Re: [PATCH/RFC 0/3] UBI: unify mouting rootfs based on cmdline parameter

From: Daniel Golle <daniel@makrotopia.org>
To: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
Cc: Boris Brezillon <boris.brezillon@free-electrons.com>,
	Brian Norris <computersforpeace@gmail.com>,
	Richard Weinberger <richard@nod.at>,
	lede-dev@lists.infradead.org,
	"linux-mtd@lists.infradead.org" <linux-mtd@lists.infradead.org>,
	Zoltan HERPAI <wigyori@uid0.hu>,
	Hauke Mehrtens <hauke@hauke-m.de>,
	Ralph Sennhauser <ralph.sennhauser@gmail.com>,
	openwrt-devel@lists.openwrt.org
Subject: Re: [PATCH/RFC 0/3] UBI: unify mouting rootfs based on cmdline parameter
Date: Sun, 28 Aug 2016 16:27:48 +0200	[thread overview]
Message-ID: <20160828142747.GD1623@makrotopia.org> (raw)
In-Reply-To: <CAAEAJfA5zgJDGm=Vdewxb8nh-n-7Ez-HWGCORHyGvD_ku1YxLA@mail.gmail.com>

Hi Ezequiel,

On Sun, Aug 28, 2016 at 11:12:50AM -0300, Ezequiel Garcia wrote:
> Daniel,
> 
> Let's try to tackle this from a different angle.
> 
> On 27 August 2016 at 16:43, Daniel Golle <daniel@makrotopia.org> wrote:
> > Hi!
> >
> > In an attempts to fix the flaws of the current set of UBI-related
> > patches we are carrying in OpenWrt, I re-wrote the way mounting the
> > rootfs from UBI in OpenWrt/LEDE works. The main requirement I face
> > which cannot be easily addressed using other means which are already
> > available in the kernel is the fact that UBIFS and squashfs-on-UBI
> > require different parameters to be set on the cmdline, e.g.
> > for UBIFS: ubi.mtd=ubi root=ubi0:rootfs rootfstype=ubifs
> > for squashfs: ubi.mtd=ubi ubiblock=0,1 root=/dev/ubiblock0_1 rootfstype=squashfs
> >
> 
> Can you help me understand the problem you are solving here?
> 
> So you currently need to do:
> 
> * for UBIFS: ubi.mtd=ubi root=ubi0:rootfs rootfstype=ubifs
> * for squashfs: ubi.mtd=ubi ubi.block=0,1 root=/dev/ubiblock0_1
> rootfstype=squashfs
> 
> [..]
> >
> > With those changes, a single set of cmdline parameters is
> > sufficient to mount either UBIFS or any other block filesystem
> > by creating a ubiblock device:
> > ubi.mtd=ubi root=ubi0:rootfs rootfstype=ubifs,squashfs
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     this is the goal state :)

> >
> 
> And you would like to do:
> 
> * for UBIFS: ubi.mtd=ubi root=ubi0:rootfs rootfstype=ubifs
> * for squashfs: ubi.mtd=ubi root=/dev/ubiblock0_1 rootfstype=squashfs

I do NOT want to pass different cmdlines depending on the filesystem
type. The lines quote above were to illustrate the current
inconsistency of cmdline parameters.

> 
> So the only thing you are trying to acomplish, is removal
> of the ubi.block parameter needed to create ubi block devices.
> 
> Is that correct?

Almost. I want a single syntax for rootfs= to refer to the rootfs
volume, no matter what the filesystem type is. Hence, in case of
non-UBIFS filesystem, a ubiblock needs to be created and mounted.

Cheers

Daniel

> 
> Thanks,
> -- 
> Ezequiel García, VanguardiaSur
> www.vanguardiasur.com.ar
> 
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