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Date: Tue, 31 Jan 2012 11:48:21 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Christoph Hellwig <hch@infradead.org>
Cc: Niels de Vos <ndevos@redhat.com>, linux-fsdevel@vger.kernel.org,
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        Mikulas Patocka <mpatocka@redhat.com>, Jeff Moyer <jmoyer@redhat.com>,
        "Bryn M. Reeves" <bmr@redhat.com>
Subject: Re: [PATCH v3] fs: Invalidate the cache for a parent block-device
 if fsync() is called for a partition
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On Tue, 31 Jan 2012 14:37:48 -0500
Christoph Hellwig <hch@infradead.org> wrote:

> On Tue, Jan 31, 2012 at 11:32:50AM -0800, Andrew Morton wrote:
> > I didn't say the kernel would support this as-is.
> > 
> > If the partitioning scheme requires writing to the individual
> > partitions then something would need to be done, such as a simple
> > offsetting DM driver.
> 
> Writing partition tables requires writing to them main block device.

This can be done via an offsetting driver.

> Seriously - if people want to support block devices nodes > 16TB dealing
> with this isn't the problem.  They'll need to find a way to do buffered
> I/O without using the pagecache to get it right,

why?  I don't see the problem - supporting /dev/sdaX should be
straightforward.  /dev/sda rarely gets used and would need a bit of
special-case handling.

Please provide all the details as you see them and stop making me email
more questions to you.

> at which point
> blkdev_get_block in either form will simply go away.