Adding upstream version 4.19.249.upstream/4.19.249

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

1 files changed, 1757 insertions, 0 deletions

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
new file mode 100644
index 000000000..1a7a1e298
--- /dev/null
+++ b/fs/overlayfs/super.c
@@ -0,0 +1,1757 @@
+/*
+ *
+ * Copyright (C) 2011 Novell Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ */
+
+#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 "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(ovl_redirect_dir_def,
+		 "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(ovl_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(ovl_index_def,
+		 "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(ovl_nfs_export_def,
+		 "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(ovl_xino_auto_def,
+		 "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(ovl_metacopy_def,
+		 "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_dentry_revalidate(struct dentry *dentry, unsigned int flags)
+{
+	struct ovl_entry *oe = dentry->d_fsdata;
+	unsigned int i;
+	int ret = 1;
+
+	for (i = 0; i < oe->numlower; i++) {
+		struct dentry *d = oe->lowerstack[i].dentry;
+
+		if (d->d_flags & DCACHE_OP_REVALIDATE) {
+			ret = d->d_op->d_revalidate(d, flags);
+			if (ret < 0)
+				return ret;
+			if (!ret) {
+				if (!(flags & LOOKUP_RCU))
+					d_invalidate(d);
+				return -ESTALE;
+			}
+		}
+	}
+	return 1;
+}
+
+static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags)
+{
+	struct ovl_entry *oe = dentry->d_fsdata;
+	unsigned int i;
+	int ret = 1;
+
+	for (i = 0; i < oe->numlower; i++) {
+		struct dentry *d = oe->lowerstack[i].dentry;
+
+		if (d->d_flags & DCACHE_OP_WEAK_REVALIDATE) {
+			ret = d->d_op->d_weak_revalidate(d, flags);
+			if (ret <= 0)
+				break;
+		}
+	}
+	return ret;
+}
+
+static const struct dentry_operations ovl_dentry_operations = {
+	.d_release = ovl_dentry_release,
+	.d_real = ovl_d_real,
+};
+
+static const struct dentry_operations ovl_reval_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 = kmem_cache_alloc(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->lower = NULL;
+	oi->lowerdata = NULL;
+	mutex_init(&oi->lock);
+
+	return &oi->vfs_inode;
+}
+
+static void ovl_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+
+	kmem_cache_free(ovl_inode_cachep, OVL_I(inode));
+}
+
+static void ovl_destroy_inode(struct inode *inode)
+{
+	struct ovl_inode *oi = OVL_I(inode);
+
+	dput(oi->__upperdentry);
+	iput(oi->lower);
+	if (S_ISDIR(inode->i_mode))
+		ovl_dir_cache_free(inode);
+	else
+		iput(oi->lowerdata);
+	kfree(oi->redirect);
+	mutex_destroy(&oi->lock);
+
+	call_rcu(&inode->i_rcu, ovl_i_callback);
+}
+
+static void ovl_free_fs(struct ovl_fs *ofs)
+{
+	unsigned i;
+
+	iput(ofs->workbasedir_trap);
+	iput(ofs->indexdir_trap);
+	iput(ofs->workdir_trap);
+	iput(ofs->upperdir_trap);
+	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(ofs->upper_mnt->mnt_root);
+	mntput(ofs->upper_mnt);
+	for (i = 0; i < ofs->numlower; i++) {
+		iput(ofs->lower_layers[i].trap);
+		mntput(ofs->lower_layers[i].mnt);
+	}
+	for (i = 0; i < ofs->numlowerfs; i++)
+		free_anon_bdev(ofs->lower_fs[i].pseudo_dev);
+	kfree(ofs->lower_layers);
+	kfree(ofs->lower_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;
+
+	if (!ofs->upper_mnt)
+		return 0;
+
+	/*
+	 * If this is a sync(2) call or an emergency sync, all the super blocks
+	 * will be iterated, including upper_sb, so no need to do anything.
