Adding upstream version 6.1.76.upstream/6.1.76upstream

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

1 files changed, 2244 insertions, 0 deletions

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
new file mode 100644
index 000000000..51eec4a8e
--- /dev/null
+++ b/fs/overlayfs/super.c
@@ -0,0 +1,2244 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *
+ * Copyright (C) 2011 Novell Inc.
+ */
+
+#include <uapi/linux/magic.h>
+#include <linux/fs.h>
+#include <linux/namei.h>
+#include <linux/xattr.h>
+#include <linux/mount.h>
+#include <linux/parser.h>
+#include <linux/module.h>
+#include <linux/statfs.h>
+#include <linux/seq_file.h>
+#include <linux/posix_acl_xattr.h>
+#include <linux/exportfs.h>
+#include <linux/file.h>
+#include "overlayfs.h"
+
+MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
+MODULE_DESCRIPTION("Overlay filesystem");
+MODULE_LICENSE("GPL");
+
+
+struct ovl_dir_cache;
+
+#define OVL_MAX_STACK 500
+
+static bool ovl_redirect_dir_def = IS_ENABLED(CONFIG_OVERLAY_FS_REDIRECT_DIR);
+module_param_named(redirect_dir, ovl_redirect_dir_def, bool, 0644);
+MODULE_PARM_DESC(redirect_dir,
+		 "Default to on or off for the redirect_dir feature");
+
+static bool ovl_redirect_always_follow =
+	IS_ENABLED(CONFIG_OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW);
+module_param_named(redirect_always_follow, ovl_redirect_always_follow,
+		   bool, 0644);
+MODULE_PARM_DESC(redirect_always_follow,
+		 "Follow redirects even if redirect_dir feature is turned off");
+
+static bool ovl_index_def = IS_ENABLED(CONFIG_OVERLAY_FS_INDEX);
+module_param_named(index, ovl_index_def, bool, 0644);
+MODULE_PARM_DESC(index,
+		 "Default to on or off for the inodes index feature");
+
+static bool ovl_nfs_export_def = IS_ENABLED(CONFIG_OVERLAY_FS_NFS_EXPORT);
+module_param_named(nfs_export, ovl_nfs_export_def, bool, 0644);
+MODULE_PARM_DESC(nfs_export,
+		 "Default to on or off for the NFS export feature");
+
+static bool ovl_xino_auto_def = IS_ENABLED(CONFIG_OVERLAY_FS_XINO_AUTO);
+module_param_named(xino_auto, ovl_xino_auto_def, bool, 0644);
+MODULE_PARM_DESC(xino_auto,
+		 "Auto enable xino feature");
+
+static void ovl_entry_stack_free(struct ovl_entry *oe)
+{
+	unsigned int i;
+
+	for (i = 0; i < oe->numlower; i++)
+		dput(oe->lowerstack[i].dentry);
+}
+
+static bool ovl_metacopy_def = IS_ENABLED(CONFIG_OVERLAY_FS_METACOPY);
+module_param_named(metacopy, ovl_metacopy_def, bool, 0644);
+MODULE_PARM_DESC(metacopy,
+		 "Default to on or off for the metadata only copy up feature");
+
+static void ovl_dentry_release(struct dentry *dentry)
+{
+	struct ovl_entry *oe = dentry->d_fsdata;
+
+	if (oe) {
+		ovl_entry_stack_free(oe);
+		kfree_rcu(oe, rcu);
+	}
+}
+
+static struct dentry *ovl_d_real(struct dentry *dentry,
+				 const struct inode *inode)
+{
+	struct dentry *real = NULL, *lower;
+
+	/* It's an overlay file */
+	if (inode && d_inode(dentry) == inode)
+		return dentry;
+
+	if (!d_is_reg(dentry)) {
+		if (!inode || inode == d_inode(dentry))
+			return dentry;
+		goto bug;
+	}
+
+	real = ovl_dentry_upper(dentry);
+	if (real && (inode == d_inode(real)))
+		return real;
+
+	if (real && !inode && ovl_has_upperdata(d_inode(dentry)))
+		return real;
+
+	lower = ovl_dentry_lowerdata(dentry);
+	if (!lower)
+		goto bug;
+	real = lower;
+
+	/* Handle recursion */
+	real = d_real(real, inode);
+
+	if (!inode || inode == d_inode(real))
+		return real;
+bug:
+	WARN(1, "%s(%pd4, %s:%lu): real dentry (%p/%lu) not found\n",
+	     __func__, dentry, inode ? inode->i_sb->s_id : "NULL",
+	     inode ? inode->i_ino : 0, real,
+	     real && d_inode(real) ? d_inode(real)->i_ino : 0);
+	return dentry;
+}
+
+static int ovl_revalidate_real(struct dentry *d, unsigned int flags, bool weak)
+{
+	int ret = 1;
+
+	if (weak) {
+		if (d->d_flags & DCACHE_OP_WEAK_REVALIDATE)
+			ret =  d->d_op->d_weak_revalidate(d, flags);
+	} else if (d->d_flags & DCACHE_OP_REVALIDATE) {
+		ret = d->d_op->d_revalidate(d, flags);
+		if (!ret) {
+			if (!(flags & LOOKUP_RCU))
+				d_invalidate(d);
+			ret = -ESTALE;
+		}
+	}
+	return ret;
+}
+
+static int ovl_dentry_revalidate_common(struct dentry *dentry,
+					unsigned int flags, bool weak)
+{
+	struct ovl_entry *oe = dentry->d_fsdata;
+	struct inode *inode = d_inode_rcu(dentry);
+	struct dentry *upper;
+	unsigned int i;
+	int ret = 1;
+
+	/* Careful in RCU mode */
+	if (!inode)
+		return -ECHILD;
+
+	upper = ovl_i_dentry_upper(inode);
+	if (upper)
+		ret = ovl_revalidate_real(upper, flags, weak);
+
+	for (i = 0; ret > 0 && i < oe->numlower; i++) {
+		ret = ovl_revalidate_real(oe->lowerstack[i].dentry, flags,
+					  weak);
+	}
+	return ret;
+}
+
+static int ovl_dentry_revalidate(struct dentry *dentry, unsigned int flags)
+{
+	return ovl_dentry_revalidate_common(dentry, flags, false);
+}
+
+static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags)
+{
+	return ovl_dentry_revalidate_common(dentry, flags, true);
+}
+
+static const struct dentry_operations ovl_dentry_operations = {
+	.d_release = ovl_dentry_release,
+	.d_real = ovl_d_real,
+	.d_revalidate = ovl_dentry_revalidate,
+	.d_weak_revalidate = ovl_dentry_weak_revalidate,
+};
+
+static struct kmem_cache *ovl_inode_cachep;
+
+static struct inode *ovl_alloc_inode(struct super_block *sb)
+{
+	struct ovl_inode *oi = alloc_inode_sb(sb, ovl_inode_cachep, GFP_KERNEL);
+
+	if (!oi)
+		return NULL;
+
+	oi->cache = NULL;
+	oi->redirect = NULL;
+	oi->version = 0;
+	oi->flags = 0;
+	oi->__upperdentry = NULL;
+	oi->lowerpath.dentry = NULL;
+	oi->lowerpath.layer = NULL;
+	oi->lowerdata = NULL;
+	mutex_init(&oi->lock);
+
+	return &oi->vfs_inode;
+}
+
+static void ovl_free_inode(struct inode *inode)
+{
+	struct ovl_inode *oi = OVL_I(inode);
+
+	kfree(oi->redirect);
+	mutex_destroy(&oi->lock);
+	kmem_cache_free(ovl_inode_cachep, oi);
+}
+
+static void ovl_destroy_inode(struct inode *inode)
+{
+	struct ovl_inode *oi = OVL_I(inode);
+
+	dput(oi->__upperdentry);
+	dput(oi->lowerpath.dentry);
+	if (S_ISDIR(inode->i_mode))
+		ovl_dir_cache_free(inode);
+	else
+		iput(oi->lowerdata);
+}
+
+static void ovl_free_fs(struct ovl_fs *ofs)
+{
+	struct vfsmount **mounts;
+	unsigned i;
+
+	iput(ofs->workbasedir_trap);
+	iput(ofs->indexdir_trap);
+	iput(ofs->workdir_trap);
+	dput(ofs->whiteout);
+	dput(ofs->indexdir);
+	dput(ofs->workdir);
+	if (ofs->workdir_locked)
+		ovl_inuse_unlock(ofs->workbasedir);
+	dput(ofs->workbasedir);
+	if (ofs->upperdir_locked)
+		ovl_inuse_unlock(ovl_upper_mnt(ofs)->mnt_root);
+
+	/* Hack!  Reuse ofs->layers as a vfsmount array before freeing it */
+	mounts = (struct vfsmount **) ofs->layers;
+	for (i = 0; i < ofs->numlayer; i++) {
+		iput(ofs->layers[i].trap);
+		mounts[i] = ofs->layers[i].mnt;
+	}
+	kern_unmount_array(mounts, ofs->numlayer);
+	kfree(ofs->layers);
+	for (i = 0; i < ofs->numfs; i++)
+		free_anon_bdev(ofs->fs[i].pseudo_dev);
+	kfree(ofs->fs);
+
+	kfree(ofs->config.lowerdir);
+	kfree(ofs->config.upperdir);
+	kfree(ofs->config.workdir);
+	kfree(ofs->config.redirect_mode);
+	if (ofs->creator_cred)
+		put_cred(ofs->creator_cred);
+	kfree(ofs);
+}
+
+static void ovl_put_super(struct super_block *sb)
+{
+	struct ovl_fs *ofs = sb->s_fs_info;
+
+	ovl_free_fs(ofs);
+}
+
+/* Sync real dirty inodes in upper filesystem (if it exists) */
+static int ovl_sync_fs(struct super_block *sb, int wait)
+{
+	struct ovl_fs *ofs = sb->s_fs_info;
+	struct super_block *upper_sb;
+	int ret;
+
+	ret = ovl_sync_status(ofs);
+	/*
+	 * We have to always set the err, because the return value isn't
+	 * checked in syncfs, and instead indirectly return an error via
+	 * the sb's writeback errseq, which VFS inspects after this call.
