Re: [f2fs-dev] [PATCH v3 2/2] f2fs: Check write pointer consistency of non-open zones

[Chao Yu <yuchao0@huawei.com>]

On 2019/11/29 13:21, Shinichiro Kawasaki wrote:
> On Nov 28, 2019 / 20:39, Chao Yu wrote:
>> On 2019/11/28 13:31, Shinichiro Kawasaki wrote:
>>> On Nov 25, 2019 / 15:37, Chao Yu wrote:
>>>> On 2019/11/14 16:19, Shin'ichiro Kawasaki wrote:
>>>>> To catch f2fs bugs in write pointer handling code for zoned block
>>>>> devices, check write pointers of non-open zones that current segments do
>>>>> not point to. Do this check at mount time, after the fsync data recovery
>>>>> and current segments' write pointer consistency fix. Or when fsync data
>>>>> recovery is disabled by mount option, do the check when there is no fsync
>>>>> data.
>>>>>
>>>>> Check two items comparing write pointers with valid block maps in SIT.
>>>>> The first item is check for zones with no valid blocks. When there is no
>>>>> valid blocks in a zone, the write pointer should be at the start of the
>>>>> zone. If not, next write operation to the zone will cause unaligned write
>>>>> error. If write pointer is not at the zone start, make mount fail and ask
>>>>> users to run fsck.
>>>>>
>>>>> The second item is check between the write pointer position and the last
>>>>> valid block in the zone. It is unexpected that the last valid block
>>>>> position is beyond the write pointer. In such a case, report as a bug.
>>>>> Fix is not required for such zone, because the zone is not selected for
>>>>> next write operation until the zone get discarded.
>>>>>
>>>>> Also move a constant F2FS_REPORT_ZONE from super.c to f2fs.h to use it
>>>>> in segment.c also.
>>>>>
>>>>> Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
>>>>> ---
>>>>>  fs/f2fs/f2fs.h    |   3 +
>>>>>  fs/f2fs/segment.c | 149 ++++++++++++++++++++++++++++++++++++++++++++++
>>>>>  fs/f2fs/super.c   |  16 ++++-
>>>>>  3 files changed, 165 insertions(+), 3 deletions(-)
>>>>>
>>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>>>> index a2e24718c13b..1bb64950d793 100644
>>>>> --- a/fs/f2fs/f2fs.h
>>>>> +++ b/fs/f2fs/f2fs.h
>>>>> @@ -3137,6 +3137,7 @@ int f2fs_lookup_journal_in_cursum(struct f2fs_journal *journal, int type,
>>>>>  			unsigned int val, int alloc);
>>>>>  void f2fs_flush_sit_entries(struct f2fs_sb_info *sbi, struct cp_control *cpc);
>>>>>  int f2fs_fix_curseg_write_pointer(struct f2fs_sb_info *sbi);
>>>>> +int f2fs_check_write_pointer(struct f2fs_sb_info *sbi);
>>>>>  int f2fs_build_segment_manager(struct f2fs_sb_info *sbi);
>>>>>  void f2fs_destroy_segment_manager(struct f2fs_sb_info *sbi);
>>>>>  int __init f2fs_create_segment_manager_caches(void);
>>>>> @@ -3610,6 +3611,8 @@ static inline bool f2fs_blkz_is_seq(struct f2fs_sb_info *sbi, int devi,
>>>>>  
>>>>>  	return test_bit(zno, FDEV(devi).blkz_seq);
>>>>>  }
>>>>> +
>>>>> +#define F2FS_REPORT_NR_ZONES   4096
>>>>>  #endif
>>>>>  
>>>>>  static inline bool f2fs_hw_should_discard(struct f2fs_sb_info *sbi)
>>>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>>>>> index 6ece146dab34..29e3b6f62f8c 100644
>>>>> --- a/fs/f2fs/segment.c
>>>>> +++ b/fs/f2fs/segment.c
>>>>> @@ -4333,6 +4333,133 @@ static int sanity_check_curseg(struct f2fs_sb_info *sbi)
