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Date:   Thu, 29 Sep 2022 11:31:44 -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: [PATCH v2 3/3] f2fs: support errors=remount-ro|continue|panic
 mountoption
Message-ID: <YzXkkL4Tatr+Lngn@google.com>
References: <20220928160949.5105-1-chao@kernel.org>
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On 09/29, Chao Yu wrote:
> This patch supports errors=remount-ro|continue|panic mount option.
> 
> Signed-off-by: Chao Yu <chao@kernel.org>
> ---
> v2:
> - fix to load sb.s_stop_reason during fill_super().
>  Documentation/filesystems/f2fs.rst |   4 +
>  fs/f2fs/checkpoint.c               |   7 +-
>  fs/f2fs/f2fs.h                     |  18 ++++-
>  fs/f2fs/super.c                    | 115 ++++++++++++++++++++++++++++-
>  4 files changed, 133 insertions(+), 11 deletions(-)
> 
> diff --git a/Documentation/filesystems/f2fs.rst b/Documentation/filesystems/f2fs.rst
> index d0c09663dae8..6aa14e03f337 100644
> --- a/Documentation/filesystems/f2fs.rst
> +++ b/Documentation/filesystems/f2fs.rst
> @@ -341,6 +341,10 @@ memory=%s		 Control memory mode. This supports "normal" and "low" modes.
>  			 Because of the nature of low memory devices, in this mode, f2fs
>  			 will try to save memory sometimes by sacrificing performance.
>  			 "normal" mode is the default mode and same as before.
> +errors=%s		 Specify f2fs behavior on critical errors. This supports modes:
> +			 "panic", "continue" and "remount-ro", respectively, triggers
> +			 panic immediately, continue without doing anything, or remount
> +			 the partition in read-only mode (default behavior).
>  ======================== ============================================================
>  
>  Debugfs Entries
> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> index 0c82dae082aa..109e96c15b84 100644
> --- a/fs/f2fs/checkpoint.c
> +++ b/fs/f2fs/checkpoint.c
> @@ -30,12 +30,9 @@ void f2fs_stop_checkpoint(struct f2fs_sb_info *sbi, bool end_io,
>  						unsigned char reason)
>  {
>  	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);
> -
> -		f2fs_handle_stop(sbi, reason);
> -	}
> +	f2fs_handle_critical_error(sbi, reason, end_io);
>  }
>  
>  /*
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 2ed00111a399..254f7f153477 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -160,6 +160,7 @@ struct f2fs_mount_info {
>  	int fs_mode;			/* fs mode: LFS or ADAPTIVE */
>  	int bggc_mode;			/* bggc mode: off, on or sync */
>  	int memory_mode;		/* memory mode */
> +	int errors;			/* errors parameter */
>  	int discard_unit;		/*
>  					 * discard command's offset/size should
>  					 * be aligned to this unit: block,
> @@ -1382,7 +1383,11 @@ enum {
>  	MEMORY_MODE_LOW,	/* memory mode for low memry devices */
>  };
>  
> -
> +enum errors_option {
> +	MOUNT_ERRORS_READONLY,	/* remount fs ro on errors */
> +	MOUNT_ERRORS_CONTINUE,	/* continue on errors */
> +	MOUNT_ERRORS_PANIC,	/* panic on errors */
> +};
>  
>  static inline int f2fs_test_bit(unsigned int nr, char *addr);
>  static inline void f2fs_set_bit(unsigned int nr, char *addr);
> @@ -1818,7 +1823,13 @@ struct f2fs_sb_info {
>  
>  	struct workqueue_struct *post_read_wq;	/* post read workqueue */
>  
> -	unsigned char errors[MAX_F2FS_ERRORS];	/* error flags */
> +	/*
> +	 * If we are in irq context, let's update error information into
> +	 * on-disk superblock in the work.
