linux-kernel - Re: [RFC PATCH v2] f2fs: record need_fsck in super

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Date:   Tue, 20 Sep 2022 23:43:43 +0800
From:   Chao Yu <chao@...nel.org>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
Cc:     linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v2] f2fs: record need_fsck in super_block

On 2022/9/20 8:56, Jaegeuk Kim wrote:
> 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@...nel.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?

Good idea, maybe:
Bit	Value				max number of type
[0]	need fsck flag			1
[1-5]	reason to stop checkpoint	32
[6-13]	reason to fsck			256

Thanks

> 
>> +	}
>>   }
>>   
>>   /*
>> 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