If journal is empty, clear the fast commit flag from the on disk
superblock. With this optimization, chances of running into backward
compatibility issues are reduced.
Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@xxxxxxxxx>
---
fs/jbd2/journal.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 79f015f7bf54..f8f55d0814ea 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -1482,6 +1482,7 @@ int jbd2_journal_update_sb_log_tail(journal_t *journal, tid_t tail_tid,
static void jbd2_mark_journal_empty(journal_t *journal, int write_op)
{
journal_superblock_t *sb = journal->j_superblock;
+ bool had_fast_commit = false;
BUG_ON(!mutex_is_locked(&journal->j_checkpoint_mutex));
lock_buffer(journal->j_sb_buffer);
@@ -1495,9 +1496,20 @@ static void jbd2_mark_journal_empty(journal_t *journal, int write_op)
sb->s_sequence = cpu_to_be32(journal->j_tail_sequence);
sb->s_start = cpu_to_be32(0);
+ if (jbd2_has_feature_fast_commit(journal)) {
+ /*
+ * When journal is clean, no need to commit fast commit flag and
+ * make file system incompatible with older kernels.
+ */
+ jbd2_clear_feature_fast_commit(journal);
+ had_fast_commit = true;
+ }
jbd2_write_superblock(journal, write_op);
+ if (had_fast_commit)
+ jbd2_set_feature_fast_commit(journal);
+
/* Log is no longer empty */
write_lock(&journal->j_state_lock);
journal->j_flags |= JBD2_FLUSHED;
--
2.25.1.481.gfbce0eb801-goog
