On Wed, Jul 07, 2010 at 09:36:29AM +1000, Neil Brown wrote:
> On Wed, 7 Jul 2010 09:23:51 +1000
> Dave Chinner <david@xxxxxxxxxxxxx> wrote:
>
> > > I can add a new syscall that returns
> > >
> > > struct fs_uuid {
> > > u8 fs_uuid[16];
> > > };
> > >
> > > long sys_get_fs_uuid(int dfd, char *name, struct fs_uuid *fsid, int flag);
> >
> > libblkid already provides the UUID to userspace applications, doesn't it?
>
> Yes and no.
>
> libblkid provides the uuid of the thing that uses a block device. That
> doesn't directly map to "UUID of a filesystem".
True.
> There are two types of filesystem that I can think of for which libblkid
> cannot give a uuid.
> - network filesystems (or virtual filesystems, or fuse )
How would you guarantee persistent uniqueness for such filesystems?
> - filesystems which share a block device, such as btrfs.
> btrfs can have 'subvols' - multiple "filesystems" within
> the one (set of) block device(s). libblkid cannot be asked about these
> different subvols.
>
> libblkid is useful, but not a real solution.
So libblkid doesn't cover everything, but I think my question is
still valid - if we want per-filesystem UUIDs, why a syscall and not
just publishing it somewhere where we already publish per-mount
information? e.g. in /proc/mounts?
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
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