * llseek SEEK_DATA or SEEK_HOLE through the radix_tree.
+ */
+static pgoff_t shmem_seek_hole_data(struct address_space *mapping,
+				    pgoff_t index, pgoff_t end, int whence)
+{
+	struct page *page;
+	struct pagevec pvec;
+	pgoff_t indices[PAGEVEC_SIZE];
+	bool done = false;
+	int i;
+
+	pagevec_init(&pvec);
+	pvec.nr = 1;		/* start small: we may be there already */
+	while (!done) {
+		pvec.nr = find_get_entries(mapping, index,
+					pvec.nr, pvec.pages, indices);
+		if (!pvec.nr) {
+			if (whence == SEEK_DATA)
+				index = end;
+			break;
+		}
+		for (i = 0; i < pvec.nr; i++, index++) {
+			if (index < indices[i]) {
+				if (whence == SEEK_HOLE) {
+					done = true;
+					break;
+				}
+				index = indices[i];
+			}
+			page = pvec.pages[i];
+			if (page && !radix_tree_exceptional_entry(page)) {
+				if (!PageUptodate(page))
+					page = NULL;
+			}
+			if (index >= end ||
+			    (page && whence == SEEK_DATA) ||
+			    (!page && whence == SEEK_HOLE)) {
+				done = true;
+				break;
+			}
+		}
+		pagevec_remove_exceptionals(&pvec);
+		pagevec_release(&pvec);
+		pvec.nr = PAGEVEC_SIZE;
+		cond_resched();
+	}
+	return index;
+}
+
+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;
+	pgoff_t start, end;
+	loff_t new_offset;
+
+	if (whence != SEEK_DATA && whence != SEEK_HOLE)
+		return generic_file_llseek_size(file, offset, whence,
+					MAX_LFS_FILESIZE, i_size_read(inode));
+	inode_lock(inode);
+	/* We're holding i_mutex so we can access i_size directly */
+
+	if (offset < 0 || offset >= inode->i_size)
+		offset = -ENXIO;
+	else {
+		start = offset >> PAGE_SHIFT;
+		end = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
+		new_offset = shmem_seek_hole_data(mapping, start, end, whence);
+		new_offset <<= PAGE_SHIFT;
+		if (new_offset > offset) {
+			if (new_offset < inode->i_size)
+				offset = new_offset;
+			else if (whence == SEEK_DATA)
+				offset = -ENXIO;
+			else
+				offset = inode->i_size;
+		}
+	}
+
+	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;
+	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_mutex */
+		if (info->seals & F_SEAL_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);
+
+	for (index = start; index < end; index++) {
+		struct page *page;
+
+		/*
+		 * Good, the fallocate(2) manpage permits EINTR: we may have
+		 * been interrupted because we are using up too much memory.
+		 */
+		if (signal_pending(current))
+			error = -EINTR;
+		else if (shmem_falloc.nr_unswapped > shmem_falloc.nr_falloced)
+			error = -ENOMEM;
+		else
+			error = shmem_getpage(inode, index, &page, SGP_FALLOC);
+		if (error) {
+			/* Remove the !PageUptodate pages we added */
+			if (index > start) {
+				shmem_undo_range(inode,
+				    (loff_t)start << PAGE_SHIFT,
+				    ((loff_t)index << PAGE_SHIFT) - 1, true);
+			}
+			goto undone;
+		}
+
+		/*
+		 * Inform shmem_writepage() how far we have reached.
+		 * No need for lock or barrier: we have the page lock.
+		 */
+		shmem_falloc.next++;
+		if (!PageUptodate(page))
+			shmem_falloc.nr_falloced++;
+
+		/*
+		 * If !PageUptodate, leave it that way so that freeable pages
+		 * can be recognized if we need to rollback on error later.
+		 * But set_page_dirty so that memory pressure will swap rather
+		 * than free the pages we are allocating (and SGP_CACHE pages
+		 * might still be clean: we now need to mark those dirty too).
+		 */
+		set_page_dirty(page);
+		unlock_page(page);
+		put_page(page);
+		cond_resched();
+	}
+
+	if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size)
+		i_size_write(inode, offset + len);
+	inode->i_ctime = current_time(inode);
+undone:
+	spin_lock(&inode->i_lock);
+	inode->i_private = NULL;
+	spin_unlock(&inode->i_lock);
+out:
+	inode_unlock(inode);
+	return error;
+}
+
+static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
+{
+	struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
+
+	buf->f_type = TMPFS_MAGIC;
+	buf->f_bsize = PAGE_SIZE;
+	buf->f_namelen = NAME_MAX;
+	if (sbinfo->max_blocks) {
+		buf->f_blocks = sbinfo->max_blocks;
+		buf->f_bavail =
+		buf->f_bfree  = sbinfo->max_blocks -
+				percpu_counter_sum(&sbinfo->used_blocks);
+	}
+	if (sbinfo->max_inodes) {
+		buf->f_files = sbinfo->max_inodes;
+		buf->f_ffree = sbinfo->free_inodes;
+	}
+	/* else leave those fields 0 like simple_statfs */
+	return 0;
+}
+
+/*
+ * File creation. Allocate an inode, and we're done..
