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

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Message-ID: <BANLkTi=d+d7FZia5b5URDmcr=4bZnMccPA@mail.gmail.com>
Date:	Thu, 19 May 2011 17:01:02 +0200
From:	"D. Jansen" <d.g.jansen@...glemail.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	tytso@....edu
Subject: Re: [rfc] Ignore Fsync Calls in Laptop_Mode

On Thu, May 19, 2011 at 4:39 PM, Alan Cox <alan@...rguk.ukuu.org.uk> wrote:
>> > That at least cuts down most failures (but not all - eg commits with a network
>> > component such as email receives)
>>
>> I don't understand your email example.
>
> Think about sendmail and SMTP
>
> Mail arrives
> Commit to disk
> fsync
> [X]
> Confirm receipt to other system
> Other system removes it from the queue it holds
>
> So if it crashes at X even though you've kept ordering and you've
> got an internally consistent view (as if it crashed earlier), that
> has been observed and acted upon by another system - so your email
> just went into the cosmic trashcan.
>
>
Ok, I think I understand your example. But isn't that the user's risk
and more a problem of the general idea of laptop mode? If I enable
laptop_mode and set MAX_LOST_WORK_SECONDS, I risk to lose data. I
would say that includes email and whatever else may happen. (And if I
don't switch it on, I risk running out of battery and being unable to
create data...). btw. I don't think it would be a good idea for people
to use sendmail or other crucial data storage applications with
laptop_mode active. I would see this as a switch for e.g. notebooks at
conferences, in class, lectures, etc.

(sorry, lost the CCs)
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