Re: [linux-pm] Re: Hibernation considerations

Rafael J. Wysocki
2007-07-20T21:22:38Z

On Friday, 20 July 2007 19:31, Jeremy Maitin-Shepard wrote:
> Milton Miller <miltonm@bga.com> writes:
>
> [snip]
>
> >>>> (7) how to avoid corrupting filesystems mounted by the hibernated kernel
> >>>
> >>> I didn't realize this was a discussion item. I thought the options were
> >>> clear, for some filesystem types you can mount them read-only, but for
> >>> ext3 (and possilby other less common ones) you just plain cannot touch
> >>> them.
> >>
> >> That's correct. And since you cannot thouch ext3, you need either to assume
> >> that you won't touch filesystems at all, or to have a code to recognize the
> >> filesystem you're dealing with.
>
> > Or add a small bit of infrastructure that errors writes at make_request if you
> > don't have a magic "i am a direct block device write from userspace" flag on the
> > bio.
>
> I still don't understand why there is this fixation on accessing dirty
> filesystems in use by the hibernated system. Even if you avoid
> corrupting the filesystem by avoiding writing to the block device, there
> isn't any real guarantee about the state of the data, except for a
> filesystem that specifically makes guarantees about such data (and I
> don't believe any of the existing ones do).
>
> It isn't necessary to be able to access such filesystems: everything can
> be done from an initramfs/initrd.

That's correct, but you need an additional ramdisk for that (yet another
complication).

Greetings,
Rafael

--
"Premature optimization is the root of all evil." - Donald Knuth