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: f211268ed1f9 ("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>

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 7b277b18a8fe7eef0ce5acaf6ed8f201cbf11e4e..ca889328fdfef8589a484297044be1d0083f03c8 100644 (file)
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1293,8 +1293,9 @@ out:
 /*
  * 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
@@ -1327,11 +1328,19 @@ 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;