[dm-crypt] Toggle read-only status of mapping

Dennis Birkholz dm-crypt at dennis.birkholz.biz
Thu Oct 25 16:50:32 CEST 2012

Am 25.10.2012 12:15, schrieb Milan Broz:
> On 10/23/2012 06:55 AM, Dennis Birkholz wrote:
>> currently it is possible to create a read-only mapping, but to me it
>> seems not possible to switch a rw mapping to a ro mapping or vice versa.
>> I use Software-RAID5->Luks->Ext4, do switch everything to read-only I
>> have to unmount, remove crypt mapping, create ro crypt mapping, mount
>> ro, switch raid to ro but it would be very nice if I only can switch
>> everything to ro.
> Hm. What is the reason for this exercise?
> Switching to read only of top layer is not enough?

The reason is relatively easy: if my raid is read-only, it can crash and
I can reassemble it without a problem, but I cannot make it read-only if
the crypt-mapping is read-write.

> Anyway, I think we can add this option to "resize" command perhaps.
> (Resize reloads mapping, so it can switch read-only flag as well.)

That would be nice.

> But it can be dangerous in some situations...
> (And you can do it already using dmsetup but that's quite complicated.)

I will have a look into it.


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