memory-hotplug : suppres "Trying to free nonexistent resource <XXXXXXXXXXXXXXXX-YYYYYYYYYYYYYYYY>" warning
Yasuaki Ishimatsu
isimatu.yasuaki at jp.fujitsu.com
Tue Oct 9 13:51:38 EST 2012
Hi Andrew,
2012/10/06 6:09, Andrew Morton wrote:
> On Thu, 4 Oct 2012 14:31:09 +0900
> Yasuaki Ishimatsu <isimatu.yasuaki at jp.fujitsu.com> 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.
Your concern is right. Overflow bug may occur in the future.
So I changed type of "i" and "sections_to_remove" to "unsigned long".
Please merge it into your tree instead of previous patch.
__remove_pages() also has same concern. So I'll fix it.
-----------------------------------------------------------------------
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.
CC: David Rientjes <rientjes at google.com>
CC: Jiang Liu <liuj97 at gmail.com>
CC: Len Brown <len.brown at intel.com>
CC: Benjamin Herrenschmidt <benh at kernel.crashing.org>
CC: Paul Mackerras <paulus at samba.org>
CC: Christoph Lameter <cl at linux.com>
Cc: Minchan Kim <minchan.kim at gmail.com>
CC: Andrew Morton <akpm at linux-foundation.org>
CC: KOSAKI Motohiro <kosaki.motohiro at jp.fujitsu.com>
CC: Wen Congyang <wency at cn.fujitsu.com>
Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki at jp.fujitsu.com>
---
arch/powerpc/platforms/pseries/hotplug-memory.c | 11 ++++++++---
mm/memory_hotplug.c | 4 ++--
2 files changed, 10 insertions(+), 5 deletions(-)
Index: linux-3.6/arch/powerpc/platforms/pseries/hotplug-memory.c
===================================================================
--- linux-3.6.orig/arch/powerpc/platforms/pseries/hotplug-memory.c 2012-10-05 14:33:09.516197839 +0900
+++ linux-3.6/arch/powerpc/platforms/pseries/hotplug-memory.c 2012-10-09 11:27:50.555709827 +0900
@@ -78,6 +78,7 @@ static int pseries_remove_memblock(unsig
unsigned long start, start_pfn;
struct zone *zone;
int ret;
+ unsigned long i, 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;
+ }
/*
* Update memory regions for memory remove
Index: linux-3.6/mm/memory_hotplug.c
===================================================================
--- linux-3.6.orig/mm/memory_hotplug.c 2012-10-05 15:21:42.856325965 +0900
+++ linux-3.6/mm/memory_hotplug.c 2012-10-05 15:21:43.047326148 +0900
@@ -596,11 +596,11 @@ int __remove_pages(struct zone *zone, un
BUG_ON(phys_start_pfn & ~PAGE_SECTION_MASK);
BUG_ON(nr_pages % PAGES_PER_SECTION);
+ release_mem_region(phys_start_pfn << PAGE_SHIFT, nr_pages * PAGE_SIZE);
+
sections_to_remove = nr_pages / PAGES_PER_SECTION;
for (i = 0; i < sections_to_remove; i++) {
unsigned long pfn = phys_start_pfn + i*PAGES_PER_SECTION;
- release_mem_region(pfn << PAGE_SHIFT,
- PAGES_PER_SECTION << PAGE_SHIFT);
ret = __remove_section(zone, __pfn_to_section(pfn));
if (ret)
break;
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