Refactor node reference counting in rbtdb.c

Refactor the pattern in the newref() and decref() functions in rbtdb.c
following the pattern, so it follows the similar pattern we already have
for QPDB.

(cherry picked from commit 9c45de94736c0a0fe101eb0c2163208c00bab988)

diff --git a/lib/dns/rbtdb.c b/lib/dns/rbtdb.c
index 2d1b143b20ba64cba054a0db8b29add3889764d5..f3d2b1b54bd627f374012e9ff6b19ebfcdb1c126 100644 (file)
--- a/lib/dns/rbtdb.c
+++ b/lib/dns/rbtdb.c
@@ -1878,6 +1878,15 @@ delete_node(dns_rbtdb_t *rbtdb, dns_rbtnode_t *node) {
        }
 }
 
+static void
+rbtnode_newref(dns_rbtdb_t *rbtdb, dns_rbtnode_t *node) {
+       if (isc_refcount_increment0(&node->references) == 0) {
+               /* this is the first reference to the node */
+               isc_refcount_increment0(
+                       &rbtdb->node_locks[node->locknum].references);
+       }
+}
+
 /*
  * Caller must be holding the node lock.
  */
@@ -1890,11 +1899,8 @@ new_reference(dns_rbtdb_t *rbtdb, dns_rbtnode_t *node,
                ISC_LIST_UNLINK(rbtdb->deadnodes[node->locknum], node,
                                deadlink);
        }
-       if (isc_refcount_increment0(&node->references) == 0) {
-               /* this is the first reference to the node */
-               isc_refcount_increment0(
-                       &rbtdb->node_locks[node->locknum].references);
-       }
+
+       rbtnode_newref(rbtdb, node);
 }
 
 /*%
@@ -2025,6 +2031,22 @@ reactivate_node(dns_rbtdb_t *rbtdb, dns_rbtnode_t *node,
        NODE_UNLOCK(nodelock, locktype);
 }
 
+static bool
+rbtnode_decref(dns_rbtdb_t *rbtdb, dns_rbtnode_t *node) {
+       uint32_t refs;
+       rbtdb_nodelock_t *nodelock = &rbtdb->node_locks[node->locknum];
+
+       /* Handle easy and/or typical case first. */
+       if (isc_refcount_decrement(&node->references) > 1) {
+               return false;
+       }
+
+       refs = isc_refcount_decrement(&nodelock->references);
+       INSIST(refs > 0);
+
+       return true;
+}
+
 /*
  * Caller must be holding the node lock; either the "strong", read or write
  * lock.  Note that the lock must be held even when node references are
@@ -2049,44 +2071,34 @@ decrement_reference(dns_rbtdb_t *rbtdb, dns_rbtnode_t *node,
        int bucket = node->locknum;
        rbtdb_nodelock_t *nodelock = &rbtdb->node_locks[bucket];
        bool no_reference = true;
-       uint_fast32_t refs;
 
 #define KEEP_NODE(n, r, l)                                  \
        ((n)->data != NULL || ((l) && (n)->down != NULL) || \
         (n) == (r)->origin_node || (n) == (r)->nsec3_origin_node)
 
-       /* Handle easy and/or typical case first. */
-       if (isc_refcount_decrement(&node->references) > 1) {
+       if (!rbtnode_decref(rbtdb, node)) {
                return false;
        }
 
-       refs = isc_refcount_decrement(&nodelock->references);
-       INSIST(refs > 0);
-
-       /* Handle easy and typical case first. */
        if (!node->dirty && KEEP_NODE(node, rbtdb, locked)) {
                return true;
        }
 
-       /*
-        * Node lock ref has decremented to 0 and we may need to clean up the
-        * node. To clean it up, the node ref needs to decrement to 0 under the
-        * node write lock, so we regain the ref and try again.
-        */
-       new_reference(rbtdb, node, nlock);
-
        /* Upgrade the lock? */
        if (nlock == isc_rwlocktype_read) {
+               /*
+                * Node lock ref has decremented to 0 and we may need to clean
+                * up the node. To clean it up, the node ref needs to decrement
+                * to 0 under the node write lock, so we regain the ref and try
+                * again.
+                */
+               rbtnode_newref(rbtdb, node);
                NODE_UNLOCK(&nodelock->lock, isc_rwlocktype_read);
                NODE_LOCK(&nodelock->lock, isc_rwlocktype_write);
-       }
-
-       if (isc_refcount_decrement(&node->references) > 1) {
-               /* Restore the lock? */
-               if (nlock == isc_rwlocktype_read) {
+               if (!rbtnode_decref(rbtdb, node)) {
                        NODE_DOWNGRADE(&nodelock->lock);
+                       return false;
                }
-               return false;
        }
 
        if (node->dirty) {
@@ -2131,9 +2143,6 @@ decrement_reference(dns_rbtdb_t *rbtdb, dns_rbtnode_t *node,
                write_locked = true;
        }
 
-       refs = isc_refcount_decrement(&nodelock->references);
-       INSIST(refs > 0);
-
        if (KEEP_NODE(node, rbtdb, locked || write_locked)) {
                goto restore_locks;
        }
@@ -2172,7 +2181,7 @@ decrement_reference(dns_rbtdb_t *rbtdb, dns_rbtnode_t *node,
        } else {
                INSIST(node->data == NULL);
                if (!ISC_LINK_LINKED(node, deadlink)) {
-                       ISC_LIST_APPEND(rbtdb->deadnodes[bucket], node,
+                       ISC_LIST_APPEND(rbtdb->deadnodes[node->locknum], node,
                                        deadlink);
                }
        }