[Lustre-discuss] renamed directory retains a dentry under its old name?

Phil Schwan phils at dugeo.com
Sun Nov 22 01:24:27 PST 2009


Hello, my good man!

2009/11/20 Oleg Drokin <Oleg.Drokin at sun.com>

>
> Yes, I think this does match bug 2969 behavior.
> We add entry to dcache without lock (not visible in the trace you
> provided). Then we do rename, then we do some sort of stat on a renamed
> entry and reobtain the lock. Then we do stat on old name, and since lock is
> on inode - we find the newly reinstantiated lock and declare
> old dentry as valid.
>

Hmm.  My first instinct was that there shouldn't be dentries without locks,
but it's been sufficiently long that I can't remember all the details of the
dentry life cycle.  What you wrote certainly sounds like a plausible
explanation.


> I wonder if my patch for 20323 would have helped this case
> (or have just always returning the lock), though on the other hand this
> is inode from mkdir and so might have never go through open path.
> Bug 16417 is what landed into 1.8.2 and is a complete rework of
> dcache caching logic for dentries and has a better chance of fixing this,
> I would say.
> If not, it would be great if the lock will start earlier in time,
> definitely
> before rename happens.
>
> I hope this problem did not ruin your day in the end.
>

No, no, it's fairly minor for us.  I just wanted to report it in case we
were the first to experience it.  We will probably upgrade at some point,
but we had a less-than-perfect experience with an upgrade this year, so I
imagine Stu will wait until it's really necessary.

Thanks for looking into it.  From skimming 16417, I agree that it stands a
good chance of fixing it, or at least permutes the system sufficiently that
it'd be worth trying to reproduce it again after an upgrade.

 And we do miss you. Does your coming with such a question means you are on
> your way back to us? ;)
>

You all seem to be doing just fine without me. :)  We certainly make intense
use of Lustre in our unending quest to find dinosaur blood, and it serves us
very well.

Cheers,

-p
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