Re: [RFC][PATCH] block: Isolate the buffer cache in it's own mappings.

[Nick Piggin <nickpiggin@yahoo.com.au>]

On Saturday 20 October 2007 07:27, Eric W. Biederman wrote:
> Andrew Morton <akpm@linux-foundation.org> writes:
> > I don't think we little angels want to tread here.  There are so many
> > weirdo things out there which will break if we bust the coherence between
> > the fs and /dev/hda1.
>
> We broke coherence between the fs and /dev/hda1 when we introduced
> the page cache years ago,

Not for metadata. And I wouldn't expect many filesystem analysis
tools to care about data.


> and weird hacky cases like 
> unmap_underlying_metadata don't change that.

unmap_underlying_metadata isn't about raw block device access at
all, though (if you write to the filesystem via the blockdevice
when it isn't expecting it, it's going to blow up regardless).


> Currently only 
> metadata is more or less in sync with the contents of /dev/hda1.

It either is or it isn't, right? And it is, isn't it? (at least
for the common filesystems).
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