zram: use memcpy_from_bvec in zram_bvec_write

Use memcpy_from_bvec instead of open coding the logic.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Link: https://lore.kernel.org/r/20220303111905.321089-5-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/zram/zram_drv.c

@@ -1465,7 +1465,6 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
 {
 	int ret;
 	struct page *page = NULL;
-	void *src;
 	struct bio_vec vec;
 
 	vec = *bvec;
@@ -1483,11 +1482,9 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
 		if (ret)
 			goto out;
 
-		src = kmap_atomic(bvec->bv_page);
 		dst = kmap_atomic(page);
-		memcpy(dst + offset, src + bvec->bv_offset, bvec->bv_len);
+		memcpy_from_bvec(dst + offset, bvec);
 		kunmap_atomic(dst);
-		kunmap_atomic(src);
 
 		vec.bv_page = page;
 		vec.bv_len = PAGE_SIZE;