Description of problem:

By default on RHEL 7.1 docker creates sparse file one upon start (systemctl start docker). That file is used as a loopback-device (seemingly using dmsetup syscall eqivalents), then issues

mkfs.ext4 -E nodiscard,lazy_itable_init=0,lazy_journal_init=0 /dev/mapper/docker-253:1-243367-base

This command may take several minutes to complete. Meanwhile the avgqu-sz gauge of sar shoots up to >25000. Then the systemctl start reports timeout.


Version-Release number of selected component (if applicable):
docker-1.7.1-115.el7.x86_64


How reproducible:
Something like 5 out of 10 cases on all-in-one Openstack VMs on machines I obtained from beaker. Setting unsafe caching of the VM disk seems to decrease the occurence


Steps to Reproduce:
# systemctl stop docker
#dmsetup remove /dev/dm-0
#dmsetup remove /dev/dm-1
# rm /var/lib/docker/devicemapper/devicemapper/*
# systemctl start docker


Actual results:
[root@test-node-compute-f429d openshift]# systemctl status -l docker.service
docker.service - Docker Application Container Engine
   Loaded: loaded (/usr/lib/systemd/system/docker.service; disabled)
  Drop-In: /usr/lib/systemd/system/docker.service.d
           └─docker-sdn-ovs.conf
   Active: failed (Result: timeout) since Út 2015-09-29 15:30:25 UTC; 1min 53s ago
     Docs: http://docs.docker.com
 Main PID: 25025

zář 29 15:27:25 test-node-compute-f429d.example.com systemd[1]: Starting Docker Application Container Engine...
zář 29 15:27:25 test-node-compute-f429d.example.com docker[25025]: time="2015-09-29T15:27:25.975880434Z" level=warning msg="--storage-opt dm.thinpooldev is preferred over --storage-opt dm.datadev or dm.metadatadev"
zář 29 15:27:25 test-node-compute-f429d.example.com docker[25025]: time="2015-09-29T15:27:25.976662822Z" level=info msg="Listening for HTTP on unix (/var/run/docker.sock)"
zář 29 15:27:25 test-node-compute-f429d.example.com docker[25025]: time="2015-09-29T15:27:25.978128795Z" level=error msg="Unable to delete device: Error running DeleteDevice dm_task_run failed"
zář 29 15:28:55 test-node-compute-f429d.example.com systemd[1]: docker.service operation timed out. Terminating.
zář 29 15:30:25 test-node-compute-f429d.example.com systemd[1]: docker.service stopping timed out (2). Killing.
zář 29 15:30:25 test-node-compute-f429d.example.com systemd[1]: Failed to start Docker Application Container Engine.
zář 29 15:30:25 test-node-compute-f429d.example.com systemd[1]: Unit docker.service entered failed state.


Expected results:
service started


Additional info:
Everything written in the Description in this BZ is just a copy of https://github.com/docker/docker/issues/16653. I suggest to discuss upstream. This bug is often triggered by using the openshift-ansible which is recommended way of deploying Openshift, but it is not packaged and branded, therefore I am quite unsure how to report it downstream to make sure it is fixed and documented somehow.