Re: dm: Fix report zone remapping

[Mike Snitzer <snitzer@redhat.com>]

On Fri, Oct 05 2018 at  6:34am -0400,
Damien Le Moal <damien.lemoal@wdc.com> wrote:

> If dm-linear or dm-flakey have targets on top of a partition of a zoned
> block device, remapping of the start sector and write pointer position
> of the zones reported by a report zones BIO must be modified to not
> only account for the target table entry mapping, but also to account
> for the partition first sector. This start sector must be substracted
> to the start sector of all zones reported. The write pointer position
> of sequential zones must also be reduced by this offset.
> 
> Since there is no easy way to access the underlying bdev of the target
> table entry from the dm_target or dm_target_io pointers, modify the
> interface of the function dm_remap_zone_report() to allow a target to
> pass the partition block device starting sector (offset).
> 
> Fixes: 10999307c14e ("dm: introduce dm_remap_zone_report()")
> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
> Cc: <stable@vger.kernel.org>

[dropping the actual stable cc from the mail, please don't cc stable in
the mail header, could be that git-send-email just pulled it in but...]

This needs a different fix.  There should be absolutely no need to pass
in a start offset for a device that is already supposed to be described
within the 'struct bio' passed to dm_remap_zone_report().

Why can't you just use the bio->bi_bdev ?  Err, since commit
74d46992e0d9d, I mean bio->bi_disk to get the start sector?

You should be able to get it from:

struct hd_struct *part = disk_get_part(bio->bi_disk, bio->bi_partno);
part->start_sect;
disk_put_part(part);

or:

struct block_device *bdev = bdget_disk(bio->bi_disk, bio->bi_partno);
get_start_sect(fc->dev->bdev);
bdput(bdev);

Mike


> ---
>  drivers/md/dm-flakey.c        |  3 ++-
>  drivers/md/dm-linear.c        |  3 ++-
>  drivers/md/dm.c               | 16 ++++++++++++----
>  include/linux/device-mapper.h |  2 +-
>  4 files changed, 17 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/md/dm-flakey.c b/drivers/md/dm-flakey.c
> index 21d126a5078c..c68c2e9cde6b 100644
> --- a/drivers/md/dm-flakey.c
> +++ b/drivers/md/dm-flakey.c
> @@ -381,7 +381,8 @@ static int flakey_end_io(struct dm_target *ti, struct bio *bio,
>  		return DM_ENDIO_DONE;
>  
>  	if (bio_op(bio) == REQ_OP_ZONE_REPORT) {
> -		dm_remap_zone_report(ti, bio, fc->start);
> +		dm_remap_zone_report(ti, bio, get_start_sect(fc->dev->bdev),
> +				     fc->start);
>  		return DM_ENDIO_DONE;
>  	}
>  
> diff --git a/drivers/md/dm-linear.c b/drivers/md/dm-linear.c
> index d10964d41fd7..f8cd367abbf6 100644
> --- a/drivers/md/dm-linear.c
> +++ b/drivers/md/dm-linear.c
> @@ -108,7 +108,8 @@ static int linear_end_io(struct dm_target *ti, struct bio *bio,
>  	struct linear_c *lc = ti->private;
>  
>  	if (!*error && bio_op(bio) == REQ_OP_ZONE_REPORT)
> -		dm_remap_zone_report(ti, bio, lc->start);
> +		dm_remap_zone_report(ti, bio, get_start_sect(lc->dev->bdev),
> +				     lc->start);
>  
>  	return DM_ENDIO_DONE;
>  }
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index 20f7e4ef5342..ffd8544eedd8 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -1162,7 +1162,8 @@ EXPORT_SYMBOL_GPL(dm_accept_partial_bio);
>   * REQ_OP_ZONE_REPORT bio to remap the zone descriptors obtained
>   * from the target device mapping to the dm device.
>   */
> -void dm_remap_zone_report(struct dm_target *ti, struct bio *bio, sector_t start)
> +void dm_remap_zone_report(struct dm_target *ti, struct bio *bio,
> +			  sector_t dev_offset, sector_t start)
>  {
>  #ifdef CONFIG_BLK_DEV_ZONED
>  	struct dm_target_io *tio = container_of(bio, struct dm_target_io, clone);
> @@ -1195,18 +1196,25 @@ void dm_remap_zone_report(struct dm_target *ti, struct bio *bio, sector_t start)
>  		/* Set zones start sector */
>  		while (hdr->nr_zones && ofst < bvec.bv_len) {
>  			zone = addr + ofst;
> +			zone->start -= dev_offset;
>  			if (zone->start >= start + ti->len) {
>  				hdr->nr_zones = 0;
>  				break;
>  			}
>  			zone->start = zone->start + ti->begin - start;
>  			if (zone->type != BLK_ZONE_TYPE_CONVENTIONAL) {
> -				if (zone->cond == BLK_ZONE_COND_FULL)
> +				switch (zone->cond) {
> +				case BLK_ZONE_COND_FULL:
>  					zone->wp = zone->start + zone->len;
> -				else if (zone->cond == BLK_ZONE_COND_EMPTY)
> +					break;
> +				case BLK_ZONE_COND_EMPTY:
>  					zone->wp = zone->start;
> -				else
> +					break;
> +				default:
> +					zone->wp -= dev_offset;
>  					zone->wp = zone->wp + ti->begin - start;
> +					break;
> +				}
>  			}
>  			ofst += sizeof(struct blk_zone);
>  			hdr->nr_zones--;
> diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
> index 6fb0808e87c8..22c1924c0ee8 100644
> --- a/include/linux/device-mapper.h
> +++ b/include/linux/device-mapper.h
> @@ -421,7 +421,7 @@ int dm_suspended(struct dm_target *ti);
>  int dm_noflush_suspending(struct dm_target *ti);
>  void dm_accept_partial_bio(struct bio *bio, unsigned n_sectors);
>  void dm_remap_zone_report(struct dm_target *ti, struct bio *bio,
> -			  sector_t start);
> +			  sector_t dev_offset, sector_t start);
>  union map_info *dm_get_rq_mapinfo(struct request *rq);
>  
>  struct queue_limits *dm_get_queue_limits(struct mapped_device *md);
> -- 
> 2.17.1
>