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Subject: Re: [PATCH v1 03/27] powerpc/mm: don't BUG() in slice_mask_for_size()
To:     "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>
Cc:     linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
References: <cover.1553076180.git.christophe.leroy@c-s.fr>
 <f67363798e1ffb7603cd6619cb867563e4126d9a.1553076180.git.christophe.leroy@c-s.fr>
 <87lg0h3xpo.fsf@linux.ibm.com>
From:   Christophe Leroy <christophe.leroy@c-s.fr>
Message-ID: <609ef207-614c-1abf-6ebc-770735ca94c7@c-s.fr>
Date:   Wed, 24 Apr 2019 16:09:52 +0200
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Le 11/04/2019 à 07:41, Aneesh Kumar K.V a écrit :
> Christophe Leroy <christophe.leroy@c-s.fr> writes:
> 
>> When no mask is found for the page size, WARN() and return NULL
>> instead of BUG()ing.
>>
>> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
>> ---
>>   arch/powerpc/mm/slice.c | 6 ++++--
>>   1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/powerpc/mm/slice.c b/arch/powerpc/mm/slice.c
>> index aec91dbcdc0b..011d470ea340 100644
>> --- a/arch/powerpc/mm/slice.c
>> +++ b/arch/powerpc/mm/slice.c
>> @@ -165,7 +165,8 @@ static struct slice_mask *slice_mask_for_size(struct mm_struct *mm, int psize)
>>   	if (psize == MMU_PAGE_16G)
>>   		return &mm->context.mask_16g;
>>   #endif
>> -	BUG();
>> +	WARN_ON(true);
>> +	return NULL;
>>   }
> 
> 
> Same here. There are not catching runtime errors. We should never find
> that true. This is to catch mistakes during development changes. Switch
> to VM_BUG_ON?

Ok, I'll switch to VM_BUG_ON()

Christophe

> 
> 
>>   #elif defined(CONFIG_PPC_8xx)
>>   static struct slice_mask *slice_mask_for_size(struct mm_struct *mm, int psize)
>> @@ -178,7 +179,8 @@ static struct slice_mask *slice_mask_for_size(struct mm_struct *mm, int psize)
>>   	if (psize == MMU_PAGE_8M)
>>   		return &mm->context.mask_8m;
>>   #endif
>> -	BUG();
>> +	WARN_ON(true);
>> +	return NULL;
>>   }
>>   #else
>>   #error "Must define the slice masks for page sizes supported by the platform"
>> -- 
>> 2.13.3