generic: don't put loop control files on the scratch mount

If we're doing write/overwrite/snapshot/resource exhaustion tests on
the scratch device, use the test directory to hold the loop
termination signal files.  This way we don't run infinitely because
we can't create the flag due to ENOSPC.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Eryu Guan <eguan@redhat.com>

tests/generic/164

@@ -34,7 +34,7 @@ trap "_cleanup; exit \$status" 0 1 2 3 7 15
 _cleanup()
 {
     cd /
-    rm -rf $tmp.*
+    rm -rf $tmp.* $finished_file
     wait
 }
 
@@ -53,6 +53,8 @@ _scratch_mkfs > $seqres.full 2>&1
 _scratch_mount >> $seqres.full 2>&1
 
 testdir=$SCRATCH_MNT/test-$seq
+finished_file=/tmp/finished
+rm -rf $finished_file
 mkdir $testdir
 
 loops=512
@@ -71,7 +73,7 @@ fbytes() {
 }
 
 reader() {
-	while [ ! -e $testdir/finished ]; do
+	while [ ! -e $finished_file ]; do
 		_read_range $testdir/file3 0 $((loops * blksz)) | fbytes
 	done
 }
@@ -91,7 +93,7 @@ for i in `seq 1 2`; do
 	done
 done
 echo "Finished reflinking"
-touch $testdir/finished
+touch $finished_file
 wait
 
 # success, all done