jbd2: remove wrong sb->s_sequence check

Journal emptiness is not determined by sb->s_sequence == 0 but rather by
sb->s_start == 0 (which is set a few lines above). Furthermore 0 is a
valid transaction ID so the check can spuriously trigger. Remove the
invalid WARN_ON.

CC: [email protected]
Signed-off-by: Jan Kara <[email protected]>
Reviewed-by: Zhang Yi <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Theodore Ts'o <[email protected]>

Author: jankara

fs/jbd2/journal.c

@@ -1869,7 +1869,6 @@ int jbd2_journal_update_sb_log_tail(journal_t *journal, tid_t tail_tid,
 
 	/* Log is no longer empty */
 	write_lock(&journal->j_state_lock);
-	WARN_ON(!sb->s_sequence);
 	journal->j_flags &= ~JBD2_FLUSHED;
 	write_unlock(&journal->j_state_lock);