Subject: Re: 2.6.3 BUG - can't write DVD-RAM - reported as write-protected
From: Olaf =?iso-8859-2?Q?Fr=B1czyk?= <olaf@cbk.poznan.pl>
To: Jens Axboe <axboe@suse.de>
Cc: linux-kernel@vger.kernel.org, td@linuxgang.com
In-Reply-To: <1080053402.1473.0.camel@venus.local.navi.pl>
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Date: Tue, 23 Mar 2004 16:32:42 +0100
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On Tue, 2004-03-23 at 15:50, Olaf Frączyk wrote:
> On Sun, 2004-03-14 at 12:22, Jens Axboe wrote:
> > On Sun, Mar 14 2004, Olaf Fr?czyk wrote:
> > > On Tue, 2004-03-09 at 10:12, Jens Axboe wrote: 
> > > > On Tue, Mar 09 2004, Olaf Fr?czyk wrote:
> > > > > On Sun, 2004-03-07 at 11:59, Jens Axboe wrote:
> > > > > > On Fri, Mar 05 2004, Olaf Fr?czyk wrote:
> > > > > > > On Fri, 2004-03-05 at 09:23, Jens Axboe wrote:
> > > > > > > > On Thu, Mar 04 2004, Olaf Fr?czyk wrote:
> > > > > > > > > Hi,
> > > > > > > > > I switched to 2.6.3 from 2.4.x serie.
> > > > > > > > > When I mount DVD-RAM it is mounted read-only:
> > > > > > > > > 
> > > > > > > > > [root@venus olaf]# mount /dev/dvdram /mnt/dvdram
> > > > > > > > > mount: block device /dev/dvdram is write-protected, mounting read-only
> > > > > > > > > [root@venus olaf]#
> > > > > > > > > 
> > > > > > > > > In 2.4 it is mounted correctly as read-write.
> > > > > > > > > 
> > > > > > > > > Drive: Panasonic LF-201, reported in Linux as:
> > > > > > > > > MATSHITA        DVD-RAM LF-D200         A120
> > > > > > > > > 
> > > > > > > > > SCSI controller: Adaptec 2940U2W
> > > > > > > > 
> > > > > > > > What does cat /proc/sys/dev/cdrom/info say? Do you get any kernel
> > > > > > > > messages in dmesg when the rw mount fails?
> > > > > > > 
> > > > > > > I get nothing in /var/log/dmesg and in /var/log/messages
> > > > > > > In /proc/sys/dev/cdrom/info I get:
> > > > > > > [olaf@venus olaf]$ cat /proc/sys/dev/cdrom/info
> > > > > > > CD-ROM information, Id: cdrom.c 3.20 2003/12/17
> > > > > > >  
> > > > > > > drive name:             sr1     sr0     hdc
> > > > > > > drive speed:            0       16      44
> > > > > > > drive # of slots:       1       1       1
> > > > > > > Can close tray:         1       1       1
> > > > > > > Can open tray:          1       1       1
> > > > > > > Can lock tray:          1       1       1
> > > > > > > Can change speed:       1       1       1
> > > > > > > Can select disk:        0       0       0
> > > > > > > Can read multisession:  1       1       1
> > > > > > > Can read MCN:           1       1       1
> > > > > > > Reports media changed:  1       1       1
> > > > > > > Can play audio:         1       1       1
> > > > > > > Can write CD-R:         0       1       1
> > > > > > > Can write CD-RW:        0       1       1
> > > > > > > Can read DVD:           1       0       0
> > > > > > > Can write DVD-R:        0       0       0
> > > > > > > Can write DVD-RAM:      1       0       0
> > > > > > > Can read MRW:           0       0       1
> > > > > > > Can write MRW:          0       0       1
> > > > > > > 
> > > > > > > The one I'm mounting is /dev/scd1.
> > > > > > > As there is capablity to write-protect DVD-RAM disk (like a 1.44"
> > > > > > > Floppy), I think that the linux kernel interprets some message from
> > > > > > > device in wrong way.
> > > > > > 
> > > > > > Please repeat with this patch applied and send back the results, thanks.
> > > > > > 
> > > > > > ===== drivers/cdrom/cdrom.c 1.48 vs edited =====
> > > > > > -- 1.48/drivers/cdrom/cdrom.c	Mon Feb  9 21:58:21 2004
> > > > > > +++ edited/drivers/cdrom/cdrom.c	Sun Mar  7 11:58:40 2004
> > > > > > @@ -645,9 +645,12 @@
> > > > > >  {
> > > > > >  	disc_information di;
> > > > > >  
> > > > > > -	if (cdrom_get_disc_info(cdi, &di))
