treewide: refresh kmalloc_obj() conversionsgrafted

This is another run of the Coccinelle script for converting kmalloc()
family of allocations to kmalloc_obj() via the existing rules in
scripts/coccinelle/api/kmalloc_objs.cocci

This catches both the set of kmalloc() uses added since the first
kmalloc_obj() conversions in v7.0 and adds a large group missed in the
first pass due to Coccinelle not interacting well with the cleanup.h
scoped_...() family of macros[1]. I worked around this with spatch's
"--macro-file" argument to a file with all the scoped_...() macros mapped
to Coccinelle's YACFE_ITERATOR[2] as that was the closest viable control
flow indicator I could find.

Build tested allmodconfig on x86, arm64, arm, loongarch, mips, powerpc,
riscv, and s390 with no new warnings.

Link: https://lore.kernel.org/lkml/202609021314.8A9C0B8@keescook/ [1]
Link: https://github.com/coccinelle/coccinelle/blob/master/standard.h [2]
Signed-off-by: Kees Cook <kees+treewide@kernel.org>

1 files changed, 2317 insertions, 0 deletions

diff --git a/fs/libfs.c b/fs/libfs.c
new file mode 100644
index 000000000..27d7dc16f
--- /dev/null
+++ b/fs/libfs.c
@@ -0,0 +1,2317 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *	fs/libfs.c
+ *	Library for filesystems writers.
+ */
+
+#include <linux/blkdev.h>
+#include <linux/export.h>
+#include <linux/filelock.h>
+#include <linux/pagemap.h>
+#include <linux/slab.h>
+#include <linux/cred.h>
+#include <linux/mount.h>
+#include <linux/vfs.h>
+#include <linux/quotaops.h>
+#include <linux/mutex.h>
+#include <linux/namei.h>
+#include <linux/exportfs.h>
+#include <linux/iversion.h>
+#include <linux/writeback.h>
+#include <linux/fs_context.h>
+#include <linux/pseudo_fs.h>
+#include <linux/fsnotify.h>
+#include <linux/unicode.h>
+#include <linux/fscrypt.h>
+#include <linux/pidfs.h>
+
+#include <linux/uaccess.h>
+
+#include "internal.h"
+
+int simple_getattr(struct mnt_idmap *idmap, const struct path *path,
+		   struct kstat *stat, u32 request_mask,
+		   unsigned int query_flags)
+{
+	struct inode *inode = d_inode(path->dentry);
+	generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat);
+	stat->blocks = inode->i_mapping->nrpages << (PAGE_SHIFT - 9);
+	return 0;
+}
+EXPORT_SYMBOL(simple_getattr);
+
+int simple_statfs(struct dentry *dentry, struct kstatfs *buf)
+{
+	u64 id = huge_encode_dev(dentry->d_sb->s_dev);
+
+	buf->f_fsid = u64_to_fsid(id);
+	buf->f_type = dentry->d_sb->s_magic;
+	buf->f_bsize = PAGE_SIZE;
+	buf->f_namelen = NAME_MAX;
+	return 0;
+}
+EXPORT_SYMBOL(simple_statfs);
+
+/*
+ * Retaining negative dentries for an in-memory filesystem just wastes
+ * memory and lookup time: arrange for them to be deleted immediately.
+ */
+int always_delete_dentry(const struct dentry *dentry)
+{
+	return 1;
+}
+EXPORT_SYMBOL(always_delete_dentry);
+
+/*
+ * Lookup the data. This is trivial - if the dentry didn't already
+ * exist, we know it is negative.  Set d_op to delete negative dentries.
+ */
+struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
+{
+	if (dentry->d_name.len > NAME_MAX)
+		return ERR_PTR(-ENAMETOOLONG);
+	if (!dentry->d_op && !(dentry->d_flags & DCACHE_DONTCACHE)) {
+		spin_lock(&dentry->d_lock);
+		dentry->d_flags |= DCACHE_DONTCACHE;
+		spin_unlock(&dentry->d_lock);
+	}
+	if (IS_ENABLED(CONFIG_UNICODE) && IS_CASEFOLDED(dir))
+		return NULL;
+
+	return d_splice_alias(NULL, dentry);
+}
+EXPORT_SYMBOL(simple_lookup);
+
+int dcache_dir_open(struct inode *inode, struct file *file)
+{
+	file->private_data = d_alloc_cursor(file->f_path.dentry);
+
+	return file->private_data ? 0 : -ENOMEM;
+}
+EXPORT_SYMBOL(dcache_dir_open);
+
+int dcache_dir_close(struct inode *inode, struct file *file)
+{
+	dput(file->private_data);
+	return 0;
+}
+EXPORT_SYMBOL(dcache_dir_close);
+
+/* parent is locked at least shared */
+/*
+ * Returns an element of siblings' list.
+ * We are looking for <count>th positive after <p>; if
+ * found, dentry is grabbed and returned to caller.
+ * If no such element exists, NULL is returned.
+ */
+static struct dentry *scan_positives(struct dentry *cursor,
+					struct hlist_node **p,
+					loff_t count,
+					struct dentry *last)
+{
+	struct dentry *dentry = cursor->d_parent, *found = NULL;
+
+	spin_lock(&dentry->d_lock);
+	while (*p) {
+		struct dentry *d = hlist_entry(*p, struct dentry, d_sib);
+		p = &d->d_sib.next;
+		// we must at least skip cursors, to avoid livelocks
+		if (d->d_flags & DCACHE_DENTRY_CURSOR)
+			continue;
+		if (simple_positive(d) && !--count) {
+			spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
+			if (simple_positive(d))
+				found = dget_dlock(d);
+			spin_unlock(&d->d_lock);
+			if (likely(found))
+				break;
+			count = 1;
+		}
+		if (need_resched()) {
+			if (!hlist_unhashed(&cursor->d_sib))
+				__hlist_del(&cursor->d_sib);
+			hlist_add_behind(&cursor->d_sib, &d->d_sib);
+			p = &cursor->d_sib.next;
+			spin_unlock(&dentry->d_lock);
+			cond_resched();
+			spin_lock(&dentry->d_lock);
+		}
+	}
+	spin_unlock(&dentry->d_lock);
+	dput(last);
+	return found;
+}
+
+loff_t dcache_dir_lseek(struct file *file, loff_t offset, int whence)
+{
+	struct dentry *dentry = file->f_path.dentry;
+	switch (whence) {
+		case 1:
+			offset += file->f_pos;
+			fallthrough;
+		case 0:
+			if (offset >= 0)
+				break;
+			fallthrough;
+		default:
+			return -EINVAL;
+	}
+	if (offset != file->f_pos) {
+		struct dentry *cursor = file->private_data;
+		struct dentry *to = NULL;
+
+		inode_lock_shared(dentry->d_inode);
+
+		if (offset > 2)
+			to = scan_positives(cursor, &dentry->d_children.first,
+					    offset - 2, NULL);
+		spin_lock(&dentry->d_lock);
+		hlist_del_init(&cursor->d_sib);
+		if (to)
+			hlist_add_behind(&cursor->d_sib, &to->d_sib);
+		spin_unlock(&dentry->d_lock);
+		dput(to);
+
+		file->f_pos = offset;
+
+		inode_unlock_shared(dentry->d_inode);
+	}
+	return offset;
+}
+EXPORT_SYMBOL(dcache_dir_lseek);
+
+/*
+ * Directory is locked and all positive dentries in it are safe, since
+ * for ramfs-type trees they can't go away without unlink() or rmdir(),
+ * both impossible due to the lock on directory.
+ */
+
+int dcache_readdir(struct file *file, struct dir_context *ctx)
+{
+	struct dentry *dentry = file->f_path.dentry;
+	struct dentry *cursor = file->private_data;
+	struct dentry *next = NULL;
+	struct hlist_node **p;
+
+	if (!dir_emit_dots(file, ctx))
+		return 0;
+
+	if (ctx->pos == 2)
+		p = &dentry->d_children.first;
+	else
+		p = &cursor->d_sib.next;
+
+	while ((next = scan_positives(cursor, p, 1, next)) != NULL) {
+		if (!dir_emit(ctx, next->d_name.name, next->d_name.len,
+			      d_inode(next)->i_ino,
+			      fs_umode_to_dtype(d_inode(next)->i_mode)))
+			break;
+		ctx->pos++;
+		p = &next->d_sib.next;
+	}
+	spin_lock(&dentry->d_lock);
+	hlist_del_init(&cursor->d_sib);
+	if (next)
+		hlist_add_before(&cursor->d_sib, &next->d_sib);
+	spin_unlock(&dentry->d_lock);
+	dput(next);
+
+	return 0;
+}
+EXPORT_SYMBOL(dcache_readdir);
+
+ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos)
+{
+	return -EISDIR;
+}
+EXPORT_SYMBOL(generic_read_dir);
+
+const struct file_operations simple_dir_operations = {
+	.open		= dcache_dir_open,
+	.release	= dcache_dir_close,
+	.llseek		= dcache_dir_lseek,
+	.read		= generic_read_dir,
+	.iterate_shared	= dcache_readdir,
+	.fsync		= noop_fsync,
+};
+EXPORT_SYMBOL(simple_dir_operations);
+
+const struct inode_operations simple_dir_inode_operations = {
+	.lookup		= simple_lookup,
+};
+EXPORT_SYMBOL(simple_dir_inode_operations);
+
+/* simple_offset_add() never assigns these to a dentry */
+enum {
+	DIR_OFFSET_FIRST	= 2,		/* Find first real entry */
+	DIR_OFFSET_EOD		= S32_MAX,
+};
+
+/* simple_offset_add() allocation range */
+enum {
+	DIR_OFFSET_MIN		= DIR_OFFSET_FIRST + 1,
+	DIR_OFFSET_MAX		= DIR_OFFSET_EOD - 1,
+};
+
+static void offset_set(struct dentry *dentry, long offset)
+{
+	dentry->d_fsdata = (void *)offset;
+}
+
+static long dentry2offset(struct dentry *dentry)
+{
+	return (long)dentry->d_fsdata;
+}
+
+static struct lock_class_key simple_offset_lock_class;
+
+/**
+ * simple_offset_init - initialize an offset_ctx
+ * @octx: directory offset map to be initialized
+ *
+ */
+void simple_offset_init(struct offset_ctx *octx)
+{
+	mt_init_flags(&octx->mt, MT_FLAGS_ALLOC_RANGE);
+	lockdep_set_class(&octx->mt.ma_lock, &simple_offset_lock_class);
+	octx->next_offset = DIR_OFFSET_MIN;
+}
+
+/**
+ * simple_offset_add - Add an entry to a directory's offset map
+ * @octx: directory offset ctx to be updated
+ * @dentry: new dentry being added
+ *
+ * Returns zero on success. @octx and the dentry's offset are updated.
