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Date:   Thu, 20 Apr 2023 09:34:55 -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, Yangtao Li <frank.li@vivo.com>
Subject: Re: [PATCH v8] f2fs: support errors=remount-ro|continue|panic
 mountoption
Message-ID: <ZEFprx0Xbv0Ol36A@google.com>
References: <20230408123153.954480-1-chao@kernel.org>
 <ZEBM5X5ngeomrWK9@google.com>
 <8cf87712-e392-bc51-08c9-f4c1096d4948@kernel.org>
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In-Reply-To: <8cf87712-e392-bc51-08c9-f4c1096d4948@kernel.org>
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On 04/20, Chao Yu wrote:
> On 2023/4/20 4:19, Jaegeuk Kim wrote:
> > On 04/08, Chao Yu wrote:
> > > This patch supports errors=remount-ro|continue|panic mount option,
> > > by default it uses "remount-ro" mode.
> > > 
> > > Signed-off-by: Chao Yu <chao@kernel.org>
> > > Signed-off-by: Yangtao Li <frank.li@vivo.com>
> > > ---
> > > v8:
> > > - record stop reason synchronously if it's from ioctl shutdown interface
> > > - fix typo in doc and commit message.
> > > - use f2fs_hw_is_readonly() instead of bdev_read_only()
> > >   Documentation/filesystems/f2fs.rst |   5 ++
> > >   fs/f2fs/checkpoint.c               |   7 +-
> > >   fs/f2fs/f2fs.h                     |  20 ++++-
> > >   fs/f2fs/file.c                     |   5 --
> > >   fs/f2fs/gc.c                       |   2 +-
> > >   fs/f2fs/super.c                    | 134 ++++++++++++++++++++++++++---
> > >   6 files changed, 149 insertions(+), 24 deletions(-)
> > > 
> > > diff --git a/Documentation/filesystems/f2fs.rst b/Documentation/filesystems/f2fs.rst
> > > index 2055e72871fe..ba4c02fad647 100644
> > > --- a/Documentation/filesystems/f2fs.rst
> > > +++ b/Documentation/filesystems/f2fs.rst
> > > @@ -351,6 +351,11 @@ age_extent_cache	 Enable an age extent cache based on rb-tree. It records
> > >   			 data block update frequency of the extent per inode, in
> > >   			 order to provide better temperature hints for data block
> > >   			 allocation.
> > > +errors=%s		 Specify f2fs behavior on critical errors. This supports modes:
> > > +			 "panic", "continue" and "remount-ro", respectively, trigger
> > > +			 panic immediately, continue without doing anything, and remount
> > > +			 the partition in read-only mode. By default it uses "remount-ro"
> > > +			 mode.
> > >   ======================== ============================================================
> > >   Debugfs Entries
> > > diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> > > index 73ae4e85e70d..e6b266bb9ce0 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 ac4942f8e83e..7d9c5a65f974 100644
> > > --- a/fs/f2fs/f2fs.h
> > > +++ b/fs/f2fs/f2fs.h
> > > @@ -162,6 +162,7 @@ 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,
> > > @@ -1370,6 +1371,12 @@ 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);
> > >   static inline void f2fs_clear_bit(unsigned int nr, char *addr);
> > > @@ -1786,8 +1793,14 @@ struct f2fs_sb_info {
> > >   	struct workqueue_struct *post_read_wq;	/* post read workqueue */
> > > -	unsigned char errors[MAX_F2FS_ERRORS];	/* error flags */
> > > -	spinlock_t error_lock;			/* protect errors array */
> > > +	/*
> > > +	 * 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/stop_reason array */
> > >   	bool error_dirty;			/* errors of sb is dirty */
> > >   	struct kmem_cache *inline_xattr_slab;	/* inline xattr entry */
> > > @@ -3522,8 +3535,9 @@ 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_save_errors(struct f2fs_sb_info *sbi, unsigned char flag);
> > > +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/file.c b/fs/f2fs/file.c
