rnbd-srv: use bdev_discard_alignment

Use bdev_discard_alignment to calculate the correct discard alignment
offset even for partitions instead of just looking at the queue limit.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Acked-by: NJack Wang <jinpu.wang@ionos.com>
Reviewed-by: NDamien Le Moal <damien.lemoal@opensource.wdc.com>
Reviewed-by: NMartin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20220418045314.360785-11-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

drivers/block/rnbd/rnbd-srv-dev.h

@@ -59,7 +59,7 @@ static inline int rnbd_dev_get_discard_granularity(const struct rnbd_dev *dev)
 
 static inline int rnbd_dev_get_discard_alignment(const struct rnbd_dev *dev)
 {
-	return bdev_get_queue(dev->bdev)->limits.discard_alignment;
+	return bdev_discard_alignment(dev->bdev);
 }
 
 #endif /* RNBD_SRV_DEV_H */