Data recovery (undeleting/salvaging files)

[t-w]

State and some notes what is still left to do.

• adf_salv.c module plus some tests in regtests/ already existed
• adf_salvage command-line prototype was recently added

In general - after some corrections, simple cases (no lost/overwritten blocks) seem to work.

There are however special cases, that may require a lot more for proper data recovery:

• corrupted / overwritten file ext. blocks
  • can be circumvented on OFS (using metadata from data blocks)
• partial reconstruction if some data blocks were overwritten
• reconstruction of files without or with corrupted file header block (probably possible only on OFS, with part of metadata duplicated in data blocks)

(these might be done later)

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There are also few more error cases where it is not sure how to treat it:

• adfUndelFile in the last part of file recovery does:

 if ( adfCreateEntry(vol, &parent, name, entry->headerKey) == -1 ) {
        rc = ADF_RC_ERROR;
        goto adfUndelFile_error_set_blocks_free;
    }
    if ( adfVolHasDIRCACHE ( vol ) ) {
        rc = adfAddInCache ( vol, &parent, (struct AdfEntryBlock *) entry );
        if ( rc != ADF_RC_OK )
            goto adfUndelFile_error_set_blocks_free;
    }

Basically, it is not quite clear what to do (or what is better to do) if adfAddInCache fails:

1. revert all changes, leaving filesystem unchanged
   • this requires reversing adfCreateEntry - it is not clear how to do it (adfRemoveEntry?)
2. if dir. cache is not critical and is updated later by the OS (this is to check/confirm), it might be reasonable not to fail in such case (maybe just issue a warning)