Date: Wed, 4 Jun 2003 21:55:46 +0200
From: Jens Axboe <axboe@suse.de>
To: Andy Polyakov <appro@fy.chalmers.se>
Cc: linux-kernel@vger.kernel.org
Subject: Re: 2.5.69-70 ide-cd to guarantee fault-free CD/DVD burning experience?
Message-ID: <20030604195546.GB477@suse.de>
References: <3ED4681A.738DA3C6@fy.chalmers.se> <3EDE4B96.21DBA04B@fy.chalmers.se>
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On Wed, Jun 04 2003, Andy Polyakov wrote:
> > ... accept ... patch which makes it possible to access the
> > sense data returned by IDE CD/DVD units from user-land with SG_IO ioctl.
> 
> The originally proposed modifications were indeed sufficient to get
> DVD+RW units working, but apparently not DVD-RW ones:-( Note though
> that [another] problem discussed here is not specific to DVD-RW
> recordings. It's generic bug/deficiency. Once a packet commands is
> terminated with an error condition the whole bio should be purged at
> once and not only the first chunk as it's currently implemented.
> 
> Attached patch should be considered as a "denoting" patch, not
> "final." Well, because it was verified with single application,
> growisofs of dvd+rw-tools, which uses mmap-ed, in other words 
> page-aligned, buffer(s). I mean I'm not 100% sure if hard_nr_sectors
> is appropriate even for general case of 4-byte aligned buffers...
> Then if-statement should probably be extended even to REQ_PC case...
> 
> Cheers. A.
> 8<--------8<--------8<--------8<--------8<--------8<--------8<--------
> --- ./drivers/ide/ide-cd.c.orig Tue Jun  3 12:21:56 2003
> +++ ./drivers/ide/ide-cd.c      Wed Jun  4 16:14:41 2003
> @@ -657,6 +657,9 @@
>         struct request *rq = HWGROUP(drive)->rq;
>         int nsectors = rq->hard_cur_sectors;
>  
> +       if (rq->flags&REQ_BLOCK_PC)
> +               nsectors = rq->hard_nr_sectors;	/* purge it all ... */
> +       else
>         if ((rq->flags & REQ_SENSE) && uptodate) {
>                 /*
>                  * For REQ_SENSE, "rq->buffer" points to the original failed

The *sector* values don't really work well for REQ_BLOCK_PC, it doesn't
even have to be set at all. One solution would be to add more rq members
(yuck), a nicer one is probably to make cdrom_end_request return
ide_end_request ret value, and simply make the error locations kill the
requests... It's not very nice, but should work.

-- 
Jens Axboe

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