maple_tree: remove maple_big_node.parent

maple_tree: remove maple_big_node.parent

Patch series "Reduce the space to be cleared for maple_big_node", v2.

Found current code may clear maple_big_node redundantly.

First we define a field parent, which is never used.  After removing this,
we reduce the size of memory to be cleared by memset.

Then mast_fill_bnode() clears part of the structure twice, since slot and
gap share some space.  By clearing the whole structure, we can avoid this.

This patch (of 2):

The member parent of maple_big_node is never used.

Let's remove it which could reduce the number of space to be cleared on
memset.

Link: https://lkml.kernel.org/r/20240908140554.20378-1-richard.weiyang@gmail.com
Link: https://lkml.kernel.org/r/20240908140554.20378-2-richard.weiyang@gmail.com
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>