Re: [PATCH] nfs: don't retry detect_trunking with RPC_AUTH_UNIX more than once

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Tested-by/Acked-by: Weston Andros Adamson <dros@xxxxxxxxxx>

I can’t reproduce the BUG() with this patch applied.

Besides the patch making complete sense to me, I have more evidence to back your explanation of the bug:

Without this patch I can run a ton of mount/umounts and eventually hit the crash. Before the crash there will be *many* (10s of thousands) pipes in /var/lib/nfs/rpc_pipefs/nfs/, which kills gssd (too many fds).

-dros


On Nov 12, 2013, at 4:30 PM, Jeff Layton <jlayton@xxxxxxxxxx> wrote:

> Currently, when we try to mount and get back NFS4ERR_CLID_IN_USE or
> NFS4ERR_WRONGSEC, we create a new rpc_clnt and then try the call again.
> There is no guarantee that doing so will work however, so we can end up
> retrying the call in an infinite loop.
> 
> Worse yet, we create the new client using rpc_clone_client_set_auth,
> which creates the new client as a child of the old one. Thus, we can end
> up with a *very* long lineage of rpc_clnts. When we go to put all of the
> references to them, we can end up with a long call chain that can smash
> the stack as each rpc_free_client() call can recurse back into itself.
> 
> This patch fixes this by simply ensuring that the SETCLIENTID call will
> only be retried in this situation if the last attempt did not use
> RPC_AUTH_UNIX.
> 
> Cc: stable@xxxxxxxxxxxxxxx # v3.10+
> Cc: Weston Andros Adamson <dros@xxxxxxxxxx>
> Cc: Chuck Lever <chuck.lever@xxxxxxxxxx>
> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> ---
> fs/nfs/nfs4state.c | 5 +++++
> 1 file changed, 5 insertions(+)
> 
> diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
> index c8e729d..4c26c01 100644
> --- a/fs/nfs/nfs4state.c
> +++ b/fs/nfs/nfs4state.c
> @@ -2097,6 +2097,11 @@ again:
> 			break;
> 	case -NFS4ERR_CLID_INUSE:
> 	case -NFS4ERR_WRONGSEC:
> +		/* No point in retrying if we already used RPC_AUTH_UNIX */
> +		if (clnt->cl_auth->au_flavor == RPC_AUTH_UNIX) {
> +			status = -EPERM;
> +			break;
> +		}
> 		clnt = rpc_clone_client_set_auth(clnt, RPC_AUTH_UNIX);
> 		if (IS_ERR(clnt)) {
> 			status = PTR_ERR(clnt);
> -- 
> 1.8.3.1
> 

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