What's with libata and DVDs ?

What's with libata and DVDs ?

[Mark Lord]

Attempting to play a known-good DVD-video in MythTV-0.21
using libata in kernel 2.6.27.7 :

sr 4:0:0:0: [sr0] unaligned transfer
Buffer I/O error on device sr0, logical block 1080
Buffer I/O error on device sr0, logical block 1081
Buffer I/O error on device sr0, logical block 1082
Buffer I/O error on device sr0, logical block 1083
Buffer I/O error on device sr0, logical block 1084
Buffer I/O error on device sr0, logical block 1085
Buffer I/O error on device sr0, logical block 1086
Buffer I/O error on device sr0, logical block 1087
Buffer I/O error on device sr0, logical block 1088
sr 4:0:0:0: [sr0] unaligned transfer
sr 4:0:0:0: [sr0] unaligned transfer
sr 4:0:0:0: [sr0] unaligned transfer

This used to work back in 2.6.25 or so.
Anyone else out there have similar DVD issues ?

-ml

Re: What's with libata and DVDs ?

[Mark Lord]

Mark Lord wrote:
> Attempting to play a known-good DVD-video in MythTV-0.21
> using libata in kernel 2.6.27.7 :
> 
> sr 4:0:0:0: [sr0] unaligned transfer
> Buffer I/O error on device sr0, logical block 1080
> Buffer I/O error on device sr0, logical block 1081
> Buffer I/O error on device sr0, logical block 1082
> Buffer I/O error on device sr0, logical block 1083
> Buffer I/O error on device sr0, logical block 1084
> Buffer I/O error on device sr0, logical block 1085
> Buffer I/O error on device sr0, logical block 1086
> Buffer I/O error on device sr0, logical block 1087
> Buffer I/O error on device sr0, logical block 1088
> sr 4:0:0:0: [sr0] unaligned transfer
> sr 4:0:0:0: [sr0] unaligned transfer
> sr 4:0:0:0: [sr0] unaligned transfer
> 
> This used to work back in 2.6.25 or so.
> Anyone else out there have similar DVD issues ?
..

Mmm.. some DVDs play, others don't.  I'll instrument the code
and see if anything obvious pops up someday.  Ignore me for now. :)

Re: What's with libata and DVDs ?

[Alan Cox]

On Sat, 06 Dec 2008 23:47:09 -0500
Mark Lord <liml@rtr.ca> wrote:

> Attempting to play a known-good DVD-video in MythTV-0.21
> using libata in kernel 2.6.27.7 :
> 
> sr 4:0:0:0: [sr0] unaligned transfer

Your system somehow generated a scsi request which was not 2K aligned.
The scsi mid layer then reported that and added padding - which
presumably didn't help because the command shouldn't have been misaligned
in the first place.

If you strace it do you see any misaligned requests coming from user
space - also btw is the cd layer reporting the sector size wrong
anywhere ?

Alan

Re: What's with libata and DVDs ?

[Mark Lord]

Alan Cox wrote:
> On Sat, 06 Dec 2008 23:47:09 -0500
> Mark Lord <liml@rtr.ca> wrote:
> 
>> Attempting to play a known-good DVD-video in MythTV-0.21
>> using libata in kernel 2.6.27.7 :
>>
>> sr 4:0:0:0: [sr0] unaligned transfer
> 
> Your system somehow generated a scsi request which was not 2K aligned.
> The scsi mid layer then reported that and added padding - which
> presumably didn't help because the command shouldn't have been misaligned
> in the first place.
> 
> If you strace it do you see any misaligned requests coming from user
> space - also btw is the cd layer reporting the sector size wrong
> anywhere ?
..

No complaints from the cd layer -- just that unaligned message.
I've changed that message to actually *show* the values it is complaining
about (what a concept, duh..), so next time I reproduce it there will be
some information as to what was really going on.

Probably just a buggy app, or maybe 64-bit porting error in it.

Cheers