f2fs: introduce new option for controlling data flush

Add a new option 'data_flush' to enable data flush functionality.
Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

Documentation/filesystems/f2fs.txt

@@ -149,6 +149,8 @@ noextent_cache         Disable an extent cache based on rb-tree explicitly, see
                        the above extent_cache mount option.
 noinline_data          Disable the inline data feature, inline data feature is
                        enabled by default.
+data_flush             Enable data flushing before checkpoint in order to
+                       persist data of regular and symlink.
 
 ================================================================================
 DEBUGFS ENTRIES

fs/f2fs/f2fs.h

@@ -54,6 +54,7 @@
 #define F2FS_MOUNT_FASTBOOT		0x00001000
 #define F2FS_MOUNT_EXTENT_CACHE		0x00002000
 #define F2FS_MOUNT_FORCE_FG_GC		0x00004000
+#define F2FS_MOUNT_DATA_FLUSH		0x00008000
 
 #define clear_opt(sbi, option)	(sbi->mount_opt.opt &= ~F2FS_MOUNT_##option)
 #define set_opt(sbi, option)	(sbi->mount_opt.opt |= F2FS_MOUNT_##option)

fs/f2fs/super.c

@@ -67,6 +67,7 @@ enum {
 	Opt_extent_cache,
 	Opt_noextent_cache,
 	Opt_noinline_data,
+	Opt_data_flush,
 	Opt_err,
 };
 
@@ -91,6 +92,7 @@ static match_table_t f2fs_tokens = {
 	{Opt_extent_cache, "extent_cache"},
 	{Opt_noextent_cache, "noextent_cache"},
 	{Opt_noinline_data, "noinline_data"},
+	{Opt_data_flush, "data_flush"},
 	{Opt_err, NULL},
 };
 
@@ -406,6 +408,9 @@ static int parse_options(struct super_block *sb, char *options)
 		case Opt_noinline_data:
 			clear_opt(sbi, INLINE_DATA);
 			break;
+		case Opt_data_flush:
+			set_opt(sbi, DATA_FLUSH);
+			break;
 		default:
 			f2fs_msg(sb, KERN_ERR,
 				"Unrecognized mount option \"%s\" or missing value",
@@ -687,6 +692,8 @@ static int f2fs_show_options(struct seq_file *seq, struct dentry *root)
 		seq_puts(seq, ",extent_cache");
 	else
 		seq_puts(seq, ",noextent_cache");
+	if (test_opt(sbi, DATA_FLUSH))
+		seq_puts(seq, ",data_flush");
 	seq_printf(seq, ",active_logs=%u", sbi->active_logs);
 
 	return 0;