selftests/damon/sysfs: hide expected write failures

DAMON selftests for sysfs (sysfs.sh) tests if some writes to DAMON sysfs
interface files fails as expected.  It makes the test results noisy with
the failure error message because it tests a number of such failures.
Redirect the expected failure error messages to /dev/null to make the
results clean.

Link: https://lkml.kernel.org/r/20230110190400.119388-8-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/tools/testing/selftests/damon/sysfs.sh b/tools/testing/selftests/damon/sysfs.sh
index a00336ffdcad4861e228935d05ee52ded94b462b..bcd4734ca094327d36438ce2e7f8d9a559189625 100644 (file)
--- a/tools/testing/selftests/damon/sysfs.sh
+++ b/tools/testing/selftests/damon/sysfs.sh
@@ -24,7 +24,7 @@ ensure_write_fail()
        content=$2
        reason=$3
 
-       if echo "$content" > "$file"
+       if (echo "$content" > "$file") 2> /dev/null
        then
                echo "writing $content to $file succeed ($fail_reason)"
                echo "expected failure because $reason"