On Wed, 2008-02-27 at 03:24 +0100, Mike Galbraith wrote:
quoted text
> On Tue, 2008-02-26 at 15:08 -0800, Andrew Morton wrote:
 
quoted text
> > So this change fixes a bug?  Can we have a recap of how it does this?
> 
> Yeah, it fixes the problem.  (wrt recap, if I could write it, it would
> be a changelog;)

Hm.  After rummaging around some more in both kernel and userland, I
think this patchlet is not only functional, but  (random accident)
technically correct.  What the heck, let's see if it flies...

snippet from userland:
/*
 * Return the residual DMA count for last command.
 * If this count is < 0, then a DMA overrun occured.
 */
EXPORT int
scg_getresid(scgp)
	SCSI	*scgp;
{
	return (scgp->scmd->resid);
}

This function is used all over the place in cdrecord to determine
transfer size.

(patchlet takes wing, and... goes splat?)
 
Fix CD burning regression introduced by
6b00769fe1502b4ad97bb327ef7ac971b208bfb5.  raw_data_len must be updated
to reflect residual data upon IO completion because it is used by
blk_complete_sghdr_rq() to set hdr->resid which eventually becomes
visible to userland.

Signed-off-by: Mike Galbraith <efault@gmx.de>

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index ba21d97..7a6f784 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -871,7 +871,7 @@ void scsi_io_completion(struct scsi_cmnd *cmd,
unsigned int good_bytes)
 			scsi_end_bidi_request(cmd);
 			return;
 		}
-		req->data_len = scsi_get_resid(cmd);
+		req->data_len = req->raw_data_len = scsi_get_resid(cmd);
 	}
 
 	BUG_ON(blk_bidi_rq(req)); /* bidi not support for !blk_pc_request yet
*/


	-Mike

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