selftests/zram: Adapt the situation that /dev/zram0 is being used

If zram-generator package is installed and works, then we can not remove
zram module because zram swap is being used. This case needs a clean zram
environment, change this test by using hot_add/hot_remove interface. So
even zram device is being used, we still can add zram device and remove
them in cleanup.

The two interface was introduced since kernel commit 6566d1a32bf7("zram:
add dynamic device add/remove functionality") in v4.2-rc1. If kernel
supports these two interface, we use hot_add/hot_remove to slove this
problem, if not, just check whether zram is being used or built in, then
skip it on old kernel.

Signed-off-by: Yang Xu <[e-mail]>
Signed-off-by: Shuah Khan <[e-mail]>

tools/testing/selftests/zram/zram.sh

···
 # SPDX-License-Identifier: GPL-2.0
 TCID="zram.sh"
 
-# Kselftest framework requirement - SKIP code is 4.
-ksft_skip=4
-
 . ./zram_lib.sh
 
 run_zram () {
···
 
 check_prereqs
 
-# check zram module exists
-MODULE_PATH=/lib/modules/`uname -r`/kernel/drivers/block/zram/zram.ko
-if [ -f $MODULE_PATH ]; then
-	run_zram
-elif [ -b /dev/zram0 ]; then
-	run_zram
-else
-	echo "$TCID : No zram.ko module or /dev/zram0 device file not found"
-	echo "$TCID : CONFIG_ZRAM is not set"
-	exit $ksft_skip
-fi
+run_zram

tools/testing/selftests/zram/zram01.sh

···
 
 zram_fill_fs()
 {
-	for i in $(seq 0 $(($dev_num - 1))); do
+	for i in $(seq $dev_start $dev_end); do
 		echo "fill zram$i..."
 		local b=0
 		while [ true ]; do
···
 
 zram_fill_fs
 zram_cleanup
-zram_unload
 
 if [ $ERR_CODE -ne 0 ]; then
 	echo "$TCID : [FAIL]"

tools/testing/selftests/zram/zram02.sh

···
 zram_makeswap
 zram_swapoff
 zram_cleanup
-zram_unload
 
 if [ $ERR_CODE -ne 0 ]; then
 	echo "$TCID : [FAIL]"

tools/testing/selftests/zram/zram_lib.sh

···
 # Author: Alexey Kodanev <[e-mail]>
 # Modified: Naresh Kamboju <[e-mail]>
 
-MODULE=0
 dev_makeswap=-1
 dev_mounted=-1
-
+dev_start=0
+dev_end=-1
+module_load=-1
+sys_control=-1
 # Kselftest framework requirement - SKIP code is 4.
 ksft_skip=4
 kernel_version=`uname -r | cut -d'.' -f1,2`
···
 {
 	echo "zram cleanup"
 	local i=
-	for i in $(seq 0 $dev_makeswap); do
+	for i in $(seq $dev_start $dev_makeswap); do
 		swapoff /dev/zram$i
 	done
 
-	for i in $(seq 0 $dev_mounted); do
+	for i in $(seq $dev_start $dev_mounted); do
 		umount /dev/zram$i
 	done
 
-	for i in $(seq 0 $(($dev_num - 1))); do
+	for i in $(seq $dev_start $dev_end); do
 		echo 1 > /sys/block/zram${i}/reset
 		rm -rf zram$i
 	done
 
-}
+	if [ $sys_control -eq 1 ]; then
+		for i in $(seq $dev_start $dev_end); do
+			echo $i > /sys/class/zram-control/hot_remove
+		done
+	fi
 
-zram_unload()
-{
-	if [ $MODULE -ne 0 ] ; then
-		echo "zram rmmod zram"
+	if [ $module_load -eq 1 ]; then
 		rmmod zram > /dev/null 2>&1
 	fi
 }
 
 zram_load()
 {
-	# check zram module exists
-	MODULE_PATH=/lib/modules/`uname -r`/kernel/drivers/block/zram/zram.ko
-	if [ -f $MODULE_PATH ]; then
-		MODULE=1
-		echo "create '$dev_num' zram device(s)"
-		modprobe zram num_devices=$dev_num
-		if [ $? -ne 0 ]; then
-			echo "failed to insert zram module"
-			exit 1
-		fi
+	echo "create '$dev_num' zram device(s)"
 
-		dev_num_created=$(ls /dev/zram* | wc -w)
+	# zram module loaded, new kernel
+	if [ -d "/sys/class/zram-control" ]; then
+		echo "zram modules already loaded, kernel supports" \
+			"zram-control interface"
+		dev_start=$(ls /dev/zram* | wc -w)
+		dev_end=$(($dev_start + $dev_num - 1))
+		sys_control=1
 
