[dm-devel] [PATCH 4/8] block: support delayed holder registration

[Christoph Hellwig]

On Sat, Aug 14, 2021 at 02:13:09PM -0700, Guenter Roeck wrote:
> On Wed, Aug 04, 2021 at 11:41:43AM +0200, Christoph Hellwig wrote:
> > device mapper needs to register holders before it is ready to do I/O.
> > Currently it does so by registering the disk early, which can leave
> > the disk and queue in a weird half state where the queue is registered
> > with the disk, except for sysfs and the elevator.  And this state has
> > been a bit promlematic before, and will get more so when sorting out
> > the responsibilities between the queue and the disk.
> > 
> > Support registering holders on an initialized but not registered disk
> > instead by delaying the sysfs registration until the disk is registered.
> > 
> > Signed-off-by: Christoph Hellwig <hch at lst.de>
> > Reviewed-by: Mike Snitzer <snitzer at redhat.com>
> 
> This patch results in lockdep splats when booting from flash.
> Reverting it fixes the proboem.

Should be fixed by:
https://git.kernel.dk/cgit/linux-block/commit/?h=for-5.15/drivers&id=6e4df4c6488165637b95b9701cc862a42a3836ba