+	 */
+	if (ret < 0) {
+		errseq_set(&sb->s_wb_err, -EIO);
+		return -EIO;
+	}
+
+	if (!ret)
+		return ret;
+
+	/*
+	 * Not called for sync(2) call or an emergency sync (SB_I_SKIP_SYNC).
+	 * All the super blocks will be iterated, including upper_sb.
+	 *
+	 * If this is a syncfs(2) call, then we do need to call
+	 * sync_filesystem() on upper_sb, but enough if we do it when being
+	 * called with wait == 1.
+	 */
+	if (!wait)
+		return 0;
+
+	upper_sb = ovl_upper_mnt(ofs)->mnt_sb;
+
+	down_read(&upper_sb->s_umount);
+	ret = sync_filesystem(upper_sb);
+	up_read(&upper_sb->s_umount);
+
+	return ret;
+}
+
+/**
+ * ovl_statfs
+ * @dentry: The dentry to query
+ * @buf: The struct kstatfs to fill in with stats
+ *
+ * Get the filesystem statistics.  As writes always target the upper layer
+ * filesystem pass the statfs to the upper filesystem (if it exists)
+ */
+static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
+{
+	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+	struct dentry *root_dentry = dentry->d_sb->s_root;
+	struct path path;
+	int err;
+
+	ovl_path_real(root_dentry, &path);
+
+	err = vfs_statfs(&path, buf);
+	if (!err) {
+		buf->f_namelen = ofs->namelen;
+		buf->f_type = OVERLAYFS_SUPER_MAGIC;
+	}
+
+	return err;
+}
+
+/* Will this overlay be forced to mount/remount ro? */
+static bool ovl_force_readonly(struct ovl_fs *ofs)
+{
+	return (!ovl_upper_mnt(ofs) || !ofs->workdir);
+}
+
+static const char *ovl_redirect_mode_def(void)
+{
+	return ovl_redirect_dir_def ? "on" : "off";
+}
+
+static const char * const ovl_xino_str[] = {
+	"off",
+	"auto",
+	"on",
+};
+
+static inline int ovl_xino_def(void)
+{
+	return ovl_xino_auto_def ? OVL_XINO_AUTO : OVL_XINO_OFF;
+}
+
+/**
+ * ovl_show_options
+ * @m: the seq_file handle
+ * @dentry: The dentry to query
+ *
+ * Prints the mount options for a given superblock.
+ * Returns zero; does not fail.
+ */
+static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
+{
+	struct super_block *sb = dentry->d_sb;
+	struct ovl_fs *ofs = sb->s_fs_info;
+
+	seq_show_option(m, "lowerdir", ofs->config.lowerdir);
+	if (ofs->config.upperdir) {
+		seq_show_option(m, "upperdir", ofs->config.upperdir);
+		seq_show_option(m, "workdir", ofs->config.workdir);
+	}
+	if (ofs->config.default_permissions)
+		seq_puts(m, ",default_permissions");
+	if (strcmp(ofs->config.redirect_mode, ovl_redirect_mode_def()) != 0)
+		seq_printf(m, ",redirect_dir=%s", ofs->config.redirect_mode);
+	if (ofs->config.index != ovl_index_def)
+		seq_printf(m, ",index=%s", ofs->config.index ? "on" : "off");
+	if (!ofs->config.uuid)
+		seq_puts(m, ",uuid=off");
+	if (ofs->config.nfs_export != ovl_nfs_export_def)
+		seq_printf(m, ",nfs_export=%s", ofs->config.nfs_export ?
+						"on" : "off");
+	if (ofs->config.xino != ovl_xino_def() && !ovl_same_fs(sb))
+		seq_printf(m, ",xino=%s", ovl_xino_str[ofs->config.xino]);
+	if (ofs->config.metacopy != ovl_metacopy_def)
+		seq_printf(m, ",metacopy=%s",
+			   ofs->config.metacopy ? "on" : "off");
+	if (ofs->config.ovl_volatile)
+		seq_puts(m, ",volatile");
+	if (ofs->config.userxattr)
+		seq_puts(m, ",userxattr");
+	return 0;
+}
+
+static int ovl_remount(struct super_block *sb, int *flags, char *data)
+{
+	struct ovl_fs *ofs = sb->s_fs_info;
+	struct super_block *upper_sb;
+	int ret = 0;
+
+	if (!(*flags & SB_RDONLY) && ovl_force_readonly(ofs))
+		return -EROFS;
+
+	if (*flags & SB_RDONLY && !sb_rdonly(sb)) {
+		upper_sb = ovl_upper_mnt(ofs)->mnt_sb;
+		if (ovl_should_sync(ofs)) {
+			down_read(&upper_sb->s_umount);
+			ret = sync_filesystem(upper_sb);
+			up_read(&upper_sb->s_umount);
+		}
+	}
+
+	return ret;
+}
+
+static const struct super_operations ovl_super_operations = {
+	.alloc_inode	= ovl_alloc_inode,
+	.free_inode	= ovl_free_inode,
+	.destroy_inode	= ovl_destroy_inode,
+	.drop_inode	= generic_delete_inode,
+	.put_super	= ovl_put_super,
+	.sync_fs	= ovl_sync_fs,
+	.statfs		= ovl_statfs,
+	.show_options	= ovl_show_options,
+	.remount_fs	= ovl_remount,
+};
+
+enum {
+	OPT_LOWERDIR,
+	OPT_UPPERDIR,
+	OPT_WORKDIR,
+	OPT_DEFAULT_PERMISSIONS,
+	OPT_REDIRECT_DIR,
+	OPT_INDEX_ON,
+	OPT_INDEX_OFF,
+	OPT_UUID_ON,
+	OPT_UUID_OFF,
+	OPT_NFS_EXPORT_ON,
+	OPT_USERXATTR,
+	OPT_NFS_EXPORT_OFF,
+	OPT_XINO_ON,
+	OPT_XINO_OFF,
+	OPT_XINO_AUTO,
+	OPT_METACOPY_ON,
+	OPT_METACOPY_OFF,
+	OPT_VOLATILE,
+	OPT_ERR,
+};
+
+static const match_table_t ovl_tokens = {
+	{OPT_LOWERDIR,			"lowerdir=%s"},
+	{OPT_UPPERDIR,			"upperdir=%s"},
+	{OPT_WORKDIR,			"workdir=%s"},
+	{OPT_DEFAULT_PERMISSIONS,	"default_permissions"},
+	{OPT_REDIRECT_DIR,		"redirect_dir=%s"},
+	{OPT_INDEX_ON,			"index=on"},
+	{OPT_INDEX_OFF,			"index=off"},
+	{OPT_USERXATTR,			"userxattr"},
+	{OPT_UUID_ON,			"uuid=on"},
+	{OPT_UUID_OFF,			"uuid=off"},
+	{OPT_NFS_EXPORT_ON,		"nfs_export=on"},
+	{OPT_NFS_EXPORT_OFF,		"nfs_export=off"},
+	{OPT_XINO_ON,			"xino=on"},
+	{OPT_XINO_OFF,			"xino=off"},
+	{OPT_XINO_AUTO,			"xino=auto"},
+	{OPT_METACOPY_ON,		"metacopy=on"},
+	{OPT_METACOPY_OFF,		"metacopy=off"},
+	{OPT_VOLATILE,			"volatile"},
+	{OPT_ERR,			NULL}
+};
+
+static char *ovl_next_opt(char **s)
+{
+	char *sbegin = *s;
+	char *p;
+
+	if (sbegin == NULL)
+		return NULL;
+
+	for (p = sbegin; *p; p++) {
+		if (*p == '\\') {
+			p++;
+			if (!*p)
+				break;
+		} else if (*p == ',') {
+			*p = '\0';
+			*s = p + 1;
+			return sbegin;
+		}
+	}
+	*s = NULL;
+	return sbegin;
+}
+
+static int ovl_parse_redirect_mode(struct ovl_config *config, const char *mode)
+{
+	if (strcmp(mode, "on") == 0) {
+		config->redirect_dir = true;
+		/*
+		 * Does not make sense to have redirect creation without
+		 * redirect following.