+ * Otherwise, a negative errno value is returned.
+ */
+int simple_offset_add(struct offset_ctx *octx, struct dentry *dentry)
+{
+	unsigned long offset;
+	int ret;
+
+	if (dentry2offset(dentry) != 0)
+		return -EBUSY;
+
+	ret = mtree_alloc_cyclic(&octx->mt, &offset, dentry, DIR_OFFSET_MIN,
+				 DIR_OFFSET_MAX, &octx->next_offset,
+				 GFP_KERNEL);
+	if (unlikely(ret < 0))
+		return ret == -EBUSY ? -ENOSPC : ret;
+
+	offset_set(dentry, offset);
+	return 0;
+}
+
+static int simple_offset_replace(struct offset_ctx *octx, struct dentry *dentry,
+				 long offset)
+{
+	int ret;
+
+	ret = mtree_store(&octx->mt, offset, dentry, GFP_KERNEL);
+	if (ret)
+		return ret;
+	offset_set(dentry, offset);
+	return 0;
+}
+
+/**
+ * simple_offset_remove - Remove an entry to a directory's offset map
+ * @octx: directory offset ctx to be updated
+ * @dentry: dentry being removed
+ *
+ */
+void simple_offset_remove(struct offset_ctx *octx, struct dentry *dentry)
+{
+	long offset;
+
+	offset = dentry2offset(dentry);
+	if (offset == 0)
+		return;
+
+	mtree_erase(&octx->mt, offset);
+	offset_set(dentry, 0);
+}
+
+/**
+ * simple_offset_rename - handle directory offsets for rename
+ * @old_dir: parent directory of source entry
+ * @old_dentry: dentry of source entry
+ * @new_dir: parent_directory of destination entry
+ * @new_dentry: dentry of destination
+ *
+ * Caller provides appropriate serialization.
+ *
+ * User space expects the directory offset value of the replaced
+ * (new) directory entry to be unchanged after a rename.
+ *
+ * Caller must have grabbed a slot for new_dentry in the maple_tree
+ * associated with new_dir, even if dentry is negative.
+ */
+void simple_offset_rename(struct inode *old_dir, struct dentry *old_dentry,
+			  struct inode *new_dir, struct dentry *new_dentry)
+{
+	struct offset_ctx *old_ctx = old_dir->i_op->get_offset_ctx(old_dir);
+	struct offset_ctx *new_ctx = new_dir->i_op->get_offset_ctx(new_dir);
+	long new_offset = dentry2offset(new_dentry);
+
+	if (WARN_ON(!new_offset))
+		return;
+
+	simple_offset_remove(old_ctx, old_dentry);
+	offset_set(new_dentry, 0);
+	WARN_ON(simple_offset_replace(new_ctx, old_dentry, new_offset));
+}
+
+/**
+ * simple_offset_rename_exchange - exchange rename with directory offsets
+ * @old_dir: parent of dentry being moved
+ * @old_dentry: dentry being moved
+ * @new_dir: destination parent
+ * @new_dentry: destination dentry
+ *
+ * This API preserves the directory offset values. Caller provides
+ * appropriate serialization.
+ *
+ * Returns zero on success. Otherwise a negative errno is returned and the
+ * rename is rolled back.
+ */
+int simple_offset_rename_exchange(struct inode *old_dir,
+				  struct dentry *old_dentry,
+				  struct inode *new_dir,
+				  struct dentry *new_dentry)
+{
+	struct offset_ctx *old_ctx = old_dir->i_op->get_offset_ctx(old_dir);
+	struct offset_ctx *new_ctx = new_dir->i_op->get_offset_ctx(new_dir);
+	long old_index = dentry2offset(old_dentry);
+	long new_index = dentry2offset(new_dentry);
+	int ret;
+
+	if (WARN_ON(!old_index || !new_index))
+		return -EINVAL;
+
+	ret = mtree_store(&new_ctx->mt, new_index, old_dentry, GFP_KERNEL);
+	if (WARN_ON(ret))
+		return ret;
+
+	ret = mtree_store(&old_ctx->mt, old_index, new_dentry, GFP_KERNEL);
+	if (WARN_ON(ret)) {
+		mtree_store(&new_ctx->mt, new_index, new_dentry, GFP_KERNEL);
+		return ret;
+	}
+
+	offset_set(old_dentry, new_index);
+	offset_set(new_dentry, old_index);
+	simple_rename_exchange(old_dir, old_dentry, new_dir, new_dentry);
+	return 0;
+}
+
+/**
+ * simple_offset_destroy - Release offset map
+ * @octx: directory offset ctx that is about to be destroyed
+ *
+ * During fs teardown (eg. umount), a directory's offset map might still
+ * contain entries. xa_destroy() cleans out anything that remains.
+ */
+void simple_offset_destroy(struct offset_ctx *octx)
+{
+	mtree_destroy(&octx->mt);
+}
+
+/**
+ * offset_dir_llseek - Advance the read position of a directory descriptor
+ * @file: an open directory whose position is to be updated
+ * @offset: a byte offset
+ * @whence: enumerator describing the starting position for this update
+ *
+ * SEEK_END, SEEK_DATA, and SEEK_HOLE are not supported for directories.
+ *
+ * Returns the updated read position if successful; otherwise a
+ * negative errno is returned and the read position remains unchanged.
+ */
+static loff_t offset_dir_llseek(struct file *file, loff_t offset, int whence)
+{
+	switch (whence) {
+	case SEEK_CUR:
+		offset += file->f_pos;
+		fallthrough;
+	case SEEK_SET:
+		if (offset >= 0)
+			break;
+		fallthrough;
+	default:
+		return -EINVAL;
+	}
+
+	return vfs_setpos(file, offset, LONG_MAX);
+}
+
+static struct dentry *find_positive_dentry(struct dentry *parent,
+					   struct dentry *dentry,
+					   bool next)
+{
+	struct dentry *found = NULL;
+
+	spin_lock(&parent->d_lock);
+	if (next)
+		dentry = d_next_sibling(dentry);
+	else if (!dentry)
+		dentry = d_first_child(parent);
+	hlist_for_each_entry_from(dentry, d_sib) {
+		if (!simple_positive(dentry))
+			continue;
+		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
+		if (simple_positive(dentry))
+			found = dget_dlock(dentry);
+		spin_unlock(&dentry->d_lock);
+		if (likely(found))
+			break;
+	}
+	spin_unlock(&parent->d_lock);
+	return found;
+}
+
+static noinline_for_stack struct dentry *
+offset_dir_lookup(struct dentry *parent, loff_t offset)
+{
+	struct inode *inode = d_inode(parent);
+	struct offset_ctx *octx = inode->i_op->get_offset_ctx(inode);
+	struct dentry *child, *found = NULL;
+
+	MA_STATE(mas, &octx->mt, offset, offset);
+
+	if (offset == DIR_OFFSET_FIRST)
+		found = find_positive_dentry(parent, NULL, false);
+	else {
+		rcu_read_lock();
+		child = mas_find_rev(&mas, DIR_OFFSET_MIN);
+		found = find_positive_dentry(parent, child, false);
+		rcu_read_unlock();
+	}
+	return found;
+}
+
+static bool offset_dir_emit(struct dir_context *ctx, struct dentry *dentry)
+{
+	struct inode *inode = d_inode(dentry);
+
+	return dir_emit(ctx, dentry->d_name.name, dentry->d_name.len,
+			inode->i_ino, fs_umode_to_dtype(inode->i_mode));
+}
+
+static void offset_iterate_dir(struct file *file, struct dir_context *ctx)
+{
+	struct dentry *dir = file->f_path.dentry;
+	struct dentry *dentry;
+
+	dentry = offset_dir_lookup(dir, ctx->pos);
+	if (!dentry)
+		goto out_eod;
+	while (true) {
+		struct dentry *next;
+
+		ctx->pos = dentry2offset(dentry);
+		if (!offset_dir_emit(ctx, dentry))
+			break;
+
+		next = find_positive_dentry(dir, dentry, true);
+		dput(dentry);
+
+		if (!next)
+			goto out_eod;
+		dentry = next;
+	}
+	dput(dentry);
+	return;
+
+out_eod:
+	ctx->pos = DIR_OFFSET_EOD;
+}
+
+/**
+ * offset_readdir - Emit entries starting at offset @ctx->pos
+ * @file: an open directory to iterate over
+ * @ctx: directory iteration context
+ *
+ * Caller must hold @file's i_rwsem to prevent insertion or removal of
+ * entries during this call.
+ *
+ * On entry, @ctx->pos contains an offset that represents the first entry
+ * to be read from the directory.
+ *
+ * The operation continues until there are no more entries to read, or
+ * until the ctx->actor indicates there is no more space in the caller's
+ * output buffer.
+ *
+ * On return, @ctx->pos contains an offset that will read the next entry
+ * in this directory when offset_readdir() is called again with @ctx.
+ * Caller places this value in the d_off field of the last entry in the
+ * user's buffer.
