nilfs2: Switch to use %ptTs

Use %ptTs instead of open coded variant to print contents
of time64_t type in human readable form.

Use sysfs_emit() at the same time in the changed functions.

Cc: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Cc: linux-nilfs@vger.kernel.org
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210511153958.34527-3-andriy.shevchenko@linux.intel.com

fs/nilfs2/sysfs.c

@@ -19,19 +19,6 @@
 /* /sys/fs/<nilfs>/ */
 static struct kset *nilfs_kset;
 
-#define NILFS_SHOW_TIME(time_t_val, buf) ({ \
-		struct tm res; \
-		int count = 0; \
-		time64_to_tm(time_t_val, 0, &res); \
-		res.tm_year += 1900; \
-		res.tm_mon += 1; \
-		count = scnprintf(buf, PAGE_SIZE, \
-				    "%ld-%.2d-%.2d %.2d:%.2d:%.2d\n", \
-				    res.tm_year, res.tm_mon, res.tm_mday, \
-				    res.tm_hour, res.tm_min, res.tm_sec);\
-		count; \
-})
-
 #define NILFS_DEV_INT_GROUP_OPS(name, parent_name) \
 static ssize_t nilfs_##name##_attr_show(struct kobject *kobj, \
 					struct attribute *attr, char *buf) \
@@ -576,7 +563,7 @@ nilfs_segctor_last_seg_write_time_show(struct nilfs_segctor_attr *attr,
 	ctime = nilfs->ns_ctime;
 	up_read(&nilfs->ns_segctor_sem);
 
-	return NILFS_SHOW_TIME(ctime, buf);
+	return sysfs_emit(buf, "%ptTs\n", &ctime);
 }
 
 static ssize_t
@@ -604,7 +591,7 @@ nilfs_segctor_last_nongc_write_time_show(struct nilfs_segctor_attr *attr,
 	nongc_ctime = nilfs->ns_nongc_ctime;
 	up_read(&nilfs->ns_segctor_sem);
 
-	return NILFS_SHOW_TIME(nongc_ctime, buf);
+	return sysfs_emit(buf, "%ptTs\n", &nongc_ctime);
 }
 
 static ssize_t
@@ -724,7 +711,7 @@ nilfs_superblock_sb_write_time_show(struct nilfs_superblock_attr *attr,
 	sbwtime = nilfs->ns_sbwtime;
 	up_read(&nilfs->ns_sem);
 
-	return NILFS_SHOW_TIME(sbwtime, buf);
+	return sysfs_emit(buf, "%ptTs\n", &sbwtime);
 }
 
 static ssize_t