Re: ext4 features

["Jeffrey V. Merkey" <jmerkey@wolfmountaingroup.com>]

H. Peter Anvin wrote:

> Bill Davidsen wrote:
>
> > > DC> Easily doable in userspace, why bother with kernel programming
> > >
> > > In userspace you can't automatically delete the files when the space
> > > becomes needed. The LD_PRELOAD/glibc methods also have the
> > > disadvantage of having to figure out where a file goes when it's
> > > deleted, depending on which device it happens to reside on. Demanding
> > > read access to /proc/mounts just to do rm could cause problems.
> > >
> > > Userspace has had 10 years to invent a good solution. If it was so
> > > easy, it would probably have been done.
> > Actually, if it were so important it WOULD have been done. I suspect 
> > that the issue is not lack of a good solution, but lack of a good 
> > problem. The behavior you propose requires a lot of kernel 
> > cleverness, including make the inodes seem to go away, so the count 
> > is "right" for what the user sees.
>
> The real solution for it is snapshots.


Peter,

Explain what you are thinking here.  What I proposed, I have already 
implemented in NetWare, it's very easy to do.  Snapshotting is not 
complex for FS's but does require a lot of space for meta-data to manage 
it.  EXT is not architecteced for something this complex.  A simple 
hidden mv is much easier to do.

Jeff

>     -hpa
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