On 2019/8/21 12:48, Shin'ichiro Kawasaki wrote:
> When sudden f2fs shutdown happens on zoned block devices, write
> pointers can be inconsistent with valid blocks counts in meta data.
> The failure scenario is as follows:
>
> - Just before a sudden shutdown, a new segment in a new zone is selected
> for a current segment. Write commands were executed to the segment.
> and the zone has a write pointer not at zone start.
> - Before the write commands complete, shutdown happens. Meta data is
> not updated and still keeps zero valid blocks count for the zone.
> - After next mount of the file system, the zone is selected for the next
> write target because it has zero valid blocks count. However, it has
> the write pointer not at zone start. Then "Unaligned write command"
> error happens.
>
> To avoid this potential error path, reset write pointers if the zone
> does not have a current segment, the write pointer is not at the zone
> start and the zone has no valid blocks.
>
> Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawas...@wdc.com>
> ---
> fsck/fsck.c | 30 +++++++++++++++++++++++++++++-
> 1 file changed, 29 insertions(+), 1 deletion(-)
>
> diff --git a/fsck/fsck.c b/fsck/fsck.c
> index 21a06ac..cc9bbc0 100644
> --- a/fsck/fsck.c
> +++ b/fsck/fsck.c
> @@ -2595,6 +2595,7 @@ static int fsck_chk_write_pointer(int i, struct
> blk_zone *blkz, void *opaque)
> int log_sectors_per_block = sbi->log_blocksize - SECTOR_SHIFT;
> unsigned int segs_per_zone = sbi->segs_per_sec * sbi->secs_per_zone;
> void *zero_blk;
> + block_t zone_valid_blocks = 0;
>
> if (blk_zone_conv(blkz))
> return 0;
> @@ -2615,8 +2616,35 @@ static int fsck_chk_write_pointer(int i, struct
> blk_zone *blkz, void *opaque)
> break;
> }
>
> - if (cs_index >= NR_CURSEG_TYPE)
> + if (cs_index >= NR_CURSEG_TYPE) {
> + for (b = zone_block; b < zone_block + c.zone_blocks &&
> + IS_VALID_BLK_ADDR(sbi, b); b += c.blks_per_seg) {
> + se = get_seg_entry(sbi, GET_SEGNO(sbi, b));
> + zone_valid_blocks += se->valid_blocks;
> + }
> + if (wp_block == zone_block || zone_valid_blocks)
> + return 0;
> +
> + /*
> + * The write pointer is not at zone start but there is no valid
> + * block in the zone. Segments in the zone can be selected for
> + * next write. Need to reset the write pointer to avoid
> + * unaligned write command error.
In SPOR (sudden power-off recovery) of kernel side, we may revalidate blocks
belong to fsynced file in such zone within range of [0, write pointer], if we
just reset zone, will we lose those data for ever?
BTW, how you think enabling f2fs kernel module to recover incorrect write
pointer of zone? Once f2fs-tools doesn't upgrade, however kernel does...
Thanks,
> + */
> + if (c.fix_on) {
> + FIX_MSG("Reset write pointer at segment 0x%x",
> + zone_segno);
> + ret = f2fs_reset_zone(dev, blkz);
> + if (ret)
> + return ret;
> + fsck->chk.wp_fixed_zones++;
> + } else {
> + MSG(0, "Inconsistent write pointer at segment 0x%x\n",
> + zone_segno);
> + fsck->chk.wp_inconsistent_zones++;
> + }
> return 0;
> + }
>
> /* check write pointer consistency with the curseg in the zone */
> cs_block = START_BLOCK(sbi, cs->segno) + cs->next_blkoff;
>
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