> > > index 14e9a20e68df..10743e864d57 100644
> > > --- a/fs/f2fs/file.c
> > > +++ b/fs/f2fs/file.c
> > > @@ -2221,7 +2221,6 @@ static int f2fs_ioc_shutdown(struct file *filp, unsigned long arg)
> > >   				ret = 0;
> > >   				f2fs_stop_checkpoint(sbi, false,
> > >   						STOP_CP_REASON_SHUTDOWN);
> > > -				set_sbi_flag(sbi, SBI_IS_SHUTDOWN);
> > >   				trace_f2fs_shutdown(sbi, in, ret);
> > >   			}
> > >   			return ret;
> > > @@ -2234,7 +2233,6 @@ static int f2fs_ioc_shutdown(struct file *filp, unsigned long arg)
> > >   		if (ret)
> > >   			goto out;
> > >   		f2fs_stop_checkpoint(sbi, false, STOP_CP_REASON_SHUTDOWN);
> > > -		set_sbi_flag(sbi, SBI_IS_SHUTDOWN);
> > >   		thaw_bdev(sb->s_bdev);
> > >   		break;
> > >   	case F2FS_GOING_DOWN_METASYNC:
> > > @@ -2243,16 +2241,13 @@ static int f2fs_ioc_shutdown(struct file *filp, unsigned long arg)
> > >   		if (ret)
> > >   			goto out;
> > >   		f2fs_stop_checkpoint(sbi, false, STOP_CP_REASON_SHUTDOWN);
> > > -		set_sbi_flag(sbi, SBI_IS_SHUTDOWN);
> > >   		break;
> > >   	case F2FS_GOING_DOWN_NOSYNC:
> > >   		f2fs_stop_checkpoint(sbi, false, STOP_CP_REASON_SHUTDOWN);
> > > -		set_sbi_flag(sbi, SBI_IS_SHUTDOWN);
> > >   		break;
> > >   	case F2FS_GOING_DOWN_METAFLUSH:
> > >   		f2fs_sync_meta_pages(sbi, META, LONG_MAX, FS_META_IO);
> > >   		f2fs_stop_checkpoint(sbi, false, STOP_CP_REASON_SHUTDOWN);
> > > -		set_sbi_flag(sbi, SBI_IS_SHUTDOWN);
> > >   		break;
> > >   	case F2FS_GOING_DOWN_NEED_FSCK:
> > >   		set_sbi_flag(sbi, SBI_NEED_FSCK);
> > > diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> > > index f1d0dd9c5a6c..6dc2bc710ba8 100644
> > > --- a/fs/f2fs/gc.c
> > > +++ b/fs/f2fs/gc.c
> > > @@ -59,7 +59,7 @@ static int gc_thread_func(void *data)
> > >   		if (gc_th->gc_wake)
> > >   			gc_th->gc_wake = false;
> > > -		if (try_to_freeze()) {
> > > +		if (try_to_freeze() || f2fs_readonly(sbi->sb)) {
> > >   			stat_other_skip_bggc_count(sbi);
> > >   			continue;
> > >   		}
> > > diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> > > index 23574894e170..1573bf123197 100644
> > > --- a/fs/f2fs/super.c
> > > +++ b/fs/f2fs/super.c
> > > @@ -164,6 +164,7 @@ enum {
> > >   	Opt_discard_unit,
> > >   	Opt_memory_mode,
> > >   	Opt_age_extent_cache,
> > > +	Opt_errors,
> > >   	Opt_err,
> > >   };
> > > @@ -243,6 +244,7 @@ static match_table_t f2fs_tokens = {
> > >   	{Opt_discard_unit, "discard_unit=%s"},
> > >   	{Opt_memory_mode, "memory=%s"},
> > >   	{Opt_age_extent_cache, "age_extent_cache"},
> > > +	{Opt_errors, "errors=%s"},
> > >   	{Opt_err, NULL},
> > >   };
> > > @@ -1268,6 +1270,25 @@ static int parse_options(struct super_block *sb, char *options, bool is_remount)
> > >   		case Opt_age_extent_cache:
> > >   			set_opt(sbi, AGE_EXTENT_CACHE);
> > >   			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);
> > > @@ -1623,6 +1644,9 @@ static void f2fs_put_super(struct super_block *sb)
> > >   	f2fs_destroy_node_manager(sbi);
> > >   	f2fs_destroy_segment_manager(sbi);
> > > +	/* flush s_error_work before sbi destroy */
> > > +	flush_work(&sbi->s_error_work);
> > > +
> > >   	f2fs_destroy_post_read_wq(sbi);
> > >   	kvfree(sbi->ckpt);
> > > @@ -2053,6 +2077,13 @@ 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;
> > >   }
> > > @@ -2081,6 +2112,7 @@ static void default_options(struct f2fs_sb_info *sbi)
> > >   	}
> > >   	F2FS_OPTION(sbi).bggc_mode = BGGC_MODE_ON;
> > >   	F2FS_OPTION(sbi).memory_mode = MEMORY_MODE_NORMAL;
> > > +	F2FS_OPTION(sbi).errors = MOUNT_ERRORS_READONLY;
> > 
> > Was the default MOUNT_ERRORS_CONTINUE?
