Created attachment 1236823 [details]
The log of valgrind

Description of problem:
As subject

Version-Release number of selected component (if applicable):
libvirt-2.0.0-10.el7_3.2.x86_64
qemu-kvm-rhev-2.6.0-28.el7_3.2.x86_64
glusterfs-3.8.4-10.el7.x86_64
kernel-3.10.0-514.6.1.el7.x86_64

How reproducible:
100%

Steps to Reproduce:
1. Prepare a running VM based on glusterfs back-end
# mount -t glusterfs xx.xx.xx.xx:/gluster-vol1 /var/tmp/gls
# virsh define gls.xml
Domain gls defined from gls.xml

# virsh start gls
Domain gls started

2. Create a external snapshot based on glusterfs
# virsh snapshot-create gls s1.xml --disk-only
Domain snapshot snap1-gluster created from 's1.xml'

# virsh snapshot-list gls
 Name                 Creation Time             State
------------------------------------------------------------
 snap1-gluster        2017-01-03 03:46:41 -0500 disk-snapshot

# cat s1.xml
<domainsnapshot>
<name>snap1-gluster</name>
<disks>
<disk name='vda' type='network'>
<driver type='qcow2'/>
<source protocol='gluster' name='gluster-vol1/gls.s1'>
<host name='xx.xx.xx.xx'/>
</source>
</disk>
</disks>
</domainsnapshot>

3. Attach a disk and create external snapshots on glusterfs
# qemu-img create -f qcow2 /var/tmp/gls/vdb.qcow2 100M
Formatting '/var/tmp/gls/vdb.qcow2', fmt=qcow2 size=104857600 encryption=off cluster_size=65536 lazy_refcounts=off refcount_bits=16
# virsh attach-device gls vdb-net.xml
Device attached successfully

# virsh snapshot-create gls s2.xml --disk-only
Domain snapshot snap2-gluster created from 's2.xml'
# virsh snapshot-list gls
 Name                 Creation Time             State
------------------------------------------------------------
 snap1-gluster        2017-01-03 03:46:41 -0500 disk-snapshot
 snap2-gluster        2017-01-03 03:46:54 -0500 disk-snapshot
# cat s2.xml
<domainsnapshot>
<name>snap2-gluster</name>
<disks>
<disk name='vda' type='network'>
<driver type='qcow2'/>
<source protocol='gluster' name='gluster-vol1/gls.s2'>
<host name='xx.xx.xx.xx'/>
</source>
</disk>
<disk name='vdb' type='network'>
<driver type='qcow2'/>
<source protocol='gluster' name='gluster-vol1/gls-TT.s2'>
<host name='xx.xx.xx.xx'/>
</source>
</disk>
</disks>
</domainsnapshot>

4. Destroy and start VM, attach disk, create external snapshots, one on local, one on glusterfs
# virsh destroy gls
Domain gls destroyed

# virsh start gls
Domain gls started

# sleep 10
# qemu-img create -f qcow2 /tmp/gls-ll.qcow2 100M
Formatting '/tmp/gls-ll.qcow2', fmt=qcow2 size=104857600 encryption=off cluster_size=65536 lazy_refcounts=off refcount_bits=16
# virsh attach-device gls vdb-local.xml
Device attached successfully

# virsh snapshot-create gls s3.xml --disk-only
Domain snapshot snap created from 's3.xml'
# virsh snapshot-list gls
 Name                 Creation Time             State
------------------------------------------------------------
 snap                 2017-01-03 03:47:44 -0500 disk-snapshot
 snap1-gluster        2017-01-03 03:46:41 -0500 disk-snapshot
 snap2-gluster        2017-01-03 03:46:54 -0500 disk-snapshot

# cat s3.xml
<domainsnapshot>
<name>snap</name>
<disks>
<disk name='vda'>
<source file='/tmp/gls.s3'/>
</disk>
<disk name='vdb' type='network'>
<driver type='qcow2'/>
<source protocol='gluster' name='gluster-vol1/gls-ll.s3'>
<host name='xx.xx.xx.xx'/>
</source>
</disk>
</disks>
</domainsnapshot>

5. Destroy and start VM, create external snapshot with memory
# virsh destroy gls
Domain gls destroyed

# virsh start gls
Domain gls started

# sleep 10
# virsh snapshot-create gls ss1.xml
Domain snapshot snap1-mem created from 'ss1.xml'
# virsh snapshot-list gls
 Name                 Creation Time             State
------------------------------------------------------------
 snap                 2017-01-03 03:47:44 -0500 disk-snapshot
 snap1-gluster        2017-01-03 03:46:41 -0500 disk-snapshot
 snap1-mem            2017-01-03 03:48:24 -0500 running
 snap2-gluster        2017-01-03 03:46:54 -0500 disk-snapshot
# <domainsnapshot>
<name>snap1-mem</name>
<memory snapshot='external' file='/tmp/gls-mem.img'/>
<disks>
<disk name='vda' type='network'>
<driver type='qcow2'/>
<source protocol='gluster' name='gluster-vol1/gls.ss1'>
<host name='xx.xx.xx.xx'/>
</source>
</disk>
</disks>
</domainsnapshot>

6. Destroy VM
# virsh destroy gls
Domain gls destroyed

Actual results:
All these operations will make libvirtd occupy over 20% memory(about 2g) and never free the memory.

Expected results:
No memory leak

Additional info:
Run above steps with valgrind monitoring libvirtd:
# valgrind --leak-check=full --trace-children=no --child-silent-after-fork=yes --log-file=val.log libvirtd 
==4455== Memcheck, a memory error detector
==4455== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==4455== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info
==4455== Command: libvirtd
==4455== Parent PID: 29376
==4455== 
==4455== Warning: noted but unhandled ioctl 0x89a2 with no size/direction hints.
==4455==    This could cause spurious value errors to appear.
==4455==    See README_MISSING_SYSCALL_OR_IOCTL for guidance on writing a proper wrapper.
==4455== 
==4455== HEAP SUMMARY:
==4455==     in use at exit: 813,802,703 bytes in 21,486 blocks
==4455==   total heap usage: 514,985 allocs, 493,499 frees, 3,627,381,515 bytes allocated
==4455== 

The full log is in the attachment.