> +	 */
> +	struct work_struct s_error_work;
> +	unsigned char errors[MAX_F2FS_ERRORS];		/* error flags */
> +	unsigned char stop_reason[MAX_STOP_REASON];	/* stop reason */
>  	spinlock_t error_lock;			/* protect errors array */
>  	bool error_dirty;			/* errors of sb is dirty */
>  
> @@ -3563,7 +3574,8 @@ 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_handle_stop(struct f2fs_sb_info *sbi, unsigned char reason);
> +void f2fs_handle_critical_error(struct f2fs_sb_info *sbi, unsigned char reason,
> +							bool irq_context);
>  void f2fs_handle_error(struct f2fs_sb_info *sbi, unsigned char error);
>  int f2fs_commit_super(struct f2fs_sb_info *sbi, bool recover);
>  int f2fs_sync_fs(struct super_block *sb, int sync);
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index ee0a5a17ba39..60bd0344f573 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -161,6 +161,7 @@ enum {
>  	Opt_nogc_merge,
>  	Opt_discard_unit,
>  	Opt_memory_mode,
> +	Opt_errors,
>  	Opt_err,
>  };
>  
> @@ -238,6 +239,7 @@ static match_table_t f2fs_tokens = {
>  	{Opt_nogc_merge, "nogc_merge"},
>  	{Opt_discard_unit, "discard_unit=%s"},
>  	{Opt_memory_mode, "memory=%s"},
> +	{Opt_errors, "errors=%s"},
>  	{Opt_err, NULL},
>  };
>  
> @@ -1253,6 +1255,25 @@ static int parse_options(struct super_block *sb, char *options, bool is_remount)
>  			}
>  			kfree(name);
>  			break;
> +		case Opt_errors:
> +			name = match_strdup(&args[0]);
> +			if (!name)
> +				return -ENOMEM;
> +			if (!strcmp(name, "remount-ro")) {
> +				F2FS_OPTION(sbi).errors =
> +						MOUNT_ERRORS_READONLY;
> +			} else if (!strcmp(name, "continue")) {
> +				F2FS_OPTION(sbi).errors =
> +						MOUNT_ERRORS_CONTINUE;
> +			} else if (!strcmp(name, "panic")) {
> +				F2FS_OPTION(sbi).errors =
> +						MOUNT_ERRORS_PANIC;
> +			} else {
> +				kfree(name);
> +				return -EINVAL;
> +			}
> +			kfree(name);
> +			break;
>  		default:
>  			f2fs_err(sbi, "Unrecognized mount option \"%s\" or missing value",
>  				 p);
> @@ -2031,6 +2052,13 @@ static int f2fs_show_options(struct seq_file *seq, struct dentry *root)
>  	else if (F2FS_OPTION(sbi).memory_mode == MEMORY_MODE_LOW)
>  		seq_printf(seq, ",memory=%s", "low");
>  
> +	if (F2FS_OPTION(sbi).errors == MOUNT_ERRORS_READONLY)
> +		seq_printf(seq, ",errors=%s", "remount-ro");
> +	else if (F2FS_OPTION(sbi).errors == MOUNT_ERRORS_CONTINUE)
> +		seq_printf(seq, ",errors=%s", "continue");
> +	else if (F2FS_OPTION(sbi).errors == MOUNT_ERRORS_PANIC)
> +		seq_printf(seq, ",errors=%s", "panic");
> +
>  	return 0;
>  }
>  
> @@ -2053,6 +2081,7 @@ static void default_options(struct f2fs_sb_info *sbi)
>  	F2FS_OPTION(sbi).compress_mode = COMPR_MODE_FS;
>  	F2FS_OPTION(sbi).bggc_mode = BGGC_MODE_ON;
>  	F2FS_OPTION(sbi).memory_mode = MEMORY_MODE_NORMAL;
> +	F2FS_OPTION(sbi).errors = MOUNT_ERRORS_READONLY;
>  
>  	sbi->sb->s_flags &= ~SB_INLINECRYPT;
>  
> @@ -3846,7 +3875,16 @@ int f2fs_commit_super(struct f2fs_sb_info *sbi, bool recover)
>  	return err;
>  }
>  
> -void f2fs_handle_stop(struct f2fs_sb_info *sbi, unsigned char reason)
> +static void save_stop_reason(struct f2fs_sb_info *sbi, unsigned char reason)
> +
> +{
> +	spin_lock(&sbi->error_lock);
> +	if (sbi->stop_reason[reason] < ((1 << BITS_PER_BYTE) - 1))
> +		sbi->stop_reason[reason]++;
> +	spin_unlock(&sbi->error_lock);
> +}
> +
