From 5059aa6334fcf4b7ddd672255aec5835aecd32b6 Mon Sep 17 00:00:00 2001 From: Wei Yang Date: Sun, 8 Sep 2024 14:05:54 +0000 Subject: [PATCH] maple_tree: memset maple_big_node as a whole 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@gmail.com Signed-off-by: Wei Yang Reviewed-by: Liam R. Howlett Signed-off-by: Andrew Morton --- 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 04cd5ce2a33ce..c5987244ff636 100644 --- a/lib/maple_tree.c +++ b/lib/maple_tree.c @@ -3157,10 +3157,7 @@ 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; -- 2.39.5