+ *
+ * Return values:
+ *   %0 - Complete
+ */
+static int offset_readdir(struct file *file, struct dir_context *ctx)
+{
+	struct dentry *dir = file->f_path.dentry;
+
+	lockdep_assert_held(&d_inode(dir)->i_rwsem);
+
+	if (!dir_emit_dots(file, ctx))
+		return 0;
+	if (ctx->pos != DIR_OFFSET_EOD)
+		offset_iterate_dir(file, ctx);
+	return 0;
+}
+
+const struct file_operations simple_offset_dir_operations = {
+	.llseek		= offset_dir_llseek,
+	.iterate_shared	= offset_readdir,
+	.read		= generic_read_dir,
+	.fsync		= noop_fsync,
+	.setlease	= generic_setlease,
+};
+
+struct dentry *find_next_child(struct dentry *parent, struct dentry *prev)
+{
+	struct dentry *child = NULL, *d;
+
+	spin_lock(&parent->d_lock);
+	d = prev ? d_next_sibling(prev) : d_first_child(parent);
+	hlist_for_each_entry_from(d, d_sib) {
+		if (simple_positive(d)) {
+			spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
+			if (simple_positive(d))
+				child = dget_dlock(d);
+			spin_unlock(&d->d_lock);
+			if (likely(child))
+				break;
+		}
+	}
+	spin_unlock(&parent->d_lock);
+	dput(prev);
+	return child;
+}
+EXPORT_SYMBOL(find_next_child);
+
+static void __simple_recursive_removal(struct dentry *dentry,
+                              void (*callback)(struct dentry *),
+			      bool locked)
+{
+	struct dentry *this = dget(dentry);
+	while (true) {
+		struct dentry *victim = NULL, *child;
+		struct inode *inode = this->d_inode;
+
+		inode_lock_nested(inode, I_MUTEX_CHILD);
+		if (d_is_dir(this))
+			inode->i_flags |= S_DEAD;
+		while ((child = find_next_child(this, victim)) == NULL) {
+			// kill and ascend
+			// update metadata while it's still locked
+			inode_set_ctime_current(inode);
+			clear_nlink(inode);
+			inode_unlock(inode);
+			victim = this;
+			this = this->d_parent;
+			inode = this->d_inode;
+			if (!locked || victim != dentry)
+				inode_lock_nested(inode, I_MUTEX_CHILD);
+			if (simple_positive(victim)) {
+				d_invalidate(victim);	// avoid lost mounts
+				if (callback)
+					callback(victim);
+				fsnotify_delete(inode, d_inode(victim), victim);
+				d_make_discardable(victim);
+			}
+			if (victim == dentry) {
+				inode_set_mtime_to_ts(inode,
+						      inode_set_ctime_current(inode));
+				if (d_is_dir(dentry))
+					drop_nlink(inode);
+				if (!locked)
+					inode_unlock(inode);
+				dput(dentry);
+				return;
+			}
+		}
+		inode_unlock(inode);
+		this = child;
+	}
+}
+
+void simple_recursive_removal(struct dentry *dentry,
+                              void (*callback)(struct dentry *))
+{
+	return __simple_recursive_removal(dentry, callback, false);
+}
+EXPORT_SYMBOL(simple_recursive_removal);
+
+void simple_remove_by_name(struct dentry *parent, const char *name,
+                           void (*callback)(struct dentry *))
+{
+	struct dentry *dentry;
+
+	dentry = lookup_noperm_positive_unlocked(&QSTR(name), parent);
+	if (!IS_ERR(dentry)) {
+		simple_recursive_removal(dentry, callback);
+		dput(dentry);	// paired with lookup_noperm_positive_unlocked()
+	}
+}
+EXPORT_SYMBOL(simple_remove_by_name);
+
+/* caller holds parent directory with I_MUTEX_PARENT */
+void locked_recursive_removal(struct dentry *dentry,
+                              void (*callback)(struct dentry *))
+{
+	return __simple_recursive_removal(dentry, callback, true);
+}
+EXPORT_SYMBOL(locked_recursive_removal);
+
+static const struct super_operations simple_super_operations = {
+	.statfs		= simple_statfs,
+};
+
+static int pseudo_fs_fill_super(struct super_block *s, struct fs_context *fc)
+{
+	struct pseudo_fs_context *ctx = fc->fs_private;
+	struct inode *root;
+
+	s->s_maxbytes = MAX_LFS_FILESIZE;
+	s->s_blocksize = PAGE_SIZE;
+	s->s_blocksize_bits = PAGE_SHIFT;
+	s->s_magic = ctx->magic;
+	s->s_op = ctx->ops ?: &simple_super_operations;
+	s->s_export_op = ctx->eops;
+	s->s_xattr = ctx->xattr;
+	s->s_time_gran = 1;
+	s->s_d_flags |= ctx->s_d_flags;
+	root = new_inode(s);
+	if (!root)
+		return -ENOMEM;
+
+	/*
+	 * since this is the first inode, make it number 1. New inodes created
+	 * after this must take care not to collide with it (by passing
+	 * max_reserved of 1 to iunique).
+	 */
+	root->i_ino = 1;
+	root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
+	simple_inode_init_ts(root);
+	s->s_root = d_make_root(root);
+	if (!s->s_root)
+		return -ENOMEM;
+	set_default_d_op(s, ctx->dops);
+	return 0;
+}
+
+static int pseudo_fs_get_tree(struct fs_context *fc)
+{
+	return get_tree_nodev(fc, pseudo_fs_fill_super);
+}
+
+static void pseudo_fs_free(struct fs_context *fc)
+{
+	kfree(fc->fs_private);
+}
+
+static const struct fs_context_operations pseudo_fs_context_ops = {
+	.free		= pseudo_fs_free,
+	.get_tree	= pseudo_fs_get_tree,
+};
+
+/*
+ * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
+ * will never be mountable)
+ */
+struct pseudo_fs_context *init_pseudo(struct fs_context *fc,
+					unsigned long magic)
+{
+	struct pseudo_fs_context *ctx;
+
+	ctx = kzalloc_obj(struct pseudo_fs_context);
+	if (likely(ctx)) {
+		ctx->magic = magic;
+		fc->fs_private = ctx;
+		fc->ops = &pseudo_fs_context_ops;
+		fc->sb_flags |= SB_NOUSER;
+		fc->s_iflags |= SB_I_NOEXEC | SB_I_NODEV;
+		fc->global = true;
+	}
+	return ctx;
+}
+EXPORT_SYMBOL(init_pseudo);
+
+int simple_open(struct inode *inode, struct file *file)
+{
+	if (inode->i_private)
+		file->private_data = inode->i_private;
+	return 0;
+}
+EXPORT_SYMBOL(simple_open);
+
+int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
+{
+	struct inode *inode = d_inode(old_dentry);
+
+	inode_set_mtime_to_ts(dir,
+			      inode_set_ctime_to_ts(dir, inode_set_ctime_current(inode)));
+	inc_nlink(inode);
+	ihold(inode);
+	d_make_persistent(dentry, inode);
+	return 0;
+}
+EXPORT_SYMBOL(simple_link);
+
+int simple_empty(struct dentry *dentry)
+{
+	struct dentry *child;
+	int ret = 0;
+
+	spin_lock(&dentry->d_lock);
+	hlist_for_each_entry(child, &dentry->d_children, d_sib) {
+		spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
+		if (simple_positive(child)) {
+			spin_unlock(&child->d_lock);
+			goto out;
+		}
+		spin_unlock(&child->d_lock);
+	}
+	ret = 1;
+out:
+	spin_unlock(&dentry->d_lock);
+	return ret;
+}
+EXPORT_SYMBOL(simple_empty);
+
+void __simple_unlink(struct inode *dir, struct dentry *dentry)
+{
+	struct inode *inode = d_inode(dentry);
+
+	inode_set_mtime_to_ts(dir,
+			      inode_set_ctime_to_ts(dir, inode_set_ctime_current(inode)));
+	drop_nlink(inode);
+}
+EXPORT_SYMBOL(__simple_unlink);
+
+void __simple_rmdir(struct inode *dir, struct dentry *dentry)
+{
+	drop_nlink(d_inode(dentry));
+	__simple_unlink(dir, dentry);
+	drop_nlink(dir);
+}
+EXPORT_SYMBOL(__simple_rmdir);
+
+int simple_unlink(struct inode *dir, struct dentry *dentry)
+{
+	__simple_unlink(dir, dentry);
+	d_make_discardable(dentry);
+	return 0;
+}
+EXPORT_SYMBOL(simple_unlink);
+
+int simple_rmdir(struct inode *dir, struct dentry *dentry)
+{
+	if (!simple_empty(dentry))
+		return -ENOTEMPTY;
+
+	__simple_rmdir(dir, dentry);
+	d_make_discardable(dentry);
+	return 0;
+}
+EXPORT_SYMBOL(simple_rmdir);
+
+/**
+ * simple_rename_timestamp - update the various inode timestamps for rename
+ * @old_dir: old parent directory
+ * @old_dentry: dentry that is being renamed
+ * @new_dir: new parent directory
+ * @new_dentry: target for rename
+ *
+ * POSIX mandates that the old and new parent directories have their ctime and
+ * mtime updated, and that inodes of @old_dentry and @new_dentry (if any), have
+ * their ctime updated.
