dom0: block_cleaner: removes ejected devices from xenstore

When device is ejected by some VM (state=6, effectively inactive), it should be
removed from xenstore to free slot for some another device. This should be done
by libxl toolstack, but not implemented in xen 4.1 - AFAIR done in xen 4.2.

dom0/aux-tools/block_cleaner_daemon.py

@@ -0,0 +1,53 @@
+#!/usr/bin/python
+
+import xen.lowlevel.xs
+import time
+import subprocess
+
+xs = xen.lowlevel.xs.xs()
+
+domain_list = []
+
+def setup_watches():
+    global domain_list
+
+    new_domain_list = xs.ls('', '/local/domain')
+    for dom in new_domain_list:
+        if dom not in domain_list:
+            print "Adding: %s" % dom
+            xs.watch('/local/domain/%s/backend/vbd' % dom, int(dom))
+    for dom in domain_list:
+        if dom not in new_domain_list:
+            print "Removing: %s" % dom
+            xs.unwatch('/local/domain/%s/backend/vbd' % dom, int(dom))
+    domain_list = new_domain_list
+
+def handle_vbd_state(path):
+    state = xs.read('', path)
+    if state == '6':
+        # Closed state; wait a moment to not interrupt reconnect
+        time.sleep(0.500)
+        state = xs.read('', path)
+        if state == '6':
+            # If still closed, detach device
+            path_components = path.split('/')
+            # /local/domain/<BACK XID>/backend/vbd/<FRONT XID>/<DEV>/...
+            vm_xid = path_components[6]
+            vm_dev = path_components[7]
+            if vm_xid in domain_list:
+                subprocess.call('xl', 'block-detach', vm_xid, vm_dev)
+
+def main():
+
+    xs.watch('@introduceDomain', 'reload')
+    xs.watch('@releaseDomain', 'reload')
+    setup_watches()
+    while True:
+        (path, token) = xs.read_watch()
+        if token == 'reload':
+            setup_watches()
+        else:
+            if path.endswith('/state'):
+                handle_vbd_state(path)
+
+main()

dom0/init.d/qubes_core

@@ -53,6 +53,8 @@ start()
     MEMINFO_DELAY_USEC=100000
     /usr/lib/qubes/meminfo-writer $MEM_CHANGE_THRESHOLD_KB $MEMINFO_DELAY_USEC &
 
+    /usr/lib/qubes/block_cleaner_daemon.py > /var/log/qubes/block_cleaner.log 2>&1 &
+
     # Reply block events to hide mounted devices from qubes-block list (at first udev run, only / is mounted)
     udevadm trigger --subsystem-match=block --action=add
 

rpm_spec/core-dom0.spec

@@ -114,6 +114,7 @@ cp aux-tools/qubes-receive-updates $RPM_BUILD_ROOT/usr/lib/qubes/
 cp ../misc/block_add_change $RPM_BUILD_ROOT/usr/lib/qubes/
 cp ../misc/block_remove $RPM_BUILD_ROOT/usr/lib/qubes/
 cp ../misc/block_cleanup $RPM_BUILD_ROOT/usr/lib/qubes/
+cp aux-tools/block_cleaner_daemon.py $RPM_BUILD_ROOT/usr/lib/qubes/
 
 mkdir -p $RPM_BUILD_ROOT/etc/qubes_rpc/policy
 cp ../qubes_rpc/qubes.Filecopy.policy $RPM_BUILD_ROOT/etc/qubes_rpc/policy/qubes.Filecopy
@@ -344,6 +345,7 @@ fi
 /usr/lib/qubes/block_add_change
 /usr/lib/qubes/block_remove
 /usr/lib/qubes/block_cleanup
+/usr/lib/qubes/block_cleaner_daemon.py*
 %attr(4750,root,qubes) /usr/lib/qubes/qfile-dom0-unpacker
 %attr(770,root,qubes) %dir /var/lib/qubes
 %attr(770,root,qubes) %dir /var/lib/qubes/vm-templates