[PATCH] UBI: add a ubi forced detach ioctl

[Luka Perkov]

On Mon, May 12, 2014 at 11:21:22AM +0200, John Crispin wrote:
> This is a ugly temporary patch that we carry around in openwrt until we
> have a real fix. why are you trying to upstream this ?

I didn't think this is a hack, other file systems can force umount as
well. What are you proposing as a real fix?
 
> Additionally the patch was written by Daniel and not me so the SoB is
> wrong.

I took it from OpenWrt and it was commited there with your SoB and
Daniel was not mentioned there.

> On 12/05/2014 09:14, Richard Weinberger wrote:
> > On Mon, May 12, 2014 at 1:17 AM, Luka Perkov <luka at openwrt.org> 
> > wrote:
> >> From: John Crispin <blogic at openwrt.org>
> >> 
> >> Signed-off-by: John Crispin <blogic at openwrt.org> Tested-by: Luka 
> >> Perkov <luka at openwrt.org> CC: Artem Bityutskiy 
> >> <dedekind1 at gmail.com>
> > 
> > The changelog fails to describe why you need this new ioctl() and 
> > what problem this patch is solving.

When running ubi rootfs upgrade on nand based OpenWrt device after
pivot_root init process is still "hooked" on the old file system. Thus,
the old file system can not be umounted. If the filesystem is mounted it
can not be upgraded with using for example ubiupdatevol or removed with
ubirmvol. Forcing umount would allow to run the before mentioned
commands.

Luka