+ */
+static int
+shmem_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
+{
+	struct inode *inode;
+	int error = -ENOSPC;
+
+	inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE);
+	if (inode) {
+		error = simple_acl_create(dir, inode);
+		if (error)
+			goto out_iput;
+		error = security_inode_init_security(inode, dir,
+						     &dentry->d_name,
+						     shmem_initxattrs, NULL);
+		if (error && error != -EOPNOTSUPP)
+			goto out_iput;
+
+		error = 0;
+		dir->i_size += BOGO_DIRENT_SIZE;
+		dir->i_ctime = dir->i_mtime = current_time(dir);
+		d_instantiate(dentry, inode);
+		dget(dentry); /* Extra count - pin the dentry in core */
+	}
+	return error;
+out_iput:
+	iput(inode);
+	return error;
+}
+
+static int
+shmem_tmpfile(struct inode *dir, struct dentry *dentry, umode_t mode)
+{
+	struct inode *inode;
+	int error = -ENOSPC;
+
+	inode = shmem_get_inode(dir->i_sb, dir, mode, 0, VM_NORESERVE);
+	if (inode) {
+		error = security_inode_init_security(inode, dir,
+						     NULL,
+						     shmem_initxattrs, NULL);
+		if (error && error != -EOPNOTSUPP)
+			goto out_iput;
+		error = simple_acl_create(dir, inode);
+		if (error)
+			goto out_iput;
+		d_tmpfile(dentry, inode);
+	}
+	return error;
+out_iput:
+	iput(inode);
+	return error;
+}
+
+static int shmem_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
+{
+	int error;
+
+	if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
+		return error;
+	inc_nlink(dir);
+	return 0;
+}
+
+static int shmem_create(struct inode *dir, struct dentry *dentry, umode_t mode,
+		bool excl)
+{
+	return shmem_mknod(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);
+		if (ret)
+			goto out;
+	}
+
+	dir->i_size += BOGO_DIRENT_SIZE;
+	inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
+	inc_nlink(inode);
+	ihold(inode);	/* New dentry reference */
+	dget(dentry);		/* Extra pinning count for the created dentry */
+	d_instantiate(dentry, inode);
+out:
+	return ret;
+}
+
+static int shmem_unlink(struct inode *dir, struct dentry *dentry)
+{
+	struct inode *inode = d_inode(dentry);
+
+	if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
+		shmem_free_inode(inode->i_sb);
+
+	dir->i_size -= BOGO_DIRENT_SIZE;
+	inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
+	drop_nlink(inode);
+	dput(dentry);	/* Undo the count from "create" - this does all the work */
+	return 0;
+}
+
+static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
+{
+	if (!simple_empty(dentry))
+		return -ENOTEMPTY;
+
+	drop_nlink(d_inode(dentry));
+	drop_nlink(dir);
+	return shmem_unlink(dir, dentry);
+}
+
+static int shmem_exchange(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
+{
+	bool old_is_dir = d_is_dir(old_dentry);
+	bool new_is_dir = d_is_dir(new_dentry);
+
+	if (old_dir != new_dir && old_is_dir != new_is_dir) {
+		if (old_is_dir) {
+			drop_nlink(old_dir);
+			inc_nlink(new_dir);
+		} else {
+			drop_nlink(new_dir);
+			inc_nlink(old_dir);
+		}
+	}
+	old_dir->i_ctime = old_dir->i_mtime =
+	new_dir->i_ctime = new_dir->i_mtime =
+	d_inode(old_dentry)->i_ctime =
+	d_inode(new_dentry)->i_ctime = current_time(old_dir);
+
+	return 0;
+}
+
+static int shmem_whiteout(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(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 inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry, unsigned int flags)
+{
+	struct inode *inode = d_inode(old_dentry);
+	int they_are_dirs = S_ISDIR(inode->i_mode);
+
+	if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
+		return -EINVAL;
+
+	if (flags & RENAME_EXCHANGE)
+		return shmem_exchange(old_dir, old_dentry, new_dir, new_dentry);
+
+	if (!simple_empty(new_dentry))
+		return -ENOTEMPTY;
+
+	if (flags & RENAME_WHITEOUT) {
+		int error;
+
+		error = shmem_whiteout(old_dir, old_dentry);
+		if (error)
+			return error;
+	}
+
+	if (d_really_is_positive(new_dentry)) {
+		(void) shmem_unlink(new_dir, new_dentry);
+		if (they_are_dirs) {
+			drop_nlink(d_inode(new_dentry));
+			drop_nlink(old_dir);
+		}
+	} else if (they_are_dirs) {
+		drop_nlink(old_dir);
+		inc_nlink(new_dir);
+	}
+
+	old_dir->i_size -= BOGO_DIRENT_SIZE;
+	new_dir->i_size += BOGO_DIRENT_SIZE;
+	old_dir->i_ctime = old_dir->i_mtime =
