Re: [REPOST][PATCH][RFC] vfs: add message print mechanism for the mount/umount into the VFS layer

[Dave Chinner <david@fromorbit.com>]

On Fri, Jan 15, 2010 at 05:44:01AM -0600, Mike Mestnik wrote:
> On Fri, Jan 15, 2010 at 5:02 AM, Dave Chinner <david@fromorbit.com> wrote:
> > On Thu, Jan 14, 2010 at 11:36:25PM -0500, Andreas Dilger wrote:
> >> On 2010-01-14, at 20:24, Dave Chinner wrote:
> >>> On Thu, Jan 14, 2010 at 10:33:42AM -0500, Andreas Dilger wrote:
> >>>> Sure, it is _possible_ to do this, but you miss the fact that there
> >>>> are
> >>>> many system monitoring tools that already scrape /var/log/messages
> >>>> and
> >>>> integrate with event managers.  What you are suggesting is that every
> >>>> such tool implement an extra, completely ad-hoc mechanism just for
> >>>> monitoring the mount/unmount of filesystems on Linux.  That doesn't
> >>>> make
> >>>> sense.
> >>>
> >>> We already report various events through a netlink interface, but not
> >>> to the log files (e.g. quota warnings), so those system monitoring
> >>> tools are already going to be missing interesting information.
> >>>
> >>> Using log files for system event notification used to be the only
> >>> way to communicate such events. Now we have much more advanced and
> >>> efficient mechanisms for notifications so I think we should use
> >>> them.
> > ....
> >> However, there are many reasons why it still makes sense to do this:
> >> - it is in plain text format.  I can't recall the number of times
> >>   people were proposing crazy schemes to have a text interface to the
> >>   kernel (via /sys/blah, or /debugfs/blah) for things that are much
> >>   better suited to an ioctl, since they are largely handled by binaries
> >>   (applications), yet in the case where we have an existing plain-text
> >>   interface (dmesg and /var/log/messages) that are meant (at least
> >>   partly) for human consumption we are proposing a binary interface
> >> - every system monitoring tool in existence has a /var/log/messages
> >>   scraping interface, because this is the lowest common denominator,
> >>   but I'd suspect that few/none have a netlink interface, or if they
> >>   do it probably can't be easily added to by a user
> >
> > A daemon that captures the events from netlink and writes them to
> > syslog is all that is needed to support log file scraping
> > monitoring tools. The message they scrape does not have to come from
> > the kernel...
> >
> klogd.  Do we need another wheel?

That's just another syslog implementation for directing printk
messages to files. It's not an event notification framework.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com
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