This function will replace next_root_backup with a much saner/cleaner
interface.
---
fs/btrfs/disk-io.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 44 insertions(+)
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index d51f76abde45..9ed3b40aa10d 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1899,6 +1899,50 @@ static void backup_super_roots(struct btrfs_fs_info
*info)
sizeof(*root_backup) * BTRFS_NUM_BACKUP_ROOTS);
}
+/*
+ * read_backup_root - Reads a backup root based on the passed priority. Prio 0
+ * is the newest, prio 1/2/3 are 2nd newest/3rd newest/4th (oldest) backup
roots
+ *
+ * fs_info - filesystem whose backup roots need to be read
+ * priority - priority of backup root required
+ *
+ * Returns backup root index on success and -EINVAL otherwise.
+ */
+static int read_backup_root(struct btrfs_fs_info *fs_info, u8 priority)
+{
+ int backup_index = find_newest_super_backup(fs_info);
+ struct btrfs_super_block *super = fs_info->super_copy;
+ struct btrfs_root_backup *root_backup;
+
+ if (priority < BTRFS_NUM_BACKUP_ROOTS && backup_index >= 0) {
+ if (priority == 0)
+ return backup_index;
+
+ backup_index = (backup_index + BTRFS_NUM_BACKUP_ROOTS -
priority) %
+ BTRFS_NUM_BACKUP_ROOTS;
+ } else {
+ return -EINVAL;
+ }
+
+ root_backup = super->super_roots + backup_index;
+
+ btrfs_set_super_generation(super,
+ btrfs_backup_tree_root_gen(root_backup));
+ btrfs_set_super_root(super, btrfs_backup_tree_root(root_backup));
+ btrfs_set_super_root_level(super,
+ btrfs_backup_tree_root_level(root_backup));
+ btrfs_set_super_bytes_used(super, btrfs_backup_bytes_used(root_backup));
+
+ /*
+ * fixme: the total bytes and num_devices need to match or we should
+ * need a fsck
+ */
+ btrfs_set_super_total_bytes(super,
btrfs_backup_total_bytes(root_backup));
+ btrfs_set_super_num_devices(super,
btrfs_backup_num_devices(root_backup));
+
+ return backup_index;
+}
+
/*
* this copies info out of the root backup array and back into
* the in-memory super block. It is meant to help iterate through
--
2.17.1
