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

[Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com>]

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"?
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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