device-mapper locking rework

[Adam Hamsik <haaaad%gmail.com@localhost>]

Hi folks,

After some discussion with rmind@ and blymn@ I tried to implement  
better locking
protocol for my dm driver. I'm attaching result of my work as diff  
against current
this diff probably can't be cleanly applied to current haad-dm sources  
therefore
I have uploaded my sources here [1].

TODO:

1) Testing

2) Think about if current state of ioctl-> ioctl synchronisation is o,  
if not add
   ioctl call reference counter like I did for io/table users.

[1] www.netbsd.org/~haad/dm09292008.tar.bz2

Attachment: dm_locking.diff
Description: Binary data

Regards

Adam.