generic radix trees

generic radix trees

Very simple radix tree implementation that supports storing arbitrary
size entries, up to PAGE_SIZE - upcoming patches will convert existing
flex_array users to genradixes.  The new genradix code has a much
simpler API and implementation, and doesn't have a hard limit on the
number of elements like flex_array does.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Kent Overstreet <[email protected]>
Cc: Alexey Dobriyan <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Eric Paris <[email protected]>
Cc: Marcelo Ricardo Leitner <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Neil Horman <[email protected]>
Cc: Paul Moore <[email protected]>
Cc: Pravin B Shelar <[email protected]>
Cc: Shaohua Li <[email protected]>
Cc: Stephen Smalley <[email protected]>
Cc: Vlad Yasevich <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>