Re: [RFC][PATCH 2/3] swsusp: Do not use page flags

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

Rafael J. Wysocki wrote:
> On Tuesday, 13 March 2007 10:23, Nick Piggin wrote:
> 

>>I wouldn't say that. You're creating an interface here that is going to be
>>used outside swsusp. Users of that interface may not need locking now, but
>>that could cause problems down the line.
> 
> 
> I think we can add the locking when it's necessary.  For now, IMHO, it could be
> confusing to someone who doesn't know the locking is not needed.

I don't know why it would confuse them. We just define the API to
guarantee the correct locking, and that means the locking _is_ needed.

You don't have to care what the callers are doing. That's the beauty
of a sane API.


>>Sure you don't _need_ an rbtree, but our implementation makes it so simple
>>that there isn't much downside.
> 
> 
> Not much, but the code is more complicated.

But it's in its own file and has a contained API, so it is very easy
to review, test and verify.


>>>mark_nosave_pages() refers to a function that's invisible outside snapshot.c
>>>and I didn't think it was a good idea to separate mark_nosave_pages()
>>>from register_nosave_region().
>>
>>But that's because you even use mark_nosave_pages in your implementation.
>>Mine uses the nosave regions directly.
> 
> 
> Well, I think we need two bits per page anyway, to mark free pages and
> pages allocated by swsusp, so using the nosave regions directly won't save us
> much.

Well I think it is a cleaner though.

-- 
SUSE Labs, Novell Inc.
Send instant messages to your online friends http://au.messenger.yahoo.com