Re: [PATCH] powerpc: mem_init crash for sparsemem

Andy Whitcroft
2005-11-04T20:19:04Z

Arnd Bergmann wrote:
> I have a Cell blade with some broken memory in the middle of the
> physical address space and this is correctly detected by the
> firmware, but not relocated. When I enable CONFIG_SPARSEMEM,
> the memsections for the nonexistant address space do not
> get struct page entries allocated, as expected.
>
> However, mem_init for the non-NUMA configuration tries to
> access these pages without first looking if they are there.
> I'm currently using the hack below to work around that, but
> I have the feeling that there should be a cleaner solution
> for this.
>
> Please comment.
>
> Signed-off-by: Arnd Bergmann <arndb@de.ibm.com>
>
> --- linux-2.6.15-rc.orig/arch/powerpc/mm/mem.c
> +++ linux-2.6.15-rc/arch/powerpc/mm/mem.c
> @@ -348,6 +348,9 @@ void __init mem_init(void)
> #endif
> for_each_pgdat(pgdat) {
> for (i = 0; i < pgdat->node_spanned_pages; i++) {
> + if (!section_has_mem_map(__pfn_to_section
> + (pgdat->node_start_pfn + i)))
> + continue;
> page = pgdat_page_nr(pgdat, i);
> if (PageReserved(page))
> reservedpages++;

Would it not make sense to use pfn_valid(), as that is not sparsemem
specific? Not looked at the code in question specifically, but if you
can use section_has_mem_map() it should be equivalent:

if (!pfn_valid(pgdat->node_start_pfn + i))
continue;

Want to spin us a patch and I'll give it some general testing.

-apw