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From: SeongJae Park <sj@kernel.org>
To: Matthew Wilcox <willy@infradead.org>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	David Hildenbrand <david@redhat.com>,
	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 4/8] mm: damon: add temporary damon_get_folio()
Date: Tue, 13 Dec 2022 19:18:51 +0000	[thread overview]
Message-ID: <20221213191851.138660-1-sj@kernel.org> (raw)
In-Reply-To: <Y5iO6VSsyDiQQ2mk@casper.infradead.org>

On Tue, 13 Dec 2022 14:40:41 +0000 Matthew Wilcox <willy@infradead.org> wrote:

> On Tue, Dec 13, 2022 at 05:27:31PM +0800, Kefeng Wang wrote:
> > -struct page *damon_get_page(unsigned long pfn)
> > +struct folio *damon_get_folio(unsigned long pfn)
> >  {
> > -	struct page *page = pfn_to_online_page(pfn);
> > +	struct folio *folio = pfn_to_online_folio(pfn);
> >  
> > -	if (!page || !PageLRU(page) || !get_page_unless_zero(page))
> > +	if (!folio || !folio_test_lru(folio) || !folio_try_get(folio))
> >  		return NULL;
> 
> Well, this is awkward.  I asked Vishal to think about exactly this problem
> and we were going to talk about it after we're both back from vacation
> in January.  But I guess we're going to do this in public instead ...
> 
> Specifically, what should the semantics be for a putative
> damon_get_folio() when it encounters a tail page?  Should it return
> the containing folio, or should it return NULL?  And if the semantics
> change here to return the containing folio, what adjustments need to
> be made to the callers?

I'd prefer to simply keep the original behavior, returning NULL, for now unless
someone complaints.


Thanks,
SJ

  reply	other threads:[~2022-12-13 19:18 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
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 [this message]
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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