external journal an data= option

From: Wolfgang Walter
Date: Mon Nov 21 2016 - 10:39:59 EST


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


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.

Wolfgang Walter
Studentenwerk München
Anstalt des öffentlichen Rechts