ext4: warn on read-only filesystem in ext4_journal_check_start()

Now that filesystem abort marks the filesystem as shutdown, we shouldn't
be ever hitting the sb_rdonly() check in ext4_journal_check_start().
Since this is a suitable place for catching all sorts of programming
errors, convert the check to WARN_ON instead of dropping it.
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20230616165109.21695-7-jack@suse.czSigned-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/ext4_jbd2.c

@@ -70,8 +70,9 @@ static int ext4_journal_check_start(struct super_block *sb)
 	if (unlikely(ext4_forced_shutdown(sb)))
 		return -EIO;
 
-	if (sb_rdonly(sb))
+	if (WARN_ON_ONCE(sb_rdonly(sb)))
 		return -EROFS;
+
 	WARN_ON(sb->s_writers.frozen == SB_FREEZE_COMPLETE);
 	journal = EXT4_SB(sb)->s_journal;
 	/*