linux-kernel - Re: [PATCH v3 4/6] mm/thp: add THP allocation helper

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Date:   Fri, 6 Nov 2020 13:09:27 -0800
From:   Ralph Campbell <rcampbell@...dia.com>
To:     Christoph Hellwig <hch@....de>
CC:     <linux-mm@...ck.org>, <linux-kselftest@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, Jerome Glisse <jglisse@...hat.com>,
        "John Hubbard" <jhubbard@...dia.com>,
        Alistair Popple <apopple@...dia.com>,
        "Jason Gunthorpe" <jgg@...dia.com>,
        Bharata B Rao <bharata@...ux.ibm.com>,
        Zi Yan <ziy@...dia.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Yang Shi <yang.shi@...ux.alibaba.com>,
        Ben Skeggs <bskeggs@...hat.com>, Shuah Khan <shuah@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v3 4/6] mm/thp: add THP allocation helper


On 11/6/20 12:01 AM, Christoph Hellwig wrote:
>> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
>> +extern struct page *alloc_transhugepage(struct vm_area_struct *vma,
>> +					unsigned long addr);
> 
> No need for the extern.  And also here: do we actually need the stub,
> or can the caller make sure (using IS_ENABLED and similar) that the
> compiler knows the code is dead?

Same problem as with prep_transhuge_device_private_page(), since
alloc_hugepage_direct_gfpmask() and alloc_hugepage_vma() are not
EXPORT_SYMBOL_GPL.

>> +struct page *alloc_transhugepage(struct vm_area_struct *vma,
>> +				 unsigned long haddr)
>> +{
>> +	gfp_t gfp;
>> +	struct page *page;
>> +
>> +	gfp = alloc_hugepage_direct_gfpmask(vma);
>> +	page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
>> +	if (page)
>> +		prep_transhuge_page(page);
>> +	return page;
> 
> I think do_huge_pmd_anonymous_page should be switched to use this
> helper as well.

Sure, I'll do that for v4.