Re: [PATCH 5/6] Teach "fsck" not to follow subproject links

From: David Lang <david.lang@digitalinsight.com>
Date: Apr 11, 2007, 23:30 UTC
Message-ID: <Pine.LNX.4.63.0704111628240.28394@qynat.qvtvafvgr.pbz>
In-Reply-To: <Pine.LNX.4.64.0704111646000.6730@woody.linux-foundation.org>

On Wed, 11 Apr 2007, Linus Torvalds wrote:

Show 15 quoted lines

> On Wed, 11 Apr 2007, David Lang wrote:
>>
>> would it make sense to have a --multiple-project option for fsck that would
>> let you specify multiple 'projects' that share a object set and have the
>> default checking not do the reachability checks that cause problems in this
>> case?
>
> Well, the thing is, sharing object directories actually makes things
> *harder* to check, rather than easier.
>
> It can be a nice space optimization, and yes, if there really is a lot of
> shared state, it can make it much cheaper to do some of the checks, but
> right now we have absolutely *no* way for fsck to then do the reachability
> check, because there is no way to tell fsck where all the refs are (since
> now the refs come in from multiple repositories!)

this is why I was suggesting a --multiple-project option to let you tell fsck about all of the repositories that it needs to look for refs in.

> So the individual objects get cheaper to fsck (no need to fsck shared
> objects over and over again), but the reachability gets much harder to
> fsck.

agreed.

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> It's not an insurmountable problem, or even necessarily a very large one,
> but it boils down to one very basic issue:
>
> - nobody seems to actually *use* the shared object directory model!
>
> The thing is, with pack-files and alternates directories, a lot of the
> original reasons for shared object directories simply don't exist..

I suspect that if it coudl be checked it would be used more, especially with the subproject support.

David Lang