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From: Qi Zheng <zhengqi.arch@bytedance.com>
To: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Jann Horn <jannh@google.com>, Barry Song <21cnbao@gmail.com>,
	akpm@linux-foundation.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, Barry Song <v-songbaohua@oppo.com>,
	"Liam R. Howlett" <Liam.Howlett@oracle.com>,
	David Hildenbrand <david@redhat.com>,
	Vlastimil Babka <vbabka@suse.cz>,
	Suren Baghdasaryan <surenb@google.com>,
	Lokesh Gidra <lokeshgidra@google.com>,
	Tangquan Zheng <zhengtangquan@oppo.com>
Subject: Re: [PATCH RFC v2] mm: use per_vma lock for MADV_DONTNEED
Date: Mon, 9 Jun 2025 14:40:09 +0800	[thread overview]
Message-ID: <5fac6f20-2643-4d98-a29a-06471f156762@bytedance.com> (raw)
In-Reply-To: <d68ba9d4-5850-4b70-bbf3-00d79f19fd3f@lucifer.local>

Hi Lorenzo,

On 6/6/25 6:44 PM, Lorenzo Stoakes wrote:

[snip]

>>
>>>
>>> We could in theory always add another callback .pmd_entry_sleep or
>>> something for this one case and document the requirement...
>>
>> Maybe, but the SRCU critical section cannot prevent the PTE page from
>> being freed via RCU. :(
> 
> Idea is we'd fall back to non-RCU in this case and take locks... but then
> ugh we'd race everything RCU and no it's all or nothing isn't it?

So maybe the RCU+refcount method is feasible. We can release the RCU
lock after incrementing the reference count, which can ensure that the
page table page is not freed.

> 
> Overall - I will stash this response somewhere and come back to it if
> somebody else doesn't in the meantime :)

Thanks!

> 
>>



  reply	other threads:[~2025-06-09  6:40 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-05-30 10:44 [PATCH RFC v2] mm: use per_vma lock for MADV_DONTNEED Barry Song
2025-05-30 14:06 ` Jann Horn
2025-05-30 14:34   ` Lorenzo Stoakes
2025-05-30 20:17     ` Barry Song
2025-06-02 17:35       ` SeongJae Park
2025-06-02 17:53         ` SeongJae Park
2025-05-30 20:40     ` Jann Horn
2025-06-02 11:50       ` Lorenzo Stoakes
2025-06-03  1:06         ` Barry Song
2025-06-03  9:48           ` Lorenzo Stoakes
2025-06-03  7:06       ` Barry Song
2025-06-03 16:52         ` Jann Horn
2025-06-05 10:27           ` Barry Song
2025-05-30 22:00   ` Barry Song
2025-06-02 14:55     ` Jann Horn
2025-06-03  7:51       ` Barry Song
2025-06-03  7:24   ` Qi Zheng
2025-06-03  9:54     ` Lorenzo Stoakes
2025-06-04  6:02       ` Qi Zheng
2025-06-04 17:50         ` Lorenzo Stoakes
2025-06-05  3:23           ` Qi Zheng
2025-06-05 14:04             ` Lorenzo Stoakes
2025-06-06  3:55               ` Qi Zheng
2025-06-06 10:44                 ` Lorenzo Stoakes
2025-06-09  6:40                   ` Qi Zheng [this message]
2025-06-09 15:08                     ` Lorenzo Stoakes
2025-06-10  7:20                     ` David Hildenbrand
2025-06-06 11:07           ` Jann Horn
2025-06-03 18:43 ` Lorenzo Stoakes
2025-06-03 20:17   ` Suren Baghdasaryan
2025-06-04  5:22     ` Lorenzo Stoakes
2025-06-06  7:18     ` Barry Song
2025-06-06 10:16       ` Lorenzo Stoakes
2025-06-03 20:59   ` Pedro Falcato
2025-06-04  5:23     ` Lorenzo Stoakes

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