Messages in this thread | | | Date | Wed, 7 Jul 2010 12:11:50 +1000 | From | Dave Chinner <> | Subject | Re: [PATCH -V14 0/11] Generic name to handle and open by handle syscalls |
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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@fromorbit.com> 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@fromorbit.com
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