[PATCH 2/2] dosfs: Lazy update of FAT32 FS info sector

Sebastian Huber sebastian.huber at embedded-brains.de
Fri Nov 9 06:44:28 UTC 2012

On 08/11/12 22:59, Claus, Ric wrote:
> On Nov 8, 2012, at 1:11 PM, Sebastian Huber wrote:
>> On 08/11/12 19:34, Claus, Ric wrote:
>>> Unlike as for Linux and Windows, there is no shutdown procedure for RTEMS.
>> What about unmount()?
>> http://www.rtems.org/onlinedocs/doxygen/cpukit/html/group__FileSystemTypesAndMount.html#ga4c8f87fc991f94992e0da1f87243f9e0
> Sounds like you didn't bother to read the rest of the message before answering.  Who calls unmount()?

I thought you mean the shutdown procedure for the file system, that is 
unmount().  You can add atexit() handler to do the unmount and use 
exit() to shutdown RTEMS.  So there are shutdown procedures, but it 
depends on the application.  Some applications do some clean up during a 
powerdown event for example.

>>> Even if there were one, I don't know how it would get invoked since everyone I know who uses RTOSes effectively pushes the reset button when they want to go again.  Consequently, the unmount is in most cases never called.  Given that, what is the effect of this patch on FAT formatted persistent storage devices that have been modified during a boot cycle?
>> For this scenario FAT is the ideal file system.

There are a lot of problems if you interrupt FAT operations at arbitrary 
points.  Thus for systems that can shutdown randomly FAT is not the 
ideal choice.

>>> Are they somehow cleaned up on the next mount?
>> Yes.
> For what context is this response?  With or without unmount()?

The clean up is performed unconditionally.  This means with and without 
the unmount().

> Honestly people, I don't understand what all these irritated e-mails are good for.  Read the e-mail 3 times before preparing an answer, then read your answer at least  3 times and press send only if you are okay with receiving such a response yourself.

Sorry for the short answers.

Sebastian Huber, embedded brains GmbH

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