Re: 2.6.3 BUG - can't write DVD-RAM - reported as write-protected

From: Olaf Frączyk
Date: Tue Mar 23 2004 - 09:47:07 EST

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

Regards,

Olaf

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