Merge tag 'i3c/for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/i3c/linuxgrafted

Pull I3C updates from Alexandre Belloni:
 "A new driver this cycle, for the AMD AXI I3C controller.

  There are also new features such as IBI wakeup support, SETAASA device
  discovery and ACPI support for the the DAA methods, meaning we can now
  communicate with the SPD devices on DDR5 modules.

  New driver:
   - AMD AXI I3C master controller

  Subsystem:
   - I3C Common Command Code (CCC) handling improvements, especially
     around GET CCCs
   - SETAASA device discovery support
   - ACPI support for all existing DAA methods like SETDASA, SETNEWDA as
     well as I2C devices on I3C bus
   - IBI-based wakeup support

  Drivers:
   - dw: SETAASA support
   - mipi-i3c-hci: advertise IBI wakeup capability, AMD_PT I3C
     controller support, PIO queue management support for HCI v1.2
   - renesas: improve suspend to RAM support, add runtime PM support"

* tag 'i3c/for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/i3c/linux: (70 commits)
  i3c: dw: reduce do_daa time if there's no client
  i3c: mipi-i3c-hci: Add support for AMD_PT I3C controller
  i3c: mipi-i3c-hci: Add PIO queue management support for HCI v1.2
  i3c: mipi-i3c-hci: Fix missing STAT_IBI_STATUS_THLD in PIO mode
  i3c: dw: rename "pclk" to "apb" to match dt-binding
  i3c: dw: make struct dw_i3c_cmd smaller
  i3c: dw: use COMMAND_PORT_TRANSFER_ARG instead of hardcoding
  i3c: renesas: Don't register devices when ENTDAA times out
  i3c: master: dw-i3c-master: fix OD timing for first broadcast
  i3c: mipi-i3c-hci: Advertise IBI wakeup capability
  i3c: mipi-i3c-hci: Factor out i3c_hci_sysdev()
  i3c: mipi-i3c-hci-pci: Propagate I3C wakeup requirements to PCI
  i3c: master: Reject IBI requests from non-IBI-capable devices
  i3c: master: Add helper to query bus wakeup requirements
  i3c: master: Report wakeup events for IBIs
  i3c: master: Support IBI-based wakeup capability
  i3c: master: Fix potential UAF in i3c_device_match()
  i3c: master: Fix potential UAF in i3c_device_uevent()
  i3c: Make dev->desc locking assumptions explicit
  i3c: master: Fix use-after-free of master->this
  ...

5 files changed, 1631 insertions, 0 deletions

diff --git a/fs/hostfs/Makefile b/fs/hostfs/Makefile
new file mode 100644
index 000000000..16be592e8
--- /dev/null
+++ b/fs/hostfs/Makefile
@@ -0,0 +1,13 @@
+#
+# Copyright (C) 2000 Jeff Dike (jdike@karaya.com)
+# Licensed under the GPL
+#
+
+hostfs-objs := hostfs_kern.o
+
+hostfs-builtin-$(CONFIG_HOSTFS) += hostfs_user.o hostfs_user_exp.o
+
+obj-y := $(hostfs-builtin-y) $(hostfs-builtin-m)
+obj-$(CONFIG_HOSTFS) += hostfs.o
+
+include $(srctree)/arch/um/scripts/Makefile.rules
diff --git a/fs/hostfs/hostfs.h b/fs/hostfs/hostfs.h
new file mode 100644
index 000000000..aa02599b7
--- /dev/null
+++ b/fs/hostfs/hostfs.h
@@ -0,0 +1,73 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_FS_HOSTFS
+#define __UM_FS_HOSTFS
+
+#include <os.h>
+#include <generated/asm-offsets.h>
+
+struct hostfs_timespec {
+	long long tv_sec;
+	long long tv_nsec;
+};
+
+struct hostfs_iattr {
+	unsigned int		ia_valid;
+	unsigned short		ia_mode;
+	uid_t			ia_uid;
+	gid_t			ia_gid;
+	loff_t			ia_size;
+	struct hostfs_timespec	ia_atime;
+	struct hostfs_timespec	ia_mtime;
+	struct hostfs_timespec	ia_ctime;
+};
+
+struct hostfs_stat {
+	unsigned long long ino;
+	unsigned int mode;
+	unsigned int nlink;
+	unsigned int uid;
+	unsigned int gid;
+	unsigned long long size;
+	struct hostfs_timespec atime, mtime, ctime, btime;
+	unsigned int blksize;
+	unsigned long long blocks;
+	struct {
+		unsigned int maj;
+		unsigned int min;
+	} rdev, dev;
+};
+
+extern int stat_file(const char *path, struct hostfs_stat *p, int fd);
+extern int access_file(char *path, int r, int w, int x);
+extern int open_file(char *path, int r, int w, int append);
+extern void *open_dir(char *path, int *err_out);
+extern void seek_dir(void *stream, unsigned long long pos);
+extern char *read_dir(void *stream, unsigned long long *pos_out,
+		      unsigned long long *ino_out, int *len_out,
+		      unsigned int *type_out);
+extern void close_file(void *stream);
+extern int replace_file(int oldfd, int fd);
+extern void close_dir(void *stream);
+extern int read_file(int fd, unsigned long long *offset, char *buf, int len);
+extern int write_file(int fd, unsigned long long *offset, const char *buf,
+		      int len);
+extern int lseek_file(int fd, long long offset, int whence);
+extern int fsync_file(int fd, int datasync);
+extern int file_create(char *name, int mode);
+extern int set_attr(const char *file, struct hostfs_iattr *attrs, int fd);
+extern int make_symlink(const char *from, const char *to);
+extern int unlink_file(const char *file);
+extern int do_mkdir(const char *file, int mode);
+extern int hostfs_do_rmdir(const char *file);
+extern int do_mknod(const char *file, int mode, unsigned int major,
+		    unsigned int minor);
+extern int link_file(const char *to, const char *from);
+extern int hostfs_do_readlink(char *file, char *buf, int size);
+extern int rename_file(char *from, char *to);
+extern int rename2_file(char *from, char *to, unsigned int flags);
+extern int do_statfs(char *root, long *bsize_out, long long *blocks_out,
+		     long long *bfree_out, long long *bavail_out,
+		     long long *files_out, long long *ffree_out,
+		     void *fsid_out, int fsid_size, long *namelen_out);
+
+#endif
diff --git a/fs/hostfs/hostfs_kern.c b/fs/hostfs/hostfs_kern.c
new file mode 100644
index 000000000..7add056d4
--- /dev/null
+++ b/fs/hostfs/hostfs_kern.c
@@ -0,0 +1,1096 @@
+/*
+ * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ * Licensed under the GPL
+ *
+ * Ported the filesystem routines to 2.5.
