linux-kernel - Re: [PATCH] mm: sysctl: fix missing numa_stat when !CONFIG_HUGETLB

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Date:   Thu, 9 Jun 2022 10:45:56 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Muchun Song <songmuchun@...edance.com>
Cc:     mcgrof@...nel.org, keescook@...omium.org, yzaikin@...gle.com,
        akpm@...ux-foundation.org, vbabka@...e.cz,
        mgorman@...hsingularity.net, peterz@...radead.org,
        dhowells@...hat.com, willy@...radead.org, Liam.Howlett@...cle.com,
        kemi.wang@...el.com, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        stable@...r.kernel.org
Subject: Re: [PATCH] mm: sysctl: fix missing numa_stat when
 !CONFIG_HUGETLB_PAGE

On Thu 09-06-22 12:03:42, Muchun Song wrote:
> "numa_stat" should not be included in the scope of CONFIG_HUGETLB_PAGE,
> if CONFIG_HUGETLB_PAGE is not configured even if CONFIG_NUMA is configured,
> "numa_stat" is missed form /proc.  Remove it out of CONFIG_HUGETLB_PAGE
> and move numa_stat sysctl handling to mm/vmstat.c.
> 
> Fixes: 4518085e127d ("mm, sysctl: make NUMA stats configurable")
> Signed-off-by: Muchun Song <songmuchun@...edance.com>
> Cc: <stable@...r.kernel.org>

It really looks like numa_stat is misplaced but I am wondering why the
fix cannot be as simple as

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 830aaf8ca08e..b9c2cd9ed3a2 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -2463,6 +2463,17 @@ static struct ctl_table vm_table[] = {
 		.extra1		= SYSCTL_ZERO,
 		.extra2		= SYSCTL_TWO_HUNDRED,
 	},
+#ifdef CONFIG_NUMA
+	{
+		.procname		= "numa_stat",
+		.data			= &sysctl_vm_numa_stat,
+		.maxlen			= sizeof(int),
+		.mode			= 0644,
+		.proc_handler	= sysctl_vm_numa_stat_handler,
+		.extra1			= SYSCTL_ZERO,
+		.extra2			= SYSCTL_ONE,
+	},
+#endif
 #ifdef CONFIG_HUGETLB_PAGE
 	{
 		.procname	= "nr_hugepages",
@@ -2479,15 +2490,6 @@ static struct ctl_table vm_table[] = {
 		.mode           = 0644,
 		.proc_handler   = &hugetlb_mempolicy_sysctl_handler,
 	},
-	{
-		.procname		= "numa_stat",
-		.data			= &sysctl_vm_numa_stat,
-		.maxlen			= sizeof(int),
-		.mode			= 0644,
-		.proc_handler	= sysctl_vm_numa_stat_handler,
-		.extra1			= SYSCTL_ZERO,
-		.extra2			= SYSCTL_ONE,
-	},
 #endif
 	 {
 		.procname	= "hugetlb_shm_group",
-- 
Michal Hocko
SUSE Labs