+	new_dir->i_ctime = new_dir->i_mtime =
+	inode->i_ctime = current_time(old_dir);
+	return 0;
+}
+
+static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
+{
+	int error;
+	int len;
+	struct inode *inode;
+	struct page *page;
+
+	len = strlen(symname) + 1;
+	if (len > PAGE_SIZE)
+		return -ENAMETOOLONG;
+
+	inode = shmem_get_inode(dir->i_sb, dir, S_IFLNK | 0777, 0,
+				VM_NORESERVE);
+	if (!inode)
+		return -ENOSPC;
+
+	error = security_inode_init_security(inode, dir, &dentry->d_name,
+					     shmem_initxattrs, NULL);
+	if (error) {
+		if (error != -EOPNOTSUPP) {
+			iput(inode);
+			return error;
+		}
+		error = 0;
+	}
+
+	inode->i_size = len-1;
+	if (len <= SHORT_SYMLINK_LEN) {
+		inode->i_link = kmemdup(symname, len, GFP_KERNEL);
+		if (!inode->i_link) {
+			iput(inode);
+			return -ENOMEM;
+		}
+		inode->i_op = &shmem_short_symlink_operations;
+	} else {
+		inode_nohighmem(inode);
+		error = shmem_getpage(inode, 0, &page, SGP_WRITE);
+		if (error) {
+			iput(inode);
+			return error;
+		}
+		inode->i_mapping->a_ops = &shmem_aops;
+		inode->i_op = &shmem_symlink_inode_operations;
+		memcpy(page_address(page), symname, len);
+		SetPageUptodate(page);
+		set_page_dirty(page);
+		unlock_page(page);
+		put_page(page);
+	}
+	dir->i_size += BOGO_DIRENT_SIZE;
+	dir->i_ctime = dir->i_mtime = current_time(dir);
+	d_instantiate(dentry, inode);
+	dget(dentry);
+	return 0;
+}
+
+static void shmem_put_link(void *arg)
+{
+	mark_page_accessed(arg);
+	put_page(arg);
+}
+
+static const char *shmem_get_link(struct dentry *dentry,
+				  struct inode *inode,
+				  struct delayed_call *done)
+{
+	struct page *page = NULL;
+	int error;
+	if (!dentry) {
+		page = find_get_page(inode->i_mapping, 0);
+		if (!page)
+			return ERR_PTR(-ECHILD);
+		if (!PageUptodate(page)) {
+			put_page(page);
+			return ERR_PTR(-ECHILD);
+		}
+	} else {
+		error = shmem_getpage(inode, 0, &page, SGP_READ);
+		if (error)
+			return ERR_PTR(error);
+		unlock_page(page);
+	}
+	set_delayed_call(done, shmem_put_link, page);
+	return page_address(page);
+}
+
+#ifdef CONFIG_TMPFS_XATTR
+/*
+ * Superblocks without xattr inode operations may get some security.* xattr
+ * support from the LSM "for free". As soon as we have any other xattrs
+ * like ACLs, we also need to implement the security.* handlers at
+ * filesystem level, though.
+ */
+
+/*
+ * Callback for security_inode_init_security() for acquiring xattrs.
+ */
+static int shmem_initxattrs(struct inode *inode,
+			    const struct xattr *xattr_array,
+			    void *fs_info)
+{
+	struct shmem_inode_info *info = SHMEM_I(inode);
+	const struct xattr *xattr;
+	struct simple_xattr *new_xattr;
+	size_t len;
+
+	for (xattr = xattr_array; xattr->name != NULL; xattr++) {
+		new_xattr = simple_xattr_alloc(xattr->value, xattr->value_len);
+		if (!new_xattr)
+			return -ENOMEM;
+
+		len = strlen(xattr->name) + 1;
+		new_xattr->name = kmalloc(XATTR_SECURITY_PREFIX_LEN + len,
+					  GFP_KERNEL);
+		if (!new_xattr->name) {
+			kfree(new_xattr);
+			return -ENOMEM;
+		}
+
+		memcpy(new_xattr->name, XATTR_SECURITY_PREFIX,
+		       XATTR_SECURITY_PREFIX_LEN);
+		memcpy(new_xattr->name + XATTR_SECURITY_PREFIX_LEN,
+		       xattr->name, len);
+
+		simple_xattr_list_add(&info->xattrs, new_xattr);
+	}
+
+	return 0;
+}
+
+static int shmem_xattr_handler_get(const struct xattr_handler *handler,
+				   struct dentry *unused, struct inode *inode,
+				   const char *name, void *buffer, size_t size)
+{
+	struct shmem_inode_info *info = SHMEM_I(inode);
+
+	name = xattr_full_name(handler, name);
+	return simple_xattr_get(&info->xattrs, name, buffer, size);
+}
+
+static int shmem_xattr_handler_set(const struct xattr_handler *handler,
+				   struct dentry *unused, struct inode *inode,
+				   const char *name, const void *value,
+				   size_t size, int flags)
+{
+	struct shmem_inode_info *info = SHMEM_I(inode);
+
+	name = xattr_full_name(handler, name);
+	return simple_xattr_set(&info->xattrs, name, value, size, flags);
+}
+
+static const struct xattr_handler shmem_security_xattr_handler = {
+	.prefix = XATTR_SECURITY_PREFIX,
+	.get = shmem_xattr_handler_get,
+	.set = shmem_xattr_handler_set,
+};
