linux-kernel - Re: [PATCH v2 2/3] powerpc: get hugetlbpage handling more generic

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Message-Id: <877fa7xq1v.fsf@linux.vnet.ibm.com>
Date:   Tue, 20 Sep 2016 07:58:44 +0530
From:   "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:     christophe leroy <christophe.leroy@....fr>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Scott Wood <oss@...error.net>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v2 2/3] powerpc: get hugetlbpage handling more generic

christophe leroy <christophe.leroy@....fr> writes:

> Le 19/09/2016 à 07:50, Aneesh Kumar K.V a écrit :
>>
>> Christophe Leroy <christophe.leroy@....fr> writes:
>>> +#else
>>> +static void hugepd_free(struct mmu_gather *tlb, void *hugepte)
>>> +{
>>> +	BUG();
>>> +}
>>> +
>>>  #endif
>>
>>
>> I was expecting that BUG will get removed in the next patch. But I don't
>> see it in the next patch. Considering
>>
>> @@ -475,11 +453,10 @@ static void free_hugepd_range(struct mmu_gather *tlb, hugepd_t *hpdp, int pdshif
>>         for (i = 0; i < num_hugepd; i++, hpdp++)
>>                 hpdp->pd = 0;
>>
>> -#ifdef CONFIG_PPC_FSL_BOOK3E
>> -	hugepd_free(tlb, hugepte);
>> -#else
>> -	pgtable_free_tlb(tlb, hugepte, pdshift - shift);
>> -#endif
>> +	if (shift >= pdshift)
>> +		hugepd_free(tlb, hugepte);
>> +	else
>> +		pgtable_free_tlb(tlb, hugepte, pdshift - shift);
>>  }
>>
>> What is that I am missing ?
>>
>
> Previously, call to hugepd_free() was compiled only when #ifdef 
> CONFIG_PPC_FSL_BOOK3E
> Now, it is compiled at all time, but it should never be called if not 
> CONFIG_PPC_FSL_BOOK3E because we always have shift < pdshift in that case.
> Then the function needs to be defined anyway but should never be called. 
> Should I just define it static inline {} ?
>

For 8M with 4K mode, we have shift >= pdshift right ?

-aneesh