linux-kernel - Re: [PATCH] mm: unhide vmstat_text definition for CONFIG

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Message-ID: <20160516073716.GB23146@dhcp22.suse.cz>
Date:	Mon, 16 May 2016 09:37:16 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Christoph Lameter <cl@...ux.com>,
	Mel Gorman <mgorman@...hsingularity.net>,
	Joonsoo Kim <iamjoonsoo.kim@....com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: unhide vmstat_text definition for CONFIG_SMP

On Wed 11-05-16 16:54:55, Arnd Bergmann wrote:
> In randconfig builds with sysfs, procfs and numa all disabled,
> but SMP enabled, we now get a link error in the newly introduced
> vmstat_refresh function:
> 
> mm/built-in.o: In function `vmstat_refresh':
> :(.text+0x15c78): undefined reference to `vmstat_text'
> 
> This modifes the already elaborate #ifdef to also cover that
> configuration.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> Fixes: mmotm ("mm: /proc/sys/vm/stat_refresh to force vmstat update")

I agree with Christoph that vmstat_refresh is PROC_FS only so we should
fix it there. It is not like this would be generally reusable helper...
Why don't we just do:
---
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 57a24e919907..c759b526287b 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1370,6 +1370,7 @@ static void refresh_vm_stats(struct work_struct *work)
 	refresh_cpu_vm_stats(true);
 }
 
+#ifdef CONFIG_PROC_FS
 int vmstat_refresh(struct ctl_table *table, int write,
 		   void __user *buffer, size_t *lenp, loff_t *ppos)
 {
@@ -1422,6 +1423,7 @@ int vmstat_refresh(struct ctl_table *table, int write,
 		*lenp = 0;
 	return 0;
 }
+#endif
 
 static void vmstat_update(struct work_struct *w)
 {
-- 
Michal Hocko
SUSE Labs