btrfs-progs: cli-tests: add test case for return value of "btrfs subvlume create"

The test case would check if "btrfs subvolume create":

- Report error on an existing path
- Still report error if mulitple paths are given and one of them already
  exists
- For above case, still created a subvolume for the good parameter

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

tests/cli-tests/025-subvolume-create-failures/test.sh

@@ -0,0 +1,31 @@
+#!/bin/bash
+# Create subvolume failure cases to make sure the return value is correct
+
+source "$TEST_TOP/common" || exit
+
+setup_root_helper
+prepare_test_dev
+
+run_check_mkfs_test_dev
+run_check_mount_test_dev
+
+# Create one subvolume and one file as place holder for later subvolume
+# creation to fail.
+run_check $SUDO_HELPER "$TOP/btrfs" subvolume create "$TEST_MNT/subv1"
+run_check $SUDO_HELPER touch "$TEST_MNT/subv2"
+
+# Using existing path to create a subvolume must fail
+run_mustfail "should report error when target path already exists" \
+	$SUDO_HELPER "$TOP/btrfs" subvolume create "$TEST_MNT/subv1"
+
+run_mustfail "should report error when target path already exists" \
+	$SUDO_HELPER "$TOP/btrfs" subvolume create "$TEST_MNT/subv2"
+
+# Using multiple subvolumes in one create go, the good one "subv3" should be created
+run_mustfail "should report error when target path already exists" \
+	$SUDO_HELPER "$TOP/btrfs" subvolume create \
+	"$TEST_MNT/subv1" "$TEST_MNT/subv2" "$TEST_MNT/subv3"
+
+run_check $SUDO_HELPER stat "$TEST_MNT/subv3"
+
+run_check_umount_test_dev