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: <1223019946.8051.45.camel@sauron> References: <1222840288.8051.24.camel@sauron> <1223018149.3328.21.camel@macbook.infradead.org> <1223019946.8051.45.camel@sauron> Content-Type: text/plain Date: Fri, 03 Oct 2008 08:57:56 +0100 Message-Id: <1223020676.3328.28.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 Fri, 2008-10-03 at 10:45 +0300, Artem Bityutskiy wrote: > "In contrast, JFFS2 does not have write-back support and all the JFFS2 > file system changes go the flash synchronously. Well, this is not > completely true and JFFS2 does have a small buffer of a NAND page > size, but it is small and we may treat JFFS2 as completely > synchronous." That's quite poorly phrased. You may _not_ treat JFFS2 as completely synchronous. You treat it like a normal file system, or it's going to eat your babies. There was a reason I was perfectly happy to make the change which made JFFS2 start requiring fsync() like normal file systems -- it was because people should have been doing it _anyway_. Anyone who was skipping the required sync handling because they 'knew' that it didn't matter on JFFS2, even though it didn't cost them anything anyway -- and who didn't wake up at 3am every morning in a cold sweat, worrying that it might have broken today -- deserves to be taken out back and shot. When it comes to correctness, people shouldn't have to do anything special for different file systems. If there is _anything_ fs-specific about the correctness issues, you are doing something WRONG (cf. NFS). -- David Woodhouse Open Source Technology Centre David.Woodhouse@intel.com Intel Corporation