Re: page_launder() bug

Marcelo Tosatti
2001-05-08T00:05:51Z

On Mon, 7 May 2001, Linus Torvalds wrote:

>
> On Mon, 7 May 2001, Marcelo Tosatti wrote:
> >
> > So the "dead_swap_page" logic is _not_ buggy and you are full of shit when
> > telling Alan to revert the change. (sorry, I could not avoid this one)
>
> Well, the problem is that the patch _is_ buggy.
>
> swap_writepage() does it right. And dead_swap_page does it wrong. It
> doesn't look at the swap counts, for one thing.

So lets fix it and make it look for the swap counts.

> The patch should be reverted. The fact that other parts of the system do
> it _right_ is not an argument for mm/vmscan.c to do it wrong.

My point is that its _ok_ for us to check if the page is a dead swap cache
page _without_ the lock since writepage() will recheck again with the page
_locked_. Quoting you two messages back:

"But it is important to re-calculate the deadness after getting the lock.
Before, it was just an informed guess. After the lock, it is knowledge."

See ?