>>>>>  
>>>>>  #ifdef CONFIG_BLK_DEV_ZONED
>>>>>  
>>>>> +static int check_zone_write_pointer(struct f2fs_sb_info *sbi,
>>>>> +				    struct f2fs_dev_info *fdev,
>>>>> +				    struct blk_zone *zone)
>>>>> +{
>>>>> +	unsigned int wp_segno, wp_blkoff, zone_secno, zone_segno, segno;
>>>>> +	block_t zone_block, wp_block, last_valid_block;
>>>>> +	unsigned int log_sectors_per_block = sbi->log_blocksize - SECTOR_SHIFT;
>>>>> +	int i, s, b;
>>>>> +	struct seg_entry *se;
>>>>> +
>>>>> +	wp_block = fdev->start_blk + (zone->wp >> log_sectors_per_block);
>>>>> +	wp_segno = GET_SEGNO(sbi, wp_block);
>>>>> +	wp_blkoff = wp_block - START_BLOCK(sbi, wp_segno);
>>>>> +	zone_block = fdev->start_blk + (zone->start >> log_sectors_per_block);
>>>>> +	zone_segno = GET_SEGNO(sbi, zone_block);
>>>>> +	zone_secno = GET_SEC_FROM_SEG(sbi, zone_segno);
>>>>> +
>>>>> +	if (zone_segno >= MAIN_SEGS(sbi))
>>>>> +		return 0;
>>>>> +
>>>>> +	/*
>>>>> +	 * Skip check of zones cursegs point to, since
>>>>> +	 * fix_curseg_write_pointer() checks them.
>>>>> +	 */
>>>>> +	for (i = 0; i < NO_CHECK_TYPE; i++)
>>>>> +		if (zone_secno == GET_SEC_FROM_SEG(sbi,
>>>>> +						   CURSEG_I(sbi, i)->segno))
>>>>> +			return 0;
>>>>> +
>>>>> +	/*
>>>>> +	 * Get last valid block of the zone.
>>>>> +	 */
>>>>> +	last_valid_block = zone_block - 1;
>>>>> +	for (s = sbi->segs_per_sec - 1; s >= 0; s--) {
>>>>> +		segno = zone_segno + s;
>>>>> +		se = get_seg_entry(sbi, segno);
>>>>> +		for (b = sbi->blocks_per_seg - 1; b >= 0; b--)
>>>>> +			if (f2fs_test_bit(b, se->cur_valid_map)) {
>>>>> +				last_valid_block = START_BLOCK(sbi, segno) + b;
>>>>> +				break;
>>>>> +			}
>>>>> +		if (last_valid_block >= zone_block)
>>>>> +			break;
>>>>> +	}
>>>>> +
>>>>> +	/*
>>>>> +	 * If last valid block is beyond the write pointer, report the
>>>>> +	 * inconsistency. This inconsistency does not cause write error
>>>>> +	 * because the zone will not be selected for write operation until
>>>>> +	 * it get discarded. Just report it.
>>>>> +	 */
>>>>> +	if (last_valid_block >= wp_block) {
>>>>> +		f2fs_notice(sbi, "Valid block beyond write pointer: "
>>>>> +			    "valid block[0x%x,0x%x] wp[0x%x,0x%x]",
>>>>> +			    GET_SEGNO(sbi, last_valid_block),
>>>>> +			    GET_BLKOFF_FROM_SEG0(sbi, last_valid_block),
>>>>> +			    wp_segno, wp_blkoff);
>>>>> +		return 0;
>>>>> +	}
>>>>> +
>>>>> +	/*
>>>>> +	 * If there is no valid block in the zone and if write pointer is
>>>>> +	 * not at zone start, report the error to run fsck.
>>>>
>>>> So we only need to report this as inconsistent status in the condition of
>>>> discard has been triggered, right? otherwise, f2fs will trigger discard later
>>>> to reset zone->wp before opening this zone?
>>>
>>> Hmm, my intent was to catch the inconsistency at mount time, assuming the
>>> inconsistency is not expected at mount time. In other words, I assume that
>>> discard is triggered for zones without valid blocks before that last clean
>>
>> IIUC, if there is too many pending discards, put_super() may drop discard entries
>> to avoid delaying umount, so we can not assume all discards are always being
>> triggered.
