Re: [f2fs-dev] [PATCH] f2fs: avoid frequent costly fsck triggers

[Chao Yu <yuchao0@huawei.com>]

On 2018/11/30 10:35, Sheng Yong wrote:
> Hi, Jaegeuk and Chao,
> 
> On 2018/11/29 1:48, Jaegeuk Kim wrote:
>> On 11/28, Chao Yu wrote:
>>> On 2018/11/28 16:10, Jaegeuk Kim wrote:
>>>> On 11/28, Chao Yu wrote:
>>>>> Hi Jaeguek,
>>>>>
>>>>> On 2018/11/28 15:31, Jaegeuk Kim wrote:
>>>>>> If we want to re-enable nat_bits, we rely on fsck which requires full scan
>>>>>> of directory tree. Let's do that by regular fsck or unclean shutdown.
>>>>>
>>>>> Reviewed-by: Chao Yu <yuchao0@huawei.com>
>>>>>
>>>>> BTW, I have patch made some month ago...
>>>>>
>>>>> In order to detect nat_bits disabling, could we introduce one more flag for
>>>>> fsck?
>>>>
>>>> Do we have a way to enable nat_bits very quickly in fsck?
>>>
>>> For image with SBI_NATBIT_NEED_REPAIR flag, can we just check metadata and
>>> rebuild nat_bits based on verified nat blocks/journals?
>>
>> I'm leaning to rely on full scan to enable nat_bits again. We may add a mount
>> count or timer to trigger fsck regularly?
> 
> I'm afraid regular full fsck would give us bad experience of booting time.
> FYI, 256GB storage, which is filled with small files, costs almost 10 min
> to do a full fsck. And it seems larger capacity storages are on the way.

Agreed.

> So, is it worth doing that only to enable nat_bits (plus checking f2fs
> consistent not that necessarily)?

In android environment, I think it may be too expensive for adding nat_bits
by triggering full scan by fsck during boot time.

If we can update all nat bitmap in free time after mount, maybe we can
rebuild nat_bits based on full nat bitmap during umount, which can be
cheaper than rebuiding in userspace.

