Re: [man-pages RFC PATCH v4] statx, inode: document the new STATX_INO_VERSION field

[NeilBrown]

On Sun, 11 Sep 2022, Al Viro wrote:
> On Thu, Sep 08, 2022 at 10:40:43AM +1000, NeilBrown wrote:
> 
> > We do hold i_rwsem today.  I'm working on changing that.  Preserving
> > atomic directory changeinfo will be a challenge.  The only mechanism I
> > can think if is to pass a "u64*" to all the directory modification ops,
> > and they fill in the version number at the point where it is incremented
> > (inode_maybe_inc_iversion_return()).  The (nfsd) caller assumes that
> > "before" was one less than "after".  If you don't want to internally
> > require single increments, then you would need to pass a 'u64 [2]' to
> > get two iversions back.
> 
> Are you serious?  What kind of boilerplate would that inflict on the
> filesystems not, er, opting in for that... scalability improvement
> experiment?
> 

Why would you think there would be any boiler plate?  Only filesystems
that opt in would need to do anything, and only when the caller asked
(by passing a non-NULL array pointer).

NeilBrown