+ * 2003-02-10 Petr Baudis <pasky@ucw.cz>
+ */
+
+#include <linux/fs.h>
+#include <linux/magic.h>
+#include <linux/module.h>
+#include <linux/mm.h>
+#include <linux/pagemap.h>
+#include <linux/statfs.h>
+#include <linux/slab.h>
+#include <linux/seq_file.h>
+#include <linux/writeback.h>
+#include <linux/mount.h>
+#include <linux/fs_context.h>
+#include <linux/fs_parser.h>
+#include <linux/namei.h>
+#include "hostfs.h"
+#include <init.h>
+#include <kern.h>
+
+struct hostfs_fs_info {
+	char *host_root_path;
+};
+
+struct hostfs_inode_info {
+	int fd;
+	fmode_t mode;
+	struct inode vfs_inode;
+	struct mutex open_mutex;
+	dev_t dev;
+	struct hostfs_timespec btime;
+};
+
+static inline struct hostfs_inode_info *HOSTFS_I(struct inode *inode)
+{
+	return list_entry(inode, struct hostfs_inode_info, vfs_inode);
+}
+
+#define FILE_HOSTFS_I(file) HOSTFS_I(file_inode(file))
+
+static struct kmem_cache *hostfs_inode_cache;
+
+/* Changed in hostfs_args before the kernel starts running */
+static char *root_ino = "";
+static int append = 0;
+
+static const struct inode_operations hostfs_iops;
+static const struct inode_operations hostfs_dir_iops;
+static const struct inode_operations hostfs_link_iops;
+
+#ifndef MODULE
+static int __init hostfs_args(char *options, int *add)
+{
+	char *ptr;
+
+	*add = 0;
+	ptr = strchr(options, ',');
+	if (ptr != NULL)
+		*ptr++ = '\0';
+	if (*options != '\0')
+		root_ino = options;
+
+	options = ptr;
+	while (options) {
+		ptr = strchr(options, ',');
+		if (ptr != NULL)
+			*ptr++ = '\0';
+		if (*options != '\0') {
+			if (!strcmp(options, "append"))
+				append = 1;
+			else printf("hostfs_args - unsupported option - %s\n",
+				    options);
+		}
+		options = ptr;
+	}
+	return 0;
+}
+
+__uml_setup("hostfs=", hostfs_args,
+"hostfs=<root dir>,<flags>,...\n"
+"    This is used to set hostfs parameters.  The root directory argument\n"
+"    is used to confine all hostfs mounts to within the specified directory\n"
+"    tree on the host.  If this isn't specified, then a user inside UML can\n"
+"    mount anything on the host that's accessible to the user that's running\n"
+"    it.\n"
+"    The only flag currently supported is 'append', which specifies that all\n"
+"    files opened by hostfs will be opened in append mode.\n\n"
+);
+#endif
+
+static char *__dentry_name(struct dentry *dentry, char *name)
+{
+	char *p = dentry_path_raw(dentry, name, PATH_MAX);
+	struct hostfs_fs_info *fsi = dentry->d_sb->s_fs_info;
+	char *root = fsi->host_root_path;
+	size_t len = strlen(root);
+
+	if (IS_ERR(p) || len > p - name) {
+		__putname(name);
+		return NULL;
+	}
+
+	memcpy(name, root, len);
+	memmove(name + len, p, name + PATH_MAX - p);
+
+	return name;
+}
+
+static char *dentry_name(struct dentry *dentry)
+{
+	char *name = __getname();
+	if (!name)
+		return NULL;
+
+	return __dentry_name(dentry, name);
+}
+
+static char *inode_name(struct inode *ino)
+{
+	struct dentry *dentry;
+	char *name;
+
+	dentry = d_find_alias(ino);
+	if (!dentry)
+		return NULL;
+
+	name = dentry_name(dentry);
+
+	dput(dentry);
+
+	return name;
+}
+
+static char *follow_link(char *link)
+{
+	char *name, *resolved, *end;
+	int n;
+
+	name = kmalloc(PATH_MAX, GFP_KERNEL);
+	if (!name) {
+		n = -ENOMEM;
+		goto out_free;
+	}
+
+	n = hostfs_do_readlink(link, name, PATH_MAX);
+	if (n < 0)
+		goto out_free;
+	else if (n == PATH_MAX) {
+		n = -E2BIG;
+		goto out_free;
+	}
+
+	if (*name == '/')
+		return name;
+
+	end = strrchr(link, '/');
+	if (end == NULL)
+		return name;
+
+	*(end + 1) = '\0';
+
+	resolved = kasprintf(GFP_KERNEL, "%s%s", link, name);
+	if (resolved == NULL) {
+		n = -ENOMEM;
+		goto out_free;
+	}
+
+	kfree(name);
+	return resolved;
+
+ out_free:
+	kfree(name);
+	return ERR_PTR(n);
+}
+
+static int hostfs_statfs(struct dentry *dentry, struct kstatfs *sf)
+{
+	/*
+	 * do_statfs uses struct statfs64 internally, but the linux kernel
+	 * struct statfs still has 32-bit versions for most of these fields,
+	 * so we convert them here
+	 */
+	int err;
+	long long f_blocks;
+	long long f_bfree;
+	long long f_bavail;
+	long long f_files;
+	long long f_ffree;
+	struct hostfs_fs_info *fsi;
+
+	fsi = dentry->d_sb->s_fs_info;
+	err = do_statfs(fsi->host_root_path,
+			&sf->f_bsize, &f_blocks, &f_bfree, &f_bavail, &f_files,
+			&f_ffree, &sf->f_fsid, sizeof(sf->f_fsid),
+			&sf->f_namelen);
+	if (err)
+		return err;
+	sf->f_blocks = f_blocks;
+	sf->f_bfree = f_bfree;
+	sf->f_bavail = f_bavail;
+	sf->f_files = f_files;
+	sf->f_ffree = f_ffree;
+	sf->f_type = HOSTFS_SUPER_MAGIC;
+	return 0;
+}
+
+static struct inode *hostfs_alloc_inode(struct super_block *sb)
+{
+	struct hostfs_inode_info *hi;
+
+	hi = alloc_inode_sb(sb, hostfs_inode_cache, GFP_KERNEL_ACCOUNT);
+	if (hi == NULL)
+		return NULL;
+	hi->fd = -1;
+	hi->mode = 0;
+	hi->dev = 0;
+	inode_init_once(&hi->vfs_inode);
+	mutex_init(&hi->open_mutex);
+	return &hi->vfs_inode;
+}
+
+static void hostfs_evict_inode(struct inode *inode)
+{
+	truncate_inode_pages_final(&inode->i_data);
+	clear_inode(inode);
+	if (HOSTFS_I(inode)->fd != -1) {
+		close_file(&HOSTFS_I(inode)->fd);
+		HOSTFS_I(inode)->fd = -1;
+		HOSTFS_I(inode)->dev = 0;
+	}
+}
+
+static void hostfs_free_inode(struct inode *inode)
+{
+	kmem_cache_free(hostfs_inode_cache, HOSTFS_I(inode));
+}
+
+static int hostfs_show_options(struct seq_file *seq, struct dentry *root)
+{
+	struct hostfs_fs_info *fsi;
+	const char *root_path;
+
+	fsi = root->d_sb->s_fs_info;
+	root_path = fsi->host_root_path;
