Ceph » CephFS

We found a bug in ceph-fuse when we set log_max_new = 0 in ceph.conf, which will lead ceph-fuse process hang when it is started. We set this option, because we want to minimize the memory used by logging subsystem.
After checking the related code, we found something incorrect in main methods within ceph_fuse.cc.
The suspicious code snippet is below:

  if (childpid == 0) {
    common_init_finish(g_ceph_context);

    //cout << "child, mounting" << std::endl;
    ::close(fd[0]);

    if (restart_log)
      g_ceph_context->_log->start();

The hang event happens when executing common_init_finish(g_ceph_context), and in AdminSocket::init it hits

ldout(m_cct, 5) << "init " << path << dendl;

This will depend on log subsystem working properly. But till then, the Log thread haven't been started in the child process.
So, I think we should start the log thread before the common_init_finish method. As far as I know to fix this issue is to bring g_ceph_context->_log->start(); before common_init_finish(g_ceph_context);