Re: [jira] [Commented] (SVN-4858) FSFS corruption - Found malformed header - Corrupt node-revision

Julian Foad (Jira) wrote on Mon, 01 Jun 2020 11:20 +0000:
> Two clues strongly suggest the corruption was originally caused by a bug rather than hardware corruption:
> * the checksum on the node-revision must account for the corrupted data, otherwise a checksum error is thrown instead;

_Which_ checksum? Do you mean the checksum of the directory
representation wherein the dangling (off-by-four) pointer was found?

> * although an off-by-4 can sometimes be a 1-bit error, this particular one (41271 vs. 41275) is not a 1-bit error.

Is there any chance that this _was_ originally a 1-bit error and then
some offset got added/subtracted to both the id in the noderev header
and the id in the directory rep?

> I do not know which revision contains the bad reference nor what version of svn committed it.

Was CONFIG_OPTION_VERIFY_BEFORE_COMMIT enabled at the time the revision
containing the dangling pointer was committed? (You may be able to
answer this even without running grep -aR to find the dangling pointer.)

>

It's curious that the wrong offset points directly to the value of the
first field. However, having glanced at svn_fs_fs__write_noderev(),
I guess that's just a coincidence.

Assuming the node-rev headers _are_ synthesized by svn_fs_fs__write_noderev()
in this user's environment, that is.
Received on 2020-06-01 15:31:43 CEST