2022-09-12 18:06:22

by Alexey Lyahkov

Subject: [PATCH] jbd2: wake up journal waiters in FIFO order, not LIFO

From: Andrew Perepechko <[email protected]>

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.

Reviewed-by: Ritesh Harjani (IBM) <[email protected]>
Signed-off-by: Alexey Lyashkov <[email protected]>
---
fs/jbd2/commit.c | 2 +-
fs/jbd2/transaction.c | 6 +++---
2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
index b2b2bc9b88d9..ec2b55879e3a 100644
--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -570,7 +570,7 @@ void jbd2_journal_commit_transaction(journal_t *journal)
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);

jbd2_debug(3, "JBD2: commit phase 2a\n");
diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index e1be93ccd81c..6a404ac1c178 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -168,7 +168,7 @@ static void wait_transaction_locked(journal_t *journal)
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);
@@ -194,7 +194,7 @@ static void wait_transaction_switching(journal_t *journal)
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);
/*
@@ -920,7 +920,7 @@ void jbd2_journal_unlock_updates (journal_t *journal)
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)
--
2.31.1

2022-09-30 03:21:40

by Theodore Ts'o

Subject: Re: [PATCH] jbd2: wake up journal waiters in FIFO order, not LIFO

On Mon, 12 Sep 2022 21:01:37 +0300, Alexey Lyashkov wrote:
> From: Andrew Perepechko <[email protected]>
>
> 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.
>
> [...]

Applied, thanks!

[1/1] jbd2: wake up journal waiters in FIFO order, not LIFO
commit: 2bf6739025dcfca3a24fbc73b8f2dbd979c0e4c9

Best regards,
--
Theodore Ts'o <[email protected]>