# getsebool -a | grep virt_use_samba
virt_use_samba --> on

Posted a couple patches upstream to resolve:

http://www.redhat.com/archives/libvir-list/2015-June/msg00155.html

After a slight adjustment to original patch, see:

http://www.redhat.com/archives/libvir-list/2015-June/msg00693.html

Pushed upstream:

commit 29230951f1430c196420e8a3a5efbe5ea98f7184
Author: John Ferlan <jferlan>
Date:   Wed Jun 3 10:20:56 2015 -0400

    storage: Generate correct parameters for CIFS
       
    When generating the path to the dir for a CIFS/Samba driver, the code
    would generate a source path for the mount using "%s:%s" while the
    mount.cifs expects to see "//%s/%s". So check for the cifsfs and
    format the source path appropriately.
    
    Additionally, since there is no means to authenticate, the mount
    needs a "-o guest" on the command line in order to anonymously mount
    the Samba directory.


$ git describe 29230951f1430c196420e8a3a5efbe5ea98f7184
v1.2.16-164-g2923095
$

John,

Source dir started with slash. So 1 redundant slash after source hostname is provided in following code. The code generates //10.66.4.164//samba_share while mount.cifs expects //10.66.4.164/samba_share


if (pool->def->source.format == VIR_STORAGE_POOL_NETFS_CIFS) {
            if (virAsprintf(&src, "//%s/%s",
                            pool->def->source.hosts[0].name,
                            pool->def->source.dir) == -1)
               return -1;

e.g.
# virsh pool-start netfs-cifs
error: Failed to start pool netfs-cifs
error: internal error: Child process (/usr/bin/mount -t cifs //10.66.4.164//samba_share /tmp/cifs -o guest) unexpected exit status 32: 2015-07-10 09:21:30.082+0000: 29237: debug : virFileClose:102 : Closed fd 28
2015-07-10 09:21:30.082+0000: 29237: debug : virFileClose:102 : Closed fd 30
2015-07-10 09:21:30.082+0000: 29237: debug : virFileClose:102 : Closed fd 26
Retrying with upper case share name
mount error(6): No such device or address
Refer to the mount.cifs(8) manual page (e.g. man mount.cifs)

Please ignore comment #5

Have a better look at patch, it says the path to the Samba share without the leading slash. I will test again.

Verified with libvirt-1.2.17-1.el7.x86_64

Steps
1. 1. define a netfs pool using cifs format
# cat nfs-cifs-pool.xml
 <pool type="netfs">
        <name>netfs-cifs</name>
        <source>
          <host name="10.66.4.164"/>
          <dir path="samba_share"/>
          <format type='cifs'/>
        </source>
        <target>
          <path>/tmp/cifs</path>
        </target>
      </pool>

#virsh pool-define nfs-cifs-pool.xml

2. build the pool
#virsh pool-build netfs-cifs

3. start the pool
# virsh pool-start netfs-cifs
Pool netfs-cifs started

Just a note that acknowledge I too had the same concern when developing - that is the "leading" slash; however, after researching usage of "relative" vs "absolute" directory path, I decided to follow the existing gluster example which requires the relative path since it felt like the cifs pool would be more alike that than perhaps some sort of "normal" (hah) file system pool.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2015-2202.html