maple_tree: don't use MAPLE_ARANGE64_META_MAX to indicate no gap

Patch series "Improve the validation for maple tree and some cleanup", v2.


This patch (of 7):

Do not use a special offset to indicate that there is no gap.  When there
is no gap, offset can point to any valid slots because its gap is 0.

Link: https://lkml.kernel.org/r/20230711035444.526-1-zhangpeng.00@bytedance.com
Link: https://lkml.kernel.org/r/20230711035444.526-3-zhangpeng.00@bytedance.com
Signed-off-by: Peng Zhang <zhangpeng.00@bytedance.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/maple_tree.h

@@ -29,14 +29,12 @@
 #define MAPLE_NODE_SLOTS	31	/* 256 bytes including ->parent */
 #define MAPLE_RANGE64_SLOTS	16	/* 256 bytes */
 #define MAPLE_ARANGE64_SLOTS	10	/* 240 bytes */
-#define MAPLE_ARANGE64_META_MAX	15	/* Out of range for metadata */
 #define MAPLE_ALLOC_SLOTS	(MAPLE_NODE_SLOTS - 1)
 #else
 /* 32bit sizes */
 #define MAPLE_NODE_SLOTS	63	/* 256 bytes including ->parent */
 #define MAPLE_RANGE64_SLOTS	32	/* 256 bytes */
 #define MAPLE_ARANGE64_SLOTS	21	/* 240 bytes */
-#define MAPLE_ARANGE64_META_MAX	31	/* Out of range for metadata */
 #define MAPLE_ALLOC_SLOTS	(MAPLE_NODE_SLOTS - 2)
 #endif /* defined(CONFIG_64BIT) || defined(BUILD_VDSO32_64) */
 

lib/maple_tree.c

@@ -1610,8 +1610,6 @@ ma_max_gap(struct maple_node *node, unsigned long *gaps, enum maple_type mt,
  * mas_max_gap() - find the largest gap in a non-leaf node and set the slot.
  * @mas: The maple state.
  *
- * If the metadata gap is set to MAPLE_ARANGE64_META_MAX, there is no gap.
- *
  * Return: The gap value.
  */
 static inline unsigned long mas_max_gap(struct ma_state *mas)
@@ -1628,9 +1626,6 @@ static inline unsigned long mas_max_gap(struct ma_state *mas)
 	node = mas_mn(mas);
 	MAS_BUG_ON(mas, mt != maple_arange_64);
 	offset = ma_meta_gap(node, mt);
-	if (offset == MAPLE_ARANGE64_META_MAX)
-		return 0;
-
 	gaps = ma_gaps(node, mt);
 	return gaps[offset];
 }
@@ -1662,10 +1657,7 @@ static inline void mas_parent_gap(struct ma_state *mas, unsigned char offset,
 ascend:
 	MAS_BUG_ON(mas, pmt != maple_arange_64);
 	meta_offset = ma_meta_gap(pnode, pmt);
-	if (meta_offset == MAPLE_ARANGE64_META_MAX)
-		meta_gap = 0;
-	else
-		meta_gap = pgaps[meta_offset];
+	meta_gap = pgaps[meta_offset];
 
 	pgaps[offset] = new;
 
@@ -1678,7 +1670,6 @@ static inline void mas_parent_gap(struct ma_state *mas, unsigned char offset,
 
 		ma_set_meta_gap(pnode, pmt, offset);
 	} else if (new < meta_gap) {
-		meta_offset = 15;
 		new = ma_max_gap(pnode, pgaps, pmt, &meta_offset);
 		ma_set_meta_gap(pnode, pmt, meta_offset);
 	}
@@ -2076,7 +2067,7 @@ static inline void mab_mas_cp(struct maple_big_node *b_node,
 	end = j - 1;
 	if (likely(!ma_is_leaf(mt) && mt_is_alloc(mas->tree))) {
 		unsigned long max_gap = 0;
-		unsigned char offset = 15;
+		unsigned char offset = 0;
 
 		gaps = ma_gaps(node, mt);
 		do {