[PATCH v2 2/2] maple_tree: memset maple_big_node as a whole

[Wei Yang]

In function mast_fill_bnode(), we first clear some fields of
maple_big_node and set the 'type' unconditionally before return. This
means we won't leverage any information in maple_big_node and it is safe
to clear the whole structure.

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 than 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 may clear some space by twice. And
this could be avoid by clearing the structure as a whole.

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

---
v2: correct the change log on clearing all maple_big_node currently
---
 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 c3370c7449c2..b459fe1a3ebe 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