dm: Check for forbidden splitting of zone write operations

JIRA: https://issues.redhat.com/browse/RHEL-97177

commit 409f928
Author: Damien Le Moal <dlemoal@kernel.org>
Date:   Wed Jun 25 18:33:27 2025 +0900

    dm: Check for forbidden splitting of zone write operations

    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: f211268 ("dm: Use the block layer zone append emulation")
    Cc: stable@vger.kernel.org
    Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
    Reviewed-by: Mikulas Patocka <mpatocka@redhat.com>
    Link: https://lore.kernel.org/r/20250625093327.548866-6-dlemoal@kernel.org
    Signed-off-by: Jens Axboe <axboe@kernel.dk>

Signed-off-by: Ming Lei <ming.lei@redhat.com>

Author: Ming Lei

drivers/md/dm.c

@@ -1309,8 +1309,9 @@ 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
@@ -1343,11 +1344,19 @@ 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;