ceph: add dentry lease metric support

For dentry leases, only count the hit/miss info triggered from the vfs
calls. For the cases like request reply handling and ceph_trim_dentries,
ignore them.

For now, these are only viewable using debugfs. Future patches will
allow the client to send the stats to the MDS.

The output looks like:

item          total           miss            hit
-------------------------------------------------
d_lease       11              7               141

URL: https://tracker.ceph.com/issues/43215
Signed-off-by: Xiubo Li <xiubli@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

1 files changed, 35 insertions, 0 deletions

diff --git a/fs/ceph/metric.c b/fs/ceph/metric.c
new file mode 100644
index 000000000000..873a3769fa0d
--- /dev/null
+++ b/fs/ceph/metric.c
@@ -0,0 +1,35 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#include <linux/types.h>
+#include <linux/percpu_counter.h>
+
+#include "metric.h"
+
+int ceph_metric_init(struct ceph_client_metric *m)
+{
+	int ret;
+
+	if (!m)
+		return -EINVAL;
+
+	atomic64_set(&m->total_dentries, 0);
+	ret = percpu_counter_init(&m->d_lease_hit, 0, GFP_KERNEL);
+	if (ret)
+		return ret;
+	ret = percpu_counter_init(&m->d_lease_mis, 0, GFP_KERNEL);
+	if (ret) {
+		percpu_counter_destroy(&m->d_lease_hit);
+		return ret;
+	}
+
+	return 0;
+}
+
+void ceph_metric_destroy(struct ceph_client_metric *m)
+{
+	if (!m)
+		return;
+
+	percpu_counter_destroy(&m->d_lease_mis);
+	percpu_counter_destroy(&m->d_lease_hit);
+}