From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: For UBIFS users: be aware of write-back! From: Artem Bityutskiy To: David Woodhouse In-Reply-To: <1223018149.3328.21.camel@macbook.infradead.org> References: <1222840288.8051.24.camel@sauron> <1223018149.3328.21.camel@macbook.infradead.org> Content-Type: text/plain; charset=utf-8 Date: Fri, 03 Oct 2008 10:45:46 +0300 Message-Id: <1223019946.8051.45.camel@sauron> Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Cc: linux-mtd@lists.infradead.org, Bruce_Leonard@selinc.com Reply-To: dedekind@infradead.org List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Fri, 2008-10-03 at 08:15 +0100, David Woodhouse wrote: > On Wed, 2008-10-01 at 08:51 +0300, Artem Bityutskiy wrote: > >=20 > > this e-mail informs about a quite important UBIFS feature which > > have already confused many people. > >=20 > > If you use UBIFS, and especially if you have been using JFFS2 before, > > please, read this documentation entry: > >=20 > > http://www.linux-mtd.infradead.org/doc/ubifs.html#L_writeback > >=20 > > 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. >=20 > 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. That's right, the above documentation even tells about this: "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." > 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. Right, agree. I'll amend the docs on the web site. --=20 Best regards, Artem Bityutskiy (=D0=91=D0=B8=D1=82=D1=8E=D1=86=D0=BA=D0=B8=D0=B9 =D0=90= =D1=80=D1=82=D1=91=D0=BC)