The new '-b' option will be responsible for converting to block group
tree compat ro feature.
The workflow looks like this for new convert:
- Setting CHANGING_BG_TREE flag
And initialize fs_info->last_converted_bg_bytenr value to (u64)-1.
Any bg with bytenr >= last_converted_bg_bytenr will have its bg item
update go to the new root (bg tree).
- Iterate each block group by their bytenr in descending order
This involves:
* Delete the old bg item from the old tree (extent tree)
* Update last_converted_bg_bytenr to the bytenr of the bg
* Add the new bg item into the new tree (bg tree)
* If we have converted a bunch of bgs, commit current transaction
- Clear CHANGING_BG_TREE flag
And set the new BLOCK_GROUP_TREE compat ro flag and commit.
And since we're doing the convert in multiple transactions, we also need
to resume from last interrupted convert.
In that case, we just grab the last unconverted bg, and start from it.
And to co-operate with the new kernel requirement for both no-holes and
free-space-tree features, the convert tool will check for
free-space-tree feature. If not enabled, will error out with an error
message to how to continue (by mounting with "-o space_cache=v2").
For missing no-holes feature, we just need to set the flag during
convert.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Qu Wenruo
David Sterba