linux-kernel - Re: [PATCH] mm/swap_state.c: use the same way to count page in [add_to|delete_from]_swap

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Message-ID: <20200315002101.GT22433@bombadil.infradead.org>
Date:   Sat, 14 Mar 2020 17:21:01 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Wei Yang <richard.weiyang@...il.com>
Cc:     akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/swap_state.c: use the same way to count page in
 [add_to|delete_from]_swap_cache

On Sat, Mar 14, 2020 at 09:59:12PM +0000, Wei Yang wrote:
> Function add_to_swap_cache() and delete_from_swap_cache() are counter
> parts, while currently they use different way to count page.
> 
> It doesn't break any thing because we only have two size for PageAnon,
> but this is confusing and not a good practice.
> 
> This patch corrects it by both using compound_nr().

You're converting in the wrong direction.  hpage_nr_pages() is optimised
away when CONFIG_TRANSPARENT_HUGEPAGE is undefined, whereas compound_nr()
is not.

I also have this patch pending:
http://git.infradead.org/users/willy/linux-dax.git/commitdiff/192b635b428ae74f680574cdcc3d5e9d213fcb64