cls/rbd: save max group snap order

Save the last used group snap order value to speed up
snapshot creation.

Signed-off-by: N Balachandran <nibalach@redhat.com>

1 files changed, 13 insertions, 27 deletions

diff --git a/src/cls/rbd/cls_rbd.cc b/src/cls/rbd/cls_rbd.cc
index 7330db8c6d3..affb986aeff 100644
--- a/src/cls/rbd/cls_rbd.cc
+++ b/src/cls/rbd/cls_rbd.cc
@@ -6899,6 +6899,7 @@ int dir_remove(cls_method_context_t hctx,
 
 static const string RBD_GROUP_SNAP_KEY_PREFIX = "snapshot_";
 static const string RBD_GROUP_SNAP_ORDER_KEY_PREFIX = "snap_order_";
+static const string RBD_GROUP_SNAP_MAX_ORDER_KEY = "snap_max_order";
 
 std::string snap_key(const std::string &snap_id) {
   ostringstream oss;
@@ -7482,37 +7483,22 @@ int group_snap_set(cls_method_context_t hctx,
       return -EEXIST;
     }
 
-    std::string last_read = group::snap_order_key("");
-    bool more;
     uint64_t max_order = 0;
-    std::map<string, bufferlist> vals;
-    do {
-      int r = cls_cxx_map_get_vals(hctx, last_read,
-                                   group::RBD_GROUP_SNAP_ORDER_KEY_PREFIX,
-                                   RBD_MAX_KEYS_READ, &vals, &more);
-      if (r < 0) {
-        return r;
-      }
-      for (auto &[key, bl] : vals) {
-        auto iter = bl.cbegin();
-        uint64_t order;
-        try {
-          decode(order, iter);
-        } catch (const ceph::buffer::error &err) {
-          CLS_ERR("error decoding snapshot order: %s", key.c_str());
-          return -EIO;
-        }
-        max_order = std::max(max_order, order);
-      }
-      if (!vals.empty()) {
-        last_read = vals.rbegin()->first;
-      } else {
-        ceph_assert(!more);
-      }
-    } while (more);
+
+    r = read_key(hctx, group::RBD_GROUP_SNAP_MAX_ORDER_KEY, &max_order);
+    if (r < 0 && r != -ENOENT) {
+      return r;
+    }
 
     bufferlist bl;
     encode(++max_order, bl);
+    r = cls_cxx_map_set_val(hctx, group::RBD_GROUP_SNAP_MAX_ORDER_KEY, &bl);
+    if (r < 0) {
+      CLS_ERR("error setting key: %s : %s",
+              group::RBD_GROUP_SNAP_MAX_ORDER_KEY.c_str(),
+              cpp_strerror(r).c_str());
+      return r;
+    }
     r = cls_cxx_map_set_val(hctx, order_key, &bl);
     if (r < 0) {
       CLS_ERR("error setting key: %s : %s", order_key.c_str(),