zram: use memcpy_to_bvec in zram_bvec_read

Use the proper helper instead of open coding the copy.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Link: https://lore.kernel.org/r/20220303111905.321089-4-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/zram/zram_drv.c

@@ -1331,12 +1331,10 @@ static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
 		goto out;
 
 	if (is_partial_io(bvec)) {
-		void *dst = kmap_atomic(bvec->bv_page);
 		void *src = kmap_atomic(page);
 
-		memcpy(dst + bvec->bv_offset, src + offset, bvec->bv_len);
+		memcpy_to_bvec(bvec, src + offset);
 		kunmap_atomic(src);
-		kunmap_atomic(dst);
 	}
 out:
 	if (is_partial_io(bvec))