+ */
+void simple_rename_timestamp(struct inode *old_dir, struct dentry *old_dentry,
+			     struct inode *new_dir, struct dentry *new_dentry)
+{
+	struct inode *newino = d_inode(new_dentry);
+
+	inode_set_mtime_to_ts(old_dir, inode_set_ctime_current(old_dir));
+	if (new_dir != old_dir)
+		inode_set_mtime_to_ts(new_dir,
+				      inode_set_ctime_current(new_dir));
+	inode_set_ctime_current(d_inode(old_dentry));
+	if (newino)
+		inode_set_ctime_current(newino);
+}
+EXPORT_SYMBOL_GPL(simple_rename_timestamp);
+
+int simple_rename_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);
+		}
+	}
+	simple_rename_timestamp(old_dir, old_dentry, new_dir, new_dentry);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(simple_rename_exchange);
+
+int simple_rename(struct mnt_idmap *idmap, struct inode *old_dir,
+		  struct dentry *old_dentry, struct inode *new_dir,
+		  struct dentry *new_dentry, unsigned int flags)
+{
+	int they_are_dirs = d_is_dir(old_dentry);
+
+	if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
+		return -EINVAL;
+
+	if (flags & RENAME_EXCHANGE)
+		return simple_rename_exchange(old_dir, old_dentry, new_dir, new_dentry);
+
+	if (!simple_empty(new_dentry))
+		return -ENOTEMPTY;
+
+	if (d_really_is_positive(new_dentry)) {
+		simple_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);
+	}
+
+	simple_rename_timestamp(old_dir, old_dentry, new_dir, new_dentry);
+	return 0;
+}
+EXPORT_SYMBOL(simple_rename);
+
+/**
+ * simple_setattr - setattr for simple filesystem
+ * @idmap: idmap of the target mount
+ * @dentry: dentry
+ * @iattr: iattr structure
+ *
+ * Returns 0 on success, -error on failure.
+ *
+ * simple_setattr is a simple ->setattr implementation without a proper
+ * implementation of size changes.
+ *
+ * It can either be used for in-memory filesystems or special files
+ * on simple regular filesystems.  Anything that needs to change on-disk
+ * or wire state on size changes needs its own setattr method.
+ */
+int simple_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
+		   struct iattr *iattr)
+{
+	struct inode *inode = d_inode(dentry);
+	int error;
+
+	error = setattr_prepare(idmap, dentry, iattr);
+	if (error)
+		return error;
+
+	if (iattr->ia_valid & ATTR_SIZE)
+		truncate_setsize(inode, iattr->ia_size);
+	setattr_copy(idmap, inode, iattr);
+	mark_inode_dirty(inode);
+	return 0;
+}
+EXPORT_SYMBOL(simple_setattr);
+
+static int simple_read_folio(struct file *file, struct folio *folio)
+{
+	folio_zero_range(folio, 0, folio_size(folio));
+	flush_dcache_folio(folio);
+	folio_mark_uptodate(folio);
+	folio_unlock(folio);
+	return 0;
+}
+
+int simple_write_begin(const struct kiocb *iocb, struct address_space *mapping,
+			loff_t pos, unsigned len,
+			struct folio **foliop, void **fsdata)
+{
+	struct folio *folio;
+
+	folio = __filemap_get_folio(mapping, pos / PAGE_SIZE, FGP_WRITEBEGIN,
+			mapping_gfp_mask(mapping));
+	if (IS_ERR(folio))
+		return PTR_ERR(folio);
+
+	*foliop = folio;
+
+	if (!folio_test_uptodate(folio) && (len != folio_size(folio))) {
+		size_t from = offset_in_folio(folio, pos);
+
+		folio_zero_segments(folio, 0, from,
+				from + len, folio_size(folio));
+	}
+	return 0;
+}
+EXPORT_SYMBOL(simple_write_begin);
+
+/**
+ * simple_write_end - .write_end helper for non-block-device FSes
+ * @iocb: kernel I/O control block
+ * @mapping: 		"
+ * @pos: 		"
+ * @len: 		"
+ * @copied: 		"
+ * @folio: 		"
+ * @fsdata: 		"
+ *
+ * simple_write_end does the minimum needed for updating a folio after
+ * writing is done. It has the same API signature as the .write_end of
+ * address_space_operations vector. So it can just be set onto .write_end for
+ * FSes that don't need any other processing. i_rwsem is assumed to be held
+ * exclusively.
+ * Block based filesystems should use generic_write_end().
+ * NOTE: Even though i_size might get updated by this function, mark_inode_dirty
+ * is not called, so a filesystem that actually does store data in .write_inode
+ * should extend on what's done here with a call to mark_inode_dirty() in the
+ * case that i_size has changed.
+ *
+ * Use *ONLY* with simple_read_folio()
+ */
+static int simple_write_end(const struct kiocb *iocb,
+			    struct address_space *mapping,
+			    loff_t pos, unsigned len, unsigned copied,
+			    struct folio *folio, void *fsdata)
+{
+	struct inode *inode = folio->mapping->host;
+	loff_t last_pos = pos + copied;
+
+	/* zero the stale part of the folio if we did a short copy */
+	if (!folio_test_uptodate(folio)) {
+		if (copied < len) {
+			size_t from = offset_in_folio(folio, pos);
+
+			folio_zero_range(folio, from + copied, len - copied);
+		}
+		folio_mark_uptodate(folio);
+	}
+	/*
+	 * No need to use i_size_read() here, the i_size
+	 * cannot change under us because we hold the i_rwsem.
+	 */
+	if (last_pos > inode->i_size)
+		i_size_write(inode, last_pos);
+
+	folio_mark_dirty(folio);
+	folio_unlock(folio);
+	folio_put(folio);
+
+	return copied;
+}
+
+/*
+ * Provides ramfs-style behavior: data in the pagecache, but no writeback.
+ */
+const struct address_space_operations ram_aops = {
+	.read_folio	= simple_read_folio,
+	.write_begin	= simple_write_begin,
+	.write_end	= simple_write_end,
+	.dirty_folio	= noop_dirty_folio,
+};
+EXPORT_SYMBOL(ram_aops);
+
+/*
+ * the inodes created here are not hashed. If you use iunique to generate
+ * unique inode values later for this filesystem, then you must take care
+ * to pass it an appropriate max_reserved value to avoid collisions.
+ */
+int simple_fill_super(struct super_block *s, unsigned long magic,
+		      const struct tree_descr *files)
+{
+	struct inode *inode;
+	struct dentry *dentry;
+	int i;
+
+	s->s_blocksize = PAGE_SIZE;
+	s->s_blocksize_bits = PAGE_SHIFT;
+	s->s_magic = magic;
+	s->s_op = &simple_super_operations;
+	s->s_time_gran = 1;
+
+	inode = new_inode(s);
+	if (!inode)
+		return -ENOMEM;
+	/*
+	 * because the root inode is 1, the files array must not contain an
+	 * entry at index 1
+	 */
+	inode->i_ino = 1;
+	inode->i_mode = S_IFDIR | 0755;
+	simple_inode_init_ts(inode);
+	inode->i_op = &simple_dir_inode_operations;
+	inode->i_fop = &simple_dir_operations;
+	set_nlink(inode, 2);
+	s->s_root = d_make_root(inode);
+	if (!s->s_root)
+		return -ENOMEM;
+	for (i = 0; !files->name || files->name[0]; i++, files++) {
+		if (!files->name)
+			continue;
+
+		/* warn if it tries to conflict with the root inode */
+		if (unlikely(i == 1))
+			printk(KERN_WARNING "%s: %s passed in a files array"
+				"with an index of 1!\n", __func__,
+				s->s_type->name);
+
+		dentry = d_alloc_name(s->s_root, files->name);
+		if (!dentry)
+			return -ENOMEM;
+		inode = new_inode(s);
+		if (!inode) {
+			dput(dentry);
+			return -ENOMEM;
+		}
+		inode->i_mode = S_IFREG | files->mode;
+		simple_inode_init_ts(inode);
+		inode->i_fop = files->ops;
+		inode->i_ino = i;
+		d_make_persistent(dentry, inode);
+		dput(dentry);
+	}
+	return 0;
+}
+EXPORT_SYMBOL(simple_fill_super);
+
+static DEFINE_SPINLOCK(pin_fs_lock);
+
+int simple_pin_fs(struct file_system_type *type, struct vfsmount **mount, int *count)
+{
+	struct vfsmount *mnt = NULL;
+	spin_lock(&pin_fs_lock);
+	if (unlikely(!*mount)) {
+		spin_unlock(&pin_fs_lock);
+		mnt = vfs_kern_mount(type, SB_KERNMOUNT, type->name, NULL);
+		if (IS_ERR(mnt))
+			return PTR_ERR(mnt);
+		spin_lock(&pin_fs_lock);
+		if (!*mount)
+			*mount = mnt;
+	}
+	mntget(*mount);
+	++*count;
+	spin_unlock(&pin_fs_lock);
+	mntput(mnt);
+	return 0;
+}
+EXPORT_SYMBOL(simple_pin_fs);
+
+void simple_release_fs(struct vfsmount **mount, int *count)
+{
+	struct vfsmount *mnt;
+	spin_lock(&pin_fs_lock);
+	mnt = *mount;
+	if (!--*count)
+		*mount = NULL;
+	spin_unlock(&pin_fs_lock);
+	mntput(mnt);
+}
+EXPORT_SYMBOL(simple_release_fs);
+
+/**
+ * simple_read_from_buffer - copy data from the buffer to user space
+ * @to: the user space buffer to read to
+ * @count: the maximum number of bytes to read
+ * @ppos: the current position in the buffer
+ * @from: the buffer to read from
+ * @available: the size of the buffer
+ *
+ * The simple_read_from_buffer() function reads up to @count bytes from the
+ * buffer @from at offset @ppos into the user space address starting at @to.
+ *
+ * On success, the number of bytes read is returned and the offset @ppos is
+ * advanced by this number, or negative value is returned on error.
+ **/
+ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos,
+				const void *from, size_t available)
+{
+	loff_t pos = *ppos;
+	size_t ret;
+
+	if (pos < 0)
+		return -EINVAL;
+	if (pos >= available || !count)
+		return 0;
+	if (count > available - pos)
+		count = available - pos;
+	ret = copy_to_user(to, from + pos, count);
+	if (ret == count)
+		return -EFAULT;
+	count -= ret;
+	*ppos = pos + count;
+	return count;
+}
+EXPORT_SYMBOL(simple_read_from_buffer);
+
+/**
+ * simple_write_to_buffer - copy data from user space to the buffer
+ * @to: the buffer to write to
+ * @available: the size of the buffer
+ * @ppos: the current position in the buffer
+ * @from: the user space buffer to read from
+ * @count: the maximum number of bytes to read
+ *
+ * The simple_write_to_buffer() function reads up to @count bytes from the user
+ * space address starting at @from into the buffer @to at offset @ppos.
