Re: frontswap: is frontswap_init called from swapoff safe?

[Cesar Eduardo Barros]

Em 06-06-2012 21:37, Konrad Rzeszutek Wilk escreveu:
> On Tue, Jun 05, 2012 at 07:41:52AM -0300, Cesar Eduardo Barros wrote:
> > I was looking at the swapfile.c parts of the recently-merged
> > frontswap, and noticed that frontswap_init can be called from
> > swapoff when try_to_unuse fails.
> >
> > This looks odd to me. Whether it is safe or not depends on what
> > frontswap_ops.init does, but the comment for __frontswap_init
> > ("Called when a swap device is swapon'd") and the function name
> > itself seem to imply it should be called only for swapon, not when
> > relinking the swap_info after a failed swapoff.
>
> <nods>
> > In particular, if frontswap_ops.init assumes the swap map is empty,
> > it would break, since as far as I know when try_to_unuse fails there
> > are still pages in the swap.
>
> Let me look at this - can't do it this week - but will get back to you
> shortly.

Did you look at it already? (Just pinging in case you forgot.)

> > (By the way, the comment above enable_swap_info at sys_swapoff needs
> > to be updated to also explain why reading p->frontswap_map outside
> > the lock is safe at that point, like it does for p->prio and
> > p->swap_map.)

--
Cesar Eduardo Barros
cesarb@xxxxxxxxxx
cesar.barros@xxxxxxxxx


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