1 struct dentry *
  2 __d_lookup(struct dentry * parent,
  3            struct qstr * name)
  4 {
  5   unsigned int len = name->len;
  6   unsigned int hash = name->hash;
  7   const unsigned char *str = name->name;
  8   struct hlist_head *head = d_hash(parent,hash);
  9   struct dentry *found = NULL;
 10   struct hlist_node *node;
 11 
 12   rcu_read_lock();
 13   hlist_for_each (node, head) { 
 14     struct dentry *dentry; 
 15     unsigned long move_count;
 16     struct qstr * qstr;
 17 
 18     smp_read_barrier_depends();
 19     dentry = hlist_entry(node, struct dentry,
 20                          d_hash);
 21     if (unlikely(dentry->d_bucket != head))
 22       break;
 23     move_count = dentry->d_move_count;
 24     smp_rmb();
 25     if (dentry->d_name.hash != hash)
 26       continue;
 27     if (dentry->d_parent != parent)
 28       continue;
 29     qstr = dentry->d_qstr;
 30     smp_read_barrier_depends();
 31     if (parent->d_op &&
 32         parent->d_op->d_compare) {
 33       if (parent->d_op->d_compare(parent, qstr,
 34                                   name))
 35         continue;
 36     } else {
 37       if (qstr->len != len)
 38         continue;
 39       if (memcmp(qstr->name, str, len))
 40         continue;
 41     }
 42     spin_lock(&dentry->d_lock);
 43     /*
 44      * If dentry is moved, fail the lookup
 45      */ 
 46     if (likely(move_count ==
 47                dentry->d_move_count)) {
 48       if (!d_unhashed(dentry)) {
 49         atomic_inc(&dentry->d_count);
 50         found = dentry;
 51       }
 52     }
 53     spin_unlock(&dentry->d_lock);
 54     break;
 55   }
 56   rcu_read_unlock();
 57   return found;
 58 }