Clean up do_vol_test in zfs_copies tests

Get rid of the `get_used_prop` function. `get_prop used` works fine.

Fix the comment describing the function parameters. The type does not
have a default, and mntp is also used for ext2.

Rename the variable for the number of copies from `copy` to `copies`.

Use a `case` statement to match the type parameter, order the cases
alphabetically, and add a little sanity checking for good measure.

Use eval to make sure the output of commands is silenced rather than
the log messages when redirecting output to /dev/null.

Simplify cases where zfs requires special behavior.

Don't allow the test to loop forever in the event space usage does not
change. Bail out of the loop and fail after an arbitrary number of
iterations.

Add more information to the log message when the test fails, to help
debugging.

Reviewed-by: John Kennedy <john.kennedy@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ryan Moeller <ryan@ixsystems.com>
Closes #9286

tests/zfs-tests/tests/functional/cli_root/zfs_copies/zfs_copies.kshlib

@@ -49,19 +49,6 @@ function cmp_prop
 	fi
 }
 
-#
-# Get the value of property used via zfs list
-# $1, the dataset name
-#
-function get_used_prop
-{
-	typeset ds=$1
-	typeset used
-
-	used=`zfs list -H -p -o used $ds`
-	echo $used
-}
-
 #
 # Check the used space is charged correctly
 # $1, the number of used space
@@ -85,64 +72,72 @@ function check_used
 
 #
 # test ncopies on volume
-# $1  test type zfs|ufs, default zfs
+# $1  test type zfs|ufs|ext2
 # $2  copies
-# $3  mntp for ufs test
+# $3  mntp for ufs|ext2 test
 function do_vol_test
 {
 	typeset type=$1
-	typeset copy=$2
+	typeset copies=$2
 	typeset mntp=$3
 
 	vol=$TESTPOOL/$TESTVOL1
 	vol_b_path=$ZVOL_DEVDIR/$TESTPOOL/$TESTVOL1
 	vol_r_path=$ZVOL_RDEVDIR/$TESTPOOL/$TESTVOL1
 
-	log_must zfs create -V $VOLSIZE -o copies=$copy $vol
+	log_must zfs create -V $VOLSIZE -o copies=$copies $vol
 	log_must zfs set refreservation=none $vol
 	block_device_wait
 
-	if [[ $type == "ufs" ]]; then
-		log_must echo y | newfs $vol_r_path >/dev/null 2>&1
-		log_must mount -F ufs -o rw $vol_b_path $mntp
-	elif [[ $type == "ext2" ]]; then
-		log_must echo y | newfs $vol_r_path >/dev/null 2>&1
+	case "$type" in
+	"ext2")
+		log_must eval "echo y | newfs $vol_r_path >/dev/null 2>&1"
 		log_must mount -o rw $vol_b_path $mntp
-	else
+		;;
+	"ufs")
+		if is_linux; then
+			log_unsupported "ufs test not implemented for linux"
+		fi
+		log_must eval "newfs $vol_r_path >/dev/null 2>&1"
+		log_must mount $vol_b_path $mntp
+		;;
+	"zfs")
 		log_must zpool create $TESTPOOL1 $vol_b_path
 		log_must zfs create $TESTPOOL1/$TESTFS1
-	fi
-
-	((nfilesize = copy * ${FILESIZE%m}))
-	pre_used=$(get_used_prop $vol)
+		;;
+	*)
+		log_unsupported "$type test not implemented"
+		;;
+	esac
+
+	((nfilesize = copies * ${FILESIZE%m}))
+	pre_used=$(get_prop used $vol)
 	((target_size = pre_used + nfilesize))
 
-	if [[ $type == "ufs" ]]; then
-		log_must mkfile $FILESIZE $mntp/$FILE
-	elif [[ $type == "ext2" ]]; then
-		log_must mkfile $FILESIZE $mntp/$FILE
-	else
+	if [[ $type == "zfs" ]]; then
 		log_must mkfile $FILESIZE /$TESTPOOL1/$TESTFS1/$FILE
+	else
+		log_must mkfile $FILESIZE $mntp/$FILE
 	fi
 
-	post_used=$(get_used_prop $vol)
-	while ((post_used < target_size)) ; do
+	post_used=$(get_prop used $vol)
+	((retries = 0))
+	while ((post_used < target_size && retries++ < 42)); do
 		sleep 1
-		post_used=$(get_used_prop $vol)
+		post_used=$(get_prop used $vol)
 	done
 
 	((used = post_used - pre_used))
 	if ((used < nfilesize)); then
 		log_fail "The space is not charged correctly while setting" \
-		    "copies as $copy"
+		    "copies as $copies ($used < $nfilesize)" \
+		    "pre=${pre_used} post=${post_used}"
 	fi
 
-	if [[ $type == "ufs" ]]; then
-		umount $mntp
-	elif [[ $type == "ext2" ]]; then
-		umount $mntp
-	else
+	if [[ $type == "zfs" ]]; then
 		log_must zpool destroy $TESTPOOL1
+	else
+		log_must umount $mntp
 	fi
 
 	log_must zfs destroy $vol