Re: which ioctls matter across filesystems

From: Steve French
Date: Fri Apr 29 2005 - 15:37:45 EST

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)?


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).
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