Re: [PATCH v2 1/1] mm: page_alloc: skip over regions of invalid pfns on UMA

[Matthew Wilcox <willy@infradead.org>]

I like the patch.  I think it could be better.

> +++ b/mm/page_alloc.c
> @@ -5344,7 +5344,7 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
>  			goto not_early;
>  
>  		if (!early_pfn_valid(pfn)) {
> -#ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
> +#ifdef CONFIG_HAVE_MEMBLOCK
>  			/*
>  			 * Skip to the pfn preceding the next valid one (or
>  			 * end_pfn), such that we hit a valid pfn (or end_pfn)

This ifdef makes me sad.  Here's more of the context:

                if (!early_pfn_valid(pfn)) {
#ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
                        /*
                         * Skip to the pfn preceding the next valid one (or
                         * end_pfn), such that we hit a valid pfn (or end_pfn)
                         * on our next iteration of the loop.
                         */
                        pfn = memblock_next_valid_pfn(pfn, end_pfn) - 1;
#endif
                        continue;
                }

This is crying out for:

#ifdef CONFIG_HAVE_MEMBLOCK
unsigned long memblock_next_valid_pfn(unsigned long pfn, unsigned long max_pfn);
#else
static inline unsigned long memblock_next_valid_pfn(unsigned long pfn,
		unsigned long max_pfn)
{
	return pfn + 1;
}
#endif

in a header file somewhere.