[PATCH v3 1/4] maple_tree: Make maple state reusable after mas_empty_area_rev()

["Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx>]

Stop using maple state min/max for the range by passing through pointers
for those values.  This will allow the maple state to be reused without
resetting.

Also add some logic to fail out early on searching with invalid
arguments.

This also fixes the currently unused mtree_alloc_range() and
mtree_alloc_rrange() functions validation of limits to work with a
window size of 1.

Fixes: 54a611b60590 ("Maple Tree: add new data structure")
Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
---
 lib/maple_tree.c | 41 +++++++++++++++++++++++------------------
 1 file changed, 23 insertions(+), 18 deletions(-)

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index 4df6a0ce1c1b6..cf4f6cdcaad38 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -4938,7 +4938,8 @@ static inline void *mas_prev_entry(struct ma_state *mas, unsigned long min)
  * Return: True if found in a leaf, false otherwise.
  *
  */
-static bool mas_rev_awalk(struct ma_state *mas, unsigned long size)
+static bool mas_rev_awalk(struct ma_state *mas, unsigned long size,
+		unsigned long *gap_min, unsigned long *gap_max)
 {
 	enum maple_type type = mte_node_type(mas->node);
 	struct maple_node *node = mas_mn(mas);
@@ -5003,8 +5004,8 @@ static bool mas_rev_awalk(struct ma_state *mas, unsigned long size)
 
 	if (unlikely(ma_is_leaf(type))) {
 		mas->offset = offset;
-		mas->min = min;
-		mas->max = min + gap - 1;
+		*gap_min = min;
+		*gap_max = min + gap - 1;
 		return true;
 	}
 
@@ -5280,6 +5281,12 @@ int mas_empty_area(struct ma_state *mas, unsigned long min,
 	unsigned long *pivots;
 	enum maple_type mt;
 
+	if (min > max)
+		return -EINVAL;
+
+	if (size == 0 || max - min < size - 1)
+		return -EINVAL;
+
 	if (mas_is_start(mas))
 		mas_start(mas);
 	else if (mas->offset >= 2)
@@ -5334,6 +5341,12 @@ int mas_empty_area_rev(struct ma_state *mas, unsigned long min,
 {
 	struct maple_enode *last = mas->node;
 
+	if (min > max)
+		return -EINVAL;
+
+	if (size == 0 || max - min < size - 1)
+		return -EINVAL;
+
 	if (mas_is_start(mas)) {
 		mas_start(mas);
 		mas->offset = mas_data_end(mas);
@@ -5353,7 +5366,7 @@ int mas_empty_area_rev(struct ma_state *mas, unsigned long min,
 	mas->index = min;
 	mas->last = max;
 
-	while (!mas_rev_awalk(mas, size)) {
+	while (!mas_rev_awalk(mas, size, &min, &max)) {
 		if (last == mas->node) {
 			if (!mas_rewind_node(mas))
 				return -EBUSY;
@@ -5368,17 +5381,9 @@ int mas_empty_area_rev(struct ma_state *mas, unsigned long min,
 	if (unlikely(mas->offset == MAPLE_NODE_SLOTS))
 		return -EBUSY;
 
-	/*
-	 * mas_rev_awalk() has set mas->min and mas->max to the gap values.  If
-	 * the maximum is outside the window we are searching, then use the last
-	 * location in the search.
-	 * mas->max and mas->min is the range of the gap.
-	 * mas->index and mas->last are currently set to the search range.
-	 */
-
 	/* Trim the upper limit to the max. */
-	if (mas->max <= mas->last)
-		mas->last = mas->max;
+	if (max < mas->last)
+		mas->last = max;
 
 	mas->index = mas->last - size + 1;
 	return 0;
@@ -6360,7 +6365,7 @@ int mtree_alloc_range(struct maple_tree *mt, unsigned long *startp,
 {
 	int ret = 0;
 
-	MA_STATE(mas, mt, min, max - size);
+	MA_STATE(mas, mt, min, min);
 	if (!mt_is_alloc(mt))
 		return -EINVAL;
 
@@ -6380,7 +6385,7 @@ int mtree_alloc_range(struct maple_tree *mt, unsigned long *startp,
 retry:
 	mas.offset = 0;
 	mas.index = min;
-	mas.last = max - size;
+	mas.last = max - size + 1;
 	ret = mas_alloc(&mas, entry, size, startp);
 	if (mas_nomem(&mas, gfp))
 		goto retry;
@@ -6396,14 +6401,14 @@ int mtree_alloc_rrange(struct maple_tree *mt, unsigned long *startp,
 {
 	int ret = 0;
 
-	MA_STATE(mas, mt, min, max - size);
+	MA_STATE(mas, mt, min, max - size + 1);
 	if (!mt_is_alloc(mt))
 		return -EINVAL;
 
 	if (WARN_ON_ONCE(mt_is_reserved(entry)))
 		return -EINVAL;
 
-	if (min >= max)
+	if (min > max)
 		return -EINVAL;
 
 	if (max < size - 1)
-- 
2.39.2