[RFC PATCH 2/2] ext4: add journal cycled recording support

[Zhang Yi <yi.zhang@huaweicloud.com>]

From: Zhang Yi <yi.zhang@huawei.com>

Introduce a new mount option names 'journal_cycle_record' to let jbd2
continue record journal log from the recovered head transaction block
or checkpointed/cleaned transactions on the previous mount.

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
---
 fs/ext4/ext4.h  |  2 ++
 fs/ext4/super.c | 17 +++++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 140e1eb300d1..b62e7886fc2c 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1267,6 +1267,8 @@ struct ext4_inode_info {
 #define EXT4_MOUNT2_MB_OPTIMIZE_SCAN	0x00000080 /* Optimize group
 						    * scanning in mballoc
 						    */
+#define EXT4_MOUNT2_JOURNAL_CYCLE_RECORD	0x00000100 /* Journal cycled record
+							    * log on empty logging area */
 
 #define clear_opt(sb, opt)		EXT4_SB(sb)->s_mount_opt &= \
 						~EXT4_MOUNT_##opt
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 260c1b3e3ef2..8260019830dc 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1591,6 +1591,7 @@ enum {
 	Opt_max_dir_size_kb, Opt_nojournal_checksum, Opt_nombcache,
 	Opt_no_prefetch_block_bitmaps, Opt_mb_optimize_scan,
 	Opt_errors, Opt_data, Opt_data_err, Opt_jqfmt, Opt_dax_type,
+	Opt_journal_cycle_record,
 #ifdef CONFIG_EXT4_DEBUG
 	Opt_fc_debug_max_replay, Opt_fc_debug_force
 #endif
@@ -1670,6 +1671,7 @@ static const struct fs_parameter_spec ext4_param_specs[] = {
 	fsparam_flag	("journal_checksum",	Opt_journal_checksum),
 	fsparam_flag	("nojournal_checksum",	Opt_nojournal_checksum),
 	fsparam_flag	("journal_async_commit",Opt_journal_async_commit),
+	fsparam_flag	("journal_cycle_record",Opt_journal_cycle_record),
 	fsparam_flag	("abort",		Opt_abort),
 	fsparam_enum	("data",		Opt_data, ext4_param_data),
 	fsparam_enum	("data_err",		Opt_data_err,
@@ -1826,6 +1828,8 @@ static const struct mount_opts {
 	{Opt_nombcache, EXT4_MOUNT_NO_MBCACHE, MOPT_SET},
 	{Opt_no_prefetch_block_bitmaps, EXT4_MOUNT_NO_PREFETCH_BLOCK_BITMAPS,
 	 MOPT_SET},
+	{Opt_journal_cycle_record, EXT4_MOUNT2_JOURNAL_CYCLE_RECORD,
+	 MOPT_SET | MOPT_2 | MOPT_NO_EXT2},
 #ifdef CONFIG_EXT4_DEBUG
 	{Opt_fc_debug_force, EXT4_MOUNT2_JOURNAL_FAST_COMMIT,
 	 MOPT_SET | MOPT_2 | MOPT_EXT4_ONLY},
@@ -2772,6 +2776,12 @@ static int ext4_check_opt_consistency(struct fs_context *fc,
 			    !(sbi->s_mount_opt2 & EXT4_MOUNT2_DAX_INODE))) {
 			goto fail_dax_change_remount;
 		}
+
+		if (ctx_test_mount_opt2(ctx, EXT4_MOUNT2_JOURNAL_CYCLE_RECORD)) {
+			ext4_msg(NULL, KERN_ERR,
+				 "can't change journal_cycle_record on remount");
+			return -EINVAL;
+		}
 	}
 
 	return ext4_check_quota_consistency(fc, sb);
@@ -5293,6 +5303,11 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
 			goto failed_mount3a;
 		}
 
+		if (test_opt2(sb, JOURNAL_CYCLE_RECORD)) {
+			ext4_msg(sb, KERN_ERR, "can't mount with "
+				 "journal_cycle_record, fs mounted w/o journal");
+			goto failed_mount3a;
+		}
 		if (test_opt2(sb, EXPLICIT_JOURNAL_CHECKSUM)) {
 			ext4_msg(sb, KERN_ERR, "can't mount with "
 				 "journal_checksum, fs mounted w/o journal");
@@ -5698,6 +5713,8 @@ static void ext4_init_journal_params(struct super_block *sb, journal_t *journal)
 		journal->j_flags |= JBD2_ABORT_ON_SYNCDATA_ERR;
 	else
 		journal->j_flags &= ~JBD2_ABORT_ON_SYNCDATA_ERR;
+	if (test_opt2(sb, JOURNAL_CYCLE_RECORD))
+		journal->j_flags |= JBD2_CYCLE_RECORD;
 	write_unlock(&journal->j_state_lock);
 }
 
-- 
2.31.1