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

[Arun KS]

On 2019-01-10 00:26, Andrew Morton wrote:
> On Wed, 09 Jan 2019 16:36:36 +0530 Arun KS <arunks@xxxxxxxxxxxxxx> 
> wrote:
>
> > On 2019-01-09 16:27, Michal Hocko wrote:
> > > On Wed 09-01-19 16:12:48, Arun KS wrote:
> > > [...]
> > >> It will be called once per online of a section and the arg value is
> > >> always
> > >> set to 0 while entering online_pages_range.
> > >
> > > You rare right that this will be the case in the most simple scenario.
> > > But the point is that the callback can be called several times from
> > > walk_system_ram_range and then your current code wouldn't work
> > > properly.
> >
> > Thanks. Will use +=
>
> The v8 patch
> https://lore.kernel.org/lkml/1547032395-24582-1-git-send-email-arunks@xxxxxxxxxxxxxx/T/#u
>
> (which you apparently sent 7 minutes after typing the above) still has
>
>  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);
>
>
> Even then the code makes no sense.
>
> static int online_pages_range(unsigned long start_pfn, unsigned long 
> nr_pages,
> 			void *arg)
> {
> 	unsigned long onlined_pages = *(unsigned long *)arg;
>
> 	if (PageReserved(pfn_to_page(start_pfn)))
> 		onlined_pages += online_pages_blocks(start_pfn, nr_pages);
>
> 	online_mem_sections(start_pfn, start_pfn + nr_pages);
>
> 	*(unsigned long *)arg += onlined_pages;
> 	return 0;
> }
>
> Either the final assignment should be
>
> 	*(unsigned long *)arg = onlined_pages;
>
> or the initialization should be
>
> 	unsigned long onlined_pages = 0;
>
>
>
> This is becoming a tad tiresome and I'd prefer not to have to check up
> on such things.  Can we please get this right?

Sorry about that. Will fix it.

Regards,
Arun