FUJITA Tomonori wrote:

quoted

- I think bugs caused by using raw_data_len instead of data_len are more
subtle than the other way around.  Using data_len instead of
raw_data_len usually affects the application layer while using
raw_data_len instead of data_len affects the DMA engine and transport layer.

If we add extra_len, we can get what raw_data_len and data_len
provide.

I can't see what changing the meaning of rq->data_len (and
investigating all the block drivers) gives us.

No matter which way you go, you change the meaning of rq->data_len and
you MUST inspect rq->data_len usage whichever way you go.  Apply your
patch and try to do sg IO on IDE cdrom w/ various transfer lengths.

-- 
tejun