+	 *
+	 * 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 = ofs->upper_mnt->mnt_sb;
+
+	down_read(&upper_sb->s_umount);
+	ret = sync_filesystem(upper_sb);
+	up_read(&upper_sb->s_umount);
+
+	return ret;
+}
+
+/**
+ * ovl_statfs
+ * @sb: The overlayfs super block
+ * @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 (!ofs->upper_mnt || !ofs->workdir);
+}
+
+static const char *ovl_redirect_mode_def(void)
+{
+	return ovl_redirect_dir_def ? "on" : "off";
+}
+
+enum {
+	OVL_XINO_OFF,
+	OVL_XINO_AUTO,
+	OVL_XINO_ON,
+};
+
+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
+ *
+ * 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.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())
+		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");
+	return 0;
+}
+
+static int ovl_remount(struct super_block *sb, int *flags, char *data)
+{
+	struct ovl_fs *ofs = sb->s_fs_info;
+
+	if (!(*flags & SB_RDONLY) && ovl_force_readonly(ofs))
+		return -EROFS;
+
+	return 0;
+}
+
+static const struct super_operations ovl_super_operations = {
+	.alloc_inode	= ovl_alloc_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_NFS_EXPORT_ON,
+	OPT_NFS_EXPORT_OFF,
+	OPT_XINO_ON,
+	OPT_XINO_OFF,
+	OPT_XINO_AUTO,
+	OPT_METACOPY_ON,
+	OPT_METACOPY_OFF,
+	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_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_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("overlayfs: 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;
+
+	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;
+			break;
+
+		case OPT_INDEX_OFF:
+			config->index = false;
+			break;
+
+		case OPT_NFS_EXPORT_ON:
+			config->nfs_export = true;
+			break;
+
+		case OPT_NFS_EXPORT_OFF:
+			config->nfs_export = false;
+			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;
+			break;
+
+		default:
+			pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p);
+			return -EINVAL;
+		}
+	}
+
+	/* Workdir is useless in non-upper mount */
+	if (!config->upperdir && config->workdir) {
+		pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
+			config->workdir);
+		kfree(config->workdir);
+		config->workdir = NULL;
+	}
+
+	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("overlayfs: 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("overlayfs: 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;
+		}
+	}
+
+	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 = ofs->upper_mnt;
+	struct dentry *work;
+	int err;
+	bool retried = false;
+	bool locked = false;
+
+	inode_lock_nested(dir, I_MUTEX_PARENT);
+	locked = true;
+
+retry:
+	work = lookup_one_len(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;
+			ovl_workdir_cleanup(dir, mnt, work, 0);
+			dput(work);
+			goto retry;
+		}
+
+		err = ovl_mkdir_real(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 = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_DEFAULT);
+		if (err && err != -ENODATA && err != -EOPNOTSUPP)
+			goto out_dput;
+
+		err = vfs_removexattr(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 = notify_change(work, &attr, NULL);
+		inode_unlock(work->d_inode);
+		if (err)
+			goto out_dput;
+	} else {
+		err = PTR_ERR(work);
+		goto out_err;
+	}
+out_unlock:
+	if (locked)
+		inode_unlock(dir);
+
+	return work;
+
+out_dput:
+	dput(work);
+out_err:
+	pr_warn("overlayfs: 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("overlayfs: empty lowerdir\n");
+		goto out;
+	}
+	err = kern_path(name, LOOKUP_FOLLOW, path);
+	if (err) {
+		pr_err("overlayfs: failed to resolve '%s': %i\n", name, err);
+		goto out;
+	}
+	err = -EINVAL;
+	if (ovl_dentry_weird(path->dentry)) {
+		pr_err("overlayfs: filesystem on '%s' not supported\n", name);
+		goto out_put;
+	}
+	if (!d_is_dir(path->dentry)) {
+		pr_err("overlayfs: '%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)
