On Mon, 7 Feb 2022, Nitesh Shetty wrote: > + goto retry; > + return PTR_ERR(bio); > + } > + > + bio->bi_iter.bi_sector = sector >> SECTOR_SHIFT; > + bio->bi_opf = op; > + bio_set_dev(bio, bdev); > @@ -346,6 +463,8 @@ int blkdev_issue_copy(struct block_device *src_bdev, int nr, > > if (blk_check_copy_offload(src_q, dest_q)) > ret = blk_copy_offload(src_bdev, nr, rlist, dest_bdev, gfp_mask); > + else > + ret = blk_copy_emulate(src_bdev, nr, rlist, dest_bdev, gfp_mask); > > return ret; > } The emulation is not reliable because a device mapper device may be reconfigured and it may lose the copy capability between the calls to blk_check_copy_offload and blk_copy_offload. You should call blk_copy_emulate if blk_copy_offload returns an error. Mikulas
