ext4: Avoid corruption of directories with hash tree indexes

While directories can be read using the old linear scan method, adding a
new file would require updating the index tree (alternatively, the whole
tree could be removed).

Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>
Reviewed-by: Lukasz Majewski <l.majewski@samsung.com>
diff --git a/fs/ext4/ext4_write.c b/fs/ext4/ext4_write.c
index a52804e..8554793 100644
--- a/fs/ext4/ext4_write.c
+++ b/fs/ext4/ext4_write.c
@@ -881,6 +881,11 @@
 		goto fail;
 	if (ext4fs_iget(parent_inodeno, g_parent_inode))
 		goto fail;
+	/* do not mess up a directory using hash trees */
+	if (le32_to_cpu(g_parent_inode->flags) & EXT4_INDEX_FL) {
+		printf("hash tree directory\n");
+		goto fail;
+	}
 	/* check if the filename is already present in root */
 	existing_file_inodeno = ext4fs_filename_unlink(filename);
 	if (existing_file_inodeno != -1) {