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From: Milan Broz <mbroz@redhat.com>
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Subject: Re: [dm-crypt] system freezes when using swap that is encrypted
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To: Carlo Wood <carlo@alinoe.com>
Cc: dm-crypt@saout.de, Nicolas Bock <nicolasbock@gmail.com>

On 11/14/2010 01:35 AM, Carlo Wood wrote:
> I use the following configuration for my swap:
> 
> /etc/fstab:
> 
> /dev/mapper/cswap none          swap    sw,pri=1        0       0
> 
> /etc/crypttab:
> 
> cswap       /dev/md1        /dev/random swap
> 
> /dev/md1 is a 16 GB partition on my RAID 5 with three disks.

Stacking devices for swap is not good idea in principle.

It should work in theory but if there is any allocation which
does not use reserved memory pools, it ends in deadlock
(waiting for itself to free some memory by swapping).

Try to set swap to individual device - if it works,
the problem is in MD RAID layer if not, it can be similar
to problem reported before.

dm-crypt uses own reserved bisosets and memory pools so
I expect that problems is in some other subsystem
(but I need to reproduce this to get some info what's going on there)

Milan