+ *
+ * On success, the number of bytes written is returned and the offset @ppos is
+ * advanced by this number, or negative value is returned on error.
+ **/
+ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos,
+		const void __user *from, size_t count)
+{
+	loff_t pos = *ppos;
+	size_t res;
+
+	if (pos < 0)
+		return -EINVAL;
+	if (pos >= available || !count)
+		return 0;
+	if (count > available - pos)
+		count = available - pos;
+	res = copy_from_user(to + pos, from, count);
+	if (res == count)
+		return -EFAULT;
+	count -= res;
+	*ppos = pos + count;
+	return count;
+}
+EXPORT_SYMBOL(simple_write_to_buffer);
+
+/**
+ * memory_read_from_buffer - copy data from the buffer
+ * @to: the kernel space buffer to read to
+ * @count: the maximum number of bytes to read
+ * @ppos: the current position in the buffer
+ * @from: the buffer to read from
+ * @available: the size of the buffer
+ *
+ * The memory_read_from_buffer() function reads up to @count bytes from the
+ * buffer @from at offset @ppos into the kernel space address starting at @to.
+ *
+ * On success, the number of bytes read is returned and the offset @ppos is
+ * advanced by this number, or negative value is returned on error.
+ **/
+ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos,
+				const void *from, size_t available)
+{
+	loff_t pos = *ppos;
+
+	if (pos < 0)
+		return -EINVAL;
+	if (pos >= available)
+		return 0;
+	if (count > available - pos)
+		count = available - pos;
+	memcpy(to, from + pos, count);
+	*ppos = pos + count;
+
+	return count;
+}
+EXPORT_SYMBOL(memory_read_from_buffer);
+
+/*
+ * Transaction based IO.
+ * The file expects a single write which triggers the transaction, and then
+ * possibly a read which collects the result - which is stored in a
+ * file-local buffer.
+ */
+
+void simple_transaction_set(struct file *file, size_t n)
+{
+	struct simple_transaction_argresp *ar = file->private_data;
+
+	BUG_ON(n > SIMPLE_TRANSACTION_LIMIT);
+
+	/*
+	 * The barrier ensures that ar->size will really remain zero until
+	 * ar->data is ready for reading.
+	 */
+	smp_mb();
+	ar->size = n;
+}
+EXPORT_SYMBOL(simple_transaction_set);
+
+char *simple_transaction_get(struct file *file, const char __user *buf, size_t size)
+{
+	struct simple_transaction_argresp *ar;
+	static DEFINE_SPINLOCK(simple_transaction_lock);
+
+	if (size > SIMPLE_TRANSACTION_LIMIT - 1)
+		return ERR_PTR(-EFBIG);
+
+	ar = kzalloc(PAGE_SIZE, GFP_KERNEL);
+	if (!ar)
+		return ERR_PTR(-ENOMEM);
+
+	spin_lock(&simple_transaction_lock);
+
+	/* only one write allowed per open */
+	if (file->private_data) {
+		spin_unlock(&simple_transaction_lock);
+		kfree(ar);
+		return ERR_PTR(-EBUSY);
+	}
+
+	file->private_data = ar;
+
+	spin_unlock(&simple_transaction_lock);
+
+	if (copy_from_user(ar->data, buf, size))
+		return ERR_PTR(-EFAULT);
+
+	return ar->data;
+}
+EXPORT_SYMBOL(simple_transaction_get);
+
+ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos)
+{
+	struct simple_transaction_argresp *ar = file->private_data;
+
+	if (!ar)
+		return 0;
+	return simple_read_from_buffer(buf, size, pos, ar->data, ar->size);
+}
+EXPORT_SYMBOL(simple_transaction_read);
+
+int simple_transaction_release(struct inode *inode, struct file *file)
+{
+	kfree(file->private_data);
+	return 0;
+}
+EXPORT_SYMBOL(simple_transaction_release);
+
+/* Simple attribute files */
+
+struct simple_attr {
+	int (*get)(void *, u64 *);
+	int (*set)(void *, u64);
+	char get_buf[24];	/* enough to store a u64 and "\n\0" */
+	char set_buf[24];
+	void *data;
+	const char *fmt;	/* format for read operation */
+	struct mutex mutex;	/* protects access to these buffers */
+};
+
+/* simple_attr_open is called by an actual attribute open file operation
+ * to set the attribute specific access operations. */
+int simple_attr_open(struct inode *inode, struct file *file,
+		     int (*get)(void *, u64 *), int (*set)(void *, u64),
+		     const char *fmt)
+{
+	struct simple_attr *attr;
+
+	attr = kzalloc_obj(*attr);
+	if (!attr)
+		return -ENOMEM;
+
+	attr->get = get;
+	attr->set = set;
+	attr->data = inode->i_private;
+	attr->fmt = fmt;
+	mutex_init(&attr->mutex);
+
+	file->private_data = attr;
+
+	return nonseekable_open(inode, file);
+}
+EXPORT_SYMBOL_GPL(simple_attr_open);
+
+int simple_attr_release(struct inode *inode, struct file *file)
+{
+	kfree(file->private_data);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(simple_attr_release);	/* GPL-only?  This?  Really? */
+
+/* read from the buffer that is filled with the get function */
+ssize_t simple_attr_read(struct file *file, char __user *buf,
+			 size_t len, loff_t *ppos)
+{
+	struct simple_attr *attr;
+	size_t size;
+	ssize_t ret;
+
+	attr = file->private_data;
+
+	if (!attr->get)
+		return -EACCES;
+
+	ret = mutex_lock_interruptible(&attr->mutex);
+	if (ret)
+		return ret;
+
+	if (*ppos && attr->get_buf[0]) {
+		/* continued read */
+		size = strlen(attr->get_buf);
+	} else {
+		/* first read */
+		u64 val;
+		ret = attr->get(attr->data, &val);
+		if (ret)
+			goto out;
+
+		size = scnprintf(attr->get_buf, sizeof(attr->get_buf),
+				 attr->fmt, (unsigned long long)val);
+	}
+
+	ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
+out:
+	mutex_unlock(&attr->mutex);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(simple_attr_read);
+
+/* interpret the buffer as a number to call the set function with */
+static ssize_t simple_attr_write_xsigned(struct file *file, const char __user *buf,
+			  size_t len, loff_t *ppos, bool is_signed)
+{
+	struct simple_attr *attr;
+	unsigned long long val;
+	size_t size;
+	ssize_t ret;
+
+	attr = file->private_data;
+	if (!attr->set)
+		return -EACCES;
+
+	ret = mutex_lock_interruptible(&attr->mutex);
+	if (ret)
+		return ret;
+
+	ret = -EFAULT;
+	size = min(sizeof(attr->set_buf) - 1, len);
+	if (copy_from_user(attr->set_buf, buf, size))
+		goto out;
+
+	attr->set_buf[size] = '\0';
+	if (is_signed)
+		ret = kstrtoll(attr->set_buf, 0, &val);
+	else
+		ret = kstrtoull(attr->set_buf, 0, &val);
+	if (ret)
+		goto out;
+	ret = attr->set(attr->data, val);
+	if (ret == 0)
+		ret = len; /* on success, claim we got the whole input */
+out:
+	mutex_unlock(&attr->mutex);
+	return ret;
+}
+
+ssize_t simple_attr_write(struct file *file, const char __user *buf,
+			  size_t len, loff_t *ppos)
+{
+	return simple_attr_write_xsigned(file, buf, len, ppos, false);
+}
+EXPORT_SYMBOL_GPL(simple_attr_write);
+
+ssize_t simple_attr_write_signed(struct file *file, const char __user *buf,
+			  size_t len, loff_t *ppos)
+{
+	return simple_attr_write_xsigned(file, buf, len, ppos, true);
+}
+EXPORT_SYMBOL_GPL(simple_attr_write_signed);
+
+/**
+ * generic_encode_ino32_fh - generic export_operations->encode_fh function
+ * @inode:   the object to encode
+ * @fh:      where to store the file handle fragment
+ * @max_len: maximum length to store there (in 4 byte units)
+ * @parent:  parent directory inode, if wanted
+ *
+ * This generic encode_fh function assumes that the 32 inode number
+ * is suitable for locating an inode, and that the generation number
+ * can be used to check that it is still valid.  It places them in the
+ * filehandle fragment where export_decode_fh expects to find them.
+ */
+int generic_encode_ino32_fh(struct inode *inode, __u32 *fh, int *max_len,
+			    struct inode *parent)
+{
+	struct fid *fid = (void *)fh;
+	int len = *max_len;
+	int type = FILEID_INO32_GEN;
+
+	if (parent && (len < 4)) {
+		*max_len = 4;
+		return FILEID_INVALID;
+	} else if (len < 2) {
+		*max_len = 2;
+		return FILEID_INVALID;
+	}
+
+	len = 2;
+	fid->i32.ino = inode->i_ino;
+	fid->i32.gen = inode->i_generation;
+	if (parent) {
+		fid->i32.parent_ino = parent->i_ino;
+		fid->i32.parent_gen = parent->i_generation;
+		len = 4;
+		type = FILEID_INO32_GEN_PARENT;
+	}
+	*max_len = len;
+	return type;
+}
+EXPORT_SYMBOL_GPL(generic_encode_ino32_fh);
+
+/**
+ * generic_fh_to_dentry - generic helper for the fh_to_dentry export operation
+ * @sb:		filesystem to do the file handle conversion on
+ * @fid:	file handle to convert
+ * @fh_len:	length of the file handle in bytes
+ * @fh_type:	type of file handle
+ * @get_inode:	filesystem callback to retrieve inode
+ *
+ * This function decodes @fid as long as it has one of the well-known
+ * Linux filehandle types and calls @get_inode on it to retrieve the
+ * inode for the object specified in the file handle.
