Re: Fix object re-hashing

From: Junio C Hamano <junkio@cox.net>
Date: Feb 12, 2006, 18:32 UTC
Message-ID: <7vaccwbf6v.fsf@assigned-by-dhcp.cox.net>
In-Reply-To: <Pine.LNX.4.64.0602121006360.3691@g5.osdl.org>

Linus Torvalds <torvalds@osdl.org> writes:

Show 16 quoted lines

> On Sun, 12 Feb 2006, Linus Torvalds wrote:
>> 
>> I actually didn't see any of this trigger in real life, so maybe my 
>> analysis is wrong. Junio? Johannes?
>
> Btw, if it does trigger, the behaviour would be that a subsequent object 
> lookup will fail, because the last old slot would be NULL, and a few 
> entries following it (likely just a couple - never mind that the event 
> triggering in the first place is probably fairly rare) wouldn't have 
> gotten re-hashed down.
>
> As a result, we'd allocate a new object, and have _two_ "struct object"s 
> that describe the same real object. I don't know what would get upset, but 
> git-fsck-index certainly would be (one of them would likely be marked 
> unreachable, because lookup wouldn't find it, but you might have other 
> issues too).

This "fix" makes the symptom that me fire two (maybe three) Grrrrr messages earlier this morning disappear. I haven't had my caffeine nor nicotine yet after my short sleep, so I need to take some time understanding your explanation first, but I am reasonably sure this must be it (not that I do not trust you, not at all -- it is that I do not trust *me* applying a patch without understanding when I have a bug reproducible).

Thanks.