f2fs crypto: avoid unneeded memory allocation in ->readdir

When decrypting dirents in ->readdir, fscrypt_fname_disk_to_usr won't
change content of original encrypted dirent, we don't need to allocate
additional buffer for storing mirror of it, so get rid of it.
Signed-off-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/dir.c

@@ -796,16 +796,9 @@ bool f2fs_fill_dentries(struct dir_context *ctx, struct f2fs_dentry_ptr *d,
 			int save_len = fstr->len;
 			int ret;
 
-			de_name.name = f2fs_kmalloc(de_name.len, GFP_NOFS);
-			if (!de_name.name)
-				return false;
-
-			memcpy(de_name.name, d->filename[bit_pos], de_name.len);
-
 			ret = fscrypt_fname_disk_to_usr(d->inode,
 						(u32)de->hash_code, 0,
 						&de_name, fstr);
-			kfree(de_name.name);
 			if (ret < 0)
 				return true;