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Subject: Re: [PATCH] mm/pgtable/debug: Fix test validating architecture page
 table helpers
To:     Anshuman Khandual <anshuman.khandual@arm.com>, linux-mm@kvack.org
Cc:     Mark Rutland <mark.rutland@arm.com>, linux-ia64@vger.kernel.org,
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References: <1892b37d1fd9a4ed39e76c4b999b6556077201c0.1568355752.git.christophe.leroy@c-s.fr>
 <527dd29d-45fa-4d83-1899-6cbf268dd749@arm.com>
From:   Christophe Leroy <christophe.leroy@c-s.fr>
Message-ID: <e2b42446-7f91-83f1-ac12-08dff75c4d35@c-s.fr>
Date:   Fri, 13 Sep 2019 09:03:46 +0200
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Le 13/09/2019 à 08:58, Anshuman Khandual a écrit :
> On 09/13/2019 11:53 AM, Christophe Leroy wrote:
>> Fix build failure on powerpc.
>>
>> Fix preemption imbalance.
>>
>> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
>> ---
>>   mm/arch_pgtable_test.c | 3 +++
>>   1 file changed, 3 insertions(+)
>>
>> diff --git a/mm/arch_pgtable_test.c b/mm/arch_pgtable_test.c
>> index 8b4a92756ad8..f2b3c9ec35fa 100644
>> --- a/mm/arch_pgtable_test.c
>> +++ b/mm/arch_pgtable_test.c
>> @@ -24,6 +24,7 @@
>>   #include <linux/swap.h>
>>   #include <linux/swapops.h>
>>   #include <linux/sched/mm.h>
>> +#include <linux/highmem.h>
> 
> This is okay.
> 
>>   #include <asm/pgalloc.h>
>>   #include <asm/pgtable.h>
>>   
>> @@ -400,6 +401,8 @@ static int __init arch_pgtable_tests_init(void)
>>   	p4d_clear_tests(p4dp);
>>   	pgd_clear_tests(mm, pgdp);
>>   
>> +	pte_unmap(ptep);
>> +
> 
> Now the preemption imbalance via pte_alloc_map() path i.e
> 
> pte_alloc_map() -> pte_offset_map() -> kmap_atomic()
> 
> Is not this very much powerpc 32 specific or this will be applicable
> for all platform which uses kmap_XXX() to map high memory ?
> 

See 
https://elixir.bootlin.com/linux/v5.3-rc8/source/include/linux/highmem.h#L91

I think it applies at least to all arches using the generic implementation.

Applies also to arm:
https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/arm/mm/highmem.c#L52

Applies also to mips:
https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/mips/mm/highmem.c#L47

Same on sparc:
https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/sparc/mm/highmem.c#L52

Same on x86:
https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/x86/mm/highmem_32.c#L34

I have not checked others, but I guess it is like that for all.

Christophe