+
+static const struct xattr_handler shmem_trusted_xattr_handler = {
+	.prefix = XATTR_TRUSTED_PREFIX,
+	.get = shmem_xattr_handler_get,
+	.set = shmem_xattr_handler_set,
+};
+
+static const struct xattr_handler *shmem_xattr_handlers[] = {
+#ifdef CONFIG_TMPFS_POSIX_ACL
+	&posix_acl_access_xattr_handler,
+	&posix_acl_default_xattr_handler,
+#endif
+	&shmem_security_xattr_handler,
+	&shmem_trusted_xattr_handler,
+	NULL
+};
+
+static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t size)
+{
+	struct shmem_inode_info *info = SHMEM_I(d_inode(dentry));
+	return simple_xattr_list(d_inode(dentry), &info->xattrs, buffer, size);
+}
+#endif /* CONFIG_TMPFS_XATTR */
+
+static const struct inode_operations shmem_short_symlink_operations = {
+	.get_link	= simple_get_link,
+#ifdef CONFIG_TMPFS_XATTR
+	.listxattr	= shmem_listxattr,
+#endif
+};
+
+static const struct inode_operations shmem_symlink_inode_operations = {
+	.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,
+};
+
+static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
+			       bool remount)
+{
+	char *this_char, *value, *rest;
+	struct mempolicy *mpol = NULL;
+	uid_t uid;
+	gid_t gid;
+
+	while (options != NULL) {
+		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)
+			continue;
+		if ((value = strchr(this_char,'=')) != NULL) {
+			*value++ = 0;
+		} else {
+			pr_err("tmpfs: No value for mount option '%s'\n",
+			       this_char);
+			goto error;
+		}
+
+		if (!strcmp(this_char,"size")) {
+			unsigned long long size;
+			size = memparse(value,&rest);
+			if (*rest == '%') {
+				size <<= PAGE_SHIFT;
+				size *= totalram_pages;
+				do_div(size, 100);
+				rest++;
+			}
+			if (*rest)
+				goto bad_val;
+			sbinfo->max_blocks =
+				DIV_ROUND_UP(size, PAGE_SIZE);
+		} else if (!strcmp(this_char,"nr_blocks")) {
+			sbinfo->max_blocks = memparse(value, &rest);
+			if (*rest)
+				goto bad_val;
+		} else if (!strcmp(this_char,"nr_inodes")) {
+			sbinfo->max_inodes = memparse(value, &rest);
+			if (*rest)
+				goto bad_val;
+		} else if (!strcmp(this_char,"mode")) {
+			if (remount)
+				continue;
+			sbinfo->mode = simple_strtoul(value, &rest, 8) & 07777;
+			if (*rest)
+				goto bad_val;
+		} else if (!strcmp(this_char,"uid")) {
+			if (remount)
+				continue;
+			uid = simple_strtoul(value, &rest, 0);
+			if (*rest)
+				goto bad_val;
+			sbinfo->uid = make_kuid(current_user_ns(), uid);
+			if (!uid_valid(sbinfo->uid))
+				goto bad_val;
+		} else if (!strcmp(this_char,"gid")) {
+			if (remount)
+				continue;
+			gid = simple_strtoul(value, &rest, 0);
+			if (*rest)
+				goto bad_val;
+			sbinfo->gid = make_kgid(current_user_ns(), gid);
+			if (!gid_valid(sbinfo->gid))
+				goto bad_val;
+#ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
+		} else if (!strcmp(this_char, "huge")) {
+			int huge;
+			huge = shmem_parse_huge(value);
+			if (huge < 0)
+				goto bad_val;
+			if (!has_transparent_hugepage() &&
+					huge != SHMEM_HUGE_NEVER)
+				goto bad_val;
+			sbinfo->huge = huge;
+#endif
+#ifdef CONFIG_NUMA
+		} else if (!strcmp(this_char,"mpol")) {
+			mpol_put(mpol);
+			mpol = NULL;
+			if (mpol_parse_str(value, &mpol))
+				goto bad_val;
+#endif
+		} else {
+			pr_err("tmpfs: Bad mount option %s\n", this_char);
+			goto error;
+		}
+	}
+	sbinfo->mpol = mpol;
+	return 0;
+
+bad_val:
+	pr_err("tmpfs: Bad value '%s' for mount option '%s'\n",
+	       value, this_char);
+error:
+	mpol_put(mpol);
+	return 1;
+
+}
+
+static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
+{
+	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
+	struct shmem_sb_info config = *sbinfo;
+	unsigned long inodes;
+	int error = -EINVAL;
+
+	config.mpol = NULL;
+	if (shmem_parse_options(data, &config, true))
+		return error;
+
+	spin_lock(&sbinfo->stat_lock);
+	inodes = sbinfo->max_inodes - sbinfo->free_inodes;
+	if (percpu_counter_compare(&sbinfo->used_blocks, config.max_blocks) > 0)
+		goto out;
+	if (config.max_inodes < inodes)
+		goto out;
+	/*
+	 * Those tests disallow limited->unlimited while any are in use;
+	 * but we must separately disallow unlimited->limited, because
+	 * in that case we have no record of how much is already in use.
