any changes between the default and the data we read

	Which is great as for some paths we've no idea what was in
before, so each boot won't write it all back, won't checksum but will
repeat the bug

Also it can still sleep for a second with IRQ off, and there is some
dubious looking error path locking marked FIXME in case anyone feels
inspired to work on it. Not a newly introduced bug, and at least its now
marked.

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
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