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Subject: Re: [PATCH] mm/hugetlb: Fix build failure with HUGETLB_PAGE but not
 HUGEBTLBFS
To:     Baoquan He <bhe@redhat.com>
Cc:     Mike Kravetz <mike.kravetz@oracle.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Nishanth Aravamudan <nacc@us.ibm.com>,
        Nick Piggin <npiggin@suse.de>, Adam Litke <agl@us.ibm.com>,
        Andi Kleen <ak@suse.de>, linux-kernel@vger.kernel.org,
        linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org
References: <7e8c3a3c9a587b9cd8a2f146df32a421b961f3a2.1584432148.git.christophe.leroy@c-s.fr>
 <20200317082550.GA3375@MiWiFi-R3L-srv>
From:   Christophe Leroy <christophe.leroy@c-s.fr>
Message-ID: <60117fd7-46ff-326b-34f1-0c7087111ca7@c-s.fr>
Date:   Tue, 17 Mar 2020 09:43:20 +0100
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Le 17/03/2020 à 09:25, Baoquan He a écrit :
> On 03/17/20 at 08:04am, Christophe Leroy wrote:
>> When CONFIG_HUGETLB_PAGE is set but not CONFIG_HUGETLBFS, the
>> following build failure is encoutered:
> 
>  From the definition of HUGETLB_PAGE, isn't it relying on HUGETLBFS?
> I could misunderstand the def_bool, please correct me if I am wrong.

AFAIU, it means that HUGETLBFS rely on HUGETLB_PAGE, by default 
HUGETLB_PAGE is not selected when HUGETLBFS is not. But it is still 
possible for an arch to select HUGETLB_PAGE without selecting HUGETLBFS 
when it uses huge pages for other purpose than hugetlb file system.

Christophe

> 
> config HUGETLB_PAGE
>          def_bool HUGETLBFS
> 
>>
>> In file included from arch/powerpc/mm/fault.c:33:0:
>> ./include/linux/hugetlb.h: In function 'hstate_inode':
>> ./include/linux/hugetlb.h:477:9: error: implicit declaration of function 'HUGETLBFS_SB' [-Werror=implicit-function-declaration]
>>    return HUGETLBFS_SB(i->i_sb)->hstate;
>>           ^
>> ./include/linux/hugetlb.h:477:30: error: invalid type argument of '->' (have 'int')
>>    return HUGETLBFS_SB(i->i_sb)->hstate;
>>                                ^
>>
>> Gate hstate_inode() with CONFIG_HUGETLBFS instead of CONFIG_HUGETLB_PAGE.
>>
>> Reported-by: kbuild test robot <lkp@intel.com>
>> Link: https://patchwork.ozlabs.org/patch/1255548/#2386036
>> Fixes: a137e1cc6d6e ("hugetlbfs: per mount huge page sizes")
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
>> ---
>>   include/linux/hugetlb.h | 19 ++++++++-----------
>>   1 file changed, 8 insertions(+), 11 deletions(-)
>>
>> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
>> index 1e897e4168ac..dafb3d70ff81 100644
>> --- a/include/linux/hugetlb.h
>> +++ b/include/linux/hugetlb.h
>> @@ -390,7 +390,10 @@ static inline bool is_file_hugepages(struct file *file)
>>   	return is_file_shm_hugepages(file);
>>   }
>>   
>> -
>> +static inline struct hstate *hstate_inode(struct inode *i)
>> +{
>> +	return HUGETLBFS_SB(i->i_sb)->hstate;
>> +}
>>   #else /* !CONFIG_HUGETLBFS */
>>   
>>   #define is_file_hugepages(file)			false
>> @@ -402,6 +405,10 @@ hugetlb_file_setup(const char *name, size_t size, vm_flags_t acctflag,
>>   	return ERR_PTR(-ENOSYS);
>>   }
>>   
>> +static inline struct hstate *hstate_inode(struct inode *i)
>> +{
>> +	return NULL;
>> +}
>>   #endif /* !CONFIG_HUGETLBFS */
>>   
>>   #ifdef HAVE_ARCH_HUGETLB_UNMAPPED_AREA
>> @@ -472,11 +479,6 @@ extern unsigned int default_hstate_idx;
>>   
>>   #define default_hstate (hstates[default_hstate_idx])
>>   
>> -static inline struct hstate *hstate_inode(struct inode *i)
>> -{
>> -	return HUGETLBFS_SB(i->i_sb)->hstate;
>> -}
>> -
>>   static inline struct hstate *hstate_file(struct file *f)
>>   {
>>   	return hstate_inode(file_inode(f));
>> @@ -729,11 +731,6 @@ static inline struct hstate *hstate_vma(struct vm_area_struct *vma)
>>   	return NULL;
>>   }
>>   
>> -static inline struct hstate *hstate_inode(struct inode *i)
>> -{
>> -	return NULL;
>> -}
>> -
>>   static inline struct hstate *page_hstate(struct page *page)
>>   {
>>   	return NULL;
>> -- 
>> 2.25.0
>>
>>