linux-kernel - [PATCH Fix] maple_tree: Use metadata for mas_dead

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Date:   Fri, 15 Jul 2022 19:43:08 +0000
From:   Liam Howlett <liam.howlett@...cle.com>
To:     "maple-tree@...ts.infradead.org" <maple-tree@...ts.infradead.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Yu Zhao <yuzhao@...gle.com>, Hugh Dickins <hughd@...gle.com>
Subject: [PATCH Fix] maple_tree: Use metadata for mas_dead_leaves() walk

When walking the dead leaves, use the nodes metadata for the end of the
node.  This avoids needing to use tricks for BE/LE unions.

Fixes: d0aac5e48048 (Maple Tree: add new data structure)
Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
 lib/maple_tree.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index 14e9ab14c1da..c661fda37665 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -5390,15 +5390,12 @@ unsigned char mas_dead_leaves(struct ma_state *mas, void __rcu **slots)
 	enum maple_type type;
 	void *entry;
 	int offset;
+	unsigned end = mas_data_end(mas);
 
-	for (offset = 0; offset < mt_slot_count(mas->node); offset++) {
+	for (offset = 0; offset <= end; offset++) {
 		entry = mas_slot_locked(mas, slots, offset);
 		type = mte_node_type(entry);
 		node = mte_to_node(entry);
-		/* Use both node and type to catch LE & BE metadata */
-		if (!node || !type)
-			break;
-
 		mte_set_node_dead(entry);
 		smp_wmb(); /* Needed for RCU */
 		node->type = type;
-- 
2.35.1