[dm-devel] Re: [lvm-devel] dm-crypt - some info, and a few development questions

[Joe Thornber]

On Thu, Jul 17, 2003 at 07:23:55PM +0200, Jon Bendtsen wrote:
> We are 2 people, can we both work on the device-mapper driver?

I don't know, do you get along ?

> i'll guess i'll try your patch first, so it also can receive some 
> testing. Which 2.5 does it work on ?

2.5.70, but it's taken from the middle of a devel patchset, so it may
not apply cleanly.

> >Encryption will require you to encrypt into your own data pages so you
> >will have to think about how to manage these pages (maybe look at the
> >page handling in kcopyd (2.4, make sure you grab the latest code from
> >our ftp site).  Remember that you cannot allocate memory from within a
> >dm target except GFP_NOIO, so use mempools to ensure progress.
> 
> i figured i would have to do that, but not that i cant allocate memory.

Imagine your machines memory is completely full of IO to your crypt
target.  If you were to then try and get some memory, and that
allocation needs to do some io (eg, to swap out a page) you will
deadlock the system.

- Joe