Really? In this case there is no need to check for return value on the
last copy_to_user() either. But I don't think so, because after you have
done the first copy_from() but before you did the copy_to() (or
__copy_to as you suggest) the other CPU may have caused some activity that
swapped out that user page. So you can't use __copy() and you do need to
check for return.
If the above is incorrect, I would appreciate if you correct me.
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