DAMON debugfs interface selftests use test_write_result() to check if
valid or invalid writes to files of the interface success or fail as
expected.  File write error messages from expected failures are only
making the output noisy.  Hide such expected error messages.

Link: https://lkml.kernel.org/r/20241028233058.283381-4-sj@kernel.org
Fixes: b348eb7abd09 ("mm/damon: add user space selftests")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Andrew Paniakin <apanyaki@amazon.com>
Cc: Brendan Higgins <brendan.higgins@linux.dev>
Cc: David Gow <davidgow@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Following change will rename 'monitor_on' DAMON debugfs file to
'monitor_on_DEPRECATED', to make the deprecation unignorable in runtime. 
Since it could make DAMON selftests fail and disturb future bisects,
update DAMON selftests to support the change.

Link: https://lkml.kernel.org/r/20240130013549.89538-7-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Alex Shi <alexs@kernel.org>
Cc: Hu Haowen <2023002089@link.tyut.edu.cn>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Yanteng Si <siyanteng@loongson.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Currently, the single test program, debugfs.sh, contains all test cases
for DAMON.  When one of the cases fails, finding which case is failed
from the test log is not so easy, and all remaining tests will be
skipped.  To improve the situation, this commit splits the single
program into small test programs having their own names.

Link: https://lkml.kernel.org/r/20211201150440.1088-12-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>