Re: [PATCH V8 2/2] arm64/mm: Enable memory hot remove

[Anshuman Khandual]

On 09/23/2019 04:47 PM, Matthew Wilcox wrote:
> On Mon, Sep 23, 2019 at 11:13:45AM +0530, Anshuman Khandual wrote:
>> +#ifdef CONFIG_MEMORY_HOTPLUG
>> +static void free_hotplug_page_range(struct page *page, size_t size)
>> +{
>> +	WARN_ON(!page || PageReserved(page));
> 
> WARN_ON(!page) isn't terribly useful.  You're going to crash on the very
> next line when you call page_address() anyway.  If this line were
> 
> 	if (WARN_ON(!page || PageReserved(page)))
> 		return;
> 
> it would make sense, or if it were just
> 
> 	WARN_ON(PageReserved(page))
> 
> it would also make sense.

I guess WARN_ON(PageReserved(page)) should be good enough to make sure
that page being freed here was originally allocated at runtime for a
previous memory hot add operation and did not some how come from the
memblock reserved area. That was the original objective for this check.
Will change it.

> 
>> +	free_pages((unsigned long)page_address(page), get_order(size));
>> +}
>