+	size_t offset = strlen(root_ino) + 1;
+
+	if (strlen(root_path) > offset)
+		seq_show_option(seq, root_path + offset, NULL);
+
+	if (append)
+		seq_puts(seq, ",append");
+
+	return 0;
+}
+
+static const struct super_operations hostfs_sbops = {
+	.alloc_inode	= hostfs_alloc_inode,
+	.free_inode	= hostfs_free_inode,
+	.drop_inode	= inode_just_drop,
+	.evict_inode	= hostfs_evict_inode,
+	.statfs		= hostfs_statfs,
+	.show_options	= hostfs_show_options,
+};
+
+static int hostfs_readdir(struct file *file, struct dir_context *ctx)
+{
+	void *dir;
+	char *name;
+	unsigned long long next, ino;
+	int error, len;
+	unsigned int type;
+
+	name = dentry_name(file->f_path.dentry);
+	if (name == NULL)
+		return -ENOMEM;
+	dir = open_dir(name, &error);
+	__putname(name);
+	if (dir == NULL)
+		return -error;
+	next = ctx->pos;
+	seek_dir(dir, next);
+	while ((name = read_dir(dir, &next, &ino, &len, &type)) != NULL) {
+		if (!dir_emit(ctx, name, len, ino, type))
+			break;
+		ctx->pos = next;
+	}
+	close_dir(dir);
+	return 0;
+}
+
+static int hostfs_open(struct inode *ino, struct file *file)
+{
+	char *name;
+	fmode_t mode;
+	int err;
+	int r, w, fd;
+
+	mode = file->f_mode & (FMODE_READ | FMODE_WRITE);
+	if ((mode & HOSTFS_I(ino)->mode) == mode)
+		return 0;
+
+	mode |= HOSTFS_I(ino)->mode;
+
+retry:
+	r = w = 0;
+
+	if (mode & FMODE_READ)
+		r = 1;
+	if (mode & FMODE_WRITE)
+		r = w = 1;
+
+	name = dentry_name(file_dentry(file));
+	if (name == NULL)
+		return -ENOMEM;
+
+	fd = open_file(name, r, w, append);
+	__putname(name);
+	if (fd < 0)
+		return fd;
+
+	mutex_lock(&HOSTFS_I(ino)->open_mutex);
+	/* somebody else had handled it first? */
+	if ((mode & HOSTFS_I(ino)->mode) == mode) {
+		mutex_unlock(&HOSTFS_I(ino)->open_mutex);
+		close_file(&fd);
+		return 0;
+	}
+	if ((mode | HOSTFS_I(ino)->mode) != mode) {
+		mode |= HOSTFS_I(ino)->mode;
+		mutex_unlock(&HOSTFS_I(ino)->open_mutex);
+		close_file(&fd);
+		goto retry;
+	}
+	if (HOSTFS_I(ino)->fd == -1) {
+		HOSTFS_I(ino)->fd = fd;
+	} else {
+		err = replace_file(fd, HOSTFS_I(ino)->fd);
+		close_file(&fd);
+		if (err < 0) {
+			mutex_unlock(&HOSTFS_I(ino)->open_mutex);
+			return err;
+		}
+	}
+	HOSTFS_I(ino)->mode = mode;
+	mutex_unlock(&HOSTFS_I(ino)->open_mutex);
+
+	return 0;
+}
+
+static int hostfs_file_release(struct inode *inode, struct file *file)
+{
+	filemap_write_and_wait(inode->i_mapping);
+
+	return 0;
+}
+
+static int hostfs_fsync(struct file *file, loff_t start, loff_t end,
+			int datasync)
+{
+	struct inode *inode = file->f_mapping->host;
+	int ret;
+
+	ret = file_write_and_wait_range(file, start, end);
+	if (ret)
+		return ret;
+
+	inode_lock(inode);
+	ret = fsync_file(HOSTFS_I(inode)->fd, datasync);
+	inode_unlock(inode);
+
+	return ret;
+}
+
+static const struct file_operations hostfs_file_fops = {
+	.llseek		= generic_file_llseek,
+	.splice_read	= filemap_splice_read,
+	.splice_write	= iter_file_splice_write,
+	.read_iter	= generic_file_read_iter,
+	.write_iter	= generic_file_write_iter,
+	.mmap_prepare	= generic_file_mmap_prepare,
+	.open		= hostfs_open,
+	.release	= hostfs_file_release,
+	.fsync		= hostfs_fsync,
+};
+
+static const struct file_operations hostfs_dir_fops = {
+	.llseek		= generic_file_llseek,
+	.iterate_shared	= hostfs_readdir,
+	.read		= generic_read_dir,
+	.open		= hostfs_open,
+	.fsync		= hostfs_fsync,
+};
+
+static int hostfs_writepages(struct address_space *mapping,
+		struct writeback_control *wbc)
+{
+	struct inode *inode = mapping->host;
+	struct folio *folio = NULL;
+	loff_t i_size = i_size_read(inode);
+	int err = 0;
+
+	while ((folio = writeback_iter(mapping, wbc, folio, &err))) {
+		loff_t pos = folio_pos(folio);
+		size_t count = folio_size(folio);
+		char *buffer;
+		int ret;
+
+		if (count > i_size - pos)
+			count = i_size - pos;
+
+		buffer = kmap_local_folio(folio, 0);
+		ret = write_file(HOSTFS_I(inode)->fd, &pos, buffer, count);
+		kunmap_local(buffer);
+		folio_unlock(folio);
+		if (ret != count) {
+			err = ret < 0 ? ret : -EIO;
+			mapping_set_error(mapping, err);
+		}
+	}
+
+	return err;
+}
+
+static int hostfs_read_folio(struct file *file, struct folio *folio)
+{
+	char *buffer;
+	loff_t start = folio_pos(folio);
+	int bytes_read, ret = 0;
+
+	buffer = kmap_local_folio(folio, 0);
+	bytes_read = read_file(FILE_HOSTFS_I(file)->fd, &start, buffer,
+			PAGE_SIZE);
+	if (bytes_read < 0)
+		ret = bytes_read;
+	else
+		buffer = folio_zero_tail(folio, bytes_read, buffer + bytes_read);
+	kunmap_local(buffer);
+
+	folio_end_read(folio, ret == 0);
+	return ret;
+}
+
+static int hostfs_write_begin(const struct kiocb *iocb,
+			      struct address_space *mapping,
+			      loff_t pos, unsigned len,
+			      struct folio **foliop, void **fsdata)
+{
+	pgoff_t index = pos >> PAGE_SHIFT;
+
+	*foliop = __filemap_get_folio(mapping, index, FGP_WRITEBEGIN,
+			mapping_gfp_mask(mapping));
+	if (IS_ERR(*foliop))
+		return PTR_ERR(*foliop);
+	return 0;
+}
+
+static int hostfs_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 = mapping->host;
+	void *buffer;
+	size_t from = offset_in_folio(folio, pos);
+	int err;
+
+	buffer = kmap_local_folio(folio, from);
+	err = write_file(FILE_HOSTFS_I(iocb->ki_filp)->fd, &pos, buffer, copied);
+	kunmap_local(buffer);
+
+	if (!folio_test_uptodate(folio) && err == folio_size(folio))
+		folio_mark_uptodate(folio);
+
+	/*
+	 * If err > 0, write_file has added err to pos, so we are comparing
+	 * i_size against the last byte written.
