btrfs: add helper to kill background process running _btrfs_stress_replace

Killing a background process running _btrfs_stress_replace() is not as
simple as sending a signal to the process and waiting for it to die.
Therefore we have the following logic to terminate such process:

   kill $pid
   wait $pid
   while ps aux | grep "replace start" | grep -qv grep; do
      sleep 1
   done

Since this is repeated in several test cases, move this logic to a common
helper and use it in all affected test cases. This will help to avoid
repeating the same code again several times in upcoming changes.

Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
diff --git a/common/btrfs b/common/btrfs
index e7df825..217373f 100644
--- a/common/btrfs
+++ b/common/btrfs
@@ -485,6 +485,20 @@
 	done
 }
 
+# Kill a background process running _btrfs_stress_replace()
+_btrfs_kill_stress_replace_pid()
+{
+       local replace_pid=$1
+
+       # Ignore if process already died.
+       kill $replace_pid &> /dev/null
+       wait $replace_pid &> /dev/null
+       # Wait for the replace operation to finish.
+       while ps aux | grep "replace start" | grep -qv grep; do
+               sleep 1
+       done
+}
+
 # find the right option to force output in bytes, older versions of btrfs-progs
 # print that by default, newer print human readable numbers with unit suffix
 _btrfs_qgroup_units()
diff --git a/tests/btrfs/064 b/tests/btrfs/064
index 58b53af..9e0b3b3 100755
--- a/tests/btrfs/064
+++ b/tests/btrfs/064
@@ -64,12 +64,7 @@
 	echo "Wait for fsstress to exit and kill all background workers" >>$seqres.full
 	wait $fsstress_pid
 	_btrfs_kill_stress_balance_pid $balance_pid
-	kill $replace_pid
-	wait $replace_pid
-	# wait for the replace operation to finish
-	while ps aux | grep "replace start" | grep -qv grep; do
-		sleep 1
-	done
+	_btrfs_kill_stress_replace_pid $replace_pid
 
 	echo "Scrub the filesystem" >>$seqres.full
 	$BTRFS_UTIL_PROG scrub start -B $SCRATCH_MNT >>$seqres.full 2>&1
diff --git a/tests/btrfs/065 b/tests/btrfs/065
index c4b6aaf..d2b0417 100755
--- a/tests/btrfs/065
+++ b/tests/btrfs/065
@@ -65,12 +65,8 @@
 	wait $fsstress_pid
 
 	touch $stop_file
-	kill $replace_pid
-	wait
-	# wait for the replace operation to finish
-	while ps aux | grep "replace start" | grep -qv grep; do
-		sleep 1
-	done
+	wait $subvol_pid
+	_btrfs_kill_stress_replace_pid $replace_pid
 
 	echo "Scrub the filesystem" >>$seqres.full
 	$BTRFS_UTIL_PROG scrub start -B $SCRATCH_MNT >>$seqres.full 2>&1
diff --git a/tests/btrfs/069 b/tests/btrfs/069
index 20f44b3..ad1609d 100755
--- a/tests/btrfs/069
+++ b/tests/btrfs/069
@@ -59,15 +59,8 @@
 
 	echo "Wait for fsstress to exit and kill all background workers" >>$seqres.full
 	wait $fsstress_pid
-	kill $replace_pid
-	wait $replace_pid
-
-	# wait for the replace operation to finish
-	while ps aux | grep "replace start" | grep -qv grep; do
-		sleep 1
-	done
-
 	_btrfs_kill_stress_scrub_pid $scrub_pid
+	_btrfs_kill_stress_replace_pid $replace_pid
 
 	echo "Scrub the filesystem" >>$seqres.full
 	$BTRFS_UTIL_PROG scrub start -B $SCRATCH_MNT >>$seqres.full 2>&1
diff --git a/tests/btrfs/070 b/tests/btrfs/070
index cefa572..3054c27 100755
--- a/tests/btrfs/070
+++ b/tests/btrfs/070
@@ -60,14 +60,7 @@
 
 	echo "Wait for fsstress to exit and kill all background workers" >>$seqres.full
 	wait $fsstress_pid
-	kill $replace_pid
-	wait $replace_pid
-
-	# wait for the replace operation to finish
-	while ps aux | grep "replace start" | grep -qv grep; do
-		sleep 1
-	done
-
+	_btrfs_kill_stress_replace_pid $replace_pid
 	_btrfs_kill_stress_defrag_pid $defrag_pid
 
 	echo "Scrub the filesystem" >>$seqres.full
diff --git a/tests/btrfs/071 b/tests/btrfs/071
index d9aaf3d..36b3934 100755
--- a/tests/btrfs/071
+++ b/tests/btrfs/071
@@ -59,14 +59,7 @@
 
 	echo "Wait for fsstress to exit and kill all background workers" >>$seqres.full
 	wait $fsstress_pid
-	kill $replace_pid
-	wait $replace_pid
-
-	# wait for the replace operationss to finish
-	while ps aux | grep "replace start" | grep -qv grep; do
-		sleep 1
-	done
-
+	_btrfs_kill_stress_replace_pid $replace_pid
 	_btrfs_kill_stress_remount_compress_pid $remount_pid $SCRATCH_MNT
 
 	echo "Scrub the filesystem" >>$seqres.full