external journal an data= option

[Wolfgang Walter <linux@stwm.de>]

Hello,

while testing ext4 with an external journal I found the following problem with 
longterm kernel 4.4.30:

I could mount the filesystem without specifying the option data=....

It seems that it is then mounted with data=ordered and indeed this is what

	cat /proc/mounts

shows.

But I could not change any option afterwards with -o remount. It always said 
that data=ordered is not valid with an external journal.

If I mount with explicitly stating data=writeback or data=journal remount 
works fine.

So It seems that ext4 does forbid (at least in 4.4.30) data=ordered as an 
option but uses it implicitly as default mode even with an external journal.

Regards,
-- 
Wolfgang Walter
Studentenwerk München
Anstalt des öffentlichen Rechts