Upstream commit:

commit 3e3c6ff10fdb0bb086d61629d75bcad9169152b9
Author: Eric Blake <eblake>
Date:   Wed Jun 11 16:22:57 2014 -0600

    blockcommit: require base below top
    
    The block commit code looks for an explicit base file relative
    to the discovered top file; so for a chain of:
      base <- snap1 <- snap2 <- snap3
    and a command of:
      virsh blockcommit $dom vda --base snap2 --top snap1
    we got a sane message (here from libvirt 1.0.5):
    error: invalid argument: could not find base 'snap2' below 'snap1' in chain for 'vda'
    
    Meanwhile, recent refactoring has slightly reduced the quality of the
    libvirt error messages, by losing the phrase 'below xyz':
    error: invalid argument: could not find image 'snap2' in chain for 'snap3'
    
    But we had a one-off, where we were not excluding the top file
    itself in searching for the base; thankfully qemu still reports
    the error, but the quality is worse:
      virsh blockcommit $dom vda --base snap2 --top snap2
    error: internal error unable to execute QEMU command 'block-commit': Base '/snap2' not found
    
    Fix the one-off in blockcommit by changing the semantics of name
    lookup - if a starting point is specified, then the result must
    be below that point, rather than including that point.  The only
    other call to chain lookup was blockpull code, which was already
    forcing the lookup to omit the active layer and only needs a
    tweak to use the new semantics.
    
    This also fixes the bug exposed in the testsuite, where when doing
    a lookup pinned to an intermediate point in the chain, we were
    unable to return the name of the parent also in the chain.
    
    * src/util/virstoragefile.c (virStorageFileChainLookup): Change
    semantics for non-NULL startFrom.
    * src/qemu/qemu_driver.c (qemuDomainBlockJobImpl): Adjust caller,
    to keep existing semantics.
    * tests/virstoragetest.c (mymain): Adjust to expose new semantics.
    
    Signed-off-by: Eric Blake <eblake>


v1.2.5-133-g3e3c6ff

Verified with libvirt-1.2.17-2.el7.x86_64 and qemu-kvm-rhev-2.3.0-12.el7.x86_64.

Steps
1. define/start a vm with following xml
<disk type='file' device='disk'>
      <driver name='qemu' type='qcow2'/>
       <source protocol='gluster' name='gluster-vol1/rhel7.qcow2'>
            <host name='10.66.4.164' port='24007'/>
       </source>
       <target dev='vda' bus='virtio'/>
</disk>
       
2. create 3 snapshots
# for i in {1..3}; do virsh snapshot-create-as vm3 s$i --disk-only --diskspec vda,file=/tmp/vm3.s$i; done
Domain snapshot s1 created
Domain snapshot s2 created
Domain snapshot s3 created

3. do blockpull by specifying base with top image
# virsh blockpull vm3 vda --base /tmp/vm3.s3 --wait --verbose
error: invalid argument: could not find image '/tmp/vm3.s3' beneath '/tmp/vm3.s3' in chain for '/tmp/vm3.s3'

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