Directory rename semantics.

[Pawel Jakub Dawidek]

On Fri, Nov 07, 2008 at 12:32:59PM +0000, Ceri Davies wrote:
> On Fri, Nov 07, 2008 at 11:44:27AM +0100, Ivan Voras wrote:
> > Ceri Davies wrote:
> > > On Thu, Nov 06, 2008 at 08:28:29PM +0100, Edward Tomasz Napierala wrote:
> > >> After discussion about this with rwatson and pjd, I decided to do
> > >> the opposite: change ZFS behaviour to match UFS.  Reason is simple:
> > >> this is security, and we want to be conservative here.  It's impossible
> > >> to make sure this change wouldn't cause security problems.
> > > 
> > > Perhaps it would have been better to either do nothing or create a zfs
> > > property that toggled this behaviour so that people who expect ZFS to
> > > behave a certain way get it.  I'm not sure why we would want all
> > > filesystems to behave the same way, to be honest.
> > 
> > That would be desirable if we want file system semantics to be a
> > property of the OS instead of individual file systems. (Though I don't
> > know if there's ever been a conscious decision about this particular
> > goal). If so, a knob that toggles between the behaviours should toggle
> > it for all file systems. Having them behave differently can create
> > problems in migration to and from ZFS.
> 
> That's essentially what has just happened, but without the knob.
> 
> I'm not really sure whether you agree with the change that was made or
> not.

From user's perspective if I want to migrate from UFS to ZFS, I don't
want to find out that there are differences in how FS behaves. I'm
trying to make ZFS to be a full functional replacement for UFS, so that
it supports chflags(2), extattrs, etc. Of course we need to draw a
line what do we really want to support and what we may skip or support
not fully.

For example...

ZFS/FreeBSD on directory creation inherits group ownership from the
parent directory and now it also obeys directory write permissions when
we want to move it to another directory.

We support FreeBSD's extattrs, not Solaris fsattrs.

We could support POSIX.1e ACLs easly (on top of extattrs), but we want
to move to NFSv4-like ACLs with UFS too, AFAIK.

We support chflags(2), but not all the flags.

(I'm talking about perforce version.)

-- 
Pawel Jakub Dawidek                       http://www.wheel.pl
pjd at FreeBSD.org                           http://www.FreeBSD.org
FreeBSD committer                         Am I Evil? Yes, I Am!
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