[PATCH V2 2/2] mm: compaction: Limit the value of interface compact_memory

[ye.xingchen]

From: Minghao Chi <chi.minghao@xxxxxxxxxx>

Available only when CONFIG_COMPACTION is set. When 1 is written to
the file, all zones are compacted such that free memory is available
in contiguous blocks where possible.
But echo others-parameter > compact_memory, this function will be
triggered by writing parameters to the interface.

Applied this patch,
sh/$ echo 1.1 > /proc/sys/vm/compact_memory
sh/$ sh: write error: Invalid argument
The start and end time of printing triggering compact_memory.

Link: https://lore.kernel.org/all/ZAJwoXJCzfk1WIBx@xxxxxxxxxxxxxxxxxxxxxx/
Signed-off-by: Minghao Chi <chi.minghao@xxxxxxxxxx>
Signed-off-by: Ye Xingchen <ye.xingchen@xxxxxxxxxx>
---
 mm/compaction.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/mm/compaction.c b/mm/compaction.c
index 5a9501e0ae01..2c9ecc4b9d23 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -2763,6 +2763,8 @@ int compaction_proactiveness_sysctl_handler(struct ctl_table *table, int write,
 	return 0;
 }

+/* The written value is actually unused, all memory is compacted */
+int sysctl_compact_memory;
 /*
  * This is the entry point for compacting all nodes via
  * /proc/sys/vm/compact_memory
@@ -2770,8 +2772,16 @@ int compaction_proactiveness_sysctl_handler(struct ctl_table *table, int write,
 int sysctl_compaction_handler(struct ctl_table *table, int write,
 			void *buffer, size_t *length, loff_t *ppos)
 {
-	if (write)
+	int ret;
+
+	ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
+	if (ret)
+		return ret;
+	if (write) {
+		pr_info("compact_nodes start\n");
 		compact_nodes();
+		pr_info("compact_nodes end\n");
+	}

 	return 0;
 }
-- 
2.25.1