Re: For UBIFS users: be aware of write-back!

Artem Bityutskiy
2008-10-03T08:03:30Z

On Fri, 2008-10-03 at 08:57 +0100, David Woodhouse wrote:
> 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).

Well, this is what I actually assume. I'll change the docs to make them
telling loudly about this.