diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 3216dcf3ace0..3ce158f70927 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -2555,14 +2555,21 @@ static int fuse_file_mmap(struct file *file, struct vm_area_struct *vma)
 {
 	struct fuse_file *ff = file->private_data;
 	struct fuse_conn *fc = ff->fm->fc;
+	struct inode *inode = file_inode(file);
 	int rc;
 
 	/* DAX mmap is superior to direct_io mmap */
-	if (FUSE_IS_DAX(file_inode(file)))
+	if (FUSE_IS_DAX(inode))
 		return fuse_dax_mmap(file, vma);
 
-	/* TODO: implement mmap to backing file */
+	/*
+	 * If inode is in passthrough io mode, because it has some file open
+	 * in passthrough mode, either mmap to backing file or fail mmap,
+	 * because mixing cached mmap and passthrough io mode is not allowed.
+	 */
 	if (fuse_file_passthrough(ff))
+		return fuse_passthrough_mmap(file, vma);
+	else if (fuse_inode_backing(get_fuse_inode(inode)))
 		return -ENODEV;
 
 	/*
@@ -2589,7 +2596,7 @@ static int fuse_file_mmap(struct file *file, struct vm_area_struct *vma)
 		 * Also waits for parallel dio writers to go into serial mode
 		 * (exclusive instead of shared lock).
 		 */
-		rc = fuse_file_cached_io_start(file_inode(file), ff);
+		rc = fuse_file_cached_io_start(inode, ff);
 		if (rc)
 			return rc;
 	}
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 53ac73739788..7bd3552b1e80 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -1474,5 +1474,6 @@ ssize_t fuse_passthrough_splice_read(struct file *in, loff_t *ppos,
 ssize_t fuse_passthrough_splice_write(struct pipe_inode_info *pipe,
 				      struct file *out, loff_t *ppos,
 				      size_t len, unsigned int flags);
+ssize_t fuse_passthrough_mmap(struct file *file, struct vm_area_struct *vma);
 
 #endif /* _FS_FUSE_I_H */
diff --git a/fs/fuse/passthrough.c b/fs/fuse/passthrough.c
index 2b119c592f02..1567f0323858 100644
--- a/fs/fuse/passthrough.c
+++ b/fs/fuse/passthrough.c
@@ -124,6 +124,22 @@ ssize_t fuse_passthrough_splice_write(struct pipe_inode_info *pipe,
 	return ret;
 }
 
+ssize_t fuse_passthrough_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	struct fuse_file *ff = file->private_data;
+	struct file *backing_file = fuse_file_passthrough(ff);
+	struct backing_file_ctx ctx = {
+		.cred = ff->cred,
+		.user_file = file,
+		.accessed = fuse_file_accessed,
+	};
+
+	pr_debug("%s: backing_file=0x%p, start=%lu, end=%lu\n", __func__,
+		 backing_file, vma->vm_start, vma->vm_end);
+
+	return backing_file_mmap(backing_file, vma, &ctx);
+}
+
 struct fuse_backing *fuse_backing_get(struct fuse_backing *fb)
 {
 	if (fb && refcount_inc_not_zero(&fb->count))