+		 */
+		config->redirect_follow = true;
+	} else if (strcmp(mode, "follow") == 0) {
+		config->redirect_follow = true;
+	} else if (strcmp(mode, "off") == 0) {
+		if (ovl_redirect_always_follow)
+			config->redirect_follow = true;
+	} else if (strcmp(mode, "nofollow") != 0) {
+		pr_err("bad mount option \"redirect_dir=%s\"\n",
+		       mode);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int ovl_parse_opt(char *opt, struct ovl_config *config)
+{
+	char *p;
+	int err;
+	bool metacopy_opt = false, redirect_opt = false;
+	bool nfs_export_opt = false, index_opt = false;
+
+	config->redirect_mode = kstrdup(ovl_redirect_mode_def(), GFP_KERNEL);
+	if (!config->redirect_mode)
+		return -ENOMEM;
+
+	while ((p = ovl_next_opt(&opt)) != NULL) {
+		int token;
+		substring_t args[MAX_OPT_ARGS];
+
+		if (!*p)
+			continue;
+
+		token = match_token(p, ovl_tokens, args);
+		switch (token) {
+		case OPT_UPPERDIR:
+			kfree(config->upperdir);
+			config->upperdir = match_strdup(&args[0]);
+			if (!config->upperdir)
+				return -ENOMEM;
+			break;
+
+		case OPT_LOWERDIR:
+			kfree(config->lowerdir);
+			config->lowerdir = match_strdup(&args[0]);
+			if (!config->lowerdir)
+				return -ENOMEM;
+			break;
+
+		case OPT_WORKDIR:
+			kfree(config->workdir);
+			config->workdir = match_strdup(&args[0]);
+			if (!config->workdir)
+				return -ENOMEM;
+			break;
+
+		case OPT_DEFAULT_PERMISSIONS:
+			config->default_permissions = true;
+			break;
+
+		case OPT_REDIRECT_DIR:
+			kfree(config->redirect_mode);
+			config->redirect_mode = match_strdup(&args[0]);
+			if (!config->redirect_mode)
+				return -ENOMEM;
+			redirect_opt = true;
+			break;
+
+		case OPT_INDEX_ON:
+			config->index = true;
+			index_opt = true;
+			break;
+
+		case OPT_INDEX_OFF:
+			config->index = false;
+			index_opt = true;
+			break;
+
+		case OPT_UUID_ON:
+			config->uuid = true;
+			break;
+
+		case OPT_UUID_OFF:
+			config->uuid = false;
+			break;
+
+		case OPT_NFS_EXPORT_ON:
+			config->nfs_export = true;
+			nfs_export_opt = true;
+			break;
+
+		case OPT_NFS_EXPORT_OFF:
+			config->nfs_export = false;
+			nfs_export_opt = true;
+			break;
+
+		case OPT_XINO_ON:
+			config->xino = OVL_XINO_ON;
+			break;
+
+		case OPT_XINO_OFF:
+			config->xino = OVL_XINO_OFF;
+			break;
+
+		case OPT_XINO_AUTO:
+			config->xino = OVL_XINO_AUTO;
+			break;
+
+		case OPT_METACOPY_ON:
+			config->metacopy = true;
+			metacopy_opt = true;
+			break;
+
+		case OPT_METACOPY_OFF:
+			config->metacopy = false;
+			metacopy_opt = true;
+			break;
+
+		case OPT_VOLATILE:
+			config->ovl_volatile = true;
+			break;
+
+		case OPT_USERXATTR:
+			config->userxattr = true;
+			break;
+
+		default:
+			pr_err("unrecognized mount option \"%s\" or missing value\n",
+					p);
+			return -EINVAL;
+		}
+	}
+
+	/* Workdir/index are useless in non-upper mount */
+	if (!config->upperdir) {
+		if (config->workdir) {
+			pr_info("option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
+				config->workdir);
+			kfree(config->workdir);
+			config->workdir = NULL;
+		}
+		if (config->index && index_opt) {
+			pr_info("option \"index=on\" is useless in a non-upper mount, ignore\n");
+			index_opt = false;
+		}
+		config->index = false;
+	}
+
+	if (!config->upperdir && config->ovl_volatile) {
+		pr_info("option \"volatile\" is meaningless in a non-upper mount, ignoring it.\n");
+		config->ovl_volatile = false;
+	}
+
+	err = ovl_parse_redirect_mode(config, config->redirect_mode);
+	if (err)
+		return err;
+
+	/*
+	 * This is to make the logic below simpler.  It doesn't make any other
+	 * difference, since config->redirect_dir is only used for upper.
+	 */
+	if (!config->upperdir && config->redirect_follow)
+		config->redirect_dir = true;
+
+	/* Resolve metacopy -> redirect_dir dependency */
+	if (config->metacopy && !config->redirect_dir) {
+		if (metacopy_opt && redirect_opt) {
+			pr_err("conflicting options: metacopy=on,redirect_dir=%s\n",
+			       config->redirect_mode);
+			return -EINVAL;
+		}
+		if (redirect_opt) {
+			/*
+			 * There was an explicit redirect_dir=... that resulted
+			 * in this conflict.
+			 */
+			pr_info("disabling metacopy due to redirect_dir=%s\n",
+				config->redirect_mode);
+			config->metacopy = false;
+		} else {
+			/* Automatically enable redirect otherwise. */
+			config->redirect_follow = config->redirect_dir = true;
+		}
+	}
+
+	/* Resolve nfs_export -> index dependency */
+	if (config->nfs_export && !config->index) {
+		if (!config->upperdir && config->redirect_follow) {
+			pr_info("NFS export requires \"redirect_dir=nofollow\" on non-upper mount, falling back to nfs_export=off.\n");
+			config->nfs_export = false;
+		} else if (nfs_export_opt && index_opt) {
+			pr_err("conflicting options: nfs_export=on,index=off\n");
+			return -EINVAL;
+		} else if (index_opt) {
+			/*
+			 * There was an explicit index=off that resulted
+			 * in this conflict.
+			 */
+			pr_info("disabling nfs_export due to index=off\n");
+			config->nfs_export = false;
+		} else {
+			/* Automatically enable index otherwise. */
+			config->index = true;
+		}
+	}
+
+	/* Resolve nfs_export -> !metacopy dependency */
+	if (config->nfs_export && config->metacopy) {
+		if (nfs_export_opt && metacopy_opt) {
+			pr_err("conflicting options: nfs_export=on,metacopy=on\n");
+			return -EINVAL;
+		}
+		if (metacopy_opt) {
+			/*
+			 * There was an explicit metacopy=on that resulted
+			 * in this conflict.
+			 */
+			pr_info("disabling nfs_export due to metacopy=on\n");
+			config->nfs_export = false;
+		} else {
+			/*
+			 * There was an explicit nfs_export=on that resulted
+			 * in this conflict.
+			 */
+			pr_info("disabling metacopy due to nfs_export=on\n");
+			config->metacopy = false;
+		}
+	}
+
+
+	/* Resolve userxattr -> !redirect && !metacopy dependency */
+	if (config->userxattr) {
+		if (config->redirect_follow && redirect_opt) {
+			pr_err("conflicting options: userxattr,redirect_dir=%s\n",
+			       config->redirect_mode);
+			return -EINVAL;
+		}
+		if (config->metacopy && metacopy_opt) {
+			pr_err("conflicting options: userxattr,metacopy=on\n");
+			return -EINVAL;
+		}
+		/*
+		 * Silently disable default setting of redirect and metacopy.
+		 * This shall be the default in the future as well: these
+		 * options must be explicitly enabled if used together with
+		 * userxattr.
+		 */
+		config->redirect_dir = config->redirect_follow = false;
+		config->metacopy = false;
+	}
+
+	return 0;
+}
+
+#define OVL_WORKDIR_NAME "work"
+#define OVL_INDEXDIR_NAME "index"
+
+static struct dentry *ovl_workdir_create(struct ovl_fs *ofs,
+					 const char *name, bool persist)
+{
+	struct inode *dir =  ofs->workbasedir->d_inode;
+	struct vfsmount *mnt = ovl_upper_mnt(ofs);
+	struct dentry *work;
+	int err;
+	bool retried = false;
+
+	inode_lock_nested(dir, I_MUTEX_PARENT);
+retry:
+	work = ovl_lookup_upper(ofs, name, ofs->workbasedir, strlen(name));
+
+	if (!IS_ERR(work)) {
+		struct iattr attr = {
+			.ia_valid = ATTR_MODE,
+			.ia_mode = S_IFDIR | 0,
+		};
+
+		if (work->d_inode) {
+			err = -EEXIST;
+			if (retried)
+				goto out_dput;
+
+			if (persist)
+				goto out_unlock;
+
+			retried = true;
+			err = ovl_workdir_cleanup(ofs, dir, mnt, work, 0);
+			dput(work);
+			if (err == -EINVAL) {
+				work = ERR_PTR(err);
+				goto out_unlock;
+			}
+			goto retry;
+		}
+
+		err = ovl_mkdir_real(ofs, dir, &work, attr.ia_mode);
+		if (err)
+			goto out_dput;
+
+		/* Weird filesystem returning with hashed negative (kernfs)? */
+		err = -EINVAL;
+		if (d_really_is_negative(work))
+			goto out_dput;
+
+		/*
+		 * Try to remove POSIX ACL xattrs from workdir.  We are good if:
+		 *
+		 * a) success (there was a POSIX ACL xattr and was removed)
+		 * b) -ENODATA (there was no POSIX ACL xattr)
+		 * c) -EOPNOTSUPP (POSIX ACL xattrs are not supported)
+		 *
+		 * There are various other error values that could effectively
+		 * mean that the xattr doesn't exist (e.g. -ERANGE is returned
+		 * if the xattr name is too long), but the set of filesystems
+		 * allowed as upper are limited to "normal" ones, where checking
+		 * for the above two errors is sufficient.
