Re: [dm-devel] linux-next - WARNING: at fs/block_dev.c:824 bd_link_disk_holder+0x92/0x1ac()

[Milan Broz <mbroz@redhat.com>]

On 01/13/2011 12:06 PM, Tejun Heo wrote:
> Urgh... gees, so there actually was a user using all that cruft.
> Sorry about the breakage, I'll see how multiple symlinks can be
> restored.  I'm curious why this was added at all tho.  What was the
> rationalization?  It's not like two subsystems can share the same
> block device so marking the currently owning subsystem should have
> been enough at the block layer.  There is no reason for block devices
> to present information which is of no use to itself.  All that's
> necessary is "this is taken by dm or md for more information, query
> those".  dm and md need their own conf/representation layer anyway.

I am not sure if I understand it correctly, but multiple holders/slaves
links are very useful in userspace to present device dependences.

We just implemented lsblk command in util-linux which simple prints
tree according to these links, so dependendes of DM/MD/whatever devices
can be printed without using any system specific callbacks, just using
sysfs. See http://karelzak.blogspot.com/2010/12/lsblk8.html

Whatever changes are needed, please keep this functionality, it can be useful.

Thanks,
Milan