linux-kernel - [PATCH 5.11 257/342] kcsan, debugfs: Move debugfs file creation out of early init

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Date:   Mon, 10 May 2021 12:20:47 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, "Rafael J. Wysocki" <rafael@...nel.org>,
        Marco Elver <elver@...gle.com>,
        "Paul E. McKenney" <paulmck@...nel.org>
Subject: [PATCH 5.11 257/342] kcsan, debugfs: Move debugfs file creation out of early init

From: Marco Elver <elver@...gle.com>

commit e36299efe7d749976fbdaaf756dee6ef32543c2c upstream.

Commit 56348560d495 ("debugfs: do not attempt to create a new file
before the filesystem is initalized") forbids creating new debugfs files
until debugfs is fully initialized.  This means that KCSAN's debugfs
file creation, which happened at the end of __init(), no longer works.
And was apparently never supposed to work!

However, there is no reason to create KCSAN's debugfs file so early.
This commit therefore moves its creation to a late_initcall() callback.

Cc: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: stable <stable@...r.kernel.org>
Fixes: 56348560d495 ("debugfs: do not attempt to create a new file before the filesystem is initalized")
Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Marco Elver <elver@...gle.com>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 kernel/kcsan/core.c    |    2 --
 kernel/kcsan/debugfs.c |    4 +++-
 kernel/kcsan/kcsan.h   |    5 -----
 3 files changed, 3 insertions(+), 8 deletions(-)

--- a/kernel/kcsan/core.c
+++ b/kernel/kcsan/core.c
@@ -639,8 +639,6 @@ void __init kcsan_init(void)
 
 	BUG_ON(!in_task());
 
-	kcsan_debugfs_init();
-
 	for_each_possible_cpu(cpu)
 		per_cpu(kcsan_rand_state, cpu) = (u32)get_cycles();
 
--- a/kernel/kcsan/debugfs.c
+++ b/kernel/kcsan/debugfs.c
@@ -261,7 +261,9 @@ static const struct file_operations debu
 	.release = single_release
 };
 
-void __init kcsan_debugfs_init(void)
+static void __init kcsan_debugfs_init(void)
 {
 	debugfs_create_file("kcsan", 0644, NULL, NULL, &debugfs_ops);
 }
+
+late_initcall(kcsan_debugfs_init);
--- a/kernel/kcsan/kcsan.h
+++ b/kernel/kcsan/kcsan.h
@@ -31,11 +31,6 @@ void kcsan_save_irqtrace(struct task_str
 void kcsan_restore_irqtrace(struct task_struct *task);
 
 /*
- * Initialize debugfs file.
- */
-void kcsan_debugfs_init(void);
-
-/*
  * Statistics counters displayed via debugfs; should only be modified in
  * slow-paths.
  */