damon.lists.linux.dev archive mirror
 help / color / mirror / Atom feed
From: Kefeng Wang <wangkefeng.wang@huawei.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: David Hildenbrand <david@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Oscar Salvador <osalvador@suse.de>, SeongJae Park <sj@kernel.org>,
	<linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>,
	<damon@lists.linux.dev>, <vishal.moola@gmail.com>
Subject: Re: [PATCH -next 1/8] mm: memory_hotplug: add pfn_to_online_folio()
Date: Wed, 14 Dec 2022 09:10:06 +0800	[thread overview]
Message-ID: <8693c37b-f709-4c63-eac6-418c32b80e7e@huawei.com> (raw)
In-Reply-To: <Y5iQkmjj1ISoTWAF@casper.infradead.org>


On 2022/12/13 22:47, Matthew Wilcox wrote:
> On Tue, Dec 13, 2022 at 08:13:31PM +0800, Kefeng Wang wrote:
>> 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?
> The caller only has a pfn; it doesn't have the folio at the time of
> the call.  David is right, this function cannot safely exist.
Thanks fro all the advises from David/Matthew/SeongJae,  will rethink 
this converting.
>

  reply	other threads:[~2022-12-14  1:10 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
2022-12-13 14:42       ` David Hildenbrand
2022-12-13 14:47       ` Matthew Wilcox
2022-12-14  1:10         ` Kefeng Wang [this message]
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=8693c37b-f709-4c63-eac6-418c32b80e7e@huawei.com \
    --to=wangkefeng.wang@huawei.com \
    --cc=akpm@linux-foundation.org \
    --cc=damon@lists.linux.dev \
    --cc=david@redhat.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=osalvador@suse.de \
    --cc=sj@kernel.org \
    --cc=vishal.moola@gmail.com \
    --cc=willy@infradead.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).