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Date:   Mon, 19 Sep 2022 17:56:45 -0700
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Chao Yu <chao@kernel.org>
Cc:     linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH v2] f2fs: record need_fsck in super_block
Message-ID: <YykPzeC4lk+F/U/2@google.com>
References: <20220913135919.2445544-1-chao@kernel.org>
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On 09/13, Chao Yu wrote:
> 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@kernel.org>
> ---
> v2:
> - remove unneeded codes.
>  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);

Let's think of putting some more context in superblock, if we want to overwrite
it. E.g., a reason to stop checkpoint?

> +	}
>  }
>  
>  /*
> 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..c99ba840593d 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 = 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