The patch titled
Subject: maple_tree: memset maple_big_node as a whole
has been added to the -mm mm-unstable branch. Its filename is
maple_tree-memset-maple_big_node-as-a-whole.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/maple_tree-memset-maple_big_node-as-a-whole.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Wei Yang <richard.weiyang@xxxxxxxxx>
Subject: maple_tree: memset maple_big_node as a whole
Date: Sun, 8 Sep 2024 14:05:54 +0000
In 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.
Link: https://lkml.kernel.org/r/20240908140554.20378-3-richard.weiyang@xxxxxxxxx
Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxx>
Reviewed-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/maple_tree.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)
--- a/lib/maple_tree.c~maple_tree-memset-maple_big_node-as-a-whole
+++ a/lib/maple_tree.c
@@ -3155,10 +3155,7 @@ static inline void mast_fill_bnode(struc
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;
_
Patches currently in -mm which might be from richard.weiyang@xxxxxxxxx are
maple_tree-i-is-always-less-than-or-equal-to-mas_end.patch
maple_tree-goto-complete-directly-on-a-pivot-of-0.patch
maple_tree-remove-maple_big_nodeparent.patch
maple_tree-memset-maple_big_node-as-a-whole.patch
