Re: Device names

[Chris Mason <chris.mason@fusionio.com>]

On Tue, Jun 19, 2012 at 06:00:11PM -0600, H. Peter Anvin wrote:
> On 06/19/2012 04:51 PM, Chris Mason wrote:
> > 
> > At mount time, we go through and verify the path names still belong to
> > the filesystem you thought they belonged to.  The bdev is locked during
> > the verification, so it won't be able to go away or change.
> > 
> > This is a long way of saying right we don't spit out device numbers.
> > Even device numbers can change.  We can easily add a uuid based listing,
> > which I think is what you want.
> > 
> 
> No, I want to find the actual devices.  I know I can get the UUID, but
> scanning all the block devices in the system looking for that UUID is a
> nonstarter.
> 
> Device path names can change while the system is operating (and, worse,
> are dependent on namespace changes and chroot); device *numbers* cannot
> as long as the device is in use (e.g. mounted.)  They can indeed change
> while not in use, of course.

Ok, my two choices for exporting this to you are a /sys/btrfs kind of
directory (representing the mounted filesystems) or an ioctl.  Which one
is most usable for you?

You want to map from /some_dir to a definitive list of devices you need
to find in syslinux to later boot off that FS, right?

-chris