[sheepdog] [PATCH v3 0/5] fix fatal MD bugs

[Liu Yuan]

v3:
 -- add assert() for empty pathname
 -- call get_objsize() to check read size
 -- add a check for empty string at collie side

v2:
 -- correct ret check in check_and_move()

This patch series is very vital. Curren master's MD isn't useable and not
upgrading friendly. This patch set solve the bugs and work it to be more friendly. 

Thanks,
Yuan