udf: Fix directory iteration for longer tail extents

When directory's last extent has more that one block and its length is
not multiple of a block side, the code wrongly decided to move to the
next extent instead of processing the last partial block. This led to
directory corruption. Fix the rounding issue.

Signed-off-by: Jan Kara <[e-mail]>

fs/udf/directory.c

···
 static int udf_fiiter_advance_blk(struct udf_fileident_iter *iter)
 {
 	iter->loffset++;
-	if (iter->loffset < iter->elen >> iter->dir->i_blkbits)
+	if (iter->loffset < DIV_ROUND_UP(iter->elen, 1<<iter->dir->i_blkbits))
 		return 0;
 
 	iter->loffset = 0;