resource: Reuse for_each_resource() macro

We have a few places where for_each_resource() is open coded.
Replace that by the macro. This makes code easier to read and
understand.

With this, compile r_next() only for CONFIG_PROC_FS=y.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20230912165312.402422-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: andy-shev

kernel/resource.c

@@ -77,28 +77,33 @@ static struct resource *next_resource_skip_children(struct resource *p)
 	     (_p) = (_skip_children) ? next_resource_skip_children(_p) : \
 				       next_resource(_p))
 
-static void *r_next(struct seq_file *m, void *v, loff_t *pos)
-{
-	struct resource *p = v;
-	(*pos)++;
-	return (void *)next_resource(p);
-}
-
 #ifdef CONFIG_PROC_FS
 
 enum { MAX_IORES_LEVEL = 5 };
 
 static void *r_start(struct seq_file *m, loff_t *pos)
 	__acquires(resource_lock)
 {
-	struct resource *p = pde_data(file_inode(m->file));
-	loff_t l = 0;
+	struct resource *root = pde_data(file_inode(m->file));
+	struct resource *p;
+	loff_t l = *pos;
+
 	read_lock(&resource_lock);
-	for (p = p->child; p && l < *pos; p = r_next(m, p, &l))
-		;
+	for_each_resource(root, p, false) {
+		if (l-- == 0)
+			break;
+	}
+
 	return p;
 }
 
+static void *r_next(struct seq_file *m, void *v, loff_t *pos)
+{
+	struct resource *p = v;
+	(*pos)++;
+	return (void *)next_resource(p);
+}
+
 static void r_stop(struct seq_file *m, void *v)
 	__releases(resource_lock)
 {
@@ -336,7 +341,7 @@ static int find_next_iomem_res(resource_size_t start, resource_size_t end,
 
 	read_lock(&resource_lock);
 
-	for (p = iomem_resource.child; p; p = next_resource(p)) {
+	for_each_resource(&iomem_resource, p, false) {
 		/* If we passed the resource we are looking for, stop */
 		if (p->start > end) {
 			p = NULL;
@@ -1641,13 +1646,12 @@ __setup("reserve=", reserve_setup);
  */
 int iomem_map_sanity_check(resource_size_t addr, unsigned long size)
 {
-	struct resource *p = &iomem_resource;
 	resource_size_t end = addr + size - 1;
+	struct resource *p;
 	int err = 0;
-	loff_t l;
 
 	read_lock(&resource_lock);
-	for (p = p->child; p ; p = r_next(NULL, p, &l)) {
+	for_each_resource(&iomem_resource, p, false) {
 		/*
 		 * We can probably skip the resources without
 		 * IORESOURCE_IO attribute?