Re: Concerns about ENETUNREACH patch series Re: [PATCH v2 0/4] Ensure that ENETUNREACH terminates state recovery

[Trond Myklebust <trondmy@hammerspace.com>]

On Tue, 2025-03-25 at 20:40 +0100, Lionel Cons wrote:
> On Tue, 25 Mar 2025 at 17:19, <trondmy@kernel.org> wrote:
> > 
> > From: Trond Myklebust <trond.myklebust@hammerspace.com>
> > 
> > With the recent patch series that caused containerised mounts which
> > return ENETUNREACH or ENETDOWN errors to report fatal errors, we
> > also
> > want to ensure that the state manager thread also triggers fatal
> > errors
> > in the processes or threads that are waiting for recovery to
> > complete.
> > 
> > ---
> > v2:
> >  - Return EIO instead of ENETUNREACH in nfs4_wait_clnt_recover()
> > 
> > Trond Myklebust (4):
> >   SUNRPC: rpcbind should never reset the port to the value '0'
> >   SUNRPC: rpc_clnt_set_transport() must not change the autobind
> > setting
> >   NFSv4: clp->cl_cons_state < 0 signifies an invalid nfs_client
> >   NFSv4: Treat ENETUNREACH errors as fatal for state recovery
> > 
> >  fs/nfs/nfs4state.c     | 14 +++++++++++---
> >  net/sunrpc/clnt.c      |  3 ---
> >  net/sunrpc/rpcb_clnt.c |  5 +++--
> >  3 files changed, 14 insertions(+), 8 deletions(-)
> 
> 1. Can this "ENETUNREACH or ENETDOWN are fatal" feature be turned
> off?
> 
> 2. We have concerns about this feature - what will happen if a switch
> or router gets rebooted? What will happen if you unplug your laptop?
> What will happen if you enable/disable your VPN software on a machine
> or container? What will happen if you switch WIFIs on your laptop?
> 
> All these scenarios will trigger a temporary ENETUNREACH or ENETDOWN,
> and should NOT be fatal for mounts or containers.

TL;DR: Yes, you can turn it off using a mount option, but we preserve
the existing hard mount behaviour unless you are actually mounting in a
container.

See the description in the first series of patches:
https://lore.kernel.org/linux-nfs/2a37ba5a-f212-4456-a7c1-3f96b1148b3b@oracle.com/T/#mf3df4516c5fcb0ef22c1c1c6f5433535f4d4805a



-- 
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@hammerspace.com