From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: For UBIFS users: be aware of write-back! From: David Woodhouse To: dedekind@infradead.org In-Reply-To: <1222840288.8051.24.camel@sauron> References: <1222840288.8051.24.camel@sauron> Content-Type: text/plain Date: Fri, 03 Oct 2008 08:15:49 +0100 Message-Id: <1223018149.3328.21.camel@macbook.infradead.org> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Cc: linux-mtd@lists.infradead.org, Bruce_Leonard@selinc.com List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, 2008-10-01 at 08:51 +0300, Artem Bityutskiy wrote: > > this e-mail informs about a quite important UBIFS feature which > have already confused many people. > > If you use UBIFS, and especially if you have been using JFFS2 before, > please, read this documentation entry: > > http://www.linux-mtd.infradead.org/doc/ubifs.html#L_writeback > > Please, remember that UBIFS is _asynchronous_ FS. JFFS2 was synchronous, > so expect some of your old applications which were fine on JFFS2 to be > not ready to handle power cuts correctly in case of UBIFS. JFFS2 wasn't synchronous on NAND. You still needed to use fsync() as appropriate to ensure that written data made it to the flash and not just to the write-buffer. Your list of things to think about is good, but it should be pointed out that it applies _generally_ to all systems and all file systems. This is "Programming 101", and there was no excuse for people getting it wrong on JFFS2, either. It's not as if an fsync() was expensive in the cases where it did nothing. -- David Woodhouse Open Source Technology Centre David.Woodhouse@intel.com Intel Corporation