Re: [PATCH] block: fix residual byte count handling

[FUJITA Tomonori]

On Mon, 03 Mar 2008 13:09:13 +0900
Tejun Heo <htejun@xxxxxxxxx> wrote:

> FUJITA Tomonori wrote:
> >> - 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.

The patch doens't change that rq->data_len means the true data
length. But yeah, it breaks rq->data_len == sum(sg). So it might break
some drivers.


> Apply your patch and try to do sg IO on IDE cdrom w/ various
> transfer lengths.

I've just tried the patch with both ata and libata and it seems to
work.

For anyone hitting this problem, please try the following patch:

http://lkml.org/lkml/2008/3/2/218


Thanks,
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/