The StorageError -> DiskError conversion dropped seven variants with
exact DiskError counterparts (FaultyRemoteDisk, DiskAccessDenied,
DriveIsRoot, IsNotRegular, VolumeNotEmpty, VolumeAccessDenied,
FileAccessDenied) into the DiskError::other fallback, degrading them to
an opaque Io error. Two of them sit on the quorum ignore-lists in
disk/error_reduce.rs, so a degraded instance would stop matching the
ignore list and count toward the dominant error in reduce_errs.
Also mirror the StorageError-side io::Error downdrill in
From<io::Error> for DiskError: recover a StorageError boxed through
From<StorageError> for io::Error instead of wrapping it as Io.
Add a round-trip identity test over every DiskError variant
(DiskError -> StorageError -> DiskError) and a boxed-StorageError
recovery test.
Zhengchao An
698ebdfb3f