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

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Message-ID: <20200315124913.GA3486@MiWiFi-R3L-srv>
Date:   Sun, 15 Mar 2020 20:49:13 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Wei Yang <richard.weiyang@...il.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 03/14/20 at 03:10pm, Wei Yang wrote:
> 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?

This is for x86_64 only, there's no node_state for N_HIGH_MEMORY.

> 
> 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
>