ANDROID: memblock: take a region intersecting an unknown region

There is case where reserved regions overlapped with already checked as
unknown regions. To get more information of the name, size, so far we
allowed only regions which are exactly matching with or located within
the unknown region.

For a region intersecting an unknown region, we did not take and just
showed that duplicated information. So total size was not perfect. To
fix this, let's allow to take even the intersecting region.

Bug: 340432773
Signed-off-by: Jaewon Kim <jaewon31.kim@samsung.com>
Link: https://lore.kernel.org/linux-mm/20240521023957.2587005-5-jaewon31.kim@samsung.com/
Change-Id: I3ab0bdcea5e9122f59b87e13afafc2c9b9606295

mm/memblock.c

@@ -2090,20 +2090,54 @@ static bool __init_memblock memsize_update_nomap_region(const char *name, phys_a
 	for (i = 0; i < memsize_rgn_count; i++)	{
 		rmem_rgn = &memsize_rgn[i];
 
+		/* skip either !nomap, !unknown, !overlap */
 		if (!rmem_rgn->nomap)
 			continue;
 		if (strcmp(rmem_rgn->name, "unknown"))
 			continue;
-		if (base < rmem_rgn->base)
+		if (base + size <= rmem_rgn->base)
 			continue;
-		if (base + size > rmem_rgn->base + rmem_rgn->size)
+		if (base >= rmem_rgn->base + rmem_rgn->size)
 			continue;
 
+		/* exactly same */
 		if (base == rmem_rgn->base && size == rmem_rgn->size) {
 			memsize_get_valid_name(rmem_rgn->name, name);
 			return true;
 		}
 
+		/* bigger */
+		if (base <= rmem_rgn->base &&
+				base + size >= rmem_rgn->base + rmem_rgn->size) {
+			memsize_get_valid_name(rmem_rgn->name, name);
+			rmem_rgn->base = base;
+			rmem_rgn->size = size;
+			return true;
+		}
+
+		/* intersect */
+		if (base < rmem_rgn->base ||
+				base + size > rmem_rgn->base + rmem_rgn->size) {
+			new_rgn = memsize_get_new_rgn();
+			if (!new_rgn)
+				return true;
+			new_rgn->base = base;
+			new_rgn->size = size;
+			new_rgn->nomap = nomap;
+			new_rgn->reusable = false;
+			memsize_get_valid_name(new_rgn->name, name);
+
+			if (base < rmem_rgn->base) {
+				rmem_rgn->size -= base + size - rmem_rgn->base;
+				rmem_rgn->base = base + size;
+			} else {
+				rmem_rgn->size -= rmem_rgn->base
+							+ rmem_rgn->size - base;
+			}
+			return true;
+		}
+
+		/* smaller */
 		new_rgn = memsize_get_new_rgn();
 		if (!new_rgn)
 			return true;