This patch works around a complex dm-related deadlock/livelock down in the
mempool allocator.
Alasdair said:
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)
and:
I've no problems with a temporary workaround like that, but Milan Broz (a
new Redhat developer in the Czech Republic) has started reviewing all the
mempool usage in device-mapper so I'm expecting we'll soon have a proper fix
for this associated problems. [He's back from holiday at the start of next
week.]
For now, this sad-but-safe little patch will allow the machine to recover.
[akpm@osdl.org: rewrote changelog]
Cc: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
0b1d647a02