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sipb-xen-lvcopy

Timestamp:

Apr 22, 2008, 4:15:57 PM (17 years ago)

Author:

price

Message:

sipb-xen-losetup: a half-sane way to use losetup

You should use this instead of plain losetup; everything that uses this
will at least not have races with other things using this.

If it's missing a feature (e.g. a losetup argument) you want,
it shouldn't be hard to add.

File:

-                      r405
+                      r449
 def losetup(source, offset=0):
+  # XXX we avoid colliding with other instances of ourself,
+  #     but when it comes to other loop-device users we just
+  #     pick a range things don't seem to use and hope...
+  lockfilename = '/tmp/losetup.lock'
+  os.close(os.open(lockfilename, os.O_CREAT+os.O_EXCL)) #lock
+  try:
+    loopdevice = None
+    for i in xrange(32,60): # totally arbitrary, just looks to be unused on black-mesa
+      filename = '/dev/loop%d'%i
+      if 0 == len(file(filename).read(1)):
+        loopdevice = filename # it's empty
+        break
+    if loopdevice is not None:
+      call(['losetup', '-o', str(offset), loopdevice, source])
+    else:
+      raise RuntimeError('out of loop devices for copying VM image: too many at once?')
+  finally:
+    os.unlink(lockfilename) #unlock
+  return loopdevice
+  # XX this means we can duplicate 28 at once.  Since it takes around 30s,
+  # this seems like an adequate capacity.
+  p = Popen(['sipb-xen-losetup', source, str(offset)], stdout=PIPE)
+  return p.communicate()[0].strip()
 def frob_copy_in_vm(target, *args):

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