[Bug 13602] some HFS CD-ROM's can't be read

[Bug 13602] some HFS CD-ROM's can't be read

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=13602


Christoph Hellwig <hch@lst.de> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|HFS/HFSPLUS                 |SCSI
         AssignedTo|hch@lst.de                  |linux-scsi@vger.kernel.org
            Product|File System                 |IO/Storage




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Re: [Bug 13602] some HFS CD-ROM's can't be read

[James Bottomley]

On Thu, 2010-10-28 at 12:53 +0000, bugzilla-daemon@bugzilla.kernel.org
wrote:
> https://bugzilla.kernel.org/show_bug.cgi?id=13602
> 
> 
> Christoph Hellwig <hch@lst.de> changed:
> 
>            What    |Removed                     |Added
> ----------------------------------------------------------------------------
>           Component|HFS/HFSPLUS                 |SCSI
>          AssignedTo|hch@lst.de                  |linux-scsi@vger.kernel.org
>             Product|File System                 |IO/Storage

Why is this actually a bug?  Linux has never supported filesystem block
sizes smaller than device ones ... we don't have the necessary RMW code
for it.  The sr driver supports 512 byte sectors but *only* if the CD
was burned with them (which isn't always possible depending on CD
burner) and the reader supports them.  I'd need the dmesgs to be sure
but i'd guess READ_CAPACITY on this cd returns 2048 as the block size.

James

[Bug 13602] some HFS CD-ROM's can't be read

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=13602





--- Comment #4 from Anonymous Emailer <anonymous@kernel-bugs.osdl.org>  2010-10-28 16:06:44 ---
Reply-To: James.Bottomley@suse.de

On Thu, 2010-10-28 at 12:53 +0000, bugzilla-daemon@bugzilla.kernel.org
wrote:
> https://bugzilla.kernel.org/show_bug.cgi?id=13602
> 
> 
> Christoph Hellwig <hch@lst.de> changed:
> 
>            What    |Removed                     |Added
> ----------------------------------------------------------------------------
>           Component|HFS/HFSPLUS                 |SCSI
>          AssignedTo|hch@lst.de                  |linux-scsi@vger.kernel.org
>             Product|File System                 |IO/Storage

Why is this actually a bug?  Linux has never supported filesystem block
sizes smaller than device ones ... we don't have the necessary RMW code
for it.  The sr driver supports 512 byte sectors but *only* if the CD
was burned with them (which isn't always possible depending on CD
burner) and the reader supports them.  I'd need the dmesgs to be sure
but i'd guess READ_CAPACITY on this cd returns 2048 as the block size.

James

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[Bug 13602] some HFS CD-ROM's can't be read

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=13602


Bill McGonigle <bill-osdl.org-bugzilla@bfccomputing.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Kernel Version|2.6.29.4-167.fc11.i586      |2.6.34.7-56.fc13.x86_64




--- Comment #5 from Bill McGonigle <bill-osdl.org-bugzilla@bfccomputing.com>  2010-10-28 16:40:30 ---
@Christoph: good workaround.  I can losetup my /dev/sr0 and mount the discs
(tested 1 anyway).  I need to omit the session=1 option on the loopback but it
does mount that way.  Just to be sure, I confirmed sr0 won't mount without the
session option.  Not sure what would happen if the data were on session=2.

For the HFS vs. SCSI question, I'm not clear why 22 out of 25 discs in this set
work OK but the remaining 3 would not.  They're factory-stamped discs, no idea
how they were mastered.

The only dmesg I get is:

 hfs: unable to set blocksize to 512
 hfs: can't find a HFS filesystem on dev sr0.

This is now kernel 2.6.34.7-56.fc13.x86_64.

Not sure if it's helpful, but here are the /sys sizes:

[bfccomputing@zpm sr0]$ more `pwd`/queue/*size
::::::::::::::
/sys/block/sr0/queue/hw_sector_size
::::::::::::::
2048
::::::::::::::
/sys/block/sr0/queue/logical_block_size
::::::::::::::
2048
::::::::::::::
/sys/block/sr0/queue/max_segment_size
::::::::::::::
65536
::::::::::::::
/sys/block/sr0/queue/minimum_io_size
::::::::::::::
2048
::::::::::::::
/sys/block/sr0/queue/optimal_io_size
::::::::::::::
0
::::::::::::::
/sys/block/sr0/queue/physical_block_size
::::::::::::::
2048

I can't even say this is a feature implemented in MacOSX for compatibility that
linux lacks - for all I know, they do some sort of loopback mount automagically
if certain kinds of discs are detected.

I don't know if there are any linux equivalents for doing something similar by
the kernel; one could imagine userland machinations that could do the right
thing, though perhaps costly.

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[Bug 13602] some HFS CD-ROM's can't be read

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=13602





--- Comment #6 from Christoph Hellwig <hch@lst.de>  2010-10-31 21:17:53 ---
Old SGI, SUN and apparently mac systems did support CDROMs with 512 byte
sectors.  In MMC5 there is only a vague reference to them beeing supported by
the deprecated block descriptors taken from older SPC specs in some drives.

Searching on the internet implies you need very specific CDROM drives to use
the SGI/SUN 512 byte sector CDROMs.

I think we safely say there is no way to properly support this in Linux and we
we can close this bug.

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[Bug 13602] some HFS CD-ROM's can't be read

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=13602


Alan <alan@lxorguk.ukuu.org.uk> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |alan@lxorguk.ukuu.org.uk
         Resolution|                            |WILL_NOT_FIX




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[Bug 13602] some HFS CD-ROM's can't be read

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=13602


Alan <alan@lxorguk.ukuu.org.uk> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |CLOSED




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