Re: "failed to read delta base object at..."

On Mon, Aug 25, 2008 at 04:59:26PM -0700, Linus Torvalds wrote:

and the difference literally seems to be just a block of less than 160 
bytes. But it's certainly not a single-bit error, and it's also not a disk 
block or anything like that.

Looking at the first line that differs, they are:

	-0003460 a0 14 8d 7d cd 12 75 81 2b c4 d9 71 27 62 ae b5
	+0003460 a0 14 8d 7d 22 00 00 00 6b 57 fe ff 55 57 fe ff

so the differences start at offset 03464. The last line is:

	-0003700 47 f7 9b 3d b6 a5 99 5a cf 49 ef e0 3f 54 08 f4
	+0003700 ae 41 49 50 aa 40 fe ff cf 49 ef e0 3f 54 08 f4

so they re-join at 03708 (octal offsets because of 'od' behavior).  But in 
between there seems to be nothing in common.

So the corrupt data looks like

                            22 00 00 00 6b 57 fe ff 55 57 fe ff
        0003500 aa 57 fe ff b0 00 0e 00 d9 66 22 00 00 00 00 e0
        0003520 19 9f fe ff ff ff d1 43 fe ff d1 43 fe ff 00 c0
        0003540 bf fe f0 33 69 bf b2 33 69 bf 00 00 00 10 01 fe
        0003560 bf fe 66 01 00 00 01 1f 37 17 2e 59 fe ff 00 00
        0003600 00 00 c2 41 fe ff 00 00 01 1f 37 17 44 42 fe ff
        0003620 00 01 fe ff 01 1f 37 07 d4 42 fe ff 02 01 a8 44
        0003640 00 f8 bf fe 6b 57 fe ff 55 57 fe ff 97 57 fe ff
        0003660 00 f8 bf fe 04 00 fe ff ab 45 fe ff 02 00 fe ff
        0003700 ae 41 49 50 aa 40 fe ff 

and I don't see what the patern is, except that there's a lot of "fe ff" 
in there.

and all aligned on 2-byte boundaries?  I don't see anything suggestive
there either.

148 bytes, no obvious source. It definitely does _not_ look like 
compressed input (it's too regular to be something zlib spits out), nor is 
it text. Nor is it valid x86 assembly, so it's not some code-segment data 
either.

And as far as I can tell, that's the _only_ corruption in the whole file, 
but I didn't really double-check.

Does anybody see a pattern?

Got me.  Thanks for taking a look at it.

--b.