Docs/admin-guide/mm/damon/usage: add DAMON debugfs interface deprecation notice

Patch series "mm/damon: deprecate DAMON debugfs interface".

DAMON debugfs interface has announced to be deprecated after >v5.15 LTS
kernel is released.  And v6.1.y has been announced to be an LTS[1].

Though the announcement was there for a while, some people might not have
noticed that so far.  Also, some users could depend on it and have
problems at movng to the alternative (DAMON sysfs interface).

For such cases, keep the code and documents with warning messages and
contacts to ask helps for the deprecation.

[1] https://git.kernel.org/pub/scm/docs/kernel/website.git/commit/?id=332e9121320bc7461b2d3a79665caf153e51732c


This patch (of 3):

DAMON debugfs interface has announced to be deprecated after >v5.15 LTS
kernel is released.  And, v6.1.y has announced to be an LTS[1].

Though the announcement was there for a while, some people might not
noticed that so far.  Also, some users could depend on it and have
problems at  movng to the alternative (DAMON sysfs interface).

For such cases, note DAMON debugfs interface as deprecated, and contacts
to ask helps on the document.

[1] https://git.kernel.org/pub/scm/docs/kernel/website.git/commit/?id=332e9121320bc7461b2d3a79665caf153e51732c

Link: https://lkml.kernel.org/r/20230209192009.7885-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20230209192009.7885-2-sj@kernel.orgSigned-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Documentation/admin-guide/mm/damon/usage.rst

@@ -25,10 +25,12 @@ DAMON provides below interfaces for different users.
   interface provides only simple :ref:`statistics <damos_stats>` for the
   monitoring results.  For detailed monitoring results, DAMON provides a
   :ref:`tracepoint <tracepoint>`.
-- *debugfs interface.*
+- *debugfs interface. (DEPRECATED!)*
   :ref:`This <debugfs_interface>` is almost identical to :ref:`sysfs interface
-  <sysfs_interface>`.  This will be removed after next LTS kernel is released,
-  so users should move to the :ref:`sysfs interface <sysfs_interface>`.
+  <sysfs_interface>`.  This is deprecated, so users should move to the
+  :ref:`sysfs interface <sysfs_interface>`.  If you depend on this and cannot
+  move, please report your usecase to damon@lists.linux.dev and
+  linux-mm@kvack.org.
 - *Kernel Space Programming Interface.*
   :doc:`This </mm/damon/api>` is for kernel space programmers.  Using this,
   users can utilize every feature of DAMON most flexibly and efficiently by
@@ -487,13 +489,17 @@ the files as above.  Above is only for an example.
 
 .. _debugfs_interface:
 
-debugfs Interface
-=================
+debugfs Interface (DEPRECATED!)
+===============================
 
 .. note::
 
-  DAMON debugfs interface will be removed after next LTS kernel is released, so
-  users should move to the :ref:`sysfs interface <sysfs_interface>`.
+  THIS IS DEPRECATED!
+
+  DAMON debugfs interface is deprecated, so users should move to the
+  :ref:`sysfs interface <sysfs_interface>`.  If you depend on this and cannot
+  move, please report your usecase to damon@lists.linux.dev and
+  linux-mm@kvack.org.
 
 DAMON exports eight files, ``attrs``, ``target_ids``, ``init_regions``,
 ``schemes``, ``monitor_on``, ``kdamond_pid``, ``mk_contexts`` and