linux-ext4 - Re: [PATCH v3 5/5] ext4: Defer mmap cmtime update until writeback

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Message-ID: <20130820023849.GF6023@dastard>
Date:	Tue, 20 Aug 2013 12:38:49 +1000
From:	Dave Chinner <david@...morbit.com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	linux-kernel@...r.kernel.org, linux-ext4@...r.kernel.org,
	Theodore Ts'o <tytso@....edu>,
	Dave Hansen <dave.hansen@...ux.intel.com>, xfs@....sgi.com,
	Jan Kara <jack@...e.cz>, Tim Chen <tim.c.chen@...ux.intel.com>,
	Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH v3 5/5] ext4: Defer mmap cmtime update until writeback

On Fri, Aug 16, 2013 at 04:22:12PM -0700, Andy Lutomirski wrote:
> A fancier implementation could probably avoid an extra journal
> transaction by adding a mapping_test_clear_cmtime call in
> ext4_writepages, but this should already be a considerable
> improvement -- we'll start one transaction per writepages call
> instead of one per page.

I'd like to see more than just an ext4 implementation - btrfs and
XFS are the other main filesystems that should behave identically.

Also, it's worthwhile to write a generic xfstest to ensure that they
all update the timestamp appropriately - if its' in xfstests, then
we can basically guarantee that it won't get randomly regressed in
future, and other filesystems can be easily verified as well sa
their implement this.

Cheers,

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