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

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Date:   Thu, 14 Mar 2019 17:57:30 +0800
From:   Baoquan He <bhe@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     mingo@...nel.org, keescook@...omium.org, kirill@...temov.name,
        yamada.masahiro@...ionext.com, tglx@...utronix.de, bp@...en8.de,
        hpa@...or.com, dave.hansen@...ux.intel.com, luto@...nel.org,
        peterz@...radead.org, x86@...nel.org, thgarnie@...gle.com
Subject: Re: [PATCH v4 3/6] mm: Add build time sanity check for struct page
 size

On 03/14/19 at 05:50pm, Baoquan He wrote:
> 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@...hat.com>
> > Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> 
> Sorry, I forgot adding 'Acked-by' tag here.
 Should be "Suggested-by:" tag.

> 
> > ---
> >  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
> >