From: Ted Ts'o <tytso@mit.edu>
Subject: Re: [PATCH 2/3] ext4: Context support
Date: Thu, 14 Jun 2012 13:05:33 -0400
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Cc: Arnd Bergmann <arnd.bergmann@linaro.org>,
	Alex Lemberg <Alex.Lemberg@sandisk.com>,
	HYOJIN JEONG <syr.jeong@samsung.com>,
	Saugata Das <saugata.das@linaro.org>,
	Artem Bityutskiy <dedekind1@gmail.com>,
	Saugata Das <saugata.das@stericsson.com>,
	linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-mmc@vger.kernel.org, patches@linaro.org, venkat@linaro.org,
	"Luca Porzio (lporzio)" <lporzio@micron.com>
To: Nicolas Pitre <nicolas.pitre@linaro.org>
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On Thu, Jun 14, 2012 at 12:14:13PM -0400, Nicolas Pitre wrote:
> Let's not forget that, in almost all cases, filesystem images are not 
> created live on the final medium.  Factories are picking a batch of 
> flash devices and a pre-built filesystem image is stamped on them, and 
> there might not even be a guarantee that those flash devices will all 
> have the same characteristics.  So to say that making this tuning at 
> mkfs time is probably not the best strategy.

Sure, that just means there needs to be a way of overriding the values
used by mke2fs.  (Because as you create the fs image, the storage
device parameters may make a difference to how blocks get allocated.)

The reason why I talk about making it work automatically at mke2fs
time is that the vast majority of created file systems (where a
specially created fs by a handset vendor counts as "one", even if it
then gets stamped on millions of devices), the end user is someone
naive/oblivious, so the right thing *has* to happen by default in the
common case of running mke2fs on the storage device where the file
system gets used.

					- Ted