From bd2336b2ac119e65457261528883d9623d41315f Mon Sep 17 00:00:00 2001 From: Nikolay Borisov Date: Tue, 15 Oct 2019 18:42:19 +0300 Subject: [PATCH] btrfs: Add read_backup_root This function will replace next_root_backup with a much saner/cleaner interface. Signed-off-by: Nikolay Borisov Reviewed-by: David Sterba Signed-off-by: David Sterba --- 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 1834ff4fabee..4d061facb416 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -1928,6 +1928,50 @@ 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; + backup_index %= 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