linux-kernel - Re: hfsplus mount regression in 2.6.38

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Date:	Fri, 27 May 2011 08:23:56 -0500
From:	Seth Forshee <seth.forshee@...onical.com>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	Anton Salikhmetov <alexo@...era.com>, linux-kernel@...r.kernel.org
Subject: Re: hfsplus mount regression in 2.6.38

On Fri, May 27, 2011 at 05:25:22AM -0400, Christoph Hellwig wrote:
> On Wed, May 25, 2011 at 09:25:21AM -0500, Seth Forshee wrote:
> > Reverting commits 52399b1 (hfsplus: use raw bio access for the volume
> > headers) and 358f26d5 (hfsplus: use raw bio access for partition tables)
> > fixes the problems. It appears the problems are due to hfsplus
> > submitting 512 byte bios to a block device whose sector size is larger
> > than 512 byts (2 KB in the log above), and the block driver is quite
> > reasonably rejecting any requests without proper sector alignment.
> > 
> > How would you suggest fixing this?  Most file systems are using
> > sb_bread() for this sort of thing, but since the offending patches are
> > intended to stop using buffer_heads I'm assuming that's not an option.
> 
> Basically all hardcoded uses of HFSPLUS_SECTOR_SIZE need to be replaced
> with a use of bdev_logical_block_size, or a per-sb variable derived from
> it, and the addressing needs to be accomodated to fit it.  I'd need to
> look into a bit more detail in what form the sectors we pass into it
> are in - we might have to convert them from 512byte to large units,
> or they might already be in it.  If they happen to be in 512 byte units
> we might have to do read-modify write cycles.

It seems reasonable to use sb->s_blocksize for this, as it shouldn't get
set to anything larger than the logical block size. That's what
sb_bread() uses in fact.

> What large sector size device do you have, a CDROM?

I don't have any large-sector devices personally, these are reports
coming in from users. Many of them are seeing this problem with iPods,
and some have reported it with HDDs. As far as I know none of the
reports have been with a CDROM. Here's a link to the bug.

  http://bugs.launchpad.net/bugs/734883
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