btrfs: use BTRFS_ATTR instead of btrfs_no_store()

we have BTRFS_ATTR define to create sysfs RO file, use that.
Signed-off-by: NAnand Jain <anand.jain@oracle.com>
Signed-off-by: NChris Mason <clm@fb.com>

fs/btrfs/sysfs.c

@@ -403,13 +403,6 @@ static ssize_t btrfs_label_store(struct kobject *kobj,
 }
 BTRFS_ATTR_RW(label, 0644, btrfs_label_show, btrfs_label_store);
 
-static ssize_t btrfs_no_store(struct kobject *kobj,
-				 struct kobj_attribute *a,
-				 const char *buf, size_t len)
-{
-	return -EPERM;
-}
-
 static ssize_t btrfs_nodesize_show(struct kobject *kobj,
 				struct kobj_attribute *a, char *buf)
 {
@@ -418,7 +411,7 @@ static ssize_t btrfs_nodesize_show(struct kobject *kobj,
 	return snprintf(buf, PAGE_SIZE, "%u\n", fs_info->super_copy->nodesize);
 }
 
-BTRFS_ATTR_RW(nodesize, 0444, btrfs_nodesize_show, btrfs_no_store);
+BTRFS_ATTR(nodesize, 0444, btrfs_nodesize_show);
 
 static ssize_t btrfs_sectorsize_show(struct kobject *kobj,
 				struct kobj_attribute *a, char *buf)
@@ -428,7 +421,7 @@ static ssize_t btrfs_sectorsize_show(struct kobject *kobj,
 	return snprintf(buf, PAGE_SIZE, "%u\n", fs_info->super_copy->sectorsize);
 }
 
-BTRFS_ATTR_RW(sectorsize, 0444, btrfs_sectorsize_show, btrfs_no_store);
+BTRFS_ATTR(sectorsize, 0444, btrfs_sectorsize_show);
 
 static ssize_t btrfs_clone_alignment_show(struct kobject *kobj,
 				struct kobj_attribute *a, char *buf)
@@ -438,7 +431,7 @@ static ssize_t btrfs_clone_alignment_show(struct kobject *kobj,
 	return snprintf(buf, PAGE_SIZE, "%u\n", fs_info->super_copy->sectorsize);
 }
 
-BTRFS_ATTR_RW(clone_alignment, 0444, btrfs_clone_alignment_show, btrfs_no_store);
+BTRFS_ATTR(clone_alignment, 0444, btrfs_clone_alignment_show);
 
 static struct attribute *btrfs_attrs[] = {
 	BTRFS_ATTR_PTR(label),