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SubjectRe: [PATCH v7] mm/page_alloc.c: memory_hotplug: free pages as higher order
On 2019-01-10 00:26, Andrew Morton wrote:
> On Wed, 09 Jan 2019 16:36:36 +0530 Arun KS <arunks@codeaurora.org>
> 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@codeaurora.org/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

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