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/20181217131929.11727-5-kent.overstreet@gmail.com
Signed-off-by: Kent Overstreet
Cc: Alexey Dobriyan
Cc: Al Viro
Cc: Dave Hansen
Cc: Eric Paris
Cc: Marcelo Ricardo Leitner
Cc: Matthew Wilcox
Cc: Neil Horman
Cc: Paul Moore
Cc: Pravin B Shelar
Cc: Shaohua Li
Cc: Stephen Smalley
Cc: Vlad Yasevich
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds