Re: [PATCH v7] mm/page_alloc.c: memory_hotplug: free pages as higher order

[Arun KS]

On 2019-01-08 23:43, Michal Hocko wrote:
> On Tue 08-01-19 09:56:09, Alexander Duyck wrote:
> > On Fri, 2019-01-04 at 10:31 +0530, Arun KS wrote:
> [...]
> > >  static int online_pages_range(unsigned long start_pfn, unsigned long nr_pages,
> > >  			void *arg)
> > >  {
> > > -	unsigned long i;
> > >  	unsigned long onlined_pages = *(unsigned long *)arg;
> > > -	struct page *page;
> > >
> > >  	if (PageReserved(pfn_to_page(start_pfn)))
> > > -		for (i = 0; i < nr_pages; i++) {
> > > -			page = pfn_to_page(start_pfn + i);
> > > -			(*online_page_callback)(page);
> > > -			onlined_pages++;
> > > -		}
> > > +		onlined_pages = online_pages_blocks(start_pfn, nr_pages);
> >
> > Shouldn't this be a "+=" instead of an "="? It seems like you are 
> > going
> > to lose your count otherwise.
>
> You are right of course. I should have noticed during the review.
> Thanks!

I think we don't need to. The caller function is setting onlined_pages = 
0 before calling online_pages_range().
And there are no other reference to online_pages_range other than from 
online_pages().

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/mm/memory_hotplug.c?h=v5.0-rc1#n845

int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int 
online_type)
{
        unsigned long flags;
        unsigned long onlined_pages = 0;

Regards,
Arun