Btrfs: superblock duplication

This patch implements superblock duplication. Superblocks
are stored at offset 16K, 64M and 256G on every devices.
Spaces used by superblocks are preserved by the allocator,
which uses a reverse mapping function to find the logical
addresses that correspond to superblocks. Thank you,

Signed-off-by: Yan Zheng <zheng.yan@oracle.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index fcbdcb3ae13e..bdebe83c3195 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -28,7 +28,6 @@ struct btrfs_device {
         struct list_head dev_alloc_list;
         struct btrfs_fs_devices *fs_devices;
         struct btrfs_root *dev_root;
-        struct buffer_head *pending_io;
         struct bio *pending_bios;
         struct bio *pending_bio_tail;
         int running_pending;
@@ -125,7 +124,10 @@ int btrfs_alloc_dev_extent(struct btrfs_trans_handle *trans,
 int btrfs_map_block(struct btrfs_mapping_tree *map_tree, int rw,
                     u64 logical, u64 *length,
                     struct btrfs_multi_bio **multi_ret, int mirror_num);
-int btrfs_read_sys_array(struct btrfs_root *root);
+int btrfs_rmap_block(struct btrfs_mapping_tree *map_tree,
+                     u64 chunk_start, u64 physical, u64 devid,
+                     u64 **logical, int *naddrs, int *stripe_len);
+int btrfs_read_sys_array(struct btrfs_root *root, u64 sb_bytenr);
 int btrfs_read_chunk_tree(struct btrfs_root *root);
 int btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
                       struct btrfs_root *extent_root, u64 type);