linux-ext4 - Re: [RFC][Patch 1/2] Persistent preallocation in ext4

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Date:	Tue, 02 Jan 2007 14:47:32 -0800
From:	Mingming Cao <cmm@...ibm.com>
To:	"Amit K. Arora" <aarora@...ux.vnet.ibm.com>
Cc:	linux-ext4@...r.kernel.org, suparna@...ibm.com, suzuki@...ibm.com,
	alex@...sterfs.com
Subject: Re: [RFC][Patch 1/2] Persistent preallocation in ext4

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.

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