+		 */
+		err = ovl_do_removexattr(ofs, work,
+					 XATTR_NAME_POSIX_ACL_DEFAULT);
+		if (err && err != -ENODATA && err != -EOPNOTSUPP)
+			goto out_dput;
+
+		err = ovl_do_removexattr(ofs, work,
+					 XATTR_NAME_POSIX_ACL_ACCESS);
+		if (err && err != -ENODATA && err != -EOPNOTSUPP)
+			goto out_dput;
+
+		/* Clear any inherited mode bits */
+		inode_lock(work->d_inode);
+		err = ovl_do_notify_change(ofs, work, &attr);
+		inode_unlock(work->d_inode);
+		if (err)
+			goto out_dput;
+	} else {
+		err = PTR_ERR(work);
+		goto out_err;
+	}
+out_unlock:
+	inode_unlock(dir);
+	return work;
+
+out_dput:
+	dput(work);
+out_err:
+	pr_warn("failed to create directory %s/%s (errno: %i); mounting read-only\n",
+		ofs->config.workdir, name, -err);
+	work = NULL;
+	goto out_unlock;
+}
+
+static void ovl_unescape(char *s)
+{
+	char *d = s;
+
+	for (;; s++, d++) {
+		if (*s == '\\')
+			s++;
+		*d = *s;
+		if (!*s)
+			break;
+	}
+}
+
+static int ovl_mount_dir_noesc(const char *name, struct path *path)
+{
+	int err = -EINVAL;
+
+	if (!*name) {
+		pr_err("empty lowerdir\n");
+		goto out;
+	}
+	err = kern_path(name, LOOKUP_FOLLOW, path);
+	if (err) {
+		pr_err("failed to resolve '%s': %i\n", name, err);
+		goto out;
+	}
+	err = -EINVAL;
+	if (ovl_dentry_weird(path->dentry)) {
+		pr_err("filesystem on '%s' not supported\n", name);
+		goto out_put;
+	}
+	if (!d_is_dir(path->dentry)) {
+		pr_err("'%s' not a directory\n", name);
+		goto out_put;
+	}
+	return 0;
+
+out_put:
+	path_put_init(path);
+out:
+	return err;
+}
+
+static int ovl_mount_dir(const char *name, struct path *path)
+{
+	int err = -ENOMEM;
+	char *tmp = kstrdup(name, GFP_KERNEL);
+
+	if (tmp) {
+		ovl_unescape(tmp);
+		err = ovl_mount_dir_noesc(tmp, path);
+
+		if (!err && path->dentry->d_flags & DCACHE_OP_REAL) {
+			pr_err("filesystem on '%s' not supported as upperdir\n",
+			       tmp);
+			path_put_init(path);
+			err = -EINVAL;
+		}
+		kfree(tmp);
+	}
+	return err;
+}
+
+static int ovl_check_namelen(const struct path *path, struct ovl_fs *ofs,
+			     const char *name)
+{
+	struct kstatfs statfs;
+	int err = vfs_statfs(path, &statfs);
+
+	if (err)
+		pr_err("statfs failed on '%s'\n", name);
+	else
+		ofs->namelen = max(ofs->namelen, statfs.f_namelen);
+
+	return err;
+}
+
+static int ovl_lower_dir(const char *name, struct path *path,
+			 struct ovl_fs *ofs, int *stack_depth)
+{
+	int fh_type;
+	int err;
+
+	err = ovl_mount_dir_noesc(name, path);
+	if (err)
+		return err;
+
+	err = ovl_check_namelen(path, ofs, name);
+	if (err)
+		return err;
+
+	*stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);
+
+	/*
+	 * The inodes index feature and NFS export need to encode and decode
+	 * file handles, so they require that all layers support them.
+	 */
+	fh_type = ovl_can_decode_fh(path->dentry->d_sb);
+	if ((ofs->config.nfs_export ||
+	     (ofs->config.index && ofs->config.upperdir)) && !fh_type) {
+		ofs->config.index = false;
+		ofs->config.nfs_export = false;
+		pr_warn("fs on '%s' does not support file handles, falling back to index=off,nfs_export=off.\n",
+			name);
+	}
+	/*
+	 * Decoding origin file handle is required for persistent st_ino.
+	 * Without persistent st_ino, xino=auto falls back to xino=off.
+	 */
+	if (ofs->config.xino == OVL_XINO_AUTO &&
+	    ofs->config.upperdir && !fh_type) {
+		ofs->config.xino = OVL_XINO_OFF;
+		pr_warn("fs on '%s' does not support file handles, falling back to xino=off.\n",
+			name);
+	}
+
+	/* Check if lower fs has 32bit inode numbers */
+	if (fh_type != FILEID_INO32_GEN)
+		ofs->xino_mode = -1;
+
+	return 0;
+}
+
+/* Workdir should not be subdir of upperdir and vice versa */
+static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
+{
+	bool ok = false;
+
+	if (workdir != upperdir) {
+		ok = (lock_rename(workdir, upperdir) == NULL);
+		unlock_rename(workdir, upperdir);
+	}
+	return ok;
+}
+
+static unsigned int ovl_split_lowerdirs(char *str)
+{
+	unsigned int ctr = 1;
+	char *s, *d;
+
+	for (s = d = str;; s++, d++) {
+		if (*s == '\\') {
+			s++;
+		} else if (*s == ':') {
+			*d = '\0';
+			ctr++;
+			continue;
+		}
+		*d = *s;
+		if (!*s)
+			break;
+	}
+	return ctr;
+}
+
+static int __maybe_unused
+ovl_posix_acl_xattr_get(const struct xattr_handler *handler,
+			struct dentry *dentry, struct inode *inode,
+			const char *name, void *buffer, size_t size)
+{
+	return ovl_xattr_get(dentry, inode, handler->name, buffer, size);
+}
+
+static int __maybe_unused
+ovl_posix_acl_xattr_set(const struct xattr_handler *handler,
+			struct user_namespace *mnt_userns,
+			struct dentry *dentry, struct inode *inode,
+			const char *name, const void *value,
+			size_t size, int flags)
+{
+	struct dentry *workdir = ovl_workdir(dentry);
+	struct inode *realinode = ovl_inode_real(inode);
+	struct posix_acl *acl = NULL;
+	int err;
+
+	/* Check that everything is OK before copy-up */
+	if (value) {
+		/* The above comment can be understood in two ways:
+		 *
+		 * 1. We just want to check whether the basic POSIX ACL format
+		 *    is ok. For example, if the header is correct and the size
+		 *    is sane.
+		 * 2. We want to know whether the ACL_{GROUP,USER} entries can
+		 *    be mapped according to the underlying filesystem.
+		 *
+		 * Currently, we only check 1. If we wanted to check 2. we
+		 * would need to pass the mnt_userns and the fs_userns of the
+		 * underlying filesystem. But frankly, I think checking 1. is
+		 * enough to start the copy-up.
+		 */
+		acl = vfs_set_acl_prepare(&init_user_ns, &init_user_ns, value, size);
+		if (IS_ERR(acl))
+			return PTR_ERR(acl);
+	}
+	err = -EOPNOTSUPP;
+	if (!IS_POSIXACL(d_inode(workdir)))
+		goto out_acl_release;
+	if (!realinode->i_op->set_acl)
+		goto out_acl_release;
+	if (handler->flags == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode)) {
+		err = acl ? -EACCES : 0;
+		goto out_acl_release;
+	}
+	err = -EPERM;
+	if (!inode_owner_or_capable(&init_user_ns, inode))
+		goto out_acl_release;
+
+	posix_acl_release(acl);
+
+	/*
+	 * Check if sgid bit needs to be cleared (actual setacl operation will
+	 * be done with mounter's capabilities and so that won't do it for us).
+	 */
+	if (unlikely(inode->i_mode & S_ISGID) &&
+	    handler->flags == ACL_TYPE_ACCESS &&
+	    !in_group_p(inode->i_gid) &&
+	    !capable_wrt_inode_uidgid(&init_user_ns, inode, CAP_FSETID)) {
+		struct iattr iattr = { .ia_valid = ATTR_KILL_SGID };
+
+		err = ovl_setattr(&init_user_ns, dentry, &iattr);
+		if (err)
+			return err;
+	}
+
+	err = ovl_xattr_set(dentry, inode, handler->name, value, size, flags);
+	return err;
+
+out_acl_release:
+	posix_acl_release(acl);
+	return err;
+}
+
+static int ovl_own_xattr_get(const struct xattr_handler *handler,
+			     struct dentry *dentry, struct inode *inode,
+			     const char *name, void *buffer, size_t size)
+{
+	return -EOPNOTSUPP;
+}
+
+static int ovl_own_xattr_set(const struct xattr_handler *handler,
+			     struct user_namespace *mnt_userns,
+			     struct dentry *dentry, struct inode *inode,
+			     const char *name, const void *value,
+			     size_t size, int flags)
+{
+	return -EOPNOTSUPP;
+}
+
+static int ovl_other_xattr_get(const struct xattr_handler *handler,
+			       struct dentry *dentry, struct inode *inode,
+			       const char *name, void *buffer, size_t size)
+{
+	return ovl_xattr_get(dentry, inode, name, buffer, size);
+}
+
+static int ovl_other_xattr_set(const struct xattr_handler *handler,
+			       struct user_namespace *mnt_userns,
+			       struct dentry *dentry, struct inode *inode,
+			       const char *name, const void *value,
+			       size_t size, int flags)
+{
+	return ovl_xattr_set(dentry, inode, name, value, size, flags);
+}
+
+static const struct xattr_handler __maybe_unused
+ovl_posix_acl_access_xattr_handler = {
+	.name = XATTR_NAME_POSIX_ACL_ACCESS,
+	.flags = ACL_TYPE_ACCESS,
+	.get = ovl_posix_acl_xattr_get,
+	.set = ovl_posix_acl_xattr_set,
+};
+
+static const struct xattr_handler __maybe_unused
+ovl_posix_acl_default_xattr_handler = {
+	.name = XATTR_NAME_POSIX_ACL_DEFAULT,
+	.flags = ACL_TYPE_DEFAULT,
+	.get = ovl_posix_acl_xattr_get,
+	.set = ovl_posix_acl_xattr_set,
+};
+
+static const struct xattr_handler ovl_own_trusted_xattr_handler = {
+	.prefix	= OVL_XATTR_TRUSTED_PREFIX,
+	.get = ovl_own_xattr_get,
+	.set = ovl_own_xattr_set,
+};
+
+static const struct xattr_handler ovl_own_user_xattr_handler = {
+	.prefix	= OVL_XATTR_USER_PREFIX,
+	.get = ovl_own_xattr_get,
+	.set = ovl_own_xattr_set,
+};
+
+static const struct xattr_handler ovl_other_xattr_handler = {
+	.prefix	= "", /* catch all */
+	.get = ovl_other_xattr_get,
+	.set = ovl_other_xattr_set,
+};
+
+static const struct xattr_handler *ovl_trusted_xattr_handlers[] = {
+#ifdef CONFIG_FS_POSIX_ACL
+	&ovl_posix_acl_access_xattr_handler,
+	&ovl_posix_acl_default_xattr_handler,
+#endif
+	&ovl_own_trusted_xattr_handler,
+	&ovl_other_xattr_handler,
+	NULL
+};
+
+static const struct xattr_handler *ovl_user_xattr_handlers[] = {
+#ifdef CONFIG_FS_POSIX_ACL
+	&ovl_posix_acl_access_xattr_handler,
+	&ovl_posix_acl_default_xattr_handler,
+#endif
+	&ovl_own_user_xattr_handler,
+	&ovl_other_xattr_handler,
+	NULL
+};
+
+static int ovl_setup_trap(struct super_block *sb, struct dentry *dir,
+			  struct inode **ptrap, const char *name)
+{
+	struct inode *trap;
+	int err;
+
+	trap = ovl_get_trap_inode(sb, dir);
+	err = PTR_ERR_OR_ZERO(trap);
+	if (err) {
+		if (err == -ELOOP)
+			pr_err("conflicting %s path\n", name);
+		return err;
+	}
+
+	*ptrap = trap;
+	return 0;
+}
+
+/*
+ * Determine how we treat concurrent use of upperdir/workdir based on the
+ * index feature. This is papering over mount leaks of container runtimes,
+ * for example, an old overlay mount is leaked and now its upperdir is
+ * attempted to be used as a lower layer in a new overlay mount.