+	 */
+	if (config.max_blocks && !sbinfo->max_blocks)
+		goto out;
+	if (config.max_inodes && !sbinfo->max_inodes)
+		goto out;
+
+	error = 0;
+	sbinfo->huge = config.huge;
+	sbinfo->max_blocks  = config.max_blocks;
+	sbinfo->max_inodes  = config.max_inodes;
+	sbinfo->free_inodes = config.max_inodes - inodes;
+
+	/*
+	 * Preserve previous mempolicy unless mpol remount option was specified.
+	 */
+	if (config.mpol) {
+		mpol_put(sbinfo->mpol);
+		sbinfo->mpol = config.mpol;	/* transfers initial ref */
+	}
+out:
+	spin_unlock(&sbinfo->stat_lock);
+	return error;
+}
+
+static int shmem_show_options(struct seq_file *seq, struct dentry *root)
+{
+	struct shmem_sb_info *sbinfo = SHMEM_SB(root->d_sb);
+
+	if (sbinfo->max_blocks != shmem_default_max_blocks())
+		seq_printf(seq, ",size=%luk",
+			sbinfo->max_blocks << (PAGE_SHIFT - 10));
+	if (sbinfo->max_inodes != shmem_default_max_inodes())
+		seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
+	if (sbinfo->mode != (0777 | S_ISVTX))
+		seq_printf(seq, ",mode=%03ho", sbinfo->mode);
+	if (!uid_eq(sbinfo->uid, GLOBAL_ROOT_UID))
+		seq_printf(seq, ",uid=%u",
+				from_kuid_munged(&init_user_ns, sbinfo->uid));
+	if (!gid_eq(sbinfo->gid, GLOBAL_ROOT_GID))
+		seq_printf(seq, ",gid=%u",
+				from_kgid_munged(&init_user_ns, sbinfo->gid));
+#ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
+	/* Rightly or wrongly, show huge mount option unmasked by shmem_huge */
+	if (sbinfo->huge)
+		seq_printf(seq, ",huge=%s", shmem_format_huge(sbinfo->huge));
+#endif
+	shmem_show_mpol(seq, sbinfo->mpol);
+	return 0;
+}
+
+#endif /* CONFIG_TMPFS */
+
+static void shmem_put_super(struct super_block *sb)
+{
+	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
+
+	percpu_counter_destroy(&sbinfo->used_blocks);
+	mpol_put(sbinfo->mpol);
+	kfree(sbinfo);
+	sb->s_fs_info = NULL;
+}
+
+int shmem_fill_super(struct super_block *sb, void *data, int silent)
+{
+	struct inode *inode;
+	struct shmem_sb_info *sbinfo;
+	int err = -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 -ENOMEM;
+
+	sbinfo->mode = 0777 | S_ISVTX;
+	sbinfo->uid = current_fsuid();
+	sbinfo->gid = current_fsgid();
+	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)) {
+		sbinfo->max_blocks = shmem_default_max_blocks();
+		sbinfo->max_inodes = shmem_default_max_inodes();
+		if (shmem_parse_options(data, sbinfo, false)) {
+			err = -EINVAL;
+			goto failed;
+		}
+	} else {
+		sb->s_flags |= SB_NOUSER;
+	}
+	sb->s_export_op = &shmem_export_ops;
+	sb->s_flags |= SB_NOSEC;
+#else
+	sb->s_flags |= SB_NOUSER;
+#endif
+
+	spin_lock_init(&sbinfo->stat_lock);
+	if (percpu_counter_init(&sbinfo->used_blocks, 0, GFP_KERNEL))
+		goto failed;
+	sbinfo->free_inodes = sbinfo->max_inodes;
+	spin_lock_init(&sbinfo->shrinklist_lock);
+	INIT_LIST_HEAD(&sbinfo->shrinklist);
+
+	sb->s_maxbytes = MAX_LFS_FILESIZE;
+	sb->s_blocksize = PAGE_SIZE;
+	sb->s_blocksize_bits = PAGE_SHIFT;
+	sb->s_magic = TMPFS_MAGIC;
+	sb->s_op = &shmem_ops;
+	sb->s_time_gran = 1;
+#ifdef CONFIG_TMPFS_XATTR
+	sb->s_xattr = shmem_xattr_handlers;
+#endif
+#ifdef CONFIG_TMPFS_POSIX_ACL
+	sb->s_flags |= SB_POSIXACL;
+#endif
+	uuid_gen(&sb->s_uuid);
+
+	inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
+	if (!inode)
+		goto failed;
+	inode->i_uid = sbinfo->uid;
+	inode->i_gid = sbinfo->gid;
+	sb->s_root = d_make_root(inode);
+	if (!sb->s_root)
+		goto failed;
+	return 0;
+
+failed:
+	shmem_put_super(sb);
+	return err;
+}
+
+static struct kmem_cache *shmem_inode_cachep;
+
+static struct inode *shmem_alloc_inode(struct super_block *sb)
+{
+	struct shmem_inode_info *info;
+	info = kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
+	if (!info)
+		return NULL;
+	return &info->vfs_inode;
+}
+
+static void shmem_destroy_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	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);
