Re: [PATCH 00/17] VFS: Filesystem information and notifications [ver #17]

[Miklos Szeredi]

On Tue, Mar 3, 2020 at 10:26 AM Miklos Szeredi <miklos@xxxxxxxxxx> wrote:
>
> On Tue, Mar 3, 2020 at 10:13 AM David Howells <dhowells@xxxxxxxxxx> wrote:
> >
> > Miklos Szeredi <miklos@xxxxxxxxxx> wrote:
> >
> > > I'm doing a patch.   Let's see how it fares in the face of all these
> > > preconceptions.
> >
> > Don't forget the efficiency criterion.  One reason for going with fsinfo(2) is
> > that scanning /proc/mounts when there are a lot of mounts in the system is
> > slow (not to mention the global lock that is held during the read).

BTW, I do feel that there's room for improvement in userspace code as
well.  Even quite big mount table could be scanned for *changes* very
efficiently.  l.e. cache previous contents of /proc/self/mountinfo and
compare with new contents, line-by-line.  Only need to parse the
changed/added/removed lines.

Also it would be pretty easy to throttle the number of updates so
systemd et al. wouldn't hog the system with unnecessary processing.

Thanks,
Miklos