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

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Date:   Wed, 26 Dec 2018 19:50:29 -0800
From:   Matthew Wilcox <willy@...radead.org>
To:     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>,
        Randy Dunlap <rdunlap@...radead.org>
Subject: Re: [PATCH] mm: compaction.c: Propagate return value upstream

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 ...

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

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,