+ */
+static int ovl_report_in_use(struct ovl_fs *ofs, const char *name)
+{
+	if (ofs->config.index) {
+		pr_err("%s is in-use as upperdir/workdir of another mount, mount with '-o index=off' to override exclusive upperdir protection.\n",
+		       name);
+		return -EBUSY;
+	} else {
+		pr_warn("%s is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior.\n",
+			name);
+		return 0;
+	}
+}
+
+static int ovl_get_upper(struct super_block *sb, struct ovl_fs *ofs,
+			 struct ovl_layer *upper_layer, struct path *upperpath)
+{
+	struct vfsmount *upper_mnt;
+	int err;
+
+	err = ovl_mount_dir(ofs->config.upperdir, upperpath);
+	if (err)
+		goto out;
+
+	/* Upperdir path should not be r/o */
+	if (__mnt_is_readonly(upperpath->mnt)) {
+		pr_err("upper fs is r/o, try multi-lower layers mount\n");
+		err = -EINVAL;
+		goto out;
+	}
+
+	err = ovl_check_namelen(upperpath, ofs, ofs->config.upperdir);
+	if (err)
+		goto out;
+
+	err = ovl_setup_trap(sb, upperpath->dentry, &upper_layer->trap,
+			     "upperdir");
+	if (err)
+		goto out;
+
+	upper_mnt = clone_private_mount(upperpath);
+	err = PTR_ERR(upper_mnt);
+	if (IS_ERR(upper_mnt)) {
+		pr_err("failed to clone upperpath\n");
+		goto out;
+	}
+
+	/* Don't inherit atime flags */
+	upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME);
+	upper_layer->mnt = upper_mnt;
+	upper_layer->idx = 0;
+	upper_layer->fsid = 0;
+
+	/*
+	 * Inherit SB_NOSEC flag from upperdir.
+	 *
+	 * This optimization changes behavior when a security related attribute
+	 * (suid/sgid/security.*) is changed on an underlying layer.  This is
+	 * okay because we don't yet have guarantees in that case, but it will
+	 * need careful treatment once we want to honour changes to underlying
+	 * filesystems.
+	 */
+	if (upper_mnt->mnt_sb->s_flags & SB_NOSEC)
+		sb->s_flags |= SB_NOSEC;
+
+	if (ovl_inuse_trylock(ovl_upper_mnt(ofs)->mnt_root)) {
+		ofs->upperdir_locked = true;
+	} else {
+		err = ovl_report_in_use(ofs, "upperdir");
+		if (err)
+			goto out;
+	}
+
+	err = 0;
+out:
+	return err;
+}
+
+/*
+ * Returns 1 if RENAME_WHITEOUT is supported, 0 if not supported and
+ * negative values if error is encountered.
+ */
+static int ovl_check_rename_whiteout(struct ovl_fs *ofs)
+{
+	struct dentry *workdir = ofs->workdir;
+	struct inode *dir = d_inode(workdir);
+	struct dentry *temp;
+	struct dentry *dest;
+	struct dentry *whiteout;
+	struct name_snapshot name;
+	int err;
+
+	inode_lock_nested(dir, I_MUTEX_PARENT);
+
+	temp = ovl_create_temp(ofs, workdir, OVL_CATTR(S_IFREG | 0));
+	err = PTR_ERR(temp);
+	if (IS_ERR(temp))
+		goto out_unlock;
+
+	dest = ovl_lookup_temp(ofs, workdir);
+	err = PTR_ERR(dest);
+	if (IS_ERR(dest)) {
+		dput(temp);
+		goto out_unlock;
+	}
+
+	/* Name is inline and stable - using snapshot as a copy helper */
+	take_dentry_name_snapshot(&name, temp);
+	err = ovl_do_rename(ofs, dir, temp, dir, dest, RENAME_WHITEOUT);
+	if (err) {
+		if (err == -EINVAL)
+			err = 0;
+		goto cleanup_temp;
+	}
+
+	whiteout = ovl_lookup_upper(ofs, name.name.name, workdir, name.name.len);
+	err = PTR_ERR(whiteout);
+	if (IS_ERR(whiteout))
+		goto cleanup_temp;
+
+	err = ovl_is_whiteout(whiteout);
+
+	/* Best effort cleanup of whiteout and temp file */
+	if (err)
+		ovl_cleanup(ofs, dir, whiteout);
+	dput(whiteout);
+
+cleanup_temp:
+	ovl_cleanup(ofs, dir, temp);
+	release_dentry_name_snapshot(&name);
+	dput(temp);
+	dput(dest);
+
+out_unlock:
+	inode_unlock(dir);
+
+	return err;
+}
+
+static struct dentry *ovl_lookup_or_create(struct ovl_fs *ofs,
+					   struct dentry *parent,
+					   const char *name, umode_t mode)
+{
+	size_t len = strlen(name);
+	struct dentry *child;
+
+	inode_lock_nested(parent->d_inode, I_MUTEX_PARENT);
+	child = ovl_lookup_upper(ofs, name, parent, len);
+	if (!IS_ERR(child) && !child->d_inode)
+		child = ovl_create_real(ofs, parent->d_inode, child,
+					OVL_CATTR(mode));
+	inode_unlock(parent->d_inode);
+	dput(parent);
+
+	return child;
+}
+
+/*
+ * Creates $workdir/work/incompat/volatile/dirty file if it is not already
+ * present.
+ */
+static int ovl_create_volatile_dirty(struct ovl_fs *ofs)
+{
+	unsigned int ctr;
+	struct dentry *d = dget(ofs->workbasedir);
+	static const char *const volatile_path[] = {
+		OVL_WORKDIR_NAME, "incompat", "volatile", "dirty"
+	};
+	const char *const *name = volatile_path;
+
+	for (ctr = ARRAY_SIZE(volatile_path); ctr; ctr--, name++) {
+		d = ovl_lookup_or_create(ofs, d, *name, ctr > 1 ? S_IFDIR : S_IFREG);
+		if (IS_ERR(d))
+			return PTR_ERR(d);
+	}
+	dput(d);
+	return 0;
+}
+
+static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
+			    const struct path *workpath)
+{
+	struct vfsmount *mnt = ovl_upper_mnt(ofs);
+	struct dentry *workdir;
+	struct file *tmpfile;
+	bool rename_whiteout;
+	bool d_type;
+	int fh_type;
+	int err;
+
+	err = mnt_want_write(mnt);
+	if (err)
+		return err;
+
+	workdir = ovl_workdir_create(ofs, OVL_WORKDIR_NAME, false);
+	err = PTR_ERR(workdir);
+	if (IS_ERR_OR_NULL(workdir))
+		goto out;
+
+	ofs->workdir = workdir;
+
+	err = ovl_setup_trap(sb, ofs->workdir, &ofs->workdir_trap, "workdir");
+	if (err)
+		goto out;
+
+	/*
+	 * Upper should support d_type, else whiteouts are visible.  Given
+	 * workdir and upper are on same fs, we can do iterate_dir() on
+	 * workdir. This check requires successful creation of workdir in
+	 * previous step.
