Re: [PATCH] mm: move page_ext_init after all struct pages are initialized

[Shi, Yang]

On 5/19/2016 4:21 PM, Andrew Morton wrote:
> On Thu, 19 May 2016 15:35:15 -0700 "Shi, Yang" <yang.shi@xxxxxxxxxx> wrote:
>
> > On 5/19/2016 3:30 PM, Andrew Morton wrote:
> > > On Thu, 19 May 2016 14:29:05 -0700 Yang Shi <yang.shi@xxxxxxxxxx> wrote:
> > >
> > > > When DEFERRED_STRUCT_PAGE_INIT is enabled, just a subset of memmap at boot
> > > > are initialized, then the rest are initialized in parallel by starting one-off
> > > > "pgdatinitX" kernel thread for each node X.
> > > >
> > > > If page_ext_init is called before it, some pages will not have valid extension,
> > > > so move page_ext_init() after it.
> > >
> > > <stdreply>When fixing a bug, please fully describe the end-user impact
> > > of that bug</>
> >
> > The kernel ran into the below oops which is same with the oops reported
> > in
> > http://ozlabs.org/~akpm/mmots/broken-out/mm-page_is_guard-return-false-when-page_ext-arrays-are-not-allocated-yet.patch.
>
> So this patch makes
> mm-page_is_guard-return-false-when-page_ext-arrays-are-not-allocated-yet.patch
> obsolete?

Actually, no. Checking the return value for lookup_page_ext() is still 
needed. But, the commit log need to be amended since that bootup oops 
won't happen anymore with this patch applied.

Thanks,
Yang

>