From: Ralph Campbell <rcampbell@nvidia.com>
To: Jerome Glisse <jglisse@redhat.com>, Pingfan Liu <kernelfans@gmail.com>
Cc: <linux-mm@kvack.org>, Andrew Morton <akpm@linux-foundation.org>,
Mel Gorman <mgorman@techsingularity.net>, Jan Kara <jack@suse.cz>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Michal Hocko <mhocko@suse.com>,
Mike Kravetz <mike.kravetz@oracle.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Matthew Wilcox <willy@infradead.org>,
<linux-kernel@vger.kernel.org>
Subject: Re: [PATCHv2] mm/migrate: clean up useless code in migrate_vma_collect_pmd()
Date: Thu, 15 Aug 2019 12:23:44 -0700 [thread overview]
Message-ID: <d0a8ab6e-1122-a101-6139-9d7dadb9e999@nvidia.com> (raw)
In-Reply-To: <20190815171918.GC30916@redhat.com>
On 8/15/19 10:19 AM, Jerome Glisse wrote:
> On Wed, Aug 07, 2019 at 04:41:12PM +0800, Pingfan Liu wrote:
>> Clean up useless 'pfn' variable.
>
> NAK there is a bug see below:
>
>>
>> Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
>> Cc: "Jérôme Glisse" <jglisse@redhat.com>
>> Cc: Andrew Morton <akpm@linux-foundation.org>
>> Cc: Mel Gorman <mgorman@techsingularity.net>
>> Cc: Jan Kara <jack@suse.cz>
>> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
>> Cc: Michal Hocko <mhocko@suse.com>
>> Cc: Mike Kravetz <mike.kravetz@oracle.com>
>> Cc: Andrea Arcangeli <aarcange@redhat.com>
>> Cc: Matthew Wilcox <willy@infradead.org>
>> To: linux-mm@kvack.org
>> Cc: linux-kernel@vger.kernel.org
>> ---
>> mm/migrate.c | 9 +++------
>> 1 file changed, 3 insertions(+), 6 deletions(-)
>>
>> diff --git a/mm/migrate.c b/mm/migrate.c
>> index 8992741..d483a55 100644
>> --- a/mm/migrate.c
>> +++ b/mm/migrate.c
>> @@ -2225,17 +2225,15 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
>> pte_t pte;
>>
>> pte = *ptep;
>> - pfn = pte_pfn(pte);
>>
>> if (pte_none(pte)) {
>> mpfn = MIGRATE_PFN_MIGRATE;
>> migrate->cpages++;
>> - pfn = 0;
>> goto next;
>> }
>>
>> if (!pte_present(pte)) {
>> - mpfn = pfn = 0;
>> + mpfn = 0;
>>
>> /*
>> * Only care about unaddressable device page special
>> @@ -2252,10 +2250,10 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
>> if (is_write_device_private_entry(entry))
>> mpfn |= MIGRATE_PFN_WRITE;
>> } else {
>> + pfn = pte_pfn(pte);
>> if (is_zero_pfn(pfn)) {
>> mpfn = MIGRATE_PFN_MIGRATE;
>> migrate->cpages++;
>> - pfn = 0;
>> goto next;
>> }
>> page = vm_normal_page(migrate->vma, addr, pte);
>> @@ -2265,10 +2263,9 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
>>
>> /* FIXME support THP */
>> if (!page || !page->mapping || PageTransCompound(page)) {
>> - mpfn = pfn = 0;
>> + mpfn = 0;
>> goto next;
>> }
>> - pfn = page_to_pfn(page);
>
> You can not remove that one ! Otherwise it will break the device
> private case.
>
I don't understand. The only use of "pfn" I see is in the "else"
clause above where it is set just before using it.
next prev parent reply other threads:[~2019-08-15 19:23 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-06 8:00 [PATCH 1/3] mm/migrate: clean up useless code in migrate_vma_collect_pmd() Pingfan Liu
2019-08-06 8:00 ` [PATCH 2/3] mm/migrate: see hole as invalid source page Pingfan Liu
2019-08-15 17:22 ` Jerome Glisse
2019-08-16 15:02 ` Pingfan Liu
2019-08-26 7:52 ` Pingfan Liu
2019-08-06 8:00 ` [PATCH 3/3] mm/migrate: remove the duplicated code migrate_vma_collect_hole() Pingfan Liu
2019-08-15 17:22 ` Jerome Glisse
2019-08-06 13:35 ` [PATCH 1/3] mm/migrate: clean up useless code in migrate_vma_collect_pmd() Matthew Wilcox
2019-08-07 5:28 ` Pingfan Liu
2019-08-07 8:41 ` [PATCHv2] " Pingfan Liu
2019-08-14 23:11 ` Ralph Campbell
2019-08-15 17:19 ` Jerome Glisse
2019-08-15 19:23 ` Ralph Campbell [this message]
2019-08-15 19:40 ` Jerome Glisse
2019-08-16 13:21 ` Pingfan Liu
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