linux-kernel - Re: [PATCH v3 1/3] mm: Call arch_swap_restore() from do_swap

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Date:   Wed, 17 May 2023 10:37:22 +0200
From:   David Hildenbrand <david@...hat.com>
To:     "Huang, Ying" <ying.huang@...el.com>,
        Peter Collingbourne <pcc@...gle.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Qun-wei Lin (林群崴) 
        <Qun-wei.Lin@...iatek.com>, linux-arm-kernel@...ts.infradead.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        "surenb@...gle.com" <surenb@...gle.com>,
        Chinwen Chang (張錦文) 
        <chinwen.chang@...iatek.com>,
        "kasan-dev@...glegroups.com" <kasan-dev@...glegroups.com>,
        Kuan-Ying Lee (李冠穎) 
        <Kuan-Ying.Lee@...iatek.com>,
        Casper Li (李中榮) <casper.li@...iatek.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        vincenzo.frascino@....com,
        Alexandru Elisei <alexandru.elisei@....com>, will@...nel.org,
        eugenis@...gle.com, Steven Price <steven.price@....com>,
        stable@...r.kernel.org
Subject: Re: [PATCH v3 1/3] mm: Call arch_swap_restore() from do_swap_page()

On 17.05.23 05:40, Huang, Ying wrote:
> Peter Collingbourne <pcc@...gle.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@...gle.com>
>> Link: https://linux-review.googlesource.com/id/I6470efa669e8bd2f841049b8c61020c510678965
>> Cc: <stable@...r.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@...iatek.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@...hat.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@...hat.com>

-- 
Thanks,

David / dhildenb