From: Steven Price <steven.price@arm.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Jérôme Glisse" <jglisse@redhat.com>,
"Arnd Bergmann" <arnd@arndb.de>,
"Dan Williams" <dan.j.williams@intel.com>
Subject: Re: [PATCH] mm: Correct guards for non_swap_entry()
Date: Fri, 6 Mar 2020 09:41:16 +0000 [thread overview]
Message-ID: <efa519d1-5f0a-11a6-e143-c83698b7e5b2@arm.com> (raw)
In-Reply-To: <20200305194431.7fe10d760d9921d0eff106c1@linux-foundation.org>
On 06/03/2020 03:44, Andrew Morton wrote:
> On Thu, 5 Mar 2020 13:05:50 +0000 Steven Price <steven.price@arm.com> wrote:
>
>> If CONFIG_DEVICE_PRIVATE is defined, but neither CONFIG_MEMORY_FAILURE nor
>> CONFIG_MIGRATION, then non_swap_entry() will return 0, meaning that the
>> condition (non_swap_entry(entry) && is_device_private_entry(entry)) in
>> zap_pte_range() will never be true even if the entry is a device private
>> one.
>>
>> Equally any other code depending on non_swap_entry() will not function
>> as expected.
>
> What are the user-visible runtime effects of this change?
>
> Is a cc:stable needed?
>
I originally spotted this just by looking at the code, I haven't
actually observed any problems.
Looking a bit more closely it appears that actually this situation
(currently at least) cannot occur:
DEVICE_PRIVATE depends on ZONE_DEVICE
ZONE_DEVICE depends on MEMORY_HOTREMOVE
MEMORY_HOTREMOVE depends on MIGRATION
So there's probably no need to back port.
Steve
prev parent reply other threads:[~2020-03-06 9:41 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-05 13:05 [PATCH] mm: Correct guards for non_swap_entry() Steven Price
2020-03-06 3:44 ` Andrew Morton
2020-03-06 9:41 ` Steven Price [this message]
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