Re: [f2fs-dev] [PATCH v4 2/2] f2fs: Check write pointer consistency of non-open zones

[Chao Yu <yuchao0@huawei.com>]

On 2019/12/2 17:40, 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, reset the write pointer
> to place at the zone start.
> 
> 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.
> 
> Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
> ---
>  fs/f2fs/f2fs.h    |   1 +
>  fs/f2fs/segment.c | 126 ++++++++++++++++++++++++++++++++++++++++++++++
>  fs/f2fs/super.c   |  11 ++++
>  3 files changed, 138 insertions(+)
> 
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 002c417b0a53..23a84d7f17b8 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -3156,6 +3156,7 @@ 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);
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 9b6c7ab67b93..48903b7a9d25 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -4370,6 +4370,90 @@ 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, ret;
> +	struct seg_entry *se;
> +
> +	if (zone->type != BLK_ZONE_TYPE_SEQWRITE_REQ)
> +		return 0;
> +
> +	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, reset the write pointer.
> +	 */
> +	if (last_valid_block + 1 == zone_block && zone->wp != zone->start) {
> +		f2fs_notice(sbi,
> +			    "Zone without valid block has non-zero write "
> +			    "pointer. Reset the write pointer: wp[0x%x,0x%x]",
> +			    wp_segno, wp_blkoff);
> +		ret = blkdev_zone_mgmt(fdev->bdev, REQ_OP_ZONE_RESET,
> +				       zone->start, zone->len, GFP_NOFS);

Should use __f2fs_issue_discard_zone() to cover multi-device support?

> +		if (ret) {
> +			f2fs_notice(sbi, "Reset zone failed: %s (errno=%d)",
> +				    fdev->path, ret);
> +			return ret;
> +		}

Just out of curiosity, how long will RESET command take normally?

Thanks,

> +	}
> +
> +	return 0;
> +}
> +
>  static struct f2fs_dev_info *get_target_zoned_dev(struct f2fs_sb_info *sbi,
>  						  block_t zone_blkaddr)
>  {
> @@ -4442,6 +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));
> @@ -4492,11 +4580,49 @@ int f2fs_fix_curseg_write_pointer(struct f2fs_sb_info *sbi)
>  
>  	return 0;
>  }
> +
> +struct check_zone_write_pointer_args {
> +	struct f2fs_sb_info *sbi;
> +	struct f2fs_dev_info *fdev;
> +};
> +
> +static int check_zone_write_pointer_cb(struct blk_zone *zone, unsigned int idx,
> +				      void *data) {
> +	struct check_zone_write_pointer_args *args;
> +	args = (struct check_zone_write_pointer_args *)data;
> +
> +	return check_zone_write_pointer(args->sbi, args->fdev, zone);
> +}
> +
> +int f2fs_check_write_pointer(struct f2fs_sb_info *sbi)
> +{
> +	int i, ret;
> +	struct check_zone_write_pointer_args args;
> +
> +	for (i = 0; i < sbi->s_ndevs; i++) {
> +		if (!bdev_is_zoned(FDEV(i).bdev))
> +			continue;
> +
> +		args.sbi = sbi;
> +		args.fdev = &FDEV(i);
> +		ret = blkdev_report_zones(FDEV(i).bdev, 0, BLK_ALL_ZONES,
> +					  check_zone_write_pointer_cb, &args);
> +		if (ret < 0)
> +			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 5111e1ffe58a..755ad57c795b 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -3544,6 +3544,17 @@ 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);
> 


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