Re: bug: git-repack -a -d produces broken pack on NFS

From: Linus Torvalds <torvalds@osdl.org>
Date: Apr 27, 2006, 22:29 UTC
Message-ID: <Pine.LNX.4.64.0604271526140.3701@g5.osdl.org>
In-Reply-To: <7v4q0ek6i3.fsf@assigned-by-dhcp.cox.net>

On Thu, 27 Apr 2006, Junio C Hamano wrote:

Show 11 quoted lines

> Linus Torvalds <torvalds@osdl.org> writes:
> 
> > That said, the pack-file should all be written with the "sha1write()" 
> > interface, which is very careful indeed.
> >
> > I wonder if the _pack-file_ itself might be ok, and the problem is an 
> > index file corruption. For some reason we check the index file first, 
> > which is insane. We should check that the pack-file matches its _own_ SHA1 
> > first, and check the index file second.
> 
> We need to check both, so I fail to see why the order matters.

It's insane to do any _cross_-file checking before you've even verified that the files themselves are valid.

Another way of saying the same thing: checking whether the SHA1 of the pack-file matches the index file is pointless before you've verified that the SHA1 itself is valid.

Basically, if the pack-file is corrupt, you want to know that. You don't want to know that it's SHA1 doesn't match the index file - that's a "secondary" issue to the fact that the SHA1 wasn't correct in the first place.

Right now, if the pack-file is corrupt, it doesn't actually tell us so. It says that it doesn't match the index file. Which is likely wrong - it probably _does_ match the index file, but it's been corrupted.

See the difference?

			Linus