> > > > > > +	if (cdrom_get_disc_info(cdi, &di)) {
> > > > > > +		printk("cdrom: read di failed\n");
> > > > > >  		return 0;
> > > > > > +	}
> > > > > >  
> > > > > > +	printk("cdrom: erasable: %d\n", di.erasable);
> > > > > >  	return di.erasable;
> > > > > >  }
> > > > > >  
> > > > > I get:
> > > > > cdrom: read di failed
> > > > 
> > > > Can you try to instrument drivers/cdrom/cdrom.c:cdrom_get_disc_info()
> > > > and find out where it fails? Change the cgc.quiet = 1 to a = 0 in there
> > > > as well (that alone might be enough to pin point the problem).
> > > Sorry for the delay. I couldn't take tha machine down.
> > > After setting cgc.quiet=0 I get no additional messages from kernel.
> > > cdrom_get_disc_info returns after FIRST:
> > > cdo->generic_packet(cdi, &cgc).
> > 
> > Ok, at least that's a little clue... Maybe your drive is buggy (I think
> > we already established that, question is what the bug is) and doesn't
> > like to return just two bytes, please try with attached patch.
> > 
> > > BTW, I suppose return codes are interpreted not well:
> > > In cdrom_get_disc_info we return after first (cdo->generic_packet) if it
> > > returns not 0. (Success?) And we return with not 0 value.
> > > And in cdrom_media_erasable we assume that not 0 is error, not success.
> > > So probably in cdrom_get_disc_info we should have:
> > >         if (!(ret = cdo->generic_packet(cdi, &cgc)))
> > >                 return ret;
> > 
> > No, you are not reading the code correctly. ->generic_packet() returns 0
> > on success, or the error (standard kernel practice).
> > cdrom_media_erasable() returns a bool, and if cdrom_get_disc_info()
> > fails then we return it's not erasable.
> > 
> > > I tried it, but it changed nothing regarding to the problem.
> > > It returns then after second cdo->generic_packet, but I still get: 
> > > read di failed.
> > 
> > You broke it, the first check simply returns the header so .erasable
> > must be 0 because we cleared the buffer first.
> > 
> > ===== drivers/cdrom/cdrom.c 1.49 vs edited =====
> > --- 1.49/drivers/cdrom/cdrom.c	Thu Mar 11 13:31:15 2004
> > +++ edited/drivers/cdrom/cdrom.c	Sun Mar 14 12:21:44 2004
> > @@ -2658,11 +2658,13 @@
> >  	/* set up command and get the disc info */
> >  	init_cdrom_command(&cgc, di, sizeof(*di), CGC_DATA_READ);
> >  	cgc.cmd[0] = GPCMD_READ_DISC_INFO;
> > -	cgc.cmd[8] = cgc.buflen = 2;
> > -	cgc.quiet = 1;
> > +	cgc.cmd[8] = cgc.buflen = 8;
> > +	cgc.quiet = 0;
> >  
> > -	if ((ret = cdo->generic_packet(cdi, &cgc)))
> > +	if ((ret = cdo->generic_packet(cdi, &cgc))) {
> > +		printk("cdrom: read_di failed, %d\n", ret);
> >  		return ret;
> > +	}
> >  
> >  	/* not all drives have the same disc_info length, so requeue
> >  	 * packet with the length the drive tells us it can supply
> > @@ -2673,6 +2675,7 @@
> >  	if (cgc.buflen > sizeof(disc_information))
> >  		cgc.buflen = sizeof(disc_information);
> >  
> > +	printk("cdrom: re-reading di, len=%d\n", cgc.buflen);
> >  	cgc.cmd[8] = cgc.buflen;
> >  	return cdo->generic_packet(cdi, &cgc);
> >  }
> On 2.6.4 with your patch I get:
> Mar 23 15:46:03 venus kernel: cdrom: read_di failed, -95
I have found, that I can't mount CD in my Yamaha 6416S now. It worked
with 2.6.3. So we have two problems now. Should I start separate thread
or continue here?

When I try to mount CD I get in command line:
[root@venus scsi]#  mount /dev/scd0 /mnt/cdrom
/dev/scd0: Invalid argument
mount: block device /dev/scd0 is write-protected, mounting read-only
/dev/scd0: Invalid argument
mount: /dev/scd0: can't read superblock

And in /var/log/messages:
Mar 23 16:23:08 venus kernel: end_request: I/O error, dev sr0, sector 0
Mar 23 16:23:08 venus kernel: FAT: unable to read boot sector

Regards,

Olaf


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