+	 */
+	if (err > 0 && (pos > inode->i_size))
+		inode->i_size = pos;
+	folio_unlock(folio);
+	folio_put(folio);
+
+	return err;
+}
+
+static const struct address_space_operations hostfs_aops = {
+	.writepages 	= hostfs_writepages,
+	.read_folio	= hostfs_read_folio,
+	.dirty_folio	= filemap_dirty_folio,
+	.write_begin	= hostfs_write_begin,
+	.write_end	= hostfs_write_end,
+	.migrate_folio	= filemap_migrate_folio,
+};
+
+static int hostfs_inode_update(struct inode *ino, const struct hostfs_stat *st)
+{
+	set_nlink(ino, st->nlink);
+	i_uid_write(ino, st->uid);
+	i_gid_write(ino, st->gid);
+	inode_set_atime_to_ts(ino, (struct timespec64){
+			st->atime.tv_sec,
+			st->atime.tv_nsec,
+		});
+	inode_set_mtime_to_ts(ino, (struct timespec64){
+			st->mtime.tv_sec,
+			st->mtime.tv_nsec,
+		});
+	inode_set_ctime(ino, st->ctime.tv_sec, st->ctime.tv_nsec);
+	ino->i_size = st->size;
+	ino->i_blocks = st->blocks;
+	return 0;
+}
+
+static int hostfs_inode_set(struct inode *ino, void *data)
+{
+	struct hostfs_stat *st = data;
+	dev_t dev, rdev;
+
+	/* Reencode maj and min with the kernel encoding.*/
+	rdev = MKDEV(st->rdev.maj, st->rdev.min);
+	dev = MKDEV(st->dev.maj, st->dev.min);
+
+	switch (st->mode & S_IFMT) {
+	case S_IFLNK:
+		ino->i_op = &hostfs_link_iops;
+		break;
+	case S_IFDIR:
+		ino->i_op = &hostfs_dir_iops;
+		ino->i_fop = &hostfs_dir_fops;
+		break;
+	case S_IFCHR:
+	case S_IFBLK:
+	case S_IFIFO:
+	case S_IFSOCK:
+		init_special_inode(ino, st->mode & S_IFMT, rdev);
+		ino->i_op = &hostfs_iops;
+		break;
+	case S_IFREG:
+		ino->i_op = &hostfs_iops;
+		ino->i_fop = &hostfs_file_fops;
+		ino->i_mapping->a_ops = &hostfs_aops;
+		break;
+	default:
+		return -EIO;
+	}
+
+	HOSTFS_I(ino)->dev = dev;
+	HOSTFS_I(ino)->btime = st->btime;
+	ino->i_ino = st->ino;
+	ino->i_mode = st->mode;
+	return hostfs_inode_update(ino, st);
+}
+
+static int hostfs_inode_test(struct inode *inode, void *data)
+{
+	const struct hostfs_stat *st = data;
+	dev_t dev = MKDEV(st->dev.maj, st->dev.min);
+
+	return inode->i_ino == st->ino && HOSTFS_I(inode)->dev == dev &&
+	       (inode->i_mode & S_IFMT) == (st->mode & S_IFMT) &&
+	       HOSTFS_I(inode)->btime.tv_sec == st->btime.tv_sec &&
+	       HOSTFS_I(inode)->btime.tv_nsec == st->btime.tv_nsec;
+}
+
+static struct inode *hostfs_iget(struct super_block *sb, char *name)
+{
+	struct inode *inode;
+	struct hostfs_stat st;
+	int err = stat_file(name, &st, -1);
+
+	if (err)
+		return ERR_PTR(err);
+
+	inode = iget5_locked(sb, st.ino, hostfs_inode_test, hostfs_inode_set,
+			     &st);
+	if (!inode)
+		return ERR_PTR(-ENOMEM);
+
+	if (inode_state_read_once(inode) & I_NEW) {
+		unlock_new_inode(inode);
+	} else {
+		spin_lock(&inode->i_lock);
+		hostfs_inode_update(inode, &st);
+		spin_unlock(&inode->i_lock);
+	}
+
+	return inode;
+}
+
+static int hostfs_create(struct mnt_idmap *idmap, struct inode *dir,
+			 struct dentry *dentry, umode_t mode)
+{
+	struct inode *inode;
+	char *name;
+	int fd;
+
+	name = dentry_name(dentry);
+	if (name == NULL)
+		return -ENOMEM;
+
+	fd = file_create(name, mode & 0777);
+	if (fd < 0) {
+		__putname(name);
+		return fd;
+	}
+
+	inode = hostfs_iget(dir->i_sb, name);
+	__putname(name);
+	if (IS_ERR(inode))
+		return PTR_ERR(inode);
+
+	HOSTFS_I(inode)->fd = fd;
+	HOSTFS_I(inode)->mode = FMODE_READ | FMODE_WRITE;
+	d_instantiate(dentry, inode);
+	return 0;
+}
+
+static struct dentry *hostfs_lookup(struct inode *ino, struct dentry *dentry,
+				    unsigned int flags)
+{
+	struct inode *inode = NULL;
+	char *name;
+
+	name = dentry_name(dentry);
+	if (name == NULL)
+		return ERR_PTR(-ENOMEM);
+
+	inode = hostfs_iget(ino->i_sb, name);
+	__putname(name);
+	if (inode == ERR_PTR(-ENOENT))
+		inode = NULL;
+
+	return d_splice_alias(inode, dentry);
+}
+
+static int hostfs_link(struct dentry *to, struct inode *ino,
+		       struct dentry *from)
+{
+	char *from_name, *to_name;
+	int err;
+
+	if ((from_name = dentry_name(from)) == NULL)
+		return -ENOMEM;
+	to_name = dentry_name(to);
+	if (to_name == NULL) {
+		__putname(from_name);
+		return -ENOMEM;
+	}
+	err = link_file(to_name, from_name);
+	__putname(from_name);
+	__putname(to_name);
+	return err;
+}
+
+static int hostfs_unlink(struct inode *ino, struct dentry *dentry)
+{
+	char *file;
+	int err;
+
+	if (append)
+		return -EPERM;
+
+	if ((file = dentry_name(dentry)) == NULL)
+		return -ENOMEM;
+
+	err = unlink_file(file);
+	__putname(file);
+	return err;
+}
+
+static int hostfs_symlink(struct mnt_idmap *idmap, struct inode *ino,
+			  struct dentry *dentry, const char *to)
+{
+	char *file;
+	int err;
+
+	if ((file = dentry_name(dentry)) == NULL)
+		return -ENOMEM;
+	err = make_symlink(file, to);
+	__putname(file);
+	return err;
+}
+
+static struct dentry *hostfs_mkdir(struct mnt_idmap *idmap, struct inode *ino,
+				   struct dentry *dentry, umode_t mode)
