linux-ext4 - [PATCHv1 2/2] jbd2: Remove CONFIG_JBD2_DEBUG to update t_max

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Message-Id: <c1424ac2e6f6f5a21bcf2fb7679203df865c8a60.1642953021.git.riteshh@linux.ibm.com>
Date:   Sun, 23 Jan 2022 22:53:28 +0530
From:   Ritesh Harjani <riteshh@...ux.ibm.com>
To:     linux-ext4@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Jan Kara <jack@...e.com>, tytso@....edu,
        Ritesh Harjani <riteshh@...ux.ibm.com>
Subject: [PATCHv1 2/2] jbd2: Remove CONFIG_JBD2_DEBUG to update t_max_wait

CONFIG_JBD2_DEBUG and jbd2_journal_enable_debug knobs were added in
update_t_max_wait(), since earlier it used to take a spinlock for updating
t_max_wait, which could cause a bottleneck while starting a txn
(start_this_handle()).
Since in previous patch, we have killed t_handle_lock completely, we
could get rid of this debug config and knob to let t_max_wait be updated
by default again.

Signed-off-by: Ritesh Harjani <riteshh@...ux.ibm.com>
---
 fs/jbd2/transaction.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index 68dd7de49aff..77634e2e118e 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -141,20 +141,19 @@ static void jbd2_get_transaction(journal_t *journal,
  * t_max_wait is carefully updated here with use of atomic compare exchange.
  * Note that there could be multiplre threads trying to do this simultaneously
  * hence using cmpxchg to avoid any use of locks in this case.
+ * With this t_max_wait can be updated w/o enabling jbd2_journal_enable_debug.
  */
 static inline void update_t_max_wait(transaction_t *transaction,
 				     unsigned long ts)
 {
-#ifdef CONFIG_JBD2_DEBUG
 	unsigned long oldts, newts;
-	if (jbd2_journal_enable_debug &&
-	    time_after(transaction->t_start, ts)) {
+
+	if (time_after(transaction->t_start, ts)) {
 		newts = jbd2_time_diff(ts, transaction->t_start);
 		oldts = READ_ONCE(transaction->t_max_wait);
 		while (oldts < newts)
 			oldts = cmpxchg(&transaction->t_max_wait, oldts, newts);
 	}
-#endif
 }

 /*
--
2.31.1