[dm-devel] dm: Get devices using name_to_dev_t

[Daniel Ehrenberg]

On Jan 14, 2015 6:26 PM, "Mike Snitzer" <snitzer at redhat.com> wrote:
>
> 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.

I want to run dm-verity on top of an ubiblock device. Ubiblock uses a
dynamic major number so I can't just refer to it as a major:minor. Because
it is the root filesystem I can't refer to it through the lookup_bdev path.

Thanks,
Dan
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