Re: git bugs

From: Ben Lynn <benlynn@gmail.com>
Date: Jun 11, 2008, 02:31 UTC
Message-ID: <832adb090806101931y754fa6b7nfcb58a9c34f0c582@mail.gmail.com>
In-Reply-To: <alpine.LFD.1.10.0806101909430.3101@woody.linux-foundation.org>

Ah, I hadn't seen that. Yes, it is better to use the first write as the timestamp. Would this catch everything? If the filesystem clock is monotonically increasing and consistent then with this setup, you can touch files even as they are being indexed? (Disregarding nonsense like changing sizes by 2^32.)

Just realized I should have paid more attention to Junio's first reply to me. My eye had skipped over the paragraph about clock skew, and this caused some confusion. Sorry about all my extra emails!

-Ben

On Tue, Jun 10, 2008 at 7:12 PM, Linus Torvalds <torvalds@linux-foundation.org> wrote:

Show 26 quoted lines

>
>
> On Tue, 10 Jun 2008, Ben Lynn wrote:
>>
>> Sorry, but if we're assuming no one is touching the files while we're
>> updating the index (including writing it to disk), why does it matter
>> whether we use the time of first or last write? In fact, if a index
>> write takes a long time, using the last write time as the mtime would
>> be beneficial for the race condition stuff.
>
> Oh, if you assume nobody is touching the files as the index is created,
> none of this matters.
>
> So if *that* was your only race worry, then git should already be
> perfectly fine.
>
> The issue with the timestamp of the index only happens if somebody ends up
> modifying the files that are being indexed _as_ they are indexed. Quite
> frankly, git will notice that too in just about all possible cases, but if
> the size stays the same and the modification time ends up still being
> smaller than the final index mtime (because writing the index took so
> long!), then you might miss some modifications that would otherwise be
> noticed.
>
>                Linus
>