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SubjectRe: Dump corrupts ext2?
Chris Mason writes:
>
>
> On Wednesday, October 10, 2001 07:33:55 PM -0600 Richard Gooch <rgooch@ras.ucalgary.ca> wrote:
>
> > Andreas Dilger writes:
>
> >> In Linus kernels 2.4.11+ the block devices and filesystems all use
> >> the page cache, so no more coherency issues.
> >
> > Um, I thought that there wasn't going to be coherency? For example, if
> > you open /dev/sda and /dev/sda1, they each have a separate cache. I
> > remember some debate about this, and Linus pointed out how hard it was
> > to make things coherent.
>
> They all use the page cache, but they still use different address
> spaces.

OK, different "address spaces". I didn't recall the precise
terminology :-)

> The block device and getblk share the same address space, so the metadata
> and the block device are on the same cache, except for ext2 directories,
> which act like files do. Each file has its own address space, so that
> isn't coherent with the block device.
>
> In other words, block device reads with the FS mounted will probably
> never give consistent results.

Indeed.

Regards,

Richard....
Permanent: rgooch@atnf.csiro.au
Current: rgooch@ras.ucalgary.ca
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