f2fs: checkpoint disabling

Note that, it requires "f2fs: return correct errno in f2fs_gc".

This adds a lightweight non-persistent snapshotting scheme to f2fs.

To use, mount with the option checkpoint=disable, and to return to
normal operation, remount with checkpoint=enable. If the filesystem
is shut down before remounting with checkpoint=enable, it will revert
back to its apparent state when it was first mounted with
checkpoint=disable. This is useful for situations where you wish to be
able to roll back the state of the disk in case of some critical
failure.

Signed-off-by: Daniel Rosenberg <drosen@google.com>
[Jaegeuk Kim: use SB_RDONLY instead of MS_RDONLY]
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

1 files changed, 123 insertions, 3 deletions

diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index a44913224e3b..19933d839008 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -136,6 +136,7 @@ enum {
 	Opt_alloc,
 	Opt_fsync,
 	Opt_test_dummy_encryption,
+	Opt_checkpoint,
 	Opt_err,
 };
 
@@ -194,6 +195,7 @@ static match_table_t f2fs_tokens = {
 	{Opt_alloc, "alloc_mode=%s"},
 	{Opt_fsync, "fsync_mode=%s"},
 	{Opt_test_dummy_encryption, "test_dummy_encryption"},
+	{Opt_checkpoint, "checkpoint=%s"},
 	{Opt_err, NULL},
 };
 
@@ -769,6 +771,23 @@ static int parse_options(struct super_block *sb, char *options)
 					"Test dummy encryption mount option ignored");
 #endif
 			break;
+		case Opt_checkpoint:
+			name = match_strdup(&args[0]);
+			if (!name)
+				return -ENOMEM;
+
+			if (strlen(name) == 6 &&
+					!strncmp(name, "enable", 6)) {
+				clear_opt(sbi, DISABLE_CHECKPOINT);
+			} else if (strlen(name) == 7 &&
+					!strncmp(name, "disable", 7)) {
+				set_opt(sbi, DISABLE_CHECKPOINT);
+			} else {
+				kfree(name);
+				return -EINVAL;
+			}
+			kfree(name);
+			break;
 		default:
 			f2fs_msg(sb, KERN_ERR,
 				"Unrecognized mount option \"%s\" or missing value",
@@ -827,6 +846,12 @@ static int parse_options(struct super_block *sb, char *options)
 		}
 	}
 
+	if (test_opt(sbi, DISABLE_CHECKPOINT) && test_opt(sbi, LFS)) {
+		f2fs_msg(sb, KERN_ERR,
+				"LFS not compatible with checkpoint=disable\n");
+		return -EINVAL;
+	}
+
 	/* Not pass down write hints if the number of active logs is lesser
 	 * than NR_CURSEG_TYPE.
 	 */
@@ -1014,8 +1039,8 @@ static void f2fs_put_super(struct super_block *sb)
 	 * But, the previous checkpoint was not done by umount, it needs to do
 	 * clean checkpoint again.
 	 */
-	if (is_sbi_flag_set(sbi, SBI_IS_DIRTY) ||
-			!is_set_ckpt_flags(sbi, CP_UMOUNT_FLAG)) {
+	if ((is_sbi_flag_set(sbi, SBI_IS_DIRTY) ||
+			!is_set_ckpt_flags(sbi, CP_UMOUNT_FLAG))) {
 		struct cp_control cpc = {
 			.reason = CP_UMOUNT,
 		};
@@ -1087,6 +1112,8 @@ int f2fs_sync_fs(struct super_block *sb, int sync)
 
 	if (unlikely(f2fs_cp_error(sbi)))
 		return 0;
+	if (unlikely(is_sbi_flag_set(sbi, SBI_CP_DISABLED)))
+		return 0;
 
 	trace_f2fs_sync_fs(sb, sync);
 
