[dm-devel] dm: Get devices using name_to_dev_t

[Mike Snitzer]

On Wed, Jan 14 2015 at  7:16pm -0500,
Dan Ehrenberg <dehrenberg at chromium.org> wrote:

> If a device is used as the root filesystem, it can't be built
> off of devices which are within the root filesystem (just like
> command line arguments to root=). For this reason, Linux has a
> pseudo-filesystem for root= and md initialization based on the
> function name_to_dev_t, which handles different ways of specifying
> devices including PARTUUID and major:minor.
> 
> This patch applies name_to_dev_t to dm initialization. Rather
> than assuming that all things which are not major:minor are paths
> in an already-mounted filesystem, this patch first attempts
> name_to_dev_t and tries the filesystem as a fallback.

What is all this talk of an already-mounted filesystem?

dm_get_device() currently assumes either a major:minor or path to the
block device is provided.  Please be specific about what functionality
this change enables that you cannot do without.