On 12/18, Peter Zijlstra wrote:
>
> On Wed, Dec 18, 2013 at 08:19:58PM +0100, Oleg Nesterov wrote:
> > @@ -247,7 +242,7 @@ bool __get_page_tail(struct page *page)
> > bool got;
> > struct page *page_head = compound_trans_head(page);
> >
> > - /* Ref to put_compound_page() comment. */
> > + /* Ref to __put_page_tail() comment. */
> > if (!__compound_tail_refcounted(page_head)) {
> > smp_rmb();
> > if (likely(PageTail(page))) {
>
> What code is this against, my local tree doesn't have that smp_rmb().
This is against -mm code.
> This suggests its a recent patch; which is good since then we can still
> drop it and wait for people to send one with a proper comment in.
put_compound_page() explains this barrier, this is what "Ref" above means,
I guess.
To remind, I think we can do more cleanups here.
Oleg.
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