+	call_rcu(&inode->i_rcu, shmem_destroy_callback);
+}
+
+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);
+}
+
+static const struct address_space_operations shmem_aops = {
+	.writepage	= shmem_writepage,
+	.set_page_dirty	= __set_page_dirty_no_writeback,
+#ifdef CONFIG_TMPFS
+	.write_begin	= shmem_write_begin,
+	.write_end	= shmem_write_end,
+#endif
+#ifdef CONFIG_MIGRATION
+	.migratepage	= migrate_page,
+#endif
+	.error_remove_page = generic_error_remove_page,
+};
+
+static const struct file_operations shmem_file_operations = {
+	.mmap		= shmem_mmap,
+	.get_unmapped_area = shmem_get_unmapped_area,
+#ifdef CONFIG_TMPFS
+	.llseek		= shmem_file_llseek,
+	.read_iter	= shmem_file_read_iter,
+	.write_iter	= generic_file_write_iter,
+	.fsync		= noop_fsync,
+	.splice_read	= generic_file_splice_read,
+	.splice_write	= iter_file_splice_write,
+	.fallocate	= shmem_fallocate,
+#endif
+};
+
+static const struct inode_operations shmem_inode_operations = {
+	.getattr	= shmem_getattr,
+	.setattr	= shmem_setattr,
+#ifdef CONFIG_TMPFS_XATTR
+	.listxattr	= shmem_listxattr,
+	.set_acl	= simple_set_acl,
+#endif
+};
+
+static const struct inode_operations shmem_dir_inode_operations = {
+#ifdef CONFIG_TMPFS
+	.create		= shmem_create,
+	.lookup		= simple_lookup,
+	.link		= shmem_link,
+	.unlink		= shmem_unlink,
+	.symlink	= shmem_symlink,
+	.mkdir		= shmem_mkdir,
+	.rmdir		= shmem_rmdir,
+	.mknod		= shmem_mknod,
+	.rename		= shmem_rename2,
+	.tmpfile	= shmem_tmpfile,
+#endif
+#ifdef CONFIG_TMPFS_XATTR
+	.listxattr	= shmem_listxattr,
+#endif
+#ifdef CONFIG_TMPFS_POSIX_ACL
+	.setattr	= shmem_setattr,
+	.set_acl	= simple_set_acl,
+#endif
+};
+
+static const struct inode_operations shmem_special_inode_operations = {
+#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,
+	.destroy_inode	= shmem_destroy_inode,
+#ifdef CONFIG_TMPFS
+	.statfs		= shmem_statfs,
+	.remount_fs	= shmem_remount_fs,
+	.show_options	= shmem_show_options,
+#endif
+	.evict_inode	= shmem_evict_inode,
+	.drop_inode	= generic_delete_inode,
+	.put_super	= shmem_put_super,
+#ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
+	.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 struct dentry *shmem_mount(struct file_system_type *fs_type,
+	int flags, const char *dev_name, void *data)
+{
+	return mount_nodev(fs_type, flags, data, shmem_fill_super);
+}
+
+static struct file_system_type shmem_fs_type = {
+	.owner		= THIS_MODULE,
+	.name		= "tmpfs",
+	.mount		= shmem_mount,
+	.kill_sb	= kill_litter_super,
+	.fs_flags	= FS_USERNS_MOUNT,
+};
+
+int __init shmem_init(void)
+{
+	int error;
+
+	/* If rootfs called this, don't re-init */
+	if (shmem_inode_cachep)
+		return 0;
+
+	shmem_init_inodecache();
+
+	error = register_filesystem(&shmem_fs_type);
+	if (error) {
+		pr_err("Could not register tmpfs\n");
+		goto out2;
+	}
+
+	shm_mnt = kern_mount(&shmem_fs_type);
+	if (IS_ERR(shm_mnt)) {
+		error = PTR_ERR(shm_mnt);
+		pr_err("Could not kern_mount tmpfs\n");
+		goto out1;
+	}
+
+#ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
+	if (has_transparent_hugepage() && shmem_huge > SHMEM_HUGE_DENY)
+		SHMEM_SB(shm_mnt->mnt_sb)->huge = shmem_huge;
+	else
+		shmem_huge = 0; /* just in case it was patched */
+#endif
+	return 0;
+
+out1:
+	unregister_filesystem(&shmem_fs_type);
+out2:
+	shmem_destroy_inodecache();
+	shm_mnt = ERR_PTR(error);
+	return error;
+}
+
+#if defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE) && defined(CONFIG_SYSFS)
+static ssize_t shmem_enabled_show(struct kobject *kobj,
+		struct kobj_attribute *attr, char *buf)
+{
+	int values[] = {
+		SHMEM_HUGE_ALWAYS,
+		SHMEM_HUGE_WITHIN_SIZE,
+		SHMEM_HUGE_ADVISE,
+		SHMEM_HUGE_NEVER,
+		SHMEM_HUGE_DENY,
+		SHMEM_HUGE_FORCE,
+	};
+	int i, count;
+
+	for (i = 0, count = 0; i < ARRAY_SIZE(values); i++) {
