[PATCH v2 0/3] mm/damon: deprecate DAMON debugfs interface

[PATCH v2 0/3] mm/damon: deprecate DAMON debugfs interface

[SeongJae Park]

Changes from v1
(https://lore.kernel.org/damon/20230209192009.7885-1-sj@kernel.org/)
- Split DAMON debugfs file open warning message (Randy Dunlap)

-----

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, 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

SeongJae Park (3):
  Docs/admin-guide/mm/damon/usage: add DAMON debugfs interface
    deprecation notice
  mm/damon/Kconfig: add DAMON debugfs interface deprecation notice
  mm/damon/dbgfs: print DAMON debugfs interface deprecation message

 Documentation/admin-guide/mm/damon/usage.rst | 20 +++++++++++++-------
 mm/damon/Kconfig                             |  7 ++++---
 mm/damon/dbgfs.c                             | 19 +++++++++++++++++++
 3 files changed, 36 insertions(+), 10 deletions(-)

-- 
2.25.1

[PATCH v2 1/3] Docs/admin-guide/mm/damon/usage: add DAMON debugfs interface deprecation notice

[SeongJae Park]

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

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 Documentation/admin-guide/mm/damon/usage.rst | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/Documentation/admin-guide/mm/damon/usage.rst b/Documentation/admin-guide/mm/damon/usage.rst
index 9237d6a25897..9b823fec974d 100644
--- a/Documentation/admin-guide/mm/damon/usage.rst
+++ b/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
-- 
2.25.1

[PATCH v2 2/3] mm/damon/Kconfig: add DAMON debugfs interface deprecation notice

[SeongJae Park]

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 Kconfig.

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

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/Kconfig | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/mm/damon/Kconfig b/mm/damon/Kconfig
index 7821fcb3f258..436c6b4cb5ec 100644
--- a/mm/damon/Kconfig
+++ b/mm/damon/Kconfig
@@ -60,7 +60,7 @@ config DAMON_SYSFS
 	  the interface for arbitrary data access monitoring.
 
 config DAMON_DBGFS
-	bool "DAMON debugfs interface"
+	bool "DAMON debugfs interface (DEPRECATED!)"
 	depends on DAMON_VADDR && DAMON_PADDR && DEBUG_FS
 	help
 	  This builds the debugfs interface for DAMON.  The user space admins
@@ -68,8 +68,9 @@ config DAMON_DBGFS
 
 	  If unsure, say N.
 
-	  This will be removed after >5.15.y LTS kernel is released, so users
-	  should move to the sysfs interface (DAMON_SYSFS).
+	  This is deprecated, so users should move to the sysfs interface
+	  (DAMON_SYSFS).  If you depend on this and cannot move, please report
+	  your usecase to damon@lists.linux.dev and linux-mm@kvack.org.
 
 config DAMON_DBGFS_KUNIT_TEST
 	bool "Test for damon debugfs interface" if !KUNIT_ALL_TESTS
-- 
2.25.1

[PATCH v2 3/3] mm/damon/dbgfs: print DAMON debugfs interface deprecation message

[SeongJae Park]

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, warn DAMON debugfs interface deprecation with contacts
to ask helps when any DAMON debugfs interface file is opened.

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

Link: https://lkml.kernel.org/r/20230209192009.7885-4-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
 mm/damon/dbgfs.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c
index b3f454a5c682..124f0f8c97b7 100644
--- a/mm/damon/dbgfs.c
+++ b/mm/damon/dbgfs.c
@@ -20,6 +20,14 @@ static int dbgfs_nr_ctxs;
 static struct dentry **dbgfs_dirs;
 static DEFINE_MUTEX(damon_dbgfs_lock);
 
+static void damon_dbgfs_warn_deprecation(void)
+{
+	pr_warn_once("DAMON debugfs interface is deprecated, "
+		     "so users should move to DAMON_SYSFS. If you cannot, "
+		     "please report your usecase to damon@lists.linux.dev and "
+		     "linux-mm@kvack.org.\n");
+}
+
 /*
  * Returns non-empty string on success, negative error code otherwise.
  */
@@ -711,6 +719,8 @@ static ssize_t dbgfs_kdamond_pid_read(struct file *file,
 
 static int damon_dbgfs_open(struct inode *inode, struct file *file)
 {
+	damon_dbgfs_warn_deprecation();
+
 	file->private_data = inode->i_private;
 
 	return nonseekable_open(inode, file);
@@ -1039,15 +1049,24 @@ static ssize_t dbgfs_monitor_on_write(struct file *file,
 	return ret;
 }
 
+static int damon_dbgfs_static_file_open(struct inode *inode, struct file *file)
+{
+	damon_dbgfs_warn_deprecation();
+	return nonseekable_open(inode, file);
+}
+
 static const struct file_operations mk_contexts_fops = {
+	.open = damon_dbgfs_static_file_open,
 	.write = dbgfs_mk_context_write,
 };
 
 static const struct file_operations rm_contexts_fops = {
+	.open = damon_dbgfs_static_file_open,
 	.write = dbgfs_rm_context_write,
 };
 
 static const struct file_operations monitor_on_fops = {
+	.open = damon_dbgfs_static_file_open,
 	.read = dbgfs_monitor_on_read,
 	.write = dbgfs_monitor_on_write,
 };
-- 
2.25.1

Re: [PATCH v2 0/3] mm/damon: deprecate DAMON debugfs interface

[SeongJae Park]

On Fri, 10 Feb 2023 04:48:35 +0000 SeongJae Park <sj@kernel.org> wrote:

> Changes from v1
> (https://lore.kernel.org/damon/20230209192009.7885-1-sj@kernel.org/)
> - Split DAMON debugfs file open warning message (Randy Dunlap)

I usually sent this kind of update for after-merged-into-mm-unstable tree
patches individusally as fixup, but this time I sent whole patchset as a new
version, because I was out of my mind.

For someone who may prefer the usual for-fixup individual patch, attaching the
version below.


Thanks,
SJ

================================= 8< ==========================================
From: SeongJae Park <sj@kernel.org>
Date: Fri, 10 Feb 2023 04:37:19 +0000
Subject: [PATCH mm-unstable] mm/damon/dbgfs: break too long deprecation
 warning message

DAMON debugfs interface deprecation message, which is introduced by
commit 234a68e24b12 ("mm/damon/dbgfs: print DAMON debugfs interface
deprecation message") of mm-unstable, is too long.  Break down into
multiple strings for better code readability.

Fixes: 234a68e24b12 ("mm/damon/dbgfs: print DAMON debugfs interface deprecation message") # mm-unstable
Suggested-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/dbgfs.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c
index e551a20b35e3..124f0f8c97b7 100644
--- a/mm/damon/dbgfs.c
+++ b/mm/damon/dbgfs.c
@@ -22,7 +22,10 @@ static DEFINE_MUTEX(damon_dbgfs_lock);

 static void damon_dbgfs_warn_deprecation(void)
 {
-       pr_warn_once("DAMON debugfs interface is deprecated, so users should move to the sysfs interface (DAMON_SYSFS).  If you depend on this and cannot move, please report your usecase to damon@lists.linux.dev and linux-mm@kvack.org.\n");
+       pr_warn_once("DAMON debugfs interface is deprecated, "
+                    "so users should move to DAMON_SYSFS. If you cannot, "
+                    "please report your usecase to damon@lists.linux.dev and "
+                    "linux-mm@kvack.org.\n");
 }

 /*
--
2.25.1