lib/interval_tree: add test case for interval_tree_iter_xxx() helpers

Verify interval_tree_iter_xxx() helpers could find intersection ranges
as expected.

[sfr@canb.auug.org.au: some of tools/ uses -Wno-unused-parameter]
  Link: https://lkml.kernel.org/r/20250312113612.31ac808e@canb.auug.org.au
Link: https://lkml.kernel.org/r/20250310074938.26756-5-richard.weiyang@gmail.com
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michel Lespinasse <michel@lespinasse.org>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

lib/interval_tree_test.c

@@ -5,6 +5,7 @@
 #include <linux/prandom.h>
 #include <linux/slab.h>
 #include <asm/timex.h>
+#include <linux/bitmap.h>
 
 #define __param(type, name, init, msg)		\
 	static type name = init;		\
@@ -125,6 +126,73 @@ static int search_check(void)
 	return 0;
 }
 
+static int intersection_range_check(void)
+{
+	int i, j, k;
+	unsigned long start, last;
+	struct interval_tree_node *node;
+	unsigned long *intxn1;
+	unsigned long *intxn2;
+
+	printk(KERN_ALERT "interval tree iteration\n");
+
+	intxn1 = bitmap_alloc(nnodes, GFP_KERNEL);
+	if (!intxn1) {
+		WARN_ON_ONCE("Failed to allocate intxn1\n");
+		return -ENOMEM;
+	}
+
+	intxn2 = bitmap_alloc(nnodes, GFP_KERNEL);
+	if (!intxn2) {
+		WARN_ON_ONCE("Failed to allocate intxn2\n");
+		bitmap_free(intxn1);
+		return -ENOMEM;
+	}
+
+	for (i = 0; i < search_loops; i++) {
+		/* Initialize interval tree for each round */
+		init();
+		for (j = 0; j < nnodes; j++)
+			interval_tree_insert(nodes + j, &root);
+
+		/* Let's try nsearches different ranges */
+		for (k = 0; k < nsearches; k++) {
+			/* Try whole range once */
+			if (!k) {
+				start = 0UL;
+				last = ULONG_MAX;
+			} else {
+				last = (prandom_u32_state(&rnd) >> 4) % max_endpoint;
+				start = (prandom_u32_state(&rnd) >> 4) % last;
+			}
+
+			/* Walk nodes to mark intersection nodes */
+			bitmap_zero(intxn1, nnodes);
+			for (j = 0; j < nnodes; j++) {
+				node = nodes + j;
+
+				if (start <= node->last && last >= node->start)
+					bitmap_set(intxn1, j, 1);
+			}
+
+			/* Iterate tree to clear intersection nodes */
+			bitmap_zero(intxn2, nnodes);
+			for (node = interval_tree_iter_first(&root, start, last); node;
+			     node = interval_tree_iter_next(node, start, last))
+				bitmap_set(intxn2, node - nodes, 1);
+
+			WARN_ON_ONCE(!bitmap_equal(intxn1, intxn2, nnodes));
+		}
+
+		for (j = 0; j < nnodes; j++)
+			interval_tree_remove(nodes + j, &root);
+	}
+
+	bitmap_free(intxn1);
+	bitmap_free(intxn2);
+	return 0;
+}
+
 static int interval_tree_test_init(void)
 {
 	nodes = kmalloc_array(nnodes, sizeof(struct interval_tree_node),
@@ -142,6 +210,7 @@ static int interval_tree_test_init(void)
 
 	basic_check();
 	search_check();
+	intersection_range_check();
 
 	kfree(queries);
 	kfree(nodes);

tools/include/linux/bitmap.h

@@ -19,6 +19,7 @@ bool __bitmap_and(unsigned long *dst, const unsigned long *bitmap1,
 		 const unsigned long *bitmap2, unsigned int bits);
 bool __bitmap_equal(const unsigned long *bitmap1,
 		    const unsigned long *bitmap2, unsigned int bits);
+void __bitmap_set(unsigned long *map, unsigned int start, int len);
 void __bitmap_clear(unsigned long *map, unsigned int start, int len);
 bool __bitmap_intersects(const unsigned long *bitmap1,
 			 const unsigned long *bitmap2, unsigned int bits);
@@ -79,6 +80,11 @@ static inline void bitmap_or(unsigned long *dst, const unsigned long *src1,
 		__bitmap_or(dst, src1, src2, nbits);
 }
 
+static inline unsigned long *bitmap_alloc(unsigned int nbits, gfp_t flags __maybe_unused)
+{
+	return malloc(bitmap_size(nbits));
+}
+
 /**
  * bitmap_zalloc - Allocate bitmap
  * @nbits: Number of bits
@@ -150,6 +156,21 @@ static inline bool bitmap_intersects(const unsigned long *src1,
 		return __bitmap_intersects(src1, src2, nbits);
 }
 
+static inline void bitmap_set(unsigned long *map, unsigned int start, unsigned int nbits)
+{
+	if (__builtin_constant_p(nbits) && nbits == 1)
+		__set_bit(start, map);
+	else if (small_const_nbits(start + nbits))
+		*map |= GENMASK(start + nbits - 1, start);
+	else if (__builtin_constant_p(start & BITMAP_MEM_MASK) &&
+		 IS_ALIGNED(start, BITMAP_MEM_ALIGNMENT) &&
+		 __builtin_constant_p(nbits & BITMAP_MEM_MASK) &&
+		 IS_ALIGNED(nbits, BITMAP_MEM_ALIGNMENT))
+		memset((char *)map + start / 8, 0xff, nbits / 8);
+	else
+		__bitmap_set(map, start, nbits);
+}
+
 static inline void bitmap_clear(unsigned long *map, unsigned int start,
 			       unsigned int nbits)
 {

tools/lib/bitmap.c

@@ -101,6 +101,26 @@ bool __bitmap_intersects(const unsigned long *bitmap1,
 	return false;
 }
 
+void __bitmap_set(unsigned long *map, unsigned int start, int len)
+{
+	unsigned long *p = map + BIT_WORD(start);
+	const unsigned int size = start + len;
+	int bits_to_set = BITS_PER_LONG - (start % BITS_PER_LONG);
+	unsigned long mask_to_set = BITMAP_FIRST_WORD_MASK(start);
+
+	while (len - bits_to_set >= 0) {
+		*p |= mask_to_set;
+		len -= bits_to_set;
+		bits_to_set = BITS_PER_LONG;
+		mask_to_set = ~0UL;
+		p++;
+	}
+	if (len) {
+		mask_to_set &= BITMAP_LAST_WORD_MASK(size);
+		*p |= mask_to_set;
+	}
+}
+
 void __bitmap_clear(unsigned long *map, unsigned int start, int len)
 {
 	unsigned long *p = map + BIT_WORD(start);