[dm-crypt] dm-crypt LUKS and USB power management

Ritesh Raj Sarraf rrs at researchut.com
Mon May 30 18:44:08 CEST 2016


On Sat, 2016-05-21 at 03:04 +0200, Axel Heider wrote:
> 
> I wonder if there are any ideas how dm-crypto or LUKS can handle this
> case. Or is the recommendation that the USB suspend should not happen
> at all for devices that are broken (ie. that disconnect and reconnect
> on resume)?
> Even if all handles on /dev/sda are released internally, there is not
> really a guarantee that the devices comes back as /dev/sda are the
> disconnect/reconnect. However, the UUID should be the same, so that
> could be used to detect it's the same device and partition then and
> accesses get re-routed to it then transparently.

I doubt if it could be done clean. Most targets in Device Mapper ask for careful
unstacking.

Red Hat (leading Linux vendor) still seems to be recommending that.
https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html-si
ngle/Storage_Administration_Guide/#removing_devices


I would rather investigate the (flaky) USB device. First, does it happen only
when Runtime PM is enabled ? If so, you should just blacklist it from Power
Management. Many devices, under Linux, report (false) PM capabilities.


-- 
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me in replies for quicker response
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