selftests/damon: skip test if DAMON is running

mainline inclusion
from mainline-v5.16-rc5
commit 964e1701
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I4RTX9

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=964e17016cf99902c79a5de095cc5e57e7d58248

--------------------------------

Testing the DAMON debugfs files while DAMON is running makes no sense,
as any write to the debugfs files will fail.  This commit makes the test
be skipped in this case.

Link: https://lkml.kernel.org/r/20211201150440.1088-8-sj@kernel.orgSigned-off-by: NSeongJae Park <sj@kernel.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit 964e1701)
Signed-off-by: NYue Zou <zouyue3@huawei.com>
Reviewed-by: Kefeng Wang<wangkefeng.wang@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

tools/testing/selftests/damon/debugfs_attrs.sh

@@ -44,6 +44,15 @@ test_content() {
 
 source ./_chk_dependency.sh
 
+ksft_skip=4
+
+damon_onoff="$DBGFS/monitor_on"
+if [ $(cat "$damon_onoff") = "on" ]
+then
+	echo "monitoring is on"
+	exit $ksft_skip
+fi
+
 # Test attrs file
 # ===============