Re: which ioctls matter across filesystems

Steve French
2005-04-29T20:34:12Z

Trond Myklebust wrote:

>What kind of real-world applications exist out there that need inotify
>functionality, and what sort of requirements do they have (in particular
>w.r.t. the notification mechanism)?
>
>Cheers,
> Trond
>
>
The two cases I can think of which matter (other than the case you
mention) are:
1) KDE File manager - autoupdate of directory listings which today calls
D_NOTIFY (a similar feature was first done IIRC in OS/2 for support of
the workplace shell). Obviously this is as or more important to
support well over the network as it is in the local fs, but the client
implications. I don't know whether their needs (and the equivalent in
Gnome) map better to fcntl DNOTIFY or inotify.

2) Support of Network File Servers - The Samba example has already been
mentioned, but it is important because it would be quite common for a
series of Samba servers to export shares that are NFS mounted to a set
of NFS servers (or on other platforms mounted to a cluster
filesystem). The CIFS network protocol has long had a notify
mechanism, and client implementations on various operating systems use
it, so there is pressure for Samba to support it better. The Linux
CIFS client can issue these calls too, but it is marked experimental and
disabled by default as more work needs to be done to clean it up.

A loosely related issue which will matter a lot in the long run are
figuring out a way to pass get/setlease requests as the network caching
mechanisms would otherwise not work in three tier environments (e.g.
SMB/CIFS client -> Samba server over NFS client mounted to -> NFS
server, or the reverse).