linux-kernel - Re: [PATCH v1] drivers/base/memory.c: Don't store end_section

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Date:   Wed, 31 Jul 2019 13:57:15 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     David Hildenbrand <david@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Michal Hocko <mhocko@...e.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Oscar Salvador <osalvador@...e.de>
Subject: Re: [PATCH v1] drivers/base/memory.c: Don't store end_section_nr in
 memory blocks

On Wed, 31 Jul 2019 14:22:13 +0200 David Hildenbrand <david@...hat.com> wrote:

> Each memory block spans the same amount of sections/pages/bytes. The size
> is determined before the first memory block is created. No need to store
> what we can easily calculate - and the calculations even look simpler now.
> 
> While at it, fix the variable naming in register_mem_sect_under_node() -
> we no longer talk about a single section.
> 
> ...
>
> --- a/include/linux/memory.h
> +++ b/include/linux/memory.h
> @@ -40,6 +39,8 @@ int arch_get_memory_phys_device(unsigned long start_pfn);
>  unsigned long memory_block_size_bytes(void);
>  int set_memory_block_size_order(unsigned int order);
>  
> +#define PAGES_PER_MEMORY_BLOCK (memory_block_size_bytes() / PAGE_SIZE)

Please let's not hide function calls inside macros which look like
compile-time constants!  Adding "()" to the macro would be a bit
better.  Making it a regular old inline C function would be better
still.  But I'd suggest just open-coding this at the macro's single
callsite.