btrfs: raid56: extract rwm write bios assembly into a helper

The helper will be later used to refactor the rmw write path.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/raid56.c

@@ -1237,65 +1237,23 @@ static void generate_pq_vertical(struct btrfs_raid_bio *rbio, int sectornr)
 		kunmap_local(pointers[stripe]);
 }
 
-/*
- * this is called from one of two situations.  We either
- * have a full stripe from the higher layers, or we've read all
- * the missing bits off disk.
- *
- * This will calculate the parity and then send down any
- * changed blocks.
- */
-static noinline void finish_rmw(struct btrfs_raid_bio *rbio)
+static int rmw_assemble_write_bios(struct btrfs_raid_bio *rbio,
+				   struct bio_list *bio_list)
 {
-	struct btrfs_io_context *bioc = rbio->bioc;
+	struct bio *bio;
 	/* The total sector number inside the full stripe. */
 	int total_sector_nr;
-	int stripe;
-	/* Sector number inside a stripe. */
 	int sectornr;
-	struct bio_list bio_list;
-	struct bio *bio;
+	int stripe;
 	int ret;
 
-	bio_list_init(&bio_list);
+	ASSERT(bio_list_size(bio_list) == 0);
 
 	/* We should have at least one data sector. */
 	ASSERT(bitmap_weight(&rbio->dbitmap, rbio->stripe_nsectors));
 
-	/* at this point we either have a full stripe,
-	 * or we've read the full stripe from the drive.
-	 * recalculate the parity and write the new results.
-	 *
-	 * We're not allowed to add any new bios to the
-	 * bio list here, anyone else that wants to
-	 * change this stripe needs to do their own rmw.
-	 */
-	spin_lock_irq(&rbio->bio_list_lock);
-	set_bit(RBIO_RMW_LOCKED_BIT, &rbio->flags);
-	spin_unlock_irq(&rbio->bio_list_lock);
-
-	atomic_set(&rbio->error, 0);
-
 	/*
-	 * now that we've set rmw_locked, run through the
-	 * bio list one last time and map the page pointers
-	 *
-	 * We don't cache full rbios because we're assuming
-	 * the higher layers are unlikely to use this area of
-	 * the disk again soon.  If they do use it again,
-	 * hopefully they will send another full bio.
-	 */
-	index_rbio_pages(rbio);
-	if (!rbio_is_full(rbio))
-		cache_rbio_pages(rbio);
-	else
-		clear_bit(RBIO_CACHE_READY_BIT, &rbio->flags);
-
-	for (sectornr = 0; sectornr < rbio->stripe_nsectors; sectornr++)
-		generate_pq_vertical(rbio, sectornr);
-
-	/*
-	 * Start writing.  Make bios for everything from the higher layers (the
+	 * Start assembly.  Make bios for everything from the higher layers (the
 	 * bio_list in our rbio) and our P/Q.  Ignore everything else.
 	 */
 	for (total_sector_nr = 0; total_sector_nr < rbio->nr_sectors;
@@ -1317,15 +1275,16 @@ static noinline void finish_rmw(struct btrfs_raid_bio *rbio)
 			sector = rbio_stripe_sector(rbio, stripe, sectornr);
 		}
 
-		ret = rbio_add_io_sector(rbio, &bio_list, sector, stripe,
+		ret = rbio_add_io_sector(rbio, bio_list, sector, stripe,
 					 sectornr, REQ_OP_WRITE);
 		if (ret)
-			goto cleanup;
+			goto error;
 	}
 
-	if (likely(!bioc->num_tgtdevs))
-		goto write_data;
+	if (likely(!rbio->bioc->num_tgtdevs))
+		return 0;
 
+	/* Make a copy for the replace target device. */
 	for (total_sector_nr = 0; total_sector_nr < rbio->nr_sectors;
 	     total_sector_nr++) {
 		struct sector_ptr *sector;
@@ -1333,7 +1292,7 @@ static noinline void finish_rmw(struct btrfs_raid_bio *rbio)
 		stripe = total_sector_nr / rbio->stripe_nsectors;
 		sectornr = total_sector_nr % rbio->stripe_nsectors;
 
-		if (!bioc->tgtdev_map[stripe]) {
+		if (!rbio->bioc->tgtdev_map[stripe]) {
 			/*
 			 * We can skip the whole stripe completely, note
 			 * total_sector_nr will be increased by one anyway.
@@ -1355,14 +1314,78 @@ static noinline void finish_rmw(struct btrfs_raid_bio *rbio)
 			sector = rbio_stripe_sector(rbio, stripe, sectornr);
 		}
 
-		ret = rbio_add_io_sector(rbio, &bio_list, sector,
+		ret = rbio_add_io_sector(rbio, bio_list, sector,
 					 rbio->bioc->tgtdev_map[stripe],
 					 sectornr, REQ_OP_WRITE);
 		if (ret)
-			goto cleanup;
+			goto error;
 	}
 
-write_data:
+	return 0;
+error:
+	while ((bio = bio_list_pop(bio_list)))
+		bio_put(bio);
+	return -EIO;
+}
+
+/*
+ * this is called from one of two situations.  We either
+ * have a full stripe from the higher layers, or we've read all
+ * the missing bits off disk.
+ *
+ * This will calculate the parity and then send down any
+ * changed blocks.
+ */
+static noinline void finish_rmw(struct btrfs_raid_bio *rbio)
+{
+	/* The total sector number inside the full stripe. */
+	/* Sector number inside a stripe. */
+	int sectornr;
+	struct bio_list bio_list;
+	struct bio *bio;
+	int ret;
+
+	bio_list_init(&bio_list);
+
+	/* We should have at least one data sector. */
+	ASSERT(bitmap_weight(&rbio->dbitmap, rbio->stripe_nsectors));
+
+	/* at this point we either have a full stripe,
+	 * or we've read the full stripe from the drive.
+	 * recalculate the parity and write the new results.
+	 *
+	 * We're not allowed to add any new bios to the
+	 * bio list here, anyone else that wants to
+	 * change this stripe needs to do their own rmw.
+	 */
+	spin_lock_irq(&rbio->bio_list_lock);
+	set_bit(RBIO_RMW_LOCKED_BIT, &rbio->flags);
+	spin_unlock_irq(&rbio->bio_list_lock);
+
+	atomic_set(&rbio->error, 0);
+
+	/*
+	 * now that we've set rmw_locked, run through the
+	 * bio list one last time and map the page pointers
+	 *
+	 * We don't cache full rbios because we're assuming
+	 * the higher layers are unlikely to use this area of
+	 * the disk again soon.  If they do use it again,
+	 * hopefully they will send another full bio.
+	 */
+	index_rbio_pages(rbio);
+	if (!rbio_is_full(rbio))
+		cache_rbio_pages(rbio);
+	else
+		clear_bit(RBIO_CACHE_READY_BIT, &rbio->flags);
+
+	for (sectornr = 0; sectornr < rbio->stripe_nsectors; sectornr++)
+		generate_pq_vertical(rbio, sectornr);
+
+	ret = rmw_assemble_write_bios(rbio, &bio_list);
+	if (ret < 0)
+		goto cleanup;
+
 	atomic_set(&rbio->stripes_pending, bio_list_size(&bio_list));
 	BUG_ON(atomic_read(&rbio->stripes_pending) == 0);