Date: Tue, 23 Aug 2011 09:21:50 +1000
From: NeilBrown <neilb@suse.de>
To: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Jamie Lokier <jamie@shareable.org>, Al Viro <viro@ZenIV.linux.org.uk>,
        Sylvain Rochet <gradator@gradator.net>, linux-kernel@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org
Subject: Re: PROBLEM: 2.6.35.7 to 3.0 Inotify events missing
Message-ID: <20110823092150.366d8899@notabene.brown>
In-Reply-To: <20110822172239.GA15960@fieldses.org>
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On Mon, 22 Aug 2011 13:22:39 -0400 "J. Bruce Fields" <bfields@fieldses.org>
wrote:

> On Mon, Aug 22, 2011 at 09:07:51AM +1000, NeilBrown wrote:
> > One is to use bind mounts. i.e. I effectively do
> >     mount --bind $HOME/.config $HOME/.config
> > and ask for events from the newly created vfsmnt.
> > This will not catch changes made through file descriptors that were opened
> > before I did the mount, or through hard links from some other directory
> > tree.  But for a particular use-case that might not be a problem.
> 
> I'm missing what the extra vfsmount gets you here.  The problems seem
> just the same as if you don't have one.
> 
> Oh, wait, I see, it's that the file descriptors are associated with
> vfsmounts, not just dentries.  Hm.

"Hm" might be right.  writes have a 'struct file', but mkdir and rename etc
just get an inode.
So to be able to notify based on vfsmnt, mkdirat - for examine - would need
to pass the path to vfs_mkdir rather than path.dentry->d_inode, and vfs_mkdir
would have to pass that path to fsnotify_mkdir.  So more intrusive that I
imagined, but still quite do-able.... if it were thought to be useful.

NeilBrown