[GSoC 2010][RESEND] Questions on Improved async/vector i/o support, fscache integration, and VFS change notification

[Mohammed Gamal]

On Sat, Apr 3, 2010 at 12:46 PM, Jeff Layton <jlayton at samba.org> wrote:
> On Sat, 3 Apr 2010 12:16:34 +0200
> Mohammed Gamal <m.gamal005 at gmail.com> wrote:
... <snip> ...

>> - VFS change notification: My understanding on a very high level is
>> that a mechanism is needed for the smb server to respond to
>> inotfiy/dnotify calls, push these calls to the clients who have the
>> corresponding shares mounted, and then reflect these changes on their
>> ends. Is that understanding correct? And which operations need to be
>> done in kernel space? Which other need to be done in userspace? And
>> what are the boundaries between the two?
>>
>
> The CIFS/SMB protocol already supports asynchronous notification when a
> file changes on the server (maybe directory too? not sure). This
> project is about hooking CIFS up to this. The problem currently is that
> the VFS doesn't call down into the lower filesystem when a program
> wants to be notified of changes.
>
> So that would have to be added at the VFS layer first, and then CIFS
> would have to turn that into a call to set up notifications on the
> server. You'd also have to have CIFS do a fanotify event when a file on
> the server changes. This is all kernel-space stuff.
>

Since inotify/dnotify calls are not delivered through the VFS then how
do do notifications get delivered to userland? and which component
delivers notifications to it if it's not the VFS or the lower
filesystem?

Regards,
Mohammed