ext4: refactor out ext4_generic_attr_show()

Refactor out the function ext4_generic_attr_show() to handle the reading
of values of various common types, with no functional changes.

Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20240319113325.3110393-4-libaokun1@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Author: LiBaokun96

fs/ext4/sysfs.c

@@ -366,13 +366,42 @@ static ssize_t __print_tstamp(char *buf, __le32 lo, __u8 hi)
 #define print_tstamp(buf, es, tstamp) \
 	__print_tstamp(buf, (es)->tstamp, (es)->tstamp ## _hi)
 
+static ssize_t ext4_generic_attr_show(struct ext4_attr *a,
+				      struct ext4_sb_info *sbi, char *buf)
+{
+	void *ptr = calc_ptr(a, sbi);
+
+	if (!ptr)
+		return 0;
+
+	switch (a->attr_id) {
+	case attr_inode_readahead:
+	case attr_pointer_ui:
+		if (a->attr_ptr == ptr_ext4_super_block_offset)
+			return sysfs_emit(buf, "%u\n", le32_to_cpup(ptr));
+		return sysfs_emit(buf, "%u\n", *((unsigned int *) ptr));
+	case attr_pointer_ul:
+		return sysfs_emit(buf, "%lu\n", *((unsigned long *) ptr));
+	case attr_pointer_u8:
+		return sysfs_emit(buf, "%u\n", *((unsigned char *) ptr));
+	case attr_pointer_u64:
+		if (a->attr_ptr == ptr_ext4_super_block_offset)
+			return sysfs_emit(buf, "%llu\n", le64_to_cpup(ptr));
+		return sysfs_emit(buf, "%llu\n", *((unsigned long long *) ptr));
+	case attr_pointer_string:
+		return sysfs_emit(buf, "%.*s\n", a->attr_size, (char *) ptr);
+	case attr_pointer_atomic:
+		return sysfs_emit(buf, "%d\n", atomic_read((atomic_t *) ptr));
+	}
+	return 0;
+}
+
 static ssize_t ext4_attr_show(struct kobject *kobj,
 			      struct attribute *attr, char *buf)
 {
 	struct ext4_sb_info *sbi = container_of(kobj, struct ext4_sb_info,
 						s_kobj);
 	struct ext4_attr *a = container_of(attr, struct ext4_attr, attr);
-	void *ptr = calc_ptr(a, sbi);
 
 	switch (a->attr_id) {
 	case attr_delayed_allocation_blocks:
@@ -391,45 +420,6 @@ static ssize_t ext4_attr_show(struct kobject *kobj,
 		return sysfs_emit(buf, "%llu\n",
 				(unsigned long long)
 			percpu_counter_sum(&sbi->s_sra_exceeded_retry_limit));
-	case attr_inode_readahead:
-	case attr_pointer_ui:
-		if (!ptr)
-			return 0;
-		if (a->attr_ptr == ptr_ext4_super_block_offset)
-			return sysfs_emit(buf, "%u\n",
-					le32_to_cpup(ptr));
-		else
-			return sysfs_emit(buf, "%u\n",
-					*((unsigned int *) ptr));
-	case attr_pointer_ul:
-		if (!ptr)
-			return 0;
-		return sysfs_emit(buf, "%lu\n",
-				*((unsigned long *) ptr));
-	case attr_pointer_u8:
-		if (!ptr)
-			return 0;
-		return sysfs_emit(buf, "%u\n",
-				*((unsigned char *) ptr));
-	case attr_pointer_u64:
-		if (!ptr)
-			return 0;
-		if (a->attr_ptr == ptr_ext4_super_block_offset)
-			return sysfs_emit(buf, "%llu\n",
-					le64_to_cpup(ptr));
-		else
-			return sysfs_emit(buf, "%llu\n",
-					*((unsigned long long *) ptr));
-	case attr_pointer_string:
-		if (!ptr)
-			return 0;
-		return sysfs_emit(buf, "%.*s\n", a->attr_size,
-				(char *) ptr);
-	case attr_pointer_atomic:
-		if (!ptr)
-			return 0;
-		return sysfs_emit(buf, "%d\n",
-				atomic_read((atomic_t *) ptr));
 	case attr_feature:
 		return sysfs_emit(buf, "supported\n");
 	case attr_first_error_time:
@@ -438,9 +428,9 @@ static ssize_t ext4_attr_show(struct kobject *kobj,
 		return print_tstamp(buf, sbi->s_es, s_last_error_time);
 	case attr_journal_task:
 		return journal_task_show(sbi, buf);
+	default:
+		return ext4_generic_attr_show(a, sbi, buf);
 	}
-
-	return 0;
 }
 
 static ssize_t ext4_generic_attr_store(struct ext4_attr *a,