From: Christoph Hellwig [mailto:email@example.com]
On Sun, Jan 22, 2017 at 03:43:09PM +0000, Matthew Wilcox wrote:
> In the case of a network filesystem being used to communicate with
> a different VM on the same physical machine, there is no backing
> device, just a network protocol.
Again, do you mean block device? For a filesystem that does not do any
pagecache writeback we already don't need a backing device, so I don't
really see an issue there to start with.
No, I mean a network filesystem like 9p or cifs or nfs. If the memcpy is supposed to be
performed by the backing device and there is no backing device, then it's going to
need to be done by the network filesystem.
(Also, the network filesystem might have a command, like RDMA has/will have, to ensure
that the write has reached persistence)