Read the comment above ext4_list_backups right above:
https://github.com/torvalds/linux/blob/d158fc7f36a25e19791d2...
/*
* Iterate through the groups which hold BACKUP superblock/GDT copies in an
* ext4 filesystem. The counters should be initialized to 1, 5, and 7 before
* calling this for the first time. In a sparse filesystem it will be the
* sequence of powers of 3, 5, and 7: 1, 3, 5, 7, 9, 25, 27, 49, 81, ...
* For a non-sparse filesystem it will be every group: 1, 2, 3, 4, ...
*/
I'm not sure what's so noteworthy about that. There's ton of arcane code in any kernel, as long as it's commented correctly there's no issue.
https://github.com/torvalds/linux/blob/d158fc7f36a25e19791d2...
I'm not sure what's so noteworthy about that. There's ton of arcane code in any kernel, as long as it's commented correctly there's no issue.