Re: [PATCH 1/2] mm: Allow architectures to request 'old' entries when prefaulting

Linus Torvalds
2020-12-18T18:58:41Z

On Fri, Dec 18, 2020 at 3:04 AM Kirill A. Shutemov <kirill@shutemov.name> wrote:
>
> This should do. See below.

Looks fine.

> > Then that second loop very naturally becomes a "do { } while ()" one.
>
> I don't see it. I haven't found a reasonable way to rework it do-while.

Now that you return early for the "HEAD == NULL" case, this loop:

for (; head; head = xas_next_entry(&xas, end_pgoff)) {
[...]
}

very naturally becomes

do {
[...]
} while ((head = xas_next_entry(&xas, end_pgoff)) != NULL);

because the initial test for 'head' being NULL is no longer needed,
and thus it's a lot more logical to just test it at the end of the
loop when we update it.

No?

Maybe I'm missing something silly.

Linus