Re: No error when inotify_add_watch(/an/NFS/file)

From: Phil Endecott
Date: Sat Nov 24 2007 - 15:12:00 EST


J. Bruce Fields wrote:
On Fri, Nov 23, 2007 at 11:20:55PM +0000, Phil Endecott wrote:
Dear Experts,

NFS doesn't work with inotify (and it looks like it can't, certainly not before NFS v4.1). However, if I give an NFS filename to inotify_add_watch(), I don't get an error.

If it indicated an error in this case then I could easily fall back to some sort of polling. Without an error, I need some other way to detect NFS (and any other non-inotify-compatible filesystems).

Any thoughts?

The one reason I can think of that you might want that behavior is if
you know you only access a given piece of the filesystem from one client
at a time, and you still want inotify to work in that situation.

That's a good point.

(I'm assuming inotify still notifies you of changes that are made on the same
client.)

A quick test suggest that it does.

But maybe you could handle that case by allowing inotify_add_watch() in
the case where the nfs filesystem was mounted with the "nolock" option,
and failing it otherwise, and telling people to turn on nolock if
they're sure they know what they're doing.

I'm not sure what your rationale for proposing that is, and I don't think it helps in my scenario; a user wants their inotify-using application to "just work", not to be told to "sudo re-mount".

I suppose that I just need some way to determine whether I will get all, some, or none of the events that I've asked for.


Phil.




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