Re: fsync in glib/gio

[Alexander Larsson <alexl redhat com>]

On Tue, 2009-03-24 at 10:38 +0100, Pavel Machek wrote:
> On Tue 2009-03-24 10:30:52, Alexander Larsson wrote:
> > On Tue, 2009-03-24 at 10:01 +0100, Pavel Machek wrote:
> >  
> > > > > It seems wrong to work around broken file-systems on the application
> > > > > level. That only takes away pressure from the file-system developers to
> > > > > address the problem properly.
> > > > 
> > > > I don't disagree, but on the other hand. Users are losing data as we
> > > > speak. (See above ubuntu bug report)
> > > 
> > > It got fixed in ext4...
> > 
> > Yes, but not in e.g. XFS.
> 
> Well, given enough pressure, I'm sure XFS can be fixed too. (And then
> it can perhaps gain its "reliable filesystem" badge).

Even if it is fixed there would be other filesystems like that flash
filesystem that nokia uses that do the same thing.

> > > > One compromise we could make it to only fsync in the case we're actually
> > > > overwriting an existing file. This would mean that we don't risk
> > > > loosing
> > > 
> > > You should fsync just before doing rename, preferably in some special
> > > way so that we can tell it apart from 'normal' fsync.
> > 
> > This is what I mean of course. And there is no such "special way"
> > infortunately.
> 
> One proposal was to create "replace()" call (doing proper replacement
> of one file with another). It could start up as "fsync(); rename()"
> initially, but it should slowly move up into glibc and kernel, and do
> the right thing.

I proposed something similar, and i've seen multiple other proposals
too. However, I belive it when i can call it on a released distro.