+	 */
+	err = ovl_check_d_type_supported(workpath);
+	if (err < 0)
+		goto out;
+
+	d_type = err;
+	if (!d_type)
+		pr_warn("upper fs needs to support d_type.\n");
+
+	/* Check if upper/work fs supports O_TMPFILE */
+	tmpfile = ovl_do_tmpfile(ofs, ofs->workdir, S_IFREG | 0);
+	ofs->tmpfile = !IS_ERR(tmpfile);
+	if (ofs->tmpfile)
+		fput(tmpfile);
+	else
+		pr_warn("upper fs does not support tmpfile.\n");
+
+
+	/* Check if upper/work fs supports RENAME_WHITEOUT */
+	err = ovl_check_rename_whiteout(ofs);
+	if (err < 0)
+		goto out;
+
+	rename_whiteout = err;
+	if (!rename_whiteout)
+		pr_warn("upper fs does not support RENAME_WHITEOUT.\n");
+
+	/*
+	 * Check if upper/work fs supports (trusted|user).overlay.* xattr
+	 */
+	err = ovl_setxattr(ofs, ofs->workdir, OVL_XATTR_OPAQUE, "0", 1);
+	if (err) {
+		pr_warn("failed to set xattr on upper\n");
+		ofs->noxattr = true;
+		if (ofs->config.index || ofs->config.metacopy) {
+			ofs->config.index = false;
+			ofs->config.metacopy = false;
+			pr_warn("...falling back to index=off,metacopy=off.\n");
+		}
+		/*
+		 * xattr support is required for persistent st_ino.
+		 * Without persistent st_ino, xino=auto falls back to xino=off.
+		 */
+		if (ofs->config.xino == OVL_XINO_AUTO) {
+			ofs->config.xino = OVL_XINO_OFF;
+			pr_warn("...falling back to xino=off.\n");
+		}
+		if (err == -EPERM && !ofs->config.userxattr)
+			pr_info("try mounting with 'userxattr' option\n");
+		err = 0;
+	} else {
+		ovl_removexattr(ofs, ofs->workdir, OVL_XATTR_OPAQUE);
+	}
+
+	/*
+	 * We allowed sub-optimal upper fs configuration and don't want to break
+	 * users over kernel upgrade, but we never allowed remote upper fs, so
+	 * we can enforce strict requirements for remote upper fs.
+	 */
+	if (ovl_dentry_remote(ofs->workdir) &&
+	    (!d_type || !rename_whiteout || ofs->noxattr)) {
+		pr_err("upper fs missing required features.\n");
+		err = -EINVAL;
+		goto out;
+	}
+
+	/*
+	 * For volatile mount, create a incompat/volatile/dirty file to keep
+	 * track of it.
+	 */
+	if (ofs->config.ovl_volatile) {
+		err = ovl_create_volatile_dirty(ofs);
+		if (err < 0) {
+			pr_err("Failed to create volatile/dirty file.\n");
+			goto out;
+		}
+	}
+
+	/* Check if upper/work fs supports file handles */
+	fh_type = ovl_can_decode_fh(ofs->workdir->d_sb);
+	if (ofs->config.index && !fh_type) {
+		ofs->config.index = false;
+		pr_warn("upper fs does not support file handles, falling back to index=off.\n");
+	}
+
+	/* Check if upper fs has 32bit inode numbers */
+	if (fh_type != FILEID_INO32_GEN)
+		ofs->xino_mode = -1;
+
+	/* NFS export of r/w mount depends on index */
+	if (ofs->config.nfs_export && !ofs->config.index) {
+		pr_warn("NFS export requires \"index=on\", falling back to nfs_export=off.\n");
+		ofs->config.nfs_export = false;
+	}
+out:
+	mnt_drop_write(mnt);
+	return err;
+}
+
+static int ovl_get_workdir(struct super_block *sb, struct ovl_fs *ofs,
+			   const struct path *upperpath)
+{
+	int err;
+	struct path workpath = { };
+
+	err = ovl_mount_dir(ofs->config.workdir, &workpath);
+	if (err)
+		goto out;
+
+	err = -EINVAL;
+	if (upperpath->mnt != workpath.mnt) {
+		pr_err("workdir and upperdir must reside under the same mount\n");
+		goto out;
+	}
+	if (!ovl_workdir_ok(workpath.dentry, upperpath->dentry)) {
+		pr_err("workdir and upperdir must be separate subtrees\n");
+		goto out;
+	}
+
+	ofs->workbasedir = dget(workpath.dentry);
+
+	if (ovl_inuse_trylock(ofs->workbasedir)) {
+		ofs->workdir_locked = true;
+	} else {
+		err = ovl_report_in_use(ofs, "workdir");
+		if (err)
+			goto out;
+	}
+
+	err = ovl_setup_trap(sb, ofs->workbasedir, &ofs->workbasedir_trap,
+			     "workdir");
+	if (err)
+		goto out;
+
+	err = ovl_make_workdir(sb, ofs, &workpath);
+
+out:
+	path_put(&workpath);
+
+	return err;
+}
+
+static int ovl_get_indexdir(struct super_block *sb, struct ovl_fs *ofs,
+			    struct ovl_entry *oe, const struct path *upperpath)
+{
+	struct vfsmount *mnt = ovl_upper_mnt(ofs);
+	struct dentry *indexdir;
+	int err;
+
+	err = mnt_want_write(mnt);
+	if (err)
+		return err;
+
+	/* Verify lower root is upper root origin */
+	err = ovl_verify_origin(ofs, upperpath->dentry,
+				oe->lowerstack[0].dentry, true);
+	if (err) {
+		pr_err("failed to verify upper root origin\n");
+		goto out;
+	}
+
+	/* index dir will act also as workdir */
+	iput(ofs->workdir_trap);
+	ofs->workdir_trap = NULL;
+	dput(ofs->workdir);
+	ofs->workdir = NULL;
+	indexdir = ovl_workdir_create(ofs, OVL_INDEXDIR_NAME, true);
+	if (IS_ERR(indexdir)) {
+		err = PTR_ERR(indexdir);
+	} else if (indexdir) {
+		ofs->indexdir = indexdir;
+		ofs->workdir = dget(indexdir);
+
+		err = ovl_setup_trap(sb, ofs->indexdir, &ofs->indexdir_trap,
+				     "indexdir");
+		if (err)
+			goto out;
+
+		/*
+		 * Verify upper root is exclusively associated with index dir.
+		 * Older kernels stored upper fh in ".overlay.origin"
+		 * xattr. If that xattr exists, verify that it is a match to
+		 * upper dir file handle. In any case, verify or set xattr
+		 * ".overlay.upper" to indicate that index may have
+		 * directory entries.
+		 */
+		if (ovl_check_origin_xattr(ofs, ofs->indexdir)) {
+			err = ovl_verify_set_fh(ofs, ofs->indexdir,
+						OVL_XATTR_ORIGIN,
+						upperpath->dentry, true, false);
+			if (err)
+				pr_err("failed to verify index dir 'origin' xattr\n");
+		}
+		err = ovl_verify_upper(ofs, ofs->indexdir, upperpath->dentry,
+				       true);
+		if (err)
+			pr_err("failed to verify index dir 'upper' xattr\n");
+
+		/* Cleanup bad/stale/orphan index entries */
+		if (!err)
+			err = ovl_indexdir_cleanup(ofs);
+	}
+	if (err || !ofs->indexdir)
+		pr_warn("try deleting index dir or mounting with '-o index=off' to disable inodes index.\n");
+
+out:
+	mnt_drop_write(mnt);
+	return err;
+}
+
+static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid)
+{
+	unsigned int i;
+
+	if (!ofs->config.nfs_export && !ovl_upper_mnt(ofs))
+		return true;
+
+	/*
+	 * We allow using single lower with null uuid for index and nfs_export
+	 * for example to support those features with single lower squashfs.
+	 * To avoid regressions in setups of overlay with re-formatted lower
+	 * squashfs, do not allow decoding origin with lower null uuid unless
+	 * user opted-in to one of the new features that require following the
+	 * lower inode of non-dir upper.
+	 */
+	if (ovl_allow_offline_changes(ofs) && uuid_is_null(uuid))
+		return false;
+
+	for (i = 0; i < ofs->numfs; i++) {
+		/*
+		 * We use uuid to associate an overlay lower file handle with a
+		 * lower layer, so we can accept lower fs with null uuid as long
+		 * as all lower layers with null uuid are on the same fs.
+		 * if we detect multiple lower fs with the same uuid, we
+		 * disable lower file handle decoding on all of them.
+		 */
+		if (ofs->fs[i].is_lower &&
+		    uuid_equal(&ofs->fs[i].sb->s_uuid, uuid)) {
+			ofs->fs[i].bad_uuid = true;
+			return false;
+		}
+	}
+	return true;
+}
+
+/* Get a unique fsid for the layer */
+static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path)
+{
+	struct super_block *sb = path->mnt->mnt_sb;
+	unsigned int i;
+	dev_t dev;
+	int err;
+	bool bad_uuid = false;
+	bool warn = false;
+
+	for (i = 0; i < ofs->numfs; i++) {
+		if (ofs->fs[i].sb == sb)
+			return i;
+	}
+
+	if (!ovl_lower_uuid_ok(ofs, &sb->s_uuid)) {
+		bad_uuid = true;
+		if (ofs->config.xino == OVL_XINO_AUTO) {
+			ofs->config.xino = OVL_XINO_OFF;
+			warn = true;
+		}
+		if (ofs->config.index || ofs->config.nfs_export) {
+			ofs->config.index = false;
+			ofs->config.nfs_export = false;
+			warn = true;
+		}
+		if (warn) {
+			pr_warn("%s uuid detected in lower fs '%pd2', falling back to xino=%s,index=off,nfs_export=off.\n",
+				uuid_is_null(&sb->s_uuid) ? "null" :
+							    "conflicting",
+				path->dentry, ovl_xino_str[ofs->config.xino]);
+		}
+	}
+
+	err = get_anon_bdev(&dev);
+	if (err) {
+		pr_err("failed to get anonymous bdev for lowerpath\n");
+		return err;
+	}
+
+	ofs->fs[ofs->numfs].sb = sb;
+	ofs->fs[ofs->numfs].pseudo_dev = dev;
+	ofs->fs[ofs->numfs].bad_uuid = bad_uuid;
+
+	return ofs->numfs++;
+}
+
+static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs,
+			  struct path *stack, unsigned int numlower,
+			  struct ovl_layer *layers)
+{
+	int err;
+	unsigned int i;
+
+	err = -ENOMEM;
+	ofs->fs = kcalloc(numlower + 1, sizeof(struct ovl_sb), GFP_KERNEL);
+	if (ofs->fs == NULL)
+		goto out;
+
+	/* idx/fsid 0 are reserved for upper fs even with lower only overlay */
+	ofs->numfs++;
+
+	/*
+	 * All lower layers that share the same fs as upper layer, use the same
+	 * pseudo_dev as upper layer.  Allocate fs[0].pseudo_dev even for lower
+	 * only overlay to simplify ovl_fs_free().
