Kernel module logging is too verbose upon error conditions

[Tyler Hicks]

eCryptfs writes far too many error messages to the syslog in error handling paths. This is a bad idea for a filesystem because many operations may be repeated rapidly, causing the logs to grow large in size. eCryptfs should only write to the syslog in very grave situations.

However, the logging is useful to developers for debugging. We should leverage something like dynamic debug to lessen the amount of information logged in normal operating conditions. When a user is seeing a problem, we can ask them to run a couple commands to enable logging.

[Stephan Sokolow (ssokolow)]

This actually made recovery from a full disk almost impossible on my mother's laptop.

We first noticed the problem when LightDM refused to start. It took a while to diagnose though, since pre-Precise Lubuntu used LXDM and LXDM didn't blow up when we encountered this problem before. (I'm assuming LightDM's un-privilieged subprocess was dying because it couldn't log into the free space ext2/3/4 reserves for root in case of this kind of situation.)

The big problem was that, because we have some programs which run on login, even in the console, and my mother's laptop has only one user account, any login that's possible with a full drive results in the console being flooded with eCryptFS's cryptic out-of-space messages so fast as to be unusable.

(And it always writes to the active virtual terminal, so the flood of messages follows you if you Ctrl+Alt+F# to another one)

I ended up having to boot from a thumbdrive and flush apt's cache of downloaded debs before I could successfully login as her at the console so it would unlock the eCryptFS and I clean out some stuff from inside it.

[Jason Xing (wlxing)]

Can "ecryptfs_verbosity" lessen the amount of messages to be printed? It seems that developers have already fixed this issue.

[Tyler Hicks (tyhicks)]

The ecryptfs_verbosity module parameter does not fix this bug. There are a number of places where printk() is called directly.

[Jason Xing (wlxing)]

I'm sorry for my wrong bug triage...