description of problem:
libvirt send a wrong command to qemu when try to do blcok migrate to a gluster volume

Version-Release number of selected component (if applicable):
libvirt-1.2.13-1.el7.x86_64

How reproducible:
100%

Steps to Reproduce:
 
1.prepare a transient vm
# virsh create test3.xml

2.prepare gluster volume xml:
# cat gluster.xml
    <disk type='network' device='disk'>
      <driver name='qemu' type='raw' cache='none'/>
      <source protocol='gluster' name='gluster-vol1/rh6.img.s2'>
        <host name='10.66.100.118'/>
      </source>
      <target dev='vdd' bus='virtio'/>
      <shareable/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x0a' function='0x0'/>
    </disk>


3. do blockcopy
# virsh blockcopy test3 hda --xml gluster.xml
error: internal error: unable to execute QEMU command 'drive-mirror': Could not create file: Permission denied

Actual results:
libvirt send a wrong command to qemu when try to do blcok migrate to a gluster volume

Expected results:
if support this do it success, if not report error more early

infomation:

2015-03-27 02:00:55.601+0000: 11778: debug : virStorageFileBackendGlusterInit:588 : initializing gluster storage file 0x7fdd58001300 (gluster://10.66.100.118:0/gluster-vol1/rh6.img.s2)[0:0]
2015-03-27 02:00:55.642+0000: 11778: debug : virStorageFileChown:2783 : chown of storage file 0x7fdd58001300 to 107:107
2015-03-27 02:00:55.644+0000: 11778: debug : virStorageFileBackendGlusterDeinit:559 : deinitializing gluster storage file 0x7fdd58001300 (gluster://10.66.100.118:0/gluster-vol1/rh6.img.s2)
2015-03-27 02:00:55.644+0000: 11778: info : virObjectUnref:259 : OBJECT_UNREF: obj=0x7fdd68186020
2015-03-27 02:00:55.644+0000: 11778: debug : qemuDomainObjEnterMonitorInternal:1548 : Entering monitor (mon=0x7fdd60000d00 vm=0x7fdd68248400 name=test3)
2015-03-27 02:00:55.644+0000: 11778: info : virObjectRef:296 : OBJECT_REF: obj=0x7fdd60000d00
2015-03-27 02:00:55.644+0000: 11778: debug : qemuMonitorDriveMirror:3430 : mon=0x7fdd60000d00, device=drive-ide0-0-0, file=/rh6.img.s2, format=raw, bandwidth=0, granularity=0, buf_size=0, flags=0
2015-03-27 02:00:55.644+0000: 11778: debug : virJSONValueToString:1665 : object=0x7fdd5829af70

2015-03-27 02:00:55.644+0000: 11778: debug : virJSONValueToString:1698 : result={"execute":"drive-mirror","arguments":{"device":"drive-ide0-0-0","target":"/rh6.img.s2","sync":"full","mode":"absolute-paths","format":"raw"},"id":"libvirt-10"}
2015-03-27 02:00:55.644+0000: 11778: debug : qemuMonitorJSONCommandWithFd:290 : Send command '{"execute":"drive-mirror","arguments":{"device":"drive-ide0-0-0","target":"/rh6.img.s2","sync":"full","mode":"absolute-paths","format":"raw"},"id":"libvirt-10"}' for write with FD -1
2015-03-27 02:00:55.644+0000: 11778: info : virEventPollUpdateHandle:152 : EVENT_POLL_UPDATE_HANDLE: watch=10 events=15
2015-03-27 02:00:55.644+0000: 11778: debug : virEventPollInterruptLocked:726 : Interrupting
2015-03-27 02:00:55.644+0000: 11778: info : qemuMonitorSend:972 : QEMU_MONITOR_SEND_MSG: mon=0x7fdd60000d00 msg={"execute":"drive-mirror","arguments":{"device":"drive-ide0-0-0","target":"/rh6.img.s2","sync":"full","mode":"absolute-paths","format":"raw"},"id":"libvirt-10"}
 fd=-1
...
2015-03-27 02:00:55.651+0000: 11774: info : qemuMonitorIOProcess:399 : QEMU_MONITOR_IO_PROCESS: mon=0x7fdd60000d00 buf={"id": "libvirt-10", "error": {"class": "GenericError", "desc": "Could not create file: Permission denied"}}
 len=110

Also i can find avc report that qemu try to create/read file in "/"

time->Fri Mar 27 09:58:07 2015
type=SYSCALL msg=audit(1427421487.828:135051): arch=c000003e syscall=4 success=yes exit=0 a0=7f070e71ce40 a1=7fff204b3370 a2=7fff204b3370 a3=7f0706262920 items=0 ppid=1 pid=10603 auid=4294967295 uid=107 gid=107 euid=107 suid=107 fsuid=107 egid=107 sgid=107 fsgid=107 tty=(none) ses=4294967295 comm="qemu-kvm" exe="/usr/libexec/qemu-kvm" subj=system_u:system_r:svirt_t:s0:c81,c359 key=(null)
type=AVC msg=audit(1427421487.828:135051): avc:  denied  { getattr } for  pid=10603 comm="qemu-kvm" path="/rh6.img.s2" dev="dm-0" ino=1055130 scontext=system_u:system_r:svirt_t:s0:c81,c359 tcontext=system_u:object_r:root_t:s0 tclass=file
----


Additional info:

From Shanzhi Yu:

The error show it is not supported to copy to no-file destination. 
What we need is a goto endjob when try to copy to a non-file destination

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index db4f0b4..f07e4fb 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -16642,6 +16642,7 @@ qemuDomainBlockCopyCommon(virDomainObjPtr vm,
     if (!virStorageSourceIsLocalStorage(mirror)) {
         virReportError(VIR_ERR_ARGUMENT_UNSUPPORTED, "%s",
                        _("non-file destination not supported yet"));
+        goto endjob;
     }
     if (stat(mirror->path, &st) < 0) {
         if (errno != ENOENT) {