Re: [PATCH] mm/page_alloc: Ensure that HUGETLB_PAGE_ORDER is less than MAX_ORDER

2021-04-09 Thread Anshuman Khandual 



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 
>> Cc: linux...@kvack.org
>> Cc: linux-kernel@vger.kernel.org
>> Signed-off-by: Anshuman Khandual 
>> ---
>>   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.
>>
> 
>

Re: [PATCH] mm/page_alloc: Ensure that HUGETLB_PAGE_ORDER is less than MAX_ORDER

2021-04-09 Thread David Hildenbrand 

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 
Cc: linux...@kvack.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual 
---
  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

[PATCH] mm/page_alloc: Ensure that HUGETLB_PAGE_ORDER is less than MAX_ORDER

2021-04-08 Thread Anshuman Khandual 
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 
Cc: linux...@kvack.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual 
---
 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