linux-kernel - Re: [PATCH] mmc: add module parameter to set whether cards are assumed removable

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Message-ID: <4B02565C.1030406@s5r6.in-berlin.de>
Date:	Tue, 17 Nov 2009 08:53:00 +0100
From:	Stefan Richter <stefanr@...6.in-berlin.de>
To:	Ben Hutchings <ben@...adent.org.uk>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-mmc@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
	504391@...s.debian.org,
	Wouter van Heyst <larstiq@...stiq.dyndns.org>,
	Pierre Ossman <pierre@...man.eu>
Subject: Re: [PATCH] mmc: add module parameter to set whether cards are assumed
 removable

Ben Hutchings wrote:
> In general, it is not possible to tell whether a card present in an MMC
> slot after resume is the same that was there before suspend.

That's true for virtually all storage devices, not just MMC.

> So there are two possible behaviours, each of which will cause data
> loss in some cases:
> 
> CONFIG_MMC_UNSAFE_RESUME=n (default): Cards are assumed to be removed
> during suspend.  Any filesystem on them must be unmounted before
> suspend; otherwise, buffered writes will be lost.
> 
> CONFIG_MMC_UNSAFE_RESUME=y: Cards are assumed to remain present during
> suspend.  They must not be swapped during suspend; otherwise, buffered
> writes will be flushed to the wrong card.
> 
> Currently the choice is made at compile time and this allows that to be
> overridden at module load time.

Can't the kernel flush the write buffer at suspend time, so that you can
remove this choice for good?
-- 
Stefan Richter
-=====-==--= =-== =---=
http://arcgraph.de/sr/
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