From: Ralph Campbell <rcampbell@nvidia.com>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: <linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] mm/thp: make set_huge_zero_page() return void
Date: Tue, 1 Oct 2019 10:54:30 -0700 [thread overview]
Message-ID: <68b384ac-b311-6ea2-81ad-053ff7f3ba64@nvidia.com> (raw)
In-Reply-To: <20191001115239.dqodyji3r32zjkea@box>
On 10/1/19 4:52 AM, Kirill A. Shutemov wrote:
> On Mon, Sep 30, 2019 at 12:55:28PM -0700, Ralph Campbell wrote:
>> The return value from set_huge_zero_page() is never checked so simplify
>> the code by making it return void.
>>
>> Signed-off-by: Ralph Campbell <rcampbell@nvidia.com>
>> ---
>> mm/huge_memory.c | 6 ++----
>> 1 file changed, 2 insertions(+), 4 deletions(-)
>>
>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
>> index c5cb6dcd6c69..6cf0ee65538d 100644
>> --- a/mm/huge_memory.c
>> +++ b/mm/huge_memory.c
>> @@ -686,20 +686,18 @@ static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
>> }
>>
>> /* Caller must hold page table lock. */
>> -static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
>> +static void set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
>> struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
>> struct page *zero_page)
>> {
>> pmd_t entry;
>> - if (!pmd_none(*pmd))
>> - return false;
>> +
>
> Wat? So you just bindly overwrite whatever is there?
>
> NAK.
No, the only two places it is called from are
do_huge_pmd_anonymous_page() which has the pmd_lock()
and already checked pmd_none() is true and
copy_huge_pmd() where the destination page table
is being filled in with no other threads accessing it.
I guess I should have put this analysis in the changelog.
Still, I guess putting a pmd_none() check in copy_huge_pmd()
as future proofing new callers of copy_huge_pmd() would
make sense.
>> entry = mk_pmd(zero_page, vma->vm_page_prot);
>> entry = pmd_mkhuge(entry);
>> if (pgtable)
>> pgtable_trans_huge_deposit(mm, pmd, pgtable);
>> set_pmd_at(mm, haddr, pmd, entry);
>> mm_inc_nr_ptes(mm);
>> - return true;
>> }
>>
>> vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
>> --
>> 2.20.1
>>
>>
>
prev parent reply other threads:[~2019-10-01 17:54 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-30 19:55 [PATCH] mm/thp: make set_huge_zero_page() return void Ralph Campbell
2019-10-01 11:52 ` Kirill A. Shutemov
2019-10-01 17:54 ` Ralph Campbell [this message]
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