+		const char *fmt = shmem_huge == values[i] ? "[%s] " : "%s ";
+
+		count += sprintf(buf + count, fmt,
+				shmem_format_huge(values[i]));
+	}
+	buf[count - 1] = '\n';
+	return count;
+}
+
+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(shmem_enabled, 0644, shmem_enabled_show, shmem_enabled_store);
+#endif /* CONFIG_TRANSPARENT_HUGE_PAGECACHE && CONFIG_SYSFS */
+
+#ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
+bool shmem_huge_enabled(struct vm_area_struct *vma)
+{
+	struct inode *inode = file_inode(vma->vm_file);
+	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
+	loff_t i_size;
+	pgoff_t off;
+
+	if (shmem_huge == SHMEM_HUGE_FORCE)
+		return true;
+	if (shmem_huge == SHMEM_HUGE_DENY)
+		return false;
+	switch (sbinfo->huge) {
+		case SHMEM_HUGE_NEVER:
+			return false;
+		case SHMEM_HUGE_ALWAYS:
+			return true;
+		case SHMEM_HUGE_WITHIN_SIZE:
+			off = round_up(vma->vm_pgoff, HPAGE_PMD_NR);
+			i_size = round_up(i_size_read(inode), PAGE_SIZE);
+			if (i_size >= HPAGE_PMD_SIZE &&
+					i_size >> PAGE_SHIFT >= off)
+				return true;
+			/* fall through */
+		case SHMEM_HUGE_ADVISE:
+			/* TODO: implement fadvise() hints */
+			return (vma->vm_flags & VM_HUGEPAGE);
+		default:
+			VM_BUG_ON(1);
+			return false;
+	}
+}
+#endif /* CONFIG_TRANSPARENT_HUGE_PAGECACHE */
+
+#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",
+	.mount		= ramfs_mount,
+	.kill_sb	= kill_litter_super,
+	.fs_flags	= FS_USERNS_MOUNT,
+};
+
+int __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));
+
+	return 0;
+}
+
+int shmem_unuse(swp_entry_t swap, struct page *page)
+{
+	return 0;
+}
+
+int shmem_lock(struct file *file, int lock, struct user_struct *user)
+{
+	return 0;
+}
+
+void shmem_unlock_mapping(struct address_space *mapping)
+{
+}
+
+#ifdef CONFIG_MMU
+unsigned long shmem_get_unmapped_area(struct file *file,
+				      unsigned long addr, unsigned long len,
+				      unsigned long pgoff, unsigned long flags)
+{
+	return current->mm->get_unmapped_area(file, addr, len, pgoff, flags);
+}
+#endif
+
+void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
+{
+	truncate_inode_pages_range(inode->i_mapping, lstart, lend);
+}
+EXPORT_SYMBOL_GPL(shmem_truncate_range);
+
+#define shmem_vm_ops				generic_file_vm_ops
+#define shmem_file_operations			ramfs_file_operations
+#define shmem_get_inode(sb, dir, mode, dev, flags)	ramfs_get_inode(sb, dir, mode, dev)
+#define shmem_acct_size(flags, size)		0
+#define shmem_unacct_size(flags, size)		do {} while (0)
+
+#endif /* CONFIG_SHMEM */
+
+/* common code */
+
+static struct file *__shmem_file_setup(struct vfsmount *mnt, const char *name, loff_t size,
+				       unsigned long flags, unsigned int i_flags)
+{
+	struct inode *inode;
+	struct file *res;
+
+	if (IS_ERR(mnt))
+		return ERR_CAST(mnt);
+
+	if (size < 0 || size > MAX_LFS_FILESIZE)
+		return ERR_PTR(-EINVAL);
+
+	if (shmem_acct_size(flags, size))
+		return ERR_PTR(-ENOMEM);
+
+	inode = shmem_get_inode(mnt->mnt_sb, NULL, S_IFREG | S_IRWXUGO, 0,
+				flags);
+	if (unlikely(!inode)) {
+		shmem_unacct_size(flags, size);
+		return ERR_PTR(-ENOSPC);
+	}
+	inode->i_flags |= i_flags;
+	inode->i_size = size;
+	clear_nlink(inode);	/* It is unlinked */
+	res = ERR_PTR(ramfs_nommu_expand_for_mapping(inode, size));
+	if (!IS_ERR(res))
+		res = alloc_file_pseudo(inode, mnt, name, O_RDWR,
+				&shmem_file_operations);
+	if (IS_ERR(res))
+		iput(inode);
+	return res;
+}
+
+/**
+ * shmem_kernel_file_setup - get an unlinked file living in tmpfs which must be
+ * 	kernel internal.  There will be NO LSM permission checks against the
+ * 	underlying inode.  So users of this interface must do LSM checks at a
+ *	higher layer.  The users are the big_key and shm implementations.  LSM
+ *	checks are provided at the key or shm level rather than the inode.
