Re: filecache/swapcache questions

[kanoj@google.engr.sgi.com (Kanoj Sarcar)]

> > While I have your attention, I think I found a bug in the
> > sys_swapoff algorithm ... basically, it needs to also look 
> > at swap_lockmap. Say an exitting process fired off some async
> > swap ins just before it exitted, and a bunch of these are in
> > flight (swap_lockmaps are set, as are swap_map, from swapcache).
> > The swap device gets deleted (with a printk warning message due
> > to non zero swap_map count). Finally, the old async swap in's 
> > start terminating, invoking swap_after_unlock_page. Interesting
> > things could happen, depending on whether the swap id has been
> > reallocated or not ... Is there any protection against this
> > scenario?
> 
> Yes --- try_to_unuse calls read_swap_cache() with wait==1, so we always
> wait for the IO to complete before swapoff can complete.  At least,
> that's the theory. :)
>

I just figured that one out all by myself :-) Duuh ...

Note to myself : read the code, stupid, before spouting off ...

Thanks, Stephen.

Kanoj 
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