0809527 Fix deadlock warning when opening snapshot device

Authored and Committed by Tim Crawford 5 years ago
    Fix deadlock warning when opening snapshot device
    
    lockdep produces a deadlock warning between the ioctl mutex and the bdev
    mutex. Convert sd_refs to atomic so we don't need to use the ioctl lock
    when opening the block device.
    
    Resolves: #170
    
        
file modified
+3 -5