+ * @name: name for dentry (to be seen in /proc/<pid>/maps
+ * @size: size to be set for the file
+ * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
+ */
+struct file *shmem_kernel_file_setup(const char *name, loff_t size, unsigned long flags)
+{
+	return __shmem_file_setup(shm_mnt, name, size, flags, S_PRIVATE);
+}
+
+/**
+ * shmem_file_setup - get an unlinked file living in tmpfs
+ * @name: name for dentry (to be seen in /proc/<pid>/maps
+ * @size: size to be set for the file
+ * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
+ */
+struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags)
+{
+	return __shmem_file_setup(shm_mnt, name, size, flags, 0);
+}
+EXPORT_SYMBOL_GPL(shmem_file_setup);
+
+/**
+ * shmem_file_setup_with_mnt - get an unlinked file living in tmpfs
+ * @mnt: the tmpfs mount where the file will be created
+ * @name: name for dentry (to be seen in /proc/<pid>/maps
+ * @size: size to be set for the file
+ * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
+ */
+struct file *shmem_file_setup_with_mnt(struct vfsmount *mnt, const char *name,
+				       loff_t size, unsigned long flags)
+{
+	return __shmem_file_setup(mnt, name, size, flags, 0);
+}
+EXPORT_SYMBOL_GPL(shmem_file_setup_with_mnt);
+
+/**
+ * shmem_zero_setup - setup a shared anonymous mapping
+ * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
+ */
+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_sem leads to a lock ordering conflict
+	 * between XFS directory reading and selinux: since this file is only
+	 * accessible to the user through its mapping, use S_PRIVATE flag to
+	 * bypass file security, in the same way as shmem_kernel_file_setup().
+	 */
+	file = shmem_kernel_file_setup("dev/zero", size, vma->vm_flags);
+	if (IS_ERR(file))
+		return PTR_ERR(file);
+
+	if (vma->vm_file)
+		fput(vma->vm_file);
+	vma->vm_file = file;
+	vma->vm_ops = &shmem_vm_ops;
+
+	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE) &&
+			((vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK) <
+			(vma->vm_end & HPAGE_PMD_MASK)) {
+		khugepaged_enter(vma, vma->vm_flags);
+	}
+
+	return 0;
+}
+
+/**
+ * shmem_read_mapping_page_gfp - read into page cache, using specified page allocation flags.
+ * @mapping:	the page's address_space
+ * @index:	the page index
+ * @gfp:	the page allocator flags to use if allocating
+ *
+ * This behaves as a tmpfs "read_cache_page_gfp(mapping, index, gfp)",
+ * with any new page allocations done using the specified allocation flags.
+ * But read_cache_page_gfp() uses the ->readpage() method: which does not
+ * suit tmpfs, since it may have pages in swapcache, and needs to find those
+ * for itself; although drivers/gpu/drm i915 and ttm rely upon this support.
+ *
+ * i915_gem_object_get_pages_gtt() mixes __GFP_NORETRY | __GFP_NOWARN in
+ * with the mapping_gfp_mask(), to avoid OOMing the machine unnecessarily.
+ */
+struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
+					 pgoff_t index, gfp_t gfp)
+{
+#ifdef CONFIG_SHMEM
+	struct inode *inode = mapping->host;
+	struct page *page;
+	int error;
+
+	BUG_ON(mapping->a_ops != &shmem_aops);
+	error = shmem_getpage_gfp(inode, index, &page, SGP_CACHE,
+				  gfp, NULL, NULL, NULL);
+	if (error)
+		page = ERR_PTR(error);
+	else
+		unlock_page(page);
+	return page;
+#else
+	/*
+	 * The tiny !SHMEM case uses ramfs without swap
+	 */
+	return read_cache_page_gfp(mapping, index, gfp);
+#endif
+}
+EXPORT_SYMBOL_GPL(shmem_read_mapping_page_gfp);