linux-kernel - Re: [patch 29/52] fs: icache lock i

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Message-ID: <20100630072702.GF24712@dastard>
Date:	Wed, 30 Jun 2010 17:27:02 +1000
From:	Dave Chinner <david@...morbit.com>
To:	npiggin@...e.de
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	John Stultz <johnstul@...ibm.com>,
	Frank Mayhar <fmayhar@...gle.com>
Subject: Re: [patch 29/52] fs: icache lock i_count

On Thu, Jun 24, 2010 at 01:02:41PM +1000, npiggin@...e.de wrote:
> Protect inode->i_count with i_lock, rather than having it atomic.
> Next step should also be to move things together (eg. the refcount increment
> into d_instantiate, which will remove a lock/unlock cycle on i_lock).
.....
> Index: linux-2.6/fs/inode.c
> ===================================================================
> --- linux-2.6.orig/fs/inode.c
> +++ linux-2.6/fs/inode.c
> @@ -33,14 +33,13 @@
>   * inode_hash_lock protects:
>   *   inode hash table, i_hash
>   * inode->i_lock protects:
> - *   i_state
> + *   i_state, i_count
>   *
>   * Ordering:
>   * inode_lock
>   *   sb_inode_list_lock
>   *     inode->i_lock
> - * inode_lock
> - *   inode_hash_lock
> + *       inode_hash_lock
>   */

I thought that the rule governing the use of inode->i_lock was that
it can be used anywhere as long as it is the innermost lock.

Hmmm, no references in the code or documentation. Google gives a
pretty good reference:

http://www.mail-archive.com/linux-ext4@vger.kernel.org/msg02584.html

Perhaps a different/new lock needs to be used here?

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com
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