f2fs: add lazytime mount option

This patch adds lazytime support.
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/super.c

@@ -93,6 +93,8 @@ enum {
 	Opt_noinline_data,
 	Opt_data_flush,
 	Opt_fault_injection,
+	Opt_lazytime,
+	Opt_nolazytime,
 	Opt_err,
 };
 
@@ -119,6 +121,8 @@ static match_table_t f2fs_tokens = {
 	{Opt_noinline_data, "noinline_data"},
 	{Opt_data_flush, "data_flush"},
 	{Opt_fault_injection, "fault_injection=%u"},
+	{Opt_lazytime, "lazytime"},
+	{Opt_nolazytime, "nolazytime"},
 	{Opt_err, NULL},
 };
 
@@ -506,6 +510,12 @@ static int parse_options(struct super_block *sb, char *options)
 				"FAULT_INJECTION was not selected");
 #endif
 			break;
+		case Opt_lazytime:
+			sb->s_flags |= MS_LAZYTIME;
+			break;
+		case Opt_nolazytime:
+			sb->s_flags &= ~MS_LAZYTIME;
+			break;
 		default:
 			f2fs_msg(sb, KERN_ERR,
 				"Unrecognized mount option \"%s\" or missing value",
@@ -613,6 +623,9 @@ static void f2fs_dirty_inode(struct inode *inode, int flags)
 			inode->i_ino == F2FS_META_INO(sbi))
 		return;
 
+	if (flags == I_DIRTY_TIME)
+		return;
+
 	if (is_inode_flag_set(inode, FI_AUTO_RECOVER))
 		clear_inode_flag(inode, FI_AUTO_RECOVER);
 
@@ -932,6 +945,7 @@ static void default_options(struct f2fs_sb_info *sbi)
 	set_opt(sbi, BG_GC);
 	set_opt(sbi, INLINE_DATA);
 	set_opt(sbi, EXTENT_CACHE);
+	sbi->sb->s_flags |= MS_LAZYTIME;
 
 #ifdef CONFIG_F2FS_FS_XATTR
 	set_opt(sbi, XATTR_USER);