mm/damon/dbgfs: print DAMON debugfs interface deprecation message

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

[[email protected]: split DAMON debugfs file open warning message, per Randy]
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: SeongJae Park <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c
index b3f454a5c6828fa2675cd7eb7c94dff5d34102c9..124f0f8c97b755f48a7e88717c5e557925f9c80b 100644 (file)
--- 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 [email protected] and "
+                    "[email protected].\n");
+}
+
 /*
  * Returns non-empty string on success, negative error code otherwise.
  */
@@ -711,6 +719,8 @@ out:
 
 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,
 };