Description of problem:
The original mirroring code ignored device failures.  The current code
raises an event and blocks I/O completion notices until a user-space
daemon responds to the event.  Old LVM code would not be listening for
dm events, and would therefore leave the device in a blocking state.
This is not a big problem for RHEL, as we ship a current LVM.  However,
the pvmove code has not yet been updated to take advantage of the
event notifications - it just thinks it means the device is in-sync.
This makes pvmove believe that its done its job, but the device is
left in a blocking state.  Since pvmove may be used to move data off
of a failing device, this is not a good situation to have.

The fix is to cause the mirror code to behave as before unless a
flag is specified letting the kernel code know that it is ok to
raise events and block I/O completion.  The pvmove code (and previous
versions of LVM) will not use this flag and will get the behaviour
they expect.  Current LVM code will use the flag and will be able
to respond to the events.

Version-Release number of selected component (if applicable):
RHEL4-U2