"Since that device included NOR flash this buffering is not used."
Do u mean to say for NOR flash we won't have this problem ? Why? - prasad On Thu, Oct 15, 2009 at 11:14 AM, Keith Mund (AZ) <keithm...@cox.net> wrote: > Here is a link to an article that discusses jffs2. It includes the quote > about NAND flash and buffers that follows. > > http://www.linux-mtd.infradead.org/faq/jffs2.html > > "On NAND FLASHM and NOR ECC FLASH we have a write-buffer for writing only > full pages to the chips. There could be a loss of data, when the > write-buffer is not flushed before power down. There are some mechanisms to > ensure, that the write-buffer is flushed. You can force the flush of the > write-buffer by using fsync() or sync() in your application. JFFS2 has a > timed flush of the write buffer, which forces the flush of the buffer to > flash, if there are no writes to the filesystem for more than about 5 > seconds. The time depends on the cycle-time of kupdated, which can be > adjusted via /proc/sys/vm/dirty_expire_centisecs" > > Adjusting kupdated would seem to affect more than just jffs2 so it may not > be the best way to improve this but it is at one person's opinion on a > salution. > > This made me rethink why this problem wasn't experienced in the last project > in which I used jffs2. Since that device included NOR flash this buffering > is not used. > > Keith > > -----Original Message----- > From: uclinux-dev-boun...@uclinux.org > [mailto:uclinux-dev-boun...@uclinux.org] On Behalf Of Allen Yang > Sent: Thursday, October 15, 2009 7:29 AM > To: uClinux development list > Subject: RE: [uClinux-dev] JFFS2 file corrupt at power down. > > I didn't realize I hijack the thread. Sorry about that. > > I can use fsync() or sync(). However, power can be turned off at any > time even during the sync() in the embedded systems. So I think using > backup file is necessary to recover from corrupt files. > > UBIFS doesn't have this type of problems? > > Regards, > > Allen > > > -----Original Message----- > From: uclinux-dev-boun...@uclinux.org > [mailto:uclinux-dev-boun...@uclinux.org] On Behalf Of Allon Stern > Sent: Thursday, October 15, 2009 8:53 AM > To: uClinux development list > Subject: Re: [uClinux-dev] JFFS2 file corrupt at power down. > > > On Oct 14, 2009, at 1:04 PM, Allen Yang wrote: >> The problem I have now is sometimes the XML files get corrupted when >> board is powered down. The corrupt XML file size is 0 or only a >> portion >> of the good file size. >> >> Is JFFS2 supposed to be power down safe? Maybe I missed something when >> using JFFS2. > > (thread hijacking aside) > > I had a number of problems with JFFS2 on my uClinux board; we ended up > switching to UBIFS, which seems to handle powerdowns pretty well. > > Filesystem notwithstanding, make sure that any changes you want > committed are followed up with an fsync. If you don't fsync, then > there's a chance that the write will be cached in memory and lost > before being stored persistently. This is true for any filesystem. > > - > allon > _______________________________________________ > uClinux-dev mailing list > uClinux-dev@uclinux.org > http://mailman.uclinux.org/mailman/listinfo/uclinux-dev > This message was resent by uclinux-dev@uclinux.org > To unsubscribe see: > http://mailman.uclinux.org/mailman/options/uclinux-dev > > ______________________________________________________________________ > This email has been scanned by the MessageLabs Email Security System. > For more information please visit http://www.messagelabs.com/email > ______________________________________________________________________ > > ______________________________________________________________________ > This email has been scanned by the MessageLabs Email Security System. > For more information please visit http://www.messagelabs.com/email > ______________________________________________________________________ > _______________________________________________ > uClinux-dev mailing list > uClinux-dev@uclinux.org > http://mailman.uclinux.org/mailman/listinfo/uclinux-dev > This message was resent by uclinux-dev@uclinux.org > To unsubscribe see: > http://mailman.uclinux.org/mailman/options/uclinux-dev > > > _______________________________________________ > uClinux-dev mailing list > uClinux-dev@uclinux.org > http://mailman.uclinux.org/mailman/listinfo/uclinux-dev > This message was resent by uclinux-dev@uclinux.org > To unsubscribe see: > http://mailman.uclinux.org/mailman/options/uclinux-dev > _______________________________________________ uClinux-dev mailing list uClinux-dev@uclinux.org http://mailman.uclinux.org/mailman/listinfo/uclinux-dev This message was resent by uclinux-dev@uclinux.org To unsubscribe see: http://mailman.uclinux.org/mailman/options/uclinux-dev