> 
> Okay, let me revise in v9.
> 
> Please note that main difference between continue mode and readonly mode once
> cp_error is set:
> 
> 		continue mode		readonly mode
> access ops:	Normal			Normal
> modify ops:	-EIO			-EROFS
> mount option	rw			ro

Could you please add the difference of all the modes in patch description?

I think it'd be good to add:
1. access ops
2. syscall errors
3. mount option
4. pending data writes
5. pending node writes
6. pending meta writes


> 
> Thanks,
> 
> > 
> > >   	sbi->sb->s_flags &= ~SB_INLINECRYPT;
> > > @@ -2282,6 +2314,9 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
> > >   	if (err)
> > >   		goto restore_opts;
> > > +	/* flush outstanding errors before changing fs state */
> > > +	flush_work(&sbi->s_error_work);
> > > +
> > >   	/*
> > >   	 * Previous and new state of filesystem is RO,
> > >   	 * so skip checking GC and FLUSH_MERGE conditions.
> > > @@ -3931,45 +3966,60 @@ 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)
> > > +{
> > > +	unsigned long flags;
> > > +
> > > +	spin_lock_irqsave(&sbi->error_lock, flags);
> > > +	if (sbi->stop_reason[reason] < GENMASK(BITS_PER_BYTE - 1, 0))
> > > +		sbi->stop_reason[reason]++;
> > > +	spin_unlock_irqrestore(&sbi->error_lock, flags);
> > > +}
> > > +
> > > +static void f2fs_record_stop_reason(struct f2fs_sb_info *sbi)
> > >   {
> > >   	struct f2fs_super_block *raw_super = F2FS_RAW_SUPER(sbi);
> > > +	unsigned long flags;
> > >   	int err;
> > >   	f2fs_down_write(&sbi->sb_lock);
> > > -	if (raw_super->s_stop_reason[reason] < GENMASK(BITS_PER_BYTE - 1, 0))
> > > -		raw_super->s_stop_reason[reason]++;
> > > +	spin_lock_irqsave(&sbi->error_lock, flags);
> > > +	memcpy(raw_super->s_stop_reason, sbi->stop_reason, MAX_STOP_REASON);
> > > +	spin_unlock_irqrestore(&sbi->error_lock, flags);
> > >   	err = f2fs_commit_super(sbi, false);
> > > -	if (err)
> > > -		f2fs_err(sbi, "f2fs_commit_super fails to record reason:%u err:%d",
> > > -								reason, err);
> > > +
> > >   	f2fs_up_write(&sbi->sb_lock);
> > > +	if (err)
> > > +		f2fs_err(sbi, "f2fs_commit_super fails to record err:%d", err);
> > >   }
> > >   void f2fs_save_errors(struct f2fs_sb_info *sbi, unsigned char flag)
> > >   {
> > > -	spin_lock(&sbi->error_lock);
> > > +	unsigned long flags;
> > > +
> > > +	spin_lock_irqsave(&sbi->error_lock, flags);
> > >   	if (!test_bit(flag, (unsigned long *)sbi->errors)) {
> > >   		set_bit(flag, (unsigned long *)sbi->errors);
> > >   		sbi->error_dirty = true;
> > >   	}
> > > -	spin_unlock(&sbi->error_lock);
> > > +	spin_unlock_irqrestore(&sbi->error_lock, flags);
> > >   }
> > >   static bool f2fs_update_errors(struct f2fs_sb_info *sbi)
> > >   {
> > > +	unsigned long flags;
> > >   	bool need_update = false;
