[PATCH V4 2/2] Add test/daxctl-famfs.sh to test famfs mode transitions:

["John Groves" <john@jagalactic.com>]

From: John Groves <John@Groves.net>

- devdax <-> famfs mode switches
- Verify famfs -> system-ram is rejected (must go via devdax)
- Test JSON output shows correct mode
- Test error handling for invalid modes

The test is added to the destructive test suite since it
modifies device modes.

Signed-off-by: John Groves <john@groves.net>
---
 test/daxctl-famfs.sh | 253 +++++++++++++++++++++++++++++++++++++++++++
 test/meson.build     |   2 +
 2 files changed, 255 insertions(+)
 create mode 100755 test/daxctl-famfs.sh

diff --git a/test/daxctl-famfs.sh b/test/daxctl-famfs.sh
new file mode 100755
index 0000000..12fbfef
--- /dev/null
+++ b/test/daxctl-famfs.sh
@@ -0,0 +1,253 @@
+#!/bin/bash -Ex
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2025 Micron Technology, Inc. All rights reserved.
+#
+# Test daxctl famfs mode transitions and mode detection
+
+rc=77
+. $(dirname $0)/common
+
+trap 'cleanup $LINENO' ERR
+
+daxdev=""
+original_mode=""
+
+cleanup()
+{
+	printf "Error at line %d\n" "$1"
+	# Try to restore to original mode if we know it
+	if [[ $daxdev && $original_mode ]]; then
+		"$DAXCTL" reconfigure-device -f -m "$original_mode" "$daxdev" 2>/dev/null || true
+	fi
+	exit $rc
+}
+
+# Check if fsdev_dax module is available
+check_fsdev_dax()
+{
+	if modinfo fsdev_dax &>/dev/null; then
+		return 0
+	fi
+	if grep -qF "fsdev_dax" "/lib/modules/$(uname -r)/modules.builtin" 2>/dev/null; then
+		return 0
+	fi
+	printf "fsdev_dax module not available, skipping\n"
+	exit 77
+}
+
+# Check if kmem module is available (needed for system-ram mode tests)
+check_kmem()
+{
+	if modinfo kmem &>/dev/null; then
+		return 0
+	fi
+	if grep -qF "kmem" "/lib/modules/$(uname -r)/modules.builtin" 2>/dev/null; then
+		return 0
+	fi
+	printf "kmem module not available, skipping system-ram tests\n"
+	return 1
+}
+
+# Find an existing dax device to test with
+find_daxdev()
+{
+	# Look for any available dax device
+	daxdev=$("$DAXCTL" list | jq -er '.[0].chardev // empty' 2>/dev/null) || true
+
+	if [[ ! $daxdev ]]; then
+		printf "No dax device found, skipping\n"
+		exit 77
+	fi
+
+	# Save the original mode so we can restore it
+	original_mode=$("$DAXCTL" list -d "$daxdev" | jq -er '.[].mode')
+
+	printf "Found dax device: %s (current mode: %s)\n" "$daxdev" "$original_mode"
+}
+
+daxctl_get_mode()
+{
+	"$DAXCTL" list -d "$1" | jq -er '.[].mode'
+}
+
+# Ensure device is in devdax mode for testing
+ensure_devdax_mode()
+{
+	local mode
+	mode=$(daxctl_get_mode "$daxdev")
+
+	if [[ "$mode" == "devdax" ]]; then
+		return 0
+	fi
+
+	if [[ "$mode" == "system-ram" ]]; then
+		printf "Device is in system-ram mode, attempting to convert to devdax...\n"
+		"$DAXCTL" reconfigure-device -f -m devdax "$daxdev"
+	elif [[ "$mode" == "famfs" ]]; then
+		printf "Device is in famfs mode, converting to devdax...\n"
+		"$DAXCTL" reconfigure-device -m devdax "$daxdev"
+	else
+		printf "Device is in unknown mode: %s\n" "$mode"
+		return 1
+	fi
+
+	[[ $(daxctl_get_mode "$daxdev") == "devdax" ]]
+}
+
+#
+# Test basic mode transitions involving famfs
+#
+test_famfs_mode_transitions()
+{
+	printf "\n=== Testing famfs mode transitions ===\n"
+
+	# Ensure starting in devdax mode
+	ensure_devdax_mode
+	[[ $(daxctl_get_mode "$daxdev") == "devdax" ]]
+	printf "Initial mode: devdax - OK\n"
+
+	# Test: devdax -> famfs
+	printf "Testing devdax -> famfs... "
+	"$DAXCTL" reconfigure-device -m famfs "$daxdev"
+	[[ $(daxctl_get_mode "$daxdev") == "famfs" ]]
+	printf "OK\n"
+
+	# Test: famfs -> famfs (re-enable in same mode)
+	printf "Testing famfs -> famfs (re-enable)... "
+	"$DAXCTL" reconfigure-device -m famfs "$daxdev"
+	[[ $(daxctl_get_mode "$daxdev") == "famfs" ]]
+	printf "OK\n"
+
+	# Test: famfs -> devdax
+	printf "Testing famfs -> devdax... "
+	"$DAXCTL" reconfigure-device -m devdax "$daxdev"
+	[[ $(daxctl_get_mode "$daxdev") == "devdax" ]]
+	printf "OK\n"
+
+	# Test: devdax -> devdax (re-enable in same mode)
+	printf "Testing devdax -> devdax (re-enable)... "
+	"$DAXCTL" reconfigure-device -m devdax "$daxdev"
