* [PATCH] mm/page_alloc: Ensure that HUGETLB_PAGE_ORDER is less than MAX_ORDER
@ 2021-04-09 5:55 Anshuman Khandual
2021-04-09 8:24 ` David Hildenbrand
0 siblings, 1 reply; 3+ messages in thread
From: Anshuman Khandual @ 2021-04-09 5:55 UTC (permalink / raw)
To: linux-mm; +Cc: Anshuman Khandual, Andrew Morton, linux-kernel
pageblock_order must always be less than MAX_ORDER, otherwise it might lead
to an warning during boot. A similar problem got fixed on arm64 platform
with the commit 79cc2ed5a716 ("arm64/mm: Drop THP conditionality from
FORCE_MAX_ZONEORDER"). Assert the above condition before HUGETLB_PAGE_ORDER
gets assigned as pageblock_order. This will help detect the problem earlier
on platforms where HUGETLB_PAGE_SIZE_VARIABLE is enabled.
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
mm/page_alloc.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 604dcd69397b..81b7460e1228 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -7068,10 +7068,17 @@ void __init set_pageblock_order(void)
if (pageblock_order)
return;
- if (HPAGE_SHIFT > PAGE_SHIFT)
+ if (HPAGE_SHIFT > PAGE_SHIFT) {
+ /*
+ * pageblock_order must always be less than
+ * MAX_ORDER. So does HUGETLB_PAGE_ORDER if
+ * that is being assigned here.
+ */
+ WARN_ON(HUGETLB_PAGE_ORDER >= MAX_ORDER);
order = HUGETLB_PAGE_ORDER;
- else
+ } else {
order = MAX_ORDER - 1;
+ }
/*
* Assume the largest contiguous order of interest is a huge page.
--
2.20.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] mm/page_alloc: Ensure that HUGETLB_PAGE_ORDER is less than MAX_ORDER
2021-04-09 5:55 [PATCH] mm/page_alloc: Ensure that HUGETLB_PAGE_ORDER is less than MAX_ORDER Anshuman Khandual
@ 2021-04-09 8:24 ` David Hildenbrand
2021-04-09 8:37 ` Anshuman Khandual
0 siblings, 1 reply; 3+ messages in thread
From: David Hildenbrand @ 2021-04-09 8:24 UTC (permalink / raw)
To: Anshuman Khandual, linux-mm; +Cc: Andrew Morton, linux-kernel
On 09.04.21 07:55, Anshuman Khandual wrote:
> pageblock_order must always be less than MAX_ORDER, otherwise it might lead
> to an warning during boot. A similar problem got fixed on arm64 platform
> with the commit 79cc2ed5a716 ("arm64/mm: Drop THP conditionality from
> FORCE_MAX_ZONEORDER"). Assert the above condition before HUGETLB_PAGE_ORDER
> gets assigned as pageblock_order. This will help detect the problem earlier
> on platforms where HUGETLB_PAGE_SIZE_VARIABLE is enabled.
>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: linux-mm@kvack.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
> ---
> mm/page_alloc.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 604dcd69397b..81b7460e1228 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -7068,10 +7068,17 @@ void __init set_pageblock_order(void)
> if (pageblock_order)
> return;
>
> - if (HPAGE_SHIFT > PAGE_SHIFT)
> + if (HPAGE_SHIFT > PAGE_SHIFT) {
> + /*
> + * pageblock_order must always be less than
> + * MAX_ORDER. So does HUGETLB_PAGE_ORDER if
> + * that is being assigned here.
> + */
> + WARN_ON(HUGETLB_PAGE_ORDER >= MAX_ORDER);
Can't that be a BUILD_BUG_ON() ?
> order = HUGETLB_PAGE_ORDER;
> - else
> + } else {
> order = MAX_ORDER - 1;
> + }
>
> /*
> * Assume the largest contiguous order of interest is a huge page.
>
--
Thanks,
David / dhildenb
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] mm/page_alloc: Ensure that HUGETLB_PAGE_ORDER is less than MAX_ORDER
2021-04-09 8:24 ` David Hildenbrand
@ 2021-04-09 8:37 ` Anshuman Khandual
0 siblings, 0 replies; 3+ messages in thread
From: Anshuman Khandual @ 2021-04-09 8:37 UTC (permalink / raw)
To: David Hildenbrand, linux-mm; +Cc: Andrew Morton, linux-kernel
On 4/9/21 1:54 PM, David Hildenbrand wrote:
> On 09.04.21 07:55, Anshuman Khandual wrote:
>> pageblock_order must always be less than MAX_ORDER, otherwise it might lead
>> to an warning during boot. A similar problem got fixed on arm64 platform
>> with the commit 79cc2ed5a716 ("arm64/mm: Drop THP conditionality from
>> FORCE_MAX_ZONEORDER"). Assert the above condition before HUGETLB_PAGE_ORDER
>> gets assigned as pageblock_order. This will help detect the problem earlier
>> on platforms where HUGETLB_PAGE_SIZE_VARIABLE is enabled.
>>
>> Cc: Andrew Morton <akpm@linux-foundation.org>
>> Cc: linux-mm@kvack.org
>> Cc: linux-kernel@vger.kernel.org
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
>> ---
>> mm/page_alloc.c | 11 +++++++++--
>> 1 file changed, 9 insertions(+), 2 deletions(-)
>>
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index 604dcd69397b..81b7460e1228 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -7068,10 +7068,17 @@ void __init set_pageblock_order(void)
>> if (pageblock_order)
>> return;
>> - if (HPAGE_SHIFT > PAGE_SHIFT)
>> + if (HPAGE_SHIFT > PAGE_SHIFT) {
>> + /*
>> + * pageblock_order must always be less than
>> + * MAX_ORDER. So does HUGETLB_PAGE_ORDER if
>> + * that is being assigned here.
>> + */
>> + WARN_ON(HUGETLB_PAGE_ORDER >= MAX_ORDER);
>
> Can't that be a BUILD_BUG_ON() ?
Yes, it can be. Probably might be appropriate as well, given that both
the arguments here are compile time constants. Okay, will change.
>
>> order = HUGETLB_PAGE_ORDER;
>> - else
>> + } else {
>> order = MAX_ORDER - 1;
>> + }
>> /*
>> * Assume the largest contiguous order of interest is a huge page.
>>
>
>
^ permalink raw reply [flat|nested] 3+ messages in thread
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2021-04-09 5:55 [PATCH] mm/page_alloc: Ensure that HUGETLB_PAGE_ORDER is less than MAX_ORDER Anshuman Khandual
2021-04-09 8:24 ` David Hildenbrand
2021-04-09 8:37 ` Anshuman Khandual
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