[PATCH V2 1/2] sysctl: Limit the value of interface compact_memory

[<ye.xingchen@zte.com.cn>]

From: Minghao Chi <chi.minghao@zte.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/
Signed-off-by: Minghao Chi <chi.minghao@zte.com.cn>
Signed-off-by: Ye Xingchen <ye.xingchen@zte.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,
 		.maxlen		= sizeof(int),
 		.mode		= 0200,
 		.proc_handler	= sysctl_compaction_handler,
+		.extra1		= SYSCTL_ONE,
+		.extra2		= SYSCTL_ONE,
 	},
 	{
 		.procname	= "compaction_proactiveness",
-- 
2.25.1