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From: Kefeng Wang <wangkefeng.wang@huawei.com>
To: David Hildenbrand <david@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Oscar Salvador <osalvador@suse.de>, SeongJae Park <sj@kernel.org>
Cc: <linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>,
	<damon@lists.linux.dev>, <vishal.moola@gmail.com>,
	<willy@infradead.org>
Subject: Re: [PATCH -next 1/8] mm: memory_hotplug: add pfn_to_online_folio()
Date: Tue, 13 Dec 2022 20:13:31 +0800	[thread overview]
Message-ID: <801ccbe2-08b8-e1cb-9aee-614d59a807d2@huawei.com> (raw)
In-Reply-To: <f07d1c95-f13c-682b-0519-0b137ccdc631@redhat.com>


On 2022/12/13 19:40, David Hildenbrand wrote:
> On 13.12.22 10:27, Kefeng Wang wrote:
>> Introduce a wrapper function pfn_to_online_folio(), which calls
>> pfn_to_online_page() and returns the folio of the page found,
>> or null if no page.
>>
>> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
>> ---
>>   include/linux/memory_hotplug.h | 7 +++++++
>>   1 file changed, 7 insertions(+)
>>
>> diff --git a/include/linux/memory_hotplug.h 
>> b/include/linux/memory_hotplug.h
>> index 9fcbf5706595..e841e4fb52a7 100644
>> --- a/include/linux/memory_hotplug.h
>> +++ b/include/linux/memory_hotplug.h
>> @@ -265,6 +265,13 @@ static inline void pgdat_kswapd_unlock(pg_data_t 
>> *pgdat) {}
>>   static inline void pgdat_kswapd_lock_init(pg_data_t *pgdat) {}
>>   #endif /* ! CONFIG_MEMORY_HOTPLUG */
>>   +static inline struct folio *pfn_to_online_folio(unsigned long pfn)
>> +{
>> +    struct page *page = pfn_to_online_page(pfn);
>> +
>> +    return page ? page_folio(page) : NULL;
>> +}
>
> Who guarantees that page_folio() is safe and stable at that point?
>
> IIRC, that's very tricky. We could have the page concurrently getting 
> freed and the folio dissolved.
So the caller should consider this,  lock or get the folio in the caller?

  reply	other threads:[~2022-12-13 12:13 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-12-13  9:27 [PATCH -next 0/8] mm: converted page idle and damon to use folios Kefeng Wang
2022-12-13  9:27 ` [PATCH -next 1/8] mm: memory_hotplug: add pfn_to_online_folio() Kefeng Wang
2022-12-13 11:13   ` kernel test robot
2022-12-13 11:36     ` Kefeng Wang
2022-12-13 11:23   ` kernel test robot
2022-12-13 11:40   ` David Hildenbrand
2022-12-13 12:13     ` Kefeng Wang [this message]
2022-12-13 14:42       ` David Hildenbrand
2022-12-13 14:47       ` Matthew Wilcox
2022-12-14  1:10         ` Kefeng Wang
2022-12-13 12:03   ` kernel test robot
2022-12-14  4:15   ` kernel test robot
2022-12-13  9:27 ` [PATCH -next 2/8] mm: page_idle: Convert page idle to use folios Kefeng Wang
2022-12-13 14:34   ` Matthew Wilcox
2022-12-13 19:14   ` SeongJae Park
2022-12-13  9:27 ` [PATCH -next 3/8] mm: huge_memory: convert split_huge_pages_all() " Kefeng Wang
2022-12-13  9:27 ` [PATCH -next 4/8] mm: damon: add temporary damon_get_folio() Kefeng Wang
2022-12-13 14:40   ` Matthew Wilcox
2022-12-13 19:18     ` SeongJae Park
2022-12-13  9:27 ` [PATCH -next 5/8] mm: damon: convert damon_ptep/pmdp_mkold() to use folios Kefeng Wang
2022-12-13  9:27 ` [PATCH -next 6/8] mm: damon: paddr: convert damon_pa_*() " Kefeng Wang
2022-12-13  9:27 ` [PATCH -next 7/8] mm: damon: vaddr: convert damon_young_pmd_entry() to use folio Kefeng Wang
2022-12-13  9:27 ` [PATCH -next 8/8] mm: damon: remove unneed damon_get_page() Kefeng Wang
2022-12-13 19:26   ` SeongJae Park

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