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

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Date:	Mon, 19 Aug 2013 20:30:02 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Dave Chinner <david@...morbit.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-ext4@...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 Mon, Aug 19, 2013 at 7:38 PM, Dave Chinner <david@...morbit.com> wrote:
> 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.

Will do.

>
> 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.
>

Is there a guide to writing an xfstest?  I've already written it as a
standalone C program, so I assume it's easy.

--Andy
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