Re: [patch 7/14] mm: remove bad_range

[Nick Piggin]

Bob Picco wrote:
> Nick Piggin wrote:	[Sun Nov 06 2005, 03:24:40AM EST]
>
> > 7/14
> >
> > --
> > SUSE Labs, Novell Inc.
>
>
> > bad_range is supposed to be a temporary check. It would be a pity to throw
> > it out. Make it depend on CONFIG_DEBUG_VM instead.
> >
> > Index: linux-2.6/mm/page_alloc.c
> > ===================================================================
> > --- linux-2.6.orig/mm/page_alloc.c
> > +++ linux-2.6/mm/page_alloc.c
> > @@ -78,6 +78,7 @@ int min_free_kbytes = 1024;
> > unsigned long __initdata nr_kernel_pages;
> > unsigned long __initdata nr_all_pages;
> >
> > +#ifdef CONFIG_DEBUG_VM
> > static int page_outside_zone_boundaries(struct zone *zone, struct page *page)
> > {
> > 	int ret = 0;
> > @@ -119,6 +120,13 @@ static int bad_range(struct zone *zone, 
> > 	return 0;
> > }
> >
> > +#else
> > +static inline int bad_range(struct zone *zone, struct page *page)
> > +{
> > +	return 0;
> > +}
> > +#endif
> > +
> > static void bad_page(const char *function, struct page *page)
> > {
> > 	printk(KERN_EMERG "Bad page state at %s (in process '%s', page %p)\n",
> > Index: linux-2.6/lib/Kconfig.debug
> > ===================================================================
> > --- linux-2.6.orig/lib/Kconfig.debug
> > +++ linux-2.6/lib/Kconfig.debug
> > @@ -172,7 +172,8 @@ config DEBUG_VM
> > 	bool "Debug VM"
> > 	depends on DEBUG_KERNEL
> > 	help
> > -	  Enable this to debug the virtual-memory system.
> > +	  Enable this to turn on extended checks in the virtual-memory system
> > +          that may impact performance.
> >
> > 	  If unsure, say N.
>
> Nick,
>
> I don't think you can do it this way. On ia64 VIRTUAL_MEM_MAP depends on 
> CONFIG_HOLES_IN_ZONE and the check within bad_range for pfn_valid. Holes in
> memory (MMIO and etc.) won't have a page structure.

Hmm, right - in __free_pages_bulk.

Could we make a different call here, or is the full array of bad_range
checks required?

Thanks,
Nick

--
SUSE Labs, Novell Inc.

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