+{
+	struct inode *inode;
+	char *file;
+	int err;
+
+	if ((file = dentry_name(dentry)) == NULL)
+		return ERR_PTR(-ENOMEM);
+	err = do_mkdir(file, mode);
+	if (err) {
+		dentry = ERR_PTR(err);
+	} else {
+		inode = hostfs_iget(dentry->d_sb, file);
+		d_drop(dentry);
+		dentry = d_splice_alias(inode, dentry);
+	}
+	__putname(file);
+	return dentry;
+}
+
+static int hostfs_rmdir(struct inode *ino, struct dentry *dentry)
+{
+	char *file;
+	int err;
+
+	if ((file = dentry_name(dentry)) == NULL)
+		return -ENOMEM;
+	err = hostfs_do_rmdir(file);
+	__putname(file);
+	return err;
+}
+
+static int hostfs_mknod(struct mnt_idmap *idmap, struct inode *dir,
+			struct dentry *dentry, umode_t mode, dev_t dev)
+{
+	struct inode *inode;
+	char *name;
+	int err;
+
+	name = dentry_name(dentry);
+	if (name == NULL)
+		return -ENOMEM;
+
+	err = do_mknod(name, mode, MAJOR(dev), MINOR(dev));
+	if (err) {
+		__putname(name);
+		return err;
+	}
+
+	inode = hostfs_iget(dir->i_sb, name);
+	__putname(name);
+	if (IS_ERR(inode))
+		return PTR_ERR(inode);
+
+	d_instantiate(dentry, inode);
+	return 0;
+}
+
+static int hostfs_rename2(struct mnt_idmap *idmap,
+			  struct inode *old_dir, struct dentry *old_dentry,
+			  struct inode *new_dir, struct dentry *new_dentry,
+			  unsigned int flags)
+{
+	char *old_name, *new_name;
+	int err;
+
+	if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
+		return -EINVAL;
+
+	old_name = dentry_name(old_dentry);
+	if (old_name == NULL)
+		return -ENOMEM;
+	new_name = dentry_name(new_dentry);
+	if (new_name == NULL) {
+		__putname(old_name);
+		return -ENOMEM;
+	}
+	if (!flags)
+		err = rename_file(old_name, new_name);
+	else
+		err = rename2_file(old_name, new_name, flags);
+
+	__putname(old_name);
+	__putname(new_name);
+	return err;
+}
+
+static int hostfs_permission(struct mnt_idmap *idmap,
+			     struct inode *ino, int desired)
+{
+	char *name;
+	int r = 0, w = 0, x = 0, err;
+
+	if (desired & MAY_NOT_BLOCK)
+		return -ECHILD;
+
+	if (desired & MAY_READ) r = 1;
+	if (desired & MAY_WRITE) w = 1;
+	if (desired & MAY_EXEC) x = 1;
+	name = inode_name(ino);
+	if (name == NULL)
+		return -ENOMEM;
+
+	if (S_ISCHR(ino->i_mode) || S_ISBLK(ino->i_mode) ||
+	    S_ISFIFO(ino->i_mode) || S_ISSOCK(ino->i_mode))
+		err = 0;
+	else
+		err = access_file(name, r, w, x);
+	__putname(name);
+	if (!err)
+		err = generic_permission(&nop_mnt_idmap, ino, desired);
+	return err;
+}
+
+static int hostfs_setattr(struct mnt_idmap *idmap,
+			  struct dentry *dentry, struct iattr *attr)
+{
+	struct inode *inode = d_inode(dentry);
+	struct hostfs_iattr attrs;
+	char *name;
+	int err;
+
+	int fd = HOSTFS_I(inode)->fd;
+
+	err = setattr_prepare(&nop_mnt_idmap, dentry, attr);
+	if (err)
+		return err;
+
+	if (append)
+		attr->ia_valid &= ~ATTR_SIZE;
+
+	attrs.ia_valid = 0;
+	if (attr->ia_valid & ATTR_MODE) {
+		attrs.ia_valid |= HOSTFS_ATTR_MODE;
+		attrs.ia_mode = attr->ia_mode;
+	}
+	if (attr->ia_valid & ATTR_UID) {
+		attrs.ia_valid |= HOSTFS_ATTR_UID;
+		attrs.ia_uid = from_kuid(&init_user_ns, attr->ia_uid);
+	}
+	if (attr->ia_valid & ATTR_GID) {
+		attrs.ia_valid |= HOSTFS_ATTR_GID;
+		attrs.ia_gid = from_kgid(&init_user_ns, attr->ia_gid);
+	}
+	if (attr->ia_valid & ATTR_SIZE) {
+		attrs.ia_valid |= HOSTFS_ATTR_SIZE;
+		attrs.ia_size = attr->ia_size;
+	}
+	if (attr->ia_valid & ATTR_ATIME) {
+		attrs.ia_valid |= HOSTFS_ATTR_ATIME;
+		attrs.ia_atime = (struct hostfs_timespec)
+			{ attr->ia_atime.tv_sec, attr->ia_atime.tv_nsec };
+	}
+	if (attr->ia_valid & ATTR_MTIME) {
+		attrs.ia_valid |= HOSTFS_ATTR_MTIME;
+		attrs.ia_mtime = (struct hostfs_timespec)
+			{ attr->ia_mtime.tv_sec, attr->ia_mtime.tv_nsec };
+	}
+	if (attr->ia_valid & ATTR_CTIME) {
+		attrs.ia_valid |= HOSTFS_ATTR_CTIME;
+		attrs.ia_ctime = (struct hostfs_timespec)
+			{ attr->ia_ctime.tv_sec, attr->ia_ctime.tv_nsec };
+	}
+	if (attr->ia_valid & ATTR_ATIME_SET) {
+		attrs.ia_valid |= HOSTFS_ATTR_ATIME_SET;
+	}
+	if (attr->ia_valid & ATTR_MTIME_SET) {
+		attrs.ia_valid |= HOSTFS_ATTR_MTIME_SET;
+	}
+	name = dentry_name(dentry);
+	if (name == NULL)
+		return -ENOMEM;
+	err = set_attr(name, &attrs, fd);
+	__putname(name);
+	if (err)
+		return err;
+
+	if ((attr->ia_valid & ATTR_SIZE) &&
+	    attr->ia_size != i_size_read(inode))
+		truncate_setsize(inode, attr->ia_size);
+
+	setattr_copy(&nop_mnt_idmap, inode, attr);
+	mark_inode_dirty(inode);
+	return 0;
+}
+
+static const struct inode_operations hostfs_iops = {
+	.permission	= hostfs_permission,
+	.setattr	= hostfs_setattr,
+};
+
+static const struct inode_operations hostfs_dir_iops = {
+	.create		= hostfs_create,
+	.lookup		= hostfs_lookup,
+	.link		= hostfs_link,
+	.unlink		= hostfs_unlink,
+	.symlink	= hostfs_symlink,
+	.mkdir		= hostfs_mkdir,
+	.rmdir		= hostfs_rmdir,
+	.mknod		= hostfs_mknod,
+	.rename		= hostfs_rename2,
