Added wear-leveling litmus tests, test_relocations_wl_*
These tests provide a litmus test for if wear-leveling is working:
- test_relocations_wl_dir_fuzz
- test_relocations_wl_file_fuzz
- test_relocations_wl_orphanzombie_fuzz
- test_relocations_wl_orphanzombiedir_fuzz
We can't test the uniformity of wear, because we only implement static
wear-leveling, but what we can test is that doubling the size of storage
results in roughly doubling the lifetime of the storage.
I did try to implement some wear-leveling tests under powerloss, this
has some promise storing the current run/state on disk, but gave up
after realizing the way our linear powerloss heuristic works would
interfere with the assumption that both runs run in identical
environments...
---
Suprisingly enough, all of this fuzz testing did find another bug! We
were returning LFS_ERR_CORRUPT instead of LFS_ERR_NOSPC if
overcompaction failed to erase/prog the revision count. This is very
hard to hit, only being reachable if a block goes bad on the same erase
cycle an mdir's recycle counter overflows, and if there are no more
blocks in our filesystem, triggering overcompaction.
Difficult to hit bug, but easy fix. Just a tiny bit of extra code:
code stack
before: 33550 2624
after: 33566 2624
I guess these wear-leveling tests are also doubling as aggressive
LFS_ERR_NOSPC exhaustion tests...
This commit is contained in:
Christopher Haster