[PATCH] mm: compaction: optimize compact_memory to comply with the admin-guide

[wenyang . linux]

From: Wen Yang <wenyang.linux@xxxxxxxxxxx>

For the /proc/sys/vm/compact_memory file, the admin-guide states:
When 1 is written to the file, all zones are compacted such that free
memory is available in contiguous blocks where possible. This can be
important for example in the allocation of huge pages although processes
will also directly compact memory as required

But it was not strictly followed, writing any value would cause all
zones to be compacted. In some critical scenarios, some applications
operating it, such as echo 0, have caused serious problems.

It has been slightly optimized to comply with the admin-guide.

Signed-off-by: Wen Yang <wenyang.linux@xxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: William Lam <william.lam@xxxxxxxxxxxxx>
Cc: Fu Wei <wefu@xxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
 mm/compaction.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/mm/compaction.c b/mm/compaction.c
index c8bcdea15f5f..3c4aa533d61c 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -2780,6 +2780,17 @@ static int compaction_proactiveness_sysctl_handler(struct ctl_table *table, int
 static int sysctl_compaction_handler(struct ctl_table *table, int write,
 			void *buffer, size_t *length, loff_t *ppos)
 {
+	struct ctl_table t;
+	int compact;
+	int ret;
+
+	t = *table;
+	t.data = &compact;
+
+	ret = proc_dointvec_minmax(&t, write, buffer, length, ppos);
+	if (ret)
+		return ret;
+
 	if (write)
 		compact_nodes();
 
@@ -3099,6 +3110,8 @@ static struct ctl_table vm_compaction[] = {
 		.maxlen		= sizeof(int),
 		.mode		= 0200,
 		.proc_handler	= sysctl_compaction_handler,
+		.extra1		= SYSCTL_ONE,
+		.extra2		= SYSCTL_ONE,
 	},
 	{
 		.procname	= "compaction_proactiveness",
-- 
2.37.2