+			if (ovl_dentry_remote(path->dentry)) {
+				pr_err("overlayfs: filesystem on '%s' not supported as upperdir\n",
+				       tmp);
+				path_put_init(path);
+				err = -EINVAL;
+			}
+		kfree(tmp);
+	}
+	return err;
+}
+
+static int ovl_check_namelen(struct path *path, struct ovl_fs *ofs,
+			     const char *name)
+{
+	struct kstatfs statfs;
+	int err = vfs_statfs(path, &statfs);
+
+	if (err)
+		pr_err("overlayfs: 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, bool *remote)
+{
+	int fh_type;
+	int err;
+
+	err = ovl_mount_dir_noesc(name, path);
+	if (err)
+		goto out;
+
+	err = ovl_check_namelen(path, ofs, name);
+	if (err)
+		goto out_put;
+
+	*stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);
+
+	if (ovl_dentry_remote(path->dentry))
+		*remote = true;
+
+	/*
+	 * 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("overlayfs: fs on '%s' does not support file handles, falling back to index=off,nfs_export=off.\n",
+			name);
+	}
+
+	/* Check if lower fs has 32bit inode numbers */
+	if (fh_type != FILEID_INO32_GEN)
+		ofs->xino_bits = 0;
+
+	return 0;
+
+out_put:
+	path_put_init(path);
+out:
+	return err;
+}
+
+/* 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 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) {
+		acl = posix_acl_from_xattr(&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(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(inode, CAP_FSETID)) {
+		struct iattr iattr = { .ia_valid = ATTR_KILL_SGID };
+
+		err = ovl_setattr(dentry, &iattr);
+		if (err)
+			return err;
+	}
+
+	err = ovl_xattr_set(dentry, inode, handler->name, value, size, flags);
+	if (!err)
+		ovl_copyattr(ovl_inode_real(inode), inode);
+
+	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 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 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_xattr_handler = {
+	.prefix	= OVL_XATTR_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_xattr_handlers[] = {
+#ifdef CONFIG_FS_POSIX_ACL
+	&ovl_posix_acl_access_xattr_handler,
+	&ovl_posix_acl_default_xattr_handler,
+#endif
+	&ovl_own_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("overlayfs: 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("overlayfs: %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("overlayfs: %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 path *upperpath)
+{
+	struct vfsmount *upper_mnt;
+	int err;
+
+	err = ovl_mount_dir(ofs->config.upperdir, upperpath);
+	if (err)
+		goto out;
+
+	/* Upper fs should not be r/o */
+	if (sb_rdonly(upperpath->mnt->mnt_sb)) {
+		pr_err("overlayfs: 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, &ofs->upperdir_trap,
+			     "upperdir");
+	if (err)
+		goto out;
+
+	upper_mnt = clone_private_mount(upperpath);
+	err = PTR_ERR(upper_mnt);
+	if (IS_ERR(upper_mnt)) {
+		pr_err("overlayfs: failed to clone upperpath\n");
+		goto out;
+	}
+
+	/* Don't inherit atime flags */
+	upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME);
+	ofs->upper_mnt = upper_mnt;
+
+	if (ovl_inuse_trylock(ofs->upper_mnt->mnt_root)) {
+		ofs->upperdir_locked = true;
+	} else {
+		err = ovl_report_in_use(ofs, "upperdir");
+		if (err)
+			goto out;
+	}
+
+	err = 0;
+out:
+	return err;
+}
+
+static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
+			    struct path *workpath)
+{
+	struct vfsmount *mnt = ofs->upper_mnt;
+	struct dentry *temp;
+	int fh_type;
+	int err;
+
+	err = mnt_want_write(mnt);
+	if (err)
+		return err;
+
+	ofs->workdir = ovl_workdir_create(ofs, OVL_WORKDIR_NAME, false);
+	if (!ofs->workdir)
+		goto out;
+
+	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;
+
+	/*
+	 * We allowed this configuration and don't want to break users over
+	 * kernel upgrade. So warn instead of erroring out.