+ */
+struct dentry *generic_fh_to_dentry(struct super_block *sb, struct fid *fid,
+		int fh_len, int fh_type, struct inode *(*get_inode)
+			(struct super_block *sb, u64 ino, u32 gen))
+{
+	struct inode *inode = NULL;
+
+	if (fh_len < 2)
+		return NULL;
+
+	switch (fh_type) {
+	case FILEID_INO32_GEN:
+	case FILEID_INO32_GEN_PARENT:
+		inode = get_inode(sb, fid->i32.ino, fid->i32.gen);
+		break;
+	}
+
+	return d_obtain_alias(inode);
+}
+EXPORT_SYMBOL_GPL(generic_fh_to_dentry);
+
+/**
+ * generic_fh_to_parent - generic helper for the fh_to_parent export operation
+ * @sb:		filesystem to do the file handle conversion on
+ * @fid:	file handle to convert
+ * @fh_len:	length of the file handle in bytes
+ * @fh_type:	type of file handle
+ * @get_inode:	filesystem callback to retrieve inode
+ *
+ * This function decodes @fid as long as it has one of the well-known
+ * Linux filehandle types and calls @get_inode on it to retrieve the
+ * inode for the _parent_ object specified in the file handle if it
+ * is specified in the file handle, or NULL otherwise.
+ */
+struct dentry *generic_fh_to_parent(struct super_block *sb, struct fid *fid,
+		int fh_len, int fh_type, struct inode *(*get_inode)
+			(struct super_block *sb, u64 ino, u32 gen))
+{
+	struct inode *inode = NULL;
+
+	if (fh_len <= 2)
+		return NULL;
+
+	switch (fh_type) {
+	case FILEID_INO32_GEN_PARENT:
+		inode = get_inode(sb, fid->i32.parent_ino,
+				  (fh_len > 3 ? fid->i32.parent_gen : 0));
+		break;
+	}
+
+	return d_obtain_alias(inode);
+}
+EXPORT_SYMBOL_GPL(generic_fh_to_parent);
+
+/**
+ * simple_fsync_noflush - generic fsync implementation for simple filesystems
+ *
+ * @file:	file to synchronize
+ * @start:	start offset in bytes
+ * @end:	end offset in bytes (inclusive)
+ * @datasync:	only synchronize essential metadata if true
+ *
+ * This function is an fsync handler for simple filesystems. It writes out
+ * dirty data, inode (if dirty), but does not issue a cache flush.
+ */
+int simple_fsync_noflush(struct file *file, loff_t start, loff_t end,
+			 int datasync)
+{
+	struct inode *inode = file->f_mapping->host;
+	int err;
+	int ret = 0;
+
+	err = file_write_and_wait_range(file, start, end);
+	if (err)
+		return err;
+
+	if (!(inode_state_read_once(inode) &
+			(I_DIRTY_ALL | I_SYNC | I_METADATA_WRITEBACK)))
+		goto out;
+	if (datasync &&
+	    !(inode_state_read_once(inode) &
+			(I_DIRTY_DATASYNC | I_SYNC | I_METADATA_WRITEBACK)))
+		goto out;
+
+	ret = sync_inode_metadata(inode, 1);
+out:
+	/* check and advance again to catch errors after syncing out buffers */
+	err = file_check_and_advance_wb_err(file);
+	if (ret == 0)
+		ret = err;
+	return ret;
+}
+EXPORT_SYMBOL(simple_fsync_noflush);
+
+/**
+ * simple_fsync - fsync implementation for simple filesystems with flush
+ * @file:	file to synchronize
+ * @start:	start offset in bytes
+ * @end:	end offset in bytes (inclusive)
+ * @datasync:	only synchronize essential metadata if true
+ *
+ * This function is an fsync handler for simple filesystems. It writes out
+ * dirty data, inode (if dirty), and issues a cache flush.
+ */
+int simple_fsync(struct file *file, loff_t start, loff_t end, int datasync)
+{
+	struct inode *inode = file->f_mapping->host;
+	int err;
+
+	err = simple_fsync_noflush(file, start, end, datasync);
+	if (err)
+		return err;
+	return blkdev_issue_flush(inode->i_sb->s_bdev);
+}
+EXPORT_SYMBOL(simple_fsync);
+
+/**
+ * generic_check_addressable - Check addressability of file system
+ * @blocksize_bits:	log of file system block size
+ * @num_blocks:		number of blocks in file system
+ *
+ * Determine whether a file system with @num_blocks blocks (and a
+ * block size of 2**@blocksize_bits) is addressable by the sector_t
+ * and page cache of the system.  Return 0 if so and -EFBIG otherwise.
+ */
+int generic_check_addressable(unsigned blocksize_bits, u64 num_blocks)
+{
+	u64 last_fs_block = num_blocks - 1;
+	u64 last_fs_page, max_bytes;
+
+	if (check_shl_overflow(num_blocks, blocksize_bits, &max_bytes))
+		return -EFBIG;
+
+	last_fs_page = (max_bytes >> PAGE_SHIFT) - 1;
+
+	if (unlikely(num_blocks == 0))
+		return 0;
+
+	if (blocksize_bits < 9)
+		return -EINVAL;
+
+	if ((last_fs_block > (sector_t)(~0ULL) >> (blocksize_bits - 9)) ||
+	    (last_fs_page > (pgoff_t)(~0ULL))) {
+		return -EFBIG;
+	}
+	return 0;
+}
+EXPORT_SYMBOL(generic_check_addressable);
+
+/*
+ * No-op implementation of ->fsync for in-memory filesystems.
+ */
+int noop_fsync(struct file *file, loff_t start, loff_t end, int datasync)
+{
+	return 0;
+}
+EXPORT_SYMBOL(noop_fsync);
+
+ssize_t noop_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
+{
+	/*
+	 * iomap based filesystems support direct I/O without need for
+	 * this callback. However, it still needs to be set in
+	 * inode->a_ops so that open/fcntl know that direct I/O is
+	 * generally supported.
+	 */
+	return -EINVAL;
+}
+EXPORT_SYMBOL_GPL(noop_direct_IO);
+
+/* Because kfree isn't assignment-compatible with void(void*) ;-/ */
+void kfree_link(void *p)
+{
+	kfree(p);
+}
+EXPORT_SYMBOL(kfree_link);
+
+struct inode *alloc_anon_inode(struct super_block *s)
+{
+	static const struct address_space_operations anon_aops = {
+		.dirty_folio	= noop_dirty_folio,
+	};
+	struct inode *inode = new_inode_pseudo(s);
+
+	if (!inode)
+		return ERR_PTR(-ENOMEM);
+
+	inode->i_ino = get_next_ino();
+	inode->i_mapping->a_ops = &anon_aops;
+
+	/*
+	 * Mark the inode dirty from the very beginning,
+	 * that way it will never be moved to the dirty
+	 * list because mark_inode_dirty() will think
+	 * that it already _is_ on the dirty list.
+	 */
+	inode_state_assign_raw(inode, I_DIRTY);
+	/*
+	 * Historically anonymous inodes don't have a type at all and
+	 * userspace has come to rely on this.
+	 */
+	inode->i_mode = S_IRUSR | S_IWUSR;
+	inode->i_uid = current_fsuid();
+	inode->i_gid = current_fsgid();
+	inode->i_flags |= S_PRIVATE | S_ANON_INODE;
+	simple_inode_init_ts(inode);
+	return inode;
+}
+EXPORT_SYMBOL(alloc_anon_inode);
+
+/**
+ * simple_get_link - generic helper to get the target of "fast" symlinks
+ * @dentry: not used here
+ * @inode: the symlink inode
+ * @done: not used here
+ *
+ * Generic helper for filesystems to use for symlink inodes where a pointer to
+ * the symlink target is stored in ->i_link.  NOTE: this isn't normally called,
+ * since as an optimization the path lookup code uses any non-NULL ->i_link
+ * directly, without calling ->get_link().  But ->get_link() still must be set,
+ * to mark the inode_operations as being for a symlink.
+ *
+ * Return: the symlink target
+ */
+const char *simple_get_link(struct dentry *dentry, struct inode *inode,
+			    struct delayed_call *done)
+{
+	return inode->i_link;
+}
+EXPORT_SYMBOL(simple_get_link);
+
+const struct inode_operations simple_symlink_inode_operations = {
+	.get_link = simple_get_link,
+};
+EXPORT_SYMBOL(simple_symlink_inode_operations);
+
+/*
+ * Operations for a permanently empty directory.
