From 34fc8768ec6089565d6d73bad26724083cecf7bd Mon Sep 17 00:00:00 2001
From: Andrew Perepechko <anserper@ya.ru>
Date: Wed, 7 Sep 2022 19:59:59 +0300
Subject: [PATCH] jbd2: wake up journal waiters in FIFO order, not LIFO
Git-commit: 34fc8768ec6089565d6d73bad26724083cecf7bd
Patch-mainline: v6.1-rc1
References: bsc#1207643

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@kernel.org
Signed-off-by: Alexey Lyashkov <alexey.lyashkov@gmail.com>
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Link: https://lore.kernel.org/r/20220907165959.1137482-1-alexey.lyashkov@gmail.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Acked-by: Jan Kara <jack@suse.cz>

---
 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
@@ -581,7 +581,7 @@ 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
@@ -173,7 +173,7 @@ 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);
@@ -199,7 +199,7 @@ 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);
 	/*
@@ -894,7 +894,7 @@ 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)