linux-kernel - [PATCH v1 5/5] jbd2: Add TASK_FREEZABLE to kjournald2 thread

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Message-Id: <20250730014708.1516-6-daijunbing@vivo.com>
Date: Wed, 30 Jul 2025 09:47:06 +0800
From: Dai Junbing <daijunbing@...o.com>
To: Alexander Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>,
	Jan Kara <jack@...e.cz>,
	Miklos Szeredi <miklos@...redi.hu>,
	"Theodore Ts'o" <tytso@....edu>,
	linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-ext4@...r.kernel.org
Cc: opensource.kernel@...o.com,
	Dai Junbing <daijunbing@...o.com>
Subject: [PATCH v1 5/5] jbd2: Add TASK_FREEZABLE to kjournald2 thread

Set the TASK_FREEZABLE flag when the kjournald2 kernel thread sleeps
during journal commit operations. This prevents premature wakeups
during system suspend/resume cycles, avoiding unnecessary CPU wakeups
and power consumption.

in this case, the original code:

	prepare_to_wait(&journal->j_wait_commit, &wait,
               	 TASK_INTERRUPTIBLE);
	if (journal->j_commit_sequence != journal->j_commit_request)
        	should_sleep = 0;

	transaction = journal->j_running_transaction;
	if (transaction && time_after_eq(jiffies, transaction->t_expires))
        	should_sleep = 0;
	......
	......
	if (should_sleep) {
        	write_unlock(&journal->j_state_lock);
        	schedule();
        	write_lock(&journal->j_state_lock);
	}

is functionally equivalent to the more concise:

	write_unlock(&journal->j_state_lock);
	wait_event_freezable_exclusive(&journal->j_wait_commit,
        	journal->j_commit_sequence == journal->j_commit_request ||
        	(journal->j_running_transaction &&
         	time_after_eq(jiffies, transaction->t_expires)) ||
        	(journal->j_flags & JBD2_UNMOUNT));
	write_lock(&journal->j_state_lock);

Signed-off-by: Dai Junbing <daijunbing@...o.com>
---
 fs/jbd2/journal.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index d480b94117cd..9a1def9f730b 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -222,7 +222,7 @@ static int kjournald2(void *arg)
 		DEFINE_WAIT(wait);
 
 		prepare_to_wait(&journal->j_wait_commit, &wait,
-				TASK_INTERRUPTIBLE);
+				TASK_INTERRUPTIBLE | TASK_FREEZABLE);
 		transaction = journal->j_running_transaction;
 		if (transaction == NULL ||
 		    time_before(jiffies, transaction->t_expires)) {
-- 
2.25.1