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Date:   Wed, 17 May 2023 10:37:22 +0200
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Subject: Re: [PATCH v3 1/3] mm: Call arch_swap_restore() from do_swap_page()
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To:     "Huang, Ying" <ying.huang@intel.com>,
        Peter Collingbourne <pcc@google.com>
Cc:     Catalin Marinas <catalin.marinas@arm.com>,
        =?UTF-8?B?UXVuLXdlaSBMaW4gKOael+e+pOW0tCk=?= 
        <Qun-wei.Lin@mediatek.com>, linux-arm-kernel@lists.infradead.org,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        "surenb@google.com" <surenb@google.com>,
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        <chinwen.chang@mediatek.com>,
        "kasan-dev@googlegroups.com" <kasan-dev@googlegroups.com>,
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        <Kuan-Ying.Lee@mediatek.com>,
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        "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        vincenzo.frascino@arm.com,
        Alexandru Elisei <alexandru.elisei@arm.com>, will@kernel.org,
        eugenis@google.com, Steven Price <steven.price@arm.com>,
        stable@vger.kernel.org
References: <20230517022115.3033604-1-pcc@google.com>
 <20230517022115.3033604-2-pcc@google.com>
 <87353v7hh1.fsf@yhuang6-desk2.ccr.corp.intel.com>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat
In-Reply-To: <87353v7hh1.fsf@yhuang6-desk2.ccr.corp.intel.com>
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On 17.05.23 05:40, Huang, Ying wrote:
> Peter Collingbourne <pcc@google.com> writes:
> 
>> Commit c145e0b47c77 ("mm: streamline COW logic in do_swap_page()") moved
>> the call to swap_free() before the call to set_pte_at(), which meant that
>> the MTE tags could end up being freed before set_pte_at() had a chance
>> to restore them. Fix it by adding a call to the arch_swap_restore() hook
>> before the call to swap_free().
>>
>> Signed-off-by: Peter Collingbourne <pcc@google.com>
>> Link: https://linux-review.googlesource.com/id/I6470efa669e8bd2f841049b8c61020c510678965
>> Cc: <stable@vger.kernel.org> # 6.1
>> Fixes: c145e0b47c77 ("mm: streamline COW logic in do_swap_page()")
>> Reported-by: Qun-wei Lin (林群崴) <Qun-wei.Lin@mediatek.com>
>> Closes: https://lore.kernel.org/all/5050805753ac469e8d727c797c2218a9d780d434.camel@mediatek.com/
>> ---
>> v2:
>> - Call arch_swap_restore() directly instead of via arch_do_swap_page()
>>
>>   mm/memory.c | 7 +++++++
>>   1 file changed, 7 insertions(+)
>>
>> diff --git a/mm/memory.c b/mm/memory.c
>> index f69fbc251198..fc25764016b3 100644
>> --- a/mm/memory.c
>> +++ b/mm/memory.c
>> @@ -3932,6 +3932,13 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
>>   		}
>>   	}
>>   
>> +	/*
>> +	 * Some architectures may have to restore extra metadata to the page
>> +	 * when reading from swap. This metadata may be indexed by swap entry
>> +	 * so this must be called before swap_free().
>> +	 */
>> +	arch_swap_restore(entry, folio);
>> +
>>   	/*
>>   	 * Remove the swap entry and conditionally try to free up the swapcache.
>>   	 * We're already holding a reference on the page but haven't mapped it
> 
> Should you add
> 
> Suggested-by: David Hildenbrand <david@redhat.com>
> 
> for 1/3 and 2/3.

For 1/3, I think I rather only explained the problem in the first patch 
and didn't really suggest this.

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

-- 
Thanks,

David / dhildenb