+ */
+static struct dentry *empty_dir_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
+{
+	return ERR_PTR(-ENOENT);
+}
+
+static int empty_dir_setattr(struct mnt_idmap *idmap,
+			     struct dentry *dentry, struct iattr *attr)
+{
+	return -EPERM;
+}
+
+static ssize_t empty_dir_listxattr(struct dentry *dentry, char *list, size_t size)
+{
+	return -EOPNOTSUPP;
+}
+
+static const struct inode_operations empty_dir_inode_operations = {
+	.lookup		= empty_dir_lookup,
+	.setattr	= empty_dir_setattr,
+	.listxattr	= empty_dir_listxattr,
+};
+
+static loff_t empty_dir_llseek(struct file *file, loff_t offset, int whence)
+{
+	/* An empty directory has two entries . and .. at offsets 0 and 1 */
+	return generic_file_llseek_size(file, offset, whence, 2, 2);
+}
+
+static int empty_dir_readdir(struct file *file, struct dir_context *ctx)
+{
+	dir_emit_dots(file, ctx);
+	return 0;
+}
+
+static const struct file_operations empty_dir_operations = {
+	.llseek		= empty_dir_llseek,
+	.read		= generic_read_dir,
+	.iterate_shared	= empty_dir_readdir,
+	.fsync		= noop_fsync,
+};
+
+
+void make_empty_dir_inode(struct inode *inode)
+{
+	set_nlink(inode, 2);
+	inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO;
+	inode->i_uid = GLOBAL_ROOT_UID;
+	inode->i_gid = GLOBAL_ROOT_GID;
+	inode->i_rdev = 0;
+	inode->i_size = 0;
+	inode->i_blkbits = PAGE_SHIFT;
+	inode->i_blocks = 0;
+
+	inode->i_op = &empty_dir_inode_operations;
+	inode->i_opflags &= ~IOP_XATTR;
+	inode->i_fop = &empty_dir_operations;
+}
+
+bool is_empty_dir_inode(struct inode *inode)
+{
+	return (inode->i_fop == &empty_dir_operations) &&
+		(inode->i_op == &empty_dir_inode_operations);
+}
+
+#if IS_ENABLED(CONFIG_UNICODE)
+/**
+ * generic_ci_d_compare - generic d_compare implementation for casefolding filesystems
+ * @dentry:	dentry whose name we are checking against
+ * @len:	len of name of dentry
+ * @str:	str pointer to name of dentry
+ * @name:	Name to compare against
+ *
+ * Return: 0 if names match, 1 if mismatch, or -ERRNO
+ */
+int generic_ci_d_compare(const struct dentry *dentry, unsigned int len,
+			 const char *str, const struct qstr *name)
+{
+	const struct dentry *parent;
+	const struct inode *dir;
+	union shortname_store strbuf;
+	struct qstr qstr;
+
+	/*
+	 * Attempt a case-sensitive match first. It is cheaper and
+	 * should cover most lookups, including all the sane
+	 * applications that expect a case-sensitive filesystem.
+	 *
+	 * This comparison is safe under RCU because the caller
+	 * guarantees the consistency between str and len. See
+	 * __d_lookup_rcu_op_compare() for details.
+	 */
+	if (len == name->len && !memcmp(str, name->name, len))
+		return 0;
+
+	parent = READ_ONCE(dentry->d_parent);
+	dir = READ_ONCE(parent->d_inode);
+	if (!dir || !IS_CASEFOLDED(dir))
+		return 1;
+
+	qstr.len = len;
+	qstr.name = str;
+	/*
+	 * If the dentry name is stored in-line, then it may be concurrently
+	 * modified by a rename.  If this happens, the VFS will eventually retry
+	 * the lookup, so it doesn't matter what ->d_compare() returns.
+	 * However, it's unsafe to call utf8_strncasecmp() with an unstable
+	 * string.  Therefore, we have to copy the name into a temporary buffer.
+	 * As above, len is guaranteed to match str, so the shortname case
+	 * is exactly when str points to ->d_shortname.
+	 */
+	if (qstr.name == dentry->d_shortname.string) {
+		strbuf = dentry->d_shortname; // NUL is guaranteed to be in there
+		qstr.name = strbuf.string;
+		/* prevent compiler from optimizing out the temporary buffer */
+		barrier();
+	}
+
+	return utf8_strncasecmp(dentry->d_sb->s_encoding, name, &qstr);
+}
+EXPORT_SYMBOL(generic_ci_d_compare);
+
+/**
+ * generic_ci_d_hash - generic d_hash implementation for casefolding filesystems
+ * @dentry:	dentry of the parent directory
+ * @str:	qstr of name whose hash we should fill in
+ *
+ * Return: 0 if hash was successful or unchanged, and -EINVAL on error
+ */
+int generic_ci_d_hash(const struct dentry *dentry, struct qstr *str)
+{
+	const struct inode *dir = READ_ONCE(dentry->d_inode);
+	struct super_block *sb = dentry->d_sb;
+	const struct unicode_map *um = sb->s_encoding;
+	int ret;
+
+	if (!dir || !IS_CASEFOLDED(dir))
+		return 0;
+
+	ret = utf8_casefold_hash(um, dentry, str);
+	if (ret < 0 && sb_has_strict_encoding(sb))
+		return -EINVAL;
+	return 0;
+}
+EXPORT_SYMBOL(generic_ci_d_hash);
+
+static const struct dentry_operations generic_ci_dentry_ops = {
+	.d_hash = generic_ci_d_hash,
+	.d_compare = generic_ci_d_compare,
+#ifdef CONFIG_FS_ENCRYPTION
+	.d_revalidate = fscrypt_d_revalidate,
+#endif
+};
+
+/**
+ * generic_ci_match() - Match a name (case-insensitively) with a dirent.
+ * This is a filesystem helper for comparison with directory entries.
+ * generic_ci_d_compare should be used in VFS' ->d_compare instead.
+ *
+ * @parent: Inode of the parent of the dirent under comparison
+ * @name: name under lookup.
+ * @folded_name: Optional pre-folded name under lookup
+ * @de_name: Dirent name.
+ * @de_name_len: dirent name length.
+ *
+ * Test whether a case-insensitive directory entry matches the filename
+ * being searched.  If @folded_name is provided, it is used instead of
+ * recalculating the casefold of @name.
+ *
+ * Return: > 0 if the directory entry matches, 0 if it doesn't match, or
+ * < 0 on error.
+ */
+int generic_ci_match(const struct inode *parent,
+		     const struct qstr *name,
+		     const struct qstr *folded_name,
+		     const u8 *de_name, u32 de_name_len)
+{
+	const struct super_block *sb = parent->i_sb;
+	const struct unicode_map *um = sb->s_encoding;
+	struct fscrypt_str decrypted_name = FSTR_INIT(NULL, de_name_len);
+	struct qstr dirent = QSTR_INIT(de_name, de_name_len);
+	int res = 0;
+
+	if (IS_ENCRYPTED(parent)) {
+		const struct fscrypt_str encrypted_name =
+			FSTR_INIT((u8 *) de_name, de_name_len);
+
+		if (WARN_ON_ONCE(!fscrypt_has_encryption_key(parent)))
+			return -EINVAL;
+
+		decrypted_name.name = kmalloc(de_name_len, GFP_KERNEL);
+		if (!decrypted_name.name)
+			return -ENOMEM;
+		res = fscrypt_fname_disk_to_usr(parent, 0, 0, &encrypted_name,
+						&decrypted_name);
+		if (res < 0) {
+			kfree(decrypted_name.name);
+			return res;
+		}
+		dirent.name = decrypted_name.name;
+		dirent.len = decrypted_name.len;
+	}
+
+	/*
+	 * Attempt a case-sensitive match first. It is cheaper and
+	 * should cover most lookups, including all the sane
+	 * applications that expect a case-sensitive filesystem.
+	 */
+
+	if (dirent.len == name->len &&
+	    !memcmp(name->name, dirent.name, dirent.len))
+		goto out;
+
+	if (folded_name->name)
+		res = utf8_strncasecmp_folded(um, folded_name, &dirent);
+	else
+		res = utf8_strncasecmp(um, name, &dirent);
+
+out:
+	kfree(decrypted_name.name);
+	if (res < 0 && sb_has_strict_encoding(sb)) {
+		pr_err_ratelimited("Directory contains filename that is invalid UTF-8");
+		return 0;
+	}
+	return !res;
+}
+EXPORT_SYMBOL(generic_ci_match);
+#endif
+
+#ifdef CONFIG_FS_ENCRYPTION
+static const struct dentry_operations generic_encrypted_dentry_ops = {
+	.d_revalidate = fscrypt_d_revalidate,
+};
+#endif
+
+/**
+ * generic_set_sb_d_ops - helper for choosing the set of
+ * filesystem-wide dentry operations for the enabled features
+ * @sb: superblock to be configured
+ *
+ * Filesystems supporting casefolding and/or fscrypt can call this
+ * helper at mount-time to configure default dentry_operations to the
+ * best set of dentry operations required for the enabled features.
+ * The helper must be called after these have been configured, but
+ * before the root dentry is created.
+ */
+void generic_set_sb_d_ops(struct super_block *sb)
+{
+#if IS_ENABLED(CONFIG_UNICODE)
+	if (sb->s_encoding) {
+		set_default_d_op(sb, &generic_ci_dentry_ops);
+		return;
+	}
+#endif
+#ifdef CONFIG_FS_ENCRYPTION
+	if (sb->s_cop) {
+		set_default_d_op(sb, &generic_encrypted_dentry_ops);
+		return;
+	}
+#endif
+}
+EXPORT_SYMBOL(generic_set_sb_d_ops);
+
+/**
+ * inode_maybe_inc_iversion - increments i_version
+ * @inode: inode with the i_version that should be updated
+ * @force: increment the counter even if it's not necessary?
+ *
+ * Every time the inode is modified, the i_version field must be seen to have
+ * changed by any observer.
+ *
+ * If "force" is set or the QUERIED flag is set, then ensure that we increment
+ * the value, and clear the queried flag.
+ *
+ * In the common case where neither is set, then we can return "false" without
+ * updating i_version.
+ *
+ * If this function returns false, and no other metadata has changed, then we
+ * can avoid logging the metadata.
+ */
+bool inode_maybe_inc_iversion(struct inode *inode, bool force)
+{
+	u64 cur, new;
+
+	/*
+	 * The i_version field is not strictly ordered with any other inode
+	 * information, but the legacy inode_inc_iversion code used a spinlock
+	 * to serialize increments.
+	 *
+	 * We add a full memory barrier to ensure that any de facto ordering
+	 * with other state is preserved (either implicitly coming from cmpxchg
+	 * or explicitly from smp_mb if we don't know upfront if we will execute
+	 * the former).
+	 *
+	 * These barriers pair with inode_query_iversion().