+	 * is_lower will be set if upper fs is shared with a lower layer.
+	 */
+	err = get_anon_bdev(&ofs->fs[0].pseudo_dev);
+	if (err) {
+		pr_err("failed to get anonymous bdev for upper fs\n");
+		goto out;
+	}
+
+	if (ovl_upper_mnt(ofs)) {
+		ofs->fs[0].sb = ovl_upper_mnt(ofs)->mnt_sb;
+		ofs->fs[0].is_lower = false;
+	}
+
+	for (i = 0; i < numlower; i++) {
+		struct vfsmount *mnt;
+		struct inode *trap;
+		int fsid;
+
+		err = fsid = ovl_get_fsid(ofs, &stack[i]);
+		if (err < 0)
+			goto out;
+
+		/*
+		 * Check if lower root conflicts with this overlay layers before
+		 * checking if it is in-use as upperdir/workdir of "another"
+		 * mount, because we do not bother to check in ovl_is_inuse() if
+		 * the upperdir/workdir is in fact in-use by our
+		 * upperdir/workdir.
+		 */
+		err = ovl_setup_trap(sb, stack[i].dentry, &trap, "lowerdir");
+		if (err)
+			goto out;
+
+		if (ovl_is_inuse(stack[i].dentry)) {
+			err = ovl_report_in_use(ofs, "lowerdir");
+			if (err) {
+				iput(trap);
+				goto out;
+			}
+		}
+
+		mnt = clone_private_mount(&stack[i]);
+		err = PTR_ERR(mnt);
+		if (IS_ERR(mnt)) {
+			pr_err("failed to clone lowerpath\n");
+			iput(trap);
+			goto out;
+		}
+
+		/*
+		 * Make lower layers R/O.  That way fchmod/fchown on lower file
+		 * will fail instead of modifying lower fs.
+		 */
+		mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
+
+		layers[ofs->numlayer].trap = trap;
+		layers[ofs->numlayer].mnt = mnt;
+		layers[ofs->numlayer].idx = ofs->numlayer;
+		layers[ofs->numlayer].fsid = fsid;
+		layers[ofs->numlayer].fs = &ofs->fs[fsid];
+		ofs->numlayer++;
+		ofs->fs[fsid].is_lower = true;
+	}
+
+	/*
+	 * When all layers on same fs, overlay can use real inode numbers.
+	 * With mount option "xino=<on|auto>", mounter declares that there are
+	 * enough free high bits in underlying fs to hold the unique fsid.
+	 * If overlayfs does encounter underlying inodes using the high xino
+	 * bits reserved for fsid, it emits a warning and uses the original
+	 * inode number or a non persistent inode number allocated from a
+	 * dedicated range.
+	 */
+	if (ofs->numfs - !ovl_upper_mnt(ofs) == 1) {
+		if (ofs->config.xino == OVL_XINO_ON)
+			pr_info("\"xino=on\" is useless with all layers on same fs, ignore.\n");
+		ofs->xino_mode = 0;
+	} else if (ofs->config.xino == OVL_XINO_OFF) {
+		ofs->xino_mode = -1;
+	} else if (ofs->xino_mode < 0) {
+		/*
+		 * This is a roundup of number of bits needed for encoding
+		 * fsid, where fsid 0 is reserved for upper fs (even with
+		 * lower only overlay) +1 extra bit is reserved for the non
+		 * persistent inode number range that is used for resolving
+		 * xino lower bits overflow.
+		 */
+		BUILD_BUG_ON(ilog2(OVL_MAX_STACK) > 30);
+		ofs->xino_mode = ilog2(ofs->numfs - 1) + 2;
+	}
+
+	if (ofs->xino_mode > 0) {
+		pr_info("\"xino\" feature enabled using %d upper inode bits.\n",
+			ofs->xino_mode);
+	}
+
+	err = 0;
+out:
+	return err;
+}
+
+static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
+				const char *lower, unsigned int numlower,
+				struct ovl_fs *ofs, struct ovl_layer *layers)
+{
+	int err;
+	struct path *stack = NULL;
+	unsigned int i;
+	struct ovl_entry *oe;
+
+	if (!ofs->config.upperdir && numlower == 1) {
+		pr_err("at least 2 lowerdir are needed while upperdir nonexistent\n");
+		return ERR_PTR(-EINVAL);
+	}
+
+	stack = kcalloc(numlower, sizeof(struct path), GFP_KERNEL);
+	if (!stack)
+		return ERR_PTR(-ENOMEM);
+
+	err = -EINVAL;
+	for (i = 0; i < numlower; i++) {
+		err = ovl_lower_dir(lower, &stack[i], ofs, &sb->s_stack_depth);
+		if (err)
+			goto out_err;
+
+		lower = strchr(lower, '\0') + 1;
+	}
+
+	err = -EINVAL;
+	sb->s_stack_depth++;
+	if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
+		pr_err("maximum fs stacking depth exceeded\n");
+		goto out_err;
+	}
+
+	err = ovl_get_layers(sb, ofs, stack, numlower, layers);
+	if (err)
+		goto out_err;
+
+	err = -ENOMEM;
+	oe = ovl_alloc_entry(numlower);
+	if (!oe)
+		goto out_err;
+
+	for (i = 0; i < numlower; i++) {
+		oe->lowerstack[i].dentry = dget(stack[i].dentry);
+		oe->lowerstack[i].layer = &ofs->layers[i+1];
+	}
+
+out:
+	for (i = 0; i < numlower; i++)
+		path_put(&stack[i]);
+	kfree(stack);
+
+	return oe;
+
+out_err:
+	oe = ERR_PTR(err);
+	goto out;
+}
+
+/*
+ * Check if this layer root is a descendant of:
+ * - another layer of this overlayfs instance
+ * - upper/work dir of any overlayfs instance
+ */
+static int ovl_check_layer(struct super_block *sb, struct ovl_fs *ofs,
+			   struct dentry *dentry, const char *name,
+			   bool is_lower)
+{
+	struct dentry *next = dentry, *parent;
+	int err = 0;
+
+	if (!dentry)
+		return 0;
+
+	parent = dget_parent(next);
+
+	/* Walk back ancestors to root (inclusive) looking for traps */
+	while (!err && parent != next) {
+		if (is_lower && ovl_lookup_trap_inode(sb, parent)) {
+			err = -ELOOP;
+			pr_err("overlapping %s path\n", name);
+		} else if (ovl_is_inuse(parent)) {
+			err = ovl_report_in_use(ofs, name);
+		}
+		next = parent;
+		parent = dget_parent(next);
+		dput(next);
+	}
+
+	dput(parent);
+
+	return err;
+}
+
+/*
+ * Check if any of the layers or work dirs overlap.
+ */
+static int ovl_check_overlapping_layers(struct super_block *sb,
+					struct ovl_fs *ofs)
+{
+	int i, err;
+
+	if (ovl_upper_mnt(ofs)) {
+		err = ovl_check_layer(sb, ofs, ovl_upper_mnt(ofs)->mnt_root,
+				      "upperdir", false);
+		if (err)
+			return err;
+
+		/*
+		 * Checking workbasedir avoids hitting ovl_is_inuse(parent) of
+		 * this instance and covers overlapping work and index dirs,
+		 * unless work or index dir have been moved since created inside
+		 * workbasedir.  In that case, we already have their traps in
+		 * inode cache and we will catch that case on lookup.
