Re: overlayfs NFS export

[Trond Myklebust <trondmy@primarydata.com>]

On Fri, 2017-04-07 at 19:10 +0300, Amir Goldstein wrote
> 
> The most important point to understand is this:
> 
> If server opens a file for write it will trigger a copy up
> and the file handle returned will be persistent and final.
> 
> The only problem is that when server opens a file for
> read *before* it opens the same file for write, the returned
> handle would be different, because first open for write
> creates a new file and the old file remains a zombie
> (as far as nfsd is concerned) only nfsd is able to to access
> the old file and only for read.

That will break the client. As Miklos already told you, NFSv3 is
stateless, so the client won't be sending you an OPEN, and won't
actually hit a problem until it tries to send a WRITE, in which case
the resulting ESTALE error will be propagated to the application.

-- 
Trond Myklebust
Linux NFS client maintainer, PrimaryData
trond.myklebust@primarydata.com