Re: drivers/md/dm.c:1324:9: sparse: sparse: cast from restricted blk_opf_t

[Mikulas Patocka]

Hi

Could you please describe what's wrong here?

If I grep the kernel for 'bi_opf.*REQ_ATOMIC', there are 14 places where 
bi_opf is tested or manipulated with the REQ_ATOMIC flag.

What should I use instead of 'bio->bi_opf & REQ_ATOMIC'?

Mikulas



On Wed, 18 Mar 2026, kernel test robot wrote:

> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   a989fde763f4f24209e4702f50a45be572340e68
> commit: de67c139b3846ece6b8bbb62abf1f010ae85c083 dm: test for REQ_ATOMIC in dm_accept_partial_bio()
> date:   3 months ago
> config: mips-randconfig-r113-20260318 (https://download.01.org/0day-ci/archive/20260318/202603181439.atBWgPQu-lkp@xxxxxxxxx/config)
> compiler: mips-linux-gcc (GCC) 8.5.0
> sparse: v0.6.5-rc1
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260318/202603181439.atBWgPQu-lkp@xxxxxxxxx/reproduce)
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@xxxxxxxxx>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202603181439.atBWgPQu-lkp@xxxxxxxxx/
> 
> sparse warnings: (new ones prefixed by >>)
> >> drivers/md/dm.c:1324:9: sparse: sparse: cast from restricted blk_opf_t
>    drivers/md/dm.c:689:16: sparse: sparse: context imbalance in 'dm_get_live_table' - wrong count at exit
> 
> vim +1324 drivers/md/dm.c
> 
>   1283	
>   1284	/*
>   1285	 * A target may call dm_accept_partial_bio only from the map routine.  It is
>   1286	 * allowed for all bio types except REQ_PREFLUSH, REQ_OP_ZONE_* zone management
>   1287	 * operations, zone append writes (native with REQ_OP_ZONE_APPEND or emulated
>   1288	 * with write BIOs flagged with BIO_EMULATES_ZONE_APPEND) and any bio serviced
>   1289	 * by __send_duplicate_bios().
>   1290	 *
>   1291	 * dm_accept_partial_bio informs the dm that the target only wants to process
>   1292	 * additional n_sectors sectors of the bio and the rest of the data should be
>   1293	 * sent in a next bio.
>   1294	 *
>   1295	 * A diagram that explains the arithmetics:
>   1296	 * +--------------------+---------------+-------+
>   1297	 * |         1          |       2       |   3   |
>   1298	 * +--------------------+---------------+-------+
>   1299	 *
>   1300	 * <-------------- *tio->len_ptr --------------->
>   1301	 *                      <----- bio_sectors ----->
>   1302	 *                      <-- n_sectors -->
>   1303	 *
>   1304	 * Region 1 was already iterated over with bio_advance or similar function.
>   1305	 *	(it may be empty if the target doesn't use bio_advance)
>   1306	 * Region 2 is the remaining bio size that the target wants to process.
>   1307	 *	(it may be empty if region 1 is non-empty, although there is no reason
>   1308	 *	 to make it empty)
>   1309	 * The target requires that region 3 is to be sent in the next bio.
>   1310	 *
>   1311	 * If the target wants to receive multiple copies of the bio (via num_*bios, etc),
>   1312	 * the partially processed part (the sum of regions 1+2) must be the same for all
>   1313	 * copies of the bio.
>   1314	 */
>   1315	void dm_accept_partial_bio(struct bio *bio, unsigned int n_sectors)
>   1316	{
>   1317		struct dm_target_io *tio = clone_to_tio(bio);
>   1318		struct dm_io *io = tio->io;
>   1319		unsigned int bio_sectors = bio_sectors(bio);
>   1320	
>   1321		BUG_ON(dm_tio_flagged(tio, DM_TIO_IS_DUPLICATE_BIO));
>   1322		BUG_ON(bio_sectors > *tio->len_ptr);
>   1323		BUG_ON(n_sectors > bio_sectors);
> > 1324		BUG_ON(bio->bi_opf & REQ_ATOMIC);
>   1325	
>   1326		if (static_branch_unlikely(&zoned_enabled) &&
>   1327		    unlikely(bdev_is_zoned(bio->bi_bdev))) {
>   1328			enum req_op op = bio_op(bio);
>   1329	
>   1330			BUG_ON(op_is_zone_mgmt(op));
>   1331			BUG_ON(op == REQ_OP_WRITE);
>   1332			BUG_ON(op == REQ_OP_WRITE_ZEROES);
>   1333			BUG_ON(op == REQ_OP_ZONE_APPEND);
>   1334		}
>   1335	
>   1336		*tio->len_ptr -= bio_sectors - n_sectors;
>   1337		bio->bi_iter.bi_size = n_sectors << SECTOR_SHIFT;
>   1338	
>   1339		/*
>   1340		 * __split_and_process_bio() may have already saved mapped part
>   1341		 * for accounting but it is being reduced so update accordingly.
>   1342		 */
>   1343		dm_io_set_flag(io, DM_IO_WAS_SPLIT);
>   1344		io->sectors = n_sectors;
>   1345		io->sector_offset = bio_sectors(io->orig_bio);
>   1346	}
>   1347	EXPORT_SYMBOL_GPL(dm_accept_partial_bio);
>   1348	
> 
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