v4.19.13 snapshot.
diff --git a/fs/btrfs/raid56.h b/fs/btrfs/raid56.h
new file mode 100644
index 0000000..f5d4c13
--- /dev/null
+++ b/fs/btrfs/raid56.h
@@ -0,0 +1,57 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2012 Fusion-io All rights reserved.
+ * Copyright (C) 2012 Intel Corp. All rights reserved.
+ */
+
+#ifndef BTRFS_RAID56_H
+#define BTRFS_RAID56_H
+
+static inline int nr_parity_stripes(struct map_lookup *map)
+{
+ if (map->type & BTRFS_BLOCK_GROUP_RAID5)
+ return 1;
+ else if (map->type & BTRFS_BLOCK_GROUP_RAID6)
+ return 2;
+ else
+ return 0;
+}
+
+static inline int nr_data_stripes(struct map_lookup *map)
+{
+ return map->num_stripes - nr_parity_stripes(map);
+}
+#define RAID5_P_STRIPE ((u64)-2)
+#define RAID6_Q_STRIPE ((u64)-1)
+
+#define is_parity_stripe(x) (((x) == RAID5_P_STRIPE) || \
+ ((x) == RAID6_Q_STRIPE))
+
+struct btrfs_raid_bio;
+struct btrfs_device;
+
+int raid56_parity_recover(struct btrfs_fs_info *fs_info, struct bio *bio,
+ struct btrfs_bio *bbio, u64 stripe_len,
+ int mirror_num, int generic_io);
+int raid56_parity_write(struct btrfs_fs_info *fs_info, struct bio *bio,
+ struct btrfs_bio *bbio, u64 stripe_len);
+
+void raid56_add_scrub_pages(struct btrfs_raid_bio *rbio, struct page *page,
+ u64 logical);
+
+struct btrfs_raid_bio *
+raid56_parity_alloc_scrub_rbio(struct btrfs_fs_info *fs_info, struct bio *bio,
+ struct btrfs_bio *bbio, u64 stripe_len,
+ struct btrfs_device *scrub_dev,
+ unsigned long *dbitmap, int stripe_nsectors);
+void raid56_parity_submit_scrub_rbio(struct btrfs_raid_bio *rbio);
+
+struct btrfs_raid_bio *
+raid56_alloc_missing_rbio(struct btrfs_fs_info *fs_info, struct bio *bio,
+ struct btrfs_bio *bbio, u64 length);
+void raid56_submit_missing_rbio(struct btrfs_raid_bio *rbio);
+
+int btrfs_alloc_stripe_hash_table(struct btrfs_fs_info *info);
+void btrfs_free_stripe_hash_table(struct btrfs_fs_info *info);
+
+#endif