+	 */
+	if (!err)
+		pr_warn("overlayfs: upper fs needs to support d_type.\n");
+
+	/* Check if upper/work fs supports O_TMPFILE */
+	temp = ovl_do_tmpfile(ofs->workdir, S_IFREG | 0);
+	ofs->tmpfile = !IS_ERR(temp);
+	if (ofs->tmpfile)
+		dput(temp);
+	else
+		pr_warn("overlayfs: upper fs does not support tmpfile.\n");
+
+	/*
+	 * Check if upper/work fs supports trusted.overlay.* xattr
+	 */
+	err = ovl_do_setxattr(ofs->workdir, OVL_XATTR_OPAQUE, "0", 1, 0);
+	if (err) {
+		ofs->noxattr = true;
+		ofs->config.index = false;
+		ofs->config.metacopy = false;
+		pr_warn("overlayfs: upper fs does not support xattr, falling back to index=off and metacopy=off.\n");
+		err = 0;
+	} else {
+		vfs_removexattr(ofs->workdir, OVL_XATTR_OPAQUE);
+	}
+
+	/* 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("overlayfs: 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_bits = 0;
+
+	/* NFS export of r/w mount depends on index */
+	if (ofs->config.nfs_export && !ofs->config.index) {
+		pr_warn("overlayfs: 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,
+			   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("overlayfs: workdir and upperdir must reside under the same mount\n");
+		goto out;
+	}
+	if (!ovl_workdir_ok(workpath.dentry, upperpath->dentry)) {
+		pr_err("overlayfs: 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, struct path *upperpath)
+{
+	struct vfsmount *mnt = ofs->upper_mnt;
+	int err;
+
+	err = mnt_want_write(mnt);
+	if (err)
+		return err;
+
+	/* Verify lower root is upper root origin */
+	err = ovl_verify_origin(upperpath->dentry, oe->lowerstack[0].dentry,
+				true);
+	if (err) {
+		pr_err("overlayfs: failed to verify upper root origin\n");
+		goto out;
+	}
+
+	ofs->indexdir = ovl_workdir_create(ofs, OVL_INDEXDIR_NAME, true);
+	if (ofs->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 "trusted.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
+		 * "trusted.overlay.upper" to indicate that index may have
+		 * directory entries.
+		 */
+		if (ovl_check_origin_xattr(ofs->indexdir)) {
+			err = ovl_verify_set_fh(ofs->indexdir, OVL_XATTR_ORIGIN,
+						upperpath->dentry, true, false);
+			if (err)
+				pr_err("overlayfs: failed to verify index dir 'origin' xattr\n");
+		}
+		err = ovl_verify_upper(ofs->indexdir, upperpath->dentry, true);
+		if (err)
+			pr_err("overlayfs: 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("overlayfs: try deleting index dir or mounting with '-o index=off' to disable inodes index.\n");
+
+out:
+	mnt_drop_write(mnt);
+	return err;
+}
+
+/* Get a unique fsid for the layer */
+static int ovl_get_fsid(struct ovl_fs *ofs, struct super_block *sb)
+{
+	unsigned int i;
+	dev_t dev;
+	int err;
+
+	/* fsid 0 is reserved for upper fs even with non upper overlay */
+	if (ofs->upper_mnt && ofs->upper_mnt->mnt_sb == sb)
+		return 0;
+
+	for (i = 0; i < ofs->numlowerfs; i++) {
+		if (ofs->lower_fs[i].sb == sb)
+			return i + 1;
+	}
+
+	err = get_anon_bdev(&dev);
+	if (err) {
+		pr_err("overlayfs: failed to get anonymous bdev for lowerpath\n");
+		return err;
+	}
+
+	ofs->lower_fs[ofs->numlowerfs].sb = sb;
+	ofs->lower_fs[ofs->numlowerfs].pseudo_dev = dev;
+	ofs->numlowerfs++;
+
+	return ofs->numlowerfs;
+}
+
+static int ovl_get_lower_layers(struct super_block *sb, struct ovl_fs *ofs,
+				struct path *stack, unsigned int numlower)
+{
+	int err;
+	unsigned int i;
+
+	err = -ENOMEM;
+	ofs->lower_layers = kcalloc(numlower, sizeof(struct ovl_layer),
+				    GFP_KERNEL);
+	if (ofs->lower_layers == NULL)
+		goto out;
+
+	ofs->lower_fs = kcalloc(numlower, sizeof(struct ovl_sb),
+				GFP_KERNEL);
+	if (ofs->lower_fs == NULL)
+		goto out;
+
+	for (i = 0; i < numlower; i++) {
+		struct vfsmount *mnt;
+		struct inode *trap;
+		int fsid;
+
+		err = fsid = ovl_get_fsid(ofs, stack[i].mnt->mnt_sb);
+		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("overlayfs: 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;
+
+		ofs->lower_layers[ofs->numlower].trap = trap;
+		ofs->lower_layers[ofs->numlower].mnt = mnt;
+		ofs->lower_layers[ofs->numlower].idx = i + 1;
+		ofs->lower_layers[ofs->numlower].fsid = fsid;
+		if (fsid) {
+			ofs->lower_layers[ofs->numlower].fs =
+				&ofs->lower_fs[fsid - 1];
+		}
+		ofs->numlower++;
+	}
+
+	/*
+	 * When all layers on same fs, overlay can use real inode numbers.
