linux-kernel - DVD-RAM cannot be mounted RW with 2.6.18/2.6.19

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Date:	Sat, 16 Dec 2006 14:55:16 -0500
From:	"A. Kalten" <akalten@...cast.net>
To:	linux-kernel@...r.kernel.org
Subject: DVD-RAM cannot be mounted RW with 2.6.18/2.6.19

Hello,

DVD-RAM disks previously made with a Linux system can
no longer be mounted in RW mode.  For some reason, as
indicated by the error message from the mount command,
the disks are detected as being write-protected (which
is not the case).  To be able to write to these disks,
the mount command must be issued again with the "-o remount"
option.

The commands given are as follows.  Although the file
type in this example is ext2, the same behavior is seen
also with the udf file type.

# modprobe ide-cd
# hdparm -d1 -X udma4 -k1 /dev/hde

# mount -t ext2 -o rw,noatime /dev/hde /cdrom
mount: block device /dev/hde is write-protected, mounting read-only

# mount -t ext2 -o remount,rw,noatime /dev/hde /cdrom

Now the DVD-RAM disk can be written normally, but there should
be no need for the second mount command.

The kernel log for this command sequence seems to show nothing abnormal:

kernel: hde: ATAPI 39X DVD-ROM DVD-R-RAM CD-R/RW drive, 2048kB Cache, UDMA(66)
kernel: Uniform CD-ROM driver Revision: 3.20
kernel: hde: CHECK for good STATUS
kernel: cdrom: hde: mrw address space DMA selected
kernel: cdrom open: mrw_status 'not mrw'

Furthermore, if I attempt to check the unmounted DVD-RAM disk with
e2fsck, the drive is still reported as read-only:

# e2fsck -p /dev/hde
e2fsck: Read-only file system while trying to open /dev/hde
Disk write-protected; use the -n option to do a read-only
check of the device.

However, as I indicated above, the disk is not write-protected.

I am reporting this problem on the lkml because of a hint
that I discovered at this link:

http://lists.opensuse.org/packet-writing/2006-10/msg00000.html

Although this problem does not involve packet-writing, it may
be related to the cdrom code.

Andrew Kalten

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