Why ceph don't write logs to file after setting `log_to_file= true` ? Ownership of ceph log files is root:root, not ceph:ceph

Issue

• Why osd and mgr logs are empty under /var/log/ceph/ directory
• Ownership of ceph log files is root:root, not ceph:ceph:

# ls -l /var/log/ceph
-rw-r--r-- 1 root root         0 Jan 11 15:47 ceph-osd.1.log
-rw-r--r-- 1 root root         0 Jan 11 15:48 ceph-osd.2.log
-rw-r--r-- 1 root root         0 Jan 11 15:48 ceph-osd.3.log