Re: [dm-devel] [PATCH 3/3] dm: separate device deletion from dm_put()

[Alasdair G Kergon <agk redhat com>]

On Tue, Jun 08, 2010 at 07:27:20PM +0900, Kiyoshi Ueda wrote:
> For the unlikely case of the forced module unload, dm_destroy_nowait(),
> which doesn't wait and forcibly deletes the mapped_device, is also
> introduced and used in dm_hash_remove_all().  Otherwise, "rmmod -f"
> may be stuck and never return.

> And now, because the mapped_device is deleted at this point, subsequent
> accesses to the mapped_device may cause NULL pointer references.

Do we get a warning message logged when this situation occurs
and md->holders is still set or should we add one?

> +	if (wait) {
> +		while (atomic_read(&md->holders))
> +			msleep(1);

Alasdair