>>>>> Stefan Sperling <stsp_at_elego.de>:
> The script probably took a wrong guess.
> Hopefully this is the known corruption problem with a duplicate block of
> data in the revision file.
> Can you check if the original revision file (i.e. not modified by
> fsfsverify.py) somewhere contains a data block which contains data
> that matches the data around byte offset 1916?
"offset 1916", is that "byte number 1916 in the 683 ref file"?
Is that 1916 decimal, or hexadecimal? I'm assuming decimal for now.
> Usually the spot where the corruption appears (offset 1916 in your case)
> contains an incomplete representation, but the representation data in the
> duplicated block is good.
> One of way of locating the duplicate block is to open the file in a
> hex editor and search the entire file for hex strings that occur
> around or after 1916.
Ok, opening the file in emacs hexl mode:
`M-x hexl-find-file /tmp/svnrepo/svn/db/revs/0/683 RET'
> Try to locate boundaries of representations, which look as follows:
> A representation begins with a line containing either "PLAIN\n" or
> "DELTA\n" or "DELTA <rev> <offset> <length>\n", where <rev>, <offset>,
> and <length> give the location of the delta base of the representation
> and the amount of data it contains (not counting the header or
> trailer). If no base location is given for a delta, the base is the
> empty stream. After the initial line comes raw svndiff data, followed
> by a cosmetic trailer "ENDREP\n".
`M-j 1916 RET', takes me here:
00000770: 4e44 5245 500a 4445 4c54 410a 5356 4e01 NDREP.DELTA.SVN.
00000780: 0000 8c0c 823d 8431 823b 8140 4c00 8844 .....=.1.;._at_L..D
00000790: 4ca8 404e 0048 8100 bf45 820d 9945 820d L._at_N.H...E...E..
The cursor is positioned on the "5" starting "5356" in the first line,
and on the "S" of "SVN".
Does that make sense?
So I should search for "ENDREP.DELTA.SVN"? The 683 revfile contains 15
istances of that string, but I have no idea of which ones are relevant
> So if you find a duplicated block of data you should be able to fix this
> problem by copying representation data from the duplicate block to the
> corrupted location.
So what I'm looking for isn't exactly "ENDREP.DELTA.SVN", but what
follows this text...?
I tried searching for "x^.Rmo.@", but the one at the cursor is the only
occurrence in the file. At least the only aligned so that search will
find it. Doesn't look like hexl-mode has the possibility to search for
a byte sequence. Maybe I should get myself a proper hex editor?
> DO NOT change any byte offsets in the file while doing this. If you
> cannot squeeze the data in because it would overlap with subsequent
> data you're out of luck but I've never seen this happen. Usually
> there is enough room to fit the data, but you might have to add
> padding. Any dummy byte will do, I usually use 0x42.
The meaning of life, the universe and everything? I thought that was 42
> Another possibility is that offset 2247 is wrong. In this case the
> expected svndiff data is probably located elsewhere and the offset
> in the representation header should be adjusted.
Right... that's the first error that fsfsverify.py tries to fix?
`M-j 2247 RET' takes the cursor over the "7" in "5878" in the first
000008c0: 8550 8b57 8585 5978 5e1d 526d 6fda 400c .P.W..Yx^.Rmo.@.
000008d0: fe1c ff0a 17f8 00d5 12fa a27d 4145 2a90 ...........}AE*.
000008e0: 8466 0da4 2361 6353 2414 ee0e b871 89a3 .f..#acS$....q..
That wasn't as easily recognizable, as the 1916 one, though. Not as
recognizable as a boundary at least.
What are the things I should look for a duplicate of? The bytes
following the troublesome position? And how many?
> This is of course not an easy task and it is unfortunate that people
> keep running into this problem. The source of the problem is not yet
> known :( If you have any further questions just ask. If you cannot
> get it fixed at all but can share the revision file privately I will
> have a go at it.
I think I need help with this one. I'll send you the revision file
Received on 2011-05-14 19:54:57 CEST