Re: [regression/bisected] corrupt CD data after media change and delay

Geert Uytterhoeven
2008-06-09T12:54:59Z

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On Fri, 6 Jun 2008, James Bottomley wrote:
> On Fri, 2008-06-06 at 16:06 +0200, Geert Uytterhoeven wrote:
> > When mounting a CD/DVD more than 30 seconds after inserting it, and reading
> > from it, we get:
> >
> > attempt to access beyond end of device
> > sr0: rw=0, want=371932, limit=371928
> > Buffer I/O error on device sr0, logical block 92982
> > attempt to access beyond end of device
> > sr0: rw=0, want=371936, limit=371928
> > Buffer I/O error on device sr0, logical block 92983
> > attempt to access beyond end of device
> > sr0: rw=0, want=371940, limit=371928
> > Buffer I/O error on device sr0, logical block 92984
> > attempt to access beyond end of device
> > sr0: rw=0, want=371944, limit=371928
> > Buffer I/O error on device sr0, logical block 92985
> > attempt to access beyond end of device
> > sr0: rw=0, want=371948, limit=371928
> > Buffer I/O error on device sr0, logical block 92986
> > ...
> >
> > It can be reproduced on a PS3 with busybox userland using:
> >
> > # Insert first CD
> > $ mount /dev/sr0 /mnt
> > $ ls -R /mnt
> > $ umount /mnt
> > $ eject
> > # Remove first CD
> >
> > # Insert second CD
> > # Wait at least 30 seconds
> > $ mount /dev/sr0 /mnt
> > $ tar cf /dev/null /mnt
> >
> > It does not happen when mounting the second CD within 30 seconds after
> > inserting it, which is consistent with
> >
> > #define SR_TIMEOUT (30 * HZ)
> >
> > I can't seem to reproduce it with a Debian or Fedora Core 6 userland.
> >
> > The problem is present in 2.6.25.
> > 2.6.24 is OK.
>
> Also, in the two different situations, what does
>
> cat /sys/block/sr0/size
>
> (assuming your cd is sr0) give you? My first theory is an incorrect
> size propagating from something.

Nice first theory!

Initially /sys/block/sr0/size is 2097151.

After inserting the first CD, and mounting it, /sys/block/sr0/size is changed
to the size of the first CD (in 512 byte blocks).

After ejecting the first CD and inserting the second CD, the behavior is like
this:
1. when immediately mounting the CD, /sys/block/sr0/size is updated to the
size of the second CD,
2. when waiting more than 30 seconds before mounting the CD,
/sys/block/sr0/size is not updated, and keeps the old value.

Surprisingly, it doesn't behave like this when inserting the first CD.
/sys/block/sr0/size is always updated, whether I wait 30 seconds before
mounting it or not.

With kind regards,

Geert Uytterhoeven
Software Architect

Sony Techsoft Centre
The Corporate Village · Da Vincilaan 7-D1 · B-1935 Zaventem · Belgium

Phone: +32 (0)2 700 8453
Fax: +32 (0)2 700 8622
E-mail: Geert.Uytterhoeven@sonycom.com
Internet: http://www.sony-europe.com/

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