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

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: [PATCH v3 5/5] ext4: Defer mmap cmtime update until writeback
From: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Date: Mon, 19 Aug 2013 20:30:02 -0700
Cc: "linux-kernel@xxxxxxxxxxxxxxx" <linux-kernel@xxxxxxxxxxxxxxx>, "linux-ext4@xxxxxxxxxxxxxxx" <linux-ext4@xxxxxxxxxxxxxxx>, "Theodore Ts'o" <tytso@xxxxxxx>, Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>, xfs@xxxxxxxxxxx, Jan Kara <jack@xxxxxxx>, Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>, Christoph Hellwig <hch@xxxxxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20130820023849.GF6023@dastard>
References: <cover.1376679411.git.luto@xxxxxxxxxxxxxx> <d59d6c9790bd3c36b93343ed91be5e0cda7e5f09.1376679411.git.luto@xxxxxxxxxxxxxx> <20130820023849.GF6023@dastard>
On Mon, Aug 19, 2013 at 7:38 PM, Dave Chinner <david@xxxxxxxxxxxxx> 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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