From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH-v4 1/7] vfs: split update_time() into update_time() and
 write_time()
Date: Thu, 27 Nov 2014 07:25:04 -0800
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Cc: Theodore Ts'o <tytso@mit.edu>,
	Linux Filesystem Development List
	<linux-fsdevel@vger.kernel.org>,
	Ext4 Developers List <linux-ext4@vger.kernel.org>,
	Linux btrfs Developers List <linux-btrfs@vger.kernel.org>,
	XFS Developers <xfs@oss.sgi.com>
To: Jan Kara <jack@suse.cz>
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On Thu, Nov 27, 2014 at 01:34:29PM +0100, Jan Kara wrote:
>   But Ted changed XFS to copy timestamps to on-disk structure from the
> in-memory inode fields after VFS updated the timestamps. So the stamps
> should be coherent AFAICT, shouldn't they?

Not coherent enough.  We need the XFS ilock to synchronize reading from
and writing to the time stamps.  update_time() only has i_mutex, which
we can't take for the transaction commit path.