Bug 903280

+++ This bug was initially created as a clone of Bug #891324 +++

+++ This bug was initially created as a clone of Bug #890039 +++

Description of problem:

libvirtd grows unbounded if you continually create and
destroy transient domains:

  PID USER      PR  NI  VIRT  RES  SHR S  %CPU %MEM    TIME+  COMMAND           
25390 rjones    20   0 10.9g  10g 8.4g S   0.0 66.8  16:34.08 libvirtd          

This seems to happen because libselinux mmap's the
following files hundreds of times:

/etc/selinux/targeted/contexts/files/file_contexts.local.bin
/etc/selinux/targeted/contexts/files/file_contexts.homedirs.bin
/etc/selinux/targeted/contexts/files/file_contexts.bin

(About one mapping per second in my tests).

Methodology:

I'm testing libvirt.git (at time of writing,
commit bf62e9953c3dde35551a0c2a91d30a294516609a).

I have applied my patch to libselinux to fix bug 903203.

I use the following command (from the libvirt.git directory)
to run libvirtd from git:

killall lt-libvirtd libvirtd
./run ./daemon/libvirtd --timeout 30

while at the same time running the following command from
the libguestfs.git directory:

while true; do echo -n .; ../libvirt/run ./run ./fish/guestfish -N fs exit; done

This creates lots of transient domains, serially.

Observations:

Valgrind shows some reachable blocks, but no significant
unreachable blocks, indicating there is no memory leak.

Examining /proc/$pid/maps shows that the number of memory mappings
is growing like crazy:

$ wc -l /proc/589/maps 
822 /proc/589/maps
$ wc -l /proc/589/maps 
837 /proc/589/maps
$ wc -l /proc/589/maps 
852 /proc/589/maps
$ wc -l /proc/589/maps 
867 /proc/589/maps
$ wc -l /proc/589/maps 
942 /proc/589/maps
$ wc -l /proc/589/maps 
1032 /proc/589/maps

Examination of /proc/$pid/maps appears to point to libselinux again:

$ awk '{print $6}' /proc/589/maps | sort | uniq -c | sort -nr | head
    340 /etc/selinux/targeted/contexts/files/file_contexts.local.bin
    340 /etc/selinux/targeted/contexts/files/file_contexts.homedirs.bin
    340 /etc/selinux/targeted/contexts/files/file_contexts.bin
     67 
      4 /usr/lib64/sasl2/libsasldb.so.2.0.25
      4 /usr/lib64/sasl2/libplain.so.2.0.25
      4 /usr/lib64/sasl2/liblogin.so.2.0.25
      4 /usr/lib64/sasl2/libgssapiv2.so.2.0.25
      4 /usr/lib64/sasl2/libdigestmd5.so.2.0.25
      4 /usr/lib64/sasl2/libcrammd5.so.2.0.25