linux-kernel - Re: [PATCH] mm: compaction.c: Propagate return value upstream

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Date:   Thu, 27 Dec 2018 08:44:45 -0800
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Matthew Wilcox <willy@...radead.org>,
        Aditya Pakki <pakki001@....edu>
Cc:     kjlu@....edu, Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        David Rientjes <rientjes@...gle.com>,
        Yang Shi <yang.shi@...ux.alibaba.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Joe Perches <joe@...ches.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Mel Gorman <mgorman@...hsingularity.net>
Subject: Re: [PATCH] mm: compaction.c: Propagate return value upstream

On 12/26/18 7:50 PM, Matthew Wilcox wrote:
> On Wed, Dec 26, 2018 at 01:42:56PM -0600, Aditya Pakki wrote:
>> In sysctl_extfrag_handler(), proc_dointvec_minmax() can return an
>> error. The fix propagates the error upstream in case of failure.
> 
> Why not just ...

Yes, this change (below) makes sense to me.

> Mel, Randy?  You seem to have been the prime instigators on this.

I expect that all I did was move the location of the source code lines of
the sysctl, but that is just a guess, based on this commit message:
  [randy.dunlap@...cle.com: Fix build errors when proc fs is not configured]

> diff --git a/include/linux/compaction.h b/include/linux/compaction.h
> index 68250a57aace..70d0256edd31 100644
> --- a/include/linux/compaction.h
> +++ b/include/linux/compaction.h
> @@ -88,8 +88,6 @@ extern int sysctl_compact_memory;
>  extern int sysctl_compaction_handler(struct ctl_table *table, int write,
>  			void __user *buffer, size_t *length, loff_t *ppos);
>  extern int sysctl_extfrag_threshold;
> -extern int sysctl_extfrag_handler(struct ctl_table *table, int write,
> -			void __user *buffer, size_t *length, loff_t *ppos);
>  extern int sysctl_compact_unevictable_allowed;
>  
>  extern int fragmentation_index(struct zone *zone, unsigned int order);
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 5fc724e4e454..e9c69247fc29 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -1439,7 +1439,7 @@ static struct ctl_table vm_table[] = {
>  		.data		= &sysctl_extfrag_threshold,
>  		.maxlen		= sizeof(int),
>  		.mode		= 0644,
> -		.proc_handler	= sysctl_extfrag_handler,
> +		.proc_handler	= proc_dointvec_minmax,
>  		.extra1		= &min_extfrag_threshold,
>  		.extra2		= &max_extfrag_threshold,
>  	},
> diff --git a/mm/compaction.c b/mm/compaction.c
> index 7c607479de4a..80b941d9b6e7 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -1876,14 +1876,6 @@ int sysctl_compaction_handler(struct ctl_table *table, int write,
>  	return 0;
>  }
>  
> -int sysctl_extfrag_handler(struct ctl_table *table, int write,
> -			void __user *buffer, size_t *length, loff_t *ppos)
> -{
> -	proc_dointvec_minmax(table, write, buffer, length, ppos);
> -
> -	return 0;
> -}
> -
>  #if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
>  static ssize_t sysfs_compact_node(struct device *dev,
>  			struct device_attribute *attr,
> 


-- 
~Randy