+	 * With mount option "xino=on", 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.
+	 */
+	if (!ofs->numlowerfs || (ofs->numlowerfs == 1 && !ofs->upper_mnt)) {
+		ofs->xino_bits = 0;
+		ofs->config.xino = OVL_XINO_OFF;
+	} else if (ofs->config.xino == OVL_XINO_ON && !ofs->xino_bits) {
+		/*
+		 * This is a roundup of number of bits needed for numlowerfs+1
+		 * (i.e. ilog2(numlowerfs+1 - 1) + 1). fsid 0 is reserved for
+		 * upper fs even with non upper overlay.
+		 */
+		BUILD_BUG_ON(ilog2(OVL_MAX_STACK) > 31);
+		ofs->xino_bits = ilog2(ofs->numlowerfs) + 1;
+	}
+
+	if (ofs->xino_bits) {
+		pr_info("overlayfs: \"xino\" feature enabled using %d upper inode bits.\n",
+			ofs->xino_bits);
+	}
+
+	err = 0;
+out:
+	return err;
+}
+
+static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
+					    struct ovl_fs *ofs)
+{
+	int err;
+	char *lowertmp, *lower;
+	struct path *stack = NULL;
+	unsigned int stacklen, numlower = 0, i;
+	bool remote = false;
+	struct ovl_entry *oe;
+
+	err = -ENOMEM;
+	lowertmp = kstrdup(ofs->config.lowerdir, GFP_KERNEL);
+	if (!lowertmp)
+		goto out_err;
+
+	err = -EINVAL;
+	stacklen = ovl_split_lowerdirs(lowertmp);
+	if (stacklen > OVL_MAX_STACK) {
+		pr_err("overlayfs: too many lower directories, limit is %d\n",
+		       OVL_MAX_STACK);
+		goto out_err;
+	} else if (!ofs->config.upperdir && stacklen == 1) {
+		pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n");
+		goto out_err;
+	} else if (!ofs->config.upperdir && ofs->config.nfs_export &&
+		   ofs->config.redirect_follow) {
+		pr_warn("overlayfs: NFS export requires \"redirect_dir=nofollow\" on non-upper mount, falling back to nfs_export=off.\n");
+		ofs->config.nfs_export = false;
+	}
+
+	err = -ENOMEM;
+	stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL);
+	if (!stack)
+		goto out_err;
+
+	err = -EINVAL;
+	lower = lowertmp;
+	for (numlower = 0; numlower < stacklen; numlower++) {
+		err = ovl_lower_dir(lower, &stack[numlower], ofs,
+				    &sb->s_stack_depth, &remote);
+		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("overlayfs: maximum fs stacking depth exceeded\n");
+		goto out_err;
+	}
+
+	err = ovl_get_lower_layers(sb, ofs, stack, numlower);
+	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->lower_layers[i];
+	}
+
+	if (remote)
+		sb->s_d_op = &ovl_reval_dentry_operations;
+	else
+		sb->s_d_op = &ovl_dentry_operations;
+
+out:
+	for (i = 0; i < numlower; i++)
+		path_put(&stack[i]);
+	kfree(stack);
+	kfree(lowertmp);
+
+	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("overlayfs: 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 (ofs->upper_mnt) {
+		err = ovl_check_layer(sb, ofs, ofs->upper_mnt->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 = 0; i < ofs->numlower; i++) {
+		err = ovl_check_layer(sb, ofs,
+				      ofs->lower_layers[i].mnt->mnt_root,
