Re: [PATCH 2/2] nfsd: implement chage_attr_type attribute

[Christoph Hellwig <hch@lst.de>]

On Mon, Nov 10, 2014 at 12:54:24PM -0500, J. Bruce Fields wrote:
> Shouldn't that be NFS4_CHANGE_TYPE_IS_MONOTONIC_INCR?
> 
> The draft says that e.g. "If the client sees
> NFS4_CHANGE_TYPE_IS_VERSION_COUNTER, it has the ability to predict what
> the resulting change attribute value should be after a COMPOUND
> containing a SETATTR, WRITE, or CREATE."
> 
> Admittedly, I'm not completely sure what that means.  (Is a SETATTR of
> multiple attributes a single atomic change?  Can we predict the change
> attribute on a newly created file, or only on the parent directory?)  I
> also don't know where the filesystems do the i_version increment (can we
> guarantee it happens once per nfs WRITE?).

Actually the server may increment it many times for a single WRITE,
for XFS it is incremented for each dirty transaction, which could
happen many times during a single write:

 (1) c/mtime update
 (2) suid/sgid bit removal
 (3) block allocation (could be multiple transactions)


So I guess we really should move to NFS4_CHANGE_TYPE_IS_MONOTONIC_INCR
instead.