linux-kernel - Re: [PATCH V2 1/2] sysctl: Limit the value of interface compact

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Date:   Wed, 8 Mar 2023 11:21:36 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     ye.xingchen@....com.cn, mcgrof@...nel.org
Cc:     keescook@...omium.org, yzaikin@...gle.com,
        akpm@...ux-foundation.org, linmiaohe@...wei.com,
        chi.minghao@....com.cn, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH V2 1/2] sysctl: Limit the value of interface
 compact_memory



On 3/6/23 07:07, ye.xingchen@....com.cn wrote:
> From: Minghao Chi <chi.minghao@....com.cn>
> 
> In Documentation/admin-guide/sysctl/vm.rst:109 say: when 1 is written
> to the file, all zones are compacted such that free memory is available
> in contiguous blocks where possible.
> So limit the value of interface compact_memory to 1.
> 
> Link: https://lore.kernel.org/all/ZAJwoXJCzfk1WIBx@bombadil.infradead.org/

I don't think the split to two patches you did, achieves Luis' request.

> Signed-off-by: Minghao Chi <chi.minghao@....com.cn>
> Signed-off-by: Ye Xingchen <ye.xingchen@....com.cn>
> 
> ---
>  include/linux/compaction.h | 1 +
>  kernel/sysctl.c            | 4 +++-
>  2 files changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/compaction.h b/include/linux/compaction.h
> index 52a9ff65faee..caa24e33eeb1 100644
> --- a/include/linux/compaction.h
> +++ b/include/linux/compaction.h
> @@ -81,6 +81,7 @@ static inline unsigned long compact_gap(unsigned int order)
>  }
> 
>  #ifdef CONFIG_COMPACTION
> +extern int sysctl_compact_memory;
>  extern unsigned int sysctl_compaction_proactiveness;
>  extern int sysctl_compaction_handler(struct ctl_table *table, int write,
>  			void *buffer, size_t *length, loff_t *ppos);
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index c14552a662ae..67f70952f71a 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -2192,10 +2192,12 @@ static struct ctl_table vm_table[] = {
>  #ifdef CONFIG_COMPACTION
>  	{
>  		.procname	= "compact_memory",
> -		.data		= NULL,
> +		.data		= &sysctl_compact_memory,

I doubt this compiles/links without patch 2, as there's no definition
until patch 2.

>  		.maxlen		= sizeof(int),
>  		.mode		= 0200,
>  		.proc_handler	= sysctl_compaction_handler,
> +		.extra1		= SYSCTL_ONE,
> +		.extra2		= SYSCTL_ONE,
>  	},
>  	{
>  		.procname	= "compaction_proactiveness",

IIUC his request was to move the compaction entries out of sysctl.c?