linux-kernel - Re: hfsplus mount regression in 2.6.38

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Message-ID: <20110630131012.GA19309@thinkpad-t410>
Date:	Thu, 30 Jun 2011 14:10:12 +0100
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 Thu, Jun 30, 2011 at 07:35:20AM -0400, Christoph Hellwig wrote:
> On Thu, Jun 02, 2011 at 04:58:21PM -0500, Seth Forshee wrote:
> > I took a crack at converting the users of direct bio to use
> > bdev_logical_block_size instead of HFSPLUS_SECTOR_SIZE. sb->s_blocksize
> > doesn't turn out to work because it may change after reading the
> > volume header. The patch is below; feedback is appreciated.
> > 
> > So far I've only done light testing, and no testing with large-sector
> > devices since I don't have any to test with. I'm still concerned about
> > duplicating data also in the page cache with this approach. Any thoughts
> > on whether or not this is something to be worried about?
> 
> Did you manage to test it on a large sector device?

I've gotten some test results back, but the results are mixed. I haven't
had much time yet to try to find out what's going wrong, but I hope to
do so soon.

> I'm be rather surprised if we actually need the read modify write
> cycles.  I've not seen any filesystem that doesn't align it's metadata
> to the sector size yet.

I agree. What I was more concerned about was that if you had e.g. a 2 KB
sector device, metadata could possibly end up in the filesystem cache
along with some file data in an adjacent block, and that as a result you
could overwrite that data structure with stale data.
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