From: Alexandre Ghiti <aghiti@upmem.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: linux-mm@kvack.org, akpm@linux-foundation.org,
kirill.shutemov@linux.intel.com, dan.j.williams@intel.com,
zi.yan@cs.rutgers.edu, gregkh@linuxfoundation.org,
n-horiguchi@ah.jp.nec.com, willy@linux.intel.com,
mark.rutland@arm.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm, THP: vmf_insert_pfn_pud depends on CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
Date: Thu, 11 Jan 2018 14:05:34 +0100 [thread overview]
Message-ID: <71853228-0beb-1e69-df47-59fa1bc5bd2f@upmem.com> (raw)
In-Reply-To: <20180111100620.GY1732@dhcp22.suse.cz>
On 11/01/2018 11:06, Michal Hocko wrote:
> On Thu 11-01-18 09:53:31, Alexandre Ghiti wrote:
>> The only definition of vmf_insert_pfn_pud depends on
>> CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD being defined. Then its declaration in
>> include/linux/huge_mm.h should have the same restriction so that we do
>> not expose this function if CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD is
>> not defined.
> Why is this a problem? Compiler should simply throw away any
> declarations which are not used?
It is not a big problem but surrounding the declaration with the #ifdef
makes the compilation of external modules fail with an "error: implicit
declaration of function vmf_insert_pfn_pud" if
CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD is not defined. I think it is
cleaner than generating a .ko which would not load anyway.
>
>> Signed-off-by: Alexandre Ghiti <aghiti@upmem.com>
>> ---
>> include/linux/huge_mm.h | 2 ++
>> 1 file changed, 2 insertions(+)
>>
>> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
>> index a8a1262..11794f6a 100644
>> --- a/include/linux/huge_mm.h
>> +++ b/include/linux/huge_mm.h
>> @@ -48,8 +48,10 @@ extern int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
>> int prot_numa);
>> int vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
>> pmd_t *pmd, pfn_t pfn, bool write);
>> +#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
>> int vmf_insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
>> pud_t *pud, pfn_t pfn, bool write);
>> +#endif
>> enum transparent_hugepage_flag {
>> TRANSPARENT_HUGEPAGE_FLAG,
>> TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
>> --
>> 2.1.4
>>
--
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next prev parent reply other threads:[~2018-01-11 13:06 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-11 8:53 [PATCH] mm, THP: vmf_insert_pfn_pud depends on CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD Alexandre Ghiti
2018-01-11 10:06 ` Michal Hocko
2018-01-11 13:05 ` Alexandre Ghiti [this message]
2018-01-12 0:28 ` Andrew Morton
2018-01-12 15:26 ` Alexandre Ghiti
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