linux-kernel - [PATCH 6/8] nilfs2: remove sc_timer

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Message-Id: <20240826174116.5008-7-konishi.ryusuke@gmail.com>
Date: Tue, 27 Aug 2024 02:41:14 +0900
From: Ryusuke Konishi <konishi.ryusuke@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-nilfs@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 6/8] nilfs2: remove sc_timer_task

After commit f5d4e04634c9 ("nilfs2: fix use-after-free of timer for
log writer thread") is applied, nilfs_construct_timeout(), which is
called by a timer and wakes up the log writer thread, is never called
after the log writer thread has terminated.

As a result, the member variable "sc_timer_task" of the
"nilfs_sc_info" structure, which was added when timer_setup() was
adopted to retain a reference to the log writer thread's task even
after it had terminated, is no longer needed, as it should be; we can
simply use "sc_task" instead, which holds a reference to the log
writer thread's task for its lifetime.  So, eliminate "sc_timer_task"
by this means.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@...il.com>
---
 fs/nilfs2/segment.c | 3 +--
 fs/nilfs2/segment.h | 2 --
 2 files changed, 1 insertion(+), 4 deletions(-)

diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c
index 206066ce6d00..225f61ef66e7 100644
--- a/fs/nilfs2/segment.c
+++ b/fs/nilfs2/segment.c
@@ -2504,7 +2504,7 @@ static void nilfs_construction_timeout(struct timer_list *t)
 {
 	struct nilfs_sc_info *sci = from_timer(sci, t, sc_timer);
 
-	wake_up_process(sci->sc_timer_task);
+	wake_up_process(sci->sc_task);
 }
 
 static void
@@ -2642,7 +2642,6 @@ static int nilfs_segctor_thread(void *arg)
 	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
 	int timeout = 0;
 
-	sci->sc_timer_task = current;
 	timer_setup(&sci->sc_timer, nilfs_construction_timeout, 0);
 
 	/* start sync. */
diff --git a/fs/nilfs2/segment.h b/fs/nilfs2/segment.h
index 2499721ebcc9..7d1160a266df 100644
--- a/fs/nilfs2/segment.h
+++ b/fs/nilfs2/segment.h
@@ -115,7 +115,6 @@ struct nilfs_segsum_pointer {
  * @sc_lseg_stime: Start time of the latest logical segment
  * @sc_watermark: Watermark for the number of dirty buffers
  * @sc_timer: Timer for segctord
- * @sc_timer_task: Thread woken up by @sc_timer
  * @sc_task: current thread of segctord
  */
 struct nilfs_sc_info {
@@ -172,7 +171,6 @@ struct nilfs_sc_info {
 	unsigned long		sc_watermark;
 
 	struct timer_list	sc_timer;
-	struct task_struct     *sc_timer_task;
 	struct task_struct     *sc_task;
 };
 
-- 
2.34.1