Re: [LTP] [PATCH v5 2/4] zram/zram_lib.sh: adapt the situation that zram device is being used

["xuyang2018.jy@fujitsu.com" <xuyang2018.jy@fujitsu.com>]

Hi Petr
> Hi Xu,
>
>> 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[1]. 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 6566d1a32("zram: add dynamic
>> device add/remove functionality")[2] in 2015.6. If kernel supports these two interface,
> nit: instead of date (a bit non standard written) I'd just mention the kernel
> release, i.e. v4.2-rc1.
Will do.
>
>> 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.
>
>> Also, zram01,02 case are adjuested to adapt the situation that CONFIG_ZRAM=y and can
>> run zram01,02 simultaneously on new kernel.
>
>> [1]https://www.kernel.org/doc/html/latest/admin-guide/blockdev/zram.html#add-remove-zram-devices
>> [2]https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=6566d1a32bf7
>
>> -	modprobe zram num_devices=$dev_num || \
>> -		tst_brk TBROK "failed to insert zram module"
>> +# On kernel that supports /sys/class/zram-control interface but doesn't load zram,
>> +# we dont' need to use hot_add/hot_remove interface. If system has loaded zram
>> +# or buitin, we need to use hot_add/hot_remove interface.
>> +# On old kernel that doesn't support /sys/class/zram-control interface, we just
>> +# check whether zram module is being used or it is built in kernel(we can't create
>> +# number of devices required). If so, skip it.
>> +	if [ ! -d "/sys/class/zram-control" ]; then
>> +		modprobe zram num_devices=$dev_num
>> +		if [ ! -d "/sys/class/zram-control" ]; then
>> +			if grep -q '^zram' /proc/modules; then
>> +				rmmod zram>  /dev/null 2>&1 || \
>> +					tst_brk TCONF "zram module is being used"
> nit: I'd be more clear already in the output.
Yes.
>
>> +			else
>> +				tst_brk TCONF "test needs CONFIG_ZRAM=m"
> Also here I'd somehow mention the old kernel.
>> +			fi
>> +			modprobe zram num_devices=$dev_num
>> +		fi
>> +		module_load=1
>> +		dev_end=$(($dev_num - 1))
>> +		tst_res TPASS "all zram devices (/dev/zram0~$dev_end) successfully created"
>> +		return
>> +	fi
>> -	dev_num_created=$(ls /dev/zram* | wc -w)
>> +	dev_start=$(ls /dev/zram* | wc -w)
>> +	dev_end=$(($dev_start + $dev_num - 1))
>> +	sys_control=1
>
>> -	if [ "$dev_num_created" -ne "$dev_num" ]; then
>> -		tst_brk TFAIL "unexpected num of devices: $dev_num_created"
>> -	fi
>> +	for i in $(seq  $dev_start $dev_end); do
>> +		cat /sys/class/zram-control/hot_add>  /dev/null
>> +	done
>
>> -	tst_res TPASS "all zram devices successfully created"
>> +	tst_res TPASS "all zram devices (/dev/zram$dev_start~$dev_end) successfully created"
>>   }
>
> IMHO this should work and be a bit more readable
> (put extra TINFO to help understand the problem on failure or what has been
> tested):
>
> 	tst_res TINFO "create '$dev_num' zram device(s)"
>
> 	# zram module loaded, new kernel
> 	if [ -d "/sys/class/zram-control" ]; then
> 		tst_res TINFO "zram module already loaded, kernel supports zram-control interface"
> 		dev_start=$(ls /dev/zram* | wc -w)
> 		dev_end=$(($dev_start + $dev_num - 1))
> 		sys_control=1
>
> 		for i in $(seq  $dev_start $dev_end); do
> 			cat /sys/class/zram-control/hot_add>  /dev/null
> 		done
>
> 		tst_res TPASS "all zram devices (/dev/zram$dev_start~$dev_end) successfully created"
> 		return
> 	fi
>
> 	modprobe zram num_devices=$dev_num
>
> 	# detect old kernel or built-in
> 	if [ ! -d "/sys/class/zram-control" ]; then
> 		if grep -q '^zram' /proc/modules; then
> 			rmmod zram>  /dev/null 2>&1 || \
> 				tst_brk TCONF "zram module is being used on old kernel without zram-control interface"
> 		else
> 			tst_brk TCONF "test needs CONFIG_ZRAM=m on old kernel without zram-control interface"
> 		fi
> 		modprobe zram num_devices=$dev_num
> 	fi
>
> 	module_load=1
> 	dev_end=$(($dev_num - 1))
> 	tst_res TPASS "all zram devices (/dev/zram0~$dev_end) successfully created"

Nice, it is easy to understand.

Best Regards
Yang Xu
> }
>
>
> Kind regards,
> Petr

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