Data recovery (undeleting/salvaging files) - Githubissues

t-w / ADFlib

A free, portable and open implementation of the Amiga filesystem

GNU General Public License v2.0

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Data recovery (undeleting/salvaging files) #9

Open t-w opened 3 months ago

t-w commented 3 months ago

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)

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)