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From: Zhang Yi <yi.zhang@huaweicloud.com>
To: linux-ext4@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org,
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	tytso@mit.edu,
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	yukuai3@huawei.com
Subject: [PATCH] ext4/jbd2: drop jbd2_transaction_committed()
Date: Mon, 13 May 2024 15:21:19 +0800
Message-Id: <20240513072119.2335346-1-yi.zhang@huaweicloud.com>
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From: Zhang Yi <yi.zhang@huawei.com>

jbd2_transaction_committed() is used to check whether a transaction with
the given tid has already committed, it hold j_state_lock in read mode
and check the tid of current running transaction and committing
transaction, but holding the j_state_lock is expensive.

We have already stored the sequence number of the most recently
committed transaction in journal t->j_commit_sequence, we could do this
check by comparing it with the given tid instead. If the given tid isn't
smaller than j_commit_sequence, we can ensure that the given transaction
has been committed. That way we could drop the expensive lock and
achieve about 10% ~ 20% performance gains in concurrent DIOs on may
virtual machine with 100G ramdisk.

fio -filename=/mnt/foo -direct=1 -iodepth=10 -rw=$rw -ioengine=libaio \
    -bs=4k -size=10G -numjobs=10 -runtime=60 -overwrite=1 -name=test \
    -group_reporting

Before:
  overwrite       IOPS=88.2k, BW=344MiB/s
  read            IOPS=95.7k, BW=374MiB/s
  rand overwrite  IOPS=98.7k, BW=386MiB/s
  randread        IOPS=102k, BW=397MiB/s

After:
  verwrite:       IOPS=105k, BW=410MiB/s
  read:           IOPS=112k, BW=436MiB/s
  rand overwrite: IOPS=104k, BW=404MiB/s
  randread:       IOPS=111k, BW=432MiB/s

CC: Dave Chinner <david@fromorbit.com>
Suggested-by: Dave Chinner <david@fromorbit.com>
Link: https://lore.kernel.org/linux-ext4/493ab4c5-505c-a351-eefa-7d2677cdf800@huaweicloud.com/T/#m6a14df5d085527a188c5a151191e87a3252dc4e2
Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
---
 fs/ext4/inode.c      |  4 ++--
 fs/jbd2/journal.c    | 17 -----------------
 include/linux/jbd2.h |  1 -
 3 files changed, 2 insertions(+), 20 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 537803250ca9..e8e2865bf9ac 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3199,8 +3199,8 @@ static bool ext4_inode_datasync_dirty(struct inode *inode)
 	journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
 
 	if (journal) {
-		if (jbd2_transaction_committed(journal,
-			EXT4_I(inode)->i_datasync_tid))
+		if (tid_geq(journal->j_commit_sequence,
+			    EXT4_I(inode)->i_datasync_tid))
 			return false;
 		if (test_opt2(inode->i_sb, JOURNAL_FAST_COMMIT))
 			return !list_empty(&EXT4_I(inode)->i_fc_list);
diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index b6c114c11b97..73737cd1106f 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -786,23 +786,6 @@ int jbd2_fc_end_commit_fallback(journal_t *journal)
 }
 EXPORT_SYMBOL(jbd2_fc_end_commit_fallback);
 
-/* Return 1 when transaction with given tid has already committed. */
-int jbd2_transaction_committed(journal_t *journal, tid_t tid)
-{
-	int ret = 1;
-
-	read_lock(&journal->j_state_lock);
-	if (journal->j_running_transaction &&
-	    journal->j_running_transaction->t_tid == tid)
-		ret = 0;
-	if (journal->j_committing_transaction &&
-	    journal->j_committing_transaction->t_tid == tid)
-		ret = 0;
-	read_unlock(&journal->j_state_lock);
-	return ret;
-}
-EXPORT_SYMBOL(jbd2_transaction_committed);
-
 /*
  * When this function returns the transaction corresponding to tid
  * will be completed.  If the transaction has currently running, start
diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index 971f3e826e15..e15ae324169d 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -1643,7 +1643,6 @@ extern void	jbd2_clear_buffer_revoked_flags(journal_t *journal);
 int jbd2_log_start_commit(journal_t *journal, tid_t tid);
 int jbd2_journal_start_commit(journal_t *journal, tid_t *tid);
 int jbd2_log_wait_commit(journal_t *journal, tid_t tid);
-int jbd2_transaction_committed(journal_t *journal, tid_t tid);
 int jbd2_complete_transaction(journal_t *journal, tid_t tid);
 int jbd2_log_do_checkpoint(journal_t *journal);
 int jbd2_trans_will_send_data_barrier(journal_t *journal, tid_t tid);
-- 
2.39.2