Re: [PATCH v13 1/5] Introduce xbitmap

From: Matthew Wilcox <redacted>

The eXtensible Bitmap is a sparse bitmap representation which is
efficient for set bits which tend to cluster.  It supports up to
'unsigned long' worth of bits, and this commit adds the bare bones --
xb_set_bit(), xb_clear_bit() and xb_test_bit().

Signed-off-by: Matthew Wilcox <redacted>
Signed-off-by: Wei Wang <redacted>
---
  include/linux/radix-tree.h |   2 +
  include/linux/xbitmap.h    |  49 ++++++++++++++++
  lib/radix-tree.c           | 139 ++++++++++++++++++++++++++++++++++++++++++++-
  3 files changed, 188 insertions(+), 2 deletions(-)
  create mode 100644 include/linux/xbitmap.h

diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h
index 3e57350..428ccc9 100644
--- a/include/linux/radix-tree.h
+++ b/include/linux/radix-tree.h