+	 */
+	cur = inode_peek_iversion_raw(inode);
+	if (!force && !(cur & I_VERSION_QUERIED)) {
+		smp_mb();
+		cur = inode_peek_iversion_raw(inode);
+	}
+
+	do {
+		/* If flag is clear then we needn't do anything */
+		if (!force && !(cur & I_VERSION_QUERIED))
+			return false;
+
+		/* Since lowest bit is flag, add 2 to avoid it */
+		new = (cur & ~I_VERSION_QUERIED) + I_VERSION_INCREMENT;
+	} while (!atomic64_try_cmpxchg(&inode->i_version, &cur, new));
+	return true;
+}
+EXPORT_SYMBOL(inode_maybe_inc_iversion);
+
+/**
+ * inode_query_iversion - read i_version for later use
+ * @inode: inode from which i_version should be read
+ *
+ * Read the inode i_version counter. This should be used by callers that wish
+ * to store the returned i_version for later comparison. This will guarantee
+ * that a later query of the i_version will result in a different value if
+ * anything has changed.
+ *
+ * In this implementation, we fetch the current value, set the QUERIED flag and
+ * then try to swap it into place with a cmpxchg, if it wasn't already set. If
+ * that fails, we try again with the newly fetched value from the cmpxchg.
+ */
+u64 inode_query_iversion(struct inode *inode)
+{
+	u64 cur, new;
+	bool fenced = false;
+
+	/*
+	 * Memory barriers (implicit in cmpxchg, explicit in smp_mb) pair with
+	 * inode_maybe_inc_iversion(), see that routine for more details.
+	 */
+	cur = inode_peek_iversion_raw(inode);
+	do {
+		/* If flag is already set, then no need to swap */
+		if (cur & I_VERSION_QUERIED) {
+			if (!fenced)
+				smp_mb();
+			break;
+		}
+
+		fenced = true;
+		new = cur | I_VERSION_QUERIED;
+	} while (!atomic64_try_cmpxchg(&inode->i_version, &cur, new));
+	return cur >> I_VERSION_QUERIED_SHIFT;
+}
+EXPORT_SYMBOL(inode_query_iversion);
+
+ssize_t direct_write_fallback(struct kiocb *iocb, struct iov_iter *iter,
+		ssize_t direct_written, ssize_t buffered_written)
+{
+	struct address_space *mapping = iocb->ki_filp->f_mapping;
+	loff_t pos = iocb->ki_pos - buffered_written;
+	loff_t end = iocb->ki_pos - 1;
+	int err;
+
+	/*
+	 * If the buffered write fallback returned an error, we want to return
+	 * the number of bytes which were written by direct I/O, or the error
+	 * code if that was zero.
+	 *
+	 * Note that this differs from normal direct-io semantics, which will
+	 * return -EFOO even if some bytes were written.
+	 */
+	if (unlikely(buffered_written < 0)) {
+		if (direct_written)
+			return direct_written;
+		return buffered_written;
+	}
+
+	/*
+	 * We need to ensure that the page cache pages are written to disk and
+	 * invalidated to preserve the expected O_DIRECT semantics.
+	 */
+	err = filemap_write_and_wait_range(mapping, pos, end);
+	if (err < 0) {
+		/*
+		 * We don't know how much we wrote, so just return the number of
+		 * bytes which were direct-written
+		 */
+		iocb->ki_pos -= buffered_written;
+		if (direct_written)
+			return direct_written;
+		return err;
+	}
+	invalidate_mapping_pages(mapping, pos >> PAGE_SHIFT, end >> PAGE_SHIFT);
+	return direct_written + buffered_written;
+}
+EXPORT_SYMBOL_GPL(direct_write_fallback);
+
+/**
+ * simple_inode_init_ts - initialize the timestamps for a new inode
+ * @inode: inode to be initialized
+ *
+ * When a new inode is created, most filesystems set the timestamps to the
+ * current time. Add a helper to do this.
+ */
+struct timespec64 simple_inode_init_ts(struct inode *inode)
+{
+	struct timespec64 ts = inode_set_ctime_current(inode);
+
+	inode_set_atime_to_ts(inode, ts);
+	inode_set_mtime_to_ts(inode, ts);
+	return ts;
+}
+EXPORT_SYMBOL(simple_inode_init_ts);
+
+struct dentry *stashed_dentry_get(struct dentry **stashed)
+{
+	struct dentry *dentry;
+
+	guard(rcu)();
+	dentry = rcu_dereference(*stashed);
+	if (!dentry)
+		return NULL;
+	if (IS_ERR(dentry))
+		return dentry;
+	if (!lockref_get_not_dead(&dentry->d_lockref))
+		return NULL;
+	return dentry;
+}
+
+static struct dentry *prepare_anon_dentry(struct dentry **stashed,
+					  struct super_block *sb,
+					  void *data)
+{
+	struct dentry *dentry;
+	struct inode *inode;
+	const struct stashed_operations *sops = sb->s_fs_info;
+	int ret;
+
+	inode = new_inode_pseudo(sb);
+	if (!inode) {
+		sops->put_data(data);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	inode->i_flags |= S_IMMUTABLE;
+	inode->i_mode = S_IFREG;
+	simple_inode_init_ts(inode);
+
+	ret = sops->init_inode(inode, data);
+	if (ret < 0) {
+		iput(inode);
+		return ERR_PTR(ret);
+	}
+
+	/* Notice when this is changed. */
+	WARN_ON_ONCE(!S_ISREG(inode->i_mode));
+
+	dentry = d_alloc_anon(sb);
+	if (!dentry) {
+		iput(inode);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	/* Store address of location where dentry's supposed to be stashed. */
+	dentry->d_fsdata = stashed;
+
+	/* @data is now owned by the fs */
+	d_instantiate(dentry, inode);
+	return dentry;
+}
+
+struct dentry *stash_dentry(struct dentry **stashed, struct dentry *dentry)
+{
+	guard(rcu)();
+	for (;;) {
+		struct dentry *old;
+
+		/* Assume any old dentry was cleared out. */
+		old = cmpxchg(stashed, NULL, dentry);
+		if (likely(!old))
+			return dentry;
+
+		/* Check if somebody else installed a reusable dentry. */
+		if (lockref_get_not_dead(&old->d_lockref))
+			return old;
+
+		/* There's an old dead dentry there, try to take it over. */
+		if (likely(try_cmpxchg(stashed, &old, dentry)))
+			return dentry;
+	}
+}
+
+/**
+ * path_from_stashed - create path from stashed or new dentry
+ * @stashed:    where to retrieve or stash dentry
+ * @mnt:        mnt of the filesystems to use
+ * @data:       data to store in inode->i_private
+ * @path:       path to create
+ *
+ * The function tries to retrieve a stashed dentry from @stashed. If the dentry
+ * is still valid then it will be reused. If the dentry isn't able the function
+ * will allocate a new dentry and inode. It will then check again whether it
+ * can reuse an existing dentry in case one has been added in the meantime or
+ * update @stashed with the newly added dentry.
+ *
+ * Special-purpose helper for nsfs and pidfs.
+ *
+ * Return: On success zero and on failure a negative error is returned.
+ */
+int path_from_stashed(struct dentry **stashed, struct vfsmount *mnt, void *data,
+		      struct path *path)
+{
+	struct dentry *dentry, *res;
+	const struct stashed_operations *sops = mnt->mnt_sb->s_fs_info;
+
+	/* See if dentry can be reused. */
+	res = stashed_dentry_get(stashed);
+	if (IS_ERR(res))
+		return PTR_ERR(res);
+	if (res) {
+		sops->put_data(data);
+		goto make_path;
+	}
+
+	/* Allocate a new dentry. */
+	dentry = prepare_anon_dentry(stashed, mnt->mnt_sb, data);
+	if (IS_ERR(dentry))
+		return PTR_ERR(dentry);
+
+	/* Added a new dentry. @data is now owned by the filesystem. */
+	if (sops->stash_dentry)
+		res = sops->stash_dentry(stashed, dentry);
+	else
+		res = stash_dentry(stashed, dentry);
+	if (IS_ERR(res)) {
+		dput(dentry);
+		return PTR_ERR(res);
+	}
+	if (res != dentry)
+		dput(dentry);
+
+make_path:
+	path->dentry = res;
+	path->mnt = mntget(mnt);
+	VFS_WARN_ON_ONCE(path->dentry->d_fsdata != stashed);
+	VFS_WARN_ON_ONCE(d_inode(path->dentry)->i_private != data);
+	return 0;
+}
+
+void stashed_dentry_prune(struct dentry *dentry)
+{
+	struct dentry **stashed = dentry->d_fsdata;
+	struct inode *inode = d_inode(dentry);
+
+	if (WARN_ON_ONCE(!stashed))
+		return;
+
+	if (!inode)
+		return;
+
+	/*
+	 * Only replace our own @dentry as someone else might've
+	 * already cleared out @dentry and stashed their own
+	 * dentry in there.
+	 */
+	cmpxchg(stashed, dentry, NULL);
+}
+
+/**
+ * simple_start_creating - prepare to create a given name
+ * @parent: directory in which to prepare to create the name
+ * @name:   the name to be created
+ *
+ * Required lock is taken and a lookup in performed prior to creating an
+ * object in a directory.  No permission checking is performed.
+ *
+ * Returns: a negative dentry on which vfs_create() or similar may
+ *  be attempted, or an error.
+ */
+struct dentry *simple_start_creating(struct dentry *parent, const char *name)
+{
+	struct qstr qname = QSTR(name);
+	int err;
+
+	err = lookup_noperm_common(&qname, parent);
+	if (err)
+		return ERR_PTR(err);
+	return start_dirop(parent, &qname, LOOKUP_CREATE | LOOKUP_EXCL);
+}
+EXPORT_SYMBOL(simple_start_creating);
+
+/* parent must have been held exclusive since simple_start_creating() */
+void simple_done_creating(struct dentry *child)
+{
+	end_creating(child);
+}
+EXPORT_SYMBOL(simple_done_creating);