linux-kernel - [PATCH 5.4 040/255] jbd2: wake up journal waiters in FIFO order, not LIFO

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Message-Id: <20221024113003.764929384@linuxfoundation.org>
Date:   Mon, 24 Oct 2022 13:29:10 +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, stable@...nel.org,
        Alexey Lyashkov <alexey.lyashkov@...il.com>,
        "Ritesh Harjani (IBM)" <ritesh.list@...il.com>,
        Theodore Tso <tytso@....edu>
Subject: [PATCH 5.4 040/255] jbd2: wake up journal waiters in FIFO order, not LIFO

From: Andrew Perepechko <anserper@...ru>

commit 34fc8768ec6089565d6d73bad26724083cecf7bd upstream.

LIFO wakeup order is unfair and sometimes leads to a journal
user not being able to get a journal handle for hundreds of
transactions in a row.

FIFO wakeup can make things more fair.

Cc: stable@...nel.org
Signed-off-by: Alexey Lyashkov <alexey.lyashkov@...il.com>
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@...il.com>
Link: https://lore.kernel.org/r/20220907165959.1137482-1-alexey.lyashkov@gmail.com
Signed-off-by: Theodore Ts'o <tytso@....edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/jbd2/commit.c      |    2 +-
 fs/jbd2/transaction.c |    6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -531,7 +531,7 @@ void jbd2_journal_commit_transaction(jou
 	journal->j_running_transaction = NULL;
 	start_time = ktime_get();
 	commit_transaction->t_log_start = journal->j_head;
-	wake_up(&journal->j_wait_transaction_locked);
+	wake_up_all(&journal->j_wait_transaction_locked);
 	write_unlock(&journal->j_state_lock);
 
 	jbd_debug(3, "JBD2: commit phase 2a\n");
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -149,7 +149,7 @@ static void wait_transaction_locked(jour
 	int need_to_start;
 	tid_t tid = journal->j_running_transaction->t_tid;
 
-	prepare_to_wait(&journal->j_wait_transaction_locked, &wait,
+	prepare_to_wait_exclusive(&journal->j_wait_transaction_locked, &wait,
 			TASK_UNINTERRUPTIBLE);
 	need_to_start = !tid_geq(journal->j_commit_request, tid);
 	read_unlock(&journal->j_state_lock);
@@ -175,7 +175,7 @@ static void wait_transaction_switching(j
 		read_unlock(&journal->j_state_lock);
 		return;
 	}
-	prepare_to_wait(&journal->j_wait_transaction_locked, &wait,
+	prepare_to_wait_exclusive(&journal->j_wait_transaction_locked, &wait,
 			TASK_UNINTERRUPTIBLE);
 	read_unlock(&journal->j_state_lock);
 	/*
@@ -810,7 +810,7 @@ void jbd2_journal_unlock_updates (journa
 	write_lock(&journal->j_state_lock);
 	--journal->j_barrier_count;
 	write_unlock(&journal->j_state_lock);
-	wake_up(&journal->j_wait_transaction_locked);
+	wake_up_all(&journal->j_wait_transaction_locked);
 }
 
 static void warn_dirty_buffer(struct buffer_head *bh)