+	[[ $(daxctl_get_mode "$daxdev") == "devdax" ]]
+	printf "OK\n"
+}
+
+#
+# Test mode transitions with system-ram (requires kmem)
+#
+test_system_ram_transitions()
+{
+	printf "\n=== Testing system-ram transitions with famfs ===\n"
+
+	# Ensure we start in devdax mode
+	ensure_devdax_mode
+	[[ $(daxctl_get_mode "$daxdev") == "devdax" ]]
+
+	# Test: devdax -> system-ram
+	printf "Testing devdax -> system-ram... "
+	"$DAXCTL" reconfigure-device -N -m system-ram "$daxdev"
+	[[ $(daxctl_get_mode "$daxdev") == "system-ram" ]]
+	printf "OK\n"
+
+	# Test: system-ram -> famfs should fail
+	printf "Testing system-ram -> famfs (should fail)... "
+	if "$DAXCTL" reconfigure-device -m famfs "$daxdev" 2>/dev/null; then
+		printf "FAILED - should have been rejected\n"
+		return 1
+	fi
+	printf "OK (correctly rejected)\n"
+
+	# Test: system-ram -> devdax -> famfs (proper path)
+	printf "Testing system-ram -> devdax -> famfs... "
+	"$DAXCTL" reconfigure-device -f -m devdax "$daxdev"
+	[[ $(daxctl_get_mode "$daxdev") == "devdax" ]]
+	"$DAXCTL" reconfigure-device -m famfs "$daxdev"
+	[[ $(daxctl_get_mode "$daxdev") == "famfs" ]]
+	printf "OK\n"
+
+	# Restore to devdax for subsequent tests
+	"$DAXCTL" reconfigure-device -m devdax "$daxdev"
+}
+
+#
+# Test JSON output shows correct mode
+#
+test_json_output()
+{
+	printf "\n=== Testing JSON output for mode field ===\n"
+
+	# Test devdax mode in JSON
+	ensure_devdax_mode
+	printf "Testing JSON output for devdax mode... "
+	mode=$("$DAXCTL" list -d "$daxdev" | jq -er '.[].mode')
+	[[ "$mode" == "devdax" ]]
+	printf "OK\n"
+
+	# Test famfs mode in JSON
+	"$DAXCTL" reconfigure-device -m famfs "$daxdev"
+	printf "Testing JSON output for famfs mode... "
+	mode=$("$DAXCTL" list -d "$daxdev" | jq -er '.[].mode')
+	[[ "$mode" == "famfs" ]]
+	printf "OK\n"
+
+	# Restore to devdax
+	"$DAXCTL" reconfigure-device -m devdax "$daxdev"
+}
+
+#
+# Test error messages for invalid transitions
+#
+test_error_handling()
+{
+	printf "\n=== Testing error handling ===\n"
+
+	# Ensure we're in famfs mode
+	"$DAXCTL" reconfigure-device -m famfs "$daxdev"
+
+	# Test that invalid mode is rejected
+	printf "Testing invalid mode rejection... "
+	if "$DAXCTL" reconfigure-device -m invalidmode "$daxdev" 2>/dev/null; then
+		printf "FAILED - invalid mode should be rejected\n"
+		return 1
+	fi
+	printf "OK (correctly rejected)\n"
+
+	# Restore to devdax
+	"$DAXCTL" reconfigure-device -m devdax "$daxdev"
+}
+
+#
+# Main test sequence
+#
+main()
+{
+	check_fsdev_dax
+	find_daxdev
+
+	rc=1  # From here on, failures are real failures
+
+	test_famfs_mode_transitions
+	test_json_output
+	test_error_handling
+
+	# System-ram tests require kmem module
+	if check_kmem; then
+		# Save and disable online policy for system-ram tests
+		saved_policy="$(cat /sys/devices/system/memory/auto_online_blocks)"
+		echo "offline" > /sys/devices/system/memory/auto_online_blocks
+
+		test_system_ram_transitions
+
+		# Restore online policy
+		echo "$saved_policy" > /sys/devices/system/memory/auto_online_blocks
+	fi
+
+	# Restore original mode
+	printf "\nRestoring device to original mode: %s\n" "$original_mode"
+	"$DAXCTL" reconfigure-device -f -m "$original_mode" "$daxdev"
+
+	printf "\n=== All famfs tests passed ===\n"
+
+	exit 0
+}
+
+main
diff --git a/test/meson.build b/test/meson.build
index 615376e..ad1d393 100644
--- a/test/meson.build
+++ b/test/meson.build
@@ -209,6 +209,7 @@ if get_option('destructive').enabled()
   device_dax_fio = find_program('device-dax-fio.sh')
   daxctl_devices = find_program('daxctl-devices.sh')
   daxctl_create = find_program('daxctl-create.sh')
+  daxctl_famfs = find_program('daxctl-famfs.sh')
   dm = find_program('dm.sh')
   mmap_test = find_program('mmap.sh')
 
@@ -226,6 +227,7 @@ if get_option('destructive').enabled()
     [ 'device-dax-fio.sh', device_dax_fio, 'dax'   ],
     [ 'daxctl-devices.sh', daxctl_devices, 'dax'   ],
     [ 'daxctl-create.sh',  daxctl_create,  'dax'   ],
+    [ 'daxctl-famfs.sh',   daxctl_famfs,   'dax'   ],
     [ 'dm.sh',             dm,		   'dax'   ],
     [ 'mmap.sh',           mmap_test,	   'dax'   ],
   ]
-- 
2.49.0