The patch adds a return value to the ctor callback for custom slab 
caches: this is needed for complex constructors, for example for
constructors that internally allocate further memory.

This was always the intention of the constructors - the GFP_ATOMIC flag 
is forwarded to the constructor, but without the ability to fail
it was useless.
The patch is quite large because it changes the prototype of the slab 
constructor, and every filesystem has a custom slab with a constructor.

Sent to Linus a few minutes ago.

--
    Manfred