Re: page_launder() bug

[Marcelo Tosatti]

On Mon, 7 May 2001, Linus Torvalds wrote:

> 
> On Mon, 7 May 2001, Marcelo Tosatti wrote:
> > 
> > So what about moving the check for a dead swap cache page from
> > swap_writepage() to page_launder() (+ PageSwapCache() check) just before
> > the "if (!launder_loop)" ? 
> > 
> > Yes, its ugly special casing. Any other suggestion ? 
> 
> My most favourite approach by far is to just remove the magic for
> different writepage's altogether, and just unconditionally do a
> writepage. But passing in enough information so that the writepage can
> come to the right decision.
> 
> So take the old code, and remove the code that does
> 
> 	if (!launder_loop) {
> 		.. move to head ..
> 		continue;
> 	}
> 	writepage(page);
> 
> and instead make it do something like
> 
> 	if (writepage(page, launderloop)) {
> 		.. not able to write, move to head ..
> 		continue;
> 	}
> 
> where "launderloop" is passed in to the writepage function as a priority.

There are two issues which I missed yesterday: we have to get a reference
on the page, mark it clean, drop the locks and then call writepage(). If
the writepage() fails, we'll have to set_page_dirty(page).

I guess this is too much overhead for the common case, don't you?