From: Mingming Cao <cmm@us.ibm.com>
Subject: Re: [RFC][Patch 1/2] Persistent preallocation in ext4
Date: Tue, 02 Jan 2007 14:47:32 -0800
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Cc: linux-ext4@vger.kernel.org, suparna@in.ibm.com, suzuki@in.ibm.com,
	alex@clusterfs.com
To: "Amit K. Arora" <aarora@linux.vnet.ibm.com>
In-Reply-To: <20070102110409.GB5932@amitarora.in.ibm.com>
Sender: linux-ext4-owner@vger.kernel.org

On Tue, 2007-01-02 at 16:34 +0530, Amit K. Arora wrote:
> Hi Mingming,
> > And, Looking at other places calling ext4_*_get_blocks() in the kernel,
> > it seems not all of them protected by i_mutex lock. I think it probably
> > okay to not holding i_mutex during calling ext4_ext4_get_blocks().
> 
> We are not holding i_mutex lock during ext4_ext_get_blocks() call.
> Above, this lock is being held inorder to avoid race while updating the
> filesize in inode (reference your comment in a previous mail "I think we
> should update i_size and i_disksize after preallocation. Oh,
> to protect parallel updating i_size, we have to take i_mutex down.").
> Perhaps, truncate_mutex lock should be used here, and not i_mutex.
> 

truncate_mutex is hold at the entry of ext4_**_get_blocks() to protect
parallel block allocation. Here I was worried about concurrent modifying
i_size and i_disksize which were protected by the i_mutex lock. Sorry
for any confusion.