[PATCH 0/4] mm/damon/sysfs: free setup failures generated zombie sub-sub dirs

[SeongJae Park <sj@kernel.org>]

Some DAMON sysfs directory setup functions generates its sub and sub-sub
directories.  For example, 'monitoring_attrs/' directory setup creates
'intervals/' and 'intervals/intervals_goal/' directories under
'monitoring_attrs/' directory.  When such sub-sub directories are
successfully made but followup setup is failed, the setup function
should recursively clean up the subdirectories.

However, such setup functions are only dereferencing sub directory
reference counters.  As a result, under certain setup failures, the
sub-sub directories keep having non-zero reference counters.   It means
the directories cannot be removed like zombies, and the memory for the
directories cannot be freed.

The user impact of this issue is limited due to the following reasons.

When the issue happens, the zombie directories are still taking the
path.  Hence attempts to generate the directories again will fail,
without additional memory leak.  This means the upper bound memory leak
is limited.  Nonetheless this also implies controlling DAMON with a
feature that requires the setup-failed sysfs files will be impossible
until the system reboots.

Also, the setup operations are quite simple.  The certain failures would
hence only rarely happen, and are difficult to artificially trigger.

SeongJae Park (4):
  mm/damon/sysfs: cleanup intervals subdirs on attrs dir setup failure
  mm/damon/sysfs: cleanup attrs subdirs on context dir setup failure
  mm/damon/sysfs-scheme: cleanup quotas subdirs on scheme dir setup
    failure
  mm/damon/sysfs-scheme: cleanup access_pattern subdirs on scheme dir
    setup failure

 mm/damon/sysfs-schemes.c | 10 ++++++----
 mm/damon/sysfs.c         |  9 ++++++---
 2 files changed, 12 insertions(+), 7 deletions(-)


base-commit: 6d039da6a260dd7919bebc70ebb65d250bb9c24e
-- 
2.47.3