On Thu, May 25, 2023 at 11:06:40AM +0100, Karim Manaouil wrote:
> Hi,
>
> In do_anonymous_page(), a new page is allocated and zeroed, and the
> corresponding page struct is initialised (setting flags PageUptodate,
> PageSwapBacked, etc. and initialising the various counters).
>
> Then, set_pte_at() is called directly without calling smp_wmb() to make
> the updates above visible on other CPUs.
How are you able to read the code without reading the comment
that explains this?
/*
* The memory barrier inside __SetPageUptodate makes sure that
* preceding stores to the page contents become visible before
* the set_pte_at() write.
*/
__SetPageUptodate(page);
entry = mk_pte(page, vma->vm_page_prot);
That comment has been there since 2013.
