On Thu, 4 Oct 2012 14:31:09 +0900
Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx> wrote:
> When our x86 box calls __remove_pages(), release_mem_region() shows
> many warnings. And x86 box cannot unregister iomem_resource.
>
> "Trying to free nonexistent resource <XXXXXXXXXXXXXXXX-YYYYYYYYYYYYYYYY>"
>
> release_mem_region() has been changed as called in each PAGES_PER_SECTION
> chunk since applying a patch(de7f0cba96786c). Because powerpc registers
> iomem_resource in each PAGES_PER_SECTION chunk. But when I hot add memory
> on x86 box, iomem_resource is register in each _CRS not PAGES_PER_SECTION
> chunk. So x86 box unregisters iomem_resource.
>
> The patch fixes the problem.
>
> --- linux-3.6.orig/arch/powerpc/platforms/pseries/hotplug-memory.c 2012-10-04 14:22:59.833520792 +0900
> +++ linux-3.6/arch/powerpc/platforms/pseries/hotplug-memory.c 2012-10-04 14:23:05.150521411 +0900
> @@ -77,7 +77,8 @@ static int pseries_remove_memblock(unsig
> {
> unsigned long start, start_pfn;
> struct zone *zone;
> - int ret;
> + int i, ret;
> + int sections_to_remove;
>
> start_pfn = base >> PAGE_SHIFT;
>
> @@ -97,9 +98,13 @@ static int pseries_remove_memblock(unsig
> * to sysfs "state" file and we can't remove sysfs entries
> * while writing to it. So we have to defer it to here.
> */
> - ret = __remove_pages(zone, start_pfn, memblock_size >> PAGE_SHIFT);
> - if (ret)
> - return ret;
> + sections_to_remove = (memblock_size >> PAGE_SHIFT) / PAGES_PER_SECTION;
> + for (i = 0; i < sections_to_remove; i++) {
> + unsigned long pfn = start_pfn + i * PAGES_PER_SECTION;
> + ret = __remove_pages(zone, start_pfn, PAGES_PER_SECTION);
> + if (ret)
> + return ret;
> + }
It is inappropriate that `i' have a signed 32-bit type. I doubt if
there's any possibility of an overflow bug here, but using a consistent
and well-chosen type would eliminate all doubt.
Note that __remove_pages() does use an unsigned long for this, although
it stupidly calls that variable "i", despite the C programmers'
expectation that a variable called "i" has type "int".
The same applies to `sections_to_remove', but __remove_pages() went and
decided to use an `int' for that variable. Sigh.
Anyway, please have a think, and see if we can come up with the best
and most accurate choice of types and identifiers in this code.
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