On Mon, Apr 26, 2010 at 03:42:45PM +0530, Aneesh Kumar K. V wrote:
> On Fri, 23 Apr 2010 16:02:14 -0600, Andreas Dilger <adilger@xxxxxxx> wrote:
> > On 2010-04-23, at 05:38, Aneesh Kumar K.V wrote:
> > > +long do_sys_name_to_handle(const char __user *name,
> > > + struct file_handle *fh)
> > > +{
> > > + /*
> > > + * name to handle conversion only done for regular files
> > > + * directories and symbolic links
> > > + */
> >
> > Out of curiosity, why not do this for other types of files? It makes
> > sense from a consistency POV, so that the userspace code doesn't have
> > to special-case each file by checking the type first (which would mean
> > doing an extra path traversal and stat for each file first, adding
> > overhead).
>
> The limitation directly came from the XFS ioctl. But I don't see a
> reason why we should limit it for this syscall. To better support
> symlink and regular files i now have did sys_name_to_handle and
> sys_lname_to_handle syscalls. I also did a freadlink syscall that will
> return the symlink target name from the handle.
>
>
>
> >
> > I'd always thought it would be cool to have a distributed filesystem where named pipes/sockets work across clients by using the IO transport of the filesystem, making single-system image environments a lot easier to implement.
> >
> > > + /* we ask for a non connected handle */
> > > + retval = exportfs_encode_fh(path.dentry, (struct fid *)handle,
> > > + &handle_size, 0);
> >
> > Since there is virtually no overhead to do so, why not always return a connected handle? This will allow the kernel to reconnect the looked-up dentries into the tree, instead of creating all disconnected dentries.
> >
>
> open by handle would return a connected dentry for directory. Since we
> use a simple acceptable function that accept any dentry alias with
> exportfs_decode_fh I was wondering whether we should return a connected
> handle ? It would be simply increasing the size of the handle ?
Well, and it means the filehandle changes when you rename the file to a
different directory. Do you really want that?
--b.
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