> > > -	spin_lock(&sbi->error_lock);
> > > +	spin_lock_irqsave(&sbi->error_lock, flags);
> > >   	if (sbi->error_dirty) {
> > >   		memcpy(F2FS_RAW_SUPER(sbi)->s_errors, sbi->errors,
> > >   							MAX_F2FS_ERRORS);
> > >   		sbi->error_dirty = false;
> > >   		need_update = true;
> > >   	}
> > > -	spin_unlock(&sbi->error_lock);
> > > +	spin_unlock_irqrestore(&sbi->error_lock, flags);
> > >   	return need_update;
> > >   }
> > > @@ -3993,6 +4043,66 @@ 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 shutdown = reason == STOP_CP_REASON_SHUTDOWN;
> > > +	bool continue_fs = !shutdown &&
> > > +			F2FS_OPTION(sbi).errors == MOUNT_ERRORS_CONTINUE;
> > > +
> > > +	set_ckpt_flags(sbi, CP_ERROR_FLAG);
> > > +
> > > +	if (!f2fs_hw_is_readonly(sbi)) {
> > > +		save_stop_reason(sbi, reason);
> > > +
> > > +		if (irq_context && !shutdown)
> > > +			schedule_work(&sbi->s_error_work);
> > > +		else
> > > +			f2fs_record_stop_reason(sbi);
> > > +	}
> > > +
> > > +	/*
> > > +	 * 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 &&
> > > +				!shutdown && !system_going_down() &&
> > > +				!is_sbi_flag_set(sbi, SBI_IS_SHUTDOWN))
> > > +		panic("F2FS-fs (device %s): panic forced after error\n",
> > > +							sb->s_id);
> > > +
> > > +	if (shutdown)
> > > +		set_sbi_flag(sbi, SBI_IS_SHUTDOWN);
> > > +
> > > +	/* continue filesystem operators if errors=continue */
> > > +	if (continue_fs || f2fs_readonly(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;
> > > +}
> > > +
> > > +static void f2fs_record_error_work(struct work_struct *work)
> > > +{
> > > +	struct f2fs_sb_info *sbi = container_of(work,
> > > +					struct f2fs_sb_info, s_error_work);
> > > +
> > > +	f2fs_record_stop_reason(sbi);
> > > +}
> > > +
> > >   static int f2fs_scan_devices(struct f2fs_sb_info *sbi)
> > >   {
> > >   	struct f2fs_super_block *raw_super = F2FS_RAW_SUPER(sbi);
> > > @@ -4223,7 +4333,9 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
> > >   	sb->s_fs_info = sbi;
> > >   	sbi->raw_super = raw_super;
> > > +	INIT_WORK(&sbi->s_error_work, f2fs_record_error_work);
> > >   	memcpy(sbi->errors, raw_super->s_errors, MAX_F2FS_ERRORS);
> > > +	memcpy(sbi->stop_reason, raw_super->s_stop_reason, MAX_STOP_REASON);
> > >   	/* precompute checksum seed for metadata */
> > >   	if (f2fs_sb_has_inode_chksum(sbi))
> > > @@ -4620,6 +4732,8 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
> > >   	f2fs_destroy_segment_manager(sbi);
> > >   stop_ckpt_thread:
> > >   	f2fs_stop_ckpt_thread(sbi);
> > > +	/* flush s_error_work before sbi destroy */
> > > +	flush_work(&sbi->s_error_work);
> > >   	f2fs_destroy_post_read_wq(sbi);
> > >   free_devices:
> > >   	destroy_device_list(sbi);
> > > -- 
> > > 2.36.1