Pull xarray fixes from Matthew Wilcox:

 - Fix a bug encountered by people using bittorrent where they'd get
   NULL pointer dereferences on page cache lookups when using XFS

 - Two documentation fixes

* tag 'xarray-6.6' of git://git.infradead.org/users/willy/xarray:
  idr: fix param name in idr_alloc_cyclic() doc
  xarray: Document necessary flag in alloc functions
  XArray: Do not return sibling entries from xa_load()