On Tue, Oct 10, 2000 at 05:58:59PM -0700, Rusty Ballinger wrote:
>
> As far as 2.4 kernels go, jrodman@xxxxxxxx mentioned that another mechanism
> for directory notification has already gone in. I'm looking at 2.4.0-test9
> now, and it looks like include/linux/dnotify.h provides a facility for being
> notified by signals when the contents of a directory changes, a lot like
> the patch from willy@thepuffingroup
> (http://oss.sgi.com/projects/fam/archive/msg00091.html). (It's not there in
> 2.4.0-test1; I don't know which version it was introduced in.) On 2.4
It just went in with -test9.
> kernels, fam should be able to use that; in fact, libfam could/should? do
> the fcntl itself instead of contacting the fam daemon. (The problem there
> is that it has to open the directory to do the fcntl, which means a client
> which monitors a lot of directories can run out of file descriptors, and if
> SIGPOLL/SIGIO is already being handled by the application, it won't like
> libfam installing its own handler which re-scans the directory--or stats the
> file, if that's what was being monitored--corresponding to the fd for which
> the signal was sent.)
>
> Anyway, an interesting thing to think about. Unless imon's hooks into the
> filesystem code are rewritten, in 2.4 kernels I think fam will probably have
> to live with the fcntl(directory, F_NOTIFY) mechanism.
>
> --Rusty
Yeah, I was looking through it yesterday. (That's part of what caused the
collision with the imon patch in -test9 that Philipp Baer fixed.) I haven't
written any code to try it out yet -- that's next on my list. It looks like
it only supports monitoring the contents of a directory; there's nothing
for monitoring a single file or watching execution(s). I think I'll send
an email to Stephen Rothwell (his name is at the top of the files) and ask
him if there are any plans to expand it to include file only notification.
Although I guess Fam could hide that from the client; when a request to
monitor a file comes in, monitor the parent dir, and then ignore changes
to the other files. As far as execution monitoring goes, how important is
that?
Brian
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