[PATCH v4 25/35] maple_tree: Revise limit checks in mas_empty_area{_rev}()

["Liam R. Howlett" <Liam.Howlett@oracle.com>]

Since the maple tree is inclusive in range, ensure that a range of 1
(min = max) works for searching for a gap in either direction, and make
sure the size is at least 1 but not larger than the delta between min
and max.

This commit also updates the testing.  Unfortunately there isn't a way
to safely update the tests and code without a test failure.

Suggested-by: Peng Zhang <zhangpeng.00@bytedance.com>
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
---
 lib/maple_tree.c      | 20 +++++++++++++-------
 lib/test_maple_tree.c | 28 +++++++++++++++++++++-------
 2 files changed, 34 insertions(+), 14 deletions(-)

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index 425ad922bb2d..580310741d89 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -5282,7 +5282,10 @@ int mas_empty_area(struct ma_state *mas, unsigned long min,
 	unsigned long *pivots;
 	enum maple_type mt;
 
-	if (min >= max)
+	if (min > max)
+		return -EINVAL;
+
+	if (size == 0 || max - min < size - 1)
 		return -EINVAL;
 
 	if (mas_is_start(mas))
@@ -5337,7 +5340,10 @@ int mas_empty_area_rev(struct ma_state *mas, unsigned long min,
 {
 	struct maple_enode *last = mas->node;
 
-	if (min >= max)
+	if (min > max)
+		return -EINVAL;
+
+	if (size == 0 || max - min < size - 1)
 		return -EINVAL;
 
 	if (mas_is_start(mas)) {
@@ -5373,7 +5379,7 @@ int mas_empty_area_rev(struct ma_state *mas, unsigned long min,
 		return -EBUSY;
 
 	/* Trim the upper limit to the max. */
-	if (max <= mas->last)
+	if (max < mas->last)
 		mas->last = max;
 
 	mas->index = mas->last - size + 1;
@@ -6409,7 +6415,7 @@ 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;
 
@@ -6429,7 +6435,7 @@ 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;
@@ -6445,14 +6451,14 @@ 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)
diff --git a/lib/test_maple_tree.c b/lib/test_maple_tree.c
index 19b130c9ddde..f167d6ef8159 100644
--- a/lib/test_maple_tree.c
+++ b/lib/test_maple_tree.c
@@ -123,7 +123,7 @@ static noinline void __init check_mtree_alloc_rrange(struct maple_tree *mt,
 	unsigned long result = expected + 1;
 	int ret;
 
-	ret = mtree_alloc_rrange(mt, &result, ptr, size, start, end - 1,
+	ret = mtree_alloc_rrange(mt, &result, ptr, size, start, end,
 			GFP_KERNEL);
 	MT_BUG_ON(mt, ret != eret);
 	if (ret)
@@ -701,7 +701,7 @@ static noinline void __init check_alloc_rev_range(struct maple_tree *mt)
 		0,              /* Return value success. */
 
 		0x0,            /* Min */
-		0x565234AF1 << 12,    /* Max */
+		0x565234AF0 << 12,    /* Max */
 		0x3000,         /* Size */
 		0x565234AEE << 12,  /* max - 3. */
 		0,              /* Return value success. */
@@ -713,14 +713,14 @@ static noinline void __init check_alloc_rev_range(struct maple_tree *mt)
 		0,              /* Return value success. */
 
 		0x0,            /* Min */
-		0x7F36D510A << 12,    /* Max */
+		0x7F36D5109 << 12,    /* Max */
 		0x4000,         /* Size */
 		0x7F36D5106 << 12,    /* First rev hole of size 0x4000 */
 		0,              /* Return value success. */
 
 		/* Ascend test. */
 		0x0,
-		34148798629 << 12,
+		34148798628 << 12,
 		19 << 12,
 		34148797418 << 12,
 		0x0,
@@ -732,6 +732,12 @@ static noinline void __init check_alloc_rev_range(struct maple_tree *mt)
 		0x0,
 		-EBUSY,
 
+		/* Single space test. */
+		34148798725 << 12,
+		34148798725 << 12,
+		1 << 12,
+		34148798725 << 12,
+		0,
 	};
 
 	int i, range_count = ARRAY_SIZE(range);
@@ -780,9 +786,9 @@ static noinline void __init check_alloc_rev_range(struct maple_tree *mt)
 	mas_unlock(&mas);
 	for (i = 0; i < req_range_count; i += 5) {
 #if DEBUG_REV_RANGE
-		pr_debug("\tReverse request between %lu-%lu size %lu, should get %lu\n",
-				req_range[i] >> 12,
-				(req_range[i + 1] >> 12) - 1,
+		pr_debug("\tReverse request %d between %lu-%lu size %lu, should get %lu\n",
+				i, req_range[i] >> 12,
+				(req_range[i + 1] >> 12),
 				req_range[i+2] >> 12,
 				req_range[i+3] >> 12);
 #endif
@@ -798,6 +804,7 @@ static noinline void __init check_alloc_rev_range(struct maple_tree *mt)
 
 	mt_set_non_kernel(1);
 	mtree_erase(mt, 34148798727); /* create a deleted range. */
+	mtree_erase(mt, 34148798725);
 	check_mtree_alloc_rrange(mt, 0, 34359052173, 210253414,
 			34148798725, 0, mt);
 
@@ -901,6 +908,13 @@ static noinline void __init check_alloc_range(struct maple_tree *mt)
 		4503599618982063UL << 12,  /* Size */
 		34359052178 << 12,  /* Expected location */
 		-EBUSY,             /* Return failure. */
+
+		/* Test a single entry */
+		34148798648 << 12,		/* Min */
+		34148798648 << 12,		/* Max */
+		4096,			/* Size of 1 */
+		34148798648 << 12,	/* Location is the same as min/max */
+		0,			/* Success */
 	};
 	int i, range_count = ARRAY_SIZE(range);
 	int req_range_count = ARRAY_SIZE(req_range);
-- 
2.39.2