linux-kernel - Re: rename() contention (BUG?)

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Date:	Thu, 26 Oct 2006 23:19:56 +0200
From:	Avi Kivity <avi@...o.co.il>
To:	Al Viro <viro@....linux.org.uk>
CC:	Josef Sipek <jsipek@....cs.sunysb.edu>, lkml@...garu.com,
	linux-kernel@...r.kernel.org
Subject: Re: rename() contention (BUG?)

Al Viro wrote:
> On Thu, Oct 26, 2006 at 08:43:34PM +0200, Avi Kivity wrote:
>   
>> The changes make the mutex more efficient, but won't decrease the 
>> contention.  It seems that all renames in one filesystem are serialized, 
>> and if the renames require I/O (which is certainly the case with nfs), 
>> rename throughput is severely limited.
>>     
>
> 	They are, and for a good reason.  For details see
> Documentation/filesystems/directory-locking.
>   

Is it possible to lock only the common subtree of the two paths?

Perhaps walk towards the root of the tree, starting with the deeper 
path, locking one component at a time.  Then walk both paths together 
locking components ordered by something to avoid deadlock.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

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