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

[Andre Przywara]

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