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From: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org
Subject: Re: [PATCH] mm: Introduce page_size()
Date: Tue, 01 Jan 2019 15:45:22 +0530	[thread overview]
Message-ID: <87imz87kg5.fsf@linux.ibm.com> (raw)
In-Reply-To: <20190101063031.GD6310@bombadil.infradead.org>

Matthew Wilcox <willy@infradead.org> writes:

> On Tue, Jan 01, 2019 at 08:57:53AM +0530, Aneesh Kumar K.V wrote:
>> Matthew Wilcox <willy@infradead.org> writes:
>> > +/* Returns the number of bytes in this potentially compound page. */
>> > +static inline unsigned long page_size(struct page *page)
>> > +{
>> > +	return (unsigned long)PAGE_SIZE << compound_order(page);
>> > +}
>> > +
>> 
>> How about compound_page_size() to make it clear this is for
>> compound_pages? Should we make it work with Tail pages by doing
>> compound_head(page)?
>
> I think that's a terrible idea.  Actually, I think the whole way we handle
> compound pages is terrible; we should only ever see head pages.  Doing
> page cache lookups should only give us head pages.  Calling pfn_to_page()
> should give us the head page.  We should only put head pages into SG lists.
> Everywhere you see a struct page should only be a head page.
>
> I know we're far from that today, and there's lots of work to be done
> to get there.  But the current state of handling compound pages is awful
> and confusing.

One exception is THP compound pages which can also be mapped as regular
pages in some page tables?

-aneesh

  parent reply	other threads:[~2019-01-01 10:15 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-12-31 13:42 [PATCH] mm: Introduce page_size() Matthew Wilcox
2018-12-31 23:02 ` Kirill A. Shutemov
2019-01-01  6:39   ` Matthew Wilcox
2019-01-01 20:11     ` Zi Yan
2019-01-02  0:58       ` Matthew Wilcox
2019-01-02  1:16         ` Zi Yan
2019-01-01  3:27 ` Aneesh Kumar K.V
2019-01-01  3:27   ` Aneesh Kumar K.V
2019-01-01  6:30   ` Matthew Wilcox
2019-01-01 10:11     ` Aneesh Kumar K.V
2019-01-02  3:14       ` Matthew Wilcox
2019-01-02 11:46         ` William Kucharski
2019-01-02 13:09           ` Matthew Wilcox
2019-01-03 10:47             ` William Kucharski
2019-01-01 10:15     ` Aneesh Kumar K.V [this message]
2019-05-10 18:12 Matthew Wilcox
2019-05-13 10:56 ` Michal Hocko
2019-05-13 12:43 ` Kirill Tkhai
2019-05-14 11:53   ` William Kucharski
2019-05-22 20:03   ` Andrew Morton
2019-05-23  1:55     ` Matthew Wilcox
2019-05-23 21:33       ` Andrew Morton
2019-05-23 21:44         ` Matthew Wilcox
2019-05-24  6:34           ` Christoph Hellwig

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