[dm-devel] Re: [PATCH] device-mapper core should use private bioset

[Alasdair G Kergon]

On Mon, Aug 14, 2006 at 02:13:32PM +0200, Stefan Bader wrote:
> I found a problem within device-mapper that occurs in low-mem
> situations. It was found using a mirror target but I think in theory it
> would hit any setup that stacks device-mapper devices (like LVM on top
> of multipath).

Several dm targets suffer from this.

Mempools are not yet used correctly everywhere in device-mapper: they
can get shared when devices are stacked, and some targets share them across
multiple instances.  I made fixing this one of the prerequisites for this
patch:
  md-dm-reduce-stack-usage-with-stacked-block-devices.patch
which in some cases makes people more likely to hit the problem.

There's been some progress on this recently with (unfinished) dm-crypt
patches at:
  http://www.kernel.org/pub/linux/kernel/people/agk/patches/2.6/editing/
    (dm-crypt-move-io-to-workqueue.patch plus dependencies)

I'll add (the first part of) your patch to the mix as it's another required
piece of the jigsaw, thanks.

Alasdair