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 ?
-aneesh
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