-		if [ "$dev_num_created" -ne "$dev_num" ]; then
-			echo "unexpected num of devices: $dev_num_created"
-			ERR_CODE=-1
-		else
-			echo "zram load module successful"
-		fi
-	elif [ -b /dev/zram0 ]; then
-		echo "/dev/zram0 device file found: OK"
-	else
-		echo "ERROR: No zram.ko module or no /dev/zram0 device found"
-		echo "$TCID : CONFIG_ZRAM is not set"
-		exit 1
+		for i in $(seq $dev_start $dev_end); do
+			cat /sys/class/zram-control/hot_add > /dev/null
+		done
+
+		echo "all zram devices (/dev/zram$dev_start~$dev_end" \
+			"successfully created"
+		return 0
 	fi
+
+	# detect old kernel or built-in
+	modprobe zram num_devices=$dev_num
+	if [ ! -d "/sys/class/zram-control" ]; then
+		if grep -q '^zram' /proc/modules; then
+			rmmod zram > /dev/null 2>&1
+			if [ $? -ne 0 ]; then
+				echo "zram module is being used on old kernel" \
+					"without zram-control interface"
+				exit $ksft_skip
+			fi
+		else
+			echo "test needs CONFIG_ZRAM=m on old kernel without" \
+				"zram-control interface"
+			exit $ksft_skip
+		fi
+		modprobe zram num_devices=$dev_num
+	fi
+
+	module_load=1
+	dev_end=$(($dev_num - 1))
+	echo "all zram devices (/dev/zram0~$dev_end) successfully created"
 }
 
 zram_max_streams()
···
 		return 0
 	fi
 
-	local i=0
+	local i=$dev_start
 	for max_s in $zram_max_streams; do
 		local sys_path="/sys/block/zram${i}/max_comp_streams"
 		echo $max_s > $sys_path || \
···
 			echo "FAIL can't set max_streams '$max_s', get $max_stream"
 
 		i=$(($i + 1))
-		echo "$sys_path = '$max_streams' ($i/$dev_num)"
+		echo "$sys_path = '$max_streams'"
 	done
 
 	echo "zram max streams: OK"
···
 {
 	echo "test that we can set compression algorithm"
 
-	local algs=$(cat /sys/block/zram0/comp_algorithm)
+	local i=$dev_start
+	local algs=$(cat /sys/block/zram${i}/comp_algorithm)
 	echo "supported algs: $algs"
-	local i=0
+
 	for alg in $zram_algs; do
 		local sys_path="/sys/block/zram${i}/comp_algorithm"
 		echo "$alg" >	$sys_path || \
 			echo "FAIL can't set '$alg' to $sys_path"
 		i=$(($i + 1))
-		echo "$sys_path = '$alg' ($i/$dev_num)"
+		echo "$sys_path = '$alg'"
 	done
 
 	echo "zram set compression algorithm: OK"
···
 zram_set_disksizes()
 {
 	echo "set disk size to zram device(s)"
-	local i=0
+	local i=$dev_start
 	for ds in $zram_sizes; do
 		local sys_path="/sys/block/zram${i}/disksize"
 		echo "$ds" >	$sys_path || \
 			echo "FAIL can't set '$ds' to $sys_path"
 
 		i=$(($i + 1))
-		echo "$sys_path = '$ds' ($i/$dev_num)"
+		echo "$sys_path = '$ds'"
 	done
 
 	echo "zram set disksizes: OK"
···
 {
 	echo "set memory limit to zram device(s)"
 
-	local i=0
+	local i=$dev_start
 	for ds in $zram_mem_limits; do
 		local sys_path="/sys/block/zram${i}/mem_limit"
 		echo "$ds" >	$sys_path || \
 			echo "FAIL can't set '$ds' to $sys_path"
 
 		i=$(($i + 1))
-		echo "$sys_path = '$ds' ($i/$dev_num)"
+		echo "$sys_path = '$ds'"
 	done
 
 	echo "zram set memory limit: OK"
···
 zram_makeswap()
 {
 	echo "make swap with zram device(s)"
-	local i=0
-	for i in $(seq 0 $(($dev_num - 1))); do
+	local i=$dev_start
+	for i in $(seq $dev_start $dev_end); do
 		mkswap /dev/zram$i > err.log 2>&1
 		if [ $? -ne 0 ]; then
 			cat err.log
···
 zram_swapoff()
 {
 	local i=
-	for i in $(seq 0 $dev_makeswap); do
+	for i in $(seq $dev_start $dev_end); do
 		swapoff /dev/zram$i > err.log 2>&1
 		if [ $? -ne 0 ]; then
 			cat err.log
···
 
 zram_makefs()
 {
-	local i=0
+	local i=$dev_start
 	for fs in $zram_filesystems; do
 		# if requested fs not supported default it to ext2
 		which mkfs.$fs > /dev/null 2>&1 || fs=ext2
···
 zram_mount()
 {
 	local i=0
-	for i in $(seq 0 $(($dev_num - 1))); do
+	for i in $(seq $dev_start $dev_end); do
 		echo "mount /dev/zram$i"
 		mkdir zram$i
 		mount /dev/zram$i zram$i > /dev/null || \