On Wed, 25 Jun 2025, Damien Le Moal wrote:
> DM targets must not split zone append and write operations using
> dm_accept_partial_bio() as doing so is forbidden for zone append BIOs,
> breaks zone append emulation using regular write BIOs and potentially
> creates deadlock situations with queue freeze operations.
>
> Modify dm_accept_partial_bio() to add missing BUG_ON() checks for all
> these cases, that is, check that the BIO is a write or write zeroes
> operation. This change packs all the zone related checks together under
> a static_branch_unlikely(&zoned_enabled) and done only if the target is
> a zoned device.
>
> Fixes: f211268ed1f9 ("dm: Use the block layer zone append emulation")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Damien Le Moal <dlemoal@xxxxxxxxxx>
Reviewed-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
> ---
> drivers/md/dm.c | 17 +++++++++++++----
> 1 file changed, 13 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index f1e63c1808b4..f82457e7eed1 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -1286,8 +1286,9 @@ static size_t dm_dax_recovery_write(struct dax_device *dax_dev, pgoff_t pgoff,
> /*
> * A target may call dm_accept_partial_bio only from the map routine. It is
> * allowed for all bio types except REQ_PREFLUSH, REQ_OP_ZONE_* zone management
> - * operations, REQ_OP_ZONE_APPEND (zone append writes) and any bio serviced by
> - * __send_duplicate_bios().
> + * operations, zone append writes (native with REQ_OP_ZONE_APPEND or emulated
> + * with write BIOs flagged with BIO_EMULATES_ZONE_APPEND) and any bio serviced
> + * by __send_duplicate_bios().
> *
> * dm_accept_partial_bio informs the dm that the target only wants to process
> * additional n_sectors sectors of the bio and the rest of the data should be
> @@ -1320,11 +1321,19 @@ void dm_accept_partial_bio(struct bio *bio, unsigned int n_sectors)
> unsigned int bio_sectors = bio_sectors(bio);
>
> BUG_ON(dm_tio_flagged(tio, DM_TIO_IS_DUPLICATE_BIO));
> - BUG_ON(op_is_zone_mgmt(bio_op(bio)));
> - BUG_ON(bio_op(bio) == REQ_OP_ZONE_APPEND);
> BUG_ON(bio_sectors > *tio->len_ptr);
> BUG_ON(n_sectors > bio_sectors);
>
> + if (static_branch_unlikely(&zoned_enabled) &&
> + unlikely(bdev_is_zoned(bio->bi_bdev))) {
> + enum req_op op = bio_op(bio);
> +
> + BUG_ON(op_is_zone_mgmt(op));
> + BUG_ON(op == REQ_OP_WRITE);
> + BUG_ON(op == REQ_OP_WRITE_ZEROES);
> + BUG_ON(op == REQ_OP_ZONE_APPEND);
> + }
> +
> *tio->len_ptr -= bio_sectors - n_sectors;
> bio->bi_iter.bi_size = n_sectors << SECTOR_SHIFT;
>
> --
> 2.49.0
>
