[PATCH 2/2] maple_tree: memset maple_big_node as a whole

[Wei Yang <richard.weiyang@gmail.com>]

In maple_big_node, we define slot and padding/gap in a union. And based
on current definition of MAPLE_BIG_NODE_SLOTS/GAPS, padding is always
less then slot and part of the gap is overlapped by slot.

For example on 64bit system:

  MAPLE_BIG_NODE_SLOT is 34
  MAPLE_BIG_NODE_GAP  is 21

With this knowledge, current code actually clear the whole
maple_big_node and even clear some space twice.

Instead of clear maple_big_node each field separately, let's clear it in
one memset.

Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
CC: Liam R. Howlett <Liam.Howlett@Oracle.com>

---
Liam:

This looks obvious, so I just run the ./maple test to see it doesn't
break anything.

Do you think I need to add a benchmark and run a perf for this kind of
change?
---
 lib/maple_tree.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index d8f10773e451..911c5e04e634 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -3134,10 +3134,7 @@ static inline void mast_fill_bnode(struct maple_subtree_state *mast,
 	bool cp = true;
 	unsigned char split;
 
-	memset(mast->bn->gap, 0, sizeof(unsigned long) * ARRAY_SIZE(mast->bn->gap));
-	memset(mast->bn->slot, 0, sizeof(unsigned long) * ARRAY_SIZE(mast->bn->slot));
-	memset(mast->bn->pivot, 0, sizeof(unsigned long) * ARRAY_SIZE(mast->bn->pivot));
-	mast->bn->b_end = 0;
+	memset(mast->bn, 0, sizeof(struct maple_big_node));
 
 	if (mte_is_root(mas->node)) {
 		cp = false;
-- 
2.34.1