ext4: Do not crash when trying to grow a directory using extents

The following command crashes u-boot:
./sandbox/u-boot -c 'i=0; host bind 0 ./sandbox/test/fs/3GB.ext4.img ;
  while test $i -lt 200 ; do echo $i; setexpr i $i + 1;
  ext4write host 0 0 /foobar${i} 0; done'

Previously, the code updated the direct_block even for extents, and
fortunately crashed before pushing garbage to the disk.

Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>
Reviewed-by: Lukasz Majewski <l.majewski@samsung.com>

fs/ext4/ext4_common.c

@@ -453,8 +453,13 @@ restart:
 			    sizeof(struct ext2_dirent) + padding_factor;
 			if ((fs->blksz - totalbytes - last_entry_dirlen) <
 				new_entry_byte_reqd) {
-				printf("1st Block Full:Allocate new block\n");
+				printf("Last Block Full:Allocate new block\n");
 
+				if (le32_to_cpu(g_parent_inode->flags) &
+						EXT4_EXTENTS_FL) {
+					printf("Directory uses extents\n");
+					goto fail;
+				}
 				if (direct_blk_idx == INDIRECT_BLOCKS - 1) {
 					printf("Directory exceeds limit\n");
 					goto fail;