##/bin/bash
# SPDX-License-Identifier: GPL-2.0+
# Copyright (c) 2017 Oracle.  All Rights Reserved.
#
# Routines for messing around with loadable kernel modules

# Return the module name for this fs.
_module_for_fs()
{
	echo "${FSTYP}"
}

# Reload a particular module.  This module MUST NOT be the module that
# underlies the filesystem.
_reload_module()
{
	local module="$1"

	_patient_rmmod "${module}" || _fail "${module} unload failed"
	modprobe "${module}" || _fail "${module} load failed"
}

# Reload the filesystem module.
_reload_fs_module()
{
	local module="$1"

	# Unload test fs, try to reload module, remount
	local had_testfs=""
	local had_scratchfs=""
	_check_mounted_on TEST_DEV $TEST_DEV TEST_DIR $TEST_DIR && had_testfs="true"
	_check_mounted_on SCRATCH_DEV $SCRATCH_DEV SCRATCH_MNT $SCRATCH_MNT && had_scratchfs="true"
	test -n "${had_testfs}" && _test_unmount
	test -n "${had_scratchfs}" && _scratch_unmount
	_reload_module "${module}"
	test -n "${had_scratchfs}" && _scratch_mount 2> /dev/null
	test -n "${had_testfs}" && _test_mount 2> /dev/null
}

# Check that we have a module that can be loaded.  This module MUST NOT
# be the module that underlies the filesystem.
_require_loadable_module()
{
	local module="$1"

	modinfo "${module}" > /dev/null 2>&1 || _notrun "${module}: must be a module."
	_patient_rmmod "${module}" || _notrun "Require ${module} to be unloadable"
	modprobe "${module}" || _notrun "${module} load failed"
}

# Test if the module for FSTYP can be unloaded and reloaded.
#
# If not, returns 1 if $FSTYP is not a loadable module; 2 if the module could
# not be unloaded; or 3 if loading the module fails.
_test_loadable_fs_module()
{
	local module="$1"

	modinfo "${module}" > /dev/null 2>&1 || return 1

	# Unload test fs, try to reload module, remount
	local had_testfs=""
	local had_scratchfs=""
	_check_mounted_on TEST_DEV $TEST_DEV TEST_DIR $TEST_DIR && had_testfs="true"
	_check_mounted_on SCRATCH_DEV $SCRATCH_DEV SCRATCH_MNT $SCRATCH_MNT && had_scratchfs="true"
	test -n "${had_testfs}" && _test_unmount
	test -n "${had_scratchfs}" && _scratch_unmount
	local unload_ok=""
	local load_ok=""
	_patient_rmmod "${module}" || unload_ok=0
	modprobe "${module}" || load_ok=0
	test -n "${had_scratchfs}" && _scratch_mount 2> /dev/null
	test -n "${had_testfs}" && _test_mount 2> /dev/null
	test -z "${unload_ok}" || return 2
	test -z "${load_ok}" || return 3
	return 0
}

_require_loadable_fs_module()
{
	local module="$1"

	_test_loadable_fs_module "${module}"
	ret=$?
	case "$ret" in
	1)
		_notrun "${module}: must be a module."
		;;
	2)
		_notrun "${module}: module could not be unloaded"
		;;
	3)
		_notrun "${module}: module reload failed"
		;;
	esac
}

# Print the value of a filesystem module parameter
# at /sys/module/$FSTYP/parameters/$PARAM
#
# Usage example (FSTYP=overlay):
#   _get_fs_module_param index
_get_fs_module_param()
{
	cat /sys/module/${FSTYP}/parameters/${1} 2>/dev/null
}

# checks the refcount and returns 0 if we can safely remove the module. rmmod
# does this check for us, but we can use this to also iterate checking for this
# refcount before we even try to remove the module. This is useful when using
# debug test modules which take a while to quiesce.
_patient_rmmod_check_refcnt()
{
	local module=$1
	local refcnt=0

	if [[ -f /sys/module/$module/refcnt ]]; then
		refcnt=$(cat /sys/module/$module/refcnt 2>/dev/null)
		if [[ $? -ne 0 || $refcnt -eq 0 ]]; then
			return 0
		fi
		return 1
	fi
	return 0
}

# Patiently tries to wait to remove a module by ensuring first
# the refcnt is 0 and then trying to persistently remove the module within
# the time allowed. The timeout is configurable per test, just set
# MODPROBE_PATIENT_RM_TIMEOUT_SECONDS prior to including this file.
# If you want this to try forever just set MODPROBE_PATIENT_RM_TIMEOUT_SECONDS
# to the special value of "forever". This applies to both cases where kmod
# supports the patient module remover (modrobe -p) and where it does not.
#
# If your version of kmod supports modprobe -p, we instead use that
# instead. Otherwise we have to implement a patient module remover
# ourselves.
_patient_rmmod()
{
	local module=$1
	local max_tries_max=$MODPROBE_PATIENT_RM_TIMEOUT_SECONDS
	local max_tries=0
	local mod_ret=0
	local refcnt_is_zero=0

	if [[ ! -z $MODPROBE_REMOVE_PATIENT ]]; then
		$MODPROBE_REMOVE_PATIENT $module
		mod_ret=$?
		if [[ $mod_ret -ne 0 ]]; then
			echo "kmod patient module removal for $module timed out waiting for refcnt to become 0 using timeout of $max_tries_max returned $mod_ret"
		fi
		return $mod_ret
	fi

	max_tries=$max_tries_max

	# We must use a string check as otherwise if max_tries is set to
	# "forever" and we don't use a string check we can end up skipping
	# entering this loop.
	while [[ "$max_tries" != "0" ]]; do
		_patient_rmmod_check_refcnt $module
		if [[ $? -eq 0 ]]; then
			refcnt_is_zero=1
			break
		fi
		sleep 1
		if [[ "$max_tries" == "forever" ]]; then
			continue
		fi
		let max_tries=$max_tries-1
	done

	if [[ $refcnt_is_zero -ne 1 ]]; then
		echo "custom patient module removal for $module timed out waiting for refcnt to become 0 using timeout of $max_tries_max"
		return -1
	fi

	# If we ran out of time but our refcnt check confirms we had
	# a refcnt of 0, just try to remove the module once.
	if [[ "$max_tries" == "0" ]]; then
		modprobe -r $module
		return $?
	fi

	# If we have extra time left. Use the time left to now try to
	# persistently remove the module. We do this because although through
	# the above we found refcnt to be 0, removal can still fail since
	# userspace can always race to bump the refcnt. An example is any
	# blkdev_open() calls against a block device. These issues have been
	# tracked and documented in the following bug reports, which justifies
	# our need to do this in userspace:
	# https://bugzilla.kernel.org/show_bug.cgi?id=212337
	# https://bugzilla.kernel.org/show_bug.cgi?id=214015
	while [[ $max_tries != 0 ]]; do
		if [[ -d /sys/module/$module ]]; then
			modprobe -r $module 2> /dev/null
			mod_ret=$?
			if [[ $mod_ret == 0 ]]; then
				break;
			fi
			sleep 1
			if [[ "$max_tries" == "forever" ]]; then
				continue
			fi
			let max_tries=$max_tries-1
		else
			break
		fi
	done

	if [[ $mod_ret -ne 0 ]]; then
		echo "custom patient module removal for $module timed out trying to remove $module using timeout of $max_tries_max last try returned $mod_ret"
	fi

	return $mod_ret
}