drivers/base/node.c: use bin_attribute to break the size limitation of cpumap ABI

Reading /sys/devices/system/cpu/cpuX/nodeX/ returns cpumap and cpulist.
However, the size of this file is limited to PAGE_SIZE because of the
limitation for sysfs attribute.

This patch moves to use bin_attribute to extend the ABI to be more
than one page so that cpumap bitmask and list won't be potentially
trimmed.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Tian Tao <tiantao6@hisilicon.com>
Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>
Link: https://lore.kernel.org/r/20210806110251.560-5-song.bao.hua@hisilicon.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/node.c

@@ -26,43 +26,47 @@ static struct bus_type node_subsys = {
 	.dev_name = "node",
 };
 
-
-static ssize_t node_read_cpumap(struct device *dev, bool list, char *buf)
+static inline ssize_t cpumap_read(struct file *file, struct kobject *kobj,
+				  struct bin_attribute *attr, char *buf,
+				  loff_t off, size_t count)
 {
-	ssize_t n;
-	cpumask_var_t mask;
+	struct device *dev = kobj_to_dev(kobj);
 	struct node *node_dev = to_node(dev);
-
-	/* 2008/04/07: buf currently PAGE_SIZE, need 9 chars per 32 bits. */
-	BUILD_BUG_ON((NR_CPUS/32 * 9) > (PAGE_SIZE-1));
+	cpumask_var_t mask;
+	ssize_t n;
 
 	if (!alloc_cpumask_var(&mask, GFP_KERNEL))
 		return 0;
 
 	cpumask_and(mask, cpumask_of_node(node_dev->dev.id), cpu_online_mask);
-	n = cpumap_print_to_pagebuf(list, buf, mask);
+	n = cpumap_print_bitmask_to_buf(buf, mask, off, count);
 	free_cpumask_var(mask);
 
 	return n;
 }
 
-static inline ssize_t cpumap_show(struct device *dev,
-				  struct device_attribute *attr,
-				  char *buf)
+static BIN_ATTR_RO(cpumap, 0);
+
+static inline ssize_t cpulist_read(struct file *file, struct kobject *kobj,
+				   struct bin_attribute *attr, char *buf,
+				   loff_t off, size_t count)
 {
-	return node_read_cpumap(dev, false, buf);
+	struct device *dev = kobj_to_dev(kobj);
+	struct node *node_dev = to_node(dev);
+	cpumask_var_t mask;
+	ssize_t n;
+
+	if (!alloc_cpumask_var(&mask, GFP_KERNEL))
+		return 0;
+
+	cpumask_and(mask, cpumask_of_node(node_dev->dev.id), cpu_online_mask);
+	n = cpumap_print_list_to_buf(buf, mask, off, count);
+	free_cpumask_var(mask);
+
+	return n;
 }
 
-static DEVICE_ATTR_RO(cpumap);
-
-static inline ssize_t cpulist_show(struct device *dev,
-				   struct device_attribute *attr,
-				   char *buf)
-{
-	return node_read_cpumap(dev, true, buf);
-}
-
-static DEVICE_ATTR_RO(cpulist);
+static BIN_ATTR_RO(cpulist, 0);
 
 /**
  * struct node_access_nodes - Access class device to hold user visible
@@ -557,15 +561,28 @@ static ssize_t node_read_distance(struct device *dev,
 static DEVICE_ATTR(distance, 0444, node_read_distance, NULL);
 
 static struct attribute *node_dev_attrs[] = {
-	&dev_attr_cpumap.attr,
-	&dev_attr_cpulist.attr,
 	&dev_attr_meminfo.attr,
 	&dev_attr_numastat.attr,
 	&dev_attr_distance.attr,
 	&dev_attr_vmstat.attr,
 	NULL
 };
-ATTRIBUTE_GROUPS(node_dev);
+
+static struct bin_attribute *node_dev_bin_attrs[] = {
+	&bin_attr_cpumap,
+	&bin_attr_cpulist,
+	NULL
+};
+
+static const struct attribute_group node_dev_group = {
+	.attrs = node_dev_attrs,
+	.bin_attrs = node_dev_bin_attrs
+};
+
+static const struct attribute_group *node_dev_groups[] = {
+	&node_dev_group,
+	NULL
+};
 
 #ifdef CONFIG_HUGETLBFS
 /*