Commit 409f9287 authored by Damien Le Moal's avatar Damien Le Moal Committed by Jens Axboe
Browse files

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: f211268e ("dm: Use the block layer zone append emulation")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarDamien Le Moal <dlemoal@kernel.org>
Reviewed-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Link: https://lore.kernel.org/r/20250625093327.548866-6-dlemoal@kernel.org


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent e5496638

drivers/md/dm.c

+13 −4
Original line number Diff line number Diff line
@@ -1293,8 +1293,9 @@ 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
@@ -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;