Re: shrink_mmap bug in 2.2?

[volodya@mindspring.com]

On Wed, 14 Jun 2000, Kanoj Sarcar wrote:

> > 
> > This code looks strange to me (possibly because I don't
> > understand it):
> > 
> >     /*
> >      * Is it a page swap page? If so, we want to
> >      * drop it if it is no longer used, even if it
> >      * were to be marked referenced..
> >      */
> >     if (PageSwapCache(page)) {
> >             if (referenced && swap_count(page->offset) != 1)
> >                     continue;
> >             delete_from_swap_cache(page);
> >             return 1;
> >     }       
> 
> Aren't you misreading the logic here? It is
> 
> 	referenced && swap_count(page->offset) != 1)
> 	          ^^^^
> and not
> 
> 	referenced || swap_count(page->offset) != 1)
>                  ^^^^^
> 
> So delete_from_swap_cache will only ever be called on a page
> with swap_count(page->offset) == 1.
> 

This evades me. We delete when the condition is false. So if referenced is
0  if will not happen and we delete the page..

                                 Vladimir Dergachev
> Kanoj
> 
> > 
> > Can pages be deleted from the swap cache if swap_count is not
> > one?  If not, then I think this code is wrong.  It should be:
> > 
> >     if (PageSwapCache(page)) {
> >             if (swap_count(page->offset) != 1)
> >                     continue;
> >             delete_from_swap_cache(page);
> >             return 1;
> >     }       
> >  
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