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Date: Tue, 30 Jan 2024 09:41:08 +0100
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Subject: Re: [PATCH v1 1/9] mm/memory: factor out zapping of present pte into
 zap_present_pte()
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To: Ryan Roberts <ryan.roberts@arm.com>, linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
 Matthew Wilcox <willy@infradead.org>,
 Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>,
 "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
 Nick Piggin <npiggin@gmail.com>, Peter Zijlstra <peterz@infradead.org>,
 Michael Ellerman <mpe@ellerman.id.au>,
 Christophe Leroy <christophe.leroy@csgroup.eu>,
 "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>,
 Heiko Carstens <hca@linux.ibm.com>, Vasily Gorbik <gor@linux.ibm.com>,
 Alexander Gordeev <agordeev@linux.ibm.com>,
 Christian Borntraeger <borntraeger@linux.ibm.com>,
 Sven Schnelle <svens@linux.ibm.com>, Arnd Bergmann <arnd@arndb.de>,
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References: <20240129143221.263763-1-david@redhat.com>
 <20240129143221.263763-2-david@redhat.com>
 <40e87333-4da9-4497-a117-9885986e376a@arm.com>
From: David Hildenbrand <david@redhat.com>
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On 30.01.24 09:13, Ryan Roberts wrote:
> On 29/01/2024 14:32, David Hildenbrand wrote:
>> Let's prepare for further changes by factoring out processing of present
>> PTEs.
>>
>> Signed-off-by: David Hildenbrand <david@redhat.com>
>> ---
>>   mm/memory.c | 92 ++++++++++++++++++++++++++++++-----------------------
>>   1 file changed, 52 insertions(+), 40 deletions(-)
>>
>> diff --git a/mm/memory.c b/mm/memory.c
>> index b05fd28dbce1..50a6c79c78fc 100644
>> --- a/mm/memory.c
>> +++ b/mm/memory.c
>> @@ -1532,13 +1532,61 @@ zap_install_uffd_wp_if_needed(struct vm_area_struct *vma,
>>   	pte_install_uffd_wp_if_needed(vma, addr, pte, pteval);
>>   }
>>   
>> +static inline void zap_present_pte(struct mmu_gather *tlb,
>> +		struct vm_area_struct *vma, pte_t *pte, pte_t ptent,
>> +		unsigned long addr, struct zap_details *details,
>> +		int *rss, bool *force_flush, bool *force_break)
>> +{
>> +	struct mm_struct *mm = tlb->mm;
>> +	bool delay_rmap = false;
>> +	struct folio *folio;
> 
> You need to init this to NULL otherwise its a random value when calling
> should_zap_folio() if vm_normal_page() returns NULL.

Right, and we can stop setting it to NULL in the original function. 
Patch #2 changes these checks, which is why it's only a problem in this 
patch.

Will fix, thanks!

-- 
Cheers,

David / dhildenb