Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <342d76b0-a94f-902a-c701-04a1e477b748@redhat.com>
Date:   Tue, 16 May 2023 14:49:38 +0200
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.11.0
Subject: Re: [PATCH v2 1/2] mm: Call arch_swap_restore() from do_swap_page()
Content-Language: en-US
To:     Peter Collingbourne <pcc@google.com>,
        Catalin Marinas <catalin.marinas@arm.com>
Cc:     =?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>,
        =?UTF-8?B?Q2hpbndlbiBDaGFuZyAo5by16Yym5paHKQ==?= 
        <chinwen.chang@mediatek.com>,
        "kasan-dev@googlegroups.com" <kasan-dev@googlegroups.com>,
        =?UTF-8?B?S3Vhbi1ZaW5nIExlZSAo5p2O5Yag56mOKQ==?= 
        <Kuan-Ying.Lee@mediatek.com>,
        =?UTF-8?B?Q2FzcGVyIExpICjmnY7kuK3mpq4p?= <casper.li@mediatek.com>,
        "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: <20230516023514.2643054-1-pcc@google.com>
 <20230516023514.2643054-2-pcc@google.com>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat
In-Reply-To: <20230516023514.2643054-2-pcc@google.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Precedence: bulk

On 16.05.23 04:35, Peter Collingbourne wrote:
> 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>
> Link: 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 01a23ad48a04..a2d9e6952d31 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3914,6 +3914,13 @@ 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

Looks much better to me, thanks :)

... staring at unuse_pte(), I suspect it also doesn't take care of MTE 
tags and needs fixing?

-- 
Thanks,

David / dhildenb