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Date:   Tue, 23 Aug 2022 12:07:04 +0200
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Subject: Re: [PATCH v6 2/2] mm: fix the handling Non-LRU pages returned by
 follow_page
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To:     Miaohe Lin <linmiaohe@huawei.com>,
        Haiyue Wang <haiyue.wang@intel.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Cc:     akpm@linux-foundation.org, apopple@nvidia.com,
        ying.huang@intel.com, songmuchun@bytedance.com,
        naoya.horiguchi@linux.dev, alex.sierra@amd.com,
        Felix Kuehling <Felix.Kuehling@amd.com>
References: <20220812084921.409142-1-haiyue.wang@intel.com>
 <20220816022102.582865-1-haiyue.wang@intel.com>
 <20220816022102.582865-3-haiyue.wang@intel.com>
 <f9bb1faf-3e09-2db4-5210-4cea09654452@huawei.com>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat
In-Reply-To: <f9bb1faf-3e09-2db4-5210-4cea09654452@huawei.com>
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On 17.08.22 04:34, Miaohe Lin wrote:
> On 2022/8/16 10:21, Haiyue Wang wrote:
>> The handling Non-LRU pages returned by follow_page() jumps directly, it
>> doesn't call put_page() to handle the reference count, since 'FOLL_GET'
>> flag for follow_page() has get_page() called. Fix the zone device page
>> check by handling the page reference count correctly before returning.
>>
>> And as David reviewed, "device pages are never PageKsm pages". Drop this
>> zone device page check for break_ksm().
>>
>> Fixes: 3218f8712d6b ("mm: handling Non-LRU pages returned by vm_normal_pages")
>> Signed-off-by: Haiyue Wang <haiyue.wang@intel.com>
>> Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
>> Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
> 
> Thanks for your fixing. LGTM with one nit below. But I have no strong opinion on it.
> So with or without fixing below nit:
> 
> Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
> 
>> ---
>>  mm/huge_memory.c |  4 ++--
>>  mm/ksm.c         | 12 +++++++++---
>>  mm/migrate.c     | 19 ++++++++++++-------
>>  3 files changed, 23 insertions(+), 12 deletions(-)
>>
>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
>> index 8a7c1b344abe..b2ba17c3dcd7 100644
>> --- a/mm/huge_memory.c
>> +++ b/mm/huge_memory.c
>> @@ -2963,10 +2963,10 @@ static int split_huge_pages_pid(int pid, unsigned long vaddr_start,
>>  		/* FOLL_DUMP to ignore special (like zero) pages */
>>  		page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP);
>>  
>> -		if (IS_ERR_OR_NULL(page) || is_zone_device_page(page))
>> +		if (IS_ERR_OR_NULL(page))
>>  			continue;
>>  
>> -		if (!is_transparent_hugepage(page))
>> +		if (is_zone_device_page(page) || !is_transparent_hugepage(page))
> 
> !is_transparent_hugepage should already do the work here? IIRC, zone_device_page can't be
> a transhuge page anyway. And only transparent_hugepage is cared here.

I agree.

Can we avoid sending a new version of a patch series as reply to another
patch series (previous version)?


Acked-by: David Hildenbrand <david@redhat.com>

-- 
Thanks,

David / dhildenb