linux-kernel - Re: [rfc] Ignore Fsync Calls in Laptop

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Message-ID: <BANLkTikVLFMX_U6brQ5OALbvJkOGuz6++Q@mail.gmail.com>
Date:	Fri, 20 May 2011 08:01:17 +0200
From:	"D. Jansen" <d.g.jansen@...glemail.com>
To:	Dave Chinner <david@...morbit.com>
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	tytso@....edu
Subject: Re: [rfc] Ignore Fsync Calls in Laptop_Mode

On Fri, May 20, 2011 at 5:39 AM, Dave Chinner <david@...morbit.com> wrote:
> On Thu, May 19, 2011 at 03:34:46PM +0200, Dennis Jansen wrote:
>> This is my first proper kernel code proposal so please bear with me!
>>
>> =Summary for busy kernel hackers=
>> Problem: laptop_mode wants to keep applications from waking the hard
>> disks but fsync calls can "sneak through". (IMHO this is a bug.)
>>
>> Proposed solution: Pretend the fsync was executed and successful.
>> Insert two lines into the fsync and fdatasync calls in fs/sync.c:
>> if (unlikely(laptop_mode))
>>    return 0;
>
> No, no, no, no, no, no, no, no, no, no.
>
> There is _absolutely no justification_ for putting people's data at
> risk like this.  If you want to do make fsync/fdatasync calls
> no-ops, then go install libeatmydata on your systems. It's your
> data, and you make the decision to risk it, not us.

1. I thought I (may) make that decision by using laptop mode.
2. libeatmydata would _always_ be active.
3. A lib doesn't fix the ordering guarantee problem.
4. It's clear that it's not the right code. (And it is a rfc and my
first one, too...)

Any suggestions?

Thanks!

Dennis
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