From: Waiman Long <waiman.long@hpe.com>
Subject: Re: [PATCH v3 1/2] ext4: Pass in DIO_SKIP_DIO_COUNT flag if inode_dio_begin()
 called
Date: Thu, 21 Apr 2016 14:15:24 -0400
Message-ID: <571918BC.2060007@hpe.com>
References: <1460484775-33359-1-git-send-email-Waiman.Long@hpe.com> <1460484775-33359-2-git-send-email-Waiman.Long@hpe.com> <20160420205801.GA24609@infradead.org>
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Cc: Theodore Ts'o <tytso@mit.edu>,
	Andreas Dilger <adilger.kernel@dilger.ca>,
	<linux-ext4@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	Tejun Heo <tj@kernel.org>, Christoph Lameter <cl@linux.com>,
	Scott J Norton <scott.norton@hpe.com>,
	Douglas Hatch <doug.hatch@hpe.com>,
	Toshimitsu Kani <toshi.kani@hpe.com>
To: Christoph Hellwig <hch@infradead.org>
Return-path: <linux-kernel-owner@vger.kernel.org>
In-Reply-To: <20160420205801.GA24609@infradead.org>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: linux-ext4.vger.kernel.org

On 04/20/2016 04:58 PM, Christoph Hellwig wrote:
> FYI, none of the Dax code even needs to ever touch the dio_count,
> as dax I/O can't be asynchronous, and we thus don't need it to protect
> against truncate.  I'd suggest to remove it and then end_io callback
> from the DAX code entirely as a start and then move from there.

Yes, it seems like we may not need to change the dio_count in 
dax_do_io() after all. BTW, what do mean by using end_io callback as a 
start?

Cheers,
Longman