Re: Beagle and logging inotify events

["J. Bruce Fields" <bfields@fieldses.org>]

On Wed, Nov 14, 2007 at 04:30:16PM +0100, Andi Kleen wrote:
> "Jon Smirl" <jonsmirl@gmail.com> writes:
> 
> > On 11/14/07, Chuck Lever <chuck.lever@oracle.com> wrote:
> >> On Nov 13, 2007, at 7:04 PM, Jon Smirl wrote:
> >> > Is it feasible to do something like this in the linux file system
> >> > architecture?
> >> >
> >> > Beagle beats on my disk for an hour when I reboot. Of course I don't
> >> > like that and I shut Beagle off.
> >>
> >> Leopard, by the way, does exactly this: it has a daemon that starts
> >> at boot time and taps FSEvents then journals file system changes to a
> >> well-known file on local disk.
> >
> > Logging file systems have all of the needed info.
> 
> Actually most journaling file systems in Linux use block logging and
> it would be probably hard to get specific file names out of a random
> collection of logged blocks. And even if you could they would
> hit a lot of false positives since everything is rounded up
> to block level.
> 
> With intent logging like in XFS/JFS it would be easier, but even
> then costly :- e.g. they might log changes to the inode but
> there is no back pointer to the file name short of searching the
> whole directory tree.

So it seems the best approach given the current api's would be just to
cache all the stat data, and stat every file on reboot.

I don't understand why beagle is reading the entire filesystem data.  I
understand why even just doing the stat's could be prohibitive, though.

--b.