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

[Bob Picco]

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.

bob

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