lfs_fs_gc is still not reimplemented, but this is accessible through the
traversal API with LFS_T_COMPACT.
This is also the first traversal operation that can mutate the
filesystem, which brings its own set of problems:
- We need to set LFS_F_DIRTY in lfsr_mtree_gc now, which really
highlights how much of a mess having two flag fields is...
We do _not_ clobber in this case, since we assume lfsr_mtree_gc knows
what it's doing.
- We can now commit to an mroot in the mroot chain outside of the normal
mroot chain update logic.
This is a bit scary, but should just work.
The only issue so far is that we need to allow mdirs to follow the
mroot during mroot splits if mid=-1, even if they aren't lfs_t's mroot
mdir.
This should now be decently tested with the new
test_traversal_compact_* tests.
- It's easy for mtraversal's mdir and mtinfo's mdir to fall out of sync
when mutating... Why do we have two of these?
The actual compaction itself is pretty straightforward: just mark as
unerased, eoff=-1, and call lfsr_mdir_commit with an empty commit. This
is now wrapped up in lfsr_mdir_compact.
Code changes:
code stack
before: 34528 2640
after: 34652 (+0.4%) 2640 (+0.0%)
Though the real hard part will be implementing gc_compact_thresh over
btree nodes...
Christopher Haster
4d06fc2e0e