Re: [PATCH v4 3/6] mm: Add build time sanity check for struct page size

[Baoquan He]

On 03/14/19 at 05:46pm, Baoquan He wrote:
> Size of struct page might be larger than 64 bytes if debug options
> enabled, or fields added for debugging intentionally. Yet an upper
> limit need be added at build time to trigger an alert in case the
> size is too big to boot up system, warning people to check if it's
> be done on purpose in advance.
> 
> Here 1/4 of PAGE_SIZE is chosen since system must have been insane
> with this value. For those systems with PAGE_SIZE larger than 4KB,
> 1KB is simply taken.
> 
> Signed-off-by: Baoquan He <bhe@xxxxxxxxxx>
> Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>

Sorry, I forgot adding 'Acked-by' tag here.

> ---
>  mm/page_alloc.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 3eb01dedfb50..eddf96c137f2 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -67,6 +67,7 @@
>  #include <linux/lockdep.h>
>  #include <linux/nmi.h>
>  #include <linux/psi.h>
> +#include <linux/sizes.h>
>  
>  #include <asm/sections.h>
>  #include <asm/tlbflush.h>
> @@ -7170,6 +7171,7 @@ void __init free_area_init_nodes(unsigned long *max_zone_pfn)
>  	unsigned long start_pfn, end_pfn;
>  	int i, nid;
>  
> +	BUILD_BUG_ON(sizeof(struct page) > min_t(size_t, SZ_1K, PAGE_SIZE/4));
>  	/* Record where the zone boundaries are */
>  	memset(arch_zone_lowest_possible_pfn, 0,
>  				sizeof(arch_zone_lowest_possible_pfn));
> -- 
> 2.17.2
>