Without this patch, vn_generic_copy_file_range() can loop for an
extended period of time when a large copy range is specified.
The problem with this is mainly response time to signal
delivery for the application that did the copy_file_range(2)
This patch makes vn_generic_copy_file_range() return after
A discussion on freebsd-hackers@ seemed to indicate that
1second was a reasonable limit for response time to a
Applying the 1second limit to file system specific
VOP_COPY_FILE_RANGE() calls such as NFSv4.2 will
be up to the file system specific VOP call.