forked from Imagelibrary/littlefs
eba5553314
This happens in rare situations where there is a failed mdir relocation, interrupted by a power-loss, containing the destination of a directory rename operation, where the directory being renamed preceded the relocating mdir in the mdir tail-list. This requires at some point for a previous directory rename to create a cycle. If this happens, it's possible for the half-orphan to contain the only reference to the renamed directory. Since half-orphans contain outdated state when viewed through the mdir tail-list, the renamed directory appears to be a full-orphan until we fix the relocating half-orphan. This causes littlefs to incorrectly remove the renamed directory from the mdir tail-list, causes catastrophic problems down the line. The source of the problem is that the two different types of orphans really operate on two different levels of abstraction: half-orphans fix failed mdir commits, while full-orphans fix directory removes/renames. Conflating the two leads to situations where we attempt to fix assumed problems about the directory tree before we have fixed problems with the mdir state. The fix here is to separate out the deorphan search into two passes: one to fix half-orphans and correct any mdir-commits, restoring the mdirs and gstate to a known good state, then two to fix failed removes/renames. --- This was found with the -Plinear heuristic powerloss testing, which now runs on more geometries. The failing case was: test_relocations_reentrant_renames:112gg261dk1e3f3:123456789abcdefg1h1i1j1k1 l1m1n1o1p1q1r1s1t1u1v1g2h2i2j2k2l2m2n2o2p2q2r2s2t2 Also fixed/tweaked some parts of the test framework as a part of finding this bug: - Fixed off-by-one in exhaustive powerloss state encoding. - Added --gdb-powerloss-before and --gdb-powerloss-after to help debug state changes through a failing powerloss, maybe this should be expanded to any arbitrary powerloss number in the future. - Added lfs_emubd_crc and lfs_emubd_bdcrc to get block/bd crcs for quick state comparisons while debugging. - Fixed bd read/prog/erase counts not being copied during exhaustive powerloss testing. - Fixed small typo in lfs_emubd trace.