linux-kernel - [PATCH 0/3] selftests: cachestat: fix build and run on older kernels

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Message-Id: <20230815155612.2535947-1-andre.przywara@arm.com>
Date:   Tue, 15 Aug 2023 16:56:09 +0100
From:   Andre Przywara <andre.przywara@....com>
To:     Shuah Khan <shuah@...nel.org>, Nhat Pham <nphamcs@...il.com>,
        Johannes Weiner <hannes@...xchg.org>
Cc:     linux-kselftest@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 0/3] selftests: cachestat: fix build and run on older kernels

I ran all kernel selftests on some test machine, and stumbled upon
cachestat failing (among others).
Those patches fix the cachestat test compilation and run on older
kernels.

Also I found that the but-last test (on a normal file) fails when run on
a tmpfs mounted directory, as it happens on an initramfs-only system, or
when the current directory happens to be /dev/shm or /tmp:
# Create/open tmpfilecachestat
# Cachestat call returned 0
# Using cachestat: Cached: 4, Dirty: 4, Writeback: 0, Evicted: 0, Recently Evicted: 0
# Cachestat call (after fsync) returned 0
# Using cachestat: Cached: 4, Dirty: 4, Writeback: 0, Evicted: 0, Recently Evicted: 0
# Number of dirty should be zero after fsync.
not ok 6 cachestat fails with normal file

That same test binary succeeds on the same machine right afterwards if
the current directory is changed to an ext4 filesystem.

I don't really know if this is expected, and whether we should try to
figure out if the test file lives on a tmpfs filesystem, or whether the
test itself is not strict enough, and requires more "flushing"
(drop_caches?) to cover tmpfs directories as well.

Any ideas how to fix this would be appreciated.

Cheers,
Andre

Andre Przywara (3):
  selftests: cachestat: properly link in librt
  selftests: cachestat: use proper syscall number macro
  selftests: cachestat: test for cachestat availability

 tools/testing/selftests/cachestat/Makefile    |  2 +-
 .../selftests/cachestat/test_cachestat.c      | 29 +++++++++++++++----
 2 files changed, 25 insertions(+), 6 deletions(-)

-- 
2.25.1