bcachefs: Avoid setting j->write_work unnecessarily

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/journal.c

@@ -416,6 +416,7 @@ static int journal_entry_open(struct journal *j)
 	} while ((v = atomic64_cmpxchg(&j->reservations.counter,
 				       old.v, new.v)) != old.v);
 
+	if (nr_unwritten_journal_entries(j) == 1)
 		mod_delayed_work(j->wq,
 				 &j->write_work,
 				 msecs_to_jiffies(c->opts.journal_flush_delay));
@@ -443,19 +444,16 @@ static void journal_quiesce(struct journal *j)
 static void journal_write_work(struct work_struct *work)
 {
 	struct journal *j = container_of(work, struct journal, write_work.work);
-	long delta;
 
 	spin_lock(&j->lock);
-	if (!__journal_entry_is_open(j->reservations))
-		goto unlock;
-
-	delta = journal_cur_buf(j)->expires - jiffies;
+	if (__journal_entry_is_open(j->reservations)) {
+		long delta = journal_cur_buf(j)->expires - jiffies;
 
 		if (delta > 0)
 			mod_delayed_work(j->wq, &j->write_work, delta);
 		else
 			__journal_entry_close(j, JOURNAL_ENTRY_CLOSED_VAL, true);
-unlock:
+	}
 	spin_unlock(&j->lock);
 }