defrag: add options to _defrag helper

Sometimes it is not easy to know number of expected extents in advance.
In that case it is reasonable to provide sane MIN and MAX values.
Also helper will check that number of extents before defragmentaion
is not greather than after.

Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

tests/generic/018

@@ -60,33 +60,33 @@ rm -f $fragfile
 
 echo "zero-length file:" | tee -a $seqres.full
 touch $fragfile
-_defrag $fragfile
+_defrag --before 0 --after 0 $fragfile
 
 echo "Sparse file (no blocks):" | tee -a $seqres.full
 $XFS_IO_PROG -f -c "truncate 1m" $fragfile
-_defrag $fragfile
+_defrag --before 0 --after 0 $fragfile
 
 echo "Contiguous file:" | tee -a $seqres.full
 dd if=/dev/zero of=$fragfile bs=4k count=4 &>/dev/null
-_defrag $fragfile
+_defrag --before 1 --after 1 $fragfile
 
 echo "Write backwards sync, but contiguous - should defrag to 1 extent" | tee -a $seqres.full
 for I in `seq 9 -1 0`; do
 	dd if=/dev/zero of=$fragfile bs=4k count=1 conv=notrunc seek=$I oflag=sync &>/dev/null
 done
-_defrag $fragfile
+_defrag --before 10 --after 1 $fragfile
 
 echo "Write backwards sync leaving holes - defrag should do nothing" | tee -a $seqres.full
 for I in `seq 31 -2 0`; do
 	dd if=/dev/zero of=$fragfile bs=4k count=1 conv=notrunc seek=$I oflag=sync &>/dev/null
 done
-_defrag $fragfile
+_defrag --before 16 --after 16 $fragfile
 
 echo "Write forwards sync leaving holes - defrag should do nothing" | tee -a $seqres.full
 for I in `seq 0 2 31`; do
 	dd if=/dev/zero of=$fragfile bs=4k count=1 conv=notrunc seek=$I oflag=sync &>/dev/null
 done
-_defrag $fragfile
+_defrag --before 16 --after 16 $fragfile
 
 rm -f $seqres.full
 status=0