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Message-ID: <cae11a08-2f5c-43ca-92fc-a78e9acf4dd8@arm.com>
Date: Tue, 30 Jan 2024 08:46:55 +0000
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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: David Hildenbrand <david@redhat.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>,
 linux-arch@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
 linux-s390@vger.kernel.org
References: <20240129143221.263763-1-david@redhat.com>
 <20240129143221.263763-2-david@redhat.com>
 <40e87333-4da9-4497-a117-9885986e376a@arm.com>
 <8d19d635-2f55-4c0d-958b-0640f99ff0ce@redhat.com>
From: Ryan Roberts <ryan.roberts@arm.com>
In-Reply-To: <8d19d635-2f55-4c0d-958b-0640f99ff0ce@redhat.com>
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On 30/01/2024 08:41, David Hildenbrand wrote:
> 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.

Yeah I only noticed that after sending out this reply and moving to the next
patch. Still worth fixing this intermediate state I think.

> 
> Will fix, thanks!
>