@@ -1186,6 +1213,11 @@ static int f2fs_statfs(struct dentry *dentry, struct kstatfs *buf)
 	buf->f_blocks = total_count - start_count;
 	buf->f_bfree = user_block_count - valid_user_blocks(sbi) -
 						sbi->current_reserved_blocks;
+	if (unlikely(buf->f_bfree <= sbi->unusable_block_count))
+		buf->f_bfree = 0;
+	else
+		buf->f_bfree -= sbi->unusable_block_count;
+
 	if (buf->f_bfree > F2FS_OPTION(sbi).root_reserved_blocks)
 		buf->f_bavail = buf->f_bfree -
 				F2FS_OPTION(sbi).root_reserved_blocks;
@@ -1365,6 +1397,9 @@ static int f2fs_show_options(struct seq_file *seq, struct dentry *root)
 	else if (F2FS_OPTION(sbi).alloc_mode == ALLOC_MODE_REUSE)
 		seq_printf(seq, ",alloc_mode=%s", "reuse");
 
+	if (test_opt(sbi, DISABLE_CHECKPOINT))
+		seq_puts(seq, ",checkpoint=disable");
+
 	if (F2FS_OPTION(sbi).fsync_mode == FSYNC_MODE_POSIX)
 		seq_printf(seq, ",fsync_mode=%s", "posix");
 	else if (F2FS_OPTION(sbi).fsync_mode == FSYNC_MODE_STRICT)
@@ -1392,6 +1427,7 @@ static void default_options(struct f2fs_sb_info *sbi)
 	set_opt(sbi, INLINE_DENTRY);
 	set_opt(sbi, EXTENT_CACHE);
 	set_opt(sbi, NOHEAP);
+	clear_opt(sbi, DISABLE_CHECKPOINT);
 	sbi->sb->s_flags |= SB_LAZYTIME;
 	set_opt(sbi, FLUSH_MERGE);
 	set_opt(sbi, DISCARD);
@@ -1413,6 +1449,57 @@ static void default_options(struct f2fs_sb_info *sbi)
 #ifdef CONFIG_QUOTA
 static int f2fs_enable_quotas(struct super_block *sb);
 #endif
+
+static int f2fs_disable_checkpoint(struct f2fs_sb_info *sbi)
+{
+	struct cp_control cpc;
+	int err;
+
+	sbi->sb->s_flags |= SB_ACTIVE;
+
+	mutex_lock(&sbi->gc_mutex);
+	f2fs_update_time(sbi, DISABLE_TIME);
+
+	while (!f2fs_time_over(sbi, DISABLE_TIME)) {
+		err = f2fs_gc(sbi, true, false, NULL_SEGNO);
+		if (err == -ENODATA)
+			break;
+		if (err && err != -EAGAIN) {
+			mutex_unlock(&sbi->gc_mutex);
+			return err;
+		}
+	}
+	mutex_unlock(&sbi->gc_mutex);
+
+	err = sync_filesystem(sbi->sb);
+	if (err)
+		return err;
+
+	if (f2fs_disable_cp_again(sbi))
+		return -EAGAIN;
+
+	mutex_lock(&sbi->gc_mutex);
+	cpc.reason = CP_PAUSE;
+	set_sbi_flag(sbi, SBI_CP_DISABLED);
+	f2fs_write_checkpoint(sbi, &cpc);
+
+	sbi->unusable_block_count = 0;
+	mutex_unlock(&sbi->gc_mutex);
+	return 0;
+}
+
+static void f2fs_enable_checkpoint(struct f2fs_sb_info *sbi)
+{
+	mutex_lock(&sbi->gc_mutex);
+	f2fs_dirty_to_prefree(sbi);
+
+	clear_sbi_flag(sbi, SBI_CP_DISABLED);
+	set_sbi_flag(sbi, SBI_IS_DIRTY);
+	mutex_unlock(&sbi->gc_mutex);
+
+	f2fs_sync_fs(sbi->sb, 1);
+}
+
 static int f2fs_remount(struct super_block *sb, int *flags, char *data)
 {
 	struct f2fs_sb_info *sbi = F2FS_SB(sb);
@@ -1422,6 +1509,8 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
 	bool need_restart_gc = false;
 	bool need_stop_gc = false;
 	bool no_extent_cache = !test_opt(sbi, EXTENT_CACHE);
+	bool disable_checkpoint = test_opt(sbi, DISABLE_CHECKPOINT);
+	bool checkpoint_changed;
 #ifdef CONFIG_QUOTA
 	int i, j;
 #endif
@@ -1466,6 +1555,8 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
 	err = parse_options(sb, data);
 	if (err)
 		goto restore_opts;
+	checkpoint_changed =
+			disable_checkpoint != test_opt(sbi, DISABLE_CHECKPOINT);
 
