Merge tag 'ext4_for_linus_cleanups' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4

Pull ext4 fixes and cleanups from Ted Ts'o:
 "More fixes and cleanups for the new fast_commit features, but also a
  few other miscellaneous bug fixes and a cleanup for the MAINTAINERS
  file"

* tag 'ext4_for_linus_cleanups' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4: (28 commits)
  jbd2: fix up sparse warnings in checkpoint code
  ext4: fix sparse warnings in fast_commit code
  ext4: cleanup fast commit mount options
  jbd2: don't start fast commit on aborted journal
  ext4: make s_mount_flags modifications atomic
  ext4: issue fsdev cache flush before starting fast commit
  ext4: disable fast commit with data journalling
  ext4: fix inode dirty check in case of fast commits
  ext4: remove unnecessary fast commit calls from ext4_file_mmap
  ext4: mark buf dirty before submitting fast commit buffer
  ext4: fix code documentatioon
  ext4: dedpulicate the code to wait on inode that's being committed
  jbd2: don't read journal->j_commit_sequence without taking a lock
  jbd2: don't touch buffer state until it is filled
  jbd2: add todo for a fast commit performance optimization
  jbd2: don't pass tid to jbd2_fc_end_commit_fallback()
  jbd2: don't use state lock during commit path
  jbd2: drop jbd2_fc_init documentation
  ext4: clean up the JBD2 API that initializes fast commits
  jbd2: rename j_maxlen to j_total_len and add jbd2_journal_max_txn_bufs
  ...

1 files changed, 10 insertions, 1 deletions

diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
index fa688e163a80..b121d7d434c6 100644
--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -450,6 +450,15 @@ void jbd2_journal_commit_transaction(journal_t *journal)
 		schedule();
 		write_lock(&journal->j_state_lock);
 		finish_wait(&journal->j_fc_wait, &wait);
+		/*
+		 * TODO: by blocking fast commits here, we are increasing
+		 * fsync() latency slightly. Strictly speaking, we don't need
+		 * to block fast commits until the transaction enters T_FLUSH
+		 * state. So an optimization is possible where we block new fast
+		 * commits here and wait for existing ones to complete
+		 * just before we enter T_FLUSH. That way, the existing fast
+		 * commits and this full commit can proceed parallely.
+		 */
 	}
 	write_unlock(&journal->j_state_lock);
 
@@ -801,7 +810,7 @@ start_journal_io:
 		if (first_block < journal->j_tail)
 			freed += journal->j_last - journal->j_first;
 		/* Update tail only if we free significant amount of space */
-		if (freed < journal->j_maxlen / 4)
+		if (freed < jbd2_journal_get_max_txn_bufs(journal))
 			update_tail = 0;
 	}
 	J_ASSERT(commit_transaction->t_state == T_COMMIT);