btrfs-progs: tests: add test for fi show and missing device

Add a test to ensure that 'btrfs fi show' on a mounted filesystem, which
has a missing device will explicitly print which device is missing.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

tests/cli-tests/017-fi-show-missing/test.sh

@@ -0,0 +1,35 @@
+#!/bin/bash
+#
+# Test that if a device is missing for a mounted filesystem, btrfs fi show will
+# show which device exactly is missing.
+
+source "$TEST_TOP/common"
+
+check_prereq mkfs.btrfs
+check_prereq btrfs
+
+setup_root_helper
+setup_loopdevs 2
+prepare_loopdevs
+
+dev1=${loopdevs[1]}
+dev2=${loopdevs[2]}
+
+run_check $SUDO_HELPER "$TOP/mkfs.btrfs" -f -d raid1 "${loopdevs[@]}"
+
+# Move the device, changing its path, simulating the device being missing
+run_check $SUDO_HELPER mv "$dev2" /dev/loop-non-existent
+
+run_check $SUDO_HELPER mount -o degraded $dev1 $TEST_MNT
+
+if ! run_check_stdout $SUDO_HELPER "$TOP/btrfs" filesystem show "$TEST_MNT" | \
+	grep -q "$dev2 MISSING"; then
+
+	_fail "didn't find exact missing device"
+fi
+
+run_check $SUDO_HELPER mv /dev/loop-non-existent "$dev2"
+
+run_check $SUDO_HELPER umount "$TEST_MNT"
+
+cleanup_loopdevs