> +void f2fs_record_stop_reason(struct f2fs_sb_info *sbi, unsigned char reason)
>  
>  {
>  	struct f2fs_super_block *raw_super = F2FS_RAW_SUPER(sbi);
> @@ -3854,8 +3892,9 @@ void f2fs_handle_stop(struct f2fs_sb_info *sbi, unsigned char reason)
>  
>  	f2fs_down_write(&sbi->sb_lock);
>  
> -	if (raw_super->s_stop_reason[reason] < ((1 << BITS_PER_BYTE) - 1))
> -		raw_super->s_stop_reason[reason]++;
> +	spin_lock(&sbi->error_lock);
> +	memcpy(raw_super->s_stop_reason, sbi->stop_reason, MAX_STOP_REASON);
> +	spin_unlock(&sbi->error_lock);
>  
>  	err = f2fs_commit_super(sbi, false);
>  	if (err)
> @@ -3909,6 +3948,74 @@ void f2fs_handle_error(struct f2fs_sb_info *sbi, unsigned char error)
>  	f2fs_up_write(&sbi->sb_lock);
>  }
>  
> +static bool system_going_down(void)
> +{
> +	return system_state == SYSTEM_HALT || system_state == SYSTEM_POWER_OFF
> +		|| system_state == SYSTEM_RESTART;
> +}
> +
> +void f2fs_handle_critical_error(struct f2fs_sb_info *sbi, unsigned char reason,
> +							bool irq_context)
> +{
> +	struct super_block *sb = sbi->sb;
> +	bool force_ro = reason == STOP_CP_REASON_SHUTDOWN;

Can we check f2fs stopped checkpoint intentionally and use it here?

> +	bool continue_fs = !force_ro &&
> +			F2FS_OPTION(sbi).errors == MOUNT_ERRORS_CONTINUE;
> +
> +	if (!continue_fs && !sb_rdonly(sb))
> +		set_ckpt_flags(sbi, CP_ERROR_FLAG);
> +
> +	if (!bdev_read_only(sb->s_bdev)) {
> +		save_stop_reason(sbi, reason);
> +
> +		if (irq_context)
> +			schedule_work(&sbi->s_error_work);
> +		else
> +			f2fs_record_stop_reason(sbi, reason);
> +	}
> +
> +	/*
> +	 * We force ERRORS_RO behavior when system is rebooting. Otherwise we
> +	 * could panic during 'reboot -f' as the underlying device got already
> +	 * disabled.
> +	 */
> +	if (F2FS_OPTION(sbi).errors == MOUNT_ERRORS_PANIC &&
> +				!force_ro && !system_going_down())
> +		panic("F2FS-fs (device %s): panic forced after error\n",
> +							sb->s_id);
> +
> +	/* continue filesystem operators if errors=continue */
> +	if (continue_fs || sb_rdonly(sb))
> +		return;
> +
> +	f2fs_warn(sbi, "Remounting filesystem read-only");
> +	/*
> +	 * Make sure updated value of ->s_mount_flags will be visible before
> +	 * ->s_flags update
> +	 */
> +	smp_wmb();
> +	sb->s_flags |= SB_RDONLY;
> +
> +	f2fs_stop_gc_thread(sbi);
> +	f2fs_stop_discard_thread(sbi);
> +}
> +
> +static void flush_error_work(struct work_struct *work)
> +{
> +	struct f2fs_sb_info *sbi = container_of(work,
> +					struct f2fs_sb_info, s_error_work);
> +	int ret;
> +
> +	if (sb_rdonly(sbi->sb))
> +		return;
> +
> +	f2fs_down_write(&sbi->sb_lock);
> +	ret = f2fs_commit_super(sbi, false);
> +	f2fs_up_write(&sbi->sb_lock);
> +	if (ret)
> +		f2fs_err(sbi, "flush_error_work() fails to commit superblock ret:%d", ret);
> +}
> +
>  static int f2fs_scan_devices(struct f2fs_sb_info *sbi)
>  {
>  	struct f2fs_super_block *raw_super = F2FS_RAW_SUPER(sbi);
> @@ -4256,8 +4363,10 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
>  		goto free_devices;
>  	}
>  
> +	INIT_WORK(&sbi->s_error_work, flush_error_work);
>  	spin_lock_init(&sbi->error_lock);
>  	memcpy(sbi->errors, raw_super->s_errors, MAX_F2FS_ERRORS);
> +	memcpy(sbi->stop_reason, raw_super->s_stop_reason, MAX_STOP_REASON);
>  
>  	sbi->total_valid_node_count =
>  				le32_to_cpu(sbi->ckpt->valid_node_count);
> -- 
> 2.36.1