From: Matthieu CASTET <matthieu.castet@parrot.com>
To: Helmut Raiger <helmut.raiger@hale.at>
Cc: "linux-mtd@lists.infradead.org" <linux-mtd@lists.infradead.org>
Subject: Re: UBIFS: How to reserve space to be used right before power cut
Date: Thu, 13 Jun 2013 13:50:31 +0200 [thread overview]
Message-ID: <20130613135031.59037201@parrot.com> (raw)
In-Reply-To: <51B9B01A.1090504@hale.at>
Hi,
Why do you do this in ubifs ?
If you do it in ubi/mtd this will be a lot's of easier.
Matthieu
Le Thu, 13 Jun 2013 12:42:18 +0100,
Helmut Raiger <helmut.raiger@hale.at> a écrit :
> Hi,
>
> we try the following:
>
> 1) setup some data in an 8kByte block in RAM
> 2) frequently modify this data during normal operation
> 3) on a power fail signal write the block to a file on an UBIFS
> partition 4) recover from the written data after the power cut
>
> The time between power failure notification and the uP-reset is
> guaranteed by hardware
> and is about 20ms.
>
> We first thought about using fallocate() to allocate a corresponding
> block on the partition
> but soon found that UBIFS does not implement a native fallocate() and
> thus the generic
> one simply wrote the file to 8k of zeros. This of course will not
> help.
>
> Simply fsync()ing the file in case of a power cut does not seem
> reliable, for
> - the file system might be full
> - write back cache operation may interfere with the synch-ing of
> our file
> - the garbage collector might run to free dirty LEBs and erase the
> corresponding PEBs
> The latter 2 overstretching our timing requirements.
>
> This is on an embedded system (i.mx31, arm1136@532MHz) running Linux
> 3.something
> (we are quite flexible in adapting new kernel versions), currently
> testing on 3.0.45.
>
> Could someone hint the course to follow for this szenario?
>
> Any pointers appreciated,
> Helmut
>
>
> --
> Scanned by MailScanner.
>
>
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/
next prev parent reply other threads:[~2013-06-13 11:51 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-13 11:42 UBIFS: How to reserve space to be used right before power cut Helmut Raiger
2013-06-13 11:50 ` Matthieu CASTET [this message]
2013-06-13 13:29 ` Raiger Helmut
2013-06-13 14:20 ` Matthieu CASTET
2013-06-17 9:02 ` Helmut Raiger
2013-06-26 8:03 ` Helmut Raiger
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