Patch series "Maple tree mas_{next,prev}_range() and cleanup", v4.

This patchset contains a number of clean ups to the code to make it more
usable (next/prev range), the addition of debug output formatting, the
addition of printing the maple state information in the WARN_ON/BUG_ON
code.

There is also work done here to keep nodes active during iterations to
reduce the necessity of re-walking the tree.

Finally, there is a new interface added to move to the next or previous
range in the tree, even if it is empty.

The organisation of the patches is as follows:

0001-0004 - Small clean ups
0005-0018 - Additional debug options and WARN_ON/BUG_ON changes
0019      - Test module __init and __exit addition
0020-0021 - More functional clean ups
0022-0026 - Changes to keep nodes active
0027-0034 - Add new mas_{prev,next}_range()
0035      - Use new mas_{prev,next}_range() in mmap_region()


This patch (of 35):

Static analyser of the maple tree code noticed that the split variable is
being used to dereference into an array prior to checking the variable
itself.  Fix this issue by changing the order of the statement to check
the variable first.

Link: https://lkml.kernel.org/r/20230518145544.1722059-1-Liam.Howlett@oracle.com
Link: https://lkml.kernel.org/r/20230518145544.1722059-2-Liam.Howlett@oracle.comSigned-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reported-by: David Binderman <dcb314@hotmail.com>
Reviewed-by: Peng Zhang<zhangpeng.00@bytedance.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Vernon Yang <vernon2gm@gmail.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>