linux-kernel - Re: [PATCH v2] x86/mm: Remove the redundant conditional check

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Date:   Sat, 14 Mar 2020 15:10:06 +0000
From:   Wei Yang <richard.weiyang@...il.com>
To:     Baoquan He <bhe@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org,
        mhocko@...e.com, akpm@...ux-foundation.org
Subject: Re: [PATCH v2] x86/mm: Remove the redundant conditional check

On Wed, Mar 11, 2020 at 09:18:23AM +0800, Baoquan He wrote:
>In commit f70029bbaacb ("mm, memory_hotplug: drop CONFIG_MOVABLE_NODE"),
>the dependency on CONFIG_MOVABLE_NODE was removed for N_MEMORY. Before
>commit f70029bbaacb, CONFIG_HIGHMEM && !CONFIG_MOVABLE_NODE could make
>(N_MEMORY == N_NORMAL_MEMORY) be true. After commit f70029bbaacb, N_MEMORY
>doesn't have any chance to be equal to N_NORMAL_MEMORY. So the conditional
>check in paging_init() doesn't make sense any more. Let's remove it.
>
>Signed-off-by: Baoquan He <bhe@...hat.com>

The change looks good. While I have one question, we set default value for
N_HIGH_MEMORY. Why we don't clear this too?

Reviewed-by: Wei Yang <richard.weiyang@...il.com>

>---
>v1->v2:
>  Update patch log to make the description clearer per Michal's
>  suggestion.
>
> arch/x86/mm/init_64.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
>diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
>index abbdecb75fad..0a14711d3a93 100644
>--- a/arch/x86/mm/init_64.c
>+++ b/arch/x86/mm/init_64.c
>@@ -818,8 +818,7 @@ void __init paging_init(void)
> 	 *	 will not set it back.
> 	 */
> 	node_clear_state(0, N_MEMORY);
>-	if (N_MEMORY != N_NORMAL_MEMORY)
>-		node_clear_state(0, N_NORMAL_MEMORY);
>+	node_clear_state(0, N_NORMAL_MEMORY);
> 
> 	zone_sizes_init();
> }
>-- 
>2.17.2

-- 
Wei Yang
Help you, Help me