Thanks,

> 
> Thanks
>>
>>>
>>> Thanks,
>>>
>>>>
>>>>>
>>>>> >From 86e8bdb2faeec904944bb6621073f4f7de51cc2d Mon Sep 17 00:00:00 2001
>>>>> From: Chao Yu <yuchao0@huawei.com>
>>>>> Date: Sun, 9 Sep 2018 05:40:20 +0800
>>>>> Subject: [PATCH] f2fs: set specified flag after invalidating nat_bits
>>>>>
>>>>> Signed-off-by: Chao Yu <yuchao0@huawei.com>
>>>>> ---
>>>>>   fs/f2fs/checkpoint.c    | 12 +++++++++++-
>>>>>   fs/f2fs/f2fs.h          |  3 ++-
>>>>>   fs/f2fs/node.c          |  3 +++
>>>>>   include/linux/f2fs_fs.h |  1 +
>>>>>   4 files changed, 17 insertions(+), 2 deletions(-)
>>>>>
>>>>> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
>>>>> index 7e17bb3dfcb1..f7fb14e0f5f9 100644
>>>>> --- a/fs/f2fs/checkpoint.c
>>>>> +++ b/fs/f2fs/checkpoint.c
>>>>> @@ -1226,13 +1226,16 @@ static void update_ckpt_flags(struct f2fs_sb_info
>>>>> *sbi, struct cp_control *cpc)
>>>>>   	unsigned long orphan_num = sbi->im[ORPHAN_INO].ino_num;
>>>>>   	struct f2fs_checkpoint *ckpt = F2FS_CKPT(sbi);
>>>>>   	unsigned long flags;
>>>>> +	bool disable_natbits = false;
>>>>>
>>>>>   	spin_lock_irqsave(&sbi->cp_lock, flags);
>>>>>
>>>>>   	if ((cpc->reason & CP_UMOUNT) &&
>>>>>   			le32_to_cpu(ckpt->cp_pack_total_block_count) >
>>>>> -			sbi->blocks_per_seg - NM_I(sbi)->nat_bits_blocks)
>>>>> +			sbi->blocks_per_seg - NM_I(sbi)->nat_bits_blocks) {
>>>>>   		disable_nat_bits(sbi, false);
>>>>> +		disable_natbits = true;
>>>>> +	}
>>>>>
>>>>>   	if (cpc->reason & CP_TRIMMED)
>>>>>   		__set_ckpt_flags(ckpt, CP_TRIMMED_FLAG);
>>>>> @@ -1270,11 +1273,18 @@ static void update_ckpt_flags(struct f2fs_sb_info
>>>>> *sbi, struct cp_control *cpc)
>>>>>   	if (is_sbi_flag_set(sbi, SBI_QUOTA_NEED_REPAIR))
>>>>>   		__set_ckpt_flags(ckpt, CP_QUOTA_NEED_FSCK_FLAG);
>>>>>
>>>>> +	if (is_sbi_flag_set(sbi, SBI_NATBIT_NEED_REPAIR))
>>>>> +		__set_ckpt_flags(ckpt, CP_NATBIT_NEED_FSCK_FLAG);
>>>>> +
>>>>>   	/* set this flag to activate crc|cp_ver for recovery */
>>>>>   	__set_ckpt_flags(ckpt, CP_CRC_RECOVERY_FLAG);
>>>>>   	__clear_ckpt_flags(ckpt, CP_NOCRC_RECOVERY_FLAG);
>>>>>
>>>>>   	spin_unlock_irqrestore(&sbi->cp_lock, flags);
>>>>> +
>>>>> +	if (disable_natbits)
>>>>> +		f2fs_msg(sbi->sb, KERN_NOTICE,
>>>>> +			"No enough space in CP area, disable nat_bits.");
>>>>>   }
>>>>>
>>>>>   static void commit_checkpoint(struct f2fs_sb_info *sbi,
>>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>>>> index f0cedbe0c536..b55341c269b2 100644
>>>>> --- a/fs/f2fs/f2fs.h
>>>>> +++ b/fs/f2fs/f2fs.h
>>>>> @@ -1107,6 +1107,7 @@ enum {
>>>>>   	SBI_QUOTA_NEED_FLUSH,			/* need to flush quota info in CP */
>>>>>   	SBI_QUOTA_SKIP_FLUSH,			/* skip flushing quota in current CP */
>>>>>   	SBI_QUOTA_NEED_REPAIR,			/* quota file may be corrupted */
>>>>> +	SBI_NATBIT_NEED_REPAIR,			/* nat full/empty bitmaps need repair */
>>>>>   };
>>>>>
>>>>>   enum {
>>>>> @@ -1628,7 +1629,7 @@ static inline void disable_nat_bits(struct
>>>>> f2fs_sb_info *sbi, bool lock)
>>>>>   {
>>>>>   	unsigned long flags;
>>>>>
>>>>> -	set_sbi_flag(sbi, SBI_NEED_FSCK);
>>>>> +	set_sbi_flag(sbi, SBI_NATBIT_NEED_REPAIR);
>>>>>
>>>>>   	if (lock)
>>>>>   		spin_lock_irqsave(&sbi->cp_lock, flags);
>>>>> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
>>>>> index e57add1e8966..0c6f8312a087 100644
>>>>> --- a/fs/f2fs/node.c
>>>>> +++ b/fs/f2fs/node.c
>>>>> @@ -2902,6 +2902,9 @@ static int __get_nat_bitmaps(struct f2fs_sb_info *sbi)
>>>>>
>>>>>   	cp_ver |= (cur_cp_crc(ckpt) << 32);
>>>>>   	if (cpu_to_le64(cp_ver) != *(__le64 *)nm_i->nat_bits) {
>>>>> +		f2fs_msg(sbi->sb, KERN_NOTICE,
>>>>> +			"Disable nat_bits due to incorrect cp_ver (%llu, %llu)",
>>>>> +			cp_ver, le64_to_cpu(*(__le64 *)nm_i->nat_bits));
>>>>>   		disable_nat_bits(sbi, true);
>>>>>   		return 0;
>>>>>   	}
>>>>> diff --git a/include/linux/f2fs_fs.h b/include/linux/f2fs_fs.h
>>>>> index 7196653833fa..1f3ae1504573 100644
>>>>> --- a/include/linux/f2fs_fs.h
>>>>> +++ b/include/linux/f2fs_fs.h
>>>>> @@ -117,6 +117,7 @@ struct f2fs_super_block {
>>>>>   /*
>>>>>    * For checkpoint
>>>>>    */
>>>>> +#define CP_NATBIT_NEED_FSCK_FLAG	0X00002000
>>>>>   #define CP_DISABLED_FLAG		0x00001000
>>>>>   #define CP_QUOTA_NEED_FSCK_FLAG		0x00000800
>>>>>   #define CP_LARGE_NAT_BITMAP_FLAG	0x00000400
>>>>> -- 
>>>>> 2.18.0.rc1
>>>>>
>>>>>
>>>>>
>>>>>>
>>>>>> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
>>>>>> ---
>>>>>>   fs/f2fs/f2fs.h | 6 +++++-
>>>>>>   1 file changed, 5 insertions(+), 1 deletion(-)
>>>>>>
>>>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>>>>> index c28a9d1cb278..aa500239baf2 100644
>>>>>> --- a/fs/f2fs/f2fs.h
>>>>>> +++ b/fs/f2fs/f2fs.h
>>>>>> @@ -1621,7 +1621,11 @@ static inline void disable_nat_bits(struct f2fs_sb_info *sbi, bool lock)
>>>>>>   {
>>>>>>   	unsigned long flags;
>>>>>>   
>>>>>> -	set_sbi_flag(sbi, SBI_NEED_FSCK);
>>>>>> +	/*
>>>>>> +	 * In order to re-enable nat_bits we need to call fsck.f2fs by
>>>>>> +	 * set_sbi_flag(sbi, SBI_NEED_FSCK). But it may give huge cost,
>>>>>> +	 * so let's rely on regular fsck or unclean shutdown.
>>>>>> +	 */
>>>>>>   
>>>>>>   	if (lock)
>>>>>>   		spin_lock_irqsave(&sbi->cp_lock, flags);
>>>>>>
>>>>
>>>> .
>>>>
>>
>>
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>>
>> .
>>
> 
> 
> .
>