[RFC PATCH v3] f2fs: record need_fsck in super_block

[Chao Yu]

Once CP_ERROR_FLAG is set, checkpoint is disallowed to be triggered to
persist CP_FSCK_FLAG, fsck won't repair the image due to lack of
CP_FSCK_FLAG.

This patch proposes to persist newly introduced SB_NEED_FSCK flag into
super block if CP_ERROR_FLAG and SBI_NEED_FSCK is set, later, once fsck
detect this flag, it can check and repair corrupted image in time.

Signed-off-by: Chao Yu <chao@xxxxxxxxxx>
---
v3:
- fix to add missing cpu_to_le16()
 fs/f2fs/checkpoint.c    |  6 +++++-
 fs/f2fs/f2fs.h          |  1 +
 fs/f2fs/super.c         | 26 ++++++++++++++++++++++++++
 include/linux/f2fs_fs.h |  5 ++++-
 4 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index c3119e4c890c..0836fce40394 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -30,8 +30,12 @@ void f2fs_stop_checkpoint(struct f2fs_sb_info *sbi, bool end_io)
 {
 	f2fs_build_fault_attr(sbi, 0, 0);
 	set_ckpt_flags(sbi, CP_ERROR_FLAG);
-	if (!end_io)
+	if (!end_io) {
 		f2fs_flush_merged_writes(sbi);
+
+		if (is_sbi_flag_set(sbi, SBI_NEED_FSCK))
+			f2fs_update_sb_flags(sbi, SB_NEED_FSCK);
+	}
 }
 
 /*
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index dee7b67a17a6..1960a98c7555 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -3556,6 +3556,7 @@ int f2fs_enable_quota_files(struct f2fs_sb_info *sbi, bool rdonly);
 int f2fs_quota_sync(struct super_block *sb, int type);
 loff_t max_file_blocks(struct inode *inode);
 void f2fs_quota_off_umount(struct super_block *sb);
+void f2fs_update_sb_flags(struct f2fs_sb_info *sbi, unsigned int flag);
 int f2fs_commit_super(struct f2fs_sb_info *sbi, bool recover);
 int f2fs_sync_fs(struct super_block *sb, int sync);
 int f2fs_sanity_check_ckpt(struct f2fs_sb_info *sbi);
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index b8e5fe244596..fe9a6e02d81f 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -3846,6 +3846,32 @@ int f2fs_commit_super(struct f2fs_sb_info *sbi, bool recover)
 	return err;
 }
 
+void f2fs_update_sb_flags(struct f2fs_sb_info *sbi, unsigned int flag)
+{
+	unsigned short s_flags;
+	int err;
+
+	if (le16_to_cpu(F2FS_RAW_SUPER(sbi)->s_flags) & SB_NEED_FSCK)
+		return;
+
+	f2fs_down_write(&sbi->sb_lock);
+
+	s_flags = le16_to_cpu(F2FS_RAW_SUPER(sbi)->s_flags);
+
+	if (s_flags & SB_NEED_FSCK)
+		goto out_unlock;
+
+	F2FS_RAW_SUPER(sbi)->s_flags = cpu_to_le16(s_flags | SB_NEED_FSCK);
+
+	err = f2fs_commit_super(sbi, false);
+	if (err) {
+		f2fs_warn(sbi, "f2fs_commit_super fails to persist flag: %u, err:%d", flag, err);
+		F2FS_RAW_SUPER(sbi)->s_flags = cpu_to_le16(s_flags);
+	}
+out_unlock:
+	f2fs_up_write(&sbi->sb_lock);
+}
+
 static int f2fs_scan_devices(struct f2fs_sb_info *sbi)
 {
 	struct f2fs_super_block *raw_super = F2FS_RAW_SUPER(sbi);
diff --git a/include/linux/f2fs_fs.h b/include/linux/f2fs_fs.h
index d445150c5350..124176e2a42c 100644
--- a/include/linux/f2fs_fs.h
+++ b/include/linux/f2fs_fs.h
@@ -73,6 +73,8 @@ struct f2fs_device {
 	__le32 total_segments;
 } __packed;
 
+#define SB_NEED_FSCK			0x00000001	/* need fsck */
+
 struct f2fs_super_block {
 	__le32 magic;			/* Magic Number */
 	__le16 major_ver;		/* Major Version */
@@ -116,7 +118,8 @@ struct f2fs_super_block {
 	__u8 hot_ext_count;		/* # of hot file extension */
 	__le16  s_encoding;		/* Filename charset encoding */
 	__le16  s_encoding_flags;	/* Filename charset encoding flags */
-	__u8 reserved[306];		/* valid reserved region */
+	__le16 s_flags;			/* super block flags */
+	__u8 reserved[304];		/* valid reserved region */
 	__le32 crc;			/* checksum of superblock */
 } __packed;
 
-- 
2.25.1