> 
> I see. In this case, current code in the patch will miss-detect the zone with
> the dropped discard entries. This is not good. Thank you for catching this :)
> 
>>
>> So what I mean is for the condition of a) there is valid (including fsycned) block,
>> b) zone->wp is not at correct position, f2fs can handle it by issuing discard. Let
>> me know if I misread this comment.
> 
> For the condition a), do you mean "there is _no_ valid (include fsynced) block"?

Oops, yes, I meant that. :)

Thanks,

> If so, yes, I agree that f2fs can issue discard and both a) and b) are true. I
> can add a simple function call of "reset zone" to discard the zone.
> 
>>
>>> umount. If the last sudden f2fs shutdown without clean umount caused the
>>> inconsistency, it should be reported and fixed, I think.
>>>
>>> SIT valid blocks are referred to check if there is no valid blocks in the zone.
>>> SIT may be broken due to software bug or hardware flaw, then I think it is the
>>> better to run fsck rather than discard by f2fs.
>>>
>>> If I miss anything, please let me know.
>>>
>>> --
>>> Best Regards,
>>> Shin'ichiro Kawasaki
>>>
>>>>
>>>> Thanks,
>>>>
>>>>> +	 */
>>>>> +	if (last_valid_block + 1 == zone_block && zone->wp != zone->start) {
>>>>> +		f2fs_notice(sbi,
>>>>> +			    "Zone without valid block has non-zero write "
>>>>> +			    "pointer, run fsck to fix: wp[0x%x,0x%x]",
>>>>> +			    wp_segno, wp_blkoff);
>>>>> +		f2fs_stop_checkpoint(sbi, true);
>>>>> +		set_sbi_flag(sbi, SBI_NEED_FSCK);
>>>>> +		return -EINVAL;
>>>>> +	}
>>>>> +
>>>>> +	return 0;
>>>>> +}
>>>>> +
>>>>> +static int check_dev_write_pointer(struct f2fs_sb_info *sbi,
>>>>> +				   struct f2fs_dev_info *fdev) {
>>>>> +	sector_t nr_sectors = fdev->bdev->bd_part->nr_sects;
>>>>> +	sector_t sector = 0;
>>>>> +	struct blk_zone *zones;
>>>>> +	unsigned int i, nr_zones;
>>>>> +	unsigned int n = 0;
>>>>> +	int err = -EIO;
>>>>> +
>>>>> +	if (!bdev_is_zoned(fdev->bdev))
>>>>> +		return 0;
>>>>> +
>>>>> +	zones = f2fs_kzalloc(sbi,
>>>>> +			     array_size(F2FS_REPORT_NR_ZONES,
>>>>> +					sizeof(struct blk_zone)),
>>>>> +			     GFP_KERNEL);
>>>>> +	if (!zones)
>>>>> +		return -ENOMEM;
>>>>> +
>>>>> +	/* Get block zones type */
>>>>> +	while (zones && sector < nr_sectors) {
>>>>> +
>>>>> +		nr_zones = F2FS_REPORT_NR_ZONES;
>>>>> +		err = blkdev_report_zones(fdev->bdev, sector, zones, &nr_zones);
>>>>> +		if (err)
>>>>> +			break;
>>>>> +		if (!nr_zones) {
>>>>> +			err = -EIO;
>>>>> +			break;
>>>>> +		}
>>>>> +
>>>>> +		for (i = 0; i < nr_zones; i++) {
>>>>> +			if (zones[i].type == BLK_ZONE_TYPE_SEQWRITE_REQ) {
>>>>> +				err = check_zone_write_pointer(sbi, fdev,
>>>>> +							       &zones[i]);
>>>>> +				if (err)
>>>>> +					break;
>>>>> +			}
>>>>> +			sector += zones[i].len;
>>>>> +			n++;
>>>>> +		}
>>>>> +		if (err)
>>>>> +			break;
>>>>> +	}
>>>>> +
>>>>> +	kvfree(zones);
>>>>> +
>>>>> +	return err;
>>>>> +}
>>>>> +