+	.permission	= hostfs_permission,
+	.setattr	= hostfs_setattr,
+};
+
+static const char *hostfs_get_link(struct dentry *dentry,
+				   struct inode *inode,
+				   struct delayed_call *done)
+{
+	char *link;
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
+	link = kmalloc(PATH_MAX, GFP_KERNEL);
+	if (link) {
+		char *path = dentry_name(dentry);
+		int err = -ENOMEM;
+		if (path) {
+			err = hostfs_do_readlink(path, link, PATH_MAX);
+			if (err == PATH_MAX)
+				err = -E2BIG;
+			__putname(path);
+		}
+		if (err < 0) {
+			kfree(link);
+			return ERR_PTR(err);
+		}
+	} else {
+		return ERR_PTR(-ENOMEM);
+	}
+
+	set_delayed_call(done, kfree_link, link);
+	return link;
+}
+
+static const struct inode_operations hostfs_link_iops = {
+	.get_link	= hostfs_get_link,
+};
+
+static int hostfs_fill_super(struct super_block *sb, struct fs_context *fc)
+{
+	struct hostfs_fs_info *fsi = sb->s_fs_info;
+	struct inode *root_inode;
+	int err;
+
+	sb->s_blocksize = 1024;
+	sb->s_blocksize_bits = 10;
+	sb->s_magic = HOSTFS_SUPER_MAGIC;
+	sb->s_op = &hostfs_sbops;
+	sb->s_d_flags = DCACHE_DONTCACHE;
+	sb->s_maxbytes = MAX_LFS_FILESIZE;
+	err = super_setup_bdi(sb);
+	if (err)
+		return err;
+
+	root_inode = hostfs_iget(sb, fsi->host_root_path);
+	if (IS_ERR(root_inode))
+		return PTR_ERR(root_inode);
+
+	if (S_ISLNK(root_inode->i_mode)) {
+		char *name;
+
+		iput(root_inode);
+		name = follow_link(fsi->host_root_path);
+		if (IS_ERR(name))
+			return PTR_ERR(name);
+
+		root_inode = hostfs_iget(sb, name);
+		kfree(name);
+		if (IS_ERR(root_inode))
+			return PTR_ERR(root_inode);
+	}
+
+	sb->s_root = d_make_root(root_inode);
+	if (sb->s_root == NULL)
+		return -ENOMEM;
+
+	return 0;
+}
+
+enum hostfs_parma {
+	Opt_hostfs,
+};
+
+static const struct fs_parameter_spec hostfs_param_specs[] = {
+	fsparam_string_empty("hostfs",		Opt_hostfs),
+	{}
+};
+
+static int hostfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
+{
+	struct hostfs_fs_info *fsi = fc->s_fs_info;
+	struct fs_parse_result result;
+	char *host_root, *tmp_root;
+	int opt;
+
+	opt = fs_parse(fc, hostfs_param_specs, param, &result);
+	if (opt < 0)
+		return opt;
+
+	switch (opt) {
+	case Opt_hostfs:
+		host_root = param->string;
+		if (!*host_root)
+			break;
+		tmp_root = kasprintf(GFP_KERNEL, "%s%s",
+				     fsi->host_root_path, host_root);
+		if (!tmp_root)
+			return -ENOMEM;
+		kfree(fsi->host_root_path);
+		fsi->host_root_path = tmp_root;
+		break;
+	}
+
+	return 0;
+}
+
+static int hostfs_parse_monolithic(struct fs_context *fc, void *data)
+{
+	struct hostfs_fs_info *fsi = fc->s_fs_info;
+	char *tmp_root, *host_root = (char *)data;
+
+	/* NULL is printed as '(null)' by printf(): avoid that. */
+	if (host_root == NULL)
+		return 0;
+
+	tmp_root = kasprintf(GFP_KERNEL, "%s%s", fsi->host_root_path, host_root);
+	if (!tmp_root)
+		return -ENOMEM;
+	kfree(fsi->host_root_path);
+	fsi->host_root_path = tmp_root;
+	return 0;
+}
+
+static int hostfs_fc_get_tree(struct fs_context *fc)
+{
+	return get_tree_nodev(fc, hostfs_fill_super);
+}
+
+static void hostfs_fc_free(struct fs_context *fc)
+{
+	struct hostfs_fs_info *fsi = fc->s_fs_info;
+
+	if (!fsi)
+		return;
+
+	kfree(fsi->host_root_path);
+	kfree(fsi);
+}
+
+static const struct fs_context_operations hostfs_context_ops = {
+	.parse_monolithic = hostfs_parse_monolithic,
+	.parse_param	= hostfs_parse_param,
+	.get_tree	= hostfs_fc_get_tree,
+	.free		= hostfs_fc_free,
+};
+
+static int hostfs_init_fs_context(struct fs_context *fc)
+{
+	struct hostfs_fs_info *fsi;
+
+	fsi = kzalloc_obj(*fsi);
+	if (!fsi)
+		return -ENOMEM;
+
+	fsi->host_root_path = kasprintf(GFP_KERNEL, "%s/", root_ino);
+	if (!fsi->host_root_path) {
+		kfree(fsi);
+		return -ENOMEM;
+	}
+	fc->s_fs_info = fsi;
+	fc->ops = &hostfs_context_ops;
+	return 0;
+}
+
+static void hostfs_kill_sb(struct super_block *s)
+{
+	kill_anon_super(s);
+	kfree(s->s_fs_info);
+}
+
+static struct file_system_type hostfs_type = {
+	.owner			= THIS_MODULE,
+	.name			= "hostfs",
+	.init_fs_context	= hostfs_init_fs_context,
+	.kill_sb		= hostfs_kill_sb,
+	.fs_flags		= 0,
+};
+MODULE_ALIAS_FS("hostfs");
+
+static int __init init_hostfs(void)
+{
+	hostfs_inode_cache = KMEM_CACHE(hostfs_inode_info, 0);
+	if (!hostfs_inode_cache)
+		return -ENOMEM;
+	return register_filesystem(&hostfs_type);
+}
+
+static void __exit exit_hostfs(void)
+{
+	unregister_filesystem(&hostfs_type);
+	kmem_cache_destroy(hostfs_inode_cache);
+}
+
+module_init(init_hostfs)
+module_exit(exit_hostfs)
+MODULE_DESCRIPTION("User-Mode Linux Host filesystem");
+MODULE_LICENSE("GPL");
diff --git a/fs/hostfs/hostfs_user.c b/fs/hostfs/hostfs_user.c
new file mode 100644
index 000000000..3bcd9f35e
--- /dev/null
+++ b/fs/hostfs/hostfs_user.c
@@ -0,0 +1,421 @@
+/*
+ * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ * Licensed under the GPL
+ */
+
