Re: invalidate_inode_pages2

[Andrew Morton <akpm@osdl.org>]

Andrea Arcangeli <andrea@suse.de> wrote:
>
> Something broke in invalidate_inode_pages2 between 2.4 and 2.6, this
> causes malfunctions with mapped pages in 2.6.

What is the malfunction?

> I guess the below untested one liner should be enough to fix it. The
> only single point of invalidate_inode_pages2, is to invalidate _mapped_
> pages too. Otherwise we could as well use invalidate_inode_pages.
> Clearly the dirty bit doesn't mean invalidate, invalidate primarly means
> clearing the uptodate bitflag.
> 
> --- sles/mm/truncate.c.~1~	2004-05-18 19:24:40.000000000 +0200
> +++ sles/mm/truncate.c	2004-05-19 02:09:28.311781864 +0200
> @@ -260,9 +260,10 @@ void invalidate_inode_pages2(struct addr
>  			if (page->mapping == mapping) {	/* truncate race? */
>  				wait_on_page_writeback(page);
>  				next = page->index + 1;
> -				if (page_mapped(page))
> +				if (page_mapped(page)) {
> +					ClearPageUptodate(page);
>  					clear_page_dirty(page);
> -				else
> +				} else
>  					invalidate_complete_page(mapping, page);
>  			}
>  			unlock_page(page);

It's currently the case that pages which are mapped into process pagetables
are always up to date, which sounds like a good invariant to have.  This
changes that rule.  I dunno if it'll break anything though.