RFC mm/damon/stat: add kdamond_pid parameter

DAMON_STAT doesn't provide the pid of its kdamond, unlike DAMON_RECLAIM and DAMON_LRU_SORT. This makes user-space management of DAMON_STAT unnecessarily complicated. Provide the information via a new parameter, namely kdamond_pid, and document it.

Changes from RFC v2
- v2: https://lore.kernel.org/[email protected]
- Rebase to latest mm-new.
Changes from RFC v1.2
- rfc v1.2: https://lore.kernel.org/[email protected]
- Detect and use fresh kdamond pid.
Changes from RFC v1.1
- rfc v1.1: https://lore.kernel.org/[email protected]
- Close the parentheses of error handling block.
Changes from RFC
- rfc: https://lore.kernel.org/[email protected]
- Fix damon_kdamond_pid() failure handling.

SeongJae Park (2):
mm/damon/stat: add a parameter for reading kdamond pid Docs/admin-guide/mm/damon/stat: document kdamond_pid parameter

 Documentation/admin-guide/mm/damon/stat.rst |  7 ++++
 mm/damon/stat.c                             | 38 +++++++++++++++++++++
 2 files changed, 45 insertions(+)

base-commit: b8e00b62c650b2aa471195f663301118fde889c2

2.47.3