+#include <stdio.h>
+#include <stddef.h>
+#include <unistd.h>
+#include <dirent.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/time.h>
+#include <sys/types.h>
+#include <sys/vfs.h>
+#include <sys/syscall.h>
+#include "hostfs.h"
+#include <utime.h>
+
+static void statx_to_hostfs(const struct statx *buf, struct hostfs_stat *p)
+{
+	p->ino = buf->stx_ino;
+	p->mode = buf->stx_mode;
+	p->nlink = buf->stx_nlink;
+	p->uid = buf->stx_uid;
+	p->gid = buf->stx_gid;
+	p->size = buf->stx_size;
+	p->atime.tv_sec = buf->stx_atime.tv_sec;
+	p->atime.tv_nsec = buf->stx_atime.tv_nsec;
+	p->ctime.tv_sec = buf->stx_ctime.tv_sec;
+	p->ctime.tv_nsec = buf->stx_ctime.tv_nsec;
+	p->mtime.tv_sec = buf->stx_mtime.tv_sec;
+	p->mtime.tv_nsec = buf->stx_mtime.tv_nsec;
+	if (buf->stx_mask & STATX_BTIME) {
+		p->btime.tv_sec = buf->stx_btime.tv_sec;
+		p->btime.tv_nsec = buf->stx_btime.tv_nsec;
+	} else {
+		memset(&p->btime, 0, sizeof(p->btime));
+	}
+	p->blksize = buf->stx_blksize;
+	p->blocks = buf->stx_blocks;
+	p->rdev.maj = buf->stx_rdev_major;
+	p->rdev.min = buf->stx_rdev_minor;
+	p->dev.maj = buf->stx_dev_major;
+	p->dev.min = buf->stx_dev_minor;
+}
+
+int stat_file(const char *path, struct hostfs_stat *p, int fd)
+{
+	struct statx buf;
+	int flags = AT_SYMLINK_NOFOLLOW;
+
+	if (fd >= 0) {
+		flags |= AT_EMPTY_PATH;
+		path = "";
+	}
+
+	if ((statx(fd, path, flags, STATX_BASIC_STATS | STATX_BTIME, &buf)) < 0)
+		return -errno;
+
+	statx_to_hostfs(&buf, p);
+	return 0;
+}
+
+int access_file(char *path, int r, int w, int x)
+{
+	int mode = 0;
+
+	if (r)
+		mode = R_OK;
+	if (w)
+		mode |= W_OK;
+	if (x)
+		mode |= X_OK;
+	if (access(path, mode) != 0)
+		return -errno;
+	else return 0;
+}
+
+int open_file(char *path, int r, int w, int append)
+{
+	int mode = 0, fd;
+
+	if (r && !w)
+		mode = O_RDONLY;
+	else if (!r && w)
+		mode = O_WRONLY;
+	else if (r && w)
+		mode = O_RDWR;
+	else panic("Impossible mode in open_file");
+
+	if (append)
+		mode |= O_APPEND;
+	fd = open64(path, mode);
+	if (fd < 0)
+		return -errno;
+	else return fd;
+}
+
+void *open_dir(char *path, int *err_out)
+{
+	DIR *dir;
+
+	dir = opendir(path);
+	*err_out = errno;
+
+	return dir;
+}
+
+void seek_dir(void *stream, unsigned long long pos)
+{
+	DIR *dir = stream;
+
+	seekdir(dir, pos);
+}
+
+char *read_dir(void *stream, unsigned long long *pos_out,
+	       unsigned long long *ino_out, int *len_out,
+	       unsigned int *type_out)
+{
+	DIR *dir = stream;
+	struct dirent *ent;
+
+	ent = readdir(dir);
+	if (ent == NULL)
+		return NULL;
+	*len_out = strlen(ent->d_name);
+	*ino_out = ent->d_ino;
+	*type_out = ent->d_type;
+	*pos_out = ent->d_off;
+	return ent->d_name;
+}
+
+int read_file(int fd, unsigned long long *offset, char *buf, int len)
+{
+	int n;
+
+	n = pread64(fd, buf, len, *offset);
+	if (n < 0)
+		return -errno;
+	*offset += n;
+	return n;
+}
+
+int write_file(int fd, unsigned long long *offset, const char *buf, int len)
+{
+	int n;
+
+	n = pwrite64(fd, buf, len, *offset);
+	if (n < 0)
+		return -errno;
+	*offset += n;
+	return n;
+}
+
+int lseek_file(int fd, long long offset, int whence)
+{
+	int ret;
+
+	ret = lseek64(fd, offset, whence);
+	if (ret < 0)
+		return -errno;
+	return 0;
+}
+
+int fsync_file(int fd, int datasync)
+{
+	int ret;
+	if (datasync)
+		ret = fdatasync(fd);
+	else
+		ret = fsync(fd);
+
+	if (ret < 0)
+		return -errno;
+	return 0;
+}
+
+int replace_file(int oldfd, int fd)
+{
+	return dup2(oldfd, fd);
+}
+
+void close_file(void *stream)
+{
+	close(*((int *) stream));
+}
+
+void close_dir(void *stream)
+{
+	closedir(stream);
+}
+
+int file_create(char *name, int mode)
+{
+	int fd;
+
+	fd = open64(name, O_CREAT | O_RDWR, mode);
+	if (fd < 0)
+		return -errno;
+	return fd;
+}
+
+int set_attr(const char *file, struct hostfs_iattr *attrs, int fd)
+{
+	struct hostfs_stat st;
+	struct timeval times[2];
+	int err, ma;
+
+	if (attrs->ia_valid & HOSTFS_ATTR_MODE) {
+		if (fd >= 0) {
+			if (fchmod(fd, attrs->ia_mode) != 0)
+				return -errno;
+		} else if (chmod(file, attrs->ia_mode) != 0) {
+			return -errno;
+		}
+	}
+	if (attrs->ia_valid & HOSTFS_ATTR_UID) {
+		if (fd >= 0) {
+			if (fchown(fd, attrs->ia_uid, -1))
+				return -errno;
+		} else if (chown(file, attrs->ia_uid, -1)) {
+			return -errno;
+		}
+	}
+	if (attrs->ia_valid & HOSTFS_ATTR_GID) {
+		if (fd >= 0) {
+			if (fchown(fd, -1, attrs->ia_gid))
+				return -errno;
+		} else if (chown(file, -1, attrs->ia_gid)) {
+			return -errno;
+		}
+	}
+	if (attrs->ia_valid & HOSTFS_ATTR_SIZE) {
+		if (fd >= 0) {
+			if (ftruncate(fd, attrs->ia_size))
+				return -errno;
+		} else if (truncate(file, attrs->ia_size)) {
+			return -errno;
+		}
+	}
+
+	/*
+	 * Update accessed and/or modified time, in two parts: first set
+	 * times according to the changes to perform, and then call futimes()
+	 * or utimes() to apply them.
