Re: [PATCH] nfsd: Implement large extent array support in pNFS

[Christoph Hellwig <hch@infradead.org>]

On Wed, Jun 11, 2025 at 03:19:29PM +0300, Sergey Bashirov wrote:
> > Normal operation should not cause that, what did you see there?
> 
> I think, this is not an NFS implementation issue, but rather a question
> of how to properly implement the client fencing. In a distributed
> storage system, there is a delay between the time NFS server requests
> a blocking of writes to a shared volume for a particular client and the
> time that blocking takes effect. If we choose an optimistic approach and
> assume that fencing is done by simply sending a request (without waiting
> for actual processing by the underlying storage system), then we might
> end up in the following situation.

I guess this is using block layout and your own fencing?  Because
with the SCSI layout we fence right from the kernel path before
force returning the layout.  The fact that block layout can't do
reliable fencing is the reason why I came up with the SCSI layout,
that can.