Re: [PATCH 0/7] btrfs-progs: tune: add resume support for csum conversion

[Anand Jain <anand.jain@oracle.com>]

Why not use the generation numbers "From" and "To" for converting
to the new checksum and keeping track of the generation number of
the most recent successful conversion?

Thanks, Anand


On 24/05/2023 15:41, Qu Wenruo wrote:
> [RESUME SUPPORT]
> This patchset adds the resume support for "btrfstune --csum".
> 
> The main part is in resume for data csum change, as we have 4 different
> status during data csum conversion.
> 
> Thankfully for data csum conversion, everything is protected by
> metadata COW and we can detect the current status by the existence of
> both old and new csum items, and their coverage.
> 
> For resume of metadata conversion, there is nothing we can really do but
> go through all the tree blocks and verify them against both new and old
> csum type.
> 
> [TESTING]
> For the tests, currently errors are injected after every possible
> transaction commit, and then resume from that interrupted status.
> So far the patchset passes all above tests.
> 
> But I'm not sure what's the better way to craft the test case.
> 
> Should we go log-writes? Or use pre-built images?
> 
> [TODO]
> - Test cases for resume
> 
> - Support for revert if errors are found
>    If we hit data csum mismatch and can not repair from any copy, then
>    we should revert back to the old csum.
> 
> - Support for pre-cautious metadata check
>    We'd better read and very metadata before rewriting them.
> 
> - Performance tuning
>    We want to take a balance between too frequent commit transaction
>    and too large transaction.
>    This is especially true for data csum objectid change and maybe
>    old data csum deletion.
> 
> - UI enhancement
>    A btrfs-convert like UI would be better.
> 
> 
> Qu Wenruo (7):
>    btrfs-progs: tune: implement resume support for metadata checksum
>    btrfs-progs: tune: implement resume support for generating new data
>      csum
>    btrfs-progs: tune: implement resume support for csum tree without any
>      new csum item
>    btrfs-progs: tune: implement resume support for empty csum tree
>    btrfs-progs: tune: implement resume support for half deleted old csums
>    btrfs-progs: tune: implement resume support for data csum objectid
>      change
>    btrfs-progs: tune: reject csum change if the fs is already using the
>      target csum type
> 
>   tune/change-csum.c | 461 ++++++++++++++++++++++++++++++++++++++++-----
>   1 file changed, 418 insertions(+), 43 deletions(-)
>