linux-kernel - Re: [PATCH] Increase lockdep MAX_LOCK

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Date:	Fri, 31 Aug 2007 08:39:49 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Eric Sandeen <sandeen@...deen.net>
Cc:	linux-kernel Mailing List <linux-kernel@...r.kernel.org>,
	xfs-oss <xfs@....sgi.com>, Dave Chinner <dgc@....com>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH] Increase lockdep MAX_LOCK_DEPTH

On Thu, 2007-08-30 at 23:43 -0500, Eric Sandeen wrote:
> The xfs filesystem can exceed the current lockdep 
> MAX_LOCK_DEPTH, because when deleting an entire cluster of inodes,
> they all get locked in xfs_ifree_cluster().  The normal cluster
> size is 8192 bytes, and with the default (and minimum) inode size 
> of 256 bytes, that's up to 32 inodes that get locked.  Throw in a 
> few other locks along the way, and 40 seems enough to get me through
> all the tests in the xfsqa suite on 4k blocks.  (block sizes
> above 8K will still exceed this though, I think)

As 40 will still not be enough for people with larger block sizes, this
does not seems like a solid solution. Could XFS possibly batch in
smaller (fixed sized) chunks, or does that have significant down sides?

> Signed-off-by: Eric Sandeen <sandeen@...deen.net>
> 
> Index: linux-2.6.23-rc3/include/linux/sched.h
> ===================================================================
> --- linux-2.6.23-rc3.orig/include/linux/sched.h
> +++ linux-2.6.23-rc3/include/linux/sched.h
> @@ -1125,7 +1125,7 @@ struct task_struct {
>  	int softirq_context;
>  #endif
>  #ifdef CONFIG_LOCKDEP
> -# define MAX_LOCK_DEPTH 30UL
> +# define MAX_LOCK_DEPTH 40UL
>  	u64 curr_chain_key;
>  	int lockdep_depth;
>  	struct held_lock held_locks[MAX_LOCK_DEPTH];
> 
> -
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