radix tree test suite: add lockdep_is_held to header

maple tree uses lockdep_is_held, so define it as external in the header.

Link: https://lkml.kernel.org/r/20220906194824.2110408-7-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Tested-by: Yu Zhao <yuzhao@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: SeongJae Park <sj@kernel.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

tools: Fix math.h breakage

Commit 98e1385ef24b ("include/linux/radix-tree.h: replace kernel.h with
the necessary inclusions") broke the radix tree test suite in two
different ways; first by including math.h which didn't exist in the
tools directory, and second by removing an implicit include of
spinlock.h before lockdep.h. Fix both issues.

Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

xarray: Add XArray unconditional store operations

xa_store() differs from radix_tree_insert() in that it will overwrite an
existing element in the array rather than returning an error. This is
the behaviour which most users want, and those that want more complex
behaviour generally want to use the xas family of routines anyway.

For memory allocation, xa_store() will first attempt to request memory
from the slab allocator; if memory is not immediately available, it will
drop the xa_lock and allocate memory, keeping a pointer in the xa_state.
It does not use the per-CPU cache, although those will continue to exist
until all radix tree users are converted to the xarray.

This patch also includes xa_erase() and __xa_erase() for a streamlined
way to store NULL. Since there is no need to allocate memory in order
to store a NULL in the XArray, we do not need to trouble the user with
deciding what memory allocation flags to use.

Signed-off-by: Matthew Wilcox <willy@infradead.org>