+		 */
+		err = ovl_check_layer(sb, ofs, ofs->workbasedir, "workdir",
+				      false);
+		if (err)
+			return err;
+	}
+
+	for (i = 1; i < ofs->numlayer; i++) {
+		err = ovl_check_layer(sb, ofs,
+				      ofs->layers[i].mnt->mnt_root,
+				      "lowerdir", true);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+
+static struct dentry *ovl_get_root(struct super_block *sb,
+				   struct dentry *upperdentry,
+				   struct ovl_entry *oe)
+{
+	struct dentry *root;
+	struct ovl_path *lowerpath = &oe->lowerstack[0];
+	unsigned long ino = d_inode(lowerpath->dentry)->i_ino;
+	int fsid = lowerpath->layer->fsid;
+	struct ovl_inode_params oip = {
+		.upperdentry = upperdentry,
+		.lowerpath = lowerpath,
+	};
+
+	root = d_make_root(ovl_new_inode(sb, S_IFDIR, 0));
+	if (!root)
+		return NULL;
+
+	root->d_fsdata = oe;
+
+	if (upperdentry) {
+		/* Root inode uses upper st_ino/i_ino */
+		ino = d_inode(upperdentry)->i_ino;
+		fsid = 0;
+		ovl_dentry_set_upper_alias(root);
+		if (ovl_is_impuredir(sb, upperdentry))
+			ovl_set_flag(OVL_IMPURE, d_inode(root));
+	}
+
+	/* Root is always merge -> can have whiteouts */
+	ovl_set_flag(OVL_WHITEOUTS, d_inode(root));
+	ovl_dentry_set_flag(OVL_E_CONNECTED, root);
+	ovl_set_upperdata(d_inode(root));
+	ovl_inode_init(d_inode(root), &oip, ino, fsid);
+	ovl_dentry_init_flags(root, upperdentry, DCACHE_OP_WEAK_REVALIDATE);
+
+	return root;
+}
+
+static int ovl_fill_super(struct super_block *sb, void *data, int silent)
+{
+	struct path upperpath = { };
+	struct dentry *root_dentry;
+	struct ovl_entry *oe;
+	struct ovl_fs *ofs;
+	struct ovl_layer *layers;
+	struct cred *cred;
+	char *splitlower = NULL;
+	unsigned int numlower;
+	int err;
+
+	err = -EIO;
+	if (WARN_ON(sb->s_user_ns != current_user_ns()))
+		goto out;
+
+	sb->s_d_op = &ovl_dentry_operations;
+
+	err = -ENOMEM;
+	ofs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
+	if (!ofs)
+		goto out;
+
+	err = -ENOMEM;
+	ofs->creator_cred = cred = prepare_creds();
+	if (!cred)
+		goto out_err;
+
+	/* Is there a reason anyone would want not to share whiteouts? */
+	ofs->share_whiteout = true;
+
+	ofs->config.index = ovl_index_def;
+	ofs->config.uuid = true;
+	ofs->config.nfs_export = ovl_nfs_export_def;
+	ofs->config.xino = ovl_xino_def();
+	ofs->config.metacopy = ovl_metacopy_def;
+	err = ovl_parse_opt((char *) data, &ofs->config);
+	if (err)
+		goto out_err;
+
+	err = -EINVAL;
+	if (!ofs->config.lowerdir) {
+		if (!silent)
+			pr_err("missing 'lowerdir'\n");
+		goto out_err;
+	}
+
+	err = -ENOMEM;
+	splitlower = kstrdup(ofs->config.lowerdir, GFP_KERNEL);
+	if (!splitlower)
+		goto out_err;
+
+	err = -EINVAL;
+	numlower = ovl_split_lowerdirs(splitlower);
+	if (numlower > OVL_MAX_STACK) {
+		pr_err("too many lower directories, limit is %d\n",
+		       OVL_MAX_STACK);
+		goto out_err;
+	}
+
+	err = -ENOMEM;
+	layers = kcalloc(numlower + 1, sizeof(struct ovl_layer), GFP_KERNEL);
+	if (!layers)
+		goto out_err;
+
+	ofs->layers = layers;
+	/* Layer 0 is reserved for upper even if there's no upper */
+	ofs->numlayer = 1;
+
+	sb->s_stack_depth = 0;
+	sb->s_maxbytes = MAX_LFS_FILESIZE;
+	atomic_long_set(&ofs->last_ino, 1);
+	/* Assume underlying fs uses 32bit inodes unless proven otherwise */
+	if (ofs->config.xino != OVL_XINO_OFF) {
+		ofs->xino_mode = BITS_PER_LONG - 32;
+		if (!ofs->xino_mode) {
+			pr_warn("xino not supported on 32bit kernel, falling back to xino=off.\n");
+			ofs->config.xino = OVL_XINO_OFF;
+		}
+	}
+
+	/* alloc/destroy_inode needed for setting up traps in inode cache */
+	sb->s_op = &ovl_super_operations;
+
+	if (ofs->config.upperdir) {
+		struct super_block *upper_sb;
+
+		err = -EINVAL;
+		if (!ofs->config.workdir) {
+			pr_err("missing 'workdir'\n");
+			goto out_err;
+		}
+
+		err = ovl_get_upper(sb, ofs, &layers[0], &upperpath);
+		if (err)
+			goto out_err;
+
+		upper_sb = ovl_upper_mnt(ofs)->mnt_sb;
+		if (!ovl_should_sync(ofs)) {
+			ofs->errseq = errseq_sample(&upper_sb->s_wb_err);
+			if (errseq_check(&upper_sb->s_wb_err, ofs->errseq)) {
+				err = -EIO;
+				pr_err("Cannot mount volatile when upperdir has an unseen error. Sync upperdir fs to clear state.\n");
+				goto out_err;
+			}
+		}
+
+		err = ovl_get_workdir(sb, ofs, &upperpath);
+		if (err)
+			goto out_err;
+
+		if (!ofs->workdir)
+			sb->s_flags |= SB_RDONLY;
+
+		sb->s_stack_depth = upper_sb->s_stack_depth;
+		sb->s_time_gran = upper_sb->s_time_gran;
+	}
+	oe = ovl_get_lowerstack(sb, splitlower, numlower, ofs, layers);
+	err = PTR_ERR(oe);
+	if (IS_ERR(oe))
+		goto out_err;
+
+	/* If the upper fs is nonexistent, we mark overlayfs r/o too */
+	if (!ovl_upper_mnt(ofs))
+		sb->s_flags |= SB_RDONLY;
+
+	if (!ofs->config.uuid && ofs->numfs > 1) {
+		pr_warn("The uuid=off requires a single fs for lower and upper, falling back to uuid=on.\n");
+		ofs->config.uuid = true;
+	}
+
+	if (!ovl_force_readonly(ofs) && ofs->config.index) {
+		err = ovl_get_indexdir(sb, ofs, oe, &upperpath);
+		if (err)
+			goto out_free_oe;
+
+		/* Force r/o mount with no index dir */
+		if (!ofs->indexdir)
+			sb->s_flags |= SB_RDONLY;
+	}
+
+	err = ovl_check_overlapping_layers(sb, ofs);
+	if (err)
+		goto out_free_oe;
+
+	/* Show index=off in /proc/mounts for forced r/o mount */
+	if (!ofs->indexdir) {
+		ofs->config.index = false;
+		if (ovl_upper_mnt(ofs) && ofs->config.nfs_export) {
+			pr_warn("NFS export requires an index dir, falling back to nfs_export=off.\n");
+			ofs->config.nfs_export = false;
+		}
+	}
+
+	if (ofs->config.metacopy && ofs->config.nfs_export) {
+		pr_warn("NFS export is not supported with metadata only copy up, falling back to nfs_export=off.\n");
+		ofs->config.nfs_export = false;
+	}
+
+	if (ofs->config.nfs_export)
+		sb->s_export_op = &ovl_export_operations;
+
+	/* Never override disk quota limits or use reserved space */
+	cap_lower(cred->cap_effective, CAP_SYS_RESOURCE);
+
+	sb->s_magic = OVERLAYFS_SUPER_MAGIC;
+	sb->s_xattr = ofs->config.userxattr ? ovl_user_xattr_handlers :
+		ovl_trusted_xattr_handlers;
+	sb->s_fs_info = ofs;
+	sb->s_flags |= SB_POSIXACL;
+	sb->s_iflags |= SB_I_SKIP_SYNC;
+
+	err = -ENOMEM;
+	root_dentry = ovl_get_root(sb, upperpath.dentry, oe);
+	if (!root_dentry)
+		goto out_free_oe;
+
+	mntput(upperpath.mnt);
+	kfree(splitlower);
+
+	sb->s_root = root_dentry;
+
+	return 0;
+
+out_free_oe:
+	ovl_entry_stack_free(oe);
+	kfree(oe);
+out_err:
+	kfree(splitlower);
+	path_put(&upperpath);
+	ovl_free_fs(ofs);
+out:
+	return err;
+}
+
+static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
+				const char *dev_name, void *raw_data)
+{
+	return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
+}
+
+static struct file_system_type ovl_fs_type = {
+	.owner		= THIS_MODULE,
+	.name		= "overlay",
+	.fs_flags	= FS_USERNS_MOUNT,
+	.mount		= ovl_mount,
+	.kill_sb	= kill_anon_super,
+};
+MODULE_ALIAS_FS("overlay");
+
+static void ovl_inode_init_once(void *foo)
+{
+	struct ovl_inode *oi = foo;
+
+	inode_init_once(&oi->vfs_inode);
+}
+
+static int __init ovl_init(void)
+{
+	int err;
+
+	ovl_inode_cachep = kmem_cache_create("ovl_inode",
+					     sizeof(struct ovl_inode), 0,
+					     (SLAB_RECLAIM_ACCOUNT|
+					      SLAB_MEM_SPREAD|SLAB_ACCOUNT),
+					     ovl_inode_init_once);
+	if (ovl_inode_cachep == NULL)
+		return -ENOMEM;
+
+	err = ovl_aio_request_cache_init();
+	if (!err) {
+		err = register_filesystem(&ovl_fs_type);
+		if (!err)
+			return 0;
+
+		ovl_aio_request_cache_destroy();
+	}
+	kmem_cache_destroy(ovl_inode_cachep);
+
+	return err;
+}
+
+static void __exit ovl_exit(void)
+{
+	unregister_filesystem(&ovl_fs_type);
+
+	/*
+	 * Make sure all delayed rcu free inodes are flushed before we
+	 * destroy cache.
+	 */
+	rcu_barrier();
+	kmem_cache_destroy(ovl_inode_cachep);
+	ovl_aio_request_cache_destroy();
+}
+
+module_init(ovl_init);
+module_exit(ovl_exit);