Re: [ 00/10] [Suspend2] Modules support.

[Nigel Cunningham <nigel@suspend2.net>]

Hi.

On Thursday 02 February 2006 21:59, Pavel Machek wrote:
> On Čt 02-02-06 21:31:55, Nigel Cunningham wrote:
> > Hi.
> >
> > On Thursday 02 February 2006 20:47, Pavel Machek wrote:
> > > Hi!
> > >
> > > > > swsusp already has a very strong API to separate image writing from
> > > > > image creation (in -mm patch, anyway). It is also very nice, just
> > > > > read() from /dev/snapshot. Please use it.
> > > >
> > > > You know that's not an option.
> > >
> > > No, I don't... please explain. Switching to this interface is going to
> > > be easier than pushing suspend2 into kernel. Granted, end result may
> > > not be suspend2, it may be something like suspend3, but it will be
> > > better result than u-swsusp or suspend2 is today...
> >
> > It's not an option because I'm not trying not to step all over your
> > codebase, because I'm not moving suspend2 to userspace and because it
> > doesn't make sense to add another layer of abstraction by sticking
> > /dev/snapshot in the middle of kernel space code. There may be more
> > reasons, but I haven't looked at the /dev/snapshot code at all.
>
> Please take a look at /dev/snapshot.
>
> Parse error at the first sentence (too many nots), anyway:
>
> 1) we do not want two implementations of same code in kernel. [swsusp
> vs. pmdisk was a mess]
>
> 2) we are not going to merge code into kernel, when it is possible to
> do same thing in userspace. (*)
>
> 3) backwards compatibility is important in stable series.
>
> 4) merging code into kernel is a lot of work.
>
> I do not think I want to remove swsusp from kernel. Even if I wanted
> to, there's 3). That means suspend2 should not go in (see 1). Even if I
> removed swsusp from kernel, suspend2 is not going to be merged,
> because of 2). Even if world somehow forgot that it is possible to do
> suspend2 in userspace, merging 10K lines of code is (4) still lot of
> work.
>
> Oops, that looks bad for suspend2 merge. I really think you should
> take a look at /dev/snapshot. Unless it is terminally broken, I can't
> see how suspend2 could be merged.

I don't want to argue Pavel. I want to give users the best suspend to disk 
implementation they can get. If you want to argue, you can do so with 
yourself. Meanwhile, I'll work on getting Suspend2 ready for merging, and let 
Andrew and Linus decide what they think should happen. If they want to step 
in now and tell me not to bother, I'll happily listen and just maintain the 
patches out of kernel until you and Rafael get swsusp up to scratch. I'll 
even cc them now so they can have the opportunity to tell me not to bother. 
But that's not what I've heard so far. In previous correspondence between us, 
Andrew has seemed keen to get a better implementation in, and Linus said 
something to the effect of "I'm sold" when I gave him an impromptu demo last 
week at LCA (Linus, if you read this, feel free to tell me if my memory is 
faulty and I'm putting words in your mouth).

As to backwards compatability, that shouldn't be hard to do.

Regards,

Nigel

> 									Pavel
> (*) or very close to same thing. We still can't save memory full of caches.

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