mm, memcg: cg2 memory{.swap,}.peak write tests

Extend two existing tests to cover extracting memory usage through the
newly mutable memory.peak and memory.swap.peak handlers.

In particular, make sure to exercise adding and removing watchers with
overlapping lifetimes so the less-trivial logic gets tested.

The new/updated tests attempt to detect a lack of the write handler by
fstat'ing the memory.peak and memory.swap.peak files and skip the tests if
that's the case.  Additionally, skip if the file doesn't exist at all.

[[email protected]: update tests]
  Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: David Finkel <[email protected]>
Acked-by: Tejun Heo <[email protected]>
Reviewed-by: Roman Gushchin <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Michal Koutný <[email protected]>
Cc: Muchun Song <[email protected]>
Cc: Shakeel Butt <[email protected]>
Cc: Shuah Khan <[email protected]>
Cc: Waiman Long <[email protected]>
Cc: Zefan Li <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions