Patchwork memory-hotplug : suppres "Trying to free nonexistent resource <XXXXXXXXXXXXXXXX-YYYYYYYYYYYYYYYY>" warning

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Submitter Yasuaki Ishimatsu
Date Oct. 4, 2012, 5:31 a.m.
Message ID <506D1F1D.9000301@jp.fujitsu.com>
Download mbox | patch
Permalink /patch/189049/
State Not Applicable
Headers show

Comments

Yasuaki Ishimatsu - Oct. 4, 2012, 5:31 a.m.
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@google.com>
CC: Jiang Liu <liuj97@gmail.com>
CC: Len Brown <len.brown@intel.com>
CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
CC: Paul Mackerras <paulus@samba.org>
CC: Christoph Lameter <cl@linux.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
CC: Wen Congyang <wency@cn.fujitsu.com>
Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
---
 arch/powerpc/platforms/pseries/hotplug-memory.c |   13 +++++++++----
 mm/memory_hotplug.c                             |    4 ++--
 2 files changed, 11 insertions(+), 6 deletions(-)
KOSAKI Motohiro - Oct. 5, 2012, 7:01 p.m.
CC to Dave Hanse.

Hello Dave,

I think following patch works both x86 and ppc. but I'm not ppc
expert. So I'm glad
if you double check it.

thank you.


<intentional full quote>

> 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@google.com>
> CC: Jiang Liu <liuj97@gmail.com>
> CC: Len Brown <len.brown@intel.com>
> CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> CC: Paul Mackerras <paulus@samba.org>
> CC: Christoph Lameter <cl@linux.com>
> Cc: Minchan Kim <minchan.kim@gmail.com>
> CC: Andrew Morton <akpm@linux-foundation.org>
> CC: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> CC: Wen Congyang <wency@cn.fujitsu.com>
> Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
> ---
>  arch/powerpc/platforms/pseries/hotplug-memory.c |   13 +++++++++----
>  mm/memory_hotplug.c                             |    4 ++--
>  2 files changed, 11 insertions(+), 6 deletions(-)
>
> Index: linux-3.6/arch/powerpc/platforms/pseries/hotplug-memory.c
> ===================================================================
> --- linux-3.6.orig/arch/powerpc/platforms/pseries/hotplug-memory.c      2012-10-04 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;
> +       }
>
>         /*
>          * Update memory regions for memory remove
> Index: linux-3.6/mm/memory_hotplug.c
> ===================================================================
> --- linux-3.6.orig/mm/memory_hotplug.c  2012-10-04 14:22:59.829520788 +0900
> +++ linux-3.6/mm/memory_hotplug.c       2012-10-04 14:23:25.860527278 +0900
> @@ -362,11 +362,11 @@ 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;
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
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> see: http://www.linux-mm.org/ .
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Andrew Morton - Oct. 5, 2012, 9:09 p.m.
On Thu, 4 Oct 2012 14:31:09 +0900
Yasuaki Ishimatsu <isimatu.yasuaki@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.

Patch

Index: linux-3.6/arch/powerpc/platforms/pseries/hotplug-memory.c
===================================================================
--- 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;
+	}
 
 	/*
 	 * Update memory regions for memory remove
Index: linux-3.6/mm/memory_hotplug.c
===================================================================
--- linux-3.6.orig/mm/memory_hotplug.c	2012-10-04 14:22:59.829520788 +0900
+++ linux-3.6/mm/memory_hotplug.c	2012-10-04 14:23:25.860527278 +0900
@@ -362,11 +362,11 @@  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;