md/raid5: make async_copy_data() to support different page offset

ops_run_biofill() and ops_run_biodrain() will call async_copy_data()
to copy sh->dev[i].page from or to bio page. For now, it implies the
offset of dev[i].page is 0. But we want to support different page offset
in the following.

Thus, pass page offset to these functions and replace 'page_offset'
with 'page_offset + poff'.

No functional change.
Signed-off-by: Yufen Yu <yuyufen@huawei.com>
Signed-off-by: Song Liu <songliubraving@fb.com>

drivers/md/raid5.c

@@ -1227,7 +1227,7 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
 
 static struct dma_async_tx_descriptor *
 async_copy_data(int frombio, struct bio *bio, struct page **page,
-	sector_t sector, struct dma_async_tx_descriptor *tx,
+	unsigned int poff, sector_t sector, struct dma_async_tx_descriptor *tx,
 	struct stripe_head *sh, int no_skipcopy)
 {
 	struct bio_vec bvl;
@@ -1273,11 +1273,11 @@ async_copy_data(int frombio, struct bio *bio, struct page **page,
 				    !no_skipcopy)
 					*page = bio_page;
 				else
-					tx = async_memcpy(*page, bio_page, page_offset,
+					tx = async_memcpy(*page, bio_page, page_offset + poff,
 						  b_offset, clen, &submit);
 			} else
 				tx = async_memcpy(bio_page, *page, b_offset,
-						  page_offset, clen, &submit);
+						  page_offset + poff, clen, &submit);
 		}
 		/* chain the operations */
 		submit.depend_tx = tx;
@@ -1350,6 +1350,7 @@ static void ops_run_biofill(struct stripe_head *sh)
 			while (rbi && rbi->bi_iter.bi_sector <
 				dev->sector + RAID5_STRIPE_SECTORS(conf)) {
 				tx = async_copy_data(0, rbi, &dev->page,
+						     dev->offset,
 						     dev->sector, tx, sh, 0);
 				rbi = r5_next_bio(conf, rbi, dev->sector);
 			}
@@ -1790,6 +1791,7 @@ ops_run_biodrain(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
 					set_bit(R5_Discard, &dev->flags);
 				else {
 					tx = async_copy_data(1, wbi, &dev->page,
+							     dev->offset,
 							     dev->sector, tx, sh,
 							     r5c_is_writeback(conf->log));
 					if (dev->page != dev->orig_page &&