+	 */
+	ma = (HOSTFS_ATTR_ATIME_SET | HOSTFS_ATTR_MTIME_SET);
+	if (attrs->ia_valid & ma) {
+		err = stat_file(file, &st, fd);
+		if (err != 0)
+			return err;
+
+		times[0].tv_sec = st.atime.tv_sec;
+		times[0].tv_usec = st.atime.tv_nsec / 1000;
+		times[1].tv_sec = st.mtime.tv_sec;
+		times[1].tv_usec = st.mtime.tv_nsec / 1000;
+
+		if (attrs->ia_valid & HOSTFS_ATTR_ATIME_SET) {
+			times[0].tv_sec = attrs->ia_atime.tv_sec;
+			times[0].tv_usec = attrs->ia_atime.tv_nsec / 1000;
+		}
+		if (attrs->ia_valid & HOSTFS_ATTR_MTIME_SET) {
+			times[1].tv_sec = attrs->ia_mtime.tv_sec;
+			times[1].tv_usec = attrs->ia_mtime.tv_nsec / 1000;
+		}
+
+		if (fd >= 0) {
+			if (futimes(fd, times) != 0)
+				return -errno;
+		} else if (utimes(file, times) != 0) {
+			return -errno;
+		}
+	}
+
+	/* Note: ctime is not handled */
+	if (attrs->ia_valid & (HOSTFS_ATTR_ATIME | HOSTFS_ATTR_MTIME)) {
+		err = stat_file(file, &st, fd);
+		attrs->ia_atime = st.atime;
+		attrs->ia_mtime = st.mtime;
+		if (err != 0)
+			return err;
+	}
+	return 0;
+}
+
+int make_symlink(const char *from, const char *to)
+{
+	int err;
+
+	err = symlink(to, from);
+	if (err)
+		return -errno;
+	return 0;
+}
+
+int unlink_file(const char *file)
+{
+	int err;
+
+	err = unlink(file);
+	if (err)
+		return -errno;
+	return 0;
+}
+
+int do_mkdir(const char *file, int mode)
+{
+	int err;
+
+	err = mkdir(file, mode);
+	if (err)
+		return -errno;
+	return 0;
+}
+
+int hostfs_do_rmdir(const char *file)
+{
+	int err;
+
+	err = rmdir(file);
+	if (err)
+		return -errno;
+	return 0;
+}
+
+int do_mknod(const char *file, int mode, unsigned int major, unsigned int minor)
+{
+	int err;
+
+	err = mknod(file, mode, os_makedev(major, minor));
+	if (err)
+		return -errno;
+	return 0;
+}
+
+int link_file(const char *to, const char *from)
+{
+	int err;
+
+	err = link(to, from);
+	if (err)
+		return -errno;
+	return 0;
+}
+
+int hostfs_do_readlink(char *file, char *buf, int size)
+{
+	int n;
+
+	n = readlink(file, buf, size);
+	if (n < 0)
+		return -errno;
+	if (n < size)
+		buf[n] = '\0';
+	return n;
+}
+
+int rename_file(char *from, char *to)
+{
+	int err;
+
+	err = rename(from, to);
+	if (err < 0)
+		return -errno;
+	return 0;
+}
+
+int rename2_file(char *from, char *to, unsigned int flags)
+{
+	int err;
+
+#ifndef SYS_renameat2
+#  ifdef __x86_64__
+#    define SYS_renameat2 316
+#  endif
+#  ifdef __i386__
+#    define SYS_renameat2 353
+#  endif
+#endif
+
+#ifdef SYS_renameat2
+	err = syscall(SYS_renameat2, AT_FDCWD, from, AT_FDCWD, to, flags);
+	if (err < 0) {
+		if (errno != ENOSYS)
+			return -errno;
+		else
+			return -EINVAL;
+	}
+	return 0;
+#else
+	return -EINVAL;
+#endif
+}
+
+int do_statfs(char *root, long *bsize_out, long long *blocks_out,
+	      long long *bfree_out, long long *bavail_out,
+	      long long *files_out, long long *ffree_out,
+	      void *fsid_out, int fsid_size, long *namelen_out)
+{
+	struct statfs64 buf;
+	int err;
+
+	err = statfs64(root, &buf);
+	if (err < 0)
+		return -errno;
+
+	*bsize_out = buf.f_bsize;
+	*blocks_out = buf.f_blocks;
+	*bfree_out = buf.f_bfree;
+	*bavail_out = buf.f_bavail;
+	*files_out = buf.f_files;
+	*ffree_out = buf.f_ffree;
+	memcpy(fsid_out, &buf.f_fsid,
+	       sizeof(buf.f_fsid) > fsid_size ? fsid_size :
+	       sizeof(buf.f_fsid));
+	*namelen_out = buf.f_namelen;
+
+	return 0;
+}
diff --git a/fs/hostfs/hostfs_user_exp.c b/fs/hostfs/hostfs_user_exp.c
new file mode 100644
index 000000000..250c91c55
--- /dev/null
+++ b/fs/hostfs/hostfs_user_exp.c
@@ -0,0 +1,28 @@
+#include <linux/module.h>
+#include "hostfs.h"
+
+EXPORT_SYMBOL_GPL(stat_file);
+EXPORT_SYMBOL_GPL(access_file);
+EXPORT_SYMBOL_GPL(open_file);
+EXPORT_SYMBOL_GPL(open_dir);
+EXPORT_SYMBOL_GPL(seek_dir);
+EXPORT_SYMBOL_GPL(read_dir);
+EXPORT_SYMBOL_GPL(read_file);
+EXPORT_SYMBOL_GPL(write_file);
+EXPORT_SYMBOL_GPL(lseek_file);
+EXPORT_SYMBOL_GPL(fsync_file);
+EXPORT_SYMBOL_GPL(replace_file);
+EXPORT_SYMBOL_GPL(close_file);
+EXPORT_SYMBOL_GPL(close_dir);
+EXPORT_SYMBOL_GPL(file_create);
+EXPORT_SYMBOL_GPL(set_attr);
+EXPORT_SYMBOL_GPL(make_symlink);
+EXPORT_SYMBOL_GPL(unlink_file);
+EXPORT_SYMBOL_GPL(do_mkdir);
+EXPORT_SYMBOL_GPL(hostfs_do_rmdir);
+EXPORT_SYMBOL_GPL(do_mknod);
+EXPORT_SYMBOL_GPL(link_file);
+EXPORT_SYMBOL_GPL(hostfs_do_readlink);
+EXPORT_SYMBOL_GPL(rename_file);
+EXPORT_SYMBOL_GPL(rename2_file);
+EXPORT_SYMBOL_GPL(do_statfs);