>>>>>  static struct f2fs_dev_info *get_target_zoned_dev(struct f2fs_sb_info *sbi,
>>>>>  						  block_t zone_blkaddr)
>>>>>  {
>>>>> @@ -4399,6 +4526,10 @@ static int fix_curseg_write_pointer(struct f2fs_sb_info *sbi, int type)
>>>>>  		    "curseg[0x%x,0x%x]", type, cs->segno, cs->next_blkoff);
>>>>>  	allocate_segment_by_default(sbi, type, true);
>>>>>  
>>>>> +	/* check consistency of the zone curseg pointed to */
>>>>> +	if (check_zone_write_pointer(sbi, zbd, &zone))
>>>>> +		return -EIO;
>>>>> +
>>>>>  	/* check newly assigned zone */
>>>>>  	cs_section = GET_SEC_FROM_SEG(sbi, cs->segno);
>>>>>  	cs_zone_block = START_BLOCK(sbi, GET_SEG_FROM_SEC(sbi, cs_section));
>>>>> @@ -4444,11 +4575,29 @@ int f2fs_fix_curseg_write_pointer(struct f2fs_sb_info *sbi)
>>>>>  
>>>>>  	return 0;
>>>>>  }
>>>>> +
>>>>> +int f2fs_check_write_pointer(struct f2fs_sb_info *sbi)
>>>>> +{
>>>>> +	int i, ret;
>>>>> +
>>>>> +	for (i = 0; i < sbi->s_ndevs; i++) {
>>>>> +		ret = check_dev_write_pointer(sbi, &FDEV(i));
>>>>> +		if (ret)
>>>>> +			return ret;
>>>>> +	}
>>>>> +
>>>>> +	return 0;
>>>>> +}
>>>>>  #else
>>>>>  int f2fs_fix_curseg_write_pointer(struct f2fs_sb_info *sbi)
>>>>>  {
>>>>>  	return 0;
>>>>>  }
>>>>> +
>>>>> +int f2fs_check_write_pointer(struct f2fs_sb_info *sbi)
>>>>> +{
>>>>> +	return 0;
>>>>> +}
>>>>>  #endif
>>>>>  
>>>>>  /*
>>>>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
>>>>> index 1443cee15863..8ca772670c67 100644
>>>>> --- a/fs/f2fs/super.c
>>>>> +++ b/fs/f2fs/super.c
>>>>> @@ -2890,8 +2890,6 @@ static int init_blkz_info(struct f2fs_sb_info *sbi, int devi)
>>>>>  	if (!FDEV(devi).blkz_seq)
>>>>>  		return -ENOMEM;
>>>>>  
>>>>> -#define F2FS_REPORT_NR_ZONES   4096
>>>>> -
>>>>>  	zones = f2fs_kzalloc(sbi,
>>>>>  			     array_size(F2FS_REPORT_NR_ZONES,
>>>>>  					sizeof(struct blk_zone)),
>>>>> @@ -3509,7 +3507,8 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
>>>>>  
>>>>>  		err = f2fs_recover_fsync_data(sbi, false);
>>>>>  		if (err < 0) {
>>>>> -			if (err != -ENOMEM)
>>>>> +			if (err != -ENOMEM &&
>>>>> +			    !is_sbi_flag_set(sbi, SBI_NEED_FSCK))
>>>>>  				skip_recovery = true;
>>>>>  			need_fsck = true;
>>>>>  			f2fs_err(sbi, "Cannot recover all fsync data errno=%d",
>>>>> @@ -3525,6 +3524,17 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
>>>>>  			goto free_meta;
>>>>>  		}
>>>>>  	}
>>>>> +
>>>>> +	/*
>>>>> +	 * If the f2fs is not readonly and fsync data recovery succeeds,
>>>>> +	 * check zoned block devices' write pointer consistency.
>>>>> +	 */
>>>>> +	if (!err && !f2fs_readonly(sb) && f2fs_sb_has_blkzoned(sbi)) {
>>>>> +		err = f2fs_check_write_pointer(sbi);
>>>>> +		if (err)
>>>>> +			goto free_meta;
>>>>> +	}
>>>>> +
>>>>>  reset_checkpoint:
>>>>>  	/* f2fs_recover_fsync_data() cleared this already */
>>>>>  	clear_sbi_flag(sbi, SBI_POR_DOING);
>>>>> .
>>>
> 
> --
> Best Regards,
> Shin'ichiro Kawasaki
> .
> 


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