diff -drupN a/fs/sdcardfs/dentry.c b/fs/sdcardfs/dentry.c
--- a/fs/sdcardfs/dentry.c	1970-01-01 03:00:00.000000000 +0300
+++ b/fs/sdcardfs/dentry.c	2022-06-12 05:28:14.000000000 +0300
@@ -0,0 +1,189 @@
+/*
+ * fs/sdcardfs/dentry.c
+ *
+ * Copyright (c) 2013 Samsung Electronics Co. Ltd
+ *   Authors: Daeho Jeong, Woojoong Lee, Seunghwan Hyun,
+ *               Sunghwan Yun, Sungjong Seo
+ *
+ * This program has been developed as a stackable file system based on
+ * the WrapFS which written by
+ *
+ * Copyright (c) 1998-2011 Erez Zadok
+ * Copyright (c) 2009     Shrikar Archak
+ * Copyright (c) 2003-2011 Stony Brook University
+ * Copyright (c) 2003-2011 The Research Foundation of SUNY
+ *
+ * This file is dual licensed.  It may be redistributed and/or modified
+ * under the terms of the Apache 2.0 License OR version 2 of the GNU
+ * General Public License.
+ */
+
+#include "sdcardfs.h"
+#include "linux/ctype.h"
+
+/*
+ * returns: -ERRNO if error (returned to user)
+ *          0: tell VFS to invalidate dentry
+ *          1: dentry is valid
+ */
+static int sdcardfs_d_revalidate(struct dentry *dentry, unsigned int flags)
+{
+	int err = 1;
+	struct path parent_lower_path, lower_path;
+	struct dentry *parent_dentry = NULL;
+	struct dentry *parent_lower_dentry = NULL;
+	struct dentry *lower_cur_parent_dentry = NULL;
+	struct dentry *lower_dentry = NULL;
+	struct inode *inode;
+	struct sdcardfs_inode_data *data;
+
+	if (flags & LOOKUP_RCU)
+		return -ECHILD;
+
+	spin_lock(&dentry->d_lock);
+	if (IS_ROOT(dentry)) {
+		spin_unlock(&dentry->d_lock);
+		return 1;
+	}
+	spin_unlock(&dentry->d_lock);
+
+	/* check uninitialized obb_dentry and
+	 * whether the base obbpath has been changed or not
+	 */
+	if (is_obbpath_invalid(dentry)) {
+		return 0;
+	}
+
+	parent_dentry = dget_parent(dentry);
+	sdcardfs_get_lower_path(parent_dentry, &parent_lower_path);
+	sdcardfs_get_real_lower(dentry, &lower_path);
+	parent_lower_dentry = parent_lower_path.dentry;
+	lower_dentry = lower_path.dentry;
+	lower_cur_parent_dentry = dget_parent(lower_dentry);
+
+	if ((lower_dentry->d_flags & DCACHE_OP_REVALIDATE)) {
+		err = lower_dentry->d_op->d_revalidate(lower_dentry, flags);
+		if (err == 0) {
+			goto out;
+		}
+	}
+
+	spin_lock(&lower_dentry->d_lock);
+	if (d_unhashed(lower_dentry)) {
+		spin_unlock(&lower_dentry->d_lock);
+		err = 0;
+		goto out;
+	}
+	spin_unlock(&lower_dentry->d_lock);
+
+	if (parent_lower_dentry != lower_cur_parent_dentry) {
+		err = 0;
+		goto out;
+	}
+
+	if (dentry < lower_dentry) {
+		spin_lock(&dentry->d_lock);
+		spin_lock_nested(&lower_dentry->d_lock, DENTRY_D_LOCK_NESTED);
+	} else {
+		spin_lock(&lower_dentry->d_lock);
+		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
+	}
+
+	if (!qstr_case_eq(&dentry->d_name, &lower_dentry->d_name)) {
+		err = 0;
+	}
+
+	if (dentry < lower_dentry) {
+		spin_unlock(&lower_dentry->d_lock);
+		spin_unlock(&dentry->d_lock);
+	} else {
+		spin_unlock(&dentry->d_lock);
+		spin_unlock(&lower_dentry->d_lock);
+	}
+	if (!err)
+		goto out;
+
+	/* If our top's inode is gone, we may be out of date */
+	inode = igrab(d_inode(dentry));
+	if (inode) {
+		data = top_data_get(SDCARDFS_I(inode));
+		if (!data || data->abandoned) {
+			err = 0;
+		}
+		if (data)
+			data_put(data);
+		iput(inode);
+	}
+
+out:
+	dput(parent_dentry);
+	dput(lower_cur_parent_dentry);
+	sdcardfs_put_lower_path(parent_dentry, &parent_lower_path);
+	sdcardfs_put_real_lower(dentry, &lower_path);
+	return err;
+}
+
+static void sdcardfs_d_release(struct dentry *dentry)
+{
+	if (!dentry || !dentry->d_fsdata)
+		return;
+	/* release and reset the lower paths */
+	if (has_graft_path(dentry))
+		sdcardfs_put_reset_orig_path(dentry);
+	sdcardfs_put_reset_lower_path(dentry);
+	free_dentry_private_data(dentry);
+}
+
+static int sdcardfs_hash_ci(const struct dentry *dentry,
+				struct qstr *qstr)
+{
+	/*
+	 * This function is copy of vfat_hashi.
+	 * FIXME Should we support national language?
+	 *       Refer to vfat_hashi()
+	 * struct nls_table *t = MSDOS_SB(dentry->d_sb)->nls_io;
+	 */
+	const unsigned char *name;
+	unsigned int len;
+	unsigned long hash;
+
+	name = qstr->name;
+	len = qstr->len;
+
+	hash = init_name_hash(dentry);
+	while (len--)
+		hash = partial_name_hash(tolower(*name++), hash);
+	qstr->hash = end_name_hash(hash);
+
+	return 0;
+}
+
+/*
+ * Case insensitive compare of two vfat names.
+ */
+static int sdcardfs_cmp_ci(const struct dentry *dentry,
+		unsigned int len, const char *str, const struct qstr *name)
+{
+	/* FIXME Should we support national language? */
+
+	if (name->len == len) {
+		if (str_n_case_eq(name->name, str, len))
+			return 0;
+	}
+	return 1;
+}
+
+static void sdcardfs_canonical_path(const struct path *path,
+				struct path *actual_path)
+{
+	sdcardfs_get_real_lower(path->dentry, actual_path);
+}
+
+const struct dentry_operations sdcardfs_ci_dops = {
+	.d_revalidate	= sdcardfs_d_revalidate,
+	.d_release	= sdcardfs_d_release,
+	.d_hash	= sdcardfs_hash_ci,
+	.d_compare	= sdcardfs_cmp_ci,
+	.d_canonical_path = sdcardfs_canonical_path,
+};
+