Re: [PATCH] common/rc: report kmemleak errors

[Eryu Guan <eguan@redhat.com>]

On Tue, Nov 28, 2017 at 05:09:37PM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> If kmemleak is enabled, scan and report memory leaks after every test.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---
>  check     |    2 ++
>  common/rc |   51 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 53 insertions(+)
> 
> diff --git a/check b/check
> index b2d251a..469188e 100755
> --- a/check
> +++ b/check
> @@ -497,6 +497,7 @@ _check_filesystems()
>  	fi
>  }
>  
> +_init_kmemleak
>  _prepare_test_list
>  
>  if $OPTIONS_HAVE_SECTIONS; then
> @@ -793,6 +794,7 @@ for section in $HOST_OPTIONS_SECTIONS; do
>  		    n_try=`expr $n_try + 1`
>  		    _check_filesystems
>  		    _check_dmesg || err=true
> +		    _check_kmemleak || err=true
>  		fi
>  
>  	    fi
> diff --git a/common/rc b/common/rc
> index cb83918..6dc77d5 100644
> --- a/common/rc
> +++ b/common/rc
> @@ -3339,6 +3339,57 @@ _check_dmesg()
>  	fi
>  }
>  
> +# set up kmemleak
> +_init_kmemleak()
> +{
> +	local _kern_knob="/sys/kernel/debug/kmemleak"

Use $DEBUGFS_MNT? e.g. $DEBUGFS_MNT/kmemleak

> +
> +	if [ ! -w "${_kern_knob}" ]; then
> +		return 0
> +	fi
> +
> +	# Scan for all the memory leaks that have happened to date and
> +	# clear them so that we can pinpoint leaks to tests accurately.
> +	# Scan twice because the first write finishes before the scan
> +	# does....
> +	echo "scan" > "${_kern_knob}"
> +	cat "${_kern_knob}" > /dev/null
> +	echo "scan" > "${_kern_knob}"
> +	cat "${_kern_knob}" > /dev/null
> +	echo "clear" > "${_kern_knob}"

So this leaves the automatic background scan on, seems this is not a
problem. But how about disabling automatic scan (echo "scan=off" >
$DEBUGFS_MNT/kmemleak) and only depend on the manual scan in
_check_kmemleak?

> +}
> +
> +# check kmemleak log
> +_check_kmemleak()
> +{
> +	local _kern_knob="/sys/kernel/debug/kmemleak"
> +	local _leak_file="${RESULT_DIR}/check_kmemleak"
> +
> +	if [ ! -w "${_kern_knob}" ]; then
> +		return 0
> +	fi
> +
> +	# Tell the kernel to scan for memory leaks.  Apparently the write
> +	# returns before the scan is complete, so do it twice in the hopes
> +	# that twice is enough to capture all the leaks.
> +	echo "scan" > "${_kern_knob}"
> +	sed -e 's/age [0-9\.]*s/age XXXX/g' < "${_kern_knob}" > "${_leak_file}.new"
> +	echo "scan" > "${_kern_knob}"
> +	sed -e 's/age [0-9\.]*s/age XXXX/g' < "${_kern_knob}" > "${_leak_file}.new"
> +
> +	diff -u -N "${_leak_file}" "${_leak_file}.new" > $seqres.kmemleak

Hmm, I think this reports false failure, e.g. let's say generic/001
leaks memory and generic/002 doesn't

 ./check generic/001	# this fails kmemleak check and populates check_kmemleak file
 ./check generic/002	# diff against the stale check_kmemleak file and fails the check too

How about just check if there's anything reported from
$DEBUGFS_MNT/kmemleak and clearing the kmemleak buffer after each test? e.g.

echo "scan" > $DEBUGFS_MNT/kmemleak
cat $DEBUGFS_MNT/kmemleak > $seqres.kmemleak
echo "clear" > $DEBUGFS_MNT/kmemleak
if [ -s $seqres.kmemleak ]; then
	_dump_err "_check_kmemleak: something found in kmemleak (see $seqres.kmemleak)"
	return 1
else
	rm -f $seqres.kmemleak
	return 0
fi

Thanks,
Eryu

> +	res=$?
> +	mv "${_leak_file}.new" "${_leak_file}"
> +
> +	if [ $res -ne 0 ]; then
> +		_dump_err "_check_kmemleak: something found in kmemleak (see $seqres.kmemleak)"
> +		return 1
> +	else
> +		rm -f $seqres.kmemleak
> +		return 0
> +	fi
> +}
> +
>  # don't check dmesg log after test
>  _disable_dmesg_check()
>  {