Maybe the subject line should say "Implemented", because these never
worked in the first place. Unfortunately our tests missed this due to a
couple reasons:
- Mroot chains are difficult to create due to the required exponential
growth.
- The only thing that actually commits to chain mroots is mdir
compaction. Though this functionality will be useful for future block
eviction/error correction.
- Previous revision count issues were making relocations in our
compaction tests unlikely.
Fortunately, now that revision count behavior is more correct, our tests
are correctly highlighting that this is broken.
---
Implementing chain mroot commits was a bit intimidating, but fortunately
it just required a bit of teasing to get lfs3_mdir_commit_ to trigger
the tail-recursive mroot chain update when the mdir is a non-active
mroot.
The gcksum is also doing a great job here with identifying bugs. Without
it this bug would have been difficult to notice, since compactions
otherwise have no observable effect on the system.
Code changes:
code stack ctx
before: 35164 2136 660
after: 35224 (+0.2%) 2136 (+0.0%) 660 (+0.0%)
code stack ctx
gbmap before: 38400 2144 776
gbmap after: 38464 (+0.2%) 2144 (+0.0%) 776 (+0.0%)
code stack ctx
preerase before: 38940 2168 796
preerase after: 39008 (+0.2%) 2168 (+0.0%) 796 (+0.0%)
Christopher Haster
5fb3600d90