On Fri 22-01-21 14:43:18, Chunguang Xu wrote:

On a multi-disk machine, because jbd2 debugging switch is global, this
confuses the logs of multiple disks. It is not easy to distinguish the
logs of each disk and the amount of generated logs is very large. Or a
separate debugging switch for each disk would be better, so that you
can easily distinguish the logs of a certain disk. 

We can enable jbd2 debugging of a device in the following ways:
echo X > /proc/fs/jbd2/sdX/jbd2_debug

But there is a small disadvantage here. Because the debugging switch is
placed in the journal_t object, the log before the object is initialized
will be lost. However, usually this will not have much impact on
debugging.

OK, I didn't look at the series yet but I'm wondering: How are you using
jbd2 debugging? I mean obviously it isn't meant for production use but
rather for debugging JBD2 bugs so I'm kind of wondering in which case too
many messages matter.

And if the problem is that there's a problem with distinguishing messages
from multiple filesystems, then it would be perhaps more useful to add
journal identification to each message similarly as we do it with ext4
messages (likely by using journal->j_dev) - which is very simple to do
after your patches 3 and 4.

								Honza
-- 
Jan Kara [off-list ref]
SUSE Labs, CR