+				      "lowerdir", true);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+
+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 cred *cred;
+	int err;
+
+	err = -ENOMEM;
+	ofs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
+	if (!ofs)
+		goto out;
+
+	ofs->creator_cred = cred = prepare_creds();
+	if (!cred)
+		goto out_err;
+
+	ofs->config.index = ovl_index_def;
+	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("overlayfs: missing 'lowerdir'\n");
+		goto out_err;
+	}
+
+	sb->s_stack_depth = 0;
+	sb->s_maxbytes = MAX_LFS_FILESIZE;
+	/* Assume underlaying fs uses 32bit inodes unless proven otherwise */
+	if (ofs->config.xino != OVL_XINO_OFF)
+		ofs->xino_bits = BITS_PER_LONG - 32;
+
+	/* alloc/destroy_inode needed for setting up traps in inode cache */
+	sb->s_op = &ovl_super_operations;
+
+	if (ofs->config.upperdir) {
+		if (!ofs->config.workdir) {
+			pr_err("overlayfs: missing 'workdir'\n");
+			goto out_err;
+		}
+
+		err = ovl_get_upper(sb, ofs, &upperpath);
+		if (err)
+			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 = ofs->upper_mnt->mnt_sb->s_stack_depth;
+		sb->s_time_gran = ofs->upper_mnt->mnt_sb->s_time_gran;
+
+	}
+	oe = ovl_get_lowerstack(sb, ofs);
+	err = PTR_ERR(oe);
+	if (IS_ERR(oe))
+		goto out_err;
+
+	/* If the upper fs is nonexistent, we mark overlayfs r/o too */
+	if (!ofs->upper_mnt)
+		sb->s_flags |= SB_RDONLY;
+
+	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) {
+			dput(ofs->workdir);
+			ofs->workdir = NULL;
+			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 (ofs->upper_mnt && ofs->config.nfs_export) {
+			pr_warn("overlayfs: 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("overlayfs: 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 = ovl_xattr_handlers;
+	sb->s_fs_info = ofs;
+	sb->s_flags |= SB_POSIXACL;
+
+	err = -ENOMEM;
+	root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, 0));
+	if (!root_dentry)
+		goto out_free_oe;
+
+	root_dentry->d_fsdata = oe;
+
+	mntput(upperpath.mnt);
+	if (upperpath.dentry) {
+		ovl_dentry_set_upper_alias(root_dentry);
+		if (ovl_is_impuredir(upperpath.dentry))
+			ovl_set_flag(OVL_IMPURE, d_inode(root_dentry));
+	}
+
+	/* Root is always merge -> can have whiteouts */
+	ovl_set_flag(OVL_WHITEOUTS, d_inode(root_dentry));
+	ovl_dentry_set_flag(OVL_E_CONNECTED, root_dentry);
+	ovl_set_upperdata(d_inode(root_dentry));
+	ovl_inode_init(d_inode(root_dentry), upperpath.dentry,
+		       ovl_dentry_lower(root_dentry), NULL);
+
+	sb->s_root = root_dentry;
+
+	return 0;
+
+out_free_oe:
+	ovl_entry_stack_free(oe);
+	kfree(oe);
+out_err:
+	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",
+	.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 = register_filesystem(&ovl_fs_type);
+	if (err)
+		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);
+
+}
+
+module_init(ovl_init);
+module_exit(ovl_exit);