 	/*
 	 * Previous and new state of filesystem is RO,
@@ -1479,7 +1570,7 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
 		err = dquot_suspend(sb, -1);
 		if (err < 0)
 			goto restore_opts;
-	} else if (f2fs_readonly(sb) && !(*flags & MS_RDONLY)) {
+	} else if (f2fs_readonly(sb) && !(*flags & SB_RDONLY)) {
 		/* dquot_resume needs RW */
 		sb->s_flags &= ~SB_RDONLY;
 		if (sb_any_quota_suspended(sb)) {
@@ -1499,6 +1590,13 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
 		goto restore_opts;
 	}
 
+	if ((*flags & SB_RDONLY) && test_opt(sbi, DISABLE_CHECKPOINT)) {
+		err = -EINVAL;
+		f2fs_msg(sbi->sb, KERN_WARNING,
+			"disabling checkpoint not compatible with read-only");
+		goto restore_opts;
+	}
+
 	/*
 	 * We stop the GC thread if FS is mounted as RO
 	 * or if background_gc = off is passed in mount
@@ -1527,6 +1625,16 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
 		clear_sbi_flag(sbi, SBI_IS_CLOSE);
 	}
 
+	if (checkpoint_changed) {
+		if (test_opt(sbi, DISABLE_CHECKPOINT)) {
+			err = f2fs_disable_checkpoint(sbi);
+			if (err)
+				goto restore_gc;
+		} else {
+			f2fs_enable_checkpoint(sbi);
+		}
+	}
+
 	/*
 	 * We stop issue flush thread if FS is mounted as RO
 	 * or if flush_merge is not passed in mount option.
@@ -2485,6 +2593,7 @@ static void init_sb_info(struct f2fs_sb_info *sbi)
 	sbi->interval_time[REQ_TIME] = DEF_IDLE_INTERVAL;
 	sbi->interval_time[DISCARD_TIME] = DEF_IDLE_INTERVAL;
 	sbi->interval_time[GC_TIME] = DEF_IDLE_INTERVAL;
+	sbi->interval_time[DISABLE_TIME] = DEF_DISABLE_INTERVAL;
 	clear_sbi_flag(sbi, SBI_NEED_FSCK);
 
 	for (i = 0; i < NR_COUNT_TYPE; i++)
@@ -3093,6 +3202,9 @@ try_onemore:
 	if (err)
 		goto free_meta;
 
+	if (unlikely(is_set_ckpt_flags(sbi, CP_DISABLED_FLAG)))
+		goto skip_recovery;
+
 	/* recover fsynced data */
 	if (!test_opt(sbi, DISABLE_ROLL_FORWARD)) {
 		/*
@@ -3132,6 +3244,14 @@ skip_recovery:
 	/* f2fs_recover_fsync_data() cleared this already */
 	clear_sbi_flag(sbi, SBI_POR_DOING);
 
+	if (test_opt(sbi, DISABLE_CHECKPOINT)) {
+		err = f2fs_disable_checkpoint(sbi);
+		if (err)
+			goto free_meta;
+	} else if (is_set_ckpt_flags(sbi, CP_DISABLED_FLAG)) {
+		f2fs_enable_checkpoint(sbi);
+	}
+
 	/*
 	 * If filesystem is not mounted as read-only then
 	 * do start the gc_thread.