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btrfs: Add read_backup_root 

This function will replace next_root_backup with a much saner/cleaner
interface.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Nikolay Borisov 2019-10-15 18:42:19 +03:00 committed by David Sterba
parent fc2e4c5b35
commit bd2336b2ac
1 changed files with 44 additions and 0 deletions
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44
fs/btrfs/disk-io.c
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@ -1928,6 +1928,50 @@ static void backup_super_roots(struct btrfs_fs_info *info)
sizeof(*root_backup) * BTRFS_NUM_BACKUP_ROOTS); 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 * this copies info out of the root backup array and back into
* the in-memory super block. It is meant to help iterate through * the in-memory super block. It is meant to help iterate through